Dentin Area Research Articles

Interpretation of the concepts of dentinal tubule and dentinal canaliculus

The biology of dentin occupies a central place in the theory of tooth integrity as an organ, and knowledge about the microstructure of dentin changes with the development of new research methods, such as scanning electron microscopy. The structures that form dentin, and the odontoblast processes, are an extremely complex biological structure due to cellular polarization. The structure of the dentin of crowns from 30 intact teeth extracted for orthodontic reasons has been studied. Dentin was examined on longitudinal chips using scanning electron microscopy, determining the average number of dentinal tubules per unit area of dentin, the length and diameter of the dentinal canaliculi along the dentinal tubule. Scanning electron microscopy of demineralized teeth showed that numerous fine fibrillar structures were found in the predentin, connecting the odontoblast processes (dentinal canaliculi) and the walls of the dentinal tubules. The odontoblast processes were always in close contact with the microfibrillar network and were located within the dentinal tubule. It was found that the dentinal canaliculi have their own anchoring microfibrillar system, which allows each dentinal canaliculus to be held in a central position. The microfibrils are attached to the wall of the dentinal tubule and form a continuous mesh structure among the dentin tissue and are directly fixed on one side to the wall of the dentinal tubule, and on the other side to the wall of the dentinal canaliculus, which is a derivative of the odontoblast process. In different areas of the dentin, the length, number, and diameter of the microfibrils have a wide variative range. Microstructures were numerous in different regions of the dentinal tubule. Their number decreased with distance from the level of the outer dentin. In the inner third of the dentinal tubule, microfibrillar structures are observed that form a dense network of different types, thicknesses and diameters. The most common direction of the microfibrils was from the surface of the odontoblast process to the wall of the dentinal tubule, and in other cases these microfibrils were attached to both opposite inner surfaces of the dentinal tubule. The base of the microfibril is attached to the wall of the dentinal tubule, as if forming a continuous structure among the dentin tissue and the surface of the odontoblast process. It is shown that the microfibrillar structures may be a previously unknown framework system that ensures the stabilization of odontoblast processes inside the dentinal tubule. In the scientific classification of dentin ultrastructure, it is advisable to use the term "dentinal tubule" and "dentinal canaliculus", since this structure is a derivative of the odontoblast process.

Assessment of Nanosilver Fluoride Application on the Microtensile Bond Strength of Glass Ionomer Cement and Resin-modified Glass Ionomer Cement on Primary Carious Dentin: An In Vitro Study.

Nanosilver sodium fluoride (NSF) has recently gained popularity in dentistry as an alternative to silver diamine fluoride (SDF) due to its drawbacks of staining the tooth black and possibly causing soft tissue injury, which has been eliminated in NSF due to the nanoparticle size of silver. This study aims to assess the microtensile bond strength of glass ionomer cement (GIC) and resin-modified glass ionomer cement (RMGIC) with pretreatment of NSF on extracted primary carious teeth. Teeth were stored in 10% formalin. The roots were severed, and the pulp chambers were cleaned. The occlusal enamel was ground, reducing the dentin thickness by 1 mm. The specimens were covered with nail varnish, leaving only the area of flat dentin exposed. Caries were induced microbiologically by inoculating Streptococcus mutans. Group I-NSF with GIC restoration, group II-NSF with RMGIC restoration, group III-restoration with GIC, and group IV-restoration with RMGIC. After different surface treatments of the carious dentin were performed, each specimen was placed in the testing jig of a universal testing machine and stressed in tension at a crosshead speed of 1 mm/minute until bond failure was observed. They were air-dried and placed under a scanning electron microscope. The failure modes-adhesive, cohesive, and mixed failure were recorded for statistical evaluation. Maximum results of microtensile bond strength were seen in the pretreatment group with NSF sealant, followed by RMGIC restoration, and the least results were observed in the conventional GIC restoration group. Of all the types of failures in our study, adhesive was the maximum type. The microtensile bond strength of pretreatment with NSF showed higher values when compared to conventional restorations of GIC and RMGIC. The failure modes in each group were not significantly varied. Pretreatment with NSF will prevent secondary caries formation, and the restorations will also be stronger. Das A, Ramamurthy N, Srinivasan I, et al. Assessment of Nanosilver Fluoride Application on the Microtensile Bond Strength of Glass Ionomer Cement and Resin-modified Glass Ionomer Cement on Primary Carious Dentin: An In Vitro Study. Int J Clin Pediatr Dent 2024;17(5):565-569.

