Objective: To compare the clinical soft tissue responses around implant-tooth supported 3-unit bridges utilizing tapered (T) abutments with those utilizing butt-joint (B) abutments.Methods: In a split-mouth design study, 8mm Ankylos® (Dentsply Friadent, Germany) implants were placed in the second mandibular molar region of 8 adult Macaca fascicularis monkeys about 1 month after extraction of all mandibular molars. Following 3 months of submerged healing, 3-unit metal bridges were constructed with second premolar as natural tooth abutment, first molar as pontic and the implants connected with a T abutment on one side and a B abutment on the contralateral side by random selection. Clinical data was collected blind to these abutment selections. Implants were clinically evaluated using Waite plaque index (PI), sulcus bleeding index (SBI), probing pocket depth (PPD), probing attachment loss (PAL), and width of keratinized mucosa (KMW) at baseline, 3-months and 6-months intervals. Results: At baseline all the clinical variables did not differ statistically between the T and B groups except for PPD (p<0.05), where the mean PPD was greater in the B group (2.75±1.02mm) as compared to the T group (1.97±0.65mm). At the 3-month assessment, there was no difference in all clinical variables. After 6-months loading, no significant difference between these 2 groups was detected in all these variables with the exception of PAL (p=0.05) where the mean PAL was greater for implants with B abutments (0.91 ± 0.86mm) in comparison to T abutments (0.50 ± 0.88mm). Conclusions: The differences in these mucogingival responses between these 2 groups at baseline (during seating of abutments, especially of B abutments) and after 6-months loading indicated enhanced peri-implant soft tissue stability around tapered abutments of this system. (Study was supported by Dentsply Friadent, Germany; R&D Vote No. 40-02-03-0002).

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