Iontophoresis use for increasing drug penetration into root canals and dentinal tubules: A proof-of-concept study

INTRODUCTION

The success of endodontic treatment depends on the significant disinfection of the root canal system, its irregularities, and dentinal tubules. However, achieving complete disinfection remains challenging, with frequent failures and occurrence of secondary infections. Here, we propose using iontophoresis to increase the penetration and distribution of disinfecting agents into root canals, using methylene blue for proof-of-concept.

METHODS

The marker was applied in bovine root canals, and the radial distribution of the dye in the dentinal tubules was evaluated by optical microscopy. Iontophoresis was applied at 0.5 and 1.5 mA for 5 and 15 min.

RESULTS

A significant statistical difference (p < 0.05) was observed in the marker penetration between passive and iontophoretic applications. Both current density and application time had an important effect on methylene blue distribution, with a greater efficacy delivery to the apical region achieved after 1.5 mA for 5 min or 0.5 mA for 15 min, showing longer application time can compensate for lower application current.

CONCLUSION

Iontophoresis increases the penetration and distribution of methylene blue into bovine root canals and dentinal tubules, including its innermost portions.

CLINICAL SIGNIFICANCE

Iontophoresis has shown to be a promising technique for root canal and dentinal tubule disinfection.

In-depth occlusion of dentine tubules via the application of (poly-L-aspartic acid)‑strontium and phosphate/fluoride to treat dentine hypersensitivity

Dentine hypersensitivity (DH) is a common oral health issue and occlusion of the exposed dentinal tubules (DTs) is regarded as the most effective therapeutic treatment nowadays. However, it is still difficult to develop easy and effective strategies for deep occlusion of DTs. In this study, we develop a strategy for occluding DTs deeply and compactly via simple application of occlusion media including (poly-L-aspartic acid)‑strontium (PAsp‑strontium) and phosphate/fluoride. The bonding of strontium ions to poly-L-aspartic acid formed a positively charged PAsp‑strontium complexes. After application of 15 min each, the PAsp‑strontium and phosphate/fluoride rapidly penetrated into the DTs in turn via the electrostatic interaction, then occluded the DTs with crystals up to a depth of 150 μm. The occlusion within DTs was resistant to abrasive and acidic challenges. The occlusion media performed better than commercial desensitizers Duraphat and Gluma. Moreover, this strategy possessed sufficient biocompatible and excellent performance in vivo. The application of occlusion media would shed light on in the management of DH.

Combined Effects of Glutaraldehyde-based Desensitizer and Nd: YAG Laser on Dentinal Tubules Occlusion

AIM

The aim of this study was to assess the impact of Nd:YAG laser, glutaraldehyde-based desensitizer (GD), or their combination on occluding dentinal tubules.

MATERIALS AND METHODS

Fifty dentin samples were obtained from non-carious human third molars and randomly divided into five groups (n = 10): (1) Control group treated with 37% phosphoric acid, (2) GD group, (3) Nd:YAG laser group (1064 nm, 100 µs, 10 Hz, 300 µm fiber, 1 W power, 100 mJ energy, and 85 J/cm2 energy density), (4) GD followed by Nd:YAG laser group, and (5) Nd:YAG laser followed by GD group. Scanning electron microscopy (SEM) was used to capture five images from each sample for analysis of dentinal tubules using Image J software. SEM/EDX elemental analysis was performed to determine the main mineral contents. Data analyzed using one-way ANOVA and Tukey's post hoc test for statistical comparisons.

RESULTS

Laser and combination groups showed a significant decrease in dentinal tubule counts compared with the control and GD groups (p < 0.0001). There were no significant differences in open dentinal tubule counts between the control and GD groups, as well as between the laser and combination groups. However, significant differences were observed in the total area, average size of the tubules, and percentage area between the control group and the treatment groups (GD, laser, GD + laser, laser + GD). No significant difference was found in the Ca/P ratio between the tested groups.

CONCLUSION

The use of Nd:YAG laser alone or in combination with GD was more effective in occluding dentinal tubules compared to GD alone.

CLINICAL SIGNIFICANCE

This study has shown that Nd:YAG laser alone and in combination with GD has superior dentinal tubule occlusion in vitro. Its clinical use in the treatment of dentinal hypersensitivity may overcome the drawback of conventional treatment approaches for dentin hypersensitivity needing repeated applications to achieve continuous relief from pain since acidic diet and toothbrushing result in the continuing elimination of precipitates and surface coatings. How to cite this article: Alzarooni AH, El-Damanhoury HM, Aravind SS, et al. Combined Effects of Glutaraldehyde-based Desensitizer and Nd: YAG Laser on Dentinal Tubules Occlusion. J Contemp Dent Pract 2024;25(1):52-57.

Effect of Commercially Available Nano-Hydroxyapatite Containing Desensitizing Toothpaste and Mouthwash on Dentinal Tubular Occlusion: A SEM Analysis

The aim of this in vitro study was to evaluate and compare the dentinal tubule occlusion using nano-hydroxyapatite (n-HAP) containing toothpaste and mouthwash under a scanning electron microscope. The specimens were randomly divided into two groups with five specimens each: group 1-toothpaste group and group 2-mouthwash group. The percentage of the occluded dentinal tubules was assessed at the baseline, 7th, 14th, 21st, and 28th days under a scanning electron microscope. The toothpaste group showed a higher percentage of occluded dentinal tubules as compared to the mouthwash group at the 7th, 14th, 21st, and 28th days, respectively. It can be concluded that brushing twice daily with n-HAP containing toothpaste for duration of 28 days produced good dentinal tubule occlusion.

Comparison of dentinal tubular penetration of Intra-canal heated and Pre-heated sodium hypochlorite through different agitation techniques

INTRODUCTION

The efficacy of sodium hypochlorite (NaOCl) as an intracanal irrigant is widely debated in endodontic therapy. This study aimed to analyze and compare the penetration abilities of different modes of NaOCl application and assess the impact of various agitation strategies on promoting root canal cleanliness.

