Mechanical properties of simulated dentin caries treated with metal cations and L-ascorbic acid 2-phosphate.

This pH cycling study aimed to investigate the effects of L-Ascorbic acid 2-phosphate (AA2P) salts of Mg, Zn, Mn, Sr, and Ba on the surface microhardness, compressive strength, diametral tensile strength (DTS), and solubility of root canal dentin. 186 cylindrical dentin specimens from 93 teeth were fortified with optimal concentrations of AA2P salts of Mg (0.18 mM), Zn (5.3 µM), Mn (2.2 × 10-8 M), Sr (1.8 µM), and Ba (1.9 µM). Saline was used as the control group. These dentin specimens underwent a 3-day cycling process simulating dentin caries formation through repeated sequences of demineralization and remineralization. Surface microhardness at 100 and 500 µm depths (n = 10/subgroup), scanning electron microscopy (n = 3/group), compressive strength (n = 10/group), DTS (n = 6/group), and solubility (n = 5/group) tests were performed to analyze the dentin specimens. Data were analyzed using Kolmogorov-Smirnov, one-way ANOVA, and Post Hoc Tukey tests (p < 0.05). The control group had significantly lower microhardness at both depths (p < 0.001), reduced DTS (p = 0.001), decreased compressive strength (p < 0.001), and higher weight loss (p < 0.001) than all other groups. The Sr group had the highest compressive strength and microhardness among all the groups. The microhardness was significantly higher for the 500 µm depth than the 100 µm depth (p < 0.001), but the difference in microhardness between depths across groups was not significant (p = 0.211). All fortifying solutions provided some protection against artificial caries lesions. Therefore, these elements might have penetrated and reinforced the demineralized dentin against acid dissolution.

Maxillary interim obturator prosthesis fabrication for a patient with limited mouth opening with a digital approach: A clinical report.

Squamous cell carcinoma is a common malignant condition affecting the oral cavity and may involve the surrounding maxillofacial regions. Treatment commonly involves resection of the tumor, followed by prosthetic rehabilitation of the resection defect. This clinical report presents a 62-year-old Asian male patient who had previously undergone surgical resection, resulting in a post-surgical Aramany Class II maxillary defect. The patient's medical history included severe trismus, characterized by restricted mouth opening, as well as a diagnosis of maxillary sinus verrucous squamous cell carcinoma. This report provides a comprehensive account of the rapid fabrication of an interim obturator using digitally assisted dentistry techniques.

Neural network approach to evaluate the physical properties of dentin.

This study intended to evaluate the effects of inorganic trace elements such as magnesium (Mg), strontium (Sr), and zinc (Zn) on root canal dentin using an Artificial Neural Network (ANN). The authors obtained three hundred extracted human premolars from type II diabetic individuals and divided them into three groups according to the solutions used (Mg, Sr, or Zn). The authors subdivided the specimens for each experimental group into five subgroups according to the duration for which the authors soaked the teeth in the solution: 0 (control group), 1, 2, 5, and 10 min (n = 20). The authors then tested the specimens for root fracture resistance (RFR), surface microhardness (SµH), and tubular density (TD). The authors used the data obtained from half of the specimens in each subgroup (10 specimens) for the training of ANN. The authors then used the trained ANN to evaluate the remaining data. The authors analyzed the data by Kolmogorov-Smirnov, one-way ANOVA, post hoc Tukey, and linear regression analysis (P < 0.05). Treatment with Mg, Sr, and Zn significantly increased the values of RFR and SµH (P < 0.05), and decreased the values of TD in dentin specimens (P < 0.05). The authors did not notice any significant differences between evaluations by manual or ANN methods (P > 0.05). The authors concluded that Mg, Sr, and Zn may improve the RFR and SµH, and decrease the TD of root canal dentin in diabetic individuals. ANN may be used as a reliable method to evaluate the physical properties of dentin.

The effect of diabetes mellitus on the shear bond strength of composite resin to dentin and enamel.

