Contour Augmentation by Means of Connective Tissue Grafting Versus Guided Bone Regeneration

Study Overview
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Brief Summary
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The most frequent aesthetic complication following single implant treatment seems to be a lack of buccal convexity. This 'alveolar process deficiency' is the result of buccal bone remodeling following tooth extraction. A traditional approach to treat alveolar process deficiency is guided bone regeneration (GBR), however post-operative complications such as swelling, bleeding and pain are common and the aesthetic outcome may not be optimal. An alternative to the traditional GBR approach could be soft tissue contour augmentation using a connective tissue graft (CTG) at the buccal aspect. Possible advantages over GBR include less morbidity at the implant site, a superior aesthetic outcome since there is no need for vertical releasing incisions and less costs since there are no biomaterials to be used. The primary study objective is to compare the GBR and CTG group in terms of 2 and 3 dimensional tissue alterations, focusing on the amount of tissue gain and volume stability over time. The secondary study objectives are morbidity, overall radiographic, clinical and aesthetic outcomes.

Detailed Description
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Aim: This study aims to compare guided bone regeneration (GBR) with connective tissue graft (CTG) to re-establish buccal convexity at single implants. Sample size calculation: The sample size calculation was based on the primary study outcome (BSP) and was performed in SAS Power using the Satterthwaite t-test (De Bruyckere et al., 2018). The calculation was based on finding a mean difference of at least 0.5 mm between these groups with a standard deviation of 0.5 mm. This standard deviation was arbitrarily chosen given the lack of comparative studies. Alpha was set at 0.05 and the power was set at 0.80. This resulted in the inclusion of at least 17 patients per group. To compensate for possible drop-outs, 21 patients were included in each group. Randomization and allocation concealment: Patients were randomly assigned to the control group (GBR) or test group (CTG). Simple randomization was performed using sealed envelopes with an equal number of envelopes for every treatment group. Group allocation was revealed just prior to surgery by the surgeon and remained concealed for the evaluating investigator during the analytical stage of the project. Surgical procedure: In brief, a mucoperiosteal flap was raised in the control group by means of a midcrestal incision, sulcular incisions at both neighbouring teeth and a vertical parapapillary releasing incision at the distal neighbouring tooth. Following implant installation (NobelActive®, Nobel Biocare, Gothenburg, Sweden), the buccal concavity was augmented with deproteinized bovine bone mineral (DBBM) (Bio-Oss®; 0.25 - 1mm; Geistlich Biomaterials, Wolhusen, Switserland) and a collagen membrane (Creos® xenoprotect; 15x20mm; Nobel Biocare, Gothenburg, Sweden). Following apical release of the tissues, a cover screw was installed and primary wound closure was achieved (Seralon® 5/0, Serag Weissner, Naila, Germany). Aftercare included the use of a chlorhexidine rinse, systemic antibiotics (amoxicillin 1g, two times a day) and anti-inflammatory medication (ibuprofen 600mg) as deemed necessary by the patient. After 3 months, the implant was uncovered by means of a pouch procedure. A screw-retained provisional crown was placed as described by De Rouck et al. (2008), which was replaced by the permanent restoration (Procera® on ASC® abutment, Nobel Biocare, Gothenburg, Sweden) 3 months later. The flap design in the test group was identical to the one in the control group, yet without a vertical parapapillary releasing incision. Instead of augmenting with DBBM, an appropriately sized CTG harvested from the palatal flap or palatal mucosa in the premolar area was pulled into the envelope and immobilized (Seralon® 5/0, Serag Weissner, Naila, Germany). Non-submerged healing was respected. Aftercare and prosthetic procedures were identical in both groups. All surgical treatments and provisional restorations were performed by the same clinician. Referring dentists made permanent restorations.

Official Title
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A Randomized Controlled Trial Comparing Guided Bone Regeneration With Connective Tissue Graft to Re-establish Buccal Convexity at Implant Sites: Three-year Results.

Conditions
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Guided Bone Regeneration

Intervention / Treatment
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* Procedure: Hard tissue augmentation at the buccal aspect of single implants.
* Procedure: Soft tissue augmentation at the buccal aspect of single implants.


