Difference assessment of composite resins and sound tooth applicable in the resin-imbedded tooth for resin repair using fluorescence, microhardness, DIAGNOdent, and X-ray image.

OBJECTIVE: Visual differentiation of resin and tooth in a tooth cavity is not simple due to their highly similar shade. The purpose of the present study was to find any noninvasive method which can effectively differentiate resin from sound tooth in a resin-imbedded tooth for resin repair. MATERIALS AND METHODS: For the study, various resin products were imbedded into the cavity of sound tooth. By applying laser of different wavelengths, autofluorescence (AF) of sound tooth and resin products were obtained. Microhardness, X-ray radiograph, and DIAGNOdent were tested for each tooth, resin product, and resin-imbedded tooth. RESULTS: For the AF spectra obtained using the 405-nm wavelength, sound tooth has emission peak at 440-470 nm and near 490 nm. Sound tooth has several times higher microhardness than resin products regardless of position in tooth subsurface. Due to the difference of radiopaque fillers' composition and concentration, resin products have different brightness in the X-ray radiograph. DIAGNOdent readings for tooth and resin products were inconsistently different, and the difference of obtained values was slightly not to be applicable for the differentiation. CONCLUSION: Among the tested methods, with noninvasive treatment, AF spectrum by the 405-nm wavelength showed the apparent difference between resin and tooth. CLINICAL SIGNIFICANCE: For the resin repair in a resin-imbedded tooth cavity, AF spectrum produced by 405-nm wavelength could be a useful method in tracing the resin-tooth boundary if combined with conventional X-ray radiography.

In Vitro Investigation of Wear of CAD/CAM Polymeric Materials Against Primary Teeth.

The aim of the study was to evaluate the effects of polymeric computer-aided design/computer-aided manufacturing CAD/CAM materials on antagonistic primary tooth wear. Five CAD/CAM polymeric materials were examined: Vipi Block Monocolor (VBM), Yamahachi polymethylmethacrylate (PMMA) (YAP), Mazic Duro (MZD), Vita Enamic (ENA), and Pekkton (PEK). All of the specimens were tested in a thermomechanical loading machine with the primary canine as the antagonist (50 N, 1.2 × 105 cycles, 1.7 Hz, 5/55 °C). The wear losses of the antagonist tooth and the restorative materials were calculated using reverse modelling software and an electronic scale. VBM and ENA showed significantly higher antagonist tooth wear than PEK (p < 0.05), but there was no significant difference observed among VBM, YAP, MZD, and ENA (p > 0.05). PEK showed the largest value in both material volumetric and weight losses. In terms of material volumetric losses, there was no significant difference between all of the groups (p > 0.05). In terms of material weight losses, PEK was significantly larger than ENA (p < 0.05), but there was no significant difference between VBM, YAP, MZD, and ENA (p > 0.05). Volumetric and weight losses of materials showed similar wear behaviour. However, the wear patterns of antagonists and materials were different, especially in PEK.

Wear of primary teeth caused by opposed all-ceramic or stainless steel crowns.

PURPOSE: This study was conducted to evaluate the effects of full-coverage all-ceramic zirconia, lithium disilicate glass-ceramic, leucite glass-ceramic, or stainless steel crowns on antagonistic primary tooth wear. MATERIALS AND METHODS: There were four study groups: the stainless steel (Steel) group, the leucite glass-ceramic (Leucite) group, the lithium disilicate glass-ceramic (Lithium) group, and the monolithic zirconia (Zirconia) group. Ten flat crown specimens were prepared per group; opposing teeth were prepared using primary canines. A wear test was conducted over 100,000 chewing cycles using a dual-axis chewing simulator and a 50 N masticating force, and wear losses of antagonistic teeth and restorative materials were calculated using a three-dimensional profiling system and an electronic scale, respectively. Statistical significance was determined using One-way ANOVA and Tukey's test (P<.05). RESULTS: The Leucite group (2.670±1.471 mm(3)) showed the greatest amount of antagonist tooth wear, followed by in decreasing order by the Lithium (2.042±0.696 mm(3)), Zirconia (1.426±0.477 mm(3)), and Steel groups (0.397±0.192 mm(3)). Mean volume losses in the Leucite and Lithium groups were significantly greater than in the Steel group (P<.05). No significant difference was observed between mean volume losses in the Zirconia and Steel groups (P>.05). CONCLUSION: Leucite glass-ceramic and lithium disilicate glass-ceramic cause more primary tooth wear than stainless steel or zirconia.

