Penetration of Calcium Silicate and Epoxy Resin Sealers Into the Lateral Canals

OBJECTIVES

The aim of this research was to compare the penetration ability of calcium silicate-based sealers (iRoot SP and TotalFill BC HiFlow) and an epoxy resin-based sealer (AH Plus) into the lateral canals using the single-cone (SC) or continuous wave compaction (CW) obturation techniques.

METHODS

Ninety single-rooted human teeth received canal instrumentation and diaphanisation before artificial lateral canals were created at 3 different root levels. The specimens were randomly allocated into 6 groups based on the combination of obturation technique and sealer used. Radiographic and photographic measurements evaluated the percentage of sealer penetration. Statistical analysis was performed to compare the penetration ability amongst different types of sealers, obturation methods, and root levels.

RESULTS

Although TotalFill BC HiFlow sealer combined with the CW technique demonstrated greater sealer penetration at the coronal level (P < .05), the overall penetration ability of iRoot SP, TotalFill BC HiFlow, and AH Plus was not significantly different. The deepest sealer penetration was observed at the apical root level.

CONCLUSIONS

All sealers showed similar penetration abilities into the lateral canals using the SC or CW techniques in vitro. Calcium silicate-based sealers have comparable penetration ability into lateral canals compared to epoxy resin-based sealers using SC or CW obturation techniques.

Effect of MMP Inhibitors on the Bond Strength of Fibre Posts After Ageing

AIM

This in vitro study aimed to evaluate the effect of matrix metalloproteinase (MMP) inhibitors on the bond strength of resin-cemented fibre posts to radicular dentin under an aged-loaded condition.

MATERIALS AND METHODS

Radicular dentin was prepared and irrigated by MMP inhibitor solution after root canal obturation in 60 extracted single-rooted teeth based on 6 groups: (1) 2% chlorhexidine (CHX) + loaded; (2) CHX + unloaded; (3) 0.5% benzalkonium chloride (BAC) + loaded; (4) BAC + unloaded; (5) 17% ethylenediaminetetraacetic acid (EDTA) + loaded; and (6) EDTA + unloaded. After final rinsing, all specimens were sliced cross-sectionally and kept in a water bath for 12 months of ageing. Groups 1, 3, and 5 were subjected to cyclic loading. Push-out tests were conducted using a universal testing machine, and failure mode was examined. The data were analysed using 3-way analysis of variance and post hoc tests at α = 0.05.

RESULTS

BAC + unloaded demonstrated the highest mean bond strength (3.12 ± 0.18 MPa; P < .001), while the BAC + loaded and CHX + loaded groups showed a significantly lower push-out bond strength than their unloaded counterparts. Mixed adhesive-cohesive failure was the most common failure mode observed.

CONCLUSIONS

Without cycling loading, BAC was superior to CHX and EDTA in preserving the bond strength of resin-cemented fibre posts after 12 months of ageing. Loading significantly weakened the effectiveness of BAC and CHX in preserving the bond strength.

Effects of L-Chg10-Teixobactin on Viability, Proliferation, and Osteo/Odontogenic Differentiation of Stem Cells from Apical Papilla

INTRODUCTION

Intracanal medicament is one of the essential steps for ensuring success in regenerative endodontic procedures. _L-Chg₁₀-teixobactin is a novel antimicrobial agent that exhibited potent antibacterial and antibiofilm effects against Enterococcusfaecalis at low concentrations compared with ampicillin. At the same time, its cytotoxicity on dental stem cells has not been studied. This study aimed to investigate the effects of _L-Chg₁₀-teixobactin on the viability, proliferation, migration, and osteo/odontogenic differentiation of stem cells from apical papilla (SCAPs).

MATERIALS AND METHODS

SCAPs isolated from immature human third molars were treated with various concentrations of _L-Chg₁₀-teixobactin, calcium hydroxide, and dimethyl sulfoxide. The viability and proliferation of SCAPs were assessed using the LIVE/DEAD Viability/Cytotoxicity Kit and Cell Counting Kit-8. A scratch wound healing test was used to evaluate the lateral migration capacity of SCAPs. Alkaline phosphatase (ALP) activity, calcium mineralization ability tests -ie, ALP staining and alizarin red S staining, and quantitative real-time polymerase chain reaction were performed to assess the osteo /odontogenic differentiation of SCAPs.

RESULTS

The tested concentrations of _L-Chg₁₀-teixobactin (0.01, 0.02, and 0.03 mg/mL), 1 mg/mL calcium hydroxide, and 0.03% dimethyl sulfoxide had no significant cytotoxic effect on SCAPs at any time point (P > .05). Besides, there were no significant differences between the control and experimental groups in SCAPs' viability, proliferation, and migration. _L-Chg₁₀-teixobactin upregulated the gene expression of osteo/odontogenic markers in SCAPs, while no significant difference was found in the ALP activity and alizarin red S staining.

