Root Coverage Procedures Research Articles

Mixed-Thickness Tunnel Access (MiTT) through a Linear Vertical Mucosal Incision for a Minimally Invasive Approach for Root Coverage Procedures in Anterior and Posterior Sites: Technical Description and Case Series with 1-Year Follow-Up.

The goal of this article was to introduce a new root coverage (RC) technique, the mixed-thickness tunnel access (MiTT) technique, which approaches a full-split design and intends to augment soft tissues coronal to the gingival margin. It was shown step-by-step, and the results were presented in a case series. Healthy individuals (non-diabetics) and non-smokers with gingival recession (GR) type 1 or 2 (RT1 or RT2) were included. After evaluation, prophylaxis was performed 14 days before the surgical procedure. During the surgical appointment, one or two vertical incision(s) on the mucosa (around 1-2 mm apical to the MGJ), lateral to the papilla base, was/were performed after anesthesia. Initially, there was a partial incision to detach the mucosa of the muscles (split design). It was permitted (but not mandatory) to perform intrasulcular incisions. Through the vertical incision, internally, subperiosteal access from the MGJ toward the gingival margin (coronally) was performed to create a full-thickness tunnel. Then, communication from the vertical incision with the gingival sulcus and the papilla base occurred, keeping the papilla tip intact. A connective tissue graft was harvested and inserted through the linear incision or intrasulcularly. There were interrupted sutures. An adjunctive material may be applied (e.g., Endogain). The root coverage was measured using a periodontal probe and considered fully covered when the gingival margin was 1 mm coronal to the cementum-enamel junction (CEJ). Nine healthy individuals (seven females and two males) aged 19 and 43 were enrolled. They were treated following the MiTT steps. Four cases had a single GR; two patients had two teeth involved; and three others had three or four GR. There were seven cases of RT1 and two RT2. All RT1 cases achieved 100% RC, while the mean RC obtained for RT2 was around 80%. The MiTT technique can be considered a more straightforward approach for minimally invasive surgical techniques, which is a feasible option to treat RC with a high success rate, predictability, and esthetic preservation. Therefore, there is a technical sensitivity to performing the full-split design procedure.

Coronally repositioned flap procedure for gingival root coverage using human derived regenerative membranes - A case series

The aim of this case series was to evaluate the effectiveness of platelet rich fibrin (PRF), Amnion and chorionic membrane for root coverage procedures using a coronally repositioned flap (CRF).Three subjects with Miller’s class I gingival recession were randomly selected for treatment using CRF with PRF, Amnion and Chorion membranes. The clinical parameters evaluated at baseline and 6 months follow up included: probing depth (PD), relative attachment level (RAL), recession height (RH), recession width (RW), width of keratinized tissue (WKT) and Gingival thickness (GT). Within the limits, this case series has shown that the use of human derived regenerative membranes along with CRF resulted in complete root coverage in Miller’s Class I gingival recessions in much lesser time. The rapid healing and regeneration of these membranes stands as an alternative for connective tissue autografts and holds promise for future.Gingival thickness (GT), Relative Attachment level (RAL), Width of Keratinized Tissue (WKT)

Influence of ternion of soft tissue attributes on gingival recession and root coverage outcome – A retrospective analysis

The independent influence of Keratinized Tissue Width (KTW) and Gingival Biotype (GB) on root coverage outcomes have been reported over the years. These parameters along with Recession Depth (RD) might act as a triad and assessing this ternion would be beneficial in determining prognosis and devising treatment plan for gingival recession. The aim of this retrospective analysis is to evaluate a possible association between KTW, GB and RD and their influence on Gingival Recession and root coverage outcome.45 isolated gingival recession defects were assessed for KTW (<2mm, >2mm), GB (thin vs thick) and RD (1-4mm). Primary outcome was to establish an association between the above-mentioned parameters. Secondary outcome was to find the percentage Root Coverage (%RC) obtained after coronally advanced flap procedure. To evaluate the relationship of KTW vs GB, GB vs RD and KTW vs RD, chi-square test was used. To analyse the intra-parametric correlation and the association between all three parameters, Pearson correlation test and ANOVA were carried out respectively.The Chi-square test results revealed a statistically significant association of p<0.03 for the relationship of KTW vs GB and GB vs RD and p<0.001 for KTW vs RD. Pearson correlation test showed a positive correlation between KTW and GB (.320), negative correlation between GB and RD (-.046), and KTW and RD (-.136). ANOVA showed a p-value of 0.041 inferring that any change in KTW and GB significantly influenced RD. Sites with <2mm KTW, thin GB and deeper RD, which can be referred to as negative ternion, exhibited 43.8% mean RC while sites with >2mm KTW, thick GB and shallow RD, which can be referred to as positive ternion had 94.7% mean RC. There is a definitive association between Keratinized Tissue Width, Gingival Biotype and Recession Depth. A ternion of these parameters greatly influences the outcome of root coverage procedures.

