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Abstract: Researchers have reported false positive/negative results of the cold test in the diagnosis of pulpitis. Knowledge of the correlation between results of the cold test and proteins could aid in decreasing the frequency of incorrect diagnosis. To associate the levels of matrix metalloproteinase-8 (MMP-8) with the responses (in seconds) to the cold test in teeth diagnosed with reversible and irreversible pulpitis.A cross-sectional study was performed. A total of 150 subjects were evaluated, of which 60 subjects met the selection criteria. The participants were divided into 3 groups: Group 1, healthy pulps, 20 subjects with 20 posterior teeth (premolars) with clinically normal pulp tissue; Group 2, reversible pulpitis, 20 patients with 20 teeth diagnosed with reversible pulpitis; and Group 3, irreversible pulpitis, 20 subjects with 20 teeth diagnosed with irreversible pulpitis. All participants were evaluated based on the following variables: medical and dental history, cold test, and expression of MMP-8 by enzyme-linked immunosorbent assay in dentin samples.Responses to the cold test between 4 to 5 seconds (second evaluation; P < .0001) were associated with high levels of MMP-8 (mean, 0.36 ng/mL) in the reversible pulpitis group. In the irreversible pulpitis group, the responses from 6 to ≥10 seconds (second evaluation; P < .0001) were associated with a higher average of MMP-8 levels (mean, 1.97 ng/mL).We determined that an increase in the duration of response to the cold test was associated with an increase in MMP-8 levels (Rho = 0.81, P < .0001) in teeth with pulpitis. The above correlations can be considered an adjunct to the clinical diagnosis of pulpitis., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2020 the Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Human dentin is a highly calcified tissue of mesenchymal origin with a heterogeneous structure. Its morphology is constantly remodelled throughout the life span of the tooth, as well as under the influence of external stimuli., Objective: The aim of the present study was to obtain information about the thermal changes in the crown and root dentin specimens of vital and devitalized teeth., Methods: The investigated samples were divided into 6 groups, depending on the patients' age and dentin location (crown, root). An additional group of endodontically treated teeth was created. The methods of choice were were combined thermal analysis (DTA-TG(DTG)-MS and gas chromatography-mass spectrometry., Results: After heating up to 1200 °C, endo- and exothermal effects were observed. The effects' dynamic was the same for all samples. The differences were in the samples' weight after the experiment, with root dentin showing the greatest mass loss percentage., Conclusions: The observed mass loss differences could be attributed to the presence of impurities in the dentin, as well as alterations in the collagen matrix. Ageing and endodontic treatment could catalyse the accumulation of such changes and affect the microstructure of the mineralized tissue.

Successful disinfection alongside complete endodontic tissue regeneration and revascularization are the most desired clinical outcomes of regenerative endodontics. Despite reported clinical successes, significant limitations to the current regenerative endodontic procedure (REP) have been elucidated. To improve the current REP, an antibiotics and nitric oxide (NO) releasing biomimetic nanomatrix gel was developed. The study evaluates antibacterial effects of an antibiotics and NO releasing biomimetic nanomatrix gel on multispecies endodontic bacteria. Antibiotics, ciprofloxacin (CF) and metronidazole (MN) were mixed and encapsulated within the NO releasing biomimetic nanomatrix gel. The gel was synthesized and self-assembled from peptide amphiphiles containing various functional groups. Antibacterial effects of the antibiotics and NO releasing biomimetic nanomatrix gel were evaluated using bacterial viability assays involving endodontic microorganisms including clinical samples. Pulp-dentin regeneration was evaluated via animal-model experiments. The antibiotics and NO releasing biomimetic nanomatrix gel demonstrated a concentration dependent antibacterial effect. In addition, NO alone demonstrated a concentration dependent antibacterial effect on endodontic microorganism. An in vivo analysis demonstrated the antibiotics and NO releasing biomimetic nanomatrix gel promoted tooth revascularization with maturation of root canals. An optimal concentration of and NO releasing nanomatrix gel is suggested for its potential as a root treatment material for REP and an appropriate protocol for human trials. Further investigation is required to obtain a larger sample size and decide upon ideal growth factor incorporation., Competing Interests: The authors have declared that no competing interests exist.

Objectives: To quantify the extent of crack-tip plasticity, crack opening displacement (COD) and crack bridging for crack growth perpendicular (HAH) and parallel (RAR) to the tubules in elephant dentin under both hydrated and dry conditions to better understand their influence on intrinsic and extrinsic toughening during crack growth., Methods: Compact tension test-pieces were prepared from a tusk of African elephant ivory. Crack-tip strain mapping and COD measurements by digital image correlation (DIC) technique were made under incremental loading and unloading of cracks for hydrated and dry dentin of different orientations., Results: For the RAR test-piece the plastic zones were significantly larger in the hydrated condition compared to when dry. By contrast, the plastic strains in the HAH test-piece were negligible in both wet and dry conditions. In the RAR condition the crack front was broken up into overlapping longitudinal 'fingers' with crack bridging regions in between, the ligaments extending 400μm behind the crack front in the dry case. This could only be seen in 3D by X-ray CT. Extrinsic shielding reduces the crack-tip stresses by 52% and 40% for hydrated and dry RAR test-pieces respectively. No significant bridging was found in the HAH case., Significance: For crack growth parallel to the tubules, collagen plasticity determines the intrinsic toughening, whereas microcracking from the tubules governs extrinsic shielding via ligament bridging, which is maintained further behind the crack in the hydrated case. For cracks grown perpendicular to the tubules, neither toughening mechanisms are significant., (Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.)

Objective: To investigate physical characteristics and behaviours of dental pulp cells of teeth isolated from a dentinogenesis imperfecta (DGI) patient with a novel dentin sialophosphoprotein (DSPP) mutation., Subjects and Methods: Whole exome and Sanger sequencing were employed to identify mutations. Physical characteristics of the teeth were examined. Pulp cells' behaviours including cell proliferation, colony-forming unit, osteogenic differentiation, pluripotent markers, and mesenchymal stem cell markers were investigated., Results: The proband had opalescent brown primary teeth with extensive loss of enamel. Mutation analysis revealed a novel heterozygous 4-bp deletion, c.1915&#95;1918delAAGT (p.K639QfsX674), in exon 5 of the DSPP associated with DGI. Analysis of the extracted primary incisor demonstrated a decrease in brightness but an increase in yellow and red chroma. The dentin showed reduced mineral density. The dentinal tubules were present in the predentin, but progressively collapsed in the dentin. The pulp cells exhibited markedly reduced CD105 expression, decreased cell proliferation, and smaller colony-forming units., Conclusions: We identified a novel mutation in the DSPP gene which disturbed dentin characteristics and pulp cells' behaviours. Our study expands the mutation spectrum and understanding of pathologic dentin phenotypes related to the frameshift deletion in the dentin phosphoprotein (DPP) region of the DSPP gene., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Since there is no consensus about whether starch increases the cariogenic potential of sucrose, we used a validated 3-species biofilm model to evaluate if starch combined with sucrose provokes higher root dentine demineralization than sucrose alone. Biofilms (n = 18) composed by Streptococcus mutans (the most cariogenic bacteria), Actinomces naeslundii (which has amylolytic activity), and Streptococcus gordonii (which binds salivary amylase) were formed on root dentine slabs under exposure 8 ×/day to one of the following treatments: 0.9% NaCl, 1% starch, 10% sucrose, or a combination of 1% starch and 10% sucrose. Before each treatment, biofilms were pretreated with human whole saliva for 1 min. The pH of the culture medium was measured daily as an indicator of biofilm acidogenicity. After 96 h of growth, the biofilms were collected, and the biomass, bacteria viability, and polysaccharides were analyzed. Dentine demineralization was assessed by surface hardness loss (% SHL). Biofilm bioarchitecture was analyzed using confocal laser scanning microscopy. Treatment with a starch and sucrose combination provoked higher (p = 0.01) dentine demineralization than sucrose alone (% SHL = 53.2 ± 7.0 vs. 43.2 ± 8.7). This was supported by lower pH values (p = 0.007) of the culture medium after daily exposure to the starch and sucrose combination compared with sucrose (4.89 ± 0.29 vs. 5.19 ± 0.32). Microbiological and biochemical findings did not differ between biofilms treated with the combination of starch and sucrose and sucrose alone (p > 0.05). Our findings give support to the hypothesis that a starch and sucrose combination is more cariogenic for root dentine than sucrose alone., (© 2018 S. Karger AG, Basel.)

