OBJECTIVES: Through the investigation of the microhardness and microstructure of permanent tooth enamel at various eruption stages during childhood, this research offers references for the early prevention of childhood dental caries. METHODS: Forty-five premolars extracted due to orthodontic reasons were collected and screened. These premolars were divided into three experimental groups according to the time since eruption: Group A (erupted for 0-1 year), Group B (erupted for 1-3 years), and Group C (erupted for 3-5 years). Additionally, the third molars that were extracted due to impaction and had not erupted were selected as the control group, with 15 teeth in each group. Samples were prepared, and the surface microhardness, microstructure, and elemental composition of the enamel were measured using Vickers microhardness tester, scanning electron microscope, and electron probe, respectively. RESULTS: Compared with that in the control group, the microhardness of enamel in groups A, B, and C increased with prolonged eruption time, the surface porosity structure decreased considerably, the contents of Na and Mg on the surface decreased, and that of F increased (P<0.05). CONCLUSIONS The microhardness and microstructure of enamel in permanent teeth at different stages vary. Permanent teeth are at a substantially higher risk of caries within one year after eruption, and early prevention should be emphasized.
Dental Enamel/ultrastructure* ; Humans ; Hardness ; Dental Caries/prevention & control* ; Microscopy, Electron, Scanning ; Tooth Eruption ; Bicuspid/chemistry* ; Dentition, Permanent ; Child ; Child, Preschool

Objective: To investigate the effect of permeable resin on the surface structure, microhardness and color of tooth enamel after bleaching. Methods: Premolars extracted for orthodontic needs were selected (provided by the Department of Oral and Maxillofacial surgery of the first affiliated Hospital of Zhengzhou University) and randomly divided into A, B and C 3 groups. Each group was randomly divided into control subgroup, resin subgroup, bleaching subgroup and combined subgroup. Samples in the control subgroup did not receive any treatment. Those in the bleaching subgroup and combined subgroup were treated with cold light whitening. Those in the resin group and combined group were treated with permeable resin. Samples in the group A were observed by scanning electron microscope immediately after treatment and 2 weeks after treatment, and the microhardness of samples in the group B was measured before treatment, immediately after treatment and 2 weeks after treatment (the sample size of each time point was 8 in each subgroup). In group C, chromaticity was measured and chromatic aberration (ΔE value) was calculated before treatment, immediately after treatment and 1 and 2 weeks after treatment (10 samples in each subgroup). Results: Scanning electron microscope showed that the enamel surface of the resin subgroup and the combined group was smooth immediately after treatment, which was basically the same as that of the control subgroup, but covered with resin, and microporous defects and mineral deposits could be seen on the surface of the bleaching subgroup. Two weeks after treatment, the enamel surface of each subgroup was smooth, there was no obvious difference. Immediately after treatment, the microhardness of the control subgroup, resin subgroup, bleaching subgroup and combined subgroup were (354±33), (364±21), (411±30) and (350±17) HV, respectively (F=9.39,P<0.05). The microhardness of the bleaching subgroup was significantly higher than that of the other subgroups (P<0.05). There was no significant difference in microhardness among the four subgroups before treatment and 2 weeks after treatment (F=0.34, 2.75, P>0.05). Immediately after treatment, the ΔE values of the control subgroup, resin subgroup, bleaching subgroup and combined subgroup were 0.00±0.00, 2.29±1.86, 7.20±1.94 and 8.00±0.88, respectively (F=74.21,P<0.05); except that there was no significant difference between bleaching subgroup and combined subgroup (P>0.05), there were significant differences among the other subgroups (P<0.05). There was no significant difference in ΔE value among control subgroup, resin subgroup and bleaching subgroup at each time point (F=1.66, 0.30, 0.96, P>0.05). The difference in the combined subgroup immediately after treatment was significantly higher than that at 1 and 2 weeks after treatment (t=4.73, 4.23,P<0.05), but there was no significant difference between 1 and 2 weeks after treatment (t=0.75, P>0.05), and the color tended to be stable. Conclusions: When whitening healthy enamel, simple cold light whitening or cold light whitening combined with permeation resin can achieve whitening effect.
Color ; Dental Enamel ; Hardness ; Humans ; Hydrogen Peroxide/pharmacology* ; Tooth Bleaching/adverse effects* ; Tooth Bleaching Agents/pharmacology*

