Landmarks

landmarks of maxilla

1. MAXILLARY ANATOMICAL LANDMARKS BY: Dr. PALAK MISHRA 1 st YEAR RESIDENT PROSTHODONTICS

2. CONTENTS Introduction Extra Oral Landmarks Intra Oral Landmarks Histology Limiting Areas Denture Bearing Areas Relief Areas Conclusion References

3. Introduction M.M. Devan Dictum stated that, “Aim of a prosthodontist is not only the meticulous replacement of what is missing but also perpetual preservation of what is present.” A prosthesis must function in harmony with the tissue that support them and those around them. Hence, the dentist must understand the macroscopic as well as microscopic and limiting structures of the denture.

4. The anatomy of edentulous ridges in the maxilla and mandible is very important for the design of the complete denture. The total area of support from the mandible is significantly less than from the maxilla. The average available denture bearing area for an edentulous mandible : 14 cm2 for edentulous maxilla : 24cm2 Therefore the mandible is less capable of resisting occlusal forces than the maxilla. ANATOMY OF DENTURE BEARING AREAS

5. EXTRA ORAL LANDMARKS

6. Vermilion border : the lip – facial surface-the skin inner surface-mucous membrane 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 . Denture provides lip support 2.Philtrum: is a midline shallow depression of the upper lip, which starts at the labial tubercle and ends at the nose.

7. 3. Nasolabial angle: angle between columella of nose and philthrum of lip Normally 90° approximately 4. Nasolabial sulcus : It is the depression that extends from ala of the nose in a downward and lateral direction to the corner of mouth Prosthetic Importance: more prominent with aging and teeth loss restored by proper: Vertical Dimension Anterior Teeth Positioning Labial Flange

8. 5.Mentolabial Groove: It is a sharp or deep groove that lies between the lower lip and the chin. 6.Angle of the Mouth: It is the lateral limit of the oral fissure. 7. Labial Commissure : It is a junction of upper and lower lips lateral to the angle of the mouth

9. 8.Labial Tubercle: It is a little swelling in the mid portion of the vermillion border of the upper lip. 9.Modiolus: This muscular knot 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 .

10. Also known as MUSCULAR NODE Chiasma of facial muscle. Muscles fibers attached are: Buccinator Zygomaticus major Orbicularis oris Risorius Levator labii superioris Levator labii inferioris Levator anguli oris Depressor anguli oris

11. UNDERLYING STRUCTURE

12. Maxillary and mandibular dentures transfer occlusal loads to supporting structures. Denture supporting areas comprises of: Underlying bone Mucosa

13. UNDERLYING BONE Ultimate support for maxillary denture are the bones of 2 maxillary process and the palatine bones Mandibular denture is supported by Mandible. There are two types of bone seen: 1) Compact or Cortical Bone 2) Trabecular or Cancellous Bone

14. ORAL MUCOUS MEMBRANE Serves as cushion between the denture base and supporting bone Mucous membrane : mucosa + submucosa The submucosa is formed by connective tissue that varies from dense to loose areolar tissue; may contain glandular, fat or muscle cells Attachment occurs between submucosa and periosteal covering of the bone and it makes the bulk of mucous membrane

15. MASTICATORY MUCOSA Covers hard palate and crest of the ridge Characterised by well defined keratinized epithelium Lacks tissue movement

16. MUCOSA OF RESIDUAL RIDGE Keratinized stratified squamous epithelium and the adjacent narrow layer of connective tissue ( lamina propria ) These crest tissue are remnant gingival tissue and are excellent stress bearing tissue. Width of keratinization : varies in height Mucous membrane covering the crest of ridge in a healthy mouth is firmly attached to periosteum of the bone by connective tissue to submucosa

17. When submucosa is loosely attached to the bone, it creates unfavourable denture situation---- soft tissue overlying the ridge may be movable from buccal to lingual --- especially in mandible. These tissue may become quiet compressible over the ridge because of resorption

18. Thickness varies of mucosa When thin soft tissue is present, it is less resilient- mucous membrane is easily traumatized. When submucosal layer is loosely attached to periosteum or is inflammed or edematous, tissue is easily displaceable.

19. Types of keratinization present in the mucous membrane Well defined keratinized epithelium : masticatory mucosa present found on the dorsum of the tongue, hard palate, and attached gingiva .

20. Non-keratinized stratified squamous epithelium: Alveolar mucosa: the lining between the buccal and labial mucosa. 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.

