The study is a prospective single-center, split-mouth, randomized, controlled clinical trial. 40 patients who are with Miller class I and II gingival recessions in need of the coverage of exposed root surfaces. The assessments, interventions, and follow-ups will be performed at First Clinical Division, Peking University School and Hospital of Stomatology (Beijing, China). This study has been approved by the biomedical ethics committee of Peking University School and Hospital of Stomatology (PKUSSIRB-202054029) and registered in International Clinical Trials Registry Platform (ICTRP) under the ID: ChiCTR2000033230.
The patients are selected according to the following inclusion criteria:
- Age ≥18 years;
- Patients willing to attend the study and provide an informed consent;
- Systemically healthy and no contraindication for periodontal surgery;
- Presence of localized bilateral Miller class I or II adjacent gingival recessions ≥ 3mm with thin periodontal phenotype in the maxillary or mandibular arches without any clinical sign of active/chronic periodontal disease;
- Having full-mouth plaque score and full-mouth bleeding score ≤15%;
- No history of surgical intervention in the relevant areas.
- Habitual tobacco smoking and/or chewing;
- Habitual alcohol consumption;
- Pregnancy or lactating women;
- Participants having crowns or restorations involving the CEJ or those with nonidentifiable CEJ;
- Individuals using medications that can interfere with healing and allergic to penicillin.
Subjects who are looking for the coverage of exposed root surfaces and are willing to join this trial will be recruited from First Clinical Division, Peking University School and Hospital of Stomatology. Subjects will receive the study information. Before subject is included in the present study, the consent form must be signed. Figure 1 shows the procedure of participants through this trial.
Randomization, grouping, and blinding
The randomization process is performed by a professor in the absence of the working investigators using a software program by a computer-generated randomly permuted block. Allocation is concealed in opaque envelopes until immediately before surgery to determine which sites of gingival recession will receive the test procedure and the contralateral teeth will receive the control procedure. All subjects will be treated by one experienced and calibrated periodontist who do not partake in the allocation, examination, and statistical analysis. The treatment plan and grouping will be confidential to the examiner and statistical analyst. Under postoperative adverse events, unblinding is permissible.
All surgical procedures are performed at the First Clinical Division, Peking University School and Hospital of Stomatology by the same periodontist. Before the surgical procedures, the periodontal status is evaluated; the comprehensive clinical examination is performed; and the etiology of the recessions is determined for each eligible participant by a calibrated examiner. Identified etiological factors are eliminated; detailed oral hygiene instructions (OHI) are given; and full-mouth supragingival scaling and tooth polishing are performed. Surgical procedures are initiated at least 4 weeks after the final appointment in which the inclusion criteria are re-evaluated and the good oral hygiene is approved.
The surgeries are performed by an experienced periodontist who has been calibrated before the trial. Both test and control surgeries are performed at the same clinical appointment. The same surgical procedure is used for both groups, except that control sites received the ADMG (test group), while contralateral sites received the CTG (control group). Following local anesthesia, a coronally advanced flap design is performed in all cases as described by Zucchelli previously . Briefly, an intracrevicular incision is made through the bottom of the crevice. Two mesial and distal vertical releasing incisions are made including both papillae adjacent to the area of gingival recession. The papillaes in the surgical site are de-epithelialised by interdental incisions considering as anatomic papilla. The flap is elevated with a split-full-split approach in the apico-coronal direction and the soft tissue apical to the root exposures is elevated in a full-thickness manner to facilitate the highest possible thickness of the flap to cover the recession area. Finally, the apical part of the flap is raised in a split-thickness manner to release residual muscle tension and to facilitate the flap passively positioned over the CEJ without tension. Following flap elevation, the exposed root surface was gently planed with sharp curets (Gracey Curettes, Hu-Friedy, Chicago, Illinois).
The control group then received CTG obtained from the palate as previously described . The connective tissue is trimmed to a shape and size designed to cover the root surface and the surrounding bone. The thickness of graft is 1mm.
The exposed root surface of the test group is treated with an ADM that is aseptically rehydrated in sterile saline, according to the manufacturer’s instructions. The graft is trimmed to a shape and size designed to cover the root surface and the surrounding bone. The basement membrane side is placed adjacent to bone and tooth, and the connective tissue side is placed facing the flap, according to Harris . The thickness of graft is 1mm.
Both the ADM and CT cover the recipient area at the level of CEJ on the coronal site and get over the vascular tissues 3 mm on the lateral and the apical borders of the recession defect. The grafts in both groups are secured on interdental areas and on lateral sites using 6-0 bioabsorbable sutures. The CAF is then positioned 1 mm coronally to the CEJ and covered the total graft surfaces in both groups. The CAF is sutured stress free at this position using 6-0 non-absorbable sutures, which are also used to secure the donor site. Microsurgical hand instruments (Hu-Friedy, Chicago, Illinois) and ×4.0 loupe (Q Optics, Texas) are used in all surgical procedures. No periodontal dressing is utilized.
