BACTERIAL PENETRATION THROUGH RESOLUT(R) RESORBABLE MEMBRANE IN-VITRO- AN HISTOLOGICAL AND SCANNING ELECTRON-MICROSCOPIC STUDY

The aim of this study was to evaluate the characteristics of resorptio n and the pattern of bacterial collonisation of polyglycolic and polyl actic resorbable membranes under controlled experimental conditions. A removable cobalt-chromium device was applied to the lower jaw of 5 st udents for a period of 4 weeks. 8 composite resin chambers were glued to the device, 4 on each side of the mouth. A small piece of PLA/PGA m embrane separated the composite chambers into 2 parts. The subjects wo re the devices 24 h a day, except for the time necessary for oral hygi ene procedures, during which time, the structure was submerged in a 0. 2% chlorexidine solution. Every week, 2 of the chambers were removed; one was processed for scanning electron microscopy, to be observed bot h on the external and internal surface, and the other one for light mi croscopy examination. Both the electron microscopic and histologic obs ervations showed a progressive increase in the plaque layer on the ext ernal surface of the membrane during the period of observation. The li ght microscopy showed an early invasion of the membrane, starting abou t 1 week after the exposure. On all the 3- and 4-week specimens, a com plete bacterial invasion over the whole thickness of the membrane was visible. After 3 weeks of plaque accumulation, bacterial colonisation of the inner portion of the membrane was detectable in all the specime ns. At 3-weeks, we observed in the light microscopy group in 4 out of 5 specimens, a large reduction of the thickness of the material and sm all voids in the membrane structure. In 1 specimen, the membrane was n o more detectable. Only in 5 specimens of the 4-week group was the mem brane still recognizable, though reduced to fragments. In conclusion, once exposed to the oral cavity, the PLA/PGA membranes start to resorb in the early stages: this process concludes itself between the 3rd an d 4th weeks of exposure. However, the particular conditions of the exp erimental design nevertheless classify this study as an in vitro, more than as an in vivo experimentation.