Selecting Artificial Teeth

CriteriaSelection of tooth size 3 dimensions Height (occlusogingival) Width (mesiodistal) Thickness (faciolingual) least significant

Selection of tooth shape Selection of tooth color (shade) Selection of tooth material

Pre-extraction guide

Diagnostic cast Photographs Radiographs Extracted teeth Previous denture

Post extraction methodDetermining tooth width Size of the face Anthropometric measurement Bizygomatic width- Bizygomatic width/3.3 = 6 upper anteriors Bizygomatic width/ 16 = single incisor Cranial circumference ratio of cranial circumference to the combined upper anterior is 10 is to 1 Corners of the mouth as guide distal surface of canine Ala of the nose middle of canine Size of maxillary arch imaginary triangle from incisive papilla to hamular notch. The combined sides are compared to mold selector for the size

Determining tooth height

High lip line- patient is asked to smile then mark the occlusion rim, the incisogingival length of the mold selected should be greater than this Interarch space- reduced (require shorter teeth)

Determining Labiolingual thickness

Thick teeth can be rotated and spaced out to give realistic appearance

Selection of tooth formFacial form Square Tapering Ovoid Lateral or proximal Straight Convex Incisal form Straight profile Convex profile

Guide

Leon Williams Theory matching tooth form to face form Dentogenic concept in selecting teeth (Frush and Fisher) sex, personality and age

Selecting of colorProperties of color Hue- basic color produce Chroma- saturation Value- brilliance Translucency- permit passage f light

Color of natural teeth same hue (yellow) but there are difference in chroma. The following are the factors to consider: Age Effect of wear Canines are darker Stains Sex Effect of deminiralization Intrinsic stains

Tips

It should be done in bright daylight (natural light) Blue is complimentary color of yellow (staring at blue for 30 sec) Bright make-up and lipstick should be removed Color selection must be quick as possible Arrange the artificial teeth in tooth selector and try in the mouth Squint test- placing the prospective shade on the side of the face, the color that fades first from view would be the least conspicuous

Selection of posterior teeth

Should be able to chew food efficiently Should contribute to denture stability Should be comfortable to underlying soft tissue Should not cause bone resorption It should contribute to esthetics Should not create any sound on impact

Criteria for selecting posterior teeth

Color Mesiodistal width mandibular arch- from canine to beginning of retromolar pad (but if it has high slope teeth should not be placed) Maxillary- from canine to maxillary tuberosity only Buccolingual width- artifial teeth should be slightly less than the natural counterparts Narrow occlusal table reduce the level of force Allows development of favourable form and polished surface

Occlusogingival Lenght- should correspond to interarch space or else you need to grind and recontour teeth for fiting Cuspal inclination define as the angle between the palatal incline of mesiobuccal cuspand the horizontal

Classification of Posterior teethNonanatomic- flat/monoplane/cuspless/zero degree teeth Indication Indicated for flat ridge Balance occlusion is not planned Abnormal jaw relationship Advantage Freedom of occlusal movement reduce lateral forces, making it more stable lack of interference when denture settle Disadvantage not esthetic looking as the cusped teeth difficult to balance effort required to chew food

Anatomic teeth

20 degree 33 degree Indication Well formed ridge When balance occlusion is planned Possible to record accurate jaw relationship Advantage Easier to balance the occlusion Better chewing efficiency Better chewing due to inadequate escapes for food Better esthetics

Selection of Tooth Material1. Acrylic resin- most widely used Indication Do not wear or damage natural teeth When opposing dentition has gold crowns and inlays In case of reduced interarch distance In RPD teeth in contact with clasp require grinding Advantage Inexpensive and easily available Easy to grind and adjust Absorb occlusal stress

Do not wear opposing natural teeth Bonds chemically to denture resin Self adjusting and self polishing Softer sound impact

Disadvantage Wears easily Vertical dimension may be lost due to wear Stains and discolour with time Loss of comminuting efficiency with time

2. Porcelain teeth - bond mechanically to resin by pins Indication Well sufficient interridge space Well formed ridge Superior esthetic is required Porcelain-acrylic combination scheme Contraindication Poor mandibular ridge When theres opposing natural teeth When opposed by gold crown or bridges

Advantage Esthetic Do not stain and discolour easily Does not wear easily Maintain vertical dimension for years Maintains mastication efficiency with years Can be reused by rebasingDisadvantage Clicking sound on impact Difficult to grind and adjust Requires adequate interridge distance Abrades or chips opposing natural teeth Abrades opposing gold crowns Does not form chemical bond to denture base Brittle, chip or fracture occasionally Does not self adjust

3. Porcelain acrylic combination scheme Resin posteriors oppose porcelain posteriors reduce clicking sound4. Acrylic teeth with amalgam inserts (amalgam stops)amalgam is condensed to prepared cavity in resin (functionally generated occlusion) Indication- reduce wear due to porcelain opposing teeth

5. Acrylic with cast gold occlusal surface Indication- opposing natural teeth Opposed by gold occlusal surface

Arrangement of artificial teethFactors influencing Esthetic Function Stability

Anteroposterior Position

Former denture Distance from incisive papilla (Schiffman) max incisor are 8 to 10 mm anterior Relation to residual alveolar ridge the greater the resorption the further away the teeth would be Fullness of lips- 2/3 of labial surface supports the lips Phonetics v and f sound and upper vermilion border of lower lip should be in contact with the incisal surface of upper incisor

Superoinferior PositionPreextraction record of former denture Visibility of upper incisor Influencing factors Lip length and tonicity Racial variations Modiolus- lower canine and first premolar are located near modiolus

Inclination of anterior teeth

Relationship to the labial plate roots of the teeth are closely related and parallel to the labial plate Relationship to the facial profile- teeth are inclined parallel to the lower third of the face

Guides in the position of posterior teeth

Residual alveolar ridge- upper and lower posterior teeth are centered over the crest of the ridge when possible to improve balance and stability

Limiting borders Anterior limit distal surface of canine Posterior limit Maxillary arch teeth should not be placed over the maxillary tuberosity Mandibular arch teeth should not be placed over retromolar pad Buccal limit teeth should not be far from the ridge

Lingual limit lingual cusp of the molar are in alignment with the mylohyoid ridge and never lingual to it Occlusal limit and plane

Classification of Teeth RelationshipAnterior teeth relationship Class I normal Class II Retruded Class III Protruded

Posterior Teeth Relationship Class I- Normal functional cusp relationship Class II- Mandibular functional cusp are located lingual to class I relationship (end-on scissorbite) Class III- mandiular functional cusp are located buccal to the class I relationship (crossbite and endon)

Feature of Class I relationship

Horizontal overlap (overjet) - mandibular incisor are 2 to 4 mm behind maxillary incisor Vertical overlap (overbite)- vertical overlap can be increased if horizontal overlap is great Canine Relation mesial slope of upper canine opposes the distal slope of lower canine

First molar relation- mesiobuccal cusp of upper first molar opposes the buccal groove of the lower first molar Functional cusp relation- upper and lower working cusp opposes the central fossa Non-functional cusp overlap (nonworking or balancing cusps) deflect cheeks and tongue and protect them from injury