pa href=http://www.hubmed.org/fulltext.cgi?uids=22572538Dent Mater/a. 2012 May 7; brNurrohman H, Nikaido T, Takagaki T, Sadr A, Ichinose S, Tagami JpOBJECTIVES: Interaction between specific functional groups and apatite crystals may contribute to adhesion. The present study investigated effects of four adhesives with different compositions on protection of crystals beneath the hybrid layer against acid-attack using transmission electron microscopy (TEM) and selected area electron diffraction (SAED). METHODS: Human dentin was bonded with four adhesives; two with a carboxylic-based functional co-polymer (PAA): three-step etch-and-rinse Scotchbond Multi-Purpose (SMP, 3M ESPE) and one-step self-etch Adper Easy Bond (AEB, 3M ESPE), and two with a phosphate-based functional monomer (MDP): two-step etch-and-rinse Clearfil Photo Bond (CPB, Kuraray Medical) and two-step self-etch Clearfil SE Bond (CSE, Kuraray Medical). The specimens were the either left untreated (control) or subjected to acid-base challenge with demineralizing solution (pH 4.5) and 5% NaClO. All specimens were processed and observed by TEM. SAED was used to identify the presence or absence of apatite crystallites at the base or beneath hybrid layer before and after acid-base challenge. RESULTS: An apatite-rich zone was observed beneath the partially demineralized hybrid layer of CSE. The zone was thinner in AEB, but a demineralization-susceptible area was found beneath it. The etch-and-rinse adhesives (SMP and CPB) demonstrated completely or predominantly demineralized hybrid layers, which were devoid of the acid-resistant apatite-rich zone. SIGNIFICANCE: TEM/SAED evidence disclosed that the preserved dentin apatite crystals beneath the thin hybrid layer of the mild self-etch adhesives were protected against acid. Diffusion of reactive components beyond the hybrid layer, and their chemical bonding potential with the remaining crystals created the acid-base resistant zone.
Effect of hydration on assessment of early enamel lesion using swept-source optical coherence tomography.
pa href=http://www.hubmed.org/fulltext.cgi?uids=22517731J Biophotonics/a. 2012 Apr 20; brNazari A, Sadr A, Campillo-Funollet M, Nakashima S, Shimada Y, Tagami J, Sumi YpEstablishing reproducible methodologies for assessment of early enamel lesions using optical coherence tomography (OCT) appears to be challenging. This in vitro study longitudinally evaluated the subsurface enamel lesion progression after 3, 9 and 15 days by cross-sectional scanning using 1310 nm centered swept-source OCT (SS-OCT) under hydrated and dry conditions. The positive difference between the depth-integrated OCT signals at dry and hydrated conditions were calculated and adopted as dehydration parameter (DH). A linear regression was found between DH and the square root of demineralization time (R(2) = 0.99). Significant differences were found in DH between sound and demineralized enamel, and between different periods of demineralization (p 0.001). Hydration state affects the reflectivity of demineralized porous enamel, and the effect can be potentially used for assessment of early enamel lesion using OCT. (© 2012 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim).
Enamel Lesion Parameter Correlations between Polychromatic Micro-CT and TMR.
pa href=http://www.hubmed.org/fulltext.cgi?uids=22476867J Dent Res/a. 2012 Apr 3; brHamba H, Nikaido T, Sadr A, Nakashima S, Tagami JpTransverse microradiography (TMR) is considered as the gold standard technique for the evaluation of enamel lesions. Micro-computed tomography (µCT) has the advantage of non-destructive measurements, but the beam-hardening effect with polychromatic x-rays is a major drawback. To date, no study has validated µCT against TMR. The objective of this study was to validate µCT measurements of enamel lesions under various x-ray conditions and software beam-hardening correction (BHC) against TMR. Human molars with natural white-spot lesions were scanned for 5 min by µCT at 100 kV in different conditions: 50 µA (0.5-mm Al filter), 165 µA (0.5-mm Al/0.3-mm Cu), and 200 µA (0.5-mm Al/0.4-mm Cu), with or without BHC. Grayscale values were converted into mineral density values using phantoms. Thin sections at the same positions were then prepared for TMR. Lesion depth (LD; µm) and mineral loss (ΔZ; vol%µm) were compared between µCT and TMR by Pearsons correlations. µCT measurements correlated well with TMR under all conditions (p 0.001, r 0.86 for LD and ΔZ), except for 0.5-mm Al without BHC (p 0.05). Even without BHC, combined Al/Cu filters successfully reduced the beam-hardening effect. µCT can be used as a non-destructive alternative to TMR with comparable parameters for the study of enamel lesions.
