Effect of medicaments used in endodontic regeneration on the morphological characteristics of bovine radicular dentin: Experimental immature tooth model

The purpose of this study was to evaluate the effect of different combinations of irrigating solutions and intracanal dressings in the pretreatment of bovine radicular dentin, using an experimental immature tooth model. Eighty healthy bovine teeth, simulated with incomplete rhizogenesis, were randomly distributed according to the protocols of root canal dentin pretreatment for a regenerative endodontic procedure (n = 10): Control (irrigation with distilled water); SH (irrigation with 1.5% Sodium Hypochlorite); EDTA (irrigation with 17% EDTA); SH/EDTA (irrigation with 1.5% SH + 17% EDTA); SH/CH/EDTA (irrigation with 1.5% SH + calcium hydroxide paste +17% EDTA); SH/MTAP/EDTA (irrigation with 1.5% SH + modified triple antibiotic paste + EDTA 17%); SH/TAP/EDTA (irrigation with 1.5% SH + triple antibiotic paste +17% EDTA) and SH/DAP/EDTA (irrigation with 1.5% SH + double antibiotic paste + EDTA 17%). After the completion of the protocol, the demineralization, the exposure of collagen fibers, and the dentin erosion was evaluated under scanning electron microscopy (SEM), by applying a score system (1–3) to classify the observed features. Statistical analysis was performed (Kruskal‐Wallis and Dunn Multiple Comparison tests—p < .05). SH/TAP/EDTA and SH/DAP/EDTA groups presented the highest rates of demineralization in both the coronal and middle thirds of the root (p < .05). In the SH/MTAP/EDTA group, the samples presented moderate demineralization. The samples from the SH/CH/EDTA group presented similar findings to the control group (p < .05). Conventional triple antibiotic (TAP) and double antibiotic (DAP) pastes promoted more pronounced morphological changes on the dentin surface.     

Surface change of root canal dentin after the use of irrigation activation protocols: Electron microscopy and an energy‐dispersive X‐ray microanalysis

This study evaluated the mineral contents of root‐canal dentin after treatment with different irrigation activation protocols. One hundred and eight maxillary lateral incisor teeth were randomly divided into eight experimental groups and one control group. Root canals were prepared using ProTaper rotary files, with the exception of the Self‐Adjusting File (SAF) group. Canals were irrigated with 2 mL of 5% sodium hypochlorite (NaOCl) at each instrument change, and received a final flush with 10 mL of 17% ethylenediaminetetraacetic acid (EDTA) and 10 mL of 5% NaOCl for 1 min. The control group was irrigated with distilled water. Group I (GI): Needle syringe irrigation; Group II (GII): NaviTip FX; Group III (GIII): CanalBrush; Group IV (GIV): Manual dynamic activation with gutta‐percha; Group V (GV): Passive ultrasonic irrigation; Group VI (GVI): EndoActivator; Group VII (GVII): EndoVac; Group VIII (GVIII): SAF. The level of elemental composition was analyzed by a scanning electron microscopy and an energy‐dispersive spectrometer (EDS) system. The results were then statistically analyzed by one‐way ANOVA and Tukey tests. Ca/P ratio was changed after treatment with SAF and EndoActivator. The Ca, P, Mg, and S level changes were not statistically significant (P > 0.05). Final irrigation activation protocols did not alter the mineral level of root dentin surface. Microsc. Res. Tech. 76:893–896, 2013. © 2013 Wiley Periodicals, Inc.     

FT‐Raman spectroscopy, µ‐EDXRF spectrometry,and microhardness analysis of the dentin of primary and permanent teeth

The chemical compositions (organic and inorganic contents) and mechanical behaviors of the dentin of permanent and deciduous teeth were analyzed and compared using X‐ray fluorescence spectrometry (µ‐EDXRF) Fourier transform Raman spectroscopy (FT‐Raman) and a microhardness test (HD). Healthy fresh human primary and permanent molars (n = 10) were selected, The buccal surfaces facing upwards were stabilized in an acrylic plate, flattened, polished, and submitted to the µ‐EDXRF, FT‐Raman, and HD analysis. The results of the analysis were subjected to ANOVAs and Mann‐Whitney U/Student's t multiple comparisons tests. The data showed similar values for the dentin of the primary and permanent teeth in P content, organic content (amide I peak), inorganic content ( – 430 and 590), and microhardness, Nevertheless, Ca content and Ca/P weight ratio were higher, and the peak was lower in the dentin of the permanent teeth compared to primary teeth. It be concluded that despite permanent teeth showed more Ca element, both substrates showed similar behavior of chemical and physical properties.     