Minimally Invasive Gingival Recession Treatment by Using Vista Combined With PRF and Collagen Membrane: A Case Report

Abstract Root exposure generates major concerns regarding aesthetics and other problems like hypersensitivity and root caries. Gingival recession has traditionally been treated by periodontal plastic surgery, often using soft tissue grafts to fill the defect with excellent clinical results. Advancements in root coverage procedures in the aesthetic zone have led to increasing the ability of clinicians to harness a treatment modality that delivers better outcomes with less surgical morbidity. Collagen membrane is most commonly used for guided tissue regeneration (GTR). On the other hand, platelet-rich fibrin (PRF) has gained popularity due to its simple method of acquisition, low cost and the presence of growth factors. Therefore, this case report describes the treatment of a 38-year-old patient with bilateral multiple Miller’s class I recession defects extending from central incisors to canines by using the vestibular incision subperiosteal tunnel access (VISTA) with PRF and collagen membrane. Clinical parameters such as recession height (RH) and width of keratinised gingiva (WKG) were measured at 6-month and 1-year follow up intervals. The 6-month follow-up revealed optimum root coverage with excellent outcomes for both sites, with an increase in the width of keratinised gingiva and a decrease in the recession height, and less discomfort in the site treated with a PRF membrane. These clinical parameters were maintained at the 1-year follow up. The increase in the width of keratinised gingiva and the decrease in the recession height in both groups and the patient compliance due to this minimally invasive procedure suggests its potential use when aesthetics and patient comfort are of paramount concern.

Levels of smoking and outcome measures of root coverage procedures: a systematic review and meta-analysis.

This systematic review and meta-analysis was performed to investigate if there was a significant association between the number of cigarettes smoked per day and the results of root coverage procedures. Electronic search was performed through PubMed, Web of Science, Embase, and Scopus until January 2023. Studies were included if evaluated the outcomes of periodontal plastic surgery procedures for the treatment of gingival recession in smokers. Statistical evaluation was conducted using random-effects method to analyze the odds ratio (OR) and mean difference (MD) with 95% confidence intervals (CI). From a total of 4494 references, 15 studies were considered relevant to be included in this study. The results showed that 44.39% sites had complete root coverage (CRC) at 6months (non-smokers: 54.06%, < 10 cigarettes/day: 48%, 10-20 cigarettes/day: 19.56%, ≥ 20 cigarettes/day: 50%). Mean root coverage at 6months were as follows: non-smokers: 74.94% ± 16.71%, < 10 cigarettes/day: 84.20% ± 2.24%, 10-20 cigarettes/day: 75.30% ± 14.69%, ≥ 20 cigarettes/day: 68.75% ± 26.51%. A significant difference was revealed between non-smokers and individuals who smoked 10-20 cigarettes/day in terms of CRC at 6months: OR = 0.15 (95% CI = 0.03 to 0.71; P = .017). However, no significant difference was detected comparing 10-20 and ≥ 20 cigarettes/day. As there was not enough data available, any definitive conclusions about the connection between an increase in the amount of cigarettes consumed per day and the results of root coverage procedures could not be reached. Further research is required with comparative studies involving individuals who smoke varying numbers of cigarettes.

Novel biomaterial advanced platelet rich fibrin plus block for multiple gingival recession.

