Radiomics based on biparametric MRI for the detection of significant residual prostate cancer after androgen deprivation therapy: using whole-mount histopathology as reference standard / 亚洲男科学杂志(英文版)

We aimed to study radiomics approach based on biparametric magnetic resonance imaging (MRI) for determining significant residual cancer after androgen deprivation therapy (ADT). Ninety-two post-ADT prostate cancer patients underwent MRI before prostatectomy (62 with significant residual disease and 30 with complete response or minimum residual disease [CR/MRD]). Totally, 100 significant residual, 52 CR/MRD lesions, and 70 benign tissues were selected according to pathology. First, 381 radiomics features were extracted from T2-weighted imaging, diffusion-weighted imaging, and apparent diffusion coefficient (ADC) maps. Optimal features were selected using a support vector machine with a recursive feature elimination algorithm (SVM-RFE). Then, ADC values of significant residual, CR/MRD lesions, and benign tissues were compared by one-way analysis of variance. Logistic regression was used to construct models with SVM features to differentiate between each pair of tissues. Third, the efficiencies of ADC value and radiomics models for differentiating the three tissues were assessed by area under receiver operating characteristic curve (AUC). The ADC value (mean ± standard deviation [s.d.]) of significant residual lesions ([1.10 ± 0.02] × 10-3 mm2 s-1) was significantly lower than that of CR/MRD ([1.17 ± 0.02] × 10-3 mm2 s-1), which was significantly lower than that of benign tissues ([1.30 ± 0.02] × 10-3 mm2 s-1; both P < 0.05). The SVM feature models were comparable to ADC value in distinguishing CR/MRD from benign tissue (AUC: 0.766 vs 0.792) and distinguishing residual from benign tissue (AUC: 0.825 vs 0.835) (both P > 0.05), but superior to ADC value in differentiating significant residual from CR/MRD (AUC: 0.748 vs 0.558; P = 0.041). Radiomics approach with biparametric MRI could promote the detection of significant residual prostate cancer after ADT.

Influence of the three-dimensional printing technique and printing layer thickness on model accuracy.

OBJECTIVE: The accuracies of three-dimensional (3D) printed dental models using various digital light processing (DLP) and stereolithography (SLA) printers at different thicknesses were compared. MATERIALS AND METHODS: Based on digital dental models (originally digitized using R700; 3Shape, Copenhagen, Denmark), physical dental models were printed using three types of DLP printers: (1) EvoDent (UnionTec, Shanghai, China) with layer thicknesses of 50 µm and 100 µm; (2) EncaDent (Encashape, WuXi, China) with layer thicknesses of 20, 30, 50 and 100 µm; (3) Vida HD (Envisioned, Dearborn, MI, USA) with layer thicknesses of 50 and 100 µm. Models with the SLA printer Form 2 (Formlabs, Somerville, MA, USA) were printed with layer thicknesses of 25, 50 and 100 µm. All 22 printed models were converted to digital dental models using a D2000 model scanner (3 Shape, Copenhagen, Denmark) and compared three-dimensionally to the source files using Geomagic Qualify 12.0 (3D Systems, Rock Hill, SC, USA). RESULTS: The printing accuracy of all printers was higher at 50 µm. When the layer thickness was set at 100 µm, the printing speed and printing accuracy of DLP printer were both superior to those of the SLA printer. In all groups, the EvoDent 50 µm group had the highest consistency with the source files (mean absolute deviation of 0.0233 mm in the maxilla and 0.0301 mm in the mandible). While the accuracy of Form 2 100 µm group was the lowest (mean absolute deviation of 0.0511 mm in the maxilla and 0.0570 mm in the mandible). CONCLUSION: For the 3D printers studied, 50 µm was the optimum layer thickness for DLP technology, and the printing accuracy using SLA technology increased with decreasing layer thickness. The DLP technology also had higher printing accuracy at a layer thickness of 100 µm. EvoDent 50 µm had the highest and Form 2 100 µm the lowest printing accuracy.

Bond strength of metal brackets bonded to a silica-based ceramic with light-cured adhesive : Influence of various surface treatment methods.