Objective: To determine if dentine at the enamel-dentine junction (EDJ) in man is more sensitive to hydrostatic pressure stimuli then deeper dentine., Design: Cavities (1mm diam.) were cut at the tips of the buccal and lingual cusps of 8 premolars in 3 subjects (ages: 22-25 years). Both cavities were initially deepened to expose the EDJ then one (the test cavity) was deepened in steps of 0.5mm to a maximum of 2.0 mm below the EDJ. The cavities were tested at each stage, before and after etching, with 5s, hydrostatic pressure stimuli between 400 mm above, and 400 mm below atmospheric. The intensity of any pain produced was recorded on a VAS scale and electrodes were placed in both cavities in an attempt to monitor any action potentials evoked in intradental nerves., Results: In all the teeth, the intensity of the pain produced by a stimulus tended to increase as the cavity was deepened, as did the number of action potentials recorded (in 6 of the 8 teeth). The responses were greater from etched than unetched dentine, and negative pressures evoked greater responses than the corresponding positive pressures., Conclusion: There was no evidence that dentine close to the EDJ was more sensitive to hydrostatic pressure stimuli than deeper dentine. It may however be more sensitive to mechanical stimuli as it is more compliant., (Copyright © 2016. Published by Elsevier Ltd.)

Introduction: The aim of this study was to correlate the bacterial viability and the presence of 2% chlorhexidine (CHX) solution on dentin by means of confocal laser scanning microscopy and high-performance liquid chromatography for 48 hours, 7 days, and 30 days., Methods: One hundred twenty-three extracted human teeth were used. Samples were divided into 4 groups according to the solution (CHX or saline) and the presence of Enterococus faecalis biofilm. Samples were kept in contact with 5 mL of the solution for 5 minutes. Each group was divided into 3 subgroups according to the evaluation period (n = 10). Statistical analysis was performed by using the Kruskal-Wallis test, the Mann-Whitney U test (P < .05), and the Spearman rank correlation coefficient (P < .01)., Results: There was a negative correlation between the percentage of live cells and the amount of remaining CHX (P = .000). CHX significantly reduced the percentage of viable cells compared with saline after 48 hours (P = .007). Differences were maintained in the 7-day evaluation period (P = .001). After 30 days, the CHX group presented an increase of viable cells, thereby becoming similar to saline (P = .623). Simultaneously, the remaining CHX was significantly reduced in the 30-day specimens (P = .000)., Conclusions: The results of this study indicate that 2% CHX solution was detected for 48 hours and 7 days with a low percentage of viable cells. The presence of microorganisms on human dentin did not affect 2% CHX maintenance., (Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to evaluate the efficacy of carboxymethyl chitosan (CMCS) and chitosan nanoparticles (CNps) to inactivate bacteria and prevent biofilm formation at sealer-dentin interfaces., Methods: The study was divided into 3 stages: first stage, the experiment was conducted to analyze the antibacterial properties of CMCS in different formulations against biofilms; second stage, direct-contact and membrane-restricted methods were used to evaluate the antibacterial properties of an epoxy resin (ThermaSeal Plus; Dentsply Tulsa Dental, Tulsa, OK) and calcium silicate (MTA Fillapex; Angelus SA, Londrina, PR, Brazil) based-sealers with or without CNps; and third stage, biofilm formation at the sealer dentin interfaces of root dentin treated with CMCS and filled with gutta-percha and CNp incorporated sealer were analyzed after 1- and 4-week aging periods. The samples were treated and filled as follows: (1) distilled water: unaltered sealer (control group), (2) CMCS: sealer+CNps (CMCS group), and (3) CMCS/rose bengal: sealer+CNps (CMCS/RB group). Enterococcus faecalis was used to infect all the samples. Microbiological and microscopic analyses were used to assess the antibacterial characteristics., Results: CMCS-based treatments effectively killed bacteria adherent on root dentin (P < .05). The addition of CNps to ThermaSeal enhanced its antibacterial ability by direct-contact and membrane-restricted tests (P < .05). The CNp incorporation significantly increased the antibacterial efficacy of root canal sealers even after a 4-week aging time (P < .05)., Conclusions: This study highlighted the ability of CMCS to disinfect root canal dentin and inhibit bacterial adhesion. CNps in root canal sealers are capable of maintaining their antibacterial activity even after prolonged aging., (Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Actinomyces naeslundii has been recovered from traumatized permanent teeth diagnosed with necrotic pulps. In this work, a triple antibiotic paste (TAP)-mimic scaffold is proposed as a drug-delivery strategy to eliminate A. naeslundii dentin biofilm., Methods: Metronidazole, ciprofloxacin, and minocycline were added to a polydioxanone (PDS) polymer solution and spun into fibrous scaffolds. Fiber morphology, mechanical properties, and drug release were investigated by using scanning electron microscopy, microtensile testing, and high-performance liquid chromatography, respectively. Human dentin specimens (4 × 4 × 1 mm(3), n = 4/group) were inoculated with A. naeslundii (ATCC 43146) for 7 days for biofilm formation. The infected dentin specimens were exposed to TAP-mimic scaffolds, TAP solution (positive control), and pure PDS (drug-free scaffold). Dentin infected (7-day biofilm) specimens were used for comparison (negative control). Confocal laser scanning microscopy was done to determine bacterial viability., Results: Scaffolds displayed a submicron mean fiber diameter (PDS = 689 ± 312 nm and TAP-mimic = 718 ± 125 nm). Overall, TAP-mimic scaffolds showed significantly (P ≤ .040) lower mechanical properties than PDS. Within the first 24 hours, a burst release for all drugs was seen. A sustained maintenance of metronidazole and ciprofloxacin was observed over 4 weeks, but not for minocycline. Confocal laser scanning microscopy demonstrated complete elimination of all viable bacteria exposed to the TAP solution. Meanwhile, TAP-mimic scaffolds led to a significant (P < .05) reduction in the percentage of viable bacteria compared with the negative control and PDS., Conclusions: Our findings suggest that TAP-mimic scaffolds hold significant potential in the eradication/elimination of bacterial biofilm, a critical step in regenerative endodontics., (Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to assess the efficacy of lasers in removing filling remnants from oval-shaped canals after retreatment procedures with rotary instruments using micro-computed tomographic imaging., Methods: The root canals of 42 mandibular canines were prepared and obturated using the warm vertical compaction technique. Retreatment was performed with rotary instruments, and the specimens were distributed in 3 groups (n = 14) according to the laser device used in a later stage of retreatment procedure: Er:YAG, Er:YAG laser-based photon-induced photoacoustic streaming, and Nd:YAG. The specimens were scanned in a micro-computed tomographic device after root canal filling and each stage of retreatment at a resolution of 13.68 μm. The percentage differences of the remaining filling material before and after laser application within and between groups were