Influence of buccal bone lamella defects on hard and soft tissues with submerged and non-submerged healing in immediate implants - an experimental study in minipigs.

Purpose: This study assessed the impact of the buccal bone on hard and soft tissues in submerged and non-submerged immediate implants using a minipig model.

Methods: Sixty-five titanium implants (Camlog Progressive Line) were placed in four minipigs immediately after tooth extraction. All non-submerged (NSM) implants received a mechanically induced buccal bone defect (NSM-BD), whereas the submerged group (SM) was classified as defective (SM-BD) and intact (SM-BI). All bone defects underwent guided bone regeneration (GBR). After four months, the minipigs were sacrificed. Harvested specimens were analysed using histomorphometry and light and fluorescence microscopy. The evaluated parameters included the sulcus (S), implant epithelium (IE), connective tissue (CT), biological width (BW), highest soft tissue point (HSTP), and first hard tissue contact (FHTC).

Results: Of the 65 implants four (6%) were lost, while all remaining implants demonstrated clinical stability (Periotest). Despite GBR failures caused by the pigs' hay consumption after one week, no significant differences (p > 0.5) were observed between SM-BD and NSM-BD in buccal parameters (NSM-BD/SM-BD: S = 0.6 mm, IE = 2.9/2.4 mm, CT = 3.5/3.4 mm, BW = 5.9/5.8 mm). Compared to SM-BI soft-tissue parameters increased in length with reduced buccal bone lamella (SM-BI/SM-BD: S = 0.4/0,6 mm; p ≤ 0.04, SM-BI/NSM-BD: IE = 1.8/2.9 mm; p ≤ 0.007, SM-BI/SM-BD: CT = 2.5/3.4 mm; p ≤ 0.01, BW = 4.0/5.8 mm; p ≤ 0.007). The buccal HSTP remained unaffected (p > 0.5; (NSM-BD = 1.8 mm, SM-BD = 1.0 mm, SM-BI = 2.0 mm; p > 0.5) for all groups.

Conclusion: A buccal bone defect resulted in prolonged S, IE, CT, and BW. However, the aesthetic parameter HSTP did not exhibit significant differences (p > 0.5) at the buccal implant site when comparing the SM and NSM healing protocols.