Microcomputed tomographic evaluation of 6 NiTi files on the pericervical dentin and the smallest dentin thickness zones in mesial root canals of mandibular molars: an in vitro study.

The aim of this study was to evaluate six files on the pericervical dentin (PCD) and the smallest dentin thickness zones (SDTZ) in mesial root canals of mandibular molars. Sixty mandibular molars with two mesial canals and Vertucci configuration were aleatory allocated in 6 experimental groups of 10 molars and 20 root canals. Specimens were scanned before instrumentation using the SkyScan 1275 (Bruker microCT, Kontich, Belgium). Group 1 was treated with WaveOne Gold (WG), group 2 with Reciproc Blue (RB), group 3 with TRUShape (TS), group 4 with XP-endo Shaper (XP), group 5 with iRace (IR), and group 6 with TruNatomy (TN). After instrumentation, the molars were scanned again and the images recorded were reconstructed with the NRecon v.1.7 (Bruker micro-CT) and analyzed with CTAn v.1.20.8 software (Bruker micro-CT) quantifying the changes produced in the surface, volume, structure thickness, SMI, and centroids at the Pericervical Dentin area of the root canals (PCD) located from the root canal orifices at the floor of the pulp chamber to 4 mm in the apical direction, and the changes in the Smallest Dentin Thickness Zones (SDTZ) located (from the furcation to 4 mm and 7 mm in the apical direction. The data obtained were compared using Wilcoxon and ANOVA with a 5% significance level. XP and TN were similar in all the parameters (P >.05) at the PCD, but TN showed significant differences from WG, RB, TS, and IR (P <.05), while XP showed significant differences from WG (P <.05) in volume, surface, and structure thickness. Regarding the changes in the SDTZ, the amount of dentin removed was similar between the groups in both canals at the middle 1/3, at the cervical 1/3 for MB canals, and in ML canals for RB, TS, XP, IR, and TN (P>.05). The action of WG was significantly different from that of XP and TN in the cervical 1/3 of the ML canal (P <.05). XP and TN rotatory files with small taper and volume maintained better with minor changes at the PCD and SDTZ, while WG reciprocation file produced the largest change. All the files were maintained centered at the PCD, and their performances were safe with a minimal thickness higher 0.5 mm at the SDTZ, and without risk of perforation. No clinical trials were indicated in this study. The choice of endodontic files is a relevant factor in the conservative performance of root canal treatments.

Stress Distribution of Endodontically Treated Tooth MOD Cavity Restored with Ribbon Fiber-Reinforced Composite (Wallpapering Technique) Using Finite Element Method.

This research aimed to describe the stress distribution of an endodontically treated tooth with a mesio-occluso-distal (MOD) cavity restored with direct composite reinforced with polyethylene and e-glass ribbon fiber. This research was a descriptive study using the finite element method. A 3D model of the mandibular first molar solid after endodontic treatment with class II MOD preparation was prepared using Solidworks software. Finite element simulation was carried out using Abaqus software. In the first simulation, 180 N force was applied (vertically 90° perpendicular to the occlusal surface) at four points of loading: the tip of the mesiobuccal and distobuccal cusp, central fossa, and distal marginal ridge. For the second simulation, a 100 N force was applied at a 45° lateral angle to the occlusal surface at two loading points: the lingual slope of the mesiobuccal and distobuccal cusp. This study showed that the stress concentration was located in the occlusal pit and fissure, CEJ distal area, bifurcation in dentin, and the 1/3 cervical area of root dentin. The stress value generated after vertical and lateral force did not exceed the tooth and restoration's compressive and tensile strength value. The failure occurred at the interface of enamel and composite near the loading point area due to vertical load, both on polyethylene and e-glass fiber ribbon-reinforced composite restoration. Stress distribution of an endodontically treated tooth with a MOD cavity restored with ribbon fiber-reinforced composite using the finite element method showed that the highest stress concentration occurred on the surface close to the loading point, in narrow, concave, and sharp areas, and more apically for endodontically treated teeth. Neither the tooth nor restoration failed after vertical and horizontal loads. The interface between enamel and composite on the occlusal surface failed.

