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Interactions between the gingiva and the margin of restorations

Interactions between the gingiva and the margin of restorations






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    Interactions between the gingiva and the margin of restorations Interactions between the gingiva and the margin of restorations Document Transcript

    • J Clin Periodontol 2003; 30: 379–385 Copyright r Blackwell Munksgaard 2003 Printed in Denmark. All rights reserved Interactions between the gingiva Allan Padbury, Jr, Robert Eber and Hom-Lay Wang Department of Periodontics/Prevention/ and the margin of restorations Geriatrics, School of Dentistry, University of Michigan, Ann Arbor, MI, USA Padbury Jr A, Eber R, Wang H-L. Interactions between the gingiva and the margin of restorations. J Clin Periodontol 2003; 30: 379–385. r Blackwell Munksgaard, 2003. Abstract An adequate understanding of the relationship between periodontal tissues and restorative dentistry is paramount to ensure adequate form, function, esthetics, and comfort of the dentition. While most clinicians are aware of this important relationship, uncertainty remains regarding specific concepts such as the biologic width and indications and applications for surgical crown lengthening. This review discusses the concept of the biologic width and its relationship to periodontal health Key words: restorations; crown margins; and restorative dentistry. The importance of restorative margin location, materials, and biological width; periodontal and gingival contours related to periodontal health is also addressed. The rationale and indications health for surgical crown lengthening are elaborated. Particular surgical principles of crown lengthening are examined in detail. Accepted for publication 27 May 2002 Periodontal tissues form the foundation and relationship of the dentogingival There is general agreement that for proper esthetics, function, and com- junction in humans. Measurements made placing restorative margins within the fort of the dentition. All prosthetic and from the dentogingival components of biologic width frequently leads to gin- restorative therapies generally require a 287 individual teeth from 30 autopsy gival inflammation, clinical attachment healthy periodontium as a prerequisite specimens established that there is a loss, and bone loss. This is thought to be for successful outcome. The interplay definite proportional relationship be- due to the destructive inflammatory between periodontics and restorative tween the alveolar crest, the connective response to microbial plaque located at dentistry is present at many fronts, tissue attachment, the epithelial attach- deeply placed restorative margins. including location of restorative mar- ment, and the sulcus depth. Gargiulo et Clinically, these changes are manifested gins, crown contours, and response of al. (1961) reported the following mean as deepened periodontal pockets or the gingival tissues to restorative pre- dimensions: a sulcus depth of 0.69 mm, gingival recession. These changes have parations. The purpose of this review an epithelial attachment of 0.97 mm, and been substantiated by studies that have paper is to summarize both past and a connective tissue attachment of assessed the histological and clinical present literature regarding basic con- 1.07 mm. Based on this work, the responses of periodontal tissues to cepts of periodontal–restorative inter- biologic width is commonly stated to be restorative margins placed within the actions, particularly with regard to 2.04 mm, which represents the sum of the biologic width. Newcomb (1974) ana- interactions at the gingival margin, epithelial and connective tissue measure- lyzed 66 anterior crowns with subgingi- including the dentogingival attachment ments. One must realize however that val margins of varying depths and and the impact of restorations, which significant variations of dimensions were compared them to uncrowned contral- encroach upon these tissues. observed, particularly the epithelial at- ateral controls. The results showed that tachment, which ranged from 1.0 to the nearer a subgingival crown margin 9.0 mm. The connective tissue attach- was to the epithelial attachment (hence Biologic Width ment, on the other hand, was relatively nearer the biologic width), the more The term biologic width is familiar to constant. Recently, similar biologic likely that severe gingival inflammation most clinicians, yet there still exists width dimensions were also reported occurred. Parma-Benfenati et al. (1986) confusion regarding its meaning and (Vacek et al. 1994). Evaluating 171 observed approximately 5 mm of oss- relevance to clinical procedures. The cadaver