CONCLUSIONS

_L-Chg₁₀-teixobactin demonstrated excellent biocompatibility on SCAPs at concentrations from 0.01 to 0.03 mg/mL and potentially enhance the osteo/odontogenic differentiation of SCAPs; suggesting its promising role as root canal medicament for regenerative endodontic procedures.

Enterococcus faecalis Shields Porphyromonas gingivalis in Dual-Species Biofilm in Oxic Condition

Aim: To develop a reproducible biofilm model consisting of Enterococcus faecalis (E. faecalis) and Porphyromonas gingivalis (P. gingivalis) and to evaluate the interaction between the two bacterial species. Methodology: E. faecalis and P. gingivalis were grown in mono-culture, sequential, and co-culture models for 96 h in a 96-well polystyrene microtiter plate under both aerobic and anaerobic conditions separately. The viability of the two bacterial species in the biofilms was quantified by polymerase chain reaction (qPCR). Biofilm thickness and protein contents were measured using confocal laser scanning microscopy (CLSM). Two-way analysis of variance (ANOVA) was performed to analyze cell viability and biofilm thickness among different culture models cultivated under either aerobic or anaerobic conditions. The level of significance was set at p < 0.05. Results: Different culture models tested did not show any significant difference between the viable cell counts of both E. faecalis and P. gingivalis cultivated under aerobic and anaerobic conditions (p > 0.05). Biofilm was significantly thicker (p < 0.05) in the co-culture models compared to the mono-culture and sequential models. Protein contents in the biofilms were more pronounced when both bacterial species were co-cultured under aerobic conditions. Conclusions: E. faecalis appeared to shield P. gingivalis and support its continued growth in oxic (aerobic) conditions. The co-culture model of E. faecalis and P. gingivalis produced a significantly thicker biofilm irrespective of the presence or absence of oxygen, while increased protein contents were only observed in the presence of oxygen.

The effectiveness and efficacy of respiratory protective equipment (RPE) in dentistry and other health care settings: a systematic review

OBJECTIVE

The global pandemic of coronavirus disease-19, caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), is the latest hazard facing healthcare workers (HCW) including dental care workers (DCW). It is clear that the major mode of SARS-CoV-2 transmission is the airborne route, through inhalation of virus-infested aerosols and droplets. Several respiratory protection equipment (RPE), including masks, face shields/visors, and respirators, are available to obviate facial and conjunctival contamination by microbes. However, as their barrier value against microbial inhalation has not been evaluated, we systematically reviewed the data on the effectiveness and efficacy of facemasks and respirators, including protective eyewear, with particular emphasis on dental healthcare.

MATERIAL AND METHODS

PubMed, MEDLINE, the Cochrane Library, and Embase databases were searched between 01January 1990 and 15 May 2020.

RESULTS

Of 310 identified English language records, 21 were included as per eligibility criteria. In clinical terms, wearing layered, face-fitting masks/respirators and protective-eyewear can limit the spread of infection among HCWs. Specifically, combined interventions such as a face mask and a face shield, better resist bioaerosol inhalation than either alone. The prolonged and over-extended use of surgical masks compromise their effectiveness.

CONCLUSIONS

In general, RPE is effective as a barrier protection against aerosolized microbes in healthcare settings. But their filtration efficacy is compromised by the (i) inhalant particle size, (ii) airflow dynamics, (iii) mask-fit factor, (iv) period of wear, (v) 'wetness' of the masks, and (vi) their fabrication quality. The macro-data presented here should inform policy formulation on RPE wear amongst HCWs.

'Evaluation of the introduction of a dental virtual simulator on the performance of undergraduate dental students in the pre-clinical operative dentistry course'

INTRODUCTION

Virtual reality-based platforms are becoming increasingly popular in education. The aim of this study was to evaluate the performance of undergraduate dental students with the introduction of the Moog Simodont dental trainer (VR) within the pre-clinical curriculum in the direct restoration module of the operative dentistry course using manual and digital methods.

METHODS

Thirty-two randomly selected year 2 undergraduate students were divided into two groups: group 1, exposed to the Moog Simodont dental trainer (VR) and group 2, no exposure to VR. All students were then evaluated in carrying out a Class I preparation in a single-blinded fashion. All preparations were evaluated by three assessors using a traditional manual approach and a digital software. Statistical analysis of the data was performed using chi-square test (alpha = 0.05).

