RESEARCH AND EDUCATION Analysis of correlation between optical and microtomography measurements of cementation space in CAD-CAM ceramic crowns Fernanda Furtado Piras, DDS, MSc, PhD, a,c Fernanda Ferruzzi, DDS, MSc, PhD, b Brunna Mota Ferrairo, DDS, MSc, c Ilana Santos Ramalho, DDS, MSc, PhD, c,d Estevam Augusto Bonfante, DDS, MSc, PhD, e and José Henrique Rubo, DDS, MSc, PhD e A well-adapted restoration is a prerequisite for success and longevity. 1 Considering the diversity of available restorative materials for computer-aided design and computer-aided manufacture (CAD-CAM) crowns, different designing and milling strate- gies should be used to obtain the best result for each mate- rial. The fabrication process is an especially important step with regard to the fit of the restoration. 2 Ceramic crowns can distort during fabrication, negatively affecting the fit and compromising the success of the restoration. 3 Cement space, as well as firing pa- rameters after milling, directly affects the marginal and in- ternal adaptation of ceramic restorations. 3-5 Different measurement methods have been used to evaluate cementation space including direct measurement, cross-sectional measurement, the impression replica technique, 6 laser videography, 7 profile This study was supported by Research Foundation of the State of Sa e o Paulo e FAPESP grant # 2013/10021-5 and in part by The Coordenacao Aperfeicoamento de Pessoal de Nivel Superior, Brasil (CAPES) - Finance Code 001. a Professor, Department of Prosthodontics and Periodontology, Faculty of Dentistry, University of Marília (UNIMAR), Marília, Brazil. b Professor, Department of Dentistry, Maringá University Center (UNINGÁ) and Maringá State University (UEM), Maringá, Brazil. c Doctoral student, Department of Prosthodontics and Periodontology, Bauru Dental School, University of São Paulo (USP), Bauru, Brazil. d Professor, Department of Prosthodontics, Faculty of Dentistry, São Paulo University Júlio de Mesquita Filho (FOAr), Araraquara, Brazil. e Professor, Department of Prosthodontics and Periodontology, Bauru Dental School, University of São Paulo (USP), Bauru, Brazil. ABSTRACT Statement of problem. Identical computer-aided design (CAD) parameters may be used to mill a variety of ceramic materials for computer-aided design and computer-aided manufacture (CAD- CAM) crowns. Whether milled crown spacing matches the designed parameters when more than a single evaluation method is applied is unknown. Purpose. The purpose of this in vitro study was to correlate the stereomicroscope and the microcomputer tomography (mCT) 2-dimensional analysis of the cementation space with the replica technique in assessing 3 different ceramic materials. Material and methods. The specimens were milled in lithium disilicate, resin nanoceramic, and zirconia (n=30). The cement space was measured at the marginal, axial, and occlusal regions. One hundred twenty measurements of each material were used to correlate the methodologies. Data were statistically evaluated with 2-way repeated measures ANOVA and the Tukey test (a=.05). The Pearson correlation coefficient was used for each region for both methodologies (mCT and optical microscopy) separately. Results. For the mCT analysis, no differences were observed (P>.05) among the materials, but the axial region showed a positive correlation with the marginal (r=0.957) and occlusal regions (r=0.349); the same was observed between the occlusal and marginal regions (r=0.338). However, for stereomicroscope evaluation, resin nanoceramic and zirconia present similar cementation space (P=960), both being different from lithium disilicate (P<.05). The marginal region presented a positive correlation with axial (r=0.149) and occlusal regions (r=0.344), but the axial region showed negative correlation with the occlusal surface (r=-0.205). Conclusions. The measurements of the scanned replicas were accurate when thinner sections were under measurement. Although the same space parameters were set in the CAD software, definitive internal dimensions varied among the milled crowns. (J Prosthet Dent 2020;-:---) THE JOURNAL OF PROSTHETIC DENTISTRY 1.e1