Implants placed in an irradiated dog mandible: A morphometric analysis

The objective of this research was to evaluate the influence of radiotherap y on the osseointegration of oral implants in a canine model. After the ext raction of all mandibular premolars and first and second molars, 11 male be agles were divided into 3 groups. The control group (3 dogs) received no ra diation. The second group (4 dogs) was irradiated 4 weeks after implantatio n. The third group (4 dogs) was irradiated 8 weeks before implantation. Eig ht implants were placed in each dog, in an alternating pattern: 4 non-subme rged ITI Bonefit titanium plasma spray-coated and 4 submerged Steri-Oss hyd roxyapatite-coated. The irradiated dogs received 4.3 Gy daily for 10 days. After 6 months of osseointegration, The dogs were sacrificed and each hemim andible was dissected to isolate the implants. Quantification of the extent of the direct bone-implant contact was carried out by scanning electron mi croscopy backscattered electron images that reproduced each implant in its entirety, using a digitizing table connected to a computer. The results wer e expressed as a percentage of direct bone-implant contact Versus total per imeter accessible to bone. The bone contact percentage for the control grou p was 87% for Steri-Oss implants and 69% for the ITI Benefit implants; for the animals irradiated after implantation, the percentages were 82 for Ster i-Oss implants and 58 for ITI Bonefit implants; and for the animals irradia ted before implantation, the percentages were 62 for Steri-Oss implants and 28 for ITI Benefit implants, A statistically significant difference appear ed between the 2 types of implants (P < .001). A statistically significant difference was also seen between the 3 groups for both types of implants, e xcept between the control group and the group irradiated after implantation (P = .14). This indicates that, overall, the timing of irradiation influen ces osseointegration. Osseointegration is possible before and after radioth erapy; however, the direct bone-implant contact increased when the implants were placed before irradiation.