Finishing techniques for amalgam restorations: Clinical assessment at three years Roland W. Bryant* Catherine J. Collinst
Key words: Amalgam restorations: clinical technique and performance. Abstract Use of the optimum finishing technique for an amalgam restoration may enhance the marginal integrity of the restoration and discourage its unnecessary early replacement. Two hundred and twenty-eight high copper amalgam restorations in 56 patients were evaluated, using clinical assessment criteria, up to three years after placement. Each patient had received at least one carved-only amalgam, at least one immediately finished restoration, and at least one amalgam that was polished at a subsequent appointment. Regardless of the finishing technique, the restorations exhibited similar marginal integrity up to three years after placement. Polished restorations were found to have substantially superior surface texture and less likelihood of surface discoloration. No evidence was found to support the use of immediate finishing techniques. The clinical significance of these findings, with respect to the need to polish amalgam restorations, is discussed. (Received for publication July 1991. Accepted September 199 1.)
Introduction Within the context of the need to minimize intervention, or the unnecessary early replacement of
*Associate Professor and Head, Department of Operative Dentistry, The University of Sydney. ?Registrar, Department of Clinical Dentistry, Westmead Hospital Dental Clinical School. Australian Dental Journal 1992;37(5):333-9
amalgam restorations, the influence of the finishing technique may be of clinical significance. Marginal fracture or poor marginal adaptation and integrity does not, per se, indicate replacement. However, clinicians have a natural wish and responsibility to minimize the patient’s need to return between ‘check-ups’ because of symptoms. This is one possible explanation for the finding by Nuttall and Elderton’ that nearly 60 per cent of amalgam restorations are replaced, despite the absence of explicit failure, because of doubt in the mind of the clinician about the integrity of the margin or doubt about the presence of recurrent caries. The three amalgams shown in Fig. 1 represent a range of marginal deterioration and identify the dilemma that may confront the clinician with respect to intervention. One of the principal aims of clinical technique should be to enhance the quality and appearance of the restoration so that, at a future time, unnecessary replacement is not encouraged. In this context, should the amalgam restoration be polished? This paper reports and discusses the findings from the clinical assessment of amalgam restorations that were finished in one of three ways.
Materials and method Two hundred and seventy-seven amalgam restorations$ were placed by one operator in 66 patients, of average age 16.9 years, each of whom required at least three Class I or I1 restorations in permanent teeth. Occlusal cavities had essentially vertical or slightly undercut walls, to provide retention, as this was the recommended technique at the time. According to the depth of the cavity, amount of base required and previous history of the tooth, STyrin, BN6828509. S. S. White, Philadelphia, PA, USA.
333
Fig. 1. -Three amalgam restorations exhibiting different amounts of marginal fracture.
deeper cavities received a quick-setting base/lining of either the zinc oxide-eugenol type8 or the calcium hydroxide type. 1 Each patient received at least three amalgam restorations. At least one restoration was carvedonly (code C), at least one was immediately finished (code I), and at least one restoration was polished (code P). Restorations were systematically allocated specific finishing techniques in a way that minimized the influence of tooth type and position, and restoration class and size. Before carving, the restorations were burnished to maximize adaptation. After the occlusion had been adjusted and carving completed, the operator was advised (by reference to the allocation form) which one of the three finishing techniques had been allocated for that restoration. Until this stage the operator, who had not been involved in allocating the techniques, was unaware which finishing technique was to be used. It was observed that, on average, proximo-occlusal restorations required at least one more capsule of amalgam and more time to place the amalgam than occlusal restorations. For this reason, immediate finishing (I) commenced eight minutes after trituration of the amalgam for Class I restorations and 10 minutes after trituration for Class I1 restorations. Fluoride-containing zirconium silicate pastel was used in unwebbed rubber cups in a low speed handpiece for a maximum of 90 seconds. At a subsequent appointment, restorations allocated for polishing (P)
were completed using tungsten carbide finishing burs and rubber polishing points.** At recall, the restorations were assessed clinically using modified based principally on those developed at the University of Michigan,2 for marginal adaptation, surface discoloration, surface texture and secondary (recurrent) caries (Table 1) and patients were asked to report any unacceptable sensitivity to thermal stimuli. Each clinical evaluation was carried out by any two of three clinicians. The two evaluators assessed independently. In the event of disagreement, a decision was reached by immediate re-examination and discussion. Differences among techniques were compared using the chi-square test.5 Written patient consent was obtained at the start of the project and the protocol was approved by the Human Ethical Research Committee of Westmead Hospital, Westmead, New South Wales, Australia.
5Kalsogen. De Trey, Weybridge, Surrey, England 1)Dycal.CaulklDentsply, Milford, DE, USA.
1Floran. Creighton Pharmaceuticals, Sydney, NSW, Australia **Shofu Dental Corporation, Menlo Park, CA, USA.
334
Results Of the original 66 patients in whom 277 restorations were placed, the data for five patients have been excluded from the results because these patients attended only one of the three recalls. All other patients attended at least two of the three recalls. The effective patient and restoration database, indicating the number of restorations available for clinical assessment, is shown in Table 2.
Australian Dental Journal 1992;37:5.
