Automatic soft-tissue analysis on orthodontic frontal and lateral facial photographs based on deep learning.

BACKGROUND: To establish the automatic soft-tissue analysis model based on deep learning that performs landmark detection and measurement calculations on orthodontic facial photographs to achieve a more comprehensive quantitative evaluation of soft tissues. METHODS: A total of 578 frontal photographs and 450 lateral photographs of orthodontic patients were collected to construct datasets. All images were manually annotated by two orthodontists with 43 frontal-image landmarks and 17 lateral-image landmarks. Automatic landmark detection models were established, which consisted of a high-resolution network, a feature fusion module based on depthwise separable convolution, and a prediction model based on pixel shuffle. Ten measurements for frontal images and eight measurements for lateral images were defined. Test sets were used to evaluate the model performance, respectively. The mean radial error of landmarks and measurement error were calculated and statistically analysed to evaluate their reliability. RESULTS: The mean radial error was 14.44 ± 17.20 pixels for the landmarks in the frontal images and 13.48 ± 17.12 pixels for the landmarks in the lateral images. There was no statistically significant difference between the model prediction and manual annotation measurements except for the mid facial-lower facial height index. A total of 14 measurements had a high consistency. CONCLUSION: Based on deep learning, we established automatic soft-tissue analysis models for orthodontic facial photographs that can automatically detect 43 frontal-image landmarks and 17 lateral-image landmarks while performing comprehensive soft-tissue measurements. The models can assist orthodontists in efficient and accurate quantitative soft-tissue evaluation for clinical application.

Antimicrobial Photodynamic Effect of Cross-Kingdom Microorganisms with Toluidine Blue O and Potassium Iodide.

Streptococcus mutans (S. mutans) and Candida albicans (C. albicans) are prominent microbes associated with rapid and aggressive caries. In the present study, we investigated the antimicrobial efficacy, cytotoxicity, and mechanism of toluidine blue O (TBO)-mediated antimicrobial photodynamic therapy (aPDT) and potassium iodide (KI). The dependence of KI concentration, TBO concentration and light dose on the antimicrobial effect of aPDT plus KI was determined. The cytotoxicity of TBO-mediated aPDT plus KI was analyzed by cell counting kit-8 (CCK-8) assay. A singlet oxygen (1O2) probe test, time-resolved 1O2 detection, and a 1O2 quencher experiment were performed to evaluate the role of 1O2 during aPDT plus KI. The generation of iodine and hydrogen peroxide (H2O2) were analyzed by an iodine starch test and Amplex red assay. The anti-biofilm effect of TBO-mediated aPDT plus KI was also evaluated by counting forming unit (CFU) assay. KI could potentiate TBO-mediated aPDT against S. mutans and C. albicans in planktonic and biofilm states, which was safe for human dental pulp cells. 1O2 measurement showed that KI could quench 1O2 signals, implicating that 1O2 may act as a principal mediator to oxidize excess iodide ions to form iodine and H2O2. KI could highly potentiate TBO-mediated aPDT in eradicating S. mutans and C. albicans due to the synergistic effect of molecular iodine and H2O2.

Nanomaterial-based drug-delivery system as an aid to antimicrobial photodynamic therapy in treating oral biofilm.

Diverse microorganisms live as biofilm in the mouth accounts for oral diseases and treatment failure. For decades, the prevention and treatment of oral biofilm is a global challenge. Antimicrobial photodynamic therapy (aPDT) holds promise for oral biofilm elimination due to its several traits, including broad-spectrum antimicrobial capacity, lower possibility of resistance and low cytotoxicity. However, the physicochemical properties of photosensitizers and the biological barrier of oral biofilm have limited the efficiency of aPDT. Nanomaterials has been used to fabricate nanocarriers to improve photosensitizer properties and thus enhance antimicrobial effect. In this review, we have discussed the challenges of aPDT used in dentistry, categorized the nanomaterial-delivery system and listed the possible mechanisms involved in nanomaterials when enhancing aPDT effect.

