pa href=http://www.hubmed.org/fulltext.cgi?uids=22043472J Adhes Dent/a. 2011 Sep 26; brHariri I, Shimada Y, Sadr A, Ichinose S, Tagami JpPurpose: To evaluate the effects of increasing thermocycling regimens on bond strength and nanoleakage of an etch-and-rinse adhesive. Materials and Methods: Adper Single Bond (3M ESPE) was used for bonding resin composite to human enamel and dentin. Specimens were stored in water (37°C, 24 h) and subjected to thermocycling (5°C and 55°C) in five groups: 1. control (no thermal cycling), 2. 100, 3. 500, 4. 2000, or 5. 10,000 cycles. The microshear bond test was performed at a crosshead speed of 1 mm/min (n = 16). Nanoleakage specimens were immersed in silver nitrate and FE-SEM micrographs were digitally analyzed to calculate silver penetration in three samples. Results: The mean bond strength to enamel was not significantly affected by thermocycling. However, artificial aging decreased dentin bond strength in groups 4 and 5 compared to control. Weibull analysis indicated that the characteristic strength decreased gradually with aging in both substrates. All groups exhibited some nanoleakage, and a significant increase in silver penetration compared to the control was observed in enamel and dentin groups 2 to 5. Conclusion: A nanoleakage increase was detected in an earlier stage of aging than when a significant drop in bond strength was observed, with the dentin bond being more susceptible to deterioration.
The Effects of Aging on Shear Bond Strength and Nanoleakage Expression of an Etch-and-Rinse Adhesive on Human Enamel and Dentin.
pa href=http://www.hubmed.org/fulltext.cgi?uids=22043472J Adhes Dent/a. 2011 Sep 26; brHariri I, Shimada Y, Sadr A, Ichinose S, Tagami JpPurpose: To evaluate the effects of increasing thermocycling regimens on bond strength and nanoleakage of an etch-and-rinse adhesive. Materials and Methods: Adper Single Bond (3M ESPE) was used for bonding resin composite to human enamel and dentin. Specimens were stored in water (37°C, 24 h) and subjected to thermocycling (5°C and 55°C) in five groups: 1. control (no thermal cycling), 2. 100, 3. 500, 4. 2000, or 5. 10,000 cycles. The microshear bond test was performed at a crosshead speed of 1 mm/min (n = 16). Nanoleakage specimens were immersed in silver nitrate and FE-SEM micrographs were digitally analyzed to calculate silver penetration in three samples. Results: The mean bond strength to enamel was not significantly affected by thermocycling. However, artificial aging decreased dentin bond strength in groups 4 and 5 compared to control. Weibull analysis indicated that the characteristic strength decreased gradually with aging in both substrates. All groups exhibited some nanoleakage, and a significant increase in silver penetration compared to the control was observed in enamel and dentin groups 2 to 5. Conclusion: A nanoleakage increase was detected in an earlier stage of aging than when a significant drop in bond strength was observed, with the dentin bond being more susceptible to deterioration.
Effect of light units on tooth bleaching with visible-light activating titanium dioxide photocatalyst.
pa href=http://www.hubmed.org/fulltext.cgi?uids=21946494Dent Mater J/a. 2011 Sep 23; brKishi A, Otsuki M, Sadr A, Ikeda M, Tagami JpThis study evaluated the influence of different light sources on the efficiency of an office bleaching agent containing visible-light activating titanium dioxide photocatalyst (VL-TiO(2)) using an artificial discoloration tooth model. Extracted bovine teeth were stained by black tea. The CIE L*a*b* values were measured before and after nine consecutive treatments by the VL-TiO(2)-containing bleaching agent (TiON in Office, GC, Tokyo, Japan). A halogen light unit (CB; CoBee, GC) or an LED unit (G-light, GC) with two modes (blue and violet: GL-BV, blue: GL-B) were used to activate the bleaching agent in three groups (n=8). Brightness (ΔL) and color difference (ΔE) increased as bleaching repeated in all groups. Two-way ANOVA showed that both number of treatments and light sources significantly affected ΔE (p0.05). GL-BV showed better bleaching effect than GL-B. In measurement of irradiation spectra, CB showed a wide spectrum (380-530 nm), GL-B had a sharp peak at 470 nm and GL-BV showed an additional peak at 405 nm. It was concluded that the light source influenced the efficiency of the tooth bleaching with VL-TiO(2).