MATERIALS AND METHODS

This study included 168 single-rooted mandibular premolars that were randomly divided into eight groups. The two modes of application of 5% NaOCl evaluated were intracanal heating and preheating, and the agitation strategies included ultrasonic, sonic, and manual dynamic agitations (MDAs). The samples were sectioned and observed at a magnification of 1000× under a scanning electron microscope.

RESULTS

The analysis of variance test showed a statistically significant difference among the various groups of agitation (P < 0.05). The post hoc Tukey test confirmed that preheated NaOCl with ultrasonic agitation, intracanal-heated NaOCl with sonic agitation, and MDA had significantly higher debris scores of 1, 4, and 5, respectively, in the apical third of the canal.

CONCLUSION

The results indicated that the combination of intracanal-heated NaOCl and ultrasonic agitation is an effective method for reducing debris in the root canal system. These findings highlight the importance of considering both the mode of application and the agitation strategies when optimizing the use of NaOCl as an intracanal irrigant in endodontic therapy.

[Antibacterial effect of low-temperature plasma on Enterococcus faecalis in dentinal tubules in vitro]

OBJECTIVE

To construct a model of Enterococcus faecalis (E. faecalis) infection in dentinal tubules by gradient centrifugation and to evaluate the antibacterial effect of low-temperature plasma on E. faecalis in dentinal tubules.

METHODS

Standard dentin blocks of 4 mm×4 mm×2 mm size were prepared from single root canal isolated teeth without caries, placed in the E. faecalis bacterial solution, centrifuged in gradient and incubated for 24 h to establish the model of dentinal tubule infection with E. faecalis. The twenty dentin blocks of were divided into five groups, low-temperature plasma jet treatment for 0, 5 and 10 min, calcium hydroxide paste sealing for 7 d and 2% chlorhexidine gel sealing for 7 d. Scanning electron microscopy and confocal laser scanning microscope were used to assess the infection in the dentinal tubules and the antibacterial effect of low-temperature plasma.

RESULTS

The results of scanning electron microscopy and confocal laser scanning microscopy showed that after 24 h of incubation by gradient centrifugation, E. faecalis could fully enter the dentinal tubules to a depth of more than 600μm indicating that this method was time-saving and efficient and could successfully construct a model of E. faecalis infection in dentinal tubules. Low-temperature plasma could enter the dentinal tubules and play a role, the structure of E. faecalis was still intact after 5 min of low-temperature plasma treatment, with no obvious damage, and after 10 min of low-temperature plasma treatment, the surface morphology of E. faecalis was crumpled and deformed, the cell wall was seriously collapsed, and the normal physiological morphology was damaged indicating that the majority of E. faecalis was killed in the dentinal tubules. The antibacterial effect of low-temperature plasma treatment for 10 min exceeded that of the calcium hydroxide paste sealing for 7 d and the 2% chlorhexidine gel sealing for 7 d. These two chemicals had difficulty entering deep into the dentinal tubules, and therefore only had a few of antibacterial effect on the bacterial biofilm on the root canal wall, and there was also no significant damage to the E. faecalis bacterial structure.

CONCLUSION

Gradient centrifugation could establish the model of E. faecalis dentin infection successfully. Low-temperature plasma treatment for 10 min could kill E. faecalis in dentinal tubules effectively, which is superior to the calcium hydroxide paste sealing for 7 d and the 2% chlorhexidine gel sealing for 7 d.

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.

Structure-function relationships in dog dentin

Investigations into teeth mechanical properties provide insight into physiological functions and pathological changes. This study sought to 1) quantify the spatial distribution of elastic modulus, hardness and the microstructural features of dog dentin and to 2) investigate quantitative relationships between the mechanical properties and the complex microstructure of dog dentin. Maxillary canine teeth of 10 mature dogs were sectioned in the transverse and vertical planes, then tested using nanoindentation and scanning electron microscopy (SEM). Microstructural features (dentin area fraction and dentinal tubule density) and mechanical properties (elastic modulus and hardness) were quantified. Results demonstrated significant anisotropy and spatial variation in elastic modulus, hardness, dentin area fraction and tubule density. These spatial variations adhered to a consistent distribution pattern; hardness, elastic modulus and dentin area fraction generally decreased from superficial to deep dentin and from crown tip to base; tubule density generally increased from superficial to deep dentin. Poor to moderate correlations between microstructural features and mechanical properties (R² = 0.032-0.466) were determined. The results of this study suggest that the other constituents may contribute to the mechanical behavior of mammalian dentin. Our results also present several remaining opportunities for further investigation into the roles of organic components (e.g., collagen) and mineral content on dentin mechanical behavior.

Novel Management of Hypersensitive Dentin Using Propolis-based Herbal Desensitizing Agents: An In Vitro Scanning Electron Microscopic Study

AIM

The objective of this in vitro study was to assess the efficacy of novel propolis-based varnish against the two conventional varnishes on quantitative and qualitative assessments of occlusion of dentin tubules and resistance to erosive and abrasive wears employing scanning electron microscope (SEM).

METHODS

Thirty human premolars free from caries extracted due to orthodontic reasons were included in the study. Experimental group was done based on treatment received and divided into three groups. Group A: ClinProXT Varnish (n = 10), Group B: MI Varnish (n = 10), and Group C: Propolis Varnish (n = 10) were applied. Teeth were cleaned and decoronation of crown was done with dentin disks. Dentin specimens of dimension 4 × 4 × 2 mm were prepared and subjected to finishing and polishing. The sample specimens were submersed in EDTA solution for a period of five minutes to open up the dentinal tubules. This was followed by treatment with varnishes and subjection to acidic-abrasive challenge. The specimens were analyzed with an image analyzer connected to SEM for the verification of the number of opened dentin tubules. The parameter assessed in SEM includes size, topography and surface characteristics of dentinal tubule were assessed. The obliteration potential of dentinal tubules was assessed with SEM images. Additionally, the dentin surface loss and resistance to acidic and abrasive wear were also evaluated with SEM. Data were analyzed with two-way analysis of variance (ANOVA) with post hoc Tukey's test.

