Five-year study of cervical erosions restored with resin and dentin-bonding agent
Erik Keith Hansen Department of Dental Materials and Technology, Royal Dental College, Copenhagen, Denmark
Hansen EK: Five-year study of cervical erosions restored with resin and dentinbonding agent. Scand J Dent Res 1992; 100: 244-7.
The cumulative retention rate of a microfilled resin in non-undercut cervical abrasion/erosion lesions was studied over a 5-yr period. The enamel was etched and the dentin was pretreated with either Gluma (« = 75) or the first marketed version of Scotchbond (« = 30). The cumulative 5-yr retention rate of the Gluma fillings was 90% and that of the Scotchbond fillings 47% (the 95% confidence limits were 83-98% for Gluma fillings and 27-67% for Scotchbond fillings). The retention rate with both bonding agents was significantly higher in the maxillary arch than in the mandibular arch.
During the last few years, many clinical studies have been published on the retention rate of composite resins in cervical erosion/abrasion lesions pretreated with a dentin-bonding agent (1-18). The results obtained in most of these trials show that the quality of many proprietary dentin-bonding agents is questionable since substantial early failures have been reported (1-7, 10-17). There are, however, recent studies which show very high retention rates with the new generation of dentinbonding agents (7-10, 12, 16, 18). The purpose of this clinical study was to evaluate the 5-yr cumulative retention rate of a light-activated microfilled resin used to restore cervical abrasion/erosion lesions without mechanical retention, but with dentin-bonding and enamel etching. The 3-yr results have been published previously (12).
Material and methods
Over an 18-month period, 105 cervical erosions in vital teeth were restored with a light-activated microfilled resin (Silux, 3M, St. Paul, MN, USA) and a dentin-bonding agent: either Gluma (Bayer, Leverkusen, Germany) or the self-cured, first marketed version of Scotchbond Dental Adhesive (3M). In the following, the latter bonding agent will be referred to as Scotchbond-1 in order to avoid confusion with the latest version of this adhesive. During the first 6 months of the study, 30 lesions were restored with Silux / Scotchbond-1, and during the following 12 months, 75 lesions were restored
Key words: dental materials; erosion, dental; in vivo study, marginal adaptation Helsingorgade 7, 3400 Hillerod, Denmark Accepted tor publication 3 August 1991
with Silux/Gluma. All restorations were inserted by the author with the following procedures: Cavity preparation - The superficial, saliva-contaminated dentin was removed with a slowly rotating, fine-grained diamond. An 0.5-mm-wide bevel was prepared in the enamel at a 45° angle to the external enamel surface. Apart from this, no further preparation was used; that is, the cavities were not undercut. No rubberdam was applied. Gluma - The freshly cut dentin in the erosion was rubbed for 10 s with a cotton pellet soaked in Gluma Cleanser. The cavity was then rinsed and dried, both for 10 s. Following this, the beveled enamel was etched for 60 s, rinsed with water for 30 s, and dried for 10 s. After this, Gluma was applied, and 10 s later the cavity was dried with compressed air until the dentin and the etched enamel looked completely dry. The primed dentin and the etched enamel was covered with a lowviscosity resin (Silux Enamel Bond, 3M), and as much as possible of this resin was blown out of the cavity until the dentin had a slightly oily look. The restorative resin and the low-viscosity resin were polymerized simultaneously for 40 s with a visible-light curing unit (3M/LC Lamp, 3M, Denmark). Scotchbond-] - According to the manufacturer, the smear layer should not be removed before this dentin-bonding agent is applied. However, in a previous in vitro study, a slight but statistically significant improvement in marginal adaptation was found when the smear layer was partly removed by an 0.05% EDTA solution with a pH of approximately 3 (19). Therefore, half the cavities were cleaned with this EDTA solution while the