Scanning electron microscopic analysis of 5% glycolic acid as a novel alternative to 17% ethylenediaminetetraacetic acid in root biomodification: An in vitro study.

Nonsurgical periodontal therapy results in the formation of a smear layer which inhibits tissue regeneration. Root biomodification (RB) using various agents has been tried for the enhancement of new attachment formation. However, no substantial therapeutic advantages of currently available root conditioning agents have been reported emphasizing the need for additional biologically acceptable agents. Glycolic acid (GA) due to its antimicrobial nature and ability of initiation and proliferation of fibroblasts may potentially modify root surface enabling regeneration. Eighty specimens from 40 single-rooted teeth were treated with 17% ethylenediaminetetraacetic acid (EDTA) and 5% GA and scanning electron microscopy analysis was done. The micrographs were examined for the evaluation of smear layer removal, total number of dentinal tubules, total number of patent dentinal tubules, mean diameter and surface area of dentinal tubules, and dentin erosion. Statistical analysis was done using unpaired t-test for intergroup comparison. The efficacy of smear layer removal (P = 0.01) and dentin erosion (P = 0.042) was significantly better in the GA group. Both the groups showed no difference in dentinal tubule-related parameters. GA showed improved RB with greater smear layer removal and lesser dentin erosion, indicating its use as a potent alternative to the conventional EDTA root conditioning.

Comparative analysis of hydrophobicity and dentin adhesion ability in Candida albicans strains.

Adhesion to dentin is a first step for a successful microbial root canal colonization. Cell hydrophobicity seems to have some influence in the Candida species adhesion to surfaces. To measure cell surface hydrophobicity and to investigate the adherence ability to human dentin among Candida albicans strains isolated from root canal and lingual dorsum via an in vitro study. adhesion was quantified in function of dentin area covered by blastospores and/or hyphae presence detected by epifluorescence microscope. Cell surface hydrophobicity was estimated by assessing the percentage migration of cells from an aqueous phase to a hydrocarbon phase. Contact angles were measured by the sessile drop technique on the dentin surface using a contact angle measurements apparatus. We also examined the correlation between adhesion ability and hydrophobicity. although there was some intra-species variation in cell surface hydrophobicity, most isolates were characterized by moderate hydrophobicity. There was no significant difference in this parameter when the isolation niche was considered. Both root canal and lingual dorsum yeasts were able to adhere to dentin. No association was found between the strains' site of isolation and adhesion. Moreover, cell surface hydrophobicity and adhesion ability were not correlated. although hydrophobicity can influence Candida albicans virulence in many ways, this study suggests that this parameter by itself was not a good predictor of adhesion to dentin.

A labeling study of dentin formation rates during crown and root growth of porcine mandibular first molars.

We used fluorochrome labeling to study spatiotemporal variation of dentin apposition (DAR) and extension (DER) rates during crown and root formation of mandibular first molars from wild boar and domestic pigs. DAR was reconstructed along the course of dentinal tubules in four zones of the crown and in the upper root area. In all five zones, mean DAR increased during the first 30% to 40% of apposition, reaching highest values (22-23 μm/day) in the upper-lateral crown zone. Lowest values were recorded near the dentin-pulp interface (DPI). Typically, DARs in contemporaneously formed dentin areas were higher in more cuspally compared to more cervically/apically located zones. DER was high (>200 μm/day) in early postnatal crown dentin and then decreased markedly in cervical direction, with lowest values in the cervical crown zone. After this nadir, DER sharply increased in the upper 30% to 40% of the root extension, reaching values equaling (wild boar) or even surpassing (domestic pigs) those recorded in the upper lateral crown. After this peak, DER again decreased. While DAR did not differ markedly between wild boar and domestic pigs, the DER showed marked differences, both regarding maximum values (208.1 μm/day in wild boar, 272.2 μm/day in domestic pigs) and the timing of the root growth spurt, which occurred earlier in the domestic pigs. We consider the more rapid recruitment of secretory odontoblasts in domestic pigs (reflected by higher DER) a side effect of selection for rapid body growth during pig domestication.

