J. Dent. 1992;

20: 85-89

85

Overhanging amalgam restorations in young adults attending a periodontal department B. E. Kells and G. J. Linden Department

of Restorative

Dentistry,

School of Clinical Dentistry,

Queen’s University,

Belfast, Northern

Ireland

ABSTRACT An important

factor affecting plaque retention is the presence of amalgam restorations which are poorly contoured at the gingival margin. The aim of the study was to investigate the occurrence and effects of overhanging amalgam restorations in young adults. One hundred patients, aged 20-29 years, referred to the Periodontal Department, School of Dentistry, Belfast were investigated. Bitewing radiographs were used to examine the restorative status of the approximal surfaces of premolar and permanent molar teeth, excluding third molars. Fifty-seven per cent of the patients investigated had at least one amalgam overhang and 27 per cent had three or more overhangs visible on the radiographs. One hundred and seventy-eight (25 per cent) of the restored approximal surfaces had detectable amalgam overhangs. The mean bone level-amelocemental junction (ACJ) distance related to the approximal surfaces with overhangs was 1.77 (s.d. 1.0) mm and 37 (32 per cent) of these surfaces had bone levels which were greater than 2 mm from the ACJ. The mean bone level-ACJ distance for the other approximal surfaces of the teeth with overhangs was 1.63 (sd. 1.2) mm. The mean bone level-ACJ distance for matching control surfaces on contralateral teeth was 1.86 (s.d. 1.2) mm. It was concluded that overhanging amalgam restorations were common in the restorations of young adults (20-29 years old) referred for periodontal treatment but were not associated with increased levels of bone destruction. KEY WORDS:

Restorations,

J. Dent. 1992;

20: 85-89

Amalgam, Periodontal disease (Received 17 June 1991:

reviewed 2 August 1991;

accepted 2 October 1991)

Correspondence should be addressed to: Dr 8. E. Kells, Department of Restorative Dentistn/, School of Clinical Dentistry, Queen’s University. Grosvenor Road, Belfast 8T12 68P, Northern Ireland.

INTRODUCTION It is widely accepted that defective restorations are an aetiological factor in the pathogenesis of inflammatory periodontal disease. Not only do they increase plaque retention but they can also change the subgingival microflora from a non-destructive to a destructive variety (Lang et al., 1983; Flores de Jacoby et al., 1989; Brunsvold and Lane, 1990). Many workers have demonstrated evidence of increased bone loss related to overhanging approximal margins when compared with homologous intact surfaces (Gilmore and Sheiham, 1971; Hakkarainen and Ainamo, 1980; Claman et al., 1986; Pack et al., 1990). Few, however, have looked specifically at their effect on the periodontium ofyoung adults (Lerviket al., 1984). The aim of the present study was to examine the occurrence of overhanging amalgam restorations and the extent of associated periodontal bone loss in a group of 20-29 year D 1992 Butterworth-Heinemann 0300-57 12/92/020085-05

Ltd.

olds referred Ireland.

for periodontal

treatment

in Northern

MATERIALS AND METHODS Subjects A consecutive group of 100 subjects was selected from new referrals to the Periodontal Department, School of Dentistry, Belfast. Each subject was aged between 20 and 29 years on initial presentation and had a pair of bitewing radiographs available for examination. Patients who were pregnant and so did not have radiographs taken or those who exhibited signs of juvenile or rapidly progressive periodontitis were not considered for inclusion.

86

J. Dent. 1992;

Radiographic

20: No. 2

examination

All radiographs were taken using a Gendex GX X-ray machine (Siemens, Bensheim, Germany) with a short cone and Ekta speed film (Kodak, Stuttgart, Germany). The central ray was directed between the mandibular second premolar and first molar at an upwards angulation of 10 degrees to the horizontal plane. All radiographs were taken by one of two senior dental radiographers, both of whom were trained in the School of Dentistry, Belfast. Each radiograph was processed in a standard manner using a Durr-Dental AC245L processor (Siemens, Bensheim, Germany). Each radiograph was mounted in a slide holder and projected onto a vertically orientated opaque glass screen at a magnification of X 10. The examiner (B.K.) was thus able to make direct measurements from the reverse side of the screen without interfering with the projected image.

