Improvement of the properties of mineral trioxide aggregate by mixing with hydration accelerators

Introduction

Mineral trioxide aggregate (MTA) is used widely in endodontic therapy. This study examined the setting time, compressive strength, and pH of MTA mixed with several hydration accelerators (calcium chloride, low-dose citric acid, calcium lactate gluconate solution).

Methods

Group 1 (control) was obtained by mixing MTA with distilled water. In group 2, MTA containing 10% calcium chloride was mixed with distilled water. In group 3, MTA was mixed with 0.1% citric acid. In group 4, MTA was mixed with a calcium lactate gluconate solution. The setting time, compressive strength, and pH were examined.

Results

The setting time of MTA mixed with hydration accelerators was significantly shorter than that of MTA mixed with water (P < .01). In particular, replacing distilled water with a calcium lactate gluconate solution provided a significant decrease in setting time. The compressive strengths of MTA mixed with hydration accelerators were significantly lower than that of MTA mixed with water (P < .01), but those values increased with time. The pH of MTA mixed with hydration accelerators was significantly lower than that of MTA mixed with water (P < .01) but stable at a high level (pH 11–12).

Conclusions

Hydration accelerators improved the setting time of MTA. Nevertheless, more study will be needed to improve MTA without impairing its preexisting advantages.     

Properties of an Accelerated Mineral Trioxide Aggregate–like Root-end Filling Material

The purpose of the study was to examine the physicochemical properties of mineral trioxide aggregate (MTA)-like cements prepared from SiO₂, CaO, and Al₂O₃ as matrices, and ZnO, MgO, and Fe₂O₃ as additives. The MTA-like cements showed a significantly (p < 0.05) faster setting time (<14 minutes) than MTA when mixed with water, although there was a significant decrease (p < 0.05) in diametral tensile strength, ranging from 0.9 to 3.1 MPa in comparison to MTA (4.4 MPa). The addition of ZnO, MgO, and Fe₂O₃ to the MTA-like cement led to a significantly (p < 0.05) higher strength than MTA-like cement without additives. The pH values of the MTA-like cements were changed from an initial 11 to a high of 13, similar to the results of MTA. Future characterization of the examined MTA-like cement with shortened setting time is needed before it is considered a viable candidate for dental root-end–filling applications.     

Evaluation of shear bond strength of two resin-based composites and glass ionomer cement to pure tricalcium silicate-based cement (Biodentine?)

Objectives

Tricalcium silicate is the major constituent phase in mineral trioxide aggregate (MTA). It is thus postulated that pure tricalcium silicate can replace the Portland cement component of MTA. The aim of this study was to evaluate bond strength of methacrylate-based (MB) composites, silorane-based (SB) composites, and glass ionomer cement (GIC) to Biodentine^® and mineral trioxide aggregate (MTA).

Material and Methods

Acrylic blocks (n=90, 2 mm high, 5 mm diameter central hole) were prepared. In 45 of the samples, the holes were fully filled with Biodentine^® and in the other 45 samples, the holes were fully filled with MTA. The Biodentine^® and the MTA samples were randomly divided into 3 subgroups of 15 specimens each: Group-1: MB composite; Group-2: SB composite; and Group-3: GIC. For the shear bond strength (SBS) test, each block was secured in a universal testing machine.

Results

The highest (17.7±6.2 MPa) and the lowest (5.8±3.2 MPa) bond strength values were recorded for the MB composite-Biodentine^® and the GIC-MTA, respectively. Although the MB composite showed significantly higher bond strength to Biodentine (17.7±6.2) than it did to MTA (8.9±5.7) (p<0.001), the SB composite (SB and MTA=7.4±3.3; SB and Biodentine^®=8.0±3,6) and GIC (GIC and MTA=5.8±3.2; GIC and Biodentine=6.7±2.6) showed similar bond strength performance with MTA compared with Biodentine (p=0.73 and p=0.38, respectively).

Conclusions

The new pure tricalcium-based pulp capping, repair, and endodontic material showed higher shear bond scores compared to MTA when used with the MB composite.     