Table 1. Criteria for clinical evaluation*
Table 3. Clinical assessment of marginal adaptation
A. Marginal adaptation Clinical criteria
Rating 0
1
2 3 4 5
Finishing technique code
Amalgam is continuous with adjacent tooth structure. Margin not detectable with a sharp probe passing in either direction. Margin defect detectable by probe only - along less than 50% of margin. (No visible evidence of crevice - no exposure of cavity wall). Margin defect detectable by probe only - along more than 50% of margin. Visible evidence of a crevice (with cavity wall exposed) into which the probe will penetrate - along less than 50% of margin. Visible evidence of a crevice into which the probe will penetrate - along more than 50% of margin. Crevice formation with exposure of underlying dentine or base.
Rating
C
0 1
2 3 0 1 2 3 0 1 2 3
I
P
Number of restorations exhibiting rating for marginal adaptation at each recall 1-year
2-year
3-year
0 16 52 17
0 16 52 17 0 22 42 18 0 35 36 11
0 22 38 18 0 23 36 15 0 35 22 19
0
16 44 21 0 22 46 15
B. Surface discoloration Rating 0 1
2 3
Clinical criteria
The principal reason for loss of patients from the study was their moving away from the locality, with no forwarding address. Data from several patients were lost, despite the patients’ availability, because it was required that at least one restoration of each type of finishing technique should be available for assessment in each patient. For example, several patients were ‘lost’ from the study because of urgent orthodontic extraction or inadvertent polishing of technique I or C restorations by another dental officer at the hospital. Although data from 60 patients were able to be included for the 1-year and 2-year recalls, two patients attended only one of these two recalls. Table 3 presents the findings of the clinical assessment of marginal adaptation. At the 1-year recall and at subsequent recalls, every amalgam restoration exhibited clinically detectable margins regardless of finishing technique. The percentage of restorations with visible evidence of a crevice varied between 13 and 25 per cent during the period of one to three years after placement. For each
Still reflective; no colour change. Light grey (slight discoloration) or ‘coppery’; nonreflective. Dull grey - dark (localized or generalized). Black - dark grey.
C. Surface texture Rating 0 1 2
3
Clinical criteria
No roughness - glossy. Slight roughness - fine granules - ‘satin’ texture’. Obvious roughness andlor scratches andlor coarse granules (granular). Very rough andlor pitted.
D. Recurrent marginal caries Rating 0
1
Clinical criteria There is no evidence of caries contiguous with the margin of the restoration. There is evidence of caries contiguous with the margin of the restoration.
*Modified criteria based on Straffon er a/.,2 Cvar and Ryge,3 and Fenton and S r n a l e ~ . ~
Table 2. Number of restorations available for inclusion in the clinical assessment at the 1-year, 2-year and 3-year recalls Average time since placement (months) Baseline 1-year 2-year 3-year
Number of patients
12.9 24.3 36.3
Australian Dental Journal 1992;37:5.
66 60 60 56
Total number of restorations available for assessment
Number of restorations evaluated for each Finishing technique C
I
P
277 249 249
94 85 85
91 81
83
228
78
82 74
82 76
92
335
Fig. 2.-Carved-only restorations. Small amount of marginal fracture at 3 years (a), compared with baseline (b). Large amount of marginal fracture at 3 years (c), compared with baseline (d).
Table 4. Clinical assessment of surface discoloration Finishing technique code
C
Rating
0 1
2 3
I
P
0 1 2 3 0 1 2 3
Number of restorations exhibiting rating for surface discoloration at each recall 1-year
2-year
3-year
65 19 1 0
40
35
36 9 0
36 7 0
53
41
27
31 10 0
31 33
1
0 65 17 1 0
54 26 2 0
10 0 48 25
2 1
finishing technique, there was a wide range of marginal fracture or loss of marginal adaptation evident by three years (Fig. 2, 3). 336
The findings for the clinical assessment of surface discoloration are shown in Table 4. The most commonly observed discoloration was either a ‘coppery tinge’ to all the amalgam restorations in the patient’s mouth or evidence of localized or generalized light grey darkening on the occlusal surfaces of the restorations. Although differences among techniques were not statistically significant at 1-year, at the 2-year and 3-year recalls a significantly greater number of polished restorations, compared with technique C and I restorations, were assessed as still showing no evidence of surface discoloration (P < 0.05, x2 = 7.04, df = 2). At each recall, the polished restorations exhibited superior surface texture to restorations that were carved-only or immediately finished (Table 5). At the 3-year recall, 87 per cent of polished restorations were rated as having smooth texture compared with only 8 per cent and 16 per cent of technique C and I restorations, respectively. Australian Dental Journal 1992;37:5.
Fig. 3.-Polished restorations. Small amount of marginal fracture at 3 years (a), compared with baseline (b). Large amount of marginal fracture at 3 years (c), compared with baseline (d).
