Mechanical properties evaluation of two resin-based three-dimensional printing materials and dentine for endodontic training model fabrication: In vitro study.

The objective of the study was to compare 4 mechanical properties of two 3-D printing resins with dentine. Four mechanical tests were performed on dentine specimens, VeroClear resin and Splint resin with 15 samples each. Vickers hardness test, samples were subjected to a 300-g load for 10 s. Flexural strength test, 8-millimetre, beam-shaped specimens were tested using the three-point bending method. Drilling force was measured on flat-surface specimens. Intra-canal torque was measured on specimens imitating root canals. The results were analysed using the Kruskal-Wallis and Mann-Whitney tests with adjusted Bonferroni's p-value (p < 0.05). Dentine exhibited the highest mechanical properties in all the tests. VeroClear's flexural strength and drilling force were higher, while the surface hardness was lower than that of Splint resin. The intra-canal torque of dentine and VeroClear resin were not significant and higher than that of Splint resin. VeroClear's mechanical properties were closer to dentine than Splint resin.

Effects of EDTA and saline as the final irrigation in regenerative endodontic procedures on the migration, proliferation, and differentiation of human stem cells from the apical papilla.

OBJECTIVES: To evaluate the effect of EDTA and saline as the final irrigation in regenerative endodontic procedures (REPS) on the attachment, proliferation, migration, and differentiation of stem cells from the apical papilla (SCAPs). MATERIALS AND METHODS: Dentin specimens from 140 human third molars were irrigated with various protocols-group 1: normal sterile saline (NSS), group 2: EDTA, group 3: EDTA then 5 mL NSS, or group 4: EDTA then 20 mL NSS. The specimens were used in cell assays. For cell proliferation, SCAPs were seeded on dentin, and the cell viability on days 1, 3, and 7 was determined using an MTT assay. At day 3, the attached cells' morphology was observed using SEM, and cell migration was investigated using a transwell migration assay. The ALP activity and odonto/osteogenic differentiation gene expression were evaluated at days 7, 14, and 21 using an ALP activity assay and RT-qPCR. RESULTS: On days 3 and 7, group 4 demonstrated more viable cells than group 1 (p < 0.01). The amount of migrated cells in groups 2, 3, and 4 was greater compared with group 1 (p < 0.05). Moreover, SCAP differentiation was similar between groups. CONCLUSIONS: Irrigating dentin with EDTA alone or with EDTA then NSS promoted SCAP migration. However, a final irrigation with 20 mL NSS after EDTA promoted SCAP proliferation without affecting their differentiation. CLINICAL RELEVANCE: When using a blood clot as a scaffold, a final flushing with 20 mL NSS after EDTA could be beneficial for clinical REP protocols.

Effect of GuttaClear on Postoperative Pain After Root Canal Retreatment: A Randomized Clinical Trial.

OBJECTIVE: The aim of this study was to evaluate postoperative pain after non-surgical root canal retreatment with or without GuttaClear. METHODS: Sixty participants were randomly distributed in this non-inferiority trial into two parallel singleblinded experimental groups (Group1: non-solvent, Group2: solvent). After root canal retreatment, the participants completed questionnaires using direct (numerical rating scales) and indirect (number of analgesics taken) measurements of postoperative pain at immediate, 6, 12, 24, 48, and 72 h post-retreatment. The predisposing postoperative pain factors were recorded and analysed using Generalized Estimating Equations to identify correlated factors (α=0.05). RESULTS: The pain incidence was not significantly different between the groups at any time point. The highest incidence of postoperative pain occurred immediately after retreatment (35%) and then decreased to 15% at 24 h (P<0.05). The number of participants requiring analgesics was 6.67% in the non-solvent group and 9.99% in the solvent group which were similar between the groups. Patients with a history of previous postoperative pain were 21.6-fold more likely to have postoperative pain than those without (P<0.05). CONCLUSION: There was no difference in postoperative pain or analgesics required after root canal retreatment with or without using GuttaClear. This study is registered in ClinicalTrial.gov (NCT04326998). (EEJ-2022-05-069).

Gap volume and sealer penetration of C-shaped root canals obturated with cold hydraulic technique and calcium silicate sealer.