Diabetes mellitus might be linked to the deterioration of certain physical properties of dentin and enamel. This study aimed to determine the effect of two types of diabetes on the shear bond strength of enamel and dentin, by using the single bond universal bonding system. Sixty specimens [from 15 teeth; 5 from each group-non-diabetic (ND), Diabetic type I (D1), and Diabetic type II (D2)], were prepared with equal amounts of dentin (n = 5) and enamel (n = 5). Enamel specimens (E20) were etched with 37% phosphoric acid, for 20 s, and dentin specimens (D15) were etched for 15 s. A standard shear bond strength test was performed on all specimens. Their failure modes were also studied under a scanning electron microscope, and the data were analyzed by using ANOVA and Post Hoc Tukey's test (a = 0.050). For the enamel groups, significant differences were only noticed between the ND and D1 (P < 0.050) groups, and between the ND and D2 (P < 0.050) groups. In the dentin groups, there was a significant difference only between the ND and D1 (P < 0.050) groups. The micrographs showed that the ND group had the highest number of specimens with cohesive failure and D1 had the highest number of specimens with adhesive failure. It can be concluded that both types of diabetes reduce the shear bond strength of composite resin on dentin and enamel. However, it seems that the negative effect of diabetes on shear bond strength of dental composite resin is more drastic in individuals with type I diabetes as compared with type II.

The effect of diabetes on the tensile bond strength of a restorative dental composite to dentin.

This study was performed to evaluate the effect of diabetes mellitus (DM) on the tensile bond strength (TBS) of dental composite resin bonding to enamel and dentin of extracted human teeth. Thirty caries-free human premolar teeth (10 from type 1 DM (D1), 10 from type 2 DM (D2), and 10 from non-diabetic individuals (control)) were wet ground and polished to obtain flat surfaces of dentin (n = 10). 37% phosphoric acid was used to etch dentin specimens for 15 s. After the application of the adhesive system, the composite resins were applied and cured for 20 s. Then, specimens were subjected to TBS testing by Universal Testing Machine (1 mm/min). One specimen from each group was prepared and observed under a scanning electron microscope (SEM) and a dot map was generated. Data were analyzed by ANOVA and post hoc Tukey tests (α = 0.05). The TBS values were significantly higher in the control group compared to the D1 and D2 groups (P < 0.05). Between DM groups, D2 values were significantly higher than those in the D1 group. Unlike DM groups, the zigzag fracture pattern was only noticed in the control group. DM adversely affected the TBS of dental composite resins to dentin; this negative effect is more exaggerated by type 1 DM than type 2 DM.

Tissue reaction to novel customized calcium silicate cement based dental implants. A pilot study in the dog.

OBJECTIVES: The purpose of this study was to determine the level of periodontal tissue regeneration in a canine model following post-extraction placement of an implant molded from a composite material made from extracted tooth dentin and a calcium silicate cement (CSC) material. The investigation used autologous dentin in conjunction with a CSC material to form a composite implant designed for immediate tooth replacement. METHODS: Two (2) beagles had a periodontal and radiographic examination performed to rule out any pre-treatment inflammation, significant periodontal disease, or mobility. Then, ination eleven (11) teeth were extracted and polyvinyl siloxane molds were made to fabricate three different types of implants: Particulate Implant (Test Group 1, n = 4), Shell Implant Alone (Test Group 2, n = 2), Shell Implant with Emdogain® (Test Group 3, n = 3). Teeth in the control group were extracted, scaled (n = 2), and then re-implanted into their respective fresh extraction sockets. At 4 weeks, a clinical, radiographic, and histologic assessment was performed. RESULTS: Clinical evaluation revealed no mobility in any of the test or control implants and no radiographic evidence of significant bone loss or active disease. Based on the MicroCT analysis, direct bone to implant contact was observed in some areas with an apparent periodontal ligament space. Implant-related inflammation, on average, was similar among all groups, with low numbers of infiltrates. Implant-related inflammatory reaction was generally minimal and not interpreted to be adverse. CONCLUSION: The proposed novel composite materials revealed that not only do these materials demonstrate high biocompatibility, but also their successful integration in the alveolus is likely secondary to a partial ligamentous attachment. The current investigation may lead to the use of calcium silicate-based materials as custom dental implants. Further research on this novel composite's biomechanical properties is necessary to develop the optimal material composition for use as a load-bearing dental implant.