tooth surfaces, they observed eous resorption when restorative mar- biologic width is defined as the dimen- mean measurements of 1.34 mm for gins were placed at the alveolar crest sion of the soft tissue, which is attached sulcus depth, 1.14 for epithelial attach- in beagle dogs. Minimal resorption to the portion of the tooth coronal to the ment, and 0.77 mm for connective tissue was observed where restorations were crest of the alveolar bone. This term was attachment. This group also found that placed 4 mm coronal to the alveolar based on the work of Gargiulo et al. the connective tissue attachment was the crest. Bone resorption was particularly (1961), who described the dimensions most consistent measurement (Fig. 1). severe in areas with thin cortical bone
    • 380 Padbury Jr et al. not disrupt the junctional epithelium or connective tissue apparatus during pre- paration and impression taking. The authors recommended limiting subgin- gival margin extension to 0.5–1.0 mm because it is impossible for the clinician to detect where the sulcular epithelium ends and the junctional epithelium begins. They also emphasized allowing a minimum 3.0 mm distance from the alveolar crest to the crown margin. Block (1987) also claimed that the biologic width was difficult for clini- cians to visualize and suggested the free gingival margin as the reference point for measurements for margin place- ment. Block stated that when restorative margins end at or near the alveolar crest level, surgical crown-lengthening pro- cedures are necessary. It is important to note that recom- mendations regarding placement of re- storations in relation to the biologic Fig. 1. Biologic width. width are based on opinion articles. They have evolved due to clinical experiences and interpretations of var- ious experimental studies. Nonetheless, it appears that a minimum of 3.0 mm of and interdental septa. Tal et al. (1989) margins must be from the bone crest to space between restorative margins and further demonstrated that biologic width avoid deleterious effects. Ingber et al. alveolar bone is a dimension that is violation results in loss of periodontal (1977) suggested that a minimum of prudent to adhere to in restorative support. Class V cavities were prepared 3 mm was required from the restorative treatment planning. in canine teeth of 43 beagle dogs so that margin to the alveolar crest to permit the apical border rested on the alveolar adequate healing and restoration of crest. Control teeth had Class V notches the tooth. Maynard & Wilson (1979) Restorative Margin Location placed at the cemento-enamel junction. divided the periodontium into three Not only do restorative margins placed All cavities were restored with amal- dimensions: superficial physiologic, subgingivally risk invading the attach- gam, and 1 year following surgery, crevicular physiologic, and subcrevicu- ment apparatus, but also unwanted gingival recession and bone loss were lar physiologic. The superficial physio- tissue effects appear to result merely significantly greater at test sites com- logic dimension represents the free and due to their subgingival location, re- pared to control teeth (3.16 and attached gingiva surrounding the tooth, gardless of depth of sulcus penetration. 1.17 mm versus 0.5 and 0.15 mm, re- while the crevicular physiologic dimen- Orkin et al. (1987) demonstrated that spectively). Recently, Gunay et al. sion represents the gingival crevice – subgingival restorations had a greater (2000) demonstrated that restorative extending from the free gingival margin chance of bleeding and exhibiting margin placement within the biologic to the junctional epithelium. The sub- gingival recession than supragingival width was detrimental to periodontal crevicular physiologic space is analo- restorations. Silness (1980) evaluated health. In a 2-year study, they evaluated gous to the biologic width described by the periodontal condition of the lingual 116 prepared teeth compared to 82 Gargiulo et al. (1961), consisting of the surfaces of 385 fixed partial denture unrestored teeth in 41 patients. Papillary junctional epithelium and connective abutment teeth. He found that a supra- bleeding score and probing depths tissue attachment. Maynard & Wilson gingival position of the crown margin increased at sites where the restorative claimed that all three of these dimen- was the most favorable, whereas mar- margin was o1 mm from the alveolar sions affect restorative treatment deci- gins below the gingival margin signifi- crest. sions and the clinician should cantly compromised gingival health. Encroachment of the biologic width ‘conceptualize’ all three areas and the Renggli & Regolati (1972) demon- becomes of particular concern when interplay