Computed microtomography evaluation of calcium hydroxide‐based root canal dressing removal from oval root canals by different methods of irrigation

The aim of this study was to evaluate the capacity of conventional irrigation, passive ultrasonic irrigation (PUI), and Easy Clean for removing calcium hydroxide‐based root canal dressing from oval root canals. Thirty mandibular uniradicular incisors with oval canals were used, and subjected to chemical–mechanical preparation with Reciproc R40 instruments. The main canal was filled with a paste based on Ca(OH)₂ P.A., iodoform and propylene glycol in the ratio of 3:1:1. The teeth were stored in 100% humidity at a temperature of 37°C for 14 days. Afterwards, the teeth were divided into three groups (n = 10) according to the method of irrigation used (conventional irrigation, PUI, and Easy Clean). The specimens were analyzed by computed microtomography at three time intervals: before placing the root canal dressing, with the root canal dressing in place, and after application of the irrigation methods for removing it. The data were submitted to Kruskal–Wallis and Dunn tests for analyzing the canal as a whole, and Friedman and Dunn for analyzing the root thirds. The results showed that conventional irrigation was less efficient for removing the root canal dressing in comparison with the methods that agitated the irrigant solution (p < .05). When the root canal was analyzed as a whole, Easy Clean, and PUI were similar (p > .05). In analysis of the thirds, Easy Clean was more efficient than conventional irrigation in all the thirds, while PUI showed this behavior only in the cervical third (p < .05). The authors concluded that in oval canals, none of the irrigation methods were capable of removing all the root canal dressing, however, the methods that agitated the irrigant solution were more efficient than conventional irrigation.     

Efficacy of ethylene‐diamine‐tetra‐acetic acid associated with chlorhexidine on intracanal medication removal: A scanning electron microscopy study

The aim of this study was to evaluate the effectiveness of 17% ethylene‐diamine‐tetra‐acetic acid (EDTA) used alone or associated with 2% chlorhexidine gel (CHX) on intracanal medications (ICM) removal. Sixty single‐rooted human teeth with fully formed apex were selected. The cervical and middle thirds of each canal were prepared with Gates Glidden drills and rotary files. The apical third was shaped with hand files. The specimens were randomly divided into two groups depending on the ICM used after instrumentation: calcium hydroxide Ca(OH)₂+CHX or Ca(OH)₂+sterile saline (SS). After seven days, each group was divided into subgroups according to the protocol used for ICM removal: instrumentation and irrigation either with EDTA, CHX+EDTA, or SS (control groups). All specimens were sectioned and processed for observation of the apical thirds by using scanning electron microscopy. Two calibrated evaluators attributed scores to each specimen. The differences between the protocols for ICM removal were analyzed with Kruskal‐Wallis and Mann‐Whitney U tests. Friedman and Wilcoxon signed rank tests were used for comparison between the score of debris obtained in each root canal third. Remains of Ca(OH)₂ were found in all specimens independently of the protocol and ICM used (P > 0.05). Seventeen percent EDTA showed the best results in removing ICM when used alone (P < 0.05), particularly in those associated with CHX. It was concluded that the chelating agent 17% EDTA significantly improved the removal of ICM when used alone. Furthermore, the type of the vehicle associated with Ca(OH)₂ also plays a role in the ICM removal. Microsc. Res. Tech. 77:735–739, 2014. © 2014 Wiley Periodicals, Inc.     