RESULTS

MI Varnish caused higher obliteration of dentin tubules followed by ClinproXT Varnish. Propolis Varnish showed the least obliteration of dentinal tubules among tested experimental groups. After acidic-abrasive challenge, Propolis Varnish was found to be more efficient with less material loss among the experimental groups tested. There was an insignificant difference among the MI Varnish and ClinProXT Varnish groups.

CONCLUSION

Simulation of hypersensitive lesions mimicking the clinical scenario was a challenging task in this in vitro study. All varnishes tested in the study had good efficacy in the management of dentin hypersensitivity (DH). Propolis-based varnish had good resistance to material loss after subjection to acidic-abrasive challenge among the tested materials. The casein phosphopeptide (CPP)-amorphous calcium phosphate (ACP)-based MI Varnish had good efficacy to obliterate the dentinal tubules among the tested materials. It was prudent to select the varnishes with good long-term efficacy to survive in the clinical scenario which still remains a challenging task for the clinicians.

CLINICAL SIGNIFICANCE

The stability of the varnish plays a vital role in maintenance of its long-term efficacy. The chemical nature along with the ability of the material to interact with the substrate plays a major role in management of DH.

Direct and indirect monomer elution from an RBC product family

OBJECTIVE

To develop a model for quantitative comparison of elutable substances by direct elution from resin-bonded composite (RBC) test specimens versus indirect elutability of substances from RBC-restored teeth. Furthermore, it was to be investigated whether the different composites of the Tetric® RBC product family release different types and amounts of substances.

METHODS

Four different composite materials from the Tetric® product family were studied. For each material subgroup ten human third molar teeth were prepared with standard Class-I occlusal cavities. These 'tooth group' specimens were provided with a three-step adhesive system (incorporating TEGDMA) and the respective composite restoration. Same sized control specimens, of each RBC restorative material, were prepared ('direct RBC' groups). All specimens were placed in individual elution chambers such that the elution media (ethanol/water, 3:1) only came into contact with either the tooth root or ¾ height of the 'direct RBC' materials. They were incubated at 37 °C for up to 7 d. Samples of the eluant were taken after 1, 2, 4 and 7 d and were analysed by high-temperature gas chromatography/mass spectrometry.

RESULTS

Bisphenol A ethoxylate dimethacrylate (bisEMA), bisphenol A glycidyldimethacrylate (bisGMA), tetraethylene glycol dimethacrylate (TEEGDMA), decan-1,10-diol dimethacrylate (DDDMA) were mostly found in the eluates of the 'direct RBC' groups in statistically significantly greater amounts than in the eluates of the 'tooth groups'. Such quantitative differences were also the case with eluates containing bisphenol A (BPA), dicyclohexyl phthalate (DCHP) and drometrizole, which are common in the environment. In contrast to the behavior found with all the other monomers, up to 3 orders of magnitude more triethylene glycol dimethacrylate (TEGDMA) was found in the 'tooth groups' compared to the 'direct RBC' groups, evidently released by the adhesive system.

SIGNIFICANCE

The release of most of the substances was clearly delayed in the 'tooth groups' indicative of their chronic, rather than acute, elution to the oral environment. A barrier function of the residual dentin layer and the adhesion layer can be inferred. The different release patterns of substances from the various composites of the RBC product family is a manifestation of their different and indication-specific compositions. Consideration of an overall restorative care (RBC plus adhesive) system, when assessing the total amount of released substances, is emphasized.

Potential for direct application of blue light for photo-disinfection of dentine

The direct application of light for photo-disinfection potentially provides a safe and novel modality to inhibit or eliminate cariogenic bacteria residing upon and within dentine. This study aimed to both; characterize the pattern of transmission of 405 nm light through molar dentine at different tooth locations, as well as, determine the irradiation parameters that are antibacterial for Streptococcus mutans under various growth conditions, including lawns, planktonic cultures, and biofilms. To determine the amount of light (405 nm) transmitted at different anatomical tooth locations; irradiance values were recorded after blue light (470-4054 mW/cm²) had traversed through occlusal, oblique, and buccal dentine sections; and three thicknesses - 1, 2 and 3 mm were investigated. To determine tubular density; scanning electron micrographs from 2 mm outer (dentine-enamel junction) and inner (pulp) dentine sections were analysed. For photo-disinfection studies; S. mutans was irradiated using the same 405 nm wavelength light at a range of doses (110-1254 J/cm²) in both biofilm and planktonic cultures. The inhibitory effect of the irradiation on bacterial lawns was compared by measuring zones of inhibition; and for planktonic cultures both spectrophotometric and colony forming unit (CFU) assays were performed. A live/dead staining assay was utilised to determine the effect of irradiation on bacterial viability in mature biofilms. Data indicated that increasing dentine thickness decreased light transmission significantly irrespective of its orientation. Occlusal and oblique samples exhibited higher transmission compared with buccal dentine. Oblique dentine 405 nm light transmission was comparable with that of occlusal dentine independent of section thickness. An increased tubule density directly positively correlated with light transmission. Irradiation at 405 nm inhibited S. mutans growth in both biofilm and planktonic cultures and a dose response relationship was observed. Irradiation at doses of 340 and 831 J/cm² led to significant reductions in bacterial growth and viability; as determined by CFU counting and live/dead staining. Data suggests that phototherapy approaches utilising a 405 nm wavelength have therapeutic potential to limit cariogenic bacterial infections both at the surface and within dentine.

Fracture micromechanics of human dentin: A microscale numerical model

In the present study, we investigate the effects of microstructural morphology and heterogeneity on the initiation and propagation of microcracks in dentin. We create 2D pre-cracked models of human dentin at the microscale level and use a brittle fracture framework of the phase-field method to analyze the crack growth. We discuss the influence of the microstructural features on crack deflection, microcracking, and uncracked ligament bridging through various regions in dentin. The results demonstrate that the difference between the critical energy release rates of peritubular (PTD) and intertubular dentin (ITD) has considerable impacts on microcracking. Our simulations reveal that tubules surrounded by PTDs play an important role in the crack deflection. Our results also indicate that the toughness of dentin increases from the inner to outer dentin. In conclusion, the findings in our study provide valuable insights into the fracture behavior in various regions of dentin.

