Maxillary and mandbular anatomical landmarks

Basic seminar on Maxillary and mandibular landmarks.

1. MAXILLARY AND MANDIBULAR ANATOMICAL LANDMARKS. Presented by: Dr. Rajvi Nahar 1 st year pg.

2. CONTENTS Introduction. Extra oral landmarks. Classification of Anatomical Landmarks. Maxillary Intraoral Anatomical Landmarks. Mandibular Intraoral Anatomical Landmarks. Conclusion References

3. INTRODUCTION A thorough knowledge of orofacial anatomy is necessary for making impressions, recording jaw relations, adjusting dentures, etc. It helps the clinician in identifying enough landmarks that in turn act as positive guides in treatment planning. The anatomical significance and the anatomy of the edentulous ridge in the maxilla and mandible is very important for the design of a complete denture.

4. EXTRAORAL LANDMARKS

5. The Extra Oral L andmarks are: Philtrum: is a midline shallow depression of the upper lip, which starts at the labial tubercle and ends at the nose. Labial Tubercle: is a little swelling in the mid portion of the vermillion border of the upper lip.

6. Vermillion Borders: the lip is covered by the skin at its facial surface and the mucous membrane at its inner surface. The transitional area between the skin and the mucous membrane of the upper and lower lips is a pink or red zone of thinner epithelium , which is called the vermillion border . Labial Commissure: is a junction of upper and lower lips lateral to the angle of the mouth.

7. Nasolabial Groove: is a furrow of variable depth that extends from the ala of nose to end at some distance from the corner of the mouth. Angle of the Mouth: is the lateral limit of the oral fissure. Mentolabial Groove: is a sharp or deep groove that lies between the lower lip and the chin.

8. Nasolabial Angle: is an angle between columella of nose and philtrum of lip, normally, approximately 90˚ as viewed in profile . Modiolus: This muscular knot is at the angle of the mouth. Modiolus may lie laterally to the lower premolars so it will displace a lower denture if those teeth are set too far buccally.

9. Maxillary and mandibular dentures transfer occlusal loads to supporting structures. Denture supporting areas comprises of: 1.UNDERLYING BONE : The nature of bone and its site of location plays an important role in determining the areas of stress distribution. Maxillary denture is supported by two pairs of bones i.e.. Maxillae and palatine bone. Mandibular denture is supported by Mandible. There are two types of bone seen: 1) Compact or Cortical Bone 2) Trabecular or Cancellous Bone

10. 2. OVERLYING MUCOSA : Denture bases rest on the mucous membrane, which serve as a cushion between denture base and supporting bone. Mucous membrane is composed of Mucosa and Submucosa. The oral mucosa is the mucous membrane lining the inside of the mouth. It comprises of stratified squamous epithelium, termed "oral epithelium", and an underlying connective tissue termed “lamina propria”. Submucosa is formed by connective tissue that varies from dense to loose areolar tissue and varies in thickness.

11. Masticatory mucosa : keratinized stratified squamous epithelium, found on the dorsum of the tongue, hard palate, and attached gingiva. Oral mucosa can be divided into three main categories based on function and histology:

12. Lining mucosa : non-keratinized stratified squamous epithelium, found almost everywhere else in the oral cavity, including the: Alveolar mucosa : the lining between the buccal and labial mucosae. It is a brighter red, smooth, and shiny with many blood vessels, and is not connected to underlying tissue by rete pegs . Buccal mucosa : the inside lining of the cheeks and floor of the mouth; part of the lining mucosa. Labial mucosa : the inside lining of the lips; part of the lining mucosa.

13. Specialized mucosa : specifically in the regions of the taste buds on lingual papillae on the dorsal surface of the tongue; contains nerve endings for general sensory reception and taste perception .