The effect of a root‐dentin pretreatment technique combining PIPS with MTAD aiming to improve the bond strength of glass fiber post

The aim of this study was to evaluate the combined effect of MTAD and photon‐induced photoacoustic streaming (PIPS) technique on the smear layer removal and the bond strength of glass fiber post. Fifty‐five human mandibular premolars were chosen. After root canal therapy and post space preparation, the teeth were equally divided to five groups according to the methods of root‐dentin pretreatment: G1: distilled water (control); G2: 2.5% NaOCl+17% EDTA; G3: MTAD; G4: PIPS; G5: MTAD+PIPS. One sample was randomly selected from each group, and scanning electron microscope (SEM) was used to observe the microscopic morphology of the coronal, middle and apical level of the root‐dentin. The remaining ten samples from each group were glued to glass fiber posts, and the bond strength was assessed by push‐out test. SEM evaluation showed that the most complete smear layer removal was found in MTAD + PIPS group, especially in coronal third. Push‐out test results exhibited that there was a statistically significant interaction between the experimental groups and root canal third (p < .0005). Significant differences could be found among five groups (p < .05): G5 > G4 > G3 > G2 > G1. G5 had the highest bond strength. In conclusion, post space pretreatments with MTAD or PIPS technique can significantly remove smear layer and improve the bond strength of glass fiber post, and combination of them works best.     

Micro‐ and nanoscale structures of mesiodens dentin: Combined study of FTIR and SAXS/WAXS techniques

A mesiodens is the most common type of supernumerary tooth present in conjunction to normal dentition. A mesiodens may commonly occur in the central region of the upper or lower jaw. A mesiodens is different from normal teeth in terms of structure and shape. The aim of this study is to evaluate the micro‐ and nanoscale structural properties of mesiodens dentin by combined small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) and Fourier transform infrared (FTIR) spectroscopy. Five freshly extracted, noncarious mesiodens and five normal dentin disks prepared from human incisor teeth were compared. Using FTIR, the phosphate‐to‐amide I, carbonate‐to‐phosphate, and carbonate‐to‐amide I band area ratios and the crystallinity index were quantified. SAXS/WAXS were used to study the nanostructure of mesiodens. An increase in the mineral content in the mesiodens dentin with respect to the normal group was found. Crystallinity was also significantly increased and the protein content decreased in the mesiodens dentin compared with that of normal dentin. SAXS/WAXS results revealed that mesiodens dentin has a more calcified tissue. Further, SAXS analysis revealed a nonuniform distribution of dentin fibrils in mesiodens. Microsc. Res. Tech., 78:52–58, 2015. © 2014 Wiley Periodicals, Inc.     

The effect of different ratios of nano‐sized hydroxyapatite fillers on the micro‐tensile bond strength of an adhesive resin

The purpose of this study was to evaluate the micro‐tensile bond strength (μTBS) of dentin bonding agents containing different ratios of nano‐sized hydroxyapatite fillers (HA). X‐ray diffraction analysis was used for characterization, and scanning electron microscope (SEM) analysis was used to determine the HA particle size after that HA were mixed a bonding agents without filler. Dentin bonding agents were divided into four groups according to addition of different ratios of nano‐sized hydroxyapatite fillers as 2% HA, 5% HA, 7% HA, and no‐filler control group. The teeth (n = 32) were sectioned with a low‐speed diamond blade under water cooling to expose the mid‐coronal dentin. Following the bonding application, restorations were applied incrementally. Each tooth was cut on the x and y axis, and each specimen was fixed to a testing device and stressed until failure occurred. The debonded specimens were examined under 250× magnification without a coating layer at 2.00 kV using a SEM to determine failure patterns. μTBS data were analyzed using a anova and Tukey's post hoc test. The failure mode data were analyzed using the Chi‐Square test. The maximum mean value of μTBS was in the 7% HA group, while the minimum mean value of μTBS was observed in the control group. 7% HA group was statistically significant and higher than other groups while there were no significant differences between the control, 2% HA, and 5% HA groups. According to SEM analysis, fracture analysis revealed that the mixed fracture type was seen more often than the other fracture types. The particle size and amount of HA fillers added to the adhesive resin seem to affect the success of the bond strength to the dentin. Adding different ratio nano‐sized HA fillers to the adhesive resin contributed positively to the immediate μTBS values in the dentin.     

