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Abstract: Introduction: It is difficult to make a definite diagnosis of a cracked tooth solely based on an inspection within the root canal, especially in case of microcracks. At present, there seems to be no established method to detect dentinal microcracks in roots; therefore, the current detection techniques need to be improved. Vibrothermography (VibroIR) helps to detect microcracks by the friction heat generated from ultrasonic vibration. The purpose of this study was to establish a novel method using VibroIR to detect dentinal microcracks. Methods: The root canals of 20 roots with cracks and control roots were prepared after removing the tooth crowns. A tapered indenter was inserted into the root canal and pressed until a microcrack was created under an optical microscope. Using VibroIR, the detection trials for dentinal microcracks were performed with an ultrasonic vibration power ranging from 0.43 to 1.48 W at an angle of 0°, 30°, 45°, 60°, and 90° between the ultrasonic vibration point and the microcrack line. After the detection test, the microcrack width was measured with an optical microscope. Results: Frictional heat was detected in the microcracks with thermography at 0.89 to 1.48 W and at an ultrasonic vibration point angle less than 60° from the crack line for 10 seconds. Microcracks with a width of 4 to 35.5 μm were detected with this method. Conclusions: VibroIR may be an effective method for the diagnosis of root dentinal microcracks. [Copyright &y& Elsevier]

Summary: Adhesive post–core restorations using a combination of fiber reinforced posts (FRPs) and resin composites have become the preferred choice worldwide in restoring pulpless teeth. The success of this method, especially because of the low incidence of root fracture, has been shown in many clinical studies in several countries. However, the method has also shown a tendency for the FRP to come detached from its post-space, and this potential flaw raises questions about the long-term durable prognoses of such restorations. The adhesive characteristics of post–core materials to root canal dentin have been widely investigated as part of the attempt to find a solution to the problem. Comprehensive understanding of the way that root canal dentin behaves in the post-space may be the key to achieving their better adhesion. Clinicians have to contend with the high stresses produced in the post-space because of its extremely high C-factor. When using light-cured and even dual-cured materials, ensuring deep and complete light penetration is essential to obtain even bonding strength throughout the post-space. Chemically cured adhesive materials, where the progress of curing is relatively slow and there is less stress caused by polymerization shrinkage, should be positively considered for the root canal bonding. In every case, careful attention needs to be paid to the negative effects that endodontic irrigation solutions, such as sodium hypochlorite and EDTA, have on root canal adhesion. Even after better adhesion of the FRP to root canal dentin has been achieved—and proved by high-quality long-term clinical studies, the concept of cusp-coverage in pulpless molars may need to be reconsidered based on a good conservative policy of minimal intervention. [Copyright &y& Elsevier]

Abstract: With the development of dental laser delivery systems that can enter into the root canals, it is possible to use Er:YAG lasers to remove the residual biofilm associated with infected root canals. We examined their effects against biofilms made of Actinomyces naeslundii, Enterococcus faecalis, Lactobacillus casei, Propionibacterium acnes, Fusobacterium nucleatum, Porphyromonas gingivalis, or Prevotella nigrescens in vitro. After Er:YAG laser irradiation with energy densities ranging between 0.38–0.98 J/cm2, the biofilm samples on hydroxyapatite disks were quantitatively and morphologically evaluated. The Er:YAG laser was effective against biofilms of 6 of the bacterial species examined, with the exception of those formed by L. casei. After irradiation, the numbers of viable cells in the biofilms were significantly decreased, whereas atrophic changes in bacterial cells and reductions in biofilm cell density were seen morphologically. Er: YAG lasers might be suitable for clinical application as a suppressive and removal device of biofilms in endodontic treatments. [Copyright &y& Elsevier]

Abstract: Discovering a durable restorative method to reconstruct and reinforce pulpless teeth is a vital key to help prevent root fractures. Complete and firm adhesion of resin cement in root canal dentin using a post is critical to achieve it. The null hypothesis in the present study was that the bond strength of dual-cured and chemical-cured adhesive resin cements to root canal dentin is not affected by their vertical locations in the root canal. In the experiments, extracted human incisors restored with fiber-reinforced posts and adhesive resin cements were subjected to microtensile bond strength testing. Then, the failure modes and the dentin-bonding interfaces were observed. Self-etch and self-adhesive dual-cured resin cements showed frequent pretesting failure despite using a silane coupling agent. Chemical-cured total-etch adhesive material showed stable bonding performances throughout the entire post space and thus has an advantage in post-core restorations. [Copyright &y& Elsevier]

There is no particular treatment established to preserve vertically fractured teeth. We evaluated the long-term prognosis of the intentional replantation of 26 vertically fractured roots after reconstruction with 4-META/MMA-TBB dentin-bonded resin. Replanted teeth were evaluated according to clinical criteria and radiographic examinations for periods ranging from 4 to 76 months. Eighteen cases were functional and retained, with six fully successful; the others needed further observation. Eight cases failed to respond to treatment because of refracture, recurrence of gingival inflammation, or both. Longevity was calculated as 88.5% at 12 months after replantation, 69.2% at 36 months, and 59.3% at 60 months. All failures occurred in premolar and molar teeth. Longitudinal fractures extending more than 2/3 from the cervical portion toward the apex showed significantly shorter longevity compared with fractures within the 2/3 area (log-rank test, p = 0.02). Intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin may be considered for incisors as an alternative to extraction, although the long-term success is not optimal. [Copyright &y& Elsevier]

