Form and Function of Teeth PDF

FORM AND FUNCTION PROXIMAL ALIGNMENT OF THE TEETH AND PROTECTION OF THE PERIODONTIUM HOUSEKEEPING SHAPES OF TEETH GE OM E T RY  SHAPES OF TEETH GEOMETRY REVIEW FACIAL AND LINGUAL SURFACES: TRAPEZOIDAL  PROXIMAL SURFACES Trapezo...

FORM AND FUNCTION PROXIMAL ALIGNMENT OF THE TEETH AND PROTECTION OF THE PERIODONTIUM HOUSEKEEPING SHAPES OF TEETH GE OM E T RY  SHAPES OF TEETH GEOMETRY REVIEW FACIAL AND LINGUAL SURFACES: TRAPEZOIDAL  PROXIMAL SURFACES Trapezoidal Anterior Max Posterior Mand. Posterior Teeth Teeth Teeth  PROXIMAL CONTACT AREAS W H E R E T H E T E E T H I N T H E A RC H T O U C H  CONTACT AREAS Small enough to prevent build-up of food and bacteria Provide support and anchorage for teeth Large enough to prevent food impaction  CONTACT AREAS: 5 GENERAL RULES 1. Contact areas more cervically located from anterior to posterior 2. Distal contact area more cervically located than mesial WHY? Cervicoincisal/occlusal length of teeth decrease as move posterior  CONTACT AREAS: 5 GENERAL RULES (CONT.) 3. Size of contact area increases from anterior to posterior WHY? Posterior teeth wider faciolingually than anterior teeth 4. Anterior contact areas are centered (F-L direction)  CONTACT AREAS 5 GENERAL RULES (CONT.) 5. Posterior contact areas are located just facial to the center (F-L direction) WHY UNDERSTAND THE GENERAL RULES The general rules are designed to: Assign form and function to the dentition Create a benchmark for variants Identify discrepancies and dysfunction in the dentition Correlate contacts to the health of the periodontium Importance of proper contacts in restorative practices Challenges associated with irregular contacts INTERPROXIMAL SPACES T H E S PA C E B E T W E E N INTERPROXIMAL SPACES Alveolar bone Proximal surface Contact area INTERPROXIMAL SPACES In health, filled by gingiva called the Interdental Papilla Papilla is wider cervically than coronally INTERDENTAL PAPILLA Proper contact and alignment = Normal shape EMBRASURES  EMBRASURES Webster’s Dictionary defines as- “an opening with sides slanting outward” Stedman’s: In dentistry: that space adjacent to the interproximal contact area that spreads in 4 directions: Facial Lingual Occlusal/incisal Cervical They provide a spill way for food to escape during mastication  Facial embrasures The spaces formed by the interproximal contours of adjacent teeth Lingual embrasures  EMBRASURES Allow for passage of food around teeth so food is not impacted into contact area or periodontium EMBRASURES: NAMED FOR THEIR LOCATION IN RELATION TO THE CONTACT AREA Will see from 2 different views: ❖ Facial/Lingual ❖ Occlusal/Incisal  FACIAL/LINGUAL VIEW Occlusal/Incisal Embrasure: located coronally to contact area Gingival/Cervical Embrasure: located cervically to contact area  OCCLUSAL/INCISAL VIEW Facial Embrasure: located facially to contact area Lingual/Palatal Embrasure: Located lingually to contact area  GINGIVAL OR CERVICAL EMBRASURE? CERVICAL EMBRASURE GINGIVAL EMBRASURE Interdental papilla Interdental papilla does NOT fill fills interproximal interproximal space space  Each tooth has 4 embrasure areas Cervical From Occlusal View From Facial/Lingual View Facial Lingual Occlusal/Incisal  EMBRASURES: 5 GENERAL RULES 1. Incisal/occlusal Contact areas embrasures become more increase in size cervically located from anterior to posterior 2. Cervical/gingival embrasures decrease in size from anterior to posterior WHY??  EMBRASURES: 5 GENERAL RULES (CONT.) 3. Facial and lingual embrasures are equal in size on anterior teeth. WHY? Anterior contact areas are centered in a faciolingual direction  EMBRASURES: 5 GENERAL RULES (CONT.) 4. LINGUAL Posterior contact EMBRASURES ARE areas are more LARGER THAN facially located FACIAL EMBRASURE WITH POSTERIOR TEETH WHY?  EMBRASURES: 5 GENERAL RULES (CONT.) What would happen if 5. Embrasures are a proximal restoration symmetrical was iatrogenically overcontoured?  EXAM “TYPE” QUESTION Posterior teeth have contact areas slightly buccal to the center of the teeth. Lingual embrasures of posterior teeth are smaller than buccal embrasures. a. Both statements are true b. The first statement is true, the second statement is false c. The first statement is false, the second statement is true d. both statements are false  Facial Lingual CERVICAL LINE CURVATURE  TERMINOLOGY REVIEW The cervical line is Cemento-enamel also referred to as junction (CEJ) the _______  CERVICAL LINE CURVATURES: 5 GENERAL RULES 1. Direction of curvature Facial/lingual: curved apically Proximal surfaces: curved incisally or occlusally Curved Curved coronally apically  CERVICAL LINE CURVATURES: 5 GENERAL RULES (CONT.) 2. Depth of curvature on the proximal surface depends on the height of the contact area diameter of the crown F-L 3. Depth of curvature on the proximal surface is greater on anterior teeth than posterior teeth Why? - Next Slide  Anterior teeth are narrower F-L but longer I-C than posterior teeth. To afford more anchorage and support, there is more bony support on the mesial and distal.  CERVICAL LINE CURVATURES: 5 GENERAL RULES (CONT.) 4. Cervical lines on 5. The depth of proximal surfaces of curvature is adjacent teeth have normally greater on approximately the the mesial than on same depth of curvature the distal WHY?  Contact areas are usually more cervically located on the distal  HEIGHT OF CONTOUR edman’s: Line encircling tooth at it’s greatest bulge or diamete  HEIGHT OF CONTOUR: FACIAL AND LINGUAL SURFACES Greatest area of crown contour inciso(occluso)-cervically Must view from PROXIMAL Allows for proper deflection of food  HEIGHT OF CONTOUR: FACIAL AND LINGUAL SURFACES Anterior teeth: Facial and lingual: cervical 1/3  HEIGHT OF CONTOUR: FACIAL AND LINGUAL SURFACES Facial: Cervical 1/3 Lingual: Middle 1/3 Posterior Teeth  HEIGHT OF CONTOUR: PROXIMAL SURFACES Greatest area of crown contour mesiodistally Proximal HOC is always found at contact area Must view from FACIAL or LINGUAL Where is the HOC located on the Lingual aspect of this molar ?  EXAM “TYPE” QUESTION What is the shape from the proximal surface for permanent mandibular molars?