A lateral ridge augmentation study to evaluate a synthetic membrane for guided bone regeneration: an experiment in the canine mandible

Membrane barriers for guided bone regeneration: An overview of available biomaterials

Dental implants revolutionized the treatment options for restoring form, function, and esthetics when one or more teeth are missing. At sites of insufficient bone, guided bone regeneration (GBR) is performed either prior to or in conjunction with implant placement to achieve a three-dimensional prosthetic-driven implant position. To date, GBR is well documented, widely used, and constitutes a predictable and successful approach for lateral and vertical bone augmentation of atrophic ridges. Evidence suggests that the use of barrier membranes maintains the major biological principles of GBR. Since the material used to construct barrier membranes ultimately dictates its characteristics and its ability to maintain the biological principles of GBR, several materials have been used over time. This review, summarizes the evolution of barrier membranes, focusing on the characteristics, advantages, and disadvantages of available occlusive barrier membranes and presents results of updated meta-analyses focusing on the effects of these membranes on the overall outcome.

Pre-Clinical Models in Implant Dentistry: Past, Present, Future

Biomedical research seeks to generate experimental results for translation to clinical settings. In order to improve the transition from bench to bedside, researchers must draw justifiable conclusions based on data from an appropriate model. Animal testing, as a prerequisite to human clinical exposure, is performed in a range of species, from laboratory mice to larger animals (such as dogs or non-human primates). Minipigs appear to be the animal of choice for studying bone surgery around intraoral dental implants. Dog models, well-known in the field of dental implant research, tend now to be used for studies conducted under compromised oral conditions (biofilm). Regarding small animal models, research studies mostly use rodents, with interest in rabbit models declining. Mouse models remain a reference for genetic studies. On the other hand, over the last decade, scientific advances and government guidelines have led to the replacement, reduction, and refinement of the use of all animal models in dental implant research. In new development strategies, some in vivo experiments are being progressively replaced by in vitro or biomaterial approaches. In this review, we summarize the key information on the animal models currently available for dental implant research and highlight (i) the pros and cons of each type, (ii) new levels of decisional procedures regarding study objectives, and (iii) the outlook for animal research, discussing possible non-animal options.

Exposure of Barriers Used in GBR: Rate, Timing, Management, And Its Effect on Grafted Bone. A Retrospective Analysis

The purpose of this study is to compare exposure rate of three different barrier types after a guided-bone regenerationprocedure, as well as to compare the percentage grafted bone dimensional loss with and without exposed barriers. Patient records from September 2007 to May 2015 were reviewed to identify subjects that had received bone graft and then implant placement procedure after the graft is completely healed. The subjects were divided into 3 groups: 1) resorbable barrier 2) non-resorbable barrier, and 3) titanium-mesh barrier. Incidences of barrier exposure were recorded.  Cone-beam computed tomography images before treatment (T0), right after grafting (T1), and after healing (T2) were used to determine percentage grafted bone dimensional loss (%) and quantitative grafted bone remained (mm 2 ). Three cross-sectioned areas, at 1mm apart, of preplanned implant positions at the grafted site were measured on cone-beam computed tomography to calculate for grafted bone remained and grafted bone dimensional change. The exposure rate of all guided bone regeneration was 36.9%. Exposure rate of resorbable barrier (23.3%) is significantly lower than Titanium mesh (68.9%) and Non-resorbable (72.7%) (Chi-Square, P < .001).  The result from this study revealed that barrier types have significant effect on exposure rate. There was also a significant different in grafted bone dimensional loss in sites with barrier exposure (58.3%) and sites with no barrier exposure (44.1%) during the healing period (Mann-Whitney U, P = .008).