Hard tissue density of permanent teeth as a radiometric biomarker of their quality

Background. The use of radiographic methods for examining patients with the ability to determine the density of examined tissues opens up wide opportunities for individually predicting damage to hard tissues of teeth, as well as determining risk groups for the development of their pathology at early stages, which requires a detailed study of the mineral density indicators of hard tissues of teeth of different groups within the norm, taking into account their age, sex, ethnic, and other characteristics. The aim of the study was to determine the density indicators of hard tissues of permanent teeth of different groups in the cervical area and compare them. Material and Methods. The density of hard tissues was determined by analyzing radiographs of 320 intact permanent teeth of 10 patients. Radiographs were made using a Siemens Sirona (XIOS XG Supreme, Germany) dental radiography unit with Trophy Radiologie software (version 7.0, Slovakia). The images were processed using Gendex VixWin Pro software (version 3.5, USA). The density was measured in Conditional Unit of Grayness (CUG). The results were presented as Me (25%; 75%), where Me represents the median, 25% denotes the 25th percentile (first quartile), and 75% denotes the 75th percentile (third quartile). Results. Incisors, canines, and premolars exhibited the highest density in the dentin area; the lowest density was observed in incisors and premolars for cementum and in canines for enamel. In molars, enamel had the highest density, while cementum had the lowest. Significant differences in enamel density were observed among incisors and premolars, incisors and molars, canines and premolars, canines and molars, and premolars and molars. Significant differences in dentin density were found among incisors and canines, incisors and premolars, incisors and molars, canines and premolars, and canines and molars. Significant differences in cementum density were observed among incisors and canines, incisors and premolars, incisors and molars, canines and premolars, and premolars and molars. Conclusion. The density indicators of enamel, dentin, and cementum established for groups of permanent incisors, canines, premolars, and molars are different for different tooth groups with characteristic density patterns. Keywords: enamel, dentin, cementum, incisors, canines, premolars, molars.

The effects of chelation on the intratubular penetration depth of mineral trioxide aggregate.

The penetration depth and extent of mineral trioxide aggregate (MTA) crystallisation into dentinal tubules at 2, 4 and 6 weeks after chelation and MTA obturation were investigated. Standardised 12 mm human root specimens (45) were prepared with NiTi rotary files using 4% NaOCl irrigation. They were randomly allocated to three irrigants (n = 15: 4% NaOCl, 15% ethylenediaminetetraacetic acid or Edgemix) and obturated with sodium fluorescein tagged ProRoot MTA. One millimetre thick apical, middle and coronal sections were examined using confocal laser scanning microscopy to determine MTA penetration depth and area. Depths varied from 352 to 1821 μm at 6 weeks depending on section level and were unaffected by chelation. No differences (p > 0.05) were found in mean maximum penetration depth or dentine area (%) between the 3 irrigants at all time intervals. MTA mineralisation penetrated up to 90% of dentinal tubules and can extend to the cementum in roots with patent, non-infected tubules.

Effect of Intracoronal Sealing Biomaterials on the Histological Outcome of Endodontic Revitalisation in Immature Sheep Teeth—A Pilot Study

