- Email: [email protected]
Three-year clinical comparison of three amalgam alloy types emphasizing an appraisal of the evaluation methods used
The marginal breakdown in restorations of a dispersion phase, a fine cut, and a m icro cut alloy were evaluated with five techniques. The rank ordering technique in which restorations as shown in photographs are ranked from best to worst proved to be the most useful.
Three-year clinical comparison of three amalgam alloy types emphasizing an appraisal of the evaluation methods used
Jo h n W . O s b o rn e , DDS, M S D R a lp h W. P h illip s, D Sc, In d ia n a p o lis E llio t N. G a le , P hD , B u ffa lo P au l P. B inon, D D S, R o s e v ille , C a lif
F ive d iffe re n t e v a lu a tio n te c h n iq u e s w e re used to m e a s u re th e m a rg in a l b re a k d o w n o f th re e -y e a r-o ld a m a lg a m
re s to ra tio n s . T h e m o s t u s e fu l m e th o d
a p p e a re d to be o n e in w h ic h p h o to g ra p h s o f all r e s to ra tio n s
w e re
ra n k e d
in
d e s c e n d in g
o rd e r
s ta rtin g w ith th e re s to ra tio n th a t had th e le a st m a r g in a l b re a k d o w n a n d e n d in g w ith th e re s to ra tio n th a t had th e g re a te s t d e te rio ra tio n . T h re e d iffe re n t a llo y s w e re e v a lu a te d and th e re s u lts c o n fir m th o s e o f p re v io u s s tu d ie s ; th e a llo y h a v in g th e
lo w e s t c re e p
w a s s u p e r io r w h e re a s
re s to ra tio n s p la c e d w ith th e a llo y h a v in g th e h ig h e st c re e p d is p la y e d th e g re a te s t m a rg in a l b re a k down.
784 ■ JADA, Vol. 93, October 1976
In the past few years, research on dental amal gams has enriched our knowledge as to what properties bear the principal relationship to clin ical failure.1,2 Likewise, theories have been pre sented that identify microstructure with dyscrasia such as marginal breakdown.2,3 Not only is marginal breakdown the most commonly evi denced type of deterioration seen in amalgam restorations, but it appears to be a characteristic inherent in present alloy systems.2,4"6 However, the research suggests that by the use of certain alloys2,7,8 and specific manipulative proce dures3,9 marginal deterioration can be controlled to a certain extent. One of the difficulties encountered when re viewing clinical studies of marginal deteriora tion is the wide variety of methods that have been used to quantitatively evaluate changes that may occur in the marginal integrity of an amalgam restoration. Classical research in this field is represented by the pioneering work of Ryge at the US Public Health Service; he developed cri teria by which examiners could monitor the changes in clinical restorations. This technique has been used in several studies.5,6,10‘12 Another procedure, developed by Mahler, Terkla, and Van Eysden,2 makes use of standardized clin ical photographs and a ridit analysis. Several other variations have been reported. For example, Watson and others13 used two ex aminers who ranked paired restorations. Duperon and others14 used the method of clinical exam ination with one examiner scoring the margins
Table 1 ■ Public Health Service c rite ria — rating of amalgam restorations and statistical analysis. Alloys Dispersalloy Aristaloy Twentieth Century Micro Cut Overall Dispersalloy vs Aristaloy Aristaloy vs Micro Cut Dispersalloy vs Micro Cut
A 17 4 0 df 4 2 2 2
Marginal adaptation for three alloys* B C (Fractured) 22 0 3 31 1 2 37
1 X2 26.65 10.47 4.48 21.80
8 P <0.001 NS NS <0.001
Note: NS, not significant. *A, no breakdown; B, breakdown; C, exposure of dentinoenamel junction.
on a scale of 1 to 4. Binon and others8 developed a technique that not only assessed the severity of marginal breakdown in a given area but also identified the locations of breakdown. In eval uating gold foil restorations, Richter and Mah ler15 used a procedure of ranking photographs taken of silver-plated impressions. Each of these methods has certain advantages and disadvantages, and thus its advocates. How ever, no attempt has been made to compare their relative effectiveness. That was the purpose of our investigation in which five evaluation tech niques were used to determine the changes that had occurred on the same amalgam restorations at a given time interval. In addition to compar ing the evaluations of these techniques, the beha vior of the alloys used was analyzed.
Method Three alloys, Dispersalloy* (a dispersion type), Aristaloyt (a fine cut type), and Twentieth Cen tury Micro Cuti (a micro cut type) had been placed in teeth by one clinician at Indiana Uni versity School of Dentistry three years before the evaluation. Eighteen-month observations on those restorations have been reported.8 In this study, 113 of those three-year-old restorations that were in 22 patients were used. The restorations were evaluated for marginal deterioration by one of five methods. The first method involved two examiners us ing mouth mirrors and explorers who examined each restoration for marginal breakdown and rated it according to the criteria developed by Ryge. This consists essentially of rating the mar ginal area of the restorations on the basis of three broad categories; A, no breakdown; B, break down; and C, breakdown to such an extent that the dentinoenamel junction was exposed. This is referred to here as the Public Health Service
criteria method. With the second method, two examiners using mouth mirrors and explorers ranked the individ ual patient’s restorations from best to worst, for example, 1, 2, 3, and so on. Although most pa tients had only three to six restorations, one did have ten. This is hereafter to be referred to as the clinical ranking method. With the third method, clinical black and white photographs were taken of each restoration at x \ V i magnification with a Medical Nikkor cam era. Four- by five-inch prints were made and the pictures matched with the patient. The photo graphs were cropped, leaving only the restored tooth. The prints were then compared and the restorations ranked from 1, 2, 3 . . . n. Except that the evaluation was made with photographs rather than by actual observation of restorations in the mouth, this technique, which has been named photographic ranking, is essentially the same as method 2. The fourth method used the techniques of Mahler, Terkla, and Van Eysden2; the black and white photographs of the 113 restorations, as described in method 3, were placed into six cate gories or ridits, according to severity of break down. The restorations were then evaluated by five examiners. This method is identified as the ridit analysis. In the fifth method, the 113 restorations, as shown in photographs, were ranked in descend ing order on the basis of the marginal breakdown of the restoration. The best was ranked 1; next best, 2; and the worst, 113. Again, the five eval uators ranked the restorations. This method is referred to as the rank ordering technique.
