Rd2 Exam 1 PDF - Composite Resin Preparations and Restorations

Section 9: Posterior composite resin preparations and restorations The composite dental restorative materials that have been developed for restoring teeth can adhere to tooth tissues. Enamel and dentin bonding agents, used in conjunction with the acid-etch technique provide a fast, economical, and conservative means of restoring carious and fractured tooth structure using composite. Other restorative applications include pit and fissure sealants, repair of enamel defects, cosmetic alterations, foundation restorations (buildups) for crowns and the splinting and replacement of missing teeth. The principles of cavity preparation as described by Black must be reassessed in light of these new restorative materials. Cavity preparations for composite materials should still be prepared according to the principles of outline form, retention & resistance form, convenience form, removal of carious dentin or remaining restorative material and finishing the cavity walls, but with evidenced based modifications. Regarding posterior composite preparations, clinical decisions must be made concerning the type of preparation required depending on the amount of decay present. Unlike amalgam which needs bulk for strength and therefore has a minimum dimension requirement, composite restorations can have variable thickness and still function successfully. Therefore, composite preparations can be extremely conservative. The outline form for Class I composite cavity preparations can be limited to decay removal with radiating fissures sealed using acid etch and sealant. Some unsupported enamel can be retained and strengthened with bonding. Pulpal floors can rise and fall depending on decay removal. Operative intervention for posterior teeth The simplest intervention for the pit and fissure anatomy on a posterior tooth is the sealant and the non-invasive type does not involve removal of tooth structure. This is a primary type of intervention and is provided to the patient in an effort to avert the initial onset of caries. There is no evidence of decay or demineralization in the pits and fissures. The pits and fissures are cleaned and sealant material is placed to prevent caries initiation. The simple method of cleaning teeth with a toothbrush or running an explorer along the length of the fissures, along with vigorous rinsing with air-water spray seems to be enough to clean the tooth surface before sealant placement. Question: Should there be any type of tooth modification or preparation to enhance sealant retention? No current guidelines recommend the use of mechanical removal of fissure enamel, either by bur or air abrasion. Removal of enamel as a routine step before sealant placement is not supported by clinical studies. Some benefit to tooth modification may include removal of aprismatic enamel, removal of organic content from fissure walls, removal of possible decay, and improved drying, but studies show that it is not necessary for successful sealant retention and prevention of caries. Sealants have also been advocated as a method to arrest caries progression by providing a physical barrier that inhibits microorganisms and food particles from collecting in pits and fissures. This is called secondary intervention and is provided to the patient to avert the progression of early caries to the point of cavitation. Teeth demonstrating early signs of enamel demineralization at the base of the fissures and evidence of demineralization radiating up the inclines should have some type of intervention to arrest the decay. But should there be operative intervention to remove the demineralized tooth structure/decay before placement of a sealant? And if so how much tooth structure should be removed and using what methods? Studies show that sealants are effective in halting progression of existing carious lesions, as long as the sealant effectively seals off the lesion from the oral environment. Therefore the clinician can use the following criteria to determine if mechanical intervention is necessary. For an active lesion, 117 the variables that influence the decision to mechanically intervene include: 1) extent of the lesion, 2) level of porosity within the lesion, and 3) strength of the remaining tooth structure. If the enamel surface is intact (any breaks are small enough to be covered by the sealant are acceptable), if the lesion does not extend up the inclines too far so as to compromise marginal seal, and if the enamel is not weakened so as to compromise compressive strength then placement of a non-invasive sealant is acceptable. If decay is present and extends into the dentin is it necessary to surgically remove the dentin decay before placement of the sealant? Is complete dentin decay removal necessary or is partial decay removal or no decay removal acceptable? The current policy at TUKSoD is that if the decay has penetrated past the DEJ and radiographically appears to be into dentin then a surgical procedure resulting in the complete removal of decay is required. Discussion regarding the need for complete decay removal in very deep preps will be covered in the lecture part of the course. The Restorative Dentistry II course is designed to teach the techniques and required skills of conservative operative dentistry. These techniques are constantly changing and undergoing revision based on the current literature and new materials. The question of exactly when to initiate operative procedures and what procedures should be performed is debatable. The operative technique to perform the invasive sealant/ PRR, while considered controversial by some, will be presented here with the disclaimer that these techniques may not be universally accepted and applied depending on individual clinician philosophy. When performed, these procedures should be conservative and in the best interest of the patient. The simplest operative restorative intervention that removes tooth structure is the invasive sealant/ preventive restorative restoration (PRR). Demineralization and / or discoloration is usually limited to the base of the fissure with some demineralization radiating up the inclines. This procedure is recommended in cases where an active lesion is suspected and the clinician determines that mechanical intervention is necessary to remove enamel caries or alteration of the tooth surface is necessary to improve bonding of the sealant. Using a small round bur or fissurotomy bur, the operator carefully removes enamel to eliminate the caries prone geometry of the pits and fissures on the occlusal of posterior teeth. The preparation is usually confined to the enamel with removal of no more than 1 mm of enamel in the suspected areas. If the tooth structure is hard and there is no evidence of dentinal involvement do not prepare further. The preparation is then restored using sealant material. When and how a clinician performs a PRR will depend on their caries removal philosophy (is tooth preparation necessary before sealant placement and to what degree) and whether or not they believe caries can be arrested through the use of sealants. In cases where limited caries (into dentin) has been diagnosed or observed during operative treatment, the conservative composite preparation (CCP) should be done. The cavity outline form is determined by decay. Remove all areas of decay but do not extend into radiating pits or fissures that do not show signs of decay (Black’s philosophy). Restore the deepest areas of the preparation with composite and the radiating pits and fissures sealed with sealant material. The need to perform any operative procedures on the radiating fissures (invasive sealant) before sealant placement is open for discussion. Criteria for determining the need for mechanical intervention before placing a sealant have been given previously in the manual. The removal of tooth structure to verify a possible diagnosis of caries is considered controversial by some clinicians because some articles show that sealants can be used to arrest the progression of dentinal decay. At TUKSoD we do not use sealants to arrest dentinal caries, operative is performed. Is it possible to have long term success of arrested decay (dentin and enamel) using sealants rather than perform surgical removal? It is generally accepted that the effectiveness of sealants for caries 118 prevention depends on long-term retention of the sealant. Full retention of sealants can be evaluated through visual and tactile examinations but a bonding failure (without the visual loss of sealant) resulting in microleakage and recurrent decay may be more difficult to detect without the use of radiographs. In situations in which a sealant has been lost or partially retained, the sealant should be reapplied to insure effectiveness. In cases where microleakage and recurrent decay is suspected radiographic examination will be necessary. So there are two possible “camps” when it comes to the subject of caries intervention procedures for posterior teeth. There are those that believe in complete but conservative decay removal (drill and fill) and those that believe in arresting the decay through the application of a sealant (seal and heal). For the purposes of teaching operative technique in RD2 we will assume the role of the “drillers”. Students will learn conservative operative techniques which may or may not be applied to all clinical situations depending on prevailing evidenced based research and potential benefit to the patient. Knowing a procedure and choosing to selectively perform it when indicated is better than not knowing a potentially beneficial procedure at all. Information that could help a clinician decide whether to be a “driller” or a “sealer” can be found in the evidenced based literature. Lifelong learning requires clinicians to study the literature and update their treatment philosophy based on the most relevant and evidenced based information. Four clinically relevant questions that clinicians should be asking themselves regarding the use of pit and fissure sealants are presented below. 