Form and function of orofacial complex

Physiologic form of tooth in detail

1. DR MONIKA NEGI Oral Pathology Microbiology and Forensic Odontology Form and Function of Orofacial Complex

2. Form follows Function Explains the inter –relation of the shape of some part and its function .

3. Size of crown and root ,root form Tooth form and jaw movements Proximal contact areas Interproximal spaces Embrasures (SPILLWAYS ) Facial and lingual contours of teeth : mesial and distal Curvature of the cervical line (CEJ ) Occlusal curvatures Form and Function of teeth

4. Should be proportional to each other and to jaw . Reflects the function of teeth . Example : Canine : long roots (extra size and length of root ensures enough anchorage and support for canine teeth bear shear forces .) Molars :Multiple roots( withstand masticatory forces ) Developmental depressions (enhance anchorage in the alveolar bone ) SIZE OF CROWN AND ROOT

5. Tooth form have direct influence on the jaw movements . Example : In animals teeth are conical ,have simple opening and closing type of jaw movements without lateral movements . Because of interlocking conical form of teeth ,TMJ morphology ,equal sized jaw and lack of muscles to carry out lateral movemnts . TOOTH FORM AND JAW MOVEMENTS

6. In humans ,jaws are not of same size Maxilla overlaps mandibular arch labially and bucally in horizontal plane . TMJ is specialized in humans as the occlusal anatomy of teeth is complex . INCREASING COMPLEXITY OF JAW MOVEMENT IS ASSOCIATED WITH COMPLEXITY OF OCCLUSAL ANATOMY OF TEETH .

7. From labial and lingual –Teeth are narrower at cervix mesiodistally than they are towards the occlusal surface . Triangular or pyramidal shaped space between the approximating teeth just cervical to contact area is created . BASE –Alveolar process between adjacent teeth Triangle are formed by proximal surface of teeth and the apex of the triangle is at the contact area of the two teeth . ACCOMMODATE AND PROTECT INTERPROXIMAL SPACES . Gingival tissue that fills the interproximal space is called the gingival papilla/ interdental papilla . INTERPROXIMAL SPACES AND PROTECTION OF INTERDENTAL GINGIVA

8. Base=alveolar bone • Sides=prox. surfaces of teeth • Apex=proximal contact area • These triangular shaped areas are normally filled with gingival tissues

9. Gingiva covers alveolar process of jaw bones (ATTACHED GINGIVA ) ,extends around the neck of tooth to form gingival crevice (free/marginal gingiva ) and fills the interdental space .(gingival/ interdental papilla ) Mucogingival line marks the junction between attached gingiva and alveolar mucosa . The part of interdental gingival tissue that lies below the contact area and extends faciolingually is called col

10. Col is non keratinized and vulnerable to trauma during mastication and invasion by bacteria . Tight contacts and proper interproximal spaces between adjacent teeth help to protect the col and interproximal gingival tissue . BUCCALLY /LINGUALLY – Roots of teeth taper from cervix to apices creating enough space between the roots of adjacent teeth . Allows sufficient alveolar bone between one tooth to another ,so that the teeth are securely anchored in the jaws .

11. Proximal Contact Areas • All teeth contact adjacent teeth at a proximal contact area except: – distal of the last tooth In the arch – diastemas – pathology. CONTACT AREA- it is formed because of wear of one proximal surface against another during physiologic tooth movement. MAXILLARY AND MANDIBULAR CENTRAL INCISORS ARE THE ONLY TEETH HAVING MESIAL SURFACE FACING EACH OTHER . PROXIMAL CONTACT AREA

12. – Ensures food will not be packed between teeth causing inflammation to the supporting tissues thereby causing gingivitis & periodontitis – It helps stabilize the dental arches by the combined anchorage of all the teeth in either arch in positive contact with each other (exception - third molars.) – Each tooth is individually supported by these contact areas. Importance:

13. CONTACTS are OBSERVED from 2 views • Labial / buccal aspect demonstrates the cervicoincisal / cervico - occlusal position • Incisal / occlusal aspect demonstrates the facio -lingual position POSITION OF CONTACT AREAS

14. • Anterior teeth have contacts that are generally centered faciolingually when view from the incisal • Posterior teeth have contacts that are generally located buccal to the center of teeth when viewed from the occlusal