Table 5. Clinical assessment of surface texture Finishing technique code
C I
P
Rating
0
1 2 0 1 2 0 1 2
Number of restorations exhibiting rating for surface texture at each recall 1-year
2-year
3-year
6 55 24 13 54 14 80 3 0
4 68 13 19 59 4 79 3 0
6 66 6 12 62 0 66 10 0
One restoration (C) required replacement at three years, because of caries at the site of a chipped marginal ridge. Sensitivity was not reported by any of the patients. Australian Dental Journal 1992;37:5
Discussion 1. Factors influencing the clinical assessment of the marginal integrity of occlusal amalgam restorations Regardless of the technique of finishing, the quality of marginal adaptation (crevice formation, chipping) was assessed to have changed relatively little during the period of one to three years after placement. This may be partly attributable to the relatively coarse (but clinically relevant) criteria used to assess changes in marginal adaptation by accepted clinical assessment techniques. Finer discrimination of changes usually requires the use of indirect techniques of assessmentY6such as the use of photographs6 or stone replicas,’ in which higher magnification and greater standardization of recording is available. During the clinical assessment, it was occasionally observed that, at a subsequent recall, the amalgam appeared to have an improved score for marginal adaptation. This may be attributable to 337
'rounding over' of the sharp edge of a fractured amalgam margin during the period of time, to wear of both amalgam and enamel thereby reducing the depth of the marginal defect, or to subjective variation by the assessors. The influence of the patient in clinical studies has been acknowledged.' It was observed in a small number of patients that all the restorations regardless of finishing technique exhibited a relatively large amount of marginal fracture and, in some other patients, that all the restorations exhibited a small amount of marginal fracture. Modified cavity preparation techniques may be particularly indicated in patients with a proven record of exaggerated marginal fracture. These modifications would increase the amalgam margin angle, as suggested by Eldertong and de Vree et al. l o
2. Immediate finishing of amalgam restorations A number of clinical studies have evaluated the technique of immediate finishing, by comparing carved-only and immediate finishing,4.11immediate finishing and delayed polishing,2.12.13 carved-only and delayed p o l i ~ h i n g ' ~ . and ' ~ carved-only, immediate finishing and delayed polishing.'6 Consistent with previously reported findings, this study found no evidence to support the technique of immediate finishing of amalgam restorations. Immediately finished restorations tend to exhibit similar marginal integrity to restorations finished by other techniques, but inferior surface texture and greater surface discoloration compared with polished restorations. This study confirmed the observation" that there is a trend for improvement in the surface texture of some C and I restorations with time. 3. Clinical signficance of the findings Three aspects of the occlusal surface of amalgam restorations were specifically assessed - marginal adaptation or integrity, surface discoloration and surface texture. Using common clinical assessment methods (a probe or explorer, and unmagnified vision), no significant differences were detectable between carved-only and polished restorations in the integrity of the occlusal margins, confirming the findings from a previous small clinical ~ t u d y . The '~ restorations in this current study were placed and finished under optimum conditions so that extrapolation of the results to the wide range of conditions experienced in general dental practice is difficult. 338
By three years, approximately 50 per cent of all restorations showed evidence of surface discoloration. The finding that fewer polished restorations exhibited discoloration was of little consequence because none of the restorations exhibited an amount of discoloration that would require more than a quick polish to remove. Restorations are rarely replaced because of their surface roughness, although patients often express appreciation for the smoothness of a polished restoration. It is most unlikely therefore that the marked superiority in surface texture, exhibited by polished restorations, would be translated into a lower rate of replacement. Although all restorations received a 'pre-carve' burnish, an alternative finishing technique that was not investigated in this study was the 'post-carve' burnish. Use of a pre-carve and post-carve burnishing technique has been found to improve adaptation, reduce marginal leakage and reduce porosity in the surface amalgam17-20 and to achieve a smoother surface finish to that obtained by carving alone." However, post-carve burnishing does increase the likelihood of excess amalgam remaining external to the cavity margin.22When it fractures, this excess amalgam usually also removes some amalgam from the body of the restoration, thereby exposing the cavity wall.23 It is usually recommended that burnished amalgam should be 'finished' and polished on a subsequent appointment to remove the excess amalgam and to achieve a smoother surfacez4and less marginal leakage.25Clinical studies are required to indicate whether subsequent polishing might influence the longevity of burnished restorations. Jeffrey and P i t t P have asked 'to what degree is finishing of amalgams necessary?. Letzel and VrijhoeP4 have questioned whether polishing substantially improves the life of the amalgam restoration. M0ffaYz7 on the basis of long-term clinical studies of the performance of amalgam restorations, has suggested that the finishing of these restorations has no influence on their longevity. Long-accepted reasons for polishing, such as microstructural advantages2*and 'professional pride', may have little influence on the restoration's survival. In summary, of the criteria assessed, only the quality of marginal adaptation (fracture, integrity, deterioration) has been considered to be responsible for the frequent replacement of amalgam restorations. Evidence from this and other studies indicates that, provided the restorations are placed and carved with care, delayed polishing (at least 24 hours after placement) will probably have no influence on the longevity of the restoration. Australian Dental Journal 1992;37:5.
When the clinician chooses to use a technique of post-carve burnishing (and there are good reasons to support this practice), the greater likelihood of excess amalgam remaining beyond the margin probably necessitates finishing/polishing at a subsequent appointment. Further clinical investigation is required to test this hypothesis.