OBJECTIVES: The aim of this in vitro study was to evaluate the microhardness and surface roughness of composite resins before and after tooth bleaching procedures.MATERIALS AND METHODS: Sixty specimens were prepared of each composite resin (Filtek Supreme XT and Opallis), and BisCover LV surface sealant was applied to half of the specimens. Thirty enamel samples were obtained from the buccal and lingual surfaces of human molars for use as the control group. The surface roughness and microhardness were measured before and after bleaching procedures with 35% hydrogen peroxide or 16% carbamide (n = 10). Data were analyzed using 1-way analysis of variance and the Fisher test (α = 0.05).RESULTS: Neither hydrogen peroxide nor carbamide peroxide treatment significantly altered the hardness of the composite resins, regardless of surface sealant application; however, both treatments significantly decreased the hardness of the tooth samples (p < 0.05). The bleaching did not cause any change in surface roughness, with the exception of the unsealed Opallis composite resin and dental enamel, both of which displayed an increase in surface roughness after bleaching with carbamide peroxide (p < 0.05).CONCLUSIONS: The microhardness and surface roughness of enamel and Opallis composite resin were influenced by bleaching procedures.
Composite Resins ; Dental Enamel ; Hardness ; Humans ; Hydrogen Peroxide ; In Vitro Techniques ; Molar ; Tooth ; Tooth Bleaching ; Urea

hardness ratio. For baseline clinical factors, we examined the maternal body mass index, blood pressure, heart rate, uterine artery Doppler indices, and fetal presentation.RESULTS: We established a specific protocol for the measurement of cervical elastography using the E cervix program. For all elastographic parameters, the intra-observer intraclass correlation coefficient (ICC) ranged from 0.633 to 0.723 for single measures and from 0.838 to 0.887 for average measures, and the inter-observer ICC ranged from 0.814 to 0.977 for single measures and from 0.901 to 0.988 for average measures. Regression analysis showed that the measurement of the elastographic parameter was not affected by baseline clinical factors.CONCLUSION: We present a standardized protocol for the measurement of cervical elastography using intrinsic compression. According to this protocol, reproducibility was acceptable and the measurement of elastographic parameters was not affected by the baseline clinical factors studied.]]>
Blood Pressure ; Body Mass Index ; Cervix Uteri ; Elasticity ; Elasticity Imaging Techniques ; Female ; Hardness ; Heart Rate ; Humans ; Jupiter ; Labor Presentation ; Pregnancy ; Pregnant Women ; Premature Birth ; Reproducibility of Results ; Uterine Artery

OBJECTIVES: The aim of this in vitro study was to test the effect of 2 finishing–polishing sequences (QB, combining a 12/15-fluted finishing bur and an EVO-Light polisher; QWB, adding a 30-fluted polishing bur after the 12/15-fluted finishing bur used in the QB sequence) on 5 nanotech-based resin composites (Filtek Z500, Ceram X Mono, Ceram X Duo, Tetric Evoceram, and Tetric Evoceram Bulk Fill) by comparing their final surface roughness and hardness values to those of a Mylar strip control group (MS). MATERIALS AND METHODS: Twelve specimens of each nanocomposite were prepared in Teflon moulds. The surface of each resin composite was finished with QB (5 samples), QWB (5 samples), or MS (2 samples), and then evaluated (60 samples). Roughness was analysed with an optical profilometer, microhardness was tested with a Vickers indenter, and the surfaces were examined by optical and scanning electron microscopy. Data were analysed using the Kruskal-Wallis test (p < 0.05) followed by the Dunn test. RESULTS: For the hardness and roughness of nanocomposite resin, the QWB sequence was significantly more effective than QB (p < 0.05). The Filtek Z500 showed significantly harder surfaces regardless of the finishing–polishing sequence (p < 0.05). CONCLUSIONS: QWB yielded the best values of surface roughness and hardness. The hardness and roughness of the 5 nanocomposites presented less significant differences when QWB was used.
Composite Resins ; Dental Polishing ; Hardness ; In Vitro Techniques ; Microscopy, Electron, Scanning ; Nanocomposites ; Polytetrafluoroethylene