1. Under what circumstances should sealants be placed to prevent caries? The following patients would benefit from sealant placement: Patient with deep retentive pits and fissures Patients with stained pits and fissures with the appearance of demineralization Patients with caries or restorations in other primary or permanent teeth (high caries index) Patients that demonstrate no evidence of proximal dentinal involvement on the teeth to be sealed Adequate moisture control is possible Teeth within 4 years of eruption are most susceptible to decay and should be sealed 2. Does placing sealants over early (noncavitated) lesions prevent progression of the lesions? Sealants are effective in halting the progression of existing carious lesions as long as the sealant effectively seals off the lesion from the oral environment. The patient’s caries risk assessment, DMF score and potential for timely recalls will influence the clinical decision to seal rather than perform operative intervention. For non-cavitated enamel lesions, an argument can be made that if a sealant placed on top of a carious lesion fails, the tooth is at no greater risk than if it had never been sealed. For non-cavitated enamel lesions that demonstrate radiographic dentin involvement the choice to seal (seal and heal) rather than perform an operative intervention (drill and fill) is controversial and is not currently advocated at TUKSoD. Teeth with dentin decay will receive operative treatment. 3. Do conditions exist that favor the placement of resin-based versus glass ionomer cement sealants in terms of retention or caries prevention? Because of poor retention rates for glass ionomer sealants resin-based sealants are usually the material of choice. One exception would be a newly erupted tooth with a high potential for initial caries formation and moisture control is compromised. In this case a glass ionomer would be placed with the intention of replacing it later (usually within several months) with resin once the tooth erupts further and moisture control is possible. 4. Are any techniques available that could improve sealants’ retention and effectiveness in caries prevention? Proper moisture control is paramount. If proper moisture control is not possible consider glass ionomer placement as a short term preventive measure. Routine removal of tooth structure with 119 mechanical or air abrasive techniques to improve retention is not recommended but some evidence literature report better sealant retention. Gently using a probe or forced air-water spray to clean the fissures and cleaning the tooth surface with a tooth brush has shown to be effective in improving sealant retention. The full text article reviewing the most current ADA recommendations regarding the use of sealants can be found at the following link, through PubMed using the PMID number19215748 or as a PDF file on the RD2 Canvas website. This article is required reading for RD 2. Evidence-based clinical recommendations for the use of pit-and-fissure sealants: a report of the American Dental Association Council on Scientific Affairs. Beauchamp J, Caufield PW, Crall JJ, Donly KJ, Feigal R, Gooch B, Ismail A, Kohn W, Siegal M, Simonsen R.Dent Clin North Am. 2009 Jan;53(1):131-47, x.PMID: 19215748 Full text here Students are required to read the article and be prepared to answer the four previously posted questions. Selection criteria and proper application technique for sealants continues to evolve and periodic review of the evidence-based literature is recommended and necessary for lifelong learning. Posterior composite preparations: Classical conservative Class I and II composite preparations: Clinical indications for posterior composites include increased esthetics, conservation of tooth structure and strengthening of remaining tooth structure. Clinical contraindications include unfavorable occlusion (occlusal stops should be on tooth structure if possible), bruxism, extensive cuspal involvement, inability to maintain isolation during placement, and subgingival margins placed on root structure. A literature review for cavity design for the Class I and II composite preparations will produce articles describing a variety of different cavity designs. Most cite the argument that conservation of tooth structure is most important and therefore the conventional amalgam-like preparation design is contraindicated. Other reasons cited for avoiding the conventional design include unfavorable C-factor, excessive tooth structure removal will result in increased pulpal irritation or pulpal involvement and increased crack initiation potential due to sharp internal line angles. While the argument for a design change for Class I and II composite preps may be compelling the literature is still controversial and the preparation design taught in the preclinic will follow the Sturdevant text. The evaluation criteria for conventional Class I and II composite preparations are the same as for amalgam preparations with minor exceptions. When design differences are discussed, indications and contraindications along with the pros and cons of each design will provide the student with the most contemporary evidenced based information. Video for Class II composite preparation #30 MO. Start at 4:36. The operator is using diamond burs similar to the 330 and 245 carbides used in the preclinic. The final preparation is very similar to the amalgam preparation. At the end of the video the clinician demonstrates removal of simulated caries on the ivorine tooth. The technique is similar to removing decay on a natural tooth. Video for Class II preparation on tooth #14 MO. Start at 0.55. 120 Sturdevant describes three types of Class I and Class II composite preparations as conventional, beveled conventional and modified. Conventional and beveled conventional have retention and resistance features similar to amalgam. They are recommended when the composite restoration is replacing a previous amalgam restoration or in large preparations or preparations subjected to heavy occlusal forces. Bevels should not be placed in areas of occlusal forces (occlusal surface) but can be used if there are buccal and lingual extensions. Bevels can be placed on the buccal and lingual proximal walls for esthetics, increased retention and reduced microleakage but only if these areas are accessible to the bur. The gingival margin should not be beveled when it is closer than 1.5 mm from the CEJ because beveling removes remaining enamel required for improved bonding. If bevels are placed, care must be taken when placing the matrix retainer so as not to cover the bevels making them inaccessible for restoring. Failure to cover the bevels with restorative material will leave an open margin and negate any potential benefits from beveling. Use of a sectional matrix with ring separators may allow for increased tooth separation and unlike a Tofflemire retainer a sectional matrix is not tightened circumferentially and therefore may allow access for placement of restorative material at the beveled margin. Some articles advocate the use of round burs rather than pear shaped burs for composite preparations because the round burs produce rounded internal angles which are thought to be better for composite adaptation. Pear shaped burs will be used in the preclinic exercises. Up to this point in the lab we have prepared many Class II preparations for amalgam using the classical technique. This preparation design is acceptable for composite preparations with an emphasis on rounded internal line angles. The modified preparation as described by Sturdevant is similar to what is described by some in the literature as the conservative composite preparation. It is recommended for small to moderate preparations. Outline form is determined by decay therefore the pulpal floor can have a varied depth. Walls can diverge occlusally and floors may be flat when necessary but otherwise can be rounded. The bur used can be a round or pear shaped bur with an initial punch cut into the area of the carious lesion (pits and fissures), extending pulpally as necessary to remove decay and extending into the primary anatomy as necessary based on amount of decay. Extensions not included in the initial outline form can be sealed with an appropriate sealant material. Diagrams above and to the right show the occlusal and proximal view of a conservative composite preparation. The outline form for a conservative composite prep would look like the dotted line shown in the figure to the right. The solid line represents the less conservative traditional restoration. Proximal bevels can be placed using the enamel hatchet or thin diamond. A 329, 330 or 245 or round bur can be used for the initial punch cut preparation. We will not be preparing any conservative composite preparations in the lab. The technique is described in the manual and the Sturdevant text. 121 Section 10: Class V Preparation (criteria summary) Class V preparations can be restored with amalgam, composite or glass ionomer (RMGI). This section will describe various types of cavity designs based on the material used and the location of the lesion. For most composite preparation done in the clinic the outline form and depth will be determined by decay. If the decay is above the CEJ the prep is usually initiated using a high speed with a pear shaped or round bur. If the lesion is below the CEJ and located entirely in dentin, the prep can be done using a round bur in slow speed. Preparation features will vary based on the restorative material used and whether the prep is above or below the CEJ. For preparations above the CEJ (in enamel), for all restorative materials, the walls should parallel with the enamel rods to prevent undermined enamel. For preparations below the CEJ undermined enamel is not an issue. For amalgam preparations and conventional composite preparations above the CEJ (in enamel) initial depth must be 0.5 mm into dentin. For conservative composite and glass ionomer preps the depth should be enough to remove all decay and can vary in depth. For preparations below the CEJ (on root surface) the initial depth for amalgam and all composite resin preps should be 0.75 – 1.0 mm. This is the minimum depth required to place a retention feature which is a mandatory feature for amalgam and composite when the prep is on root