Objective: Peri-implant bone loss is a significant parameter that determines the survival rate of implant-supported prosthetic restorations. The aim of this study is to compare the peri-implant bone level between the parallel technique commonly used in everyday practice and a modified right-angle technique. In particular, studies with long follow-up periods may be subject to projection-related deviations in the determination of radiological peri-implant bone loss. The following study investigates whether these projection-related deviations can be minimised by using a modified right-angle technique.
Material and method: Three mandibular segments with a deviant bone course were printed from radio-opaque PLA (Nanovia PLA XRS, Nanovia) using a 3D printer (Ender 3v2, Creality), as was a modifiable bite block. A Straumann RC BL 4.1 x 12mm implant (Straumann) was then inserted into each model at the same location. A total of 15 radiographs were taken for each model and radiographic technique (parallel vs. right-angle) by two clinicians. Another clinician measured the maximum radiographic bone loss to the implant shoulder mesially and distally in each of the 90 radiographs. The measurements of the individual models were examined for variance homogeneity using a Levene test to determine how strongly the scatter of the results depends on the X-ray technique.
Results: The Levene test showed that there was no variance homogeneity for the mesial measurements on model 2 and for the distal measurements on model 1, model 2, and model 3. The standard deviation was lower for the modified right-angle technique in each case. The measurements varied between the models (and measuring points) between 0.2 mm and 0.6 mm for the modified right-angle technique and between 0.3 mm and 0.7 mm for the parallel technique.
Summary: In summary, it can be said that the modified right-angle technique can help to minimise the projection-related deviations between consecutive X-ray images.