statistically compared using the paired sample t test and 1-way analysis of variance test, respectively. Significance level was set at 5%., Results: Overall, filling residues were located mainly in the apical third and into canal irregularities after the retreatment procedures. After using rotary instruments, the mean percentage volume of the filling remnants ranged from 13%-16%, with no statistical significant difference between groups (P > .05). Within groups, additional laser application had a significant reduction in the amount of the remaining filling materials (P < .05). A comparison between groups showed that Er:YAG laser application after the use of rotary instruments had a significantly higher removal of filling remnants (~13%) than Er:YAG laser-based photon-induced photoacoustic streaming (~4%) and Nd:YAG (~3%) (P < .05)., Conclusions: None of the retreatment procedures completely removed the filling materials. The additional use of lasers improved the removal of filling material after the retreatment procedure with rotary instruments., (Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to investigate the incidence of apical crack initiation and propagation in root dentin after several endodontic procedures., Methods: Sixty intact mandibular premolars were sectioned perpendicular to the long axis at 1 mm from the apex, and the apical surface was polished. Thirty teeth were left unprepared and served as a control, and the remaining 30 teeth were instrumented with ProTaper Universal instruments (Dentsply Maillefer, Ballaigues, Switzerland) up to size F5. The root canals were filled with the single-cone technique. Gutta-percha was removed with drills of the Rebilda post system (VOCO, Cuxhaven, Germany). Glass fiber-reinforced composite fiber posts were cemented using a dual-cure resin cement. The fiber posts were removed with a drill of the post system. Retreatment was completed after the removal of the gutta-percha. Crack initiation and propagation in the apical surfaces of the samples were examined with a stereomicroscope after each procedure. The absence/presence of cracks was recorded. Logistic regression was performed to analyze statistically the incidence of crack initiation and propagation with each procedure., Results: The initiation of the first crack and crack propagation was associated with F2 and F4 instruments, respectively. The logistic regression analysis revealed that instrumentation and F2 instrument significantly affected apical crack initiation (P < .001). Post space preparation had a significant effect on crack propagation (P = .0004). The other procedures had no significant effects on crack initiation and propagation (P > .05)., Conclusions: Rotary nickel-titanium instrumentation had a significant effect on apical crack initiation, and post space preparation with drills had a significant impact on crack propagation., (Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to compare the incidence of root cracks after root canal instrumentation with the TF Adaptive, WaveOne, ProTaper Next, and ProTaper Universal systems., Methods: Seventy-five extracted mandibular central incisors with mature apices and straight root canals (<5°) were selected and kept in distilled water. The root canals were instrumented by using the ProTaper Universal, ProTaper Next, WaveOne, and TF Adaptive systems. All the roots were horizontally sectioned 3, 6, and 9 mm from the apex with a low-speed saw under water cooling. The slices were then viewed through a stereomicroscope at ×25 magnification. The samples were photographed with a camera to determine the presence of dentinal cracks., Results: The control group had no cracks, and the difference between the control group and the experimental groups was statistically significant (P < .001). The ProTaper Next and TF Adaptive systems produced significantly less cracks than the ProTaper Universal and WaveOne systems in the apical section (3 mm) (P < .05)., Conclusions: Under the study conditions and within the limitations of this study, it can be concluded that the ProTaper Universal, ProTaper Next, WaveOne, and TF Adaptive instruments can result in dentinal cracks., (Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this prospective clinical study was to evaluate the clinical outcome of endodontic microsurgery on roots exhibiting the presence or absence of dentinal defects at 1-year and 3-year follow-up period., Methods: One hundred fifty-five teeth were treated with periapical microsurgery using a modern microsurgical protocol in a private practice setting. The root apices were resected and inspected for dentinal defects with a surgical operating microscope and a 0.8-mm head diameter light-emitting diode microscope diagnostic probe light. After inspection, root-end preparations were performed using ultrasonic tips, and root-end fillings were placed. Follow-up visits occurred at 1 year and 3 years postoperatively. The primary outcome measure used was the change in the radiographic apical bone density, and the secondary outcome measure used was the absence of clinical symptoms., Results: Of the 155 treated teeth, a total of 134 teeth were assessed at the 1-year follow-up and 127 teeth at the 3-year evaluation. In the "intact" group, 94.8% healed at 1 year, and 97.3% healed at 3 years. In the "dentinal defect" group, 29.8% healed at 1 year, and 31.5% healed at 3 years. The baseline root condition of either "dentinal defect" or "intact" showed a statistical difference in the healing outcome at both 1 and 3 years., Conclusions: This prospective periapical microsurgery study showed a significant superior clinical outcome for intact roots when compared with roots with dentinal defects at both 1 year and at 3 years postoperatively., (Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to investigate the effect of conditioned medium (CM) from murine preameloblasts on the cellular differentiation of mesenchymal stem cells (MSCs) in immature teeth with necrotic pulp and apical periodontitis., Methods: Pulp necrosis and apical periodontitis were induced in 30 immature permanent double-rooted premolars of 3 beagles and were randomly assigned to the following treatment groups: group CM (n = 10), revascularization treatment was performed using CM from preameloblasts of C57BL/6 mice apical bud cells; group CR (n = 10), conventional revascularization treatment was performed; positive control group (n = 5), left infected; and negative control group (n = 5), untreated. The dogs were followed up for 12 weeks and assessed for treatment outcomes with radiographic and histologic analyses. The effect of the CM on sequential Runx2 and osterix messenger RNA gene expression during the differentiation of MG63 osteoblastlike cells was analyzed with real-time polymerase chain reaction., Results: The overall treatment outcomes were not significantly different between the 2 treatment groups. However, the teeth in the CM group showed significantly more mature apices and a higher degree of hard tissue formation with projections intercalating into the pre-existing root dentin (P < .05). In CM-treated teeth, regenerated pulplike tissue was more frequently observed (P < .05). During differentiation, the CM induced early peak expression of Runx2 followed by sustained osterix overexpression., Conclusions: CM from preameloblasts rendered a favorable effect in providing a physiologic microenvironment for the differentiation of MSCs after revascularization treatment., (Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

