The Effects of Three Remineralizing Agents on the Microhardness and Chemical Composition of Demineralized Enamel

This study aimed to determine the effects of three different varnish materials (containing casein phosphopeptide-amorphous calcium phosphate, nano-hydroxyapatite, and fluoride) on enamel. Thirty-three extracted human third molars were used for specimen preparation. These were demineralized using phosphoric acid. Three experimental groups (n = 11) were treated with 3M™ Clinpro™ White Varnish, MI Varnish^®, and Megasonex^® toothpaste, respectively, every twenty-four hours for fourteen days. Analysis of the microhardness of the specimens’ enamel surfaces was carried out via the Vickers method, and by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Analysis was performed at three stages: at baseline value, after demineralization, and after the period of remineralization. Data were subjected to Scheffe’s post hoc test. The mean microhardness values (HV0.1) obtained for the group of samples treated with MI Varnish^® were higher compared with the other two groups (p = 0.001 for both comparisons), while the first and third groups did not differ significantly from each other (p = 0.97). SEM analysis showed uneven patterns and porosities on all samples tested. EDS results showed an increase in the mineral content of the examined samples, with the highest mineral content observed in the MI Varnish^® group. It can be concluded that MI Varnish^® use has a better remineralization effect on enamel than the other two materials.     

Effect of Bioactive Glass-Containing Light-Curing Varnish on Enamel Remineralization

This study aimed to evaluate the effect of novel experimental light-curing bioactive glass (BAG)-containing varnish on enamel remineralization. An experimental light-curing, BAG-containing varnish and two commercial varnishes (Nupro White Varnish; Dentsply International, York, PA, USA and Tooth Mousse; GC Corporation, Tokyo, Japan) were used. Microhardness tests (n = 3), field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray spectroscopy (EDS) (n = 5), and X-ray diffraction (XRD) analysis (n = 5) were performed to compare the remineralization effect of three varnishes with and without ultrasonication. The data of microhardness test were analyzed using one-way ANOVA and Tukey’s post hoc comparison (P < 0.05). Microhardness of demineralized enamel increased after the application of three varnishes (P < 0.05). The experimental BAG-containing varnish showed the highest microhardness among the three varnishes (P < 0.05). Ultrasonication decreased microhardness of Tooth Mousse and BAG-containing varnish groups (P < 0.05). FE-SEM and XRD revealed precipitates of hydroxyapatite (HAP) or fluorapatite (FAP) crystals of three varnishes. The novel experimental BAG-containing varnish may be a promising clinical strategy for the remineralization of early carious lesions or demineralized enamel surfaces.     

Effect of Silver Diamine Fluoride and Potassium Iodide Solution on Enamel Remineralization and Discoloration in Artificial Caries

Silver diamine fluoride (SDF) is a strong fluoride agent for caries control, remineralization, and reducing the incidence of dental caries. This study used 38% SDF with potassium iodide (KI) on enamel remineralization and compared it with the currently used 38% SDF and 5% sodium fluoride (NaF) varnish to treat artificial caries. Bovine incisors were demineralized for 120 h and randomly distributed for treatment by the remineralization agents for 120 h as follows: control (n = 15), SDF/KI (n = 15), SDF (n = 15), and NaF (n = 15). Colorimetric analysis was performed using the ΔE value. The Vickers microhardness (VHN) was determined to evaluate the enamel remineralization of the specimens. Polarized light microscopy (PLM) and scanning electron microscopy (SEM) were performed to confirm the surfaces precisely and histologically. SDF/KI caused no significant difference in discoloration between the control and NaF groups. There was also no significant difference in the VHN after remineralization, but SDF/KI exhibited the highest mean microhardness. PLM revealed that SDF/KI had the greatest remineralization ability. In conclusion, SDF/KI is effective for dental enamel remineralization even with KI, which reduces discoloration.     