Effect of dual-peak LED unit on the polymerization of coinitiator-containing composite resins.

The purpose of the present study was to evaluate the effect of dual-peak LED on the polymerization of coinitiator-containing composite resins. For this, microhardness, degree of conversion (DC), and polymerization shrinkage were evaluated. Specimens (coinitiator-containing: Aelite LS Posterior, Tetric EvoCeram, and Vit-l-escence; only camphorquinone-containng: Filtek Z350 and Grandio) were light cured using a quartz-tungsten-halogen (QTH: OP), a single-peak light-emitting diode (LED) (L. E. Demetron: DM), and a dual-peak LED (G-light: GL), respectively. All specimens light cured using GL showed the highest microhardness both on the top and bottom surfaces compared with the values obtained using the rest light-curing units (LCUs). DC had no consistent trend correspond to the LCU, but rather product specific. OP yielded the lowest polymerization shrinkage on the specimens. The coinitiator-containing composite resins achieved the highest microhardness by the dual-peak LED (GL). However, the influence of GL on DC and polymerization shrinkage of the specimens was not consistent.

The evaluation of resin infiltration for masking labial enamel white spot lesions.

OBJECTIVE: The aim of this study was to clinically assess the effectiveness of masking white spot enamel lesions using a resin infiltration technique that was recently developed to arrest incipient caries in a micro-invasive concept. METHODS: Twenty teeth with a Developmental Defect of Enamel (DDE) and 18 teeth with Post-orthodontic Decalcification (POD) were selected and treated with resin infiltration. Standardized photographs were taken before, immediately after, and 1 week after treatment and were analysed using image analysing software to calculate the ΔE values. The results were classified into three groups: completely masked, partially masked, and unchanged. RESULTS: Among the 20 teeth with DDE, five teeth (25%) were classified as completely masked, whereas seven (35%) and eight teeth (40%) were partially masked and unchanged, respectively. Among the 18 teeth with POD, 11 teeth (61%) were completely masked, six teeth (33%) were partially masked, and one tooth (6%) was unchanged. In some teeth, the result was more improved after 1 week than immediately after infiltration. CONCLUSION: The masking effect was dramatic in some cases but not in others. The long-term colour stability of the result should be followed up through continuous clinical and scientific studies.

The effect of resin shades on microhardness, polymerization shrinkage, and color change of dental composite resins.

The present study sought to evaluate the effect of resin shades on the degree of the polymerization. To this end, response variables affected by the degree of polymerization were examined in this study - namely, microhardness, polymerization shrinkage, and color change. Two commercial composite resins of four different shades were employed in this study: shades A3, A3.5, B3, and C3 of Z250 (Z2) and shades A3, A3.5, B3, and B4 of Solitaire 2 (S2). After light curing, the reflectance/absorbance, microhardness, polymerization shrinkage, and color change of the specimens were measured. On reflectance and absorbance, Z2 and S2 showed similar distribution curves regardless of the resin shade, with shade A3.5 of Z2 and shade A3 of S2 exhibiting the lowest/highest distributions. Similarly for attenuation coefficient and microhardness, the lowest/highest values were exhibited by shade A3.5 of Z2 and shade A3 of S2. On polymerization shrinkage, no statistically significant differences were observed among the different shades of Z2. Similarly for color change, Z2 specimens exhibited only a slight (DeltaE*=0.5-0.9) color change after immersion in distilled water for 10 days, except for shades A3 and A3.5. Taken together, results of the present study suggested that the degree of polymerization of the tested composite resins was minimally affected by resin shade.