OBJECTIVE: The purpose of this work was to evaluate the effects of several surface treatment methods on the shear bond strengths of metal brackets bonded to a silica-based ceramic with a light-cured adhesive. MATERIALS AND METHODS: Silica-based ceramic (IPS Classic(®)) with glazed surfaces was cut into discs that were used as substrates. A total of 80 specimens were randomly divided into four groups according to the method used: 9.6 % hydrofluoric acid (group 1), 9.6 % hydrofluoric acid (HF) + silane coupling agent (group 2), sandblasting (aluminum trioxide, 50 µm) + silane (group 3), and tribochemical silica coating (CoJet™ sand, 30 µm) + silane (group 4). Brackets were bonded to the treated specimens with a light-cure adhesive (Transbond XT, 3 M Unitek). Shear bond strength was tested after bracket bonding, and the Adhesive Remnant Index (ARI) scores were quantified after debonding. RESULTS: Group 4 showed the highest bond strength (12.3 ± 1.0 MPa), which was not significantly different from that of group 3 (11.6 ± 1.2 MPa, P > 0.05); however, the bond strength of group 4 was substantially higher than that of group 2 (9.4 ± 1.1 MPa, P < 0.05). The shear bond strength of group 1 (3.1 ± 0.6 MPa, P< 0.05) was significantly lower than that of the other groups. CONCLUSION: Shear bond strengths exceeded the optimal range of ideal bond strength for clinical practice, except for the isolated HF group. HF acid etching followed by silane was the best suited method for bonding on IPS Classic(®). Failure modes in the sandblasting and silica-coating groups revealed signs of damaged ceramic surfaces.

[Analysis of stress in periodontal ligament of the maxillary first molar on distal movement by nonlinear finite element method].

PURPOSE: To analyze the stress distribution in periodontal ligament of maxillary first molar during distal movement with nonlinear finite element analysis, and to compare it with the result of linear finite element analysis, consequently to provide biomechanical evidence for clinical application. METHODS: The 3-D finite element model including a maxillary first molar, periodontal ligament, alveolar bone, cancellous bone, cortical bone and a buccal tube was built up by using Mimics, Geomagic, ProE and Ansys Workbench. The material of periodontal ligament was set as nonlinear material and linear elastic material, respectively. Loads of different combinations were applied to simulate the clinical situation of distalizing the maxillary first molar. RESULTS: There were channels of low stress in peak distribution of Von Mises equivalent stress and compressive stress of periodontal ligament in nonlinear finite element model. The peak of Von Mises equivalent stress was lower when it was satisfied that Mt/F minus Mr/F approximately equals 2. The peak of compressive stress was lower when it was satisfied that Mt/F was approximately equal to Mr/F. The relative stress of periodontal ligament was higher and violent in linear finite element model and there were no channels of low stress in peak distribution. CONCLUSIONS: There are channels in which stress of periodontal ligament is lower. The condition of low stress should be satisfied by applied M/F during the course of distalizing the maxillary first molar.

Shear bond strength of an experimental composite bracket.

OBJECTIVE: The in vitro shear bond strength of MZ100 brackets (an experimental composite bracket developed by the Dental Biomaterial Laboratory at Boston University) and the effect of different treatment methods on these brackets were evaluated. MATERIALS AND METHODS: As the bonding substrates, 80 Vitablocs® Mark II (Vident, Brea, CA, USA) were chosen. Three treatment methods were employed on 60 MZ100 bracket bases (20 brackets per treatment): silane coupling agent (Porcelain Primer; Ormco, Orange, CA, USA), sandblasting (Basic Professional Model Sandblaster; Renfert GmbH, Germany), and non-treatment. Two different orthodontic adhesives were also used: Blugloo™ (Ormco, Orange, CA, USA) and Enlight™ (Ormco, Orange, CA, USA). Twenty metal brackets were used as controls. Shear bond strength tests were performed after sample preparation and bracket bonding. RESULTS: The mean shear bond strength of non-treated MZ100 brackets bonded with Enlight™ had the lowest value (7.9 MPa), while that of sandblasted MZ100 brackets bonded with Blugloo™ showed the highest value (17.9 MPa). The mean shear bond strength of non-treated MZ100 brackets was significantly lower than that of the other groups (p<0.05). The mean shear bond strength of sandblasted MZ100 brackets bonded with Blugloo™ was significantly higher than that of those bonded with Enlight™ (p<0.05). With the exception of the silane-Blugloo™ group, the treated MZ100 brackets demonstrated shear bond strengths that did not significantly differ from metal brackets. CONCLUSION: The use of sandblasting and silane coupling agent significantly increases the shear bond strength of the MZ100 brackets to values resembling those of metal brackets.

[The development and clinical applications of aesthetic brackets].

Due to the significantly increasing demand of aesthetics during orthodontic treatments, aesthetic brackets have gained popularity in clinic. In general, the current aesthetic brackets are either ceramic brackets or plastic brackets. This article provided a review of the latest information about the aesthetic brackets' materials, designs, and their clinical applications. Although significant improvements have been made in recent years on aesthetic brackets, more laboratory studies and clinical trials are needed to further demonstrate the critical issues of bonding, debonding and recycling to meet their optimal uses in orthodontics.