Conclusions 1. Clinical assessment of amalgam restorations up to three years after placement indicated that restorations that are polished at least 24 hours after placement have superior surface texture and somewhat less evidence of surface discoloration than carved-only or immediately finished restorations. 2. During the period from one to three years after placement, the marginal adaptation (integrity) of the restorations was similar, regardless of which of the three finishing techniques had been used. 3. There is no long-term advantage to be gained from the use of the immediate finishing technique compared with the carved-only or delayed polishing techniques. 4. There is mounting evidence to suggest that carefully placed and carved high copper amalgam restorations may enjoy a similar longevity to polished restorations. 5. The effect of post-carve burnishing, without subsequent polishing, on the longevity of the restoration requires clinical investigation. Acknowledgement The authors would like to thank Dr I. Martin, Westmead Hospital Dental Clinical School, for his assistance with the clinical assessment. This research was partly funded by the Australian Dental Research Fund Inc. References 1. Nuttall NM, Elderton RJ. The nature of restorative dental treatment decisions. Br Dent J 1983;154:363-5. 2. Straffon LH, Corpron RE, Dennison J. Clinical study of early polishing of Class I1 amalgam restorations in primary teeth. J Dent Res 1984;63:336:Abstr 1486. 3. Cvar JF, Ryge G. Clinical evaluation of dental restorative materials. San Francisco: US Department of Health, Education and Welfare, 1973. In: Monograph GPO 790-244. Also reported in: Ryge G. Clinical criteria. Int Dent J 1980;30:347-58. 4. Fenton RA, Smales RJ. Immediate-polishedand as-carved Tytin restorations after 12 months. J Dent 1984;12:165-74. 5. Phillips DS. Basic statistics for health science students. San Francisco: Freeman, 1978:123-4. 6. Mahler DB, Marantz RL. Clinical assessments of dental amalgam restorations. Int Dent J 1980;30:327-34. Australian Dental Journal 1992;37:5
7. Bryant RW, Mahler DB, Engle JA. A comparison of methods for evaluating the marginal fracture of amalgam restorations. Dent Mater 1985;1:235-7. 8. Letzel H, Aardening CJMW, Fick JM, Vrijhoef MMA. Tarnish, corrosion, marginal fracture and creep of amalgam restorations: a two-year clinical study. Oper Dent 1978;3:82-92. 9. Elderton RJ. Cavo-surface angles, amalgam margin angles and occlusal cavity preparations. Br Dent J 1984,156:319-24. 10. deVree JHP, Peters MRCB, Plasschaert AJM. The influence of modification of cavity design on distribution of stresses in a restored molar. J Dent Res 1984;63:1217-20. 11. Smales RJ, Fenton RA. Immediate-polishedand as-carved Tytin restorations after three years. J Dent 1985;13:79-83. 12. Corpron R, S t d o n L, Dennison J, Carron S, Asgar K.Clinical evaluation of amalgams polished immediately after insertion: 5 year results. J Dent Res 1984;63:178:Abstr 69. 13. Murrey AJ, Watkins TR. Polishing of amalgams at 30 minutes compared to 24 hours. J Dent Res 1985;64:180 Abstr 49. 14. Letzel H, Vrijhoef MMA. The influence of polishing on the marginal integrity of amalgam restorations. J Oral Rehabil 1984;11:89-94. 15. Mayhew RB, Schmeltzer LD, Pierson WP. Effect of polishing on the marginal integrity of high-copper amalgam restorations. Oper Dent 1986;11:8-13. 16. Bryant RW, Collins CJ. The finishing and early marginal fracture of clinical amalgam restorations. J Dent 1989; 17:111-6. 17. Bauer JB, Wong AY. A study of the parameters of burnishing. J Dent Res 1975;64:179:Abstr 52. 18. Symons AL, Wing G, Hewitt GH. Adaptation of dental amalgam to the cavosurface margin of Class I cavity preparations. J Oral Rehab 1987;14:65-76. 19. Geiger F, Reller U, Lutz F. Burnishing, finishing, and polishing amalgam restorations: A quantitative scanning electron microscopic study. Quintessence Int 1989;20:46 1-8. 20. Icenhower TJ, Arcoria CJ, Wagner MJ. Microleakage in amalgam restorations following burnishing, polishing and time-varied thermocycling. J Dent Res 1990;69: 131:Abstr 180. 21. Richeson JS, Sarrett DC. Profilometric and scanning electron microscopic analyses of amalgam polishing techniques. Gen Dent 1986;34:481-5. 22. Bryant RW. Finishing techniques for high copper amalgam restorations. A laboratory study. J Dent Res 1988;67:633: Abstr 66. 23. Mahler DB, Terkla LG. Relationship of cavity design to restorative materials. Dent Clin North Am 1965;9: 149-57. 24. Chan KC, Edie JW, Boyer DB. Microstructure of amalgam surfaces. J Prosthet Dent 1976;36:644-8. 25. Geiger F, Reller U, Lutz F. Burnishing, finishing and polishing amalgam restorations: A quantitative SEM study. J Dent Res 1987;66:329:Abstr 1781. 26. Jeffrey IWM, Pitts NB. Finishing of amalgam restorations: to what degree is it necessary? J Dent 1989;17:55-60. 27. Moffa JP. The longevity and reasons for replacement of amalgam alloys. J Dent Res 1989;68:188:Abstr 56. 28. Wing G. Clinical use of spherical particle amalgams. Aust Dent J 1970;15:185-92.