Morphological categorization of acid-base resistant zones with self-etching primer adhesive systems.
pa href=http://www.hubmed.org/fulltext.cgi?uids=22447057Dent Mater J/a. 2012 Mar 23; brInoue G, Nikaido T, Sadr A, Tagami JpThis study investigated the influence of the composition of self-etching primer adhesive systems on the morphology of acid-base resistant zones (ABRZs). One-step self-etching primer systems (Clearfil Tri-S Bond, G-Bond, and One-Up Bond F Plus) and two-step self-etching primer systems (Clearfil SE Bond, Clearfil Protect Bond, UniFil Bond, and Mac Bond II) were used in this study. Each adhesive was applied on prepared dentin disk surfaces, and a resin composite was placed between two dentin disks. All resin-bonded specimens were subjected to acid-base challenge. Observation under a scanning electron microscope (SEM) revealed the creation of an ABRZ adjacent to the hybrid layer for all the self-etch primer adhesive systems, even when non-fluoride releasing adhesives were used. The presence of fluoride in two-step self-etching adhesive significantly increased the thickness of ABRZ created. Results suggested that an ABRZ was created with the use of self-etching primer adhesive systems, but its morphology differed between one-and two-step self-etching primer adhesive systems and was influenced by fluoride release activity.
Effects of structural orientation of enamel and dentine on light attenuation and local refractive index: An optical coherence tomography study.
pa href=http://www.hubmed.org/fulltext.cgi?uids=22342164J Dent/a. 2012 Feb 7; brHariri I, Sadr A, Shimada Y, Tagami J, Sumi YpOBJECTIVES: To investigate optical properties of human enamel and dentine in relationship to structural orientation of enamel prisms and dentinal tubules by optical coherence tomography (OCT). METHODS: Discs of 300-400μm thickness including enamel with cross-cut or long-cut prisms and mid-coronal dentine with cross-cut, long-cut or oblique-cut tubules were obtained from 28 non-carious freshly extracted human third molars sectioned at different directions. Each disc was placed over a metal plate and B-scan images were obtained by a swept-source OCT at 1330nm centre wavelength (Dental SS-OCT Prototype 1, Panasonic Healthcare Co., Ltd, Japan). Refractive index (n) calculated from optical path length and real thickness, and OCT signal slope (OCTSS) in relation to structural orientation were statistically compared among groups (α=0.05). The discs were sectioned and observed under SEM to confirm prism or tubule orientations. RESULTS: No significant differences were found in n and OCTSS among cross-cut and long-cut enamel groups (p0.05). However, in dentine, there was a significant difference in both variables among different regions. In cross-cut tubule orientation, the average n and OCTSS values were significantly lower compared to other two groups (long-cut and oblique-cut) (p0.05). There was a significant difference in both variables between enamel and dentine (p0.05). CONCLUSIONS: Unlike enamel, refractive index and OCT signal patterns in dentine vary according to structural orientation, with dentine tubules playing the role. Attenuation of OCT signal intensity was small in enamel. The findings may contribute to a better understanding of the interactions of light with the dental tissue. CLINICAL SIGNIFICANCE: Precise records of refractive indices and OCT signal patterns may be important for clinical diagnosis of caries and measurement of structural depth for operative purposes using this technology. Effects of dentine structural orientation on refractive index and scattering pattern must be considered when observing human teeth by OCT cross-sectional imaging.