surface. For glass ionomer the retention feature is optional. Abbreviations for amalgam (A), composite resin (CR) and glass ionomer/resin modified glass ionomer (RMGI) will be used when describing the preparations features. Composite resin can have a butt joint margin or a bevel. For this exercise we will describe the conventional composite resin preparation which has similar features to the amalgam prep. We will discuss modification to the composite resin prep when we cover Class III, IV and V resin preps later in the course. OUTLINE FORM AND INITIAL DEPTH The outline form for a Class V preparation is determined by decay. Extend the margins to sound tooth structure with an initial axial depth of 0.5 mm into dentin (above the CEJ). Class V preparations frequently extend subgingival and require placement of the 212 retraction clamp, electrosurgery or gingival flap surgery to provide adequate access. For the preclinical exercise provide the following outline form simulating clinical decay. The incisal gingival height of the prep is 2.0 mm. The incisal and gingival walls should parallel the pink gingival with the gingival margin of the prep ending 0.5 mm above the pink gingiva. For the preclinic exercise, for tooth # ? the prep extends around the transitional line angle and extends into the proximal to a depth that places the lingual wall almost directly under the contact point. The axial wall should follow the external contour of the tooth with a uniform axial depth of 0.5 mm into dentin. For the preclinic exercise on a molar tooth, the incisal wall should be 2.0 mm wide and the gingival wall 1.5 mm wide. Extend margins to sound tooth structure (preclinical dimensions given) (overextended under-extended) (I - G - M - D) This criterion applies to A, CR and RMGI above and below the CEJ Smooth and flowing outline This criterion applies to A, CR and RMGI above and below the CEJ Axial wall follows the external contour of the tooth This criterion applies to A, and large preparations for CR and RMGI. This applies to preps above and below the CEJ Uniform adequate axial depth 122 Clinical (0.5mm into dentin) Preclinical (2.0 mm incisal; 1.5 mm gingival) (shallow deep irregular) This criterion applies to A and conventional CR preparations. Conservative CR and RMGI preps can have variable depths. This applies to preps above and below the CEJ When the gingival margin extends subgingival placement of a 212 gingival retraction clamp is A necessary. The clamp should always be supported by green stick compound (A). Gingival retraction can also be obtained using retraction cord placed into the sulcus. Enter the lesion with the proper bur (start the prep with a 330 bur in a high speed; finish the outline form with a 330 or 56 in the slow speed contra-angle) and extend the margins to sound tooth structure. Visualize the external cavosurface margins relative to the internal line angles. Remember, above the CEJ, the mesial and distal walls of the preparation must be flared as the outline form approaches the transitional line angles so that the cavity walls are parallel to the B enamel rods creating a 90 degree cavosurface margin (B). Therefore be careful not to overextend the initial outline form creating unsupported enamel. RESISTANCE FORM / CAVOSURFACE GEOMETRY Above the CEJ, the cavosurface margin can have a cavosurface C angle of 90 degrees (A, CR, RMGI) or have a bevel (CR). Below the CEJ all materials (A, CR and RMGI) must have a butt joint margin. Above the CEJ, the internal outline form is extended such that it does not undermine the enamel. Above the CEJ as the preparation approaches the transitional line angles the mesial and distal of the preparation should flare producing walls that are perpendicular to the external surface and parallel to the enamel rods (C). The top of the handpiece should parallel the external surface of the tooth. Excessive extension of the internal form will produce D undermined enamel (D). Below the CEJ this flaring is not necessary. 90 degree cavosurface angle / No undermined enamel (M D I G) This criterion applies to A, CR and RMGI above and below the CEJ Gingival margin planed This criterion applies to A, CR and RMGI above the CEJ 123 RETENTION FORM A box-like internal form can be used to provide additional retention (A, CR and RMGI). Internal retention features, if indicated, should be rounded and placed in the dentin of the gingival and incisal walls just axial to the DEJ. On the root surface the retention grooves should be 1.0 mm from the cavomargin. Retention is tactilely and visually present. Box like internal form Box like form is required for amalgam, optional for CR and RMGI. Incisal retention groove (location and size) (inadequate excessive / undermined enamel irregular) Gingival retention groove (location and size) (inadequate excessive / undermined enamel irregular) Incisal and gingival retention grooves are required for amalgam above and below the CEJ. Retention groves are optional for CR above the CEJ (enamel can be beveled for additional retention) but are required for CR below the CEJ. Retention features are optional or RMGI E The size and location of the retention grooves should provide retention without undermining the enamel. The uniform depth into dentin conserves axial tooth structure and aids in protecting the pulp. Preparation depth must penetrate 0.5 mm into dentin to allow placement of the retention grooves without undermining the enamel. Depth must be uniform from point angle to point angle to ensure retention grooves are placed entirely in dentin (E). When placing the secondary retention grooves care must be taken not to undermine the enamel (F). Use a ¼ round bur or a 33 1/3 inverted cone, mounted in a slow speed to place the dentin grooves. (G). Hand instruments can be used for slight refinements. The gingival and incisal walls (especially in the area of the point angles) must be of adequate depth and uniform width to allow placement of the grooves without undermining enamel. The location and size of the retention grooves is important. The grooves should be placed entirely in dentin just pulpal to the DEJ. Grooves are placed at the incisoaxial and gingivoaxial line angles. Grooves are directed mostly incisal and gingival (slightly pulpally), and should be large enough to be felt by an explorer. In the gingival third of enamel of the smooth surfaces in the permanent dentition the enamel rods incline slightly apically; therefore a slight planing of the gingival margin using a gingival margin trimmer is recommended to remove unsupported enamel rods (H). 124 correct F G H REFINEMENT AND INTERNAL DEFINITION All prepared surfaces are smooth with well-defined internal features. Smooth walls (I G M D A) Slightly rounded, well-defined line angles When using pear shaped burs (330) internal line angles will be well defined and rounded. If a round bur is used to prepare a composite prep the line angles will be less defined and the axial wall less flat. Proper finishing of the external walls should remove unsupported enamel and rounding of the internal line angles should provide for proper amalgam condensation with reduced stress generation. Use burs (34 or 169) mounted on a slow speed or hand instruments to refine the preparation. Gingival margin trimmer 34 inverted cone Differences between the Class V amalgam preparation and the Class V conventional composite preparation: For both amalgam and composite preparations the outline form is determined by decay. For large composite preparations, the axial wall usually extends into dentin enough to remove all decay. Islands of enamel can remain provided all decay has been removed. For composite, enamel cavosurface margins can be beveled using a round bur (produces a chamfer margin) or a flame shaped bur (produces a long bevel) to increase retention and decreased microleakage. Beveling of the gingival margin when it is within 0.5 mm of the CEJ should be minimal or avoided so as not to remove the remaining enamel which is required for predictable bonding. Planing to remove unsupported enamel is recommended. For composite, gingival walls extending onto the root surface remain as butt joint and should receive a gingival retention groove. 125 CLASS V CONVENTIONAL PREP – evaluation rubric ==================================================================== SEVERE PREPARATION ERRORS - FAILURE lack of concept outline form depth/width damaged adjacent teeth ===================================================================== Place an “X” for each criteria evaluated as unacceptable. Multiple checks should be used for major errors and multiple minor errors in the same criteria. RUBBER DAM APPLICATION DAMAGE TO ADJACENT TEETH OUTLINE FORM AND INITIAL DEPTH Extend margins to sound tooth structure (preclinical dimensions given) (over-extended under-extended) (I - G - M - D) Incisal & gingival walls parallel to CEJ (gingival tissue) (gingival margin supragingival whenever possible) Smooth and flowing outline Axial wall follows the external contour of the tooth Uniform adequate axial depth (1.5 mm incisal; 1.0 mm gingival) (shallow deep irregular) RESISTANCE FORM / CAVOSURFACE GEOMETRY 90 degree cavosurface angle / No undermined enamel (M D I G) Gingival margin planed Excessive extension of the internal form producing undermined enamel (M D I G) RETENTION FORM Box like internal form Incisal retention groove (location and size) (inadequate excessive / undermined enamel irregular) Gingival retention groove (location and size) (inadequate excessive / undermined enamel irregular) REFINEMENT AND INTERNAL DEFINITION Smooth walls (I G M D A) Slightly rounded, well-defined line angles Total checks Faculty evaluator Student evaluator 126 Section 11: Class III large preparation (criteria summary) Distal of the canine The following is a description of the cavity preparation for a conservative Class III prep on the distal of the canine. This design is acceptable for both amalgam and composite differing only in the use of retention grooves. Unlike the incisors, the canine tooth has a large buccal lingual dimension making the Class III prep somewhat difficult to identify and remove decay. The simple Class III slot prep will be presented