The acid-etch restoration
Class III composite
resin
Dennis 1. Torney, D.D.S., MS.,* Gerald E. Denehy, D.D.S., Luiz C. Teixeira, C.D., D.C.*** The University of Iowa College of Dentistry, Iowa City, Iowa
MS.,**
and
C
omposite resins are the best and most esthetic restorative materials that are currently available. Their solubility is less than that of silicate cements and their susceptibility to abrasion is less than that of acrylic resins. The composite resins, however, are still not the ideal esthetic restorative materials. Marginal leakage is always associated with them and sensitivity is often experienced postoperatively.’ Although composite resins do not percolate like the acrylic resins they do exhibit some marginal discoloration with the passage of time. All of these particular drawbacks are at least in part related to microleakage. Elimination or reduction of microleakage would result in a decrease in sensitivity, discoloration, and recurrent caries and thereby result in greater longevity of composite resin restorations. The acid-etch technique is a possible solution to the problem of microleakage. The technique was originally proposed as a method of increasing retention of resin r&orations.2 Studies done in vitro, in vivo, and in vitro under load have shown that marginal leakage can be virtually eliminated by acid-etching of the cavosurface margins of a preparation before placing the composite resin material.3-7 Thus by combining the acid-etch technique with the more conventional preparations, one should expect to produce a restoration with improved properties. We will describe the incorporation of the acid-etch technique into the Class III restorative procedure. The description and illustrations of the Class III preparation relate to the design currently taught at the University of Iowa College of Dentistry. The marginal sealing technique may however be incorporated into preparations of virtually any design provided the cavosurface margins are situated within enamel.
*Assistant
Professor,
**Professor,
Department
***Visiting
Professor,
Department
of Operative
of Operative University
Dentistry.
Dentistry. of
SHo
Paulo,
Ribel-Rao
Preto,
Sslo
Paulo,
Brazil.
623
624
Torney,
Denehy,
Fig. 1. Cross-sectional enamel; D, the dentin;
and
J. Prosthet. Dent. December, 1977
Teixeira
view of 0.5 mm. C, the composite
45 degree bevel resin. (Origin
of enamel magnification
cavosurface x20.)
margin:
E, the
TECHNIQUE The conventional Class III preparation form is first established. The lingual approach is advocated for the maxillary anterior teeth since a good color match of the composite resins to tooth structure cannot be consistently guaranteed. In the mandibular’ arch where esthetics is less of a problem, the labial approach is suggested so that the strong marginal ridge that lends support to the weakened incisal angle is maintained. Definite internal and external outline form and retention are necessary since the acid-etch technique is used primarily for marginal sealing and not for retention. The conventional composite resin preparation utilizes 90 degree cavosurface angles. With the acid-etch technique, however, the preparation is modified by the placement of a 0.5 mm. 45 degree enamel cavosurface bevel (Fig. 1) . This bevel exposes more etched enamel to the resin thereby increasing resistance to microleakage.* It has been shown that the ends of the rods are etched preferentially to the sides of the rodsg; the bevel allows the ends of the rods to be exposed to the etching process. It also forms a gradual transition from tooth structure to composite resin, providing a better esthetic result. The bevel is easily placed on the lingual cavosurface margin with rotary instruments. A 12 bladed finishing bur is recommended for this procedure because it produces a smooth bevel (Fig. 2). Any margins inaccessible to rotary instruments such as the gingival, incisal, or labial margins may be beveled with a gingival margin
Volume Number
38 6
Acid-etch
Fig.
2. Placement
of the lingual
Fig.
3. Placement
of the gingival
Fig.
4. Completed
preparation
bevel bevel showing
with with
a 12 bladed a gingival
a continuous
Fig. 5. Excessive amount of unfilled resin at gingival pearance to a Class III acid-etched restoration.
composite
flame-shaped margin 0.5 mm.
margin
resin
finishing
restoration
625
bur.
trimmer. 45 degree
enamel
bevel.
