Published online Jun 24, 2021.
https://doi.org/10.5051/jpis.2007320366
A retrospective comparison of 3 approaches of vestibuloplasty around mandibular molar implants: apically positioned flap versus free gingival graft versus modified periosteal fenestration
Abstract
Purpose
This study aimed to clinically evaluate the efficacy of vestibuloplasty around lower molar implants using 3 different modalities: apically positioned flap alone (APF), APF with a free gingival graft (FGG), and APF with modified periosteal fenestration (mPF).
Methods
Three different vestibuloplasty procedures during second-stage implant surgery were performed at the mandibular molar area in 61 patients with a shallow vestibule and insufficient keratinized tissue (KT). The clinical measurements of KT width were recorded at baseline, immediately after surgery (T0), 6 months after surgery (T6), and 12 months after surgery (T12). Soft tissue esthetic scores were measured.
Results
An additional KT width gain from baseline to T12 of approximately 2 mm was obtained with FGG and mPF compared to that with APF. Shrinkage of the re-established tissue was lower with mPF and FGG than with APF, whereas the esthetic profile was better with APF and mPF than with FGG.
Conclusions
Within the limitations of this study, mPF showed potential as a promising approach for vestibuloplasty around the lower molar implants compared to the traditional APF and FGG.
Graphical Abstract
INTRODUCTION
Many studies have focused on the relationship between the width of keratinized tissue (KT) and peri-implant health. Several reports have presented associations between improved esthetic results, peri-implant health, implant survival, and adequate KT width [1, 2, 3]. However, other reports have found that there were minimal or no associations among involution of the peri-implant tissue, implant survival, and the width of KT [4, 5]. Therefore, the association between KT width and peri-implant health remains controversial, although insufficient KT width was found to be correlated with a shallow vestibule [6, 7, 8]. Management of oral hygiene in patients with inadequate KT width or a shallow vestibule at the molar area could result in severe plaque accumulation, and consequently, a higher prevalence of peri-implant mucositis and peri-implantitis [9, 10].
Various vestibuloplasty procedures to attain adequate vestibular depth and KT width have been introduced, the most common of which are the apically positioned flap (APF) [11] and APF combined with a free gingival graft (FGG) [12]. APF is a relatively simple technique that does not involve a secondary donor site; however, it has the disadvantage of an increased risk of relapse due to wound contraction [13]. FGG is the most common mucogingival surgical procedure used to increase KT width [14], but it involves a secondary donor site for supplying the graft, which increases the patient's discomfort, operation time, and risk of complications [15].
In the 1960s, various periosteal fenestration techniques were introduced to overcome the tendency of relapse after APF and to increase the KT width [16, 17, 18]. Yadav et al. [19] reported that periosteal fenestration in a patient with narrow KT and shallow vestibule around the mandibular anterior teeth achieved results comparable to those with FGG. Recently, Lee and Kwon [20] reported that the modified periosteal fenestration (mPF) procedure, which builds upon the traditional method suggested by Corn [17], could be an alternate treatment modality for vestibuloplasty around dental implants.
The current retrospective study aimed to compare the clinical outcomes of 3 approaches—APF only, FGG, and mPF—around lower molar implants.
MATERIALS AND METHODS
Study design
This was a retrospective cohort study; patients who visited the Department of Periodontology of Chosun University Dental Hospital between January 2014 and December 2018 were screened according to the selection criteria. The inclusion criteria were as follows: 1) patients who underwent treatment with APF, APF with FGG, or APF with mPF along with second-stage implant surgery at the mandibular molar sites; 2) patients with a shallow vestibule and insufficient KT width (≤2 mm in the apico-coronal direction from the middle crest) at baseline, and 3) patients whose KT width measurements were recorded on the electronic medical record (EMR) chart and whose clinical pictures were taken during the postoperative follow-up period. In total, 61 patients (23 men and 38 women) aged between 35 and 79 years (mean age, 58.7±10.4 years) were identified. Each patient was allocated to the APF, FGG, or mPF group according to the vestibuloplasty procedure performed. The research protocol was approved by the Institutional Review Board of Chosun University Dental Hospital (CUDHIRB-1806-004).