In vivo dentin-bonding other half were treated with copious water spray. The use of water spray and EDTA was randomized. After application of the bonding agent, a gentle stream of air was used to spread the adhesive and to evaporate the solvent. The restorative resin was then applied and polymerized as described under "Gluma". Polishing - All Scotchbond-1 restorations were finished within 5-15 min, whereas poHshing of the gingival area of the 75 Gluma fillings was postponed for at least 1 day; the reason for handling Scotchbond-1 and Gluma restorations in different ways has been discussed previously (12). Statistics - The patients were recalled approximately every 6 months, making it possible to register whether any restoration had been lost since the last recall. The survival time was arranged into intervals of 6 months, and for each interval the effective number of exposed restorations was calculated. The cumulative retention rate of Gluma fillings and of Scotchbond-1 fillings was analyzed with life tables and log-rank tests at the 5% level of significance (20). All analyses were carried out with a computerized statistical program (MEDSTAT, version 2.1, Astra, Copenhagen, Denmark). Results
During the study, 11 Gluma fillings and 4 Scotchbond-1 fillings were withdrawn or lost to followup: four teeth were crowned, one patient died (three fillings), one tooth was extracted because of periodontal problems, and one tooth fractured. A further three patients (six fillings) moved to another part of the country and were lost to followup. The lower part of Table 1 shows that the Scotchbond-1 fillings, the cavities of which had been cleaned with the weak EDTA solution, did not have a better 5-yr survival rate than the Scotchbond-1 fillings where the cavities had been cleaned with water spray; the log-rank test, which was used to compare the overall structure of the two survival
Table 1 Cumulative survival rates for Gltinia and for Seotelihond-1 fillings: 95% cottfidenee limits in parentheses Cumulative survival rate (%) DB' 3yr 4 yr 5yr GL 96 (91-100) 95 (89-100) 90 (83-98) SC 66 (49-83) 47 (27-67) 55 (37-74) SC/EDTA 80 (61-99) 58 (32-84) 50 (22-78) SC/water 52 (28-75) 52 (28-75) 43 (15-72) ' GL = Gluma. SC = Scotchbond.
CUMULATIVE RETENTION RATE
% 100
245 ' ,
75
50
25
1
5 YEARS Fig. 1. Cumulative retention rate for Gluma fillings (GL) and Scotchbond-1 fillings (SC).
curves, gave a /"-value of 0.51. The two sets of Scotchbond data were therefore pooled. The cumulative 5-yr survival rate for the Gluma fillings and the pooled Scotchbond-1 fillings are depicted in Fig. 1. After 5 yr, 90% of the Gluma fillings survived in contrast to 47% of the Scotchbond-1 fillings: the 95% confidence limits are seen in Table 1. One may argue that the dropouts make the 5-yr retention rates shown in Fig. 1 questionable, but life table analyses handle this problem by increasing the confidence limits, i.e., one must assess the 5-yr retention rate depicted in Fig. 1 on the basis of the confidence limits shown in Table 1. With both dentin-bonding agents, there was a highly significant trend (P< 0.005): the retention rate was highest in the maxillary incisor/canine region, followed by the maxillary premolar area, the mandibular incisor/canine region, and lastly the mandibular premolar area (Table 2). It should be mentioned that ISO 3950 (Table 2, second footnote) is the new designation system for teeth and areas of the oral cavity (previously called Viohl's two-digit system). Table 2 Cumulative 5-yr retention rate vs looth position Cumulative Tooth survival rate DB' GL
II, 12, 13 14, 15 41,42,43 44,45 SC 11, 12, 13 14, 15 1, 42, 43 44,45 ' GL = Gluma. SC = Scotchbond-1. - ISO 3950.