21. Intra oral landmarks

22. Correlation of anatomical landmarks SNO. Landmark on mouth Landmark on impression 1 Labial frenum Labial notch 2 Labial vestibule Labial flange 3 Buccal frenum Buccal notch 4 Buccal vestibule Buccal flange 5 Coronoid bulge Coronoid contour 6 Residual alveolar ridge Alveolar groove 7 Maxillary tuberosity Maxillary tubercular fossa 8 Hamular notch Pterygomaxillary seal 9 Posterior palatal seal area Posterior palatal seal 10 Fovea palatinae Fovea palatinae 11 Median palatal raphe Median palatal groove 12 Incisive papilla Incisive fossa 13 Rugae Rugae 14 Displaceable soft and hard palate Butterfly outline of PPS

23. MAXILLARY ANATOMICAL LANDMARKS

24. Primary stress bearing area Thicker mucosa Underlying bone – cortical bone- less subject to resorption Areas perpendicular to the vertical occlusal forces No underlying structures should be present that will get harmed due to stress

25. Secondary stress bearing area areas more than 90° to or perpendicular to occlusal forces but resorb easily Cancellous bone Resists the lateral forces of occlusion Appear deeper pink due to ↑ sed vascularity Subject to resorptive modelling after dental extraction and with long term denture wear.

26. Relief area These area resorb under constant load contain fragile structures within. relief → reduction or elimination of pressure from a specific area under a denture base. Neurovascular bundle

27. LIMITING AREAS Limiting structures are sites that will guide us in having an optimum extension of denture so as to engage maximum surface area without encroaching upon the muscle action. They are: 1.Labial Frenum 2.Labial Vestibule 3.Buccal Frenum 4.Buccal Vestibule 5.Hamular notch 6.Fovea Palatini 7.Vibrating lines 8.Postdam Area

28. LABIAL FRENUM Single or double fibrous band covered by mucous membrane which extends from labial aspect of residual alveolar ridge to the lip. Absence of muscle fibers. It starts superiorly as a fan shape and converges as it descends to its terminal attachment on the labial side of the ridge.

29. CLINICAL SIGNIFICANCE Limits labial flange of denture. It has to be relieved while making impression to prevent dislodgement of the denture and to prevent ulceration. It is seen as a V-shaped notch in the impression 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.

30. LABIAL VESTIBULE “ The portion of the oral cavity that is bounded on one side by the teeth, gingiva and alveolar ridge (in the edentulous mouth – residual ridge) and on the other side by the lips anterior to the buccal frenula ” ¹- GPT -9 It is bounded laterally by the labial mucosa, medially by maxillary residual alveolar ridge. It is lined by lining mucosa. Reflection of the mucous membrane superiorly reflects the height. The area of mucous membrane reflection has no muscle.

31. 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.

32. BUCCAL FRENUM Band of fibrous tissue overlying the levator anguli oris , that divides labial vestibule from buccal vestibule. Fold or folds of mucous membrane extending from mucous membrane reflection area to the slope or crest of residual alveolar ridge. It forms the dividing line between the labial and the buccal vestibule.

33. CLINICAL SIGNIFICANCE Since it has muscular attachments, adequate relief must be provided to prevent the dislodgment of denture.(that is, it can move posteriorly as a result of the buccinator muscle and anteriorly as a result of the orbicularis oris .) The orbicularis oris pulls frenum forward and the buccinator pulls it backward. It requires more clearance for its action than labial frenum because it moves mesially , buccally and vertically by orbicularis oris , buccinator and levator anguli oris respectively. 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 .

34. 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. The size of the vestibule varies with the contraction of the buccinator muscle.

35. Clinical Consideration : 1.During impression procedure the vestibule should be completely filled with impression material for proper border contact between denture and tissues. 2.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.

36. DISTOBUCCAL SPACE N. S. Arbree , D.D.S.,* A. A. Yurkstas , D.M.D., M.S.,** and J. H. Kronman , D.D.S., Ph.D.*** Tufts University, School of Dental Medicine, Boston, Mass Also k/a: Buccal space/vestibule Buccal pocket Tuberosity sulcus Distobuccal angle of buccal vestibule Buccal sulcus Buccal pocket Buccal mucous membrane reflection region Post malar area

37. The coronomaxillary space: Literature review and anatomic description The coronomaxillary space is that anatomic region that lies medial to the coronoid process and lateral to the maxillary tuberosity . It is bounded anteriorly -by the base of the zygomatic process. posterior boundary- pterygomaxillary or hamular notch inferior boundary - crest of the residual ridge. The coronomaxillary flange of the maxillary denture is that portion of the buccal flange that extends from the zygomatic eminence to the hamular notch

38. Muscular influence Muscles affecting disto-buccal space interaction b/w buccinator & masseter Superior constrictor of pharynx Medial pterygoid muscle, temporalis muscle Pterygomandibular raphae

39. The coronoid process may be relatively straight or vertical in some individuals . For these patients opening of the mandible can result in narrowing of the space. In some individuals, however, the coronoid process appears to flare laterally at its height With a stronger temporal muscle insertion, this flare can be increased. If the individual with a lateral flare of the coronoid process is observed during opening, the space often remains the same or becomes wider.