Radiographic

measurements

Each pair of bitewings was examined in a darkened room by the technique described. The approximal surfaces of each tooth, excluding third molars, were recorded as sound or restored, the restored surfaces being subdivided into acceptable or overhanging. A restoration was considered to have an overhang when there was a distinct ledge of amalgam which did not conform to the interproximal contour of the tooth. The horizontal projection from the long axis of the tooth was measured for every overhang to the nearest tenth of a millimetre and this was recorded as the overhang size. The distance from the amelocemental junction (ACJ) to the bone level was also recorded to the nearest tenth of a millimetre. Bone level was defined as the highest point at which the periodontal ligament was of normal width and morphology. This meant that in angular bony defects measurements were made from the base, i.e. the point where the lamina dura became parallel to root surface establishing a periodontal ligament of constant width. If a point at which the periodontal ligament was judged radiographically normal could not *be identified no measurement was recorded. Once an overhang had been identified, the bone levelACJ distance was recorded for that surface, for the other approximal surface of the same tooth and for the matching surface of the contralateral tooth, i.e. if an overhang was identified on the mesial surface of an upper right first molar then measurements were also made for the distal surface of that tooth (same side control) and for the mesial surface of the upper left first molar (contralateral control). If either of the control surfaces had a defect such as a measurable overhang or a negative ledge then they were not included as a match. Thus only sound or acceptably restored surfaces were compared with overhanging surfaces. Any sites for which measurements could not be made were recorded as unreadable. This included surfaces for which bone levels could not be identified, as already described, and sites for which the

ACJ could not be identified. Often amalgam extended below the ACJ or teeth were rotated or overlapped. The technique was practised until scoring became automatic and determinations could be made without hesitation. Statistical

analysis

Student’s t-test for paired observations was applied to the mean bone level-ACJ distance for all surfaces measured. Differences at the 5 per cent level of probability were considered statistically significant. Reproducibility The radiographs from 10 subjects were randomly selected and re-evaluated to study intraexaminer variability. The 10 pairs of bitewings which were re-examined contained 100 interproximal restorations. Thirty-five overhangs were consistently identified at both assessments. In addition, five overhangs (all with a horizontal projection of 0.1 mm) were detected at only one of the assessments; two at the first and three at the second. Using these values a kappa statistic of 0.89 was calculated for overhang detection. There was no significant difference between mean overhang size at the first estimation (0.54 mm) and at the second estimation (0.59 mm), t = 0.53, P = 0.59. Twenty bone level-ACJ distances were readable at both estimations and those greater than 2.0 mm were taken to represent bone loss. Kappa for the presence or absence of bone loss was calculated at 0.58. There was no significant difference between mean bone level-ACJ distances at the first estimation (1.70 mm) and at the second (1.59 mm), t = 0.55, P = 0.58.

RESULTS A total of 100 young adult patients with a mean age of 24.7 (s.d. 3) years were included in the study. Fifty-seven per cent of the subjects had at least one amalgam overhang and 27 per cent had three or more overhangs. The maximum number recorded for any one individual was 11 overhanging restorations. Out of a possible 1600 teeth, 1337 were present (83.6 per cent), giving a total number of 2674 approximal surfaces available for assessment. Of these surfaces, 710 were restored and 178 had a measurable overhang. Thus 6.6 per cent of available surfaces and 25 per cent of restored surfaces exhibited an overhang. Bone level-ACJ distances were measured for 115 sites which had an overhanging restoration. The remaining 63 surfaces with overhangs were classed as unreadable either because bone level could not be readily determined or the ACJ could not be identified. The mean bone levelACJ distance recorded at sites with overhangs was 1.77 (sd. 1.0) mm. Thirty-two per cent of the overhangs had bone level-ACJ distances which were greater than 2 mm and 7 per cent were greater than 3 mm. When the other approximal surfaces of the teeth with overhangs were

Kells and Linden: Overhanging

Tab/e 1. Mean bone level-A&l matching control surfaces

amalgam restorations

87

distances related to overhangs compared with

Bone level-ACJ Matched Overhang

Pairs (no.)

(mm) * control

Paired t

Same side

79

1.71 t- 1.1

1.63 + 1.2

0.89

Contralateral

75

1.77 + 1.1

1.86 + 1.2

ON:8 NS

*Results shown are mean + s.d.

