The peri-implant mucosa at implants with two different geometries of the transmucosal area: a randomized controlled experimental in vivo investigation

ESGZC ePOSTER BASIC RESEARCH

Background: Recently, a new implant design has been introduced (Prama, Sweden & Martina, Italy), which presents a tissue level connection, a convergent trans mucosal neck inspired to the biologically oriented preparation technique (BOPT) described for natural teeth, and a surface of the implant neck provided with a Ultrathin Threaded Microsurface (UTM). Albeit favorable results were reported from NO controlled clinical studies, a histological validation of this implant design is lacking.

Aim/Hypothesis: To compare the soft tissue morphology, height and thickness around Prama implants (test) vs. conventional bone level implants with a cylindrical, maCHINAd surface abutment (control), at 4 and 12 weeks of healing. The null hypothesis was that no difference could be observed among the two groups.

Materials and Methods: According to a random allocation sequence, 8 beagle dogs received 16 Prama (test) and 16 Premium One (control) implants, 8 weeks after the extraction of the mesial roots of 1M1 and 2P2. Implant platforms were placed at the level of the buccal bone crest and both groups received a trans-mucosal healing abutment. Animals were sacrificed at 4 and 12 weeks for histological examination. Samples from 7 dogs where processed with ground sections for histometry and descriptive histology, while samples from 1 dog where processed with decalcified sections for a descriptive immunohistochemical analysis. The buccal and lingual position of the mucosal margin, the soft tissue height in its connective tissue and barrier epithelium components, and the soft tissue thickness at different reference points, where measured by a single calibrated examiner (DP). Intra-examiner differences were assessed via K analysis. Comparisons were performed via a One-way Anova test with Bonferroni correction (⍺ = 0.05).

Results: Buccally, test implants displayed a more coronal gingival margin by 0.97 mm (P = 0.572) at 4 weeks and 0.30 mm (P = 1.000) at 12 weeks, and a more coronal first bone to implant contact by 1.08 mm (P = 0.174) at 4 weeks and by 0.83 mm (P = 0.724) at 12 weeks. The resulting buccal soft tissue height was smaller at test implants by 0.12 mm (P = 1.000) at 4 weeks and 0.53 mm (P = 1.000) at 12 weeks, showing a longer barrier epithelium by 0.23 mm (P = 1.000) at 4 weeks and 0.29 mm(P = 1.000) at 12 weeks, and a shorter connective tissue contact by 0.32 mm (P = 1.000) and 0.79 mm (P = 1.000) at 12 weeks. At 4 weeks, the buccal soft tissue thickness at the level of the implant platform and 1, 2, and 3 mm apically to the gingival margin, was consistently higher at test vs. control implants by a difference ranging from 0.42 to 0.53 mm (P > 0.05), while at 12 weeks, an inverse pattern was observed, with control implants showing a thicker buccal mucosa by 0.30 to 0.64 mm (P > 0.05).

Conclusions and Clinical Implications: Results from this study suggest that: a) Prama implants are a safe alternative to conventional bone level implants, in which the morphogenesis of the peri-implant mucosa undergoes equivalent processes; b) Prama implants tented to present a more coronal gingival margin and first bone to implant contact as compared to control implants.

Keywords: Prama implant, Soft tissue height, Soft tissue thickness