The influence of intracoronal sealing biomaterials on the newly formed regenerative tissue after endodontic revitalisation therapy remains unexplored. The objective of this study was to compare the gene expression profiles of two different tricalcium silicate-based biomaterials alongside the histological outcomes of endodontic revitalisation therapy in immature sheep teeth. The messenger RNA expression of TGF-β, BMP2, BGLAP, VEGFA, WNT5A, MMP1, TNF-α and SMAD6 was evaluated after 1 day with qRT-PCR. For evaluation of histological outcomes, revitalisation therapy was performed using Biodentine (n = 4) or ProRoot white mineral trioxide aggregate (WMTA) (n = 4) in immature sheep according to the European Society of Endodontology position statement. After 6 months' follow-up, one tooth in the Biodentine group was lost to avulsion. Histologically, extent of inflammation, presence or absence of tissue with cellularity and vascularity inside the pulp space, area of tissue with cellularity and vascularity, length of odontoblast lining attached to the dentinal wall, number and area of blood vessels and area of empty root canal space were measured by two independent investigators. All continuous data were subjected to statistical analysis using Wilcoxon matched-pairs signed rank test at a significance level of p < 0.05. Biodentine and ProRoot WMTA upregulated the genes responsible for odontoblast differentiation, mineralisation and angiogenesis. Biodentine induced the formation of a significantly larger area of neoformed tissue with cellularity, vascularity and increased length of odontoblast lining attached to the dentinal walls compared to ProRoot WMTA (p < 0.05), but future studies with larger sample size and adequate power as estimated by the results of this pilot study would confirm the effect of intracoronal sealing biomaterials on the histological outcome of endodontic revitalisation.

Histologic Features of External Cervical Resorption Affecting Impacted Maxillary Canines: A Report of 2 Cases

Reports on the histopathologic features of external cervical resorption (ECR) in unerupted teeth are scarce. This article reports on 2 maxillary impacted canines from different patients that showed ECR lesions and were surgically removed and histologically evaluated. Case 1 showed symptoms associated with oral communication of the dental follicle and pulpal exposure. Radiographs and cone-beam computed tomographic imaging showed that resorption affected a large part of the root and the crown. Case 2 was asymptomatic, and the resorption cavity was restricted to the tooth crown. Both teeth were extracted and subjected to histologic processing and analysis. In case number 1, the coronal pulp was necrotic and infected, showing areas of exposure to the resorption channels. The apical pulp was vital and uninflamed. The pulp space was surrounded by a continuous pericanalar resorption-resistant sheet. Part of the resorbed area of dentin was occupied by inflamed granulation tissue. More apically, a network of trabecular bone was present in the resorbed area. In case number 2, the pulp around the resorbed area was uninflamed and vital. A large fraction of the lost dentin was replaced by trabecular bone, closely adapted to the irregularly resorbed dentin surface, and no inflammatory cells. Our findings indicate that impacted teeth with ECR may remain asymptomatic until associated with infection. Histologic features of resorption in impacted teeth were similar to those in erupted teeth. In the case associated with infection, the resorbed area was occupied by inflamed tissue and newly formed bone. In the case with no infection, the resorption area was filled with bone undergoing a remodeling process.

The Indicators of Molar Coefficients of the Chemical Elements in Dentin and their Correlation with Enamel

Objectives:Determination of molar coefficients of the chemical elements in dentin, their possible correlation with tooth enamel. Material and Methods:There were examined 29 clinically extracted teeth of both jaws and their longitudinal sections (12 clinically intact teeth, 10 teeth with wedge-shaped defects, 7 teeth with cervical caries) of the patients aged 25to 54 with the help of JSM-6490 LV focused beam electron microscope (scanning) with system of energy-dispersive X-ray microanalysis. We have determined the chemical composition of 290 enamel areas and 235 dentine areas in the incisal region (tubercle), equator, cervical area as a percentage of the weight amounts of carbon, oxygen, calcium, phosphorus, sodium, magnesium, sulfur, chlorine, zinc, potassium, aluminum, we have identified their molar coefficients. Results: The chemical composition of dentin differed in the values of Na/Mg, Al/Zn, Mg/Ca, K/Na (p≤0.05) in all studied topographical regions of the samples. Higher values of Na/Mg and lower values of Al/Zn were identified in the teeth with cervical caries (p≤0.05). Correlation was found in dentin: inverse between Ca/P and P/Ca, Mg/Ca and Na/Mg, Ca/Mg and Mg/Ca, Mg/P and Na/Mg, Mg/P and Ca/Mg, direct between Ca/Mg and Na/Mg, Mg/P and Mg/Ca (p≤0.05). High correlation was determined between molar coefficients in enamel and dentin: Mg/Ca and Mg/P (direct), Ca/P and P/Ca (inverse), p&amp;lt;0.0001. Conclusions:The differences in the indicators of molar coefficients in dentin, their correlation with enamel are probably associated with the peculiarities of the pathological processes in the cervical region and it requires further study.

