Risk Factors for Wound Dehiscence after Guided Bone Regeneration in Dental Implant Surgery

Occlusive and Proliferative Properties of Different Collagen Membranes-An In Vitro Study

Different collagen barrier membranes come in various sources and crosslinking that may affect barrier function and tissue integration. This study investigated barrier function and tissue integration of the three different collagen membranes (Jason®: porcine pericardium, GENOSS: bovine tendon, and BioMend® Extend: cross-linked bovine tendon) with human gingival fibroblasts. The barrier function and tissue integration properties were determined under confocal microscopy. Morphological characteristics were observed using scanning electron microscopy. Our results showed that all collagen membranes allowed a small number of cells to migrate, and the difference in barrier function ability was not significant. The cross-linked characteristics did not improve barrier ability. The native collagen membrane surfaces allowed evenly scattered proliferation of HGF, while the cross-linked collagen membrane induced patchy proliferation. Statistically significant differences in cell proliferation were found between Jason and BioMend Extend membranes (p = 0.04). Scanning electron microscope showed a compact membrane surface at the top, while the bottom surfaces displayed interwoven collagen fibers, which were denser in the crosslinked collagen membranes. Within the limitations of this study, collagen membranes of different origins and physical properties can adequately prevent the invasion of unwanted cells. Native collagen membranes may provide a better surface for gingival cell attachment and proliferation.

Effect of Exposure Rates with Customized versus Conventional Titanium Mesh on Guided Bone Regeneration: A Systematic Review and Meta-Analysis

Titanium mesh exposure is the main complication of bone regeneration. In this study, a meta-analysis and performed to clarify the effect of customized titanium mesh versus conventional titanium mesh complications and the time of mesh exposure on edentulous alveolar ridge GBR. Databases, including PubMed, EMBASE, Web of Science and Cochrane Central Register Controlled Trials, were searched by two independent reviewers to retrieve articles published from January 2010 to March 2020, regarding the incidence of complications after GBR surgery, with language limited to English articles. A total of 705 articles were found, and 9 articles were quantitatively analyzed. A funnel plot was made for 10 comprehensive datasets. The combined value of the total exposure rate of titanium mesh was 0.44 (44%, 95% CI=0.30~0.58). The results of subgroup analysis showed that the combined value of the customized titanium mesh exposure rate was 0.31 (31%, 95% CI=0.15~0.51), and the combined value of the conventional titanium mesh exposure rate was 0.51 (51%, 95% CI=0.33~0.69). Based on the findings of the present study, the exposure rate of customized titanium mesh is lower than that of conventional titanium mesh. The design of 3D printing customized titanium mesh avoids nerves and blood vessels, which is of great significance to improve the accurate reconstruction of GBR and provides enough space for implantation and reducing the exposure rate. Soft tissue management (i.e., technical sensitivity) is also an important factor to avoid soft tissue fractures.

Clinical and histological outcomes of maxillary sinus floor augmentation with synthetic bone substitutes for dental implant treatment: A meta-analysis

The objective of the present review was to gather all available human randomized clinical trials comparing the clinical and histological results of synthetic bone substitutes used in maxillary sinus floor augmentation. Authors electronically searched in Pubmed/Medline, Scopus and Cochrane databases to analyse the success of endosseous dental implant, implant failure, peri-implant marginal bone loss, newly formed bone and residual bone graft material.  After the search, ten randomized clinical trials were included. Four studies ranging from low to unclear risk of bias were used for meta-analysis, being able to compare only biphasic calcium phosphate (BCP) and deproteinized bovine bone (DBB). A greater amount of residual graft material (mean difference -MD- 4.80 mm; 95% CI, 9.35 to 0.26; P= 0.040) was found in DBB group. No other statistically significant differences were found between BCP and DBB for the rest of outcomes. Thus, our results suggested that BCP can be considered a suitable alternative to DBB in maxillary sinus floor augmentation due to its clinical and histological results.

Guided bone regeneration

Guided bone regeneration (GBR) is a surgical procedure that utilizes bone grafts with barrier membranes to reconstruct small defects around dental implants. This procedure is commonly deployed on dehiscence or fenestration defects ≥2 mm, and mixing with autogenous bone is recommended on larger defects. Tension-free primary closure is a critical factor to prevent wound dehiscence, which is critical cause of GBR failure. A barrier membrane should be rigidly fixed without mobility. If the barrier is exposed, closed monitoring should be utilized to prevent secondary infection.

