Structured light for touchless 3D registration in video-based surgical navigation.

PURPOSE: Arthroscopic surgery, with its inherent difficulties on visibility and maneuverability inside the joint, poses significant challenges to surgeons. Video-based surgical navigation (VBSN) has proven to have clinical benefits in arthroscopy but relies on a time-consuming and challenging surface digitization using a touch probe to accomplish registration of intraoperative data with preoperative anatomical models. This paper presents an off-the-shelf laser scanner for noninvasive registration that enables an increased area of reachable region. METHODS: Our solution uses a standard arthroscope and a light projector with visual markers for real-time extrinsic calibration. Nevertheless, the shift from a touch probe to a laser scanner introduces a new challenge-the presence of a significant amount of outliers resulting from the reconstruction of nonrigid structures. To address this issue, we propose to identify the structures of interest prior to reconstruction using a deep learning-based semantic segmentation technique. RESULTS: Experimental validation using knee and hip phantoms, as well as ex-vivo data, assesses the laser scanner's effectiveness. The integration of the segmentation model improves results in ex-vivo experiments by mitigating outliers. Specifically, the laser scanner with the segmentation model achieves registration errors below 2.2 mm, with the intercondylar region exhibiting errors below 1 mm. In experiments with phantoms, the errors are always below 1 mm. CONCLUSION: The results show the viability of integrating the laser scanner with VBSN as a noninvasive and potential alternative to traditional methods by overcoming surface digitization challenges and expanding the reachable region. Future efforts aim to improve hardware to further optimize performance and applicability in complex procedures.

Effect of preheating on the physicochemical properties and bond strength of composite resins utilized as dental cements: An in vitro study.

STATEMENT OF PROBLEM: Little is known regarding the use of preheated composite resins to bond indirect restorations and its impact on mechanical properties when compared with resin cements. PURPOSE: The purpose of this in vitro study was to compare the chemical and physical properties and bond strength to enamel and ceramics of preheated composite resins and resin cements. MATERIAL AND METHODS: Two composite resins, the microhybrid Filtek Z250XT and the nanoparticulate Z350XT were tested, and 2 commercially available resin cements, the dual-polymerized Rely-X ARC and the light-polymerized Rely-X Veneer were used as controls. A device (HotSet) was used to preheat the composite resins to 69 °C before light-polymerization. The following properties were tested: flexural strength, modulus of elasticity, fracture toughness, microshear bond strength to enamel and ceramics, degree of conversion, flow, sorption and solubility, and color stability. Statistical analysis was done with ANOVA and Holm-Sidak for multiple comparisons (α=.05). RESULTS: Preheating had no significant effect on the degree of conversion, flexural strength, fracture toughness, solubility, or microshear bond strength to the enamel of the tested composite resins (P>.05). However, preheating increased the sorption and reduced the microshear bond strength to the ceramic (P<.05). The flowability of the composite resins increased with heating but showed lower values when compared with both resin cements (P<.05). Color stability was more affected in the preheated composite resins than in the resin cements. CONCLUSIONS: The preheating process resulted in little to no benefit in the evaluated properties for the composite resins. Resin cements appear to be the best option for cementing indirect restorations.

Video-based computer navigation in knee arthroscopy for patient-specific ACL reconstruction.

PURPOSE: The anterior cruciate ligament tear is a common medical condition that is treated using arthroscopy by pulling a tissue graft through a tunnel opened with a drill. The correct anatomical position and orientation of this tunnel are crucial for knee stability, and drilling an adequate bone tunnel is the most technically challenging part of the procedure. This paper presents the first guidance system based solely on intra-operative video for guiding the drilling of the tunnel. METHODS: Our solution uses small, easily recognizable visual markers that are attached to the bone and tools for estimating their relative pose. A recent registration algorithm is employed for aligning a pre-operative image of the patient's anatomy with a set of contours reconstructed by touching the bone surface with an instrumented tool. RESULTS: Experimental validation using ex-vivo data shows that the method enables the accurate registration of the pre-operative model with the bone, providing useful information for guiding the surgeon during the medical procedure. Experiments also demonstrate that the guided drilling of the tunnel leads to errors as low as 2.5 mm in the footprint and [Formula: see text] in orientation, which compares favourably to other works in the field. CONCLUSION: The high accuracy and short time overhead evinced by the experimental validation combined with no additional incisions or capital equipment make this video-based computer-aided arthroscopy solution an appealing alternative to the existing approaches.

Deep segmentation leverages geometric pose estimation in computer-aided total knee arthroplasty.

Knee arthritis is a common joint disease that usually requires a total knee arthroplasty. There are multiple surgical variables that have a direct impact on the correct positioning of the implants, and an optimal combination of all these variables is the most challenging aspect of the procedure. Usually, preoperative planning using a computed tomography scan or magnetic resonance imaging helps the surgeon in deciding the most suitable resections to be made. This work is a proof of concept for a navigation system that supports the surgeon in following a preoperative plan. Existing solutions require costly sensors and special markers, fixed to the bones using additional incisions, which can interfere with the normal surgical flow. In contrast, the authors propose a computer-aided system that uses consumer RGB and depth cameras and do not require additional markers or tools to be tracked. They combine a deep learning approach for segmenting the bone surface with a recent registration algorithm for computing the pose of the navigation sensor with respect to the preoperative 3D model. Experimental validation using ex-vivo data shows that the method enables contactless pose estimation of the navigation sensor with the preoperative model, providing valuable information for guiding the surgeon during the medical procedure.

Piecewise-Planar StereoScan: Sequential Structure and Motion Using Plane Primitives.