Effects of two fast-setting calcium-silicate cements on cell viability and angiogenic factor release in human pulp-derived cells

Mineral trioxide aggregate (MTA) is considered a pulp-capping agent of choice, but has the drawback of a long setting time. This study aimed to assess two different types of calcium-silicate cements as pulp-capping agents, by investigating their in vitro cytotoxicity and angiogenic effects in human pulp cells. ProRoot MTA, Endocem Zr, and Retro MTA were prepared as set or freshly mixed pellets. Human pulp-derived cells were grown in direct contact with these three cements, Dycal, or no cement, for 7 days. Initial cell attachment, viability, calcium release, and the levels of vascular endothelial growth factor (VEGF), angiogenin, and basic fibroblast growth factor (FGF-2) were evaluated statistically using a linear mixed model (P < 0.05). The biocompatibility of Retro MTA was similar to those of the control and ProRoot MTA. Endocem Zr groups showed fewer and more rounded cells after a 3-day culture; however, the initial cytotoxicity appeared transient. All test materials showed significant increases in calcium concentration compared with the control group (P < 0.05). VEGF and angiogenin levels in ProRoot MTA and Retro MTA groups were significantly higher than those in the Endocem Zr group (P < 0.05). FGF-2 levels were not significantly different between groups (P > 0.05). We demonstrate that Retro MTA, which has a short setting time, has similar biocompatibility and angiogenic effects on human pulp cells, and can therefore potentially be as effective in pulp capping as ProRoot MTA. Endocem Zr showed intermittent cytotoxicity and elicited lower levels of VEGF and angiogenin expression.     

The effect of various concentrations of iodine potassium iodide on the antimicrobial properties of mineral trioxide aggregate – a pilot study

Abstract – Background: Mineral trioxide aggregate (MTA) is a multi‐purpose dental material with various uses in dentistry. Iodine potassium iodide (IKI) is the most commonly used iodine compound in endodontics. We aimed to assess the antimicrobial activity of tooth‐colored ProRoot MTA combined with IKI. Materials and methods: The antimicrobial activity of IKI was assessed at three concentrations (1%, 2%, and 4%) as the mixing agents combined with MTA against Enterococcus faecalis, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. For each microorganism, three plates were inoculated with 100 μl of a microbial suspension (McFarland 0.5). Four wells were prepared in each plate. MTA (70 mg) was mixed with any of the three concentrations of IKI (25 μl) or sterile distilled water (25 μl) and placed in each well. The plates were incubated for 24 h at 37°C. Zones of inhibition (ZOI) were measured in millimeters by a blinded observer. Data were analyzed using analysis of variance and the Dunnett t‐test. Results: All MTA mixtures with water or IKI solutions showed inhibitory zones. The mean ZOI of each MTA/IKI mixture was not significantly different from MTA/water mixture (P > 0.05). MTA/1% IKI had smaller ZOI than MTA/water against E. coli, E. faecalis, and C. albicans. MTA/2% IKI showed larger ZOI only against P. aeruginosa. MTA/4% IKI showed larger ZOI against P. aeruginosa and E. coli (P < 0.05). Conclusions: Substitution of IKI solutions (1%, 2%, and 4%) for water did not significantly increase the antimicrobial activity of MTA.     

Treatment of open apex teeth using two types of white mineral trioxide aggregate after initial dressing with calcium hydroxide in children

Abstract – Background: The clinical and radiographic success of two types of white mineral trioxide aggregate (MTA) as apical barriers in non‐vital immature permanent incisors in children was investigated. Materials and methods: Following an initial dressing with calcium hydroxide, MTA apical barriers were placed in 22 non‐vital traumatized, permanent incisors with open apices in 21 children (mean age 10 years). Teeth were alternately assigned to either white MTA ProRoot^® or white MTA Angelus groups and treated by two operators. Clinical and radiographic reviews took place at baseline, 3 months and every 6 months thereafter. Two other calibrated, blinded examiners evaluated all radiographs. Examiner agreement was assessed using Kappa–Cohen tests. Results were analysed using Fisher’s exact tests and repeated measures anova . Results: The mean follow‐up time was 23.4 months. There were no statistically significant differences in clinical or radiographic outcomes between the two groups. The overall clinical success and relative radiographic success rate was 95.5%. Statistically significant reduction in periapical pathosis was shown over time in both groups (P < 0.05). A significant relationship was identified between non‐divergent apical anatomy and ideal positioning of the MTA plug in all teeth (P = 0.04). Interestingly, coronal discolouration was observed in 22.7% of teeth following white MTA placement. Conclusions: Apical barrier placement using both white MTA ProRoot^® and white MTA Angelus after an initial calcium hydroxide dressing showed similar favourable clinical and radiographic outcomes.     

