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Life on earth is regulated by biological rhythms, some of which oscillate with a circadian, monthly or lunar cycle. Recent research suggests that there is a near weekly biorhythm that may exert an influence on human skeletal growth. Evidence for the timing of this biorhythm is retained in tooth enamel as the periodicity of Retzius lines. Studies report that Retzius periodicity (RP) relates to adult human stature and enamel thickness. Adult human stature is sexually dimorphic, and so is enamel thickness of maxillary third molars (M3) but not mandibular M3. Yet, previous studies report sex differences in RP are apparent in some populations but not others, and it is unknown if dimorphism in enamel thickness relates to RP. To further our understanding of this biorhythm we analysed sex-related variation in RP and its relationship with enamel thickness in a sample of M3's (n = 94) from adults in Northern Britain. Results reveal RP was significantly higher in our sample of female molars compared to those of males, which is consistent with the previously reported correlation between the biorhythm and adult stature. The RP of maxillary M3 related to sex differences in enamel thickness, but this relationship was not present in mandibular M3. Our results support previous findings suggesting that this biorhythm is sexually dimorphic and provide the first evidence that RP may be one factor influencing sex differences in enamel thickness. Our study also shows that correlations between RP and enamel thickness appear to be most readily detected for tooth types with sufficiently wide ranges of enamel thickness variation, as is the case for maxillary but not mandibular M3. Achieving a sufficient sample size was critical for detecting a sex difference in periodicity., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Farnesol is a sesquiterpene from propolis and citrus fruit that shows promising anti-bacterial activity for caries treatment and prevention, but its hydrophobicity limits the clinical application. We aimed to develop the novel polymeric micelles (PMs) containing a kind of derivative of farnesol and a ligand of pyrophosphate (PPi) that mediated PMs to adhere tightly with the tooth enamel., Results: Farnesal (Far) was derived from farnesol and successfully linked to PEG via an acid-labile hydrazone bond to form PEG-hyd-Far, which was then conjugated to PPi and loaded into PMs to form the aimed novel drug delivery system, PPi-Far-PMs. The in vitro test about the binding of PPi-Far-PMs to hydroxyapatite showed that PPi-Far-PMs could bind rapidly to hydroxyapatite and quickly release Far under the acidic conditions. Results from the mechanical testing and the micro-computed tomography indicated that PPi-Far-PMs could restore the microarchitecture of teeth with caries. Moreover, PPi-Far-PMs diminished the incidence and severity of smooth and sulcal surface caries in rats that were infected with Streptococcus mutans while being fed with a high-sucrose diet. The anti-caries efficacy of free Far can be improved significantly by PPi-Far-PMs through the effective binding of it with tooth enamel via PPi., Conclusions: This novel drug-delivery system may be useful for the treatment and prevention of dental caries as well as the targeting therapy of anti-bacterial drugs in the oral disease.

Objective: This in vitro study is aimed at investigating the caries preventive effectiveness of 445 nm diode laser in combination with topical fluoridation., Materials and Methods: A total of 30 caries-free bovine teeth were used in this study. Eighteen teeth were covered with nail varnish except four windows on the labial surface. The windows were assigned to no treatment/control (C), laser (L) (0.3 W, 60 s, and 90 J/cm 2 ), fluoride (F), and fluoride followed by laser (FL) treatment groups. Artificial caries lesions were created, and the teeth were sectioned and investigated under polarized light microscopy for quantitative measurement of the resulted lesion depth. Ten teeth were used for surface temperature measurement and two teeth for scanning electron microscopy (SEM). Extra twelve human molars were used for the intrapulpal temperature measurement. The absorbance of fluoride at 445 nm was measured., Results: The means of lesion depth for the C, L, F, and FL groups were 123.48 (±21.93), 112.33 (±20.42), 99.58 (±30.68), and 89.03 (±30.38) μ m, respectively. The pairwise differences of the L, F, and FL groups compared with the C group were significant ( p < 0.05). The differences between groups were tested: FL versus L p =0.02, F versus L p =0.16, and FL versus F p =0.91, and the difference of the F versus FL was not significant ( p =0.91). Temperature increment at the enamel surface and pulp roof were ∆ T  = 16.67 (±4.11) and 2.12 (±0.66)°C, respectively. The topical fluoride absorbance at 445 nm is five orders higher than that at 810 nm. SEM shows that after laser irradiation the enamel surface was intact and without thermal damage., Conclusions: The 445 nm laser irradiation may be useful for caries prevention, and its effectiveness is lower than those previously achieved using the argon ion laser., Competing Interests: The authors of this article have no conflicts of interest to declare., (Copyright © 2019 Mohammed Abbood Al-Maliky et al.)

Determining surface topography of different tissues of the molar tooth with novel analytical methods has opened new horizons in dental surface measurements which characterize tooth surface quality in dentistry. Studying surface topological measurements and comparing surface morphology of hard tissue of the molar tooth are the ultimate goals of the present study. Ten molar teeth have been chosen for investigating their surface characteristics through image processing techniques. The power spectral density (PSD) and fast Fourier transform algorithms of every molar tooth containing enamel, dentin, and cementum have determined that the characterization of surface profiles is possible. As can be seen, PSD along with fractal dimensions leads to good results for teeth surface topography. Moreover, PSD angular plot assures appropriate description of surface., (© 2019 Wiley Periodicals, Inc.)

The functional monomer 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), used in many dental adhesives, self-assembles in nano-layers at adhesive-tooth interfaces. Recently, several states of the POH groups of 10-MDP&#95;Ca salts were suggested, while their actual status has not been elucidated yet. We mechanistically investigated 10-MDP&#95;Ca-salt nano-layering at adhesive-dentin interfaces, correlatively using scanning transmission electron microscopy with energy-dispersive X-ray spectrometry (STEM-EDS), X-ray diffraction (XRD) and solid state nuclear magnetic resonance (NMR). STEM-EDS confirmed the presence of Ca and P in each nano-layer. Both XRD and NMR revealed that the two terminal POH groups of 10-MDP reacted with Ca. This twofold POH interaction of 10-MDP with Ca was stable in water and is therefore expected to contribute to durable nano-layering of 10-MDP&#95;Ca salts in the hybrid and adhesive layer. STATEMENT OF SIGNIFICANCE: The functional monomer 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), commonly used in dental adhesives with favorable long-term clinical outcome, has been documented to self-assemble into nano-layers at adhesive-tooth interfaces. Characterizing ultra-morphologically (STEM) and chemically (STEM-EDS, XRD, NMR) the mechanisms of interaction of 10-MDP with bulk dentin in a similar manner as what occurs clinically, it was found that the water stable 10-MDP&#95;Ca salts consist of CaRPO 4 , meaning that the two OH groups of the phosphate group of 10-MDP ionically reacted with Ca. This stable structure is expected to contribute to durable nano-layering of 10-MDP&#95;Ca salts in the hybrid and adhesive layer and hence to clinical longevity of the adhesively bonded tooth restoration., (Copyright © 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

The study aimed at finding an optimal combination of acid concentration and etching time when nitric acid is used as etchant for the study of the finer details of human dental enamel structure. Four hundred 2-3-mm-thick segments of facio-lingually sectioned human third molar crowns were assigned to 20 groups with 20 specimens in each group, each group differing with respect to acid concentration (0.1, 1, 2.5, and 5%) and etching time (15, 30, 45, 90, and 180 s). After etching and preparation, specimens were observed in the scanning electron microscope (SEM). Surface roughness/topography increased with increasing acid concentration and increasing etching time, but not in a linear fashion; generally, prisms tended to go from flat-surfaced to cone-shaped and prism sheaths from fissure-like to wedge-shaped. Intragroup variations and intergroup similarities were considerable. The two major enamel factors determining the etch effect are crystal orientation and prism sheath properties. Other factors, such as distribution of porosities and crystal quality, also contribute probably. Slight to moderate topography is best for observing the finer enamel structure, for example, etching with concentrations in the range 0.1-1% and with etching times in the range 15-90 s, the stronger the acid, the shorter the time. The depth effect of nitric acid is judged to be relatively small. Considerable variations in expression of prism cross-striations were observed. SEM observations of acid-etched enamel in carefully selected planes are a powerful method for the study of enamel structure, bearing in mind the artifactual aspects of the observed surface., (© 2019 The Authors. Microscopy Research and Technique Published by Wiley Periodicals, Inc.)

