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Restoration of fractured incisors with an ultraviolet light polymerized composite resin
341
Quarterly Dental Review
CONSERVATIVE
DENTISTRY
STERNBERG V. M. and MARSHALL M. Biological basis for placament of crown margins, NY state Dent. J. 42 (1976) 608-611. Supragingival restorations are always preferable from the standpoint of periodontal health. Unfortunately, sometimes full coverage requires to be extended subgingivally (because of, for example, aesthetics, caries, cervical erosions, existing restorations and root sensitivity). The tooth preparation should be kept coronal to the epithelial attachment to maintain its integrity. The margins should be barely into the sulcus. Gingival inflammation increases as the apical extent of the restoration increases. Minimal subgingival extension gives a better-fitting crown margin, and allows the patient to perform plaque control more easily. Placement of margins into inflamed tissue will perpetuate the disease. Tooth preparation and impression-taking will be made more difficult owing to the presence of bleeding and hyperplasia. Obviously, restorative dentistry can be greatly facilitated when gingival health and minimal sulcus depth is achieved beforehand. Final connective tissue maturation takes 35 days after periodontal surgery, and some creeping incisally of the gingival margin continues for some time, until the normal distance between the bone crest and the sulcus base has bean produced. Periodontal surgery done et the same time as final tooth prep aration is unacceptable because it is difficult to know where the new sulcus base will be until it has actually formed. Completing the final tooth preparation before the tissue has completed its coronal migration will result in impingement upon the connective tissue attachment and will initiate periodontal disease. Provisional tooth preparation should be done prior to periodontal surgery with the preparation carried to the gingival margin. Final preparation should wait until 6-12 weeks following periodontal surgery. The final step is the cementation of a well-fitting accurately contoured restoration. At best, the fit of a crown leaves a microscopic defect between the gold and the tooth. The size of the marginal deficiency will affect the accumulation of plaque and
the patient’s ability to remove it. Dvercontouring of the crown will result in an increase in plaque retention. That portion of the crown which extends subgingivally will distend and stretch the gingival sulcular wall. The subtle contours of the natural tooth are difficult to reproduce in the materials available. Adequate tooth removal must be achieved to allow sufficient bulk for correct contouring. E. R. Smart KIN P. K. A simple technic for treatment of dental trauma, Dent. Survey 53 (1977) 49-41. A technique is described for the splinting of teeth displaced by trauma. Heat-treated stainless steel wire is shaped to fit the arch. The teeth are polished and acid-etched and the wire is attached to stable teeth with composite resin. Displaced teeth are aligned with finger pressure and cemented to the wire with generous quantities of composite resin which may be trimmed after it has set. Andrew Richardson WATKINS J. I. and ANDLAW FL J. Restoration of fractured incisors with an ultraviolet light polymerized composite rasin, Br. Dent J. 142 (1977) 249-252. Fractured incisor teeth having at least 4 mm of available labial and palatal enamel were selected for the study. There was no mechanical preparation for the retention of restorations. After polishing with a commercial paste the enamel surface was etched for at least 1 minute to 4 mm from the fractured edge. NuvaSeal resin was painted on to the etched area and was polymerized by ultra violet light. Nuvefil paste contained in a prepared crown form was placed in position and excess material was removed. The paste was polymerized bv ultraviolet light applied from both labial and palatal surfaces. Large restorations were built incrementally. Each restoration was assessedfor colour match and the presence of edges. Altogether 132 restorations were placed, the mean age of the patients being 1199 years. After at least 1 year 83 per cent of the restorations were retained. Most restorations were lost during the first 12 months, the most common cause of loss of restorations
342
Journal of Dentistry, Vol. ~/NO. 4
being direct trauma. The colour of 78 per cant of the retained restorations was considered to be satisfactory, whilst the margins of only 66 per cent were satisfactory. The method was considered suitable for the restoration of fractured incisors as a semi-permanent measure only. C. McD. Hannah GROSS0 F. P. and SEARS P. G. Placement of a temporary crown prior to root canal therapy, Dent. Survey 53 (1977) 31-33. A gingival line fracture of an anterior tooth presents problems of isolation for root canal therapy and temporary restoration. A technique is described which solves both problems. The root face is prepared to receive a crown and the orifice of the root canal is enlarged with a No. 8 round bar to receive a hollow sprue pin. A straightened paper clip is inserted into the root canal orifice to act as a guide for the sprue pin. A hole is made in a temporary polycarbonate crown to receive the sprue pin, the crown filled with a thick acrylic and the crown seated on the prepared root end. After trimming of excess acrylic the crown is cemented in place and routine endodontic therapy carried out through the sprue pin. Andrew Richardson
