Teeth selection in complete dentures

Step in complete denture fabrication

1. Teeth Selection in Complete Dentures Presented by: Dr. Rajvi Nahar 1 st year Post-Graduate

2. Contents Introduction History Objectives of teeth selection Anterior teeth selection Posterior teeth selection Shade matching: Past to Recent Advances Anterior teeth arrangement Posterior teeth arrangement Errors in teeth arrangement Teeth selection and arrangement in digital dentures Conclusion References

3. INTRODUCTION Esthetic tooth placement and physiological tooth arrangement are biologically compatible and desirable as end products of proper complete denture construction. Proper placement of teeth should be functional as well as esthetically pleasing. Denture esthetics is defined as “the cosmetic effect produced by a dental prosthesis which affects the desirable beauty, attractiveness, character, and dignity of the individual.” This tends towards art and less to science and while the principles which follow will enable any clinician of average artistic ability to select teeth suitable for the average patient, the most pleasing results will always be obtained by those with an aesthetic sense.

4. Anterior teeth are primarily selected to satisfy esthetic requirements. The selection of artificial teeth for edentulous patients requires a knowledge and understanding of a number of physical and biologic factors that are directly related to each patient. The selection of artificial teeth is a relatively simple, non-time consuming procedure, but it requires development of experience and confidence. Any choice of artificial teeth must be considered as a preliminary selection until the teeth are arranged on the trial denture bases and can be critically viewed in the patient’s mouth.

5. HISTORY OF ANTERIOR TEETH SELECTION During the ivory age, teeth were selected, mostly by dimensional measurements, with slight consideration given to face form or other qualities. The geometric classification of face form and profile, which was projected by Madame Schimmelpeinik in 1815 for artists use was considered in dentistry for esthetic teeth selection. The ‘‘correspondence and harmony’’ concept was projected by J.W. White in 1872. The basis of this concept was that the temperaments called for a characteristic association of the tooth form and color, and that harmony called for a corresponding proportion and size of tooth to that of the face, and a tooth color in harmony with facial complexion; that both form and color were modified to be in harmony with sex and age. The ‘‘Temperamental technic’’ of selecting tooth form was the first technique from the point of view of influence and universal acceptance.

6. The ‘‘Typal form concept’’ projected by W.R. Hall in 1887 . Hall gave the first measurements of the typal tooth forms. ‘‘Berry’s biometric ratio method’’ , was projected in 1906 . He discovered that the proportions of the upper central incisor tooth had a definite proportional ratio to face proportions. The tooth was one sixteenth of the face width and one twentieth the face length. Clapp’s ‘ ‘Tabular Dimension Table Method’’ ,was presented around 1910 . This method was based on selecting tooth size from the overall dimension of six anterior teeth and the vertical tooth space present in the patient. ‘‘Molar Tooth Basis’’ ,was projected by Valderrama in 1913 . According to this method, the tooth size was measured on a one-fourth increment of the size of a Bonwill triangle, and is determined by measuring the edentulous mandible.

7. Cigrande in 1913 used the outline form of the fingernail to select the outline form of the upper central incisor tooth. The size was modified to meet the requirements of tooth space and other relationship. Williams ‘‘Typal form method’’ , projected in 1914 . He classified the facial form into square, tapering and ovoid forms. Later the selection was based on ‘‘Mould Guide Sample Teeth’’. Leon Williams Face Forms

8. ‘‘Wavrin Instrumental Guide Technique’’ , projected about 1920 , which was a combination of Berry’s Biometric ratio method and the William’s typal form teeth. In 1920 Nelson projected a technique for selecting a tooth mould and he called it as ‘‘Maxillary Arch Outline Form’’. This technique assumed that the arch outline form was the valid method. In 1936 ‘‘Wright’s Photometric Method’’ was projected. This was based on using a photograph of the patient with natural teeth, and establishing a ratio by comparative computation of measurements of like areas of the face and photograph.

9. The ‘‘Multiple Choice Method,’’ projected by Myersonin 1937 . This was based on a need for a selective range in labial surface characteristics of transparent labial and mesial surfaces, varying surface color tone, and characterizations of teeth by time, wear. The ‘‘House Instrumental Method’’ of projecting typal outline and profile silhouettes onto the face by means of a telescopic projector instrument and silhouette form plates. It was projected by House in 1939 . ‘‘Stein’s coordinated size technic,’’ projected in 1940 . This was based on the coronal index of 70–100, commonly used in prosthetics on four model teeth representing the range of maximum frequency of use, and on the common variability in size of individual natural teeth.

10. ‘‘Anthropometric Cephalic Index Method,’’ projected by Sears in 1941 . This was based on the fact that width of the upper central incisor could be determined by dividing either the transverse circumference of the head by 13 or the bizygomatic width by 3.3. The tooth length was in proportion to the face length. Sear’s anthropometric cephalic index method

11. ‘‘Frame Harmony Method’’ projected by the Justi Company in 1949 . The basis of the method is the size and proportions of the teeth are in harmony with the general proportions of the skeleton. The overall tooth size was selected by the mathematical formula, one seventeenth the total dimension of the upper and lower bearing areas, with the dimensions of the individual anterior teeth correlated with a developed table of tooth dimensions to give the indicated overall dimension. The ‘‘Bioform technic’’ was projected by Dentists Supply Company in 1950 which is based on the House classification. The ‘‘Selection Indicator Instrument method’’ projected by the Dentists’ Supply Company, which is correlated with Williams’ and Houses’ typal tooth form theory and the tabular table technic.

12. The ‘‘Automatic Instant Selector Guide’’ of the Austenal company projected in 1951 . This technique correlates form, size, and appearance in such a manner that a single reading only is required to select the appropriate tooth mold based on dimensions of denture space and harmony of face and tooth form. The dentogenic concept of teeth selection was put forth by Frush and Fischer in 1955 . Kumar MV, Ahila SC, Devi SS. The science of anterior teeth selection for a completely edentulous patient: a literature review. The Journal of Indian Prosthodontic Society. 2011 Mar 1;11(1):7-13.

13. Objectives of Teeth Selection Teeth selection is very important as the selection of the appropriate shade, size, and form of the artificial teeth determines the esthetic and function of the denture. The teeth should be in harmony with the surrounding tissues. They should maintain the vertical dimension. They should be efficient for mastication. Anterior teeth are selected predominantly based on esthetic, whereas the posterior teeth should be selected based on the function

14. Anterior teeth selection Anterior teeth are primarily selected to satisfy esthetic requirements, so the dentist's professional obligation is to give the patient adequate information, guidance, and opportunity to choose their teeth. Anterior teeth selection is the area of prosthodontic care in which the patient should be given a primary responsibility to determine the esthetic outcome. The selection of artificial teeth for edentulous patients when all records of form, color, and size have been lost is a clinical procedure. Trial in the patient’s mouth is the best way.

15. Much of the effectiveness of tooth selection depends on the ability of dentists to interpret what they see. Careful examination of the faces and teeth of people with natural teeth will develop a sense of dentofacial harmony that is the objective of tooth selection and esthetics. There must be harmony of color, form, size, and arrangement of teeth Factors to be considered for selection of anterior teeth: A. Shade (color) B. Size. C. Form.

16. SHADE: A knowledge of the physics, physiology, and psychology of color is of value in the selection of the color . The color of most concern to dentist is the yellow color, because the colors of teeth and faces are primarily yellow. Colors have four qualities — Hue Saturation (chroma) Brilliance (value) Translucency All these are involved in selection of teeth.

17. Hue: It refers to the dominant wavelengths present in a spectral distribution e.g. red, green, yellow, etc. The hue of the teeth must be in harmony with the hue of the patient’s face. Disharmony will make dentures look artificial. Saturation: It is the amount of color per unit of area of an object.

18. Brilliance: It refers to the lightness or darkness of an object. Patient’s with fair complexion have lighter teeth than the patient with dark complexion. Translucency : It is the property of an object that permits the passage of light through it but cannot give any distinguishable image. Presence of translucency makes the teeth looks alive.