Long-term regional bond strength of three MMA-based adhesive resins in simulated vertical root fracture.
pa href=http://www.hubmed.org/fulltext.cgi?uids=21946486Dent Mater J/a. 2011 Sep 23; brNurrohman H, Nikaido T, Sadr A, Takagaki T, Kitayama S, Ikeda M, Waidyasekera K, Tagami JpThe purpose of this study was to investigate bond durability of MMA-based adhesives to root dentin in a simulated complete vertical root fracture (CVRF). The fractured fragments of human premolar root were reattached using Super-Bond CB (SB; Sun Medical), M-Bond or M-Bond II (MB or MB II; Tokuyama Dental). After storage for 1 day, 1 month, 6 months and 1 year, the reattached specimens were subjected to microtensile bond strength (µTBS) test at cervical and apical regions. Results showed that µTBS was significantly higher to cervical dentin than to apical dentin in MB and MB II, but not SB (p0.05). Significant decrease in µTBS was found for MB and MB II after 1 year, whereas no significant difference was found for SB (p0.05). Analysis of failure mode by SEM indicated differences over time. In conclusion, significant differences were found in the regional bond durability among MMA-based adhesives used to restore CVRF, that may lead to different clinical performances.
Effect of functional monomers in all-in-one adhesive systems on formation of enamel/dentin acid-base resistant zone.
pa href=http://www.hubmed.org/fulltext.cgi?uids=21946477Dent Mater J/a. 2011 Sep 23; brNikaido T, Ichikawa C, Li N, Takagaki T, Sadr A, Yoshida Y, Suzuki K, Tagami JpThis study aimed at evaluating the effect of functional monomers in all-in-one adhesive systems on formation of acid-base resistant zone (ABRZ) in enamel and dentin. Experimental adhesive systems containing one of three functional monomers; MDP, 3D-SR and 4-META were applied to enamel or dentin surface and light-cured. A universal resin composite was then placed. The specimens were subjected to a demineralizing solution (pH 4.5) and 5% NaClO for acid-base challenge and then observed by SEM. The ABRZ was clearly observed in both enamel and dentin interfaces. However, enamel ABRZ was thinner than dentin ABRZ in all adhesives. Morphology of the ABRZ was different between enamel and dentin, and also among the adhesives. Funnel-shaped erosion was observed only in the enamel specimen with the 4-META adhesive. The formation of enamel/dentin ABRZ was confirmed in all adhesives, but the morphology was influenced by the functional monomers.
Effects of a chewing gum containing phosphoryl oligosaccharides of calcium (POs-Ca) and fluoride on remineralization and crystallization of enamel subsurface lesions in situ.
