Barrier membranes for ridge augmentation is there an optimal pore size? /

by Gutta, Rajesh.

Background: - Alveolar bone loss is often a sequelae of edentulism. However, several reconstruction procedures with bone grafts and barrier membranes are used to restore the lost bony architecture. The value of titanium mesh barriers has been shown to be reliable both in vertical and horizontal ridge augmentation procedures. However, there is a paucity of literature supporting the role of pore size of barrier membranes in preventing soft tissue ingrowth during ridge augmentation procedures. There are multiple reports describing a layer of soft tissue with varying thickness beneath the mesh and adhering to the newly regenerated bone. The objective of this study was 1) to identity the presence of an optimal pore size that facilitates qualitative bone regeneration, 2) to identify the critical pore size that excludes soft tissue ingrowth into regenerative sites, 3) to determine if cortical perforations have any effect on bone regeneration, and 4) to reiterate that bone graft containment is an important parameter for successful regeneration. Methods: - The study involved 4 adult hound dogs that were randomly divided into 3 groups. Groups 1 and 2 consisted of one animal each, sacrificed at one month and two months respectively. Group 3 consisted of two animals, sacrificed at the end of four months after the surgical procedure. All the animals received corticocancellous tibial bone grafting to the bilateral mandibular body/ramus areas. The left mandible received ii cortical perforations in all animals. The experiment analyzed three different pore sized meshes compared to the controls without mesh. Two different pore sized titanium meshes (1.2mm and 600 µm) and a resorbable mesh (1mm) were pre-formed into the shape to a cube with one face open. Each side of the cube measured approximately 10 millimeters in size. The cubes were open face on the surface facing the bone. A total of 31 sites were included in the study. Prior to sacrifice, all the animals received 2 doses of tetracycline as a marker for new bone formation. Data Analysis: Histomorphometry was performed by using Bioquant image analysis software. Areas of new bone and soft tissue were measured. The rate of mineral apposition was also calculated. All the values obtained with histomorphometry were statistically analyzed with a student’s t-test procedure. Results: The amount of new bone growth into the macroporous titanium mesh was significantly higher than the other groups. The mean area of new bone formation in large and small titanium meshes was 66.26 mm 2 and 52.82 mm2 respectively. In the resorbable mesh group, the mean area of new bone formed is 46.76 mm2. The amount of new bone formed in the control group was 29.80 mm 2. There was no significant difference in the amount of bone formation between the left and right sides (p=0.3172). Resorbable meshes had significant soft tissue ingrowth (23.47 mm2) compared to macroporous titanium mesh (16.96 mm2), and microporous titanium mesh (22.29 mm2). The controls had least amount of soft tissue ingrowth (9.41 mm 2). Mineral apposition rate was found to be higher in the resorbable group (2.41µm/day) and the rate was least (1.09 µm/day) in the large pore titanium mesh group. iii Conclusion: - The macroporous membranes facilitated greater bone regeneration compared to microporous and resorbable membranes. The macroporous mesh also prevented significant soft tissue ingrowth compared to other meshes. Containment of the bone graft is the most critical issue in successful bone regeneration. The presence of cortical perforations did not have any effect on the quality or the quantity of regenerated bone. Further research should be directed towards identifying a critical pore size and manufacturing a reliable mesh that would prevent excessive soft tissue ingrowth in ridge augmentation procedures. iv