The purpose of this study was to: (a) evaluate the role of enamel surface roughness on bond fatigue durability and (b) evaluate statistical differences in roughness values based on measurement technique, including the use of spatial filtering for optical profilometry (OP). OptiBond XTR (Kerr Corp), Prime & Bond elect (DENTSPLY Caulk), Scotchbond Universal (3 M Oral Care), and XTR pre-etched with Ultra-Etch phosphoric acid (35%) (Ultradent) self-etch adhesives were used to treat enamel. A flat ground enamel surface was included as a control. Atomic force microscopy (AFM) and OP were used to measure the surface topography of each enamel surface following the application of adhesives. AFM, OP, and filtered OP (FOP) roughness values, where FOP was designed to only include the lateral spatial resolution consistent with AFM roughness values, were collected. Spatial resolution filtering with OriginPro was used to compare line scans from the two imaging techniques and generate the FOP group. These micro- versus nanoscale lateral roughness values were correlated with shear bond and shear fatigue strengths of the adhesives bonded to enamel. Roughness values showed differences based on measurement technique and strong correlations with bond and fatigue strength. The filtered OP group demonstrated the importance of careful usage and reporting of atomic force microscopy and OP metrics in adhesive dentistry. Best practices for surface roughness analysis were also discussed., (© 2019 Wiley Periodicals, Inc.)

Teeth are subjected to compressive loads during mastication. Under small loads the soft tissue periodontal ligament (PDL) deforms most. However when the loads increase and the PDL is highly compressed, the tooth and the alveolar bone supporting the tooth, begin to deform. Here we report on the structure of this alveolar bone in the upper furcation region of the first molars of mature minipigs. Using light microscopy and scanning electron microscopy (SEM) of bone cross-sections, we show that this bone is hypermineralized, containing abundant small pores around 1-5 μm in diameter, lacunae around 10-20 μm as well as larger spaces. This bone does not possess the typical lamellar motif or other repeating structures normally found in cortical or trabecular mammalian bone. We also use high resolution focused ion beam scanning electron microscopy (FIB-SEM) in the serial surface mode to image the 3D organization of the demineralized bone matrix. We show that the upper furcation bone matrix has a disordered isotropic structure composed mainly of individual collagen fibrils with no preferred orientation, as well as highly staining material that is probably proteoglycans. Much larger aligned arrays of collagen fibers - presumably Sharpey's fibers - are embedded in this material. This unusual furcation bone material is similar to the disordered material found in human lamellar bone. In the upper furcation region this disordered bone comprises almost all the volume excluding Sharpey's fibers. We surmise that this most unusual bone type functions to resist the repeating compressive loads incurred by molars during mastication., (Copyright © 2019. Published by Elsevier Inc.)

Treatment of carious root surfaces remains challenging due to the complex pathological processes and difficulty in restoring the original structure of root dentine. Current treatments targeting the de-/re-mineralisation processes are not entirely satisfactory in terms of the protection of the dentinal organic matrix and the highly organised structure of dentine. In this in vitro study, a cross-linking agent - proanthocyanidin (PA) was used in conjunction with a fluoride-based treatment - silver diamine fluoride/potassium iodide (SDF/KI) to putatively stabilise the organic dentinal framework as well as strengthen the collagen-mineral phase interaction. The effectiveness of this strategy was evaluated 24 h after application in terms of the distribution of ion uptake and microstructure of dentine after treatment as well as analysis of the nano-mechanical properties using a dynamic behaviour model. Results showed that individual use of SDF/KI significantly improved the surface microhardness and integrated mineral density (Z) up to 60 µm depth and the recovery of creep behaviour of demineralised dentine in the surface area compared to that treated with deionised distilled water (DDW). The combined treatment of PA and SDF/KI achieved a more homogenous mineral distribution throughout the lesions than SDF/KI alone; a more significant incremental increase in surface microhardness and Z was observed. Specifically, a superior effect on the subsurface area occurred with PA + SDF/KI, with significant improvements in microhardness, elastic modulus and recovery of creep behaviour of the demineralised dentine. Application of SDF/KI induced small discrete crystal formation distributed over the dentine surface and PA contributed to the formation of slit-shaped orifices of the dentinal tubules that were partially occluded. STATEMENT OF SIGNIFICANCE: Demographic transitions and improved oral health behaviour have resulted in increased tooth retention in elderly people. As a consequence, the risk of root dentine caries is increasing due to the age-associated gingival recession and the related frequent exposure of cervical root dentine. Root caries is difficult to repair because of the complex aetiology and dentine structure. The recovery of dentine quality depends not only on reincorporation of minerals but also an intact dentinal organic matrix and the organic-inorganic interfacial structure, which contribute to the biomechanics of dentine. With the capability of dentine modification, cross-linking agents were applied with a fluoride regimen, which improved its treatment efficacy of root caries regarding the distribution of ion uptake and recovery of dentine biomechanics., (Copyright © 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

X-ray micro CT has become a popular methodology for the nondestructive analysis of dental tissues and has been used extensively in the amelogenesis field. The aim of this chapter is to introduce ImageJ/Fiji to researchers new to CT scanning and the analysis of CT image data. The program can be applied to analyzing X-ray CT images of enamel but can be extrapolated to other tissues as well.

In this study, natural molar human tooth specimens were investigated for determining their micro- and nanoscale structural morphology, chemistry and crystallinity. The differences were tracked comparatively for both enamel and dentin layers and at their interfaces. Although dental material structures are hard and tough and the cross-sectioning of these materials using mechanical methods is challenging, FIB-SEM dual-beam instruments serve for preparing ultra-thin homogenous lamella sections. In this work, both FIB-SEM and TEM based advanced characterization methods were applied to reveal different morphological characteristics of dental tissue via complementary imaging and diffraction analysis. In addition, SEM-EDS and Raman spectroscopy techniques provided additional information about the elemental distribution and the chemical composition differences of the dental tissues. According to electron microscopy examinations at the intersection between the enamel and the dentin layers, it was shown that the enamel was denser and polycrystalline, while the dentin layer was porous, fibrillar and of negligible long-range order, due to its tubular structure and organic components. In particular, EDS mapping and linescan analyses showed almost no differences in the elemental distribution. Raman results confirmed that both tissues had similar chemical composition except dentin showed spectral background effects in the spectrum due to its tubular structure and organic components., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study aims to explore the feeding ecology of two terrestrial papionins, Papio and Theropithecus from the Shungura Formation in Ethiopia, the most complete stratigraphic and paleontological record of the African Plio-Pleistocene. Two aspects were evaluated using Dental Microwear Texture Analysis: differences in diet between the extinct genera and their extant relatives, and any potential dietary fluctuations over time. Amongst more than 2,500 cercopithecid dental remains, 154 Theropithecus molars and 60 Papio molars were considered. Thirty-nine extant wild baboons and 20 wild geladas were also considered. The results show that diets of extinct monkeys from Member G already differed between genera as it is the case for their extant representatives. The shearing facets on the Theropithecus molars display significant variations in microwear textures, suggesting several dietary shifts over time. Two events point to higher intakes of herbaceous monocots (tougher than dicots foliages), at about 2.91 Ma (between members B and C) and at 2.32 Ma (between members E and F). These two events are separated by an inverse trend at about 2.53 Ma (between members C and D). Some of these variations, such as between members E and F are supported by the enamel carbon isotopic composition of herbivorous mammals and with paleovegetation evidence.

