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American Journal of Orthodontics and... Sep 2020Enameloplasty of maxillary canines is often needed for aesthetic substitution in patients with congenitally missing lateral incisors. The exact enamel thicknesses for...
INTRODUCTION
Enameloplasty of maxillary canines is often needed for aesthetic substitution in patients with congenitally missing lateral incisors. The exact enamel thicknesses for the various canine surfaces are unknown because previous studies failed to employ accurate measurement tools to report and compare detailed enamel thicknesses for each surface at various crown heights.
METHODS
Thirty-two extracted maxillary canines were collected and scanned in a microcomputed tomography scanner. The scans were imported into a custom-written MATLAB software (version 9.2; MathWorks, Natick, Mass) and the enamel thickness on the mesial, distal, labial, fossa, cingulum, and incisal edge of each tooth was computed, obtaining the mean value from slices at 0.1 mm intervals. The overall mean enamel thickness for each surface was also calculated, and these values were compared using paired t tests. Incisal wear stage and incisal enamel thickness that was measured were compared using Spearman rank correlation coefficient.
RESULTS
The mean enamel thickness was significantly thinner at the gingival level when compared with the incisal for all surfaces that were analyzed (1-tailed, P <0.001). The mean enamel coverage at the mesial was significantly thinner than the distal when measured gingival to the widest mesiodistal area. The mean enamel coverage of the cingulum was particularly thin and therefore requires extreme care in reshaping it. Incisal edge enamel thickness was highly negatively correlated with the wear stage of the scoring system that was used (1-tailed, P <0.001).
CONCLUSIONS
The enamel coverage of the maxillary canine varies depending on the tooth surface and the incisogingival measurement location.
Topics: Cuspid; Dental Enamel; Esthetics, Dental; Humans; Maxilla; Odontometry; X-Ray Microtomography
PubMed: 32653347
DOI: 10.1016/j.ajodo.2019.09.013 -
Using artificial intelligence to predict the final color of leucite-reinforced ceramic restorations.Journal of Esthetic and Restorative... Jan 2023The aim of this study was to evaluate the accuracy of machine learning regression models in predicting the final color of leucite-reinforced glass CAD/CAM ceramic veneer...
OBJECTIVES
The aim of this study was to evaluate the accuracy of machine learning regression models in predicting the final color of leucite-reinforced glass CAD/CAM ceramic veneer restorations based on substrate shade, ceramic shade, thickness and translucency.
METHODS
Leucite-reinforced glass ceramics in four different shades were sectioned in thicknesses of 0.3, 0.5, 0.7, and 1.2 mm. The CIELab coordinates of each specimen were obtained over four different backgrounds (black, white, A1, and A3) interposed with an experimental translucent resin cement using a calibrated spectrophotometer. The color change (CIEDE2000) values, as well as all the CIELab values for each one of the experimental groups, were submitted to 28 different regression models. Each regression model was adjusted according to the weights of each dependent variable to achieve the best-fitting model.
RESULTS
Different substrates, ceramic shades, and thicknesses influenced the L, a, and b of the final restoration. Of all variables, the substrate influenced the final ceramic shade most, followed by the ceramic thickness and the L, a, and b of the ceramic. The decision tree regression model had the lowest mean absolute error and highest accuracy to predict the shade of the ceramic restoration according to the substrate shade, ceramic shade and thickness.
CLINICAL SIGNIFICANCE
The machine learning regression model developed in the study can help clinicians predict the final color of the ceramic veneers made with leucite-reinforced glass CAD/CAM ceramic HT and LT when cemented with translucent cements, based on the color of the substrate and ceramic thicknesses.
Topics: Dental Porcelain; Artificial Intelligence; Ceramics; Aluminum Silicates; Resin Cements; Color; Materials Testing; Surface Properties
PubMed: 36592128
DOI: 10.1111/jerd.13007 -
European Journal of Ophthalmology Jul 2022To determine the possible impact of wearing N95 respirator or surgical masks on retinal vessel diameters and choroidal thickness in healthy healthcare workers.
PURPOSE
To determine the possible impact of wearing N95 respirator or surgical masks on retinal vessel diameters and choroidal thickness in healthy healthcare workers.
METHODS
Diameters of peripapillary retinal arteries and veins and choroidal thickness values at the foveal center and at 1000 μm distances from the foveal center in both nasal and temporal directions were measured before mask wearing using a spectral-domain optical coherence tomography. After four hours (h) of N95 or surgical mask wearing vessel diameter and choroidal thickness measurements were repeated.
