In vitro study of a modified sagittal split osteotomy fixation technique of the mandible: a mechanical test.

This study was performed to evaluate the compressive mechanical strength of rigid internal fixation (RIF) using 1.5-mm L-shaped plates fixed with monocortical screws in sagittal split osteotomy (SSO). Thirty synthetic hemimandibles, which had all undergone a 5-mm advancement, were divided into three groups: three 12-mm bicortical titanium screws were placed in an inverted L pattern in group A; one straight 2.0-mm system spaced titanium plate fixed with four 5-mm monocortical screws was used in group B; two 1.5-mm system L-shaped titanium plates, each fixed with four 5-mm monocortical screws, were used in group C. The models were subjected to compressive and progressive mechanical tests with forces applied in the area between the second premolar and first molar to verify resistance in Newtons (N). A displacement speed of 1mm/min was applied, with a maximum 10mm displacement of the distal segment or until disruption of the fixation. The deformity and/or eventual rupture of the plates were evaluated, and consequently their technical stability was determined. The results showed that the modified fixation technique tested in this study on synthetic mandibles resulted in adequate stability and superior mechanical behaviour compared to simulated osteosynthesis with the use of a straight 2.0-mm titanium plate.

Accuracy assessment of prototypes produced using multi-slice and cone-beam computed tomography.

The objective of this study was to assess and quantify the dimensional error of prototypes produced using multi-slice and cone-beam computed tomography (MSCT and CBCT). Titanium screws were inserted into a dry skull at different points of the midface. The skull was scanned using MSCT (LightSpeed16) with pixel size 0.3 mm and CBCT (i-CAT Cone-Beam 3D) with voxel sizes 0.25 and 0.4 mm. Prototypes were printed (fabricated) using a ZPrinter 310 device. Both the dry skull (gold standard) and the prototypes were measured using a Mitutoyo 3D coordinate measuring system with three perpendicular axes (X, Y, and Z). The prototype produced from MSCT data presented a mean dimensional error of 0.62%; the two models produced with CBCT images yielded errors of 0.74% with voxel size 0.25 mm and 0.82% with voxel size 0.40 mm. No significant differences in dimensional errors were observed across the prototypes (p=0.767; Friedman's non-parametric test). Prototypes produced from CBCT data using voxel sizes of 0.25 and 0.4mm, and also the one produced from MSCT data using pixel size 0.3mm, showed acceptable dimensional errors and can therefore be used in the fabrication of prototypes in dentistry.

3-Year clinical evaluation of posterior packable composite resin restorations.

This study evaluated the clinical performance of four packable resin composite restorative materials in posterior teeth (Class I and II) compared with one hybrid composite after 3 years. Eighty-four restorations were placed in 16 patients. The tested materials were: (i) Solitaire + Solid Bond; (ii) ALERT + Bond-1; (iii) Surefil + Prime & Bond NT; (iv) Filtek P60 + Single Bond and (v) TPH Spectrum + Prime & Bond 2.1. All restorations were made using rubber dam isolation, and the cavity design was restricted to the elimination of carious tissue. Deeper cavities were covered with calcium hydroxide and/or glass-ionomer cement. Each adhesive system and composite resin was placed according to the manufacturer's instructions. One week later, the restorations were finished/polished and evaluated according USPHS modified criteria. Fourteen patients attended the 3-year recall and 75 restorations were evaluated at that time based on the same evaluation criteria. Friedman repeated measures analysis of variance by rank and Wilcoxon sign-ranked test for pair-wise comparison was used for data analysis (alpha = 0.05). The analysis was performed only for the baseline and for the 3-year period. Solitaire showed some fractures at marginal ridges in 25% of the cases. Solitaire and ALERT showed some concerns related to colour match (43 and 77%, respectively) and surface texture (86 and 77%, respectively). TPH Spectrum showed a great percentage of colour mismatch after 3 years, around 50%. Surefil and Filtek P60 showed an excellent clinical performance after 3 years, similar to the hybrid resin tested, TPH Spectrum. Solitaire did not fulfil the ADA acceptance criteria for restorative materials and, therefore, is not recommended for use in posterior restorations.