pa href=http://www.hubmed.org/fulltext.cgi?uids=21875640J Dent/a. 2011 Aug 19; brKitasako Y, Tanaka M, Sadr A, Hamba H, Ikeda M, Tagami JpOBJECTIVES: Manufacturers are adding fluoride (F) to calcium-containing chewing gums to further promote enamel remineralization. The aim of this study was to assess the effect of a chewing gum containing phosphoryl oligosaccharides of calcium (POs-Ca) and fluoride on remineralization of enamel subsurface lesions, in a double-blind, randomized controlled in situ trial. METHODS: Thirty-six volunteer subjects wore removable buccal appliances with three different insets of bovine enamel with subsurface demineralized lesions. For 14 days the subjects chewed one of the three chewing gums (placebo, POs-Ca, POs-Ca+F), three times a day. After each treatment period, the insets were removed from the appliance, embedded, sectioned, polished and then subjected to laboratory tests; mineral level was determined by transverse microradiography (TMR; n=36), and hydroxyapatite (HAp) crystallites were assessed by synchrotron radiation wide-angle X-ray diffraction (WAXRD; n=13). Data were analysed by t-test or Wilcoxon rank-sum test with Bonferroni corrections at 0.05 significance level. RESULTS: Chewing POs-Ca and POs-Ca+F gums resulted in 21.9±10.6 and 26.3±9.4 (mean±SD) percentage mineral recovery, which was significantly higher than that of placebo gum (15.0±11.4) (p0.05). Chewing POs-Ca+F gum resulted in 24.9±5.4 (mean±SD) percentage HAp crystallites recovery, which was significantly higher compared to POs-Ca (16.0±4.1%) or placebo (11.1±4.8%) gums (p0.05). CONCLUSIONS: Addition of POs-Ca to the chewing gum resulted in significant remineralization of enamel subsurface lesions. Although POs-Ca+F gum was not superior in TMR recovery rate when compared with POs-Ca gum, WAXRD results highlighted the importance of fluoride ion bioavailability in the formation of HAp crystallites in enamel subsurface lesions in situ (NCT01377493).
Evaluation of resin composite polymerization by three dimensional micro-CT imaging and nanoindentation.
pa href=http://www.hubmed.org/fulltext.cgi?uids=21820729Dent Mater/a. 2011 Aug 4; brCho E, Sadr A, Inai N, Tagami JpOBJECTIVES: Light-cured composites undergo shrinkage during polymerization. The aim of this study was to evaluate regional shrinkage within a light-cured composite during polymerization by microcomputed tomography and mechanical properties by nanoindentation in bonded or non-bonded class-I cavity. METHODS: Zirconium oxide spherical fillers (30μm diameter) were added as markers to a composite resin, filled into a box-shaped class I cavity with or without a bonding agent. The marker fillers were traced in 3D scans obtained by micro-CT before and after polymerization using a software (TRI/3D-BON). The average hardness of the resin composites determined by nanoindentation at each 250μm depth was plotted against depth. RESULTS: In the bonded cavity, the filler particles at the top region moved toward the bottom of cavity, but at deeper depths, the direction of vertical movement changed toward the top of cavity (irradiated surface). A significant linear regression was found between filler displacement and composite depth (R(2)=0.9761). In the unbounded cavity, all the fillers moved toward the light curing source, and a significant power-law regression was found between filler displacement and composite depth (R(2)=0.849). In both groups, the data scattering increased at regions deeper than 3.5mm, where the hardness, representing degree of conversion of composite, significantly decreased compared to the surface region. SIGNIFICANCE: The magnitude and direction of regional polymerization shrinkage depends on boundary conditions, depth and conversion degree. Polymerization shrinkage effect is most significant at the deepest part of the cavity. The application of micro-CT combined with sophisticated image analysis is a novel approach to investigate shrinkage mechanisms of dental composites.
Estimation of lesion progress in artificial root caries by swept source optical coherence tomography in comparison to transverse microradiography.
J Biomed Opt. 2011 Jul; 16(7): 071408
Natsume Y, Nakashima S, Sadr A, Shimada Y, Tagami J, Sumi Y
This study aimed to investigate whether swept source optical coherence tomography (SS-OCT) could estimate the lesion depth and mineral loss quantitatively without the use of polarization sensitivity, and to examine a relationship between OCT data and transverse microradiography (TMR) lesion parameters. Twenty-four bovine root dentin specimens were allocated to three groups of 4-, 7-, and 14-day demineralization. Cross-sectional images of the specimens before and after the demineralization were captured by OCT at 1319 nm center wavelength. Following the demineralization, these specimens were cut into sections for TMR analysis. Correlations between the OCT data and TMR lesion parameters were examined. TMR images of the specimens showed cavitated lesions (lesion depth or LD(TMR): 200 to 500 μm, ΔZ or mineral loss: 10,000 to 30,000 vol % μm). The OCT images showed “boundaries,” suggesting the lesion front. Integrated dB values before and after the demineralization and their difference (R(D), R(S), and ΔR, respectively) were calculated from the lesion surface to the corrected depth of boundary (LD(OCT)). A statistically significant correlation was found between LD(OCT) and LD(TMR) (p < 0.05, r = 0.68). Similarly, statistically significant correlations were found between ΔZ and R(D) or ΔR. The OCT showed a potential for quantitative estimation of lesion depth and mineral loss with cavitated dentin lesions in vitro.
