202

J. Dent. 1992; 20: 202-206

Finishing of amalgam restorations: three-year clinical study

a

C. J. Collins and R. W. Bryant* Westmead Hospital Dental Clinical School, Sydney, New South Wales, Australia

Westmead

and *Department

of Operative

Dentistry,

University

of

ABSTRACT Class I and Class II amalgam restorations were placed in the permanent teeth of 66 patients, each of whom received a minimum of three restorations. At least one of these restorations was carved-only, at least one was immediately finished (using a prophylaxis paste on rubber cups at low speed, 8 or 10 min after trituration), and at least one restoration was polished (using finishing burs and polishing points, more than 24 h after placement). The number of restorations available for assessment of marginal fracture using the 11-unit photographic scale developed by Mahler was 253 at baseline. 249 at l-year and 2-year recalls and 228 at the 3year recall. Although polished restorations exhibited greater initial (baseline) marginal fracture, at I-year. 2-year and 3-year recalls the restorations were found to exhibit a similar amount of marginal fracture regardless of the finishing technique. The amount of perceived marginal fracture increased steadily after 1 year. The immediate finishing of amalgam restorations showed no long-term benefit over the other techniques and has little to commend it. The clinical finishing of amalgam restorations is discussed in the light of this and other research. KEY WORDS: J. Dent. 1992)

1992;

Amalgam, 20:

Operative technique,

202-206

(Received

Clinical performance

9 July 199 1; reviewed

3 October

1991;

accepted

20 January

Correspondence should be addressed to: Professor R. W. Bryant, Department of Operative Dentistry, University of Sydney, Westmead Hospital Dental Clinical School, Westmead, NSW 2145, Australia.

INTRODUCTION Nearly 60per cent of amalgam restorations may be being replaced, not because of specific failure but because of doubts in the minds of the clinicians as to the integrity of the margin region or the possibility of caries at the margin (Nuttall and Elderton, 1983).This has emphasized the need to examine clinical techniques that might facilitate dentists modifying their usually ‘well-meaning’ but interventional philosophy with respect to replacement. A previous paper (Bryant and Collins. 1989) reviewed previous research in this field and reported the initial (baseline) and l-year clinical performance in 60 patients of amalgam restorations finished in one of three ways. The restorations had been evaluated both clinically and using the well-documented Mahler photographic technique to identify early changes at the margins of restorations (Mahler and Marantz, 1979; Mahler et al., 1980). The restorations were either carved-only. or @ 1992 Buttenvorth-Heinemann 0300-57 12/92/040202-05

Ltd.

immediately finished (using a fluoride-containing prophylaxis paste in a rubber cup at low speed, approximately 8 or 10 min after trituration) (Carronet al., 1983;Fenton and Smales, 1984; Straffon et al., 1984) or polished at least 24 h after placement, using tungsten carbide finishing burs and rubber polishing points. The purpose of this paper is to report 2-year and 3-year data, to examine whether the trends noted at 1 year continue, and to identify long-term consequences of the finishing technique for amalgam restorations that may have implications for clinical practice.

MATERIALS

AND METHOD

A total of 277 amalgam restorations (Tytin, BN 6828509, S.S. White, Philadelphia, PA. USA) were placed in a total of 66 patients, of average age 16.9 years, each of whom required at least three Class I or II restorations in

Collins

Table 1. Number of restorations fracture

Recall

Average time since placement (mth)

Baseline 1 -year 2-year 3-year C, carved-only;

available for inclusion

12.9 24.3 36.3 I, immediately

finished;

and Bryant:

in the photographic

(no.)

Total no. of restorations available for evaluation

61 60 60 56

253 249 249 228

Patients attending

Finishing

evaluation

of amalgams

203

of marginal

Restorations evaluated for each finishing technique (no.) I P C 86 85 85 78

83 81 82 74

84 83 82 76

P, polished.

permanent teeth. (Of the restorations evaluated at 3 years. 156 were occlusal, 60 were proximo-occlusal and 12 were mesio-occluso-distal.) The buccal and lingual walls of the occlusal cavities diverged only slightly towards the pulpal wall to provide retention, as this was the recommended technique at the time. Cavities received a quick-setting zinc oxide-eugenol or calcium hydroxide type of base if required. Each patient received at least three restorations (Table I). At least one of these was carved only (Code C), at least one was immediately finished (Code I). and at least one restoration was polished at least 24 h after placement (Code P). A description of the systematic allocation of the finishing techniques and of details of each of these techniques has been presented in a previous paper (Bryant and Collins, 1989). Baseline photographs were obtained within 4 weeks of finishing (by one of the three techniques). Subsequently. photographs of the restorations were obtained at an average of 12.9 months after placement (for the l-year recall). 24.3 months after placement (for the 2-year recall) and 36.3 months after placement (for the 3-year recall). Differences among finishing techniques in the times since placement were small. For example. for the 2-year recall. technique C restorations were photographed 24.2 (sd. 1.4) months after placement. technique I restorations at 24.4 (s.d. 1.1) months and technique P restorations were photographed 24.2 (s.d. 1.0) months after placement. Each of four evaluators (Codes W, X, Y. Z) independently assessed. in turn, the baseline, l-year, 2-year and 3year photographs for each restoration before progressing to the assessment of the next restoration. The technique of assessment was consistent with that described and used by Mahler (Mahler and Marantz, 1979; Mahler et al., 1980). The expanded. eight photograph reference set for the 1 lunit category scale was used to assist in the evaluation of early changes (Bryant et al.. 1985). A detailed description. both of the technique used to obtain the black and white prints for evaluation and of the statistical treatment of the data, has been presented previously (Bryant and Collins, 1989). Written patient or guardian consent was obtained at the start of the project and the protocol was approved by the Human Ethical Research Committee, Westmead Hospital (Westmead, NSW. Australia).