[Box: see text].

In vitro effect of Er: YAG laser irradiation in caries cavity preparation on biobehaviors of adjacent human dental pulp cells in the pulp chamber.

The erbium-doped yttrium aluminum garnet (Er: YAG) laser has been successfully applied in caries removal; however, little is known about proper parameters of Er: YAG laser on different conditions of caries removal, especially the influence of Er: YAG irradiation on human dental pulp cells (hDPCs). Here, we tested the effects of Er: YAG laser at different output energy levels (100, 200, 300, 400, and 500 mJ) on biobehaviors of hDPCs. To simulate clinical deep caries conditions, hDPCs were cultured on the pulpal side of 500-µm-thick dentin disks in an in vitro pulp chamber model. Temperature change, structural change, and ablation depth of dentin disk were also recorded. The findings suggested that the biological behaviors of hDPCs are strongly correlated with the energy output of the Er: YAG laser. Er: YAG laser irradiation at 100 mJ may be proper and safe for deep caries removal since it would not cause any adverse effect on hDPCs biobehaviors.

STSN-Net: Simultaneous Tooth Segmentation and Numbering Method in Crowded Environments with Deep Learning.

Accurate tooth segmentation and numbering are the cornerstones of efficient automatic dental diagnosis and treatment. In this paper, a multitask learning architecture has been proposed for accurate tooth segmentation and numbering in panoramic X-ray images. A graph convolution network was applied for the automatic annotation of the target region, a modified convolutional neural network-based detection subnetwork (DSN) was used for tooth recognition and boundary regression, and an effective region segmentation subnetwork (RSSN) was used for region segmentation. The features extracted using RSSN and DSN were fused to optimize the quality of boundary regression, which provided impressive results for multiple evaluation metrics. Specifically, the proposed framework achieved a top F1 score of 0.9849, a top Dice metric score of 0.9629, and an mAP (IOU = 0.5) score of 0.9810. This framework holds great promise for enhancing the clinical efficiency of dentists in tooth segmentation and numbering tasks.

Hydrogen peroxide potentiates antimicrobial photodynamic therapy in eliminating Candida albicans and Streptococcus mutans dual-species biofilm from denture base.

BACKGROUND: Candida albicans (C.albicans) is the primary pathogen of denture biofilm. Moreover, it could establish a cross-kingdom relationship with bacteria to enhance its virulence and resistance to antifungal drugs. This study aimed to investigate the efficacy of antimicrobial photodynamic therapy (aPDT) in combination with hydrogen peroxide (H2O2) against C.albicans and Streptococcus mutans (S.mutans) dual-species biofilm formed on polymethyl methacrylate (PMMA) disk, and explore its involved mechanisms. METHODS: C.albicans and S.mutans were grown on PMMA disk for 48 h to form biofilm and received different treatments. The treatments included:1) phosphate-buffered saline (PBS) group,2) 100 mM H2O2 group,3) aPDT group,4) aPDT+ H2O2 and 5) H2O2+aPDT group. Colony forming units (CFU), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and scanning electron microscope (SEM) were used to evaluate the antimicrobial effects. Extracellular polysaccharide substance (EPS) production and observation, cell permeability of biofilm, and uptake of toluidine blue O (TBO) by biofilm were assessed to investigate the involved mechanism. RESULTS: There was no significant difference between PBS group and H2O2 group in viable microorganisms and metabolic activity of biofilm. The treatment protocols containing aPDT group reduced microorganism numbers and metabolic activity when compared to PBS group or H2O2 group (P<0.05). H2O2+aPDT treatment showed the highest antimicrobial efficacy in comparison with other treatments (P<0.05). Pretreatment with H2O2 could decrease EPS production and enhance cell permeability, leading to increased TBO uptake in biofilm. CONCLUSION: Pretreatment with H2O2 improved aPDT efficiency in eliminating dual-species biofilm from PMMA disk by reducing EPS amount, enhancing cell permeability, and increasing TBO uptake.

