A COMPARATIVE-STUDY OF FLEXIBLE (POLYACTIVE(R)) VERSUS RIGID (HYDROXYLAPATITE) PERMUCOSAL DENTAL IMPLANTS .1. CLINICAL ASPECTS

Recently, an elastomeric polyethyleneoxide polybutylene-terephthalate (PEO:PBT) copolymer (Polyactive(R)) was introduced, which exhibits bon e-bonding characteristics. In contrast to ceramics, bioglass, titanium and other metals, PEO:PBT copolymers are flexible materials that coul d reduce undesirable peak stresses along the neck of a permucosal impl ant. The application of three types of Polyactive(R) permucosal dental implants (one dense and two porous types) and one dense hydroxylapati te (HA) implant were clinically tested and compared during 30 weeks of loading in a dog experiment. With respect to the porous Polyactive(R) implants, it was observed that the pore diameter had decreased to suc h an extent that optimal bone ingrowth was not achieved. Polyactive(R) is known to expand due to water uptake, and, as a consequence, the si zes of the pores of the press-fit inserted implants had decreased to a large extent. This feature explained the high loss of the implants wi th the porous outer layer (6 out of 22). None of the dense Polyactive( R) implants and only one of the HA implants were lost. Statistical ana lysis was performed solely on the dense Polyactive(R) and the HA impla nts. At the lingual sites, plaque scores, gingiva indices, bleeding in dices and corresponding pocket depths were statistically significantly lower for both implant types, when compared to the corresponding valu es at the buccal, mesial and distal sites, irrespective of the observa tion period. Differences between the dense Polyactive(R) and the HA im plants were not observed. A considerable difference in mobility was re gistered between the Polyactive(R) and the hydroxylapatite implants, a s measured by the Periotest(R). The dense Polyactive(R) implants funct ioned adequately and had mobility resembling natural teeth. As such, t hese dense flexible materials showed a favourable clinical function an d they seem promising for reducing undesired peak stresses when applie d as a dental implant.