'Bronze teeth' reflect the mechanical properties of natural teeth to a certain extent. Their mechanical properties resemble those of a tough metal, and the gradient of these properties lies in the direction from outside to inside. These attributes confer human teeth with effective mastication ability. Understanding the various mechanical properties of human teeth and dental materials is the basis for the development of restorative materials. In this study, the elastic properties, dynamic mechanical properties (visco-elasticity) and fracture mechanical properties of enamel and dentin were reviewed to provide a more thorough understanding of the mechanical properties of human teeth.

Statement of Problem: Some patients may opt for a prosthetic rehabilitation without replacing all missing teeth, finishing treatment with a reduced dental arch. This choice may be due to biologic reasons or financial restrictions. It is unclear if a reduced dental arch functions as well as a complete dental arch., Purpose: The purpose of this study was to analyze whether shortened dental arches could result in tooth displacement., Material and Methods: Four different 3-dimensional maxillary and mandibular arches with different levels of arch length reduction were created. In all models, anatomic structures that represent the temporomandibular joint, cortical and cancellous bone, enamel, dentin, and periodontal ligament were modeled. Mechanical properties were attributed to each anatomic component, and a total occlusal load of 100 N on masseter, temporal, and medial pterygoid muscles was simulated for each model. The MSC. Patran software was used for the preprocessing and postprocessing of the biomechanical analysis of the models. One complete dental arch was used as the control., Results: The simulations showed that shortened dental arches presented greater tooth displacements than those found in a complete dental arch. The changes in mandibular tooth position were greater than those observed in the maxillary arches. In finite element models 1 and 2, the largest maxillary displacements were found for posterior teeth., Conclusions: Decreasing numbers of occlusal units resulted in increasing amounts of displacements of the remaining teeth, which may compromise dental stability in patients with shortened dental arches., (Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Unlabelled: The purpose of this study was to investigate the mechanical properties of intertubular dentin in sound, natural caries-affected (NCAD) and artificial caries-affected dentin (ACAD) using nanoindentation., Materials and Methods: Non-caries molars and caries molars with International Caries Detection and Assessment System (ICDAS II) score 5 at the occlusal site were used and caries was excavated using a spoon excavator, a round bur at low speed without water and a dye solution as guidance to detect the infected tissue. Specimens with remaining dentin thickness (RDT) >2mm were selected. ACAD teeth were created from sound teeth over 7 days in a demineralizing solution. Specimens were embedded into plastic rings with acrylic resin and then sagittal mesial-distal sectioned from crown to the long axis of the root under cooling water using a low-speed diamond blade. The surface of interest was fine polished sequentially. Hardness measurement was performed within an axial depth of 1000μm with at least of 320 indentations on each sample. Mann-Whitney U Test was used to compare the hardness as the variable among different dentin types (SOUND, NCAD and ACAD) at each dentin depth level., Results: There was no significant difference in nanohardness between NCAD and ACAD up to a depth of 130μm (p>0.05). NCAD consistently showed lower hardness. ACAD showed no significant difference in hardness with SOUND dentin beyond 190μm (p<0.05). The lesion front in ACAD was considered to be located around the depth of 180μm., Conclusion: Natural and artificial caries-affected dentin tissues were superficially comparable in intertubular nanohardness. There is a certain layer within the natural caries-affected dentin with higher hardness; however the long-term effects of caries beneath the lesion extend deeply through intertubular dentin. Sound dentin at deep areas (close to the pulp chamber) is considered to be soft., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Objectives: The purpose of this study was to evaluate some physical-mechanical and morphological changes of demineralised dentine at early stages of dentine remineralisation., Methods: Extracted human third molars were sectioned to obtain dentine discs. After polishing the dentine surfaces, three groups were established: (1) untreated dentine - UD, (2) 37% phosphoric acid application for 15s (partially demineralised dentine - PDD) and (3) 10% phosphoric acid for 12h, at 25°C (totally demineralised dentine - TDD). Five different remineralizing fluids were used for 30min: chlorhexidine (CHX), artificial saliva (AS), phosphated solution (PS), ZnCl2 and ZnO solutions. Atomic force microscopy (AFM) imaging/nano-indentation, surface nano-roughness and fibrils diameter were determined. X-ray diffraction (XRD), energy dispersive elemental analyses (EDX) and high resolution scanning electron microscopy analysis (HRSEM) were applied., Results: PDD and TDD preserved some mineral contents. After demineralisation and immersion in all solutions, width of nanomechanical properties and fibrils was increased, and total nanoroughness was decreased. Peritubular and intertubular dentine were remineralised., Conclusion: Mineral exists in PA-demineralised dentine matrix and it is important since it may work as a constant site for further nucleation. The dentine surface remineralisation process may be stimulated as early as 30min in abiotic conditions, with a pH ranging from 7.0 to 7.5., Clinical Significance: The existence of enzymes and remineralising factors within the dentine matrix may facilitate early dentine remineralisation under favourable conditions. This process should be stimulated by new reparative materials., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Objective: This study investigates the potential of a novel guided tissue regeneration strategy, using fully demineralized dentin infiltrated with silica and hydroxyapatite (HA) nanoparticles (NPs), to remineralize dentin collagen that is completely devoid of native hydroxyapatite., Methods: Dentin blocks were fully demineralized with 4N formic acid and subsequently infiltrated with silica and HA NPs. The remineralizing potential of infiltrated dentin was assessed following a twelve week exposure to an artificial saliva solution by means of TEM, EDS and micro-CT. Measurements were taken at baseline and repeated at regular intervals for the duration of the study to quantify the P and Ca levels, the mineral volume percentage and mineral separation of the infiltrated dentin specimens compared to sound dentin and non-infiltrated controls., Results: Infiltration of demineralized dentin with nano-HA restored up to 55% of the P and Ca levels at baseline. A local increase in the concentration of calcium phosphate compounds over a period of twelve weeks resulted in a higher concentration in P and Ca levels within the infiltrated specimens when compared to the non-infiltrated controls. Remineralization of demineralized dentin with silica NPs by immersion in artificial saliva was the most effective strategy, restoring 20% of the P levels of sound dentin. Micro-CT data showed a 16% recovery of the mineral volume in dentin infiltrated with silica NPs and a significant decrease in the mineral separation to levels comparable to sound dentin., Significance: Demineralized dentin infiltrated with silica NPs appears to encourage heterogeneous mineralization of the dentin collagen matrix following exposure to an artificial saliva solution., (Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

Objectives: Incomplete excavation reduces the risk of pulpal complications, but doubts remain regarding the mechanical properties of incompletely excavated teeth. Remaining carious dentine is suspected to not sufficiently support the restoration and to reduce bond strengths between the tooth and the restoration, with effects possibly varying depending on the depth of the remaining caries lesion. This study investigated fracture resistance (FR) and cuspal deflection (CD) of premolars after leaving or removing demineralized dentine in vitro., Methods: In 48 premolars, shallow and deep artificial lesions (depths [mean ± SD] of 64 ± 18 μm and 771 ± 176 μm) were created on pulpo-axial walls of standardised mesial-distal-occlusal cavities. Demineralized dentine was either removed or left before adhesively restoring the tooth (n=12/group). Restored teeth were submitted to thermo-mechanical cycling. CD was subsequently measured at loads of 200 N and 400 N, and teeth submitted to occlusal-perpendicular loading until fracturing occurred., Results: FR was not significantly different between teeth with or without remaining demineralized dentine regardless of the lesion depth (p>0.30, t-test). Irrespective of the removal technique, teeth with deep lesions showed significantly decreased FR (p ≤ 0.001). In contrast, CD was significantly increased in teeth with remaining demineralized dentine compared with completely excavated teeth (p ≤ 0.05; Mann-Whitney test)., Conclusions: Remaining demineralized dentine did not significantly decrease the fracture resistance of premolars in vitro. Effects of increased cuspal deflection on restoration margins should be assessed. This study showed no indication that incomplete excavation increases the risk of non-pulpal complications., Clinical Significance: Incomplete caries removal seems suitable to treat especially deep lesions. Leaving demineralized dentine does not seem to affect the fracture resistance of incompletely excavated teeth regardless of the lesion depth., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Dental wear can be differentiated into different types on the basis of morphological and etiological factors. The present research was carried out on twelve extracted human teeth with dental wear (three teeth showing each type of wear: erosion, attrition, abrasion, and abfraction) studied by scanning electron microscopy (SEM). The study aimed, through analysis of the macro- and micromorphological features of the lesions (considering the enamel, dentin, enamel prisms, dentinal tubules, and pulp), to clarify the different clinical and diagnostic presentations of dental wear and their possible significance. Our results, which confirm current knowledge, provide a complete overview of the distinctive morphology of each lesion type. It is important to identify the type of dental wear lesion in order to recognize the contributing etiological factors and, consequently, identify other more complex, nondental disorders (such as gastroesophageal reflux, eating disorders). It is clear that each type of lesion has a specific morphology and mechanism, and further clinical studies are needed to clarify the etiological processes, particularly those underlying the onset of abfraction.

Several studies have reported the mechanism of crack propagation with aging. Although structural modifications of dentinal microcracks with aging have been evaluated by observing the cracked surface using scanning electron microscope (SEM), very few attempts have been made at sectional observation of the microcracks inside dentine using transmission electron microscopy (TEM). The objectives of this study were to: (1) examine the process of dentinal microcrack formation using TEM and (2) to morphologically evaluate the relation between dentinal microcrack propagation and human aging. Molars from 'young' (16-28 years) and 'aged' (62-76 years) subjects were evaluated. Dentine blocks were cracked with an indenter and sectioned using a diamond knife and ultramicrotome after embedding in epoxy resin. Microcracks were observed by TEM and ultra-high-voltage electron microscope tomography to determine the characteristics of crack propagation in the young and aged teeth. The results show that, in young teeth, crack propagation tended to pass through the dentinal tubules, while in aged teeth, it tended to deflect to the outer side of peritubular dentine (PTD), especially in coronal dentine. The advantage of this method is that it allows visualization and evaluation of the ultrastructural propagation of microcracks in dentine. The differences in crack propagation between young and aged dentine could be explained by differences in PTD thickness.

The aim of the current investigation was to assess the rate and magnitude of dentin fluid flow of dentinal surfaces irradiated with Er,Cr:YSGG laser. Twenty extracted third molars were sectioned, mounted, and irradiated with Er,Cr:YSGG laser at 3.5 and 4.5 W power settings. Specimens were connected to an automated fluid flow measurement apparatus (Flodec). The rate, magnitude, and direction of dentin fluid flow were recorded at baseline and after irradiation. Nonparametric Wilcoxon signed ranks repeated measure t test revealed a statistically significant reduction in fluid flow for all the power settings. The 4.5-W power output reduced the flow significantly more than the 3.5 W. The samples showed a baseline outward flow followed by inward flow due to irradiation then followed by decreased outward flow. It was concluded that Er,Cr:YSGG laser irradiation at 3.5 and 4.5 W significantly reduced dentinal fluid flow rate. The reduction was directly proportional to power output.