between them and restorative strated that gingivitis and plaque accu- considering the restoration of a tooth margins. In particular, the authors mulation were more pronounced in that has fractured or been destroyed by claimed that margin placement into the interdental areas with well-adapted sub- caries near the alveolar crest level. Also, subcrevicular physiologic space should gingival amalgam fillings compared to esthetic demands often require ‘‘bury- be avoided to prevent the placement of sound tooth structure Waerhaug (1978) ing’’ of restorative margins subgingiv- ‘permanent calculus’ beyond the cre- stated that subgingival restorations are ally, which can lead to violation of this vice. Nevins & Skurow (1984) stated plaque-retentive areas that are inacces- space. Various authors have recom- that when subgingival margins are sible to scaling instruments. These mended minimal distances restorative indicated, the restorative dentist must retentive areas continue to accumulate
    • Interactions between gingiva and margin of restorations 381 plaque even in the presence of adequate although crown margins may be placed changes in the associated microflora to supragingival plaque control. subgingivally, it is highly likely that that of one resembling the flora ob- In a cross-sectional study of 134 over time the margins will eventually be served in adult chronic periodontitis. periodontitis patients, Wang et al. located supragingivally. Valderhaug & Increased proportions of Gram-negative (1993) demonstrated that posterior teeth Birkeland (1976) evaluated 114 patients anaerobic rods, in particular black with crowns or proximal restorations with 329 total crown restorations. Most pigmented Bacteroides, were observed. were associated with more furcation of the crowns (59%) were located Chen et al. (1987) evaluated human involvement and greater attachment loss subgingivally at the beginning of the extracted teeth with overhanging re- than teeth without proximal restora- study period. After 5 years, only 32% of storations compared to nonrestored tions. Stetler & Bissada (1987) evalu- the crown margins remained below the teeth and reported greater attachment ated the effects of width of keratinized gingival margin. They also demon- loss associated with overhang surfaces. gingiva and subgingival restorations on strated that greater mean attachment Pack et al. (1990) assessed the preva- periodontal health. Teeth with subgin- loss was associated with subgingival lence of restoration overhangs and gival restorations and narrow zones of restorations compared to supragingival associated periodontal disease of 100 keratinized gingiva showed significantly margins (1.2 versus 0.6 mm). patients who had recently completed higher gingival index scores than teeth treatment. Sixty-two percent of all with submarginal restorations with wide proximal restorations had overhanging zones of keratinized gingiva. Thus, margins, and periodontal disease was clinicians should consider gingival Restoration Overhangs more severe when overhangs were augmentation for teeth with minimal Overhanging dental restorations have present. When adjacent to neighboring keratinized gingiva before placing long been viewed as a contributing teeth, overhanging margins also signifi- subgingival restorations. factor to gingivitis and possible period- cantly affected the periodontal status of Waerhaug (1980) demonstrated gin- ontal attachment loss. They pose a those teeth. givitis and attachment loss associated significant concern as their prevalence Thus, overhangs not only increase with submarginal restorations in mon- has been estimated at 25–76% for all plaque mass but also increase the keys and dogs. Clinical and histological restored surfaces (Brunsvold & Lane specific periodontal pathogens in the observations of human teeth by Dragoo 1990). It is generally accepted that plaque. Most overhanging restorations & Williams (1981, 1982) demonstrated overhanging restorations contribute to can be recontoured without replacing compromised healing associated with gingival inflammation due to their the restoration, and this should be gingival bevel crown margins compared retentive capacity for bacterial plaque. considered a standard component of to shoulder preparations. Flores-de-Ja- Gilmore & Sheiham (1971) illustrated nonsurgical treatment. A variety of coby et al. (1989) studied the effects of interproximal radiographic bone loss devices have been suggested for over- crown margin location on periodontal adjacent to posterior teeth with over- hang removal, most based on clinical health and bacterial morphotypes in hanging restorations. Highfield & Po- opinions. One study demonstrated that a humans 6–8 weeks and 1 year post- well (1978) demonstrated that overhang motor-driven diamond tip is faster for insertion. Subgingival margins demon- removal plus professional plaque con- removing overhangs and led to smooth- strated increased plaque, gingival index trol improved gingival indices and bone er restorations compared to sonic scalers scores, and probing depths. Further- scores. Jeffcoat and Howell (1980) and curettes, respectively (Spinks et al. more, more spirochetes, fusiforms, rods, demonstrated a link to the severity of 1986). and filamentous bacteria were found to the overhang and the amount of period- be associated with subgingival margins. ontal destruction. Based upon radio- The location of restorative margins is graphic evaluations of 100 teeth with determined by many factors, including overhangs and 100 without, they re- Artificial Crown Contour esthetics, retentive factors, susceptibil- ported greater bone loss around teeth Regarding crown contour, conflicting ity to root caries, and degree of gingival with large overhangs. The severity of reports exist regarding the proper con- recession. While many clinicians place bone loss was directly proportional to tours necessary for maintaining gingival restorative margins subgingivally, the the severity of the overhang. Overhangs health. Some report that an artificial detrimental effects of margins below the were designated as large if they occu- crown should follow the original anat- free gingival margin is obviously well pied 451% of the interproximal space. omy of tooth contour to permit func- documented. While most periodontists Small and medium overhangs (o20% tional stimulation and to maintain would prefer restorative margins to and 20–50% of the interproximal space, gingival health. Others advise that remain coronal to the sulcus, it is respectively) were not associated with crowns should be undercontoured for understood that certain conditions ne- bone loss. Lang et al. (1983) investi- better periodontal health. Yuodelis et al. cessitate placement of subgingival mar- gated the specific aspects of the local (1973) demonstrated that the greater the gins. These may include esthetic bacterial accumulation associated with amount of facial and lingual bulge of an concerns, need for increased retention overhanging restorations. Five gold artificial crown, the more the plaque form, refinement of preexisting margins, MOD onlays with 1 mm overhangs were retained at the cervical margin. Ehrlich root caries, cervical abrasion, and root placed in mandibular molars of period- & Hochman (1980) evaluated differ- sensitivity. However, if none of these ontally healthy dental students for 9–27 ences in subgingival crown contours in factors is of concern, it appears prudent weeks. They were replaced in a cross- four periodontally healthy patients and to place restorative margins supragin- over design by onlays with clinically determined that factors other than var- givally. It is also important for clin- perfect margins. The placement of iations in crown contour of 71 mm icians and patients to understand that subgingival overhangs resulted in determined gingival response. In a
    • 382 Padbury Jr et al. review of periodontal–prosthetic inter- esthetic deficiencies, and teeth shor- reduction are limited because bone actions, Becker & Kaldahl (1981) tened by incomplete exposure of the removal is often necessary to provide opined that buccal and lingual crown anatomic crown are all candidates for adequate distance from the osseous crest contours should be ‘‘flat’’, not ‘‘fat’’, surgical lengthening. Oftentimes, failure to the anticipated restoration margin, usually o0.5 mm wider than the CEJ, to perform surgery prior to margin allowing for biologic width. Therefore, and that furcation areas should be placement in these situations leads to APF with osseous surgery is the most ‘‘fluted’’ or ‘‘barreled out’’ to accom- margins placed too near the alveolar common technique for crown-lengthen- modate oral hygiene in these areas. crest, thus invading the biologic width ing surgery. APF with osseous surgery space. Therefore, in the early stages of consists of a reverse bevel incision and restorative treatment planning, if the subsequent mucoperiosteal flap reflec- Proximal Contact Relationships clinician believes that the margin of the tion. Vertical releasing incisions are final restoration will be r3 mm from often made to allow better access and Clinical impressions suggest loose or the alveolar bone crest, crown lengthen- apical positioning of the flap. Initial open proximal contacts to be contri- ing should be recommended. This can incisions may be intrasulcular if gingi- buting factors to periodontal pocket not only be accomplished by surgery but val width is narrow, or scalloped