100 91 86
56 75 40 27 0
246
Hansen Table 4
Discussion There was no statistically significant difference between the 5-yr retention rates of Scotchbond-1 fillings in cavities treated with water spray and cavities treated with the weak EDTA-solution (Table 1). There may be two explanations: either the in vitro test (19) does not reflect the clinical conditions, or the bond strength mediated by Scotchbond-1 is so poor that even part removal of the smear layer does not improve the long term retention rate obtained with this bonding agent. The low retention rate of the pooled Scotchbond-1 fillings in the present study is in good agreement with other trials where this bonding agent has been tested; the general pattern in long term studies has been a 3-yr retention rate of approximately 60%, regardless of the enamel being etched or the pohshing postponed (7, 12, 13, 17). With such a high failure rate, Scotchbond-1 must be categorized as a poor dentin-bonding agent; and the same applies to other first generation "adhesives" (3, 5-7, 14, 16, 17). Both from the patient's and from the dentist's point of view, it is in no way acceptable that four proprietary dentin-bonding agents have shown a 1-yr retention rate as low as 0-17% (3, 5, 6). As to Gluma, the clinical results with this dentinbonding agent are extremely varying (Table 3). In cavities with non-etched enamel, VANHERLE et al. obtained a 2-yr retention rate of 33% (VANHERLE, personal communication) while the 2-yr retention rate found by VAN DIJKEN was 86%, i.e. two and a half times higher (18). One should compare these two studies with results obtained by TYAS (16) and by HoRSTED-BiNDSLEV et al. (7): VANHERLE et al. used Gluma in combination with a hybrid resin, Lumifor; in 95% of the cases, the final polishing was done at the placement visit (VANHERLB, personal communication). TYAS (16) used the same restorative material, but postponed the final polishing. The 2-yr retention rate obtained by TYAS was 64%, i.e. nearly twice as high as that Table 3 Two-year retention rates with Gluma in cervical abrasion/erosion lesions without mechanical retention or enamel etching Cumulative Postponed Restorative retention Authors polishing resin rate (2-yr) _ VANHERLE et al. (10) 33% Lumifor' TYAS (5) + Lumifor' 64% HORSTED-BlNDSLEV
al. (7) VAN DlIKEN (17)
' Hybrid resin. ^ Microfilled resin.
et
+ +
Pekalux" Silux-
77% 86%
Two-year retention rates in cervical abrasion/erosion lesions with and without enamel etching Two-yr retention rates (%) Adhesive/resin No etching Etching 98 Clearfil New Bond/Clearfil Ray' 79 Gluma/Lumifor' 93 33 __ Gluma/Lumifor.: 64 Gluma/Lumifor^ 100 Gluma/Pekalux' 100 11 Gluma/Silux"* — 97 Gluma/Silux' _ 86 100 Scotchbond 2/Silux Plus' 88 ' VANHERLE et at. (personal communication). " TYAS (16). ^
"
.
:
•
'
.
' HORSTED-BlNDSLEV et al. (7). * HANSEN (12).
^ VAN DtJKEN (18).
found by VANHERLE et al. HORSTED-BINDSLEV et al (7) used Gluma in combination with a microfilled resin, Pekalux; they also postponed the polishing, and their 2-yr retention rate was 77%. Finally, VAN DIJKEN, with postponed polishing and the microfilled resin, Silux, as restorative resin, obtained a 2-yr retention rate of 86% (18). There may be two explanations for the very pronounced discrepancy between the retention rates in these four studies: 1) Postponed polishing seems to be of no importance when it comes to the first generation of dentin-bonding agents, but it may be an essential variable for the new generation of adhesives (21). Final polishing at the placement visit could be one reason for the low retention rate found by VANHERLE et al. compared to that found by TYAS who, apart from the polishing, seems to have used the same restorative procedures (Table 3). 2) Even the improved second generation of dentin-bonding agents does not have the same gapreducing efficacy with heavily filled restoratives as with microfilled resins (22). In our laboratories, we have tested the gap-reducing efficacy of Gluma and of Scotchbond 2 with more than 30 different composite resins. With both adhesives, we found the smallest marginal gap with Silux as restorative resin, followed by Pekalux; and the results obtained with both Silux and Pekalux were better than those obtained with Lumifor. The choice of restorative resin in clinical trials may therefore be another important variable (Table 3). Concluding this part of the study, it is difficult to compare the retention rates mediated by dentinbonding agents in clinical trials. One of the reasons may be that the polishing procedures and the choice of restorative resin is not specified in the ADA acceptance program for dentinal adhesives. According to the ADA requirements, dentinbonding agents must be tested in cervical erosions without mechanical retention or enamel etching.