An alternate methodology for studying diffusion and elution kinetics of dimethacrylate monomers through dentinal tubules

OBJECTIVE

Ethoxylated bisphenol A dimethacrylate (bisEMA) is a base monomer in several dental resin composites. It was the main aim of the present study to determine if bisEMA can reach the dental pulp by generally passive diffusion through the coronal dentinal tubules stimulated via eluent liquids surrounding the root structures only.

METHODS

In 20 human third molar teeth, standard Class-I occlusal cavities were prepared and provided either with an adhesive system alone or additionally with a composite restoration, according to the instructions of the manufacturer. The teeth were placed in an elution chamber such that the elution media only came into contact with the tooth root/tooth base where they were incubated at 37 °C for up to 7 d. Samples were taken after 1, 2, 4 and 7 d. Gas chromatography/mass spectrometry was used to identify bisEMA and other monomers in ethanol/water (3:1) and aqueous eluates.

RESULTS

bisEMA was only found in ethanol/water eluates, where the teeth had received a composite restoration. Traces of bisEMA with up to three ethylene oxide units could be detected in these eluates. Depending on the dentin thickness, different elution kinetics of bisEMA were determined. Regardless of the treatment of teeth, triethylene glycol dimethacrylate (TEGDMA) and tetraethylene glycol dimethacrylate (TEEGDMA) were found in ethanolic/aqueous eluates in equal amounts. Most TEGDMA and TEEGDMA diffused through the dentin within the first 24 h.

SIGNIFICANCE

Depending on the dentin layer thickness, bisEMA was released for varied time periods, resulting in varied concentrations and exposure times for the different cells of the dental pulp. The concentrations of TEGDMA and TEEGDMA were greatest for cells of the dental pulp within the first 24 h.

Toothpaste factors related to dentine tubule occlusion and dentine protection against erosion and abrasion

OBJECTIVES

To investigate the effect of toothpastes on dentine surface loss and tubule occlusion, and the association of toothpaste-related factors to each of the outcomes.

MATERIALS AND METHODS

One hundred and sixty human dentine specimens were randomly distributed into 10 groups, according to different toothpastes. The specimens were submitted to artificial saliva (60 min), citric acid (3 min), and brushing abrasion (25 s; totalizing 2 min in toothpaste slurries). This was repeated five times and two outcome variables were analyzed: dentine surface loss (dSL; μm) and tubule occlusion by measurement of the total area of open tubules (Area-OT; μm²). Data were analyzed with Kruskal-Wallis and Mann-Whitney tests (α = 0.05); bivariate and multivariate regressions were used to model the association of the chemical (pH, concentration of F^-, Ca²⁺, and PO₄^3- and presence of Sn²⁺) and physical (% weight of solid particles, particle size, and wettability) factors of the toothpastes to both outcome variables.

RESULTS

Toothpastes caused different degrees of dSL and did not differ in Area-OT. All chemical and physical factors, except the presence of Sn²⁺, were associated with dSL (p < 0.001). Area-OT was associated only with the presence of Sn²⁺ (p = 0.033).

CONCLUSION

Greater dSL was associated with lower pH, lower concentration of F^-, higher concentration of Ca²⁺ and PO₄^3-, greater % weight of solid particles, smaller particle size, and lesser wettability, whereas tubule occlusion was associated with the presence of Sn²⁺.

CLINICAL RELEVANCE

Depending on their chemical and physical composition, toothpastes will cause different degrees of dentine tubule occlusion and dentine surface loss. This could, in turn, modulate dentine hypersensitivity.

Diffusion of calcium hydroxide through dentinal tubules of retreated root canals: An in vitro study

Objective:

Studies about the dispersion of hydroxyl ions through dentin of endodontically retreated teeth are scarce. The present study aims at examining the diffusion of calcium hydroxide in vitro by recording the pH changes of retreated root canal using two types of calcium hydroxide preparations.

Materials and Methods:

A total of 45 recently extracted single-rooted mandibular first premolars were collected and cleaned from calculus and remains of periodontal tissue. The teeth so collected were stored in thymol 10% solution till use. During collection, teeth with cracks, open apices, and restorations were excluded. Root canal preparations were performed using Protaper rotary system files, till #F3 file. All canals were obturated using cold lateral condensation and zinc oxide-based sealer. After 7 days, all gutta-percha were removed and the canals were irrigated with normal saline. The teeth were then randomly distributed into three groups. Canals in Group I were kept empty without any dressing to serve as a negative control group, Canals in Group II were filled with a freshly prepared mixture of calcium hydroxide powder with normal saline solution, and Group III was filled with Metapex. Periodically, the calcium hydroxide material was removed and the pH was measured using pH meter at 7, 10, 14, and 30 days.

Results:

The pH values of Group II and III ranged between 9.2 and 11.2. This was found to be highly significant against the negative control group. After 7 and 10 days, freshly mixed Ca(OH)₂ showed the higher pH than the creamy Metapex, and statistically the difference was highly significant after 10 days (P<0.001). After 14 days, Metapex group pH was higher than freshly mixed Ca(OH)₂, but it was not statistically significant as they reached nearly the same pH after 30 days (P>0.05).

Conclusion:

All Ca(OH)₂ preparations had high pH around the roots after 7 and 10 days. Metapex continued to have higher pH after 14 days.

Effect of Dentin Bonding Agent on Intrapulpal Temperature during Fabrication of Provisional Restorations by a Direct Method: An In Vitro Study

AIM

To determine the effect of three different provisional restorative materials (PRMs) and application of dentin bonding agent (DBA) on intrapulpal temperature rise during fabrication of provisional crowns using a direct method.

MATERIALS AND METHODS

Three PRMs-polymethyl methacrylate resin (PMMA), bis-acrylic resin, and dimethyl methacrylate resin (DMMA)-were used in the study. Dentin bonding agent (Single Bond 2, 3M ESPE, Germany) was applied in a single layer or double layer as an insulating material. A total of 45 molars were prepared for complete coverage restoration with chamfer finish line and 1.5 mm axial and 2 mm occlusal reduction. After application of a single or double layer of DBA, provisional materials were polymerized according to the manufacturer's instructions. The temperature increase inside the pulp chamber was measured with a T-type thermocouple wire. The readings were averaged for each group to determine the mean value of temperature rise.

