The study design and protocol were conducted according to the Helsinki Declaration as revised in 2000 and were approved by the Institutional Ethics Committee of Ninth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (SH9H-2021-T102-1).
This retrospective study included patients with GRs who had treated with MCAT at the Department of Periodontology of Shanghai Ninth People’s Hospital attached to Shanghai JiaoTong University School of Medicine between March 2017 and March 2021.
The baseline date was defined as the time of mucogingival surgery. The primary endpoint was root coverage esthetic score (RES) at 12 months.
The follow-up was the time between the baseline date until the primary endpoint, or the end of study follow-up period set as March 31, 2021 to allow at least a minimum follow-up of 12 months for all patients. All patients were recalled at 2 weeks, 1 month, 6 months and 12 months after surgery.
Baseline demographic characteristics of all patients were collected as following: age, gender, orthodontic history, frenum attachment, single or multiple GRs, classification of periodontitis (classified into 6 categories: periodontal health, gingivitis, periodontitis stage I, periodontitis stage II, periodontitis stage III, and periodontitis stage IV), periodontal phenotype (classified into 3 categories: thin-scalloped, thick-scalloped, and thick flat), position of the involved tooth (6 categories: anterior maxilla, maxillary premolars, maxillary molars, anterior mandible, mandibular premolars, and mandibular molars).
The primary outcome variable was root coverage esthetic score (RES). The secondary outcome variables were mean root coverage (mRC), complete root coverage (CRC), gain in clinical attachment level (CAL), increase in keratinized tissue width (KTW), changes in periodontal probing depth (PPD), changes in gingival index (GI), changes in plaque index (PLI), and changes in patients’ aesthetic satisfaction by a visual analogue scale (VAS).
This study was performed according to the STROBE checklist.
Inclusion and exclusion criteria
Patients satisfying the following criteria were enrolled in this study:
≥ 18 years old
Single or multiple GR defects of type I (RT1) (≤ 5 mm)
Identifiable cemento-enamel junction (CEJ)
Surgical treatment of GRs with modified coronally advanced tunnel technique (MCAT)
Minimum of 12 months of follow-up
Availability at regular follow-up appointments for clinical examination, intra-oral photographs and periodontal maintenance therapy
To minimize the confounding factor of clinical and aesthetic outcomes following root-coverage procedure, patients were excluded from the study if they met 1 or more of the following criteria: smoking; extruded or malpositioned teeth; existing caries, pulpal and periapical diseases, dental restorations, or non-cavitated caries lesions (NCCL) in the area to be treated; have mucogingival surgery or other periodontal surgery on involved sites.
These exclusions are unlikely to cause major selection bias.
We defined the average of the angles of the distal and mesial gingival papillae of the involved teeth as the gingival papilla width. The area of the gingival papilla is approximated as an isosceles triangle. The value of the apex angle of the papilla can be obtained by measuring the two lateral sides of the same length and the corresponding bottom side and then applying the trigonometric function. The measurements were rounded to the nearest 0.5mm (Fig. 1).
An independent investigator (CHW) measured all trial outcomes. A total of six patients not included in the study with at least two GRs were used to calibrate the investigator, who assessed all GRs in each patient with an interval of 24 h between recordings. Calibration was accepted when ≥ 90% of the recordings were reproduced within a difference of 1.0 mm.
All subjects were evaluated by periodontal clinical examination (UNC-15 periodontal probe, Hu-Friedy®, Chicago, USA) and intra-oral photographs (Digital SLR camera, Cannon 700D, Cannon Inc., Tokyo, Japan) at baseline, 2 weeks after surgery, 1-month post-surgery, 6 months post-surgery and 1-year post-surgery.
Clinical assessments of the involved tooth were evaluated at baseline, 1, 6, and 12 months after surgery. The following measurements were collected: mRC and CRC at 12 months after surgery, periodontal probing depth (PPD) (baseline & after 12 months), clinical attachment level (CAL) (baseline & after 12 months), keratinized tissue width (KTW) (baseline & after 12 months), gingival index (GI) (Löe and Silness, 1963) (baseline, after 1, 6, 12 months) and plaque index (PLI) (Silness and Löe, 1964) (baseline, after 1, 6, 12 months).
