physiologic tooth form .pdf

Physiologic tooth form There is tooth and protecting tissue This tissue that called periodontium which consist from ; Alveolar bone for support the tooth Cementum for investing the root Periodontal ligament for attachment the tooth Gingiva for covering the tooth The form of tooth divided in...

Physiologic tooth form There is tooth and protecting tissue This tissue that called periodontium which consist from ; Alveolar bone for support the tooth Cementum for investing the root Periodontal ligament for attachment the tooth Gingiva for covering the tooth The form of tooth divided into direct and indirect form 1- indirect form which involved 1. Crown form 2. Root form 3. Angulation of root and crown form 4. Self cleaning ability of the tooth 5. Occlusal anatomy 6. Continuity of marginal ridge 7. Continuity of central groove Direct form include the following ; Proximal contact relation Interproximal space Embrasures Cervical line Crown form ; 1- crown outline ; the shape of crown buccally , labially and occlusally Most shapes are triangle, a trapezoid or rhomboid This arrangement and design brings out the following fundamentals of form: 1-Create interproximal spaces to accommodate the interproximal gingival. 2-Create a space between the roots of the adjacent teeth which allow enough space for bone and supporting structures required to hold up the gingival tissue to normal level and to provide sufficient circulation of blood to region. 3- Provides a contact area between adjacent teeth which help to protect the interproximal gingiva. 2- proximal maximal contour Crest of curvature which is the maximum height point in the surface tooth The site anterior ;incisal third Posterior ;middle third Significance ;responsible for developing interproximal space and embrasure 3- facial and lingual contour Anterior teeth labial contour mostly cervical third ( cervical ridge ) lingual contour also cervical third ( cingulum ) Posterior teeth buccal contour cervical third lingual contour middle third Significance in normal position this lead to food pass gently on the gingiva which make massage for the gingiva If the contour over (too large convexity ) the gingiva lost its tone and lead to gingival inflammation If the contour under ( small convexity ) lead to trauma from food impaction and cause gum recession 2- Root form 1- number and length of the root ---- function 2- distribution of root ------decrease bone resorption 3- root outline------ facially more bone support the tooth while mesiodistally root broad which compensate the root for strength 3- angulation of crown and root lingual angulation of lower teeth for normal occlusion if there is no inclination lead to cusp to cusp contact that cause trauma which called cusp clash Distal inclination of crown and root this is happen due to progressive tilt to the occlusal surface for preserve the contact mesially which lead to root shape tilt distally 4- self cleaning ability of the tooth Proper form ( rounded surface ) Proper alignment of the teeth Normal gingival attachment Brushing activity Saliva 5-occlusal anatomy 6- continuity of marginal ridge 7-facial line angle 8- continuity of central groove 5,6,7and 8 the important for follow pattern mastication Physiologic tooth Direct form 1- proximal contact relation Formation Observation Location Significance Sequence of abnormal proximal contact Affecting factors Proximal contact formation in early eruption pointed contact with time converted into contact area ? Also each tooth with two contact except ? 2- observation two view ? For cervico-incisally and for facio-lingually 3- location - individual tooth DCA more cervically except one tooth MCA more cervically ? and 3 teeth at the same level ? - all teeth distal contact more cervically and increase size of contact more --------------- 4- significance ; ❖ Prevent impaction of food ❖ Protect the gingiva ❖ Distribute the force of mastication ❖ Stabilization of arch ❖ Food follow pattern 5- sequence of abnormal proximal contact this form which called diastema 6- affecting factors ❑ Length and width of the tooth ❑ Proximal wear ❑ Malocclusion ❑ Anomalies ❑ Extraction ❑ No relation between size of the teeth and size of the arch Interproximal space Triangle shape which base to the alveolar bone and apex to the contact area this space depend on contact area position and tooth form Significance ; Provide space for alveolar bone Preserve internal gingival tissue (blood supply , nerve supply ) Provide good oral hygiene Embrasure Also called spill way Position - incisal embrasure - occlusal embrasure - buccal embrasure - lingual embrasure Size depend on position Significance ; esthetic Spill way ( food can be escape ) Decrease masticatory force Cervical line Cervical line is the junction of enamel with cementum Curvature depend on 1-contact area 2-diameter of crown facio-lingually Gingival line ?