14. CLASSIFICATION OF INTRAORAL ANATOMICAL LANDMARKS. INTRAORAL LANDMARKS Supporting Structures Limiting Structures Relief Areas

15. Maxillary Anatomical Landmarks Limiting Structures 1.Labial Frenum 2.Labial Vestibule 3.Buccal Frenum 4.Buccal Vestibule 5.Hamular notch 6.Fovea Palatini 7.Vibrating lines 8.Postdam Area Stress Bearing Areas Relief Areas 1.Incisive Papilla 2.Median palatine raphe 3. Maxillary Torus Primary SBA 1.Hard palate 2.Postero-lateral slopes of the residual alveolar ridge Secondary SBA 1.Anterior Residual Ridge 2. Rugae 2.Maxillary Tuberosity

16. Maxillary Anatomical Landmarks

17. Limiting Structures The limiting structures guide us in having an optimum extension of the denture so as to engage maximum surface area without encroaching upon the muscle actions. Encroaching upon these structures will lead to dislodgement of the denture and/or soreness of the area while failure to cover the areas up to the limiting structure will imply decreased retention stability and support. They are as follows:

18. Labial Frenum : It is normally a single band of fibrous connective tissue and may consist of two or more fibrous bands. It appears as a fold of mucous membrane extending from the mucous lining of the lip to or towards the crest of residual ridge on the labial surface. It may be single / multiple. It may be narrow / broad. It contains no muscle fibres of significance. Clinical Considerations : Sufficient relief should be given during final impression procedure and in completed prosthesis because overriding of function of frenum will cause pain and dislodgement of denture. During impression procedure the lip should be stretched horizontal outwards for the proper recording of frenum. If frenum is attached close to the crest frenectomy is done, failure of which will lead to the denture border being placed on the bone tissue which will cause decreased border seal.

19. Clinical Consideration : For effective border contact between denture and tissue, vestibule should be completely filled with impression material. The major muscle of the lip is the orbicularis oris, whose fibres are horizontal, so careful border molding is necessary because it is easy to overextend the impression. Labial Vestibule : The labial vestibule extends between the right and left buccal frenums or between the area of the right and left first premolars if the frenums are absent. It is bounded laterally by the labial mucosa medially by maxillary residual alveolar ridge.

20. Clinical Consideration : During final impression procedure and in final prosthesis sufficient relief should be given for the movement of frenum because overriding of function of frenum will cause pain and dislodgement of denture. During impression procedure the cheek should be reflected laterally and posteriorly. If frenum is attached close to the crest of alveolar ridge, frenectomy can be done. Buccal Frenum : It consists of one or more bands, may be totally absent or may be in an entirely different location. Most of the muscles of expression converge at the corner of the mouth to form a nodule called the Modiolus. The major muscles in this area are the Buccinator, Levator anguli oris and Zygomticus.

21. Clinical Consideration : During impression procedure the vestibule should be completely filled with impression material for proper border contact between denture and tissues. When the vestibular space that is distal and lateral to the alveolar tubercles is properly filled with denture flange the stability and retention of the maxillary denture is greatly enhanced. To effectively record the maxillary buccal sulcus the mouth should be half way closed because wide opening of the mouth narrows the space and does not allow proper contouring of sulcus because the coronoid process of mandible comes closer to the sulcus. Buccal Vestibule : It extends from buccal frenum or from the first premolar area to the hamular notch. It is bounded anteriorly by the buccal frenum, laterally by the buccal mucosa and medially by residual alveolar ridge. It is influenced mainly by the modiolus and buccinator muscle, and distally by the coronoid process.

22. Clinical Considerations : Overextending distal to the notch will usually cause extreme discomfort and soarness due to interference with the ascending ramus of the mandible. Under extension will lead to poor retention. It aids in achieving posterior palatal seal area. Discomfort and loss of seal in posterior border will occur if dentist is incapable of identifying and marking this critical area. Hamular Notch : Also called as Pterygomandibular Notch is a displaceable area , about 2mm wide, between the tuberosity of the maxilla and the hamulus of the medial pterygoid plate. It is necessary to locate this area because it identifies the important distal end of the denture.

23. Clinical Considerations : They are used by dental technicians to determine the posterior border of denture but they are not so reliable. There are no clinical significance. Fovea Palatini : They are two small indentations that are on each side of the midline usually on the distal end of the hard palate. They are the remnants of ducts coalescence. They indicate the vicinity of posterior palatine seal area.

