Giuseppe Merlati

The use of miniscrews as Temporary Skeletal Anchorage Devices (TSAD) in orthodontics has allowed clinicians to perform challenging tooth movements by dissipating undesired forces into the bone structure; thus, avoiding unwanted movement of the adjacent teeth. It is essential for miniscrews to be highly resistant to fracture during clinical use. While many studies have analysed torsional loads, none have measured the changes in flexural and bending strength of miniscrews before and after an ageing process. This study aims to analyse the resistance to orthogonal forces of miniscrews with different diameters, focusing on both new and aged materials, the latter subjected to thermocycling and autoclaving laboratory processes to simulate a 3- and a 6-month exposure to the oral environment. A total of 105 pristine miniscrews have been tested; specimens were divided into seven groups based on the different endosseous body diameters. Each group was further subdivided into three subgroups, according to the simulated ageing of the miniscrews (intact, 3 months of ageing and 6 months of ageing, respectively). An Instron Universal Testing Machine has been used to measure deflection at 0.1 mm and 0.2 mm, as well as maximum load at fracture. The results evidenced that miniscrews respond differently to cutting forces; in particular, the resistance to orthogonal loads increases as the diameter of the miniscrews increases. Linear regression analysis revealed a significant influence between all the dependent variables—maximum load, 0.1 mm deflection load, and 0.2 mm deflection load—and the independent variables, such as diameter and thermocycling (p < 0.05). Both new and aged miniscrews are suitable for orthodontic and orthopaedic loads; moreover, ageing up to 6 months does not seem to significantly decrease the resistance to shear forces for the same diameter. Linear regression analysis of the miniscrews subjected to experimental ageing showed a slight but significant decrease in resistance to orthogonal loading.

Objective. Prolonged use of oral devices as a substitute for traditional treatments has been studied in relation to the dental and skeletal changes associated with obstructive sleep apnea syndrome (OSA), which is a sleep-breathing disorder. Materials and Methods. A review of articles indexed in PubMed, Google Scholar, Cochrane Library, Scopus, Web of Sciences, and CINHAL databases in September 2022 based on MeSH-based keywords with dental and skeletal and oral appliance and obstructive sleep apnea was examined to ensure that the keywords alone or cross-linked, depending on which base of the searched data, were used. 16 articles out of 289 articles were included in the research, and 273 articles were excluded due to lack of study. Conclusions. CPAP treatment has limited dental or skeletal effects in short-term or long-term use. OAs and MADs show significant dental changes with prolonged use. MAS and TSD are more effective in short-term goals than CPAP. OAs increase may cause dental and skeletal changes. MPD shows notable cephalometric alterations.

The aim of this investigation was to assess the influence of several surface treatments on the shear bond strength (SBS) of a self-adhesive resin cement containing 10-methacryloxydecyl-dihydrogenphosphate monomer to densely sintered zirconia ceramic, before and after thermal cycles. Hundred densely sintered zirconia cylinders were divided into five groups (n = 20). Each of them received a different surface treatment: (1) control [No_T], with the zirconia surface unconditioned, (2) low pressure air abrasion [Sand_S], (50 μm, 1 bar), (3) standardized air abrasion [Sand_H], (50 μm, 2.8 bar), (4) standardized Rocatec™ Plus (silica-coated alumina oxide) air abrasion (2.8 bar) and silanization [Roc_H], (5) low pressure Rocatec™ Plus (silica-coated alumina oxide) air abrasion (1 bar) and silanization [Roc_S]. Five more surface-treated specimens were addressed to scanning electron microscope for qualitative observations. After specimen fabrication, subgroups of 10 bonded samples were stored in water either for 24 h (T1) or subjected to 5000 thermal cycles (T2); SBSs were determined with a universal testing machine at a crosshead speed of 1 mm/min. At T1, mean SBSs (MPa) obtained for the examined groups were: [Sand_H] 16.24 ± 2.95; [Sand_S] 16.01 ± 2.68; [Roc_H] 17.17 ± 1.64; [Roc_S] 15.92 ± 1.99. All surface treatments positively affected (p < 0.05) the initial self-adhesive cement adhesion to zirconia with respect to No_T (13.29 MPa). Artificial aging decreased the bond strength in all test groups significantly, but no spontaneous debonding was observed in [No_T]: at T2, SBS values ranged from 7.76 ± 2.37 (No_T) to 8.89 ± 1.74 (Sand_S), with no statistically significant difference between groups (p = 0.5293). Both air abrasion with alumina oxide and Rocatec™ universal bonding system, used with hard or low air pressure, produced comparable effects on cement–zirconia interface before and after thermal cycles. After artificial aging, minimal differences in bond strength values between sandblasted and control groups were not of statistical significance.

Short Communication selected from the Oral Presentations of the 56th Congress of the Groupèment International pour la Recherche Scientifique en Stomatologie et Odontologie, Peñafiel (Portugal) May 2012.

Recently introduced FIB/SEM analysis in microscopy seems to provide a high-resolution characterization of the samples by 3D (FIB) cross-sectioning and (SEM) high resolution imaging. The aim of this study was to apply the FIB/SEM and SEM/EDS analysis to the interfaces of a metal-ceramic vs. two zirconia-ceramic systems. Plate samples of three different prosthetic systems were prepared in the dental lab following the manufacturers' instructions, where metal-ceramic was the result of a ceramic veneering (porcelain-fused-to-metal) and the two zirconia-ceramic systems were produced by the dedicated CAD-CAM procedures of the zirconia cores (both with final sintering) and then veneered by layered or heat pressed ceramics. In a FIB/SEM equipment (also called DualBeam), a thin layer of platinum (1 μm) was deposited on samples surface crossing the interfaces, in order to protect them during milling. Then, increasingly deeper trenches were milled by a focused ion beam, first using a relatively higher and later using a lower ion current (from 9 nA to 0.28 nA, 30KV). Finally, FEG-SEM (5KV) micrographs (1000-50,000X) were acquired. In a SEM the analysis of the morphology and internal microstructure was performed by 13KV secondary and backscattered electrons signals (in all the samples). The compositional maps were then performed by EDS probe only in the metal-ceramic system (20kV). Despite the presence of many voids in all the ceramic layers, it was possible to identify: (1) the grain structures of the metallic and zirconia substrates, (2) the thin oxide layer at the metal-ceramic interface and its interactions with the first ceramic layer (wash technique), (3) the roughness of the two different zirconia cores and their interactions with the ceramic interface, where the presence of zirconia grains in the ceramic layer was reported in two system possibly due to sandblasting before ceramic firing.