Results The data derived by use of the Public Health Ser vice criteria are given in Table 1. Analysis of Osborne—others: COMPARISON OF THREE AMALGAM ALLOYS ■ 785
rable 2 ■ Clinical and ph otographic ranking m e th o d s— pooled results of two evaluators for the clinica l and the photographic ranking methods and the statistical analysis.
Clinical ranking method Dispersalloy Aristaloy Twentieth Century Micro Cut
2
3
40 5
15 21
15 15
4 15
4 3
16
7
15
0
Jverall Jispersalloy vs Aristaloy iristaloy vs Micro Cut )ispersalloy vs Micro Cut
fa df 8 4 4 4
Dverall Dispersalloy vs Aristaloy \ristaloy vs Micro Cut Dispersalloy vs Micro Cut
’ hotographic ranking method Dispersalloy Aristaloy Twentieth Century Micro Cut
No. of restorations* 4 5 6 7 8
1
9
10
Av/SD
0 2
0 0
1.9±1.1 3.6±2.0
14 6 7 4 2 P X2 124.12 <0.001 41.62 <0.001 33.70 <0.001 83.07 <0.001 No. of restorations* 3 4 5 6 7 8 9 10
5.3±2.1
0 4
0 4
0 3
1
2
42 2
16 27
14 12
5 9
1 8
0 7
0 5
0 2
Ü
1
18
12
13
11
6
8
df 8 4 4 4
X2 144.43 59.50 35.58 100.70
Av/SD
0 0
1.8±1.0 3.5±1.8
2 5 P <0.001 <0.001 <0.001 <0.001
5.4±2.1
0 0
'Last five categories collapsed so as not to violate chi-square test.
these data resulted in a highly significant differ ence between materials (x2=26.7; d f = 4; P < 0.001). However, further analysis of these data indicated that this was the result of the differenc es between Dispersalloy and Twentieth Century Micro Cut (x2=21.8; d f = 2; PcO.OOl). By the use of this scoring system, no significant differences were found between Dispersalloy and Aristaloy or between Aristaloy and Micro Cut (x2= 10.4 and 4.5, respectively, d f = 2). Table 2 gives results from the clinical and pho tographic ranking techniques. Initially, there were ten categories in these methods. However, since most patients did not have six or more res torations, there were many zeros in the last five categories, thus violating some assumptions of the chi-square test. Therefore, the last five cat egories were collapsed into one category. For both the clinical ranking and photographic ranking methods, there were overall significant chi-square values (124.1 and 144.4, respectively; PcO.OOl) as well as highly significant differences between all three materials. By the use of these two evaluation methods, clinical ranking of Dis persalloy versus Aristaloy resulted in a chi square of 41.6 whereas photographic ranking re sulted in a chi square of 59.5, both significant at better than the PcO.OOl level. Results for Dis persalloy versus Twentieth Century Micro Cut also resulted in highly significant (PcO.OOl) chisquare values of 83.0 and 100.7, respectively, for both the clinical and photographic ranking meth 786 ■ JADA, Vol. 93, October 1976
ods. In a comparison of Aristaloy with Twenti eth Century Micro Cut, clinical ranking resulted in a chi square of 33.7; photographic ranking re sulted in a chi square of 35.5 (PcO.OOl). The chisquare values between the two methods were not significantly different, although there was a consistently higher chi-square value for the pho tographic ranking method than for the clinical ranking method. The ridit analysis is given in Table 3. The ridits obtained from the analyses of the categoriza tions were subjected to an analysis of variance. This resulted in a significant difference between materials (F=265.02; d f = 2/12; PcO.OOl). All differences between materials also were signifi cant when Scheffe tests were used to compare the ridit means. The last method, rank ordering of all restora tions, proved to be the most interesting and the results are given in Table 4. There were five eval uators; thus, it was possible to compare evalua tors as well as materials. Initially, it was found that the raters did not significantly disagree with one another. Results from a Kruskal-Wallis analysis of variance by rank indicated no signifi cant differences in the order in which raters ranked the restorations. Furthermore, Spear man’s rho correlations between the five raters ranged from a high of 0.993 to a low of 0.982, for surprisingly consistent relationships. Analyses of differences between the alloys for all five raters indicated that each rater found a highly significant difference between each ma terial. The results from all of the raters indicated Table 3 ■ Ridit analysis — distribution means and variances. Alloy Evaluator 1
2
3
Dispersalloy Aristaloy Micro Cut Dispersalloy Aristaloy Micro Cut Dispersalloy Aristaloy Micro Cut
4
Dispersalloy Aristaloy Micro Cut
5
Dispersalloy Aristaloy Micro Cut
Total
1
2
3
4
5
6
N
Mean
17 1 0 9 0 0
19 12 0 26 10 1 19 7 0 16 6 1
8 2 0 54
16 12 1 146
0 6 14 0 8 13 2 10 9 2 9 15 4 8 8 108
0 2 10 0 3 12 0 3 16 0 2 10 0 1 14 73
0 1 8 0 0 6
8 0 0 7 2 0
3 14 6 4 15 6 10 16 4 14 17 6 11 13 8 147
39 36 38 39 36 38 39 36 38 39 36 38 39 36 38
0.220 0.505 0.782 0.225 0.517 0.766 0.243 0.481 0.781 0.279 0.475 0.751 0.309 0.434 0.759
0 0 9 0 0 6 0 0 7 37
Two-factor analysis of variance Source Materials Evaluators Interaction
Sum of squares 0.65862 0.00075 0.01416
df 2 4 8
Mean square 0.32931 0.00019 0.00177
F 265.02
Sui sqi
0.( 0.( 0.( 0.( 0.( 0,( 0.( 0.( 0.( 0.( 0.( O.C 0.( 0.( 0.(
Table 4 ■ Total rank method — mean, median, and standard deviation. Evaluator/Rank 1 Mean rank Median rank SD 2 Mean rank Median rank SD 3 Mean rank Median rank SD 4 Mean rank Median rank SD 5 Mean rank Median rank SD
Dispersalloy 25.6 23.0 16.6 28.9 26.0 20.5 26.7 24.0 18.6 29.1 24.0 20.1 26.0 23.0 17.5