This study compared the gap volume and sealer penetration in C-shaped root canals prepared with adaptive core rotary files and obturated with cold hydraulic compaction using calcium-silicate sealer, warm vertical hybrid compaction, or lateral compaction using epoxy-resin sealer. Thirty-six extracted mandibular molars with pulpal floor configuration Types I and III were used. The teeth were prepared using XP-Shaper and XP-Finisher and obturated with: group 1: cold hydraulic compaction/calcium silicate, group 2: warm vertical hybrid compaction/epoxy resin, or group 3: lateral compaction/epoxy resin. The gap volume was evaluated using µ-CT. The sealer penetration depth and area were evaluated using confocal laser scanning microscopy. The gap volume in groups 1, 2, and 3 was 0.82%, 0.24%, 0.80%, respectively, which were not significantly different (p > 0.05). The gap volumes in the obturated C-shaped canals were not significantly different among the CHC/CSBS, WHC/ERS, or LC/ERS groups. CHC/CSBS was the most convenient technique.

Effect of solvent on root canal filling material removal by two different rotary file systems in C-shaped root canals.

This study compared the percentage reduction of total obturation materials, gutta-percha and sealer, using two rotary file systems with/without solvent in retreating C-shaped root canals and to evaluate the effect of the solvent on instrument separation. C-shaped root canals were scanned using micro-CT to identify the root canal morphology and randomly assigned to four groups (n = 12). Retreatment was performed using ProTaper Universal Retreatment (PTUR) or XP-endo systems with/without solvent. The number of separated instruments were recorded. The samples were scanned pre- and post-retreatment. The percentage reduction of total obturation materials, gutta-percha and sealer, were calculated. The percentage reduction of gutta-percha in the PTUR without solvent group was significantly lower than the other groups (P = 0.018). The number of separated instruments in the solvent groups were significantly lower than the no solvent groups (P < 0.05). Solvent increased gutta-percha removal, when using PTUR and decreased the occurrence of separated instruments for both systems.

The Effects of EDTA on Blood Clot in Regenerative Endodontic Procedures.

INTRODUCTION: In regenerative endodontic procedures (REPs), a blood clot acts as a natural scaffold for regenerating dental pulp tissue. In current protocols, 17% EDTA is recommended for liberating growth factors from root dentin. Although EDTA affects clot formation in periodontal studies, the anticoagulant effect of EDTA has not been shown in REPs. Therefore, this study aimed to evaluate the effects of 17% EDTA on the characteristics and fiber density of blood clots using in vitro dentin blocks. METHODS: The roots of 35 human mandibular premolars were prepared to simulate open apices and irrigated with the following protocols: (1) normal saline solution (NSS), (2) EDTA (1 minute) + NSS (E1N), (3) EDTA (5 minutes) + NSS (E5N), (4) EDTA (1 minute) (E1), and (5) EDTA (5 minutes) (E5). The roots were split, and human blood was placed. The characteristics and fibrin density of clots were observed using a scanning electron microscope. Fibrin densities in all irrigation groups were evaluated using ImageJ software (National Institutes of Health, Bethesda, MD) and statistically analyzed using the Friedman test and the Kruskal-Wallis test with Bonferroni adjustment. RESULTS: Samples in the NSS, E1N, and E5N groups revealed denser fibers with an abundance of erythrocytes when compared with those in the E1 and E5 groups. Fiber densities in the E1 and E5 groups showed significantly lower values than those in the NSS, E1N, and E5N groups in all regions of roots (P < .05). No statistically significant difference at all levels was observed in all irrigation groups. CONCLUSIONS: A decrease in clot formation was affected by EDTA irrigation for 1 and 5 minutes. Final flushing with NSS could improve fibrin formation.

Post-treatment apical periodontitis related to the technical quality of root fillings and restorations in Thai population.

The aim of this study was to investigate the post-treatment apical periodontitis in endodontically treated teeth related to the technical quality of root fillings and restorations in Thai population. Full-mouth periapical radiographs from Thai patients attending the Faculty of Dentistry, Mahidol University, Thailand were examined. The periapical status, quality of root fillings and coronal restorations, existence of intraradicular post and its relationship to the root fillings were evaluated. Among 1586 patients, 37.4% presented endodontically treated teeth. The total number of endodontically treated teeth was 1511, and 35% presented apical periodontitis. Combined data for root filling and coronal restoration qualities revealed significantly better outcome in teeth with adequate qualities of both parameters than the other combinations (P < 0.001). The prevalence of post-treatment apical periodontitis among Thai population was relatively high and significantly associated with substandard technical quality of root fillings and restorations.

Bacterial leakage and marginal adaptation of various bioceramics as apical plug in open apex model.

