A laboratory study to assess the formation of effluent volatile compounds and disinfection by-products during chemomechanical preparation of infected root canals and application of activated carbon for their removal.

AIM: To assess in a laboratory setting using extracted teeth the formation of volatile compounds (VOCs) and disinfection by-products (DBPs) in effluent aliquots, during chemomechanical preparation of artificially infected root canal specimens, and determine the role of silver-impregnated activated carbon (Ag-AC) in their removal. METHODOLOGY: Single-rooted human teeth were decoronated to obtain 15 mm-long root specimens and a nutrient-stressed multispecies biofilm was grown in the root canals. Specimens were randomly assigned into three groups [Group 1; instrumentation with rotary files and irrigation with sterile saline, Groups 2 and 3; instrumentation with rotary files and irrigation with 2.5% NaOCl and 17% EDTA]. A portable medical suction device was used to collect the effluent aliquots during root canal irrigation. In Groups 1 and 2, the reaction products of the collected effluents were analysed by selected ion flow tube mass spectrometry (SIFT-MS). The effluents from Group 3 were treated with Ag-AC prior to SIFT-MS analysis, to assess the removal capacity of Ag-AC against the reaction products. The synthesis of Ag-AC was characterized with scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Two-way analysis of variance (anova) with post hoc Tukey tests was used for data analysis and determination of a significant difference (P < 0.05). RESULTS: In Group 1, effluent VOCs and DBPs were detectable at very low levels. In Group 2, the collected effluent aliquots released high concentrations of methanol, propanol, ammonia, chloroform and formaldehyde, which were significantly greater compared to Group 1 (P < 0.001). SEM/EDS analysis confirmed impregnation of Ag within the AC matrix. The treatment of effluent aliquots with Ag-AC (Group 3) resulted in a significant reduction in concentrations of acetone, acetic acid, propanol, acetaldehyde, acetonitrile and chloroform, compared to Group 2 (P < 0.001). The concentration levels of ethanol, methanol, ammonia and formaldehyde remained unaffected (P > 0.05). CONCLUSIONS: In this laboratory setting using extracted human teeth, the chemomechanical preparation of artificially infected root canals resulted in the formation of toxic VOCs and DBPs as effluent suspensions. Their release during aspiration with dental suction indicates that potential environmental hazards should be investigated. The use of silver-impregnated activated carbon had potential for the point-of-use treatment of post-irrigation effluent aliquots.

The restoration of root filled teeth: a review of the clinical literature.

Clinicians often face dilemmas regarding the most appropriate way to restore a tooth following root canal treatment. Whilst there is established consensus on the importance of the ferrule effect on the predictable restoration of root filled teeth, other factors, such as residual tooth volume, tooth location, number of proximal contacts, timing of the definitive restoration and the presence of cracks, have been reported to influence restoration and tooth survival. The continued evolution of dental materials and techniques, combined with a trend towards more conservative endodontic-restorative procedures, prompts re-evaluation of the scientific literature. The aim of this literature review was to provide an updated overview of the existing clinical literature relating to the restoration of root filled teeth. An electronic literature search of the PubMed, Ovid (via EMBASE) and MEDLINE (via EMBASE) databases up to July 2020 was performed to identify articles that related the survival of root filled teeth and/or restoration type. The following and other terms were searched: restoration, crown, onlay, root canal, root filled, post, clinical, survival, success. Wherever possible, only clinical studies were selected for the literature review. Full texts of the identified articles were independently screened by two reviewers according to pre-defined criteria. This review identifies the main clinical factors influencing the survival of teeth and restorations following root canal treatment in vivo and discusses the data related to specific restoration type on clinical survival.

A prospective study on the effect of coronal tooth structure loss on the 4-year clinical survival of root canal retreated teeth and retrospective validation of the Dental Practicality Index.

