Scand. J. Dent. Res. 1978: 86: 404-407 {Key words: dental amalgam; dental fillings)

Reasons for replacement of amalgam dental restorations JON E. DAHL AND HARALD M. ERIKSEN Department of Operative Dentistry, Dental Faculty, University of Oslo, Oslo, Norway

ABSTRACT - Recurrent caries appears to be the most frequently occurring reason for

replacement of amalgam dental restorations. Recent developments of amalgam alloys have improved the clinical appearance of such fillings but the possible influence on their

durability is uncertain. (Accepted for publication 24 June 1978)

Ease in manipulation, adequate mechanical properties and long experience are factors which have established amalgam as the most widely used dental restorative material. However, the durability of such restorations seems to be shorter than generally anticipated. In a recent survey ALLAN (1977) concluded that 5096 of all amalgam restorations had to be replaced within 8 years of function. This high turnover of amalgam restorations corroborates the results from investigations by MOORE & STEWART (1967), RICHARDSON &; BOYD (1973), ELDERTON (1976) and LAVELLE (1976). In the past decade many important advances have been made in the composition of dental amalgam alloys (see survey by HOWARD, BAUM, HAMILTON, PHILLIPS, PRUDEN & RAMFJORD 1977). Lower

dynamic and static creep, higher initial strength and less corrosion and marginal "ditching" are all properties associated with the new high-copper alloys (EAMES &: MACNAMARA 1976, ESPEVIK 1977).

Clinical studies have indicated that these improvements will lead to better clinical performance of amalgam restorations (MAHLER,

TERKLA & EYSDEN PHILLIPS, GALE & BINON

1973,

OsBORNE, 1976). However, a majority of the failures of amalgam restorations seem to arise from operative failures rather than from inherent shortcomings of the material itself (HEALEY & PHILLIPS 1949, RICHARDSON

&

BOYD

1973,

LAVELLE

1976). It therefore remains to be seen to what extent the present improvements of dental amalgam alloys will positively influence the durability and thereby the rate of replacement of amalgam restorations. The aim of the present investigation was to record the reasons for replacement of Class 2 amalgam restorations in patients treated at the Department of Operative Dentistry, University of Oslo. And furthermore to analyze through a comparative literature survey to what extent tlie main factors responsible for replace-

405

AMALGAM DENTAL RESTORATIONS

ment correspond with factors leading to poor quality ratings of amalgam restorations. Material and methods The present recording of the reasons for replacement of Class 2 amalgam restorations was based on information obtained from accepted treatment plans in the student clinic. The data were always confirmed by clinical and radiographic examinations of the patients. A total of 200 amalgam restorations of unknown age and past history were included in this study. The reasons for replacement were grouped according to the following set of criteria: failure of the anatomical form (contour, occlusion, contact point and extension); fractures (body or marginal); surface texture ("pitting" and corrosion); overhangs and caries (secondary and residual). No efforts were made U) rank the observations according to various levels oi severity. In about one of four restorations more than one reason was found to cause replacement. The final distribution of the collected data has therefore been made in percent of the total number of failures recorded. Results

Recurrent caries accounted for 53% of the registered reasons for replacement of amalgam restorations. Fractures, mainly marginal, came closest to that frequency (3396) while overhangs and deviations in anatomical form accounted for only a few percent each (Table 1). Although frequently observed, pitted and/or corroded surfaces only caused replacement in two instances. When more than one reason for

replacement was recorded, caries in association with marginal fractures dominated and was found in connection with 36 of all the restorations investigated. Discussion

Recurrent caries appears to be the single most important factor leading to replacement of amalgam restorations, followed by marginal fractures (Table 1). This corroborates the findings of the other investigations by HEALEY8C PHILLIPS (1949), MOORE & STEWART (1967), RICHARDSON & BOYD (1973) and LAVELLE (1976) (Fig. 1). Cavity design, cavity wall treatment and proper handling and condensation of a high quality amalgam alloy are factors considered to be of importance in relation to the prevention of recurrent caries and marginal fractures. In addition, proper contour and finishing of the restorations, particularly in the interproximal regions, eliminating plaque-retentive irregularities and restoring optimal oral hygiene conditions are of decisive caries-preventive importance. HEALEY ^ PHILLIPS (1949) reached the embarrassing conclusion that over 90% of all amalgam replacements could be traced back to the operative procedure. This indicates that benefits obtained by metallurgic improvements may be of marginal importance for the durability of amalgam restorations. The results from the present investigation and from recently published articles in this

Table I Reasons for replacement of 200 amalgam restorations. More than one reason for replacement was detected from 61 of the restorations and the calculation ofpercentiles is based on the total number of failures recorded

Anatomical form No. of restorations

(396)

Fractures 87 (3396)

Surface texture

Overhangs

Caries

25 (1096)

(5396)

139

DAHL AND ERIKSEN

406

I

QUALITY

STUDIES

REPLACEMENT

STUDIES

70--

50'

30

I0--

A BC D E

ABODE

ABC D E

AB C D E

AB C DE

ANAT FORM

FRACTURES

SURF. TEXT.