Surgical procedure
All vestibuloplasty procedures during second-stage implant surgery were performed by an experienced periodontal surgeon (WPL). In the APF group, intra-oral gargling with 0.1% chlorhexidine solution (Hexamedine solution, Bukwang Pharm. Co., Seoul, Korea) was performed 1 minute prior to surgery. Under local anesthesia, a partial-thickness flap was prepared with a 1-mm width of KT at the coronal boundary of the APF, if possible. Periosteal sutures were used to stabilize the apical region. Subsequently, an inner mucoperiosteal flap was elevated from the alveolar ridge or the punching technique was performed to fix the healing abutment to the implant fixture. After fixation, the buccolingual full-thickness flap was secured with interrupted sutures if needed. In the FGG group, 1.5-mm-thick FGG was harvested from the palate after preparation of the periosteal recipient bed as in the APF group. FGG was secured at the recipient site with interrupted sutures and crossed mattress sutures. After stabilizing the graft, a wet gauze was firmly applied for several minutes to allow only a thin layer of fibrin clot under the donor tissue. In the mPF group, the same procedure as in the APF group was performed. Subsequently, a horizontal parallel periosteal fenestration incision was made from the coronal border of the APF toward the crown of the tooth at 2 mm, using a No. 15c blade. A full-thickness flap was elevated in the apical direction with a periosteal elevator from the incision site to create an osseous exposure of ≥2 mm in the form of a linear island of denuded bone (Figure 1). The wound was covered with a resorbable periodontal pack (Reso-Pac®, Hager & Werken GmbH & Co. KG, Duisburg, Germany).
Figure 1
Representative clinical photographs at each measurement time point for each group.
APF: apically positioned flap, FGG: free gingival graft, mPF: modified periosteal fenestration, T0: immediately after surgery, T6: 6 months after surgery, T12: 12 months after surgery.
After surgery, the patients were instructed to gargle with 0.1% chlorhexidine solution twice daily for 2 weeks. Additionally, antibiotics (Augmentin [625 mg], Ilsung Pharm. Co., Seoul, Korea) 3 times daily and analgesics (aceclofenac [100 mg], Dong-A ST, Seoul, Korea) twice daily for 1 week were prescribed. The non-absorbable sutures were removed after 7 days.
Outcome measures
KT width
In this study, KT width was defined as the distance from the mucogingival junction (MGJ) to the free KT margin [21]. At baseline, KT width was defined as the distance from the MGJ to the middle crest. In each implant crown, KT width was measured at the mid-buccal level using a periodontal probe (UNC 15, Osung MND Co., Seoul, Korea) with a 1-mm gradation. The measurement values were obtained at baseline, immediately after surgery (T0), 6 months after surgery (T6), and 12 months after surgery (T12) by a single clinician (WPL). The MGJ was identified by the rolling technique comprised of rolling the mucosa until the non-movable part of the KT was visualized. Each patient was regarded as a statistical unit for each statistical analysis. The mean KT width was calculated at each time point (baseline, T0, T6, and T12). KT width gain from baseline was defined as the difference in KT width between baseline and each time point. In addition, the percentage of KT width relative to T0 (100%) and shrinkage rate (%) of KT width relative to T0 (0%) were calculated [13].
Evaluation of esthetics
Color matching, contour, and texture were evaluated on clinical photographs acquired at T12 by 2 independent investigators (WPL and KHL). The scoring method of Lim et al. [22], which comprises 4 grades (1, poor; 2, fair; 3, good; and 4, perfect) was used. Both investigators performed calibration before the assessment using 5 randomly selected clinical photographs. Cohen's kappa was calculated for all parameters, and a kappa value of 0.656 was considered to indicate moderate agreement according to the revised interpretation of Cohen's kappa proposed by McHugh [23].