RESULTS

The number of students who performed satisfactory preparations was more in group 1 (12/16), compared to group 2 (7/16). The percentage of satisfactory domains was significantly higher in group 1, compared to group 2, both in the manual evaluation (83.9% (94/112) and 59.8% (67/112) in groups 1 and 2, respectively) and in the digital evaluation (85.7% (96/112) and 55.4% (62/112) in groups 1 and 2, respectively) (P < .05). There was no significant difference between the manual and digital methods of evaluation with regard to the percentage of satisfactory or unsatisfactory preparations (P > .05).

CONCLUSIONS

The use of the Moog Simodont dental trainer (VR) significantly improved the satisfactory performance of students. The virtual reality simulator may be a valuable adjunct in the undergraduate direct restorations course and for remedial student.

Quality of root canal fillings using three gutta-percha obturation techniques

Objectives

The goal of this study was to compare the density of gutta-percha root fillings obturated with the following techniques: cold lateral (CL) compaction, ultrasonic lateral (UL) compaction, and warm vertical (WV) compaction.

Materials and Methods

Thirty-three extracted mandibular first molars, with two separate mesial canals in each, were selected. After instrumentation, the canals were stratified into three groups based on canal length and curvature, and underwent obturation with one of the techniques. No sealer was used in order to avoid masking any voids. The teeth were imaged pre- and post-obturation using micro-computed tomography. The reconstructed three-dimensional images were analyzed volumetrically to determine the amount of gutta-percha present in every 2 mm segment of the canal. P values < 0.05 were considered to indicate statistical significance.

Results

The overall mean volume fraction of gutta-percha was 68.51 ± 6.75% for CL, 86.56 ± 5.00% for UL, and 88.91 ± 5.16% for WV. Significant differences were found between CL and UL and between CL and WV (p < 0.05), but not between UL and WV (p = 0.526). The gutta-percha density of the roots treated with WV and UL increased towards the coronal aspect, but this trend was not noted in the CL group.

Conclusions

WV compaction and UL compaction produced a significantly denser gutta-percha root filling than CL compaction. The density of gutta-percha was observed to increase towards the coronal aspect when the former two techniques were used.

Efficacy of Needle, Ultrasonic, and Endoactivator Irrigation and Photon-Induced Photoacoustic Streaming in Removing Calcium Hydroxide from the Main Canal and Isthmus: An In Vitro Micro-Computed Tomography and Scanning Electron Microscopy Study

OBJECTIVE

The aim of this in vitro study was to use high-resolution micro-computed tomography (micro-CT) and scanning electron microscopy (SEM) to compare the efficacy of four irrigation techniques [needle, ultrasonic, EndoActivator, and photon-induced photoacoustic streaming (PIPS)] in removing calcium hydroxide (Ca[OH]2) from the root canal and isthmus of maxillary premolars.

METHODS

Twenty-four maxillary first premolars were selected based on the presence of isthmus regions on micro-CT scans. Root canals were instrumented with an F2 file using ProTaper rotary instruments and filled with Ca(OH)2 paste. Samples were stored at 37°C and 100% humidity for 1 week and randomly divided into four groups (n=6 each), according to irrigation technique. Samples were scanned with micro-CT before instrumentation, after Ca(OH)2 filling, and after irrigation. Ca(OH)2 reduction in the coronal, middle, and apical thirds and in the isthmus were assessed with three-dimensional image analysis. Next, specimens were split longitudinally, and canal walls were examined with SEM for Ca(OH)2 residues. Data were statistically evaluated with the Kruskal-Wallis and Mann-Whitney tests (p=0.05).

RESULTS

The PIPS and ultrasonic groups showed greater Ca(OH)2 reduction in the apical third and higher cleanliness of the isthmus than the EndoActivator and needle irrigation groups (p<0.05). Ca(OH)2 residue scores in the PIPS and ultrasonic groups were significantly lower than those in the EndoActivator and needle groups in all regions of the root canals (p<0.05). There was no significant difference between PIPS and ultrasonic groups (p>0.05), or between EndoActivator and needle groups (p>0.05).

CONCLUSIONS

PIPS and ultrasonic irrigation more effectively removed Ca(OH)2 from the main canal and isthmus in maxillary premolars than did EndoActivator or needle irrigation.

Blended learning in situated contexts: 3-year evaluation of an online peer review project

BACKGROUND

Situated and sociocultural perspectives on learning indicate that the design of complex tasks supported by educational technologies holds potential for dental education in moving novices towards closer approximation of the clinical outcomes of their expert mentors. A cross-faculty-, student-centred, web-based project in operative dentistry was established within the Universitas 21 (U21) network of higher education institutions to support university goals for internationalisation in clinical learning by enabling distributed interactions across sites and institutions. This paper aims to present evaluation of one dental faculty's project experience of curriculum redesign for deeper student learning.