19. The factors of shade selection are:- 1 . Age: The younger the patient, the lighter the color is preferred. The color of natural teeth darken with age because of : deposition of secondary dentin , wearing away of enamel external staining from oral fluids, foods or tobacco, consequent reduction in size of the pulp chamber. 2. Sex: The sex may effect color, it seems that females given brighter teeth than males.

20. 3. Complexion: The color of the face should harmonize the color of teeth. Lighter teeth are suitable for lighter skin, while darker teeth are suitable for darker skin, although darker people with dark skin seemed to have very light teeth. This is because of contrast in the skin and tooth color. 4. Patient –preference: Show the patient a complete shade guide and select the two tabs that are lightest and darkest, hold them against the patient lip and ask them to point to the one that they prefer. More than two or three shades should be selected and comparison between them would help in final right selection.

21. Color of Anterior Teeth Bilmeyer and Saltzman defined color as the result of the physical modification of light by colorants as observed by the human eye and interpreted by the brain. The definition of color is indicative of the variables inherent in seeing and controlling color. When a tooth is viewed for the purpose of determining its color, two principle colors––yellow and grey––are evident. The yellow is more dominant in the gingival third and the grey is more prominent in the incisal third.

22. The factors controlling color can be controlled into three basic variables: observer variables, object variables and light source variables. This is referred to as geometric metamerism or a conditional color match. The shade of the central incisor has been selected from an appropriate shade guide. In choosing this shade, the dentist should consider the age of the patient, the individual complexion pattern, and the patient’s desires. The position of the patient and source of light are very important in color selection. The patient should be in upright position. The dentist should be in a position so that the teeth are viewed in a plane perpendicular to the dentist plane of vision.

23. White light of wavelength between 380 and 750 nm in the electromagnetic spectrum is considered suitable. Eyes fatigue to color perception very rapidly, for this reason they should not be focused on a tooth more than few seconds. The teeth and the shade guide should be placed at a distance of 6–8 feet. Lombardi RE (1973) The principles of visual perception and their clinical application to denture esthetics. J Prosthet Dent 23:358–382 Method of Pair comparison Shade Guide

24. To select the size of anterior teeth, we have to consider the following: Length: The length of anterior teeth is controlled by: 1. Length of upper lip: In short lip more than 2 mm seen from the maxillary central incisors. In medium lip length 1.5-2 mm seen from the maxillary central incisors. In long lip nothing can be seen from the maxillary central incisors. 2. Level of upper lip: Length of mandibular anterior teeth should be with the level of lower lip. 3. Inter-ridge distance : When the space is available, it is more esthetically acceptable to use a tooth long enough to eliminate the display of the denture base. SIZE

25. Width The width from the tip of left canine to the tip of right canine is almost equal to the width of the nose (interalar width) when measured by the caliper. (Width of six anterior teeth = interalar width + 7 mm) The width of maxillary central incisor equals approximately to 1/16 of bizygomatic width, and the width of maxillary anterior teeth equals to 1/3.36 of bizygomatic width. Width of the anterior teeth can be measured on maxillary occlusal rim depending on the intraoral anatomical landmarks like: (buccal frenum, corner of the mouth, and canine eminence).

26. Patient Preference Use the method of pair comparison to assist a patient to decide what size of tooth they prefer. Set two different sizes of teeth on a piece of wax rope, place them under the upper lip, and find out which one the patient prefers. Two or three presentations may have to be made to reach a suitable decision.

27. • The size of the teeth should be in proportion to the size of the face and head. • Women’s teeth are often smaller than men’s. • A distinct difference between CI & LI is desirable in women. • Following factors are used as a guide to select the size of the teeth: 1. Methods using pre-extraction guides 2. Methods using anthropological measurements of the patient 3. Methods using theoretical concepts 4. Methods using anatomical landmarks

28. Methods using pre-extraction guides DIAGNOSTIC CASTS Diagnostic cast of natural teeth are the most reliable guides in both selecting arranging anterior teeth. The size and form of the anterior teeth can be determined on the diagnostic cast, and comparable artificial teeth are selected.

29. PHOTOGRAPHS: • Provides information about the width of the teeth and possibly the outline form • An algebraic proportions may be established with some known and unknown factors such as interpupillary distance in patient and in the photograph, and the width or length of the CI in the photograph. EXTRACTED TEETH: • Provides excellent information as to size and form for the artificial teeth. • Cannot be used in selecting color.

30. INTRA-ORAL RADIOGRAPHS: • Radiographs made before the natural teeth were lost can supply information about the size and form of the teeth to be replaced. • However, radiographic image is slightly enlarged and may be distorted because of divergence of the x-ray. OBSERVATION OF TEETH OF CLOSE RELATIVES and OLD DENTURES

31. Methods using anthropological measurements of the patient These methods measures certain anatomical dimensions and derive the size of teeth using certain formula: Anthropometric cephalic index Berry’s biometric index H. Pound’s formula

32. Anthropometric cephalic index (Sears) – Transverse circumference of the head is measured using a measuring tape at the level of the forehead. Circumference of the head Width of the upper CI = ------------------------------------------- 13 Bi-zygomatic width Total Width of the upper anterior =------------------------------------------- 3.36 4 Total Width of the lower anterior =---- Width of the upper anteriors 5

33. Berry’s biometric index bi-zygomatic width Width of the upper CI= ----------------------------- 16 length of the face Width of the upper CI=----------------------------- 20

34. H. Pound’s formula Evaluated tooth width by ‘‘measuring the distance from zygoma to zygoma, one to one half inches back of the lateral corner of the eyes’’ . bi-zygomatic width Width of the upper CI=----------------------------- 16 length of the face Length of the upper CI=----------------------------- 16 Pound E (1954) Lost fine arts in the fallacy of ridges. J Prosthet Dent 4:6–16

35. White’s Concept This method was based on a 5th century BC concept attributed to Hippocrates. Temperamental types were: sanguine, nervous, billious Lymphatic named for the physiologic functions of blood, nerves, bile and lymph of the individual. Artificial teeth were arbitrarily selected to suit the patient’s temperament. A ‘‘bilious’’ individual would be expected to have short, broad, tapering incisor teeth, whereas a ‘‘sanguineous’’ individual would possess long, thin, and narrow teeth. Methods using theoretical concepts Young HA (1954) Selecting the anterior tooth mould. J Prosthet dent 4:748–760

36. Winkler’s Concept This concept emphasizes on three points. Biological-physiological, Biomechanical Psychological The biological-physiological view point stated the importance of harmony of the facial musculature and physiological limit with teeth arrangement. Facial musculature contributes to the esthetics of a patient. Increasing the thickness of the denture base in the labial and Buccal sulci can produce a puffy appearance. Facial wrinkles fade when the vertical dimension is increased. Land LS (1996) Anterior tooth selection and guidelines complete denture esthetics. In: Winkler S (ed) Essentials of complete denture prosthodontics, 2nd edn. Ishiyaku Euro America Inc., St. Louis, pp 200–216

37. Biomechanical shows the mechanical limitations in placement of anterior teeth. According to this teeth should be set in the neutral zone. Psychological view is based on esthetics and facial appearance. Camper’s line is the psychological plane of orientation. It is raised in happy people. It is tilted in depressed people.

38. Dentogenic Concept Tooth selection using the concepts of dentogenics is based on the age, sex and personality of the patient put forth by Frush and Fisher 1955. This concept has been explained as the prosthodontic appearance interpretation of three vital factors which every patient possess. The factors are : Sex, Personality Age of the patient. Frush JP, Fisher RD (1958) The dynesthetic interpretation of dentogenic concept. J Prosthet Den 8:558–581

39. Leon William’s Concept William formulated a method called the law of harmony. He believed that a relationship exists between the inverted face form and the form of maxillary central incisor in most people. He described three typal forms of teeth square, tapering, ovoid. Williams JL (1914) A new classification of natural and artificial teeth. Dentists supply Co, New York City

40. Methods using anatomical landmarks Nine anatomical entities are used as guides to select anterior teeth according to size. Size of the Face Size of the Maxillary Arch Incisive Papilla and the Canine Eminence or the Buccal Frenum Maxillomandibular Relations Contour of the Residual Ridge Vertical Distance Between the Ridges Lips Nasal Width as a Guide Boucher Inner Canthal Distance as a Guide Kumar MV, Ahila SC, Devi SS. The science of anterior teeth selection for a completely edentulous patient: a literature review. The Journal of Indian Prosthodontic Society. 2011 Mar 1;11(1):7-13.