Comparison of the Biological Properties of ProRoot MTA,OrthoMTA, and Endocem MTA Cements

Introduction

OrthoMTA (BioMTA, Seoul, Korea) and Endocem MTA (Maruchi, Wonju-si, Korea) were recently developed to overcome the disadvantages of ProRoot MTA (Dentsply, Tulsa, OK). This study aimed to compare the biological properties of OrthoMTA and Endocem MTA with those of ProRoot MTA using the preosteoblastlike cell line MC3T3-E1.

Methods

The setting times of calcium silicate–based cements (CSCs) and their effects on the pH of distilled water during storage were determined according to ISO standards. MC3T3-E1 cells were cultured with ProRoot MTA, OrthoMTA, and Endocem MTA. The viability of the cells was assessed using the Cell Counting Kit-8 assay (Dojindo Laboratory, Kumamoto, Japan) on the supernatants of CSCs, and the cells' osteopontin production was determined by an enzyme-linked immunosorbent assay on a culture with the materials on days 3 and 7 of incubation.

Results

Endocem MTA exhibited a significantly shorter setting time (15.3 ± 0.5 minutes) than did ProRoot MTA and OrthoMTA (318.0 ± 56.0 and 324.3 ± 2.1 minutes, P < .05). Additionally, all CSCs caused their storage water to become highly alkaline after 7 days. OrthoMTA was significantly more cytotoxic than ProRoot and Endocem MTA (P < .05). ProRoot MTA induced significantly more OPN production than OrthoMTA and Endocem MTA on both days 3 and 7 (P < .05).

Conclusions

ProRoot MTA appeared to be superior to OrthoMTA and Endocem MTA in terms of biological properties although Endocem MTA exhibited the shortest setting time and presented lower cytotoxicity with osteoblastlike cells.     

Effects of a novel hydration accelerant on the biological and mechanical properties of white mineral trioxide aggregate

Introduction

The objective of this study was to investigate the antibacterial, biocompatibility, and mechanical properties of mineral trioxide aggregate (MTA) set using a calcium lactate gluconate (CLG) solution.

Methods

ProRoot white MTA (WMTA) (Dentsply Tulsa Dental, Tulsa, OK) was used as the control group; MTA-like cement was prepared by mixing Portland cement/bismuth oxide/calcium sulfate (75/20/5) as the experiment group. A solution of 23.1 wt% CLG was used as a hydration accelerant and was compared with deionized water (DDW). Changes in pH values, antibacterial properties, in vitro cell viability, and diametral tensile strength (DTS) of the hydrated cements were assessed.

Results

Like WMTA, pH values for the MTA-like cement set using DDW and the CLG solution showed minor but statistically significant differences (P < .05). The antibacterial effects of hydrated specimens set by DDW and CLG against Streptococcus mutans assessed with an in vitro tube dilution test showed a significant difference in the early hydration time but no significant difference after 60 minutes (P > .05). A mouse osteoblastic cell (MC3T3-E1)-based MTT assay revealed that WMTA set using CLG had significantly higher cell viability than that set using DDW (P < .05). The DTS test for hydrated MTA-like cement with different liquids showed a significant difference on day 1 but no statistical difference on day 21.

Conclusions

The results suggest that using a CLG solution as the hydration accelerant may enhance the biocompatibility but not compromise WMTA’s antibacterial and mechanical properties.     

Apical Sealing Ability of a Novel Material: Analysis by Fluid Filtration Technique

Aim

The aim of this study is to evaluate the sealing ability of Biodentine^TM, which is new calcium-silicate based dental cement and has endodontic indications similar to those of MTA.

Methods

The study sample consists of 21extracted human mandibular anterior teeth. The teeth were submitted to root-end preparation and instrumented up to file #40 by step back technique and randomly divided into 3 study groups (n=7): White MTA Angelus^TM (Angelus, Angelus Odontológica, Londrina, PR, Brazil), Biodentine^TM (Septodont, SeptodontSpecialités, Saint-MaurdesFosses, France) and the controls. The length of dye penetration between the filling material and tooth structure was measured in millimetres, using a calibrated stereo microscope (Leica MZ75, Germany) at 20× magnification under the same conditions. One-way Analysis of Variance (ANOVA) was used to indicate differences between the experimental groups and the controls. In addition, Tukey Multiple Comparisons Test was used to indicate differences within each group.