Minimally invasive injectable lumbar interbody fusion with mineralized collagen-modified PMMA bone cement: A new animal model.

This study was to develop a feasible and safe animal model for minimally invasive injectable lumbar interbody fusion using a novel biomaterial, mineralized collagen-polymethylmethacrylate bone cement (MC-PMMA), with unilateral pedicle screw fixation in an in vivo goat model. Eight goats (Capra aegagrus hircus) were divided into three groups: MC-PMMA, unmodified commercial-polymethylmethacrylate bone cement (UC-PMMA), and a control group (titanium cage filled with autogenous bone, TC-AB). Each group of goats was treated with minimally invasive lumbar interbody fusion at the L3/L4 and L5/L6 disc spaces (injected for MC-PMMA and UC-PMMA, implanted for TC-AB). The pedicle screws were inserted at the L3, L4, L5, and L6 vertebrae, respectively, and fixed on the left side. The characteristics of osteogenesis and bone growth were assessed at the third and the sixth month, respectively. The methods of evaluation included the survival of each animal, X-ray imaging, and 256-layer spiral computed tomography (256-CT) scanning, imaged with three-dimensional microfocus computed tomography (micro-CT), and histological analysis. The results showed that PMMA bone cement can be extruded smoothly after doping MC, the MC-PMMA integrates better with bone than the UC-PMMA, and all goats recovered after surgery without nerve damage. After 3 and 6 months, the implants were stable. New trabecular bone was observed in the TC-AB group. In the UC-PMMA group a thick fibrous capsule had formed around the implants. The MC-PMMA was observed to have perfect osteogenesis and bone ingrowth to adjacent bone surface. Minimally invasive injectable lumbar interbody fusion using MC-PMMA bone cement was shown to have profound clinical value, and the MC-PMMA showed potential application prospects.

[Influence of different NaCl concentration on passive behavior of Cr alloy in vitro].

OBJECTIVE: To investigate the properties of passive film of three Cr alloys and to analyze their corrosion resistance in the artificial saliva with different NaCl mass fraction in vitro. METHODS: Artificial saliva with 1%, 2% and 3% NaCl mass fraction was prepared. Cobalt-chromium alloy, nickel-chromium alloy and Ti-Ni-Cr alloy were employed as the working electrode in the artificial saliva. Semi-conductor properties of passive film on Cr alloy was analyzed by Mott-Schottky plots. In addition, the factors which affect the semi-conductive compact characteristic of the passive film was also discussed. RESULTS: The passive film exhibits n-type semi-conductive characters. With the increasing of NaCl mass fraction, the carrier density of the Cr alloys also increased. The carrier density of the cobalt-chromium alloy, nickel-chromium alloy and Ti-Ni-Cr alloy are 3.71 x 108, 2.34 x 109, and 7.66 x 109/cm³ respectively. This decreases its donor density and its film stability. CONCLUSIONS: When exposed to saliva environment with high concentration of chlorine ion, corrosion resistance of the three types of Cr alloys decrease. This will reduce the service life of Cr alloy prosthesis.

Preparation and mechanical properties of chitosan/carbon nanotubes composites.

Biopolymer chitosan/multiwalled carbon nanotubes (MWNTs) nanocomposites have been successfully prepared by a simple solution-evaporation method. The morphology and mechanical properties of the chitosan/MWNTs nanocomposites have been characterized with field emission scanning electron microscopy (SEM), bright field transmission electron microscopy (TEM), optical microscopy (OM), wide-angle X-ray diffraction (XRD), and tensile as well as nanoindentation tests. The MWNTs were observed to be homogeneously dispersed throughout the chitosan matrix. When compared with neat chitosan, the mechanical properties, including the tensile modulus and strength, of the nanocomposites are greatly improved by about 93% and 99%, respectively, with incorporation of only 0.8 wt % of MWNTs into the chitosan matrix.