Impact of Type and Duration of Application of Commercially Available Oral Moisturizers on Their Antifungal Effects.

PURPOSE: To examine the impact of oral moisturizer type and application time on antifungal effects. MATERIALS AND METHODS: Seventeen oral moisturizers (7 liquids, 10 gels) and amphotericin B (AMPH-B) were tested. Antifungal effects were evaluated with newly opened moisturizer samples (0 hour) and with samples incubated for 8 hours to simulate contact during sleep. Candida albicans samples (108 cells/ml) were placed into cylindrical holes in 50% trypticase soy agar plates. Antifungal effects were evaluated based on growth-inhibitory zones after 24 hours. Equal quantities of moisturizers showing growth-inhibitory zones were mixed as additional samples. The effects of moisturizer type and application time on growth-inhibitory zones were evaluated with ANOVA. Growth-inhibitory zone sizes were compared with multiple comparisons. RESULTS: Growth-inhibitory zones were found with two liquids, one gel, moisturizer mixtures, and AMPH-B. Significant differences in antifungal effects were found among different moisturizer types and between the 0- and 8-hour groups. The growth-inhibitory zones of the 8-hour group were significantly smaller than those of the 0-hour group. In both the 0- and 8-hour groups, the growth-inhibitory zones of the liquid-gel mixtures were significantly larger than those of other moisturizer types, and were the same size as those of AMPH-B at two concentrations (1.25 and 2.5 µg/ml). Growth-inhibitory zones of individual moisturizers and liquid-liquid mixtures were the same size as those of lower AMPH-B concentrations (0.16, 0.31, and 0.63 µg/ml). CONCLUSION: Our findings suggest that mixing liquid and gel moisturizers improves their antifungal efficiency.

Impact of Types of Moisturizer and Humidity on the Residual Weight and Viscosity of Liquid and Gel Oral Moisturizers.

PURPOSE: Oral moisturizers need to be selected based on their material properties. The purpose of this study was to investigate the effects of moisturizer type and humidity on the residual weight and viscosity of oral moisturizers. MATERIALS AND METHODS: The weight and viscosity of 17 oral moisturizers (7 liquid and 10 gel) at baseline and after 8 hours were measured using an incubator maintained at 37°C at either 85% or 40% relative humidity (RH). The rate of change in weight (RCW) and the rate of change in viscosity (RCV) were calculated. Data were analyzed with two-way analysis of variance (ANOVA) and Scheffe's test to evaluate the effect of the type of moisturizer (liquid or gel) and humidity (85% or 40% RH) on RCW and RCV. Pearson's correlation coefficient was used to evaluate the relationship between RCW and RCV. RESULTS: Two-way ANOVA results indicated that the type of moisturizer and RH had a significant effect on RCW and RCV (p < 0.05); however, the interaction between them was not significant. The results of multiple comparisons showed that gel moisturizers had a significantly lower RCW and higher RCV than liquid moisturizers (p < 0.05). The RCW and RCV at 40% RH were significantly higher than those at 85% RH (p < 0.05). There was no correlation between RCW and RCV in the liquid moisturizer group, but a significant negative correlation was found in the gel moisturizer group (pp = 0.01). CONCLUSION: Because viscosity of gel moisturizers increases as weight decreases, selecting gel moisturizers with a minimal change in weight and viscosity would be preferable in the case of a long-time application and severe dry mouth.

Cemental Tear in an Autotransplanted Tooth That Had Been Functioning for 15 Years.

INTRODUCTION: Cemental tears have been described as specific types of root surface fractures that are seen infrequently but can cause rapid collapse of the periodontal tissue. However, to the best of the authors' knowledge, cases of cemental tears in autotransplanted teeth and their recovery by autotransplantation have not been reported previously. This case report presents the clinical and histopathologic features of a rare case of a cemental tear that occurred on an autotransplanted tooth. This meant a total long-term treatment course of 20 years involving two separate treatment procedures. CASE PRESENTATION: In 1995, the mandibular left second molar of a 40-year-old woman was extracted, and autogenous tooth transplantation was performed simultaneously using a third molar from the same side. Good clinical and radiologic progress was observed for >10 years after tooth transplantation. After discovery of a vertical bone defect in the distal area in 2006, conservative periodontal treatment was conducted on the diseased periodontal pocket over the course of several years. In 2010, autogenous tooth transplantation and a subsequent histopathologic examination of the extracted tooth were performed. After recovery treatment, a 5-year follow-up examination provided good results. CONCLUSIONS: This case report concerns the suspected contributing factors of cemental tears and the recovery treatment. When cemental tears are suspected after radiographic and other clinical examinations, interventional surgical treatment should be performed immediately. When autogenous tooth transplantation is performed, following careful consideration of the advantages and disadvantages of appropriate treatment and proper selection, continuous monitoring should be a prerequisite because of the possible occurrence of cemental tear.