In vivo dent in-bonding The ADA acceptance program for dentinal adhesives grants a provisional acceptance after 6 months if 95% of the fillings are retained, and a full acceptance after 2 yr if at least 80% are retained. But a 2-yr retention rate of 80% seems to be much too low; a dentinal adhesive should not be considered acceptable if 1 out of 5 fillings is lost within just 2 yr. In contrast to the first generation of adhesives, the retention rate with dentin-bonding agents from the second generation can be markedly improved if the enamel is etched, as done in this study where the 2-yr retention rate with Gluma/Silux was 97% and the 5-yr retention rate 90%. The improved retention rate after acid-etching of the adjacent enamel has been confirmed in several studies where the new generation of adhesives has been tested in cervical abrasion/erosion lesions with and without enamel etching (Table 4). Finally, the retention rate vs the position of the restored tooth should be addressed (Table 2). ZIEMiECKi et al. (23) seem to be the first to mention this relationship; they found that "Retention was 6% higher in the maxillary arch than in the mandibular arch at 6 months, and 14.9% higher at 12 months". The present study confirms this observation of ZiEMiECKi et al. (23). The trend shown in Table 2 may reflect an increasing difficulty with humidity and especially saliva control. If other authors find the same relationship between tooth position and retention rate, future studies should specify the location of the restored teeth. Actcnowtedgment - This paper was supported by the Research Foundation of the Danish Dental Association. ,
Clinical investigation of dental adhesive systems. Part I: An in vivo study. / Prosthet Dent 1986; 55: 157-63. 5. TYAS MJ. Clinical evaluation of two materials for the bonding of composite resins lo dentine: one-year results. Aust DentJ 1988; 33: 5-8. 6. TYAS MJ. Clinical performance of three dentine bonding agents in Class V abrasion lesions without enamel etching. Aust Dent J 1988; 33: 177-80. 7. HORSTED-BINDSLEV P, KNUDSEN J, BAELUM V. Dentin adhe-
sive materials for restoration of cervical erosions. Two and three year clinical observations. Am J Dent 1988; 1: 195-9, Special Issue. 8. JORDAN RE, SUZUKI M , MACLEAN DF. Early clinical eval-
uation of Tenure and Scotchbond 2 for conservative restoration of cervical erosion lesions. J Esttietie Dentistry 1989; 1: 10-3. 9. DUKE ES, ROBBINS JW, SNYDER DE. Dentin adhesive eval-
uation for restoring cervical abrasions and root caries. J Dent Res 1989; 68: 206, Abstr. No. 199. 10. VANHERLE G , LAMBRECHTS P, BRAEM M . In-vivo retention
rate of cervical composite restorations. / Dent Res 1989; 68: Abstr. No. 98. 11. BRAEM M , LAMBRECHTS P, VAN MEERBEEK B, VANHERLE G .
Clinical evaluation of two adhesive promoters in cervical abrasive and/or erosive lesions after six months. J Dent Res 1989; 68: 621, Abstr. No. 99. 12. HANSEN EK. Three-year study of cervical erosions restored with resin and dentin-bonding agent. Aeta Odontot Scand 1989; 47: 301-6. 13. TYAS MJ, BURNS GA, BYRNE P F , CUNNINGHAM PJ, DOBSON
14. 15. 16. 17. 18. 19.