followed by a design change to accommodate decay that extends deeper possibly subgingival. OUTLINE FORM / INITIAL DEPTH Outline form provides adequate access for complete removal of caries and/or previous restorative material and insertion of composite. Access is appropriate to the location of caries and tooth position with lingual access preferable in order to preserve the facial enamel. The gingival contact must be broken; the incisal contact need not be broken unless indicated by the location of the caries. If a lingual approach is initiated facial contact is broken extending 0.3 mm into the facial embrasure. The axial wall follows the external contours of the tooth and the depth should not exceed 0.5 mm beyond the DEJ. (For the preclinic exercise the facial contact should be broken 0.3 mm and the preparation dimensions should be 3 mm incisal gingival length with an axial depth of 1.5 mm incisal and 1.0 mm gingival.) Cavosurface margins form a smooth continuous curve with no sharp angles. Outline margins terminate in sound tooth structure. Smooth & flowing lingual outline form (cavosurface irregularities sharp angles) slot or semi-elliptical outline form depending on the size of the decay Proper inciso-gingival placement (too incisal into contact point too gingival) Proper dimension of the preparation (inadequate excessive) inciso-gingival height (large small) axial depth (deep shallow) Axial wall follows the external contours of the tooth / Uniform adequate axial depth Facial contact broken correctly (0.3 mm into the facial embrasure) RESISTANCE FORM / CAVOSURFACE GEOMETRY The cavosurface margin should produce a cavosurface angle of 90 degrees. 90 degree cavosurface angles / no unsupported enamel Gingival margin planed RETENTION FORM A box-like internal form is produced to provide additional retention. Internal retention features should be rounded and placed in the dentin of the gingival and incisal walls just axial to the DEJ. Retention is tactilely and visually present. For a preparation where the decay extends gingivally, a box- like gingival extension is prepared that preserves the lingual wall providing additional retention. Removal of the lingual wall creating a large slot preparation is not indicated. A lingual retention dovetail can be placed. The dovetail should have minimal dimensions as it removes sound tooth structure. The dovetail should extend uniformly 0.5 mm into dentin and not extend past the M/D midpoint of the tooth. Occlusally converging walls can be created using an inverted cone (33½). The axiopulpal line should be rounded. Incisal/gingival retention groove (location and size) (excessive inadequate irregular) Lingual dovetail (if necessary) with properly rounded axio pulpal line angle (excessive inadequate irregular) Box-like gingival extension (when indicated) preserving the lingual wall for retention 127 REFINEMENT AND INTERNAL DEFINITION All prepared surfaces are smooth with well-defined internal features. Smooth walls Slightly rounded, well-defined line angles Differences between the Class III distal of the canine amalgam preparation and the Class III conventional composite preparation for the distal of the canine. Amalgam would be a better material choice for large preparations on the distal of the canine where proper isolation is a problem. For reasons of esthetics composite may be used as the restorative material. If the facial enamel wall is preserved esthetics is usually not a problem. For both preparations the outline form is determined by decay. For both amalgam and composite, the axial wall extends into dentin 0.5 mm. For composite, lingual enamel cavosurface margins can be beveled using a round bur (produces a chamfer margin) to increase retention and decrease microleakage. Examine the occlusion of maxillary teeth to determine if he margin will be in an occlusal contact area. Beveling the facial cavomargin for esthetics is an option if for the bur is adequate. Beveling of the gingival margin when it is within 0.5 mm of the CEJ should be minimal so as not to remove the remaining enamel which is required for predictable bonding. 128 Class III Preparation (evaluation criteria) OUTLINE FORM & INITIAL DEPTH Lingual approach is preferred to preserve facial esthetics. Use a 329/330 pear shaped bur or a # 2 round bur for initial entry. The outline form is determined by decay. Extend the margins to sound tooth structure keeping the initial axial depth 0.5 mm into dentin. From the lingual view, the axial, incisal and gingival walls combine to form a boxlike (slot) outline (A, B). This outline can become semi elliptical depending on the extent of the decay. Contact is broken facially, gingivally but not incisally. The outline form is smooth and flowing with no cavosurface irregularities. Decay occurs below the contact point; a slot A B shaped boxlike preparation helps to avoid contact point involvement (A). If the decay is extensive and involves the contact point or extends gingivally, the preparation begins to assume a semi-elliptical shape (C) so that the cavity walls create a butt joint cavosurface margin with the external surface of the tooth. (especially in the maxillary canine). C The initial depth of the axial wall is 0.5 mm into dentin to provide resistance form and provide adequate room for proper placement of the retention grooves. Clinically, the outline form is determined by decay. For classical conservative preparations the operator must break contact facially and D gingivally (not incisally) (D). Maintaining incisal contact conserves tooth structure, provides for improved esthetics, E improves retention, increases longevity of the restoration and helps to maintain arch form. Remember that decay occurs below the contact point. Therefore in a conservative preparation the outline form (incisal margin) should be below the contact point (D). It is important to place margins in an area where they can be finished by the operator and cleansed by the patient. The operator must also be sure to include all areas of decay. The large buccolingual dimension of the canine makes access and visibility difficult. To insure removal of all decay, the facial cavosurface margin is extended 0.2 - 0.3 mm into the facial embrasure and is parallel to the long axis of the tooth (E). The operator should just see the facial cavosurface margin when viewing from the side (F). 129 During preparation, the bur is held perpendicular to the lingual G surface. Aim for the decay with the initial punch cut (G). Extend the outline form incisogingivally to extend to sound tooth structure. Preclinically, the incisogingival dimension is 2.0 - 3.0 mm (2 mm for the smaller mandibular canine; up to 3 mm for the larger maxillary canine). When moving F the bur, preserve a thin area of the proximal enamel to protect the adjacent tooth during preparation (H). Extend H the facial wall 0.3 mm into the facial embrasure (the cavosurface margin is slightly visible from the facial) (F). Proper bur position provides for cavity walls that create a butt joint cavosurface margin. Gingival and facial margins must minimally break contact with the adjacent tooth. RESISTANCE FORM / CAVOSURFACE GEOMETRY For proper resistance form the axial wall should be 0.5 mm into dentin and follow the mesiodistal and incisogingival contour of the tooth. This conserves tooth structure, protects the pulp and provides for uniform depth into dentin to allow groove placement that does not undermine the adjacent enamel. All cavosurface margins should be 90 degrees with no unsupported enamel The incisal and gingival walls diverge slightly from the axial wall to the proximal surface and the incisal and gingival walls converge slightly from facial to lingual. Some retention is provided by incisal and gingival walls that converge slightly toward the lingual but secondary retention grooves are necessary. 130 When viewed from the distal, the facial wall is straight and parallel to I the long axis of the tooth (I) just breaking contact with the adjacent tooth. Minimal extension into the facial embrasure provides for maximum esthetics and insures decay removal. This provides for margins that are accessible for finishing by the operator and cleansable by the patient. RETENTION FORM For large preps, retention can be provided by L K incisal and gingival retention grooves extending DEJ from the facial to the lingual (J). Do not extend the grooves into the enamel of the lingual tooth surface and take care not to undermine the enamel of the incisal J and gingival walls (K). A Retention groove lingual dovetail is only required for retention if adequate retention is not possible using incisal and gingival grooves. The bur is held perpendicular to the lingual surface of the tooth; the pulpal wall is parallel to the lingual surface; and pulpal depth is 1.0 mm. The preparation should not extend beyond the mesiodistal midpoint of the tooth, have a smooth and flowing outline and have rounded line angles (axiopulpal) (L). Maintain a narrow isthmus above the axial pulpal line as this is necessary for retention. Additional retention can be obtained by using a 33 ½ inverted cone to create undercut at the pulpal line angle. The above prep design is appropriate for both amalgam and composite preparations. It is highly unlikely you would restore a small Class III slot preparation with amalgam therefore the use of retention grooves for composite would not be necessary. Prepare a conservative Class III slot perp on the distal of a canine and show it to your instructor. See sign off sheet for tooth number. 131 Sometimes the conservative Class III slot prep will become larger due to gingival decay that may or may not extend below the CEJ. The following narrative describes a larger prep design that can be used when decay extends gingivally. It is appropriate for both amalgam and composite When decay extends gingivally, extend the preparation to remove decay and create box-like retention form. Do not remove the lingual wall as this wall provides much needed retention. Lingual view Proximal view The following slide series shows the correct preparation design for a large Class III distal of the canine prep where decay extends gingivally. A lingual dovetail can be added for additional retention. Enlarge entry cut Establish facial wall Establish incisal wall Remove gingival decay and establish the lingual wall Internal refinement Smooth facial & incisal Smooth lingual wall walls 132 Final prep Final prep lingual proximal view view REFINEMENT AND INTERNAL DEFINITION Proper finishing of the external walls should remove unsupported enamel and rounding of the internal line angles. Use burs mounted on a slow speed or hand instruments to refine the preparation. 