Osseous Surgery for Crown Lengthening: a 6-Month Clinical Study
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30181.qxd 9/16/04 2:22 PM Page 1288 Volume 75 • Number 9 Case Series Osseous Surgery for Crown Lengthening: A 6-Month Clinical Study David E. Deas,* Alan J. Moritz,* Howard T. McDonnell,* Charles A. Powell,* and Brian L. Mealey* Background: Despite the fact that surgical crown Results: Throughout the entire 6-month healing lengthening is a commonly performed treatment, little period, descriptive statistics revealed no significant time is known about the specific surgical endpoints of the or group differences in plaque and bleeding scores. At procedure or the stability of the newly attained crown treated sites, the mean gain of crown height at surgery height over time. Recent clinical reports have ranged was 2.27 ± 1.1 mm. This was reduced to 1.91 ± 1.08 mm across a spectrum from significant tissue rebound to at 1 month, 1.69 ± 1.02 mm at 3 months, and 1.57 ± 1.01 remarkable stability using similar surgical techniques. mm at 6 months. At adjacent sites, the gain of crown The purpose of this study was to assess the stability of length was 2.18 ± 0.98 mm, 1.61 ± 0.98 mm, 1.43 ± surgical crown lengthening procedures performed by 0.96 mm, and 1.30 ± 0.96 mm at surgery, 1, 3, and various surgeons using specific guidelines to determine 6 months, respectively. At non-adjacent sites the crown surgical endpoints. Specifically, we sought to determine height increased 1.06 ± 1.07 mm, 1.00 ± 0.93 mm, the following: 1) What is the immediate increase in clin- 0.84 ± 1.00 mm, and 0.76 ± 0.85 mm, respectively. These ical crown height following surgery? 2) How stable is mean measurements were significantly different for each the established crown length over a 6-month period? treatment group at each time interval and appeared not 3) How much supporting bone is removed to establish to have stabilized between 3 and 6 months. The mean the new crown length? 4) How does the position of the osseous reduction at treated, adjacent, and non-adjacent flap margin relative to the alveolar bone at surgical clo- sites was 1.13 ± 0.90 mm, 0.78 ± 0.75 mm, and 0.065 ± sure relate to the stability of crown height? 0.69 mm, respectively. Frequency distribution of osseous Methods: Twenty-five patients requiring crown length- reduction demonstrated that 23.6% of treated sites had ening of 43 teeth were included in this study. Clinical 0 mm, 44.3% had 1 mm, 25.4% had 2 mm, 6.2% had indices recorded at eight sites on each molar and six sites 3 mm, and less than 1% had ≥4 mm of bone removed on each premolar included plaque, bleeding on probing, to establish crown height. More bone removal was noted probing depth, and relative attachment level from a cus- at premolar than at molar sites; however, this was not tomized probing stent. Surgical measurements at the statistically significant. When tissue rebound following same sites included the distance from stent to alveolar surgery was plotted against post-surgical flap position, bone both before and after osseous surgery and the dis- it was noted that the closer the flap margin was sutured tance from flap margin to alveolar bone after suturing. to the alveolar crest, the greater the tissue rebound dur- Clinical measurements were repeated at 1, 3, and 6 ing the post-surgical period. This rebound ranged from months after surgery. Sites were divided into three 1.33 ± 1.02 mm when the flap was sutured ≤1 mm from groups. All sites on teeth targeted for crown lengthening the alveolar crest, to −0.16 ± 1.15 mm when the flap were labeled treated sites (TT). Interproximal sites on was sutured ≥4 mm from the alveolar crest. neighboring teeth were labeled adjacent (AA) if they Conclusions: These data suggest that there is a sig- shared a proximal surface with a treated tooth and non- nificant tissue rebound following crown-lengthening adjacent (AN) if they were on the opposite side, away surgery that has not fully stabilized by 6 months. The from the treated tooth. amount of tissue rebound seems related to the posi- tion of the flap relative to the alveolar crest at suturing. These findings support the premise that clinicians should establish proper crown height during surgery without overreliance on flap placement at the osseous crest. J Periodontol 2004;75:1288-1294. * U.S. Air Force Periodontics Residency, Wilford Hall Medical Center, Lackland Air Force Base, TX. KEY WORDS The views expressed in this article are those of the authors and are not to be construed as official nor as reflecting the views of the United States Air Alveolar bone; follow-up studies; surgical flaps; Force or Department of Defense. tooth/anatomy and histology; tooth crown/surgery. 