The study was aimed to assess and compare hard and soft tissue augmentation clinicoradiographically with and without advanced platelet rich fibrin + (A-PRF+) block for the treatment of multiple gingival recession using vestibular incision subperiosteal tunnel access (VISTA). A total of 24 patients, exhibiting multiple Miller's Class I or II recession in maxillary esthetic zone were included. Participants were divided into 2 groups, Group 1 treated with VISTA & A-PRF+ block whereas Group 2 with VISTA technique alone. Clinical parameters Probing Depth (PD), Width of Keratinized Gingiva (WKG), Gingival Biotype (GB), Recession Depth (RD) and Clinical Attachment Level (CAL) were recorded at baseline and at the end of 6 months. The radiographic CBCT measurements of labial plate thickness was taken at baseline and 6 months postoperatively. From baseline to 6 months both the groups showed a clinical and statistical improvement in the parameters. However, a statistically significant difference between both the treatment modalities was not observed. In the inter group comparison radiographically, labial plate thickness was statistically significant at the end of 6 months when compared to the baseline. A-PRF+ block along with VISTA technique can be an alternative effective root coverage procedure for the management of multiple gingival recession in the maxillary esthetic zone. This article is protected by copyright. All rights reserved.

Evaluation of Root Coverage Procedures Using Root Coverage Esthetic Score System – A Case Series

ABSTRACT Background: Gingival recession, characterized by root surface exposure due to apical gingival margin migration, is a prevalent condition in the general populace, frequently prompting patient intervention. Mucogingival therapy may be indicated for recession control, plaque management, and dentin hypersensitivity; nevertheless, the consideration of esthetics correction as a therapeutic rationale is increasingly significant in contemporary clinical practice. Objective: The goal of this case series was to evaluate the most esthetic root coverage procedure of the three procedures performed. Methods: Patients with localized recession were treated with three different root coverage procedures, namely the free gingival graft (FGG), connective tissue graft + coronally repositioned flap (CTG + CAF), and platelet-rich fibrin (PRF) + coronally positioned flap. The root coverage procedures were assessed for the root coverage esthetic score (RES) system after 6 months. The RES scores of these procedures were compared to determine if one procedure offered a greater esthetic result over the other. Results: All three procedures were effective in obtaining root coverage and improved clinical parameters. However, CTG with CAF, along with complete root coverage (CRC), produced a better esthetic outcome than other root coverage procedures compared in this case series. The success of root coverage procedures is based on the overall esthetic outcome along with CRC. Thus through the incorporation of the RES into everyday clinical practice, clinicians can enhance the accuracy and consistency of their evaluations, leading to improved patient care and optimizing treatment planning.

Effect of Microneedling and Injectable Platelet-Rich Fibrin on Gingival Phenotype – A Case Series

Introduction: Gingival phenotype is a crucial determinant of the periodontium. It not only maintains the health of the tissue but also plays a decisive role in the prediction of periodontal treatment outcomes. Thin gingival phenotype poses certain risks of poor periodontal treatment outcome in cases of implant, coronally advanced flap, and other root coverage procedures. Thus it becomes the duty of the clinician to deal with such cases by prior planning treatments which can improve the gingival phenotype and thereby enhancing the postperiodontal treatment outcomes to benefit patients. In this case series, a nonsurgical treatment modality microneedling (MN) and injectable platelet-rich fibrin (i-PRF) are employed in an attempt to increase the thickness of thin gingival phenotype. Methods: Five systemically healthy patients with thin gingival phenotypes were included in this study. The lower anterior teeth with split-mouth study pattern have been randomly allocated to nonsurgical treatment modality, i.e., MN alone and MN along with i-PRF. All the patients were followed up for 9 months. Outcomes Assessed: Gingival thickness (GT), Width of Keratinized Tissue (WKT), oral hygiene index, gingival index (GI), the patient reported outcome measures. Results: Both the groups showed an increase in the thickness of gingiva in 9-month follow-up. The mean increase of 0.62 mm in thickness was seen in Group 1 (42%), whereas Group 2 showed a 0.34 mm (27.3%) of increment. No difference is seen with respect to the change in the width of keratinized gingiva in both groups. Conclusion: MN along with i-PRF can provide an efficient nonsurgical option to clinicians to increase GT in cases of thin gingival phenotype.

Comparison of Amnion Membrane and Hyaluronic Acid in Gingival Recession Coverage and Gain in Clinical Attachment Level following Coronally Advanced Flap Procedure-A Clinical Study.