Chemical and morphological changes in human dentin after Er:YAGlaser irradiation: EDS and SEM analysis

Sixty samples of human dentin were divided into six groups (n = 10) and were irradiated with Er:YAG laser at 100 mJ–19.9 J/cm², 150 mJ–29.8 J/cm², 100 mJ–35.3 J/cm², 150 mJ–53.0 J/cm², 200 mJ–70.7 J/cm², and 250 mJ–88.5 J/cm², respectively, at 7 Hz under a water spray. The atomic percentages of carbon, oxygen, magnesium, calcium, and phosphorus and the Ca‐to‐P molar ratio on the dentin were determined by energy dispersive X‐ray spectroscopy. The morphological changes were observed using scanning electron microscopy. A paired t‐test was used in statistical analysis before and after irradiation, and a one‐way ANOVA was performed (P ≤ 0.05). The atomic percent of C tended to decrease in all of the groups after irradiation with statistically significant differences, O and Mg increased with significant differences in all of the groups, and the Ca‐to‐P molar ratio increased in groups IV, V, and VI, with statistically significant differences between groups II and VI. All the irradiated samples showed morphological changes. Major changes in the chemical composition of dentin were observed in trace elements. A significant increase in the Ca‐to‐P ratio was observed in the higher energy density groups. Morphological changes included loss of smear layer with exposed dentinal tubules. The changes produced by the different energy densities employed could have clinical implications, additional studies are required to clarify them. Microsc. Res. Tech. 78:1019–1025, 2015. © 2015 Wiley Periodicals, Inc.     

Presence of voids after warm vertical compaction and single‐cone obturation in band‐shaped isthmuses using micro‐computed tomography: A phantom study

The present micro‐computed tomography (micro‐CT) study compared the presence of voids in the band‐shaped isthmuses obturated by warm vertical compaction (WVC) and single‐cone (SC) techniques. Twenty mesial roots from mandibular first molar teeth showing a band‐shaped isthmus were selected and assigned into two groups based on their preoperative anatomical dimensions (n = 10), according to the filling technique: WVC or SC. Post‐filling micro‐CT scanning was performed. The percentage volume of root canal filling materials and voids were calculated and data were analyzed using the Mann–Whitney U test with a significance level of 5 and 95% confidence interval. Mean percentage volumes of filling materials and voids were 86.88 ± 8.53 and 13.11 ± 8.53 for the WVC group, 84.39 ± 8.30 and 15.60 ± 8.30 for the SC group, respectively, with no significant difference between them (p > .05). Neither WVC nor SC produced void‐free root canal fillings in the band‐shaped isthmuses and both techniques resulted in a similar quality of root canal filling.     

Microstructure and mineral composition of dental enamel of permanent and deciduous teeth

Purpose: This study evaluated and compared in vitro the microstructure and mineral composition of permanent and deciduous teeth's dental enamel. Methods: Sound third molars (n = 12) and second primary molars (n = 12) were selected and randomly assigned to the following groups, according to the analysis method performed (n = 4): Scanning electron microscopy (SEM), X‐Ray diffraction (XRD) and Energy dispersive X‐ray spectrometer (EDS). Qualitative and quantitative comparisons of the dental enamel were done. The microscopic findings were analyzed statistically by a nonparametric test (Kruskal‐Wallis). The measurements of the prisms number and thickness were done in SEM photomicrographs. The relative amounts of calcium (Ca) and phosphorus (P) were determined by EDS investigation. Chemical phases present in both types of teeth were observed by the XRD analysis. Results: The mean thickness measurements observed in the deciduous teeth enamel was 1.14 mm and in the permanent teeth enamel was 2.58 mm. The mean rod head diameter in deciduous teeth was statistically similar to that of permanent teeth enamel, and a slightly decrease from the outer enamel surface to the region next to the enamel‐dentine junction was assessed. The numerical density of enamel rods was higher in the deciduous teeth, mainly near EDJ, that showed statistically significant difference. The percentage of Ca and P was higher in the permanent teeth enamel. Conclusions: The primary enamel structure showed a lower level of Ca and P, thinner thickness and higher numerical density of rods. Microsc. Res. Tech., 2010. © 2009 Wiley‐Liss, Inc.     