Address for correspondence/reprints: Department of Operative Dentistry, Faculty of Dentistry, University of Sydney, Westmead Hospital Dental Clinical School, Westmead, New South Wales, 2145. 339
Key words: Amalgam restorations: clinical technique and performance. Abstract Use of the optimum finishing technique for an amalgam restoration may enhance the marginal integrity of the restoration and discourage its unnecessary early replacement. Two hundred and twenty-eight high copper amalgam restorations in 56 patients were evaluated, using clinical assessment criteria, up to three years after placement. Each patient had received at least one carved-only amalgam, at least one immediately finished restoration, and at least one amalgam that was polished at a subsequent appointment. Regardless of the finishing technique, the restorations exhibited similar marginal integrity up to three years after placement. Polished restorations were found to have substantially superior surface texture and less likelihood of surface discoloration. No evidence was found to support the use of immediate finishing techniques. The clinical significance of these findings, with respect to the need to polish amalgam restorations, is discussed. (Received for publication July 1991. Accepted September 199 1.)
Introduction Within the context of the need to minimize intervention, or the unnecessary early replacement of
*Associate Professor and Head, Department of Operative Dentistry, The University of Sydney. ?Registrar, Department of Clinical Dentistry, Westmead Hospital Dental Clinical School. Australian Dental Journal 1992;37(5):333-9
amalgam restorations, the influence of the finishing technique may be of clinical significance. Marginal fracture or poor marginal adaptation and integrity does not, per se, indicate replacement. However, clinicians have a natural wish and responsibility to minimize the patient’s need to return between ‘check-ups’ because of symptoms. This is one possible explanation for the finding by Nuttall and Elderton’ that nearly 60 per cent of amalgam restorations are replaced, despite the absence of explicit failure, because of doubt in the mind of the clinician about the integrity of the margin or doubt about the presence of recurrent caries. The three amalgams shown in Fig. 1 represent a range of marginal deterioration and identify the dilemma that may confront the clinician with respect to intervention. One of the principal aims of clinical technique should be to enhance the quality and appearance of the restoration so that, at a future time, unnecessary replacement is not encouraged. In this context, should the amalgam restoration be polished? This paper reports and discusses the findings from the clinical assessment of amalgam restorations that were finished in one of three ways.
Materials and method Two hundred and seventy-seven amalgam restorations$ were placed by one operator in 66 patients, of average age 16.9 years, each of whom required at least three Class I or I1 restorations in permanent teeth. Occlusal cavities had essentially vertical or slightly undercut walls, to provide retention, as this was the recommended technique at the time. According to the depth of the cavity, amount of base required and previous history of the tooth, STyrin, BN6828509. S. S. White, Philadelphia, PA, USA.
333
Fig. 1. -Three amalgam restorations exhibiting different amounts of marginal fracture.
deeper cavities received a quick-setting base/lining of either the zinc oxide-eugenol type8 or the calcium hydroxide type. 1 Each patient received at least three amalgam restorations. At least one restoration was carvedonly (code C), at least one was immediately finished (code I), and at least one restoration was polished (code P). Restorations were systematically allocated specific finishing techniques in a way that minimized the influence of tooth type and position, and restoration class and size. Before carving, the restorations were burnished to maximize adaptation. After the occlusion had been adjusted and carving completed, the operator was advised (by reference to the allocation form) which one of the three finishing techniques had been allocated for that restoration. Until this stage the operator, who had not been involved in allocating the techniques, was unaware which finishing technique was to be used. It was observed that, on average, proximo-occlusal restorations required at least one more capsule of amalgam and more time to place the amalgam than occlusal restorations. For this reason, immediate finishing (I) commenced eight minutes after trituration of the amalgam for Class I restorations and 10 minutes after trituration for Class I1 restorations. Fluoride-containing zirconium silicate pastel was used in unwebbed rubber cups in a low speed handpiece for a maximum of 90 seconds. At a subsequent appointment, restorations allocated for polishing (P)
were completed using tungsten carbide finishing burs and rubber polishing points.** At recall, the restorations were assessed clinically using modified based principally on those developed at the University of Michigan,2 for marginal adaptation, surface discoloration, surface texture and secondary (recurrent) caries (Table 1) and patients were asked to report any unacceptable sensitivity to thermal stimuli. Each clinical evaluation was carried out by any two of three clinicians. The two evaluators assessed independently. In the event of disagreement, a decision was reached by immediate re-examination and discussion. Differences among techniques were compared using the chi-square test.5 Written patient consent was obtained at the start of the project and the protocol was approved by the Human Ethical Research Committee of Westmead Hospital, Westmead, New South Wales, Australia.
5Kalsogen. De Trey, Weybridge, Surrey, England 1)Dycal.CaulklDentsply, Milford, DE, USA.
1Floran. Creighton Pharmaceuticals, Sydney, NSW, Australia **Shofu Dental Corporation, Menlo Park, CA, USA.
334
Results Of the original 66 patients in whom 277 restorations were placed, the data for five patients have been excluded from the results because these patients attended only one of the three recalls. All other patients attended at least two of the three recalls. The effective patient and restoration database, indicating the number of restorations available for clinical assessment, is shown in Table 2.
Australian Dental Journal 1992;37:5.
