Oral tissue response to soft tissue expanders prior to bone augmentation: analysis and histological study in dogs.

PURPOSE

To determine whether the swelling and mechanical properties of osmotic self-inflating expanders allow or not the induction of intraoral soft tissue expansion in dogs.

METHODS

Three different volumes (0.15, 0.25, and 0.42 mL; referred to respectively as the , , and groups) of soft tissue expanders (STEs) consisting of a hydrogel core coated with a silicone-perforated membrane were investigated to assess their swelling behavior (volume swelling ratio) and mechanical properties (tensile strength, tensile strain). For investigations, the STEs were subperiosteally inserted for 4 weeks in dogs (n=5). Soft tissue expansion was clinically monitored. Histological analyses included the examination of alveolar bone underneath the expanders and thickness measurements of the surrounding fibrous capsule.

RESULTS

The volume swelling ratio of all STEs did not exceed 5.2. In tensile mode, the highest mean strain was registered for the group (98.03±0.3 g/cm), whereas the lowest mean value was obtained in the group (81.3±0.1 g/cm), which was a statistically significant difference (<0.05). In addition, the and groups were significantly different in terms of tensile strength (1.5±0.1 g/cm for the group and 2.2±0.1 g/cm for the group, <0.05). Clinical monitoring showed successful dilatation of the soft tissues without signs of inflammation up to 28 days. The STEs remained volumetrically stable, with a mean diameter of 6.98 mm, close to the post-expansion findings (6.69 mm). Significant histological effects included highly vascularized collagen-rich fibrous encapsulation of the STEs, with a mean thickness of 0.67±0.12 mm. The bone reaction consisted of resorption underneath the STEs, while apposition was observed at their edges.

CONCLUSIONS

The swelling and mechanical properties of the STEs enabled clinically successful soft tissue expansion. A tissue reaction consisting of fibrous capsule formation and bone loss were the main histological events.