Micro/nanostructured calcium phytate coating on titanium fabricated by chemical conversion deposition for biomedical application

A bioactive micro/nanostructured calcium phytate coating was successfully prepared on titanium surfaces by chemical conversion deposition, mainly through hydrothermal treatment of a mixed solution of phytic acid and saturated calcium hydroxide solution. Ultraviolet radiation was carried out to improve the adhesion of the coating to the titanium substrate. Pure titanium with a sandblasted/acid-etched surface was used as the control group. The topography and chemical composition of the modified surfaces were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and static water contact angle measurement. A pull-off test was performed to measure the coating-to-substrate adhesion strength. Bovine serum albumin was used as a model to study the protein adsorption effect. Cells were cultured on titanium surfaces for 7 days in osteogenic differentiation medium, then the osteoblast compatibility in vitro were explored by alkaline phosphatase and alizarin red staining. After 1, 2, 4 and 8 wks of immediate implantation of titanium implants into the mandibles of New Zealand white rabbits, biological effects in vivo were researched by microcomputed tomography analysis and histological evaluation. The results indicated that the roughness and hydrophilicity of the modified surfaces with micro/nanostructure remarkably increased compared to those of the control group. The pull-off test showed the average adhesion strength at the coating-substrate interface to be higher than 13.56 ± 1.71 MPa. In addition, approximately 4.41 mg/L calcium ion was released from the calcium phytate micro/nano coatings to the local environment after 48 h of immersion. More importantly, the micro/nanostructure titanium substrates significantly promoted cellular differentiation in vitro and in vivo. After 8 wks, the bone implant contact ratio (BIC, %) of the modified implants was higher than that of the control group, at 94.09 ± 0.55% and 86.18 ± 1.99% (p < 0.05). Overall, this study provided new insights into the factors promoting early osseointegration of titanium alloys, which had great potential not only for dental implants but also for various other biomaterial applications.

The effect of resorbable membranes on one-stage ridge augmentation in anterior single-tooth replacement: A randomized, controlled clinical trial

AIM

To evaluate the effect of resorbable membranes on one-stage ridge augmentation procedures in small (2-4 mm) buccal bony dehiscences in anterior maxillary single-tooth replacement.

MATERIALS AND METHODS

Patients with a buccal bony dehiscence after implant placement in the esthetic zone were randomly allocated to one-stage ridge augmentation with (M+) or without a membrane (M-). Second-phase surgery was performed after 8 weeks, and follow-up was performed 1, 6, and ≥12 months after loading. Outcomes included implant survival and success, complications, clinical and radiographic parameters, esthetic results and patient satisfaction.

RESULTS

Fifty-two patients were randomized to one-stage ridge augmentation with (n = 25) or without use of a membrane (n = 27). No significant differences in implant survival and success have been observed. The risk of having a small mucosal dehiscence was more than six times higher in the M+ group than in the M- group (RR 6.24, 95% CI 0.81 to 48.21). At the last follow-up, the bleeding index (BI) was marginally higher in the M+ group (14/9/2/0) compared to the M- group (24/2/0/0) (U = 205, Z = -2.97, p = .003, r = .42). The median change in marginal bone level was statistically lower in the M+ group (0.06 mm) than the M- group (0.60 mm) at last follow-up (U = 120, Z = -2.73 a p = .006 r = .42). Total pink esthetic index (PES) and white esthetic score (WES) and combined PES/WES were not significantly different between treatment groups at more than 12 months after loading. Only the subcategory root convexity/soft tissue color scored significantly lower in the M+ group (1.5) compared to the M- group (2.0) at the last follow-up (U = 172, Z = -2.34, p = .019 r = .34). No differences were found in patient satisfaction.

CONCLUSION

The use of a resorbable membrane in small buccal bony dehiscences in anterior maxillary single-tooth replacement resulted in less marginal bone loss, but showed more mucosal dehiscences, higher bleeding scores and lower scores on root convexity and soft tissue color after at least one year of loading. No effect was seen on implant survival and success, overall esthetic results, and patient satisfaction. The research protocol was registered at the Dutch Trial Register (NTR) with ID NTR6137.

