Evaluation of zirconia surface roughness after aluminum oxide airborne-particle abrasion and the erbium-YAG, neodymium-doped YAG, or CO2 lasers: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Veneer chipping and crown decementation are the most frequent failures in restorations using zirconia as an infrastructure. Increasing the roughness of the zirconia surface has been suggested to address this problem. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate yttria-stabilized tetragonal zirconia polycrystal surface roughness, produced with aluminum oxide airborne-particle abrasion and the erbium yttrium aluminum garnet (YAG), neodymium-doped YAG, or CO2 lasers. MATERIAL AND METHODS: This study was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. The review identified relevant studies through December 2017 with no limit on the publication year in the search databases: Web of Science, Scopus, and MEDLINE via PubMed. The selected studies were submitted to a risk of bias assessment. The means and standard deviations of roughness were evaluated for the meta-analysis using Review Manager software. RESULTS: The 17 studies that met all inclusion criteria presented a medium risk of bias. All the treatment methods tested were able to create a roughness on the yttria-stabilized tetragonal zirconia polycrystal surface. The I2 test values presented a high heterogeneity among the studies. CONCLUSIONS: The presintered specimens submitted to airborne-particle abrasion had higher surface roughness compared with abrasion after the sintering process. Irradiation with the neodymium-doped YAG and CO2 lasers was destructive to the zirconia surfaces. The erbium laser used with lower energy intensity appears to be a promising method for surface treatment.

Accuracy and reproducibility of dental measurements on tomographic digital models: a systematic review and meta-analysis.

OBJECTIVES: The aim of this systematic review with meta-analysis was to assess the accuracy and reproducibility of dental measurements obtained from digital study models generated from CBCT compared with those acquired from plaster models. METHODS: The electronic databases Cochrane Library, Medline (via PubMed), Scopus, VHL, Web of Science, and System for Information on Grey Literature in Europe were screened to identify articles from 1998 until February 2016. The inclusion criteria were: prospective and retrospective clinical trials in humans; validation and/or comparison articles of dental study models obtained from CBCT and plaster models; and articles that used dental linear measurements as an assessment tool. The methodological quality of the studies was carried out by Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. A meta-analysis was performed to validate all comparative measurements. RESULTS: The databases search identified a total of 3160 items and 554 duplicates were excluded. After reading titles and abstracts, 12 articles were selected. Five articles were included after reading in full. The methodological quality obtained through QUADAS-2 was poor to moderate. In the meta-analysis, there were statistical differences between the mesiodistal widths of mandibular incisors, maxillary canines and premolars, and overall Bolton analysis. Therefore, the measurements considered accurate were maxillary and mandibular crowding, intermolar width and mesiodistal width of maxillary incisors, mandibular canines and premolars, in both arches for molars. CONCLUSIONS: Digital models obtained from CBCT were not accurate for all measures assessed. The differences were clinically acceptable for all dental linear measurements, except for maxillary arch perimeter. Digital models are reproducible for all measurements when intraexaminer assessment is considered and need improvement in interexaminer evaluation.

In vivo comparison of the friction forces in new and used brackets.

Studies that evaluate frictional force on orthodontic brackets usually compare ligature, archwire size, bracket alloys, and systems. However, these studies do not simulate in vitro specific conditions of in vivo situations. Aiming to evaluate some conditions not created in vitro, 30 used standard edgewise brackets (30.7 months) collected from patients in the end of treatment (group 1) and 20 as-received brackets (group 2) of the same brand were compared. The brackets used in vivo were carefully removed to avoid deformation. Frictional resistance tests of both groups were performed in a universal testing machine using a system that standardizes normal force. Five brackets from each group were analyzed with scanning electron microscopy (SEM). Student t tests were used to compare the frictional force between groups 1 and 2 and showed a statistically difference (32.91 and 21.22 g, respectively). The Mann-Whitney test showed that group 1 had more organic matter attached to the slot surface compared with group 2 (P < .05). However, a comparison of topography between the groups did not show a statistically significant difference. SEM analysis showed a statistically high correlation (r = 0.73) between organic matter adhesion to the slot surface and frictional resistance. However, the results were not significant. These results indicate the clearance of brackets and wires during sliding mechanics.