1288 30181.qxd 9/16/04 2:22 PM Page 1289 J Periodontol • September 2004 Deas, Moritz, McDonnell, Powell, Mealey ccording to the 2003 American Academy of excess of that reported in the prior studies. However, Periodontology Practice Profile Survey, one of the authors reported no significant change in the posi- Athe most common reasons for periodontal tion of the free gingival margin between 3 and 6 months surgery is for purposes of crown lengthening.1 The crown post-surgery. lengthening procedure is often necessary both to pro- The purpose of the present investigation was to fur- vide adequate retention and resistance form by gaining ther assess the short-term stability of surgical crown supracrestal tooth length,2-5 as well as to prevent im- lengthening procedures using an osseous resective pingement of restoration margins on the attachment technique and specific guidelines to determine the sur- apparatus by reestablishing the biologic width.6,7 While gical endpoint. This study sought to answer the follow- many restorative dentists are very specific in their re- ing questions: 1) What is the immediate increase in quests for crown lengthening, others simply trust the sur- crown height following surgery? 2) What happens to geon to return the patient to them with longer crowns that this newly established crown height over time? 3) How will allow for adequate restoration. Without specific guid- much supporting bone is removed during crown length- ance, the surgical goal may become nothing more than to ening surgery? 4) How does the position of the flap make the tooth “a little longer.” In addition, there is scant margin relative to the alveolar crest at surgical closure information in the literature relating post-surgical flap relate to the stability of surgically created crown height? position at the alveolar crest to the stability of crown lengthening over time. Knowing that an optimal flap MATERIALS AND METHODS placement will enhance the outcome of these procedures The experimental protocol was approved by the Institu- may be of significant benefit to the surgeon and restora- tional Review Board for human studies, Wilford Hall Med- tive dentist alike. ical Center (WHMC), Lackland Air Force Base, San Consistent with studies of the dimensions of the peri- Antonio, Texas. This study evaluated 25 consecutively odontal attachment apparatus described as the biologic treated periodontally healthy patients (18 males, seven width,8,9 several authors have proposed that crown females) referred to the Department of Periodontics at lengthening procedures optimally create at least 3 mm WHMC for crown lengthening surgery on 43 posterior of tooth structure between the alveolar crest and future teeth between December 2001 and August 2002. Med- restorative margin to allow for proper restoration.10-12 ical and dental histories were reviewed and no con- Ingber et al.,10 for example, proposed 3 mm to allow traindications to surgical therapy were noted. All but one 1 mm for the connective tissue attachment, 1 mm for patient required crown lengthening prior to complete cov- the epithelial attachment, and 1 mm for placement of erage crown or fixed partial denture fabrication; the other a margin. Although some clinicians have favored an patient required surgical access for placement of an amal- amount >3 mm,4,13 the 3 mm distance from crest to gam restoration. All patients were restored by the end of crown margin has over the years become fairly ingrained the study and prosthetic treatment was begun no sooner in the dental literature. Attempting to attribute a fixed than 6 weeks after surgery. measurement to the biologic width may indeed disre- Each patient received an initial examination and treat- gard surface-to-surface, tooth-to-tooth, and patient-to- ment planning session. Oral hygiene procedures were patient variability; however, it is our observation that reviewed, and scaling and/or prophylaxis were scheduled many practitioners delivering surgical crown lengthen- if deemed necessary by the examining periodontist. After ing therapies commonly rely on the 3 mm figure. treatment plan presentation, patients were provided infor- While numerous technique and case report articles mation about the study and indicated willingness to parti- are available, few controlled examinations of the post- cipate by providing written informed consent. An alginate surgical changes following crown lengthening surgery impression was then made of each arch to be surgically have been published. Of the controlled studies we treated in order to fabricate customized probing stents. reviewed, two had as a surgical goal a 3 mm distance Full-arch probing stents were made from a 2 mm clear between the alveolar crest and restorative margin14,15 copolyester plastic† using a pressure form matrix ma- and a third did not mention a surgical endpoint.16 Inter- chine.‡ To insure proper fit after restorative procedures, the estingly, each of these studies reported that the desired teeth to be restored were overwaxed by 1 mm.