RESULTS
A total of 52 eyes from 52 participants (28 F [53.8%]; 24 M [46.2%]) were enrolled in this study. The mean age of patients was 34.58 ± 5.24 years (25-44 years). The diameters of all measured arteries [inferior temporal artery (p = 0.003), superior temporal artery (p < 0.001), inferior nasal artery (p = 0.003), and superior nasal artery (p = 0.004)] and veins,with the exception of superior nasal vein, (inferior temporal vein (p = 0.031), superior temporal vein (p = 0.027), inferior nasal vein (p < 0.001), and superior nasal vein (p = 0.063)] increased significantly after four hour use of N95 respirators and surgical maskswhen compared to baseline. There was also a significant diameter increase of the superior temporal (p < 0.001), inferior nasal veins (p < 0.001), and superior temporal artery (p = 0.037) for N95 respirators and surgical masks use, respectively. The differences in central subfoveal, temporal, and nasal choroidal thickness between baseline and after 4 h use of N95 respirators were statistically significant (From 366.73 ± 70.81 μm to 381.23 ± 69.29μm,p < 0.001 for the subfoveal; from 324.00 ± 64.13μm to 335.40 ± 61.35 μm, p = 0.007 for the temporal; from 297.40 ± 68.18 μm to 308.23 ± 74.51μm, p = 0.002 for the nasal thicknesses). Choroidal thickness values were also increased with surgical mask use. But only the increase in central subfoveal thickness was statistically significant (From 366.78 ± 71.00 μm to 372.58 ± 76.56 μm, p = 0.031 for the central subfoveal; from 297.42 ± 68.35 μmto 302.79 ± 73.05 μm, p = 0.068 for the nasal; from 324.01 ± 64.21μm to 330.33 ± 65.84, p = 0.117 for the temporal thicknesses).
CONCLUSION
With four hours use of N95 respirators or surgical face masks, retinal vessel diameters and choroidal thicknesses showed an increase in comparison to baseline measurements. Hemodynamic changes seen secondary to hypercapnia due to prolonged use of N95 respirators or surgical masks may also be observed in the retinal and choroidal circulation. Furthermore, the use of face masks should be taken into account while assessing the retinal microvasculature.
Topics: Adult; Choroid; Humans; Masks; Microvessels; N95 Respirators; Retina; Tomography, Optical Coherence
PubMed: 35410534
DOI: 10.1177/11206721221093199 -
Indian Journal of Ophthalmology Apr 2022To determine the pattern of corneal thickness and epithelial thickness distribution in healthy North Indian eyes by using spectral domain optical coherence tomography... (Observational Study)
Observational Study
PURPOSE
To determine the pattern of corneal thickness and epithelial thickness distribution in healthy North Indian eyes by using spectral domain optical coherence tomography (SD-OCT).
METHODS
The observational study measured total corneal and epithelial thickness in the central 2 mm zone and eight sectors each in paracentral 2-5 mm (ring 1) and midperipheral 5-7 mm (ring 2) zones on SD-OCT.
RESULTS
The study included 67 eyes of 67 subjects with a male:female ratio of 32:35 and mean age of 25.04 ± 4.54 years. The mean central corneal and epithelial thicknesses were 505.97 ± 30.12 μm and 60.48 ± 8.37 μm, respectively. The epithelium of inferior and infero-nasal sectors in ring 1 and inferior sector in ring 2 was significantly thicker than the radially opposite sectors of the respective rings (P = 0.001; P = 0.01 and P = 0.02, respectively). Sector-wise analysis did not reveal any significant correlation between the total corneal thickness and epithelial thickness (all P > 0.05) except in the outer superior sector where there was a weak positive correlation (r = 0.28, P = 0.02). Central epithelial thickness in males (60.59 ± 9.28 μm) and females (60.37 ± 7.58 μm) was comparable (P = 0.91). Pachymetry was thinnest in the inferior, inferonasal, and inferotemporal sectors in 44.79% of eyes (n = 30), while thinnest epithelium was seen in the superior, superonasal, and superotemporal quadrants in 50.75% of eyes (n = 34).
CONCLUSION
The epithelial thickness distribution in this sample of topographically normal healthy North Indian eyes was nonuniform and independent of the underlying corneal thickness. Epithelium was thinner in the superior cornea, whereas total corneal thickness was minimum in the inferior part.
