Antimicrobial efficacy of DJK-5 peptide in combination with EDTA against biofilms in dentinal tubules: Primary irrigation, recovery and re-irrigation.

AIM: To investigate the dynamic recovery of biofilms within dentinal tubules after primary irrigation with different protocols, and to evaluate the efficacy of various re-irrigation protocols on recovered biofilm, considering factors such as smear layer, nutrient conditions, and primary irrigants. METHODOLOGY: A total of 416 mono or multi-species biofilms samples were prepared from human teeth and incubated for 3 weeks. After inducing a smear layer on half of the samples, all specimens were irrigated with one of the following irrigant sequences: (1) 6% NaOCl +17% EDTA, (2) 6% NaOCl +8.5% EDTA, (3) 6% NaOCl and (8.5% EDTA +10 µg/mL DJK-5 antimicrobial peptide), or (4) sterile water. Thirty-two samples were used to assess immediate effect, whilst the rest were re-incubated to assess biofilms recovery. Nutrient conditions were defined based on whether culture media were changed (nutrient-rich) or not (nutrient-poor) during re-incubation. After 16 weeks, recovered biofilms underwent re-irrigation using four additional protocols, with or without DJK-5 peptide, based on primary irrigants. Confocal laser scanning microscopy was employed to evaluate immediate irrigant effects, biofilms recovery intervals (1, 3, 5, 8, 12, and 16 weeks after primary irrigation), and re-irrigation effects at the 16-week. Statistical analysis included one-way anova and two-way mixed anova tests. RESULTS: The DJK-5 peptide irrigation protocols demonstrated the highest killing rates during primary irrigation and resulted in a longer biofilms recovery time of 16 weeks compared to non-peptide protocols (p < .001). Both primary irrigation type and smear layer presence significantly influenced biofilms recovery (p < .001). In the absence of smear layer, re-irrigation efficacy didn't significantly differ from primary irrigation, regardless of primary irrigation type or nutrient conditions. However, with a smear layer present, re-irrigation led to significantly higher proportion of dead bacteria compared to primary irrigation (p < .05). Inclusion of the DJK-5 peptide into the re-irrigation protocol displayed superior killing rate compared to other protocols (p < .001). CONCLUSIONS: Biofilms exhibited susceptibility to both peptide and non-peptide protocols during re-irrigation, irrespective of nutrient conditions or primary irrigation protocols. The DJK-5 peptide irrigation protocols consistently displayed superior effectiveness compared to non-peptide protocols.

Antimicrobial effects of agitational irrigation on single- and multispecies biofilms in dentin canals.

This study aimed to compare the antibacterial effects of different agitation devices on single- and multispecies biofilms in dentin canals using confocal laser scanning microscopy (CLSM). Dentin blocks were prepared from human root dentin. Enterococcus faecalis and multiple species were introduced into the dentinal tubules via centrifugation and incubation. Two infected dentin samples were placed at 8 and 16 mm in a customized model. Samples were randomly divided into eight groups according to the agitation device used: syringe needle irrigation, EndoActivator, passive ultrasonic irrigation (PUI), and EDDY, at 2.5% or 6% NaOCl concentrations. The samples were stained and observed using CLSM. Statistical analysis was performed using an independent sample t test and analysis of variance. Linear models were used to assess the joint impact of the experimental groups on the proportion of biofilms killed. No significant differences were observed between the killing rates of the single- and multispecies biofilms. Both concentrations of NaOCl significantly increased the percentage of dead bacteria compared with the control. Biofilms in dentin tubules was more effectively killed when NaOCl was agitated; however, the difference between PUI and EDDY was not significant. Significantly more bacteria were killed in dentin blocks placed at 8 mm than at 16 mm (p < 0.05). In conclusion, EDDY was as effective as PUI when combined with NaOCl. However, the apical portion, which had a low antimicrobial efficiency, remains a concern. Mechanical instrumentation is incapable of completely eradicating bacteria, and additional research is required to improve the efficacy of root canal disinfection.

The effect of acidity on the physicochemical properties of two hydraulic calcium silicate-based cements and two calcium phosphate silicate-based cements.