Clinical and Histomorphometric Assessment of Lateral Alveolar Ridge Augmentation Using a Corticocancellous Freeze-Dried Allograft Bone Block

Horizontal ridge augmentation with allografts has attracted notable attention because of its proper success rate and the lack of disadvantages of autografts. Corticocancellous block allografts have not been adequately studied in humans. Therefore, this study clinically and histomorphometrically evaluated the increase in ridge width after horizontal ridge augmentation using corticocancellous block allografts as well as implant success after 12 to 18 months after implantation. In 10 patients receiving implants (3 women, 7 men; mean age = 45 years), defective maxillary alveolar ridges were horizontally augmented using freeze-dried bone allograft blocks. Ridge widths were measured before augmentation, immediately after augmentation, and ∼6 months later in the reentry surgery for implantation. This was done at points 2 mm (A) and 5 mm (B) apically to the crest. Biopsy cores were acquired from the implantation site. Implant success was assessed 15.1 ± 2.7 months after implantation (range = 12-18 months). Data were analyzed using Friedman and Dunn tests (α = 0.05). At point A, ridge widths were 2.77 ± 0.37, 8.02 ± 0.87, and 6.40 ± 0.66 mm, respectively, before surgery, immediately after surgery, and before implantation. At point B, ridge widths were 3.40 ± 0.39, 9.35 ± 1.16, and 7.40 ± 1.10 mm, respectively, before surgery, immediately after surgery, and before implantation. The Friedman test showed significant increases in ridge widths, both at point A and point B (both P = .0000). Postaugmentation resorption was about 1.5-2 mm and was statistically significant at points A and B (P < .05, Dunn). The percentage of newly formed bone, residual graft material, and soft tissue were 33.0% ± 11.35% (95% confidence interval [CI] = 24.88%-41.12%), 37.50% ± 19.04% (95% CI = 23.88%-51.12%), and 29.5%, respectively. The inflammation was limited to grades 1 or zero. Twelve to 18 months after implantation, no implants caused pain or showed exudates or pockets. Radiographic bone loss was 2.0 ± 0.7 mm (range = 1-3). It can be concluded that lateral ridge augmentation with corticocancellous allograft blocks might be successful both clinically and histologically. Implants might have a proper clinical success after a minimum of 12 months.

Bone augmentation at peri-implant dehiscence defects comparing a synthetic polyethylene glycol hydrogel matrix vs. standard guided bone regeneration techniques

OBJECTIVES

The aim of the study was to test whether or not the use of a polyethylene glycol (PEG) hydrogel with or without the addition of an arginylglycylaspartic acid (RGD) sequence applied as a matrix in combination with hydroxyapatite/tricalciumphosphate (HA/TCP) results in similar peri-implant bone regeneration as traditional guided bone regeneration procedures.

MATERIAL AND METHODS

In 12 beagle dogs, implant placement and peri-implant bone regeneration were performed 2 months after tooth extraction in the maxilla. Two standardized box-shaped defects were bilaterally created, and dental implants were placed in the center of the defects with a dehiscence of 4 mm. Four treatment modalities were randomly applied: i)HA/TCP mixed with a synthetic PEG hydrogel, ii)HA/TCP mixed with a synthetic PEG hydrogel supplemented with an RGD sequence, iii)HA/TCP covered with a native collagen membrane (CM), iv)and no bone augmentation (empty). After a healing period of 8 or 16 weeks, micro-CT and histological analyses were performed.

RESULTS

Histomorphometric analysis revealed a greater relative augmented area for groups with bone augmentation (43.3%-53.9% at 8 weeks, 31.2%-42.8% at 16 weeks) compared to empty controls (22.9% at 8 weeks, 1.1% at 16 weeks). The median amount of newly formed bone was greatest in group CM at both time-points. Regarding the first bone-to-implant contact, CM was statistically significantly superior to all other groups at 8 weeks.

CONCLUSIONS

Bone can partially be regenerated at peri-implant buccal dehiscence defects using traditional guided bone regeneration techniques. The use of a PEG hydrogel applied as a matrix mixed with a synthetic bone substitute material might lack a sufficient stability over time for this kind of defect.