AIM: The aim of the present study was to investigate bacterial leakage and marginal adaptation of bioceramic apical plugs. METHODS: Extracted human mandibular premolars were prepared to simulate open apex using No. 4 Peeso reamer in retrograde direction. In total, 150 specimens were divided into 10 groups by obturation with five bioceramics in two thicknesses. Groups 1, 3, 5, 7, and 9 were obturated with ProRootMTA, Biodentine, TotalFill BC RRM paste, TotalFill BC RRM putty, and RetroMTA at 3 mm, and groups 2, 4, 6, 8, and 10 were obturated with the same materials at 4 mm. Ten specimens in each group were evaluated for bacterial leakage of Enterococcus faecalis for 75 days. Five specimens from each group were sectioned to investigate the gap area under scanning electron microscope. RESULTS: The 3- and 4-mm Biodentine and TotalFill BC RRM putty groups and the 4-mm ProRootMTA group exhibited less bacterial leakage and lower mean percentage of gap area than those of the other groups. TotalFill BC RRM paste showed the highest leakage for both the 3- and 4-mm groups. CONCLUSION: The 3- and 4-mm Biodentine and TotalFill BC RRM putty groups and the 4-mm ProRootMTA group exhibited the best sealing ability and marginal adaptation of apical plugs.

A Comparison of 3 Quantitative Radiographic Measurement Methods for Root Development Measurement in Regenerative Endodontic Procedures.

INTRODUCTION: The outcomes of an immature tooth with necrotic pulp treated with regenerative endodontic procedures (REPs) were assessed clinically and radiographically. Root maturation is an important outcome of REPs, and several radiographic measurement methods have been used to measure this. The aim of this study was to compare radiographic measurement methods, measuring root maturation in immature teeth with necrotic pulp treated with REPs. METHODS: Seventy-one radiographic images of REP cases were measured and compared using 3 radiographic measurement methods described by Bose et al (2009), Alobaid et al (2014), and Flake et al (2014). The intraclass correlation coefficient values were evaluated using the intra- and interobserver reliability test and the effect of the stage of root development. RESULTS: The intra- and interobserver reliability for Alobaid et al's method and Flake et al's method were slightly higher than Bose et al's method as quantified by the intraclass correlation coefficient without a significant difference (P > .05). The stage of root development did not affect the reliability of the measurement methods. A high level of agreement was found among the 3 stages of root development for all 3 quantitative radiographic measurement methods. CONCLUSIONS: All 3 quantitative radiographic measurement methods exhibited high agreement regarding reliability. The stage of root development did not have an impact on the reliability of the measurement methods.

Effect of Bioceramic Materials on Proliferation and Odontoblast Differentiation of Human Stem Cells from the Apical Papilla.

INTRODUCTION: In regenerative endodontic treatment (RET), practitioners favor the placement of bioceramics as sealing materials over blood clots. It is important to understand the interaction between sealing material and cells in the root canal. The purpose of this study was to compare the effectiveness of various bioceramic materials (ProRoot MTA [Dentsply, Tulsa, OK], Biodentine [Septodont, Saint-Maur-des-Fossés, France], and RetroMTA [BioMTA, Seoul, Korea]) as sealing materials in RET for the proliferation and differentiation of stem cells from the apical papilla (SCAPs). METHODS: SCAPs were seeded at 20,000 cells/well and cultured with soluble agents of testing materials through a transwell culture plate. The proliferation of SCAPs was investigated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay on days 1, 3, 7, and 14 of testing. Alizarin red staining and quantitative real-time polymerase chain reaction were used for SCAP differentiation at different time points (1, 7, 14, and 21 days). The odontoblast genes expressed are dentin matrix acidic phosphoprotein 1, dentin sialophosphoprotein, osteocalcin, and matrix extracellular phosphoglycoprotein, which were used in this study. The SCAPs were cultured in odonto/osteogenic induction medium and also contacted soluble agents from the testing materials. RESULTS: All 3 tested biomaterials induced SCAP proliferation. The Biodentine, ProRootMTA, and RetroMTA groups showed significant SCAP proliferation on days 7 and 14 compared with the control. In regard to odontoblastic differentiation, only Biodentine showed positive alizarin red staining. The highest expressions of dentin matrix acidic phosphoprotein 1, dentin sialophosphoprotein, and matrix extracellular phosphoglycoprotein were found on day 21 in the Biodentine group. The expression of osteocalcin was found to be significant on day 7. CONCLUSIONS: Biodentine, ProRootMTA, and RetroMTA can induce SCAP proliferation. Biodentine induced significant SCAP differentiation among the 3 materials.