DENTAL
EDUCATION
GUILD R. E. Self instruction in dentistry: a critique, J. Dent Educ. 41 (1977) 239-247. This paper is prompted by recent activity and interest in self-instruction methods in dentistry. Tape/slide sequences are a useful means of presenting information, but the great majority do not fulfil the requirements of an effective self-instruction technique. Such a technique demands that stimuli or material should be presented, that a response should be required from the learner and that immediate feedback should be provided as to the correctness of this response. In addition, such a machine should permit selfpacing by the student. The author recommends the use of self-teaching programmes which fulfil all these requirements. J. D. Eccles
DENTAL
MATERIALS
RIDER M., TANNER A. N. and KENNY 8. Investigation of adhesive properties of dental composite materials using an improved tensile test procedure and scanning electron microscopy, J. Dent Res. 56 (1977) 368378. The authors describe a new tens&strength measurement technique which they have used to investigate the adhesion of several dental composites and one polycarboxylate cement to enamel and dentine. Standardized specimens of enamel and dentine were etched with either 50 per cent orthophosphoric acid with 7 per cent zinc oxide or with the etchant supplied for particular resins by the manufacturers. After drying, the specimens were mounted in pairs in a special jig to allow the forma tion of a sandwich of composite between two specimens of enamel or dentine. When setting was complete the specimen was subjected to a tensile load in a testing machine. The scanning electron microscopic appearances were also studied. None of the composite materials showed bonding to dentine although there was resin penetration into tubular spaces. The polycarboxylate did show bonding and the bond strength was reduced by the etching procedure. All the composites were found to bond well to enamel. When ranked by bond strength Concise was best and HL72 the poorest. No significant difference was noted between the tensile bond strength for Concise alone and that with an intermediate unfilled resin layer. G. A. Smith
EtVDODONTlCS ROWE A. H. R. and BINNIE W. H. The incidence and location of microorganisms following endodontic treatment, Br. Dent J. 142 (1977) 91-95. The purpose of the investigation was to determine the incidence of micro-organisms in root canals, dentine, cementurn and apical tissues following root filling with a variety of materials.
Quarterly Dental Review
CONSERVATIVE
DENTISTRY
STERNBERG V. M. and MARSHALL M. Biological basis for placament of crown margins, NY state Dent. J. 42 (1976) 608-611. Supragingival restorations are always preferable from the standpoint of periodontal health. Unfortunately, sometimes full coverage requires to be extended subgingivally (because of, for example, aesthetics, caries, cervical erosions, existing restorations and root sensitivity). The tooth preparation should be kept coronal to the epithelial attachment to maintain its integrity. The margins should be barely into the sulcus. Gingival inflammation increases as the apical extent of the restoration increases. Minimal subgingival extension gives a better-fitting crown margin, and allows the patient to perform plaque control more easily. Placement of margins into inflamed tissue will perpetuate the disease. Tooth preparation and impression-taking will be made more difficult owing to the presence of bleeding and hyperplasia. Obviously, restorative dentistry can be greatly facilitated when gingival health and minimal sulcus depth is achieved beforehand. Final connective tissue maturation takes 35 days after periodontal surgery, and some creeping incisally of the gingival margin continues for some time, until the normal distance between the bone crest and the sulcus base has bean produced. Periodontal surgery done et the same time as final tooth prep aration is unacceptable because it is difficult to know where the new sulcus base will be until it has actually formed. Completing the final tooth preparation before the tissue has completed its coronal migration will result in impingement upon the connective tissue attachment and will initiate periodontal disease. Provisional tooth preparation should be done prior to periodontal surgery with the preparation carried to the gingival margin. Final preparation should wait until 6-12 weeks following periodontal surgery. The final step is the cementation of a well-fitting accurately contoured restoration. At best, the fit of a crown leaves a microscopic defect between the gold and the tooth. The size of the marginal deficiency will affect the accumulation of plaque and