when formation. Nonetheless, the literature also by orthodontic forced eruption, or a gingival width is wide. Generally, an proposes conflicting views on the sub- combination of both. Numerous factors adjacent tooth on each side of the tooth ject. This may be due to different oral may determine if crown lengthening is to be lengthened is included in the hygiene levels of the different study needed and often, more important, if a surgical procedure to allow for proper populations. Kepic & O’Leary (1978), particular tooth (or teeth) is indeed a contour of the gingiva and underlying for example, demonstrated no differ- candidate for crown-lengthening sur- bone. Initial osseous recontouring is ence in periodontal breakdown at sites gery. Before proceeding with surgery, completed with the use of rotary with deficient proximal contacts com- the clinician should always first con- handpieces and then completed with pared to satisfactory sites, provided sider whether orthodontic extrusion is chisels and curettes to achieve the adequate oral hygiene was maintained. appropriate. Failure to consider ortho- desired reduction while maintaining a Larato (1971) evaluated 121 dry adult dontic extrusion can lead to poor scalloped, parabolic bony contour to human skulls and found that only 38 of cosmetic outcomes (i.e. gingival reces- follow the desired contour of the over- 206 intrabony lesions (18%) were sion, particularly in anterior teeth), lying gingiva. In addition, end cutting associated with factors able to cause poorer crown:root ratios, and loss of burs are currently available that are food impaction. While the role of bone support on adjacent teeth (Ingber designed for removing bone with mini- deficient interproximal integrity may et al. 1977). mal risk of damaging the root. be unclear, open contacts leading to Often, caries or lack of tooth struc- Most authors agree that a minimum food impaction are often uncomfortable ture necessitates bone removal to a distance of 3 mm is required from the to the patient, and it is still generally point where the periodontal support of osseous crest to the final restorative accepted that tight interproximal con- the tooth is compromised, a furcation is margin following a crown-lengthening tacts are important for gingival health. exposed, or an inadequate crown:root procedure to allow the margin to finish Hancock et al. (1980) evaluated 40 ratio results. If these situations are ¨ supragingivally (Bragger et al. 1992). naval recruits to determine the relation- anticipated, the treatment plan must be Thus, 3 mm allows for 1 mm of supra- ship of interdental contacts on period- reevaluated and the strategic value of crestal connective tissue attachment, ontal status. Results revealed no the tooth considered. Also, esthetic 1 mm of junctional epithelium, and significant relationship between contact issues must be evaluated presurgically, 1 mm for sulcus depth. It should be type and gingival index or probing particularly if crown lengthening is noted again, however, that 3 mm as- depth. However, a significant relation- needed for the anterior teeth. sumes a biologic width of approxi- ship was seen between food impaction While many situations require it, mately 2.04 mm, based on Gargiulo’s and contact type (greater food impac- crown-lengthening surgery is often un- findings. It is important to remember tion at sites with open or loose con- derutilized. Because of this, too much that there was significant individual tacts), and between food impaction and reliability is placed on post and core variation in Gargiulo’s study, especially probing depth. These findings help restorations and deep subgingival mar- at the epithelial attachment. Therefore, support the notion that food impaction gin placement to gain adequate reten- it may be more reasonable to allow contributes to periodontal disease. tion for restorative purposes (Allen more than 3 mm between the restorative 1993). This often leads to root fractures margin and the crestal bone to allow for in the case of post and core restorations, individual variation. Wagenberg et al. Surgical Crown Lengthening and violation of the biologic width in (1989), in fact, suggested a 5 mm Crown-lengthening surgery is designed the case of deep subgingival margins. distance from bone to the restorative to increase clinical crown length for These factors contribute to greater margin. They clarified that the length of various reasons. The clinical crown is expense and frustration for the patient, the clinical crown, furcation locations, that portion of the tooth that extends hence further complicating restorative and esthetic considerations limit sur- occlusally or incisally from the invest- and periodontal therapy. gery. They also advocated waiting 8–12 ing soft tissue, usually the gingiva Surgical methods for crown length- weeks before final prosthetic treatment. (American Academy of Periodontology ening include (a) gingivectomy, (b) This group noted that bone removal is 1992). Teeth with subgingival caries or apically positioned flap surgery (APF), inherently unnatural to the periodontist shortened by extensive caries, fractures, and (c) APF with osseous reduction. and thus clinicians have a tendency to short clinical crowns with or without Gingivectomy and APF without osseous remove too little bone during crown
