The effect of loading in regenerated bone in dehiscence defects following a combined approach of bone grafting and GBR

Objectives: To evaluate by histology the effect of loading on the regenerated bone at dehiscence type defects around implants when treated with a combined approach of bone grafting and guided bone regeneration (GBR). Materials and methods: In twelve Gottingen mini-pigs, the lower premolars and first molars were extracted and the alveolar process was reduced in width. After 3 months, two Straumann SLActive (R) (Straumann AG, Basel, Switzerland) implants were placed in each hemi-mandible. Twelve implants were placed into the reduced alveolar ridge (group P) with no further defect or treatment on the site, while on 36 implants, buccal dehiscence defects were created and treated as follows: Group T1: synthetic bone substitute (Straumann Bone Ceramic (R), SBC, Straumann AG). Group T2: SBC with a polyethylene glycol membrane (Straumann MembraGel (R), Straumann AG); Group N: the dehiscence remained untreated. Three months following implantation, long, custom-made, healing abutments were placed in one hemi-mandible only to ensure functional loading. After 2 months, histological analysis was performed. Results: A trend for lower residual defect height and higher bone-to-implant contact was observed in the loaded sites compared with non-loaded sites in groups P, T1 and N. In group T2, the opposite effect was observed. In terms of bone formation, sites treated with SBC grafting and GBR (group T2) exhibited the largest surface area of regenerated bone followed by T1 and N. Significant resorption of the graft particles was noted in group T2 and the graft surface area occupied by SBC was significantly higher in group T1 compared with group T2 (P < 0.05). Conclusions: Loading may have a positive effect on bone-to-implant contact in implants inserted in pristine bone or inserted in dehiscence sites and treated by grafting/no grafting.