Results

The results showed that none of the groups were completely sealed. The mean and standard deviation for dye penetration in Biodentine^TM group was 0.63±0.20 and in MTA Angelus^TM group, it was 0.26±0.25. Regarding the comparisons between each group, significant differences were not observed (P=0.0193). The comparison between materials only found a significant difference only between MTA Angelus^TM and Biodentine^TM (P<0.05).

Conclusions

This study evaluated the possibility of Biodentine^TM’s sealing ability and marginal adaptation, since no studies are available on Biodentine. However, further in vitro and in vivo investigations should be conducted to determine the suitability of Biodentine^TM for clinical application.Key Words: Mineral tiroxide aggregate, Biodentine™, apical sealing, Fluid infiltration     

Comparative Micro–computed Tomographic Evaluation of the Sealing Quality of ProRoot MTA and MTA Angelus Apical Plugs Placed with Various Techniques

Introduction

This study compared the effects of different mixing and placement techniques on sealing of ProRoot MTA (Dentsply Maillefer, Ballaigues, Switzerland) and MTA Angelus (Soluçoes Odontologicas, Londrina, Brazil) apical plugs using micro–computed tomographic (micro-CT) imaging.

Evaluation of mineral trioxide aggregate (MTA) versus calcium hydroxide cement (Dycal(®) ) in the formation of a dentine bridge: a randomised controlled trial

Aim: To assess the effectiveness of mineral trioxide aggregate (MTA) used as an indirect pulp‐capping material in human molar and premolar teeth. Methodology: We conducted a clinical evaluation of 60 teeth, which underwent an indirect pulp‐capping procedure with either MTA or calcium hydroxide cement (Dycal^®). Calcium hydroxide was compared with MTA and the thickness of the newly formed dentine was measured at regular time intervals. The follow‐up was at 3 and 6 months, and dentine formation was monitored by radiological measurements on digitised images using Mesurim Pro^® software. Results: At 3 months, the clinical success rates of MTA and calcium hydroxide were 93% and 73%, respectively (P = 0.02). At 6 months, the success rate was 89.6% with MTA, and remained steady at 73% with calcium hydroxide (P = 0.63). The mean initial residual dentine thickness was 0.23 mm, and increased by 0.121 mm with MTA and by 0.136 mm with calcium hydroxide at 3 months. At 6 months, there was an increase of 0.235 mm with MTA and of 0.221 mm with calcium hydroxide. Conclusions: A higher success rate was observed in the MTA group relative to the Dycal^® group after 3 months, which was statistically significant. After 6 months, no statistically significant difference was found in the dentine thickness between the two groups. Additional histological investigations are needed to support these findings.     

A randomised titrated crossover study comparing two oral appliances in the treatment for mild to moderate obstructive sleep apnoea/hypopnoea syndrome

The objective of this study was to compare the efficiency of two oral appliances in patients with mild to moderate obstructive sleep apnoea/hypopnoea syndrome (OSAHS) by the analysis of objective and subjective evaluations and measurement of upper airway parameter. A randomised crossover design trial was carried out on 16 patients with OSAHS. Two different types of oral appliances were tested in each patient, a one‐piece monoblock and the SILENT NITE^® (GlideWell Laboratories, Newport Beach, CA, USA), a two‐piece appliance. Each oral appliance needed to be worn for two 3‐month periods separated by a 2‐week wash‐out period in between. The objective and subjective efficiency and upper airway parameters associated with the oral appliances were assessed. One‐way analysis of variance (anova ) test was performed to compare the changes in upper airway morphology and the treatment efficiency between the appliances. The monoblock and SILENT NITE^® (GlideWell Laboratories) appliances reduced Apnoea Hypopnoea Index (AHI) from 26·38 ± 4·13 to 7·58 ± 2·28 (P < 0·001) and 8·87 ± 2·88 (P < 0·001), respectively. The monoblock appliance was statistically more efficient in reducing AHI and Apnoea Index (AI) than the SILENT NITE^® (GlideWell Laboratories) (P < 0·05). The scores on Epworth's Sleepiness Scale (ESS) and Snoring Scale (SS) were improved significantly by both appliances. The upper airway spaces showed considerable enlargement by both mandibular advancement appliances (MAAs) (P < 0·05), while no significant differences were found between the two appliances (P > 0·05). Both MAAs showed good efficacy in the treatment for mild to moderate OSAHS. Use of the monoblock appliance should be considered when patients with OSAHS choose MAA treatment, as it was more efficient in reducing the AHI and AI compared to the two‐piece appliance and was preferred by most patients. Long‐term efficiency should be evaluated in future prospective studies.     

