Clinical evaluation of subepithelial connective tissue graft and guided tissue regeneration for treatment of Miller’s class 1 gingival recession (comparative, split mouth, six months study)

Objectives: The present study aims to clinically compare and evaluate subepithelial connective tissue graft and the GTR based root coverage in treatment of Miller’s Class I gingival recession. Study Design: 30 patients with at least one pair of Miller’s Class I gingival recession were treated either with Subepithelial connective tissue graft (Group A) or Guided tissue regeneration (Group B). Clinical parameters monitored included recession RD, width of keratinized gingiva (KG), probing depth (PD), clinical attachment level (CAL), attached gingiva (AG), residual probing depth (RPD) and % of Root coverage(%RC). Measurements were taken at baseline, three months and six months. A standard surgical procedure was used for both Group A and Group B. Data were recorded and statistical analysis was done for both intergroup and intragroup. Results: At end of six months % RC obtained were 84.47% (Group A) and 81.67% (Group B). Both treatments resulted in statistically significant improvement in clinical parameters. When compared, no statistically significant difference was found between both groups except in RPD, where it was significantly greater in Group A. Conclusions: GTR technique has advantages over subepithelial connective tissue graft for shallow Miller’s Class I defects and this procedure can be used to avoid patient discomfort and reduce treatment time. Key words:Collagen membrane, comparative split mouth study, gingival recession, subepithelial connective tissue graft, guided tissue regeneration (GTR).


Introduction
Nowadays, patients have become increasingly aware of the gingival recession and its unaesthetic features. The exposure of cementum and dentin leading to dentinal hypersensitivity becomes a constant discomforting factor to patients in everyday life. Patients present with complaints of dentinal sensitivity in areas of recession even where the defect is shallow. Such defects associated with or without abrasion cavities, increase the susceptibility to root caries (1). With changing paradigms in dentistry, aesthetic dentistry has evolved as an interdisciplinary approach treating multitude of problems and meeting patients' expectations. Amongst various techniques that have been described for the treatment of gingival recession, their efficacy and predictability are important parameters for both the patient and clinician. From the patient's perspective, an attempt to reduce the number of surgeries and cost factor must be taken into consideration. Subepithelial connective tissue graft [SCTG] technique, initially described by Langer & Langer (2) is a standard technique with predictable and reproducible results. It yields 84.84% (3) to 96% (4) in areas ≥ 3 mm and 80% to 100% (5) results in areas with ≤ 3 mm of recession depth. Recently, use of collagen membranes in Guided tissue regeneration [GTR] for root coverage has also shown promising results (1,3,5,6). Bilayered collagen membranes provide sufficient space below the flap which promotes new connective tissue formation and effectively inhibits epithelial migration (7).They are readily absorbed and hence eliminate need for second surgery or a graft harvest site (3). Like subepithelial connective tissue, the bilayered membrane may act as a scaffold and increase the recipient site tissue thickness (8). GTR based recession coverage procedures have demonstrated results comparable to that obtained by SCTG (1,3,5,6). The purpose of this study was to compare and evaluate the GTR based root coverage using bioabsorbable bilayer collagen membrane [#: ProGide ™, Bi-textured resorbable barrier, Equinox] and SCTG based root coverage procedure for treatment of shallow Miller's Class I recession defects. An attempt has been made to evaluate the utility of GTR based root coverage as compared to subepithelial connective tissue with respect to patient acceptation and aesthetic results.

Material and Methods
The study was a clinical, comparative, split mouth, randomized control trial with a time period of six months. An Ethical Committee approval was obtained before commencement of the study. The sample subjects were selected randomly from amongst the patients referred to the Department of Periodontology and Implantology, Government Dental College and Hospital, Ahmedabad, for complaints associated with gingival recession like unaesthetic looks & dentinal hypersensitivity, in maxillary and mandibular anterior teeth and premolars. A total of 30 pairs of defects were treated. Patient inclusion criteria was systemically healthy adults with realistic expectations and age up to 50 years, non pregnant, nonsmokers, with no history of antibiotic treatment within three months from the time of commencement of study, at least one pair of comparable Miller's class I recession defects in anterior teeth and premolars of maxillary and mandibular arches, good oral hygiene and sufficient palatal donor tissue. All selected subjects were explained nature of the study and a written consent was obtained on a consent form approved by the Ethical Committee. Initial therapy consisted predominantly of oral hygiene instructions. Inappropriate or faulty oral hygiene maintenance techniques were rectified. Patients were instructed to adopt Modified Stillman's method for cleaning in areas with gingival recession. Scaling and root planing was done prior to surgical therapy. Any existing trauma from occlusion was eliminated. An appointment for the surgical procedure generally was arranged 10 days after the initial procedure. At the pre-operative examination, the teeth demonstrating recession were examined with respect to soft tissue parameters. Most paired defects were treated in the same surgical session or in two consecutive appointments. Randomization for Subepithelial Connective Tissue graft [Group A] and Guided tissue regeneration based root coverage [Group B] was performed by coin toss at the beginning of the study. The right side was selected for Group A and left side for Group B. RD, KG were recorded pre-operatively and post-operatively at 10 days ,one month, three months and six months. CAL, PD, AG were recorded pre-operatively and post-operatively at three months and six months. %RC was calculated at six months post operative.
-Preparation of the recipient sites: (Fig. 1,2) The surgical area was prepared with adequate local anesthesia, using 2% Lignocaine incision in a mesio-distal direction, extending into the adjacent interdental area slightly coronal to the tooth's CEJ. Care was taken not to involve the entire papilla. An intrasulcular incision was made to join the horizontal incision. Two apically divergent vertical incisions placed at each end of the horizontal incisions extending apically into the alveolar mucosa were placed. A full thickness flap was elevated and 2 mm color of bone was exposed, after which a partial thickness flap was elevated to the mucogingival junction and a partial thickness dissection was done into the alveolar mucosa to allow for the release and coronal positioning of the flap. The intact papillae mesial and distal to the recession site were de-epithilized. The exposed, affected root surface was scaled and planed. After all site preparation was completed, the measurements were recorded for the size of the membrane and the graft.  (Fig. 1,2) was given. Post surgical instructions were given. Antibiotic & Antiinflammatory drugs were prescribed. Sutures were removed after 10 days. -Follow Up Care: Patients were seen at 10 days (Fig. 1,2) one month, three months, and six months (Fig. 1,2). After removing periodontal dressing, brushing was avoided at the treated site. Instead, cotton pellet was used to clean and slightly comb the area an apical to coronal direction for the next 4 weeks. Data was recorded at every visit. Reinforcement of oral hygiene instruction was also performed. At the end of six months, each patient was evaluated for queries related to their experience of each surgical procedure (Table 1).  -Statistical methodology: The data gathered from the present study was tabulated and analyzed using suitable techniques. Data were reported as Mean ± Standard Deviation [mean ± std] in millimeters [mm]. To study the effect overtime within groups the paired "t" test was used. The changes in average RD, KG values at one month, three months and six months from pre-operative values were tested. The changes in AG, CAL and RPD values at three months and six months from pre-operative values were tested. Further the average change from pre-operative to six months of the above mentioned parameters were compared in between groups to see the difference using Student "t" test. The "t" test values were compared with table values to show the level of significance.  (Table 2) and no difference between the groups at baseline for all the clinical parameters ( Table 3). The mean reduction of RD at six months post-operative in Group A was 1.83 ± 0.67 mm; p value <0.001 ( Table  2). The %RC obtained at sis months post-operatively was 84.47 ± 21.07 % (  (Table 2). When both the treatments were compared at six months for the difference in AG, the difference was found significant with more gain of attached gingiva in Group B [0.67 ± 0.69 mm; p value <0.05] ( Table 3). After six months all the patient response forms were collected and data was grouped (Table 5).