Alloy Aristaloy 56.4 60.5 23.6 54.7 61.5 25.2 57.2 56.0 25.3 56.9 57.0 28.7 56.9 59.5 24.3
Micro Cut 89.8 92.5 17.2 87.9 92.5 19.9 88.8 92.0 17.5 85.7 88.5 19.7 88.9 92.5 17.7
Table 5 ■ Typical rank ordering of an evaluator. Dispersalloy 1 15 35 2 17 37 3 18 39 4 19 40 6 20 41 7 21 43 8 23 44 9 25 46 10 27 48 11 29 49 12 31 53 13 32 55 14 34 57
Aristaloy 5 54 52 16 58 72 22 59 73 24 60 75 26 61 79 28 62 83 30 63 84 33 65 85 36 67 94 38 68 109 42 69 47 70 50 71
Micro Cut 45 87 101 51 88 102 56 89 103 64 90 104 66 91 105 74 92 106 76 93 107 77 95 108 78 96 110 80 97 111 98 112 81 82 99 113 86 100
that, in respect to marginal breakdown, Dispers alloy is significantly better than Aristaloy ( P < 0.001) and that both Dispersalloy and Aristaloy are significantly better than Micro Cut (P<0.001). A typical ranking given by an evaluator is shown in Table 5. The ability to discriminate be tween the alloys is evident. For example, of the first 21 restorations that were ranked in descend ing order from the best, all but two were of Dis persalloy. However, in the ranking of the worst 25 restorations, all but two were of Twentieth Century Micro Cut.
Discussion Of five methods for evaluating the three-year marginal breakdown of restorations placed with three commercial alloys, four of them showed consistent and highly significant differences be tween the materials. The Public Health Service criteria method was the only one that failed to show differences between all the materials, al though it did discriminate between the best and the worst alloys. Comparison of the different methods for eval uation of marginal breakdown, at least for the in
vestigators involved in this study, indicates that the clinical ranking method was the easiest one to use and resulted in the detection of highly sig nificant differences between materials at the three-year interval. These differences most like ly could have been noted even earlier in the life time of the restorations, and where large differ ences are to be expected, this technique should be satisfactory. However, with the clinical rank ing method, more than six restorations in pa tients were difficult to rank. As with the clinical ranking method, ridit an alysis significantly discriminated between the types of alloys. A major advantage in using ridit analysis would be in prediction, as a result of transforming data for use with parametric statis tics. It is possible, however, that this transform ation could result in the loss of power of the sta tistic under certain restricted conditions. The extra effort required to do a ridit analysis does not result in greater statistical separation of the materials than is found with other methods. A big disadvantage in the use of photographs is the difficulty in obtaining consistently accept able pictures. Not only must the equipment be of high caliber, but also the photographer-dentist must take the time to photograph each situa tion so that all the occlusal margins of the restor ation are observed. This requires the use of mir rors so that the long axis of the tooth and the cam era lens are parallel. The restoration must be thoroughly dried and plaquefree. With these dis advantages overcome, and with experience, ex cellent results can be obtained. We think that the best technique of those used was the rank ordering method. This evaluation method resulted in highly significant differences between materials. No doubt these differences could have been observed even earlier than the three-year observation period used in this study. The extremely high correlations obtained be tween raters probably indicates that when photo graphs of restorations are compared in close proximity the raters are able to observe minute differences that they are unable to detect when using the other methods. The particular advan tage of this technique, compared with the other methods, is that each photograph can be com pared with the photographs surrounding it and thus can be more correctly categorized. There is a consistent rechecking of the placement of the photograph in the total order, which makes it possible to observe minute differences. In the other methods, there can be little checking once Osborne—others: COMPARISON OF THREE AMALGAM ALLOYS ■ 787
Fig 1 ■ Dispersalloy restoration that was con- Fig 2 ■ Dispersalloy restoration sidered one of the best. breakdown for this alloy.
a photograph or a clinical restoration has been categorized. However, a disadvantage of this method is that it requires a greater amount of time to place photographs in successively “better or worse” position than it does to categorize the photo graphs in a smaller group of ranks. However, we think that this increase in categorization time would be more than justified with a decrease in the amount of time (in years) needed to observe significant differences in the marginal break down of restorations. This advantage could per mit one to compare materials or techniques more rapidly than has been possible in the past. With the emphasis now on alloy systems that have a slower rate of marginal breakdown, it may be dif ficult to keep a study group intact for the three to five years that are required to make meaningful observations. When the differences in behavior are not distinct, this evaluation technique may
that showed Fig 3 ■ Aristaloy restoration that showed little marginal failure.