An alkasite restorative material effectively remineralized artificial interproximal enamel caries in vitro

Objective

To evaluate the remineralization of artificial interproximal enamel caries (AIEC) adjacent to alkasite, high viscous glass ionomer cement (HVGIC), and resin composite in class II restorations.

Materials and methods

Human enamel specimens were randomly assigned to 3 groups (n?=?22): Filtek? Z350, EQUIA Forte^®, and Cention N^®. The baseline hardness was determined using a Knoop microhardness assay. AIEC was formed in the specimens, and they were placed in contact with the proximal restorative materials then subjected to a 7-day pH cycling. Microhardness was determined post-artificial caries formation and post-pH cycling. The differences in the percentage of surface hardness recovery (%SHR) between the groups were compared using the Kruskal–Wallis test. The Dunn’s test was used for between-group comparisons (p?<?0.05). Specimen surface morphology was evaluated using scanning electron microscopy (SEM), and the calcium, phosphorus, and fluoride contents were analyzed by energy-dispersive spectroscopy (EDS). ANOVA with the post hoc Tukey multiple comparison test was used to evaluate the differences between groups (p?<?0.05).

Results

The Cention N^® %SHR was the highest, followed by EQUIA Forte^®, and Filtek? Z350. There was a significant difference in the %SHR between Cention N^® and Filtek? Z350 (p?<?0.05). In contrast, there were no significant difference between Cention N^® and EQUIA Forte^®. Significantly increased enamel surface fluoride content was observed in the Cention N^® compared with Filtek? Z350 specimens (p?<?0.05). The SEM image of the Cention N^® specimens demonstrated the greatest mineral deposition.

Conclusions

Cention N^® markedly increased the surface hardness and fluoride content of adjacent AIEC compared with Filtek? Z350 restorations.

Clinical relevance

Cention N^® is a promising alternative restorative material to remineralize initial enamel lesions in approximal adjacent surfaces, especially in high-risk caries patients.

     

Effect of self-setting α-tricalcium phosphate between segments for bone healing and hypoaesthesia in lower lip after sagittal split ramus osteotomy

AimsThe aim of this study was to evaluate hypoaesthesia of the lower lip and bone formation using self-setting α-tricalcium phosphate (Biopex^®) between the proximal and distal segments following sagittal split ramus osteotomy (SSRO) with bent absorbable plate fixation.Subjects and methodsThe subjects were 40 patients (80 sides) who underwent bilateral SSRO setback surgery. They were divided into a Biopex^® group (40 sides) and a control group (40 sides). The Biopex^® was inserted into the anterior part of the gap between the segments in the Biopex^® group. Trigeminal nerve hypoaesthesia in the region of the lower lip was assessed bilaterally using the trigeminal somatosensory-evoked potential (TSEP) method. Ramus square, ramus length, and ramus width, the square of the Biopex^® at the horizontal plane under the mandibular foramen were assessed preoperatively, immediately after surgery, and 1 year postoperatively by computed tomography (CT).ResultsThe mean measurable period and standard deviation were 9.3 ± 15.7 weeks in the control group, 5.3 ± 8.3 weeks in the Biopex^® group, and there was no significant difference. Ramus square after 1 year was significantly larger than that prior to surgery and new bone formation was found between the segments in both groups (P < 0.05). In the Biopex^® group, the square of the Biopex^® after 1 year was significantly smaller than that immediately after surgery (P < 0.05).ConclusionThis study suggested that inserting Biopex^® in the gap between the proximal and distal segments was useful for new bone formation and it did not prevent the recovery of lower lip hypoaesthesia after SSRO with bent absorbable plate fixation.     

