38 J Dent. 1986; 14: 38-41 Punted In Great Brltaln

The value of an amalgam condensation exercise in pre- and postgraduate education J. E. Wiegman, D. J. Purdell-Lewis and A C. M. van de Poe1 The Departments of Periodontology, Prosthodontics and Restorative Dentist/y, Dental School State university of Groningen, The Netherlands

ABSTRACT

The quality of condensation and adaptation of amalgams placed in a standard test cavity by three groups was evaluated in this study. These groups were compared with a baseline group of first-year preclinical students who used the test as a preclinical exercise. The ranking order of the median scores from best to worst was: baseline first-year students > academic staff > fourthyear students > private practitioners. The private practitioners’ scores for the normally visible parts of the restoration were higher than their scores for the normally invisible areas. This was not found in the other two experimental groups, or in the baseline group. The participants’ assessment oftheirown work shows that they were not on the whole satisfied with their amalgam restorations. The results of this study show that adaptation and condensation of amalgams can be significantly improved using a teaching method which provides information on the quality of the normally invisible parts of a restoration.

INTRODUCTION

Research into the lifespan of silver amalgam restorations has shown that 42 per cent need replacement after 4-5 years (Elderton, 1983). The criteria used in the decision to replace restorations has been evaluated (Merrett and Elderton, 1984), as has the quality of the preparation and that of the new restoration compared to the old (Elderton, 1984). The factors which may cause the failure of a restoration (Elderton, 1976) and the relationship between cavity shape, the type of amalgam used and the quality of the completed restoration have also been examined (Jorgensen, 1967; Osborne et al., 1978; Peters et al., 198 1). The way in which the amalgam is placed in the cavity, which would appear to be at least as important, has received relatively little attention. The adaptation and condensation of a correctly mixed amalgam is directly under the control of the operator and is also of importance when the life expectancy of the restoration is being considered (American Dental Association, 1974).

The purpose of this article is to describe a technique in which the placement of amalgam in a preparation can be evaluated The results achieved by private practitioners, students and staff at a dental school are presented and discussed

MATERIALS AND METHODS

Dentists and dental students in three separate study groups were asked to place an amalgam restoration in a standard test cavity. All participants used a standard instrumentation and lathe-cut amalgam (Cavex non- gamma 2) prepared according to the manufacturer’s instructions. The test cavity was placed in the upperjaw of a modified manikin. The class II cavity was formed by three steel plates which could be removed from the manikin and dismantled when the amalgam restoration had hardened (Fig. 1). It was thus possible to examine the normally ‘invisible’ parts of the restoration from the buccal and lingual sides. The evaluation of adaptation and condensation was carried out under a stereomicroscope (20 X) using a checklist of nine items (Table I>. A tw@ option system was used in this assessment: acceptable, 1 point unacceptable, 0 points. The maximum score which could be attained was 18 points when all nine items on the checklist had been completed satisfactorily on both sides. All the restorations were evaluated, in random order, by the same member of the staff who had trained to 90 per cent reliability in the use of the assessment system. This test cavity and scoring system has recently been intro duced as a standard part of the preclinical course to teach students the value of condensation and adaptation

Wiegman et al.: Amalgam condensation exercise in educatton 39

Fig. 1. The class II test cavity, formed by three steel plates, in the manrkin.

Table /. The checklist and criteria per item

Items

(1) Adaptation location 1

The amalgam should be in contact with the walls, internal line angles and corner of the cavity, judged at six locations

(2) Adaptation

(3) ,Z,“~P,“,it 4 +I- location 3

(4) Adaptation location 4

(5) Adaptation location 5

(6) Adaptation location 6

(7) Occlusal marginal adaptation

I 2 6-k t

c5

l- 2 8 “-74

t

(8) Homogeneity

(9) Surface form

3

Before the mould is opened the marginal adaptation is judged, this should be flush with the occlusai outline and neither over- or underfilled No bubbles, pores or visible layering between portions of condensed amalgam should be present The occlusal surface of the amalgam is smooth

(Wiegman et al.. 1985). A score of 14 of the 18 items acceptable is required before the students are considered to have achieved the required standard

Before the restorations were evaluated, all the partici- pants were asked to give an overall assessment of their own work classifying it as either ‘good’, ‘reasonable’ or ‘poor’, based on the appearance of both buccal and lingual sides viewed under the stereomicroscope (20 X).