BACKGROUND: Bioceramic cements have been widely used in endodontic treatment. This study aimed to compare the microhardness, elastic modulus, internal microstructure and chemical compositions of Biodentine, WMTA, ERRM Putty, iRoot FS and IRM after exposure to PBS, butyric acid, and butyric acid followed by PBS. METHODS: Specimens of each material were prepared and randomly divided into 5 subgroups (n = 5): subgroup A: PBS (pH = 7.4) for 4 days, subgroup B: PBS (pH = 7.4) for 14 days, subgroup C: butyric acid (pH = 5.4) for 4 days, subgroup D: butyric acid (pH = 5.4) for 14 days, subgroup E: butyric acid for 4 days followed by 10 days in contact with PBS. The surface microhardness, elastic modulus, internal morphologic and chemical compositions of specimens were analyzed. RESULTS: The microhardness and elastic modulus values of all materials were significantly higher in the presence of PBS compared to exposure to butyric acid, with the same setting time (P < 0.01). After 4-day exposure to butyric acid followed by 10-day exposure to PBS, the microhardness values returned to the same level as 4-day exposure to PBS (P > 0.05). Biodentine showed significantly higher microhardness and elastic modulus values than other materials, while IRM displayed the lowest (P < 0.01). CONCLUSION: Biodentine seems the most suitable bioceramic cements when applied to an infected area with acidic pH. Further storage at neutral pH, e.g. PBS reverses the adverse effects on bioceramic cements caused by a low pH environment.

External cervical resorption - Treatment outcomes and determinants: A retrospective cohort study with up to 10 years of follow-up.

AIM: To assess long-term external cervical resorption (ECR) treatment outcomes in relation to both local and treatment-related determinants. METHODOLOGY: Information was available for 76 patients (98 teeth) who were diagnosed with ECR during the period from 2008 to 2018 at the University of British Columbia graduate endodontics clinic. The ECR patients were followed up, and a clinical and radiographic examination was conducted. Chi-square test compared failure rates amongst different subgroups. The survival analysis was used to evaluate the overall ECR survival/failure rates in relation to several local and treatment-related determinants. RESULTS: Overall, 67 patients (89 teeth) were followed up. The mean follow-up time was 3.9 years, and the minimum was 1 year. Twenty-four teeth failed (19 extracted, 5 not functional), and the overall probability of failure was 50.0% 8 years after the diagnosis. Significant (p < .05) local ECR determinants were tooth location and the Heithersay classification, and treatment-related determinants were root canal treatment (RCT) and the ECR repair combined with RCT. Treatment outcomes for Heithersay class 1 and 2 cases were better than for class 3 and 4 cases. CONCLUSIONS: Higher failure rates were associated with posterior tooth location and higher Heithersay class, whilst RCT and ECR repair combined with RCT were associated with lower failure rates.

Long-term porosity and retreatability of oval-shaped canals obturated using two different methods with a novel tricalcium silicate sealer.

OBJECTIVE: To evaluate the percentage volume of voids and gaps in oval-shaped canals obturated using two different methods with a tricalcium silicate-based sealer after short- or long-term storage. The long-term effect of storage on the efficiency of removing filling material was also investigated. MATERIALS AND METHODS: Forty premolar teeth with oval-shaped canals were instrumented to Reciproc R25 and obturated using single cone obturation (SCO) or warm vertical compaction (WVC) techniques with gutta-percha and HiFlow sealer. The specimens were stored at 100% humidity and 37°C for 2 weeks or 6 months and scanned using micro-computed tomography. Initial retreatment was performed up to a Reciproc R40, and the operating time was recorded. The residual material in the canal received a supplementary procedure using XP-endo Finisher R (XPFR) files. After each retreatment procedure, the specimens were rescanned. RESULTS: The percentage volume of voids and gaps in the SCO group was higher than that of the WVC group at both 2 weeks and 6 months (P < 0.05). The percentage volume of the filling material removed after initial retreatment and XPFR cleaning was significantly higher in the 6-month group than in the 2-week groups (P < 0.05). The proportion of the residual material decreased significantly when XPFR files were used, compared to the initial retreatment group (P < 0.05) in both storage times. CONCLUSION: The efficiency of retreatment in the oval-shaped canal was closely related to the storage time rather than the filling technique using a tricalcium silicate sealer. The XPFR instrument proved effective in the removal of the remaining materials from the oval-shaped canal. CLINICAL RELEVANCE: Obturation of the oval-shaped canal with TSBS using the SCO technique in the coronal area needs to be optimized. The retreatment was less efficacious in freshly filled canals than aged filled canals.

