The Influence of the Amalgam Alloy on the Survival of Amalgam Restorations: A Secondary Analysis of Multiple Controlled Clinical Trials

Abstract

Data from 14 independent controlled clinical trials on the oral behavior of Classes 1 and 2 amalgam restorations, with a follow-up between five and 15 years, were re-evaluated by secondary analysis for the influence of alloy composition on the survival of amalgam restorations. For the analysis, 3119 restorations were available, which were made from 24 different alloys by a group of seven operators. The alloys were divided into four groups according to their zinc content (zinc-containing and zinc-free) and their copper content (conventional and high-copper). During the follow-up of the trials, the restorations were annually assessed for failures, which were classified as to (1) restoration-, (2) restorative process-, and (3) patient-related reasons. With the restoration-related failures, survival functions of the restorations were estimated by alloy and alloy group. The total number of failed restorations was 481, of which 77% were restoration-related and 14% process-related. Eighty percent of the restoration-related failures were due to some form of fracture of the amalgam. Restorations of conventional zinc-free alloys had the shortest survival. After 13 years, only 25% survived. Zinc and a high copper content had an equally favorable influence on the survival rate, which was 70% after 13 years when either was present. The highest survival rates were of restorations of zinc-containing high-copper alloys: 85% after 13 years. The zinc and copper contents of the alloy contributed to the corrosion resistance of the amalgams, which in turn influenced the survival of the restoration. The current ISO Standard 1559 on alloys for dental amalgam should be modified to account for these factors that influence the survival of amalgam restorations.

Keywords

amalgam alloy restoration survival clinical trials secondary analysis corrosion.

Get full access to this article

View all access options for this article.

References

Allan DN (1977). A longitudinal study of dental restorations. Br Dent J 143:87-89.

Bengel W. (1990). Amalgam-Werkstof und Klinik. Die Quintessenz 41:1129-1144.

Berry TG , Osborne JW , Hatch RA (1986). A clinical study of zinc-containing high-copper amalgams. Gen Dent 34:463-465.

Black GV (1908). A work on operative dentistry. Vol. two. The technical procedures in filling teeth. Chicago: Medico-Dental Publishing Co.

Cox DR (1972). Regression models and life tables. J R Stat Soc Br 34:187-202.

Crabb HS (1981). The survival of dental restorations in a teaching hospital. Br Dent J 150:315-318.

Creugers NH , Van 't Hof MA (1991). An analysis of clinical studies on resin-bonded bridges. J Dent Res 70:146-149. Doglia R. , Herr P. , Holz J. , Baume LJ (1986). Clinical evaluation of four amalgam alloys: A five-year report. J Prosthet Dent 56:406-415.

El-Mowafy OM , Lewis DW , Benmergui C. , Levinton C. (1994). Meta-analysis on long-term clinical performance of posterior composite restorations. J Dent 22:33-43. European Economic Community (1984). Council directive of 8 March 1984 on limit values and quality objectives for mercury discharges by sectors other than the chloralkali electrolysis industry. Off J European Communities L74:49-54.

Glass GV (1976). Primary, secondary, and meta-analysis of research . Educ Researcher 5:3-8.

10.

Hendriks FH , Letzel H. , Vrijhoef MM (1986). Composite versus amalgam restorations. J Oral Rehabil 13:401-411. International Standardization Organization (1986). ISO Standard 1559, Alloys for dental amalgam. Geneva: ISO. International Standardization Organization (1991). ISO/DIS Standard 10993, Biological evaluation of medical devices; Part 8: Clinical evaluation. Geneva: ISO.

11.

Johansson B. , Derand T. (1983). Corrosion of amalgams with special regard to zinc . Scand J Dent Res 91:320-324. Jørgensen KD (1965). The mechanism of marginal fracture of amalgam fillings. Acta Odontol Scand 22:347-389.

12.

Kaplan EL , Meier P. (1958). Non-parametric estimation from incomplete observations . J Am Stat Assoc 53:457-481. Letzel H. (1989). Survival rates and reasons for failure of posterior composite restorations in a multicentre clinical trial. J Dent 17(Suppl):10S-17S.