The aim of the present study was to identify the stage during acid etching of dental enamel where scratches introduced by sectioning and grinding procedures were eliminated. Nitric acid was used as etchant. Four hundred 2-3 mm-thick longitudinal sections of human third molar crowns were assigned to 80 groups, each group differing with respect to grinding procedure (silicon carbide paper grit 600; 1,000; 1,200; and 1,200 + polishing), acid concentration (0.1%, 1%, 2.5%, and 5%) and etching time (15, 30, 45, 90, and 180 s). Observation of the specimens with scanning electron microscopy (SEM) showed that elimination of scratches was facilitated by increasing fineness of grinding paper and polishing, and by increasing acid concentration and increasing etching time. An acid concentration of 0.1% did not remove scratches totally irrespective of grinding procedure or etching time, 1% acid removed most scratches after 45-90 s, while 2.5% and 5% acids removed most scratches after 30-45 s. It is proposed that the scratches are eliminated/obscured through a combined effect of the acid and the inherent structure of the enamel. The results of the present study may serve as a guide in choosing the best procedures for obtaining scratch-free enamel surfaces through acid etching with the least possible loss of enamel substance. Research highlights Sectioning and grinding produce scratches in dental enamel. Scratches are eliminated by acid etching prior to SEM studies of enamel structure. Scratch elimination increases with increasing acid strength and etching time and is facilitated by finer grit grinding paper and polishing., (© 2018 Wiley Periodicals, Inc.)

The aim of this study was to investigate (i) the effect of direct or indirect polymerisation of adhesive-impregnated ribbon fibre under 4-mm bulk-filled composites on fracture strength; (ii) to compare polyethylene ribbon fibre-reinforcement composites with short fibre-reinforced composite; and (iii) the effectiveness of polyethylene ribbon fibre according to the restorative materials used (low-viscous bulk-fill composite, high-viscous flowable composite or conventional paste composite). Seventy molars were divided into seven groups; (groups 1-2) Ribbond-reinforced Surefil-SDR; (group 3) Ribbond-reinforced G Aenial Flo; (group 4) Ribbond-reinforced G Aenial Posterior; (group 5) short fibre-reinforced composite everX Posterior; (group 6) unfilled cavity; (group 7) intact teeth. Ribbond was adopted to cavity walls by impregnating an adhesive and using a flowable composite. In group 1, adhesive-impregnated Ribbond was polymerised directly using a light-curing-unit, and indirectly in group 2 under 4-mm bulk-filled composite. Direct or indirect polymerisation of adhesive impregnated ribbon fibre under 4-mm bulk-filled composite did not change the fracture strength results. Polyethylene ribbon fibre-reinforced groups (groups 1-4) and short fibre-reinforced composite group (group 5) displayed similar results. Polyethylene ribbon fibre can be used safely under 4-mm bulk-filled composites. Ribbond-reinforced low-viscous bulk-fill, high-viscous flowable, and conventional paste composite exhibited similar fracture strength results., (© 2016 Australian Society of Endodontology Inc.)

Aims: The structural organization of collagen from mineralized tissues, such as dentin and bone, has been a topic of debate in the recent literature. Recent reports have presented novel interpretations of the complexity of collagen type I at different hierarchical levels and in different tissues. Here, we investigate the nanostructural organization of demineralized dentin collagen following the digestion of non-collagenous components with a trypsin enzyme., Materials and Methods: Dentin specimens were obtained from healthy third-molars, cut into small cubes, and polished down to 1 µm roughness. Samples were then demineralized with 10% citric acid for 2 min. Selected specimens were further treated with a solution containing 1 mg/ml trypsin for 48 hours at 37 °C (pH 7.9-9.0). Both untreated and trypsin digested samples were analyzed using SDS-PAGE, Field Emission Scanning Electron Microscopy (FE-SEM), and nanoindentation, where surface hardness and creep properties were compared before and after treatments., Results: FE-SEM images of demineralized dentin showed the banded morphology of D-periodical collagen type I, which upon enzymatic digestion with trypsin appeared to dissociate longitudinally, consistently unraveling ~20 nm structures (microfibril bundles). Such nanoscale structures, to the best of our knowledge, have not been characterized in dentin previously. Mechanical characterization via nanoindentation showed that the unraveling of such microfibril bundles affected the creep displacement and creep rate of demineralized dentin., Conclusion: In summary, our results provide novel evidence of the organization of collagen type I from dentin, which may have important implications for the interaction of dental materials with the organic dentin matrix and the mechanical properties of mineralized tissues.

In the current study, we evaluate the equivalent stiffness of peritubular reinforcement effect (PRE) of porous dentine optimized by the thickness of peritubular dentine (PTD). Few studies to date have evaluated or quantitated the effect of PRE on composite dentine. The miscrostructure of porous dentine is captured by scanning electron microscope images, and then finite element modeling is used to quantitate the deformation and stiffness of the porous dentine structure. By optimizing the radius of PTD and dentine tubule (DT), the proposed FE model is able to demonstrate the effect of peritubular reinforcement on porous dentine stiffness. It is concluded that the dentinal equivalent stiffness is reduced and degraded with the increase of the radius of DT (i.e., porosity) in the certain ratio value of Ep/Ei and certain radius of PTD, where Ep is the PTD modulus and Ei is the intertubular dentine modulus. So in order to ensure the whole dentinal equivalent stiffness is not loss, the porosity should get some value while the Ep/Ei is certain. Thus, PTD prevents the stress concentration around DTs and reduces the risk of DTs failure. Mechanically, the overall role of PTD appears to enhance the stiffness of the dentine composite structure. These results provide some new and significant insights into the biological evolution of the optimal design for the porous dentine microstructure. These findings on the biological microstructure design of dentine materials are applicable to other engineering structural designs aimed at increasing the overall structural strength.

Aim: The aim of this study is to evaluate and compare therapeutic effects of mesenchymal stem cell (MSCs) and osteoprotegerin (OPG) gene transfer applications on inhibition and/or repair of orthodontically induced inflammatory root resorption (OIIRR)., Materials and Methods: Thirty Wistar rats were divided into four groups as untreated group (negative control), treated with orthodontic appliance group (positive control), MSCs injection group, and OPG transfected MSCs [gene therapy (GT) group]. About 100g of orthodontic force was applied to upper first molar teeth of rats for 14 days. MSCs and transfected MSC injections were performed at 1st, 6th, and 11th days to the MSC and GT group rats. At the end of experiment, upper first molar teeth were prepared for genetical, scanning electron microscopy (SEM), fluorescent microscopy, and haematoxylin eosin-tartrate resistant acid phosphatase staining histological analyses. Number of total cells, number of osteoclastic cells, number of resorption lacunae, resorption area ratio, SEM resorption ratio, OPG, RANKL, Cox-2 gene expression levels at the periodontal ligament (PDL) were calculated. Paired t-test, Kruskal-Wallis, and chi-square tests were performed., Results: Transferred MSCs showed marked fluorescence in PDL. The results revealed that number of osteoclastic cells, resorption lacunae, resorption area ratio, RANKL, and Cox-2 were reduced after single MSC injections significantly (P < 0.05). GT group showed the lowest number of osteoclastic cells (P < 0.01), number of resorption lacunae, resorption area ratio, and highest OPG expression (P < 0.001)., Conclusions: Taken together all these results, MSCs and GT showed marked inhibition and/or repair effects on OIIRR during orthodontic treatment on rats., (© The Author 2016. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com)

of this study was to analyze the effects of carbon dioxide (CO2) laser light on the structure and elemental composition of dentine., Methods: The evaluation was conducted on samples from extracted teeth. The surface of the dentine was exposed to the radiation from a CTL 1401 CO2 laser (Centre of Laser Technology, Poland). The radiation and frequency parameters were as follows: group I with 5 W and 1 Hz, group II with 10 W and 1 Hz, group III with 5 W and 5 Hz, and group IV with 10 W and 5 Hz. The altered dentine structure was macroscopically and microscopically evaluated using a Nova NanoSEM 200 Scanning Electron Microscope (FEI Europe) with integrated microanalysis X-ray system for elemental analysis in points., Results: There were significant differences between groups in the macro- and microstructure of laser defects., Conclusions: CO2 laser radiation causes irreversible, destructive changes in dentine. The structural dentine lesions developed under the influence of the CO2 laser radiation may hinder proper adhesion of bonding systems with the damaged tissue. Laser defects in the structure should be treated like defects of noncarious origin requiring preparation and filling with composite materials in accordance with the procedures.