    • Interactions between gingiva and margin of restorations 383 lengthening procedures. Others have distance will account for individual Some investigators have questioned also advocated allowing 5 mm from biologic width variations and most whether the biologic width dimensions bone to restoration to ensure adequate likely ‘‘assure’’ that enough space will return following crown-lengthening osseous reduction. It is felt that 5 mm exist between the bone crest and the procedures. Caton’s group observed that will allow for individual variations in eventual restorative margin. For teeth following osseous surgery and apically biologic width dimensions and will that are planned for post and core positioned flap, there was a reduced prevent the clinician from removing restorations, the surgeon should provide distance between the gingival margin too little bone. The phenomenon of at least 5–6 mm of exposed tooth above and the apical extent of the junctional underreduction was recently demon- the osseous crest. This again allows for epithelium (Caton & Nyman 1981). strated by Herrero et al. (1995). They 4 mm from the alveolar crest to the Also, since it is widely known that evaluated the amount of actual surgical restorative margin while also account- osseous surgery results in crestal bone crown lengthening achieved during ing for a 1.5 mm ferrule length. The resorption (Wilderman et al. 1970), surgery in relation to the desired 3 mm ferrule effect refers to the idea that a questions have arisen as to the exact goal. Clinicians of different experience 3601 metal collar of crown surrounding nature of the dento-gingival unit follow- levels performed the lengthening proce- the parallel walls of the dentin should ing osseous resective surgery. Oakley et dures, and a separate examiner com- extend at least 1.5 mm apical to the al. (1999) investigated the formation of pleted the measurements before, during, shoulder of the preparation (Libman & the dento-gingival unit following and 8 weeks after surgery. Results Nicholls 1995). crown-lengthening surgery in nonhu- demonstrated a mean reduction of For teeth planned for crown restora- man primates. Crown lengthening was 2.4 mm, 0.6 mm less than that required tions, generally these cases present with performed in the incisor region of three to achieve the 3 mm goal. Also, experi- the tooth or portions of the tooth adult monkeys. Histometric analysis enced clinicians achieved greater oss- fractured or decayed at the gingival revealed that the biologic width is eous reduction. The authors concluded margin. The clinician should provide reestablished following the procedure. that clinicians might need to be more enough coronal tooth exposure to allow The junctional epithelium is established aggressive and take measurements dur- for adequate retention of the crown at the apical extent of root planing. ing surgery to achieve their desired goal along with planing for a 4 mm distance Space for the supracrestal connective of osseous reduction. Pontoriero & from the restorative margin to the tissue attachment is created by crestal Carnevale (2001) demonstrated the un- alveolar crest. The clinician should also resorption of alveolar bone. This contra- wanted effects of minimal osseous bear in mind that bone resorption dicts the views of some authors who reduction during crown-lengthening usually follows osseous resective sur- opined that the supracrestal connective surgery. Eighty-four teeth underwent gery. It has been estimated that an tissue would reform coronal to the crown-lengthening procedures and were additional 0.6–0.8 mm of bone resorp- apical extent of root planing, thus followed for 1 year postoperatively. tion occurs up to 1 year following necessitating a greater exposure of tooth While initially a mean of 3.9 mm of osseous surgery (Wilderman et al. structure during surgery. new tooth structure was exposed, 1 year 1970, Selipsky 1976). later a mean of 3.05 mm of coronal ¨ Bragger et al. (1992) completed one displacement of the gingival occurred, of the few controlled studies evaluating thus resulting in an overall mean gain of periodontal changes in the healing