be the only way to determine differences be tween materials in a reasonable period of time. Further research is now in progress to substan tiate this hypothesis. Although the main thrust of this investigation was to compare evaluation techniques, it should be noted that the behavior of the various alloys used corroborated the 18-month evaluation data on these same restorations,8 the publications of Mahler, Terkla, and Van Eysden,2 and the known creep values of the respective alloys.16 Dispersalloy was the dispersion type of alloy used, and in general, at three years the Dispers alloy restorations were excellent to good (Fig 1, 2). Aristaloy was used as the fine cut type. Al though there were a few excellent and a few bad Aristaloy restorations, most were in the mid range (Fig 3, 4). The greatest failure rate was with the Twentieth Century Micro Cut alloy (Fig 5, 6). In not 1 of the 22 patients was a Micro
Fig 4 ■ Aristaloy restoration that showed severe Fig 5 ■ Restoration of Twentieth Century Micro Fig 6 ■ Restoration showing most severe marmarginal dyscrasia. Cut that was best of this alloy, at three years. ginal breakdown at three years (Twentieth Cen tury Micro Cut).
788 ■ JADA, Vol. 93, October 1976
Cut restoration rated best when compared with restorations placed with other alloys. It also showed the greatest number of gross fractures.8
Conclusion and summary Five evaluation techniques were applied to 113 clinical amalgam restorations in 22 patients. Four of the five methods for the evaluation of amalgams showed consistent and highly signifi cant differences between the marginal break down rates of the three alloys. Of the methods used for evaluating differ ences in marginal breakdown rates, the rank or dering technique appeared to be most useful. With this method, photographs are ranked from that which shows the least marginal breakdown (number one) continuing to the photograph that shows the greatest amount of marginal break down. The major advantage of this method is that it allows for side-by-side comparisons, thereby permitting the detection of subtle differ ences. The technique also allows for more pow erful statistical analyses than when photographs are placed into categories. At the end of three years, Dispersalloy was significantly better than Aristaloy and Twentieth Century Micro Cut, and Aristaloy was signifi cantly better than Twentieth Century Micro Cut. These results confirm findings from pre vious studies that relate creep to marginal break down.
Dr. Osborne is associate professor of dental materials and Dr. Phillips is associate dean for research and research profes sor of dental materials, Indiana University School of Dentistry, Indianapolis. Dr. Gale is associate professor of behavioral sci ence at the State University of New York at Buffalo. Dr. Blnon is in private practice at 311 Oakridge Dr, Roseville, Calif. Address
reprint requests to Dr. Phillips, Indiana University School of Dentistry, 1121 W Michigan St, Indianapolis, 46202. ♦American Silver-Mercury Producers, now marketed by John son & Johnson Co., East Windsor, NJ 08520. tEnglehard Industries, Carteret, NJ 07008. £L. D. Caulk Co., Milford, Del 19963. 1. Mahler, D.B., and Van Eysden, J. Dynamic creep of dental amalgam. J Dent Res 48:501 July-Aug 1969. 2. Mahler, D.B.; Terkla, L.G.; and Van Eysden, J. Marginal fracture of amalgam restorations. J Dent Res 52:823 July-Aug 1973. 3. Espevick, S., and Sorensen, S.E. Creep of dental amalgam. J Dent Res (suppl) 53:1104 abstract no. 5 Sept-Oct 1974. 4. Phillips, R.W. Skinner’s science of dental materials, ed 7. Philadelphia, W. B. Saunders Co., 1973 p 359. 5. Weaver, R.G., and others. Three-year clinical evaluation of spherical dental amalgam alloy is abstracted. IADR Program and Abstracts no. 267 March 1970. 6. Osborne, J.W., and Gale, E.N. Long term follow-up of clinical evaluation of lathe-cut versus spherical amalgam. J Dent Res 53:1204 Sept-Oct 1974. 7. Mahler, D.B.; Van Eysden, J.; and Terkla, L.G. Relationship of creep to marginal fracture of amalgam. J Dent Res 54 (special issue):183 abstract no. 553 Feb 1975. 8. Binon, P., and others. Clinical behavior of amalgam as re lated to certain mechanical properties. J Dent Res 52 (special issue):186 abstract no. 509 April 1973. 9. Osborne, J.W., and others. Static creep as effected by tri turation time and condensation pressure. J Dent Res 53 (special issue):62 abstract no. 30 Feb 1974. 10. Ryge, G., and others. Clinical studies of restorative mater ials: zinc versus non-zinc alloy. J Dent Res 53 (special issue):61 abstract no. 28 Feb 1974. 11. McCune, R.J., and others. Clinical comparison for pos terior restorative materials. Abstracted, IADR Program and Ab stracts no. 546 March 1967. 12. Phillips, R.W., and others. Observations on a composite resin for class II restorations: three-year report. J Prosthet Dent 30:891 Dec 1973. 13. Watson, P.A., and others. A comparison of zinc-containing and zinc-free amalgam restorations. J Prosthet Dent 29:536 May 1973. 14. Duperon, D.F.; Nevile, M.D.; and Kasloff, Z. Clinical evalu ation of corrosion resistance of conventional alloy, sphericalparticle alloy, and dispersion phase alloy. J Prosthet Dent 25:650 June 1971. 15. Richter, W.A., and Mahler, D.B. Physical properties vs clin ical performance of pure gold restoration. J Prosthet Dent 29: 434 April 1973. 16. Osborne, J.W., and others. Static creep of certain commer cial amalgam alloys. JADA 89:620 Sept 1974.