AIM: First, to examine the impact of the residual volume of coronal tooth structure in posterior teeth measured with an intra-oral scanner on the 4-year clinical survival of root canal retreated teeth. Secondly, to assess retrospectively the effectiveness of the Dental Practicality Index (DPI) in predicting the survival of root canal retreated teeth. METHODOLOGY: A total of 156 posterior root canal treated teeth (140 patients) had baseline periapical radiographs (PA) and cone-beam computed tomography (CBCT) scans taken prior to root canal retreatment. These teeth were followed up with a clinical examination at 1, 2, 3 and 4 years (T12, T24, T36 and T48) with periapical radiographs and CBCT images taken at T12, and PA taken at T24, T36 and T48 where appropriate. Root canal retreated teeth were dichotomized into 'survived' versus 'extracted'. Fisher's exact test was used to determine the association between the volume of remaining coronal tooth structure and the 4-year tooth survival. The Dental Practicality Index for each tooth was established using the preoperative clinical and radiographical data. Fisher's exact test was used to establish a relationship between categorical variables, the total score of DPI vs tooth outcome. RESULTS: The percentage of extractions associated with teeth with <29.5% remaining coronal tooth structure was 3 times higher (12.5%) compared to that of teeth with a residual tooth structure > 29.5% (3.5%), but with no significant difference (P = 0.073). There was a significant correlation between the outcome of root canal retreatments at 1 year, assessed by both PA and CBCT, and the 4-year survival (Fisher's exact test, P = 0.007 and P = 0.001, respectively). Teeth with DPI scores ≥ 6 were more likely to be extracted than teeth with DPI score < 6 (18.8% vs. 3.9%) (Fisher's exact test, P = 0.045). CONCLUSION: Teeth with <30% of remaining tooth structure were associated with a survival rate above 80% and teeth with more than 30% of residual tooth structure survived in more than 94% of the cases. The radiographic outcome of root canal treatment can also help to predict tooth survival with teeth having an unfavourable outcome at 1 year more likely to be extracted within 4 years of completion of treatment. The DPI score can potentially be used to identify teeth with failed root canal treatment, which are likely to be extracted following retreatment and cuspal coverage.

Ex vivo detection and quantification of apically extruded volatile compounds and disinfection by-products by SIFT-MS, during chemomechanical preparation of infected root canals.

OBJECTIVES: To assess the release and apical extrusion of toxic volatile compounds and disinfection by-products during instrumentation and irrigation of artificially infected root canal specimens, with sodium hypochlorite and ethylene diamine tetra acetic acid. METHODS: Forty-two single-rooted human teeth were decoronated to obtain 15mm-long root specimens and working length was determined 1mm short of root apex. All specimens were initially preflared, to create sufficient conical space for the development of a nutrient-stressed multispecies biofilm. The specimens were randomly assigned into three groups [Group 1; no endodontic intervention, Group 2; instrumentation with rotary files and irrigation with sterile saline, Group 3; instrumentation with rotary files and irrigation with 2.5% sodium hypochlorite (NaOCl) and 17% ethylene diamine tetra acetic acid (EDTA)]. A customised experimental model apparatus was fabricated for each specimen. The apical root third was inserted in a glass vial filled with sterile ultrapure water, to simulate high-compliance periradicular space. The reaction products of the aliquots obtained from the glass vials were analysed in real time, by selected ion flow tube mass spectrometry (SIFT-MS) in triplicates. Two-way analysis of variance (ANOVA) with post hoc Tukey tests were used for data analysis. The level of statistical significance was set at P<0.05. RESULTS: The group of teeth that were not subjected to endodontic intervention did not show any volatile compounds (VOCs) or disinfection by products (DBPs) whilst instrumentation and irrigation of root canals (Groups 2 and 3) resulted in the apical extrusion of VOCs and DBPs. In Group 3, the aliquots obtained from periradicular space released high concentrations of methanol, propanol, ammonia, chloroform, together with unexpected higher levels of formaldehyde, which were statistically significant compared to Group 2 (P<0.05). SIGNIFICANCE: The mechanical preparation and irrigation of artificially infected root canals with rotary files, 2.5% NaOCl and 17% EDTA resulted in the formation of toxic VOCs and DBPs in a water-closed periradicular space. The chemical interaction of NaOCl and EDTA resulted in the generation of high concentrations of formaldehyde. The formation of chloroform and formaldehyde indicate that risk assessment of the potential hazards to health should be carried out.

European Society of Endodontology position statement: Use of cone beam computed tomography in Endodontics: European Society of Endodontology (ESE) developed by.