Gum Containing Calcium Fluoride Reinforces Enamel Subsurface Lesions in situ.
pa href=http://www.hubmed.org/fulltext.cgi?uids=22337700J Dent Res/a. 2012 Feb 15; brKitasako Y, Sadr A, Hamba H, Ikeda M, Tagami JpThe aim of this study was to assess the effect of chewing gum containing phosphoryl oligosaccharides of calcium (POs-Ca) and a low concentration of fluoride (F) on the hardness of enamel subsurface lesions, utilizing a double-blind, randomized, and controlled in situ model. Fifteen individuals wore removable lingual appliances with 3 bovine-enamel insets containing subsurface demineralized lesions. Three times a day for 14 days, they chewed one of the 3 chewing gums (placebo, POs-Ca, POs-Ca+F). After the treatment period, cross-sectional mineral content, nanoindentation hardness, and fluoride ion mapping by time-of-flight secondary ion mass spectrometry (TOF-SIMS) were evaluated. Although there were no statistical differences in overall mineral content and hardness recovery rates between POs-Ca and POs-Ca+F subsurface lesions (p 0.05), nanoindentation at 1-μm distance increments from the surface showed statistical differences in hardness recovery rate between POs-Ca and POs-Ca+F in the superficial 20-μm region (p 0.05). Fluoride mapping revealed distribution of the ion up to 20 μm from the surface in the POs-Ca+F group. Nanoindentation and TOF-SIMS results highlighted the benefits of bioavailability of fluoride ion on reinforcement of the superficial zone of subsurface lesions in situ (NCT01377493).
Ultramorphological Evaluation of the Dentin Acid-Base Resistant Zone of Two-step Self-etching Systems After Long-term Storage in Water.
pa href=http://www.hubmed.org/fulltext.cgi?uids=22282751J Adhes Dent/a. 2012 Jan 11; brIchikawa C, Nikaido T, Inoue G, Sadr A, Tagami JpPurpose: To evaluate the morphological changes in the acid-base resistant zone (ABRZ) at the resin/dentin interface after long-term storage in water. Materials and Methods: Two-step self-etching adhesive systems, Clearfil SE Bond (SE) and Clearfil Protect Bond (PB) (Kuraray Medical) were used. Human dentin disk sandwiches with resin composite were prepared, sectioned, and embedded in epoxy resin. The specimens were stored in water for 1 day, 1, 3 or 6 months, and then subjected to demineralizing solution and 5% NaOCl. The specimens were finally sectioned again, polished, argon-ion etched, and observed with SEM. Results: The outer lesion (OL) thickness at 1 day ranged from 10 to 15 μm but increased to approximately 30 μm after 6 months, suggesting gradual loss of dentin stored in water. A lower electron density was noted in the adhesives at the locations that were exposed to water. The ABRZs were observed clearly in all groups; the thickness of the ABRZ at the mid-point of the OL gradually decreased with time for SE. For PB, the thickness was stable up to 1 month, but decreased after 3 months. The bottom of the ABRZ in SE formed a right angle with dentin; in contrast, in PB, it sloped down toward dentin with a broadening bottom. Conclusions: Water storage resulted in changes both in the dentin substrate and the adhesive layer. An ABRZ was observed beneath the hybrid layer after long-term storage in water in both SE and PB. The ABRZ was thicker and relatively more stable in PB, probably due to fluoride release.
Intraoral pH measurement of carious lesions with qPCR of cariogenic bacteria to differentiate caries activity.
pa href=http://www.hubmed.org/fulltext.cgi?uids=22222970J Dent/a. 2011 Dec 23; brKuribayashi M, Kitasako Y, Matin K, Sadr A, Shida K, Tagami JpOBJECTIVES: A low pH environment is created by cariogenic bacteria. This study was aimed to measure pH of carious lesions intraorally using a micro-pH sensor, and assess predominant acid-producing cariogens by qPCR to differentiate caries activities. METHODS: 103 dentine lesions classified as active or arrested caries based on the clinical and radiological examinations were collected from patients after intraoral measurement of the lesion surface pH using a micro-pH sensor. Quantitative detection of genomic DNA copies of target cariogenic bacteria (mutans streptococci and Lactobacillus spp.) in each lesion was performed using real-time PCR. Correlation between the pH ranges and the number of bacterial species was examined by Spearman test. RESULTS: 50 samples were diagnosed as active and 53 as arrested lesions. Statistically significant difference was observed on average surface pH value between active and arrested lesions (p0.05). Prevalence of Lactobacillus spp. was higher in active lesions than in arrested lesions (76% vs. 58% of samples, respectively). When the carious lesions were categorised into four different pH ranges (up to 5.5, from 5.6 to 5.8, from 5.9 to 6.1 and 6.2 or above), increased prevalence of Lactobacillus spp. was observed with decrease of pH levels. A significant negative relationship was found between pH value and number of Lactobacillus spp. (r=-0.209, p0.05) but no such correlation was found for mutans streptococci. CONCLUSIONS: Intraoral pH measurement might be clinically useful to determine acidity of the local environment of carious lesions as one aspect of the caries activity assessment. CLINICAL SIGNIFICANCE: The population of certain bacteria may indicate activity of carious lesions. Intraoral pH measurement of the carious lesions using a micro-pH sensor may be a clinically feasible method for assessment of lesion acidity.