At suture removal date, possible soft tissue complications (necrosis, infection, bleeding) were collected.
Aesthetic evaluation was carried out using the root coverage esthetic score (RES) at 12 months post-surgery. The RES system contained five variables: Gingival margin (GM: 0, 3 or 6), Marginal Tissue Contour (MTC: 0 or 1), Muco-Gingival Junction (MGJ: 0 or 1), Soft Tissue Texture (STT: 0 or 1) and Gingival Color (0 or 1), with final RES value ranging from 0 to 10. Patients’ aesthetic satisfaction with surgical site was evaluated quantitatively by a visual analogue scale (VAS) from 0 to 10 at baseline and at the 12-month evaluation.
All patients received oral hygiene instruction (to modify traumatic tooth brushing habits), full-mouth supragingival scaling, subgingival scaling and polishing by the same periodontal specialist (DJC). 4–6 weeks later, reevaluation was performed. The mucogingival surgery was performed only when adequate plaque control was reached (Full-mouth plaque score and full-month bleeding score < 25%).
All surgical procedures were performed at the Department of Periodontology of Shanghai Ninth People’s Hospital attached to Shanghai JiaoTong University School of Medicine by the same surgeon (DJC), who has 9-year experience as a periodontal specialist. Before the surgery, a 0.12% chlorhexidine rinse was applied for intraoral antisepsis. After disinfection of the oral cavity, injection of local anesthetics (Primacaine™ adrenaline 1/100000, Produits Dentaires Pierre Rolland, France) was performed. The tunnel flap was performed started with intrasulcular incisions by using microsurgical blade. To ensure a coronal positioning of the tunnel flap, the intrasulcular incisions were extended to the neighboring teeth. A split-full-split thickness flap was then preparation: after reaching the buccal bone crest with intrasulcular cuts, flap elevation was continued by full-thickness preparation for the next 3–4 mm with microsurgical periosteal separator (Stoma®, German). Subsequently, a sharp horizontal dissection of the periosteum had to be performed. The supraperiosteal dissection was extended well beyond the mucogingival junction, deep into the mucosal tissues, in order to gain sufficient flap mobility from the apical aspect. The full-thickness flap elevation was carefully performed at the buccal papillary regions. A subepithelial connective tissue graft (SCTG) was harvested from the palate according to the gingival recession width and height and then carefully inserted into the tunnel by guided sutures (5 − 0 polyglactin suture). Finally, sling sutures were performed with 6 − 0 nylon monofilament non-absorbable suture to position the flap coronal for completely covering the SCTG.
Patients were instructed to 0.12% chlorhexidine rinse three times a day for 1 minute every day and lightly brush surgical sites with an ultra-soft bristle toothbrush after 2 weeks postoperatively. In addition, amoxicillin (500 mg 3 times per day for 3 days) and ibuprofen (1 tablet per day when necessary) for infection and pain control. The suture was removed 10–14 days after surgery. A clinical case is shown in Fig. 2.
Patients’ characteristics were presented as absolute and relative frequencies for categorical outcomes. The Shapiro-Wilk test was carried out to evaluate the normality. The normally distributed variables were described using the mean and standard deviation (SD) including 95% confidence intervals (CI), while the median and interquartile range (IQR) was used to describe non-normally distributed data.
Clinical parameters’ changes from baseline through 12 months after surgery were analyzed with paired-samples t-test (or Wilcoxon signed-rank test) and repeated-measures ANOVA (or Friedman test) with a Bonferroni's post-test for multiple comparisons. In an attempt to determine whether the papilla width was associated with 12-month clinical and aesthetic outcomes, five multiple line regression models were set by the following dependent variables: RES, mRC, VAS change, gain in CAL, and gain in KTW (continuous dependent variables); and a logistic regression was set by CRC (binary variable). Multivariate analysis was performed to adjust for age, sex, periodontal phenotype, position of the involved tooth, and other potential confounders. All hypothesis tests were conducted at the 5% level of significance.
All data were analyzed by a statistical program (SPSS Statistical for Windows, IBM Corp., Armonk, NY, USA, Version 25.0). Patients' names were hidden during all of data analysis.