(arrow)
giving
an unesthetic
ap-
trimmer (Fig. 3). The finished preparation should exhibit a smooth flowing bevel on all enamel cavosurface margins (Fig. 4) . Since phosphoric acid may be detrimental to the pulp placement of a calcium hydroxide liner on any deep areas of dentin before etching is advisable.lO The etchant is placed and allowed to remain on the enamel for 60 to 90 seconds and then rinsed thoroughly with water and air-dried. The beveled enamel cavosurface margins should appear dull and chalky after drying. In preparations designed so that the cavosurface margins approximate or contact the adjacent tooth, care must be taken to cover the etched margin with the unfilled resin and yet avoid splinting the restoration to the adjacent inter-proximal surface. Since the placement of a celluloid matrix often hinders the application of the unfilled resin, the dentist may elect to place the matrix between the insertion of the unfilled and the filled resins. However, to avoid the splinting problem it must be in place before the unfilled resin polymerizes. The unfilled resin is placed .in the cavity preparation, with a brush or cotton pellet, ensuring coverage of both the retention angles and the etched beveled surfaces.
626
Torney,
Denehy,
and Teixeira
J. Prosthet. Dent. December, 1977
Care should be taken to keep this material as thin as possible since a thick layer at the margins may have adverse esthetic effects (Fig. 5) ; an air syringe or a dry cotton pellet may be used to remove any excess from the preparation and the margins. The celluloid matrix is then quickly positioned and wedged and the filled composite resin is inserted. Conventional finishing techniques are then performed on the restoration up to the beveled margin. The self-polymerizing systems are advocated for the Class III acid-etch technique; ultraviolet-light-polymerized (UV) systems would unnecessarily increase the working time. There is also a possible problem of incomplete polymerization with UV systems due to the interference of the walls of the preparation with the ultraviolet rays. CONCLUSION The acid-etch systems have become a familiar part of the dentist’s armamentarium for achieving retention in the treatment of major esthetic problems in anterior teeth. They have another advantage, however, that has not been fully utilized. By combining the acid-etch technique with conventional cavity preparations such as the Class III, the common problems associated with microleakage can be greatly reduced and composite resin restorations can be placed with better esthetic results and greater longevity. References 1. Br;innstrijm, 2.
3. 4. 5. 6. 7. 8. 9. 10.
M., and Nyborg, H.: The Presence of Bacteria in Cavities Filled With Siliand Composite Resin Materials, Swed. Dent. J. 64: 149-155, 1971. M. G.: A Simple Method of Increasing the Adhesion of Acrylic Filling Materials to Enamel Surfaces, J. Dent. Res. 34: 849-853, 1955. Buonocore, M. G., Sheykholeslam, Z., and Glena, R.: Evaluation of an Enamel Adhesive to Prevent Marginal Leakage: An In Vitro Study, J. Dent. Child. 40: 119-124, 1973. Al Rafei, S., and Moore, D. L.: Marginal Penetration of Composite Resin Restorations as Indicated by a Tracer Dye, J. PROSTHET. DENT. 34: 435-439, 1975. Dogon, I. L., and Henry, P.: Calcium 45 Penetration and Scanning Electronmicroscopy Study of the Acid Etch System, IADR Abst. No. 19, 1975. Hembree, J. H., and Andrews, J. T.: In Situ Evaluation of Marginal Leakage Using an Ultraviolet-Light-Activated Resin System, IADR Abst. No. 2, 1975. Jorgensen, K. D., Matono, R., and Chimokobe, H.: Deformation of Cavities and Resin Fillings in Loaded Teeth, Stand. J. Dent. Res. 84: 46-50, 1976. Hawkins, I. K., Fairhurst, C. W., Kinzer, R. L., and Okabe, T.: Effects of Cavity Design on Microleakage in Class V Restorations, IADR Abst. No. 316, 1976. Taylor, C. L., and Gwinnett, A. J.: A Study of the Penetration of Sealants Into Pits and Fissures, J. Am. Dent. Assoc. 87: 1181-1188, 1973. Stanley, H. R., Going, R. E., and Chauncey, H. H.: Human Pulp Response to Acid Pretreatment of Dentin and to Composite Restoration, J. Am. Dent. Assoc. 91: 817-825, 1975. cate Cement Buonocore,
THE UNIVERSITY OF IOWA COLLEGE OF DENTISTRY IOWA CITY, IOWA 52242
Class III composite
resin