24. Posterior Palatal Seal Area/ Post Dam Area : PPS area lies between the anterior and posterior vibrating lines. It is the soft tissue at or along the juntion of soft and hard palate on which the pressure within physiological limits of the tissue can be applied by a denture to aid in the retention of the denture. It consists of: 1. Pterygomaxillary seal- The part of the PPSA that extends across the hamular notch. It extends 3-4mm anterolaterally to end in the mucogingival junction on the posterior part of the maxillary ridge. 2. Posterior Palatal Seal- This is a part of PPSA that extends between the two maxillary tuberosity.

25. Clinical Considerations : It reduces the tendency of gag reflex. It maintains contact of the denture with the soft tissue and decreases food accumulation with adequate tissue compressibility. It increases retention and stability by creating partial vacuum. Vibrating Lines : Also called “Ah” line is an area at, or distal to the junction of hard and soft palate where the movement occurs when the patient says “ah”. The Anterior vibrating line is an imaginary line located at the junction of attached tissue overlying the hard palate and adjacent movable tissue overlying the soft palate. The Posterior vibrating line is an imaginary line at the junction of the aponeurosis of the Tensor veli palatini muscle and the muscular portion of the soft palate.

26. HOUSE CLASSIFICATION Class I : More than 5mm of movable tissue available for post-damming; Ideal for retention. The posterior border and the posterior palatal seal are two of the most critical areas for maxillary denture retention. In most instances , the denture should end distal to the hard palate, it should not extend too far or there will be irritation to the muscles of the soft palate

27. Class II : 1-5mm of movable tissue available for post-damming; good retention is usually possible. Class III : Less than 1mm movable tissue available for post-damming; retention is usually poor.

28. Stress Bearing Areas: Primary Stress Bearing Area- The areas that are most capable of bearing the masticatory load providing a proper support to the denture. The Primary Stress Bearing area are: 1. Hard Palate : The shape of the hard palate in cross section is either flat , rounded U-shaped or V-shaped. It is covered by Keratinized squamous epithelium. Anterolaterally the mucosa contains adipose tissue and posterolaterally it contains glandular tissue. Clinical Significance : The horizontal portion of the hard palate provides the primary denture stress bearing area.

29. Clinical Considerations : It is the foundation of the denture. 2.Posterior Residual Alveolar Ridges : They are the residual bone left after removal of all the teeth. They are considered as the most important areas of support because the ridges are considered least likely to resorb under pressure. The residual ridge consists of mucosa , submucosa, periosteum and residual alveolar bone.

30. Secondary Stress Bearing Area- Anterior Residual Ridge : The anterior alveolar ridge is considered as a secondary area of support as the anterior ridge seems to be more susceptible to resorption Rugae : They are raised areas of dense connective tissue radiating from the midline in the anterior one-third of the palate. Clinical Considerations: Both acts as Secondary stress bearing areas. Rugae are concerned with phonetics. It increases the surface area of the foundation and thus supplement the values of retention. It is the denture stabilizing area in the maxillary foundation. They are often compressed or distorted from an ill fitting denture and should be allowed to return to their normal form prior to impression making.

31. Clinical Considerations : Often there is lateral and vertical growth of tuberosity and the area assumes importance when maxillary antrum extends laterally with undercuts at the tuberosity region. It is important to prevent oro-antral fistula so it is important to have radiograph before resection of the tuberosity. It can be used for the retention of the denture. Tuberosity should be resected on one side only i.e. if patient is right side chewer we should retain that sided tuberosity. Maxillary Tuberosity : It is the distal most part of the residual alveolar ridge and presents the hard tissue landmarks. It is the bulbous extension of the residual ridge in the 2 nd and 3 rd molar region.

32. Relief Areas: Incisive Papilla : It is a pad of fibrous connective tissue overlying the bony exit of the nasopalatine vessels and nerves. Clinical Considerations : It should not be displaced or compressed while impression making. Denture pressure on the papilla can cause parasthesia, pain, a burning sensation, other vague complaints, so some relief should be provided. It is a biometric guide giving information on positional relation to central incisors which are about 8-10 mm anterior to incisive papilla. Biometric guide which gives us information about location of maxillary canines.

33. Clinical Considerations : During final impression procedure this raphe is relieved in order to create equilibrium between the resilient and non-resilient tissues. Median Palatine Raphe/ Mid Palatine Suture : The junction of palatine processes of the maxillae are often raised and covered with only a thin layer of mucosa. It is the area extending from the incisive papilla to the distal end of the hard palate .