Reference
247
BC, WiDDOP FT. Clinical evaluation of Scotchbond: threeyear results. Aust Dent J 1989; 34: 277-9. TYAS MJ. Clinical evaluation of three dentine bonding agents. Aust Dent J 1989; 34: 559-62. TYAS MJ. Clinical performance of dentine bonding agents in the enamel-etched Class V abrasion lesion. Aust Dent f 1990; 35: 459-62. TYAS MJ. Three year clinical evaluation of dentine bonding agents. Aust Dent J 1991; 36: in press. DiJKHN VAN JWV. The effect of cavity pretreatment procedures on dentin bonding: A four-year clinical evaluation. J Prosttiet Dent 1990; 60: 148-52. DiJKEN VAN JWV. A 3-year evaluation of GLUMA and GLUMA/Scotchbond for restoration of cervical erosions. Scand J Dent Res 1990; 98: 341-4. HANSEN EK. Effect of Scotchbond dependent on cavity cleaning, cavity diameter and cavosurface angle. Scand J Dent Res 1984; 92: 141-7.
20. PETO R , PIKE M C , ARMITAGE O, et at. Design and analysis
1. TvAS MJ, BEECH DR. Clinical performance of three restorative materials for non-undercut cervical abrasion lesions. Aust Dent J 1985; 30: 260^. 2. DENNISON JB, ZiEMiECKi TL, CHARBENEAU GT. Retention
of unprepared cervical restorations utiUzing a dentin bonding agent - two year report. J Dent Res 1986; 65: 173, Abstr. 35. 3. DoERiNG JV, JENSEN ME. Clinical evaluation of dentin bonding materials on cervical "abrasion" lesions. / Dent Res 1986; 65: 173, Abstr. 36. 4. VANHERLE G , VERSCHUEREN M , LAMBRECHTS P, BRAEM M .
of randomized clinical trials requiring prolonged observation of each patient. Br J Cancer 1977; 35: 1-39. 21. HANSEN EK, ASMUSSEN E . Effect of postponed polishing on marginal adaptation of resin used with dentin-bonding agent. Scand J Dent Res 1988; 96: 260-4. 22. HANSEN EK, ASMUSSEN E. Marginal adaptation of posterior resins. Effect of dentin-bonding agent and hygroscopic expansion. Dent Mater 1990; 5: 122-6. 23. ZiEMicKi TL, DENNISON JB, CHARBENEAU GT. Clinical evaluation of cervical composite resin restorations placed without retention. Oper Dent 1987; 12: 27-33.
Erik Keith Hansen Department of Dental Materials and Technology, Royal Dental College, Copenhagen, Denmark
Hansen EK: Five-year study of cervical erosions restored with resin and dentinbonding agent. Scand J Dent Res 1992; 100: 244-7.
The cumulative retention rate of a microfilled resin in non-undercut cervical abrasion/erosion lesions was studied over a 5-yr period. The enamel was etched and the dentin was pretreated with either Gluma (« = 75) or the first marketed version of Scotchbond (« = 30). The cumulative 5-yr retention rate of the Gluma fillings was 90% and that of the Scotchbond fillings 47% (the 95% confidence limits were 83-98% for Gluma fillings and 27-67% for Scotchbond fillings). The retention rate with both bonding agents was significantly higher in the maxillary arch than in the mandibular arch.
During the last few years, many clinical studies have been published on the retention rate of composite resins in cervical erosion/abrasion lesions pretreated with a dentin-bonding agent (1-18). The results obtained in most of these trials show that the quality of many proprietary dentin-bonding agents is questionable since substantial early failures have been reported (1-7, 10-17). There are, however, recent studies which show very high retention rates with the new generation of dentinbonding agents (7-10, 12, 16, 18). The purpose of this clinical study was to evaluate the 5-yr cumulative retention rate of a light-activated microfilled resin used to restore cervical abrasion/erosion lesions without mechanical retention, but with dentin-bonding and enamel etching. The 3-yr results have been published previously (12).