Cytotoxicity and migration of fibroblasts on two types of calcium sulfate dihydrate.

AIM: The aim of the present study was to compare cytotoxicity and migration ability of L929 on medical-grade calcium sulfate dihydrate (MCS) with commercial calcium sulfate dihydrate (CCS). METHODS: Samples of both freshly-mixed and set states of MCS and CCS were extracted in culture medium and tested for cytotoxicity according to International Organization of Standardization 10993-5:2009. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used, and the percentage of cell viability was calculated. Thirty petri dishes were divided into three equal groups: polystyrene (control), CCS, and MCS. In each petri dish, triplicate wells were made on the agarose overlay on the material. The central well was occupied with L929 cell suspension, one well was filled with platelet-derived growth factor-BB, and the remaining well with Hanks' Balanced Salt Solution. After incubation, the migration distances were measured and the corrected migration distances were calculated. The final step involved scanning electron microscopy (SEM). RESULTS: The CCS had significantly less cell viability than MCS at a high extracted concentration (P < 0.001) in both samples. The mean corrected migration of MCS was significantly greater than that of CCS (P < 0.05). SEM showed that L929 cells on MCS exhibited an elongated spindle shape. CONCLUSION: MCS was less cytotoxic and provided greater migration of L929 fibroblasts compared with CCS.

Shotgun proteomics analysis of proliferating STRO-1-positive human dental pulp cell after exposure to nacreous water-soluble matrix.

INTRODUCTION: For dental treatment, dentin regeneration is required after a tooth injury with dental pulp exposure. The effects of the water-soluble matrix (WSM) extracted from the nacreous layer of the bivalve Pinctada maxima on human dental pulp cells in vitro were challenging and useful for clinical application. MATERIAL AND METHODS: The biological activity of the STRO-1-positive human dental pulp cells in response to WSM compared to Dulbecco's modified Eagle medium (DMEM) as a normal control was monitored. The cell survival rate was analyzed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Proteomic profiles among inducers and noninducers with time dependency were compared by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis combined with liquid chromatography-tandem mass spectrometry (GeLC-MS/MS). RESULTS: The human dental pulp cells cultured in nacreous WSM exhibited higher relative cell viability than those in DMEM with similar morphological appearance. Significant changes were found in the relative abundance of 44 proteins in cells after exposure to WSM for 2 weeks. They play a role in cell adhesion, cell proliferation, metabolic process, signal transduction, stress response, transcription, translation, and transport. CONCLUSION: These results indicate that WSM of P. maxima has the ability to induce proliferation of human dental pulp cells. CLINICAL RELEVANCE: This finding initiated the study to evaluate the suitability of nacre as biomaterial for dentistry.

Influence of file motion on cyclic fatigue of new nickel titanium instruments.

AIM: The aim of the present study was to compare the resistance to cyclic fatigue of Hyflex® (Coltene-Whaledent, Allstatten, Switzerland) size 40 taper.04 nickel titanium instruments used in continuous rotation versus the use with a reciprocating motion. The null hypothesis was that different file motions had no influence on the lifetime of instruments subjected to a cyclic fatigue test. METHODOLOGY: 24 Hyflex® size 40 taper.04 nickel titanium instruments were randomly divided in two groups (n=12 each), and submitted to a cyclic fatigue test. The first group (CR group) were used with a continuous rotation, while the second one (RCP group) with a reciprocating motion. The cyclic fatigue tests were performed by using a stainless steel block containing an artificial canal shaped with a 135° angle. All instruments were rotated or reciprocated until fracture occurred. The time to fracture was recorded visually with a 1/100 second chronometer. Data were recorded and statistically analysed. RESULTS: Results indicated that instruments used with a reciprocating motion showed a significant increase in the meantime to failure when compared to those used in continuous rotation. CONCLUSIONS: The null hypothesis was rejected. Results of the present study showed that reciprocating motion extended resistance to cyclic fatigue of the tested nickel titanium instruments, when compared to continuous rotation.

Efficacy of grapefruit, tangerine, lime, and lemon oils as solvents for softening gutta-percha in root canal retreatment procedures.