We immunohistologically examined the prevalence and localization of bacteria invading dentinal tubules of the roots of teeth with infected canals. Forty extracted teeth with apical lesions were selected and divided into two groups: a group of untreated teeth and a group of canal-enlarged teeth. The bacteria in the specimens were detected by Brown-Brenn stain and the labeled-streptavidin-biotin method with specific antisera for 16-bacteria. Seventy percent of the examined teeth showed bacteria invading the dentinal tubules of the roots. Fusobacterium nucleatum, Eubacterium alactolyticum, E. nodatum, Lactobacillus casei, and Peptostreptococcus micros were abundant. Even in the canal-enlarged group, invasion of bacteria was observed in 65% of teeth. This study revealed the actual condition of bacteria in infected root dentin and suggested that the canal-enlargement procedure could not completely remove all the bacteria in the infected dentinal tubules of the root. [Copyright &y& Elsevier]

The aim of this study was to examine morphologically the participation of extraradicular biofilm in refractory periapical periodontitis. Six teeth and five extruded root filling gutta-percha points associated with refractory periapical periodontitis were investigated by scanning electron microscope. In nine of 11 samples examined, bacterial biofilms were seen at the extraradicular area. The gutta-percha surface was covered with glycocalyx-like structures, and filaments, long rods, and spirochete-shaped bacteria were predominant in the extraradicular sites. Planktonic cells, which were filaments and spirochete-shaped bacteria, emigrated from the glycocalyx structures in some spots. In the extracted teeth, biofilm consisting of both bacteria and glycocalyx-like structures were observed on the periapical root surfaces. Next to the residual periodontal ligament, a few filaments, rods, and fusiforms were attached on the healthy cementum surface. The present findings suggested that bacterial biofilms formed in the extraradicular areas were related to refractory periapical periodontitis. [Copyright &y& Elsevier]

The purpose of this study was to evaluate intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin. Twenty vertically fractured teeth were extracted intentionally and reconstructed with 4-META/MMA-TBB dentin-bonded resin. After reconstruction, the teeth were replanted into the original sockets. The replanted teeth were evaluated by clinical criteria and radiographic examination. The observation periods ranged between 4 and 45 months. Longevity was calculated by the Kaplan-Meier method, and factors that had significant influence on the longevity were analyzed with the Log rank test at a 95% level of confidence. From this short-term observation, 14 of 20 cases were functioned in the oral environment. Of these 14 cases, 6 could be considered truly successful and 8 cases needed further observation. The other six cases were total failures and were extracted. The longevity was calculated as 83.3% at 12 months and 36.3% at 24 months. Teeth with thin roots or with longitudinal fractures extending over of the root from the cervical portion toward the apex showed significantly lower longevity. It was concluded that this method had the potential to preserve vertically fractured teeth. [Copyright &y& Elsevier]

The most comfortable positioning for a dental operating microscope (DOM) during nonsurgical endodontics for operators was investigated. Operators were categorized into 3 groups according to height. We recorded the time taken to obtain magnified images, and the angles of binoculars, microscope body, and the mirror to floor surfaces. For the group of shorter operators, observations were also made with an angled optics or a short objective lens (200 mm). It took longer to observe the mandibular molars than maxillary in every group. Although the differences in angles among each group were not remarkable for maxillary observation, we confirmed significant differences for the mandibular. Shorter operators had to adopt a strained position for mandibular observation in a standard setup but were more comfortable using angled optics or a short objective lens. By understanding the proper position, operators could learn to perform microendodontics more efficiently. [Copyright &y& Elsevier]

The case reported demonstrates dramatic healing of the periapical region of retreated root canals with open apices by the successful use of mineral trioxide aggregate (MTA). Unsuccessful conventional root canal therapy for the mandibular central incisors had been followed by surgical treatment. The severely damaged root canals were obturated using MTA in anticipation of the formation of artificial apical plugs. The treated teeth were asymptomatic, and radiographic examination demonstrated apparent regeneration of periradicular tissue 2 years after the obturation. MTA can be considered a very effective material to promote regeneration of apical tissue, even in teeth with large open apices. [Copyright &y& Elsevier]

This case report presents a case of internal root resorption originating from inadequate caries removal and orthodontic therapy in maxillary right lateral incisor in a 13-yr-old female. A preoperative, panoramic radiograph taken at the orthodontic office showed no evidence of resorption, however, the composite restoration in the coronal portion was inadequate. During 4 months of nickel titanium orthodontic wire activation, the patient suffered spontaneous pain. Periapical radiographs revealed internal root resorption in the middle third of the root. Endodontic treatment was accomplished and coronal restorations were completed with composite resin. Periodical radiograph examination as well as orthodontic treatment was continued. The tooth was clinically and radiographically healthy at the 18-month follow-up. The importance of the preoperative radiographic examination as well as radiographs during orthodontic treatment is affirmed. [Copyright &y& Elsevier]