Clinical and Histologic Aspects of Cervical Cemental Tear as a Risk for Periodontal Diseases.

INTRODUCTION: Cemental tear (CeT) has been classified as a specific type of root fracture. It can lead to rapid periodontal breakdown, and recently not many reports have focused on periodontal concerns. This case report presents macroscopy, light microscopy (LM), and scanning electron microscopy (SEM) observations of fragments of CeT. Progression of periodontal disease is discussed in terms of anatomic characteristics of the cementum. CASE PRESENTATION: CeT was observed at a maxillary right central incisor of an 83-year-old male. After clinical examination and initial treatment, surgical periodontal therapy was performed in association with fragment extirpation, apicoectomy, replantation, and simultaneous regenerative treatment. Extirpated torn fragments and granulation tissue masses were subsequently examined by LM and SEM. Bacterial colonies were observed in and around peripheral crevices of cemental fragments. CONCLUSIONS: Characteristics of cervical CeT are similar to common periodontitis features, such as rapid, periodic, sporadic, and site-specific advance, with occasional spiral pattern of pathologic pockets. In this case report, these features correspond to progression of bacterial pollution along the periphery of the overlapping scales of the cementum. In cases with such advanced periodontitis features, CeT should be discussed as a possible diagnosis. Optimum treatment should be more interventional, such as removal of degraded and torn cemental layers, when definite diagnosis is made by intrasurgical inspection.

A comparison of stress relaxation in temporary and permanent luting cements.

PURPOSE: The stress relaxation and compressive strength of resin, resin-modified glass ionomer, glass ionomer, polycarboxylate, and zinc oxide eugenol cements were measured to determine the characteristics of these materials after setting. METHODS: A total of 19 luting cements including 12 permanent cements and 7 temporary cements were used. Cylindrical cement specimens (10mm long and 6mm in diameter) were obtained by chemical setting or light curing. The specimens were stored for 24-36 h in water at 37°C and were then used for the stress relaxation and compression tests. The stress relaxation test was carried out using three constant cross-head speeds of 5, 50, and 100 mm/min. Upon reaching the preset dislocation of 0.5 mm, the cross-head movement was stopped, and the load was recorded for 60s. Fractional stress loss at 1s was calculated from the relaxation curves. The compressive strength and modulus were measured at a cross-head speed of 1mm/min. Data were analyzed with the Kruskal-Wallis test and Holm's test. RESULTS: A zinc oxide eugenol cement [TempBOND NX] exhibited the largest fractional stress loss. A resin cement [ResiCem] showed the largest compressive strength, while a glass ionomer cement [HY-BOND GLASIONOMER CX] showed the largest compressive modulus among all tested cements (p<0.05). CONCLUSION: The fractional stress loss could not be classified by the cement type. Two implant cements [Multilink Implant and IP Temp Cement] showed similar properties with permanent resin cements and temporary glass ionomer cements, respectively. Careful consideration of the choice of cement is necessary.

A method for improving the light intensity distribution in dental light-curing units.

A method for improving the uniformity of the radiation light from dental light-curing units (LCUs), and the effect on the polymerization of light-activated composite resin are investigated. Quartz-tungsten halogen, plasma-arc, and light-emitting diode LCUs were used, and additional optical elements such as a mixing tube and diffusing screen were employed to reduce the inhomogeneity of the radiation light. The distribution of the light intensity from the light guide tip was measured across the guide tip, as well as the distribution of the surface hardness of the light-activated resin emitted with the LCUs. Although the additional optical elements caused 13.2-25.9% attenuation of the light intensity, the uniformity of the light intensity of the LCUs was significantly improved in the modified LCUs, and the uniformity of the surface hardness of the resin was also improved. Our results indicate that the addition of optical elements to the LCU may be a simple and effective method for reducing inhomogeneity in radiation light from the LCUs.

Flexural properties of ethyl or methyl methacrylate-UDMA blend polymers.

