A randomized clinical trial evaluating the efficacy of the sandwich bone augmentation technique in increasing buccal bone thickness during implant placement surgery

Objectives: Sandwich bone augmentation (SBA) has been proposed to augment the width of edentulous ridges for implant placement. This study aimed to investigate the effect of a membrane on SBA for the regeneration of buccal implant dehiscence defects. Material and methods: Twenty-six healthy patients, each with a single defect, were randomly assigned into two groups. Both groups received an inner and outer layer of mineralized human cancellous and cortical particulate allograft. In the test group, a bovine pericardium membrane covered the bone grafts, while no membrane was placed in the control group. Cone beam computed tomography (CBCT) scans were taken before and immediately after implant placement and at 6 months post-surgery. Results: All implants placed were successfully osseointegrated at 6 months. Clinical re-entry measurements showed significant buccal bone gain in the test group compared with the control group (P < 0.05). The test group had 1.12, 2.21 and 2.44 mm more buccal bone thickness at 2, 4 and 6 mm below the bone crest. There were no significant differences in the mid-buccal vertical bone height, defect height and width reductions and bone fill between the two groups (P > 0.05). Cone beam computed tomography analysis demonstrated significant buccal bone gain of 1.22 mm in the test group. Radiographic vertical bone loss at 1-year post-surgery showed no significant differences between the groups. Conclusion: Sandwich bone augmentation is a predictable technique for regenerating buccal bone on implant dehiscence defects. Addition of a barrier membrane prevented significant horizontal buccal bone resorption as space was maintained more effectively when compared with sites treated without a membrane. Research has shown that a dental implant placed in a non-ideal three-dimensional position may lead to peri-implantitis, functional and esthetic failure and eventual removal of the implant (Szmukler-Moncler et al. 1998; Fu et al. 2012). To obtain optimal function and esthetics, the position of the implant in the arch has to be in a biologically accepted and prosthetically driven location (Buser et al. 2004; Bashutski & Wang 2007). When the implant is placed in a compromised position, for example, a bone-dictated position, the use of angulated abutments and/or pink porcelain may be inevitable. In addition, the resulting non-axial masticatory forces directed on the implant-supported restoration may increase the risk of prosthetic complications, such as abutment screw loosening, and fracture of veneering material, abutment, screw and/or the implant fixture itself (Fu et al. 2012). Taking all into consideration, performing predictable bone augmentation procedures to ensure the proper position of the implant in the arch is preferred. Despite the availability of different techniques, guided bone regeneration (GBR) has been widely used for implant site development (Hammerle et al. 2002; Aghaloo & Moy Date: Accepted 17 March 2013 To cite this article: Fu J-H, Oh T-J, Benavides E, Rudek I, Wang H-L. A randomized clinical trial evaluating the efficacy of the sandwich bone augmentation technique in increasing buccal bone thickness during implant placement surgery. I. Clinical and radiographic parameters. Clin. Oral Impl. Res. 25, 2014, 458–467 doi: 10.1111/clr.12171 458 © 2013 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd 2007). It is because this technique is predictable, easy to use and relatively less invasive compared with other advanced bone grafting methods (Lee et al. 2009). This technique can be performed prior to (Buser et al. 1995, 1996) or simultaneously with implant placement (Oh et al. 2003; Wang et al. 2004; Park & Wang 2006; Park et al. 2008; Lee et al. 2009) and is typically used with bone grafts, such as autograft, allograft or xenograft, and nonresorbable and absorbable barrier membranes. In recent years, a novel bone grafting procedure known as the sandwich bone augmentation (SBA) technique has been proposed and developed (Oh et al. 2003; Wang et al. 2004; Park et al. 2008; Lee et al. 2009). This procedure, which is performed simultaneously with implant placement, utilizes cancellous and cortical bone allografts in separate layers together with a collagen barrier membrane to simulate a healing environment similar to the composition of native bone. This concept uses the different healing properties of particulate cortical and cancellous bone allografts to achieve bone regeneration. The inner cancellous layer undergoes creeping substitution, which allows for faster