The effects of direct polymethylmethacrylate and zirconia-on-Ti-base abutments on peri-implant soft tissue integration: A study in minipigs.

Purpose: To assess two types of abutment materials routinely used in daily prac-tice-direct polymethyl methacrylate (PMMA) and a zirconia-on-Ti-base abut-ment-and their effects on peri-implant soft tissues and bone remodeling in a mini-pig model.

Materials and methods: A total of 40 implants were placed in five mini-pigs in a single-stage surgery. Four different types of abutment materials (n = 10 per group) were used: (1) titanium (control); (2) zirconia (control); (3) PMMA (test 1); and (4) Ti-base (zirconia bonded to a titanium framework; test 2). After 3 months of healing, the samples were collected and subjected to nondecalcified histology. The soft tissue dimensions (sulcus, junctional epithelium, and connective tissue attach-ment) were assessed on each abutment mesially and distally, and the distance from the implant margin to the first bone-to-implant contact (BIC) was measured.

Results: No statistically significant differences were found among the four groups regarding soft tissue dimensions (P = .21), and a long junctional epithelium (mean: 4.1 mm) and a short connective tissue attachment (mean: 0.3 mm) were found in the majority of abutments. In some samples, the junctional epithelium extended all the way to the bone level. The measured peri-implant bone remodeling was similar in all four groups (P = .25).

Conclusion: The present findings indicate that both di-rect PMMA and zirconia-on-Ti-base abutments seem to allow soft tissue integration similar to that of titanium and zirconia abutments. However, clinical studies are war-ranted to either confirm or refute the observed findings and to further investigate the influence of different materials on mucointegration.