Light-curing polyethyl methacrylate (PEMA)-urethane dimethacrylate (UDMA) resins and polymethyl methacrylate (PMMA)-UDMA resins were prepared by two processes. For first step, PEMA or PMMA powders were fully dissolved in ethyl methacrylate (EMA) or methyl methacrylate (MMA) and then the PEMA-EMA/PMMA-MMA mixtures were mixed with UDMA. The flexural properties of cured PEMA-UDMA and PMMA-UDMA polymers were measured using two PEMA (Mw: 300,000-400,000 and 650,000-1,000,000) and three PMMA (Mw: 30,000-60,000, 350,000 and 650,000-1,000,000) powders with different molecular weight, four mixing ratios of PMMA-MMA, and three mixing ratios of PMMA-MMA mixture and UDMA oligomer. Polymers with PMMA(Mw: 350,000) MMA=25/50, and with PMMA(Mw: 350,000)-MMA/UDMA=1/2 and =1/1, showed no-fracture in a flexural test at 1 mm/min and flexural strength and flexural modulus showed no significant difference compared with those of commercially available heat- and self-curing acrylic resins (p>0.01). Within limitation of this investigation, methyl methacrylate-UDMA blend polymer of this composition is available for denture base resin.

Light transmittance characteristics and refractive indices of light-activated pit and fissure sealants.

We examined the light transmittance characteristics and refractive indices of light-activated pit and fissure sealants. Five commercial pit and fissure sealants and human enamel were studied, along with the CIE L*a*b* color values of the materials and enamel. The light transmittance spectra of the pit and fissure sealants showed a similar trend to the enamel, especially at wavelengths below 530 nm. The average light transmittance values from 400 to 500 nm of the materials at 0.5-mm-thick ranged from 10.0% to 40.4%. The refractive indices at 589.3 nm ranged from 1.504 to 1.546, and were approximately 4-8% lower than that of enamel. The measurements for the surface hardness of materials indicate that the light-attenuating effect of enamel and the material itself reduced the polymerization efficiency of the material. For all materials, chromatic a* showed negative and b* showed positive values, as did enamel. Significant differences in light transmittance characteristics and refractive indices between the materials and enamel may affect color matching between them.

Effect of various visible light photoinitiators on the polymerization and color of light-activated resins.

The purpose of this study was to investigate effects of various visible light photoinitiators on the polymerization efficiency and color of the light-activated resins. Four photoinitiators, including camphorquinone, phenylpropanedione, monoacrylphosphine oxide (TPO), and bisacrylphosphine oxide (Ir819), were used. Each photoinitiator was dissolved in a Bis-GMA and TEGDMA monomer mixture. Materials were polymerized using dental quartz-tungsten halogen lamp (QTH), plasma-ark lamp and blue LED light-curing units, and a custom-made violet LED light unit. The degree of monomer conversion and CIE L*a*b* color values of the resins were measured using a FTIR and spectral transmittance meter. The degree of monomer conversions of TPO- and Ir819-containing resins polymerized with the violet-LED unit were higher than camphorquinone-containing resin polymerized with the QTH light-curing unit. The lowest color values were observed for the TPO-containing resin. Our results indicate that the TPO photoinitiator and the violet-LED light unit may provide a useful and improved photopolymerization system for dental light-activated resins.

Mechanical properties and cytotoxicity of experimental soft lining materials based on urethane acrylate oligomers.

The purpose of this investigation was to determine whether experimental light-curing soft lining materials (ESLMs) based on commercially available urethane acrylate oligomers (UA-160TM, UV-3200B, UV-3500BA, and UV-3700B) are suitable for clinical use by measuring their viscosity, compressive modulus, Shore A hardness, tensile strength, adhesive strength, and cytotoxicity. The viscosities of the four ESLMs at 25 degrees C were 10.5 Pa.s, UV-3500BA; 144.0 Pa.s, UA-160TM; 328.8 Pa.s, UV-3700B; and 1079.7 Pa.s, UV-3200B. Polymerized UV-3700B was very soft, whereas the softness of the other ESLMs was similar to that of conventional soft lining materials. No significant difference in adhesive strength was observed between UV-3500BA and UV-3700B at 1 day and those at 12 months. Cytotoxicity was measured by a MTT-based assay using HeLa S3 and Ca9-22 cells. UV-3200B and UV-3700B oligomers and all four polymerized ESLMs showed cell viability over 95.2% (p < 0.05).

Bactericidal efficacy of glycine-type amphoteric surfactant as a denture cleaner and its influence on properties of denture base resins.