Modification of denture teeth for improved occlusal stability of a maxillary removable complete denture opposed by a mandibular implant-supported fixed complete denture: A clinical report.

Wear of artificial teeth is the most common complication associated with an implant-supported fixed complete denture (ISFCD). This wear alters the occlusal scheme, with loss of eccentric occlusal balance and vertical dimension of occlusion (VDO). This clinical report describes the fabrication of a new maxillary removable complete denture opposing an existing ISFCD with occlusal modifications. Both prostheses received splinted zirconia crowns cemented with composite resin cement.

Evaluation of the accuracy of 2 digital intraoral scanners: A 3D analysis study.

STATEMENT OF PROBLEM: Evidence for the accuracy of a recently introduced intraoral scanner is lacking. PURPOSE: The purpose of this in vitro study was to evaluate and compare the trueness (validity) and precision (reliability) of 2 intraoral scanners by scanning a quadrant and a sextant. MATERIAL AND METHODS: A maxillary typodont with plastic teeth made from a shade A3 polymethyl methacrylate was scanned (n=10) with each intraoral scanner (Planmeca Emerald and 3Shape TRIOS 3) to obtain sextant and quadrant scans. Control scans were made with an industrial optical scanner. The scans were analyzed with a 3D reverse engineering software program and an independent samples t test and general linear model 2-way analysis of variance (α=.05). RESULTS: The 3Shape TRIOS 3 scanner showed no significant difference between the sextant and quadrant scans in trueness (P=.118) or in precision (P<.285). The Emerald scanner had statistically significant higher trueness for the sextant scan (P=.007). The 3Shape TRIOS 3 scanner had better performance in trueness and precision when compared with the Emerald scanner. CONCLUSIONS: The 3Shape TRIOS 3 scanner was found to be more accurate than the Emerald scanner in terms of trueness and precision, regardless of the scanning field. The Emerald scanner's trueness decreased as the scanning field increased from a sextant to a quadrant.

Effect of thermocycling on the surface texture and release of titanium particles from titanium alloy (Ti6Al4V) plates and dental implants: An in vitro study.

STATEMENT OF PROBLEM: The release of titanium (Ti) particles from the surface of endosseous dental implants is not well understood. PURPOSE: The purpose of this in vitro study was to evaluate the effect of thermocycling on the surface texture and release of Ti particles from the surface of dental implants. MATERIAL AND METHODS: Three MSI dental implants and 3 Ti alloy (Ti6Al4V) plates were divided into 6 subgroups (n=3). Specimens in each group were subjected to 0 (control group), 100, 200, 500, 1000, and 2000 thermocycles. After each cycling process, artificial saliva was collected, and the concentrations of released Ti particles were quantified by inductively coupled plasma-mass spectrophotometry (ICP-MS). The surfaces of the dental implants and Ti plates were evaluated before and after thermocycling by scanning electron microscopy (SEM), and SEM images were analyzed by using the ImageJ software program. Data were analyzed by mixed-model ANOVA and post hoc Tukey tests (α=.05). RESULTS: The greatest Ti release was seen after 2000 thermocycles. After increasing the number of cycles, additional Ti particles were released. SEM images of the surfaces of the dental implants and Ti plates displayed significant changes in surface texture. CONCLUSIONS: Thermocycling continuously removed the protective TiO2 layer on the surface of dental implants, resulting in the release of Ti particles. The surface treatment and texture did not affect the release of Ti particles.

Effect of length of LOCATOR abutment and cement type on retention to intraradicular dentin in overdentures.