Table 1. Criteria for clinical evaluation*
Table 3. Clinical assessment of marginal adaptation
A. Marginal adaptation Clinical criteria
Rating 0
1
2 3 4 5
Finishing technique code
Amalgam is continuous with adjacent tooth structure. Margin not detectable with a sharp probe passing in either direction. Margin defect detectable by probe only - along less than 50% of margin. (No visible evidence of crevice - no exposure of cavity wall). Margin defect detectable by probe only - along more than 50% of margin. Visible evidence of a crevice (with cavity wall exposed) into which the probe will penetrate - along less than 50% of margin. Visible evidence of a crevice into which the probe will penetrate - along more than 50% of margin. Crevice formation with exposure of underlying dentine or base.
Rating
C
0 1
2 3 0 1 2 3 0 1 2 3
I
P
Number of restorations exhibiting rating for marginal adaptation at each recall 1-year
2-year
3-year
0 16 52 17
0 16 52 17 0 22 42 18 0 35 36 11
0 22 38 18 0 23 36 15 0 35 22 19
0
16 44 21 0 22 46 15
B. Surface discoloration Rating 0 1
2 3
Clinical criteria
The principal reason for loss of patients from the study was their moving away from the locality, with no forwarding address. Data from several patients were lost, despite the patients’ availability, because it was required that at least one restoration of each type of finishing technique should be available for assessment in each patient. For example, several patients were ‘lost’ from the study because of urgent orthodontic extraction or inadvertent polishing of technique I or C restorations by another dental officer at the hospital. Although data from 60 patients were able to be included for the 1-year and 2-year recalls, two patients attended only one of these two recalls. Table 3 presents the findings of the clinical assessment of marginal adaptation. At the 1-year recall and at subsequent recalls, every amalgam restoration exhibited clinically detectable margins regardless of finishing technique. The percentage of restorations with visible evidence of a crevice varied between 13 and 25 per cent during the period of one to three years after placement. For each
Still reflective; no colour change. Light grey (slight discoloration) or ‘coppery’; nonreflective. Dull grey - dark (localized or generalized). Black - dark grey.
C. Surface texture Rating 0 1 2
3
Clinical criteria
No roughness - glossy. Slight roughness - fine granules - ‘satin’ texture’. Obvious roughness andlor scratches andlor coarse granules (granular). Very rough andlor pitted.
D. Recurrent marginal caries Rating 0
1
Clinical criteria There is no evidence of caries contiguous with the margin of the restoration. There is evidence of caries contiguous with the margin of the restoration.
*Modified criteria based on Straffon er a/.,2 Cvar and Ryge,3 and Fenton and S r n a l e ~ . ~
Table 2. Number of restorations available for inclusion in the clinical assessment at the 1-year, 2-year and 3-year recalls Average time since placement (months) Baseline 1-year 2-year 3-year
Number of patients
12.9 24.3 36.3
Australian Dental Journal 1992;37:5.
66 60 60 56
Total number of restorations available for assessment
Number of restorations evaluated for each Finishing technique C
I
P
277 249 249
94 85 85
91 81
83
228
78
82 74
82 76
92
335
Fig. 2.-Carved-only restorations. Small amount of marginal fracture at 3 years (a), compared with baseline (b). Large amount of marginal fracture at 3 years (c), compared with baseline (d).
Table 4. Clinical assessment of surface discoloration Finishing technique code
C
Rating
0 1
2 3
I
P
0 1 2 3 0 1 2 3
Number of restorations exhibiting rating for surface discoloration at each recall 1-year
2-year
3-year
65 19 1 0
40
35
36 9 0
36 7 0
53
41
27
31 10 0
31 33
1
0 65 17 1 0
54 26 2 0
10 0 48 25
2 1
finishing technique, there was a wide range of marginal fracture or loss of marginal adaptation evident by three years (Fig. 2, 3). 336
The findings for the clinical assessment of surface discoloration are shown in Table 4. The most commonly observed discoloration was either a ‘coppery tinge’ to all the amalgam restorations in the patient’s mouth or evidence of localized or generalized light grey darkening on the occlusal surfaces of the restorations. Although differences among techniques were not statistically significant at 1-year, at the 2-year and 3-year recalls a significantly greater number of polished restorations, compared with technique C and I restorations, were assessed as still showing no evidence of surface discoloration (P < 0.05, x2 = 7.04, df = 2). At each recall, the polished restorations exhibited superior surface texture to restorations that were carved-only or immediately finished (Table 5). At the 3-year recall, 87 per cent of polished restorations were rated as having smooth texture compared with only 8 per cent and 16 per cent of technique C and I restorations, respectively. Australian Dental Journal 1992;37:5.
Fig. 3.-Polished restorations. Small amount of marginal fracture at 3 years (a), compared with baseline (b). Large amount of marginal fracture at 3 years (c), compared with baseline (d).