RESULTS

Statistical analysis was performed with analysis of variance (ANOVA) followed by post hoc Tukey test (a = 0.05). The temperature rise varied according to the provisional restoration material used (PMMA > DMMA > bis-acrylic resin) (p < 0.001) and the single or double layer of DBA (p < 0.001). Polymethyl methacrylate resin produced a higher intrapulpal temperature.

CONCLUSION

Application of a double layer of DBA resulted in a significantly lower intrapulpal temperature.

Comparison of bacterial removal from dentinal tubules with different irrigant agitation techniques: An in vitro study

Aim

This investigation was conducted to assess the ability of various irrigant agitation devices to eradicate Enterococcus faecalis from the dentinal tubules of extracted teeth.

Methodology

Fifty roots of extracted human teeth were instrumented to size 30 k with a 0.04 taper. The roots were autoclaved and then injected with E. faecalis. The canals were assigned to one of four intervention groups and disinfected using (A) standard needle irrigation, (B) EndoUltra® Ultrasonic Activator, (C) the EndoActivator system, or (D) EDDY sonic activation and to two control groups that were (E) treated with saline and (F) not inoculated with any bacteria. The roots were split in half, dyed with a LIVE/DEAD Back Light Bacterial Viability Kit, and then scanned with a confocal laser scanning microscope (CLSM) to identify live/dead bacteria in the dentinal tubules.

Results

CLSM images revealed differences among the groups. Both the EndoUltra® Ultrasonic Activator group and the EDDY group had a combination of dead and live bacteria, while the EndoActivator group had mostly dead bacteria, in contrast to single needle irrigation which had mostly live bacteria. Activation of the irrigating solution resulted in more dead bacteria than standard needle irrigation at the coronal, middle, and apical parts of the roots. Overall, the EndoActivator system was superior to all other techniques in reducing live bacteria within the root canal.

Conclusion

Activation of sodium hypochlorite with sonic and ultrasonic systems dramatically reduced live bacteria contamination in the dentinal tubules of infected root canals.

Is it really penetration? Part 2. Locomotion of Enterococcus faecalis cells within dentinal tubules of bovine teeth

OBJECTIVE

The aim of the present vitro study was to examine the question whether devitalized Enterococcus faecalis (E. faecalis) cells can migrate into dentinal tubules and if that process takes place in a time-dependent manner.

DESIGN

Sixty bovine root canals were incubated with devitalized and vital streptomycin-resistant E. faecalis strains after root canal enlargement (size 80, taper .02) with 3% NaOCl solution. Incubation times 7, 14, 21, 28, 35, and 42 days. Samples were processed for analysis by scanning electron microscopy (SEM) and DAPI (4',6-diamidino-2-phenylindole) staining. The penetration depth was calculated with the measurement tool of the Axio Vision program (Zeiss, Jena, Germany). Statistical analysis was performed by Kruskal-Wallis (α = 0.05) and Mann-Whitney U test (p < 0.05).

RESULTS

Devitalized E. faecalis strains were able to migrate into dentinal tubules. The total number and penetration depth of devitalized E. faecalis cells was lower compared to the vital suspension of E. faecalis. It was noted, that bacterial penetration was not common to all of the dentinal tubules in the vital E. faecalis control and especially in the devitalized control. The migration took place in a time-dependent migration characteristic.

CONCLUSIONS

Devitalized E. faecalis cells are still able to migrate into the dentinal tubules due to possible electrokinetic and osmotic processes. Thereby, increased exposure times lead to a time-dependent penetration characteristic.

CLINICAL RELEVANCE

Since devitalized bacteria can migrate as well into dentinal tubules, the presence of bacteria within dentinal tubules cannot be interpreted as a failure of tested preparation regimens.

Anti-biofilm efficacy of root canal irrigants against in-situ Enterococcus faecalis biofilms in root canals, isthmuses and dentinal tubules

OBJECTIVE

To investigate the anti-biofilm efficacy of root canal irrigants in canal spaces, isthmi and dentinal tubules of root canals ex vivo.

METHODS

Fifty-one single-rooted premolars, each containing an isthmus, were instrumented, autoclaved and inoculated with Enterococcus faecalis for 4 weeks. One specimen was sectioned for bacteria-specific staining to confirm the presence of biofilms using light microscopiy. The remaining specimens were randomly divided to five groups: (1) 0.9% NaCl, (2) SilverSol/H₂O₂, (3) HYBENX, (4) QMix 2 in1, (5) 6% NaOCl. Bacterial sampling was performed before (S1) and after (S2) canal irrigation. Diluted bacteria suspension was cultured for 48 h for counting the colony forming units (CFU). Percentages of dead bacteria and biofilm thickness were evaluated by confocal laser scanning microscopy (CLSM). Metabolic activity, lactic acid and polysaccharide synthesis of E. faecalis derived from S2 samples were analysed.

RESULTS

The percentages of dead bacteria were significantly affected by the factor "irrigant" (p < 0.001) and the factor "location" (p = 0.017). The percentages of dead bacteria in the isthmi and canals were both in the ordor: NaCl < SilverSol/H₂O₂ < HYBENX < QMix 2 in1 < NaOCl (p < 0.05). Only 6% NaOCl disrupted biofilms and significantly reduced their thickness. The CFU, metabolic activity, polysaccharide and lactic acid production of E. faecalis were all reduced by the disinfecting solutions.

CONCLUSIONS

SilverSol/H₂O₂ and HYBENX were less adept than QMix 2 in1 at killing biofilm bacteria in root canals. None of these antibacterial irrigants were effective, compared with 6% NaOCl, in disrupting biofilms.

CLINICAL SIGNIFICANCE

There is advantage in using HYBENX or QMix 2 in1 to kill intratubular bacteria biofilms because of their capability in removing the inorganic component of the smear layer. SilverSol/H₂O₂ requires extra time to eradicate intratubular biofilms upon removal of the organic and inorganic components of the smear layer by other root canal irrigants.

Effects of two disinfection/sterilization methods for dentin specimens on dentin permeability

OBJECTIVES

To investigate the effects of two disinfection/sterilization methods on the permeability of dentin specimens.

