Quantitative analysis of peri-implant collagen fiber orientation around external hexagon and Morse taper implant connections: A dog model study.

Abstract

Background: Peri-implant soft tissue stability depends on the implant-abutment interface and collagen fiber organization. Unlike natural teeth, peri-implant fibers exhibit a less favorable orientation, potentially weakening the biological seal. Implant connection design may influence this collagen arrangement and tissue integrity.

Materials and methods: Eighteen immediately loaded implants (n = 9 per group) were placed in nine mongrel dogs. Group I received external hexagon implants, while Group II received Morse taper implants. After a 4-month healing period, animals were euthanized and specimens were processed for histological evaluation. Collagen fiber orientation was analyzed using polarized light microscopy and quantified with ImageJ software. Statistical analysis was performed using the Mann-Whitney U test ( = 0.05).

Results: Group I exhibited predominantly parallel and parallel-oblique collagen fibers, with mean orientations of 19.88° (buccal) and 21.92° (lingual). In contrast, Group II showed mainly oblique and oblique-perpendicular fibers, with mean orientations of 70.20° (buccal) and 54.73° (lingual). No significant differences were observed between buccal and lingual aspects within each group (p > 0.05). However, a significant difference was observed between implant connection types, with Group II presenting a significantly higher proportion of oblique and oblique-perpendicular fibers compared with Group I (p = 0.004; r = 0.71).

Conclusions: Morse taper implants were associated with a more perpendicular collagen fiber orientation, which may enhance the biological seal of peri-implant soft tissues.