ABSTRACT
The radiographic analysis is the best non-invasive method for bone level determination proximal to osseointegrated dental implants and is mandatory to ascertain the outcome of both routine practice and clinical trials. (Hermann et al. 2001, De Smet et al. 2002, Hanggi et al. 2005) In 1986, Albretksson et al. proposed criteria for the assessment of the long-term efficacy of implant therapy and established as radiologically acceptable a marginal bone level change inferior to 1.5 mm in the first year, and less than 0.2 mm of continuing annual vertical bone loss. However, the diagnosis of progressive bone loss or the identification of bone gain from one radiographic examination to the next may be difficult to interpret due to confounding issues such as projection errors in the alignment of successive images or the lack of examiner training and measurement calibration on the evaluation of radiographs that generates intra and inter-examiner variability. (Benn 1992, Mol & Dunn
2003, Huh et al. 2005, Lanning et al. 2006, Wakoh et al. 2006, Cochran et al. 2009)
Recently, dedicated imaging software such as ImageJ (https://rsbweb.nih.gov/ij/) or VixWin (Gendex Dental Systems, Hatfield, USA) have been introduced to carry out diverse measurements in radiographs. (Grandi et al. 2012) However, these programs only make use of a simple pixel-counter ruler to measure linear distances between two points identified by the operator, which can arise intra and interexaminer errors. This is particularly true in conventional periapical radiographs of dental implants where projection errors lead to superimposition of structures and image distortion. The operator can be misguided in the correct identification of the first bone-toimplant contact and other landmarks that correspond to the edge points of the distance to be determined, as the implant shoulder. Image distortion can also induce miscalculations in the calibration procedure, thereby inflating inaccuracies in the measurements obtained.