OVERHANGS

CARIES

Fig. 1. Distribution of defects of amalgam dental restorations recorded from two quality studies A et al. 1967) and B (MJOR & HAUGEN 1976) compared with reasons for replacement according to C (HEALEY & PHILLIPS 1949), D (LAVELLE 1976), and E (DAHL& ERIKSEN, present study). Some of the criteria described are not used in all the investigations, marked N.E. = not evaluated.

(MATHEWSON

held (RICHARDSON &; BOYD 1973, LAVELLE 1976) indicate that operative failures still constitute the dominating factors leading to replacement. It is, however, difficult to make a difFerentiation between operative and material errors in relation to many types ot amalgam failures and a multiiactorial etiolog)' may frequently exist. Many of the quality studies of amalgam restorations seem to concentrate mainly on the integrity of the occlusal part of the restorations (MAHLER et al. 1973, OsBORNE et al. 1976). Inferior surface texture, a typical material shortcoming, constitutes the single most dominating factor leading to poor quality ratings of amalgam restorations (MATHEWSON, BRUNER

8C

HAUGEN

1976). This factor is, however, of

NOONAN

1967,

MJOR

&

minor importance when the durability of amalgam restorations is considered (Fig. 1). The low frequency of overhangs reported in many clinical quality studies of amalgam restorations compared with the high frequency found in investigations studying this aspect in particular (BJORN, BjORN 8c GRCOVIC 1969) indicates that the gingival/interproximal conditions may have been neglected in many quality evaluations of amalgam restorations. Results from quality studies of amalgam restorations have incited the development of new amalgam alloys with low corrosion potential, high initial strength and low marginal fracture tendency (EAMES & MACNAMARA 1977). These factors undoubtedly improve the quality and clinical performance. But it remains

407

AMALGAM DENTAL RESTORATIONS

to be seen to what extent they will expand the durability of amalgam restorations. To obtain a more balanced impression of the correlation between quality factors and reasons for replacement of amalgam restorations, these two aspects should be combined in future studies. Such a combined study is in progress at our clinic. RYGE & SNYDER (1973) have presented a well-designed model, but in their investigation the average age of the restorations evaluated was only a few months, which is too short for a proper estimation of reasons for replacement. References A longitudinal study of dental restorations. Br. Dent. J. 1977: 143: 87-89.

ALLAN, D . N . : BJORN,

A.-L.,

BJORN,

H.

&

GRCOVIC,

B.:

Marginal fit of restorations and its relation to periodontal bone level. Odontol. Revy 1969: 20:311-321. EAMES, W . B. & MACNAMARA, J. E.: Eight highcopper amalgam alloys and six conventional alloys compared. Oper. Dent. 1976: 1:98-107. ELDERTON, R. J.: The prevalence of failure of restorations: a literature review. J. Dent. 1976:4:207-210. ESPEVIK, S.: Creep of dental amalgam and its phases.

Scand.

J.

Dent.

Res.

1977:

A cross-sectional longitudinal survey into the durability of amalgam restorations. / . Dent. 1976: 4: 139-143.

LAVELLE, C. L. B.:

MAHLER, D. B., TERKLA, L. G. & EYSDEN, J. V.:

Marginal fracture of amalgam restorations. J. Dent. Res. 1973: 52: 823-827. MATHEWSON, R. J., BRUNER, F. W . & NOONAN,

R. G.: The clinical comparison of a spherical amalgam alloy and a conventional amalgam alloy: A pilot study. J. Dent, Child. 1967:34: 176-182. MjOR, I. A. & HAUGEN, E.: Clinical evaluation ol amalgam restorations. Scand. J. Dent. Res. 1976:84:333-337. MOORE, D . L. & STEWART, J. L.: Prevalence of defective dental restorations. / . Prosthet. Dent. 1967: 17: 372-378. OsBORNE, J. W., PHILLIPS, R. W., GALE, E. N . & BINON, P. P.: Three-year clinical comparison of three amalgam alloy types emphasizing an appraisal of the evaluation methods used./. Am. Dent. Assoc. 1976: 93: 784-789. RICHARDSON,

A.

85:

492-495. J. & PHILLIPS, R. W . : A clinical study of amalgam failures. J. Dent. Res. 1949: 28:439-446.

HEALEY, H .

HOWARD, W. W., BAUM, L., HAMILTON, A. L, PHILLIPS, R. W . , PRUDEN, W . H . & RAMFJORD, S. P.: Report of the committee

on scientific investigation of the American Academy of Restorative Dentistry./. Prosthet. Dent. 197 7:38:552-588.

S.

&

BOYD,

M.

A.:

Replacement of silver amalgam restorations by 50 dentists during 246 working days. J, Can. Dent. Assoc. 1973: 39: 556-559. RYGE, G. & SNYDER, M . : Evaluating the clinical quality of restorations. / . Am. Dent. Assoc. 1973: 87:369-377.

Address: University of Oslo Dental Faculty Box 1109 Blindem Oslo 3 Norway

Reasons for replacement of amalgam dental restorations.

Scand. J. Dent. Res. 1978: 86: 404-407 {Key words: dental amalgam; dental fillings) Reasons for replacement of amalgam dental restorations JON E. DAH...
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