The ability of different irrigation methods to remove mixtures of calcium hydroxide and barium sulphate from isthmuses in 3D printed transparent root canal models.

The purpose is to evaluate the efficacy of different irrigation techniques in the removal of various calcium hydroxide [Ca(OH)2] and barium sulfate [BaSO4] formulations from three isthmuses in 3-dimensional (3D) printed molar root canal models. 3D printed transparent models were designed, fabricated, and filled with pure Ca(OH)2 paste, Ca(OH)2-BaSO4 8:1 paste, Ca(OH)2-BaSO4 1:1 paste, pure BaSO4 paste, all in water, and Diapaste. Open-ended needle irrigation (ONI) at 5 and 15 mL/min, double-side-vented needle irrigation (DNI) at 5 mL/min, the GentleWave system (GW), PiezoFlow (PF), and passive ultrasonic activation (PUI) with distilled water, 0.5% sodium hypochlorite (NaOCl) and 3% NaOCl were used to remove the materials from the isthmuses. Ninety groups (n = 10) were established. The removal time was recorded from the start of irrigation to the completion of removal. GW and PF were the only methods that removed all tested materials from the isthmuses. PF required 2-3 × as much time as GW for complete removal, depending on the BaSO4 content of the paste. ONI at 15 mL/min removed pure Ca(OH)2 paste, Ca(OH)2-BaSO4 (8:1) paste, Ca(OH)2-BaSO4 (1:1) completely but could not completely remove pure BaSO4 paste and Diapaste. PUI with intermittent needle irrigation, ONI, and DNI at 5 mL/min were not able to completely remove any of the materials within 7.5 min. The GW removed all materials faster than PF, whereas other methods failed to remove all materials from the isthmuses. Pure Ca(OH)2 and the mixture with BaSO4 paste in the proportion 8:1 were removed in less time than the other mixtures by the GW, PF and ONI systems, the latter only when using 15 mL/min flow rate.

Epidermal growth factor receptor signaling suppresses αvß6 integrin and promotes periodontal inflammation and bone loss.

In periodontal disease (PD), bacterial biofilms cause gingival inflammation, leading to bone loss. In healthy individuals, αvß6 integrin in junctional epithelium maintains anti-inflammatory transforming growth factor-ß1 (TGF-ß1) signaling, whereas its expression is lost in individuals with PD. Bacterial biofilms suppress ß6 integrin expression in cultured gingival epithelial cells (GECs) by attenuating TGF-ß1 signaling, leading to an enhanced pro-inflammatory response. In the present study, we show that GEC exposure to biofilms induced activation of mitogen-activated protein kinases and epidermal growth factor receptor (EGFR). Inhibition of EGFR and ERK stunted both the biofilm-induced ITGB6 suppression and IL1B stimulation. Furthermore, biofilm induced the expression of endogenous EGFR ligands that suppressed ITGB6 and stimulated IL1B expression, indicating that the effects of the biofilm were mediated by autocrine EGFR signaling. Biofilm and EGFR ligands induced inhibitory phosphorylation of the TGF-ß1 signaling mediator Smad3 at S208. Overexpression of a phosphorylation-defective mutant of Smad3 (S208A) reduced the ß6 integrin suppression. Furthermore, inhibition of EGFR signaling significantly reduced bone loss and inflammation in an experimental PD model. Thus, EGFR inhibition may provide a target for clinical therapies to prevent inflammation and bone loss in PD.

Effect of canal curvature location on the cyclic fatigue resistance of reciprocating files.