This Position Statement represents a consensus of an expert committee convened by the European Society of Endodontology (ESE) on the use of Cone Beam Computed Tomography (CBCT) in Endodontics. This paper is an update of the ESE CBCT position statement which was published in 2014 (European Society of Endodontology 2014, https://doi.org/10.1111/iej.12267). Recent review articles provide more detailed background information and the basis for this position statement. It is intended that this position statement will be updated at least every 4-5 years to keep abreast of relevant research. The aim of this paper is to provide clinicians with evidence-based guidance on the application of CBCT in Endodontics. Since 2014, there has been an increase in the number of clinical studies confirming the positive impact of CBCT on treatment planning, decision-making when reviewing cases and reduced practitioner stress levels.

Validation of the effectiveness of the Dental Practicality Index in predicting the outcome of root canal retreatments.

AIM: To assess the effectiveness of the Dental Practicality Index (DPI) in predicting the outcome of root canal retreatment in posterior teeth. METHODOLOGY: One hundred and thirty-seven posterior teeth with symptoms and/or signs of post-treatment endodontic disease requiring root canal retreatment and previously included in a clinical trial were selected. Clinical and radiographic examinations including digital periapical and cone beam computed tomography (CBCT) were obtained pre-treatment and 1-year postoperatively from a previous study. Two calibrated and trained assessors who were unaware of the treatment outcome assessed the pre-treatment clinical records of these cases using the DPI. The DPI score was then compared to the outcome of the root canal retreatment. A Chi-square/Fisher's exact test was used to establish a relationship between categorical variables, the total score of DPI vs outcome. RESULTS: Retreated teeth with DPI scores equal to 6 or above had an unfavourable outcome of 50% vs 14% of teeth with DPI below 6. Teeth with DPI score equal to 3 or above had an unfavourable outcome of 23% versus 2%, for teeth below 3. Molar teeth with a DPI score below 3 had a favourable outcome percentage of 96%. CONCLUSIONS: This study highlighted that using the DPI gave a good outcome prediction for root canal retreatments. However, further research, including the prospective assessment of a wider range of cases undertaken by a larger group of examiners is needed to further validate the DPI.

Unconscious Racial Bias May Affect Dentists' Clinical Decisions on Tooth Restorability: A Randomized Clinical Trial.

METHODS: In this single-center cross-sectional survey, 57 dentists were given a clinical scenario in combination with a patient's relevant clinical photographs and radiographs depicting either a Black or White patient presenting with a decayed tooth and associated symptoms of irreversible pulpitis. Explicit bias was measured through a questionnaire, which evaluated participants' course of treatment, strength of recommendation, and their perception of patients' dental cooperativeness. Implicit bias was evaluated through brief implicit associate tests. RESULTS: Recommendation for root canal treatment (RCT) in the White patient condition was significantly higher than in the Black patient condition (χ2 = 4.77, P < 0.05). Overall, participants were significantly more likely to recommend root canal treatment to White patients (t = 2.46, P = 0.0172) and significantly more likely to recommend extraction for Black patients (t = 3.03, P = 0.0034). In total, 91.23% and 78.95% of all participants displayed high Brief Implicit Association Test race and cooperation scores, respectively, showing a pro-White bias in both categories. This trend was shown to be irrespective of the patient condition. CONCLUSIONS: Dentists' decision making was affected by the race of the patient, resulting in a greater likelihood of extractions (less RCT) for Black patients presenting with a broken-down tooth and symptoms of irreversible pulpitis. KNOWLEDGE TRANSFER STATEMENT: The results of this study can be used by clinicians to understand the impact that unconscious racial bias may have on their treatment planning decisions. This information can create awareness, thereby reducing the impact that potential biases can have on the treatment patients receive.

Self-Limiting versus Conventional Caries Removal: A Randomized Clinical Trial.