Statement of Problem: Periodontally compromised teeth (PCT) that serve as terminal abutments (TAs) are often challenging depending on the post-and-core treatment, the type of partial fixed dental prosthesis (PFDP), and the periodontal support., Purpose: The purpose of this study was to investigate the biomechanical impact of 3 types of PFDP supported by cast post-and-cores on PCT serving as terminal abutments., Material and Methods: A 3-dimensional (3D) model of a human mandible was fabricated by using computed tomography (CT) images and parameterized in a computer-aided design (CAD) environment as follows: Right premolar preparation geometries were designed. The second premolar was assembled with 7-mm or 10-mm cast post-and-core models. Both premolar-models were designed to support single, splinted, or 1-unit cantilever splinted crowns. In each situation, their periodontium geometries were designed to be reduced by 10%, 50%, and 70%. All models were imported into a 3D finite element analysis (FEA) environment and loaded; von Mises stress values and distribution patterns were evaluated., Results: Insertion of the post primarily affected the apical areas of both the root and post; the type of PFDP and periodontal support mainly affected stress distribution. In patients with a normal periodontium, splinting the teeth did not contribute to their stress relief. By extending the post length, a stressful area close to the apex of the post was developed. Splinting mitigated the stress field of the coronal part of the 50% PCT (up to 98.9%); the 30% PCT experienced a substantial decrease (up to 215.9%) in stress in the radical part as well. The increase in the length of the post produced negligible stress-related differences in the apical part of the 50% PCT (0.2% to 2.6%). The use of the 7-mm post effectively relieved the radical part of the splinted 30% PCT. The magnitude of the stress on the radical part of post-restored PCT was considerably increased in the presence of a cantilever., Conclusions: Splinted crowns supported by a 7-mm cast post-and-core are a favorable biomechanical approach for the restoration of PCT with severe loss of coronal structure. The use of a cantilever greatly aggravates the biomechanical response, especially of post-restored PCT., (Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

Objectives: The purpose was to assess the influence of ferrule effect and length of cast post and cores, and FRC posts on the strength of anterior teeth., Materials and Methods: The investigations were conducted by means of finite element analysis with the application of contact elements. Thirteen 3D models of maxillary first incisors were generated: model 1 was an intact tooth; 2A - a tooth with all-ceramic crown with ferrule effect, 2B-D a teeth restored with, ferrule and FRC posts of various lengths 13mm, 8mm, 4mm, 3A - a tooth with ceramic crown without, ferrule effect, 3B and C teeth without ferrule and 10mm, 5mm length FRC posts, 4B-D teeth with ferrule, restored by cast posts and cores of 13mm, 8mm, 4mm lengths and 5B and C teeth without ferrule, restored with cast posts and cores of 10mm, 5mm lengths. Each model was subject to a load with a total force of 100N uniformly distributed under the lingual cingulum, at an angle of 130°. To evaluate, the strength of tooth tissues, ceramics and composites, the modified von Mises failure criterion was used, for FRC the Tsai-Wu criterion and for cast NiCr alloy the von Mises criterion. Contact stresses were calculated at the luting cement-tissue interface., Results: Ferrule effect in teeth reduces mvM stresses in dentin, in posts and in luting cement. The contact tensile stresses around posts in teeth with ferrule effect were 1.7-3.0 times smaller than in, teeth without ferrule. Lower mvM stresses occurred in teeth with cast posts in comparison with FRC posts. The mvM stresses in teeth with posts of various lengths were similar, irrespective of post material., Significance: Ferrule effect in teeth with posts and cores has a critical influence on stress reduction. Using posts and cores made of rigid materials leads to stress reduction in teeth. Post length has a small, effect on stress values in tooth structures., (Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

An incompletely formed tooth is left with thin dentin walls and experiences a higher incidence of cervical root fracture that reduces the long-term overall prognosis of the tooth. Faced with these situations, clinicians have attempted to use various restorative methods to reinforce the remaining root. Various techniques have been reported, and the scientific evidence for each has been reviewed. The biomechanical considerations of reinforcing a weakened root are also reviewed, and the most current information about failure analysis, fracture characteristics of natural dentin, and in vitro test configurations used have been considered. In light of these additional considerations, some recommendations for future understanding of this complex problem have been proposed., (Copyright © 2013 American Academy of Pediatric Dentistry and American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

In the current trend of materials used for dentin hypersensitivity treatment, calcium-phosphate-containing desensitizers are expected to have advantages in oral environment. A newly formulated desensitizer containing tetracalcium phosphate and dicalcium phosphate anhydrous (CPD-100) was evaluated in comparison to oxalate containing desensitizer (SS) regarding permeability reduction (PR%) by measuring hydraulic conductance on the etched dentin discs in vitro. CPD-100 exhibited mean PR% of 91%, which significantly increased to 98% after immersion in artificial saliva (AS) for 4 weeks (p < 0.001), while SS showed a significant decrease from 99% to 93% (p < 0.01). SEM observation showed newly formed crystallites on CPD-100 treated dentin, which did not exist in SS treated dentin after AS immersion, suggesting that calcium oxalate inhibited formation of new calcium-phosphate minerals. Five-minute acid challenge did not significantly affect PR% of dentin treated by any of the desensitizers. The energy dispersive X-ray spectroscopy (EDS) analysis indicated that the formed layer of CPD-100 were minerals with similar Ca/P ratio to hydroxyapatite. In conclusion, the newly developed calcium-phosphate desensitizer has the potential to exhibit long-term stability in the oral environment, owing to its chemical properties that promote the crystal growth in salivary fluid., (Copyright © 2012 Wiley Periodicals, Inc.)

Tissue-nonspecific alkaline phosphatase (TNAP) is expressed in mineralizing tissues and functions to reduce pyrophosphate (PP(i) ), a potent inhibitor of mineralization. Loss of TNAP function causes hypophosphatasia (HPP), a heritable disorder marked by increased PP(i) , resulting in rickets and osteomalacia. Tooth root cementum defects are well described in both HPP patients and in Alpl(-/-) mice, a model for infantile HPP. In Alpl(-/-) mice, dentin mineralization is specifically delayed in the root; however, reports from human HPP patients are variable and inconsistent regarding dentin defects. In the current study, we aimed to define the molecular basis for changes in dentinogenesis observed in Alpl(-/-) mice. TNAP was found to be highly expressed by mature odontoblasts, and Alpl(-/-) molar and incisor roots featured defective dentin mineralization, ranging from a mild delay to severely disturbed root dentinogenesis. Lack of mantle dentin mineralization was associated with disordered and dysmorphic odontoblasts having disrupted expression of marker genes osteocalcin and dentin sialophosphoprotein. The formation of, initiation of mineralization within, and rupture of matrix vesicles in Alpl(-/-) dentin matrix was not affected. Osteopontin (OPN), an inhibitor of mineralization that contributes to the skeletal pathology in Alpl(-/-) mice, was present in the generally unmineralized Alpl(-/-) mantle dentin at ruptured mineralizing matrix vesicles, as detected by immunohistochemistry and by immunogold labeling. However, ablating the OPN-encoding Spp1 gene in Alpl(-/-) mice was insufficient to rescue the dentin mineralization defect. Administration of bioengineered mineral-targeting human TNAP (ENB-0040) to Alpl(-/-) mice corrected defective dentin mineralization in the molar roots. These studies reveal that TNAP participates in root dentin formation and confirm that reduction of PP(i) during dentinogenesis is necessary for odontoblast differentiation, dentin matrix secretion, and mineralization. Furthermore, these results elucidate developmental mechanisms underlying dentin pathology in HPP patients, and begin to explain the reported variability in the dentin/pulp complex pathology in these patients., (Copyright © 2013 American Society for Bone and Mineral Research.)

