title: Clinical evaluation of the supraosseous gingivae before and after crown lengthening. Effect of posterior crown margin placement on gingival health. Surgical crown lengthening: evaluation of the biological width. Placement of the preparation line and periodontal health--a prospective 2-year clinical study.
abstract: BACKGROUND Despite the broad use of  crown-lengthening surgery ( CLS )  , there is no complete agreement as to the desired amount of exposed sound tooth structure needed to accommo date both the restorative needs and the reformation of the supraosseous gingiva ( SOG ) . Classically , it has been proposed that approximately 3 mm of SOG , the amount considered by most to be present before surgery , will be reformed after CLS . The purpose of this study was to test the viability of transsulcular probing ( TSP )  and to determine whether the SOG that forms after CLS is the same as that measured preoperatively . METHODS Nineteen patients underwent CLS with the surgical tooth acting both as the control and the test site . The SOG dimension was measured by TSP before and 6 months after surgery . Stents were used as fixed reference points . Intraclass correlations were calculated to test for the reliability of TSP measurements versus direct-bone-level ( DBL ) measurements . A Wilcoxon signed-rank test was used to compare the means for the mean buccal , mean lingual , and overall mean SOG dimensions at baseline to corresponding measurements at 6 months . RESULTS Intraclass correlation coefficients for TSP measures of SOG to DBL measures of SOG ranged from 83.4 % agreement to 91.9 % agreement , with all correlations being highly significant ( P < 0.001 ) , indicating a high degree of agreement between TSP and DBL . The differences in SOG dimensions , 6 months after surgery compared to baseline , were as follows : mean buccal , 0.51 mm ; mean lingual/palatal , 0.61 mm ; overall mean , 0.56 mm . These differences were significant for all three comparisons ( P < 0.001 , P < 0.004 , and P < 0.001 , respectively ) . CONCLUSIONS TSP is an accurate alternative method to DBL in clinical ly determining SOG dimensions . Six months after CLS , the SOG dimension was reduced by 0.51 to 0.61 mm compared to the presurgical measurement , with these mean differences being statistically significant STATEMENT OF PROBLEM The clinical impact of  posterior crown margin placement on gingival health has not been thoroughly quantified . PURPOSE This study evaluated the effect of posterior crown margin placement with multivariate analysis . MATERIAL AND METHODS Ten general dentists review ed 240 patients with 480 metal-ceramic crowns in a prospect i ve clinical trial . The alloy was r and omly selected from 2 high gold , 1 low gold , and 1 palladium alloy . Variables were the alloy used , oral hygiene index score before treatment , location of crown margins at baseline , and plaque index and sulcus bleeding index scores recorded for restored and control teeth after 1 year . The effect of crown margin placement on sulcular bleeding and plaque accumulation was analyzed with regression models ( P<.05 ) . RESULTS The probability of plaque at 1 year increased with increasing oral hygiene index score before treatment . The lingual surfaces demonstrated the highest probability of plaque . The risk of bleeding at intrasulcular posterior crown margins was approximately twice that at supragingival margins . Poor oral hygiene before treatment and plaque also were associated with sulcular bleeding . Facial sites exhibited a lower probability of sulcular bleeding than lingual surfaces . Type of alloy did not influence sulcular bleeding . CONCLUSION In this study , placement of crown margins was one of several parameters that affected gingival health BACKGROUND Previous surgical crown lengthening studies have investigated positional changes of the free gingival margin but not the biological width . Histological studies utilizing animal models have shown that postoperative crestal resorption allowed reestablishment of the biological width . However , very little work has been done in humans . Therefore , the purpose of this study was to evaluate the positional changes of the periodontal tissues , particularly the biological width , following surgical crown lengthening in human subjects . METHODS Twenty-three ( 23 ) patients who needed surgical crown lengthening to gain retention necessary for prosthetic treatment and /or to access caries , tooth fracture , or previous prosthetic margins entered the study . The following parameters were obtained from line angles of treated teeth ( teeth requiring surgical crown lengthening ) and adjacent teeth with adjacent and non-adjacent sites : plaque and gingival indexes , free gingival margin , probing depth , attachment level , bone level , direct bone level , and biological width . During surgery , the bone level was reduced based on the future prosthetic margin and predetermined biological width ; flaps were placed at the bony crest . Patients were examined at baseline and at 3 and 6 months postoperatively . RESULTS Eighteen patients completed the study . Overall , the amount of bone resected was 1 to 5 mm . At 90 % of treated sites , > or = 3 mm of bone was removed . At 3 months , the apical displacement of the free gingival margin at non-adjacent , adjacent , and treated sites was 2.46 + /- 0.25 mm , 2.68 + /- 0.20 mm , and 3.07 + /- 0.16 mm , respectively . There was no significant change in the position of the free gingival margin from 3 to 6 months . The biological width at all sites was smaller at 3 and 6 months compared to baseline ( P<0.05 ) except for the treated sites , which were not significantly different from baseline at 6 months . CONCLUSIONS During surgical crown lengthening , the bone level was lowered for placement of the prosthetic margin and reestablishment of the biological width . The biological width , at treated sites , was reestablished to its original vertical dimension by 6 months . In addition , a consistent 3 mm gain of coronal tooth structure was observed at the 3- and 6-month examinations The aim of this prospect i ve clinical 2-year study was to determine whether the placement of the proximal margins of crowns within the zone of the biologic width results in periodontal alterations . In 41 patients , 116 prepared teeth as well as 82 unrestored , healthy contralateral teeth were examined . The following indices were determined before as well as 3 , 6 , 12 , and 24 months after preparation :  hygiene index , papillary bleeding index ( PBI ) , and probing depth .  After preparation , the distance between the restoration margins and the alveolar crest was measured with a modified periodontal probe on both proximal aspects of each tooth . These values were classified into 3 groups : I = < or = 1 mm between crown margin and alveolar crest , II = 1 to 2 mm , and III = > 2 mm . In addition , radiographs were taken directly after cementation of each restoration and after 12 and 24 months . The hygiene index did not significantly vary during the investigation , but PBI increased in all groups . The highest PBI increase was found in group I ; in this group , the most significant increase was found between 3 and 6 months after preparation . The mean probing depth only increased in group I during the first 3 months after preparation on the mesial aspects . Only minor changes were found on the distal aspects of the teeth in group I and on all aspects in groups II and III . No alterations of the bone levels were diagnosed on the radiographs . These results indicate that the location of the restoration margins within the zone of the biologic width may impair the periodontal health of restored teeth
target: No universal dimension of the biologic width appears to exist .
background: BACKGROUND Consideration of the biologic width in restorative dentistry seems to be important for maintaining periodontal health .
  OBJECTIVE To evaluate the dimensions of the biologic width in humans .