Analysis of adhesive interface in root canals irradiated by Er,Cr:YSGG laser after luting a fiber post

This study evaluated the effect of Er,Cr:YSGG laser on the root canal dentin after luting a fiber post. Twenty‐four bovine teeth roots were prepared using NiTi instruments and filled with Sealer 26 and gutta‐percha. Post spaces were prepared and roots were distributed according to dentin treatment (n = 8): 2.5%NaOCl (group control), Er,Cr:YSGG laser (1.5 W, 20 Hz, 20 s) (group test 1) or 2.5%NaOCl + Er,Cr:YSGG laser (group test 2). Fiber posts were luted using adhesive cement (Rely X U200, 3M) and roots were prepared to confocal laser scanning microscopy (CLSM) and scanning electron microscope (SEM). The morphology of interface, thickness of cement, and the gaps and tags were analyzed. Non‐parametrical data for thickness of cement were submitted to Friedman and Kruskall–Wallis tests (α = 0.05) and parametrical data for gaps to ANOVA (α = 0.05). CLSM of the cement thickness and gaps revealed no significant difference in surface treatment (NaOCl, Er,Cr:YSGG laser and NaOCl + Er,Cr:YSGG laser) (p > .05) and canal thirds (cervical, middle, and apical) (p > 0.05). SEM showed tags and a residual layer of cement adhered to dentin, mainly in laser‐irradiated specimens. The pretreatment of root canal with Er,Cr:YSGG laser previously to luting the fiber post with a self‐adhesive cement did not influence the cement thickness and gaps but affected the dentin interaction.     

Effect of laser preparation on adhesion of a self‐adhesive flowable composite resin to primary teeth

The aim of the study was to evaluate the adhesion of a self‐adhering flowable composite resin to primary tooth enamel and dentin after silicon carbide paper (SiC) and laser pretreatment. Adhesive properties were evaluated as shear bond strength (SBS) and scanning electron microscopic (SEM) characteristics. A total 120 primary canine teeth were randomly divided into two groups to study enamel and dentin. Each group was divided into 6 subgroups (n = 10) according to type of surface preparation (SiC or Er:YAG laser) of enamel or dentin. Three methods were used to build cylinders of restoration on tooth surface: OptiBond All‐In‐One + Premise Flowable composite, OptiBond All‐In‐One + Vertise Flow and Vertise flow. After restoration, samples were tested for SBS and failure mode. Twenty eight samples were examined by SEM. The results of the study showed SBS of Vertise Flow was lower than others in enamel and dentin samples pretreated with SiC and in dentin samples pretreated with laser (P < 0.001). Compared to SiC pretreatment, laser pretreatment led to a significantly higher SBS with Vertise Flow on enamel (P < 0.001). Vertise Flow associated with the adhesive led to a higher SBS in enamel and dentin compared to Vertise Flow alone. Adhesive and mixed failure modes were observed more frequently in Vertise Flow groups. SEM images showed that Vertise Flow led to more irregularities on enamel and more open dentinal tubules after laser ablation compared SiC pretreatment. Microsc. Res. Tech. 79:334–341, 2016. © 2016 Wiley Periodicals, Inc.     

