Class I & II Cavity Preparation For Composite Restoration PDF

CLASS I&II CAVITY PREPARATION FOR COMPOSITE RESTORATION Dr. Ahmed A. Holiel BDs, M.sc, PhD Lecturer of conservative Dentistry Faculty of Dentistry - Alexandria University ‫‪To the memory of‬‬ ‫‪my Brother‬‬ ‫ي ﷺ‪ :‬إذا مات ابنُ آدم انقطع عملُه إال من ثالث‪ :‬صدقة جارية‪ ،‬أو‬ ‫يقول النب ُّ‬ ‫علم...

CLASS I&II CAVITY PREPARATION FOR COMPOSITE RESTORATION Dr. Ahmed A. Holiel BDs, M.sc, PhD Lecturer of conservative Dentistry Faculty of Dentistry - Alexandria University ‫‪To the memory of‬‬ ‫‪my Brother‬‬ ‫ي ﷺ‪ :‬إذا مات ابنُ آدم انقطع عملُه إال من ثالث‪ :‬صدقة جارية‪ ،‬أو‬ ‫يقول النب ُّ‬ ‫علم يُنتفع به‪ ،‬أو ولد صالح يدعو له‬ OBJECTIVES OF CAVITY PREPARATION Tooth preparation for direct posterior composites involves (1) Creating access to the faulty structure, (2) Removal of faulty structures (caries, defective restoration and base material, if present), (3) Creating convenience form for the restoration. 4 • Retention is obtained by bonding, so it is not necessary to use mechanical retention features in the tooth preparation CLINICAL TECHNIQUE FOR CLASS I DCR Small to Moderate Class I Direct Composite Restorations • Do not require typical resistance and retention form features. • These preparations are less specific in form, having a scooped-out appearance. • They are prepared with a small round or elongated pear diamond or bur with round features. Moderate to Large Class I Direct Composite Restorations ▪ Conservative, follows outline of decay only. ▪ The cuspal and marginal ridge areas should be preserved as much as possible. ▪ 0.2 mm inside the DEJ ▪ No occlusal bevel ▪ Rounded internal line angles. CLINICAL TECHNIQUE FOR CLASS II DCR 7 ▪ First Assessment of the expected tooth preparation extension (outline form) Preliminary determination of the presence of enamel margins especially at the gingival margin for adequate adhesion. If not, you can use glass ionomer material on the root surface. 8 ▪ Second assessment of pre-operative occlusal relationship to detect presence of heavy occlusal contacts. ▪ Third preoperative wedging in the gingival embrassure and bitine rings is beneficial in separation of teeth, which may be beneficial in the re-establishment of the proximal contact with the composite restoration. SMALL CLASS II DIRECT COMPOSITE RESTORATIONS 1. SCOOPED-OUT APPEARANCE PREP • Often used for primary caries lesions • A small round or elongated pearl diamond or bur with round features may be used for this preparation to scoop out the carious from the proximal surface. • The pulpal and axial depths are dictated only by the depth of the lesion and are not uniform. • The proximal extensions may require the use of another instrument with straight sides to prepare walls that are 90 degrees or greater 2. BOX-ONLY TOOTH PREP -This design is indicated when only the proximal surface is defective, with no lesions on the occlusal surface. D.E.J -A proximal box is prepared with a small elongated pear instrument or round instrument, held parallel to the long axis of the tooth crown. • The instrument is extended through the marginal ridge in a gingival direction. • The axial depth is dictated by the extent of the caries lesion or fault. • The facial, lingual, and gingival extensions are dictated by the defect or caries. • No beveling or secondary retention is indicated. 3. THE FACIAL OR LINGUAL SLOT PREP • Where the lesion is detected on the proximal surface and can be accessed from either a facial or lingual aspect in a gingival direction, rather than through the marginal ridge • Usually, a small round diamond is used to gain access to the lesion. The diamond is oriented at the correct gingivoocclusal position. • The axial depth is determined by the extent of the lesion. The occlusal, facial, and gingival cavosurface margins are 90 degrees or greater. • Care should be taken not to undermine the marginal ridge during the preparation. • This preparation is similar to a Class III preparation for an anterior tooth. Moderate to Large Class II Direct Composite Restorations • The tooth preparation for moderate to large Class II direct