STATEMENT OF PROBLEM: Limited information is available on the effect of LOCATOR abutment length and luting cement type on retention to intraradicular dentin in overdentures. PURPOSE: The purpose of this in vitro study was to evaluate the effect of the length of a commercially available LOCATOR abutment and cement type on retention in the root canal. MATERIAL AND METHODS: Eighty LOCATOR abutments with a standard length of 6 mm were obtained. Half of them were shortened to 3 mm. Eighty recently extracted single-rooted teeth were divided into 2 groups. The post space was prepared to 6 mm in the first group and 3 mm in the second. After preparation, the LOCATOR abutments were luted with one of the following cements: dual-polymerized glass-reinforced resin cement (Parapost Paracore), dual-polymerized resin cement (Variolink II), self-adhesive resin cement (RelyX Unicem), and conventional cement (zinc phosphate). The tensile force required for the removal of the LOCATOR abutments from their corresponding roots was recorded. Data were statistically analyzed with 2-way ANOVA and the Tukey multiple comparison test. RESULTS: Both the cement type (P<.001) and the length of the LOCATOR abutment (P<.001) significantly affected the mean tensile forces. Dual-polymerized glass-reinforced resin cement (Parapost Paracore) presented significantly higher mean tensile forces for the LOCATOR abutment retention among all cements (P<.05). CONCLUSIONS: Regardless of the length, LOCATOR abutments luted with Parapost Paracore resin cement presented higher mean resistance to tensile forces compared with those luted with the other cements. LOCATOR abutments of 6 mm in length were more resistant to tensile forces than those of 3 mm in length in combination with all cements.

Retentive strength and marginal discrepancies of a ceramic-reinforced calcium phosphate luting agent: An in vitro pilot study.

STATEMENT OF PROBLEM: Information on the properties of a relatively new luting agent with a unique formulation (ceramic-reinforced calcium phosphate) is limited. PURPOSE: The purpose of this in vitro study was to compare the retentive strengths and marginal discrepancies of a ceramic-reinforced calcium phosphate luting agent (CM) with a self-adhesive resin luting agent (RX) and to determine and compare the mode of failure of dislodged cemented copings. MATERIAL AND METHODS: Forty extracted human molar teeth were prepared to receive zirconia copings. After cementation, the specimens were divided into 4 subgroups (n=10): CM A (axial loading), CM OA (off-axis loading), RX A (axial loading), and RX OA (off-axis loading). For each subgroup, 9 of the specimens received experimental treatment (thermocycling and dynamic loading), and the tenth received no experimental treatment. Eight copings were pulled off in a universal testing machine (MTS Insight; MTS). The ninth specimen was treated experimentally but was not pull tested. The marginal discrepancy and the dentin interface of the specimens that were not pull tested were analyzed with scanning electron microscopy and energy dispersion spectroscopy. The mode of failure of the dislodged copings was also subjectively evaluated. RESULTS: The mean retentive strengths were 5.92 MPa for CM A, 5.81 MPa for CM OA, 5.75 MPa for RX A, and 5.69 MPa for RX OA. The marginal discrepancy recorded for both CM and RX ranged from 30 to 45 µm, (mean, 36 ±4.6 µm). Energy dispersion spectroscopy analysis showed the presence of calcium, phosphorus, silicon, and aluminum for the CM marginal discrepancy and the presence of aluminum in the dentinal tubules adjacent to the CM. Calcium and phosphorus were detected in lesser amounts adjacent to the RX marginal discrepancy. The mode of failure for CM was primarily adhesive to the tooth preparation, and, for RX, the failure mode was predominantly adhesive to the coping. CONCLUSIONS: CM had statistically significantly higher mean retentive strength compared with RX. Subgroups loaded axially had statistically significantly higher retentive strengths compared with those loaded off axis.

Pull-out retentive strength of fiber posts cemented at different times in canals obturated with a eugenol-based sealer.