Gingival recession is defined as the apical migration of gingival margin to the cementoenamel junction. Recently, amnion membrane, the third-generation membrane which is a placental-derived tissue, has been introduced. Study included 45 subjects with age group of 20-60 years of both genders. Patients with Miller's Class I and Class II gingival recession were selected for the study. The progress was assessed at baseline one, three, and six months observation interval through clinical parameters RD, RW, PD, and CAL at the end of six months. Recession depths in the first, third, and sixth month were 1.82 ± 0.442, 1.31 ± 0.47 mm, and 0.91 ± 0.29, respectively, which showed a significant reduction from the baseline. Recession widths in the first, second, and third weeks were 3.04 ± 0.442 mm, 1.31 ± 0.47 mm, and 1.49 ± 0.59 mm, respectively. There was a statistically significant reduction (P > 0.005) when compared to the baseline. Pocket depths in the first, third, and sixth month were 0.93 ± 0.447, 0.42 ± 0.50, and 0.24 ± 0.43 (P > 0.005) which is significant when compared to baseline. Clinical attachment levels in the first, third, and sixth month were 2.73 ± 0.751, 1.78 ± 0.70, and 1.18 ± 0.53 (P > 0.005) which is significant compared to six months. Within the limitations of the present study, the data obtained by periodic assessment of the clinical parameters indicate the use of amnion membrane and hyaluronic acid, and proper technique may thus be the panacea for root coverage procedure.

Assessment of Clinical Outcome of Root Coverage Following Coronally Advanced Flap with or without Amniotic Membrane.

The present study aimed to assess the clinical outcome of root coverage following coronally advanced flap with or without amniotic membrane in Miller's class I or class II localized gingival recession in relation to anteriors. Five patients with bilaterally symmetrical Miller's class I or class II localized gingival recession were included in the study. Each patient was divided into control (without amniotic membrane) and test sites (with amniotic membrane) arbitrarily. Clinical parameters including plaque index, probing pocket depth (PPD), clinical attachment level (CAL), and depth and width of the gingival recession were recorded in a pro forma at baseline and in the 2nd, 4th, 12th week. The results were tabulated and subjected to statistical analysis using analysis of variance (ANOVA). A 0.600-mm, 0.400-mm, 2.630-mm, and 2.616-mm reduction in PPD and gain in CAL were observed at control and test sites in the 12th week postoperatively and was found to be statistically insignificant (P = 0.580 and P = 0.871, respectively). Changes in depth and width of the gingival recession were observed and found to be maximum between base line (2.28 mm, 3.01 mm, 2.71, and 3.09 mm) and 2nd week (0.00, 0.00 mm, 0.23, and 0.20 mm) but without statistical significance. From the above results of the study, it could be concluded that the use of amniotic membrane as a barrier along with coronally advanced flap did not influence the clinical outcome of root coverage procedure.

Keep it simple: correction of anterior cross bite – an ortho-perio interdisciplinary approach

This case report explores the treatment of a 13-year-old male patient with severe dental crowding and periodontal issues using non-extraction orthodontic treatment combined with a root coverage procedure. The patient presented with a skeletal class 1 base malocclusion, and multiple anterior crossbites, along with a compromised lower central incisor and gingival recession. Despite the option of extraction, the patient declined this approach, and the final goal was to achieve stable class 1 occlusion and an improved smile.The treatment plan utilized pre-adjusted edgewise appliance (MBT 0.022 inch slot), distalization of the canine, inversion of the maxillary right lateral bracket, and the cautious use of open coil spring in the upper and lower anterior segments. After alignment was completed, a root coverage procedure was performed on the lower right central incisor. The treatment lasted for 20 months, and the results showed successful alignment of both arches, canine protected occlusion, and improved periodontal health.Overall, this case report highlights the complex relationship between orthodontic treatment and periodontal health and the importance of careful treatment planning and patient communication to achieve successful and stable results. The non-extraction approach combined with root coverage procedure proved to be an effective treatment option for this patient, leading to an improved occlusion, smile, and periodontal health.