Material and methods
Over an 18-month period, 105 cervical erosions in vital teeth were restored with a light-activated microfilled resin (Silux, 3M, St. Paul, MN, USA) and a dentin-bonding agent: either Gluma (Bayer, Leverkusen, Germany) or the self-cured, first marketed version of Scotchbond Dental Adhesive (3M). In the following, the latter bonding agent will be referred to as Scotchbond-1 in order to avoid confusion with the latest version of this adhesive. During the first 6 months of the study, 30 lesions were restored with Silux / Scotchbond-1, and during the following 12 months, 75 lesions were restored
Key words: dental materials; erosion, dental; in vivo study, marginal adaptation Helsingorgade 7, 3400 Hillerod, Denmark Accepted tor publication 3 August 1991
with Silux/Gluma. All restorations were inserted by the author with the following procedures: Cavity preparation - The superficial, saliva-contaminated dentin was removed with a slowly rotating, fine-grained diamond. An 0.5-mm-wide bevel was prepared in the enamel at a 45° angle to the external enamel surface. Apart from this, no further preparation was used; that is, the cavities were not undercut. No rubberdam was applied. Gluma - The freshly cut dentin in the erosion was rubbed for 10 s with a cotton pellet soaked in Gluma Cleanser. The cavity was then rinsed and dried, both for 10 s. Following this, the beveled enamel was etched for 60 s, rinsed with water for 30 s, and dried for 10 s. After this, Gluma was applied, and 10 s later the cavity was dried with compressed air until the dentin and the etched enamel looked completely dry. The primed dentin and the etched enamel was covered with a lowviscosity resin (Silux Enamel Bond, 3M), and as much as possible of this resin was blown out of the cavity until the dentin had a slightly oily look. The restorative resin and the low-viscosity resin were polymerized simultaneously for 40 s with a visible-light curing unit (3M/LC Lamp, 3M, Denmark). Scotchbond-] - According to the manufacturer, the smear layer should not be removed before this dentin-bonding agent is applied. However, in a previous in vitro study, a slight but statistically significant improvement in marginal adaptation was found when the smear layer was partly removed by an 0.05% EDTA solution with a pH of approximately 3 (19). Therefore, half the cavities were cleaned with this EDTA solution while the
In vivo dentin-bonding other half were treated with copious water spray. The use of water spray and EDTA was randomized. After application of the bonding agent, a gentle stream of air was used to spread the adhesive and to evaporate the solvent. The restorative resin was then applied and polymerized as described under "Gluma". Polishing - All Scotchbond-1 restorations were finished within 5-15 min, whereas poHshing of the gingival area of the 75 Gluma fillings was postponed for at least 1 day; the reason for handling Scotchbond-1 and Gluma restorations in different ways has been discussed previously (12). Statistics - The patients were recalled approximately every 6 months, making it possible to register whether any restoration had been lost since the last recall. The survival time was arranged into intervals of 6 months, and for each interval the effective number of exposed restorations was calculated. The cumulative retention rate of Gluma fillings and of Scotchbond-1 fillings was analyzed with life tables and log-rank tests at the 5% level of significance (20). All analyses were carried out with a computerized statistical program (MEDSTAT, version 2.1, Astra, Copenhagen, Denmark). Results
During the study, 11 Gluma fillings and 4 Scotchbond-1 fillings were withdrawn or lost to followup: four teeth were crowned, one patient died (three fillings), one tooth was extracted because of periodontal problems, and one tooth fractured. A further three patients (six fillings) moved to another part of the country and were lost to followup. The lower part of Table 1 shows that the Scotchbond-1 fillings, the cavities of which had been cleaned with the weak EDTA solution, did not have a better 5-yr survival rate than the Scotchbond-1 fillings where the cavities had been cleaned with water spray; the log-rank test, which was used to compare the overall structure of the two survival
Table 1 Cumulative survival rates for Gltinia and for Seotelihond-1 fillings: 95% cottfidenee limits in parentheses Cumulative survival rate (%) DB' 3yr 4 yr 5yr GL 96 (91-100) 95 (89-100) 90 (83-98) SC 66 (49-83) 47 (27-67) 55 (37-74) SC/EDTA 80 (61-99) 58 (32-84) 50 (22-78) SC/water 52 (28-75) 52 (28-75) 43 (15-72) ' GL = Gluma. SC = Scotchbond.