STATEMENT OF PROBLEM: Currently, no standard luting protocol exists for fiber posts. In addition, no agreement has been reached on the time interval between canal obturation and post space preparation and cementation. PURPOSE: The purpose of this in vitro study was to evaluate the retention of fiber posts cemented with 3 different types of cement: Paracore, Variolink II, and RelyX Unicem cement after 24 hours or 2 weeks in root canals obturated with gutta percha and a eugenol-based sealer. MATERIAL AND METHODS: Seventy-two caries-free, freshly extracted, single-rooted human mandibular first premolar teeth with straight root canals were prepared and obturated with gutta percha and Endofil sealer. Specimens were divided into 2 groups (n=36): post spaces prepared 24 hours after obturation and post spaces prepared 2 weeks after obturation. Posts in both groups were luted with 1 of 3 different luting agents (n=12), ParaCore, Variolink II, or RelyX Unicem cement. Each tooth specimen was vertically secured in a universal testing machine, and a constant pull-out loading rate of 0.5 mm/min was applied until cement failure occurred. Data were statistically analyzed with 2-way and 1-way ANOVAs and t tests. RESULTS: Two-way ANOVA indicated statistically significant differences in mean post retention among the 3 cement types (P<.001) and among the means of the different time intervals investigated (P<.001). Significant differences were noted among all cement types tested between the 24-hour and 2-week time intervals (P<.05). CONCLUSIONS: Time elapsed between canal obturation and post cementation significantly influenced fiber post retention, regardless of the type of resin cement. Fiber posts showed significantly higher retention if cemented after 24 hours of obturation than if cementation occurred after 2 weeks.

In vitro shear bond strength of Y-TZP ceramics to different core materials with the use of three primer/resin cement systems.

STATEMENT OF PROBLEM: Durability of the bond between different core materials and zirconia retainers is an important predictor of the success of a dental prosthesis. Nevertheless, because of its polycrystalline structure, zirconia cannot be etched and bonded to a conventional resin cement. PURPOSE: The purpose of this in vitro study was to compare the effects of 3 metal primer/resin cement systems on the shear bond strength (SBS) of 3 core materials bonded to yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic retainers. MATERIAL AND METHODS: Zirconia ceramic (Cercon) disks (5×3 mm) were airborne-particle abraded, rinsed, and air-dried. Disk-shaped core specimens (7×7 mm) that were prepared of composite resin, Ni-Cr, and zirconia were bonded to the zirconia ceramic disks by using one of 3 metal primer/cement systems: (Z-Prime Plus/BisCem, Zirconia Primer/Multilink Automix, or Clearfil Ceramic Primer/Clearfil SA). SBS was tested in a universal testing machine. Stereomicroscopy was used to evaluate the failure mode of debonded specimens. Data were analyzed using 2-way ANOVA and post hoc analysis using the Scheffe procedure (α=.05). RESULTS: Clearfil SA/Clearfil Ceramic Primer system with an Ni-Cr core yielded the highest SBS value (19.03 MPa), whereas the lowest SBS value was obtained when Multilink Automix/Zirconia Primer system was used with the zirconia core group (4.09 MPa). Differences in mean SBS values among the cement/primer groups were statistically significant, except for Clearfil SA and BisCem with both composite resin and zirconia cores. Differences in mean SBS values among the core subgroups were not statistically significant, except for zirconia core with BisCem, Multilink, and Clearfil SA. The predominant failure mode was adhesive, except for Clearfil SA and BisCem luting agents with composite resin cores, which displayed cohesive failure, and Multilink Automix with a composite resin, core as well as Clearfil SA with Ni-Cr cores, where the debonded specimens of each group displayed a mixed (adhesive/cohesive) failure pattern. CONCLUSIONS: Use of the Clearfil SA/Clearfil Ceramic Primer system, based on methacryloyloxydecyl dihydrogen phosphate (MDP), increased the bond strength of Y-TZP ceramics to core materials.

Mechanical behavior and color change of facial prosthetic elastomers after outdoor weathering in a hot and humid climate.