Excessive Dental Bleaching with 22% Carbamide Peroxide Combined with Erosive and Abrasive Challenges: New Insights into the Morphology and Surface Properties of Enamel

This study aimed to evaluate the effects of 22% carbamide peroxide combined with an erosive challenge and simulated brushing on enamel. Bovine incisor teeth were divided into G1, tooth bleaching; G2, tooth bleaching + erosive challenge; and G3, tooth bleaching + erosive challenge + simulated brushing, and evaluated at T0, before any intervention; T1, 14 days after the proposed treatments; and T2, 28 days after the proposed treatments. Tooth bleaching was performed daily for 1 h for 28 days. The microhardness, surface roughness, mass variation, and ultrastructure were analyzed at T0, T1, and T2. Two-way analysis of variance for repeated measures was performed and Tukey’s post hoc test (α = 5%) was used. The surface roughness increased in groups G2 and G3 as a function of time, whereas microhardness and mass measurements demonstrated a significant reduction for groups associated with challenges. Ultrastructural evaluation indicated a loss of the aprismatic layer and exposure of the enamel prisms in all groups after 14 days of bleaching, with more pronounced results in G2 and G3 after 28 days. In conclusion, abrasive and erosive challenges potentiated the deleterious effects of tooth whitening on microhardness, ultramorphology, and mass, without affecting the roughness of dental enamel.     

饮水氟含量与儿童龋齿和氟斑牙关系的调查

目的　调查不同饮水氟含量与龋齿和氟斑牙发病的关系 ,探讨在河南省实施饮水加氟的可行性。方法　选择河南省农村 4个不同饮水氟含量的自然村 ,调查 8～ 12岁儿童龋齿和氟斑牙患病率。结果　 4个不同饮水氟含量的村庄 8～ 12岁儿童龋齿患病率有随饮水氟含量升高而下降的趋势 ,但差异无显著意义 (P >0 .0 5 ) ,而氟斑牙患病率随饮水氟含量的升高而明显升高 (P <0 .0 1)。结论　水氟浓度的升高在导致氟斑牙的作用方面明显强于对龋齿的预防作用 ,而河南省是地方性氟中毒流行最严重的省份之一 ,在河南省实行饮水加氟导致氟斑牙流行的危险性较大     

Effect of Enamel Pretreatment with Pastes Presenting Different Relative Dentin Abrasivity (RDA) Values on Orthodontic Bracket Bonding Efficacy of Microfilled Composite Resin: In Vitro Investigation and Randomized Clinical Trial

Bonding failure is a clinical issue frequently encountered in orthodontic practice. The aim of this study was to evaluate enamel pretreatment both in vitro and clinically using agents with different RDA values before brackets’ bonding, to assess if RDA can affect the Shear Bond Strength (SBS), Adhesive Remnant Index (ARI) and clinical failure rate of orthodontic brackets. For the in vitro study, 220 bovine teeth were pretreated with agents with different RDA values. Subsequently, brackets were bonded. For the clinical study, 20 patients underwent bonding of 20 brackets each with a split-mouth design. Low and high RDA toothpastes were used for enamel pretreatment. SBS, ARI and failures were recorded. Higher SBS values were found for teeth pretreated with lower RDA agents; conversely, lower SBS values were found for teeth pretreated with higher RDA agents (p < 0.05). For high ARI values, RDA increased too (p > 0.05). In the clinical study, a significantly lower failure rate was reported for teeth pretreated with low RDA toothpaste (2.5% in low RDA group, 7.0% in high RDA group; p < 0.05). No significant differences were assessed comparing the two dental arches and anterior and posterior sites. Enamel pretreatment with low RDA toothpastes could increase brackets’ survival rate. Further in vitro and clinical studies would be welcomed to confirm these findings.     

The Measurement of Contact Angle,pH, and Conductivity of Artificial Saliva and Mouthwashes on Enamel,Glass-Ionomer,and Composite Dental Materials

The aim of this study was to tackle the topic of appropriate recommendations for artificial-saliva and mouthwash usage. The contact angle, pH, and conductivity of two artificial saliva solutions, four mouthwashes, and their mixtures on enamel, glass-ionomer, and composite dental materials were measured. The measurements were conducted with a MATLAB algorithm to minimize human error. The obtained values for the contact angle were in the range from 7.98° to 52.6°, and they showed completely nonlinear and nonuniform behavior for all investigated liquids and on all investigated substrates. Results reveal statistically significant differences among all tested liquids on all investigated substrates (p < 0.05). pH values ranged from 1.54 to 7.01. A wide range of conductivity values were observed, from 1205µS/cm in the saliva-stimulating solution to 6679 mS/cm in the artificial saliva. Spearman’s test showed a moderate positive correlation between the pH and conductivity of the tested fluids (R = 0.7108). A comparison of the data obtained using Image J software and the MATLAB algorithm showed consistency, not exceeding 5% error. When an experiment uses human material and bioactive materials THAT are used in biomedicine as substrates, an additional definition of protocols is highly recommended for future research on this topic.     