Table 5. Clinical assessment of surface texture Finishing technique code
C I
P
Rating
0
1 2 0 1 2 0 1 2
Number of restorations exhibiting rating for surface texture at each recall 1-year
2-year
3-year
6 55 24 13 54 14 80 3 0
4 68 13 19 59 4 79 3 0
6 66 6 12 62 0 66 10 0
One restoration (C) required replacement at three years, because of caries at the site of a chipped marginal ridge. Sensitivity was not reported by any of the patients. Australian Dental Journal 1992;37:5
Discussion 1. Factors influencing the clinical assessment of the marginal integrity of occlusal amalgam restorations Regardless of the technique of finishing, the quality of marginal adaptation (crevice formation, chipping) was assessed to have changed relatively little during the period of one to three years after placement. This may be partly attributable to the relatively coarse (but clinically relevant) criteria used to assess changes in marginal adaptation by accepted clinical assessment techniques. Finer discrimination of changes usually requires the use of indirect techniques of assessmentY6such as the use of photographs6 or stone replicas,’ in which higher magnification and greater standardization of recording is available. During the clinical assessment, it was occasionally observed that, at a subsequent recall, the amalgam appeared to have an improved score for marginal adaptation. This may be attributable to 337
'rounding over' of the sharp edge of a fractured amalgam margin during the period of time, to wear of both amalgam and enamel thereby reducing the depth of the marginal defect, or to subjective variation by the assessors. The influence of the patient in clinical studies has been acknowledged.' It was observed in a small number of patients that all the restorations regardless of finishing technique exhibited a relatively large amount of marginal fracture and, in some other patients, that all the restorations exhibited a small amount of marginal fracture. Modified cavity preparation techniques may be particularly indicated in patients with a proven record of exaggerated marginal fracture. These modifications would increase the amalgam margin angle, as suggested by Eldertong and de Vree et al. l o
2. Immediate finishing of amalgam restorations A number of clinical studies have evaluated the technique of immediate finishing, by comparing carved-only and immediate finishing,4.11immediate finishing and delayed polishing,2.12.13 carved-only and delayed p o l i ~ h i n g ' ~ . and ' ~ carved-only, immediate finishing and delayed polishing.'6 Consistent with previously reported findings, this study found no evidence to support the technique of immediate finishing of amalgam restorations. Immediately finished restorations tend to exhibit similar marginal integrity to restorations finished by other techniques, but inferior surface texture and greater surface discoloration compared with polished restorations. This study confirmed the observation" that there is a trend for improvement in the surface texture of some C and I restorations with time. 3. Clinical signficance of the findings Three aspects of the occlusal surface of amalgam restorations were specifically assessed - marginal adaptation or integrity, surface discoloration and surface texture. Using common clinical assessment methods (a probe or explorer, and unmagnified vision), no significant differences were detectable between carved-only and polished restorations in the integrity of the occlusal margins, confirming the findings from a previous small clinical ~ t u d y . The '~ restorations in this current study were placed and finished under optimum conditions so that extrapolation of the results to the wide range of conditions experienced in general dental practice is difficult. 338
By three years, approximately 50 per cent of all restorations showed evidence of surface discoloration. The finding that fewer polished restorations exhibited discoloration was of little consequence because none of the restorations exhibited an amount of discoloration that would require more than a quick polish to remove. Restorations are rarely replaced because of their surface roughness, although patients often express appreciation for the smoothness of a polished restoration. It is most unlikely therefore that the marked superiority in surface texture, exhibited by polished restorations, would be translated into a lower rate of replacement. Although all restorations received a 'pre-carve' burnish, an alternative finishing technique that was not investigated in this study was the 'post-carve' burnish. Use of a pre-carve and post-carve burnishing technique has been found to improve adaptation, reduce marginal leakage and reduce porosity in the surface amalgam17-20 and to achieve a smoother surface finish to that obtained by carving alone." However, post-carve burnishing does increase the likelihood of excess amalgam remaining external to the cavity margin.22When it fractures, this excess amalgam usually also removes some amalgam from the body of the restoration, thereby exposing the cavity wall.23 It is usually recommended that burnished amalgam should be 'finished' and polished on a subsequent appointment to remove the excess amalgam and to achieve a smoother surfacez4and less marginal leakage.25Clinical studies are required to indicate whether subsequent polishing might influence the longevity of burnished restorations. Jeffrey and P i t t P have asked 'to what degree is finishing of amalgams necessary?. Letzel and VrijhoeP4 have questioned whether polishing substantially improves the life of the amalgam restoration. M0ffaYz7 on the basis of long-term clinical studies of the performance of amalgam restorations, has suggested that the finishing of these restorations has no influence on their longevity. Long-accepted reasons for polishing, such as microstructural advantages2*and 'professional pride', may have little influence on the restoration's survival. In summary, of the criteria assessed, only the quality of marginal adaptation (fracture, integrity, deterioration) has been considered to be responsible for the frequent replacement of amalgam restorations. Evidence from this and other studies indicates that, provided the restorations are placed and carved with care, delayed polishing (at least 24 hours after placement) will probably have no influence on the longevity of the restoration. Australian Dental Journal 1992;37:5.
When the clinician chooses to use a technique of post-carve burnishing (and there are good reasons to support this practice), the greater likelihood of excess amalgam remaining beyond the margin probably necessitates finishing/polishing at a subsequent appointment. Further clinical investigation is required to test this hypothesis.