A single-blind randomized controlled clinical trial in patients with deep caries and symptoms of reversible pulpitis compared outcomes from a self-limiting excavation protocol using chemomechanical Carisolv gel/operating microscope (self-limiting) versus selective removal to leathery dentin using rotary burs (control). This was followed by pulp protection with mineral trioxide aggregate (MTA) and restoration with glass ionomer cement and resin composite, all in a single visit. The pulp sensibility and periapical health of teeth were assessed after 12 mo, in addition to the differences in bacterial tissue concentration postexcavation. Apical radiolucencies were assessed using cone beam computed tomography/periapical radiographs (CBCT/PAs) taken at baseline 0 mo (M0) and 12 mo (M12). In total, 101 restorations in 86 patients were placed and paired subsurface, and deep (postexcavation) dentin samples were obtained. DNA was extracted and bacteria-specific 16S ribosomal RNA gene quantitative polymerase chain reaction was performed. No significant difference was found in bacterial copy numbers normalized to mass of dentin ("bacterial tissue concentration") between the self-limiting (96.3% reduction) and control protocols (97.1%, P = 0.33). The probability of 12-mo success was 4 times (odds ratio [OR] = 4.33; confidence interval [CI], 1.2-15.6; P = 0.025) higher in the self-limiting protocol compared to the control (conventional excavation technique), with pulp survival rates of 73.3% and 90%, respectively ( P = 0.049). Molars had a 4 times higher probability of success compared to premolars (OR, 4.17; CI, 1.17-14.9; P = 0.028), and symptom severity did not statistically predict outcome (OR, 0.41; CI, 0.12-13.9, P = 0.153). CBCT detected significantly more periapical (PA) lesions than PA radiographs at the baseline visit ( P < 0.001). In conclusion, the self-limiting caries excavation protocol under magnification increased pulp survival rate compared to rotary bur excavation ( ClinicalTrials.gov NCT03071588).

The comparative effectiveness and safety of three activated irrigation techniques in the isthmus area using a transparent tooth model.

AIM: To compare the effectiveness and safety of three activated irrigation techniques when removing pulp tissue from the isthmus of a transparent tooth model. The three techniques assessed were: the EndoVac (EV), passive ultrasonic irrigation (PUI) and ultrasonic wave aspiration (TUWA). Conventional syringe irrigation (CSI) was used as a control. METHODOLOGY: A transparent tooth model was created using the mesial root of an extracted mandibular first molar that had an isthmus and two independent mesial canals. An artificial 0.3-mL cylindrical chamber was created below the apical foramen. The tooth was then cleared. After preparation, the root canals were filled with fuchsine-stained bovine pulp tissue. The irrigation protocols were compared in respect of their effectiveness at removing pulp tissue from the isthmus and their safety with regard to irrigant extrusion. For all four groups, 5.25% sodium hypochlorite solution was used as the irrigant. Photographs were taken and analysed using an imaging software. A Kruskal-Wallis test was used to detect the differences between groups (statistical significance was set at P < 0.05). RESULTS: No group was associated with extrusion of irrigant beyond the apex. Significant differences were observed between the groups: TUWA was the most effective technique at removing pulp tissue from the isthmus (3.39 mm2 ; standard deviation (SD) = 0.67; range = 1.25-3.69), followed by PUI (2.16 mm2; SD = 0.38; range = 1.37-2.96), EV (0.73 mm2 ; SD = 0.14; range = 0.49-0.98) and CSI (0.27 mm2 ; SD = 0.01; range = 0.26-0.28). CONCLUSION: Ultrasonic wave aspiration was the most effective technique at removing artificial pulp tissue from the isthmus of a transparent tooth model. None of the techniques extruded irrigant.

Pooled analysis of 1-year recall data from three root canal treatment outcome studies undertaken using cone beam computed tomography.

AIM: To provide an estimate of the proportion of successful outcomes of primary and secondary root canal treatments (retreatments) determined by periapical radiographs and cone beam computed tomography (CBCT), a pooled analysis of the data collected from three previous prospective clinical outcome studies was undertaken. METHODOLOGY: The analysis pooled the 1-year results for 354 teeth, including 123 primary treatments and 231 retreatments. All root canals were instrumented with ProTaper Universal and filled using a warm vertical condensation technique. Comparisons of favourable results between root canal treatments and retreatments and between different tooth types were made using chi-square/Fisher's exact test. RESULTS: The overall percentage of favourable results was 91% using periapical radiographs and 80% for CBCT (P < 0.001). With CBCT, the percentage of favourable results for primary treatments (84.7%) was not significantly different (P = 0.316) from that of retreatments (77.9%). When assessed by tooth group, the overall percentage of favourable results with CBCT was 75.5%, 90.6% and 91.1% for molar, premolar and anterior teeth, respectively. When CBCT is used to assess the outcome, the proportion of favourable outcomes in molars was significantly lower than that of premolars and anterior teeth (P < 0.05). Teeth with root fillings terminating more than 2 mm short of the radiographic apex had less favourable outcomes (73%) compared to long (83%) and adequate root filling length (84%). CONCLUSIONS: The proportions of favourable outcomes of primary root canal treatments and retreatments assessed with CBCT were lower when compared to periapical radiographs, and also lower than those historically reported by periapical radiograph-based outcome studies. Considering the very high favourable outcome of anterior teeth and premolars compared to molar teeth, future studies assessing the effect of new materials and techniques on the outcome of root canal treatments should be based on preoperative and postoperative CBCT images, and focus on molar teeth.