STATEMENT OF PROBLEM: A common reason for replacing a maxillofacial prosthesis is the deterioration of its properties. PURPOSE: The purpose of this study was to compare the effect of weathering in a hot and humid climate on the tear strength, tensile strength, modulus of elasticity, elongation percentage, and color of 3 maxillofacial materials. MATERIAL AND METHODS: Three silicone materials were tested. Specimens were exposed to outdoor weathering for 6 months in a hot and humid environment. Tear and tensile strengths were measured with a universal testing machine before and after outdoor weathering. Color change was evaluated by recording L*, a*, and b* values at base line and after outdoor weathering with a spectrophotometer. The ΔE, ΔL*, Δa*, and Δb* of the specimens were calculated. Data were analyzed with 2-way ANOVA and the post hoc Scheffé test (α=.05). RESULTS: For all tested elastomers, outdoor weathering decreased the tear strength and modulus of elasticity values significantly (P<.001). Also, weathering reduced percentage elongation values significantly (P<.05). Tensile strength values were significantly reduced for TechSil S25 and MED-4210 specimens only (P<.05). The effect of weathering on the color of pigmented specimens was greater than the acceptable value (ΔE>3.0). The color change (ΔE) of pigmented specimens ranged from 4.31 to 6.68. A-2186 silicone elastomer experienced the greatest color changes (P<.05). Within nonpigmented specimens, none of the tested silicone elastomers showed significant color changes (P>.05). CONCLUSIONS: Outdoor weathering in a hot and humid climate adversely affected the properties of silicone elastomers. The heat-polymerized TechSil S25 elastomer showed better mechanical durability and color stability compared with the room-temperature polymerized A-2186 and MED-4210 materials. TechSil S25 showed the greater values of tear and tensile strengths and elongation of specimens exposed to outdoor weathering conditions. It also showed the least amount of color change among the pigmented specimens exposed to outdoor weathering.

Effect of surface treatment and type of cement on push-out bond strength of zirconium oxide posts.

STATEMENT OF PROBLEM: The effect of the surface treatment of zirconium oxide posts on their push-out bond strength is controversial. PURPOSE: The purpose of this study was to compare the effects of 2 surface treatments on the bond strength of zirconium oxide posts cemented with different cements and to assess the failure mode. MATERIAL AND METHODS: Seventy extracted human teeth were divided into 7 groups (n=10). Custom zirconium oxide posts (Cercon; Degudent) were fabricated for 6 groups. Posts in 3 groups were airborne-particle abraded (A). Posts in the other 3 groups were tribochemical silica coated (T). Three cements were used. Zinc phosphate cement was used to cement the zirconium oxide posts in groups AZ and TZ, RelyX ARC cement was used in groups ARA and TRA, and RelyX Unicem cement was used in groups ARU and TRU. Group C contained custom metal posts cemented with zinc phosphate cement. Specimens were horizontally sectioned into 3 sections and subjected to a push-out test. A mixed model analysis of variance, 1-way ANOVA, and the Tukey multiple comparison tests were used for statistical analysis. RESULTS: The highest push-out bond strength was recorded for Group ARU (21.03 MPa), and the lowest was recorded for Group ARA (7.57 MPa). No significant difference in push-out bond strength was found among the different surface treatments and root regions (P>.05). The type of cement had a significant effect on the push-out bond strength of zirconium oxide posts (P=.049). RelyX Unicem cement recorded (19.57 ±8.83 MPa) significantly higher push-out bond strength compared with zinc phosphate (9.95 ±6.31 MPa) and RelyX ARC cements (9.39 ±5.45 MPa). Adhesive failure at the post-cement interface was recorded for 75% of the posts cemented with zinc phosphate and RelyX ARC cements, while mixed failure was recorded for 75% of the posts cemented with RelyX Unicem cement. CONCLUSIONS: The type of cement used resulted in a statistically significant difference in the push-out bond strength of zirconium oxide posts, while both the surface treatment and root region resulted in no statistically significant effect after artificial aging. RelyX Unicem cement had significantly higher push-out bond strength than did zinc phosphate and RelyX ARC cements.

Fracture resistance and failure mode of fatigued endodontically treated teeth restored with fiber-reinforced resin posts and metallic posts in vitro.