Table II. Mean overhang size and bone level-ACJ distance in relation to tooth position Size (mm)* Bone level-ACJ Overhang First premolar Second premolar First molar Second molar

0.41 0.48 0.56 0.63

f + k +

0.2 0.3 0.3 0.4

1.75 1.65 1.93 1.61

f + -t +

0.8 0.7 1.2 1.2

Table Ill. Overhang prevalence Gilmore and Sheiham (1971)

25% of restored surfaces 32% of subjects

Hakkarainen and Ainamo (1980)

50% of posterior restorations

Than et al. (1982)

60% of all restorations 87% of subjects

Claman et al, (1986)

27% of restored surfaces

*Results shown are mean + s.d.

examined (same side control), 79 surfaces were either unrestored or acceptably restored. The mean bone levelACJ distance for these same side control surfaces was 1.63 (s.d. 1.2) mm and 34 per cent were greater than 2 mm. When the approximal surfaces of the contralateral teeth were examined (contralateral control), 75 surfaces were either unrestored or acceptably restored. The mean bone level-ACJ distance for these contralateral control surfaces was 1.86 (s.d. 1.2) mm an8 37 per cent were greater than 2 mm. Students t-test for paired observations was applied to these results and no significant differences were found between the bone levels associated with overhangs and control surfaces (Table I). There was no relationship between overhang size and the related periodontal bone level-ACJ distances (Pearson product moment coefficient of correlation, r = 0.02). There was a progressive increase in the mean size of overhangs associated with each tooth from first premolar to second molar, however, this was not paralleled by an increase in bone level-ACJ distances (Table II).

DISCUSSION The aim of the present investigation was to determine the occurrence of overhanging amalgam restorations and the extent of associated periodontal bone loss in a selected group of patients. It was found that although overhangs were common in the restorations of young adults referred for periodontal treatment, they were not associated with increased levels of bone destruction. The reproducibility of detecting overhangs by the method described in the present study was excellent, as shown by the kappa value of 0.89. The value of kappa varies between zero which represents random agreement

and one which represents perfect agreement (Hunt, 1986). However, 35 per cent of sites exhibiting overhanging amalgam restorations could not be used in the study, either because the ACJ could not be identified or was obscured by amalgam or teeth was rotated or overlapped. Some additional sites could not be used because they were not shown on the radiograph or the bone level could not be readily determined. Control surfaces presented similar difficulties and in addition some overhangs were unmatched for statistical analysis because the contralateral tooth was absent. It is possible that a larger number of readable sites could have been measured if periapical radiographs had been used. Bjorn et al. (1969) described a method which expressed bone level as a percentage of total tooth length. Their reference points were crown tip, root tip and alveolar crest, so the problem of detecting the ACJ was eliminated. In the present study bitewing radiographs, taken for diagnostic purposes, were used because they were available on file for all referrals and this avoided exposing subjects to additional radiation. The occurrence of overhangs in the young adults referred for periodontal treatment was compared with the results of other studies (Table III). The figure of 25 per cent of restored surfaces with overhangs in periodontal referrals was similar to that reported by Gilmore and Sheiham (1971) who examined a random sample of adult patients both clinically and radiographically. They did, however, report a prevalence of only 32 per cent of individuals with one or more overhangs, compared with 57 per cent of our patient sample. This may be explained by the different groups examined in the respective studies. However, in general, most studies have reported a higher percentage of restored surfaces with overhangs than were found in the present investigation. This may be because the use of radiographic methods alone underestimates the

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presence of overhangs. Gorzo et al. (1979) and Pack et al. (1990) concluded that a combined clinical and radiographic examination was required for more comprehensive overhang detection. Than et al. (1982) reported that a very high proportion of interproximal restorations have overhangs which may be attributed to their methodology which involved direct examination of extracted teeth. Nevertheless, overhanging amalgam restorations were common amongst the restorations in this group of periodontal referrals and would have constituted a considerable risk factor in predisposing to gingival problems. It is not clear why so many of these restorations placed in general dental practice had overhangs, however, access was probably one factor as there was a gradual increase in the size of overhangs from first premolar to second molar. In this and other studies, bone loss was measured by radiographic methods (Gilmore and Sheiham, 1971; Lerviketal., 1984; Kallestal and Matsson, 1989; Packet al., 1990). The validity of this technique was studied by Stoner (1972) who compared radiographic and direct measurements from the ACJ to the alveolar crest on dried mandibles. She demonstrated that bone level-ACJ distances were equal or differed by only 1 mm in 88 per cent of measurements and concluded that a dimensionally accurate radiographic image was obtainable. Kallestal and Matsson (1989) measured the distance from the ACJ to the alveolar crest on bitewing radiographs for 737 clinically healthy sites in 30 individuals aged 18 years. They found normal bone level-ACJ distances in the majority of disease-free sites to be 1.5 mm or less and no site exceeded 2 mm, and concluded that measurements greater than 2 mm from bone level to ACJ should be the criterion of choice in epidemiologial studies of bone loss. The reproducibility of the method we used for measuring bone loss (taken as a site with a bone level-ACJ distance of more than 2 mm) had a kappa value of 0.58 which represents fair agreement beyond chance (Hunt, 1986). This was not as accurate as for overhang detection which was not surprising, as bone level-ACJ distances were more difficult to measure. In the present study of young adults referred to a periodontal department, it would appear that there was some degree of periodontal involvement with bone levelACJ distances of more than 2 mm at 32 per cent of measurable surfaces with overhangs. Bone loss was not significantly greater related to overhangs, as 34 per cent of same side and 37 per cent of contralateral control surfaces also had such bone loss. It seems reasonable to conclude that approximately one-third of all the sites measured in these individuals had mild periodontal problems. The findings indicated more widespread bone destruction than found by Lervik et al. (1984) who assessed overhanging approximal restorations in Norwegian 21 year olds. Lervik et al. used both clinical and radiographic techniques and although gingivitis was present in all of the individuals they examined, very few were found to have radiographically measurable periodontitis.