External cervical resorption: a three-dimensional classification.

This article describes a novel three-dimensional classification for external cervical resorption (ECR). The European Society of Endodontology and American Association of Endodontists & American Academy of Oral & Maxillofacial Radiology position statements advise that Cone beam computed tomography should be considered for the assessment and/or management of root resorption if it appears to be clinically amenable to treatment following clinical and conventional radiographic examination. The new classification takes into account the ECR lesion height (1: at CEJ level or coronal to the bone crest (supracrestal), 2: extends into the coronal third of the root and apical to the bone crest (subcrestal), 3: extends into the mid-third of the root, 4: extends into the apical third of the root), circumferential spread (A: ≤90° B: ≤180° C: ≤270° D: >270°) and proximity to the root canal (d: lesion confined to dentine, p: probable pulpal involvement), thus classifying ECR in three dimensions. At present, there is no classification to accurately describe ECR. This novel and clinically relevant three-dimensional classification should allow effective and accurate communication of ECR lesions between colleagues. It will also allow the effect of the nature of ECR on the outcome of treatment to be assessed objectively.

Rapid Bacterial Detection during Endodontic Treatment.

Bacteria present in the root canal (RC) space following an RC treatment (RCT) can lead to persistent infections, resulting in treatment failure and the need for reintervention or extraction. Currently, there are no standardized methods in use to clinically detect bacterial presence within RC spaces. The use of paper point sampling and fluorescence staining was shown to be a rapid method, able to detect residual bacteria following treatment. The study demonstrated that Calcein acetoxymethyl (AM) proved to be a suitable dye for detecting vital bacteria within mature endodontic biofilms, with an improved sensitivity over colony-forming unit counting in a stressed biofilm model. Furthermore, in a clinical trial with primary RCTs, 53 infected teeth were sampled in vivo, and increased detection of vital cells was found when compared with colony-forming unit counting, highlighting the sensitivity of the technique in detecting low cell numbers. By combining fluorescent staining and microspectroscopy with software-based spectral analysis, successful detection of vital cells from RCs was possible after 5 min of Calcein AM incubation. Application of this technology during RCT has the potential to reduce persistent infections through vital cell detection and additional treatment. Furthermore, this technique could be applied to antimicrobial research and disinfection control in clinical settings ( ClinicalTrials.gov NCT03055975).

Evaluation of dental adhesive systems incorporating an antibacterial monomer eugenyl methacrylate (EgMA) for endodontic restorations.