The article describes a pipeline that receives as input a sequence of stereo images, and outputs the camera motion and a Piecewise-Planar Reconstruction (PPR) of the scene. The pipeline, named Piecewise-Planar StereoScan (PPSS), works as follows: the planes in the scene are detected for each stereo view using semi-dense depth estimation; the relative pose is computed by a new closed-form minimal algorithm that only uses point correspondences whenever plane detections do not fully constrain the motion; the camera motion and the PPR are jointly refined by alternating between discrete optimization and continuous bundle adjustment; and, finally, the detected 3D planes are segmented in images using a new framework that handles low texture and visibility issues. PPSS is extensively validated in indoor and outdoor datasets, and benchmarked against two popular point-based SfM pipelines. The experiments confirm that plane-based visual odometry is resilient to situations of small image overlap, poor texture, specularity, and perceptual aliasing where the fast LIBVISO2 [1] pipeline fails. The comparison against VisualSfM+CMVS/PMVS [2] , [3] shows that, for a similar computational complexity, PPSS is more accurate and provides much more compelling and visually pleasant 3D models. These results strongly suggest that plane primitives are an advantageous alternative to point correspondences for applications of SfM and 3D reconstruction in man-made environments.

Influence of heat treatment on the sorption and solubility of direct composite resins.

CONTEXT: Heat treatment allows the use of direct composite resins for fabrication of inlays/onlays restorations because it improves some mechanical and physical properties. AIM: The aim of this study is to analyze the influence of heat treatment on the water sorption and solubility of direct composite resins compared with an indirect composite resin. MATERIALS AND METHODS: A total of 50 cylindrical specimens were fabricated (6 mm diameter × 2 mm high) and divided into five groups (n = 10): G1 (FillMagic without heat treatment-control 1), G2 (heat-treated FillMagic), G3 (P60 without heat treatment-control 1), G4 (heat-treated P60) and G5 (indirect resin Epricord-control 2). After fabrication, the specimens were placed in a desiccator containing silica gel and maintained at 37°C for 24 h. This cycle was repeated until a constant weight was achieved (m1). Following, the specimens were stored in individual flasks containing 2 ml of distilled water in an oven at 37°C. The specimens were weighed after intervals of 1, 7 and 21 days of immersion in water (m2). After 21 days of storage in water, the specimens were once again desiccated until a constant weight was achieved (m3). The mean diameter and thickness of specimens were obtained using a digital pachymeter. STATISTICAL ANALYSIS USED: Two - way analysis of variance and Tukey's test were used to compare the sorption and solubility (α = 0.05). RESULTS: The type of resin significantly influenced the sorption (P = 0.01) and solubility (P = 0.00). The heat treatment also significantly influenced the sorption (P = 0.026) and solubility (P = 0.01). CONCLUSION: It was concluded that the heat treatment is an additional curing method that improves strength to the sorption and solubility of composite resins.

Shear bond strength of self-etch and total-etch adhesives to bovine enamel and dentin / Resistência ao cisalhamento de adesivo autocondicionante e convencional ao esmalte e dentina bovinos

PURPOSE: To evaluate the shear bond strength of a self-etch adhesive and an etch-and-rinse adhesive when bonded to bovine enamel and dentin. METHODS: The labial surfaces of 28 bovine mandibular incisors were wet ground to achieve a flat enamel or dentin surface. A 1-step self-etch adhesive and a 3-step etch-and-rinse adhesive were bonded to enamel or dentin according to the manufacturer's instructions (Adper Easy One and Adper Scotchbond, respectively). A composite resin cylinder (Filtek Z350 XT) was built upon the adhesive layer using a silicon mold (2 mm in diameter × 3 mm high). The specimens were stored in 37°C distilled water for 24 h. The bond strength was measured by a universal testing machine at a crosshead speed of 1.0 mm/min. Student's t-test was used to compare bond strength values between adhesives at the 95% confidence level. RESULTS: For the enamel specimens, Adper Scotchbond had significantly higher values of bond strength than Adper Easy One (P=0.007). For the dentin specimens, there were no statistically significant differences between adhesives (P=0.12). CONCLUSION: Adper Easy One showed lower shear bond strength than Adper Scotchbond on enamel. For dentin, Adper Easy One showed bond strength similar to Adper Scotchbond.

OBJETIVO: Avaliar a resistência ao cisalhamento de adesivo autocondicionante e adesivo convencional ao esmalte e dentina bovinos. METODOLOGIA: As superfícies vestibulares de 28 incisivos mandibulares bovinos foram lixadas, sob refrigeração, para obtenção de superfícies de esmalte ou dentina planas. Um adesivo autocondicionante de passo único e um convencional de três passos foram utilizados de acordo com as instruções dos fabricantes (Adper Easy One and Adper Scotchbond, respectivamente). Um cilindro de resina composta foi confeccionado sobre a camada adesiva usando um molde de silicone (2 mm de diâmetro × 3 mm altura). Os espécimes foram armazenados a 37°C em água destilada por 24 h. A resistência de união foi mensurada através de máquina de ensaios universal à velocidade de 0.1 mm/min. Teste t de Student comparou os resultados de resistência de união entre os adesivos com nível de confiança de 95%. RESULTADOS: Para os espécimes de esmalte, Adper Scotchbond apresentou valores significativamente maiores que Adper Easy One (P=0.007). Para espécimes de dentina, não houve diferenças significativas entre os adesivos (P=0.12). CONCLUSÃO: Adper Easy One mostrou menor resistência ao cisalhamento do que Adper Scotchbond no esmalte. Para dentina, Adper Easy One mostrou resistência de união similar ao Adper Scotchbond.