composite restorations has features that resemble a more traditional Class II amalgam tooth preparation and include an occlusal step and a proximal box. OCCLUSAL PORTION: • The occlusal portion of the Class II preparation is prepared similarly as described for the Class I preparation. • Initial occlusal extension toward the involved proximal surface should go through the marginal ridge area at initial pulpal floor depth. • Pulpal floor is prepared to a depth of 1.5 mm, as measured from the central groove. • A No. 330 or No. 245 shaped bur is used to enter the pit next to the carious proximal surface. • The instrument is positioned parallel with the long axis of the tooth crown. • If only one proximal surface is being restored, the opposite marginal ridge dentinal support should be maintained. Occlusal extension into faulty proximal surface. A and B, Extension exposes the dentinoenamel junction (DEJ) but does not hit the adjacent tooth. Facial and lingual extensions as preoperatively visualized PROXIMAL BOX PORTION: • Although it is not required to extend the proximal box beyond contact with the adjacent tooth (i.e., provide clearance with the adjacent tooth as with amalgam). It may simplify the preparation, matrix, composite insertion, and contouring procedures. • Hold the diamond over the DEJ with the tip of the diamond positioned to create a gingival directed cut that will be 0.2 mm inside the DEJ • The diamond is then extended facially, lingually, and gingivally to include the entire caries. • The faciolingual cutting motion follows the DEJ with axial wall 0.2 mm inside DEJ, and therefore is usually in a slightly convex arc outward. • The facial and lingual margins are extended as necessary and should result in at least a 90-degree margin. • Bevels can be placed on the proximal facial and lingual margins if the proximal box is already wide facio-lingually • The gingival floor is prepared flat with an approximately 90degree cavosurface margin. • Gingival extension should be as minimal as possible, trying to maintain an enamel margin. Facial and lingual proximal margins: Bevel if the external cavosurface margin forms a right angle with the tooth surface. BEVELING Perform conservative bevels(0.5mm) should be placed approximately 45 – degree angle to the surface Advantage: this exposes enamel rods transversely to achieve more effective etching pattern. Also it aids in placing the margins in a more accessible location for finishing and polishing. However ,take care don’t bevel if the preparation exits the tooth at an obtuse angle. Gingival Margins: The gingival margin should be beveled ONLY: If the margin in enamel is well away from the cementoenamel margin and an adequate band of enamel remains. BEVELING Use an inverse or so called internal bevel. Advantage: Significantly reduces microleakage compared to butt joint. Occlusal Margins: The use of occlusal cavosurface margin bevel is contraindicated: Why? BEVELING Normally the preparation in the occlusal surface will result in end –cut enamel rods because of orientation of enamel rods in cuspal inclines. A bevel results in loss of sound tooth structure. Increases the surface area of the final restoration. Increases Occlusal contact on the restoration. Increases thin areas of composite that are susceptible to fracture and wear. Clinical tip: ▪ Composite does not require bulk for strength as does amalgam, so traditional preparations with external and internal outlines with minimum width and depth are unnecessary. ▪ Bonded composite reinforces tooth structure, including the enamel, so removal of a slightly undermined tooth is unnecessary. ▪ Bonded composites do not need mechanical retention, as they rely on adhesive. Mesio-occlusal (MO) Class II direct composite restoration, which does not require a liner. A, Mesial primary caries and occlusal secondary caries exists preoperatively. B, Rubber dam isolation. C, Matrix application and placement of the adhesive. D, Insertion and light-activation of the composite. Thank you Dr Ahmed Holiel [email protected] Sturdevants Art and Science of Operative Dentistry-Sixth Edition chapter 10 .266-271