OBJECTIVES: To determine the effect of the location of the canal curvature on the fatigue resistance of WaveOne (WO), WaveOne Gold (WOG), Reciproc (Rec), and Reciproc Blue (RecB) files, and to examine the phase transformation behaviors of the reciprocating file systems. MATERIAL AND METHODS: The instruments were subjected to fatigue testing in five artificial canals with a curvature of 60° angle and a 3-mm radius. The location of the curvature was unique for each canal. Each file was inserted 16 mm into the canal and operated until fracture occurred. The time to fracture was recorded and the length of the fragment was measured. Differential scanning calorimetry was used to characterize the thermal behavior of the files. The number of cycles to failure was analyzed using two-way analysis of variance and the post hoc Tukey test. The Kruskal-Wallis test was used to compare the mean fragment lengths between groups. RESULTS: The instruments had significantly lower fatigue resistance in canals with curvatures in the middle and coronal canals compared with those with apical curvatures (p < 0.05). At all tested curvature locations, RecB had superior fatigue resistance compared with WO and Rec (p < 0.05). There were no significant differences between WOG and Rec in canals with curvatures in the middle and coronal canals. The DSC thermograms for RecB exhibit a single exothermic peak during cooling but double endothermic peaks during heating indicating that a two-step phase transformation from martensite to R-phase to austenite takes place. CONCLUSIONS: The reciprocating instruments experience decreased cyclic fatigue resistance when operated in canals with coronal- and middle-third curvatures when compared with curvatures in the apical-third. Instrumenting coronally positioned curvatures with reciprocating files needs to be performed with caution. CLINICAL RELEVANCE: The location of the root canal's curvature influences the fracture resistance of rotary files that are used with reciprocating movements. Therefore, caution needs to be exercised when using reciprocating instruments in canals with coronal or middle curvatures.

Effect of apical size on apical pressure during syringe-needle and multisonic negative pressure irrigation.

Apical pressure during root canal irrigation is regarded as a key factor affecting the risk of irrigant extrusion. The aim of this study was to examine the effect of apical size on the apical pressure by positive and negative pressure syringe-needle and multisonic negative pressure irrigation. An extracted maxillary first molar with two separate buccal roots, one palatal root and four canals was selected. The roots of the molar were fixed in a specially made apparatus to acquire the apical pressure of the four root canals separately. The apical sizes tested were from sizes 10, 30, 40, 50, 60, 70, 80, 90, 110. Multisonic negative pressure irrigation protocol was as recommended by the manufacturer (45 mL/min), syringe-needle irrigation was done using 30-G side-vented needle 3 mm from the working length at 5 mL/min as a conventional positive pressure irrigation (SNI), and as negative pressure irrigation (NPSNI) using suction. Apical pressure by SNI was measured also at 10 mL/min with an open-ended 30G needle, for the smallest and largest apical sizes. Apical pressures by SNI stayed positive, except when suction was used (NPSNI). The apical pressure by multisonic negative pressure irrigation remained negative in all situations. With increasing apical size, apical pressure by SNI decreased, whereas with multisonic negative pressure irrigation and NPSNI, it was not affected by apical size. Large apical size did not result in higher apical pressure values compared to small apical sizes.

In vitro evaluation by quantitative real-time PCR and culturing of the effectiveness of disinfection of multispecies biofilms in root canals by two irrigation systems.