Effect of Ibuprofen on Cyclooxygenase and Nitric Oxide Synthase of Gastric Mucosa: Correlation with Endoscopic Lesions and Adverse Reactions

The aim of this study was to evaluate the effect of ibuprofen on gastric mucosa and enzymes involved in gastroprotection in healthy volunteers. Twenty-four Helicobacter pylori-negative subjects were randomized to treatment with ibuprofen or ibuprofen-arginate (each 600 mg/6 hr during 3 days). Endoscopies were performed 1 week before and after treatment. Biopsies were taken from the gastric antrum and corpus for determination of prostaglandin E2 (PGE2) by ELISA and cyclooxygenase (COX-1 and COX-2) and nitric oxide synthase (eNOS and iNOS) by western blot. All subjects had at least one gastric lesion except for two individuals taking ibuprofen-arginate. Ibuprofen-arginate caused a lower rate of clinical adverse reactions than ibuprofen. Subjects with gastric lesions or adverse reactions had lower PGE2 levels. COX-1, COX-2, eNOS, and iNOS were detectable in all subjects. The constitutive enzymes (COX-1 and eNOS) did not change after treatment. COX-2 was higher in corpus than antrum and it increased after ibuprofen treatment. iNOS tended to increase mildly in the corpus in subjects with adverse reactions or endoscopic lesions. There were no significant differences between ibuprofen and ibuprofen-arginate in PGE2, or enzymes.     

Effects of Temperature on Albunex and FS069 Echocardiographic Contrast Agents: In Vitro Investigation Using Ultrasonic Irradiation

The effects of temperature on the stability of two contrast agents, Albunex and perfluoropropane filled albumin microspheres (FS069), were investigated by studying the variations in their reflective properties, induced by high dose ultrasound irradiation at different temperatures. Diluted contrast agents were introduced into a 3.5-mL latex balloon, placed in a plastic water tank, and continuously irradiated over a period of 6 minutes using different power levels: 0, 20, 25, and 30 dB. The irradiation was interrupted for imaging every 30 seconds for 2 seconds. The protocol was carried out at three different temperatures: 8°C, 22°C, and 37°C. For each temperature, the concentration of contrast solution was matched to produce approximately the same initial video intensity. Time variations in mean video intensity in the balloon cross section were studied. Contrast enhancement was found to be directly related to temperature. Under continuous ultrasonic irradiation, video intensity gradually decreased over time. This decrease was dependent on both transmitted power and temperature, and was more pronounced with Albunex when compared to FS069 (P < 0.05). Abruptly dropping temperature consistently resulted in rapid, irreversible disappearance of contrast induced by Albunex. Temperature affects the reflectivity and stability of diluted Albunex and FS069. To enhance the reproducibility of contrast enhancement achieved by these agents, their temperature should be carefully controlled.     

The Biomechanical Impact of Loss of an Implant in the Treatment with Mandibular Overdentures on Four Nonsplinted Mini Dental Implants: A Finite Element Analysis

The aim of this study was to evaluate the biomechanical impact, in terms of stress and displacement, at the level of a mandibular overdenture, on four mini dental implants (MDIs) after the loss of an implant. A three-dimensional virtual model was obtained by scanning the overdenture, and a biomechanical analysis was carried out, using the finite element method (FEM). The displacements of the overdenture and the equivalent von Mises stresses were evaluated using logarithmic scales. In the case of a mandibular overdenture on four MDIs inserted in the interforaminal area, the frontal loading generated the lowest values for the von Mises stresses, and the bilateral loading generated the least displacement when two implants were inserted in the canine area and two in the molar area. The highest von Mises stress was observed during frontal loading in the situation of the mandibular overdenture on four MDIs, two of which were inserted in the canine area and two in the molar area, following the loss of an implant in the canine area. The largest displacement was noted in the mandibular overdenture on four interforaminal MDIs during unilateral loading, following the loss of a distally inserted implant. The FEM analysis showed aspects that correlated with clinical observations, with predictive value. The concentration of von Mises stresses, and the occurrence of some displacements of the prosthodontic restoration, can explain the emergence of some complications in the overdenture’s biodynamics, and the increased risk of fracture. Complications can be prevented by choosing a certain number of implants and a topographical distribution correlated with biomechanical aspects, and by proposing a correct occlusal scheme with optimal functional loading.