Osborne—others: COMPARISON OF THREE AMALGAM ALLOYS ■ 789
Three-year clinical comparison of three amalgam alloy types emphasizing an appraisal of the evaluation methods used
Jo h n W . O s b o rn e , DDS, M S D R a lp h W. P h illip s, D Sc, In d ia n a p o lis E llio t N. G a le , P hD , B u ffa lo P au l P. B inon, D D S, R o s e v ille , C a lif
F ive d iffe re n t e v a lu a tio n te c h n iq u e s w e re used to m e a s u re th e m a rg in a l b re a k d o w n o f th re e -y e a r-o ld a m a lg a m
re s to ra tio n s . T h e m o s t u s e fu l m e th o d
a p p e a re d to be o n e in w h ic h p h o to g ra p h s o f all r e s to ra tio n s
w e re
ra n k e d
in
d e s c e n d in g
o rd e r
s ta rtin g w ith th e re s to ra tio n th a t had th e le a st m a r g in a l b re a k d o w n a n d e n d in g w ith th e re s to ra tio n th a t had th e g re a te s t d e te rio ra tio n . T h re e d iffe re n t a llo y s w e re e v a lu a te d and th e re s u lts c o n fir m th o s e o f p re v io u s s tu d ie s ; th e a llo y h a v in g th e
lo w e s t c re e p
w a s s u p e r io r w h e re a s
re s to ra tio n s p la c e d w ith th e a llo y h a v in g th e h ig h e st c re e p d is p la y e d th e g re a te s t m a rg in a l b re a k down.
784 ■ JADA, Vol. 93, October 1976
In the past few years, research on dental amal gams has enriched our knowledge as to what properties bear the principal relationship to clin ical failure.1,2 Likewise, theories have been pre sented that identify microstructure with dyscrasia such as marginal breakdown.2,3 Not only is marginal breakdown the most commonly evi denced type of deterioration seen in amalgam restorations, but it appears to be a characteristic inherent in present alloy systems.2,4"6 However, the research suggests that by the use of certain alloys2,7,8 and specific manipulative proce dures3,9 marginal deterioration can be controlled to a certain extent. One of the difficulties encountered when re viewing clinical studies of marginal deteriora tion is the wide variety of methods that have been used to quantitatively evaluate changes that may occur in the marginal integrity of an amalgam restoration. Classical research in this field is represented by the pioneering work of Ryge at the US Public Health Service; he developed cri teria by which examiners could monitor the changes in clinical restorations. This technique has been used in several studies.5,6,10‘12 Another procedure, developed by Mahler, Terkla, and Van Eysden,2 makes use of standardized clin ical photographs and a ridit analysis. Several other variations have been reported. For example, Watson and others13 used two ex aminers who ranked paired restorations. Duperon and others14 used the method of clinical exam ination with one examiner scoring the margins
Table 1 ■ Public Health Service c rite ria — rating of amalgam restorations and statistical analysis. Alloys Dispersalloy Aristaloy Twentieth Century Micro Cut Overall Dispersalloy vs Aristaloy Aristaloy vs Micro Cut Dispersalloy vs Micro Cut
A 17 4 0 df 4 2 2 2
Marginal adaptation for three alloys* B C (Fractured) 22 0 3 31 1 2 37
1 X2 26.65 10.47 4.48 21.80
8 P <0.001 NS NS <0.001
Note: NS, not significant. *A, no breakdown; B, breakdown; C, exposure of dentinoenamel junction.
on a scale of 1 to 4. Binon and others8 developed a technique that not only assessed the severity of marginal breakdown in a given area but also identified the locations of breakdown. In eval uating gold foil restorations, Richter and Mah ler15 used a procedure of ranking photographs taken of silver-plated impressions. Each of these methods has certain advantages and disadvantages, and thus its advocates. How ever, no attempt has been made to compare their relative effectiveness. That was the purpose of our investigation in which five evaluation tech niques were used to determine the changes that had occurred on the same amalgam restorations at a given time interval. In addition to compar ing the evaluations of these techniques, the beha vior of the alloys used was analyzed.
Method Three alloys, Dispersalloy* (a dispersion type), Aristaloyt (a fine cut type), and Twentieth Cen tury Micro Cuti (a micro cut type) had been placed in teeth by one clinician at Indiana Uni versity School of Dentistry three years before the evaluation. Eighteen-month observations on those restorations have been reported.8 In this study, 113 of those three-year-old restorations that were in 22 patients were used. The restorations were evaluated for marginal deterioration by one of five methods. The first method involved two examiners us ing mouth mirrors and explorers who examined each restoration for marginal breakdown and rated it according to the criteria developed by Ryge. This consists essentially of rating the mar ginal area of the restorations on the basis of three broad categories; A, no breakdown; B, break down; and C, breakdown to such an extent that the dentinoenamel junction was exposed. This is referred to here as the Public Health Service
criteria method. With the second method, two examiners using mouth mirrors and explorers ranked the individ ual patient’s restorations from best to worst, for example, 1, 2, 3, and so on. Although most pa tients had only three to six restorations, one did have ten. This is hereafter to be referred to as the clinical ranking method. With the third method, clinical black and white photographs were taken of each restoration at x \ V i magnification with a Medical Nikkor cam era. Four- by five-inch prints were made and the pictures matched with the patient. The photo graphs were cropped, leaving only the restored tooth. The prints were then compared and the restorations ranked from 1, 2, 3 . . . n. Except that the evaluation was made with photographs rather than by actual observation of restorations in the mouth, this technique, which has been named photographic ranking, is essentially the same as method 2. The fourth method used the techniques of Mahler, Terkla, and Van Eysden2; the black and white photographs of the 113 restorations, as described in method 3, were placed into six cate gories or ridits, according to severity of break down. The restorations were then evaluated by five examiners. This method is identified as the ridit analysis. In the fifth method, the 113 restorations, as shown in photographs, were ranked in descend ing order on the basis of the marginal breakdown of the restoration. The best was ranked 1; next best, 2; and the worst, 113. Again, the five eval uators ranked the restorations. This method is referred to as the rank ordering technique.