CUMULATIVE RETENTION RATE
% 100
245 ' ,
75
50
25
1
5 YEARS Fig. 1. Cumulative retention rate for Gluma fillings (GL) and Scotchbond-1 fillings (SC).
curves, gave a /"-value of 0.51. The two sets of Scotchbond data were therefore pooled. The cumulative 5-yr survival rate for the Gluma fillings and the pooled Scotchbond-1 fillings are depicted in Fig. 1. After 5 yr, 90% of the Gluma fillings survived in contrast to 47% of the Scotchbond-1 fillings: the 95% confidence limits are seen in Table 1. One may argue that the dropouts make the 5-yr retention rates shown in Fig. 1 questionable, but life table analyses handle this problem by increasing the confidence limits, i.e., one must assess the 5-yr retention rate depicted in Fig. 1 on the basis of the confidence limits shown in Table 1. With both dentin-bonding agents, there was a highly significant trend (P< 0.005): the retention rate was highest in the maxillary incisor/canine region, followed by the maxillary premolar area, the mandibular incisor/canine region, and lastly the mandibular premolar area (Table 2). It should be mentioned that ISO 3950 (Table 2, second footnote) is the new designation system for teeth and areas of the oral cavity (previously called Viohl's two-digit system). Table 2 Cumulative 5-yr retention rate vs looth position Cumulative Tooth survival rate DB' GL
II, 12, 13 14, 15 41,42,43 44,45 SC 11, 12, 13 14, 15 1, 42, 43 44,45 ' GL = Gluma. SC = Scotchbond-1. - ISO 3950.
100 91 86
56 75 40 27 0
246
Hansen Table 4
Discussion There was no statistically significant difference between the 5-yr retention rates of Scotchbond-1 fillings in cavities treated with water spray and cavities treated with the weak EDTA-solution (Table 1). There may be two explanations: either the in vitro test (19) does not reflect the clinical conditions, or the bond strength mediated by Scotchbond-1 is so poor that even part removal of the smear layer does not improve the long term retention rate obtained with this bonding agent. The low retention rate of the pooled Scotchbond-1 fillings in the present study is in good agreement with other trials where this bonding agent has been tested; the general pattern in long term studies has been a 3-yr retention rate of approximately 60%, regardless of the enamel being etched or the pohshing postponed (7, 12, 13, 17). With such a high failure rate, Scotchbond-1 must be categorized as a poor dentin-bonding agent; and the same applies to other first generation "adhesives" (3, 5-7, 14, 16, 17). Both from the patient's and from the dentist's point of view, it is in no way acceptable that four proprietary dentin-bonding agents have shown a 1-yr retention rate as low as 0-17% (3, 5, 6). As to Gluma, the clinical results with this dentinbonding agent are extremely varying (Table 3). In cavities with non-etched enamel, VANHERLE et al. obtained a 2-yr retention rate of 33% (VANHERLE, personal communication) while the 2-yr retention rate found by VAN DIJKEN was 86%, i.e. two and a half times higher (18). One should compare these two studies with results obtained by TYAS (16) and by HoRSTED-BiNDSLEV et al. (7): VANHERLE et al. used Gluma in combination with a hybrid resin, Lumifor; in 95% of the cases, the final polishing was done at the placement visit (VANHERLB, personal communication). TYAS (16) used the same restorative material, but postponed the final polishing. The 2-yr retention rate obtained by TYAS was 64%, i.e. nearly twice as high as that Table 3 Two-year retention rates with Gluma in cervical abrasion/erosion lesions without mechanical retention or enamel etching Cumulative Postponed Restorative retention Authors polishing resin rate (2-yr) _ VANHERLE et al. (10) 33% Lumifor' TYAS (5) + Lumifor' 64% HORSTED-BlNDSLEV
al. (7) VAN DlIKEN (17)
' Hybrid resin. ^ Microfilled resin.