MATERIALS AND METHODS

Forty intact human third molars were freshly extracted and cut, close to the pulp chamber, into dentin disks with a 500-μm thickness. The disks were randomized (n = 20 each) into a 70% ethanol group (acid-etched dentin disks soaked in 70% ethanol for 15 min) and a steam autoclaving group (acid-etched dentin disks autoclaved for 25 min). The permeability (Lp) of each dentin disk was measured before and after either treatment using a hydraulic device, and intra- and inter-group differences in values before and after treatment were analyzed using t tests. Field emission scanning electron microscopy (FE-SEM) micrographs of the dentin surface were acquired and examined. FE-SEM samples were prepared using the critical point drying (CPD) method.

RESULTS

Immersion in 70% ethanol increased the Lp values of dentin specimens by 17%, which was not statistically significant. Steam autoclaving significantly reduced dentin permeability by 66% because the dentin collagen mesh became compact and collapsed, as detected by FE-SEM.

CONCLUSIONS

The disinfection of acid-etched dentin disks using 70% ethanol for 15 min does not significantly affect dentin permeability, whereas sterilization of acid-etched dentin disks via autoclaving significantly reduces dentin permeability.

CLINICAL RELEVANCE

Considering the influences of dentin permeability by disinfection/sterilization methods, the disinfection of the acid-etched dentin disks using 70% ethanol for 15 min could be used for the study related to dentin permeability, while the sterilization of autoclaving could not.

The evaluation of E. faecalis colonies dissolution ability of sodium hypochlorite in microenvironment by a novel device

Enterococcus faecalis(E. faecalis) is a common microorganism could be isolated from the infected canals, especially in the case of refractory apical periodontitis. Due to its ability to invade the dentinal tubules and highly resistant to antimicrobial strategies, the thorough debridement of E.faecalis is hard to achieve. And that may be one of the reasons to cause reinfection and therapeutic failure. According to the anatomy of dentinal tubules published before and the results of our team previous work, we designed six types of microtubes with different sizes. By using the method of centrifugation and incubation, a standard infected model mimicking dentinal tubules was established. Sodium hypochlorite (NaClO) is the most popular irrigant applied in root canal treatment. We used three different concentrations with four distinct irrigation duration to observe the antibacterial process of E. faecalis colonies within microtubes dynamically. We concluded that the role of NaClO in the microtubes is concentration dependent and duration dependent. And the interpretation of the results has a certain reference value for clinicians.

Comparative evaluation of micron- and nano-sized intracanal medicaments on penetration and fracture resistance of root dentin - An in vitro study

Intracanal medicaments play a vital role in disinfection of root canal system. The aim of this study was to evaluate intratubular penetration and fracture resistance of roots filled with micron- and nano-sized intracanal medicaments: calcium hydroxide (CH), nanocalcium hydroxide (NCH), chitosan (CS) and nanochitosan (NCS). Their antibacterial effect on E. faecalis was tested using agar diffusion method. NCH and NCS were prepared by precipitation method and ionic crosslinking respectively. NCH and NCS particles were spherical, with an average particle size of 102±11.3nm and 130±17.6nm respectively. The medicaments were filled in extracted human teeth. Depth of penetration of the medicaments into dentinal tubules at coronal (C), middle (M) and apical (A) thirds was measured. Fracture resistance of the teeth was evaluated after 1 week and 1-month intervals. NCH showed the highest depth of penetration (C ∼746.98μm, M ∼700.30μm, A ∼134.69μm). CS showed the highest fracture resistance, whereas no significant difference was found between other medicaments, at both the time intervals. NCH (8.07±0.06) and NCS (8.13±0.06) showed significantly higher zone of inhibition than CH (7.7±0.17) and CS (7.37±0.15). Under the conditions of this study, it can be concluded that NCH and NCS can be used as potential intracanal medicaments.

Bacterial invasion into radicular dentine-an in vitro study

OBJECTIVES

We wanted to investigate differences in invasiveness into radicular dentinal tubules by monocultured and co-cultured bacteria frequently found in infected root canals.

METHODS

Fifty-one human roots were incubated for 8 weeks with monocultured Streptococcus gordonii ATCC 10558, Streptococcus sanguinis ATCC 10556, and with five capnophiles/anaerobes as well as with capnophiles/anaerobes co-cultured with a streptococcal species. Thereafter, bacterial samples were cultured from the inner, middle, and outer third of the root dentine of longitudinally broken teeth (n = 5). In addition, scanning electron microscopy (SEM) images were obtained.

RESULTS

Single gram-positive species were able to penetrate into the middle and outer third of the root dentine. Fusobacterium nucleatum ATCC 25586 was not found in any of the dentine specimens. Prevotella intermedia ATCC 25611 and Porphyromonas gingivalis ATCC 33277 were found in the inner and middle third. The bacterial load of streptococci was higher in all thirds in co-cultures compared to single infections. In co-cultures with streptococci, Actinomyces oris ATCC 43146 was found in the outer third in 9/10 samples, whereas P. intermedia ATCC 25611 was not detectable inside dentine. Co-culture with S. sanguinis ATCC 10556 enabled F. nucleatum ATCC 25586 to invade dentine; SEM images showed that F. nucleatum ATCC 25586 had a swollen shape.

CONCLUSIONS

Invasiveness of bacteria into dentinal tubules is species-specific and may change depending on culturing as a single species or co-culturing with other bacteria.

CLINICAL RELEVANCE

Oral streptococci may promote or inhibit invasion of capnophiles/anaerobes into radicular dentine.

Effects of air polishing and an amino acid buffered hypochlorite solution to dentin surfaces and periodontal ligament cell survival, attachment, and spreading

OBJECTIVES

The aim of this study is to examine morphological changes of dentin surfaces following air polishing or amino acid buffered hypochlorite solution application and to assess their influence on periodontal ligament (PDL) cell survival, attachment, and spreading to dentin discs in vitro.

