title: An Indirect Method to Measure Abutment Screw Preload: A Pilot Study Based on Micro-CT Scanning.
abstract: This study aimed to measure the preload in different implant platform geometries based on micro-CT images. External hexagon (EH) implants and Morse Tapered (MT) implants (n=5) were used for the preload measurement. The abutment screws were scanned in micro-CT to obtain their virtual models, which were used to record their initial length. The abutments were screwed on the implant with a 20 Ncm torque and the set composed by implant, abutment screw and abutment were taken to the micro-CT scanner to obtain virtual slices of the specimens. These slices allowed the measurement of screw lengths after torque application and based on the screw elongation. Preload values were calculated using the Hooke's Law. The preloads of both groups were compared by independent t-test. Removal torque of each specimen was recorded. To evaluate the accuracy of the micro-CT technique, three rods with known lengths were scanned and the length of their virtual model was measured and compared with the original length. One rod was scanned four times to evaluate the measuring method variation. There was no difference between groups for preload (EH = 461.6 N and MT = 477.4 N), but the EH group showed higher removal torque values (13.8 ± 4.7 against 8.2 ± 3.6 N cm for MT group). The micro-CT technique showed a variability of 0.053% and repeatability showed an error of 0.23 to 0.28%. Within the limitations of this study, there was no difference between external hexagon and Morse taper for preload. The method using micro-CT may be considered for preload calculation.
authors.affiliation: Department of Dentistry, UP - Universidade Positivo, Curitiba, PR, Brazil.
authors.forename: Carlos Eduardo E
authors.initials: CE
authors.lastname: Rezende
authors.affiliation: Department of Biomedical Materials Science, School of Dentistry, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: Jason Alan
authors.initials: JA
authors.lastname: Griggs
authors.affiliation: Department of Biomedical Materials Science, School of Dentistry, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Duan
authors.affiliation: Department of Dentistry, UP - Universidade Positivo, Curitiba, PR, Brazil.
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Mushashe
authors.affiliation: Master of Science and PhD Program, UP - Universidade Positivo, Curitiba, PR, Brazil.
authors.forename: Gisele Maria Correr
authors.initials: GM
authors.lastname: Nolasco
authors.affiliation: Department of Dental Materials, Bauru Dental School, USP - Universidade de São Paulo, Bauru, SP, Brazil.
authors.forename: Ana Flávia Sanches
authors.initials: AF
authors.lastname: Borges
authors.affiliation: Department of Prosthodontics, Bauru Dental School, USP - Universidade de São Paulo, Bauru, SP, Brazil.
authors.forename: José Henrique
authors.initials: JH
authors.lastname: Rubo
mesh_terms: D001863:Bone Screws; D000044:Dental Abutments; D006801:Humans; D010865:Pilot Projects; D015203:Reproducibility of Results; D055114:X-Ray Microtomography / Q000379:methods*