The bactericidal efficacy of 1.00-4.50% glycine-type amphoteric surfactant (Gly) was evaluated by measuring its microorganism removal rate in denture plaque. Physical and mechanical properties such as surface roughness, color difference, and bending strength of two different denture base resins were determined before and after cleaning in Gly solutions, a commercial denture cleaner, and tap water. The microorganism removal rates of all the Gly solutions were higher than those of a commercial enzymatic denture cleaner (Polident) (p>0.05). The removal rate of Candida spp. by Polident was not significantly different from the removal rate using water. Changes in the surface roughness and color difference among the specimens were slight. There were no significant differences in the bending strengths of the two resins for all concentrations of Gly solution (p>0.05). These results suggested that glycine-type amphoteric surfactant solution may be effective as a denture cleaner in conjunction with an ultrasonic cleaning device.

Effect of inhomogeneity of light from light curing units on the surface hardness of composite resin.

This study investigated the characteristics of output light from different types of light curing units, and their effects on polymerization of light-activated composite resin. Three quartz-tungsten-halogen lamps, one plasma arc lamp, and one LED light curing unit were used. Intensity distribution of light emitted from the light guide tip was measured at 1.0-mm intervals across the guide tip. Distribution of Knoop hardness number on the surface of resin irradiated with the light curing units was also measured. For all units, inhomogeneous distribution of light intensity across the guide tip was observed. Minimum light intensity values were 19-80% of the maximum values. In terms of surface hardness, inhomogeneous distribution was also observed for the materials irradiated with the tested units. Minimum values were 53-92% of the maximum values. Our results indicated that markedly inhomogeneous light emitted from light curing unit could result in inhomogeneous polymerization in some areas of the restoration below the light guide tip.

Effects of adding methacrylate monomers on viscosity and mechanical properties of experimental light-curing soft lining materials based on urethane (meth)acrylate oligomers.

We investigated the viscosity and mechanical properties of experimental light-curing soft lining materials based on six commercially available urethane (meth)acrylate oligomers. The viscosities of the six oligomers were 1.9, 20.6, 26.8, 144.0, 185.3, and 8803.4 Pa*s at 25 degrees C. Two monomers (ethyl- and butyl-methacrylate) were added at 20 wt% to these oligomers to decrease the viscosity, resulting in viscosity reductions of 0.2 to 13.6 Pa*s for the six oligomers. The mechanical properties (compressive modulus, Shore A hardness, and tensile strength) were measured after two times light-polymerization for 3 min. The addition of the monomers to the oligomers only slightly changed the mechanical properties, in contrast to the large viscosity changes. Based on these results, it appears that the addition of ethyl- or butyl-methacrylate monomers is useful for decreasing the viscosity of experimental light-curing soft lining materials without changing their mechanical properties.

Effect of filler properties in composite resins on light transmittance characteristics and color.

The purpose of this investigation was to examine the effect of filler particle size and shape as well as filler content on light transmittance characteristics and color of experimental composite resins. A mixture of 30 mol% Bis-GMA and 70 mol% TEGDMA was prepared as a base monomer and to which a photoinitiator (camphorquinone) and a co-initiator (N,N-dimethylaminoethyl methacrylate) were added. Four different irregular- and spherical-shaped filler types with an average particle size of 1.9-11.1 microm were added to the mixture in three different filler contents of 20, 30, and 40 vol%. Light transmittance characteristics including light diffusion characteristics of the materials were evaluated. Color values and color differences among filler contents of the materials were also determined. Materials containing smaller and irregular-shaped fillers showed higher light transmittance and diffusion angle distribution with a sharper peak, as compared with those containing larger and spherical-shape fillers. It was also found that there was a significant correlation between the specific surface area of fillers and the color difference of the materials containing the fillers. Our results indicated that the shape of filler particles, as well as particle size and filler content, significantly affected the light transmittance characteristics--including light diffusion characteristics--and color of composite resins.

Mechanical properties of woven glass fiber-reinforced composites.

The aim of this investigation was to measure the flexural and compressive strengths and the corresponding moduli of cylindrical composite specimens reinforced with woven glass fiber. Test specimens were made by light-curing urethane dimethacrylate oligomer with woven glass fiber of 0.18-mm standard thickness. Tests were conducted using four reinforcement methods and two specimen diameters. Flexural strength and modulus of woven glass fiber-reinforced specimens were significantly greater than those without woven glass fiber (p < 0.01). Likewise, compressive strength of reinforced specimens was significantly greater than those without woven glass fiber (p < 0.01), except for specimens reinforced with woven glass fiber oriented at a tilt direction in the texture (p > 0.05). In terms of comparison between the two specimen diameters, no statistically significant differences in flexural strength and compressive strength (p > 0.05) were observed.

Deformation and flexural properties of denture base polymer reinforced with glass fiber sheet.