Topics: Adult; Asian People; Cornea; Corneal Pachymetry; Epithelium, Corneal; Female; Health Status; Humans; Male; Tomography, Optical Coherence; Young Adult
PubMed: 35326008
DOI: 10.4103/ijo.IJO_2259_21 -
Cutaneous and Ocular Toxicology Sep 2023To investigate the effect of oral isotretinoin therapy on central macular thickness (CMT) thickness and choroidal thickness (CT) using optical coherence tomography (OCT).
PURPOSE
To investigate the effect of oral isotretinoin therapy on central macular thickness (CMT) thickness and choroidal thickness (CT) using optical coherence tomography (OCT).
METHODS
CT and CMT thickness of 43 eyes were evaluated at baseline, the third, and sixth month of isotretinoin therapy by spectral-domain OCT. For assessment of CT, OCT measurements were obtained at the fovea with six additional measurements at adjacent locations (at 500-1000 µm temporal to the fovea and 500-1000 µm nasal to the fovea).
RESULTS
Forty-three eyes from 43 patients with acne vulgaris, including 33 females (76.7%), who had a mean age of 24.81 ± 6.60 years, completed the study. The mean CMT was 231.49 ± 19.52 at the baseline and significantly decreased to 229.0 ± 19.57 ( = 0.02) and 229.28 ± 18.83 after three and six months, respectively ( < 0.03). The change in the macular thicknesses measured at four quadrants and choroidal thicknesses were not statistically significant during the study ( > 0.05).
CONCLUSION
The result of our study demonstrated choroidal thickness change is not significant in patients with acne vulgaris after systemic isotretinoin therapy during six months of follow-up. The decreased CMT amount was 2.2 microns; even if statistically significant, this amount is clinically insignificant.
Topics: Female; Humans; Adolescent; Young Adult; Adult; Isotretinoin; Acne Vulgaris; Choroid; Fovea Centralis; Tomography, Optical Coherence
PubMed: 37399081
DOI: 10.1080/15569527.2023.2227895 -
Plastic Surgery (Oakville, Ont.) May 2023The increasing prevalence of obesity in patients with breast cancer has prompted a reappraisal of the role of the latissimus dorsi flap (LDF) in breast reconstruction....
The increasing prevalence of obesity in patients with breast cancer has prompted a reappraisal of the role of the latissimus dorsi flap (LDF) in breast reconstruction. Although the reliability of this flap in obese patients is well-documented, it is unclear whether sufficient volume can be achieved through a purely autologous reconstruction (eg, extended harvest of the subfascial fat layer). Additionally, the traditional combined autologous and prosthetic approach (LDF + expander/implant) is subject to increased implant-related complication rates related to flap thickness in obese patients. The purpose of this study is to provide data on the thicknesses of the various components of the latissimus flap and discuss the implications for breast reconstruction in patients with increasing body mass index (BMI). Measurements of back thickness in the usual donor site area of an LDF were obtained in 518 patients undergoing prone computed tomography-guided lung biopsies. Thicknesses of the soft tissue overall and of individual layers (e.g., muscle, subfascial fat) were obtained. Patient, demographics including age, gender, and BMI were obtained. A range of BMI from 15.7 to 65.7 was observed. In females, total back thickness (skin, fat, muscle) ranged from 0.6 to 9.4 cm. Every 1-point increase in BMI resulted in an increase of flap thickness by 1.11 mm (adjusted of 0.682, < .001) and an increase in the thickness of the subfascial fat layer by 0.513 mm (adjusted of 0.553, < .001). Mean total thicknesses for each weight category were 1.0, 1.7, 2.4, 3.0, 3.6, and 4.5 cm in underweight, normal weight, overweight, and class I, II, III obese individuals, respectively. The average contribution of the subfascial fat layer to flap thickness was 8.2 mm (32%) overall and 3.4 mm (21%), 6.7 mm (29%), 9.0 mm (30%), 11.1 mm (32%), and 15.6 mm (35%) in normal weight, overweight, class I, II, III obese individuals, respectively. The above findings demonstrate that the thickness of the LDF overall and of the subfascial layer closely correlated with BMI. The contribution of the subfascial layer to overall flap thickness tends to increase as a percentage of overall flap thickness with increasing BMI, which is favourable for extended LDF harvests. Because this layer cannot be separated from overall thickness on examination, these results are useful in estimating the amount of additional volume obtained from an extended latissimus harvest technique.
PubMed: 37188129
DOI: 10.1177/22925503211031927 -
Journal of Prosthodontics : Official... Dec 2020To assess the effect of yttria mol% concentration and material thickness on the biaxial fracture load (N) of zirconia with and without mastication simulation.
PURPOSE
To assess the effect of yttria mol% concentration and material thickness on the biaxial fracture load (N) of zirconia with and without mastication simulation.