Morphological and chemical changes in human deciduous dentin after phosphoric acid,self‐etching adhesive and Er: YAG laser conditioning

The morphological and chemical changes in deciduous dentin produced by different conditioning protocols were evaluated in this in vitro study. Eighty primary dentin samples were divided into eight groups (n = 10): G1, acid etching; G2, self‐etching adhesive; G3, G4, Er: YAG laser irradiation at 25.5 and 38.2 J cm^?2, respectively; 10 Hz and spray irrigation. Groups 5, 6, 7, and 8 were irradiated at previous densities, and then phosphoric acid or self‐etching adhesive conditioning was applied. Scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDS) were used to evaluate chemical and morphological changes. Paired t‐test and One‐way ANOVA were used for statistical analysis (p ≤ 0.05). All samples showed different morphology with specific characteristics according to the conditioning protocol. Changing element concentration values are expressed in atomic percent (at %). After conditioning, there were statistically significant differences (p ≤ 0.05) for p at% and Ca/P in all groups; highlighting the following additional findings by group: G1, G7, and G8 showed changes in all elements studied, G2 presented a decrease in C at% and increased Ca at%, G3 and G4 exhibited at% changes in C, trace elements and Ca. Furthermore, G5 showed at% changes in O and trace elements; while G6 changes were observed on C at%, O at% and trace elements at%. Dentin morphology and chemical composition varied in accordance with the conditioning protocol, with characteristics specific for each one that could have clinical implications for the retention and bond strength performance of adhesive materials.     

Effect of EDTA,sodium, and calcium hypochlorite on the inorganic component of root canal dentin: A SEM analysis

This study evaluated the influence of canal irrigation protocols with 5.25% calcium hypochlorite [Ca(OCl)₂], 5.25% sodium hypochlorite (NaOCl) and 17% EDTA solution on the inorganic component of root canal dentin. Sixty roots were randomly divided into six groups (n = 10): Saline solution (SS) (control); Saline solution (SSE) +17% EDTA; CH ? 5.25% Ca(OCl)₂; CHE ? 5.25% Ca(OCl)₂ + 17% EDTA; SH ? 5.25% NaOCl; SHE ? 5.25% NaOCl +17% EDTA. After canal irrigation, the specimens were longitudinally split and analyzed by scanning electron microscopy (SEM). Dentinal tubules were observed in transverse (middle and apical thirds) direction. The images were classified in scores, according to smear layer removal and peritubular dentin alteration, and data were analyzed by Kruskal–Wallis's test, followed by Dunn's test (α = 0.05). In the middle third, all groups with EDTA presented better removal of the smear layer with higher peritubular dentin alteration (p < .05). In the apical third, this happened only in SHE (p < .05). Ca(OCl)₂ and NaOCl exhibit similar performance to remove smear layer and alteration of the inorganic component in the middle third. In the apical third, NaOCl associated with EDTA showed better performance in smear layer removal.     

Effect of different irrigation protocols on the radicular dentin interface and bond strength with a metacrylate‐based endodontic sealer

This study assessed the influence of different endodontic chemical substances on the adhesion of the Epiphany SE/Resilon system (with and without resinous solvent) to radicular dentin walls, using the push‐out test and scanning electron microscopy (SEM). Forty‐eight root canals of human canines were prepared biomechanically with ProTaper rotary files (crown‐down technique) and the radicular dentin was treated with either 17% EDTA, 2% chlorhexidine gel (CHX) or 2.5% NaOCl (control). The root canals were filled with Resilon cones and Epiphany SE sealer with and without resinous solvent. Six groups of eight canals each had their roots sectioned transversally to obtain 1‐mm thick slices. Data were subjected to statistical analysis by ANOVA and Tukey's tests. The specimens treated with 17% EDTA (1.59 ± 0.91) presented higher bond strength (P < 0.05) than those treated with 2.5% NaOCl (0.93 ± 0.27) and 2% CHX (0.92 ± 0.22). Significantly higher bond strength (P < 0.05) was observed when the Epiphany SE was prepared with (1.37 ± 0.78) than without (0.92 ± 0.33) solvent. Adhesive failures were predominant in all groups. SEM analysis showed greater homogeneity of the filling mass when the solvent was added to the sealer. Treatment of root canal walls with 17% EDTA, and addition of a resinous solvent to Epiphany SE produced the highest adhesion to radicular dentin. Microsc. Res. Tech. 77:446–452, 2014. © 2014 Wiley Periodicals, Inc.     