MATERIALS AND METHODS

Bovine dentin discs were treated with either (i) Classic, (ii) Plus, or (iii) Perio powder (EMS). Furthermore, Perisolv® a hypochlorite solution buffered with various amino acids was investigated. Untreated dentin discs served as controls. Morphological changes to dentin discs were assessed using scanning electron microscopy (SEM). Human PDL cells were seeded onto the respectively treated discs, and samples were then investigated for PDL cell survival, attachment, and spreading using a live/dead assay, adhesion assay, and SEM imaging, respectively.

RESULTS

Both control and Perisolv®-rinsed dentin discs demonstrated smooth surfaces at low and high magnifications. The Classic powders demonstrated the thickest coating followed by the Powder Plus. The Perio powder demonstrated marked alterations of dentin discs by revealing the potential to open dentinal tubules even before rinsing. Seeding of PDL cells demonstrated an almost 100 % survival rate on all samples demonstrating very high biocompatibility for all materials. Significantly higher PDL cell numbers were observed on samples treated with the Perio powder and the Perisolv® solution (approximately 40 % more cells; p < 0.05). SEM imaging revealed the potential for PDL cells to attach and spread on all surfaces.

CONCLUSION

The results from the present study demonstrate that cell survival and spreading of PDL cells on root surfaces is possible following either air polishing or application with Perisolv®. Future in vitro and animal testing is necessary to further characterize the beneficial effects of either system in a clinical setting.

CLINICAL RELEVANCE

The use of air polishing or application with Perisolv amino acid buffered hypochlorite solution was effective in treating root surfaces and allowed for near 100 % PDL cell survival, attachment, and spreading onto all root surfaces.

Study of invasion and colonization of E. faecalis in microtubes by a novel device

Enterococcus faecalis (E. faecalis) is a species that has frequently been isolated from root canal of patients suffering from persistent periodontitis. To a great degree, the resistance of E. faecalis to irrigating solutions and intracanal medicaments is due to its invasion into the dentinal tubules. In this study, we developed a device to observe the dynamic process of the bacterial invasion into microtubes. According to the diameter of the dentinal tubules and other microstructures in the root canals, we designed four different size microtubes with different lengths in this device. As expected, E. faecalis is able to steadily grow in this device and penetrate into the microtubes, and a continuous observation is achieved. We found that the depth and speed of bacterial penetration, the extent of colonization and the arrangement of the bacteria in the microtubes are strongly influenced by the size of the microtube. The length of the microtube also influences the speed and depth of the bacterial invasion. Bacteria in microtubes with a similar diameter to the real dentinal tubules showed a discontinuous distribution, which is consistent with the final bacterial distribution in the native dentinal tubules. Considering the device's advantages such as its ability to provide real-time observations, its ability to be modified as necessary, and its standardized operation, it has great potential to be widely used as a platform for the observation of the interaction of different bacteria during an invasion course and to test the efficacy of new antibacterial agents in dentistry.

Comparative Morphologic Evaluation and Occluding Effectiveness of Nd: YAG, CO2 and Diode Lasers on Exposed Human Dentinal Tubules: An Invitro SEM Study

INTRODUCTION

Dentinal hypersensitivity is one of the most common problem, encountered in dental practice but has least predictable treatment outcome. The advent of lasers in dentistry has provided an additional therapeutic option for treating dentinal hypersensitivity. Although various lasers have been tried over a period of time to treat dentinal hypersensitivity, but still the doubt persist as to which laser leads to maximum dentinal tubular occlusion and is most suitable with minimal hazardous effects.

AIM

To compare the effects of Nd: YAG, CO2 and 810-nm diode lasers on width of exposed dentinal tubule orifices and to evaluate the morphologic changes on dentinal surface of human tooth after laser irradiation by scanning electron microscope (SEM).

MATERIALS AND METHODS

Forty root specimens were obtained from ten freshly extracted human premolars, which were randomly divided into four groups of ten each. Group I: control group treated with only saline, Group II: Nd:YAG laser, Group III: CO2 laser and Group IV: 810-nm diode laser. The specimens were examined using SEM. After calculating mean tubular diameter for each group, the values were compared statistically using parametric one-way ANOVA test and Turkey's post hoc multiple comparison test.

RESULTS

All the three lased groups showed a highly statistical significant result with p-value of <0.001 as compared to non-lased group. On intergroup comparison within the lased groups, all the three groups showed statistically significant difference in the reduction of dentinal tubular diameter (p-value < 0.001).

CONCLUSION

Nd: YAG laser was found to be most effective, followed by the CO2 laser and 810-nm diode laser was found to be least effective. The morphologic changes like craters, cracks and charring effect of the dentine were seen maximum by the use of CO2 laser.

Evaluation of the Antibacterial Efficacy of Azadirachta Indica, Commiphora Myrrha, Glycyrrhiza Glabra Against Enterococcus Faecalis using Real Time PCR

AIM

To compare the antibacterial efficacy of Azadirachta indica (Neem), Commiphora myrrha (Myrrh), Glycyrrhiza glabra (Liquorice) with 2% Chlorhexidine (CHX) against E. faecalis by using Real Time PCR.

MATERIALS AND METHODS

A total of fifty teeth specimens (n=50) were inoculated with E. faecalis for 21 days. Specimens were divided into five groups (Group 1: Myrrh, Group 2: Neem, Group 3: Liquorice, Group 4: 2% CHX and Group 5: Saline (negative control)). The intracanal medicaments were packed inside the tooth. After 5 days, the remaining microbial load was determined by using real time PCR.

RESULTS

Threshold cycle (Ct) values of Myrrh extract, Neem extract, Liquorice Extract, 2% CHX and saline were found to be 30.94, 23.85, 21.38, 30.93 and 17.8 respectively.

CONCLUSION

Myrrh extract showed inhibition of E.faecalis equal to that of 2% CHX followed by Neem, Liquorice and Saline.

Surface Treatment by Different Parameters of Erbium:Yttrium-Aluminum-Garnet (Er:YAG) Laser: Scanning Electron Microscope (SEM) Evaluation

INTRODUCTION

This study aimed to assess the Scanning Electron Microscope (SEM) analysis of tooth surface irradiated by erbium:yttrium-aluminum-garnet (Er:YAG) laser with various parameters.