All patients are instructed to discontinue tooth brushing and to avoid trauma or pressure at the surgical site. A 0.12% chlorhexidine digluconate gargle is prescribed 3 times daily for 14 days, and amoxicillin (500 mg, tid) was prescribed for 7 days.
The sutures are removed after 14 days, and the patients are instructed to clean the surgical sites with a 0.12% chlorhexidine digluconate gargle 3 times daily for 14 days. After this period, they will resume mechanical tooth cleaning of the treated areas using a soft toothbrush and a careful roll technique. During the follow-up recalls, oral hygiene instructions are reinforced and professional tooth cleaning is performed if needed.
Individual acrylic stents are prepared to use as the reference points to align the probe properly, and to ensure reproducibility during reevaluation examinations.
Clinical parameters including plaque index (PLI) , gingival index (GI) , probing depth (PD), clinical attachment level (CAL), gingival recession depth (GRD), gingival recession width (GRW), and keratinized tissue width (KTW) are measured using a periodontal probe (PCP-UNC 15; Hu-Friedy Manufacturing, Chicago, IL, USA) and rounded to the nearest 0.5 mm by a calibrated examiner (not the therapist), who has been trained to adequate levels of accuracy and reproducibility. Thin phenotype decision is given after gingival thickness (GT) measurement as described by Ahmedbeyli .
Examination during the follow-ups
All subjects will be recalled for follow-up at weeks 2, 4, 12, 24, 48 and 96 after the surgery. We will like to make a phone call to remind participants to promote complete follow-up. At weeks 4, 12, 24, 48 and 96 after the surgery, PLI, GI, PD, CAL, GRD, GRW, KTW, periodontal phenotype and the color measurements using an intraoral spectrophotometer (SpectroShade, Medical High Technologies) will be examined by a calibrated examiner. Aesthetic outcomes are evaluated using the Root Coverage Esthetic Score (RES) .
Patient satisfaction is assessed using a Visual Analogue Scale/Score (VAS) [73, 74]. Each patient is questioned about his/her satisfaction with regard to the following patient-centred criteria: root coverage; gingival colour, shape and contour; surgical procedure in terms of pain and discomfort related to the duration of the procedure; post-surgical phase in terms of the pain, swelling and post-operative complications.
The primary parameters of this trial are mean root coverage (MRC), CRC, KTW, RES, and color change (∆E). MRC percentage is calculated as [(GRD baseline-GRD 12, 24, 48, 96 weeks)/GRD baseline] x 100%. CRC is evaluated at tooth level and is calculated as the percentage of teeth with gingival recession having complete coverage achieved as the gingival margin at or over CEJ [(Teeth with CRC)/(All treated teeth)] x 100%.
The secondary parameters of this trial are PD, CAL, and VAS scale to patient satisfaction.
The sample size of this trial is calculated based on the formula: According to the preliminary experiment results and data analysis from currently published articles, the mean difference of the reduction in gingival recession (δ) is around 0.1 mm and the standard deviation in groups (σ) is around 0.3 mm.
If the inspection level (α) is set at 0.05 and the power of test (β) is set at 90%, then 36 subjects will be required for each group. Given a loss to follow-up is around 10%, this study will require 40 subjects for each group.
The recruitment began in June 2020, and the intervention period will be ending in June 2023. Figure 2 shows the schedule of enrollment, intervention, and assessments.
Data collection and management
The data of the patients will be documented both on spreadsheets and databases. The statistical analysis will be performed by two experimenters independently. The data monitoring committee is composited. There is not competing interests in the data monitoring committee.
The statistical analysis will be performed using a software program (SPSS version 22; SPSS, USA). The distribution of the variables was validated by D'Agostino-Pearson omnibus normality test and parametric tests are used for inter- and intra-group comparisons. Paired t test was used for inter-group comparisons of PI, GI, PD, CAL, GRD, GRW, KTW and the changes of these parameters. Intragroup comparisons for the same variables are done using repeated measures one-way ANOVA test and followed by Bonferroni correction for post hoc multiple comparisons. The number of teeth with MRC and CRC between groups were compared using Fisher's exact test. Multiple imputation will be used to handle missing data. Two-tailed p-values < 0.05 are considered statistically significant. Data analyses will be performed by SPSS software.
The trial has been approved by the biomedical ethics committee of Peking University School and Hospital of Stomatology (PKUSSIRB-202054029). Before subjects are officially recruited into this study, they will be given a study information and will be asked to sign the consent form. During the trial, any important protocol modifications will communicate to relevant parties.
Subjects will be informed that they have the right to withdraw from this trial at any time without providing a reason. If the withdrawal occurs, treatment will also be provided to the subject. Under postoperative adverse events, discontinuing intervention for a given trial participant is permissible.
Dissemination of results
The results of this trial will be saved at International Clinical Trials Registry Platform (ICTRP) and published in an international peer-reviewed journal which will allow for anyone access to obtain the results.