41. Size of the Face The width of the anterior teeth in accordance with the face can be calculated as below. Average width of the maxillary central incisor = 1/16th of the width of the face measured between the zygoma. Combined width of the six maxillary anterior teeth = slightly less than 1/3rd of the bizygomatic breadth of the face. The face bow can be used as a caliper to record the bizygomatic breadth.

42. The trubyte tooth indicator is useful in determining the size of the maxillary central incisors. It can be determined by placing the indicator on the patient’s face, allowing the nose to come through the center triangle.

43. Center the pupil in the eye slots, and hold the indicator with its central line coinciding with the median line. Slide the side indicator bar until it touches the face and the width of the upper central tooth can be read in millimeters. The length of the tooth can be determined by sliding the bottom indicator bar up to position immediately underneath the chin with lips at rest and the length of the upper central incisor in millimeters.

44. Size of the Maxillary Arch The mould selectors are used to make measurements of the maxillary cast. Measurements are made from the crest of the incisive papilla to the hamular notches and from one hamular notch to the opposite side hamular notch. The combined length of the three legs of the triangle in millimeters is used as the selector. The circular slide rule indicates the anterior and posterior tooth size.

45. The universal mould selectors are commonly used. The measurements are made from the midline of the maxillary occlusal rim to the distal of the cuspid eminence. An arrow designates on the selector which mould is indicated. When discrepancies exist between the face size and arch size, the selection of anterior tooth should be governed more by face size than arch size, since resorbed tissue can leave one astray.

46. Incisive Papilla and the Canine Eminence or the Buccal Frenum. If the canine eminences are discernible a line can be placed on the cast at the distal termination of the eminence. If eminences are not discernible attachments of buccal frenum are used as guide. A line placed slightly anterior to the buccal frenum will be distal to the eminence. A flexible ruler is used and the distance between the two canine eminences at their distal side through the anterior of the incisive papilla is measured in millimeters and this measurement gives the combined width of the six anterior teeth. Incisive Papilla Buccal Frenum

47. Another method of marking the canine eminence is to place the fabricated occlusal rim in the patient’s mouth and ask the patient to relax with the lips closed. With a sharp marker, mark at the corner of the lips. The vertical line drawn from this mark coincides with the pupil of the eye. The distance between the marks following the contour of the arch marked in millimeters is the combined width of six maxillary anterior teeth.

48. Maxillomandibular Relations : Any disproportion in size between the maxillary and mandibular arches influences the length, width and position of the teeth. This is of importance in class II and class III maxillomandibular relations. The sizes and the positions of the teeth will have to vary from the accepted normal if the teeth in the one arch are to complement the teeth in the other arch. In instances of protruded mandibles the mandibular teeth are frequently larger than normal. If the mandibles are retruded, the mandibular teeth are frequently smaller.

49. Contour of the Residual Ridge: The artificial teeth should be placed to follow the contour of the residual ridges that existed when natural tooth were present. A knowledge of direction of resorption of the two arches will allow a fairly accurate visualization of the original contour. Resorption of maxillae in anterior segment is in a vertical and palatal direction, Posteriorly in vertical and medial direction . In mandible in in anterior segment is in vertical and lingual direction, Posteriorly in vertical and lingual direction.

50. Vertical Distance Between the Ridges : The length of the teeth is determined by the available space between the existing ridges. It is advisable to use a tooth long enough to eliminate the display of the denture base. Lips Labial surface of the maxillary anterior teeth supports the relaxed lip. Frequently incisal edges extends inferior to or slightly below the lip margin. When the teeth are in occlusion and lips closed the labial incisal third of the maxillary anterior teeth supports the superior border of the lower lip. In speech, incisal edges of maxillary anterior teeth contacts the lower lip at the junction of the moist and dry surfaces of the vermilion border. It is best demonstrated when the letter F, as in fifty five is pronounced.

51. Nasal Width as a Guide Boucher and Hoffman et al. referred to the nasal index as a guide to select the anterior teeth as it relates the inter alar width to the space available for setting the anterior teeth. Wehner et al. suggested that the ‘‘parallel lines’’ extended from the lateral surface of the ala of the nose onto the labial surface of the upper occlusal rim could be used to give an estimation of the midline vertical axis of the upper canine teeth. Kern made measurements on 509 dried skulls and found that most of the measurements of nasal width are equal to or within 0.5 mm of the measurements of the four maxillary anterior teeth. Mavroskoufis and G.M. Ritchie gave a formula for the selection of the mesiodistal width of the anterior artificial teeth (A = N + 7 mm) where N is the nasal width.

52. Inner Canthal Distance as a Guide: The inner canthal distance is defined as the distance between the medial angles of the palpebral fissures. Abdullah in 2002 has proposed a formula to calculate the width of the central incisor from the inner canthal distance. The ICD was found to be greater than the combined width of maxillary central incisors. Thus the ICD was multiplied by 0.618. The resultant product was then divided by 2 to obtain the width of a single central incisor. FCIW = ICD/ 2 × 0.618.

53. FORM OF TOOTH Three factors are used as guides in the selection of anterior tooth form. 1. Shape of the patient’s face or facial form 2. Patient’s profile 3. Dentogenic concept and dynesthetics

54. Form and Contour of the Face : The shape of the artificial tooth should harmonize with the patient’s facial form. The classification of tooth forms by Leon Williams, though not scientifically correct, is undoubtedly the simplest and the most useful guide. Leon Williams claimed that the shape of the upper incisors bears a definitive relationship to the shape of the face. He classified the form of the human face into three types: square, tapering and ovoid forms. The operator imagines two lines, one on either side of the face, running about 2.5 cm in front of the tragus of the ear and through the angle of the jaw.

55. Square––lines are almost parallel Tapering––lines converge towards the chin Ovoid––lines diverge towards the chin The other method of determining the tooth shape is by the use of a trubyte tooth indicator. Place the indicator on the patient’s face, allowing the nose to come through the central triangle. Center the pupils of the eye in the eye slots and hold the indicator with its central line coinciding with the median line of the face.

56. In Square form––the sides of the face will approximately follow the vertical lines of the indicator. In square tapering, the upper third of the lower 2/3rds will taper inward. In tapering faces, the side of the face from the forehead to the angle of the jaw will taper at an inward diagonal. Ovoid faces will be best determined by examination of the curved outline of the face against the straight vertical of the indicator. TRUBYTE TOOTH INDICATOR.

57. Facial Profile: To determine the facial profile, observe the relative straightness or curvature. The facial profile is determined by three points: The forehead, the base of the nose and the prominent point of the chin. Straight—three points are in line Curved—points of the forehead or chin are recessive.

58. Based on these three points the profile can be straight, convex or concave. The labial surface of the tooth viewed from mesial should show a contour similar to that when viewed in profile. The labial surface of the tooth when viewed from the incisal should show a convexity or flatness similar to that seen when the face is viewed from under the chin or from the top of the head.