Objective: To compare the effect of different endodontic irrigants on microleakage of adhesives used within pulp chamber of primary molars., Study Design: 72 Primary molars were divided into 6 groups, according to 3 irrigants and 2 adhesives used. After de-roofing the pulp chamber, pulp was extirpated. In 36 samples, pulp chambers were bonded with Xeno V + after irrigation with either QMix (Group1); 17%EDTA+5%NaOCl (Group2) or normal saline (Group3) and in other half samples, pulp chambers were bonded with SinglebondUniversal after irrigation with either QMix (Group 4); 17%EDTA+5% NaOCl (Group5) or normal saline (Group 6). All the samples were restored with Filtek Z350. Ten teeth from each group were assessed for dye penetration. Two samples in each group were viewed under scanning electron microscope. Data was statistically analyzed using Mann-Whitney and Kruskal Wallis tests at a significance level of P < 0.05., Results: Mean microleakage scores were: Group 1-1.5±0.70, Group 2-1.6±.51, Group 3-2.4±0.96, Group 4-1.2±0.42, Group 5-1.2±0.42, Group 6-1.1±0.32., Conclusions: Irrigation with QMix significantly reduced the microleakage of XenoV + but had no significant effect on microleakage of SinglebondUniversal. Irrigation with EDTA/NaOCl or QMix had no detrimental effect on the sealing ability of either of the adhesive tested.

Objective: The present study was designed to elucidate whether three soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) core proteins, syntaxin-1, synaptosomal-associated protein of 25kDa (SNAP-25), and vesicle-associated membrane protein-2 (VAMP-2), are present in the dental pulp of the rat molar at both the light and electron microscopic levels., Design: Immunohistochemistry for protein gene product 9.5 (PGP 9.5), a pan-neuronal marker, syntaxin-1, SNAP-25, and VAMP-2 was performed on decalcified rat molars for light and electron microscopic analyses. Double-immunolabeling of PGP 9.5 and the SNARE core proteins, as well as combinations of the SNARE core proteins, was also carried out., Results: PGP 9.5-immunoreactive nerve fibers ran toward the coronal region, ramified at the subodontoblast layer, and formed the subodontoblastic nerve plexus. Most nerve fibers penetrated the predentin and dentin along the dentinal tubules. Most, if not all, nerve fibers displayed immunoreactivity for syntaxin-1, SNAP-25, and VAMP-2. Immunoelectron microscopic analyses confirmed the presence of immunoreactivity for the SNARE core proteins within the intradental axonal elements., Conclusions: The present findings suggest that, since SNARE core proteins participate in the docking and exocytosis of synaptic vesicles in the central nervous system, they may contribute to vesicle exocytosis from the dental nerve fibers even though there are no apparent synapses., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Introduction: The perception of pain varies individually. Chronic stress leads to analgesia. The use of animal chronic mild stress model to mimic human condition was previously developed and now applied in the evaluation of pain perception in rats with dentin hypersensitivity (DH)., Aims: Using DH model induced by dentin erosion (DE) mediated by acidic solution, the present study aimed the evaluation of the interaction of chronic stress and pain induced by DH in rats with DE., Methods: DH was induced by ad libitum 30-day intake of acidic solution. Stress was induced by the New York subway model. Body weight was weekly taken, during treatment. Groups WO (water, no stress), WS (water and stress), EO (acidic solution, no stress) and ES (acidic solution, stress) were submitted to treatments., Results: After 30 days, all groups were submitted to DH test assessed by cold water stimuli in the labial surface of molars, for 5s, and the rats responses were scored as grades 0, 0.5, 1, 2, or 3. After euthanasia, blood was taken to obtain the levels of corticosterone, stomachs were observed in fresh preparations, kidneys and livers were submitted to histological evaluation. Open field model supported stress evaluation, as did corticosterone analysis. Stressed animals showed significant increase in pain perception and a decrease in locomotion frequency, tending to be more frequent in the periphery of the arena, corroborating stressed behavior and the need of protection as a pain relief. Corticosterone levels were increased in the stressed rats with dentin erosion and also corroborate present findings. Finally, reduction in weight gain was impaired in stressed group with dentin erosion., Conclusion: The animal model enabled the evaluation of how chronic mild stress interfered in DH pain perception., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The "lead line" was described by Henry Burton in 1840. Rodents are used as sentinels to monitor environmental pollution, but their teeth have not been used to determine lead. To determine whether lead deposits can be observed in the teeth of lead-exposed animals, since the gingival deposits known as "lead line" would likely have a correlate in the calcified tissue to which the gums are opposed during life. Male Wistar rats were exposed to lead in the drinking water (30 mg/L) since birth until 60 days-old. Molars and the incisors of each hemimandible were analyzed by scanning electron microscopy (SEM) on regular and backscattered electrons (BSE) mode. Elements were determined using electron dispersive spectroscopy (EDS). Clean cervical margins were observed on control teeth, as opposed to the findings of extensive deposits on lead-exposed animals, even in hemimandibles that had been exhumed after being buried for 90 days. BSE/EDS indicated that those deposits were an exogenous material compatible with lead sulfite. Presence of calcium, phosphorus, magnesium, carbon, lead, and oxygen is presented. Lead-exposed animals presented marked root resorption. The lead deposits characterized here for the first time show that the "lead line" seen in gums has a calcified tissue counterpart, that is detectable post-mortem even in animals exposed to a low dose of lead. This is likely a good method to detect undue lead exposure and will likely have wide application for pollution surveillance using sentinels.

Objective: The etiology of dental microwear is incompletely understood, despite copious documentation of wear patterns from wild and captive specimens across numerous vertebrate taxa. Among the contested issues with respect to microwear formation is the question of whether materials softer than enamel (specifically, foods themselves) can produce wear features., Design: We examine the creation of enamel microwear features in vitro from foods that vary in hardness and toughness on a sample of mammalian lower molars (pig, bear, deer, and primate). These experiments involved applying loads at a constant displacement rate perpendicular to an occlusal enamel surface. Changes in surface microwear textures were assessed after 10 loads., Results: Our experiments demonstrate that even relatively soft foods free of exogenous abrasives modify surface texture to produce distinctive microwear fabrics. Consequently, these data provide clear evidence that materials softer than enamel are capable of indenting and abrading enamel surfaces. Foods with a relatively high elastic modulus are associated with larger and more extensive microwear features, although the relationship between food stiffness and rate of microwear formation does not appear to be a simple one., Conclusions: These observations refute recent arguments that food material is an insignificant agent in the formation and accumulation of enamel microwear. Relative hardness of ingested materials is only one factor in the etiology of microwear formation., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Aim: This study evaluated the influence of acid-etching time on collagen exposure in adhesive interfaces established on primary and permanent dentin., Materials and Methods: Flat dentin surfaces were produced on sound primary molars and premolars (n = 8). The surfaces were divided into mesial and distal halves, and each half was etched with phosphoric acid for 5 or 15 seconds. The teeth were randomly allocated into two groups according to the adhesive system applied: Prime & Bond NT or Prime & Bond 2.1. After the adhesive application, the specimens were processed for Goldner's trichrome staining. The thickness of the uninfiltrated collagen zone (UCZ) in the hybrid layer was measured under optical microscopy. Data were analyzed by analysis of variance and Tukey tests (α = 0.05)., Results: The thickness of UCZ was adhesive dependent. Within the same substrate, the specimens treated with Prime & Bond 2.1 presented thicker UCZ when etched for 15 seconds. Collagen exposure was significantly higher for the primary teeth etched for 5 seconds and treated with Prime & Bond 2.1., Conclusion: The thickness of UCZ in hybrid layers is directly affected by acid-etching time and by the adhesive system applied. Primary dentin seems to be more susceptible to collagen exposure than is permanent dentin., Clinical Significance: Both acid-etching time and adhesive system can influence the amount of exposed collagen interfering on resin-dentin bond quality, especially on primary dentin.

Purpose: Alumina air abrasion is an alternative for acid-etch technique for tooth preparation before placement of a fissure sealant. The aim of this study was to compare the retention of sealants placed subsequent to air abrasion with alumina and bioactive glass (BAG) particles., Methods: Sixty-two 6-12 year old children were included in this study. Using a halfmouth design, the fissures were prepared using air abrasion with alumina particles on randomly assigned permanent mandibular or/and maxillary first molars on one side of the mouth (Group 1) and air abrasion with BAG on the contralateral side of the mouth (Group 2). Sealants were applied on 180 teeth, and were scored as missing, partially retained, and completely retained after three, six, nine and 12 months. Data were analyzed using Friedman and Wilcoxon tests (α=0.05)., Results: Sealant retention rates in the alumina group were higher than those in the BAG group at all time periods (P<0.001)., Conclusions: Sealant retention after air abrasion with alumina particles was higher than BAG over 12 months.