Conclusions crown length of 0.85 mm. In all these phase after surgical crown lengthening. The health of the periodontal tissues is surgical procedures, while the gingival Twenty-five patients who received sur- dependent on properly designed restora- margin was repositioned apically fol- gery were monitored for 6 months. tive materials. Overhanging restorations lowing surgery, minimal osseous reduc- Clinical parameters of 43 test and 42 and open interproximal contacts should tion was completed (approximately control teeth were evaluated using an be addressed and remedied during the 1 mm). This study demonstrates the acrylic splint as a reference. The results disease control phase of periodontal importance of adequate alveolar crest demonstrated alveolar crest reduction of therapy. Regarding restorative margins, reduction in order to allow for a 1–2 mm following surgery in 53% of undoubtedly it is preferable if margins desirable final gingival margin location. cases. 3–4 mm of bone removal was can remain coronal to the free gingival A common problem during crown- carried out in 4% of cases. Mean tissue margin. Obviously, subgingival margin lengthening surgery is that the surgeon recession following surgery was placement is often unavoidable. How- cannot precisely determine where the 1.32 mm, while 29% of sites demon- ever, care must be taken to involve as restorative dentist will place the final strated 1–4 mm gingival recession be- little of the sulcus as possible. Evidence restorative margin. Hence, it is impera- tween 6 weeks and 6 months suggests that even minimal encroach- tive that the surgeon and the restorative postoperatively. Attachment levels or ment on the subgingival tissue can lead dentist communicate prior to treatment. probing depths did not change after 6 to deleterious effects on the period- When uncertainty remains, a successful ¨ weeks of healing (Bragger et al. 1992). ontium. Furthermore, deep margin pla- outcome can usually be achieved if the This study lends support to the concept cement risks invading the soft tissue surgeon follows certain basic principles. of refraining from restorative treatment attachment of the gingiva to the tooth, When an amalgam or composite re- for at least 6 weeks following crown- often leading to a more pronounced storation is planned for a particular lengthening surgery. Furthermore, due plaque-induced inflammatory response. tooth, the clinician must allow for to the possibility of recession, delaying If restorative margins need to be placed approximately 4 mm distance between margin placement for 6 months follow- near the alveolar crest, crown-lengthen- the apical extent of the planned restora- ing surgery in areas of esthetic concerns ing surgery or orthodontic extrusion tive margin and the alveolar crest. This may be indicated. should be considered to provide ade-
    • 384 Padbury Jr et al. quate tooth structure while simulta- ´ chirurgicale sont analyses. Des principes chir- tional Journal of Periodontics and Restora- neously assuring the integrity of the ´ urgicaux particuliers de l’elongation coronaire tive Dentistry 20, 171–181. biologic width. Although individual ´ ´ sont examines en detail. Hancock, E. B., Mayo, C. V., Schwab, R. R. & variations exist in the soft tissue attach- Wirthlin, M. R. (1980) Influence of inter- dental contacts on periodontal status. Journal ment around teeth, there is general References of Periodontology 51, 445–449. agreement that a minimum of 3 mm Herrero, F., Scott, J. B., Maropis, P. S. & should exist from the restorative margin Allen, E. P. (1993) Surgical crown lengthening Yukna, R. A. (1995) Clinical comparison of to the alveolar bone, allowing for 2 mm for function and esthetics. Dental Clinics of desired versus actual amount of surgical of biologic width space and 1 mm for North America 37, 163–179. crown lengthening. Journal of Periodontol- sulcus depth. American Academy of Periodontolgy (1992) ogy 66, 568–571. Glossary of periodontal terms, 3rd edition, p. Highfield, J. E. & Powell, R. N. (1978) Effects 11. Chicago: American Academy of Period- of removal of posterior overhanging metallic ontolgy. margins of restorations upon the periodontal Acknowledgments Becker, C. M. & Kaldahl, W. B. (1981) Current tissues. Journal of Clinical Periodontology 5, This work was partially supported by theories of crown contour, margin placement, 169–181. the University of Michigan, Periodontal and pontic design. Journal of Prosthetic Ingber, J. S., Rose, L. F. & Coslet, J. G. (1977) Graduate Student Research Fund. Dentistry 45, 268–277. The biologic width’’ – a concept in period- Block, P. L. (1987) Restorative margins and ontics and restorative dentistry. 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