Clinical and microbic ^ dgical effects of sub - gingival restoration # with overhanging or clinicaily perfect margins

The close association between restorations with overhanging margins and chronic destructive periodontitis has been known for many years. However, the mechanisms by which overhanging restorations will interact in the pathogenesis of periodontal disease are still unknown. Generally it is accepted that overhanging restorations contribute to the promotion of the disease process by virtue of their capacity to retain bacteria! plaque. The purpose of the present study was to determine ii" the placement of subgingival-restQra.tlQns with overhajiging margins resuits in changes m the subgingival microflora. 9 dental students with clean teeth and clinically healthy gingivae (GKO.!) gave their consent to participate in the study. 5 MOD cast gold onlays with 1 mm proximal overhanging margins were placed in mandibular molars for 19-27 weeks. They were replaced in a cross-over design by 5 similar oniays with clinically perfect margins which served as controls. Another 5 onlays were placed in reverse order in the remaining patients. Prior to and every 2-3 weeks after insertion, subgingival microbiological samples were obtained by inserting a fine sterile paper point for 30 sec into the gingival sulcus subjacent to the restoration. The predominant cultivable flora was determined using continuous anaerobic culturing techniques. Following the placement of restorations with overhanging margins, a subgingival flora was detected which closely resembled that of ehronic_£^iod.Qiititis. Increased proportions, of. Gram-negative anaerobic bacteria, black-pigmented Bacteraides and an increased anaerobe: facultative ratio were noted. Following the placement of the restorations with clinically perfect margins, a microflora characteristic for gingival health or initial gingivitis was observed. Biack-pigmentedSuc/eraii/uj were detected in very low proportions (1.6-3.8%). These changes in the subgingival microflora were obvious irrespective of whether the restorations with the overhanging margins were placed in the first period of the experiment or following the cross-over. Clinically, increasing gingival indices were detected al the site.s where overhanging margins were placed. Bleeding on gentle probing always preceded the peak level of black-pigmented Bacteroides. Loss of attachment was not detected in any site. Changes in the subgingivai microflora after the placement of restorations with overhanging margins document a potential mechanism for the initiation of periodonta! disease associated with iatrogenic factors. The close association between iatrogetiic facRegolati 1972, Rodriguez-Ferrer et al. 1980) tors such as overhanging restorations and de~ have repeatedly doctimented these relationstructive periodontitis has been recognized ships. Only one recent study (Than et al. 1982) since the early 1900's (Black 1912). Epidemion extracted teeth challenged the close associaologicai (Wright 1963, von Fitchner 1964, Alextion between overhanging restorations and the ander 1967, 1968, Giimore & Sheiham 1971) as promotion of the periodontal disease process, well as clinical experimental studies (Renggli & However, also in this study a greater loss of 564 LANG, KIEL AND ANDERHALDEN attachment was found associated with ill-fitting and overhanging amalgam margins in molar teeth where these lesions are known to be located most frequently (Alexander 1967, 1968, Gilmore & Sheiham 1971). In daily practice overhanging margins of dental restorations present a very frequently observed problem (Bjorn et al. 1969, 1970) which may greatly impinge on the maintenance of gingival and periodontal health (for review see Leon 1977). Consequently overhanging restorations will result in excessive loss of the alveolar bone support if they are not recognized and removed for a few years (Hakkarainen & Ainamo 1980, Jeffcoat & Howeli 1980). Although the contributory factor of overhanging restorations in the etiology of periodontal disease has been generally accepted by the dental profession, the mechanisms by which overhanging margins interact in the pathogenesis of periodontal disease are still not completely understood. Some of the irritant effects proposed included the physical and/or chemical properties of dental materials used in restorative procedures (Waerhaug 1956, Waerhaug & Zander 1957, Zander 1957, App (961). Furthermore, the surface characteristics of dental materials which may lead to a greater tendency of plaque retention (Wise & Dykema 1975, von Rothen et al. 1978) have been mentioned. Even though it is now generally accepted that overhanging restorations may contribute to moTE accentuated gingival inflammation by virtue of their retentive capacity for bacterial plaque rather than as a result of mechanical irritation (Ramfjord et al. 1966: World Workshop in Periodontics), the specific aspects of this Local bacterial accumulation have never been elucidated. This concept suggests that the plaque mass per se may be responsible for the inflammation of the gingiva and the loss of the periodontal supporting tissues. However, recent studies on the microbiota associated with _ various forms of periodontiti.s suggested a more specific approach. The fact that the total mass of bacteria may be less important than its composition has led to our current concept of periodontitis being an opportunistic infection (Loesche 1976, Socransky 1977, Kornman et al. 1981) with specific periodontopathic microorganisms. In view of these recent observations in oral microbiology earlier conclusions concerning the role of overhanging subgingival margins and periodontal disease may in fact be inaccurate. No investigation has made an attempt to assess the individual components of the plaque associated with these restorations. Hence, it was the purpose of this study to examine the clinical and microbiological effects of the placement of subgingival restorations with either clinically perfect or overhanging margins in patients with periodontal health. Material and Methods 9 patients in excellent systemic health, aged between 20 and 30 years, requiring molar MOD cast gold restorations for the treatment of caries volunteered and gave their informed consent to participate in this study. One restoration was placed in a mandibular molar tooth of each patient with the exception of one patient who received two such restorations. Hence, a total of 10 teeth with 20 sites (mesial and distal) was available for evaluation. Prior to the preparation of the test teeth, all_patients received comprehensive dental treatment for ail other dental problems including oral hygiene instructions and thorough scaling and tO-Qtplaning. None_pf the patients required surgical periodontal therapy. At the beginning of the study all patients, therefore, presented with clean teeth and healthy gingivae with mean Plague and Gingival Indices apprq^aching 0. Furthermore, it was ascertained that there was no history of administration of antibiotics for at least 6 months prior to the study.