Abstract: Objectives: The purpose of this study was to evaluate the ability of an experimental self-etching resin coating system to protect against demineralization of the root surface in vitro, comparing its effectiveness with two commercial one-step self-etching adhesives. Methods: The experimental resin coating system (EC), consisting of a self-etching primer and an acrylate-based resin, or the two commercial self-etching adhesives, Adper Prompt-L Pop (AD) and Clearfil Tri-S Bond (S3), was applied to the cementum of a human extracted tooth root. The specimens were immersed in acetate buffer at pH 5.5 for 4 weeks, and the degree of demineralization underneath the materials was evaluated by microscopic observation and contact microradiography. Each material''s sealing and interfacial ultrastructure on the cementum was morphologically examined by scanning electron microscopy, and their bonding ability to cementum was determined by microtensile bond strength (MTBS) tests. Results: Application of AD and S3 showed limited effects to protect against demineralization, but no demineralization was observed for EC. EC showed greater coating thickness than the other two materials, with formation of integral hybridized layers with cementum. Although the MTBS values for EC were significantly lower than those for AD and S3, cohesive failure in resins was the prevalent fracture mode for EC, showing no possible disadvantages in bonding ability. Significance: The experimental resin coating system effectively prevented acid demineralization on root surfaces due to its ability to produce an appropriately thick coating and an integral hybridized layer. [Copyright &y& Elsevier]

Summary: Objectives: It has been reported that dental unit waterlines (DUWLs) are contaminated with bacterial biofilm, and that water discharged from a DUWL contains bacteria that might be opportunistic pathogens. This study aimed to investigate the ability of polyvinylidene fluoride (PVDF) tubing to inhibit bacterial contamination in DUWLs. Methods: Newly installed dental units were equipped with either a conventional polyurethane tube (unit A) or a PVDF tube (unit B), and the numbers of bacteria discharged from high- and low-speed handpiece lines were counted using R2A agar plates. Bacterial attachment on surfaces was observed with a scanning electron microscope (SEM) up to 185 days. Bacterial outflow during 1-day clinical service from a DUWL after 1-year usage was also examined. The surface free energy of each tube was determined based on the measurement of contact angles. Results: The number of bacteria discharged from unit B was lower than from unit A at 80 days and thereafter. SEM examination demonstrated that the unit A tube was covered by biofilm constituting rods and filaments after 94 days, while no biofilm was observed in the unit B tube even after 185 days. After 1-year of usage, the unit B released significantly less bacteria than the unit A at every sampling period of 1-day clinic work. Surface free energies, calculated from contact angles measured, of PVDF and polyurethane tubes were 37.7 and 77.8, respectively. Significance: The present results indicate that PVDF tubes, which have lower surface free energy than the conventional tubes, were effective in inhibiting biofilm formation and reducing bacterial outflow from DUWLs. [Copyright &y& Elsevier]

• Subjective impressions of 40 stimuli based on dental drill sounds were measured. • Overall attenuation of the sound level by 5 dB and 10 dB statistically improved. • Attenuation of a part of the acoustical peaks alone was not sufficient for improving. • High-frequency components over 9 kHz influenced unpleasantness. The sound produced by a dental air turbine handpiece (dental drill) can markedly influence the sound environment in a dental clinic, and many patients have reported that the sound of a dental drill elicits unpleasant feelings. A comfortable sound environment for patients is desirable in medical care. To identify approaches for improving the sound quality of dental drills, we need to determine systematically the effects of the physical properties of the sounds of dental drills on their impressions. We, therefore, prepared 40 sound stimuli by processing different sound levels or frequency components comprising the sounds emitted by four kinds of dental drills. This study is designed to use psychoacoustic experiments to determine the effects of dental drill sounds on subjective impressions. The analysis resulted in the following findings: the overall attenuation of each original sound stimulus by 5 dB or 10 dB had statistically significant effects and improved the unpleasant impression. Attenuation of the frequency components above 9 kHz by 10 dB also improved the impressions, relative to those for the original sound stimuli. When the prominent frequency components at approximately 6 kHz were attenuated by 10 dB, no statistically significant differences were observed between the impressions corresponding to the original and processed stimuli. The Comfort Index (CI), which consists of the equivalent continuous A-weighted sound pressure level (L Aeq) and calculated sharpness, showed a good correlation with unpleasant impressions. The present findings suggest that the consideration of acoustical characteristics based on the CI is useful in reducing the sound pressure level and refining the frequency characteristics of sounds emitted by dental drills, and this can aid in the development of new dental devices to create a comfortable sound environment in dental clinics. [ABSTRACT FROM AUTHOR]

Previously, we reported that biofilm formation of Eikenella corrodens is regulated by autoinducer-2 (AI-2), based on observations that biofilm-forming efficiency of ΔluxS mutant was greater than that of the wild type (Azakami et al., J. Biosci. Bioeng., 102, 110–117, 2006). To determine whether the AI-2 molecule affects biofilm formation directly, we added purified AI-2 to luxS mutant and wild-type E. corrodens and compared biofilm formations by using a static assay. Results indicated that biofilm formation in E. corrodens was enhanced by the addition of AI-2. We also compared the biofilms formed by flow cell system for the luxS mutant and the wild type by using scanning electron microscopy and confocal laser scanning microscopy. The number of viable bacteria in the luxS mutant biofilm was dramatically reduced and more sparsely distributed than that of the wild type, which suggested that AI-2 might enhance the mature biofilm. Conversely, further analysis by modified confocal reflection microscopy indicated that the wild-type biofilm was matured earlier than that of the luxS mutant, and became thinner and more sparsely distributed with time. These data suggest that LuxS may facilitate the maturation and detachment of biofilm in E. corrodens. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: We had previously discovered that the flexural and tensile strengths of human dentin were 2–2.4 times greater after being heated to 140°C, and deduced that the generation of higher-density structures and therefore dehydration probably promoted the increased strength. Our test hypotheses were that intertubular dentin, which constitutes a major part of organic components, was selectively affected by heating, and such changes could happen without critical damages to the basic structure of dentin type I collagen. Methods: Micro-mechanical changes of human dentin by heating at 140°C were investigated by nano-indentation. Chemical changes in dentin collagen after heating were also investigated by X-ray diffraction study, a microscopic Fourier transform infrared (micro-FTIR) and a laser Raman spectroscopic analyses, and a cross-linking analysis by high-performance liquid chromatography. Results: The results of nano-indentation showed that the micro-hardness of intertubular dentin increased after heating at 140°C to 1.8 times more than unheated dentin; on the other hand, peritubular dentin was unchanged. Results of X-ray diffraction showed that the lateral packing of collagen molecules shrank from 13.6±0.3 to 10.6±0.1Å after heating, but the shrinkage reversed to the original after rehydration for seven days. After heating, no substantial chemical changes in the collagen molecules were detected in tests by micro-FTIR or Raman analyses, or by cross-linking analysis. Significance: These results suggest that intertubular dentin, which contains most of the type I collagen, was selectively affected by heating at 140°C without critical damage to its collagen. [Copyright &y& Elsevier]