15. HEIGHT OF CROWN DECREASES FROM INCISOR –MOLAR MORE CERVICALLY POSITIONED WHEN MOVING AWAY FROM THE MIDLINE . DISTAL CONTACT AREA IS MORE CERVICALLY PLACED THAN MESIAL . EXCEPT – mand 1 ST PREMOLAR ( mesial more cervically ) Mand CI ( both at same ) GENRALLY

16. 1. Contact area move cervically from anterior to posterior in each quadrant 2. On individual teeth the distal contact is more cervically located then the mesial contact 3. Contacts increase in size from anterior to posterior 2 **Note: Contacts on incisors in incisal1/ 3, Where as contacts on molars in middle /3

17. Mandibular Teeth: Contact their class counterpart and the tooth mesial • Maxillary Teeth: Contact their class counterpart and the tooth distal

18. The curvature formed by two adjacent teeth in an arch form a spillway space that is called an embrasure Note the Symmetry of the embrasure of the central incisors EMBRASURES

19. Embrasures are named relative to the contact area – Facial or lingual views show the occlusal / incisal embrasures and cervical/ gingival embrasures – Occlusal views show the buccal / labial and lingual embrasures

20. Facial or lingual aspects: – The incisal / occlusal embrasures increase in size from anterior to posterior – The cervical embrasure decreases in size from anterior to posterior – The incisal embrasure of the maxillary lateral/canine =greatest or longest – The incisal embrasure of the maxillary canine/premolar= widest angle

21. Embrasures • Mandibular posterior area occlusal view • Arrows denote the facial and lingual embrasure areas • The lingual embrasures are larger than the facial embrasures, because of lingual convergence of the crown.

22. • Serves as a spillway for food material during mastication • Prevents food from being forced through the contact area and injuring the periodontal tissues. • Also, Enhances the self-cleansing process of the tooth by exposing the surfaces to oral fluids, mechanical cleansing, and friction from the tongue, lips, and cheeks Significance of Embrasure form

23. It is a line encircling a tooth In more or less horizontal plane, representing its greatest circumference. The facial and lingual contours: • Protect the gingiva by the deflection of foods and help prevent trauma Buccal Lingual FACIAL AND LINGUAL PHYSIOLOGIC CONTOURS OF TEETH

24. Buccal Lingual The height of contour on both the facial and lingual surfaces of anterior teeth is located in the cervical third.

25.  The height of contour of the buccal surfaces of posterior teeth is located in the gingival third • The height of contour of the lingual surface of posterior teeth is located in the middle or occlusal third • The average curvature is around 0.5mm , with mandibular posterior having a lingual curvature of 1 mm . • Mandibular anteriors having curvature of less than 0.5mm.

26. The CEJ is a stable line whose curvature is related to the widths and lengths of the crown and the location of the contact areas interproximally The extent of the curvature depends on • Height of the contact area above the crown cervix • Diameter of the crown labiolingually . CURVATURES OF CERVICAL LINE CEJ (MESIALLY AND DISTALLY )

27. The CEJ is curved toward the apical on the facial and lingual surfaces of teeth • The CEJ is curved toward the incisal or occlusal surfaces on the proximal surfaces of teeth • The depth of the curvature is greater on the mesial than on the distal aspect • The depth of curvature on the CEJ on all surfaces is greater on anterior teeth and decreases toward the posterior

28. CURVE OF SPEE CURVE OF WILSON CURVE OF MONSON OCCLUSAL CURVATURES

29. OCCLUSAL CURVATURES Curve of Spee  Curvature which begins at the tip of canines & follows buccal cusp tips of premolars & molars posteriorly , when viewed from their facial aspect  OCCLUSAL CURVATURE

30. Curve of Wilson  The medio -lateral curvature of the occlusal plane of posterior teeth.  Two dimensional & approax . right angles to that of the Curve of Spee .  Complement paths of condyles during movements of mandible.

31.  The crowns of mandibular posterior teeth must incline to lingual, while crowns of maxillary posterior teeth must incline toward buccal  This curve becomes deeper posteriorly , so that molars inclination is greater than that of premolars

32.  Because of this curve & associated tooth inclinations, buccal cusps of mandibular molars & lingual cusps of maxillary molars usually appear to be longer

33. It is a curve obtained by extending the curve of spee and curve of wilson to all cusps and incisal edges . Curve of Monson