(-)-Epigallocatechin-3-gallate (EGCG) increases the viability of serum-starved A549 cells through its effect on Akt.

The effect of epigallocatechin gallate (EGCG) on cell survival was studied by using serum-starved A549 non-small cell lung carcinoma (NSCLC) cells. A MTT assay showed that EGCG significantly increased the viability of serum-starved A549 cells compared to the control cells, though EGCG at high concentration (approximately 300 microM) had no protective effect against serum withdrawal-induced cell apoptosis. Western blots showed increased immunoreactivity for phospho-Akt and phospho-GSK3beta in EGCG-treated cells. To determine the mechanism for Akt phosphorylation, cells were pretreated with various kinase inhibitors before exposure to EGCG. Only LY294002 inhibited Akt activation induced by EGCG, implying that EGCG-induced Akt activation is PI3K dependent. Both phospho-Raf-1 and Raf-1 proteins were significantly decreased, whereas B-raf expression was not altered. This suggests that the Raf kinases have no role in the increased cell survival caused by EGCG. This study has shown that EGCG protects A549 cells from apoptosis induced by serum deprivation via Akt activation and this protective effect may limit the clinical use of EGCG in treating and preventing NSCLC.

Biosynthesis of rubradirin as an ansamycin antibiotic from Streptomyces achromogenes var. rubradiris NRRL3061.

The four overlapping cosmids from the rubradirin producer, Streptomyces achromogenes var rubradiris NRRL 3061, have 58 ORFs within a 105.6 kb fragment. These ORFs harbored essential genes responsible for the formation and attachment of four distinct moieties, along with the genes associated with regulatory, resistance, and transport functions. The PKS (rubA) and glycosyltransferase (rubG2) genes were disrupted in order to demonstrate a complete elimination of rubradirin production. The rubradirin biosynthetic pathway was proposed based on the putative functions of the gene products, the functional identification of sugar genes, and the mutant strains.

Effects of LEDs on microhardness and temperature rise of dental composite resins.

The purpose of this study was to examine the effects of LEDs on the polymerization of dental composite resins. Three composite resins and two LED units were used to evaluate the latter's effects on microhardness and temperature rise. In particular, two composite resins contained a coinitiator in addition to camphorquinone (CQ). The emission peak of the tested LEDs matched well with the absorption peak of CQ, while G-Light had one additional but weak peak near 410 nm. As for the coinitiators, their absorption peaks were lower than 400 nm. Within the specimens, incident photons from the LED units showed an exponential decrease in their counts as the specimens became thicker. However, microhardness values decreased and became almost linear at subsurface levels regardless of the curing unit. Among the composite resins, Z250 showed the highest microhardness value. As for the temperature rise (degrees C) due to exothermic reaction at polymerization, it was higher than 5 degrees C for the 40-second light curing with both LED units. Among the specimens, Solitaire 2 cured with G-Light showed the highest temperature rise.

A preventive approach to oral self-mutilation in Lesch-Nyhan syndrome: a case report.

Lesch-Nyhan syndrome is a rare X-linked recessive disorder of purine metabolism, caused by complete absence of the enzyme hypoxanthine-guanine phosphoribosyl transferase. Persons affected with this incurable disease are developmentally and physically delayed, and suffer from self-injurious behavior. The most typical feature results in partial or total destruction of perioral tissues. The purpose of this paper was to discuss a case of Lesch-Nyhan syndrome with self-mutilative behavior and lip injuries, including some suggestions of a preventive approach avoiding the extraction of teeth. A soft mouthguard fabricated to prevent the destruction of perioral soft tissues and combined psychiatric pharmacologic therapy proved to have satisfactory results.