Vivosorb, Bio-Gide, and Gore-Tex as barrier membranes in rat mandibular defects: an evaluation by microradiography and micro-CT.

OBJECTIVES: The objectives of this study were to determine whether a new degradable synthetic barrier membrane (Vivosorb) composed of poly(dl-lactide-epsilon-caprolactone) (PDLLCL) can be useful in implant dentistry and to compare it with collagen and expanded polytetrafluoroethylene (ePTFE) membranes. MATERIAL AND METHODS: In 192 male Sprague-Dawley rats, a standardized 5 mm circular defect was created through the right angle of the mandible. New bone formation was evaluated by post-mortem microradiography and micro-CT (muCT) imaging. Four groups (control, PDLLCL, collagen, ePTFE) were evaluated at three time intervals (2, 4, and 12 weeks). In the membrane groups the defects were covered; in the control group the defects were left uncovered. Data were analysed using a multiple regression model. RESULTS: New bone formation could be detected by post-mortem microradiography in 130 samples and by muCT imaging in 112 samples. Bone formation was progressive in 12 weeks, when the mandibular defect was covered with a membrane. Overall, more bone formation was observed underneath the collagen and ePTFE membranes than the PDLLCL membranes. CONCLUSIONS: In contrast to uncovered mandibular defects, substantial bone healing was observed in defects covered with a PDLLCL membrane. However, bone formation in PDLLCL-covered defects tended to be less than in the defects covered with collagen or ePTFE. The high variation in the PDLLCL samples at 12 weeks may be caused by the moderate adherence of this membrane to bone compared with collagen. These results indicate that further study is needed to optimize the properties of PDLLCL membranes.

A comparison of micro-CT, microradiography and histomorphometry in bone research.

OBJECTIVE: Intraobserver reliability and agreement were determined for microradiography (MR), micro-computed tomography (microCT) and histomorphometry (HM). These three modalities were compared for quantitative measurements of bone formation and graft modelling in rat mandibular defects and grafts. DESIGN: Twelve rats were randomly selected from a larger experiment, evaluating bone formation in rat mandibular defects and bone modelling in grafts. Twelve lateral microradiographs were taken of the grafts. microCT images were obtained from all defects and grafts (24 specimens). Defects and grafts were cut perpendicularly through their centre. Microradiographs, microCT images and histological sections were obtained from the resulting 48 specimens. New bone volume and graft volume were measured using image analysis software on MR and microCT images. Defect width and graft width were measured using images from HM, MR and microCT. The results were compared to each other. RESULTS: The intraobserver reliabilities for the measurements of new bone volume by microCT, and the measurement of graft modelling by MR and graft volume by microCT were high. The differences between MR, HM and microCT were larger in defect width measurements than in graft width measurement. MR measured smaller defects than HM and microCT. The 95% confidence interval was larger in defect width measurements compared to graft width measurements. CONCLUSIONS: The methods of MR and microCT image analysis are reliable but preferably should be used in combination as to obtain valid conclusions. HM, MR and microCT for graft widths measurements showed more agreement than for defect width measurements. MR appears to overestimate bone formation.

Is there evidence that barrier membranes prevent bone resorption in autologous bone grafts during the healing period? A systematic review.

INTRODUCTION: Autologous bone is considered the "reference standard" for bone-grafting procedures. A barrier membrane covering an autologous bone graft (guided bone regeneration [GBR]) is expected to prevent graft resorption. Good clinical results have been reported for GBR, although potential complications and relatively high costs have been implicated as disadvantages. However, most studies on the subject have been uncontrolled. PURPOSE: The aim of this systematic review was to evaluate the available evidence that barrier membranes prevent bone resorption in autologous onlay bone grafts. The primary outcome measure was bone resorption. RESULTS: The search yielded 182 articles. Two observers independently appraised 32 relevant studies methodologically, yielding 14 controlled studies. The articles included human and animal experiments with heterogenous objectives and outcome variables. Although most authors concluded that they had found evidence for the protective effect of barrier membrane on bone resorption in bone grafts, this systematic review reveals that the available evidence is too weak to support this. Most included studies were animal experiments; thus, extrapolation to the human situation is difficult. Most studies also had a small number of test sites, and sample size justification was generally not reported. Furthermore, ambiguity and lack of significance were found in many studies, along with additional limitations such as implantation site, nonsuitable designs, and varying outcome measures. CONCLUSION: Based on a systematic review of the literature, further evidence is needed to determine whether barrier membranes prevent bone resorption in autologous onlay bone grafts.

The influence of three barrier membranes on modeling and incorporation of autologous onlay bone grafts in rats. An evaluation by transversal microradiography.

OBJECTIVES: To determine whether covering an autologous bone grafts with three different barrier membranes prevents graft resorption, and to compare these membranes to each other. DESIGN: In 192 rats a standardised 4.0mm diameter bone graft was harvested from the right mandibular angle and transplanted to the left. Membranes used to cover the grafts were a new poly(DL-lactide-epsilon-caprolactone) membrane, a collagen and expanded polytetrafluoroethylene membrane. The controls were left uncovered. Graft resorption and incorporation were measured with transversal microradiography (TMR) in the four groups at 2, 4 and 12 weeks. Data were analysed using multiple regression analyses. RESULTS: Overall, there were no differences in modeling with resorption between the four groups. ePTFE at 12 weeks showed a lower mineralization ratio and graft height of the graft as compared to the other groups. The mean graft incorporation was progressive and nearly identical from 2 to 12 weeks in all groups. CONCLUSIONS: Membranes have an equal effect on bone graft modeling and resorption as found in non-covered controls. Therefore, the indication to use a barrier membrane to prevent bone modeling with resorption and enhance incorporation of autologous onlay bone grafts is disputable.