MATERIALS AND METHODS
Disk-shaped specimens (N = 120) of 3 mol% yttria-partially stabilized zirconia, 3Y-PSZ (Katana High Translucent, Kuraray Noritake), 4 mol% yttria-partially stabilized zirconia, 4Y-PSZ (Katana Super Translucent Multi Layered) and 5 mol% Yttria-partially stabilized zirconia, 5Y-PSZ (Katana Ultra Translucent Multi Layered) were prepared to thicknesses of 0.7 and 1.2 mm. For each thickness, the biaxial fracture load (N) was measured with and without mastication simulation with 1.2 million cycles at a 110-N load and simultaneous thermal cycling at 5°C to 55°C. The data were analyzed by three-way Analysis of Variance (α = 0.05) and Tukey-Kramer adjusted multiple comparison test.
RESULTS
Yttria mol% concentration and material thickness had a statistically significant effect on the mean biaxial fracture load (F = 388.16, p < 0.001 and F = 714.33, p < 0.001 respectively). The mean biaxial fracture load ranged from the highest to the lowest; 3Y-PSZ, 4Y-PSZ, and 5Y-PSZ (p = 0.012). The mean biaxial fracture load of the 1.2 mm thickness groups was significantly higher than 0.7 mm thickness at any given condition (p = 0.002). Not all specimens survived the mastication simulation protocol. Fifty percent of the 0.7-mm-thick 4Y-PSZ specimens, 70% of the 0.7-mm-thick 5Y-PSZ specimens and 20% of 1.2-mm-thick 5Y-PSZ specimens fractured during mastication simulation. Mastication simulation had no statistically significant effect on the biaxial fracture load (F = 1.24, p = 0.239) of the survived specimens.
CONCLUSIONS
Lowering yttria mol% concentration and increasing material thickness significantly increases the fracture load of zirconia. At 0.7 mm thickness, only 3Y-PSZ survived masticatory simulation. A minimum material thickness of 1.2 mm is required for 4Y-PSZ or 5Y-PSZ.
Topics: Dental Materials; Dental Stress Analysis; Mastication; Materials Testing; Zirconium
PubMed: 32840940
DOI: 10.1111/jopr.13242 -
Arquivos Brasileiros de Oftalmologia 2020To evaluate changes in ocular blood flow and subfoveal choroidal thickness in patients with symptomatic carotid artery stenosis after carotid artery stenting.
PURPOSES
To evaluate changes in ocular blood flow and subfoveal choroidal thickness in patients with symptomatic carotid artery stenosis after carotid artery stenting.
METHODS
We included 15 men (mean age, 63.6 ± 9.1 years) with symptomatic carotid artery stenosis and 18 healthy volunteers (all men; mean age, 63.7 ± 5.3 years). All participants underwent detailed ophthalmologic examinations including choroidal thickness measurement using enhanced depth-imaging optic coherence tomography. The patients also underwent posterior ciliary artery blood flow measurements using color Doppler ultrasonography before and after carotid artery stenting.
RESULTS
Patients lacked ocular ischemic symptoms. Their peak systolic and end-diastolic velocities increased to 10.1 ± 13.1 (p=0.005) and 3.9 ± 6.3 (p=0.064) cm/s, respectively, after the procedure. Subfoveal choroidal thicknesses were significantly thinner in patients with carotid artery stenosis than those in the healthy controls (p=0.01). But during the first week post-procedure, the subfoveal choroidal thicknesses increased significantly (p=0.04). The peak systolic velocities of the posterior ciliary arteries increased significantly after carotid artery stenting (p=0.005). We found a significant negative correlation between the mean increase in peak systolic velocity values after treatment and the mean preprocedural subfoveal choroidal thickness in the study group (p=0.025, r=-0.617).
CONCLUSIONS
In patients with carotid artery stenosis, the subfoveal choroid is thinner than that in healthy controls. The subfoveal choroidal thickness increases after carotid artery stenting. Carotid artery stenting treatment increases the blood flow to the posterior ciliary artery, and the preprocedural subfoveal choroidal thickness may be a good predictor of the postprocedural peak systolic velocity of the posterior ciliary artery.
Topics: Aged; Blood Flow Velocity; Carotid Arteries; Carotid Stenosis; Choroid; Humans; Male; Middle Aged; Ophthalmic Artery; Regional Blood Flow; Stents; Tomography, Optical Coherence
PubMed: 33084820
DOI: 10.5935/0004-2749.20200081 -
Journal of Dentistry Jul 2024To evaluate the effect of polishing and layering thickness on the wear resistance of 3D-printed occlusal splint materials.