OBJECTIVES: The purpose of this in vitro study was by using quantitative real-time PCR and culturing to determine the effectiveness of two irrigation and cleaning systems in removing multispecies oral biofilms from root canals. MATERIAL AND METHODS: Twenty extracted human molars were instrumented to size #15/.02 and then cleaned with the GentleWave (GW) System. The teeth were autoclaved to provide the same sterile baseline. The molars were filled with mixed plaque suspended in BHI and centrifuged to inoculate the biofilms. After 2 weeks of incubation, the teeth were randomly divided into two treatment groups. In GW group (26 canals), the teeth were further instrumented to size #15/04, and in PiezoFlow (PF) group (30 canals) to #35/.04. The teeth were then cleaned either with GW System or ProUltra PiezoFlow Active Ultrasonic System using 3% sodium hypochlorite NaOCl, 8% EDTA, and sterile water as irrigants. Samples (S1, S2, and S3) for bacterial cultures were taken from 13 canals before and after instrumentation and after final cleaning. Quantitative real-time PCR was performed from all 56 canals, and universal bacterial, one genus, and one species-specific primers were used to determine the presence of microorganisms in samples from root canals before and after instrumentation and after final cleaning. Statistical analyses were performed using the Mann-Whitney U test with the significance level set at P < 0.05. RESULTS: Bacterial culturing from the canal samples revealed strong reduction of bacteria from S1 to S2 in both groups after instrumentation and irrigation with water only. No growth was detected in any of the S3 samples after cleaning in either group. A highly significant reduction in bacterial DNA was recorded by qPCR for both groups (P < 0.001). GW System showed more constant and a significantly higher reduction of total microbial DNA (P = 0.007), Enterococcus faecalis DNA (P = 0.011) and Streptococcus spp. DNA (P = 0.029) than the Ultrasonic System. The amount of residual microbial DNA calculated as an average of residual DNA in each individual canal in PF group was 1.99% and in GW group 0.09%. CONCLUSIONS: While both systems demonstrated a highly effective reduction of intracanal bacterial DNA, the final total amount and variation in the number of residual bacterial DNA was significantly smaller in the GW group. CLINICAL RELEVANCE: Elimination of microbes from the infected root canal system is regarded as the key for long-term clinical success. While both GentleWave and Ultrasonic Systems used with NaOCl and EDTA demonstrated a highly effective reduction of intracanal bacterial DNA; GW produced higher reduction and better predictability.

A novel hydroxyapatite-binding antimicrobial peptide against oral biofilms.

OBJECTIVES: Novel synthetic antimicrobial peptides which consist of a new immunomodulatory peptide 1018 and two different modifications with hydroxyapatite-binding affinity were developed. We compared the effect(s) of these peptides against oral plaque biofilms and measured their effectiveness in killing biofilm microbes and in reducing biofilm volume. MATERIALS AND METHODS: The high affinity hydroxyapatite (HA)-binding peptide 1018 (SHABP), the mild affinity HA-binding peptide 1018 (MHABP), and peptide 1018 without additional amino acid sequence (peptide 1018) were synthesized. Oral multispecies biofilms were grown anaerobically for 3 days. The biofilms were exposed to three peptides at two different concentrations (0.65 and 3.25 µmol/L) for 24, 48, and 72 h. The biofilms were also treated for 3 or 9 min with the peptides (3.25 µmol/L). The percentage of killed biofilm bacteria and biofilm volume were determined by using LIVE/DEAD viability staining and confocal laser scanning microscopy. RESULTS: SHABP was superior to MHABP and peptide 1018 in its killing efficacy of the pre-formed biofilms, especially at concentration of 3.25 µmol/L (p < 0.05). SHABP performed also better than MHABP and peptide 1018 in reducing the overall biofilm volume at both concentrations (p < 0.05). During the 3 days of long-term exposure, MHABP and peptide 1080 killed more bacteria in the top half of the biofilms, compared to bottom half. SHABP killed more bacteria in the bottom half (39%) of the biofilms than in the top half (29%) at day 1 (p < 0.05), whereas more bacteria were killed in the upper layers on days 2 and 3. SHABP killed a much higher percentage of plaque biofilm bacteria when used on 3-day-old biofilms for one or three times for 3 min than MHABP or peptide 1018 at high concentration (p < 0.05). CONCLUSIONS: The modified peptide 1018 with high HA-binding affinity had higher antimicrobial activity against biofilm microbes and reduced biofilm volume more than the other peptides tested. CLINICAL RELEVANCE: Modified peptide 1018 with high hydroxyapatite-binding affinity is a promising agent for use in oral antibiofilm strategies in the future.

Chemotherapeutic decontamination of dental implants colonized by mature multispecies oral biofilm.

AIM: No studies have tested disinfectants on mature multispecies oral biofilms on titanium substrata. The aim of this study was to investigate the efficacy of commonly used antimicrobial agents in decontamination of multispecies mature oral biofilm on sandblasted, large-grit, acid-etched (SLA) titanium implants. METHODS: SLA titanium disks were inoculated with dental plaque and cultured anaerobically for 21 days. The disks were rinsed with 0.9% NaCl, exposed for 2 min. to tetracycline paste, 1% Chlorhexidine gel (CHX), 35% phosphoric acid gel (Etch) or a novel chemical formula (0.3% cetrimide, 0.1% CHX and 0.5% EDTA) and then rinsed again with 0.9% NaCl. Bacteria were quantified from scanning electron micrographs of the implant surfaces. Living bacteria were quantified with confocal laser scanning microscopy (CLSM). RESULTS AND CONCLUSIONS: Rinsing the surfaces with 0.9% NaCl removed the majority of the biofilm. However, bacteria persisted in all specimens and none of the disinfectants was superior to the double saline rinse group. CLSM analysis showed that CHX and Etch groups had a statistically significant reduction of viable bacteria, although small. Overall the results show that many disinfection agents used in the clinic are ineffective in biofilm removal and leave live bacteria on the surface.