133 Matrix band application and restoration Cut a piece 15 to 20 mm long at a 45-degree angle from the end of a universal (No 1) matrix band. Round the sharp edges and contour properly. Contour the band and position it interproximally. The cut end should parallel the marginal ridge of the prepared tooth and should extend into the lingual embrasure slightly. Wrap the free end of the matrix strip around the facial surface of the prepared tooth and slip it past the other proximal contact. Wedge the band from the lingual and burnish it against the adjacent tooth for improved contact. A small amount of green stick compound may be required for additional stabilization. 134 Name: Seat #: Fac sig: Date: Lab exercise Class III distal of canine extended gingival prep (Daily work grade form) ==================================================================== SEVERE PREPARATION ERRORS - FAILURE lack of concept outline form depth/width damaged adjacent teeth ===================================================================== Prepare and restore one Class III restoration on a mandibular canine. First prepare the simple slot prep and after evaluation with an instructor extend the preparation gingivally to simulate deep proximal decay. The lingual wall should be preserved for retention. Place a lingual dovetail for added retention. Evaluate the preparation and the restoration slot dovetail and gingival box RUBBER DAM APPLICATION DAMAGE TO ADJACENT TEETH OUTLINE FORM / INITIAL DEPTH Smooth & flowing lingual outline form (cavosurface irregularities sharp angles) slot or semi-elliptical outline form depending on the size of the decay Proper inciso-gingival placement (too incisal into contact point too gingival) Proper dimension of the preparation (inadequate excessive) inciso-gingival height (large small) axial depth (deep shallow) Uniform adequate axial depth following external contour of the tooth deep shallow irregular Facial contact broken correctly (0.3 mm into the facial embrasure) excessive inadequate RESISTANCE FORM / CAVOSURFACE GEOMETRY 90 degree cavosurface angles / no unsupported enamel Gingival margin planed RETENTION FORM Lingual dovetail (if necessary) with properly rounded axio pulpal line angle (excessive inadequate irregular) Box-like gingival extension (when indicated) preserving lingual wall REFINEMENT AND INTERNAL DEFINITION Smooth walls (rough irregular) Slightly rounded, well-defined line angles (rough stepped irregular) Total checks Faculty evaluator: Student evaluator: 135 Name: Seat #: Fac sig: Date: Restoration (Class III with dovetail) Margin Integrity and Surface Finish: No marginal excess or deficiency is detectable at the restoration-tooth interface either visually or with the tine of an explorer. There is no evidence of voids or open margins. The surface of the restoration is uniformly smooth and free of pits and voids. There is no evidence of unwarranted or unnecessary removal, modification, or recontouring of tooth structure adjacent to the restoration. Contour, Contact and Occlusion: Interproximal contact is present, the contact is visually closed and is properly shaped and positioned; and there is definite, but not excessive, resistance to dental floss when passed through the interproximal contact area. When checked with articulating ribbon or paper, all centric and excursive contacts on the restoration are consistent in size, shape and intensity with such contacts on other teeth, in that quadrant. The restoration reproduces the normal physiological proximal contours of the tooth, occlusal anatomy and marginal ridge anatomy. The restoration reproduces normal heights of contour P / F 136 Section 12: Anterior Composite Preparations Class III, IV and V composite preparations Class III, IV and V composite preparations will be discussed together since many of the cavity design principles apply to all three classifications. Much of the discussion will involve comparing and contrasting the composite prep design to the Class III and V amalgam preparations previously studied. Composite cavity designs for anterior teeth can be described and classified based on the size of the decay and the need for addition retention and resistance. The three basic designs are presented below. TYPES OF CAVITY DESIGNS 1. Modified: This is the simplest cavity design and is indicated for small new cavitated carious lesions surrounded entirely by enamel and for correcting enamel defects. The preparation is small and entirely in enamel. Outline form and pulpal depth is determined by decay usually producing a scooped-out appearance. Margins are beveled and retention is obtained through acid etch bonding. Removal of sound tooth structure is not necessary to produce a cavity design with “box-like” features to increase retention. The most common modified prep will be the Class 5. The top picture would receive a modified prep while the bottom picture would receive a combination prep which will be discussed. Using a round bur, extend the margins of the cavity preparation to sound tooth structure. The depth of the preparation should remove all of the decay. Bevel accessible enamel margins. 2. Conventional / Beveled conventional and Larger more extensive cavity preparations have features similar to amalgam preparations. The following general rules can be applied to most large composite cavity preparations and can be used to help guide decision making for individual clinical situations. 1. Beveling enamel margins improves marginal seal (decreases microleakage), improves bonding strength by increasing the surface area available for bonding, and improves esthetics due to color blending. Bevels should not be placed in areas that are inaccessible to the bur such as the incisal, gingival and facial margins of conservative Class III preparations, or in areas of heavy occlusion (maxillary lingual) unless necessary for retention. Avoid beveling the gingival margin if it is close to the CEJ because the enamel in this area is thin and beveling may remove remaining enamel necessary for bonding. Planing of the gingival margin to remove unsupported enamel is acceptable. 2. Margins extending onto the root surface require a 90° cavomargin and macro dentinal groove. The groove increases retention and helps to minimize the debonding effects of tooth flexure under function and composite shrinkage during polymerization. Macro dentinal retention grooves and coves are also recommended when micro-mechanical retention (acid etch) is questionable due to poor quality or quantity of enamel. The technique for groove placement is the same as that used to place amalgam retention grooves. 137 3. Box-like internal form and retention grooves should be used for large preparations requiring additional retention and those preparations extending onto the root surface. Composite preparations that have box-like amalgam features are not the preferred cavity design for conservative preparations where the lesion is located entirely in enamel. If adequate retention can be obtained from acid etch then creating additional preparation retention features may unnecessarily remove sound tooth structure. *****However, a Class III composite cavity preparation with boxlike internal features is the design favored by most national examinations and it is necessary for students to demonstrate operative competency. For the practical exam in the preclinic students will prepare a Class III conservative slot shaped preparation. Retention grooves and bevels will not be placed. 3. Combination prep This preparation combines the features of the previous prep designs and provides a customized prep to meet the individual needs of more complex restorations. Examples would be Class III and V preparations where the incisal margin is above the CEJ in enamel and the gingival margin below the CEJ on cementum. Margins in enamel MAY receive a bevel while margins in dentin / cementum MUST receive a 90º cavomargin and a retention groove. Another example would be a preparation where some of the defect (decay) extends into dentin where as other defective areas are demineralized but are confined to the enamel. For these lesions a conventional prep design would extend the prep into dentin to remove decay and in areas where the demineralization is confined to enamel a modified design would be employed. The need to bevel margins would follow the guidelines given previously. Examples are shown. Round burs are usually the operative bur of choice for the modified types of composite preparations. 