Abstract: Objectives: Being able to predict an individual''s risks of dental caries would offer a potentially huge natural step forward toward better oral heath. As things stand, preventive treatment against caries is mostly carried out without risk assessment because there is no proven way to analyse an individual''s risk factors. The purpose of this study was to try to identify those patients with high and low risk of caries by using Classification and Regression Trees (CART). Methods: In this historical cohort study, data from 442 patients in a general practice who met the inclusion criteria were analysed. CART was applied to the data to seek a model for predicting caries by using the following parameters according to each patient: age, number of carious teeth, numbers of cariogenic bacteria, the secretion rate and buffer capacity of saliva, and compliance with a prevention programme. The risks of caries were presented by odds ratios. Multiple logistic regression analysis was performed to confirm the results obtained by CART. Results: CART identified high and low risk patients for primary caries with relative odds ratios of 0.41 (95%CI: 0.22–0.77, p =0.0055) and 2.88 (95%CI: 1.49–5.59, p =0.0018) according the numbers of cariogenic bacteria. High and low risk patients for secondary caries were also identified with the odds ratios of 0.07 (95%CI: 0.01–0.55, p =0.00109) and 7.00 (95%CI: 3.50–13.98, p <0.0001) according the numbers of bacteria and existing caries. Conclusions: Cariogenic bacteria play a leading role in the incidence of caries. CART proved effective in identifying an individual patient''s risk of caries. [Copyright &y& Elsevier]

Abstract: A dentin primer incorporating an antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) shows strong antibacterial effects, and may provide better prognosis for direct capping of infected pulp exposed by caries removal compared with conventional adhesives. However, influences of MDPB on healing of the pulp have not yet been fully elucidated. The purpose of this study was to compare the influences of unpolymerized MDPB on proliferation, differentiation and mineralization of odontoblast-like MDPC-23 cells with those of other resin monomers, Bis-GMA, MDP, TEGDMA and HEMA. The inhibitory effects of MDPB on the proliferation of MDPC-23 were lower than those of Bis-GMA. While MDPB strongly affected the differentiation compared with the other monomers, it was less inhibitory than Bis-GMA and MDP on the mineralization ability of odontoblast-like cells. These findings indicate that MDPB has superior biocompatibility than Bis-GMA in terms of hard tissue formation by odontoblastic cells, suggesting its possible less negative influences on dentinogenesis. [Copyright &y& Elsevier]

Abstract: Ammonium hexafluorosilicate [SiF: (NH4)2SiF6] was prepared in order to overcome the tooth discoloration caused by diamine silver fluoride [AgF: (NH3)2AgF] application. We employed a single concentration of SiF solution in our previous study; therefore, it is still unclear how the concentration of SiF solution affects the occlusion of dentin tubules and composition of the precipitate. Objective: The aim of this study was to evaluate the effects of changing the concentration of SiF on its clinical use as a dentin hypersensitivity treatment. Methods: To simulate dentin tubules subject to dentin hypersensitivity, dentin disks were treated with EDTA for 2min. Then, the disks were treated with several concentrations of SiF solution (from 100 to 19,400ppm) for 3min. The occlusion of dentin tubules was evaluated using scanning electron microscopy (SEM), and the composition of the precipitate formed in the tubules after SiF treatment was assessed using energy dispersive X-ray analysis (EDXA). Results: SEM photographs demonstrated that dentin tubules after treatment with SiF were occluded homogeneously and fully regardless of the concentration of SiF solution. The Ca/P molar ratio of the precipitate formed in dentin tubules after SiF treatment was increased with the concentration of SiF solution. Significance: It was concluded that the capacity to occlude dentin tubules was the same regardless of the concentration of SiF solution. However, the composition of the precipitate formed in the tubules was dependent on the concentration of SiF solution. [Copyright &y& Elsevier]

Abstract: Objectives: This study investigated the effects of light penetration and removal of smear layer on the adhesive properties of self-etching adhesives to root canal dentin when using fiber posts. Methods: Altogether 54 human incisors and premolars were decoronated, and the roots after preparing the post space were randomly assigned into six groups. Three groups were treated with a light-cured self-etching adhesive and the other three with a dual-cured self-etching adhesive. In a further sub-division, the first group was light-cured with an irradiation unit; the second was light-cured with the irradiation unit and a light-guiding attachment; and the third was light-cured with the irradiation unit and the attachment after removing smear layer by EDTA and NaOCl. Then, a glass-fiber post was luted into the post space by a dual-cured composite. After 24h, an hourglass-shaped specimen was trimmed and subjected to MTBS testing. Results: Using the light-guiding attachment and removing the smear layer reduced the incidence of pre-testing failure significantly from 57.1% to 19.0% (p <0.05) in the light-cured adhesive groups and from 68.3% to 3.2% (p <0.01) in the dual-cured adhesive groups. The MTBS in different locations within a post space were in the range from 8.9 to 17.5MPa in the light-cured group and from 11.2 to 17.2MPa in the dual-cured group. Significance: Better light penetration in post spaces and removal of the smear layer are effective in improving the adhesive properties of self-etching adhesives to root canal dentin when using fiber posts. [Copyright &y& Elsevier]