OBJECTIVE: The purpose of this study was to incorporate EgMA, an antibacterial monomer into two commercial dental adhesive systems for their application in endodontic restoration with the aim to disinfect the root canal space before curing and to inhibit bacterial growth on their surfaces after being cured. METHODS: EgMA monomer was added at 20%wt. into the formulation of the single-component self-etch, Clearfil Universal Bond™ (CUB) and into the catalyst and the adhesive components of the total-etch Adper Scotchbond-multipurpose™ (SBMP) adhesive systems. The degree of conversion (DC) was calculated from FTIR spectra, glass transition temperature (Tg) determined by DSC, water sorption and solubility were measured gravimetrically, and surface free energy (SFE) via contact angle measurements. The bonding performance to coronal and middle root canal dentin was assessed through push-out bond strength after filling the canals with a composite core material and the surface integrity was observed using SEM and confocal laser scanning microscopy (CLSM). The standard agar diffusion test (ADT) was used to identify the sensitivity of three endodontically pathogenic bacteria, Enterococcus faecalis, Streptococcus mutans and Propionibacterium acnes to uncured EgMA modified adhesives. Multispecies biofilm model from these strains was grown on the disc surface of cured adhesives and investigated using quantitative microbial culture and CLSM with live/dead staining. MTT assay was also used to determine the cytotoxicity of these adhesives. RESULTS: The incorporation of EgMA lowered polymerization exotherm and enhanced the hydrophobic character of these adhesives, without changing the DC and Tg in comparison to the controls (without EgMA). The total push-out bond strengths of the EgMA-containing adhesives were not significantly different from those of the controls (p>0.05). The modification of self-etch adhesive system enhanced the bond strength in the middle region of the roots canal. SEM of debonded specimens and CLSM examination showed the integrity of the resin-dentin interfaces. For all three bacteria tested, the sizes of the inhibition zones produced by uncured EgMA modified adhesives were significantly greater (p<0.05) than those of the controls. The results of biofilm inhibition tests showed less CFU for total bacteria on bonding agents with EgMA compared to the control materials (p<0.05). The modification at 20% monomer concentration had no adverse effects on cytocompatibility of both adhesives tested. SIGNIFICANCE: The inclusion of EgMA endows dental adhesives with effective antibacterial effects without influencing their curing properties, bonding ability to root canal dentin, and cytotoxicity against human gingival fibroblasts, indicating the usefulness of their application in endodontic restorations.

A prospective study assessing the effect of coronal tooth structure loss on the outcome of root canal retreatment.

AIM: To evaluate the outcome of secondary root canal treatment (retreatment) on posterior teeth in relation to the residual volume of coronal tooth structure, measured with an intraoral scanner, using periapical radiography and cone beam computed tomography (CBCT). METHODOLOGY: A total of 137 posterior teeth in 121 patients were assessed clinically and radiographically using periapical radiographs and CBCT scans at baseline and 1 year after root canal retreatment. The increase or decrease in the size of preoperative periapical radiolucencies and development of new radiolucencies were assessed by a consensus panel consisting of two pre-calibrated examiners. A clinical impression was obtained for each tooth after completion of root canal retreatment, before the placement of the temporary restoration and following cast restoration placement to produce two casts. All casts were scanned using an intraoral digital scanner and the three-dimensional volume of remaining tooth structure calculated. Teeth were also classified according to the number of remaining coronal walls before core build-up. χ2 test was used to determine the association between the outcome of root canal retreatments and the volume of remaining coronal tooth structure. RESULTS: At the 1-year recall, teeth retaining less than 30% of their original tooth structure volume had a significantly higher proportion of unfavourable outcomes (χ2 , P < 0.05, odds ratio [OR], 2.58; 95% CI, 1.026-6.487). CONCLUSIONS: The loss of tooth structure volume is an objective parameter that can be used to predict the probability of success of root canal retreatments. At 1-year follow-up, the percentage of unfavourable outcomes of root canal retreated teeth was significantly higher when less than 30% of the original tooth tissue structure was present at baseline.

Diagnostic accuracy of periapical radiography and cone beam computed tomography in detecting apical periodontitis using histopathological findings as a reference standard.

AIM: To compare the diagnostic accuracy of periapical radiography (PR) and cone beam computed tomography (CBCT) in detecting apical periodontitis (AP) using histopathological findings as a reference standard. METHODOLOGY: Jaw sections containing 67 teeth (86 roots) were collected from unclaimed bodies due for cremation. Imaging was carried out to detect AP by digital PR with a central view (DP group), digital PR combining central with 10˚ mesially and distally angled (parallax) views (DPS group) and CBCT scans. All specimens underwent histopathological examination to confirm the diagnosis of AP. Sensitivity, specificity and predictive values of PR and CBCT were analysed using rater mean (n = 5). Receiver-operating characteristic (ROC) analysis was carried out. RESULTS: Sensitivity was 0.27, 0.38 and 0.89 for DP, DPS and CBCT scans, respectively. CBCT had specificity and positive predictive value of 1.0 whilst DP and DPS had specificity and positive predictive value of 0.99. The negative predictive value was 0.39, 0.44 and 0.81 for DP, DPS and CBCT scans, respectively. Area under the curve (AUC) for the various imaging methods was 0.629 (DP), 0.688 (DPS), and 0.943 (CBCT). CONCLUSIONS: All imaging techniques had similar specificity and positive predictive values. Additional parallax views increased the diagnostic accuracy of PR. CBCT had significantly higher diagnostic accuracy in detecting AP compared to PR, using human histopathological findings as a reference standard.