Results The data derived by use of the Public Health Ser vice criteria are given in Table 1. Analysis of Osborne—others: COMPARISON OF THREE AMALGAM ALLOYS ■ 785
rable 2 ■ Clinical and ph otographic ranking m e th o d s— pooled results of two evaluators for the clinica l and the photographic ranking methods and the statistical analysis.
Clinical ranking method Dispersalloy Aristaloy Twentieth Century Micro Cut
2
3
40 5
15 21
15 15
4 15
4 3
16
7
15
0
Jverall Jispersalloy vs Aristaloy iristaloy vs Micro Cut )ispersalloy vs Micro Cut
fa df 8 4 4 4
Dverall Dispersalloy vs Aristaloy \ristaloy vs Micro Cut Dispersalloy vs Micro Cut
’ hotographic ranking method Dispersalloy Aristaloy Twentieth Century Micro Cut
No. of restorations* 4 5 6 7 8
1
9
10
Av/SD
0 2
0 0
1.9±1.1 3.6±2.0
14 6 7 4 2 P X2 124.12 <0.001 41.62 <0.001 33.70 <0.001 83.07 <0.001 No. of restorations* 3 4 5 6 7 8 9 10
5.3±2.1
0 4
0 4
0 3
1
2
42 2
16 27
14 12
5 9
1 8
0 7
0 5
0 2
Ü
1
18
12
13
11
6
8
df 8 4 4 4
X2 144.43 59.50 35.58 100.70
Av/SD
0 0
1.8±1.0 3.5±1.8
2 5 P <0.001 <0.001 <0.001 <0.001
5.4±2.1
0 0
'Last five categories collapsed so as not to violate chi-square test.
these data resulted in a highly significant differ ence between materials (x2=26.7; d f = 4; P < 0.001). However, further analysis of these data indicated that this was the result of the differenc es between Dispersalloy and Twentieth Century Micro Cut (x2=21.8; d f = 2; PcO.OOl). By the use of this scoring system, no significant differences were found between Dispersalloy and Aristaloy or between Aristaloy and Micro Cut (x2= 10.4 and 4.5, respectively, d f = 2). Table 2 gives results from the clinical and pho tographic ranking techniques. Initially, there were ten categories in these methods. However, since most patients did not have six or more res torations, there were many zeros in the last five categories, thus violating some assumptions of the chi-square test. Therefore, the last five cat egories were collapsed into one category. For both the clinical ranking and photographic ranking methods, there were overall significant chi-square values (124.1 and 144.4, respectively; PcO.OOl) as well as highly significant differences between all three materials. By the use of these two evaluation methods, clinical ranking of Dis persalloy versus Aristaloy resulted in a chi square of 41.6 whereas photographic ranking re sulted in a chi square of 59.5, both significant at better than the PcO.OOl level. Results for Dis persalloy versus Twentieth Century Micro Cut also resulted in highly significant (PcO.OOl) chisquare values of 83.0 and 100.7, respectively, for both the clinical and photographic ranking meth 786 ■ JADA, Vol. 93, October 1976
ods. In a comparison of Aristaloy with Twenti eth Century Micro Cut, clinical ranking resulted in a chi square of 33.7; photographic ranking re sulted in a chi square of 35.5 (PcO.OOl). The chisquare values between the two methods were not significantly different, although there was a consistently higher chi-square value for the pho tographic ranking method than for the clinical ranking method. The ridit analysis is given in Table 3. The ridits obtained from the analyses of the categoriza tions were subjected to an analysis of variance. This resulted in a significant difference between materials (F=265.02; d f = 2/12; PcO.OOl). All differences between materials also were signifi cant when Scheffe tests were used to compare the ridit means. The last method, rank ordering of all restora tions, proved to be the most interesting and the results are given in Table 4. There were five eval uators; thus, it was possible to compare evalua tors as well as materials. Initially, it was found that the raters did not significantly disagree with one another. Results from a Kruskal-Wallis analysis of variance by rank indicated no signifi cant differences in the order in which raters ranked the restorations. Furthermore, Spear man’s rho correlations between the five raters ranged from a high of 0.993 to a low of 0.982, for surprisingly consistent relationships. Analyses of differences between the alloys for all five raters indicated that each rater found a highly significant difference between each ma terial. The results from all of the raters indicated Table 3 ■ Ridit analysis — distribution means and variances. Alloy Evaluator 1
2
3
Dispersalloy Aristaloy Micro Cut Dispersalloy Aristaloy Micro Cut Dispersalloy Aristaloy Micro Cut
4
Dispersalloy Aristaloy Micro Cut
5
Dispersalloy Aristaloy Micro Cut
Total
1
2
3
4
5
6
N
Mean
17 1 0 9 0 0
19 12 0 26 10 1 19 7 0 16 6 1
8 2 0 54
16 12 1 146
0 6 14 0 8 13 2 10 9 2 9 15 4 8 8 108
0 2 10 0 3 12 0 3 16 0 2 10 0 1 14 73
0 1 8 0 0 6
8 0 0 7 2 0
3 14 6 4 15 6 10 16 4 14 17 6 11 13 8 147
39 36 38 39 36 38 39 36 38 39 36 38 39 36 38
0.220 0.505 0.782 0.225 0.517 0.766 0.243 0.481 0.781 0.279 0.475 0.751 0.309 0.434 0.759
0 0 9 0 0 6 0 0 7 37
Two-factor analysis of variance Source Materials Evaluators Interaction
Sum of squares 0.65862 0.00075 0.01416
df 2 4 8
Mean square 0.32931 0.00019 0.00177
F 265.02
Sui sqi
0.( 0.( 0.( 0.( 0.( 0,( 0.( 0.( 0.( 0.( 0.( O.C 0.( 0.( 0.(
Table 4 ■ Total rank method — mean, median, and standard deviation. Evaluator/Rank 1 Mean rank Median rank SD 2 Mean rank Median rank SD 3 Mean rank Median rank SD 4 Mean rank Median rank SD 5 Mean rank Median rank SD
Dispersalloy 25.6 23.0 16.6 28.9 26.0 20.5 26.7 24.0 18.6 29.1 24.0 20.1 26.0 23.0 17.5