Abstract: Objectives: Glass-ionomer cements (GICs) are known to have inhibitory effects on bacterial growth, but the biochemical mechanism of this property has not been fully understood. This study aimed to evaluate inhibitory effects of GIC on the acid production of caries-related oral streptococci, and to identify the components responsible for the inhibition. Methods: An eluate was prepared by immersing set GIC in phosphate-buffered saline at 37°C for 24h. Fluoride and other elements in the eluate were quantified by fluoride ion electrode and atomic absorption photometry, respectively. Streptococcus mutans NCTC 10449 and Streptococcus sanguinis NCTC 10556 were used to evaluate the pH fall and the rate of acid production after the addition of glucose in the presence or absence of the eluate. Acidic end products from glucose were also assayed by carboxylic acid analyzer. Results: The eluate contained silicon (1.24±0.26mM), fluoride (0.49±0.02mM) and aluminum (0.06±0.00mM), and inhibited the pH fall and the acid production rate of both streptococci at acidic pH, with a concomitant decrease in lactic acid production. These effects were comparable to those of a potassium fluoride solution containing the same concentration of fluoride as the eluate. Significance: These results indicate that the GIC eluate inhibits the acid production of caries-related oral streptococci at acidic pH and that the effect is due to fluoride derived from the GIC. Thus, adjacent to GIC fillings, bacterial acid production and the subsequent bacterial growth may decrease, establishing a cariostatic environment. [Copyright &y& Elsevier]

Abstract: Objectives: Superior restorative methods for effectively strengthening pulpless teeth need to be identified, since vertical root fractures of pulpless teeth are still a major problem in everyday clinical practice. The present study tested the null hypothesis that there were no differences in static and fatigue fracture resistances of pulpless teeth restored with different types of post–core systems. Methods: Extracted human premolars were restored with a combination of either a fiber post or metallic post and a composite resin core. Teeth with full crown preparations without post–core restorations served as a control. A 90° vertical or 45° oblique static compressive load was applied to restored teeth, and fracture loads and modes of fracture were recorded. Fatigue fracture tests were conducted by applying sinusoidal cyclic loads to restored teeth from vertical or oblique directions. Fatigue limits for each restoration were calculated using the staircase approach. Results: In both static and fatigue fracture testing under vertical or oblique loadings, the fracture loads of teeth restored with fiber posts were significantly greater than those of teeth restored with metallic posts. The fatigue limits of teeth restored with fiber and metallic posts were 112kgf and 82kgf respectively under vertical loadings and 26kgf and 20kgf under oblique loadings. Significance: The combination of a fiber post and a composite resin core showed superior fracture resistance against both static and fatigue loadings compared to restorations using a metallic post, and is therefore recommended in restoring pulpless teeth. [Copyright &y& Elsevier]

Interleukin-6 (IL-6) is a multifunctional cytokine produced by various cells to regulate hematopoiesis, inflammation, immune responses, and bone homeostasis. IL-6 is also known to modulate the differentiation of osteoblasts and osteoclasts. IL-6 is believed to play a positive regulatory role in osteoclast differentiation by inducing the expression of receptor activator of NF-KB ligand (RANKL) on the surface of osteoblasts: RANKL then interacts with RANK expressed on osteoclast progenitors, inducing osteoclast differentiation via the RANK signaling pathway, which involves NF-KB, JNK, and p38. In this report, we demonstrate that IL-6 can also directly act on osteoclast progenitors to suppress their differentiation via an inhibition of RANK signaling pathways. IL-6 specifically suppressed RANK-mediated 1KB degradation and JNK activation, Microarray analysis revealed that costimulation with IL-6 and RANKL up-regulates the transcription of MKP1 and MKP7, which encode enzymes that dephosphorylate JNK, and down-regulates the transcription of Senp2 and Cu14A, which are related to the ubiquitin pathway. Thus, IL-6 directly acts on osteoclast progenitors and suppresses their differentiation by regulating the transcription of specific genes related to MAPK phosphatases and the ubiquitin pathway. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To investigate the relationship between the color of carious dentin with varying lesion activity, and bacterial detection in the lesions. Methods: In 26 extracted human molars with coronal dentin caries and four extracted sound human molars, dentin was removed by a round bur every 150μm from the dentin surface, in the direction of the pulp chamber. Before and after removal, images of nine-color samples and the dentin surface stained with a caries detector dye (1% acid red in propylene glycol) were taken simultaneously by a charge-coupled device (CCD), and dentinal tissue samples were taken with a new round bur. From the images, corrected L*, a* and b* values (CIE 1976 L*a*b* color system) of the dentin surfaces were calculated from the color changes of the nine-color samples. Bacterial DNA in the dentinal tissues was detected by polymerase chain reaction. Results: Before removal of dentin, the L* of sound molars (L*>50) was significantly larger than that of carious molars (L*<50) (ANOVA, Scheffe''s F-test, P <0.05). In addition, the carious molars were divided into type I (a*>20, characteristics of active caries) and type II (a*<20, characteristics of arrested caries), and there was a significant difference in the a* value (P <0.05). For both carious types, the area under the receiver operating characteristic curve of L* was significantly larger than that of a* or b* (univariate Z score test, P <0.05), and the rate of bacterial detection decreased as the L* of dentinal tissue increased, and bacterial DNA was not detected when L* was >60. Conclusions: Sound and types I and II carious dentin were discriminated by the combination of L* and a* values of dentinal tissue stained with the caries detector dye before removal of dentin. In carious lesions, the a* values of carious dentin stained with the dye were related to the carious lesion activity before removal of carious tissue, and the L* values were related to the degree of caries progression. [Copyright &y& Elsevier]