Evaluation of sexual dimorphism in human premolars using longitudinal ground sections- A cross sectional study

Introduction: Sex determination plays an important role in forensics. On average, males possess larger tooth crowns than females in contemporary human populations, although the degree of dimorphism varies within different populations. Ground sectioning of teeth can provide an accurate measurement of enamel and dentinal thickness and can be used for gender determination in forensic analysis.&#x0D; Aim: The main aim of this study is to evaluate sexual dimorphism in human premolars using longitudinal ground sections.&#x0D; Materials &amp; Method: In this study extracted premolar teeth of males and females were taken. Longitudinal ground sectioning of these teeth was made and later examined under light microscope under customized grids.&#x0D; Results: Data was statistically analyzed and results were tabulated. It was found that enamel area and average enamel thickness was higher in females than males and coronal dentinal areas were more in males.&#x0D; Conclusion: Results of this study suggest that the differences in crown morphology among males and females can be used as a potential tool in forensic analysis.

Biodegradation of an injectable treated dentin matrix hydrogel as a novel pulp capping agent for dentin regeneration

BackgroundA novel injectable mixture termed treated dentin matrix hydrogel (TDMH) has been introduced for restoring dentin defect in DPC. However, no study evaluated its physiological biodegradation. Therefore, the present study aimed to assess scaffold homogeneity, mechanical properties and biodegradability in vitro and in vivo and the regenerated dentin induced by TDMH as a novel pulp capping agent in human permanent teeth.MethodsThree TDMH discs were weighted, and dry/wet ratios were calculated in four slices from each disc to evaluate homogeneity. Hydrogel discs were also analyzed in triplicate to measure the compressive strength using a universal testing machine. The in vitro degradation behavior of hydrogel in PBS at 37 °C for 2 months was also investigated by monitoring the percent weight change. Moreover, 20 intact fully erupted premolars were included for assessment of TDMH in vivo biodegradation when used as a novel injectable pulp capping agent. The capped teeth were divided into four equal groups according to extraction interval after 2-, 8-, 12- and 16-weeks, stained with hematoxylin–eosin for histological and histomorphometric evaluation. Statistical analysis was performed using F test (ANOVA) and post hoc test (p = 0.05).ResultsNo statistical differences among hydrogel slices were detected with (p = 0.192) according to homogeneity. TDMH compression modulus was (30.45 ± 1.11 kPa). Hydrogel retained its shape well up to 4 weeks and after 8 weeks completely degraded. Histological analysis after 16 weeks showed a significant reduction in TDMH area and a simultaneous significant increase in the new dentin area. The mean values of TDMH were 58.8% ± 5.9 and 9.8% ± 3.3 at 2 and 16 weeks, while the new dentin occupied 9.5% ± 2.8 at 2 weeks and 82.9% ± 3.8 at 16 weeks.ConclusionsTDMH was homogenous and exhibited significant stability and almost completely recovered after excessive compression. TDMH generally maintained their bulk geometry throughout 7 weeks. The in vivo response to TDMH was characterized by extensive degradation of the hydrogel and dentin matrix particles and abundant formation of new dentin. The degradation rate of TDMH matched the rate of new dentin formation.Trial registration: PACTR201901866476410: 30/1/2019.

Histological characteristics of bovine dentin using Masson's Trichrome staining

Identify the histological characteristics of bovine dentin using histological technique by decalcification with Masson's Trichrome staining. This was an observational and descriptive study using units of analysis. Bovine teeth were used, which were subjected to a decalcification technique and Masson's trichrome staining. Microscopic observation and registration of the structures was carried out. In the microscopic observation of the teeth subjected to decalcification, dentin, predentin and the structural organization of the tubular and peritubular dentin were observed. The odontoblasts arranged in a palisade with the odontoblastic process included within the dentinal tubule and the periprocedural space. The presence of interglobular dentin is not observed in areas of coronary dentin. The histomorphological pattern corresponding to dentin-predentin-pulp is arranged in a similar way to human teeth. Bovine dentin constitutes an ideal substrate for in vitro research work with dental biomaterials, since it presents histological characteristics similar to bovine teeth; the absence of interglobular dentin would not represent a significant difference according to what was observed in this study.