59. Dentogenic concept and dynesthetics: Dentogenics is the art, practice and technique of creating the illusion of natural teeth in artificial dentures and is based on the elementary factor influenced by sex, personality and age of the patient. It was first described by Frush and Fisher . The term “Dynesthetics” is derived from Greek word “dynamics” meaning power. It supports in working factor of dentogenic concept. Dentogenic concept: SEX: In female, the incisal angles are more rounded and the teeth have lesser angulation while in males, the incisal angles are rounded to a lesser degree and teeth are more rounded. The incisal edge of the CI is parallel to the lips and the laterals are above the occlusal plane in males. But in females it follows curve of the lower lip (CI & LI) . The distal surface of CI are rotated posteriorly for females. Frush JP, Fisher RD (1958) The dynesthetic interpretation of dentogenic concept. J Prosthet Den 8:558–581

60. Lateral incisors :Mesial surface are rotated anteriorly in relation to CI in females. The mesial ends are hidden by the CI. This makes the canine very prominent in males. Canines : Only the mesial thirds are visible in females because they are rotated anteriorly in relation to the CI whereas even the middle two-thirds of the canine are visible in males. PERSONALITY Teeth should be selected according to the patients personality More squarish and large teeth should be used for vigorous people. The anteriors should be in flat plane for executive people, also the teeth should be relatively smaller and more symmetrical . It seems reasonable that a large vigorous type of persons have teeth of a size and form with prominent markings, different from those of a delicate appearing patient.

61. AGE: Age can be easily separated into young, middle or elderly. Due to decrease in muscle tone, sagging of the cheeks and the lower lips occur. To prevent cheek biting, horizontal overlap of the posterior teeth can be increased. Inter occlusal distance reduces with age. Hence, mandibular teeth are more visible than the maxillary teeth. In old patients the teeth tend to have square form due to attrition, more round features disappears and line angle quite seen in those patients. Old patient have gingival recession, & can be reproduced in the dentures. The color of the teeth also changes with age .

62. Dynesthetics: The term “Dynesthetics” is derived from Greek word “dynamics” meaning power. It supports in working factor of dentogenic concept. The technique of Dynesthetics is an auxiliary stimulus in the creation of a dentogenic restoration. It is secondary to sex, personality and age factors. These are rules, which concern the three important division of denture fabrication The tooth Its position Its matrix To achieve a more natural-appearing denture, three ingredients were necessary: the right teeth, placed in the proper position, and held in place by a natural-appearing matrix (visible denture base).

63. MATERIALS OF ANTERIOR TEETH:- Acrylic teeth: They are made from acrylic resin, indicated when there is insufficient inter-occlusal distance, and grinding becomes necessary, also in situation where there are opposing natural teeth, partial denture and gold bridge. They are inferior when they are compared with porcelain because they can not maintain luster for long time and abraded easily. ACRYLIC TEETH PORCELAIN TEETH Not brittle, but poor abrasion resistance Brittle, more resistance to abrasion Esthetic is very good. Excellent (does not stain). Chemical bonding with denture base. Mechanical bonding by pins or undercuts holes. Easy to ground and polish Difficult to grind and polish. Transmit fewer forces to the mucosa Transmits more forces to the mucosa No clicking on contact Clicking on contact Thermal expansion same as acrylic denture base Much lower than acrylic, causes stresses in acrylic denture base.

64. Posterior tooth selection The shade of posterior teeth should harmonize to shade of anterior teeth. As bulk influences shade of teeth, so lighter shade for bicuspids should be used if it is used as aesthetic purpose. They should be slightly lighter than posterior teeth but not lighter than anterior teeth. Posterior teeth are selected by: Color Buccolingual width Mesiodistal length Vertical height (occluso-gingival length) Occlusal form.

65. Shade (color): Shade of posterior teeth should be harmonized to the shade of anterior teeth, maxillary first premolars are sometimes used for esthetic more than function, so it's advisable to select premolar teeth with lighter color than the other posterior teeth, but not lighter than anterior teeth. Generally the shades of posterior teeth are slightly darker than anterior teeth.

66. Bucco-lingual width: The buccolingual width of posterior teeth should be slightly narrower than natural teeth, because the broader occlusal surfaces which direct more stress during function to supporting tissue, leading to increase in the rate of ridge resorption. Broader teeth encroach into the tongue space leading to instability of the denture. Also, the teeth should not encroach into the buccal corridor space to avoid cheek biting. The narrow artificial posterior teeth enhance the development of the correct form of the polished surfaces by allowing the buccal and lingual denture flanges to slope away from the occlusal surface.

67. Mesio-distal width: The combined mesiodistal lengths of all maxillary posterior teeth in that side of the arch should be equal to the distance between canine line, and anterior border of maxillary tuberosity. For mandibular posterior teeth, the mesiodistal lengths should be equal to distance between the canine line and anterior border of retromolar pad. If the residual ridge anterior to retromolar pad area slopes upward, smaller teeth or even fewer in number must be used.

68. Placing a tooth on an inclined plane (steep anteroposterior ridge slope) should be avoided, otherwise this would lead to forward displacement of the denture and dislodgment of denture occurs. Similarly the teeth should not be placed over displaceable tissues like the retromolar pad as it will cause tipping of the denture during function. In case with inadequate mesiodistal length, the premolar can be omitted

69. Occluso-gingival length It is determined by the available interarch distance. The occlusal plane should be located at the midpoint of the interocclusal distance. The length of the maxillary first premolar should be comparable to that of maxillary canine to have the proper esthetic effect. The height of posterior teeth usually divided into long, medium, and short. Long posterior teeth are generally more esthetic in appearance than are shorter teeth.

70. Occlusal form: Selecting the tooth to be used is based on the concept of occlusion to be developed, the philosophy of occlusion to be fulfilled, and the accomplishment approached. Types of teeth to be used :- Balancing in centric and eccentric: cusp form tooth Disocclude during eccentric jaw movements: cusp or monoplane teeth Arranged in a plane and balanced only in centric: monoplane is used It is given in the table below.

71. 10º Anatomic teeth 20º Anatomic teeth 33º Anatomic teeth 0º Anatomic teeth

72. Shade Matching in Aesthetic Dentistry SHADE GUIDE A shade guide serves to accurately determine a tooth shade. A shade guide, based on the three-dimensional Munsell Color Order System would be a boon to dentistry and to the color matching of ceramo-metal restorations. In the Munsell system, the relationship of any of the color chips to the chips surrounding it is instantly known by geographic location. If the achromatic axis is to the left, any color chip to the right will be more saturated in color, i.e., have a higher chroma. Any chip lie left will have a weaker chroma. Any chip above will be higher in value, and any chip below will be flower in value. Chips on the same level will be equal in value. Hue changes are predictable from the location ahead or behind the chip on the hue circle. Smitha AJ, Savitha PN. Shade matching in aesthetic dentistry–from past to recent advances. J Dent Oral Care Med. 2017;3(1):102.

73. DENTAL SHADE GUIDES Hyashi shade guides: The guide, which has been published in Japan, uses fully controlled paper tabs to represent each equally spaced 125 locations in color space. Although it is not a commercial guide, it is a concept that can serve as a guideline for future guides. This illustration is a representation of the five hues in the shade guide designed by Hayashi and printed on paper. The illustrated Hayashi guide is based on the Munsell Color Order System with Hue steps of 1.25 intervals, Value steps of 0.5 intervals, and Chroma steps in unit intervals as shown below: Five Hues—8.75 YR to 3.75 Y with 1.25 interval. Five Values for each Hue—6 to 8 with 0.5 intervals. Five Chromas for each Hue—I to 5 with unit interval.

74. Clark shade guide (Tooth color indicator): A similar guide was developed in porcelain by Clark 60 years ago. There was 60 in the Clark guide. It contain 60 tab - 3 basic hue, 19 value, 6 chroma. According to him, “Value” is the important dimension to control. Spectatone: used 12 hues, but the shade guide had only every other hue represented. The missing hues could be selected by interpolation. Once the closest hue was selected, the viewer had 36 value and chroma variations of this hue. Since there were 6 hues, a total of 256 selection tabs were available, and an additional 256 tabs could be created by interpolation. The system enabled the viewer to move about in the color space to every hue, value, and chroma needed to achieve the closest match to the tooth being replicated. Even though the initial consideration of 256 tabs seemed overwhelming, the guide was simpler and more effective than the illogically ordered systems having fewer tabs.