bone resorption and apposition, thus facilitating earlier osseointegration and improved bone-to-implant contact. The outer cortical layer undergoes reverse creeping substitution, where bone resorption occurs before bone apposition, thus demonstrating better space maintenance property (Burchardt 1983). Compared with xenografts, allografts have demonstrated complete resorption and thus were selected for this procedure (Skoglund et al. 1997). Other studies have compared the effect of various barrier membranes for bone regeneration of peri-implant defects, and no significant differences between dissimilar membranes were reported (Oh et al. 2003; Park et al. 2008). However, there are limited human clinical trials investigating the use of a bovine pericardium membrane and mineralized bone allografts with the SBA technique in bone regeneration. Therefore, this study was designed to investigate the efficacy of a bovine pericardium membrane (CopiOs pericardium membrane; Zimmer Dental Inc., Carlsbad, CA, USA) and mineralized human allograft (Puros ; Zimmer Dental Inc.) in augmenting facial or buccal implant dehiscence defects using the SBA technique. The study objectives were to determine whether there were differences in horizontal bone width gains at different levels on facial or buccal implant dehiscence defects between the test (with pericardium membrane) and control (without pericardium membrane) groups and to determine the incidence of membrane exposure and its effect on horizontal bone width gain. Material and methods Patient recruitment This 12-month-long randomized, controlled, single-masked, clinical trial received approval from the University of Michigan Institutional Review Board (Study e-Research ID: HUM0 0026657) to be conducted from January 15, 2009 to September 19, 2011 (Appendix S1). From the patient population at the University of Michigan, School of Dentistry, 116 patients were screened and 26 patients were recruited into this study, thus achieving a statistical power of 80%. The primary researcher (JHF) screened the patients according to the inclusion and exclusion criteria (Table 1) and enrolled those who fulfilled the criteria for this study. A signed informed consent was subsequently obtained. The enrolled patients were randomly assigned to two experimental groups with 13 patients each in the test and control groups. The process of randomization involved the primary researcher (JHF) picking a number from an enclosed brown bag. Patients who had number ‘0’ were allocated to the control group, while those with number ‘1’ were allocated to the test group. The control group was treated with the SBA technique, which used only cancellous and cortical particulate allograft (Puros ; Zimmer Dental Inc.) as the inner and outer layers, respectively. The test group was treated in a similar manner but a bovine pericardium membrane (CopiOs pericardium membrane; Zimmer Dental Inc.) was used to protect the bone grafts, when augmenting the facial or buccal implant dehiscence defect. Pre-surgical procedures After the patients were enrolled in the study, a comprehensive oral examination was performed and a baseline periapical radiograph of the surgical site was taken using a radiographic positioning device (XCP ; Rinn Corp., Elgin, IL, USA) and the paralleling technique. Plaque (O’Leary et al. 1972) and Gingival Index (Loe 1967) scores were determined at baseline and during each follow-up appointment. A baseline cone beam computed tomography (CBCT) scan was taken to determine the initial residual ridge width of each patient. A customized measuring template was fabricated on the study model using light-cured acrylic resin (Triad TruTray; Dentsply, York, PA, USA). The measuring template was designed to fit onto the occlusal surfaces of the adjacent teeth to be stable and reproducible. A vertical guide was positioned at 4 mm buccal to the edentulous site and secured onto the occlusal portion of the measuring template (Fig. 1), thus serving to standardize the amount of bone graft placed buccal to the exposed implant surface. After the flap was reflected, grooves at 2 mm intervals, starting from the ridge crest to 6 mm apical to the crest, were made on to the vertical guide. Surgical templates to serve as guides for the three-dimensional positioning of the implant were fabricated based on the prosthetic location of the restoration using lightcured acrylic resin (Triad TruTray; Dentsply; Shotwell et al. 2005). A removable, tooth-supported provisional acrylic prosthesis (Essix; Dentsply ) was fabricated for the purpose of protecting the surgical site from mechanical trauma and soft tissue contact during the healing period. Table 1. Inclusion and exclusion criteria