Statistical analysis
Quantitative parameters were expressed as mean±standard deviation and median. Data analysis was performed using SPSS software (version 20.2, IBM Corp., Armonk, NY, USA). The Shapiro-Wilk test was used for the normality of data distribution. The Kruskal-Wallis test was used for intergroup comparisons, and the Wilcoxon signed-rank test was used for intragroup comparisons (T0 vs. T6; T6 vs. T12). The Bonferroni correction was used as a post hoc test, and the Mann-Whitney U test was used repeatedly. The χ2 test was used to evaluate intergroup differences in soft-tissue esthetic scores. Pairwise comparisons were performed using the Fisher exact test with the Bonferroni correction (0.05/3 = 0.0167). A P value <0.05 was considered to indicate statistical significance. The methodology was reviewed by an independent statistician.
RESULTS
Of the 61 patients (90 sites), 19 (27 sites), 20 (30 sites), and 22 (33 sites) patients were included in the APF, FGG, and mPF groups, respectively (Table 1). In the course of the study, wound healing was uneventful in all groups.
Table 1
Demographic and clinical characteristics of the study population
Change of KT width
The KT width data are presented in Table 2. At baseline, KT width was 1.21±0.42, 1.13±0.36, and 1.05±0.53 mm in the APF, FGG, and mPF groups, respectively. No statistically significant differences were observed among the groups. At T0, KT width due to surgical interventions was 6.24±1.01, 6.35±1.01, and 6.39±0.95 mm in the APF, FGG, and mPF groups, respectively. No statistically significant differences were observed among the groups.
Table 2
Quantitative (mm) change of KT width in the APF, FGG, and mPF groups
A trend of decrease in KT width was observed at T6 and T12, and with regard to intragroup changes in KT width, the decrease in KT width between each time point was statistically significant in all groups.
At T12, KT width was 1.72±0.79, 3.65±1.09, and 3.52±1.02 mm in APF, FGG, and mPF groups, respectively, with statistically significant differences between the APF group and other groups. The relative change in KT width was 28.85%±14.69% for the APF group, 57.05%±11.84% for the FGG group, and 55.76%±15.89% for mPF. This indicates that the APF group achieved a significant loss of the re-established tissue as compared to the other groups. However, no statistically significant difference was observed between the FGG and mPF groups. A similar trend was observed at T6 (Figure 2).
Figure 2
Changes in KT width in the APF, FGG, and mPF groups.
KT: keratinized tissue, APF: apically positioned flap, FGG: free gingival graft, mPF: modified periosteal fenestration, T0: immediately after surgery, T6: 6 months after surgery, T12: 12 months after surgery.
Evaluation of esthetics
The esthetic data for all subjects are presented in Table 3. After 12 months of healing, the esthetic scores of the re-established tissue were lower in the FGG group than in the other groups in terms of color, contour, and texture. However, an overall excellent esthetic score was attained in the APF group, and a comparable score was attained in the mPF group except for texture.
Table 3
Soft tissue esthetic scores
DISCUSSION
This study retrospectively evaluated the effectiveness of 3 approaches of vestibuloplasty (APF only, FGG, and mPF) to increase the KT width around lower molar implants. To the best of our knowledge, this is the first study to report the results of a comparison of these 3 modalities. Moreover, we focused on the clinical and patient benefits of mPF [20], which we recommend over conventional APF alone and FGG. At the 12-month follow-up, the mPF group showed a significantly lower likelihood of relapse of the re-established tissue than the APF group. In addition, although mPF is a simpler and quicker surgical procedure than FGG, the mPF group showed comparable changes in KT width to the other groups and achieved superior esthetic outcomes as compared to the FGG group.