75. VITA Shade guide (VITAPAN CLASS-I): Introduced in 1956, it is a very popular shade guide (Figure 1). Tabs of similar hue are grouped into letter groups like: A (hue of red-yellow) - A1, A2, A3, A3.5, A4 B (hue of yellow) - B1, B2, B3, B4 C (hue of gray) - C1, C2, C3, C4 D (hue of red-yellow-gray) - D2, D3, D4 Chroma is designated with numerical values 1, 2, 3 and 4

76. Limitations: a. Not uniformly positioned throughout tooth color space. b. No standard incremental difference between adjacent shades. c. In between shades (A2.5) are inaccurate. Shade selection with VITAPAN Classic

77. Vitapan 3D-Master Shade Guide: The manufacturer of this recently introduced shade system claims that it covers the entire color space. It was introduced in 1998 and reflects distribution of tooth shades in nature. There is systematic and equidistant coverage of the natural tooth shade spectrum. The shade sample are grouped in six lightness levels each of which has chroma variations in evenly spaced steps. The shade is spaced in steps (ΔE) of CIELAB 4 units in the lightness dimension and 2 CIELAB units in the hue and chroma dimensions. Because the guide is evenly spaced, intermediate shades can be predictably formulated by combining porcelain powders. The manufacturer recommends selecting the lightness level first with this system and then selecting the chroma or saturation and finally the hue.

78. Vitapan 3D-Master Shade Guide:

79. A form is available to facilitate the laboratory shade prescription, which can include intermediate step. Two types of shade guides are available for shade selection in Vitapan 3D master shade guide : Vitapan 3D master tooth guide (blue chips) – vita 3D master tooth guide features fired porcelain shade samples built up with cervical, dentine, incisal powders as known to you from most conventional shade guide. Vitapan 3D master color guide (red chips) – in contrast to Vitapan 3D master tooth guide porcelain sample contain dentin color without cervical, incisal distinction used to determine basic body color help to see value, chroma, hue in each third that do not match gradations of color in blue chips. The 3D master is based on the value system rather than grouping the shade by hue as in vita classical and Chromascop lvoclar, Vivodent.

80. The tabs arranged in 5 value level. Within each level tabs present different chroma, hue. Five levels cover that area of the CIELAB color solid occupied by natural teeth, with 50% of natural tooth shades occupying middle value level. The highest value level has 2 chroma steps of single hue. Darkest value level has 3 chroma steps of one hue about 2% natural teeth occupy this.

81. Dentin shade guides – When using a translucent all-ceramic system for a crown or veneer communicating the shade of the prepared dentin to the dental laboratory is helpful. One system provides specially colored die materials that match the dentin shade guide and enable the technician to judge restoration esthetics. Custom shade guide – Unfortunately, certain teeth may be impossible to match to commercial shade samples. In addition difficulties may be encountered in reproducing the shade guides in the final restorations. The extensive use of surface staining has severe drawbacks, because the stains increase surface reflection and vent light from being transmitted through porcelain. One approach to this problem is to extend concept of a commercial shade guide by making custom shade guide. The fabrication of a custom shade guide, especially one having an expanded shade range can be very helpful.

82. Although fabrication of such a guide is time consuming it provides a more realistic representation of what is achievable. Unlike most shade guides, a custom guide is made of the same material as the final restoration, thus reducing metamerism. Miller has recommended the addition of red (pink) modifiers to supplement the conventional guide in this area of the color space where such guides are lacking. Fabrication of a custom guide should include a metal backing for metal ceramic restorations, and should be of realistic thickness, achievable with clinical restorations. Guides having varying textures and gloss may also be helpful.

83. Modified shade guide – When a tooth closely approximates a specific shade selection tab, but has characterizations or deviations, those variations may be defined and communicated using a shade guide with the glaze removed and a set of dental surface colorants (“stains”). Airborne particle abrading using aluminum oxide is recommended to remove the glaze although this may also be done using emery discs. The colorant may be applied, and removed or modified until the proper effect is achieved. Once the guide closely resembles the tooth to be matched, it should be placed in a vial to avoid smearing, and sent to the laboratory along with a description of the colorants used and the effects desired.

84. Drawback of Shade Guides The inaccuracy in the name of the shade guides is less a problem than the guides themselves they have historically been a weak link in an orderly; approach to color matching in dentistry. The colors of shade guides, from a given manufacturer, vary from guide to guide. The porcelain for the guide is not necessarily the same as the porcelain used for the restoration. The guides do not duplicate the manner in which porcelain restorations must be constructed (thickness of opaque, thickness of body and incisal porcelain, metal bonding, etc.). The colors of the guides are illogically arranged and do not cover the volume of color space of the natural teeth. All standard shade tabs are thick (3-4.5mm) as compared to a crown (1-1.5mm), and are made of synthetic resin. Light is reflected and transmitted through a shade guide tab giving it translucency and vitality whereas in the restoration, light is reflected and barely transmitted making it look dense and opaque

85. Recent Advances Advances in electronic technology have provided solutions for many of the current problems in shade selection and color matching in dentistry: Colorimeters Spectrophotometer Digital cameras as filter colorimeters Spectrophotometers and spectroradiometers All color-measuring devices consist of, a detector, signal conditioner and a software that process the signal in a manner that makes the data usable in the dental operatory or laboratory. Because of the complex relationship between these elements, accurate colorimetric analysis is difficult at best.

86. Colorimeters Filter colorimeters generally use three or four silicon photodiodes that have spectral correction filters that closely simulate the standard observer functions. These filters act as analog function generators that limit the spectral characteristic of the light that strikes the detector surface. The inability to match the standard observer functions with filters while retaining adequate sensitivity for low light levels is the reason that the absolute of filter colorimeters is considered inferior to scanning device like Spectrophotometers and spectroradiometers . However, because of the consistent and rapid sensing nature, these devices can be precise with differential measurements. T his is why they often are used for quality control.

87. Fiber optic colorimeter Burget., et al. (1990) described the advantage of fiber optic colorimeter. Tooth color is caused by volume reflection, that is, passage of incident light through the tooth followed by backward emergence. This passage is concurrent with sideward displacement of photons that, in effect, influence the result of usual instrumental methods of determining tooth color. This problem is overcome by the use of large-field illumination and small-field observation. A fiber-optics colorimeter based on this principle is described. The color observed through two holes in a double box was visually matched by subtractive adjustment of the illuminating color in one box, whereas the other box showed the central part of the tooth diffusely illuminated by illuminant C light. This colorimeter was tested on wet, extracted human incisors in the tooth arch of a phantom-head. Results were compared with a visual standard-strip method and with a conventional spectrophotometer. It was concluded that the fiber-optics colorimeter is a promising instrument, although technical improvement is necessary.

88. Spectrophotometer A spectrophotometer is a device that measures the spectral reflectance of a body. It is a photometer (a device for measuring light intensity) that can measure intensity as a function of the color, or more specifically, the wavelength of light. A spectrophotometer is a more complicated instrument and there are several configurations. To get a precise measurement of color, it is advisable to use a spectrophotometer. A spectrophotometer measures the reflectance for each wavelength, and allows to calculate values. The general principle is that a light source is diffracted (that is the various wavelengths are spatially separated by a grating or prism). The various wavelengths pass through an entrance slit and the test sample (in some configurations the sample and entrance slit are reversed).

89. The sample selectively absorbs the various wavelengths of light in varying amounts. The light then passes through another slit, called the exit slit, and impinges upon a detector. The detector converts the light intensity at the particular wavelength into an electrical signal that is amplified and displayed on a screen or traced on a chart (light absorbed versus wavelength). There are many variations on this basic design. For example, in some cases the light passing through the sample is compared to a reference signal that passes through some reference sample -- which may contain just the solvent but no active absorber. Today’s spectrophotometers contain monochromators and photodiodes that measure the reflectance curve of a product’s color every 10 nm or less. In short, a colorimeter provides an overall measure of the light absorbed, while a Spectrophotometer measures the light absorbed at varying wavelengths .