Effect of Temporary Cement, Surface Pretreatment and Tooth Area on the Bond Strength of Adhesively Cemented Ceramic Overlays—An In Vitro Study

Several viewpoints have been reported regarding the effect of temporary cements, different surface pretreatment protocols before adhesive cementation, and predictive factors. This in vitro study tested if temporary cement, pretreatment of the tooth surface, the size of enamel or dentine influence adhesive cementation to zirconia ceramics. Twenty premolars were prepared for determination of enamel and dentin area, bond strength test and failure analysis. The samples were divided into two groups: untreated prior adhesive cementation (n = 10) and with temporary cementation done, pretreated prior adhesive cementation (n = 10). Zirconia overlays (Katana Zirconia STML) were cemented on the grounded flat teeth surfaces using Panavia V5. An additional six premolars underwent dentine tubule analysis with SEM to detect temporary cement residues after temporary cementation on an untreated tooth surface (n = 3) and on a pretreated surface (n = 3). The independent sample t-test was used to compare the two groups and the means of the total tooth, dentin or enamel areas did not differ significantly between the untreated and pretreated specimens. The mean tensile bond strength was significantly (p = 0.005) higher in the pretreated specimens (337N) than in the untreated ones (204N). The overall multivariable linear regression model with three predictors (surface pre-treatment, enamel area and dentine area) was significant (p = 0.003), among which the size of enamel was the strongest predictor (β = 0.506; p = 0.049), followed by the pretreatment effect (β = 0.478; p = 0.001) and the size of dentin area (β = -0.105; p = 0.022).

Hardness and indentation modulus of human enamel and dentin

Information on mechanical properties of human enamel and dentin and effect of load on their deformation and damage tolerance is very important in the development of successful dental materials. In this study, the hardness, indentation modulus and deformation characteristics of tooth have been investigated across the lingual–buccal enamel and dentin cross‐section by instrumented indentation up to 1500‐nm indentation depth. We realized and examined the distribution of hardness and modulus at different areas of enamel and dentin with the aim to understand deformation behaviour at these different locations. Scanning electron microscopy was used for the microstructure characterization of the enamel and dentin and their deformation behaviour. Raman spectroscopy analyses were carried out for determination of the enamel and dentin composition as well. The average values of hardness and modulus for enamel in the occlusal area are 5.35 ± 0.19 and 98.1 ± 1.5 GPa, in the inner area 3.68 ± 0.5 and 81.8 ± 5 GPa and in the area close to the dentin–enamel junction 2.83 ± 0.27 and 71.4 ± 4.1 GPa, respectively. The average values of hardness and modulus of dentin in the area close to the dentin–enamel junction are 0.71 ± 0.05 and 21.27 ± 0.76 GPa and in the inner area 0.65 ± 0.06 and 19.79 ± 0.93 GPa, respectively. The effect of the indentation location on deformation and mechanical properties was clarified.

Interfacial characteristics of BIOfactor MTA and Biodentine with dentin.