The three participating groups were:

1. One year group of 55 fourth-year students studying at the Dental School in Groningen, who had completed 9

months of clinical patient treatment. These students, therefore, had some experience in the placement of amalgam restorations and theoretical knowledge of the value of good condensation and adaptation of amalgam. They had not, however, either seen or completed the exercise.

2. A group of40 dentists, all members of the staff of the Department of Restorative Dentistry at the Dental School in Groningen. All the members of this group were experienced clinicians and participated in undergraduate teaching Therefore they had a thorough knowledge of restorative materials.

3. A group of 29 dentists, all working in private practice were chosen at random from 90 practitioners participating in a postgraduate course on theoretical and practical aspects of amalgam restorations. It can be assumed that the members of this group had clinical experience, but the extent of their theoretical knowledge, a number of years after graduation, was unknown.

None of the participants had ever used the practice manikin; those members of the staff teaching this new exercise in the preclinical course having been excluded from the test group.

To provide a baseline value for the results of the three groups studied, the results of the first examination attempts of 421 tirst-year preclinicai students were included These students had no clinical experience, but because of the value of the exercise and the degree of feedback obtained by continually evaluating and discuss- ing their own work with members of staff during the training period, they were fully aware of the value of good condensation and adaptation. These students learnt about amalgam during the first year of their studies. They determined the length of the training period themselves and decided when to take the exam.

40 J. Dent. 1986; 14: No. 1

percentage of 30 r participants

I

I

25 / I

-private practitioners ..‘. .-4th years students --.---1st years Students -.- - -.staff

r.

‘0 2 4 6 8 10 12 14 16 ““-L scores

percentage good 100

90

80

70

60

50

40

30

20

10

0 r. 6

qth years students staff

q private practitioners

0 lSt years students

7 8 9 item

Fig. 2. The results of each group presented to show the Fig. 3. The percentages of acceptable scores per Item for the distribution of the participants’ scores over the ISpoInt four groups. scale. Curves obtained using spllne functtons smoothmg (Reinsch, 1967).

Table //: The participants’ overall assessment of their own work

Private Students Staff members practitioners

Judgement 155) n = 55 140) n = 40 (29) n = 29 Total 1248)

Good 15 (19%) 15 29% 39 (16%) Reasonable 7; $2; 46 (58%) 29% 140 (59%) Poor 19 (18%) 19 (24%) :2” 42% 60 25%

Total 107* 80 52t 239

*Three of the 55 students judged only one side of the restoratlon, the total number of judgements madewasZx55-3=107. tSix of the nine private practmoners judged only one side of the restoratlon, the total number of ludgements made was 2 x 29 - 6 = 52

RESULTS

The participants in the three groups were not on the whole satisfied with their amalgam restorations. Only 39 ( 16 per cent) assessed one or both sides as good (see Table If). The results of the 18-point assessment are given in Fig 2 which includes for comparison the results for the baseline first-year preclinical students group. It can be seen that the ranking order of the median scores was: first-year preclinical students > academic staff > fourthyear clinical students > private practitioners.

An analysis per item (Fig. 3) shows that the baseline first-year preclinical student group’s result at their first test attempt after training with the apparatus were superior to the other three groups on all nine items (P < 0.00 1). with an average item score of 86 per cent satisfactory. They were significantly weaker on home geneity than the other eight items (P < 0.001) but still significantly better than the three experimental groups. The results for the three experimental groups show that 4 1

per cent of the items of the fourth-year clinical students were scored as satisfactory. This figure was 5 8 per cent for the staff members and 31 per cent for the private practitioners. Members of the staff were significantly better than both the fourth-year students (P < 0.01 or P< 0.001 for the different items) and the private practitioners (P < 0.001). Equally, the fourth-year students scored higher than the private practitioners (P < 0.1 or P < 0.05). The normally visible items (7 and 9) were scored significantly higher than the invisible items (l-6 and 8) by the private practitioners (P < O-05). This was not found in the other two experimental groups, or in the first-year students group.

Comparison of the participants’ grading of their own work with the results of the checklist using the chi square test showed that the members of staff were the most accurate judges of their own work (P < 0.002). followed by the students (P < 0.01). By contrast, the private practitioners had a highly significant negative correlation (P-c 0.001).