90. Digital cameras as filter colorimeters The newest devices used for dental shade matching are based on digital camera technology. Instead of focusing light upon film to create a chemical reaction, digital cameras capture images using CCDs, which contain many thousands or even millions of microscopically small light-sensitive elements (photosites). Like the photodiodes, each photosite responds only to the total light intensity that strikes its surface. To get a full color image, most sensors use filtering to look at the light in its three primary colors in a manner analogous to the filtered colorimeter described previously. There are several ways of recording the three colors in a digital camera. The highest-quality cameras use three separate sensors, each with a different filter over it. Light is directed to the different filter/sensor combinations by placing a beam splitter in the camera. The beam splitter allows each detector to see the image simultaneously. The advantage of this method is that the camera records each of the three colors at each pixel location.

91. Spectrophotometers and spectroradiometers They are instruments designed to produce the most accurate color measurements. Spectrophotometers differ from spectroradiometers primarily because they include a stable light source. There are two types of basic designs commonly used for these instruments. The traditional scanning instrument consists of a single photodiode detector that records the amount of light at each wavelength. The light is divided into small wavelength intervals by passing through a monochromator. A more recent design uses a diode array with a dedicated element for each wavelength. This design allows for the simultaneous integration of all wavelengths. Both designs are considerably slower than filter colorimeters but remain the tools that are required to examine and develop accurate color-measuring devices.

92. Currently Available Devices There are at least six commercially available systems, ranging from simple to complicated, with capabilities and prices to match. The devices are generally one of three types—colorimeters, Spectrophotometers, or digital color analyzers—and use various measuring geometries a. Shofu’s Shade Chroma Meter b. The Vita Easyshade c. The Shade Scan d. Shade Rite Dental Vision System e. The Spectro Shade f. Clear Match System

93. Shofu’s Shade Chroma Meter Shofu’s Shade NCC (Natural Color Concept) Chroma Meter (Shofu Dental, Mcnlo Park, California) has been available since the 1990s. It consists of a freestanding, hand-held contact probe that is about 3 mm in diameter. The probe is placed against the tooth, and an activation button is pushed. This sends a Hash of light to the tooth, from the periphery of the probe, and the reflected light is transported through the center of the probe to the detector where the collected light is evenly distributed through color filters that closely match the three standard observer functions. Data are transmitted to the docking unit via an infrared signal . There is a database of porcelain samples stored in memory, and the closest match of the target with the stored data is presented.

94. Shofu’s Shade NCC (Natural Color Concept) Chroma Meter Readout is generated that includes the tooth number; the closest Vita Lumin shade guide designation; and specific opaque, body, and enamel powders. Although the ShadeEye was developed for use with the Vintage Halo Porcelain system (Shofu Dental), updated software versions reference other popular porcelains as well .

95. The Vita Easyshade The Vita Easyshade (Vident, Brea, California) is a hand-held spectro-photometer that consists of a hand piece connected to a base unit by a monocoil fiber optic cable assembly. The contact probe tip is approximately 5 mm in diameter. It contains 19 1-mm-diameter fiber optic bundles. During the measurement process, the tooth is illuminated by the periphery of the tip, directing the light from a halogen bulb in the base unit into the tooth surface. There are several spectrometers in the hand piece that monitor the light source and measure the internally scattered light. A combination of various filters and photodiode arrays receive the light as it is directed through the return fibers located in the center of the probe tip.

96. Through this arrangement, spectral reflectance of the scattered light is essentially measured in 25 nm bandwidths. Before measurement, it is necessary to select a measurement mode (tooth, crown, or shade tab). The display presents the closest Vita shade in the classical or 3D shade guide designation.

97. The Shade Scan Shade Scan is a hand-held device with a color LCD screen to aid in image location and focus. Through a fiber optic cable, a. halogen light source illuminates the tooth surface at a 45° angle and collects the reflected light at 0°. Light intensity and calibration to gray and color standards are continuously monitored and adjusted to provide consistent color reproduction. The image is recorded on a flashcard, obviating the need for a computer in the operatory. The transmitted data can be downloaded to a computer with the Shade Scan software.

98. Shade and translucency mapping can therefore be transmitted to the dental laboratory by e-mail or by including a printout or flashcard with the clinical items required for ShadeScan is in basic Vita Lumin shade designations. Higher-resolution shade mapping, additional shade guide designation conversions, and Hue/Value Chroma values are possible with additional software for dental laboratories .

99. Shade Rite Dental Vision System Shade Rite Dental Vision System (X-Rite Inc., Grand Rapids, Michigan) is another instrument that combines digital color analysis with colorimetric analysis. It consists of a hand-held device with its own light source, and an LCD screen facilitates positioning on the tooth. To focus and align the camera, a “glare spot” must be located at the junction of the gingival and middle thirds of the tooth. Measurements are taken through a series of rotating filters that simulate the CIE standard observer functions. The device is freestanding and is placed in its docking station for calibration and data transmission to the computer.

100. Shade and translucency mapping, are possible, and colorimetric data (CIE L*a*b* values) can be downloaded from the computer. The laboratory must have the required software, and an LCD screen facilitates positioning on the tooth.

101. The Spectro Shade Spectro Shade (MHT, Niederhasli, Switzerland) is the dental shade-taking device most complex in design and is the most cumbersome in terms of hardware. It offers the most flexibility in terms of color analysis and colorimetric data and is by far the most expensive. It is the only one that combines digital color imaging with spectrophotometric analysis. The hand piece is relatively large compared with the contact probe designs, and positioning can be tricky. Calibration is a two-step process involving positioning the hand piece against white and green tiles. Light from a halogen source is delivered through fiber optic bundles and lenses to the tooth surface at 45°. The image of the tooth is displayed on the computer screen so that positioning can be verified.

102. The incident light is monochromatic as it strikes the tooth, and as it is reflected back the spectral scanning process is completed at 10-nm bandwidths by a black and white and a color-filtered CCD. Because there is a spectral curve associated with each pixel of the CCD, a significant amount of data are generated for analysis. Color differences can be calculated between compared images, and shade maps of increasing complexity and one for translucency are possible. The software contains shade guide references for most porcelain systems, and mere can be added. The closest shade and the magnitude of the color difference from that reference are specified. A digital image of the tooth, the shade mapping, and the colorimetric data can be transmitted to the laboratory electronically or by printout.

103. ClearMatch System ClearMatch System (Smart Technology, Hood River, Oregon) with this system, a different approach to digital color matching is achieved. This is a software system that requires a Window platform PC and a digital camera. To properly calibrate the digital color signal, a black and white standard and a shade tab must be included in each photograph. Detailed shade mapping is provided in shade guide designations, and standard and custom shade tab information can be entered into the system database. Because this system is software only, it is the most reasonably priced.

104. Advantage of Digital shade analysis Eliminates the subjectivity of color analysis and provides exact information for laboratory fabrication of the prosthesis Influence is more objective, can be repeatedly verified. Not influenced by external factors like surrounding environment Involves less chair-side time. The quality control aspect is a real advantage. The technician can verify that the color replication process was accurate for the shade requested, and. with the more sophisticated systems, a “virtual try-in” can be accomplished. The reading can be translated to materials that can reproduce those characteristics in the fabricated restorations.

105. Limitations of Digital Shade Analysis Accuracy of color measurement is affected by the phenomenon of edge loss. Translucency mapping is inadequate with all of the systems. Positioning of the probe or mouthpiece seems to be critical to the repeatability of the measurement. None of the above instruments are sophisticated enough to function in a formulation mod: (i.e. specifying powders and layering to achieve the actual color designation of any tooth color or translucency distribution measured). For this approach to be efficient the laboratory must have system as well. A few models are available in the market, but are very expensive.

