The effect of bone regeneration according to maintenance period of the non-resorbable membrane in rabbit calvarial defects

Abstract

When the tooth loss is due to trauma or congenital abscence, often a ridge augmentation procedure is requested to correct the bone defect prior to implant placement.(2) Although many clinicians have tried GTR, they haven't sure about maintaing period of non-resorbable membrane used here such as PTFE. The purpose of this study is to?figure out ?how maintaining period of PTFE? membrane used in GTR with autogeneous bone, heterogeneous bone and synthetic bone on rabbits' cranial defect ?effect on bone formation. Eight adult New Zealand white rabbits were used in this study. Four defects were surgically made in their calvaria. Using a trephine bur, 4 'through and through' defects were created and classified into 4 groups, which were consisted of control(no graft), experimental group 1(autogeonous bone)and experimental group 2(deproteiniwed bovine bone:OCS-BⓇ), experimental group 3(Xenogenic graft: MBCP). The defects were covered with PTFE membrane(CytoplastⓇ ). Membranes were romoved after 1, 2, 4 and 8 weeks post-GBR in each 2 rabbits. And then, all rabbits were sacrificed, specimens were taken and observed histologically. The results were as follow: 1) After removing the membranes in a week, bone formation was not evident in a control group but the area was took place with only loose fibrous connective tissue. In group 1, thin bone formation and infiltration of connective tissue on the superficial layer were observed. Initial bone formation and infiltration of fibrous connective tissue were evident in group 2 and 3.

2) When the membranes were removed after 2 weeks of the experiment, bridge shaped bone formation was shown in control group but mostly connective tissue took place. More increased bone thickness was evident in group 1 and increased bone formation than first week was shown in group 2 and 3.

3) When the membranes were removed after 4 weeks, 2/3 of normal bone thickness was formed in control group still with infiltration of connective tissue. In group 1, regular bone formation with normal bone thickness were shown and in group 2 and 3, similar bone thickness to the normal one was evident.

4) After the removal of the membranes in 8 weeks, bone thickness formed in control group was increased than 4th week but could not reach normal bone thickness. In group 1, normal bone thickness was formed and similar bone thickness to that of normal one was observed in group 2 and 3.

5) After GBR, the membrane was removed in initial time, the usage of nonabsorbable membrane and autogenous bone resulted in the most favorable bone formation. When heterogeneous bone and synthetic bone were used, similarly favorable result was observed and in the group without any graft material showed the least bone formation.

6) In GBR, at least 4-week period of maintaining the membrane is required and when xenograft or synthetic bone is used more maintaining time than that of autogenous bone is needed for better bone regeneration. In the future, additional studies with more species and other graft materials will be needed and clinical studies based on this will also be required.