40. Various studies demonstrates alteration in coronomaxillary space on wide opening of mouth, and some says no change in opening. If the coronomaxillary space broadens or remains the same size on opening , the functional filling of this space with the denture flange becomes important.” If the space is not completely filled or even slightly overfilled,‘,’ maximum retention may be lost. In this instance it is advisable not to have the patient open wide, protrude, or move laterally during border molding or impression procedures.“,’ A gentle molding of the region by pulling the cheek out, down, and in will be more successful

41. 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. Located by using T- burnisher .

42. 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. Constitutes the lateral boundary of posterior palatal seal area in maxillary foundation. The pterygomandibular raphe attaches to hamulus .

43. FOVEA PALATINAE : 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. Usually two in number on either side of the midline. Its position also influences the position of the posterior border of the denture. Denture can extend 1-2 mm across it.

44. Clinical Considerations : The secretion of the fovea spreads as a thin film on the denture therefore aiding in retention. They are used by dental technicians to determine the posterior border of denture but they are not so reliable. There are no clinical significance. In patients with thick ropy saliva, the fovea palatinae should be left uncovered or else the thick saliva flowing between the tissue and the denture can increase the hydrostatic pressure and displace the denture.

45. POSTERIOR PALATAL SEAL AREA - Also known as post dam or post palatal seal. Defined as- The soft tissue at or along the junction of hard and soft palate on which pressure along the physiological limits of the tissues can be applied by the denture to aid in the retention of the denture- GPT9

46. • Boundaries of posterior palatal seal area – i . Anteriorly – Anterior vibrating line ii. Posteriorly - Posterior vibrating line iii.Laterally – Pterygomaxillary notch 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 .

47. Difference Between Pterygomaxillary Seal And Postpalatal Seal PTERYGOMAXILLARY SEAL POSTPALATAL SEAL It is the part of the posterior palatal seal that extends across the hamular notch and extends 3 to 4 mm antero -lateral to end in the mucogingival junction on the posterior part of maxillary ridge It is the part of the posterior palatal seal area that extends between 2 maxillary tuberosities

48. VIBRATING LINE According to GPT-9 an imaginary line across the posterior part of the soft palate marking the division between the movable and immovable tissues; this line can be identified when the movable tissues are functioning. Denture should extend 1-2mm posterior to the vibrating line. Types- Anterior vibrating line. Posterior vibrating line.

49. Anterior vibrating line It is an imaginary line lying at the junction between the immovable tissue over the hard palate and the slightly movable tissues of the soft palate. It is cupid bow shaped(because of the shape of the underlying bone) Valsalva maneuver: The patient is asked to close his nostrils firmly and gently blow through his nose, to locate the anterior vibrating line. Patient is asked to say “ah” with short vigorous bursts

50. Posterior vibrating line It is an imaginary line located at the junction of the soft palate that shows limited movement and the soft palate that shows marked movement. This line is usually straight. 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.

51. Clinical Considerations : It reduces the tendency of gag reflex. It maintains contact of the denture with the soft tissue Decreases food accumulation with adequate tissue compressibility. It increases retention and stability by creating partial vacuum. Decreases patient discomfort of tongue with posterior part of denture. Permits normal movements of muscle and ligament.

52. Classification of PPS Based on Soft Palate Configuration: Class 1: more than 5mm of movable tissue available for post damming. It is the ideal for retention, usually thin denture base is advised Class 2 : 1-5mm of movable tissue available for post damming; good retention is usually possible. A medium thickness denture base is quiet adequate. Class 3 : less than 1 mm movable tissue available for post damming; retention is poor.