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: At least 18 years old. Good oral hygiene defined as full-mouth plaque score ≤ 25% (O'Leary et al.1972 Presence of a single tooth gap in the anterior maxilla (15 - 25) with both neighbouring teeth present Failing tooth at least 3 months earlier removed Class I defect at the single tooth gap as clinically assessed (buccopalatal loss of tissue with a normal apicocoronal ridge height) (Seibert, 1983) Signed informed consent Buccopalatal bone dimension of at least 6 mm at the central and crestal aspect of the single tooth gap to ensure complete embedding of an implant by bone Exclusion Criteria: Systemic diseases Smoking (History of) periodontal disease Untreated caries lesions Need for horizontal bone augmentation at the time of implant placement

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: randomized clinical trial
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Guided bone regeneration: Control<br>Deproteinized bovine derived xenograft (Geistlich Bio-Oss® 0.25 - 1 mm, Geistlich Pharma AG, Wolhusen, Switzerland) | Procedure: Hard tissue augmentation at the buccal aspect of single implants.<br>* One or two releasing incisions are made. The periosteum is released and multiple bone perforations are made in the buccal bone prior to the application of deproteinized bovine derived xenograft. A Creos® membrane (Nobel Biocare, Gothenburg, Sweden) is used to cover the occlusal part of the alveolar crest and the xenograft particles. Finally, multiple single monofilament sutures are used for primary tension-free wound closure.<br>|
| Active Comparator: Connective tissue graft: Test<br>Connective tissue graft harvested from the palate | Procedure: Soft tissue augmentation at the buccal aspect of single implants.<br>* A CTG is taken from the palate and transplanted to the buccal side between the alveolar bone and the buccal flap. The CTG is secured with single monofilament sutures.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Buccal soft tissue profile | The volumetric analysis software (Swissmeda/SMOP, Zürich, Switzerland) calculated a mean dimensional change (mm3) within the AOI (area of interest) for each patient at T5 (3 years). Given the variable size in AOI (mm2) among patients, the mean dimensional change per area was transformed to a mean linear change in buccal soft tissue profile (BSP) in mm. | Year 1 and 3 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Midfacial recession | Midfacial recession was registered between 6 months, 1 year and 3 years on the basis of digital surface models in STL format superimposed and imported in designated software (Swissmeda/SMOP, Zürich, Switzerland). Midfacial recession was calculated by subtracting the data from 1 and 3 years to 6 months of follow-up. | Month 6; Year 1 and 3 | 
| Buccal bone thickness | The thickness of the buccal bone was measured (in mm) at t2 (1 year) and t3 (3 years) perpendicular to the long axis of the implant. Buccal bone was measured from the implant surface to the bone-soft tissue interface at 3 levels. | Year 1 and 3 | 
| Buccal soft tissue thickness | The thickness of the soft tissues was measured (in mm) at t2 (1 year) and t3 (3 years) perpendicular to the long axis of the implant. Buccal soft tissue thickness was measured from the bone-soft tissue interface to the buccal soft tissue outline at the same levels as buccal bone thickness. | Year 1 and 3 | 
| Pink Esthetic Score | The PES awards 7 parameters: mesial papilla, distal papilla, soft tissue level, soft tissue contour, alveolar process deficiency, soft tissue colour, soft tissue texture. Each parameter is assessed with a 0-1-2 score, yielding a PES score ranging from 0 (worst aesthetic outcome) to 14 (perfect aesthetic outcome). | Year 1 and 3 | 
| Mucosal Scarring Index | The MSI is a composite index based on five parameters: width, height/contour, colour, suture marks and overall appearance. Each parameter is assessed with a 0-1-2 score, yielding an MSI score ranging from 0 (no scar) to 10 (most extreme scar). | Year 1 and 3 | 
| Marginal bone loss | Marginal bone loss was recorded at the mesial and distal aspect of each implant. The distance from the implant-abutment interface to the first bone-to-implant contact (so-called bone level) was assessed on peri-apical radiographs taken with the long-cone paralleling technique. Mesial and distal values were averaged to receive one value per implant. | Year 1 and 3 | 
| Probing depth | Probing depth was registered at four locations (mesiobuccal, buccal, distobuccal and palatal) around the implant to the nearest 0.5 mm. A mean value was calculated per implant. | Year 1 and 3 | 
| Plaque | Plaque was assessed at four locations (mesiobuccal, buccal, distobuccal and palatal) around the implant. Each location was scored 0 or 1 (the absence or presence of plaque, respectively). Plaque was expressed as a percentage. | Year 1 and 3 | 
| Bleeding on probing | Bleeding on probing was assessed at four locations (mesiobuccal, buccal, distobuccal and palatal) around the implant. Each location was scored 0 or 1 (the absence or presence of bleeding, respectively). Bleeding on probing was expressed as a percentage. | Year 1 and 3 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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connective tissue graft, dental implant, guided bone regeneration, single tooth