Dennis 1. Torney, D.D.S., MS.,* Gerald E. Denehy, D.D.S., Luiz C. Teixeira, C.D., D.C.*** The University of Iowa College of Dentistry, Iowa City, Iowa
MS.,**
and
C
omposite resins are the best and most esthetic restorative materials that are currently available. Their solubility is less than that of silicate cements and their susceptibility to abrasion is less than that of acrylic resins. The composite resins, however, are still not the ideal esthetic restorative materials. Marginal leakage is always associated with them and sensitivity is often experienced postoperatively.’ Although composite resins do not percolate like the acrylic resins they do exhibit some marginal discoloration with the passage of time. All of these particular drawbacks are at least in part related to microleakage. Elimination or reduction of microleakage would result in a decrease in sensitivity, discoloration, and recurrent caries and thereby result in greater longevity of composite resin restorations. The acid-etch technique is a possible solution to the problem of microleakage. The technique was originally proposed as a method of increasing retention of resin r&orations.2 Studies done in vitro, in vivo, and in vitro under load have shown that marginal leakage can be virtually eliminated by acid-etching of the cavosurface margins of a preparation before placing the composite resin material.3-7 Thus by combining the acid-etch technique with the more conventional preparations, one should expect to produce a restoration with improved properties. We will describe the incorporation of the acid-etch technique into the Class III restorative procedure. The description and illustrations of the Class III preparation relate to the design currently taught at the University of Iowa College of Dentistry. The marginal sealing technique may however be incorporated into preparations of virtually any design provided the cavosurface margins are situated within enamel.
*Assistant
Professor,
**Professor,
Department
***Visiting
Professor,
Department
of Operative
of Operative University
Dentistry.
Dentistry. of
SHo
Paulo,
Ribel-Rao
Preto,
Sslo
Paulo,
Brazil.
623
624
Torney,
Denehy,
Fig. 1. Cross-sectional enamel; D, the dentin;
and
J. Prosthet. Dent. December, 1977
Teixeira
view of 0.5 mm. C, the composite
45 degree bevel resin. (Origin
of enamel magnification
cavosurface x20.)
margin:
E, the
TECHNIQUE The conventional Class III preparation form is first established. The lingual approach is advocated for the maxillary anterior teeth since a good color match of the composite resins to tooth structure cannot be consistently guaranteed. In the mandibular’ arch where esthetics is less of a problem, the labial approach is suggested so that the strong marginal ridge that lends support to the weakened incisal angle is maintained. Definite internal and external outline form and retention are necessary since the acid-etch technique is used primarily for marginal sealing and not for retention. The conventional composite resin preparation utilizes 90 degree cavosurface angles. With the acid-etch technique, however, the preparation is modified by the placement of a 0.5 mm. 45 degree enamel cavosurface bevel (Fig. 1) . This bevel exposes more etched enamel to the resin thereby increasing resistance to microleakage.* It has been shown that the ends of the rods are etched preferentially to the sides of the rodsg; the bevel allows the ends of the rods to be exposed to the etching process. It also forms a gradual transition from tooth structure to composite resin, providing a better esthetic result. The bevel is easily placed on the lingual cavosurface margin with rotary instruments. A 12 bladed finishing bur is recommended for this procedure because it produces a smooth bevel (Fig. 2). Any margins inaccessible to rotary instruments such as the gingival, incisal, or labial margins may be beveled with a gingival margin
Volume Number
38 6
Acid-etch
Fig.
2. Placement
of the lingual
Fig.
3. Placement
of the gingival
Fig.
4. Completed
preparation
bevel bevel showing
with with
a 12 bladed a gingival
a continuous
Fig. 5. Excessive amount of unfilled resin at gingival pearance to a Class III acid-etched restoration.
composite
flame-shaped margin 0.5 mm.
margin
resin
finishing
restoration
625
bur.
trimmer. 45 degree
enamel
bevel.