Furthermore, it is not clear whether the method identified the full extent of periodontal bone loss. Stoner (1972) demonstrated that alveolar resorption usually commenced at the midpoint of the crest and that craters produced, at an early stage of resorption, could be masked by the adjacent cortical plates. Lang and Hill (1977) also concluded that early periodontal lesions may not be detected radiographically. In the present study there was no means of determining whether a restoration extended subgingivally or not. Flores de Jacoby et al. (1989) demonstrated that the subgingival location of restoration margins was clinically significant, increasing the gingival index, probing depth and sulcular flow rate. Plaque accumulation was also increased with an alteration of the microbial flora. Langet al. (1983) showed this change in microflora to be consistent with adult periodontitis. Therefore, subgingival location of restoration margins seems to be implicated as an initiator of periodontitis. Arneberg et al. (1980) showed that contact between amalgam and gingiva was more important in promoting an inflammatory response in the periodontal tissues than the presence of a moderately sized overhang. Inflammation may not always manifest as bone loss and as this was the only criterion used in the present study, the gingival reaction to overhanging amalgam restorations could not be assessed. Indeed gingival problems may have been the reason for many of the subjects being referred for treatment. Further studies are required to investigate the relationship between overhanging restorations, their location and gingival inflammation. This was a retrospective cross-sectional study of a specialized group perceived by their dentist to be in need of periodontal treatment. The large number of variables (e.g. wide range in extent of restorative treatment, different operators, etc.) makes analysis of the results difficult. The length of time which the overhangs had been in situ was a confounding factor in the analysis and accordingly there were limitations on the conclusions which could be drawn. It was not possible to determine how long the restorations had been in place as the majority of patients had been referred for specialist treatment by their own general dental practitioner and so this information was not available in the case notes. The present study showed no significantly increased bone loss associated with overhanging amalgam restorations. Similar studies on older age groups have demonstrated radiographically increased bone loss related to overhangs (Gilmore and Sheiham, 1971; Hakkarainen and Ainamo, 1980; Claman et al., 1986; Pack et al., 1990). It is well known that bone loss increases with age and Hakkarainen and Ainamo (1980) showed that bone loss associated with overhanging restorations was enhanced with age. They assumed that the increase in plaque retention associated with these restorations gives apical migration a better start than on intact surfaces. Perhaps the overhanging amalgam restorations measured in the present study had not been in situ long enough to have caused measurable bone

Kells and Linden:

destruction. Eid (1987) did attempt to correlate restoration age with the extent of periodontal bone loss and concluded that those in place for more than 2 years caused greater bone loss than those in place for a short time. The available evidence strongly suggests that it is important to prevent the formation of overhangs by the use of matrix bands and wedges during the placement of all approximal restorations. It is also important to remove overhangs as soon as possible so that their effects may be minimized. In conclusion, overhanging amalgam restorations were common in young adults referred for periodontal treatment but these overhangs were not associated with significantly increased levels of bone destruction.