AIM: In the present study, we evaluate the efficiency of four kinds of oil as solvents for softening gutta-percha in root canal retreatment procedures. The performance of grapefruit, tangerine, lime, and lemon oils specifically were evaluated and compared to chloroform. METHODS: Eighty-four cylinder-shaped glass tubes (5 × 30 mm) were filled with gutta-percha. A total of 0.1 mL solvent was added to the upper part of the glass tubes. After 5 min, the spreader attached to the universal testing machine was moved downward through gutta-percha with header speed of 5 mm/min into a depth of 5 mm. An initial depth of spreader penetration without force produced was recorded in millimeters. The load used to penetrate the spreader into the 5-mm depth was recorded in Newton. RESULTS: The results of the surface-dissolving depth and maximum force used to penetrate the spreader to 5 mm revealed that chloroform was significantly the best solvent in softening gutta-percha (P < 0.05), followed by grapefruit oil and tangerine oil, while the least effective solvents were lime oil and lemon oil. CONCLUSIONS: Under the conditions of the present study, grapefruit oil and tangerine oil performed best as gutta-perch solvents among four natural oils.

Mahidol study 1: comparison of radiographic and survival outcomes of immature teeth treated with either regenerative endodontic or apexification methods: a retrospective study.

INTRODUCTION: There are numerous challenges in treating immature permanent teeth with a diagnosis of pulp necrosis. Three general treatment options are calcium hydroxide apexification, mineral trioxide aggregate (MTA) apexification, and revascularization. The objective of this retrospective study was to evaluate radiographic and clinical outcomes of immature teeth treated with 1 of these 3 methods. METHODS: Clinical outcome data and radiographs were collected from 61 cases (ie, 22 calcium hydroxide apexification cases, 19 MTA apexification cases, and 20 revascularization cases). Both tooth survival and clinical success rates were analyzed. In addition, the preoperative and recall radiographs were analyzed to calculate the percentage increase in root width and length. RESULTS: The percentage change of root width was significantly greater in the revascularization group (28.2%) compared with the MTA apexification (0.0%) and calcium hydroxide apexification groups (1.5%). In addition, the percentage increase of root length was significantly greater in the revascularization group (14.9%) compared with the MTA (6.1%) and calcium hydroxide apexification groups (0.4%). Moreover, the survival rate of the revascularization-treated teeth (100%) and MTA apexification-treated teeth (95%) were greater than the survival rates observed in teeth treated with calcium hydroxide (77.2%). CONCLUSIONS: In this study, revascularization was associated with significantly greater increases in root length and thickness in comparison with calcium hydroxide apexification and MTA apexification as well as excellent overall survival rates.

Biocompatibility of furcal perforation repair material using cell culture technique: Ketac Molar versus ProRoot MTA.

OBJECTIVE: The objective of this study was to evaluate the cytotoxicity of furcal perforation repair materials, GI and MTA, using cell culture technique. STUDY DESIGN: The extract of ProRoot MTA and Ketac Molar were treated on PDL cells in a 96-well tissue-culture plate. Cell proliferation after an incubation period of 3 days was determined by using MTT assay. RESULTS: The growth of cultured human periodontal fibroblast cells were suppressed by both perforation repair materials. The percent of cell viability in the Ketac Molar group was lower than in the ProRoot MTA group (P = .000). CONCLUSIONS: Although Ketac Molar has the advantage of adhering to dentine, it is more cytotoxic to the PDL cells than MTA. In selecting the perforation repair material, it is recommended not only to consider the sealing ability of the material with dentine but also the biocompatibility of material to the underlying tissue.

Time-dependent properties of human root dentin.

OBJECTIVES: The aim of this study was to investigate the creep, stress relaxation and strain rate behavior of human root dentin under compressive loading. METHODS: Cylindrical root dentin samples of 3.5mm outer diameter, 1.5mm internal canal diameter and 6-10mm long were prepared from freshly extracted teeth. The samples were tested in a closed-loop servohydraulic testing machine at constant load or displacement, and varied strain rate. In vivo strain rates were estimated using strain gauges bonded to human teeth. RESULTS: A family of creep curves, determined at different loads within dentin's elastic region, was found to be consistent with a material having linear viscoelastic behavior. A positive correlation (r(2)=0.79, P<0.001) was found between creep rate and stress. Young's modulus (E) was found to be a function of the strain rate with rates of loading in the range 10-500,000Ns(-1). Loading at constant displacement showed stress to be a decreasing function of time (i.e. stress relaxation). SIGNIFICANCE: Dentin showed linear-viscoelastic behavior under various conditions of compressive loading. Time dependent properties of dentin should be taken into account in restorative dentistry.