Nano-indentation testing of new and fractured nickel-titanium endodontic instruments.
pa href=http://www.hubmed.org/fulltext.cgi?uids=22211861Int Endod J/a. 2011 Dec 23; brJamleh A, Sadr A, Nomura N, Yahata Y, Ebihara A, Hanawa T, Tagami J, Suda HpJamleh A, Sadr A, Nomura N, Yahata Y, Ebihara A, Hanawa T, Tagami J, Suda H. Nano-indentation testing of new and fractured nickel-titanium endodontic instruments. International Endodontic Journal. ABSTRACT: Aim To investigate the effect of cyclic fatigue on nickel-titanium (NiTi) endodontic instruments using a nano-indentation test. Methodology Eight ProFile NiTi rotary instruments (size 30, taper 0.06; Dentsply Maillefer, Ballaigues, Switzerland) were tested using a cyclic fatigue set-up until fracture. The fractured instruments and eight new NiTi instruments of the same size and taper were used for a nano-indentation test on the internal surfaces of a NiTi instruments in the region just adjacent to their fractured edge (group I) and in the same region of the new group (group II), and the cutting part beside the shaft for both instruments [group III (fractured) and group IV (new)]. Data were statistically analyzed using one-way analysis of variance and Games-Howell post hoc test. The alpha-type error was set at 0.05. Results Significant differences in terms of hardness and elastic modulus for each group (P 0.05) were found, with group I having the lowest mean values followed by group III. Additionally, standard deviations increased remarkably after failure, as represented by groups I and III. Conclusion The nano-indentation technique can be applied to determine the performance and the failure mechanism of NiTi instruments. The fatigue process revealed a significant decrease in the hardness and elastic modulus of the NiTi instrument. As indicated by the low hardness, the fatigue process did not result in work hardening but rather work softening.
Nano-indentation testing of new and fractured nickel-titanium endodontic instruments.
pa href=http://www.hubmed.org/fulltext.cgi?uids=22211861Int Endod J/a. 2011 Dec 23; brJamleh A, Sadr A, Nomura N, Yahata Y, Ebihara A, Hanawa T, Tagami J, Suda HpJamleh A, Sadr A, Nomura N, Yahata Y, Ebihara A, Hanawa T, Tagami J, Suda H. Nano-indentation testing of new and fractured nickel-titanium endodontic instruments. International Endodontic Journal. ABSTRACT: Aim To investigate the effect of cyclic fatigue on nickel-titanium (NiTi) endodontic instruments using a nano-indentation test. Methodology Eight ProFile NiTi rotary instruments (size 30, taper 0.06; Dentsply Maillefer, Ballaigues, Switzerland) were tested using a cyclic fatigue set-up until fracture. The fractured instruments and eight new NiTi instruments of the same size and taper were used for a nano-indentation test on the internal surfaces of a NiTi instruments in the region just adjacent to their fractured edge (group I) and in the same region of the new group (group II), and the cutting part beside the shaft for both instruments [group III (fractured) and group IV (new)]. Data were statistically analyzed using one-way analysis of variance and Games-Howell post hoc test. The alpha-type error was set at 0.05. Results Significant differences in terms of hardness and elastic modulus for each group (P 0.05) were found, with group I having the lowest mean values followed by group III. Additionally, standard deviations increased remarkably after failure, as represented by groups I and III. Conclusion The nano-indentation technique can be applied to determine the performance and the failure mechanism of NiTi instruments. The fatigue process revealed a significant decrease in the hardness and elastic modulus of the NiTi instrument. As indicated by the low hardness, the fatigue process did not result in work hardening but rather work softening.