Earlier studies reported that APF alone resulted in minimum KT gain because of high wound contraction and muscle reattachment [14]. Basegmez et al. reported a gain of 2 mm at 3 months after surgery with APF, which subsequently decreased to 1.15 mm after 12 months [24]. Lim et al. [22] reported that APF achieved a shrinkage rate of 65% at T12. Our results indicated an approximately 0.5-mm increase in KT width from baseline and a 71% shrinkage rate at 12 months after surgery with APF (Figure 2). In the present study, the proximity of the buccinator muscle insertion to the recipient site may have been a contributing factor to relapse, as it included only the lower molar sites with shallow vestibules [22, 25].
Conversely, APF combined with FGG [13, 22, 24] or periosteal fenestration techniques [16, 17, 18] achieved higher KT gains. In this study, the mPF group achieved an increase in the KT width of 2.5 mm at baseline and a shrinkage rate of approximately 44% after 12 months of healing. This indicates that by adding a simple procedure such as mPF to APF, the additional KT width gain increased by approximately 2 mm, with a reduction in the tendency to relapse (Figure 2). Despite no clear conclusion on the clinical benefits of gaining greater KT, investigators should consider using a minimum KT width of 2 mm [26, 27, 28]. mPF achieved an additional 2 mm gain in KT width compared to APF alone, and this finding may have important clinical implications in implant dentistry. Moreover, the FGG group showed a similar tendency to the mPF group.
FGG has been considered the gold standard based on its high success rate, predictability, and a lack of comparable alternatives [13, 29, 30]. However, as presented in Table 3, the FGG group showed a less favorable esthetic tissue profile of color, contour, and texture than the other groups [22]. To overcome this, Urban et al. [31] conducted vestibuloplasty with a combined strip gingival graft at the apical part of the recipient bed and a xenogenic collagen matrix at the coronal level. The strip gingival graft at the apical part of the recipient bed acted as a mechanical barrier against mucosal and/or muscular re-attachment similar to the role of scar formation in periosteal fenestration surgery. In our study, the mPF procedure achieved a comparable esthetic outcome to that of the APF group, except for texture. This suggests that mPF is an effective potential alternative to the conventional FGG procedure, especially in cases of implantation at the posterior maxilla that present with difficulty in periosteal suturing, or at the anterior region, which has a high esthetic impact.
This study has some limitations inherent to its retrospective design. The selection of the patient population may have been biased. There was no control over other conditions that affect the results of soft tissue healing, such as the soft tissue phenotype. A surgical stent was not used to reproduce clinical measurements made using a periodontal probe, which may affect the reliability of the measurements. A prospective clinical study with a robust design is needed to confirm the findings of the present study.
Within the study's limitations, mPF achieved an additional KT width gain of approximately 2 mm and showed a lower tendency for relapse after vestibuloplasty around molar implants in comparison to APF alone. Compared to the FGG procedure, mPF was simpler to perform and showed superior esthetic outcomes, but a comparable change of KT width. For vestibuloplasty around lower molar implants, mPF is a potential alternative treatment modality to conventional APF alone or FGG procedures.
Funding:This study was supported by a research fund from Chosun University, 2018.
Author Contributions:
Conceptualization: Won-Pyo Lee.
Formal analysis: Kyoung-Hoon Lee.
Investigation: Kyoung-Hoon Lee.
Methodology: Won-Pyo Lee.
Project administration: Won-Pyo Lee, Sang-Joun Yu, Byung-Ock Kim.
Writing - original draft: Won-Pyo Lee.
Writing - review & editing: Kyoung-Hoon Lee, Sang-Joun Yu, Byung-Ock Kim.
Conflict of Interest:No potential conflict of interest relevant to this article was reported.
ACKNOWLEDGEMENTS
The authors thank Dong-Su Lee (Professor, Department of Computer Science and Statistics, Chosun University, Gwangju, Korea) for statistical consulting and some of the data analysis.
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