Abstract: Diamine silver fluoride [AgF: (NH3)2AgF] has been used clinically in Japan, as it reduces dental caries and dentin hypersensitivity. However, AgF stains the teeth black due to silver precipitation. To overcome this drawback, the authors prepared ammonium hexafluorosilicate [SiF: (NH4)2SiF6], which does not stain the teeth, and SiF occluded open dentin tubules completely with silica–calcium phosphate precipitate. Objectives: The aim of this study was to evaluate the duration of dentin tubule occlusion after SiF treatment in a simulated oral environment. Methods: To simulate dentin tubules subject to dentin hypersensitivity, dentin disks were treated with EDTA for 2min. The disks were treated with 0.476mol/L SiF for 3min, and then the disks were immersed in synthetic saliva, which was regularly replenished to maintain its ionic concentration, for up to 7 days. The occluding ability of the dentin tubules was evaluated using scanning electron microscopy (SEM), and the hydraulic conductance was measured following Pashley''s method at regular intervals. Results: SEM photographs demonstrated that dentin tubules were occluded homogeneously and completely with the precipitate at 7 days after treatment with SiF. In addition, newly formed calcium phosphate precipitate was present at the dentin surface. The dentin permeability showed a consistently low value throughout the experimental period. The values immediately after SiF treatment and 7 days after immersion were 11.9±3.7% and 7.9±2.9%, respectively. Significance: Ammonium hexafluorosilicate is useful for the treatment of dentin hypersensitivity, since ammonium hexafluorosilicate induced calcium phosphate precipitation from the saliva; therefore, it has a continuous effect on dentin tubules occlusion under a simulated oral environment. [Copyright &y& Elsevier]

Abstract: Objectives: This laboratory study evaluated the objectivity of caries removal with a caries detector dye by color and bacterial evaluations. Methods: In 41 cases of dentin caries (32 extracted human molars), carious tissues were removed using a caries detector dye. Images of dentin surfaces with color-matching stickers were acquired using a CCD camera, and dentinal tissue samples were collected with new round burs. Corrected L*, a* and b* values (CIE 1976 L*a*b* color system) of dentin surfaces were calculated from the sticker color changes. In addition, bacterial DNA in dentinal tissues was detected by the polymerase chain reaction. Results: The intra-class correlation coefficient of the corrected L*, a* and b* values was 0.34, 0.30 and 0.49, respectively. There were significant inter-operator differences (P <0.05). Seventeen of 41 specimens contained bacterial DNA after caries removal. Conclusions: Results showed that objectivity of caries removal using the caries detector dye with visual inspection was low. [Copyright &y& Elsevier]

Abstract: Objectives: This in vitro study aimed to investigate the accuracy of an electrical method for the evaluation of microleakage by a three-dimensional analysis of dye penetration. Methods: Coronal cavities were prepared on buccal, palatal or lingual surfaces in extracted human molars. The cavities were then filled with resin composites and were subjected to 10,000 load cycles (425g). Before cavity preparation and after load cycling, physiological saline was applied and wiped off, and the change in conductance was measured across the margin of the restoration in each specimen. After dye penetration, the specimens were reduced by 100μm in a direction parallel to the cavity floor, from the surface of the restoration to the cavity floor. The sequence of reducing the sections by 100μm and image taking was repeated. Three-dimensional images of dye penetration were made and the proportions of the interface showing penetration were calculated. Results: Pearson''s correlation coefficients between changes in conductance and the surface area of dye penetration, between these and the rate of dye penetration, and between these and the depth of dye penetration were 0.932, 0.920 and 0.732, respectively. The correlations were significant (p <0.05). Conclusions: The results of this electrical method for microleakage evaluation showed stronger correlations with the three-dimensional amount of marginal leakage (surface area of dye penetration and rate of dye penetration) than the two-dimensional amount (depth of dye penetration). [Copyright &y& Elsevier]

Abstract: Objectives: This study examined the in vivo bonding ability to sound dentin of antibacterial adhesive systems incorporating an antibacterial monomer MDPB based on morphological evaluation of the resin–dentin interface. Methods: Class V cavities were prepared on the buccal surfaces of the teeth of a beagle dog and a composite filling performed using (1) commercial self-etching system Liner Bond 2 (LB primer+LB bond), (2) experimental primer containing 5% MDPB and LB bond, (3) LB primer and experimental bonding-resin containing 2.5% MDPB, or (4) combination of experimental primer and bonding-resin. After 7 days, the tooth crown was cut and fixed in half-Karnovsky''s solution, and the sectioned surface observed under scanning electron microscopy (SEM) after treatment with phosphoric acid and NaOCl. The ultrastructure of the bonding interface was also examined by transmission electron microscopy (TEM). Microtensile bond strengths (μTBS) of each group were measured using extracted teeth. Results: SEM demonstrated that all groups produced a 1–2μm thick hybrid layer with funnel shaped resin tags, although the length of tags was shorter for the group in which MDPB-containing bonding-resin was used. TEM examination supported good adhesion of the comprehensive adhesive system employing MDPB-containing primer/bonding-resin, showing integrity between resin and dentin. There were no significant differences in μTBS among the four groups tested (p >0.05, ANOVA). Significance: This study confirmed that the experimental antibacterial adhesive systems employing MDPB-containing primer or/and bonding-resin could produce an effective bond under in vivo conditions. [Copyright &y& Elsevier]

