Conservative Dentistry PDF

Conservative dentistry Lec: 4 Dr. Linz Classification of Cavity 1. According to tooth surface involvement: Simple cavity: cavity involve only one surface of the tooth Ex: occlusal cavity...

Conservative dentistry Lec: 4 Dr. Linz Classification of Cavity 1. According to tooth surface involvement: Simple cavity: cavity involve only one surface of the tooth Ex: occlusal cavity (O) CL I. Compound cavity: cavity that involved two surfaces Ex: mesio-occlusal (MO) CLII. Complex cavity: cavity involve three or more surfaces. 2. According to site involved: Site 1: pits, fissure and enamel defects on occlusal surfaces of posterior or other smooth surfaces. Site 2: proximal enamel in relation to areas in contact with adjacent teeth. Site 3: the cervical one third of the crown or following gingival recession and the exposed root surface. 3. According to G.V. Black: CLI restorations: these restorations are used in CL I lesions the following surfaces are involved: - Occlusal pits and fissures of premolars and molars fig 1a. - Facial & lingual pits and fissures of mandibular molars fig 1b. - Palatal pits of maxillary incisors, most frequently in the pit near the cingulum. 1  Conservative dentistry A b c Fig 1: Cl I CL II restorations: is the extension of CLI restoration into the proximal surfaces of premolars and molars, the following surfaces are involved: - Two surface restoration of posterior teeth fig 2a. - Three surface restoration of posterior teeth fig 2b. - Four surface (or more) restoration of posterior teeth fig 2c. a b c Fig 2. Cl II 2  Conservative dentistry CLIII: affects the interproximal surface of incisors and canines fig 3. Fig 3: CL III CLIV: involves a larger surface area, including the incisal edges and interproximal surface of incisors and canine fig 4. Fig 4: CL IV CL V: - gingival third of the facial or lingual surfaces of any tooth. - -Root of a tooth near the cemento-enamel junction fig 5. Fig 5: CL V 3  Conservative dentistry Cl IV: incisal edge of anterior teeth or on cusp tip of posterior teeth Objectives of cavity preparation 1- To remove diseased tissue as necessary and at the same time provides the protection to the pulp. 2- To locate the margins of the restoration as conservative as possible. 3- To ensure the cavity form, it should not be under the force of mastication of the tooth. 4- To allow the functional placement of the restorative material. Steps in the cavity preparation (Given by G. V. Black) Obtain outline form. Obtain resistance form Obtain retention form. Obtain convenience form. Removal of remaining carious dentin. Finishing of enamel walls & margins Performing the toilet of the cavity. Class I cavity 1. Outline form: is the shape of the cavity which the Cavosurface line angle of the cavity assumes after preparation. Access: - Gain initial access via the most carious part of the tooth. - Margins should be placed on sound tooth structures. - In cl I all occlusal fissures and at least that in the developmental grooves have been included in the preparation even hen caries has not extended through out 4  Conservative dentistry the fissure because it has been noted that carious dentin although not evident visually or radiographically seen at the base of fissures. There is a strong evidence that carious dentine may be present at the base of a sealed fissure, (extension for prevention). 2. Retention form: is the shape of the cavity that permits the restoration to resist displacement through the tipping or lifting force. To provide retention the cavity have the following: Opposing wall of should be parallel to each other or converge occlusally (50) this convergence done on buccal and lingual wall fig 7. The floor of the cavity should be flat to prevent restoration movement. Outline form should be small as possible to prevent displacing force on it. 3. Resistance form Is the shape of the cavity that enables both the tooth and restoration to withstand occlusal forces without fracture. And this includes: 1. Prevention of fracture of the tooth - The facio-lingual width of the preparation should not exceed 1\4 intercuspal distance fig 6. 5  Conservative dentistry Cavo-surface line angle should be 900- 1100 Fig 6: resistance means of CL I. - Removal of unsupported enamel by making the margin (900-1100) because less than 900 the tooth is more subjected to fracture. - Smooth pulpal floor to prevent stress concentration area. - Mesial & distal walls of the cavity should be parallel and slightly diverge occlusally to be within the enamel rod direction and prevent any unsupported enamel at the marginal ridge. - All internal line angle should be rounded to prevent stress concentration area. Facio-lingual walls converge occlusally Rounded internal line angle Fig 7 6  Conservative dentistry Preventing fracture of restoration - The margins or Cavosurface line angle should be (900-1100) if more than this lead to fracture of restoration. - Facio-lingual width should be 1\4 intercuspal distance because large surface area exposed to more force and fracture occur. - Occlusal amalgam should have thickness of (1.5-2.0 mm) to resist fracture during function. - The pulpal floor should be smooth to prevent concentration area on restoration. 4. Convenience form: Is the shape of the cavity that allows an adequate observation, accessability this achieved by giving good depth (1.5-2mm) and width (1\4) intercuspal distance. 5. Removal of remaining caries Deep dentinal caries can be removed by using spoon excavator or large round bur with slow speed hand piece. 6. Finish enamel walls Involve making the wall smooth and removing of unsupported enamel. 7. Clean the preparation: Removal of all debris by washing the cavity and drying it. - 7