A 3D numerical study of antimicrobial persistence in heterogeneous multi-species biofilms.

We develop a 3D hydrodynamic model to investigate the mechanism of antimicrobial persistence in a multi-species oral biofilm and its recovery after being treated by bisbiguanide chlorhexidine gluconate (CHX). In addition to the hydrodynamic transport in the spatially heterogeneous biofilm, the model also includes mechanisms of solvent-biomass interaction, bacterial phenotype conversion, and bacteria-drug interaction. A numerical solver for the model is developed using a second order numerical scheme in 3D space and time and implemented on GPUs for high-performance computing. The model is calibrated against a set of experimental data obtained using confocal laser scan microscopy (CLSM) on multi-species oral biofilms, where a quantitative agreement is reached. Our numerical results reveal that quorum sensing molecules and growth factors in this model are instrumental in biofilm formation and recovery after the antimicrobial treatment. In particular, we show that (i) young biofilms are more susceptible to the antimicrobial treatment than the mature ones, (ii) this phenomenon is strongly correlated with volume fractions of the persister and EPS in the biofilm being treated. This suggests that antimicrobial treatment should be best administered to biofilms earlier before they mature to produce a thick protective EPS layer. In addition, the numerical study also indicates that an antimicrobial effect can be achieved should a proper mechanism be devised to minimize the conversion of susceptible bacteria to persisters during and even after the treatment.

Apical pressure created during irrigation with the GentleWave™ system compared to conventional syringe irrigation.

OBJECTIVES: The purpose of this study is to compare pressures at the apical foramen created by conventional syringe irrigation and the GentleWave™ System, which releases high-velocity degassed irrigants to the pulp chamber and uses broad-spectrum sound energy for cleaning. MATERIALS AND METHODS: The apical pressure generated during irrigation was measured for palatal and distobuccal root canals of four extracted maxillary molars after no instrumentation, minimal instrumentation to a size #15/.04, instrumentation to a size #40/.04 taper, and after perforating the apical foramen to size #40. The root canals opened into an air-tight custom fixture coupled to a piezoresistive pressure transducer. Apical pressures were measured for the GentleWave™ System and syringe-needle irrigation at different irrigant flow rates, with the needle tip at 1 and 3 mm from the apical foramen using 30-gauge (G) open-ended or side-vented safety tip needles. RESULTS: The GentleWave™ System generated negative apical pressures (P < 0.001 compared with syringe irrigation); the mean pressures were between -13.07 and -17.19 mmHg. The 30 G needles could not reach the 1 and 3 mm from the working length in uninstrumented and 1 mm in minimally instrumented canals. The mean positive pressures between 6.46 and 110.34 mmHg were measured with needle irrigation depending on the flow rate, needle insertion depth, and size of the root canal. CONCLUSIONS: The GentleWave™ System creates negative pressure at the apical foramen during root canal cleaning irrespective of the size of canal instrumentation. Positive apical pressures were measured for syringe irrigation. CLINICAL RELEVANCE: Negative pressure during irrigation contributes to improved safety as compared to high-positive pressure.

Physical properties and hydration behavior of a fast-setting bioceramic endodontic material.