Amelogenin and ameloblastin are 2 extracellular matrix proteins that are essential for the proper development of enamel. We recently reported that amelogenin and ameloblastin colocalized during the secretory stage of enamel formation when nucleation of enamel crystallites occurs. Direct interactions between the 2 proteins have been also demonstrated in our in vitro studies. Here, we explore interactions between their fragments during enamel maturation. We applied in vivo immunofluorescence imaging, quantitative co-localization analysis, and a new FRET (fluorescence resonance energy transfer) technique to demonstrate ameloblastin and amelogenin interaction in the maturing mouse enamel. Using immunochemical analysis of protein samples extracted from 8-d-old (P8) first molars from mice as a model for maturation-stage enamel, we identified the ~17-kDa ameloblastin (Ambn-N) and the TRAP (tyrosine-rich amelogenin peptide) fragments. We used Ambn-N18 and Ambn-M300 antibodies raised against the N-terminal and C-terminal segments of ameloblastin, as well as Amel-FL and Amel-C19 antibodies against full-length recombinant mouse amelogenin (rM179) and C-terminal amelogenin, respectively. In transverse sections, co-localization images of N-terminal fragments of amelogenin and ameloblastin around the prism boundary revealed the "fish net" pattern of the enamel matrix. Using in vivo FRET microscopy, we further demonstrated spatial interactions between amelogenin and ameloblastin N-terminal fragments. In the maturing mouse enamel, the association of these residual protein fragments created a discontinuity between enamel rods, which we suggest is important for support and maintenance of enamel rods and eventual contribution to unique enamel mechanical properties. We present data that support cooperative functions of enamel matrix proteins in mediating the structural hierarchy of enamel and that contribute to our efforts to design and develop enamel biomimetic material., (© International & American Associations for Dental Research 2016.)

Introduction: Partial caries removal has been shown to be an effective method to treat deep carious lesions in deciduous teeth. Nevertheless, the possibility of keeping infected dentin in the cavity still requires additional investigation. The objective of this research was to describe changes in primary infected dentin after restoration with glass ionomer cement., Methods: Dentin from 45 primary molars with deep and active carious lesions was evaluated using clinical and laboratory criteria, before and 60 days after restoration. The clinical analysis evaluated dentin colour (CO), dentin consistency (COS) and laser fluorescence (LF). The laboratory procedures assessed bacterial contamination and mineral content (MC), and evaluated the dentin ultrastructure and collagen content. Data on CO, COS, LF and colony forming units were analysed using the Wilcoxon signed-rank test; MC, bacterial counts and collagen evaluations were evaluated using the Student's t-test., Results: After 60 days, lower values of LF were observed, together with a lower bacterial count, and a higher COS was found, with an increase in calcium, phosphorus and collagen contents. Differences were not detected for CO or for fluorine content. Baseline samples showed enlarged tubules with bacterial invasion; 60-day samples showed better organised tissue, with a more compact intertubular dentin and narrower tubules., Conclusion: It is concluded that appropriate cavity sealing can promote beneficial changes in deep carious lesions of primary teeth, even in the presence of infected dentin., (© 2016 FDI World Dental Federation.)

The aim of the study was to propose the artefact index on cone-beam computed tomography (CBCT) images of clinical prosthodontics materials, and to compare the effect of the artefacts on CBCT image clarity of normal oral tissues. Seven spheres of different materials were secured on the centre of a resin baseboard, respectively, and four human molars in vitro were placed at 10 mm front, back, left and right of the sphere. The board was scanned using CBCT with the same setting. 10 tomographic images from each of the seven data sets with clear artefacts was selected. The grayscale measuring tool of Photoshop software was used to measure the grayscale (G0) within the boundary of tomographic image and the grayscales of the streaky artefacts that were 1 mm and 20 mm outside the circular boundary (G1 and G2). The arc length, L1, of the circular boundary with artefacts was measured; the circumference, L2, was calculated. The artefact index, A, was determined as (G1/G0) × 0.5 + (G2/G1) × 0.4 + (L2/L1) × 0.1. The artefact index A can comprehensively represent the effect of artefacts on CBCT image clarity for oral tissue.

UltraSeal XT hydro is a new hydrophilic, light-cured, methacrylate-based pit and fissure sealant which has been developed by Ultradent Products, USA. The sealant is highly filled with a 53 wt.% mixture of inorganic particles which confer both thixotropy and radiopacity. The principal purpose of this study was to investigate the microleakage of UltraSeal XT hydro as a function of different enamel etching techniques. The occlusal surfaces of sound, extracted human molars were either acid etched, Er:YAG laser irradiated or successively laser irradiated and acid etched. UltraSeal XT hydro was applied to each group of teeth (n = 10) which were subjected to a thermocycling process consisting of 2500 cycles between 5 and 50 °C with a dwell time of 30 s. Microleakage assessments were then carried out using 0.5% fuchsin dye and optical microscopy. The microleakage score data were analysed using the Kruskal-Wallis, Mann-Whitney U test with Bonferroni adjustment. No significant differences in microleakage were noted between the individually acid etched and laser-irradiated groups (p > 0.05); however, teeth treated with a combination of laser irradiation and acid etching demonstrated significantly lower microleakage scores (p < 0.001). Electron microscopy with energy-dispersive X-ray analysis revealed that the mineral filler component of UltraSeal XT hydro essentially comprises micrometre-sized particles of inorganic silicon-, aluminium- and barium-bearing phases. Laser etching increases the roughness of the enamel surface which causes a concentrated zoning of the filler particles at the enamel-sealant interface.

Matrix extracellular phosphoglycoprotein (MEPE) is an extracellular matrix protein found in dental and skeletal tissues. Although information regarding the role of MEPE in bone and disorders of phosphate metabolism is emerging, the role of MEPE in dental tissues remains unclear. We performed RNA in situ hybridization and immunohistochemistry analyses to delineate the expression pattern of MEPE during embryonic and postnatal development in craniofacial mineralizing tissues. Mepe RNA expression was seen within teeth from cap through root formation in association with odontoblasts and cellular cementoblasts. More intense expression was seen in the alveolar bone within the osteoblasts and osteocytes. MEPE immunohistochemistry showed biphasic dentin staining in incisors and more intense staining in alveolar bone matrix and in forming cartilage. Analysis of Mepe null mouse molars showed overall mineralized tooth volume and density of enamel and dentin comparable with that of wild-type samples. However, Mepe(-/-) molars exhibited increased thickness of predentin, dentin, and enamel over controls and decreased gene expression of Enam, Bsp, Dmp1, Dspp, and Opnby RT-PCR. In vitro Mepe overexpression in odontoblasts led to significant reductions in Dspp reporter activity. These data suggest MEPE may be instrumental in craniofacial and dental matrix maturation, potentially functioning in the maintenance of non-mineralized matrix., (© 2016 The Histochemical Society.)

Objectives: To assess leakage of class-I restorations using a gas-enhanced permeation test (GEPT) as compared with conventional SEM or dye analysis., Materials and Methods: Pressure differences over time and penetrating water volumes were measured simultaneously in a two-chamber system (GEPT) before and after class I cavity preparation in 30 molars. Ten teeth were restored with a composite restoration without bonding (A1), a composite restoration with bonding (A2) or a ceramic indirect restoration (B). Five intact teeth served as controls (C). Another GEPT measurement was performed and impressions were taken. Teeth were subjected to thermodynamic loading (1 200 000 cycles) and final GEPT measurements and impressions were made. SEM evaluation of the marginal continuity was performed and teeth were subjected to a Fuchsin dye penetration test. Spearman's rank test was used to compare results from different tests., Results: The GEPT and SEM values did not correlate before loading (0.359, p = 0.051), but significantly correlated afterwards (0.662, p < 0.0001). The correlations between the Fuchsin dye penetration test and GEPT and SEM surface marginal analysis were significant (0.777 and 0.534, p-values < 0.0001 and 0.002, respectively)., Conclusions: SEM marginal analysis was mainly limited in reflecting the surface restoration integrity. GEPT evaluation may, therefore, serve as a tool to non-destructively assess restoration sub-surface integrity over time., Clinical Relevance: The current study provided proof that restoration margin quality does not necessarily reflect its leakage behaviour.