(arrow)
giving
an unesthetic
ap-
trimmer (Fig. 3). The finished preparation should exhibit a smooth flowing bevel on all enamel cavosurface margins (Fig. 4) . Since phosphoric acid may be detrimental to the pulp placement of a calcium hydroxide liner on any deep areas of dentin before etching is advisable.lO The etchant is placed and allowed to remain on the enamel for 60 to 90 seconds and then rinsed thoroughly with water and air-dried. The beveled enamel cavosurface margins should appear dull and chalky after drying. In preparations designed so that the cavosurface margins approximate or contact the adjacent tooth, care must be taken to cover the etched margin with the unfilled resin and yet avoid splinting the restoration to the adjacent inter-proximal surface. Since the placement of a celluloid matrix often hinders the application of the unfilled resin, the dentist may elect to place the matrix between the insertion of the unfilled and the filled resins. However, to avoid the splinting problem it must be in place before the unfilled resin polymerizes. The unfilled resin is placed .in the cavity preparation, with a brush or cotton pellet, ensuring coverage of both the retention angles and the etched beveled surfaces.
626
Torney,
Denehy,
and Teixeira
J. Prosthet. Dent. December, 1977
Care should be taken to keep this material as thin as possible since a thick layer at the margins may have adverse esthetic effects (Fig. 5) ; an air syringe or a dry cotton pellet may be used to remove any excess from the preparation and the margins. The celluloid matrix is then quickly positioned and wedged and the filled composite resin is inserted. Conventional finishing techniques are then performed on the restoration up to the beveled margin. The self-polymerizing systems are advocated for the Class III acid-etch technique; ultraviolet-light-polymerized (UV) systems would unnecessarily increase the working time. There is also a possible problem of incomplete polymerization with UV systems due to the interference of the walls of the preparation with the ultraviolet rays. CONCLUSION The acid-etch systems have become a familiar part of the dentist’s armamentarium for achieving retention in the treatment of major esthetic problems in anterior teeth. They have another advantage, however, that has not been fully utilized. By combining the acid-etch technique with conventional cavity preparations such as the Class III, the common problems associated with microleakage can be greatly reduced and composite resin restorations can be placed with better esthetic results and greater longevity. References 1. Br;innstrijm, 2.
3. 4. 5. 6. 7. 8. 9. 10.
M., and Nyborg, H.: The Presence of Bacteria in Cavities Filled With Siliand Composite Resin Materials, Swed. Dent. J. 64: 149-155, 1971. M. G.: A Simple Method of Increasing the Adhesion of Acrylic Filling Materials to Enamel Surfaces, J. Dent. Res. 34: 849-853, 1955. Buonocore, M. G., Sheykholeslam, Z., and Glena, R.: Evaluation of an Enamel Adhesive to Prevent Marginal Leakage: An In Vitro Study, J. Dent. Child. 40: 119-124, 1973. Al Rafei, S., and Moore, D. L.: Marginal Penetration of Composite Resin Restorations as Indicated by a Tracer Dye, J. PROSTHET. DENT. 34: 435-439, 1975. Dogon, I. L., and Henry, P.: Calcium 45 Penetration and Scanning Electronmicroscopy Study of the Acid Etch System, IADR Abst. No. 19, 1975. Hembree, J. H., and Andrews, J. T.: In Situ Evaluation of Marginal Leakage Using an Ultraviolet-Light-Activated Resin System, IADR Abst. No. 2, 1975. Jorgensen, K. D., Matono, R., and Chimokobe, H.: Deformation of Cavities and Resin Fillings in Loaded Teeth, Stand. J. Dent. Res. 84: 46-50, 1976. Hawkins, I. K., Fairhurst, C. W., Kinzer, R. L., and Okabe, T.: Effects of Cavity Design on Microleakage in Class V Restorations, IADR Abst. No. 316, 1976. Taylor, C. L., and Gwinnett, A. J.: A Study of the Penetration of Sealants Into Pits and Fissures, J. Am. Dent. Assoc. 87: 1181-1188, 1973. Stanley, H. R., Going, R. E., and Chauncey, H. H.: Human Pulp Response to Acid Pretreatment of Dentin and to Composite Restoration, J. Am. Dent. Assoc. 91: 817-825, 1975. cate Cement Buonocore,
THE UNIVERSITY OF IOWA COLLEGE OF DENTISTRY IOWA CITY, IOWA 52242