The objective of this study was to characterize the interface between dentin and MTA-Angelus (Angelus, Londrina, Brasil), Biodentine (Septodont, France) and BIOfactor MTA (Imicryl, Konya, Turkey) using scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (SEM-EDS) and confocal laser scanning microscopy (CLSM). Fifteen dentin segments were obtained from previously extracted single-rooted human teeth. Canal lumens were instrumented with diamond burs and then randomly filled with MTA-Angelus, Biodentine or BIOfactor MTA and placed in distilled water or Hanks' Balanced Salt Solution (HBSS) for 28-days. The samples were examined with SEM and the thickness of the interfacial layer measured. SEM-EDS analysis was performed to determine principal elemental composition of the material, dentin, and interfacial area. The marginal adaptation of cements to dentin was assessed by confocal microscopy and the percentage of material penetration was calculated. An interfacial layer was evident in approximately 70% of SEM images in both MTA-Angelus and BIOfactor samples. The thickness of interfacial layer was significantly higher in HBSS than in distilled water for all groups. MTA Angelus resulted in the thickest interfacial layer in distilled water while Biodentine had the thickest interfacial layer in HBSS. Calcium levels within the BIOfactor MTA-dentin interface were higher than both dentin and cement. Dentin penetration was higher in BIOfactor MTA and silicon was evident in all material-dentin interfaces. All calcium silicate-based materials promoted the formation of an interfacial layer. BIOfactor MTA exhibited promising characteristics with its good marginal adaptation even though it presented a moderately thick interfacial layer. RESEARCH HIGHLIGHTS: A distinguishable interfacial layer was observed in most of the samples within the BIOfactor MTA, MTA-Angelus and Biodentine groups. The elemental constitution of the interfacial layer was different from that of the calcium silicate based materials.

Desensitizing toothpastes for dentin sealing and tertiary dentin formation in vitro and in vivo: a comparative analysis

BackgroundDentin hypersensitivity is a painful response to external stimuli applied to exposed dentinal tubules. Various toothpastes with active desensitizing ingredients for the relief of dentin hypersensitivity are commercially available. However, data from several studies suggest that the effects of desensitizing toothpastes are unstable and brief. This study aimed to investigate the effect of toothpastes containing CPNE7-derived oligopeptide (CPNE7-DP) and other active desensitizing ingredients in the dentin microleakage, tubule occlusion and tertiary dentin formation.MethodsUsing scanning electron microscopy (SEM), we evaluated the patency of dentinal tubules on the surface of human dentin disks after brushing experiments with the various toothpastes. Dentin was histologically evaluated in a hypersensitivity model of canine teeth, after the exposed dentin area was brushed for 6 weeks. The toothpaste used in group 1 (control) did not contain any desensitizing ingredients; that used in group 2 contained CPNE7-DP; Colgate Sensitive was used in group 3; and Sensodyne Rapid Relief was used in group 4. Finally, we conducted microleakage analysis to investigate the dentin sealing effect. The microleakage analysis data were subjected to one-way ANOVA and post-hoc Tukey tests (alpha = 0.05).ResultsIn the SEM images, all four groups of teeth exhibited partial occlusion of the dentinal tubules on the tooth surface. In the in vivo hypersensitivity model, group 2 exhibited a newly formed tertiary dentin, whereas no new hard tissue formation was observed in groups 1, 3, and 4. Microleakage analysis revealed that the volume of dentinal fluid flow was significantly smaller in group 2 than in group 1.ConclusionsThese results indicate that CPNE7-DP is a promising active ingredient with long-term dentin sealing effects.

Biomechanical properties of mandibular first molar with truss and conventional access cavities

Aim: The aim of this study was to compare the biomechanical strength properties of the mandibular first molar with truss and conventional endodontic access cavities using the finite element method. Methods: Two finite element analysis (FEA) models of a mandibular first molar were designed and constructed with truss endodontic cavity (TREC) and Conventional endodontic cavity (CEC). Each model was subjected to three different force loads directed at the occlusal surface. The stress distribution patterns and the maximum von Mises (VM) stresses were calculated and compared. FEM software ANSYS was used for evaluation. Results: The peak VM stress on both models was at the site of the force load. The occlusal stresses were spread in an approximate actinomorphic pattern from where the force was loaded, and the stress was much higher when the force load was close to the access cavity margin. The peak root VM stresses on the root-filled teeth occurred at the apex and were significantly higher than that on the intact tooth, which appeared on the pericervical dentin. The area of pericervical dentin experiencing high VM stress increased as the cavity size increased and became concentrated in the area between the filling materials and the dentin. Conclusion: Under all loading conditions, the TREC model showed low-stress concentration compared to the CEC model. With enlargement of the access cavity, the stress on the pericervical dentin increased significantly.