Objective: To analyze the effect of different combinations of post and core materials on stress distribution in dentin of an endodontically treated tooth., Materials and Methods: This was an experimental stress analysis study. Models were made in photoelastic material, i.e., epoxy resin. Different combinations of post and core materials used were: Glass fiber post with composite core, stainless steel post with composite core, and cast metal post and core. Stresses generated were frozen, models were sliced and viewed under circular polariscope, and photographs were taken. Stress was calculated by counting the number of fringes., Results: For the combination of glass fiber post with composite core, the shear stresses calculated were 1.196, 1.196, and 2.898 MPa in the apical, mid-root, and cervical region, respectively. For the combination of stainless steel post with composite core, the apical, mid-root and cervical stresses were 1.534, 0.511, and 2.557 MPa, respectively. For cast metal post and core, the apical, mid-root, and cervical stresses were 0.852, 0.511, and 1.534 MPa, respectively., Conclusion: The cervical region of the teeth is subjected to the highest stresses irrespective of the material used. The stainless steel post with the composite core generated the highest stress concentration in different regions. A glass fiber post generated a uniform stress distribution. A cast metal post and core combination generated lesser stress than the other combinations. The vast difference in the elastic modulus of the restorative materials can lead to nonuniform stress distribution and concentration of stresses in different areas which can have deleterious effect on the survival of already compromised teeth and restoration. Such combinations should be avoided and the material which has an elastic modulus close to that of dentin should be preferred.

This study aimed to investigate an artificial caries-affected dentin (ACAD) model for in vitro bonding studies in comparison to natural caries-affected dentin (NCAD) of human teeth. ACAD was created over 7 days in a demineralizing solution. Mineral density (MD) at different depth levels (0-150 µm) was compared between NCAD and ACAD by transverse microradiography. Micro-tensile bond strengths (µTBS) of two two-step self-etch adhesives to sound dentin, NCAD and ACAD were evaluated. Caries-affected dentin type was not a significant factor when comparing MD at different lesion levels (p>0.05). Under SEM, the dentinal tubules appeared occluded with crystal logs 1-2 µm in thickness in the NCAD; whereas they remained open in the ACAD. The µTBS to caries-affected dentin was lower than sound dentin, but was not affected by the type of caries (p>0.05). In spite of their different morphologies, the ACAD model showed similar MD and µTBS compared to NCAD.

Purpose: To examine morphologically the hybrid layer of one-step self-etching adhesive, Clearfil S3 Bond (S3bond), in caries-affected dentin (CAD) and deep sound dentin (DSD) cavities performed clinically. For a comparative group, the two-step self etching adhesive Clearfil Protect Bond (Pbond) was used in a similar clinical situation., Methods: This study was carried out on carious and sound teeth clinically selected for extraction. In carious teeth, CAD was obtained by way of subjective criteria by removing infected tissue to form a cavity bottom. DSD was obtained at a depth of 4 mm in the dentin cavity of sound teeth. S3bond and Pbond were applied in the CAD and DSD cavities as indicated by the manufacturer, followed by a composite restoration. Teeth were extracted about 20 minutes after the bonding procedure, and processed for TEM analysis., Results: Expression of S3bond in CAD was morphologically highly variable. When affected tubules were occluded by intratubular mineralized deposits, the interface displayed a dense poly-HEMA hydrogel as water sorption by the hydrophilic S3bond toward the porous affected collagen. Conversely, when tubules appeared empty, voids of various sizes were formed by tubular fluid shift. In DSD, S3bond clearly exhibited voids and water channels as signs of the high permeability of the sub-surface. Although porosities were somewhat retained, Pbond expression showed a hermetic character which was independent of the dentin substrate.

Context: In dental practice, dentin hypersensitivity is a commonly presenting condition, which consists of sharp pain arising from exposed dentin in response to a varied assortment of stimuli; for example, dietary factors, such as an ice-cold beverage, to even environmental considerations, such as the exposure to atmospheric air on a cold winter's day. The heterogeneity of this presentation, ranging from minor inconvenience to the patient, to a near incapacitating quality-of-life disturbance, as well as the wide range of treatment strategies, as is discussed in this article, certainly pose a challenge to the clinician., Evidence Acquisition: A search was performed on the MEDLINE database (2002 to present) by way of OVID. Search terms, such as dentin hypersensitivity and variants (eg, dentinal hypersensitivity, cervical dentin hypersensitivity) were used. Select references of review-type articles from the original search were sought., Evidence Synthesis: Efforts were made to identify multiple comparative clinical treatment studies that were of highest quality study design-specifically, randomized control trials. Efforts also were made to identify rigorous meta-analysis in the literature on the subject of dentin hypersensitivity treatment., Conclusion: Although multiple treatment approaches appear to provide clinical success in managing dentin hypersensitivity, the entire body of clinical research literature is far from being unequivocal in pronouncing one superior strategy. Equally as important is the clinician's consideration of the predisposing factors that initially localized the lesion on the tooth surface. Together, personalized preventive measures and therapies focusing on disrupting pathophysiology form the core of effective dentin hypersensitivity management., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Objectives: The management of demineralized dentin resulting from dental caries or acid erosion remains an oral healthcare clinical challenge. This paper investigates, through a range of studies, the ability of colloidal silica and hydroxyapatite (HA) nanoparticles to infiltrate the collagen structure of demineralized dentin., Methods: Dentin samples were completely demineralized in 4 N formic acid. The remaining collagen matrix of the dentin samples was subsequently infiltrated with a range of nano-particulate colloidal silica and HA solutions. The effectiveness and extent of the infiltration was evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS)., Results: Silica nanoparticles have the ability to penetrate dentin and remain embedded within the collagen matrix. It is suggested that particle size plays a major role in the degree of dentin infiltration, with smaller diameter particles demonstrating a greater infiltrative capacity. The infiltration of demineralized dentin with sol-gel HA nanoparticles was limited but was significantly increased when combined with the deflocculating agent sodium hexametaphosphate. The use of acetone as a transport vehicle is reported to enhance the infiltration capacity of sol-gel HA nanoparticles., Significance: Collagen infiltrated with HA and silica nanoparticles may provide a suitable scaffold for the remineralization of dentin, whereby the infiltrated particles act as seeds within the collage matrix and given the appropriate remineralizing environment, mineral growth may occur., (Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

Dental erosion is the non-carious dental substance loss induced by direct impact of exogenous or endogenous acids. It results in a loss of dental hard tissue, which can be serious in some groups, such as those with eating disorders, in patients with gastroesophageal reflux disease, and also in persons consuming high amounts of acidic drinks and foodstuffs. For these persons, erosion can impair their well-being, due to changes in appearance and/or loss of function of the teeth, e.g., the occurrence of hypersensitivity of teeth if the dentin is exposed. If erosion reaches an advanced stage, time- and money-consuming therapies may be necessary. The therapy, in turn, poses a challenge for the dentist, particularly if the defects are diagnosed at an advanced stage. While initial and moderate defects can mostly be treated non- or minimally invasively, severe defects often require complex therapeutic strategies, which often entail extensive loss of dental hard tissue due to preparatory measures. A major goal should therefore be to diagnose dental erosion at an early stage, to avoid functional and esthetic impairments as well as pain sensations and to ensure longevity of the dentition.