References Arneberg P., Silness J. and Nordbo H. (1980) Marginal fit and cervical extent of class II amalgam restorations related to periodontal condition. J. Periodont. Res. 15, 669-677. Bjorn H., Halling A and Thyberg H. (1969) Radiographic assessment of marginal bone loss. Odontol. Revy 20, 165-179. Brunsvold M. A. and Lane J. J. (1990) The prevalence of overhanging dental restorations and their relationship to periodontal disease. J. Clin. Periodontol. 17, 67-72. Claman L. J., Koidis P. T. and Burch J. G. (1986) Proximal tooth surface quality and periodontal probing depth. J. Am. Dent. Assoc. 113, 890-893. Eid M. (1987) Relationship between overhanging amalgam restorations and periodontal disease. Quintessence ht. 18, 775-781. Flores de Jacoby L.. Zafiropoulos G. G. and Cianco S. (1989) The effect of crown margin location on plaque and periodontal health. In?. J. Periodont. Rest. Dent. 9, 197-205.

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Gilmore N. and Sheiham A. (1971) Overhanging dental restorations and periodontal disease. J. Periodonfol. 42, 8-12. Gorzo I., Newman H. N. and Strahan J. D. (1979) Amalgam restorations, plaque removal and periodontal health. J. Clin. Periodontol. 6, 98-105. Hakkarainen K. and Ainamo J. (1980) Influence of overhanging posterior tooth restorations on alveolar bone height in adults. J. Clin. Periodonfof. 7, 114-120. Hunt R. J. (1986) Percent agreement, Pearson’s correlation and Kappa as measures of inter-examiner reliability. J. Dent. Res. 65, 128-130. Kallestal C. and Matsson L. (1989) Criteria for assessment of interproximal bone loss on bite-wing radiographs in adolescents. J. Clin. Periodontal. 16, 300-304. Lang N. P. and Hill R. W. (1977) Radiograph5 in periodontics. J. Clin. Periodontol. 4, 16-28. Lang N. P.. Kiel R. A. and Anderhalden K. (1983) Clinical and microbiological effects of sub-gingival restorations with overhanging or clinically perfect margins. J. Clin. Periodontol. 10,563-578. Lervik T., Riordan P. J. and Haugejorden 0. (1984) Periodontal disease and approximal overhangs on amalgam restorations in Norwegian 21-year-olds. Community Dent. Oral Epidemiol. 12,264-268. Pack A. R. C., Coxhead L. J. and McDonald B. W. (1990) The prevalence of overhanging margins in posterior amalgam restorations and periodontal consequences. J. Clin. Periodontal. 17, 145-152. Stoner J. E. (1972) An investigation into the accuracy of measurements made on radiographs of the alveolar crests of dried mandibles. J. Periodontol. 43, 699-711. Than A., Duguid R. and McKendrick A. J. W. (1982) Relationship between restorations and the level of periodontal attachment. J. Clin. Periodontal. 9, 193-202.

Book Review The Metabolism and Toxicity of Fluoride. G. M. Whitford. Pp. 160. 1989. Basle, Karger. Hardback, DM 176.00. Professor Gary Whitford is perhaps the world’s leading authority in his field and, as such, his book carries a guarantee as a bona fide account of the state of the art. This excellent monograph gives a thoughtfully critical review of the area, referring to a careful selection from the undigestibly massive fluoride literature. The book’s six chapters cover fluoride’s general metabolism, its presence in soft tissues and body fluids and its renal excretion. The beneficial effects on teeth and its possible benefits to the skeletal tissues and health in general are discussed together with the factors which might affect its metabolism and the potential consequences of overdose. In particular, however, the monograph carefully places the author’s own extensive work on fluoride absorption, excretion and metabolism into the more general context of other fluoride studies. His work has made a signal contribution to this literature. It has pointed to the crucial

influence of local pH gradients and acid-base balance, emphasizing the fact that the undissociated HF molecule readily penetrates tissue barriers relatively impermeable to the negatively charged fluoride ion. He has added substantially to our understanding of the renal excretion of fluoride, the movements of fluoride in and out of the biological fluids and the influence this might have on its various biological effects. His work, as described in this book, is in my opinion the major recent contribution to the fluoride literature. The author does not pretend to have solved the many major questions about the element’s effects on the organism. Indeed, some of these often controversial areas are highlighted in his introduction. The monograph is, however, an excellent and timely treatise on some areas which have not previously been so well documented. No one interested in, or concerned, about the metabolism of this scientifically, medically and socially important element can aford to miss it. It is a very good and highly authoritative read. J. Weatherell

Overhanging amalgam restorations in young adults attending a periodontal department.

An important factor affecting plaque retention is the presence of amalgam restorations which are poorly contoured at the gingival margin. The aim of t...
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