138 CLASS III COMPOSITE PREP (Slot prep) – evaluation criteria The following describes a clinically acceptable anterior Class III composite preparation that would receive no “checks” during a preclinic exam. External Outline Form: The outline form provides adequate access for complete removal of caries and/or previous restorative material and insertion of composite resin without excess removal of tooth structure. Access entry is appropriate to the location of caries and tooth position. (Preclinic: lingual access, incisal-gingival length should be 2.5 mm). The gingival contact must be broken 0.3 mm. The incisal contact need not be broken, unless indicated by the location of the caries. If a lingual approach is initiated, facial contact may or may not be broken as long as the margin terminates in sound tooth structure (For the preclinic exercise break facial contact 0.3 mm). Cavosurface margins form a smooth continuous curve with no sharp angles. Cavosurface margin terminates in sound natural tooth structure. There is no previous restorative material, including sealants, at the cavosurface margin. All unsupported enamel is removed unless it compromises facial esthetics. Enamel cavosurface margins may be beveled. Internal Form: The axial wall follows the external contours of the tooth and the depth should not exceed 0.5 mm beyond the DEJ (Preclinic: gingival wall width 1.0; incisal wall width 1.5 mm). All prepared surfaces are smooth and well-defined. If used, rounded internal retention is placed in the dentin of the gingival and incisal walls 0.5 mm axial to the DEJ as dictated by cavity form. Retention, when needed, is tactilely and visually present. All carious tooth structure and/or previous restorative materials are removed. Treatment Management: The isolation dam is adequate to isolate sufficient teeth for visibility and accessibility with no debris, saliva or hemorrhagic leakage into the preparation. This would include isolation of the treated tooth and both proximal adjacent teeth, if possible. The patient has adequate anesthesia for pain control. The adjacent teeth and/or restorations are free from damage. The soft tissue is free from damage or there is tissue damage that is consistent with the procedure. A preparation that exhibits changes from the ideal as described below would be considered minimally substandard in the clinic and would receive “checks” during preclinic grading. External Outline Form: The wall opposite the access, if broken, may extend no more than 1 mm beyond the contact area. The gingival clearance is > 0.5 mm but < 1.0 mm. Incisal-gingival length is greater than 2.5 mm but less than 3.5 mm). The cavosurface margins are slightly irregular. There is a small area of unsupported enamel which is not necessary to preserve facial esthetics. Enamel cavosurface margin bevels, if present, do not exceed 1 mm in width. Internal Form: The depth of the axial wall at the gingival level (gingival wall width) is greater than 1.0 mm but less than 2 mm. Incisal wall width is > 1.5 but < 2.5 mm. The gingival wall clearance is > 0.5 mm but < 1.0 mm. The internal walls are slightly rough and irregular. When used retention is inadequate or undermines enamel. Treatment Management: Damage to adjacent tooth/teeth can be removed with polishing without adversely altering the shape of the contour and/or contact. 139 A restoration that exhibits changes from the ideal as described below would be considered critically deficient in the clinic and would receive a grade of failure during preclinic grading. External Outline Form: The incisogingival outline form is underextended (< 1.0 mm) making it impossible to manipulate and finish the restorative material. The outline form is overextended incisogingivally > 3.5 mm. The incisal cavosurface margin is overextended so that the incisal angle is removed or fractured. A Class IV restoration is now necessary without justification. The gingival clearance is greater than 2 mm. The wall opposite the access opening extends more than 2.5 mm beyond the contact area. There are caries remaining Internal Form: Caries or previous restorative material remains. The width of gingival wall is > 2.0 mm. The width of the incisal is more than 2.5 mm. Axial wall deviates greatly from external contour. Extremely rough walls, severely “stepped” line angles. Severe unsupported enamel. Treatment Management: There is gross damage to adjacent tooth/teeth which requires a restoration. There is gross iatrogenic damage to the soft tissue that is inconsistent with the procedure and preexisting condition of the soft tissue. Video for Class III composite preparation #8 DL Video for Class III composite preparation on #7 ML 140 Sub errors CLASS III PREPARATION Faculty evaluator Critical errors CODE # DATE Tooth # Group A B --------------------------------------------------------------------------------------------------------------------------------- Consult the evaluation criteria narrative for details regarding the criteria defining excellent, minimally substandard and critically deficient. The errors listed below would be critically deficient in the clinic requiring re-restoration therefore these errors will result in auto fail in the preclinic. SEVERE ERRORS FAILURE Excessive or inadequate internal or external outline form Gross damage to adjacent / proximal tooth Lack of concept -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Evaluate each criterion as acceptable, clinically substandard (CS) or clinically deficient (CD). Criteria Clinically Clinically substandard / minor errors CS Critically deficient / major errors CD acceptable Rubber dam Correct number of Incorrect number of isolated teeth, gaps No rubber dam applied application isolated teeth, no present, improper frame placement, no CS Isolation does not properly isolate the CD gaps, proper frame inversion treated tooth and dam inversion Damage to No visible damage Slight damage that can be corrected Damage to adjacent tooth requiring adjacent tooth (polished) without altering adjacent proximal CS placement of a restoration. Severe CD or soft tissue contour. Slight soft tissue damage. soft tissue damage. EXTERNAL OUTLINE FORM / CAVOSURFACE GEOMETRY / RESISTANCE FORM Lingual outline Smooth & flowing Some irregularity. Does not affect restoration Significant irregularity. Adversely form lingual outline form longevity CS affects restoration longevity CD (sharp angles (sharp angles cavosurface irregularities cavosurface irregularities Inciso-gingival Proper inciso- Incisal contact broken placement gingival placement (too incisal into contact point CS Class IV CD too gingival) Inciso-gingival 2.5 mm Less than 1.5 mm Less than 1 mm height Greater than 2.5; less than 3.5 mm CS Greater than 3.5 mm CD (inadequate excessive) Facial contact (0.3 mm into the Contact broken > 0.5 but < 1.0 mm Contact not visibly broken broken facial embrasure) (inadequate excessive) CS Contact broken > 1.0 mm CD correctly (inadequate excessive) Cavosurface Cavomargins meet Slight deviation from 90 degrees or some Significant deviation from 90 degrees margins the enamel at 90° unsupported enamel. Does not jeopardize or significantly unsupported enamel CD restoration longevity CS which jeopardizes restoration No unsupported Facial Gingival Incisal walls longevity enamel (enamel spurs /unsupported enamel) (Slight deviation from 90 degrees) Facial Gingival Incisal walls Gingival Contact is open Gingival clearance is greater than 0.5 mm The gingival wall is in contact with the clearance gingivally 0.5 mm. but not greater than 1.0 mm. CS adjacent tooth. Gingival clearance is CD (excessive inadequate) greater than 1 mm. Total sub errors (CS) Total critical errors (CD) 141 Criteria Clinically Clinically substandard / minor errors CS Critically deficient / major errors CD acceptable Axial depth at 1.0 mm Less than 1 mm Less than 0.5 mm gingival margin > 1.0 but < 2.0 mm). CS Greater than 2.0 mm) CD (excessive inadequate irregular ) Axial depth at 1.5 mm Less than 1.5 mm Less than 0.5 mm incisal margin > 1.5 but < 2.5 mm). CS Greater than 2.5 mm) CD (excessive inadequate irregular ) Axial wall Axial wall deviates slightly from external Axial wall deviates greatly from follows the contour but pulpal health and resistance form CS external contour. Pulpal health and/or CD external tooth not adversely affected resistance form adversely affected contour (Concave irregular) (Concave irregular) Gingival Unsupported tooth Rough cavomargin / slight unsupported Lip of enamel remains margin planed structure removed. enamel CS Excessive planing resulting in CD No lip of enamel (inadequate) excessive enamel removal Walls Smooth walls. Walls, line and point angles can have some Extremely rough walls, Severely Line angles Slightly rounded irregularity but it does not compromise CS “stepped” line angles CD Point angles and defined line & restoration longevity. point angles RETENTION FORM Converging Proper lingual Some deviation from ideal. Does not affect Excessive deviation from ideal. walls convergence restoration longevity Adversely affects restoration based on CS longevity CD restorative material (Divergent ( F / L) (Divergent ( F / L) Excessive convergence) ( Excessive convergence) Secondary Proper placement Placement of secondary retention features Placement of secondary retention retention of secondary resulting in poor retention or compromised features resulting in poor retention or features retention features resistance form. Slight impact on restoration compromised resistance form. (slots, locks, when needed. longevity. Severe impact on restoration boxes) Location CS longevity CD Located in dentin, (undermines enamel too pulpal) Location No secondary no undermined Dimensions (undermines enamel too pulpal) retention in the enamel (excessive inadequate irregular) Dimensions conservative (excessive inadequate irregular) preclinic Class III Bevels When necessary, Slightly inadequate or excessive bevels. No Grossly inadequate or excessive properly placed adverse effect of restoration longevity. bevels. Adverse effect of restoration No bevels in the bevels for retention Location and Dimension CS longevity. CD preclinic Class and esthetics (excessive / wide inadequate Location and Dimension III rough irregular) (excessive / wide inadequate rough irregular) Box-like internal Facial, gingival & Some deviation from ideal. Does not affect Excessive deviation from ideal. form incisal walls meet restoration longevity CS Adversely affects restoration CD axial wall at right longevity angle Total sub errors (CS) Total critical errors (CD) 142 CLASS III COMPOSITE PREPARATION The goal of this evaluation form is to elaborate on the narrative for a clinically acceptable preparation by placing the cavity descriptors into the steps of cavity preparation as described by GV Black providing students with a blueprint for evaluation. Applied correctly, the principles of cavity preparation can be applied to all types of preparations ranging from conventional to ultra conservative. Students should develop a pattern for cavity preparation evaluation that can be universally applied across all types of preparations based on restorative material used and extent of the decay. The cavity design features of this preparation are similar to those of the Class III amalgam slot preparation on the distal of the canine discussed previously. The cavity features maximize retention at the