METHODS

A mixed-method case study approach was utilised. Three cohorts of second-year students from a 5-year bachelor of dental surgery (BDS) programme were invited to participate in annual surveys and focus group interviews on project completion. Survey data were analysed for differences between years using multivariate logistical regression analysis. Thematic analysis of questionnaire open responses and interview transcripts was conducted.

RESULTS

Multivariate logistic regression analysis noted significant differences across items over time indicating learning improvements, attainment of university aims and the positive influence of redesign. Students perceived the enquiry-based project as stimulating and motivating, and building confidence in operative techniques. Institutional goals for greater understanding of others and lifelong learning showed improvement over time. Despite positive scores, students indicated global citizenship and intercultural understanding were conceptually challenging.

CONCLUSIONS

Establishment of online student learning communities through a blended approach to learning stimulated motivation and intellectual engagement, thereby supporting a situated approach to cognition. Sociocultural perspectives indicate that novice-expert interactions supported student development of professional identities.

Effect of chlorhexidine and ethanol-wet bonding with a hydrophobic adhesive to intraradicular dentine

PURPOSE

To evaluate the effect of adjunctive application of ethanol-wet bonding and chlorhexidine (CHX) with a hydrophobic adhesive on bond durability of fibre posts to intraradicular dentine.

METHODS

Ninety-six extracted human teeth with a single root and root canal were prepared for post placement after endodontic treatment. The teeth were randomly divided into four groups (n=24) after etching and rinsing for rewetting: Group 1: water-wet bonding, Group 2: water-wet bonding with CHX, Group 3: ethanol-wet bonding and Group 4: ethanol-wet bonding with CHX. Teeth in Groups 1 and 2 were treated with either distilled water or distilled water with 2% CHX for 60 s; while teeth in Groups 3 and 4 were treated with either 100% ethanol or 100% ethanol with 2% CHX. Two coats of primer, followed by neat resin were applied and light-cured for 40 s. Fibre posts were luted to bonded root dentine using dual-cure resin cement. Bonded roots were subjected to push-out bond strength testing and interfacial nanoleakage evaluation after 24 h, 6 and 12 months of storage. Data were analyzed using 3-way ANOVA (rewetting solutions, time and post space regions) and SNK tests.

RESULTS

Groups 3 and 4 showed significantly (p<0.05) higher bond strengths and lower nanoleakage than Groups 1 and 2 after 12 months of ageing. Addition of 2% chlorhexidine to ethanol-wet bonding with a hydrophobic adhesive did not further improve the bonding of a fibre post to intraradicular dentine, when compared to ethanol-wet bonding alone after 12 months of ageing.

CLINICAL SIGNIFICANCE

Ethanol-wet bonding with a hydrophobic adhesive alone could improve the bond durability of fibre post to intraradicular dentine and therefore would increase the success rate of post and core restorations of endodontically treated teeth.

Effect of culture media and nutrients on biofilm growth kinetics of laboratory and clinical strains of Enterococcus faecalis

OBJECTIVE

Enterococcus faecalis is a bacterial pathogen that is often associated with endodontic infections. Biofilm formation is a key virulence attribute in the pathogenicity of E. faecalis. In the present study, we comprehensively examined the effect of various culture media and nutrients on the development of E. faecalis biofilms.

DESIGN

A reference strain and a clinical isolate of E. faecalis were used in all experiments for comparison. Commonly used liquid culture media with different nutrient compositions were used to support the development of E. faecalis biofilms in a time-dependent assay. E. faecalis biofilms were quantified by colony forming unit (CFU) and crystal violet (CV) assays. Biofilm architecture and cellular viability were evaluated by scanning electron microscopy and confocal laser scanning microscopy.

RESULTS

Growth kinetics evaluated by CFU and CV assays and by microscopy showed that E. faecalis biofilms reached maturity at 72h. "Pg broth" (Tryptic Soy Broth with yeast extract, hemen and vitamin K) promoted E. faecalis biofilm formation more than Brain Heart Infusion broth or Tryptic Soy Broth. Addition of 2% glucose enhanced biofilm formation. Thus, it seems that nutrients such as hemen, vitamin K and glucose are important for E. faecalis for the formation of biofilms.

CONCLUSION

The present study demonstrated that nutrient-rich media containing glucose enhances the formation of E. faecalis biofilms, which exhibit maturation at 72h.