Collagen Membrane for Guided Bone Regeneration in Dental and Orthopedic Applications

Treatment of cortical bone defects is a clinical challenge. Guided bone regeneration (GBR), commonly used in oral and maxillofacial dental surgery, may show promise for orthopedic applications in repair of cortical bone defects. However, a limitation in the use of GBR for cortical bone defects is the lack of an ideal scaffold that provides sufficient mechanical support to bridge the cortical bone with minimal interference in the repair process. We have developed a new collagen membrane, CelGro™, for use in GBR. We report the material characterization of CelGro and evaluate the performance of CelGro in translational preclinical and clinical studies. The results show CelGro has a bilayer structure of different fiber alignment and is composed almost exclusively of type I collagen. CelGro was found to be completely acellular and free from xenoantigen, α-gal (galactose-alpha-1,3-galactose). In the preclinical study of a rabbit cortical bone defect model, CelGro demonstrated enhanced bone-remodeling activity and cortical bone healing. Microcomputed tomography evaluation showed early bony bridging over the defect area 30 days postoperatively, and nearly complete restoration of mature cortical bone at the bone defect site 60 days postoperatively. Histological analysis 60 days after surgery further confirmed that CelGro enables bridging of the cortical bone defect by induction of newly formed cortical bone. Compared to a commercially available collagen membrane, Bio-Gide^®, CelGro showed much better cortical alignment and reduced porosity at the defect interface. As selection of orthopedic patients with cortical bone defects is complex, we conducted a clinical study evaluating the performance of CelGro in guided bone regeneration around dental implants. CelGro was used in GBR procedures in a total of 16 implants placed in 10 participants. Cone-beam computed tomography images show significantly increased bone formation both horizontally and vertically, which provides sufficient support to stabilize implants within 4 months. Together, the findings of our study demonstrate that CelGro is an ideal membrane for GBR not only in oral and maxillofacial reconstructive surgery but also in orthopedic applications (Clinical Trial ID ACTRN12615000027516).

Minimizing risk of customized titanium mesh exposures - a retrospective analysis

BACKGROUND

Recommendations for soft tissue management associated with customized bone regeneration should be developed. The aim of this study was to evaluate a new protocol for customized bone augmentation in a digital workflow.

METHODS

The investigators implemented a treatment of three-dimensional bone defects based on a customized titanium mesh (Yxoss CBR®, ReOSS, Filderstadt, Germany). Patients and augmentation sites were retrospectively analysed focussing on defect regions, demographic factors, healing difficulties and potential risk factors. An exposure rate was investigated concerning surgical splint application, A®- PRF and flap design.

RESULTS

In total, 98 implants could be placed. Yxoss CBR® was removed after mean time of 6.53 ± 2.7 months. Flap design was performed as full flap preparation (27.9%), full flap and periosteal incision (39.7%), periosteal incision (1.5%), poncho/split flap (27.9%) and rotation flap (2.9%). In 25% of the cases, exposures of the meshes were documented. Within this exposure rate, most of them were slight and only punctual (A = 16.2%), like one tooth width (B = 1.5%) and complete (C = 7.4%). A®- PRF provided significantly less exposures of the titanium meshes (76.5% no exposure vs. 23.5% yes, p = 0.029). Other parameters like tobacco abuse (p = 0.669), diabetes (p = 0.568) or surgical parameters (mesh size, defect region, flap design) did not influence the exposure rate. Surgical splints were not evaluated to reduce the exposure rate (p = 0.239). Gender (female) was significantly associated with less exposure rate (78,4% female vs. 21.6% male, p = 0.043).

CONCLUSIONS

The results of this study suggest that the new digital protocol including patient-specific titanium meshes, resorbable membranes and bone grafting materials was proven to be a promising technique. To improve soft tissue healing, especially A®-PRF should be recommended.

Risk factors in bone augmentation procedures

Bone augmentation is an extremely common procedure in implant dentistry today because of significant advancements with reactive biomaterials, a better understanding of the mechanism of action that is found with growth factors contained in platelets, and improvements in surgical techniques. The expectation is for the surgeon to place the dental implant in the position that best serves the requirements of the prosthetic restorations. With the increasing demands that patients have for ideal prosthetic results, surgeons are expected to predictably augment both hard and soft tissues to provide the anticipated esthetic and functional outcomes. Bone grafting can be performed before, during, and after the implant placement; however, these augmentation procedures come with increased cost, the risk of complications such as infection or failure, and lengthening of the total treatment time. In addition, a plethora of grafting materials are available commercially, where they are often inadequately studied, or there is minimal information regarding their predictability or long-term success, or ability to support dental implants. It is clear that although the surgical field has seen major progress since early implant surgical techniques in the 1980s, major challenges still exist with hard tissue augmentation procedures. This review will discuss these challenges that are increased and often specific to bone graft healing, and which are becoming more common as implant site development often requires bone augmentation to improve volume or contour deficiencies. The risk factors that patients may present with that will affect outcomes with bone augmentation procedures are identified, and recommendations for the prevention of complications or managing complications once they have occurred are provided.