BACKGROUND: To investigate the physical properties and the hydration behaviour of the fast-setting bioceramic iRoot FS Fast Set Root Repair Material (iRoot FS) and three other endodontic cements. METHODS: iRoot FS, Endosequence Root Repair Material Putty (ERRM Putty), gray and white mineral trioxide aggregate (G-MTA & W-MTA), and intermediate restorative material (IRM) were evaluated. The setting time was measured using ANSI/ADA standards. Microhardness was evaluated using the Vickers indentation test. Compressive strength and porosity were investigated at 7 and 28 days. Differential scanning calorimetry (DSC) was employed for the hydration test. RESULTS: iRoot FS had the shortest setting time of the four bioceramic cements (p < .001). The microhardness values of iRoot FS, ERRM Putty and MTA increased at different rates over the 28 days period. At day one, ERRM Putty had the lowest microhardness of the bioceramic cements (p < .001), but reached the same level as MTA at 4, 7 and 28 days. The microhardness of iRoot FS was lower than that of W-MTA at 7 and 28 days (p < .05). The porosity of the materials did not change after 7 days (p < .05). The compressive strength values at 28 days were significantly greater for all bioceramic groups compared to those at 7 days (p < .01). ERRM Putty had the highest compressive strength and the lowest porosity of the evaluated bioceramic cements (p < .05), followed by iRoot FS, W-MTA, and G-MTA, respectively. DSC showed that iRoot FS hydrated fastest, inducing an intense exothermic reaction. The ERRM Putty did not demonstrate a clear exothermic peak during the isothermal calorimetry test. CONCLUSIONS: iRoot FS had a faster setting time and hydrating process than the other bioceramic cements tested. The mechanical properties of iRoot FS, G-MTA and W-MTA were relatively similar.

Critical role for αvß6 integrin in enamel biomineralization.

Tooth enamel has the highest degree of biomineralization of all vertebrate hard tissues. During the secretory stage of enamel formation, ameloblasts deposit an extracellular matrix that is in direct contact with the ameloblast plasma membrane. Although it is known that integrins mediate cell-matrix adhesion and regulate cell signaling in most cell types, the receptors that regulate ameloblast adhesion and matrix production are not well characterized. We hypothesized that αvß6 integrin is expressed in ameloblasts where it regulates biomineralization of enamel. Human and mouse ameloblasts were found to express both ß6 integrin mRNA and protein. The maxillary incisors of Itgb6(-/-) mice lacked yellow pigment and their mandibular incisors appeared chalky and rounded. Molars of Itgb6(-/-) mice showed signs of reduced mineralization and severe attrition. The mineral-to-protein ratio in the incisors was significantly reduced in Itgb6(-/-) enamel, mimicking hypomineralized amelogenesis imperfecta. Interestingly, amelogenin-rich extracellular matrix abnormally accumulated between the ameloblast layer of Itgb6(-/-) mouse incisors and the forming enamel surface, and also between ameloblasts. This accumulation was related to increased synthesis of amelogenin, rather than to reduced removal of the matrix proteins. This was confirmed in cultured ameloblast-like cells, in which αvß6 integrin was not an endocytosis receptor for amelogenins, although it participated in cell adhesion on this matrix indirectly via endogenously produced matrix proteins. In summary, integrin αvß6 is expressed by ameloblasts and it plays a crucial role in regulating amelogenin deposition and/or turnover and subsequent enamel biomineralization.

Intra-operative application of chlorhexidine gel reduces bacterial counts in internal implant cavity.

A prospective clinical trial was conducted to assess the bacterial-inhibitory potential of 1% chlorhexidine (CHX) gel in the internal cavity of implant screw holes, when utilized at the time of implant placement. A total of 40 Straumann (S) and Nobel Biocare (N) implants were divided into test (ST or NT; implant + CHX gel) and control (SC or NC; implant only) groups. Total numbers of colony-forming units (CFUs ml(-1) ) were assessed at a minimum of 3 months postsurgery by aerobic and anaerobic culture. A set of specimens was stained with Gram stain. The mean sample-collection time was 110 d for the test population and 98 d for the controls. The use of 1% CHX gel significantly reduced bacterial counts in both the ST and NT samples by over three logs compared with controls. No statistical differences in the numbers of CFUs ml(-1) were evident between aerobic and anaerobic cultures. Differences in the numbers of CFUs ml(-1) between ST and NT groups were not statistically significant. Microscopic analysis showed mainly Gram-positive coccoid species in most samples.

Dentistry in the 21st century: challenges of a globalising world.