The purpose of this study was to investigate the deformation and flexural properties of acrylic and urethane polymers reinforced with glass fiber sheet. Four types of specimen--self-curing resin plate (R), light-curing oligomer plate containing a reinforcement (GO), and self-curing resin plate containing a reinforcement on one (GR) or both (GRG) sides--were prepared with three thicknesses: 1.5, 2.4, and 3.0 mm. Gaps between polymerized test specimen and a standard metal plate were measured at the corner (C), middle of the long sides (LS), and middle of the short sides (SS). The gaps for R were 0-2.0 microm. GO and GR markedly deformed at Points C, LS, and SS, and the degree of deformation increased as GO became thinner. Flexural strength was significantly increased by the reinforcement (p < 0.05). The flexural moduli of 3.0-mm thick R, GO, and GR were significantly smaller than that of 1.5-mm thick specimens.

Mechanical properties of an experimental soft lining material based on urethane oligomer.

The purpose of this study was to investigate the apparent viscosities and mechanical properties of two experimental light-curing soft lining materials (SLM-1 and SLM-2) based on soft-type urethane oligomers, as well as the shear bond strength and dye penetration between the denture base resin and the polymerized SLMs after storage in water. The apparent viscosities of SLM-1 and SLM-2 were 144.0-146.9 and 1.9 Pa x s respectively. After storage in water for two prescribed periods (one day and three months), the mechanical properties of the SLMs on the overall were 10.6-20.6 MPa for elastic modulus, 69.3-72.1 for hardness, and 3.8-4.0 MPa for adhesive strength. Tensile strength was observed to decrease after three months' storage in water, when compared to that after one-day storage (p < 0.01). Water sorption rates also differed significantly (p < 0.05)--namely 3.0 and 2.8 mg/cm2 for SLM-1 after one day and three months respectively, and 2.0 and 2.2 mg/cm2 for SLM-2. As for dye penetration, no infiltration was observed at the denture base resin-SLM interface after three months' storage. Based on the results of this study, it seemed like the SLMs possess many suitable properties for use with a new technique that we recently developed for preparing denture base resin and soft lining material.

Effect of radiation light characteristics on surface hardness of paint-on resin for shade modification.

The purpose of this study was to investigate the effect of radiation light characteristics--of different types of clinical light-curing unit--on polymerization efficiency, as determined by the surface hardness of light-cured paint-on resins. Four shades of paint-on resin for shade modification of restorative resins were used. Materials were cured using one laboratory and three clinical light-curing units with different light sources, namely tungsten-halogen, LED, plasma arc, and xenon flash lamps. Knoop hardness measurements were taken at both the top and bottom surfaces of the specimens to assess the mechanical properties and degree of polymerization. Both LED and plasma arc light units caused significantly poorer surface hardness than the halogen and laboratory xenon lights. In addition, the transparent shade was more sensitive to surface hardness than other chromatic shades. Our results indicated that the polymerization efficiency of paint-on resin was significantly influenced by the radiation light characteristics of clinical light-curing units.

Mechanical properties and bond strength of silicone-based resilient denture liners.

To evaluate the ease of manipulation and durability of 11 commercially available silicone-based resilient denture liners, extrusion force, hardness, weight change, and bond strength were determined. Extrusion force from the cartridge of each material ranged from 0.25 to 1.26 MPa at an extrusion rate of 1 cm/min. Durometer hardness, after set materials were stored in distilled water at 37 degrees C for one day, ranged from A5.9 to A47.7, and after four weeks their values increased by 4.0 to 275%. Bond strength ranged from 1.01 to 2.88 MPa after set materials were stored in distilled water at 37 degrees C for one day, but decreased to 0.59 to 1.99 MPa after 10,000 thermal cycles. These results suggested that except for one material, the rest of the evaluated materials exhibited good handling properties--for example, mixing and spreading of material can be done easily. However, some materials exhibited inadequate durability for clinical service, because hardness increased during storage and/or bond strength decreased after thermal cycling.

Light-curing reinforcement for denture base resin using a glass fiber cloth pre-impregnated with various urethane oligomers.

The purpose of this study was to investigate the flexural properties of denture base resin reinforced using glass fiber cloth and a urethane oligomer. The five types of oligomer used in this study were S5, S9, S3, U4, and U6, which have varying functional groups and viscosities. The flexural properties of S9 with glass fiber cloth could not be measured because S9 is elastic. In the heat-cured resin reinforced with S9, the reinforcement peeled away from the resin. In the self- and light-cured resins reinforced with S9, the flexural properties increased significantly. When reinforced with the other four oligomers (S5, S3, U4, and U6), the flexural strength and flexural modulus of the self-, heat-, and light-cured resins increased significantly (p<0.01).