53. STRESS BEARING AREAS: Primary Stress Bearing Hard Palate Postero -lateral Slopes Of The Residual Alveolar Ridge Secondary Stress Bearing Area Rugae Maxillary Tuberosity Alveolar Tubercle

54. PRIMARY STRESS BEARING AREAS 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.

55. Clinical Significance : The horizontal portion of the hard palate provides the primary denture stress bearing area. Trabecular pattern in the bone is perpendicular to the direction of force, making it capable of withstanding any amount of force without marked resorption . Shape of hard palate is either flat, rounded U shape or V shape

56. 2)POSTERIOR RESIDUAL ALVEOLAR RIDGE 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. “The portion of the alveolar ridge and its soft tissue covering which remains following removal of the teeth.”-GPT

57. Lined by thick stratified squamous epithelium. Even though the sub-mucosa is thin it sufficiently provide adequate resiliency to support the denture. It resorbs rapidly following extractions and continues throughout life at a reduced rate. CLINICAL SIGNIFICANCE The vertical forces during physiological activities like mastication falls on denture and is transmitted posteriorly . The postero -lateral slopes of the ridge bears the force and hence is the primary supporting structure.

58. SECONDARY STRESS BEARING AREAS 1) RUGAE They are raised areas of dense connective tissue radiating from the midline in the anterior one-third of the palate. These are the mucosal folds located in the anterior region of the palatal mucosa. In the area of rugae , the palate is set at an angle to the residual alveolar ridge and is thinly covered by soft tissue which contributes to the secondary stress bearing area.

59. Clinical significance: It is associated with the sensation of taste and function of speech. It assist the tongue to absorb via its papilla. It also enables the tongue to form a perfect seal when it is pressed against the palate in making linguopalatal constant stop of speech Rugae should not be displaced, otherwise the rebounding may dislodge the denture. It provides anterioposterior resistance movement of the denture and increased surface area helps in retention.

60. 2) MAXILLARY TUBEROSITY It is the bulbous extension of the residual ridge in the 2 nd and 3 rd molar region. It is the distal aspect of the posterior ridge terminating in the hamular notch.

61. CLINICAL SIGNIFICANCE The area is less likely to resorb . Artficial teeth are not set on tuberosity region. The tuberosities sometimes exhibit buccal undercuts, if it is unilateral it can be utilized for the retention. Important to prevent oro-antral fistula so it is important to have radiograph before resection of the tuberosity

62. 3) ANTERIOR RESIDUAL RIDGE The anterior alveolar ridge is considered as secondary stress bearing area because of the fact that bone is subjected to continuous resorption though it decreases as the span of edentulism increases.

63. RELIEF AREAS These are the areas which either resorb under constant load or have fragile structure within or are covered by thin mucosa which can be easily traumatised and hence should be relieved. They are: Incisive papilla Mid palatine raphe Palatine torus

64. INCISIVE PAPILLA: It is a pad of fibrous connective tissue overlying the orifice of the nasopalatine canal marking the exit of nasopalatine nerves and vessels. It is a mass of fibrous tissue about 1 cm behind the upper incisor. Incisive foramen lies beneath the papillae

65. CLINICAL SIGNIFICANCE While making final impression pressure should not be applied on this region. Its position in edentulous mouth indicates where the incisor and canines should be set. Should be relieved, failure of which would result in necrosis of the distributing areas and paresthesia of anterior palate, burning sensation and pain. Denture base should be relieved over the area to avoid pressure to nerves and vessels.

66. MEDIAN PALATINE RAPHE Also known as mid palatine suture. The junction of palatine processes of the maxillae are often raised and covered with only thin layer of mucosa. It is area extending from the incisive papilla to the distal end of hard palate. Median suture area is covered by a thin submucosa , so the mucosa layer is in close contact with the underlying bone. For this reason, the soft tissue covering the median raphe is non-resilient in nature and may need to be relieved.

67. Clinical Considerations : During final impression procedure this raphe is relieved in order to create equilibrium between the resilient and non-resilient tissues. If pressure is applied during impression making,the denture base will cause soreness over the midpalatine raphe area.

68. MAXILLARY TORUS/ TORUS PALATINUS A developmental bony prominence sometimes seen in the centre of the palate. This structure is often covered by relatively incompressible mucoperiosteum 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.

69. CLINICAL SIGNIFICANCE If it is small, the denture is relieved A mucosally supported denture may need to be relieved over the torus to prevent the denture rocking and flexing about the mid line. Can be small size that can be relieved using pressure indicating paste or a very large growth that should be surgically removed.

70. 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.

71. CONCLUSION The basic goal of a successful complete denture therapy is reaching the patients expectations in fulfillment of better masticatory ability, unaltered speech and a better esthetics. It is necessary to review the important structures that are directly related to impression making.; 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. Extensions of the borders to get a good seal facilitates the clinician to obtain the compromised treatment approach.

72. REFERENCE 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 H.R.Kolb -Variable denture limiting structures of the edentulous mouth,Part 1 ,maxillary border areas,JPD 1966,16:194-204 Colie H Millsap-The posterior palatal seal area for complete denture. DCNA,Nov.1964,663