The pulp-dentin complex is a strategic and dynamic barrier to various insults that plague the dentition. Researchers have yet to understand the complete potential of this shifting junction and its components. The most common cause of injury to the pulp-dentin complex is carious breakdown of enamel and dentin. In recent years, there has been a change in restorative management of caries. The emphasis is on strategies to preserve dentin and protect the pulp. This article provides a brief review of the effect of caries on the pulp, of subsequent events on the periradicular tissues, and of current understanding of treatment modalities., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Objectives: The purpose of this study was to perform a finite element analysis to determine whether adhesive reconstruction is able to restore the original biomechanical behaviour of weakened roots, in terms of fracture resistance, when compared with post/crown-restored teeth with intact roots., Methods: A three-dimensional model of a maxillary central incisor was created. The model simulated an endodontically treated tooth restored with a glass-fibre post, a composite-resin core and a metal crown (Model 1). Based on Model 1, a new volume was created in the root cervical third that represented the area where the dentine structure was lost, resulting in a structurally damaged root (Model 2). A 100N load was applied to the palatal surface at 130° from the long axis of the tooth. After processing (Ansys(®) 10.0 - Canonsburg, PA, USA), the principal normal stress data were analyzed (S1, tensile; S3, compressive)., Results: The models demonstrated a similar S1 distribution concentrated in the lingual cervical region but different S1 levels (Model 1: 28.7MPa; Model 2: 35.3MPa). The S3 distribution indicated differences in behaviour between the models (Model 1: -18 to -27MPa along the buccal root surface; Model 2: -25 to -32MPa on the post buccal surface and along the buccal root wall)., Conclusions: Although the stress distribution within the root walls remained below the ultimate stress limit of the root dentine, the adhesive reconstruction of the weakened roots did not recover the load resistance of structurally intact roots., Clinical Significance: The decision of when to prosthetically rehabilitate weakened roots with cervical dentine structural tissue loss is a challenge for clinicians. A 'monoblock' adhesive reconstruction has been proposed for root reinforcement. During treatment planning, the possibility of restoring the mechanical resistance of the root must be evaluated if successful long-term results are to be achieved., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Objectives: A low pH environment is created by cariogenic bacteria. This study was aimed to measure pH of carious lesions intraorally using a micro-pH sensor, and assess predominant acid-producing cariogens by qPCR to differentiate caries activities., Methods: 103 dentine lesions classified as active or arrested caries based on the clinical and radiological examinations were collected from patients after intraoral measurement of the lesion surface pH using a micro-pH sensor. Quantitative detection of genomic DNA copies of target cariogenic bacteria (mutans streptococci and Lactobacillus spp.) in each lesion was performed using real-time PCR. Correlation between the pH ranges and the number of bacterial species was examined by Spearman test., Results: 50 samples were diagnosed as active and 53 as arrested lesions. Statistically significant difference was observed on average surface pH value between active and arrested lesions (p<0.05). Prevalence of Lactobacillus spp. was higher in active lesions than in arrested lesions (76% vs. 58% of samples, respectively). When the carious lesions were categorised into four different pH ranges (up to 5.5, from 5.6 to 5.8, from 5.9 to 6.1 and 6.2 or above), increased prevalence of Lactobacillus spp. was observed with decrease of pH levels. A significant negative relationship was found between pH value and number of Lactobacillus spp. (r=-0.209, p<0.05) but no such correlation was found for mutans streptococci., Conclusions: Intraoral pH measurement might be clinically useful to determine acidity of the local environment of carious lesions as one aspect of the caries activity assessment., Clinical Significance: The population of certain bacteria may indicate activity of carious lesions. Intraoral pH measurement of the carious lesions using a micro-pH sensor may be a clinically feasible method for assessment of lesion acidity., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Objective: To compare the mineralisation density (MD), morphology and histology of alveolar bone and cementum amongst VDR +/+, VDR -/-, and VDR -/- groups supplemented with a diet TD 96348, containing 20% lactose, 2.0% calcium and 1.25% phosphorous., Methods: Four groups of mice (6 mice/group) were identified by genotyping: VDR +/+ mice (VDR wild type), VDR -/- mice (VDR deficient), VDR -/- offsprings derived from VDR -/- parents receiving a supplemental diet (early rescued), and VDR -/- mice fed with a supplemental diet beginning at age one month (late rescued). All mice were sacrificed at age 70.5 days. Micro-CT was used to compare MD and morphology of alveolar bone and cementum. H-E and Toluidine blue staining was used to examine the ultrastructure of the alveolar bone and cementum at matched locations., Results: In VDR -/- group, alveolar bone and cementum failed to mineralise normally. Early rescue increased MD of alveolar bone in VDR -/- mice with excessive alveolar bone formation, but which not observed in late rescue group. MD and morphology of cementum-dentine complex in both early and late rescue groups were comparable with VDR +/+ group when feeding with high-calcium rescue diet., Conclusions: VDR affects alveolar bone mineralisation and formation systemically and locally. However, cementum apposition and mineralisation is mainly regulated by calcium concentrations in serum., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Purpose: Unresolved controversy exists concerning the optimum restorative material to reinforce the thin-walled roots of endodontically treated teeth to improve their fracture resistance under occlusal load. This study evaluated the effectiveness of irrigant, dowel type, and root-reinforcing material on the fracture resistance of thin-walled endodontically treated teeth., Materials and Methods: The root canals of 140 maxillary central incisors were enlarged and equally divided into seven groups according to the canal irrigant: no irrigant (control), 5% hydrogen peroxide, 5% sodium hypochlorite, a combination of 5% hydrogen peroxide and sodium hypochlorite, 15% ethylenediaminotetraacetic acid (EDTA), 10% lactic acid, or 20% lactic acid. Within each group, root canals were lined with composite resin (PermaFlo) or glass ionomer cement (Fuji II LC). A light-transmitting plastic dowel (Luminex) was used to create space for a quartz fiber-reinforced dowel (Aestheti Post) or a titanium alloy dowel (ParaPost XH) and to cure the restorative materials. Following dowel cementation and restoration of the roots with composite core, the teeth were submitted to fracture resistance testing, and data were analyzed with 3-way ANOVA followed by Ryan-Einot-Gabriel-Welsch Multiple Range Test (α= 0.05)., Results: Fracture resistance values were significantly different among irrigants, restorative materials, and their interaction (p < 0.001); however, the dowel type was not significantly different (p= 0.51)., Conclusions: Thin-walled roots that had the smear layer removed with lactic acid and that were then lined with composite resin had a higher fracture resistance., (© 2011 by The American College of Prosthodontists.)

Background: The authors conducted a study to analyze the stress concentration areas in a tooth restored with a post-retained crown under various conditions., Materials and Methods: The authors constructed a three-dimensional finite element model describing a maxillary second premolar restored with an all-ceramic crown supported by a titanium post and a resin-based composite core. They applied static vertical and horizontal loads of 100 newton to the cusp tip of the crown and recorded Von Mises and tensile stress values. The variables investigated were the presence of the post, coronal and apical post extensions, post diameter, post shape, and post and core material., Results: The study results showed that horizontal loading generated higher levels of stress than did vertical loading. The greatest stress levels were concentrated at the cervical region and at the post-dentin interface in all models. Under both loads, a higher modulus of elasticity of the post material and a wider post diameter were associated with increased stress values at the post-dentin interface. Reduction of the post extension above the level of bone was associated with increased dentinal stresses near the apex of the post., Conclusions: Although endodontic posts provide retention for coronal restorations, they result in dentinal stress values higher than those of crowns without posts. Posts that had a similar modulus of elasticity to dentin and smaller diameters were associated with better stress distribution. Resting coronal restorations on sound dental tissues affected stress distribution more than did the core material or the length of the coronal post extension., Clinical Implications: Many factors influence the distribution of stress within dentin and, consequently, the fracture resistance of teeth restored with post-retained crowns. Clinicians need to keep these factors in mind when performing endodontic procedures that involve placement of post-retained crowns to ensure optimal success.