34. Clinical Considerations : The area of the torus can be cut out of the centre of the denture and the use of 1.5mm wide and 1mm deep bead on the inside of the denture around the torus may suffice adequate retention. A roofless denture is indicated when the ridges are large and the opposing arch is a denture. The patient should be informed that the retention may be compromised in cased where surgery is not performed. Maxillary Torus/ Torus Palatinus : It is often found near the centre of hard palate. It can be of small size that can be relieved using pressure-indicating paste or a very large growth that should be surgically removed.

35. Mandibular Anatomical Landmarks Limiting structures 1.Labial Frenum 2.Labial Vestibule 3.Buccal Frenum 4.Buccal Vestibule 5.Lingual Frenum 6. Pterygomandibular raphe 7. Alveolingual sulcus Stress Bearing Areas 1.Buccal Shelf Area 2.Retromolar pad 3. Residual Alveolar Ridge Relief Areas 1.Torus Mandibularis 2.Genial Tubercle 3. Mental Foramen

36. Clinical Consideration : During final impression procedure the lip has to be reflected anteriorly and horizontally. During final impression procedure and in final prosthesis provision should be made in the form of notch to prevent overriding of function which may result in laceration. The activity in this area seems to be vertical thus notch in denture should be narrow. Limiting Structures : Labial Frenum: It is usually a single narrow band but may consists of two or more bands. The mandibular frenum is usually shorter and often wider than maxillary labial frenum.

37. Clinical Consideration : For effective border contact between denture and tissue, the vestibule should be completely filled with impression material during impression procedure. Due to orbicularis oris the impression should not be overextended. Careful Border Molding is required. Labial Vestibule : It is the sulcus between the buccal frenums, or between the first premolars if the frenums are absent or in an unusual location. The major muscle in this area is the orbicularis oris whose fibres are mainly horizontal. The mentalis muscle originates from the mental tubercles and inserts in the lower lip. It is vertical muscle and may be very active in some patients.

38. Clinical Consideration : During final impression procedure and final prosthesis sufficient relief should be given to prevent overriding of function of frenum which may result in laceration. The contour of the denture will be a little narrower in this area due to activity of depressor anguli oris muscle. Buccal Frenum : They are usually in the area of the first premolar. It may be single band but it is often two or more bands . The oral activities in this area are horizontal as well as vertical. Movements such as puckering and grinning etc. are seen.

39. Clinical Consideration : This space constitutes an area to be completely filled by impression material during impression procedure. It is necessary to limit the lateral content of buccal flange in the region where the masseter muscle is in function (anterior fibers) may push against the distal part of buccinator muscle, failure of which may cause soreness of tissue when heavy pressure is applied. Buccal Vestibule : It is bounded anteriorly by the buccal frenum, posteriorly by the massetric notch area, medially by residual alveolar ridge and laterally by buccal mucosa. It is an area of esthetic consideration. The buccal flange covers about 5 mm or more of fibers of buccinator in this area but since it runs in a horizontal manner in the anteroposterior direction, it is not a dislodging factor. Anatomically the buccinator muscle is three muscles with separate innervations. The middle fibres are primarily active in food bolus formation. The upper and lower fibres are relatively flaccid especially at area of origin.

40. Clinical Consideration : Sufficient relief should be given in the final impression and the final denture to prevent overriding of function of frenum. During impression procedure touch the tip of the tongue to the incisive papilla region. Careful clearance is required as inadequate clearance may result in pain and displacement of the denture. Lingual Frenum : It is a fibrous band of tissue that overlies the centre of the genioglossus muscle. It is usually a narrow single band of tissue but may be broad and exist as two or more frenums. It is the mucobuccal fold that joins the alveolar mucosa to the tongue.

41. Clinical Considerations : It is quite prominent in some patients and may even require a notch-like clearance. A simple wide-open visual and digital inspection will usually determine whether or not clearance is necessary. Pterygomandibular Raphe : It originates from the pterygoid hamulus of the medial pterygoid lamina and attaches to the distal end of the mylohyoid ridge. It is partly the origin of the buccinator muscle laterally and the superior constrictor muscle medially

42. Alveolingual Sulcus/ The Lingual Vestibule : The space between the residual ridge and the tongue. It extends from the lingual frenum to the retromylohyoid curtain. It is divided into: 1. Anterior vestibule / the sublingual crescent area / premylohyoid / anterior sublingual fold. 2. Middle vestibule/the alveolingual sulcus/ mylohyoid area. 3. Distolingual vestibule / lateral throat form / retromylohyoid fossa / lingual pouch.

