Effect of industrial scanner and framework material interaction on the marginal gaps of CAD-CAM complete arch implant frameworks

Abstract

Statement of problemStructured-light and computed tomography industrial scanners have been used as reference scanners to measure marginal gaps between implants and superstructures. However, the effect of framework material on the scanners' ability to detect gaps and on precision has not yet been evaluated. PurposeThe purpose of this in vitro study was to investigate the interaction between the industrial scanner and framework material on measured marginal gaps of implant-supported fixed complete arch frameworks made from titanium and polymethylmethacrylate and on the precision of scans. Material and methodsA completely edentulous maxillary model with 4 implants and multiunit abutments at the first molar and canine sites was digitized by using a laboratory scanner. Implant-supported frameworks were milled from titanium and polymethylmethacrylate (n=5). Each framework was secured on the left molar site abutment. The marginal gaps between the frameworks and abutment sites without a screw were measured by using an industrial structured-light scanner and an industrial computed tomography scanner. The effect of the scanner, the framework material, and their interaction on measured gaps was analyzed by applying linear regressions and weighted least square methods. The F-statistics was used with Bonferroni corrections for precision analysis (α=.05). ResultsNo significant effect of scanner, material, or their interaction was found on the marginal gaps at the canine sites. The titanium framework gaps detected by using the computed tomography scanner were greater than those detected by using the structured-light scanner at the right molar site (estimated difference in means=0.054 mm; P=.003) and overall (estimated difference in means=0.023 mm; P=.033). The structured-light scanner’s precision was higher than that of the computed tomography scanner when titanium frameworks were scanned (P=.001). The computed tomography scanner’s precision was higher when scanning polymethylmethacrylate frameworks than when scanning titanium frameworks (P=.03). ConclusionsFramework material and industrial scanner interaction affected the measured gaps. The computed tomography scanner detected greater marginal gaps with low precision when scanning titanium frameworks than the structured-light scanner. The sample size, the use of only 2 types of materials, and a laboratory scanner to obtain the computer-aided design file should be considered when interpreting the results.