106. Anterior Teeth Arrangement It is important that the artificial anterior teeth are placed in the same antero-posterior position and at the same length as the original natural esthetics and phonetics. Guides for arrangement of anterior teeth: 1. Residual alveolar ridge 2. Incisive papilla 3. Reflections of soft tissues under the lip. The carved occlusal rims should provide reliable guides for placement of the anterior teeth in wax occlusion rims. They indicate the likely antero-posterior and vertical positions of the incisor teeth

107. Residual alveolar ridge In patient with long edentulous period, much bone could have been lost from the residual alveolar ridge. In this situation, artificial teeth should not be placed against the ridge . As a general rule: the longer the natural teeth have been out the farther the artificial teeth should be from the ridge. The teeth should be placed closer to the residual ridge when there is less shrinkage and farther from ridge when there has been more resorption

108. Relationship To Incisive Papilla Incisive papilla is a guide to anterior tooth position because it has a constant relationship to the natural CI. A line marking the centre of the incisive papilla on the cast is extended forward onto the labial surface of the cast and CI are set on either side of this line. Incisive papilla is also a guide to the antero-posterior position of the teeth. Labial surfaces of the CI are usually 8-10 mm in front of the papilla. Labial surfaces and incisal edges of the teeth are anterior to the tissues at the reflection where the denture borders would be placed. The accuracy of this guide decreases as the resorption of the residual ridge progresses Relationship To Reflection Of Soft Tissue

109. In placing and positioning the maxillary anterior teeth the objective is to provide balance between maximum esthetics and proper phonetics. The maxillary anterior teeth should support the upper lip in a natural position. After the loss of the natural anterior teeth, bone resorption usually occurs more on the labial aspect than on the palatal aspect of the maxillary ridge. To compensate for this loss of bone structure the maxillary anterior teeth should be placed labial to the residual ridge. The incisive papilla in the edentulous maxillary arch acts as a guide to proper placement of the maxillary central incisors. Arrangement of the maxillary anterior teeth:

110. The maxillary central incisors fall approximately 8 to 10 mm anterior to the point of intersection of a line that bisects the midline of the palate perpendicularly through the incisive papilla. (mid line is between the labial frenum and the incisive papilla). The labial contour of the teeth should follow the labial contour of the occlusal rim. The right and left maxillary anterior teeth should be positioned symmetrically on either side of the arch. Position of the maxillary central incisor: Mesio-distal inclination: The maxillary central incisor is placed, so that the long axis shows a slight distal inclination, when viewed from front. Labio-lingual inclination: The neck of the tooth should be slightly depressed when viewed from this side, the tooth slopes (incisal edge ) towards the labial side. The incisal edge: is in contact with the occlusal plane.

111. Position of the maxillary lateral incisor: Mesio-distal inclination: The maxillary lateral incisor is placed with its long axis inclined distally when viewed from the front. Labio-lingual inclination: The neck of the maxillary lateral incisor is depressed more than the central incisor, although the labial surface will be nearly in line with the central incisor. The incisal edge: is ½ to 1mm above the level of the occlusal plane. Position of maxillary canine: Mesio-distal inclination: The maxillary canine is placed so that the long axis has slight distal inclination from the front view. Labio-lingual inclination: The neck of the maxillary canine is prominent. The tooth axis is vertical (straight ) when viewed from the side. The cusp tip: Is in contact with the occlusal plane. The maxillary canine has two planes on the labial surface; mesial plane should follow the contour of the anterior teeth while the distal plane will be in line with the posterior teeth.

112. labiolingual inclinations of anterior teeth Mesiodistal inclination of anterior teeth

113. Arrangement of the mandibular anterior teeth: 1. The midline of the maxillary central incisor should be followed while placing the mandibular central incisor. 2. The imaginary roots of the mandibular anterior teeth should be directed towards the residual ridge. this will often place the mandibular teeth labial to the residual ridge. 3. The mandibular anterior teeth should not be in contact horizontally with the maxillary teeth (over jet). 4. The mandibular anterior teeth should not be in contact vertically with the maxillary anterior teeth (over bite).

114. Position of the mandibular central incisor: Mesio-distal inclination: The long axis is perpendicular to the occlusal plane (vertically upright). Labio-lingual inclination: The central incisor is placed with its neck depressed and the tooth will show that it’s labially inclined when viewed from one side. The incisal edge: Are 1-2 mm above the occlusal plane. Position of the mandibular lateral incisor : Mesio-distal inclination: The mandibular lateral incisor is placed with its long axis showing a slight distal inclination. Labio-lingual inclination: The labial surface is perpendicular to the occlusal plane. The incisal edge: Are 1-2 mm above the occlusal plane.

115. Position of the mandibular canine: Mesio-distal inclination: The mandibular canines are placed with a more distal inclination (neck distally placed) than the mandibular lateral incisors. Labio-lingual inclination: The neck of the tooth is placed prominently. The tooth shows a slight lingual inclination (at the incisal edge) when viewed from the side. The incisal tip: Lies 1-2 mm above the occlusal plane. labiolingual inclinations of anterior teeth Mesiodistal inclination of anterior teeth

116. Horizontal overlap (over jet): This the horizontal distance between the incisal edge of the maxillary central incisor and the labial surface of the mandibular central incisor. Vertical overlap (over bite): The maxillary anterior teeth overlap the mandibular anterior teeth and this overlap on the vertical axis is called the vertical overlap.

117. Incisal guide angle: The incisal guide angle is the angle formed with the horizontal plane by drawing a line in the sagittal plane between the incisal edges of the maxillary and mandibular central incisors when the teeth are in centric occlusion. The amount of vertical and horizontal overlap determines the sagittal incisal guidance. Incisal guidance is the path traveled by the mandibular central incisor from centric occlusion position to the protrusive occlusal position.

118. Posterior Teeth Arrangement Posterior teeth are set up in tight centric occlusion. The mandibular teeth are set in the wax occlusion rim over the residual ridge in their ideal bucco-lingual position and the maxillary teeth are set in tight centric occlusion with them regardless of their bucco-lingual position. The objective here is to have the intercuspation of the posterior teeth so precise that any deviation of this occlusion in the mouth will be easily detected. Teeth Standardized parameters 1. Curve of Wilson' as transversal compensating curve. 2. Curve of Spee' as sagittal compensating curve. 3.Optimum intercuspation of the antagonists.

119. Curve of Wilson : Transversal compensating curve. It runs frontally (transversally), touching the cusp tips of the posterior teeth. In the lower arch, it is produced by an even inclination of the right and left molars towards the lingual, corresponding to an inclination towards the buccal in the maxilla. When setting-up complete dentures, the teeth should be positioned along this curve

120. Curve of Spee: Sagittal compensating curve. Its bow-shaped line of occlusion in dentition. Spee described it as the "shifting path" of the mandible. The segment of the circle drawn has its center in the orbital cavity. The curvature that begins at the tip of canines and follows the buccal cusp tips of premolars and molars posteriorly when viewed from facial aspect.

121. The guide lines used in arrangement of posterior teeth: The line of the crest of lower residual ridge, which extend between the middle of retromolar pad, and tip of lower canine, the central grooves of the lower posterior teeth should coincide with this line. The line extending between the tip of lower canine and upper 2/3 of retromolar pad will determine the height of lower posterior teeth.

122. Arrangement of maxillary posterior teeth:- Maxillary premolars: 1. Premolars are set vertically to occlusal plane. 2. Facial cusp of maxillary 1st premolar touch the occlusal plane while the lingual cusp is raised from occlusal plane approximately 12 mm 3. The facial cusp of maxillary 1st premolar should be seat into the embrasure between the mandibular 1st and 2nd premolars. 4. Lingual cusp should be over the crest of the ridge 5. Facial and lingual cusp of maxillary 2nd premolar touch the occlusal plane.

123. Maxillary molars: The inclination of maxillary molars are mesially and slightly lingually to create a 6 degree upward curve. Mesio-lingual cusp of maxillary 1st molar should touch the occlusal plane and the lingual cusps are over the crest of the mandibular ridge The mesiobuccal cusp of upper 1st molar should rest in the buccal groove of the lower 1st molar, and the mesio-lingual cusp should seat into the central fossa of lower 1st molar. Maxillary 2nd molar are set with no cusp touches the occlusal plane. All the lingual cusps are over the crest of the mandibular ridge.