Abstract: Signal transduction and activator of transcription (Stat) 3 is a transcription factor that is activated by a variety of cytokines and growth factors, including IL-6 family cytokines. These cytokines regulate bone homeostasis and have been reported to regulate the differentiation of osteoblasts and osteoclasts through Stat3 activation in vitro, but the in vivo physiological role of Stat3 in bone homeostasis is unknown. Here, we report that gp130 knock-in mice gp130 F759/F759 , in which IL-6 family cytokine-mediated Stat3 activation is enhanced, showed an osteosclerotic phenotype. To further clarify the role of Stat3 in bone formation, we generated mice with osteoblast-specific disruption of the Stat3 gene via the Cre-LoxP recombination system using α1(I)-collagen promoter Cre transgenic mice. The α1(I)Cre;Stat3 flox/− mice showed an osteoporotic phenotype because of a reduced bone formation rate. Thus, the Stat3 signal in osteoblasts plays a pivotal role in bone formation in vivo. [Copyright &y& Elsevier]

Summary: Objectives: Since atraumatic restorative treatment (ART) involves removal of carious lesions with manual instruments, improvement of filling materials to guarantee greater success should be considered. This study aimed to evaluate antibacterial, physical, and bonding properties of glass-ionomer cements (GIC) containing chlorhexidine (CHX), and to determine optimal concentrations for incorporation of agents to obtain antibacterial GICs for use with the ART approach. Methods: CHX diacetate combined with CHX dihydrochloride was added to control GIC powder to obtain concentration ratios of 1/0, 2/0, 3/0, 1/1, or 2/2% w/w. Antibacterial activity of each cement against Streptococcus mutans, Lactobacillus casei or Actinomyces naeslundii was examined using agar-diffusion methods, and release of CHX was analyzed by HPLC. Compressive strength, bond strength to dentin, and setting time were measured, and compared with those of control samples. Results: All experimental GICs exhibited inhibition of three bacteria, but sizes of inhibition zones and concentrations of CHX released were not dependent upon CHX content. Incorporation of CHX diacetate at 2% or greater, significantly decreased compressive strength, and bond strength to dentin was adversely affected by addition of CHX diacetate at 2% or more (p<0.05, ANOVA, Fisher''s PLSD test), although setting time was extended a little by addition of any concentrations of CHX. Significance: The present results demonstrate that experimental GICs containing CHX are effective in inhibiting bacteria associated with caries, and incorporation of 1% CHX diacetate is optimal to give appropriate physical and bonding properties. [Copyright &y& Elsevier]

Summary: Objectives: This study aimed to investigate the antibacterial effects of the dentin primer of a commercially available self-etching adhesive system, Clearfil Protect Bond, which contains antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB). Methods: Inhibitory effects against Streptococcus mutans, Lactobacillus casei, or Actinomyces naeslundii were examined by an agar-disc diffusion method using the Clearfil Protect Bond primer containing 5% MDPB and an acidic adhesion-promoting monomer MDP, the primer only with MDP, and the primer with 1% cetylpyridinium chloride. The minimum inhibitory/bactericidal concentrations (MIC/MBC) of each primer for the three bacterial species were determined by serial microdilution assays. For testing the bactericidal effects seen in dentin, the primer was applied to demineralized dentin blocks in which S. mutans had been impregnated, and numbers of viable bacteria were counted. Results: For all three bacteria, the sizes of the inhibition zones produced by Clearfil Protect Bond primer were significantly greater than for the other primers (p<0.05, ANOVA and Scheffe''s F-test). The MIC/MBC values of Clearfil Protect Bond primer were less than those of the primer without MDPB, and comparable to those of the primer containing cetylpyridinium chloride. No bacterial recovery was obtained after application of Clearfil Protect Bond primer to the bacteria-impregnated dentin, although the primer without MDPB showed some bactericidal effect. Significance: Clearfil Protect Bond primer has strong antibacterial activity based upon MDPB against S. mutans, L. casei and A. naeslundii, and the capability to disinfect cavities containing residual bacteria. [Copyright &y& Elsevier]

Summary: Objectives: The present study was designed to test the null hypothesis that there is no difference in the fracture resistance of pulpless teeth restored with different types of post-core systems and full coverage crowns. Methods: Extracted human upper premolars were restored with a fiber post, prefabricated metallic post or cast metallic post-core. Teeth with full crown preparations without post-core restorations served as a control. All teeth were restored with full coverage crowns. A 90-degree vertical or 45-degree oblique load was applied to the restored teeth with a crosshead speed of 0.5mm/min, and the fracture loads and mode of fracture were recorded. Results: Under the condition of vertical loading, the fracture load of teeth restored with the cast metallic post-cores was greatest among the groups (two-factor factorial ANOVA and Scheffe''s F test, P<0.05). All fractures in teeth restored with all types of post-core systems propagated in the middle portions of roots, including the apices of the posts. Under the condition of oblique loading, the fracture load of teeth restored with pre-fabricated metallic posts was significantly smaller than that in other groups. Two-thirds of fractures in the fiber post group propagated within the cervical area, while most fractures in other groups extended beyond the middle of the roots. Significance: From the results of the present investigations, it was concluded that under the conditions of vertical and oblique loadings, the combination of a fiber post and composite resin core with a full cast crown is most protective of the remaining tooth structure. [Copyright &y& Elsevier]