Wiegman et al.: Amalgam condensation exercise in education 41

DISCUSSION

These results are of particular interest since the amalgam restorations were placed under near optimum conditions. The scores would probably have been lower in the clinical situation.

There is no simple explanation as to why both members of staff and students should score higher than the private practitioners. It is unlikely to have been due to a lack of manual dexterity. or strange instrumentation, since all the practitioners were of some years’ standing. The type of amalgam. spherical or lathe-cut, and the instrumentation normally used by some of the general practitioners might have been different from those chosen for the study, and this could have negatively biased some results. However, the poor results achieved by all the practitioners indicate that this is unlikely. It is perhaps significant that the private practitioners scored highest on the visible items (7 and 9) and lowest on the normally invisible parts of the filling. Both staff and students at the dental school are, in contrast, also aware of the theoretical requirements for a good amalgam restoration. The negative correlation between the private practitioners’ evaluation of their work and their actual scores supports the hypothesis that they probably based their evaluation more on the visible items. and had little regard for homogeneity and adaptation: 22 per cent and 7 per cent acceptable respectively (Fig. 3). The results of the fourth-year clinical students and members of staff demonstrate that practical skills and theoretical knowledge alone are insuficient to produce a good restoration. The feedback obtained by the first-year preclinical students by viewing their own work is indispensable. Seeing the shortcomings in homogeneity and adaptation during their training period resulted in better instrumentation and a high mean score of 86 per cent of items acceptable at their first test attempt. The average practice and test time taken by first-year students who have successfully mastered the preclinical amalgam exercise is 9.3 h. This demonstrates the efficiency of this learning method. The generally poor adaptation and homogenity obtained by the three experimental groups, in particular, the private practitioners must have an effect on the lifespan of their restorations and the need for early replacement.

There is no reason to think that this cross section of dental manpower was radically different from the total

dental population. if anything the pt ibate practitioners participating in the study represent the more highly motivated end of the spectrum, since postgraduate education in The Netherlands is voluntary and extremely expensive. The results presented here show that at least one aspect of restorative dentistry, which is under direct control of the operator, can be significantly improved using new teaching methods.

When the scores of the private practitioners are considered. it can be concluded that this exercise should be carried out regularly, either on an individual basis in the practice setting, or as part of a postgraduate course in restorative techniques. This would ensure the practi- tioners remain aware of the importance of a totally adequate restoration.

Acknowledgements

The authors would like to thank MS C. A. F. M. Gottmer- Schrijer for typing the manuscript and Mr ‘E. van Ommen for preparing of the illustrations.

REFERENCES American Dental Association ( 1974) Guide to Dental

Materials and Devices, 7th edn. Chicago. American Dental Association.

Elderton R J. (1976) The prevalence of failure of restor- ations: a literature review. L Dent. 4, 207.

Elderton R J. (1983) Longitudinal study of dental treatment in the general dental service. Rr. Dent. J. 155, 9 1.

Elderton R J. ( 1984) Cave-surface angles. amalgam margin angles and occlusal cavity preparations. RF: Dcrtt. J. 156, 310.

Jorgensen K. D. ( 1967) Structure studies of amalgam. III. The marginal structure of class 11 amalgam fillings. ,.!ctu Odontol. Stand. 25, 85.

Merret M. C. W. and Elderton R J. (1084) An i/l l’rtro study of restorative dental treatment decisions and dental caries. BK Dent. J. 157, 128.

Osborne J. W., Gale E. N.. Chew C. L. et al. ( 1978) Clinical performance and physical properties of twelve amalgam alloys. .I Dent. Rex 57, 983.

Peters M. C. R B.. Poort H. W.. Plasschaert A. J. M. et al. ( 198 1) Biomechanical aspects of restored teeth. Clerics Rex 15, ?I?.

Reinsch C. H. (1967) Smoothing by spline I’unctions. Numerische Mathematik 10, 177.

Wiegman J. E.. Poe1 A. C. M. van de and Purdell-Lewis D. J. (1985) The value of an assessment system in a preclinical exercise. J. Dent. Educ 49. 3 12.

Correspondence should be addressed to: Dr J. E. Wiegman. Department of Periodontology. Prosthodontics and Restorative Dentistry. Dental School, State University of Groningen. Groningen. The Netherlands.