Books

Purpose: The objective of this study was to determine whether a synthetic bioresorbable polyethylene glycol (PEG) hydrogel membrane could provide similar clinical and radiographic outcomes as a standard collagen membrane, both in combination with a membrane-supporting material, during follow-up periods of 1 and 3 years. Materials and Methods: This study enrolled patients requiring implant treatment with an expected osseous defect in the posterior maxilla or mandible. Defects around the implants were grafted with deproteinized bovine bone mineral and covered with either a collagen membrane or a PEG hydrogel membrane, which is applied as a liquid and becomes a solid gel in situ. Surgical re-entry was performed after 6 months, and fixed partial dentures were inserted subsequently. Patients were examined clinically and radiographically 1 and 3 years after loading. Results: Thirty-six of the 37 included patients were reexamined in the third year. The implant survival rate at 3 years was 100%. The peri-implant tissues were healthy, with no differences between the two groups. Compared to the time of surgery, the mean changes in the distance between the first bone-to-implant contact to the transition point (ie, rough implant surface to polished neck portion) were 0.43 ± 0.56 mm (PEG) and 0.21 ± 0.36 mm (collagen) at 1 year and 0.61 ± 0.89 mm (PEG) and 0.33 ± 0.64 mm (collagen) at 3 years. The respective differences between groups were 0.13 mm (1 year) and 0.31 mm (3 years), which were not significant at either time point (analysis of covariance). Conclusion: The tested PEG hydrogel was as successful as a standard collagen membrane for the treatment of bony dehiscence defects around dental implants after follow-up periods of 1 and 3 years. Keywords: bone substitute, dental implant, graft material, guided bone regeneration, membranes, randomized controlled trial

Purpose: The aim of this randomised controlled double-blinded clinical trial was to determine the efficacy of a new cross-linked membrane (VN) in guided bone regeneration (GBR) around exposed dental implants compared to a native collagen membrane (BG). Material and methods: A total of 16 patients in need of implant treatment at two different sites with osseous defects were planned for this split-mouth study. After inserting the dental implants, periimplant defects were treated according to the GBR technique using a VN membrane with prolonged resorption time in the randomised test site and a BG membrane in the control site. After a healing time of 6 months, mucoperiosteal flaps were elevated for the evaluation of the primary (vertical bone fill [ΔDL] and quality of newly formed tissue [QT]) and secondary outcome variables (infrabony defect height [DH], defect width [DW], defect depth [DD] and augmentation depth [AD]) and the sampling of biopsies apical to the implant shoulder. Results: A total of 16 patients fulfilled the initial non-surgical inclusion and exclusion criteria. However, the study was discontinued early after 9 surgically treated patients because unacceptable safety issues arose and severe infection related to the VN membranes. The VN membrane revealed statistically significantly more soft tissue dehiscence than the BG membrane (56% and 11%, respectively, P = 0.0455). In 3 of these 9 patients the VN membrane had to be removed due to infection early after the first follow-up visit. For the statistical analyses these sites were designated as the value of the baseline. The mean ΔDL values were 1.8 ± 1.6 mm at the VN site and 4.7 ± 3.3 mm at the BG site. The ΔDD values were 0.6 ± 1.0 mm and 1.1 ± 1.2 mm, respectively, and reached statistical significance (P = 0.0208, CI 95% = -2.9 [-5.2;-0.6]). The corresponding linear defect fill (DF) values were 44% and 78%, respectively. The clinical assessment of QT showed comparable median values at sites treated with VN (3, interquartile range: 0; 3.5) and BG (3, interquartile range: 3; 4) without statistical significance. The histomorphometric analysis showed an average area density of 24.4% (SD 10.3, range 8-35%) newly formed bone at the test sites and of 35.0% (SD 20.6, range 8-60%) at the control sites. The histological data showed only some trends and did not reach statistical significance. Conclusion: In the present study, the VN membranes with prolonged resorption time demonstrated significantly more adverse events and insufficient bone regeneration compared to the native BG membranes and no advantages in favour of the VN membranes were detectable. Keywords: clinical research, collagen membrane, cross-linking, guided bone regeneration