Introduction: Repair of root resorption cavities has been studied under light microscopy, scanning electron microscopy, and transmission electron microscopy. The aim of this investigation was to demonstrate the use of microcomputed tomography (micro-CT) to assist in the identification of the region of interest for light microscopy preparation. This study also qualitatively illustrated the root resorption craters with 4 or 8 weeks of retention after 4 weeks of continuous light or heavy orthodontic force application., Methods: Four patients who required bilateral extractions of maxillary first premolars as part of their orthodontic treatment were divided into 2 groups (groups I and II) of 2. The maxillary left and right first premolars were loaded with light (25 g) or heavy (225 g) orthodontic force for 4 weeks. After 4 or 8 weeks of retention, the maxillary first premolars were extracted. The extracted teeth were investigated with micro-CT. By using 3-dimensional images created by the micro-CT, the largest resorption craters on the buccal and lingual sides were identified. Parasagittal sections of these resorption craters were studied histologically under hematoxylin and eosin staining., Results: The use of micro-CT improved the efficiency and accuracy of histologic techniques. Comparatively, less root resorption was repaired by new cementum after heavy orthodontic force application and short retention time. The reparative processes seemed to depend on time, with longer retention time yielding the most amount of repair. Reparative cementum was a mixture of acellular and cellular cementum. Reparative processes seemed to commence at the central part of the resorption cavity and expand to the periphery., Conclusions: Root resorption cavities have the potential to repair regardless of the orthodontic force magnitude. Correlative microscopy with micro-CT and conventional light microscopy adds a new dimension to current root resorption investigation techniques., (Copyright © 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Objectives: Dental tissue disease and trauma provides an excellent model for the interaction between tissue defence and regenerative processes and has application to many of the body's other tissues. Following dental tissue infection, characterised by caries, the molecular and cellular mediators of the immune/inflammatory processes clearly impact on the dental tissues' natural regenerative responses. This review of the literature was performed to better understand how these two processes interact and identify whether cross-talk may provide novel areas for future research and subsequent translation into clinical application., Data and Sources: A review of the literature was performed using the PubMed database resource and this was followed by extensive hand searching using reference lists from relevant articles., Conclusions: Frequently, the dental tissue inflammatory and regenerative processes are seen as both distinct and antagonistic and subsequently have often been studied in isolation; however, both direct and indirect data are now emerging which indicate significant inter-relationship. Whilst the ensuing inflammatory process will result in dental tissue breakdown and molecular signalling which may impede regeneration, low grade inflammation, potentially induced by mechanical trauma and tissue necrosis, may promote regenerative mechanisms, including angiogenic and stem cell processes. Notably, the locally derived growth factors, neuropeptides, cytokines and chemokines, released from the host dentine matrix and by resident pulpal cells, immune cells, neurons and/or dying cells, will modulate defence and repair processes within the tissue., (Copyright 2010 Elsevier Ltd. All rights reserved.)

High energy X-ray scattering (80.7keV photons) at station 1-ID of the Advanced Photon Source quantified internal strains as a function of applied stress in mature bovine tooth. These strains were mapped from dentin through the dentinoenamel junction (DEJ) into enamel as a function of applied compressive stress in two small parallelepiped specimens. One specimen was loaded perpendicular to the DEJ and the second parallel to the DEJ. Internal strains in enamel and dentin increased and, as expected from the relative values of the Young's modulus, the observed strains were much higher in dentin than in enamel. Large strain gradients were observed across the DEJ, and the data suggest that the mantle dentin-DEJ-aprismatic enamel structure may shield the near-surface volume of the enamel from large strains. In the enamel, drops in internal strain for applied stresses above 40MPa also suggest that this structure had cracked., (2010 Elsevier Ltd. All rights reserved.)

The purpose of this study was to investigate the strain and temperature change in dentin induced by laser irradiation of human root canals with or without water cooling. Twenty-eight palatal roots of extracted human maxillary first molars were used. The strain in dentin was measured using strain gauges fixed on the apical third of the buccal root surface. The temperature change of the root dentin was monitored using thermocouples embedded into dentin near the apex. The root canal was irradiated with Er:YAG or Nd:YAG laser at an output of 1 W (100 mJ, 10 pps) for 5 s. The tip of the irradiation fibre was located 2.0 mm from the root apex. With water cooling, the mean maximum strain induced by Er:YAG laser was significantly lower than that by Nd:YAG laser (P < 0.05). However, without water cooling, no significant difference between the two lasers (P > 0.05) was found. The results suggest that the strain induced by Er:YAG laser irradiation in dentin with water cooling may be minimal, but there still might be a risk of root micro-fracture if cooling is not sufficient.

Objective: Teeth that have been endodontically treated and restored with postcore crown may experience fracture sometimes. Some researchers have analyzed the stress of the anterior teeth after postcore crown restoration, but the stress of the posterior teeth after such restoration has not been reported. We used three-dimension finite element methods to analyze the stress magnitude and distribution of remaining dentin in posterior tooth residual root restored with postcore crown. The binding material, loading direction, number, length and material of posts were studied., Methods: The models of residual root of maxillary first molar restored with postcore crown were created by CT scanning, mimics software and abaqus software. Different number, length and material of posts were used in the modeling. The posts were cemented with zinc-phosphate cement or composited resin. A load of 240 N was applied to the occlusal surface in four directions and tensile, shear, and von Mises stresses were calculated., Result: (i) The maximum stress on remaining dentin changed irregularly as the number and length of posts changed. (ii) The maximum stress on remaining dentin decreased slightly as elastic modulus of the material of posts increased. (iii) The maximum stress on bonding layer and remaining dentin was lower when bonded with resin luting agent than with zinc-phosphate cement. (iv) The maximum stress on remaining dentin increased markedly as loading angle increased., Conclusion: The number, length, material of posts, bonding material and loading angle all have influence on the magnitude and distribution of stress. The influence of loading angle is most apparent.

Objective: The aim of this study was to evaluate the fracture strength and failure mode of flared bovine roots restored with different intraradicular posts., Material and Methods: Fifty bovine incisors with similar dimensions were selected and their roots were flared until 1.0 mm of dentin wall remained. Next, the roots were allocated into five groups (n=10): GI- cast metal post-and-core; GII- fiber posts plus accessory fiber posts; GIII- direct anatomic post; GIV- indirect anatomic post and GV- control (specimens without intraradicular post). A polyether impression material was used to simulate the periodontal ligament. After periodontal ligament simulation, the specimens were subjected to a compressive load at a crosshead speed of 0.5 mm/min in a servo-hydraulic testing machine (MTS 810) applied at 135 masculine to the long axis of the tooth until failure. The data (N) were subjected to ANOVA and Tukey's post-hoc test (alpha=0.05)., Results: GI and GIV presented higher fracture strength (p<0.05) than GII. GIII presented intermediate values without statistically significant differences (p>0.05) from GI, GII and GIV. Control specimens (GV) produced the lowest fracture strength mean values (p<0.05). Despite obtaining the highest mean value, GI presented 100% of unfavorable failures. GII presented 20% of unfavorable failures. GIII, GIV and GV presented only favorable failures., Conclusions: Although further in vitro and in vivo studies are necessary, the results of this study showed that the use of direct and indirect anatomic posts in flared roots could be an alternative to cast metal post-and-core.

Objective: To investigate the role of dentinal tubules in the fracture properties of human root dentin and whether resin-filled dentinal tubules can enhance fracture resistance., Materials and Methods: Crack propagation in human root dentin was investigated in 200 microm thick longitudinal samples and examined by light and scanning electron microscopy. 30 maxillary premolar teeth were prepared for work of fracture (Wf) test at different tubule orientations, one perpendicular and two parallel to dentinal tubules. Another 40 single canal premolars were randomly divided into four groups of 10 each: intact dentin, prepared but unobturated canal, canal obturated with epoxy rein (AH Plus/gutta percha), or with UDMA resin sealer (Resilon/RealSeal. The samples were prepared for Wf test parallel to dentinal tubules. Wf was compared under ANOVA with statistical significance set at p<0.05., Results: Dentinal tubules influenced the path of cracks through dentin, with micro-cracks initiated in peritubular dentin of individual tubules ahead of the main crack tip. A significant difference (p<0.001) was found between Wf perpendicular to tubule direction (254.9 J/m(2)) vs. parallel to tubule direction from inner to outer dentin (479.4 J/m(2)). Neither canal preparation nor obturation using epoxy- or UDMA-based resins as sealer cements substantially influenced fracture properties of root dentin, despite extensive infiltration of dentinal tubules by both sealer cements.