Objective: To evaluate the root canal surfaces in teeth previously treated using RF resin by SEM., Material and Methods: 20 distal roots of mandibular molars with typical discoloration of tooth crown were used in this study: 10 brownish - red and 10 non-colored roots. The roots were removed from the crowns, splinted longitudinally and subjected to SEM in a back-scattered electron mode., Results: In discolored root samples canal walls appeared without smear layer and varying amount of remaining debris, the observed morphology of dentine was ordinary. In the non-colored root samples the dentin profile revealed: in coronal third of the root just few open dentinal tubules were detected, while in the middle and apical thirds no open dentinal tubules were observed, dentin profile was similar to sclerotic dentin. The multiple dentinal defects were detected in all samples, however significantly more dentinal defects were found in the colored roots. The RF paste was well adhered to the root canal dentine and multiple tags of RF resin penetrating deeply into the dentinal tubules were detected., Conclusions: The surfaces of the root canal walls of the teeth treated using RF paste exhibits usual appearance and ordinary dentin morphology in colored roots while the dentin of non-colored samples has the profile of sclerotic dentin. Multiple dentinal defects could be determined by damaging effect of RF resin on dentin. The adaptation and adhesion of RF paste to the dentin, capability to penetrate into dentinal tubules is comparable with the modern resin based sealers.

Purpose: To evaluate the influence of enamel condition and etching strategy on bond strength of a universal adhesive in primary teeth., Materials and Methods: Thirty-six primary molars were randomly assigned to six groups (n = 6) according to the enamel condition (sound [S] and demineralized [DEM]/cariogenic challenge by pH cycling prior to restorative procedures) and adhesive system (Scotchbond Universal Adhesive [SBU]) used in either etch-and-rinse (ER) or selfetching (SE) mode, with Clearfil SE Bond as the self-etching control. The adhesives were applied to flat enamel surfaces and composite cylinders (0.72 mm2) were built up. After 24-h storage in water, specimens were subjected to the microshear test. Bond strength (MPa) data were analyzed using two-way ANOVA and Tukey's post-hoc tests (α = 0.05)., Results: Significant differences were found considering the factors adhesive system (p = 0.003) and enamel condition (p = 0.001). Demineralized enamel negatively affected the bond strength, with μSBS values approximately 50% lower than those obtained for sound enamel. SBU performed better in etch-and-rinse mode, and the bond strength found for SBU applied in self-etching mode was similar to that of CSE., Conclusions: Enamel etching with phosphoric acid improves the bond strength of a universal adhesive system to primary enamel. Demineralized primary enamel results in lower bond strength.

Objective: To evaluate the effect of ethanolic extracts of propolis (EEP) addition in different proportions to glass ionomer cement (GIC) on microleakage and microhardness of GIC., Study Design: The cement was divided into four groups: one using the original composition and three with 10%, 25%, and 50% EEP added to the liquid and then manipulated. For microleakage assessment, sixty primary molars were randomly divided into four groups (n=15). Standard Class II cavities were prepared and then filled with EEP in different proportions added to GICs. Microleakage test was performed using a dye penetration method. The data were analyzed using one-way ANOVA and Mann-Whitney U tests (α = 0.05). Disc shaped specimens were prepared from the tested GIC to determine Vickers hardness (VHN). The data were analyzed using one-way ANOVA and post hoc Tukey test (α = 0.05)., Results: There were no statistically significant differences between the groups in terms of microleakage (p > 0.05). There were statistically significant differences between the VHN values of groups (p < 0.05). Increasing addition of EEP to GIC statistically significantly increased VHN value of GIC (p < 0.05)., Conclusions: The addition of EEP to GIC increased the microhardness of the GIC and did not adversely affect the microleakage. Thus, it might be used during routine dental practice due to its antibacterial properties.

The purpose of this study was to analyze, by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM), the morphology of sealant/enamel interface after surface treatment with Biosilicate. Before pits and fissures sealing, the occlusal surfaces of 10 sound human molars were sectioned perpendicularly at the fissures in order to obtain three slices for each tooth. Slices were randomly assigned into three groups (n = 10) according to sealing protocol: Group 1- Acid etching + Biosilicate + glass ionomer-based sealant (Clinpro XT Varnish, 3M ESPE); Group 2- Acid etching + glass ionomer-based sealant (Clinpro XT Varnish, 3M ESPE); Group 3- No sealing. All slices were subjected to thermal cycling (5,000 cycles; 5-55°C; dwell time: 30s). Half of the slices from each group (n = 5) were analyzed by CLSM and the other half by SEM. Groups 1 and 2 were also submitted to EDS analysis and their data were evaluated by Two-Way ANOVA e Tukey's test (α=5%). EDS data analysis showed higher amounts of silicon (Si) ions than calcium (Ca) ions in Group 1 (P < 0.05); Group 2 presented higher amounts (P < 0.05) of Ca ions than Si ions. It may be concluded that the use of Biosilicate for surface treatment did not affect the morphology of glass ionomer-based sealant/enamel interfaces., (© 2015 Wiley Periodicals, Inc.)

Many types of behavioral and dietary information can be extracted from studies of tooth microwear. Some studies have even been successful at determining the overall directionality of microwear in order to establish gross masticatory movement (Williams et al., 2009, PNAS, 106, 11194-11199). However, microwear has never been successfully visualized in situ in 3 dimensions (3D), visualized virtually and quantified. The ability to accomplish this yields information on exact masticatory movement which can then be used to address any number of eco-biological and physiological questions in extant and extinct organisms. In order to create 3D virtual reality (VR) representation of microwear, fossil molars from the Javanese Sangiran 7 (S7) Homo erectus tooth collection and from historic hunter/gatherer meta-populations were imaged, the microwear in 3 dimensions was extracted, this information was then placed back on VR representations of the molars and quantified. The methodology contained herein demonstrates the efficacy and importance of such a technique in determining gross masticatory movement in fossil and recent hominin molars. This methodology could, in theory, be applied to any organism which produces microwear on its dentition. Applications in the fields of dentistry, orthodontics, climatology and dietary and habitat reconstructions can also be envisioned., (© Wiley Periodicals, Inc.)