RESULTS Of the original 66 patients in whom 277 restorations were placed, the data for live patients have been excluded from the results because these patients attended only one of the three recalls. The effective patient and restoration database. indicating the number of restorations available for inclusion in the photographic evaluation, is shown in Table I.

The principal reason for loss of patients from the study was their moving away from the locality, with no forwarding address. Because of the statistical technique used to analyse the data, a patient could only be included if at least one restoration of each type of finishing technique was available for evaluation. For this reason, several additional patients were lost from the study because of the need for urgent orthodontic extraction or the inadvertent polishing of technique I and C restorations by an over-zealous dental officer in another department of the hospital. Although data from 60 patients were included for the l-year and 2-year recalls, two patients attended only one of these two recalls. Averaged marginal fracture indexes for each evaluator’s assessment of restorations for each finishing technique are shown in Table II and statistical analyses of paired comparisons for the evaluation of marginal fracture among the three finishing techniques are shown in Table III. It is evident that for each evaluator, from the l-year recall onwards, differences between paired comparisons of finishing techniques were small. With one exception. these differences were not statistically significant (P > 0.05). For any evaluator, the difference between average results for pairs of techniques was less than 0.36 marginal fracture units (Mahler scale). As reported in a previous evaluation (Bryant and Collins, 1989). at baseline, polished (P) restorations that were finished at least 24 h after placement showed a greater extent of marginal fracture than either technique C or I restorations. Average marginal fracture indexes, for each technique and at baseline and each recall. were averaged across the four evaluators. Averaged indexes (of four evaluators) were, at baseline: C, 1.24; I, 1.35; P. 1.62 units: at the l-year recall: C, 2.90: I. 3.00; P. 2.93 units: at the 2-year recall: C,

204

J. Dent.

1992;

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No. 4

Table II. Marginal fracture assessed by photographic evaluation: average marginal fracture indexes for each of the four evaluators at baseline and three recalls for the three finishing techniques Average marginal

fracture index at each evaluation

Evaluator

Finishing technique code

time

Baseline

7-year recall

2-year recall

3-year recall

W

C

W W

I P

1.25 (0.41)* 1.36 (0.27) 1.48 (0.3 1)

3.01 (0.80) 3.12 (0.97) 2.96 (0.82)

3.57 (1.01) 3.62 (1.01) 3.41 (0.95)

4.12 (1.32) 4.06 (I .17) 3.77 (I .07)

X X X

C I P

1.24 (0.30) 1.33 (0.30) 1.58 (0.39)

2.9 1 (0.84) 3.03 (0.98) 2.9 1 (0.84)

3.56 (I .04) 3.50 (1.03) 3.5 1 (0.93)

4.14(1.23) 4.05 (1 .I 6) 4.02 (I .02)

Y Y

Y

C I P

1.23 (0.30) 1.28 (0.27) 1.56 (0.35)

2.88 (0.69) 2.95 (0.77) 2.84 (0.66)

3.50 (0.76) 3.41 (0.73) 3.36 (0.73)

4.06 (I.05) 3.95 (0.91) 3.80 (0.87)

Z Z Z

C I P

1.24 (0.37) 1.41 (0.38) 1.87 (0.44)

2.80 (0.68) 2.90 (0.74) 3.01 (0.5 1)

3.31 (0.68) 3.40 (0.69) 3.45 (0.45)

3.77 (0.76) 3.8 1 (0.78) 3.80 (0.5 1)

Average for 4 evaluators

C I P

1.24 1.35 1.62

2.90 3.00 2.93

3.49 3.48 3.43

4.02 3.97 3.85

C, carved-only; I, immediately finished; P, polished. *Value for one standard deviation in parentheses.

Table Ill. Marginal fracture assessed by photographic evaluation: statistical analysis of comparisons between pairs of finishing techniques

Evaluator

Finishing techniques compared

Statistical significance of the difference between the two techniques Baseline 1-year 2-year 3-year

W W W

C and P I and P C and I

c

Finishing of amalgam restorations: a three-year clinical study.

Class I and Class II amalgam restorations were placed in the permanent teeth of 66 patients, each of whom received a minimum of three restorations. At...
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