expense of removing sound tooth structure and therefore may not be the design of choice for small lesions. Additional retention obtained from box-like internal form may not be necessary given the strong predictable bond to enamel that is possible using the bonding procedures currently available. This would be the preferred cavity design if the preparation extends onto the root surface where debonding may occur. What: Rubber dam application: Correct number of isolated teeth, no gaps, proper frame and dam inversion Why: Discussed previously How: Discussed previously What: Damage to adjacent tooth or soft tissue Why: Obvious reasons How: Discussed previously. Good hand piece control. Proper vision and use of fender wedges/interguard. EXTERNAL OUTLINE FORM / CAVOSURFACE GEOMETRY / RESISTANCE FORM OUTLINE FORM / INITIAL DEPTH What: Lingual outline form and placement (too incisal into contact point / too gingival) What: Proper dimension of the preparation (inadequate excessive) inciso-gingival height (large small) axial depth (deep shallow) What: Facial contact broken correctly (0.3 mm into the facial embrasure) What: Smooth & flowing outline 143 Why and How: Clinically, the outline form is determined by the extent of the decay. Outline A B form should begin as a slot shaped design to conserve tooth structure (A). The outline form becomes more semi-elliptical as the preparation becomes larger (B). The semi-elliptical design helps to provide 90º cavosurface margins. Enter using a 329/330 or small round bur aiming for the decay. The bur should be perpendicular to the lingual surface of the tooth with the neck of the bur close to the adjacent C tooth. Initial pulpal depth should be 0.5 mm into dentin. The facial cavosurface margin should extend 0.3 mm into the facial embrasure to insure removal of the decay (C), (occurs below the contact point) and allow for margins Preparations should be just below the contact that are cleansable by the point; these are located too far gingival patient and finishable by the operator. Using this design, the facial wall of enamel is usually unsupported but rarely fractures because it is not in direct occlusal function and is strengthen by the composite bonding. Preserve the incisal contact whenever possible to help preserve arch integrity. RESISTANCE FORM / UNSUPPORTED ENAMEL What: 90 degree cavosurface margins in non-beveled areas RETENTION FORM What: Boxlike internal form (Facial, gingival & incisal walls meet the axial wall at right angle) What: Properly placed lingual bevel (when necessary) (wide rough irregular) What: Proper retention grooves: size & placement (incisal gingival) Why and How: Box-like cavity features maximize the retention of the preparation; however, it is questionable D E whether removal of sound tooth structure is necessary to produce retention that is available through enamel and dentin bonding. Planing the gingival margin is recommended to remove friable unsupported enamel that can fracture during bonding. Bevels are placed to increase retention, improve esthetics, and decrease microleakage. Bevels are placed using a round bur (D) or flame (E) shaped bur. Bevels should not be placed in areas of heavy occlusal contact, in areas that are inaccessible to the bur (incisal and gingival margins in conservative Class III preparations), or on root surfaces. 144 Small conservative Class III preparations with cavosurface margins located entirely in enamel do not need macro dentinal retention features (grooves and coves). Proper use of acid etch bonding should provide adequate retention. For larger preparations, if the grooves are placed the procedure is similar to the placement of the grooves for a Class III amalgam. The grooves are placed entirely in dentin using a 1/4 round bur on a slow speed handpiece. The gingival groove may be slightly larger than the incisal due to greater bulk of dentin in this area. When placing the incisal groove (cove) avoid undermining the enamel of the incisal corner. What: Gingival clearance: Contact is open 0.5mm Why: Ensure decay removal. This criteria is not always necessary if all decay is removed How: Use the explorer to measure proper clearance. Slightly more than the tip of the explorer should pass between the prepared tooth and the adjacent tooth. When extending the outline form after removal of the thin slice of protective tooth structure a protective fenderwedge or interguard should be used to protect the adjacent tooth. 145 INTERNAL OUTLINE FORM / RESISTANCE FORM / REFINEMENT What: Axial depth at gingival margin (1.0 mm); Axial depth at incisal margin (1.5 mm) What: Axial wall follows the external tooth contour What: Gingival margin planed; Unsupported tooth structure removed. No lip of enamel What: Smooth walls. Slightly rounded and defined line & point angles Why: Resistance form. Extend into dentin to ensure decay removal. How: Proper use of burs and hand instruments REFINEMENT AND INTERNAL DEFINITION What: Slightly rounded, well-defined line angles What: Smooth axial, gingival, incisal & facial walls Why and How: Line angles should be rounded to reduce stress buildup in the tooth and restoration. Composite will flow / pack easier into rounded line angles and some clinicians recommend preparing Class III composite restorations using round burs only. RETENTION FORM What: When viewed from the proximal the incisal and gingival walls should converge lingually. Proper lingual convergence based on restorative material. Why: Mechanical retention supplements micromechanical retention How: Proper use of the bur. 146 What: Proper placement of secondary retention features (slots, locks, boxes) when needed. Retention located in dentin, no undermined enamel. No secondary retention needed in the conservative Class III. Secondary retention may be needed in larger Class III preps. Why: Mechanical retention supplements micromechanical retention How: Small grooves placed into gingival and incisal dentin wall using small round burs (1/2 or ¼). No retention grooves will be place for the Conservative Class III prep. What: When necessary, properly placed bevels for retention and esthetics; No bevels in the preclinic Conservative Class III Why: Mechanical retention supplements micromechanical retention How: The lingual wall is the only wall accessible for bevel placement. A chamfer type bevel is placed using a round bur. What: Facial, gingival & incisal walls meet axial wall at right angle; Box-like internal form Why: Retention 147 Operative procedure – anterior preparations A casual observer may not be able to detect a small carious A B lesion centered on the proximal surface of an anterior tooth, but it usually can be diagnosed with the aid of radiography (A, C) or transillumination (B). Root caries, as seen in (D) must be distinguished from cervical burnout. Access to such a Class III lesion is achieved by penetrating through either the labial or lingual plate of enamel. The primary objectives of Class III tooth preparation for composite resin are to remove all the diseased tooth structure; remove weak, friable enamel and create a retentive cavity for the restorative material. C D Non-carious enamel and dentin are preserved whenever possible. Extending the cavity's outline to cleansable areas is not always essential or desirable. For example, breaking contact with an adjacent tooth in an incisal direction will usually weaken the angle of the incisal edge and result in a fracture. A facial margin, which could become stained through years of service, may be left in contact with the adjacent tooth, out of view, for esthetic reasons. Some enamel that has lost its dentin support, but still appears substantial and fracture- resistant, may also be preserved in order to achieve a better esthetic result. The Class III lesion should be approached from the labial surface if the lesion can be seen directly from the facial or if it appears with transillumination to be located closer to the facial plate of enamel. The labial approach would also be indicated if the alignment of the teeth within the arch makes lingual access especially difficult. The lingual approach is recommended in most cases because it is more conservative of visible tooth structure. The minimal Class III preparation for composite resin resembles the "slot” preparation for amalgam, but it is more rounded internally, in its’ outline, and its accessible cavosurface margins in enamel may be beveled and etched for retention. PROCEDURE: Conservative Class III Restoration Using Lingual Approach Lecture notes and the Sturdevant text should be consulted for detailed pictures illustrating the Class III composite preparation. Administer an anesthetic. With hand and rotary instrumentation, remove all traces of calculus, plaque, stain and food debris from the teeth in the operating area. In the laboratory, students can draw the projected outline on the lingual surface of the tooth. The small Class III lesion is usually located slightly gingival to the proximal contact area. A conservative cavity preparation in dentin is approximately 1.5 – 2.0 mm high in the occlusogingival direction and 1.0 – 1.5 mm wide in the mesiodistal direction. For the preclinic exercise we will use an incisal gingival dimension of 2.5 to 3.0mm. 148 Choose a shade for the restorative material before applying the rubber dam. Dehydration can occur after rubber dam placement changing the apparent shade of the tooth. Placement of a fender wedge or Intergard to protect the adjacent tooth is not necessary until removal of the thin sliver of protective tooth structure is removed after the initial punch cut. Placement of a wedge to separate the teeth slightly is recommended. Break through the enamel of the lingual surface with the #330 bur in the high speed handpiece and penetrate in a facial direction approximately 1.5 mm (the full length of the #330 bur). Hold the bur perpendicular to the lingual surface of the tooth during this operation. Create an oval slot within the outline limits established previously, leaving a thin shell of enamel in contact with the adjacent tooth. Break the remaining proximal enamel shell away with a sharp spoon excavator and smooth the enamel walls and margins, taking care not to scar