43. Clinical Considerations : If the mandibular ridge is highly resorbed the attachment of the genioglossus lies almost at the level of the crest of the alveolar ridge. Surgical sulcus deepening may be required in such scenarios. The width of the border of the denture in this region is usually about 2mm.But the width depends on the tonicity of the genioglossus.The genioglossus and the lingual frenum are recorded by asking the patient to moderately protrude the tongue as these tissues do not tolerate impingement. Anterior Lingual Vestibule : Also known as sublingual crescent area or anterior sublingual fold. It extends from the lingual foramen to the point where the mylohyoid ridge curves down below the level of the sulcus. Lingual frenum is superimposed over the genioglossus which raises the tongue

44. Clinical Considerations : The length and width of the mylohyoid flange is determined by the membranous attachment of the tongue to the mylohyoid ridge and the width of the hypoglossus muscle and can only be determined by skillful border molding and impression procedures. Middle Vestibule : Also known as mylohyoid vestibule. Forms the largest part of the alveololingual sulcus Influenced by: Mylohyoid muscle Sublingual glands

45. Distolingual Vestibule :Also known as lateral throat form or retromylohyoid fossa. Boundaries - Anteriorly– Mylohyoid Muscle Laterally– Pear Shaped Pad Postero-laterally– Superior Constrictor Muscle Postero-medially– Palatoglossus Medially– Tongue

46. NEIL CLASSIFICATION •Class I: Low -1/2 inch or more from the mylohyoid ridge to the bottom of the retro-mylohyoid fold, visible when the tongue is in a slightly protruded position. Most favorable. •Class II:Medium -Less than 1/2 inch under the same conditions as above. •Class III: High -Retromylohyoid fold at same level as mylohyoid ridge. Least favorable.

47. Retromylohyoid Curtain : It is a wall of mucous membrane which limits distolingual part of denture flange. It overlies the superior constrictor muscle in the postero-lateral portion and covers the palatoglossus and the lateral surface of the tongue in the postero-medial portion. The medial pterygoid muscle lies just posterior to it. Contraction of medial pterygoid can cause a bulge in the wall of Retromylohyoid curtain.

48. The “S” curve of the mandibular denture, results from the stronger intrinsic and extrinsic tongue muscles, which usually places the retromylohyoid borders more laterally and toward the retromolar fossa than in the mylohyoid area. The proper extension of the mandibular denture into the lingual sulcus, within their anatomical and functional limits, ensure a proper peripheral seal. Also, these flanges present favorable inclined planes to the tongue resulting in vectors of forces that help maintaing the mandibular denture in place.

49. Clinical Consideration : When mouth is opened widely the borders cut into the tissue so it should be recorded. During impression procedure in the area of massetric notch downward pressure is applied and the patient is asked to close the mouth against the pressure. Overextension of denture causes dislodgement of denture and laceration Massetric Notch : It is immediately lateral to retromolar pad and continuous anteriorly to buccal vestibular sulcus.. It is due to the contraction of masseter that a depression is formed at the distobuccal corner of retromolar pad.

50. Clinical Considerations : It presents an area of compact bone which by virtue of its deposition is horizontal and therefore is best suited to receive masticatory stresses in the vertical direction. It is the primary stress bearing area in the mandibular foundation. It is advisable to extend the impression beyond the external oblique ridge failures may be due to: Inadequate selection of impression tray. Involuntary effort on part of the operator. Primary Stress Bearing Area: Buccal Shelf Area: It can range from 4-6mm wide on an average mandible to 2-3mm or less in a narrow mandible. Area of compact bone which is bounded laterally by external oblique ridge and medially by crest of mandibular ridge.