et
+ +
Pekalux" Silux-
77% 86%
Two-year retention rates in cervical abrasion/erosion lesions with and without enamel etching Two-yr retention rates (%) Adhesive/resin No etching Etching 98 Clearfil New Bond/Clearfil Ray' 79 Gluma/Lumifor' 93 33 __ Gluma/Lumifor.: 64 Gluma/Lumifor^ 100 Gluma/Pekalux' 100 11 Gluma/Silux"* — 97 Gluma/Silux' _ 86 100 Scotchbond 2/Silux Plus' 88 ' VANHERLE et at. (personal communication). " TYAS (16). ^
"
.
:
•
'
.
' HORSTED-BlNDSLEV et al. (7). * HANSEN (12).
^ VAN DtJKEN (18).
found by VANHERLE et al. HORSTED-BINDSLEV et al (7) used Gluma in combination with a microfilled resin, Pekalux; they also postponed the polishing, and their 2-yr retention rate was 77%. Finally, VAN DIJKEN, with postponed polishing and the microfilled resin, Silux, as restorative resin, obtained a 2-yr retention rate of 86% (18). There may be two explanations for the very pronounced discrepancy between the retention rates in these four studies: 1) Postponed polishing seems to be of no importance when it comes to the first generation of dentin-bonding agents, but it may be an essential variable for the new generation of adhesives (21). Final polishing at the placement visit could be one reason for the low retention rate found by VANHERLE et al. compared to that found by TYAS who, apart from the polishing, seems to have used the same restorative procedures (Table 3). 2) Even the improved second generation of dentin-bonding agents does not have the same gapreducing efficacy with heavily filled restoratives as with microfilled resins (22). In our laboratories, we have tested the gap-reducing efficacy of Gluma and of Scotchbond 2 with more than 30 different composite resins. With both adhesives, we found the smallest marginal gap with Silux as restorative resin, followed by Pekalux; and the results obtained with both Silux and Pekalux were better than those obtained with Lumifor. The choice of restorative resin in clinical trials may therefore be another important variable (Table 3). Concluding this part of the study, it is difficult to compare the retention rates mediated by dentinbonding agents in clinical trials. One of the reasons may be that the polishing procedures and the choice of restorative resin is not specified in the ADA acceptance program for dentinal adhesives. According to the ADA requirements, dentinbonding agents must be tested in cervical erosions without mechanical retention or enamel etching.
In vivo dent in-bonding The ADA acceptance program for dentinal adhesives grants a provisional acceptance after 6 months if 95% of the fillings are retained, and a full acceptance after 2 yr if at least 80% are retained. But a 2-yr retention rate of 80% seems to be much too low; a dentinal adhesive should not be considered acceptable if 1 out of 5 fillings is lost within just 2 yr. In contrast to the first generation of adhesives, the retention rate with dentin-bonding agents from the second generation can be markedly improved if the enamel is etched, as done in this study where the 2-yr retention rate with Gluma/Silux was 97% and the 5-yr retention rate 90%. The improved retention rate after acid-etching of the adjacent enamel has been confirmed in several studies where the new generation of adhesives has been tested in cervical abrasion/erosion lesions with and without enamel etching (Table 4). Finally, the retention rate vs the position of the restored tooth should be addressed (Table 2). ZIEMiECKi et al. (23) seem to be the first to mention this relationship; they found that "Retention was 6% higher in the maxillary arch than in the mandibular arch at 6 months, and 14.9% higher at 12 months". The present study confirms this observation of ZiEMiECKi et al. (23). The trend shown in Table 2 may reflect an increasing difficulty with humidity and especially saliva control. If other authors find the same relationship between tooth position and retention rate, future studies should specify the location of the restored teeth. Actcnowtedgment - This paper was supported by the Research Foundation of the Danish Dental Association. ,
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