BACKGROUND: Fracture of restored endodontically treated teeth is a common complication. The mechanical properties of post systems may play a role in the incidence of tooth fracture. AIM: The purpose of this study was to evaluate in vitro the fracture resistance and pattern of fracture of endodontically treated teeth restored with three different post systems. MATERIAL AND METHODS: Posts used were fiber-reinforced composite resin posts (FRC post), custom cast silver-palladium, and nickel-chromium posts and cores. A 3-point bending test was performed to calculate flexural strengths and elastic moduli of the specimens. Sixty extracted human maxillary canines were endodontically treated and divided into three groups (n = 20). All-ceramic crowns were fabricated and cemented with Variolink II resin cement. Ten specimens of each group were subjected to a constantly increasing load until fracture. The other 10 specimens were fatigued for 106 cycles in a custom-made fatigue machine. Recorded failure loads and modes were statistically compared with one-way anova and Tukey-HSD tests (α = 0.05). RESULTS: The resistance to fracture of teeth restored with FRC posts, composite resin cores, and Empress II crowns was similar to that of teeth restored with cast posts and cores (P = 0.162). Supracrestal (above root/level of acrylic resin base) oblique fracture was the predominant mode of fracture associated with teeth restored with FRC posts (70%), while vertical root fractures were more common with teeth restored with cast posts and cores. CONCLUSIONS: Teeth restored with the FRC post system did not exhibit vertical root fractures and were less likely to show root fracture. Sixty to 80% of teeth restored with both types of cast posts and cores showed vertical and subcrestal root fractures.

Evaluating the Solubility of Endodontic Sealers in Response to Static and Dynamic Stress: An In Vitro Study.

OBJECTIVE: This study investigated the effect of static and dynamic conditions on the solubility of three en-dodontic sealers: AH Plus (an epoxy-resin-based sealer), Bio-C Sealer (a bioceramic sealer), and EndoSequence BC (a bioceramic sealer). METHODS: Plastic moulds were used to create 150 specimens, which were divided into three groups, with each group being filled with one of the three sealers. After the setting time, the specimens were removed from the moulds, dried, and weighed. Thirty specimens from each group were subdivided into three subgroups and stored in distilled water for 30, 60, or 90 days, while the remaining 20 specimens in each group were subdivid-ed into four subgroups and subjected to 0, 20, 50, or 100 thermocycling cycles. After storage time and thermo-cycling, the specimens were reweighed, and the weight loss and solubility percentage were calculated. The data were analysed using one-way ANOVA, Post Hoc Tukey, and Pearson correlation tests (p<0.05). RESULTS: The results showed that AH Plus had the lowest solubility, followed by EndoSequence BC and then Bio-C Sealer (p<0.0001). Both static and dynamic conditions had a negative effect on the solubility of all tested sealers, with the effect being more pronounced in bioceramic sealers. The increase in storage days and the number of thermocycling cycles were significantly correlated with the increasing solubility levels of all tested sealers (p<0.0001). CONCLUSION: The increased solubility of endodontic sealers may have a negative impact on long-term treat-ment outcomes. Both static and dynamic conditions can affect the solubility of endodontic sealers.

Effects of Diabetes on Elemental Levels and Nanostructure of Root Canal Dentin.

INTRODUCTION: This study evaluated the effects of diabetes mellitus (DM) on the nanostructure of root canal dentin using high-resolution transmission electron microscopy (HRTEM) and inductively coupled plasma mass spectrometry (ICP-MS). METHODS: Twenty extracted human premolars from diabetic and nondiabetic patients (n = 10 in each group) were decoronated and sectioned horizontally into 40 2-mm-thick dentin discs, with each disc designated for a specific test. ICP-MS was used to determine the different elemental levels of copper, lithium, zinc, selenium, strontium, manganese, and magnesium in diabetic and nondiabetic specimens. HRTEM was used to analyze the shape and quantity of the apatite crystals in diabetic and nondiabetic dentin at the nanostructural level. Statistical analysis was performed using Kolmogorov-Smirnov and Student t test (P < .05). RESULTS: ICP-MS revealed significant differences in trace element concentrations between the diabetic and nondiabetic specimens (P < .05), with lower levels of magnesium, zinc, strontium, lithium, manganese, and selenium (P < .05), and higher levels of copper in diabetic specimens (P < .05). HRTEM revealed that diabetic dentin exhibited a less compact structure with smaller crystallites and significantly more crystals in the 2500 nm2 area (P < .05). CONCLUSION: Diabetic dentin exhibited smaller crystallites and altered elemental levels more than nondiabetic dentin, which could explain the higher root canal treatment failure rate in diabetic patients.