the adjacent tooth. A fender wedge or Intergard should be placed if further refinement with rotary instruments is necessary. Excavate remaining carious dentin with an appropriately sized round bur in the low-speed handpiece. Evaluate the texture and hardness of the dentin with the spoon excavator. Enlarge the outline to remove weak, undermined enamel, as necessary. If necessary for retention, prepare a small chamfer bevel along the lingual enamel cavomargin with the #2 round diamond bur or the tip of a football bur. Inaccessible cavosurface margins should not be beveled. The lingual chamfer should be approximately 0.5-1.0 mm wide and not more than half the thickness of the enamel (about 0.5 mm in the typodont tooth). Final preparation 149 PROCEDURE: Conservative Class III Restoration Using labial Approach If necessary, apply a fender wedge or interguard to protect the adjacent tooth. If the lesion is small, use the #2 round bur or 330 to prepare the labial approach Class III cavity. The outline form is usually circular or oval. For more extensive lesions, where the enamel has been undermined to a greater degree, a longer bur, such as the #330 or #256, may be more effective. The internal form, as well as the outline, should be rounded. This prep resembles the modified prep described in the lecture. Evaluate the texture and hardness of the dentin with a sharp spoon excavator. Extend the outline to remove weak, friable enamel, but take care not to over-extend the facial margin unnecessarily. Doing so would compromise the esthetic result. If staining exists at the cavomargin, do not extend the outline form if the defect can be removed by placement of a bevel. Prepare a small chamfer along the accessible margins in enamel with a small round diamond (often the facial margin, only). Restore the tooth using the same techniques presented earlier for the lingual approach restoration. A Mylar matrix strip should be used to compress the composite resin in the cavity. Finishing and polishing techniques are also like those presented for the lingual approach restoration, but here the polishing discs (Soflex and Shofu) are especially useful. DISCUSSION The design for a Class III, IV & V composite preparation is based on the extent of the decay. As a rule of thumb, as the decay becomes more extensive and additional retention is needed, the cavity design begins to approach that of an amalgam preparation with boxlike internal features and macro dentinal retention grooves. The following section provides general criteria to help guide clinical decision-making regarding cavity design for composite resin Class III, IV and V preparations OUTLINE FORM / INITIAL DEPTH Extend cavity walls to sound tooth structure; initial pulpal depth removes decay. The depth of the preparation varies depending on the extent of the decay. For all preparations, the cavity walls are extended to sound tooth structure both laterally and pulpally. In shallow preparations the axial wall may be in enamel. With the conventional preparations the axial wall must penetrate 0.5 mm into dentin (similar to amalgam). If the lesion was classified as a D1 then cavity preparation should penetrate into the dentin. For Class III conventional preparations, the initial punch cut is just pulpal to the DEJ. If the preparation extends onto the root surface, extend the axial wall minimally 0.75 mm into the tooth to allow adequate space for dentin groove placement. 150 RESISTANCE FORM Butt joint margins or beveled margins are acceptable; Removal of weak unsupported enamel that cannot aid in retention is necessary. Always plane the gingival margin to remove friable enamel. Cavosurface margins can be butt joint or beveled. Clinical conditions influence the decision to remove unsupported enamel. Some unsupported enamel, as may be found on the facial wall, may be retained to provide surface area for bonding and preserve esthetics but weak friable enamel at the gingival margin must be removed. Research has shown that composite bonding strengthens remaining tooth structure. If the preparation extends onto the root surface the cavosurface margin must be butt joint (90º). Rules for placement of a bevel / chamfer A If the cavity is completely in the anatomic crown (A), a chamfer should be prepared around the entire circumference, but the chamfer in the gingival half of the preparation must be shallow since the enamel is very thin in the area of the CEJ. If the cavity is completely in the anatomic root (B), a chamfer is not prepared at all. Instead, the cavosurface angle is a butt joint. B Retention is provided by incisal and gingival dentin grooves like the preparation for amalgam. If the cavity is partially in the anatomic crown and partially in the anatomic root (C), a chamfer is prepared only where the margin lies in enamel. A retention groove is required in the gingival wall. C Retentive grooves may be placed into the incisal and gingival walls in addition to the cavosurface chamfers if the quality and quantity of remaining enamel is determined to be inadequate D for proper bonding (D) 151 RETENTION FORM Micromechanical through beveling and acid etch; Macro dentinal grooves (optional) Box form retention with parallel walls for large preparations Retention form is provided by micromechanical (beveled margins and acid etch), macromechanical (dentin grooves) and/or box-like internal form. Unnecessary removal of sound tooth structure should be avoided if adequate retention and resistance are available using acid etch. However, if the preparation extends onto the root surface or additional retention is needed, box-like internal form and macro dentinal grooves should be used. REFINEMENT (finishing the external walls) & INTERNAL DEFINITION Cavosurface bevel; smooth walls; well-defined, slightly rounded line angles Beveling increases the surface area for retention, improves esthetic blending of composite and when combined with acid etch decreases microleakage. Use a flame shaped or round diamond bur to produce an adequate bevel. The flame shaped bur produces a flat bevel whereas the round bur produces a hollow-ground or chamfer-like bevel. Do not bevel the root surface, areas with heavy occlusion (maxillary lingual), or areas that are inaccessible (incisal, gingival & facial of conservative Class 3 preparations). DISCUSSION Class V lesions are commonly seen on the facial and lingual surfaces of all posterior teeth and the facial surfaces of the anterior teeth. They occur between the margin of the free gingiva and the height of contour of the clinical crown in areas that collect plaque readily. A white line following the gingival contour is an early sign of caries activity. As the demineralization progresses the enamel becomes chalky and rough, and finally crumbles away, revealing softened dentin beneath. Early recognition and treatment are necessary to prevent rapid destruction of the tooth. Untreated, the lesion spreads proximally, as well as occlusally, gingivally and axially, undermining and weakening the entire crown of the tooth and threatening the pulp. Recurrence of decay is common around gingival third restorations and complicates cavity design when replacement is necessary. Failure to control moisture during restorative procedures, poorly designed and finished cavity walls and margins and continued poor home care are major factors that contribute to this high failure rate. The health of the gingival tissue can also be adversely affected if the Class V restoration is poorly contoured or if its surface is irregular and rough. 152 Anterior teeth with Class V lesions are usually restored with composite resin because of the obvious esthetic requirement. Similarly, the facial surfaces of the maxillary premolars and, less often, the mandibular premolars usually need to be restored with a tooth- colored material in patients who are conscious of their appearance and have broad smiles. The outline form of the Class V cavity is determined primarily by the shape of the lesion. The carious dentin, unsupported enamel and peripheral demineralized enamel must be removed and the cavity should be gently rounded, free of any sharp corners. Some typical outlines for Class V lesions are pictured. 153 Slide series sample preps Class III, IV and V Classical Class III Facial view of Class composite III composite prep. preparation. Contact Extend facial wall is broken facial just far enough to lingual and gingival break contact. – not incisal. Pulpal Margin should be wall 0.5 mm into visible from the dentin. Optional facial view as beveled margins shown. and dentin grooves. Class V composite Class III composite preparation with prep on the distal of boxlike internal form a canine. Large prep and beveled extends into contact. cavosurface margins. Semi-elliptical outline form produces butt joint margins. Classical Class V Class V lesion. composite preparation. Preparation outline Pulpal depth extended and initial depth to remove decay. Box- should extend to like internal form and sound tooth beveled enamel structure. The use of margins used for box-like internal form retention. Retention and a gingival grooves unnecessary retention groove may because the cavity be necessary if the margins are entirely in preparation extends enamel. onto the root surface. 154 Incisal view of Class IV composite Class IV prep. Beveled enamel showing box- margins; boxlike form like internal prepared on the form for added proximal during decay retention. All removal. Unsupported accessible enamel is retained for enamel margins added retention. are beveled. Facial and lingual incisal enamel is unsupported but retained to provide bonding surface and retention. Combination preps. Box-like internal form for added retention. Class III composite prep. Semi-elliptical shape. No bevels placed Beveled enamel margins and 90 degree (butt joint) cavosurface on the lingual because of the heavy wear facets indicating an margin on the root surface with a gingival retention groove. unfavorable occlusion. Large Class III composite prep extending through the facial. Bevel enamel margins for retention and

Rd2 Exam 1 PDF - Composite Resin Preparations and Restorations

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