Conclusions 1. Clinical assessment of amalgam restorations up to three years after placement indicated that restorations that are polished at least 24 hours after placement have superior surface texture and somewhat less evidence of surface discoloration than carved-only or immediately finished restorations. 2. During the period from one to three years after placement, the marginal adaptation (integrity) of the restorations was similar, regardless of which of the three finishing techniques had been used. 3. There is no long-term advantage to be gained from the use of the immediate finishing technique compared with the carved-only or delayed polishing techniques. 4. There is mounting evidence to suggest that carefully placed and carved high copper amalgam restorations may enjoy a similar longevity to polished restorations. 5. The effect of post-carve burnishing, without subsequent polishing, on the longevity of the restoration requires clinical investigation. Acknowledgement The authors would like to thank Dr I. Martin, Westmead Hospital Dental Clinical School, for his assistance with the clinical assessment. This research was partly funded by the Australian Dental Research Fund Inc. References 1. Nuttall NM, Elderton RJ. The nature of restorative dental treatment decisions. Br Dent J 1983;154:363-5. 2. Straffon LH, Corpron RE, Dennison J. Clinical study of early polishing of Class I1 amalgam restorations in primary teeth. J Dent Res 1984;63:336:Abstr 1486. 3. Cvar JF, Ryge G. Clinical evaluation of dental restorative materials. San Francisco: US Department of Health, Education and Welfare, 1973. In: Monograph GPO 790-244. Also reported in: Ryge G. Clinical criteria. Int Dent J 1980;30:347-58. 4. Fenton RA, Smales RJ. Immediate-polishedand as-carved Tytin restorations after 12 months. J Dent 1984;12:165-74. 5. Phillips DS. Basic statistics for health science students. San Francisco: Freeman, 1978:123-4. 6. Mahler DB, Marantz RL. Clinical assessments of dental amalgam restorations. Int Dent J 1980;30:327-34. Australian Dental Journal 1992;37:5
7. Bryant RW, Mahler DB, Engle JA. A comparison of methods for evaluating the marginal fracture of amalgam restorations. Dent Mater 1985;1:235-7. 8. Letzel H, Aardening CJMW, Fick JM, Vrijhoef MMA. Tarnish, corrosion, marginal fracture and creep of amalgam restorations: a two-year clinical study. Oper Dent 1978;3:82-92. 9. Elderton RJ. Cavo-surface angles, amalgam margin angles and occlusal cavity preparations. Br Dent J 1984,156:319-24. 10. deVree JHP, Peters MRCB, Plasschaert AJM. The influence of modification of cavity design on distribution of stresses in a restored molar. J Dent Res 1984;63:1217-20. 11. Smales RJ, Fenton RA. Immediate-polishedand as-carved Tytin restorations after three years. J Dent 1985;13:79-83. 12. Corpron R, S t d o n L, Dennison J, Carron S, Asgar K.Clinical evaluation of amalgams polished immediately after insertion: 5 year results. J Dent Res 1984;63:178:Abstr 69. 13. Murrey AJ, Watkins TR. Polishing of amalgams at 30 minutes compared to 24 hours. J Dent Res 1985;64:180 Abstr 49. 14. Letzel H, Vrijhoef MMA. The influence of polishing on the marginal integrity of amalgam restorations. J Oral Rehabil 1984;11:89-94. 15. Mayhew RB, Schmeltzer LD, Pierson WP. Effect of polishing on the marginal integrity of high-copper amalgam restorations. Oper Dent 1986;11:8-13. 16. Bryant RW, Collins CJ. The finishing and early marginal fracture of clinical amalgam restorations. J Dent 1989; 17:111-6. 17. Bauer JB, Wong AY. A study of the parameters of burnishing. J Dent Res 1975;64:179:Abstr 52. 18. Symons AL, Wing G, Hewitt GH. Adaptation of dental amalgam to the cavosurface margin of Class I cavity preparations. J Oral Rehab 1987;14:65-76. 19. Geiger F, Reller U, Lutz F. Burnishing, finishing, and polishing amalgam restorations: A quantitative scanning electron microscopic study. Quintessence Int 1989;20:46 1-8. 20. Icenhower TJ, Arcoria CJ, Wagner MJ. Microleakage in amalgam restorations following burnishing, polishing and time-varied thermocycling. J Dent Res 1990;69: 131:Abstr 180. 21. Richeson JS, Sarrett DC. Profilometric and scanning electron microscopic analyses of amalgam polishing techniques. Gen Dent 1986;34:481-5. 22. Bryant RW. Finishing techniques for high copper amalgam restorations. A laboratory study. J Dent Res 1988;67:633: Abstr 66. 23. Mahler DB, Terkla LG. Relationship of cavity design to restorative materials. Dent Clin North Am 1965;9: 149-57. 24. Chan KC, Edie JW, Boyer DB. Microstructure of amalgam surfaces. J Prosthet Dent 1976;36:644-8. 25. Geiger F, Reller U, Lutz F. Burnishing, finishing and polishing amalgam restorations: A quantitative SEM study. J Dent Res 1987;66:329:Abstr 1781. 26. Jeffrey IWM, Pitts NB. Finishing of amalgam restorations: to what degree is it necessary? J Dent 1989;17:55-60. 27. Moffa JP. The longevity and reasons for replacement of amalgam alloys. J Dent Res 1989;68:188:Abstr 56. 28. Wing G. Clinical use of spherical particle amalgams. Aust Dent J 1970;15:185-92.
Address for correspondence/reprints: Department of Operative Dentistry, Faculty of Dentistry, University of Sydney, Westmead Hospital Dental Clinical School, Westmead, New South Wales, 2145. 339