OBJECTIVE
To evaluate the effect of polishing and layering thickness on the wear resistance of 3D-printed occlusal splint materials.
METHODS
Specimens with 3 different layer thicknesses (50, 75, 100 µm) were produced in the form of a disc 3 mm thick using V-Print splint resin on a 3D-printer with digital light processing technology. (n = 16 for each thickness) All specimens were washed and cured according to the manufacturer's instructions. Half of the specimens of each layer thickness were polished with silicon carbide papers. All specimens were subjected to 120.000 cycles of a chewing simulator for 2-body wear tests. Before and after the wear test, the specimens were scanned with a laser scanner, and the images were overlaid using a 3D analysis program and the volume loss was calculated. The wear patterns of the specimens were examined under a scanning electron microscope. Statistical evaluation was performed using a Shapiro-Wilk test, 2-way ANOVA, 1-way ANOVA, and Tukey post hoc test (α = 0.05).
RESULTS
While polishing had a significant effect (p = 0.003) on the wear volume of the occlusal splints, layer thickness (p = 0.105) and their interaction between polishing and layer thickness (p = 0.620) did not significantly affect the wear volume. Regardless of the polishing, the lowest mean wear was observed for D50 (0.064 mm), followed by D75 (0.078 mm), and D100 (0.096 mm). However, a significant difference was observed only between polished D50 and unpolished D100.
CONCLUSION
The polished 3D-printed occlusal splint resin showed higher wear resistance than the unpolished one, regardless of the layer thickness.
CLINICAL SIGNIFICANCE
Since different layer thicknesses of 50 µm and greater had no effect on the wear resistance of the material, a layer thickness of 100 µm may be preferred for faster printing. However, polishing occlusal splints may reduce the amount of wear and improve clinical performance.
Topics: Materials Testing; Surface Properties; Occlusal Splints; Dental Polishing; Humans; Printing, Three-Dimensional; Microscopy, Electron, Scanning; Carbon Compounds, Inorganic; Silicon Compounds; Dental Restoration Wear; Lasers; Dental Materials; Computer-Aided Design; Mastication
PubMed: 38801940
DOI: 10.1016/j.jdent.2024.105101 -
The British Journal of Ophthalmology Mar 2022To investigate the changes in macular vessel density (mVD) and its relationship to macular ganglion cell-inner plexiform layer (mGCIPL) thickness in patients receiving...
AIM
To investigate the changes in macular vessel density (mVD) and its relationship to macular ganglion cell-inner plexiform layer (mGCIPL) thickness in patients receiving ethambutol (EMB) therapy for tuberculosis without recognisable clinical symptoms or signs of EMB-induced optic neuropathy (EON).
METHODS
A total of 23 eyes of 13 patients using EMB therapy for 6 months without EON (preclinical EON) as the EMB group, 40 eyes of 23 healthy individuals as the normal control group and 18 eyes of 10 patients with tuberculosis before receiving EMB therapy as the blank control group were retrospectively analysed. The mean peripapillary retinal nerve fibre layer (pRNFL) and mGCIPL thicknesses and mVD were measured using optical coherence tomography angiography. Patients in the EMB group were compared with individuals in the normal and blank control groups, and changes in macular parameters were evaluated.
RESULTS
Central circle mVD (cCVD) was significantly lower in the EMB group than in both control groups (generalised estimating equation (GEE), p=0.003 and 0.029, respectively). The mGCIPL thickness in all regions and the mean pRNFL thickness were not significantly different between the EMB group and both control groups (GEE, p=1.000 for all). There were no significant differences in mVD, mGCIPL thickness and mean pRNFL thickness between the normal control and blank control groups (p>0.05). In the generalised linear model analyses, the minimum and inferonasal mGCIPL thicknesses were positively correlated with cCVD in the EMB group (β=1.285, p=0.003 and β=0.770, p=0.024, respectively).
CONCLUSIONS
cCVD decreased with no changes in mGCIPL and mean pRNFL thicknesses in patients with preclinical EON. The minimum and inferonasal mGCIPL thicknesses were positively correlated with cCVD. cCVD might be an early indicator for monitoring early-stage EMB toxicity.
Topics: Angiography; Ethambutol; Humans; Intraocular Pressure; Nerve Fibers; Optic Nerve Diseases; Retinal Ganglion Cells; Retrospective Studies; Tomography, Optical Coherence; Tuberculosis
PubMed: 33243831
DOI: 10.1136/bjophthalmol-2020-317742