PURPOSE: The purpose of this study was to compare mechanical and physical properties of injection-molded thermoplastic denture base resins. MATERIALS AND METHODS: In this study, six commercially available products (VA; Valplast, LC; Lucitone, ST; Smiltone, ES; Estheshot-Bright, AC; Acrytone, WE; Weldenz) were selected from four types of thermoplastic denture base materials (Polyamide, Polyester, Acrylic resin and Polypropylene). The flexural properties and shore D hardness have been investigated and water sorption and solubility, and color stability have evaluated. RESULTS: For the flexural modulus value, ES showed the highest value and WE showed significantly lower value than all other groups (P < .05). Most of experimental groups showed weak color stability beyond the clinically acceptable range. CONCLUSION: Within the limits of this study, thermoplastic denture base resin did not show sufficient modulus to function as a denture base. In addition, all resins showed discoloration with clinical significance, and especially polyamides showed the lowest color stability.
Denture Bases ; Dentures ; Hardness ; Nylons ; Polyesters ; Solubility ; Water

OBJECTIVES: This paper presents a systematic review and meta-analysis of the effect of preheating on the hardness of nanofilled, nanoceramic, nanohybrid, and microhybrid resin composites. MATERIALS AND METHODS: An electronic search of papers on MEDLINE/PubMed, ScienceDirect, and EBSCOhost was performed. Only in vitro studies were included. Non-English studies, case reports, clinical trials, and review articles were excluded. A meta-analysis of the reviewed studies was conducted to quantify differences in the microhardness of the Z250 microhybrid resin composite using the Comprehensive Meta-Analysis software. RESULTS: Only 13 studies met the inclusion criteria for this systematic review. The meta-analysis showed that there were significant differences between the non-preheated and preheated modes for both the top and bottom surfaces of the specimens (p < 0.05). The microhardness of the Z250 resin composite on the top surface in the preheated mode (78.1 ± 2.9) was higher than in the non-preheated mode (67.4 ± 4.0; p < 0.001). Moreover, the microhardness of the Z250 resin composite on the bottom surface in the preheated mode (71.8 ± 3.8) was higher than in the non-preheated mode (57.5 ± 5.7, p < 0.001). CONCLUSIONS: Although the results reported in the reviewed studies showed great variability, sufficient scientific evidence was found to support the hypothesis that preheating can improve the hardness of resin composites.
Hardness ; In Vitro Techniques

Objective of this study was to compare the color stability, mechanical and chemical properties of three different types of temporary crown resins. Commercially available powder-liquid (Group PL), light-cured (Group LC) and auto-mix syringe (Group AM) types' temporary crown resins were used as experimental groups for each of the evaluation. All the test groups were evaluated after 1 day and 7 days of immersion in various staining solutions. The colors of all groups before and after storage in the staining solutions were measured by a spectrophotometer based on CIE Lab system, and the color differences (ΔE(*)) thereby calculated. Micro hardness test was performed before water storage and aging after 7 days at 37 ℃. In addition, flexural strength, water sorption and solubility tests were performed according to international standard, ISO 10477. All experimental groups showed significant color change in staining solutions when compared to those stored in the control solution (distilled water) (p<0.05). Group PL showed the least color change among the three groups followed by Group AM (p<0.05). This tendency was observed after 7 days of immersion. In terms of the micro hardness test, Group PL showed the highest value among the three groups followed by Group AM (p<0.05). Additionally, the flexural strength decreased in the following order: AM > PL > LC (p<0.05). Water sorption and solubility increased in the following order: AM < PL < LC (p<0.05). The results of this study would provide useful information when choosing temporary crown resin types in various clinical situations.
Aging ; Crowns ; Hardness Tests ; Immersion ; Solubility ; Syringes ; Water