Oral health is - literally - vital to good general health, not least because the mouth is the sentinel of the body. Dentistry, the Cinderella of health care, faces immense challenges of globalisation. Governments, having spent freely on everything from defence to social security, face mountains of debts which make budget cutbacks essential. Simultaneously, most developed countries have to pay increasing costs of caring for rapidly ageing populations. Dentistry is being pulled two ways: wealthy members of society demand high-end expensive treatment, much of it cosmetic rather than necessary to deal with disease, whereas many millions of poor people in developing countries cannot afford basic dental treatment and may never see a dentist. Too many governments and dentists persist with the expensive and destructive regime of 'drill and fill (and bill)'. International advances in care may not reach the clinician's chair because treatment guidelines and payments are set locally. An international symposium to celebrate Mikako Hayashi becoming Professor of Restorative Dentistry and Endodontology at Osaka University concluded that dentistry should move from an increasingly un-affordable curative model to a cost-effective evidence-based preventive model. The goal is to help people retain healthy natural teeth throughout their lives, as an essential part of enhancing their general health.

Antibacterial activity of various root canal sealers and root-end filling materials in dentin blocks infected ex vivo with Enterococcus faecalis.

OBJECTIVE: The aim was to investigate the antibacterial activity of the root-end filling materials MTA and IRM, different endodontic sealers and calcium hydroxide [Ca(OH)2] in experimentally infected dentinal tubules. MATERIALS AND METHODS: Ninety-four human root segments were prepared and the root canals were enlarged to ISO size 90. After smear removal, the specimens were infected with Enterococcus faecalis for 3 weeks. The roots were divided into eight groups and filled either with MTA, IRM, Ca(OH)2, gutta-percha and EndoRez (ER)/GuttaFlow (GF)/AH Plus (AH+) or with Resilon and Epiphany (EpRe). One group of specimens was left unfilled for control. Half of the specimens were treated for 1 day and the other half for 7 days in humid conditions at 37°C. Dentin samples from each canal were collected by enlarging the canals to ISO size 150; thus a dentinal depth of 300 µm was sampled. The number of cultivable bacteria was determined for each specimen. Statistical significance was set to 5%. RESULTS: After 1-day or 7-days of treatment, compared to control, all materials (except ER and GF at day 7) significantly reduced the number of bacteria. At day 1 and day 7, no significant difference was found between ER and GF and between Ca(OH)2, AH+, EpRe, IRM and MTA. However, a significant difference was found between these two groups of materials (except between GF and EpRe at day 7). Significantly more bacteria were cultured in the ER, GF, EpRe and IRM groups at day 7 compared to day 1. CONCLUSIONS: All materials exerted varying degrees of antibacterial activity which generally tended to decrease with time. The most stable antibacterial effect throughout the 7-day period was for Ca(OH)2, AH+ and MTA.

Effects of Sodium Hypochlorite Concentration and Application Time on Bacteria in an Ex Vivo Polymicrobial Biofilm Model.

INTRODUCTION: In endodontic treatment, it is important to remove or inactivate biofilms in the root canal system. We investigated the effects of different concentrations and application times of sodium hypochlorite (NaOCl) on the viability of bacteria in ex vivo polymicrobial biofilms of different maturation levels. METHODS: Polymicrobial biofilms were prepared from dental plaque samples and grown for 1, 2, and 3 weeks under anaerobic conditions on collagen-coated hydroxyapatite discs as an ex vivo biofilm model. The biofilms were then exposed to NaOCl at concentrations ranging from 0.1% to 2% for 1 or 3 minutes. The control group was exposed to sterile distilled water. Viability staining was performed and examined by confocal laser scanning microscopy to determine the percentage of biofilm bacteria killed by NaOCl. Scanning electron microscopy was also performed to visually examine the biofilms. RESULTS: Application of NaOCl at 0.5%-2% for both 1 and 3 min killed significantly more bacteria when compared to the controls (P < .05). Cell viability tended to be lower after the application of NaOCl for 3 minutes than that for 1 minute. CONCLUSIONS: Our experiments using an ex vivo model showed that within the range of 0.1%-2% of NaOCl, higher NaOCl concentrations and longer application times were more effective in killing biofilm bacteria, and that mature biofilms were more resistant to NaOCl than younger biofilms.