Influence of loading and grafting on hard- and soft tissue healing at immediately placed implants. An experimental study in minipigs.

OBJECTIVES To histologically evaluate the influence of i) loading and ii) grafting on osseointegration and peri-implant soft tissue healing at immediately placed, self- cutting progressive tissue- level implants (TLX) in a minipig model. MATERIAL & METHODS TLX implants (n=56) were immediately placed following the extraction of the mandibular first and second premolars, bilaterally, in a total of n=14 minipigs. In each animal, the implant sites were allocated to the following four groups: 1. unloaded with simultaneous grafting using a bovine bone mineral; 2. unloaded without grafting; 3. loaded with simultaneous grafting; 4. loaded without grafting. Histomorphometrical assessments at 4 and 12 weeks (n=7 animals each) included primary (i.e. bone-to-implant contact - BIC) and secondary outcome measures (e.g. first bone-to-implant contact - fBIC, junctional epithelium length- JE, connective tissue contact length - CTC, biological width - BW = JE + CTC). RESULTS At 4 weeks, mean BIC values ranged from 74.5 ± 11.6% in group 2 to 83.8 ± 13.3% in group 1, and, at 12 weeks, from 75.5% ± 7.9% in group 2 to 79.9 ± 8.6% in group 1, respectively. Multivariate linear mixed regression did not reveal any associations between BIC and implant loading or grafting at 4 and 12 weeks. At 12 weeks, significantly higher fBIC values were noted in group 2 when compared with group 1. All groups showed comparable JE, CTC and BW values. CONCLUSIONS Implant loading and grafting had no major effects on osseointegration and peri-implant soft tissue healing at TLX implants