51. Clinical Consideration : Helps in maintaining the occlusal plane. Divide retromolar pad into anterior 2/3rd and posterior 1/3rd. Posterior height of occlusal rim should not cross anterior 2/3rd. Helps in arranging mandibular posterior teeth. Draw a line from highest point in canine region to the apex of the retro molar triangle extending it to the land of the cast. The central fossa of all posterior teeth should lie on this crestal line. Teeth should not be placed on the retro molar pad. Because of muscular tendinous elements the area should not be subjected to pressure Retromolar Pad/ Retromolar Triangle : It is pear shaped body at the distal end of the residual alveolar ridge. It represents distal limit of mandibular denture. It has muscular and tendinous elements. Few fibers of temporalis. Few fibers of masseter. Few fibers of buccinator. Fibers of superior constrictor muscles of pharynx. Tendinous mandibular raphe.

52. Retromolar Papilla 1. Termed by Craddock . 2. Refers to the area formed by the residual scar of 3rd molar and retromolar papilla. The mucosa is usually attached gingiva. 3. Mucosa: Firm. Stippled. Dull appearance. Pear Shaped Pad 1. Termed by Sicher. 2. A soft elevation of mucosa that lies distal to the 3rd molar. It contains loose connective tissue with an aggregation of mucous glands. It is covered by a smoother, less hornified epithelium than that seen over the gingiva. 3. Mucosa: Soft. Non stippled. Shiny appearance.

53. Clinical Considerations : It is used as stress bearing area. Secondary Stress Bearing Area: Residual Alveolar Ridge : The alveolar process is the process of the mandible that surrounds the roots of the natural teeth. The right and left alveolar processes combine to form the mandibular arch. After natural teeth are extracted, the remnant of the alveolar process is called the residual ridge . As time goes on, a residual ridge usually resorbs. As the ridge is often poor so it is considered as secondary stress bearing area.

54. Clinical Consideration : It is best to cover the torus to the height of contour and finish the denture borders around the torus as thick as tongue will tolerate. If surgical correction is contraindicated then the patient should be informed that the results will be compromised. Lingual Tori/ Torus Mandibularis : They are bony protuberances that are ordinarily located in the premolar area. They are usually bilateral and sometimes may be on one side only. The tori rarely increases in size but the mucosal covering tends to be very thin and any settling will cause pain and discomfort. Relief Areas:

55. Clinical Considerations : It should be relieved with the wax spacer, failure of which lead to ulceration. In severly resorbed ridge it is seen above the residual alveolar ridge and hence it should be relieved. Genial Tubercle : Usually seen below the crest of the ridge. Mucosa covering the genial tubercles is thin and tightly adherent to the underlying bone.

56. Clinical Considerations : In these cases, relief of the denture is necessary to avoid excessive pressure on the nerve fibers which exit from this foramen, compression results in loss of sensation in the lower lip.Relief in this case is defined as space provided between the undersurface of the denture and the soft tissue to reduce or eliminate pressure on certain anatomical structures. Mental Foramen : They are the foramina in bone normally found on the buccal surface of the alveolar ridge. It is located between and slightly below the root tips of the first and second premolar teeth. When resorption of the alveolar ridge is drastic, the mental foramen is found below the oral mucosa on the crest of the alveolar process.

57. CONCLUSION It is necessary to review the important structures that are directly related to impression making. It is also important to know their function and to be aware of anatomical variations. Successful accomplishment of complete denture treatment constitutes a joint responsibility of both the operator and the patient by way of correctly participating in the treatment procedures. It is imperative that apart from the knowledge of all the above factors of anatomical and physiological relevance in treatment procedures, execution of the factors, digital dexterity and communication skills of the operator are of paramount importance. Thus, the diagnostic and clinical acumen of the operator constitute important considerations in the application of above knowledge.

58. REFERENCES Impressions for complete denture, Bernard Levin Zarb,Bolender,Carlson Boucher’s prosthodontic treatment for edentulous patients,13th edition ,9th edition Sheldon Winkler Essentials of complete denture Prosthodontics,ed.2 Heartwell Charles syllabus for complete dentures Ed.4,Philadelphia B D Chaurasia Human Anatomy Fifth Edition Orban’s Oral histology and embryology Anatomic landmarks in a maxillary and mandibular ridge - A clinical perspective by Mohd. Azeem, Ashraf Mujtaba, Shrestha Subodh, Ahmad Naeem, Gaur Abhishek and Pandey Kaushik Kumar

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