Crestal bone changes around titanium implants : a methodologic study comparing linear radiographic with histometric measurements

Aim of the study

To compare the peri-implant crestal bone loss, as determined by standardised radiographs or by histomorphometric measures, in order to assess possible clinical implications (a follow up of peri-implant health with standardized radiographs).

Materials and methods

The protocol followed was that of the studies by Hermann et al. (1997 and 2000) on the peri-implant crestal area : 59 implants (ITI prototypes) were placed in the edentulous mandibles of 5 dogs. Some were submerged and abutments fitted three months later, others were not submerged (one-part implants) and fitted at variable heights above or at the crest. In the case of the submerged implants, the junction of implant and abutment served as the reference point and in the case of the non-submerged implants it was the junction between the smooth and rough parts. Standardized radiographs were taken on Day 0 and six months later, following which the animals were sacrificed for histological measurements.

Conclusion

In 89 % of cases there was correlation between the radiographs and histology within 0.2 mm (73.4 % within 0.1 mm, 15.9 % between 0.1 mm and 0.2 mm and only 2.7 % at greater than 0.2 mm).

Commentary

These studies (the present one and those of 1997 and 2000) are very interesting. Because of the protocol used and especially their results, they will become key references in the future :

- the postoperative level of peri-implant bone was determined by reference to the junction between the rough and smooth parts of the implant (resorption stopped at the rough part) and the junction between the implant and abutment (this is simply the concept of biological space !). This must lead to a standardisation of the concept and… the insertion of implants ;

- radiographic assessment of peri-implant bone is reliable if care is taken to make individualised film holders.