Objectives: To evaluate the effect of adhesion strategy on the enamel microshear bond strengths (μSBS), etching pattern, and in situ degree of conversion (DC) of seven universal adhesives., Methods: 84 extracted third molars were sectioned in four parts (buccal, lingual, proximal) and divided into 21 groups, according to the combination of the main factors adhesive (AdheSE Universal [ADU], All-Bond Universal [ABU], Clearfil Universal [CFU], Futurabond U [FBU], G-Bond Plus [GBP], Prime&Bond Elect (PBE), and Scotchbond Universal Adhesive [SBU]), and adhesion strategy (etch-and-rinse, active self-etch, and passive self-etch). Specimens were stored in water (37°C/24h) and tested at 1.0mm/min (μSBS). Enamel-resin interfaces were evaluated for DC using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a field-emission scanning electron microscope (direct and replica techniques). Data were analyzed with two-way ANOVA and Tukey's test (α=0.05)., Results: Active self-etch application increased μSBS and DC for five out of the seven universal adhesives when compared to passive application (p<0.001). A deeper enamel-etching pattern was observed for all universal adhesives in the etch-and-rinse strategy. A slight improvement in etching ability was observed in active self-etch application compared to that of passive self-etch application. Replicas of GBP and PBE applied in active self-etch mode displayed morphological features compatible with water droplets. The DC of GBP and PBE were not affected by the application/strategy mode., Conclusions: In light of the improved performance of universal adhesives when applied actively in SE mode, selective enamel etching with phosphoric acid may not be crucial for their adhesion to enamel., Clinical Significance: The active application of universal adhesives in self-etch mode may be a practical alternative to enamel etching in specific clinical situations., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objectives: To evaluate the fracture strength and the mode of failure of endodontically treated molars restored with CAD/CAM overlays with fiber reinforced composite build-up of the pulp chamber., Methods: 40 Devitalized molars were cut over the CEJ and divided into five groups (n=8). The pulp chamber area was filled with: group 0 (control), no resin build-up; group 1, hybrid composite build-up (G-aenial posterior, GC); group 2, as in group 1 but covered with 3 nets of bi-directional E-glass fibers (EverStickNET, Stick Tech Ltd.); group 3, a FRC resin (EverX posterior, GC); group 4, as in group 3 but covered by the bi-directional fibers. The crowns were restored with CAD-CAM composite restorations (Lava Ultimate, 3M ESPE). Maximum fracture loads were recorded in Newton and data were analyzed using Kruskal-Wallis test (p<0.05). Fragments were analyzed using SEM., Results: The mean static loads in Newton were: group 0: 2448 (546); group 1: 2817 (873); group 2: 2128 (952); group 3: 2429 (1091); group 4: 2577 (833). No significant differences were found between the groups (p>0.05). All specimens fractured in a catastrophic way, under the CEJ. The main crack evolved in the corono-apical direction. In groups 2 and 4 secondary fracture paths with apico-coronal direction were detected close to the bi-directional fibers' layer., Conclusions: For the restoration of endodontically treated molars, the incorporation of FRCs did not influence the load-bearing capacity of the tooth-restoration complex. The SEM analysis showed a low ability of the bi-directional fibers net in deviating the fracture but this effect was not sufficient to lead more favorable fracture patterns, over the CEJ., Clinical Significance: The use of FRCs to reinforce the "core" of devitalized molars against vertical fractures under static loads seems useless when the thickness of the CAD/CAM composite overlay restoration is high., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Paleoanthropologists and vertebrate paleontologists have for decades debated the etiology of tooth wear and its implications for understanding the diets of human ancestors and other extinct mammals. The debate has recently taken a twist, calling into question the efficacy of dental microwear to reveal diet. Some argue that endogenous abrasives in plants (opal phytoliths) are too soft to abrade enamel, and that tooth wear is caused principally by exogenous quartz grit on food. If so, variation in microwear among fossil species may relate more to habitat than diet. This has important implications for paleobiologists because microwear is a common proxy for diets of fossil species. Here we reexamine the notion that particles softer than enamel (e.g., silica phytoliths) do not wear teeth. We scored human enamel using a microfabrication instrument fitted with soft particles (aluminum and brass spheres) and an atomic force microscope (AFM) fitted with silica particles under fixed normal loads, sliding speeds, and spans. Resulting damage was measured by AFM, and morphology and composition of debris were determined by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Enamel chips removed from the surface demonstrate that softer particles produce wear under conditions mimicking chewing. Previous models posited that such particles rub enamel and create ridges alongside indentations without tissue removal. We propose that although these models hold for deformable metal surfaces, enamel works differently. Hydroxyapatite crystallites are "glued" together by proteins, and tissue removal requires only that contact pressure be sufficient to break the bonds holding enamel together.

Severe tooth wear is the most common non-caries dental disease, and it can seriously affect oral health. Studying the tooth wear process is time-consuming and difficult, and technological tools are frequently lacking. This paper presents a novel method of digital simulation modeling that represents a new way to study tooth wear. First, a feature extraction algorithm is used to obtain anatomical feature points of the tooth without attrition. Second, after the alignment of non-attrition areas, the initial homogeneous surface is generated by means of the RBF (Radial Basic Function) implicit surface and then deformed to the final homogeneous by the contraction and bounding algorithm. Finally, the method of bilinear interpolation based on Laplacian coordinates between tooth with attrition and without attrition is used to inversely reconstruct the sequence of changes of the 3D tooth morphology during gradual tooth wear process. This method can also be used to generate a process simulation of nonlinear tooth wear by means of fitting an attrition curve to the statistical data of attrition index in a certain region. The effectiveness and efficiency of the attrition simulation algorithm are verified through experimental simulation.

Mapping the distribution of dentin tubules is vital to understanding the structure-function relationship of dentin, an important indicator of tooth stability. This study compared the distances between and density of tubules in the external dentin located in the crown region of an adult human incisor and molar to determine if analysis could be conducted using light-level microscopy. Teeth were processed for routine histology, cut in cross-section, images captured using Advanced SPOT Program, and microstructure was analyzed using ImageJ (NIH). Intratubular (peritubular) dentin with or without odontoblast processes were observed and although incisor and molar images appeared visually similar, plot profile graphs differed. Distance-intervals between tubules in the incisor (5.45-7.67 μm) had an overall range of 2.22 μm and in the molar (7.43-8.42 μm) an overall range of 0.99 μm. While molar tubule distribution displayed a tighter overall range, there was a smaller distance between most incisor tubules. The average densities observed in incisors were 15,500 tubules/mm(2), compared with 20,100 tubules/mm(2) in molars. ImageJ analysis of prepared histology microscopic slides provides researchers with a rapid, inexpensive assessment tool when compared with advanced/ultrastructural methodologies. By combining routine histological processing and light microscopic observations followed by ImageJ analysis, tooth structure can be converted into numerical data and easily mastered by laboratory personnel., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Dentin is the main supporting structure of teeth, but its mechanical properties may be adversely affected by pathological demineralization. The purposes of this study were to develop a quantitative approach to characterize the viscoelastic properties of dentin after de- and re-mineralization, and to examine the elastic properties using a nanoindentation creep test. Dentin specimens were prepared to receive both micro- and nano-indentation tests at wet and dry states. These tests were repeatedly performed after demineralization (1% citric acid for 3 days) and remineralization (artificial saliva immersion for 28 days). The nanoindentation test was executed in a creep mode, and the resulting displacement-time responses were disintegrated into primary (transient) and secondary (viscous) creep. The structural changes and mineral densities of dentin were also examined under SEM and microCT, respectively. The results showed that demineralization removed superficial minerals of dentin to the depth of 400 μm, and affected its micro- and nano-hardness, especially in the hydrate state. Remineralization only repaired the minerals at the surface layer, and partially recovered the nanohardness. Both the primary the secondary creep increased in the demineralized dentin, while the hydration further enhanced creep deformation of untreated and remineralized dentin. Remineralization reduced the primary creep of dentin, but did not effectively increase the viscosity. In conclusion, water plasticization increases the transient and viscous creep strains of demineralized dentin and reduces load sustainability. The nanoindentation creep test is capable of analyzing the elastic and viscoelastic properties of dentin, and reveals crucial information about creep responses., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objectives: To comparatively evaluate the efficiency of various chemomechanical caries removal agents in smear layer removal., Materials and Methods: Class V cavities were prepared on the buccal surface of 45 extracted, noncarious molars and were divided into three groups according to the chemical treatment received. The samples were then gold palladium coated and viewed under scanning electron microscope. The presence of smear layer was evaluated based on the microscopic observations. Result and Observation: The results indicated that smear layer removal was significantly higher in the sodium hypochlorite-based chemomechanical caries removal agents than in the papain-based chemomechanical caries removal agent and was least in the control group treated with saline., Conclusion: The smear layer removal was maximum with Carisolv followed by the cariecare and was minimum in the saline-treated group.

Aim: To evaluate and compare the effect of double-application of single-step self-etch adhesives using microleakage study and to analyze the dentin-adhesive interfacial micromorphology., Methods: In total, 72 extracted human premolars were divided into three groups for different self-etch adhesives (G Bond, GC [GB], Optibond, Kerr [OB], and Xeno V Plus, Dentsply [XV]). Class V cavities were prepared. Each group was further divided into two subgroups (n = 10) according to the placement technique of the adhesive, using the single-application [subgroup (a)] or double-application method [subgroup (b)]. Resin composite (Z 250, 3M ESPE, St. Paul, MN) was used to restore the cavities and light cured for 40 s. Twenty samples from each group were subjected to microleakage study. Two samples from both the subgroups of the three adhesives were used for scanning electron microscopic examination of the resin-dentin interfacial ultrastructure. Dye leakage scores were subjected to statistical analysis using Kruskal-Wallis and Mann-Whitney U-tests at significance level of P < 0.05., Results: GB depicted significantly more microleakage which was significantly greater than OB and XV. The double application led to significant decrease in microleakage of GB with no significant effect on the microleakage scores of other two all-in-one adhesives, that is OB and XV., Conclusion: Double application of all-in-one self-etch adhesives improves the marginal sealing ability in dentin although it appears to be product dependent., (© 2015 Wiley Periodicals, Inc.)

