TiO2scaffolds in peri-implant dehiscence defects: an experimental pilot study

Peri-implant bone regeneration in pigs

PURPOSE

To review the current literature to answer the focused question: in the experimental pig model (population), which types of peri-implant bone defects (exposure) have been used evaluate different modes of therapy and what is their capacity for spontaneous healing and regeneration (outcome)?

METHODS

Following PRISMA guidelines, electronic databases were searched for studies reporting peri-implant bone defects in the maxillae or mandibles of pigs. Those studies which reported a control group of untreated defects with assessment of spontaneous regeneration [new bone area (BA)] and/or re-osseointegration [new bone-to-implant contact (BIC)] via quantitative radiography or histomorphometry were included in a random effects meta-analysis for the outcomes BA and BIC.

RESULTS

Overall, 21 studies, mostly performed in the mandibles of minipigs, were included. Most studies reported 'acute' intrabony (circumferential and/or dehiscence; n = 12) or supra-alveolar defects (horizontal; n = 4). Five studies attempted to induce 'chronic' peri-implantitis lesions using ligatures with conflicting results. Meta-analyses revealed pooled estimates (with 95% confidence intervals) of 48.07% BIC (30.14-66%) and 64.31% BA (42.71-85.91%) in intrabony defects, and 52.09% BIC (41.83-62.35%) and 28.62% BA (12.97-44.28%) in supra-alveolar defects. Heterogeneity in the meta-analysis was high (I2 > 90%).

CONCLUSION

Current evidence for peri-implant bone regeneration in pigs is mainly based on acute intrabony defects, which demonstrate a high capacity for spontaneous regeneration and re-osseointegration. The evidence for chronic peri-implantitis is limited and does not clearly indicate a spontaneous progression of the disease in this animal model.

Cyanoacrylate versus Collagen Membrane as a Sealing for Alveolar Ridge Preservation: A Randomized Clinical Trial

This study involved a randomized clinical trial that included 140 patients. Alveolar ridge preservation was performed with xenografts. Sealing in the control group consisted of a collagen membrane versus cyanoacrylate in the test group. The dental implants were placed immediately after extraction. The variables were evaluated at 3, 12, and 18 months of follow-up. Pearson's chi-squared test was used for qualitative variables and the Student t-test for related samples was used for quantitative variables. The change in buccolingual alveolar bone width was significantly greater in the CMX group than in the CX group after three months (p < 0.005). However, significance was not reached at the other follow-up timepoints (p > 0.005). CAL showed significantly greater values in the CMX group than in the CX group (p < 0.005), and MBL proved greater in the CMX group than in the CX group, with p < 0.001. Five membrane exposures were recorded in the CMX group. Cyanoacrylate as a sealing method for alveolar ridge preservation seems to afford better clinical and radiological results than collagen membrane.

Immunohistochemical comparison of lateral bone augmentation using a synthetic TiO2 block or a xenogeneic graft in chronic alveolar defects

OBJECTIVES

To evaluate osteogenic markers and alveolar ridge profile changes in guided bone regeneration (GBR) of chronic noncontained bone defects using a nonresorbable TiO₂ block.

MATERIALS AND METHODS

Three buccal bone defects were created in each hemimandible of eight beagle dogs and allowed to heal for 8 weeks before GBR. Treatment was assigned by block randomization: TiO₂ block: TiO₂ -scaffold and a collagen membrane, DBBM particulates: Deproteinized bovine bone mineral (DBBM) and a collagen membrane, Empty control: Only collagen membrane. Bone regeneration was assessed on two different healing timepoints: early (4 weeks) and late healing (12 weeks) using several immunohistochemistry markers including alpha-smooth muscle actin (α-SMA), osteopontin, osteocalcin, tartrate-resistant acid phosphatase, and collagen type I. Histomorphometry was performed on Movat Pentachrome-stained and Von Kossa/Van Gieson-stained sections. Stereolithographic (STL) models were used to compare alveolar profile changes.

RESULTS

The percentage of α-SMA and osteopontin increased in TiO₂ group after 12 weeks of healing at the bone-scaffold interface, while collagen type I increased in the empty control group. In the defect area, α-SMA decreased in the empty control group, while collagen type I increased in the DBBM group. All groups maintained alveolar profile from 4 to 12 weeks, but TiO₂ group demonstrated the widest soft tissue contour profile.

CONCLUSIONS

The present findings suggested contact osteogenesis when GBR is performed with a TiO₂ block or DBBM particulates. The increase in osteopontin indicated a potential for bone formation beyond 12 weeks. The alveolar profile data indicated a sustained lateral increase in lateral bone augmentation using a TiO₂ block and a collagen membrane, as compared with DBBM and a collagen membrane or a collagen membrane alone.