Intra-marrow penetrations and root coverage outcomes: a systematic review

BackgroundIntra-marrow penetrations (IMPs) have been performed during guided tissue regeneration (GTR) procedures with reported clinical benefits. The aim of this systematic review was to investigate the use and effect of IMPs during root coverage procedures.MethodA broad search for human and animal studies was performed on PubMed, Cochrane Database of Systematic Reviews and Cochrane Central Registry of Controlled Trials and Web of Science, following a registered review protocol (PROSPERO). All prospective study designs, case series and case reports on gingival recession treatment (follow-up ≥ 6 months) that employed IMPs were included. Root coverage, complete root coverage prevalence, and adverse effects were recorded, and risk of bias was assessed.ResultsOf 16,181 screened titles, 5 articles (all of them human studies) met inclusion criteria. All studies (including two randomized clinical trials) treated Miller class I and II recession defects, using coronally advanced flap with IMPs alone or in conjunction with GTR protocols. Therefore, all treated defects received IMPs and no studies compared protocols with and without IMPs. Outcomes were indirectly compared with existing root coverage literature. Mean root coverage was 2.7 mm and 68.5% at 6.8 months (median: 6 months, range 6–15 months) for sites treated with IMPs.ConclusionIMPs are rarely used during root coverage procedures, have not been associated with intra-surgical or wound healing adverse effects and have not been investigated as independent factor. Future clinical studies are needed to directly compare treatment protocols with and without IMPs and investigate the potential benefits of IMPs for root coverage.

Comparative evaluation between collagen membrane (PerioCol®) and periosteum membrane in the treatment of gingival recession defects of maxillary anterior teeth: a clinical study

Abstract Background: The most common mucogingival defect is gingival recession (GR), which is characterized by apical displacement of the gingival margin from the cementoenamel junction and root exposure. Several techniques are available for treating GR and are collectively termed root coverage (RC) procedures. This study presents 3 months’ results of a randomized clinical trial comparing RC in areas of isolated GR by coronally advanced flap (CAF) with periosteum membrane and PerioCol® membrane. Materials and Methods: Twenty recession sites were selected for the study and further divided into two groups (Test group 1 [C AF + Periosteum membrane] and Test group 2 [CAF + Guided tissue regeneration membrane]) and completed the 3-month follow-up. Result: Satisfactory result obtained after three months in both the cases but CAF+Periosteum showed better and fast healing. Conclusion: Both treatment modalities showed a significant improvement in clinical parameters at 3 months postoperatively.

Cover Image

The cover image is based on the Original Article Long‐term comparison of root coverage procedures at single RT2 maxillary gingival recessions: Ten‐year extension results from a randomized, controlled clinical trial by Francesco Cairo et al., https://doi.org/10.1111/jcpe.13778. image

Treatment of Gingival Recession Defects with Pouch and Tunnel Technique Using Connective Tissue Graft and Lyophilized Chorion Membrane in Smokers.

BACKGROUND The chorion membrane has been used for several decades as an allograft in tissue repair and various periodontal regenerative procedures. The present study, conducted at a single center in India, aimed to evaluate and compare the clinical outcomes of 26 gingival recession sites in chronic smokers treated using a pouch and tunnel technique with connective tissue graft (CTG) and lyophilized chorion membrane (LCM). MATERIAL AND METHODS The study included 22 smokers with 26 sites of recession defect, with Miller's class I and class II gingival recession, which were allotted into control and test groups. The control group (13 sites) was treated with CTG, and the test group (13 sites) was treated with LCM. Clinical parameters like recession depth, recession width, relative clinical attachment level (RCAL), relative gingival position, width of attached gingiva, and width of keratinized gingiva were recorded at baseline and 6 months postoperatively. Visual analogue scores for pain and wound-healing index scores were assessed in the first week after surgery. RESULTS All clinical parameters showed significant improvements from baseline to 6 months postoperatively in the control and test groups. Recession width, RCAL, width of attached gingiva, and width of keratinized gingiva demonstrated significant differences, whereas mean root coverage percentage and recession depth did not show any significant differences between the study groups at 6 months postoperatively. CONCLUSIONS This study supports the role of LCM allograft as a scaffold to promote soft tissue regeneration and has demonstrated a favorable role for its use in root coverage procedures in patients who smoke.

Bridge Flap for the Treatment of Multiple Gingival Recession

Because of aesthetic concerns or root sensitivity, gingival recession in anterior teeth is frequently of concern. For aesthetic reasons, gingival recession is extremely concerning, particularly in cases when there are several anterior teeth involved. Root coverage is possible by a variety of mucogingival procedures. This case study introduces a novel bridge flap technique that enables the dentist to enlarge the zone of attached gingiva while simultaneously covering the previously exposed root surfaces. A root coverage procedure was done in this instance to address a multiple recession type defect using a coronally advanced flap and vestibular deepening approach. To widen the associated gingiva in this instance, vestibular deepening technique is employed. An aesthetically healthy periodontium, increased keratinized tissue, and positive patient acceptance are all outcomes of this procedure's predictability.