Comparison of centring ability and transportation between four nickel titanium instrumentation techniques by micro-computed tomography.

AIM: To compare the centring ability and transportation of ProTaper Next (PTN), ProTaper Universal (PTU), Race 123 and RevoS using micro-computed tomography (µCT). METHODOLOGY: Sixty mesial root canals of thirty mandibular molars were divided virtually into coronal, middle and apical thirds, and two reproducible reference points were marked on the external surface of the roots creating 360 measurement points. Samples were randomly allocated to four NiTi instrumentation techniques. Group 1: PTU up to F2 (n = 16), group 2: PTN up to X2 (n = 18), group 3: Race 123 up to T2 (n = 12) and group 4: RevoS up to SU (n = 14). To reproduce a clinical situation, samples were prepared on a phantom head using a surgical operating microscope. Samples were scanned pre- and postoperatively using µCT to compare and calculate the transportation and centring ratio. The data were analysed using parametric statistics. RESULTS: In the coronal and middle third of the root canals, there were significant differences in centring between PTN and PTU (coronal P < 0.001), PTN and RevoS (coronal P < 0.001), Race and PTU (coronal P < 0.01), Race and RevoS (coronal P < 0.01), PTN and RevoS (middle P < 0.01) and Race and RevoS (P < 0.05). Furthermore, there were significant differences in centring between PTN root canal preparations and other instruments in the apical third (PTN and PTU P < 0.01, PTN and Race P < 0.001, PTN and RevoS P < 0.001). In terms of transportation, in the coronal third, there was a significant difference between PTN and PTU (P < 0.05). However, there were no significant differences between the other instruments. In the middle third, significant differences were observed between PTN and PTU (P < 0.05), PTN and RevoS (P < 0.05), Race and PTU (P < 0.05) and Race and RevoS (P < 0.05). However, there were no significant differences between other systems. There was no significant difference in terms of transportation between the four systems in the apical third. CONCLUSIONS: ProTaper Next prepared more centred root canal shapes when compared with Race, PTU and RevoS. In the coronal and middle third of the root canals, the differences in centring between PTN and PTU/RevoS were significant. PTN root canal preparations were more centred than those achieved with all other instruments in the apical third.

Influence of a polymerizable eugenol derivative on the antibacterial activity and wettability of a resin composite for intracanal post cementation and core build-up restoration.

OBJECTIVES: Eugenol has been used in dentistry due to its ability to inhibit the growth of a range of microorganisms, including facultative anaerobes commonly isolated from infected root canals. The aim of this study was to evaluate the antibacterial activity of the experimental composites containing eugenyl methacrylate monomer (EgMA), a polymeric derivative of eugenol, against a range of oral bacteria, commonly associated with failure of coronal and endodontic restorations. In vitro composite behavior and wettability were also studied in conjunction with their antibacterial activity. METHODS: EgMA monomer (5 and 10% by weight) was added into BisGMA/TEGDMA resin based formulations with filler mixtures of hydroxyapatite (HA) and zirconium oxide ZrO2. The antibacterial activity of the experimental composites against Enterococcus faecalis, Streptococcus mutans and Propionibacterium acnes were evaluated by direct contact test and compared with composite formulation without inclusion of EgMA. To clarify the antibacterial mode of action, agar diffusion test (ADT) was also performed. Water sorption, solubility, diffusion coefficient, contact angle and surface free energy as complementary clinically relevant properties were determined. RESULTS: Water sorption and wettability studies showed reduction of water uptake and surface free energy values with increasing content of EgMA monomer, resulting in significant increase in the hydrophobicity of the composites. No inhibition zones were detected in any of the composites tested against the three bacteria employed as expected, due to the absence of any leachable antibacterial agent. The covalently anchored EgMA monomer with the composite surface exhibited an effective bacteriostatic activity by reducing the number of CFUs of the three species of bacteria tested with no significant dependence on the concentration of EgMA at 5 and 10% by weight. The surface antibacterial activity R of the experimental composites were different against the three tested species with values in the range 2.7-6.1 following the order E. faecalis