Alloy Aristaloy 56.4 60.5 23.6 54.7 61.5 25.2 57.2 56.0 25.3 56.9 57.0 28.7 56.9 59.5 24.3
Micro Cut 89.8 92.5 17.2 87.9 92.5 19.9 88.8 92.0 17.5 85.7 88.5 19.7 88.9 92.5 17.7
Table 5 ■ Typical rank ordering of an evaluator. Dispersalloy 1 15 35 2 17 37 3 18 39 4 19 40 6 20 41 7 21 43 8 23 44 9 25 46 10 27 48 11 29 49 12 31 53 13 32 55 14 34 57
Aristaloy 5 54 52 16 58 72 22 59 73 24 60 75 26 61 79 28 62 83 30 63 84 33 65 85 36 67 94 38 68 109 42 69 47 70 50 71
Micro Cut 45 87 101 51 88 102 56 89 103 64 90 104 66 91 105 74 92 106 76 93 107 77 95 108 78 96 110 80 97 111 98 112 81 82 99 113 86 100
that, in respect to marginal breakdown, Dispers alloy is significantly better than Aristaloy ( P < 0.001) and that both Dispersalloy and Aristaloy are significantly better than Micro Cut (P<0.001). A typical ranking given by an evaluator is shown in Table 5. The ability to discriminate be tween the alloys is evident. For example, of the first 21 restorations that were ranked in descend ing order from the best, all but two were of Dis persalloy. However, in the ranking of the worst 25 restorations, all but two were of Twentieth Century Micro Cut.
Discussion Of five methods for evaluating the three-year marginal breakdown of restorations placed with three commercial alloys, four of them showed consistent and highly significant differences be tween the materials. The Public Health Service criteria method was the only one that failed to show differences between all the materials, al though it did discriminate between the best and the worst alloys. Comparison of the different methods for eval uation of marginal breakdown, at least for the in
vestigators involved in this study, indicates that the clinical ranking method was the easiest one to use and resulted in the detection of highly sig nificant differences between materials at the three-year interval. These differences most like ly could have been noted even earlier in the life time of the restorations, and where large differ ences are to be expected, this technique should be satisfactory. However, with the clinical rank ing method, more than six restorations in pa tients were difficult to rank. As with the clinical ranking method, ridit an alysis significantly discriminated between the types of alloys. A major advantage in using ridit analysis would be in prediction, as a result of transforming data for use with parametric statis tics. It is possible, however, that this transform ation could result in the loss of power of the sta tistic under certain restricted conditions. The extra effort required to do a ridit analysis does not result in greater statistical separation of the materials than is found with other methods. A big disadvantage in the use of photographs is the difficulty in obtaining consistently accept able pictures. Not only must the equipment be of high caliber, but also the photographer-dentist must take the time to photograph each situa tion so that all the occlusal margins of the restor ation are observed. This requires the use of mir rors so that the long axis of the tooth and the cam era lens are parallel. The restoration must be thoroughly dried and plaquefree. With these dis advantages overcome, and with experience, ex cellent results can be obtained. We think that the best technique of those used was the rank ordering method. This evaluation method resulted in highly significant differences between materials. No doubt these differences could have been observed even earlier than the three-year observation period used in this study. The extremely high correlations obtained be tween raters probably indicates that when photo graphs of restorations are compared in close proximity the raters are able to observe minute differences that they are unable to detect when using the other methods. The particular advan tage of this technique, compared with the other methods, is that each photograph can be com pared with the photographs surrounding it and thus can be more correctly categorized. There is a consistent rechecking of the placement of the photograph in the total order, which makes it possible to observe minute differences. In the other methods, there can be little checking once Osborne—others: COMPARISON OF THREE AMALGAM ALLOYS ■ 787
Fig 1 ■ Dispersalloy restoration that was con- Fig 2 ■ Dispersalloy restoration sidered one of the best. breakdown for this alloy.
a photograph or a clinical restoration has been categorized. However, a disadvantage of this method is that it requires a greater amount of time to place photographs in successively “better or worse” position than it does to categorize the photo graphs in a smaller group of ranks. However, we think that this increase in categorization time would be more than justified with a decrease in the amount of time (in years) needed to observe significant differences in the marginal break down of restorations. This advantage could per mit one to compare materials or techniques more rapidly than has been possible in the past. With the emphasis now on alloy systems that have a slower rate of marginal breakdown, it may be dif ficult to keep a study group intact for the three to five years that are required to make meaningful observations. When the differences in behavior are not distinct, this evaluation technique may
that showed Fig 3 ■ Aristaloy restoration that showed little marginal failure.