BACKGROUND/AIMS: Endoscopic ultrasound (EUS) has a limited ability to determine the nature of solid pancreatic lesions (SPLs). Most recent ultrasound processors are provided with elastography software, which allows quantification of the tissue hardness. The aim of this study is to evaluate the effectiveness of the elasticity score (ES) and strain ratio (SR) in the differentiation of benign pancreatic lesions from malignant pancreatic lesions. METHODS: The study had a retrospective design; it included 97 patients with SPLs and 19 patients with inflammatory lesions. The ES and SR were determined during the examination; finally, EUS-guided fine needle aspiration was performed. RESULTS: In this 2-year study, 116 patients were enrolled (97 with malignant lesions and 19 with benign lesions). There were 69 men and 47 women. Their median age was 55.9 years. A cut-off point was detected at SR of 7.75 with a specificity of 99.9%, sensitivity of 90.7%, positive predictive value (PPV) of 99.9%, negative predictive value (NPV) of 67.9%, and accuracy of 92.2%. After adding the ES to the SR, the cut-off point at 7.75 resulted in a specificity of 94.6%, sensitivity of 99%, PPV of 98%, NPV of 98.5%, and accuracy of 97%. CONCLUSIONS: The use of the ES combined with the SR increases the accuracy of differentiation between benign and malignant SPLs and is an effective method for the evaluation of pancreatic masses.
Biopsy, Fine-Needle ; Elasticity ; Elasticity Imaging Techniques ; Female ; Hardness ; Humans ; Male ; Methods ; Pancreas ; Retrospective Studies ; Sensitivity and Specificity ; Ultrasonography

BACKGROUND: Erosion is a gradual process that occurs fairly quickly, and the full extent of the erosive effects of acidic beverages is not yet clear. The present study aimed to determine the differences in the erosive potentials among four naturally acidic fruit nectars within the same range of titratable acidity and to determine the influence of the components of organic acids on tooth erosion. METHODS: Diluted fruit nectars (mandarin 1:1.1, orange 1:1.7, lemon 1:15, grapefruit 1:20) with the same range of titratable acidity (7.9 ml) and their corresponding organic acids (0.05%, 0.1%, 0.3%, and 0.5% citric acid, malic acid, and a citric and malic acid mixture [pH 2.8], respectively) were used. Specimens were placed in conical tubes with 50 ml of each of the test solutions for 1 hour. A microhardness test and scanning electron microscopy were used to measure enamel erosion. Acid separation was carried out using high-performance liquid chromatography to analyze the composition of each test solution. RESULTS: Similar decreases in the Vickers hardness number (VHN) were observed among the groups treated with the following diluted fruit nectars: diluted mandarin nectar (75.9 ΔVHN), diluted lemon nectar (89.1 ΔVHN), diluted grapefruit nectar (91.7 ΔVHN), and diluted orange nectar (92.5 ΔVHN). No statistically significant differences were found in the enamel surface hardness after erosion (p>0.05). Citric and malic acids were the major organic acids in the test fruits. The lemon and orange groups had the highest malic acid concentrations, and the mandarin group had the lowest malic acid concentration. CONCLUSION: The titratable acidity and the citric and malic acid contents of the fruits could be crucial factors responsible for enamel erosion. Therefore, fruit-based drinks should be regarded as potentially erosive.
Beverages ; Chromatography, Liquid ; Citric Acid ; Citrus paradisi ; Citrus sinensis ; Dental Enamel ; Fruit ; Hardness ; In Vitro Techniques ; Microscopy ; Microscopy, Electron, Scanning ; Plant Nectar ; Tooth Erosion