Discussion
The present study was designed as randomized split mouth study, in order to eliminate patient response bias and patient related factors like post operative care, healing and oral hygiene maintenance. 30 patients were selected such that, at baseline no significant difference was present among the clinical parameters recorded. For both Groups A and B, same surgical technique was used to prepare recipient site so as to standardize comparisons. All patients completed study without any un-eventful healing during initial and later phase of treatment. This can be attributed to strict surgical protocol, aseptic conditions and patient co-operation to follow post surgical instructions. Bilayered collagen membranes are known to effectively inhibit epithelial migration and provide sufficient space for appropriate cells [e.g. PDL cells, bone cells] to repopulate the area (10). No case of exposure of membrane was reported. This could be due to the use of bilayered collagen membrane (3) and properties of collagen to augment flap thickness by providing a collagenous scaffold (1). One of the important factors increasing the risk for gingival recession may be a thin and delicate marginal tissue covering a non-vascularized root surface (11). In case of surgical coverage of denuded root surface, it might therefore be desirable to increase the dimensions of the tissue i.e. width and thickness of keratinzed gingiva for preventive reasons (11). Subepithelial connective tissue graft offers similar advantage of increasing recipient site thickness. Some site may require a gingivoplasty procedure to achieve final form and contour. Two cases in the present study required gingivoplasty. An important criterion for success of GTR is the post surgical stability of the coronally advance flap [CAF] that completely covers the membrane. At least 2 mm of width of keratinized gingiva [KG] ( Table 2) has been known to improve treatment results (6,12). Hence Miller's Class I recession defects with at least 2 mm of KG yield satisfactory results with GTR technique (  (14). Better results were obtained by many studies (15)(16)(17)(18)(19). This can be explained by the fact that in the above studies deep and Class II recession defects were used. Deeper defects result in more %RC as compared to shallow defects (20 (5). Various biological determinants are impli-cated in the alteration of gingival dimensions that occur following mucogingival surgery, including induced differentiation of the gingival epithelium by morphogenetic stimuli from the underlying connective tissue, intrinsic specialization resting within the basal cells of the epithelium and post surgery reversal of the mucogingival junction towards its genetically determined location (13). Conversely, in GTR procedures, a moderate increase in width of keratinized tissue derives from the proliferation of granulation tissue from the periodontal, which is able to induce keratinization (18).  (Table 2). When Groups A and B were compared, there was significant difference with more increase in AG and gain in CAL in Group B (Table 3). This can be correlated to the highly significant difference in RPD with significant increase in RPD in Group A and decrease in RPD in Group B (Table 2). However in Group B the difference in RPD is not significant. These findings suggest formation of a new attachment on a portion of the covered root surface. Considering the limitation of this study of being only clinical, it is not possible to state whether this gain in attachment in Group B is facilitated by formation of a new attachment. On histological evaluation of healing of SCTG (24), at 60 days long junctional epithelium with no new bone or cementum formation was found. Another histologic case report suggested that various types of tissue attachments including periodontal regeneration may occur over a recession defect after placement of SCTG (25). Whereas histologic evaluation of healing after GTR in other case reports have reported the possibility of obtaining new connective tissue attachment, crestal bone regeneration in the treatment of human buccal recession (26)(27)(28). An interesting observation in this study was that subjects viewed the two techniques as equivalent in terms of outcomes and overall satisfaction (Table 5). Subjects reported greater overall satisfaction with the Group B, possibly explained elimination of the need for a second surgical procedure and reduction of treatment time.
In conclusion, the purpose of this randomized control trial was to compare the clinical outcomes of traditional subepithelial connective tissue graft  Table 2. Clinical parameters at baseline and 6 months.