Relationship between perception of difficulty and clinical experience of approximal composite restorations in final-year undergraduate students at Tokyo Medical and Dental University
J Med Dent Sci 2011； 58： 1－5 Kitasako Y, Sadr A, Nikaido T, Tagami J.
The aims of this study were to clarify which steps in approximal restorative procedure were difficult for the final-year undergraduate students at Tokyo Medical and Dental University, and to examine the relationship between perception of difficulty and clinical experience. At mid-term of the clinical education experience, a self-questionnaire was performed by final-year undergraduate students to clarify the difficulty of restorative procedures at the time. There were statistically significant differences in the number of clinical cases experienced at the time between students who designated the matrix application, shade selection and finishing as the easy steps and those who considered them as the difficult ones (Fisher exact test with Bonferroni correction, p<0.05). There was a significant difference in the total number of procedures designated as difficult between students who had treated above 15 cases and those who had fewer than 15 cases (Wilcoxon rank-sum test, p<0.05). In the final-year clinical education for operative dentistry, students might need to treat over 15 cases to gain confidence in performing approximal composite restorations independently.
Effect of Curing Modes of Dual-curing Core Systems on Microtensile Bond Strength to Dentin and Formation of an Acid-Base Resistant Zone.
J Adhes Dent. 2011 May 4;
Li N, Takagaki T, Sadr A, Waidyasekera K, Ikeda M, Chen J, Nikaido T, Tagami J
Purpose: To evaluate the microtensile bond strength (μTBS) and acid-base resistant zone (ABRZ) of two dualcuring core systems to dentin using four curing modes. Materials and Methods: Sixty-four caries-free human molars were randomly divided into two groups according to two dual-curing resin core systems: (1) Clearfil DC Core Automix; (2) Estelite Core Quick. For each core system, four different curing modes were applied to the adhesive and core resin: (1) dual-cured and dual-cured (DD); (2) chemically cured and dual-cured (CD); (3) dual-cured and chemically cured (DC); (4) chemically cured and chemically cured (CC). The specimens were sectioned into sticks (n = 20 for each group) for the microtensile bond test. μTBS data were analyzed using two-way ANOVA and the Dunnett T3 test. Failure patterns were examined with scanning electron microscopy (SEM) to determine the proportion of each mode. Dentin sandwiches were produced and subjected to an acid-base challenge. After argon-ion etching, the ultrastructure of ABRZ was observed using SEM. Results: For Clearfil DC Core Automix, the μTBS values in MPa were as follows: DD: 29.1 ± 5.4, CD: 21.6 ± 5.6, DC: 17.9 ± 2.8, CC: 11.5 ± 3.2. For Estelite Core Quick, they were: DD: 48.9 ±5.7, CD: 20.5 ± 4.7, DC: 41.4 ± 8.3, CC: 19.1 ± 6.0. The bond strength was affected by both material and curing mode, and the interaction of the two factors was significant (p < 0.001). Within both systems, there were significant differences among groups, and the DD group showed the highest μTBS (p < 0.05). ABRZ morphology was not affected by curing mode, but it was highly adhesive-material dependent. Conclusion: The curing mode of dual-curing core systems affects bond strength to dentin, but has no significant effect on the formation of ABRZ.
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Effect of Curing Modes of Dual-curing Core Systems on Microtensile Bond Strength to Dentin and Formation of an Acid-Base Resistant Zone.