be the only way to determine differences be tween materials in a reasonable period of time. Further research is now in progress to substan tiate this hypothesis. Although the main thrust of this investigation was to compare evaluation techniques, it should be noted that the behavior of the various alloys used corroborated the 18-month evaluation data on these same restorations,8 the publications of Mahler, Terkla, and Van Eysden,2 and the known creep values of the respective alloys.16 Dispersalloy was the dispersion type of alloy used, and in general, at three years the Dispers alloy restorations were excellent to good (Fig 1, 2). Aristaloy was used as the fine cut type. Al though there were a few excellent and a few bad Aristaloy restorations, most were in the mid range (Fig 3, 4). The greatest failure rate was with the Twentieth Century Micro Cut alloy (Fig 5, 6). In not 1 of the 22 patients was a Micro
Fig 4 ■ Aristaloy restoration that showed severe Fig 5 ■ Restoration of Twentieth Century Micro Fig 6 ■ Restoration showing most severe marmarginal dyscrasia. Cut that was best of this alloy, at three years. ginal breakdown at three years (Twentieth Cen tury Micro Cut).
788 ■ JADA, Vol. 93, October 1976
Cut restoration rated best when compared with restorations placed with other alloys. It also showed the greatest number of gross fractures.8
Conclusion and summary Five evaluation techniques were applied to 113 clinical amalgam restorations in 22 patients. Four of the five methods for the evaluation of amalgams showed consistent and highly signifi cant differences between the marginal break down rates of the three alloys. Of the methods used for evaluating differ ences in marginal breakdown rates, the rank or dering technique appeared to be most useful. With this method, photographs are ranked from that which shows the least marginal breakdown (number one) continuing to the photograph that shows the greatest amount of marginal break down. The major advantage of this method is that it allows for side-by-side comparisons, thereby permitting the detection of subtle differ ences. The technique also allows for more pow erful statistical analyses than when photographs are placed into categories. At the end of three years, Dispersalloy was significantly better than Aristaloy and Twentieth Century Micro Cut, and Aristaloy was signifi cantly better than Twentieth Century Micro Cut. These results confirm findings from pre vious studies that relate creep to marginal break down.
Dr. Osborne is associate professor of dental materials and Dr. Phillips is associate dean for research and research profes sor of dental materials, Indiana University School of Dentistry, Indianapolis. Dr. Gale is associate professor of behavioral sci ence at the State University of New York at Buffalo. Dr. Blnon is in private practice at 311 Oakridge Dr, Roseville, Calif. Address
reprint requests to Dr. Phillips, Indiana University School of Dentistry, 1121 W Michigan St, Indianapolis, 46202. ♦American Silver-Mercury Producers, now marketed by John son & Johnson Co., East Windsor, NJ 08520. tEnglehard Industries, Carteret, NJ 07008. £L. D. Caulk Co., Milford, Del 19963. 1. Mahler, D.B., and Van Eysden, J. Dynamic creep of dental amalgam. J Dent Res 48:501 July-Aug 1969. 2. Mahler, D.B.; Terkla, L.G.; and Van Eysden, J. Marginal fracture of amalgam restorations. J Dent Res 52:823 July-Aug 1973. 3. Espevick, S., and Sorensen, S.E. Creep of dental amalgam. J Dent Res (suppl) 53:1104 abstract no. 5 Sept-Oct 1974. 4. Phillips, R.W. Skinner’s science of dental materials, ed 7. Philadelphia, W. B. Saunders Co., 1973 p 359. 5. Weaver, R.G., and others. Three-year clinical evaluation of spherical dental amalgam alloy is abstracted. IADR Program and Abstracts no. 267 March 1970. 6. Osborne, J.W., and Gale, E.N. Long term follow-up of clinical evaluation of lathe-cut versus spherical amalgam. J Dent Res 53:1204 Sept-Oct 1974. 7. Mahler, D.B.; Van Eysden, J.; and Terkla, L.G. Relationship of creep to marginal fracture of amalgam. J Dent Res 54 (special issue):183 abstract no. 553 Feb 1975. 8. Binon, P., and others. Clinical behavior of amalgam as re lated to certain mechanical properties. J Dent Res 52 (special issue):186 abstract no. 509 April 1973. 9. Osborne, J.W., and others. Static creep as effected by tri turation time and condensation pressure. J Dent Res 53 (special issue):62 abstract no. 30 Feb 1974. 10. Ryge, G., and others. Clinical studies of restorative mater ials: zinc versus non-zinc alloy. J Dent Res 53 (special issue):61 abstract no. 28 Feb 1974. 11. McCune, R.J., and others. Clinical comparison for pos terior restorative materials. Abstracted, IADR Program and Ab stracts no. 546 March 1967. 12. Phillips, R.W., and others. Observations on a composite resin for class II restorations: three-year report. J Prosthet Dent 30:891 Dec 1973. 13. Watson, P.A., and others. A comparison of zinc-containing and zinc-free amalgam restorations. J Prosthet Dent 29:536 May 1973. 14. Duperon, D.F.; Nevile, M.D.; and Kasloff, Z. Clinical evalu ation of corrosion resistance of conventional alloy, sphericalparticle alloy, and dispersion phase alloy. J Prosthet Dent 25:650 June 1971. 15. Richter, W.A., and Mahler, D.B. Physical properties vs clin ical performance of pure gold restoration. J Prosthet Dent 29: 434 April 1973. 16. Osborne, J.W., and others. Static creep of certain commer cial amalgam alloys. JADA 89:620 Sept 1974.
Osborne—others: COMPARISON OF THREE AMALGAM ALLOYS ■ 789