13.

Letzel H. , Vrijhoef MMA (1983). Experimental clinical research on dental amalgam restorations. In: Advances in biomaterials. Vol. 3. Winters GD , Gibbons DF , Plenk H , editors. New York: J. Wiley and Sons, pp. 341-346.

14.

Letzel H. , Vrijhoef MM (1984a). The influence of polishing on the marginal integrity of amalgam restorations. J Oral Rehabil 11:89-94.

15.

Letzel H. , Vrijhoef MMA (1984b). Long-term influences on marginal fracture of amalgam restorations. Oral Rehabil 11:95-101.

16.

Letzel H. , Aardening CJ , Fick JM , Van Leusen J. , Vrijhoef MM (1978). Tarnish, corrosion, marginal fracture and creep of amalgam restorations: A two-year clinical study. Oper Dent 3:82-92.

17.

Letzel H. , Van 't Hof MA , Vrijhoef MM (1987). The influence of the condensation instrument on the clinical behavior of

18.

amalgam restorations. J Oral Rehabil 14:133-138.

19.

Letzel H. , Van 't Hof MA , Vrijhoef MM , Marshall GW Jr , Marshall SJ (1989). A controlled clinical study of amalgam restorations: survival, failures and causes of failure. Dent Mater 5:115-121.

20.

Light RJ , Smith PV (1971). Accumulating evidence: Procedures for resolving contradictions among different research studies. Harvard Educ Rev 41:429-471.

21.

Mahler DB , Terkla LG , Van Eysden J. , Reisbick MH (1970). Marginal fracture vs. mechanical properties of amalgam. J Dent Res 49:1452-1459.

22.

Marshall GW Jr , Marshall SJ , Letzel H. , Vrijhoef MM (1987). Microstructures of Cu-rich amalgam restorations with moderate clinical deterioration. Dent Mater 3:135-143. Marshall GW , McCoy DD , Kinney JH , Letzel H. , Marshall SJ (1992). Microstructural changes in retrieved amalgam restorations. Cells and Materials 2:29-36.

23.

Mjor IA ( 1981). Placement and replacement of restorations. Oper Dent 6:49-54.

24.

Osborne JW , Berry TG (1992). Zinc-containing high copper amalgams: A 3-year clinical evaluation. Am J Dent 5:43-45. Osborne JW , Gale EN ( 1990). Relationship of restoration width, tooth position and alloy to fracture at the margins of 13- to 14-year-old amalgams. J Dent Res 69:1599-1601. Osborne JW , Norman RD (1990). 13-year clinical assessment of 10 amalgam alloys. Dent Mater 6:189-194.

25.

Osborne JW , Binon PP , Gale EN ( 1980a). Dental amalgam: Clinical behavior up to eight years . Oper Dent 5:24-28. Osborne JW , Leinfelder KF , Gale EN , Sluder TB (1980b). Two independent evaluations of ten amalgam alloys. J Prosthet Dent 43:622-626.

26.

Van Dijken JWV (1991). A six year follow-up of three dental alloy restorations with different copper contents. Swed Dent J 15:259-264.

27.

Vrijhoef MM , Letzel H. (1986). Creep versus marginal fracture of amalgam restorations . J Oral Rehabil 13:299-303. Vrijhoef MM , Hendriks FH , Letzel H. (1985). Loss of substance of dental composite restorations. Dent Mater 1:101-105.

28.

Wagner E. (1962). Beitrag zur Klarung des Korrosionsverhaltens der Silber-Zinn-Amalgame. Dtsch Zahnärtzl Z 17:99-106.

29.

Watson PA , Phillips RW , Swartz ML , Gilmore HW (1973). A comparison of zinc-containing and zinc-free amalgam restorations. J Prosthet Dent 29:536-541.

30.

Wilson CJ , Ryge G. ( 1963). Clinical study of dental amalgam. J Am Dent Assoc 66:764-771.