BACTERIAL PENETRATION IN-VITRO THROUGH GTAM MEMBRANE WITH AND WITHOUTTOPICAL CHLORHEXIDINE APPLICATION - A LIGHT AND SCANNING ELECTRON-MICROSCOPIC STUDY

Premature exposure of membrane in the oral cavity is considered the mo st common complication as well as a reason for failure or incomplete s uccess of guided tissue regeneration, as the exposed membrane undergoe s plaque accumulation. A method to control, or at least to reduce the bacterial invasion of the membrane allowing a delay in the membrane re moval, could be of clinical interest. The purpose of the present study was to evaluate the possibility of treating, with topical chlorhexidi ne application, the bacterial colonization of exposed membranes. A spe cial device was developed in order to evaluate, under an experimental environment, the bacterial colonization. This device was made from a r emovable acrylic denture base to which 5 gold cups were attached. The cups consisted of an internal compartment, isolated from the oral cavi ty by a GTAM membrane, and an external compartment exposed to the oral environment. 3 healthy subjects had this device fitted, bilaterally, in the molar-premolar region of the upper jaw. The cups of one side of each subject had 0.2% chlorhexidine gluconate gel applied 2X a day fo r 1 min, whereas those of the other side served as controls. 12 cups w ere removed after 2 weeks and the remainder removed after I month. The non-treated control specimens were characterized by greater amounts o f plaque accumulation. In all the test sites, plaque deposits increase d in thickness and quantity during the 4 weeks of the experiment. Comp lete invasion of the membrane and initial colonization of its internal surface were observed only in 4-week specimens. A relatively simple f lora consisting mainly of cocci and short rods, was found in bacterial deposits forming under the influence of chlorhexidine, whereas in non -treated specimens, it was possible to observe a more mature and compl ex plaque, composed mostly of filamentous bacteria. In conclusion, top ical application of chlorhexidine gel is an effective method of reduci ng plaque and calculus formation on the surface of GTAM membranes expo sed to the oral cavity for up to 4 weeks. This study has, however, fai led to demonstrate the capacity of chlorhexidine to prevent or to reta rd bacterial penetration through the thickness of the inner portion of the membranes.