Evaluación de la actividad osteoblástica en la interfase de implantes dentarios con diferentes superficies mediante gammagrafía ósea con TC99 MDF. Estudio en un modelo animal.

Abstract

"Technetium 99-MDP scintigraphy as a method to evaluate osteoblastic activity around implants. Comparison between machined and TiUnite(r) surfaces in rabbit model". Work hypothesis: 1- the scintigraphy is an approach to study the osseous integration process and allows to differentiate between surfaces biologic response. 2- There is a relation between scintigraphic activity and quantity of bone-implant contact. Materials and Methods: 24 implants (MKIII 10 x 3.75) where installed in 12 New Zealand rabbits, were (12 in femur, 12 in tibia) with different surfaces (machined or TiUnite(r)). Two kind of scintigraphy (185 mBq of Tc99MDP tracer) were performed one week before the surgery and then every 15 days, 1, 2, 3 months (1 planar and 2 pinhole collimator: 1 in femur, 1 in tibia on the same leg) on each rabbit. AI was calculated (AI= count pixels in implant region/ count in control leg in the same region). When the IA was similar to the baseline, the animals were sacrificed. The 240 AI was processed statistically to evaluate the results (SAS(r) v8.0 for windows, SAS Institute Inc., Cary, EE.UU.) with an a= 5%. Results: - We found more osseous activity, independent on the anatomic place (tibia or femur), around machined implants in the first post-op scintigraphies (p=0.0260 pinhole, p=0.0375 planar). - Global activity was less in tibia than in femur independent on the surface (p=0.0001). - Comparing the percentage of implant bone contact at the end of the study, there was no statistically difference. Discussion: In our study scintigraphy has been effective to compare the activity generated by two types of implant surfaces, but the results demonstrate that more osseous activity around implant not correlates with a better bioactive surface (TiUnite(r)) or a major percentage of bone contact analyzed by SEM at 3 months. This aspect never has been studied before even though other authors are interested about this kind of diagnostic technique to study the osteoblastic activity at the implant site. It can be caused because machined surface create greater reaction to foreign body, and more studies must be done to confirm these hypothesis. Respect to the bone-implant percentage there is no statistically differences probably because the bioactive surfaces are better in the poor bone quality and in the early period of osseointegration but not at the end of the process. Conclusions: 1- Scintigraphy (planar or pinhole) is a diagnostic technique useful to evaluate metabolic activity around implants in animal model. 2- The gammagraphic activity descrives a curve characterized by a significant increase in the first post-op exam, and gradually falloff and returned to pre-implant levels at about 3 months. 3- We can consider the duration of the osseointegration process is equivalent to the time that scintigraphy is approximately the same as the pre-op period, and is the same for the two implant surfaces. 4- There is no differences respect the time necessary of osseointegration related on location. 5- A greater gammagraphyc activity not correlates with a greater percentage of bone-implant contact. "