the patient’s ability to remove it. Dvercontouring of the crown will result in an increase in plaque retention. That portion of the crown which extends subgingivally will distend and stretch the gingival sulcular wall. The subtle contours of the natural tooth are difficult to reproduce in the materials available. Adequate tooth removal must be achieved to allow sufficient bulk for correct contouring. E. R. Smart KIN P. K. A simple technic for treatment of dental trauma, Dent. Survey 53 (1977) 49-41. A technique is described for the splinting of teeth displaced by trauma. Heat-treated stainless steel wire is shaped to fit the arch. The teeth are polished and acid-etched and the wire is attached to stable teeth with composite resin. Displaced teeth are aligned with finger pressure and cemented to the wire with generous quantities of composite resin which may be trimmed after it has set. Andrew Richardson WATKINS J. I. and ANDLAW FL J. Restoration of fractured incisors with an ultraviolet light polymerized composite rasin, Br. Dent J. 142 (1977) 249-252. Fractured incisor teeth having at least 4 mm of available labial and palatal enamel were selected for the study. There was no mechanical preparation for the retention of restorations. After polishing with a commercial paste the enamel surface was etched for at least 1 minute to 4 mm from the fractured edge. NuvaSeal resin was painted on to the etched area and was polymerized by ultra violet light. Nuvefil paste contained in a prepared crown form was placed in position and excess material was removed. The paste was polymerized bv ultraviolet light applied from both labial and palatal surfaces. Large restorations were built incrementally. Each restoration was assessedfor colour match and the presence of edges. Altogether 132 restorations were placed, the mean age of the patients being 1199 years. After at least 1 year 83 per cent of the restorations were retained. Most restorations were lost during the first 12 months, the most common cause of loss of restorations
342
Journal of Dentistry, Vol. ~/NO. 4
being direct trauma. The colour of 78 per cant of the retained restorations was considered to be satisfactory, whilst the margins of only 66 per cent were satisfactory. The method was considered suitable for the restoration of fractured incisors as a semi-permanent measure only. C. McD. Hannah GROSS0 F. P. and SEARS P. G. Placement of a temporary crown prior to root canal therapy, Dent. Survey 53 (1977) 31-33. A gingival line fracture of an anterior tooth presents problems of isolation for root canal therapy and temporary restoration. A technique is described which solves both problems. The root face is prepared to receive a crown and the orifice of the root canal is enlarged with a No. 8 round bar to receive a hollow sprue pin. A straightened paper clip is inserted into the root canal orifice to act as a guide for the sprue pin. A hole is made in a temporary polycarbonate crown to receive the sprue pin, the crown filled with a thick acrylic and the crown seated on the prepared root end. After trimming of excess acrylic the crown is cemented in place and routine endodontic therapy carried out through the sprue pin. Andrew Richardson
DENTAL
EDUCATION
GUILD R. E. Self instruction in dentistry: a critique, J. Dent Educ. 41 (1977) 239-247. This paper is prompted by recent activity and interest in self-instruction methods in dentistry. Tape/slide sequences are a useful means of presenting information, but the great majority do not fulfil the requirements of an effective self-instruction technique. Such a technique demands that stimuli or material should be presented, that a response should be required from the learner and that immediate feedback should be provided as to the correctness of this response. In addition, such a machine should permit selfpacing by the student. The author recommends the use of self-teaching programmes which fulfil all these requirements. J. D. Eccles
DENTAL
MATERIALS
RIDER M., TANNER A. N. and KENNY 8. Investigation of adhesive properties of dental composite materials using an improved tensile test procedure and scanning electron microscopy, J. Dent Res. 56 (1977) 368378. The authors describe a new tens&strength measurement technique which they have used to investigate the adhesion of several dental composites and one polycarboxylate cement to enamel and dentine. Standardized specimens of enamel and dentine were etched with either 50 per cent orthophosphoric acid with 7 per cent zinc oxide or with the etchant supplied for particular resins by the manufacturers. After drying, the specimens were mounted in pairs in a special jig to allow the forma tion of a sandwich of composite between two specimens of enamel or dentine. When setting was complete the specimen was subjected to a tensile load in a testing machine. The scanning electron microscopic appearances were also studied. None of the composite materials showed bonding to dentine although there was resin penetration into tubular spaces. The polycarboxylate did show bonding and the bond strength was reduced by the etching procedure. All the composites were found to bond well to enamel. When ranked by bond strength Concise was best and HL72 the poorest. No significant difference was noted between the tensile bond strength for Concise alone and that with an intermediate unfilled resin layer. G. A. Smith
EtVDODONTlCS ROWE A. H. R. and BINNIE W. H. The incidence and location of microorganisms following endodontic treatment, Br. Dent J. 142 (1977) 91-95. The purpose of the investigation was to determine the incidence of micro-organisms in root canals, dentine, cementurn and apical tissues following root filling with a variety of materials.