The mucosal barrier following abutment dis/reconnection - An experimental study in dogs

In the present experiment, the effect on the marginal peri-implant tissues following repeated abutment removal and subsequent reconnection was studied. 5 beagle dogs were used. The mandibular premolars were extracted and 2 fixtures of the Branemark System(R) were installed, 1 in each mandibular quadrant. 3 months later, abutment connection uas performed. A 6-month period of plaque control was initiated. Once a month during the plaque control period, the abutment of the right side (test) in each dog was disconnected, cleaned and reconnected to the fixture. Thus, each test abutment was removed and reconnected altogether 5x during this period. The contralateral abut-ment remained undisturbed for 6 months and served as control. 1 month after the last reconnection, the animals were sacrificed and tissue samples, comprising the implant and the surrounding soft and hard peri-implant tissues, were obtained, decalcified, embedded in Epon and sectioned. The following landmarks were identified and used for linear measurements: PM (the marginal portion of the peri-implant mucosa). aJE (the level of the apical termination of the junctional epithelium), B (the marginal level of bane to implant contact), A/F (the abutment/fixture border). The findings indicate that the dis- and subsequent reconnections of the abutment component of the implant compromised the mucosal barrier and resulted in a more ''apically'' positioned zone of connective tissue. The additional marginal bone resorption observed at the test sites following abutment manipulation may be the result of tissue reactions initiated to establish a proper ''biological width'' of the mucosal-implant barrier.