Electromyographic assessment of jaw muscles in patients with All‐on‐Four fixed implant‐supported prostheses

This study evaluated the electromyographic (EMG) characteristics of masticatory muscles in patients with fixed implant‐supported prostheses according to All‐on‐Four^® principles and in control healthy dentate subjects. Twenty‐six subjects aged 50–74 years were examined. Eighteen were edentulous and had been successfully rehabilitated with (i) mandibular All‐on‐Four^® implant‐supported fixed prostheses and maxillary complete dentures (10 patients) and (ii) mandibular and maxillary All‐on‐Four^® implant‐supported fixed prostheses (eight patients). Eight reference subjects had natural dentition. Surface EMG recordings of the masseter and temporalis muscles were performed during maximum voluntary teeth clenching and during unilateral gum chewing. All values were standardised as percentage of a maximum clenching on cotton rolls. During clenching, a good global neuromuscular equilibrium was found in all participants. During chewing, all groups had similar values of working‐side muscle activities and of chewing frequency. No significant differences in the analysed EMG parameters were found between the patients with mandibular and maxillary All‐on‐Four^® implant‐supported prostheses and the reference subjects. In contrast, standardised pooled muscle activities and standardised muscular activities per cycle were larger in patients with a maxillary removable prosthesis than in control subjects (Kruskal–Wallis test, P < 0·01). Also, patients wearing a complete maxillary denture showed a poor neuromuscular coordination with altered muscular pattern and lower values of the index of masticatory symmetry than dentate control subjects (P < 0·01). EMG outcomes suggest that All‐on‐Four^® implant‐supported prostheses may be considered a functionally efficient treatment option for the rehabilitation of edentulous patients with reduced residual bone volume.     

Scanning electron microscopy evaluation of the hard tissue barrier after pulp capping with calcium hydroxide,mineral trioxide aggregate (MTA) or ProRoot MTA

The aim of this study was to investigate the morphology and localisation of calcium hydroxide‐ and mineral trioxide aggregate (MTA)‐induced hard tissue barriers after pulpotomy in dogs' teeth. Pulpotomies were performed on maxillary and mandibular premolars of five dogs. The teeth were assigned into three groups according to the pulp‐capping agent used. The pulpal wounds were capped with calcium hydroxide (Ca(OH)₂– control), MTA or ProRoot MTA, and the cavities were restored with amalgam. After a 90‐day follow‐up period, the dogs were euthanised and the teeth were examined under scanning electron microscopy (SEM). An image‐processing and analysis software was used to delimit the perimeters of the root canal area and the hard tissue barrier to determine the percentage of root canal obliteration. SEM data were used to assess the morphology, localisation and extension of the reparative hard tissue barriers. ProRoot MTA was statistically different from MTA and Ca(OH)₂ (P < 0.05) regarding tissue barrier morphology. Localisation data showed that ProRoot MTA was significantly different from Ca(OH)₂ (P < 0.05) and similar to MTA (P > 0.01; P > 0.05). No statistically significant difference (P > 0.01; P > 0.05) was observed between MTA and Ca(OH)₂. A larger number of complete (centroperipheral) hard tissue barriers with predominance of dentinal tubules was observed to the ProRoot MTA when compared with the Ca(OH)₂ group.     

Acid and Microhardness of Mineral Trioxide Aggregate and Mineral Trioxide Aggregate–like Materials

Introduction

The aim of this study was to compare the surface microhardness of BioAggregate, ProRoot MTA, and CEM Cement when exposed to an acidic environment or phosphate-buffered saline (PBS) as a synthetic tissue fluid.

Methods

Ninety cylindrical molds made of polymethyl methacrylate with an internal diameter of 6 mm and height of 4 mm (according to ASTM E384 standard for microhardness tests) were fabricated and filled with BioAggregate (n = 30), tooth-colored ProRoot MTA (n = 30), or CEM Cement (n = 30). Each group was then divided into 3 subgroups of 10 specimens consisting of those exposed to distilled water, exposed to PBS (pH = 7.4), or exposed to butyric acid (pH = 5.4). After 1 week the Vickers surface microhardness test was performed. Statistical analysis included 2-way analysis of variance, followed by post hoc Dunnett T3 in cases with lack of homoscedasticity and Tukey honestly significant difference in cases with homoscedasticity.

Results

The indentations obtained from the CEM Cement specimens exposed to an acidic pH were not readable because of incomplete setting. There was a significant difference between the microhardness of the materials regardless of the environmental conditions (P < .001). In all the environmental conditions, MTA had significantly higher and CEM Cement had significantly lower microhardness values (P < .001). All experimental cements had significantly higher microhardness values when exposed to PBS (P < .001) and had significantly lower microhardness values when exposed to butyric acid (P < .001).

Conclusions

The surface microhardness of BioAggregate, ProRoot MTA, and CEM Cement was reduced significantly by exposure to butyric acid and increased significantly by exposure to PBS. In all environmental conditions, MTA had significantly higher microhardness values.     