124. 5. Facial cusps of maxillary teeth form a gentle curve, while the lingual cusps form a similar curve about 12 mm below the facial cusps . 6. Use a template to check the buccal alignment of, canine, premolars and mesial buccal cusp of maxillary 1st molar should touch the template, while the distobuccal cusp not touch. 7. To check the buccal alignment of maxillary posterior teeth, all four cusps of maxillary molars touch the template while the premolar do not touch the template.

125. Arrangement of mandibular posterior teeth The Mandibular 1st molar is first set into centric occlusion. Mesio-buccal cusp of maxillary 1st molar fit in to the buccal groove of mandibular first molar. The mesiolingual cusp of Mandibular 1st molar fit into the central fossa of the maxillary first molar. Set the mandibular 2nd molar, the mesio-buccal cusp of maxillary 2nd molar fit in to the buccal groove of mandibular 2nd molar.

126. 6. Then set mandibular 2nd premolar, its cusp tip should be positioned in the embrasure between maxillary 1st and 2nd premolars. 7. The last tooth are mandibular 1st premolar which should be position in the embrasure between maxillary canine and maxillary 1st premolar. 8. Mandibular premolars follow the curvature of the canine. 9. Mandibular posterior teeth are set on or slightly lingual to the crest of the ridge.

127. Problem Horizontal and Vertical Overlap and Occlusal Plane Arch Form and Vertical Dimension MORPHOLOGIC FACTORS Bulging lip Anterior teeth too far forward, move teeth back Arch form too far forward, too broad Falling in of upper lip Maxillary anteriors too far in, may be too low; move anteriors forward, or higher Arch form too narrow, too far in; vertical dimension may be insufficient Severe overbite Increase horizontal overlap Slightly increase vertical dimension Contracted arch Use more horizontal overlap Broaden and widen arch form; vertical dimension may be insufficient Crowded teeth Increase horizontal overlap Widen arch form; give each tooth sufficient room; do not crowd Canine too prominent Reduce horizontal overlap Narrow arch form; push canine back and in Anterior teeth show too much Reduce horizontal overlap; raise occlusal plane Narrow arch form; slightly decrease vertical dimension

128. Problem Horizontal and Vertical Overlap and Occlusal Plane Arch Form and Vertical Dimension Posterior teeth show too much Raise occlusal plane Narrow arch form; slightly decrease vertical dimension; Broaden arch form Denture base material too obvious Occlusal plane too low, should be raised Arch form may be too full “Picket fence” appearance, too white Raise plane slightly; occlusal plane may be too low Narrow arch form slightly PHYSIOLOGIC FACTORS Clicking sounds Decrease vertical dimension Phonetic sh instead of s Have a slight vertical overlap Increase vertical dimension Drooling Arch form too constricted, vertical dimension usually closed; restore proper vertical dimension Lateral emissions, lisping May be too much horizontal overlap Arch form too broad; vertical dimension may be insufficient; lingual (palatal) contour too restricted; broaden and thicken contour for tongue contact

129. Digital teeth selection and virtual teeth arrangement In dentistry, the complete denture is a conventional treatment for edentulous patients. The computer-aided design and computer-aided manufacturing (CAD/CAM) has been applied on the digital complete denture which is developed rapidly. Tooth selection and arrangement is one of the most important parts in digital complete denture. Yu X, Cheng X, Dai N, Chen H, Yu C, Sun Y. Study on digital teeth selection and virtual teeth arrangement for complete denture. Computer methods and programs in biomedicine. 2018 Mar 1;155:53-60.

130. Teeth Selection Teeth set-up with all these factors: the distal surface of maxillary cuspid is consistent with the maxillary cuspid line in the direction of mesiodistal, the distal surface of mandibular second molar does not exceed the retromolar pad. Teeth selection usually base on the experience of the dental technician, they predict teeth location on the wax rim and then choose teeth subjectively. However, unreasonable tooth selection makes it difficult to meet the teeth set-up requirement. For this purpose, we used the teeth database as described above to establish a digital teeth selection system.

131. According to the experience skills of dentists, we get the appropriate teeth by comparing the width of the teeth and the length of the patient's arch. The calculating formula of the width of artificial teeth in a dataset is following: Where p near and p far are mesial and distal points of i -th tooth, respectively, and n is the number of teeth in the dataset. We denote the width of anterior maxillary and mandibular teeth dataset by w ua , and w da , respectively, and the width of left and right maxillary posterior teeth by w lp and w rp .

132. Anterior teeth selection . The maxillary anterior teeth with shape, size, and color are the main factors for the facial aesthetic of people. For maxillary anterior teeth, w ua equals to the arc length between the lines of angulus oris, which is the condition of choosing teeth. We find the tooth dataset which w ua is less than but closest to c ua (the arrangement curve of maxillary anterior teeth). The mandibular anterior teeth are selected in a similar way. Posterior teeth selection. Posterior teeth focus on function recovery, we mainly consider its size and occlusion. Posterior teeth selection is similar to the anterior teeth, we choose the teeth according to the length of posterior teeth w p ( w lp / w rp ) and the arrange line l p .

133. For the purpose of better occlusion, the left opposite teeth (include the upper and lower teeth) use the upper teeth size as their only index in the database. Since the lengths of the posterior teeth are not necessarily equal, the posterior teeth of both sides are asymmetrically aligned. The formula is as follows: argmin (w aj -c a ) ‹ 0 w= {w ua , w ud }; j=0,1,2…n argmin (w pj -c p ) ‹ 0 w= {w lp , w rp }; j=0,1,2…n where w aj and w pj are the width of anterior teeth and posterior teeth of j -th datasets, and n is the number of teeth in the dataset, Formulas illustrate the selection principles of different types teeth, they are using both the teeth arrange lines or curves of patients and the size information of teeth. Likewise, the height of teeth should be considered, but because the problem is complex, this paper put it aside temporarily.

134. The automatic teeth selection, we have just described, is followed, optionally, by the manual teeth selection, in which the dental technician has to select all the types of teeth in turn. All the types of teeth may be or may not be of the same shape, size, and color. In dentistry, the maxillary teeth and the mandibular teeth have a combination of fixed models and use the former as the benchmark, so the size of former is used as the index of anterior teeth. Rich databases fulfilled the requirements of patients in different sex, personality, and age (SPA) by offering several options.

135. Technique: First, scan and extract the feature points of the 3D triangular mesh data of artificial teeth (PLY format), then establish a tooth selection system. Second, scan and mark the anatomic characteristics of the maxillary and mandibular cast surfaces, such as facial midline, the curve of the arches. Third, select the preferred artificial teeth and automatically arrange them virtually in the correct position by using our own software. After that, design the gingival part of the dentures on the basic of the arranged teeth on the screen and then fabricated it by using Computerized Numerical Control (CNC) technology, Rapid Prototyping (RP) technology or 3D printer technology. Finally, selected artificial teeth were embedded in wax rims.

136. Anterior teeth placement Posterior maxillary teeth placement Posterior mandibular teeth placement

137. Conventional full denture and with digital design

138. Conclusion Dental art does not occur automatically. It must be purposely and carefully incorporated into the treatment plan by the dentist. This artistry strives to soften the marks imposed upon the face by time and enables people to face their world with renewed enthusiasm and confidence. Art in collaboration with science of denture construction eases the geriatric patient in maintaining physical and psychological health. Teeth selection should be in harmony in color, shape and size with the patient’s face, sex and age for a successful fabrication of complete denture prosthesis with a natural looking also pleasing appearing teeth. Teeth should be positioned in harmony with intraoral and circumoral muscle activity and adjusted so that they occlude and articulate evenly. Several different prosthetic tooth molds have been produced, and each has some purported advantages. In the absence of a clear advantage, dentists should use tooth molds that are esthetically pleasing and have a simple procedure to set up.

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140. Thank you