Impact of simultaneous placement of implant and block bone graft substitute: an in vivo peri-implant defect model

Background

Insufficient bone volume around an implant is a common obstacle when dental implant treatment is considered. Limited vertical or horizontal bone dimensions may lead to exposed implant threads following placement or a gap between the bone and implant. This is often addressed by bone augmentation procedures prior to or at the time of implant placement. This study evaluated bone healing when a synthetic TiO₂ block scaffold was placed in circumferential peri-implant defects with buccal fenestrations.

Methods

The mandibular premolars were extracted and the alveolar bone left to heal for 4 weeks prior to implant placement in six minipigs. Two cylindrical defects were created in each hemi-mandible and were subsequent to implant placement allocated to treatment with either TiO₂ scaffold or sham in a split mouth design. After 12 weeks of healing time, the samples were harvested. Microcomputed tomography (MicroCT) was used to investigate defect fill and integrity of the block scaffold. Distances from implant to bone in vertical and horizontal directions, percentage of bone to implant contact and defect fill were analysed by histology.

Results

MicroCT analysis demonstrated no differences between the groups for defect fill. Three of twelve scaffolds were partly fractured. At the buccal sites, histomorphometric analysis demonstrated higher bone fraction, higher percentage bone to implant contact and shorter distance from implant top to bone 0.5 mm lateral to implant surface in sham group as compared to the TiO₂ group.

Conclusions

This study demonstrated less bone formation with the use of TiO₂ scaffold block in combination with implant placement in cylindrical defects with buccal bone fenestrations, as compared to sham sites.

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.

Guided bone regeneration of chronic non-contained bone defects using a volume stable porous block TiO2 scaffold: An experimental in vivo study

OBJECTIVES

To evaluate new lateral bone formation and lateral volume augmentation by guided bone regeneration (GBR) in chronic non-contained bone defects with the use of a non-resorbable TiO₂ -block.

MATERIALS AND METHODS

Three buccal bone defects were created in each hemimandible of eight beagle dogs and allowed to heal for 8 weeks before treatment by GBR. Each hemimandible was randomly allocated to 4- or 12-week healing time after GBR, and three intervention groups were assigned by block randomization: TiO₂ block: TiO₂ -scaffold and a collagen membrane, DBBM particles: Deproteinized bovine bone mineral (DBBM) and a collagen membrane, Empty control: Collagen membrane only. Microcomputed tomography (microCT) was used to measure the lateral bone formation and width augmentation. Histological outcomes included descriptive analysis and histomorphometric measurements.

RESULTS

MicroCT analysis demonstrated increasing new bone formation from 4 to 12 weeks of healing. The greatest width of mineralized bone was seen in the empty controls, and the largest lateral volume augmentation was observed in the TiO₂ block sites. The DBBM particles demonstrated more mineralized bone in the grafted area than the TiO₂ blocks, but small amounts and less than the empty control sites.

CONCLUSION

The TiO₂ blocks rendered the largest lateral volume augmentation but also less new bone formation compared with the DBBM particles. The most new lateral bone formation outward from the bone defect margins was observed in the empty controls, indicating that the presence of either graft material leads to slow appositional bone growth.

Synthetic Blocks for Bone Regeneration: A Systematic Review and Meta-Analysis

This systematic review is aimed at evaluating the effectiveness of synthetic block materials for bone augmentation in preclinical in vivo studies. An electronic search was performed on Pubmed, Scopus, EMBASE. Articles selected underwent risk-of-bias assessment. The outcomes were: new bone formation and residual graft with histomorphometry, radiographic bone density, soft tissue parameters, complications. Meta-analysis was performed to compare new bone formation in test (synthetic blocks) vs. control group (autogenous blocks or spontaneous healing). The search yielded 214 articles. After screening, 39 studies were included, all performed on animal models: rabbits (n = 18 studies), dogs (n = 4), rats (n = 7), minipigs (n = 4), goats (n = 4), and sheep (n = 2). The meta-analysis on rabbit studies showed significantly higher new bone formation for synthetic blocks with respect to autogenous blocks both at four-week (mean difference (MD): 5.91%, 95% confidence intervals (CI): 1.04, 10.79%, p = 0.02) and at eight-week healing (MD: 4.44%, 95% CI: 0.71, 8.17%, p = 0.02). Other animal models evidenced a trend for better outcomes with synthetic blocks, though only based on qualitative analysis. Synthetic blocks may represent a viable resource in bone regenerative surgery for achieving new bone formation. Differences in the animal models, the design of included studies, and the bone defects treated should be considered when generalizing the results. Clinical studies are needed to confirm the effectiveness of synthetic blocks in bone augmentation procedures.