Minimal invasiveness in gingival augmentation and root coverage procedures.

Minimally invasive surgical procedures aim at optimal wound healing, a reduction of postoperative morbidity and, thus, at increased patient satisfaction. The present article reviews the concept of minimal invasiveness in gingival augmentation and root coverage procedures, and critically discusses the influencing factors, technical and nontechnical ones, and relates them to the underlying biological mechanisms. Furthermore, the corresponding outcomes of the respective procedures are assessed and evaluated in relation to a possible impact of a minimized surgical invasiveness on the clinical, aesthetic, and patient-related results.

Long-term comparison of root coverage procedures at single RT2 maxillary gingival recessions: Ten-year extension results from a randomized, controlled clinical trial.

The purpose of the present study was to assess root coverage outcomes 10 years after connective tissue graft plus coronally advanced flap (CTG + CAF) or CAF alone, at single RT2 maxillary gingival recession. Twenty-one of the original 29 patients (11 treated with CAF + CTG and 10 with CAF alone) were available for the 10-year follow-up. A blinded and calibrated examiner performed all the measurements. Outcome measures included complete root coverage (CRC), recession reduction (RecRed), root coverage aesthetic score (RES), and keratinized tissue (KT) gain. A visual analogue scale was used to evaluate patient satisfaction. CRC was maintained in 63% of the test group and 20% of the control group after 10 years, with a significant difference favouring CAF + CTG (p=.030). Furthermore, the addition of CTG was associated with greater KT gain (p=.0002) and greater papilla tip recession (p=.023) than with CAF at the last follow-up. No difference was detected regarding RecRed, RES, and patient satisfaction. Adding CTG under CAF improved the probability of maintaining complete root coverage 10 years after single maxillary RT2 recession treatment.

Complications and treatment errors in root coverage procedures.

Root coverage procedures have become very common in clinical dental practice. Even though these techniques are considered safe, the clinician may face several issues during the therapy due to their surgical nature. Some of these issues can be defined strictly as complications inherent to the procedure, whereas others are medical errors or treatment errors. This review will focus on describing treatment errors and complications that may arise during different phases of the root coverage therapeutic process and on how to prevent and manage them.

ASSESSMENT OF THE FREQUENCY OF REPORTING DENTAL PATIENT-REPORTED OUTCOMES (dPROs) IN A SAMPLE OF RANDOMIZED CONTROLLED TRIALS ON ROOT COVERAGE PROCEDURES

Dental patient-reported outcomes (dPROs) are important for understanding the impact of proposed therapies on patients' oral health. The aims of the present study were to investigate the frequency of the reporting of dPROs in randomized controlled trials (RCTs) of root coverage procedures and to assess associations between the study/article characteristics and the reporting level of the dPROs. The PubMed database was searched for RCTs of root coverage procedures in March 16, 2022 and articles published up to March 2022 were included. Information on the types of outcomes and the characteristics of the studies/articles were extracted and reported as frequencies and percentages. Univariate and multivariate binary logistic regression analyses were performed to investigate the associations between the study/article characteristics and the reporting level of dPROs. The search initially identified 387 articles, and after applying the eligibility criteria, 135 articles reporting 135 RCTs were included. A combination of dPROs and non-dPROs was reported in 61.5% of the selected trials, while 37.8% of the trials reported only non-dPROs. Pain or discomfort was the most frequently reported dPRO (n = 58, 43% of the RCTs). More recently published RCTs reported more dPROs. The country of the first author (odds ratio [OR]: 4.39; 95% CI: 1.76-10.95; P < .01), protocol registration (OR: 0.36; 95% CI: 0.16-0.83; P = .02), and RCT type (OR: 0.38; 95% CI: 0.17-0.83; P = .02) were significantly associated with the reporting level of the dPROs. Researchers in recent years seem to be paying more attention to the importance of dPROs. RCTs in which the first authors were from developed countries, registered trials, and RCTs with a parallel design were more likely to report dPROs than RCTs with first authors from developing countries, unregistered trials, and RCTs with a split-mouth design.