Background: Mechanical compression of cells during mesenchymal condensation triggers cells to undergo odontogenic differentiation during tooth organ formation in the embryo. However, the mechanism by which cell compaction is stabilized over time to ensure correct organ-specific cell fate switching remains unknown., Results: Here, we show that mesenchymal cell compaction induces accumulation of collagen VI in the extracellular matrix (ECM), which physically stabilizes compressed mesenchymal cell shapes and ensures efficient organ-specific cell fate switching during tooth organ development. Mechanical induction of collagen VI deposition is mediated by signaling through the actin-p38MAPK-SP1 pathway, and the ECM scaffold is stabilized by lysyl oxidase in the condensing mesenchyme. Moreover, perturbation of synthesis or cross-linking of collagen VI alters the size of the condensation in vivo., Conclusions: These findings suggest that the odontogenic differentiation process that is induced by cell compaction during mesenchymal condensation is stabilized and sustained through mechanically regulated production of collagen VI within the mesenchymal ECM., (© 2015 Wiley Periodicals, Inc.)

This study evaluated the effect of different pulse widths in the morphological characteristics of human dentin irradiated with Er:YAG in cavity preparation protocols and dentin pretreatment. Dentin discs with 2 mm thickness were obtained from 18 human molars. The experimental groups were composed from two variables: (1) clinical protocol-cavity preparation (E = 200 mJ/20 Hz)-and pretreatment (E = 80 mJ/2 Hz); and (2) pulse duration-50, 300, and 600 μs. This formed six experimental groups (n = 3): G1 (E = 200 mJ/20 Hz/50 μs); G2 (E = 200 mJ/20 Hz/300 μs); G3 (E = 200 mJ/20 Hz/600 μs); G4 (E = 80 mJ/2 Hz/50 μs); G5 (E = 80 mJ/2 Hz/300 μs); G6 (E = 80 mJ/2 Hz/600 μs). The samples were irradiated with the Er:YAG laser by noncontact mode at a focal distance of 7 mm from the target point under continuous water spray (60% water and 40% air). After the irradiation, they were processed for scanning electron microscopy (SEM). Morphological analysis showed an irregular dentin surface, absence of smear layer with opening of the exposure of dentinal tubules and protruding peritubular dentin-without indications of changes for all protocols used. Regardless of the analyzed experimental group, the dentin surface showed a microretentive morphology characteristic of ablation. The G1 and G4 showed a rougher surface when compared to other groups. Finally, we concluded that the pulse width can influence the morphological characteristics of the irradiated dentin tested in different clinical indications. The larger surface irregularity caused by regulation with less pulse width (50 µs) seems more appropriate to get a microretentive pattern necessary for successful adhesives restoration procedures., (© 2015 Wiley Periodicals, Inc.)

Objective: Molar-incisor malformation (MIM) is a newly discovered type of dental anomaly that involves a characteristic root malformation of the permanent first molars. The aim of this study was to reveal the microstructure of MIM teeth in order to determine their origin., Study Design: Four MIM teeth were extracted from a 9-year-old girl due to severe mobility. The detailed microstructure of the teeth was determined by examinations with micro-computed tomography (micro-CT), hematoxylin and eosin (H&E) staining, immunohistochemical staining, and scanning electron microscopy to reveal the detailed microstructure., Results: Micro-CT and H&E staining revealed the pulpal floor comprising three layers: upper, middle, and lower. Amorphous hard tissues and hyperactive cells were observed in the middle layer of the pulpal floor, and the cells stained positively for dentin sialoprotein and osteocalcin, but not for collagen XII., Conclusion: The results of the present study imply that MIM-affected molars probably result from inappropriate differentiation of the apical pulp and dental follicle., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Aim: The aim of this study was to evaluate the effects of a smear layer generated by a high-speed diamond or carbide bur on the durability of microtensile bond strength (μTBS) of a self-etching adhesive to primary dentin., Study Design: Flat occlusal dentin surfaces of 105 human primary molars were exposed using 600 grit silicon carbide paper before being divided into 2 groups for further grinding with either a highspeed diamond or carbide bur. Ten prepared dentin surfaces treated by each bur were evaluated for the characteristics of the smear layer using a scanning electron microscope (SEM). Seventy-five specimens from each bur-prepared group were applied with a 2-step self-etching adhesive (Clearfil SE Bond(®)) then built up with a resin composite. Each bonded specimen was sectioned into a 1-mm thick slab and trimmed to a dumbbell shape with a cross-sectional area of approximately 1 mm(2). All slabs were divided into 3 groups (n=25) according to 3 storage times of 24 hrs, 3 months, and 6 months, in distilled water at 37°C. After storage, the μTBS was determined using a universal testing machine. All fracture specimens were prepared for observation of failure modes. Ten bonded specimens of each bur group were prepared for observation of the resin-dentin interface using an SEM. Smear-layer thickness, μTBS, and failure mode distributions were statistically analyzed., Results: The high speed carbide bur created a significantly thinner smear layer than the diamond bur (p < 0.05). Dentin surfaces treated with a high-speed carbide bur generally obtained significantly higher μTBS than the diamond bur group (p < 0.05). The μTBS gradually decreased over time such that specimens stored for 6 months had significantly lower bond strength than those stored for 24 hrs (p < 0.05). Self-etching adhesive created a hybrid layer of the same thickness when prepared with either a carbide bur or diamond bur, but the carbide bur group had longer and more resin tags., Conclusion: Highspeed carbide bur groups had a higher μTBS than diamond bur groups for all storage times, and bond strengths decreased over time in both substrate groups. The use of a carbide bur produced a thinner smear layer and therefore is recommended when using this 2-step self-etching adhesive to bond the resin composite to primary dentin.

The resin infiltration technique might be used for occlusal caries lesions in order to arrest their progression. This in vitro study evaluated the influence of various modifications of the infiltration technique on the penetration abilities of the infiltrant into occlusal lesions. Extracted human molars and premolars (n = 140) with non-cavitated white spot lesions were randomly allocated to 7 groups. As control, specimens were etched with 15% hydrochloric acid (HCl) gel for 120 s and resin infiltrated for 180 s (Icon; DMG). As modification HCl gel reduced in surface tension and viscosity with and without abrasives was applied using 3 different types of brushes either to oscillate or rub the HCl gel onto the enamel surface. The median maximum lesion depth was 1,232 µm (interquartile range 882-1,513). Compared with the control procedure [23% (16/50)] a higher percentage penetration was observed if the HCl gel was mixed with a small amount of abrasives were rubbed into the fissures using a modified brush with stiff bristles that were adjusted to the fissure relief for either 120 s [100% (64/100)] or 30 s [98% (61/100); p < 0.05; Mann-Whitney test]. All other experimental treatments resulted in penetration results in-between. It can be concluded that the use of an abrasive HCl gel in conjunction with a modified brush mostly enhances resin infiltration into fissure caries lesions., (© 2014 S. Karger AG, Basel.)

The purpose of this study was to investigate the effect of ultrasonic scaling on teeth restored with a light-cured resin. Ultrasonic scaling is a very popular periodontal therapy among dentists, and used for the removal of dental plaque and calculus in order to reduce and eliminate inflammation. Given the fact that most ultrasonic devices are used at high frequencies to perform scaling, undesirable consequences, such as loss of adhesion and increase in surface roughness, may occur in teeth that have been restored with light-cured resins. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy were used to investigate the effects of ultrasonic treatments at the dental material-hard dental tissue interface. After ultrasonic scaling, EIS measurements were performed on a human tooth that had been restored with a light-cured resin filling. The data were analyzed and the influence of ultrasound was shown after visualization of the hard dental tissues and the dental material as equivalent electrical circuits. The study revealed, through EIS measurements, that ultrasonic scaling affected the resistance of the light-cured resin filling and dentin, whereas the enamel was affected only slightly. Scanning electron microscopy revealed an increase in roughness of the dental material., (© 2014 Eur J Oral Sci.)