Abstract: Eikenella corrodens (Ec) is one of a group of periodontopathogenic bacteria. A plasmid DNA (8.7 kb) isolated from Ec 1073 was designated pMU1. Agarose gel electrophoresis and Southern analysis suggested that pMU1-like plasmids were carried in 2 Ec strains, including 1073, with higher hemagglutination (HA) activity than other strains. We determined the nucleotide sequence of this plasmid and identified 7 ORFs. A homology search revealed that 4 ORFs of pMU1 were homologous to ORFs in pJTPS1, found in a spontaneous avirulent mutant of the phytopathogenic bacterium, Ralstonia solanacearum. pJTPS1 is a putative hypovirulent plasmid, which is thought to control the virulence of R. solanacearum. We also found the ORF to be homologous to the recombinase specific to the type IV pilin gene. We introduced a part of pMU1 into the Ec 23834 strain, which has a pilus structure on its cell surface and forms corroding colonies on solid medium. No pilus structure was observed on the surface of transformants, most of which formed non-corroding colonies. When such transformants (or Ec 1073) were cured of pMU1 with acridine orange, they remained non-foliated and non-corroding. The results suggest that pMU1 might irreversibly affect pilus formation and colony morphology, and might be involved in the pathogenicity and virulence of Ec. [Copyright &y& Elsevier]

Summary: Objectives: In some studies gap formation has been evaluated in just one section of the restorative. This in vitro study aimed to design a quantitative three-dimensional method for evaluation of the contraction gap in restoratives. Methods: Cervical cavities were prepared on buccal, palatal or lingual surfaces in human extracted molars and were then filled with resin composites. Specimens were reduced every 100μm in a direction parallel to the tooth axis, and perpendicular to the cavity floor from one proximal side to the other. The sequence of reducing the sections by 100μm, image taking (250×) and observation of these images (maximal 2500×) were repeated. Three-dimensional images of the contraction gap were made using analytical software and the proportions of the interface with gap formation calculated. Results: The mean proportions of the interface with gap formation of the self-etching system (Clearfil Liner Bond II Σ) was 41.7±6.3% and that of the self-priming system (Single Bond) was 38.2±3.9%; there was no significant difference. Conclusions: Approximate three-dimensional images of the in vitro contraction gap could be drawn and the mean proportions of the interface with gap formation could be more precisely calculated than by previous methods. [Copyright &y& Elsevier]

This study examined the antibacterial activity of prepolymerized resin filler, in which the bactericide quaternary ammonium was immobilized. The experimental filler was prepared by grinding prepolymerized resin blocks of methacrylate monomers, silica particles, and the antibacterial monomer methacryloyloxydodecylpyridinium bromide (MDPB). The number of Streptococcus mutans after incubation for 18 h in contact with the experimental filler with or without protein adsorption by saliva treatment was determined, and adherence of bacteria to the filler surface was evaluated by scanning electron microscopy. Elution of unpolymerized MDPB from the filler and its influence on bacterial growth were also investigated. The growth of S. mutans was completely inhibited by contact with the experimental filler without saliva treatment. Although the effects were attenuated, the saliva-treated filler still exhibited growth inhibition at >99.9%. Less bacteria attached to the experimental filler than the control filler without MDPB, indicating that the reduction in bacterial number after contact with the experimental filler was not due to bacterial adherence to the particles. Unpolymerized MDPB at 1 μg/ml was eluted from the filler particles but was confirmed to have little effect on bacterial growth. The results indicate that the bactericide-immobilized filler containing MDPB shows significant bacteriostatic effects without releasing antibacterial components, and is useful for incorporation into various resin-based restoratives. [Copyright &y& Elsevier]

Objectives. The aims of this study were to investigate the antibacterial activity of an adhesive resin incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) as well as its bonding characteristics in terms of bond strength into dentin and curing ability.Methods. An experimental adhesive resin was prepared by incorporation of 2.5% MDPB into proprietary adhesive (LB Bond), and the inhibitory effect of cured specimen against the growth of Streptococcus mutans on its surface was determined. Bond strength to human dentin and degree of conversion of the experimental adhesive in combination with 1, 2, or 5% MDPB-containing primers, which were previously reported to possess bactericidal effect, were evaluated by conventional tensile bond strength test and Fourier transformation infrared spectroscopy.Results. The cured experimental adhesive exhibited an inhibitory effect on S. mutans growth, reducing the number of bacteria to approximately 3% of control adhesive without MDPB. Tensile bond strength of experimental adhesive was not significantly different from that of the control (p>0.05), and use in combination with MDPB-containing primer did not show any adverse influence on bond strength. The degree of conversion of the bonding system was not different (p>0.05) between control and experimental adhesive irrespective of addition of MDPB into primer.Significance. These results indicate that an adhesive resin with antibacterial activity after curing could be produced by incorporation of MDPB without influencing bond strength or curing performance, suggesting that the comprehensive bonding system including MDPB-containing primer and adhesive should be highly effective in its antibacterial effect before and after curing. [Copyright &y& Elsevier]