Effect of dentin and fiber post surface treatments with fumaric acid on the bonding ability of fiber posts

This study investigated the effects of fumaric acid on push‐out bond strength when applied to dentin surfaces and fiber posts. The root canals of 60 mandibular premolar teeth were instrumented and obturated. After removing two thirds of filling material, teeth were prepared according to six randomized groups (n = 10/group) defined by two fiber post surface treatments (0.7% fumaric acid or 9% hydrofluoric acid) and three dentin conditioning treatments [control (no conditioning); 17% ethylenediamine tetraacetic acid (EDTA); or 0.7% fumaric acid]. After fiber post‐cementation, three 1‐mm thick discs were obtained from each tooth by transverse sectioning, and each disc underwent push‐out bond strength testing. Data were analyzed with a one‐way analyses of variance (anova ) and t tests; p < .05 was considered statistically significant. Failure modes were determined by stereomicroscopy, and the surface characteristics of dentin and fiber posts were observed by scanning electron microscopy. Push‐out bond strength was greater for the group in which the post surface treated with hydrofluoric acid and the dentin surface treated with fumaric acid than the nontreated dentin and hydrofluoric acid‐treated post group (p < .05). There were no significant differences between other comparison pairs (p > .05). A combination of fumaric acid dentin conditioning and hydrofluoric acid fiber post treatment strengthened the bonding ability of fiber posts.     

A cone‐beam computed tomography study of the anatomical relationships between mandibular teeth and the mandibular canal,with a review of the current literature

The purpose of this study was to evaluate age‐ and sex‐related changes in the anatomical relationships between the roots of the molars and premolars and the mandibular canal using cone‐beam computed tomography (CBCT) images. A total of 243 patients (116 males, 127 females) aged 16–83 years for whom previous CBCT scans were available were enrolled in this study. The patients were subcategorized by sex and age (Group I, <21 years; Group II, 21–40 years; and Group III, >40 years). The distances between the mandibular canal and the molars and premolars were measured. The mandibular canal was significantly closer to the root apices of the second and third molars than to the apices of other evaluated teeth (p < 0.05). All measurements were significantly higher in male than in female subjects (p < 0.05). Group I subjects exhibited significantly shorter distances between the mandibular canal and root apices of the first and second premolars, and the molars, than those of Group II and III subjects (p < 0.05). Direct contact relationships were found in 1.6%, 3.3%, 3.3%, 16%, and 32.2% of teeth (running from the first premolar to the third molar, respectively). Age and sex influenced the anatomical relationships between mandibular teeth and the mandibular canal, and these should be considered when planning endodontic and surgical procedures to avoid potential nerve injury.     

Effect of dentin pretreatment with potassium oxalate: A 6‐year follow‐up

Oxalate‐based products are effective against dentine sensitivity and have been studied as an option to improve long‐term adhesive bonding strength. Our aim was to evaluate the effect of potassium oxalate on the microtensile bond strength (µTBS) of the dentin/resin interface after 24 h, 1, and 6 years. Dentin on the occlusal surface of 16 human premolars was exposed and etched with 35% phosphoric acid. The teeth were divided into four groups. Two groups received 3% monohydrated potassium oxalate and the following adhesive systems and composites: Adper Scotchbond Multipurpose + FiltekZ350 (3M/ESPE) and Prime & Bond NT + Esthet‐X (Dentsply). Two control groups did not receive potassium oxalate. Teeth were cut into sticks and kept in distilled water at 37°C for 24 h, 1, and 6 years. The sticks underwent µTBS testing after storage. ANOVA, Tukey's post hoc test, and paired t test were used to compare storage times (α = 0.05). The fracture mode of the specimens was classified under a stereomicroscope (40×). Morphology of the hybrid layer and the fracture pattern were observed with scanning electronic microscopy (SEM). Mean µTBS was high at 24 h and decreased after 1 and 6 years. After 6 years, the mean µTBS values were similar with no statistically significant difference between the groups (p = .121). SEM images showed proper dentin hybridization. Dentin pretreatment with potassium oxalate did not affect hybrid layer formation, but bond strength decreased over time after 24 h. Therefore, the clinical use of potassium oxalate to increase dentin bond durability is not indicated.