Evaluation of the removal of 2-Hydroxyisocaproic acid from the root canal and its effect on the bond strength of MTA

This study aimed to evaluate the removal of 2-hydroxyisocaproic acid (HICA) from the root canal system and its effect on the bond strength of the mineral trioxide aggregate (MTA). 126 single-rooted teeth were divided into 3 experimental groups (n = 36) that were treated with double antibiotic paste (DAP), HICA and calcium hydroxide (CH) and one control group (n = 18). In the first part, 18 teeth from each experimental group (n = 54) were examined to remove HICA from the root canal. In the second part, 72 teeth (3 experimental groups (n = 54) and one control group (n = 18)) were used for the evaluation of the push-out bond strength of MTA. There was no statistically significant difference between HICA, DAP and CH residues (p > 0.05). HICA group showed significantly less push-out bond strength (p < 0.05). DAP, HICA and CH could not be removed entirely from the root canal. HICA significantly reduced the bond strength of the MTA.     

Fracture resistance of immature teeth filled with BioAggregate,mineral trioxide aggregate and calcium hydroxide

Abstract – Background: The aim of this in vitro study was to assess the long‐term fracture resistance of human immature permanent teeth filled with BioAggregate (BA), mineral trioxide aggregate (MTA) and calcium hydroxide (CH). Materials and methods: The study consisted of single rooted premolar teeth with immature root formation extracted for orthodontic reasons. A total of 28 immature premolars with average root length of 10.7 mm and apical diameter of 3 mm were included in the study. The pulps were extirpated and the canals were prepared using an apical approach. The teeth were randomly assigned to four groups: Group I: DiaRoot^® BA (DiaDent, Burnaby, BC, Canada), Group II: Angelus MTA (MTA‐A; Angelus, Londrina, Brazil), Group III: ProRoot^® MTA (MTA‐PR; Dentsply, Tulsa, OK, USA), Group IV: CH (Sultan Chemists Inc., Englewood, NJ, USA). The teeth were placed in saline solution at 4°C for 1 year. The root of each tooth was then embedded in an acrylic resin block. All specimens were loaded at a crosshead speed of 1 mm min^?1 in an Instron testing machine and the peak loads up to fracture were recorded. Data were analysed statistically by Kruskal–Wallis and Mann–Whitney U‐tests. Results: Mean (±SD) failure loads (MPa) were: 37.69 ± 14.43 for BA group, 32.94 ± 8.15 for MTA‐A group, 28.74 ± 9.49 for MTA‐PR group and 23.18 ± 8.48 for CH group. The BA group exhibited the highest fracture resistance and the CH group showed the lowest resistance to fracture. Significant differences (P < 0.05) in fracture resistance were found between the DiaRoot‐BA and CH groups, and also between the MTA‐A and CH groups. Conclusion: Within the limitations of this study, data suggest that DiaRoot‐BA‐filled immature teeth demonstrate higher fracture resistance than other groups at 1 year. Considering the long‐term risk of cervical root fracture associated with immature teeth, the use of DiaRoot‐BA as a root canal filling material appears to be the most advantageous of the materials tested.     

Effect of Nano Silica on Setting Time and Physical Properties of Mineral Trioxide Aggregate

IntroductionMineral trioxide aggregate (MTA) has been widely used in all fields of endodontics. One of the major drawbacks of this material is the long setting time. MTA is primarily composed of type 1 Portland cement and bismuth oxide. In cement, nanoscale SiO₂ behaves as a filler to improve microstructure and to accelerate hydration process. The aforementioned reaction is also expected in MTA because of the same structure. Thus, the aim of this study was to evaluate the effect of addition of nano-SiO₂ to MTA on the setting time and its physical properties.MethodsTwo concentrations (8% and 10%) of nano-SiO₂ were added to the white MTA powder. After mixing with water, the setting time, compressive strength, and flexural strength were investigated and compared with pure MTA.ResultsWith the addition of 8% and 10% of nano-SiO₂ to the MTA, the setting time of both mixtures decreased significantly (P < .05). However, the compressive strength (after 1 day and 1 week) and flexural strength increased; this was not significant (P > .05). There was no significant difference between MTA mixed with 8% and 10% nano-SiO₂ in setting time, compressive strength, and flexural strength (P > .05).ConclusionsThe addition of 8% and 10% of nano-SiO₂ to MTA accelerated the hydration process, reduced the setting time, and had no adverse effect on the compressive and flexural strength of MTA.