METHODS

Number of 25 extracted human third molars free of caries were used in this study. The teeth were put into 5 groups for laser irradiation as follows: group 1 (power: 0.5 W, Energy: 50 mJ); group 2 (power: 1 W, Energy: 100 mJ); group 3 (power: 1.5 W, Energy: 150 mJ); group 4 (power: 2 W, Energy: 200 mJ); group 5 (power: 2.5 W, Energy: 250 mJ). All samples were prepared by repetition rate of 10 Hz and duration of 230 μs, using a non-contact handpiece at a distance of 4 mm. Then, the samples were prepared for SEM examination.

RESULTS

SEM evaluation of every 25 samples, treated by Er:YAG, showed that all groups had exposed dentinal tubules without any melted area or cracks.

CONCLUSION

In this study we used SEM to investigate ablated dentine with different parameters of Er:YAG laser energy. Our findings support these conclusions. All powers of laser below 3 W are proper for ablation, and make no cracks.

The Effect of Addition of an EPS Degrading Enzyme with and without Detergent to 2% Chlorhexidine on Disruption of Enterococcus faecalis Biofilm: A Confocal Laser Scanning Microscopic Study

BACKGROUND

Enterococcus faecalis is one of the most commonly occurring organisms retrieved from root canal treated teeth that show refractory apical periodontitis. Though it is well known that the ability of E. faecalis to form a matrix-encased biofilm contributes to its pathogenicity, the role of extracellular dextran and DNA in biofilm formation and its effect on the susceptibility of the biofilm to chlorhexidine remains poorly understood. It was hypothesized that the addition of an Extracellular Polymeric Substance (EPS) degrading enzyme along with a detergent to chlorhexidine may increase the susceptibility of the E. faecalis biofilm.

AIM

To evaluate the sensitivity of Enterococcus faecalis biofilms treated with DNase enzyme and their susceptibility to 2% chlorhexidine used alone or in conjunction with a detergent in a dentin disinfection model and examine under confocal laser scanning microscopy (CLSM).

MATERIALS AND METHODS

Semi cylindrical shaped dentin specimens were infected with E. faecalis and incubated for 24 hours. Following incubation, the infected dentin specimens were exposed for 3 minutes to the four disinfecting solutions and grouped accordingly. {Group I- Sterile saline, Group II- 2% Chlorhexidine (CHX), Group III- Dnase1 Enzyme + 2% CHX, Group IV- DNase1 Enzyme + 2% CHX & Tween 80. Bacterial viability was then assessed by staining the specimens and examining under CLSM to analyse the proportion of dead and live bacteria within the dentinal tubules.

RESULTS

The Groups II, III and IV showed statistically significant (p<0.05) percentage of dead bacteria compared to the control (Group I). However there was no significant difference in the killing effectiveness within the experimental groups (II-IV) at (p<0.05).

CONCLUSION

EPS degrading enzyme (DNase I) disrupts the biofilm and increases the susceptibility of E.faecalis when exposed to 2% Chlorhexidine and the use of a surfactant with this combination significantly contributes to improving the antibacterial efficacy.

The deposition and imaging of silica sub-micron particles in dentine

OBJECTIVES

Sub-micron particles may assist in the delivery of compounds into dentine tubules. The surface interactions of the particles with dentine may prevent them from entering the tubules. The aim of this study is to investigate whether silica particles, treated with surfactants improves dentine tubules occlusion using both artificial and human tooth models

METHODS

Spherical silica particles (size 130-810nm) bearing an encapsulated ruthenium luminescent complex were coated with the following surfactants: Zonyl(®) FSA, Triton(®) X-100 and Tween20(®). The particles were prepared as 0.004% w/v and 0.04% w/v solutions with deionized water and were applied to the surface of; (1) in vitro model of PET ThinCert™ cell culture inserts; (2) 0.1mm thick sections of human molar teeth.

RESULTS

Scanning electron and confocal fluorescence microscopy images show that particles without any coating and with TritonX-100 coating had the highest aggregation. Particles with Tween-20 are less aggregated on the surface and show inclusion in the tubules. Particles coated with fluorosurfactant Zonyl show a preference for aggregation at the tubule. With the ThinCert™ membranes high aggregation within the artificial tubules was increased by particle concentration.

CONCLUSIONS

The use of silica sub-micron particles on hard dental tissues is dependent on the modification of the surface chemistry of both the particle and the dentine and the employment of the fluorοsurfactant may improve tubule occlusion. The use of ThinCerts™ membrane is useful in vitro model to mimic dentinal tubules and observe the ability of particles to occlude small channels.

CLINICAL SIGNIFICANCE

The use of silica sub-micron particles on hard dentine tissues is dependent on the modification of the surface coating of the particles. This may influence how particles are incorporated in potential delivery vehicles applied to the dentine surface with the employment of a fluorosurfactant showing promise.

Ultrastructural analysis of the root canal walls after preparation with two rotary nickel-titanium endodontic instruments

Background:

Root canal preparation may produce a large quantity of smear layer that covers canal walls.

Aims:

The aim of this study was to evaluate by Scanning Electron Microscope (SEM) the root canal dentine after instrumentation with nickel-titanium rotary files, in order to evaluate the presence/absence of smear layer and the presence/absence of open tubules on the root canal walls at the coronal, middle, and apical third of each sample.

Materials and Methods:

A total of 20 single-rooted freshly extracted teeth were selected and divided into two groups. For each group, root canals were shaped with Mtwo and Revo-S instruments under irrigation with Sodium hypochlorite and 17% ethylenediaminetetraacetic acid. Specimens were fractured longitudinally and SEM analyzed at standard magnification of ×1000 and ×5000. The presence/absence of smear layer and the presence/absence of open tubules at the coronal, middle, and apical third of each canal were evaluated using a three-step scale for scores.

Statistical Analysis Used:

Numeric data were analyzed using the Kruskall-Wallis and Mann-Whitney U-Statistical tests and significance was pre-determined at P < 0.05.

Results and Conclusions:

This study did not reveal differences among the two groups. Mtwo and Revo-S showed no significant difference between them and both presented very low smear layer scores and open tubules scores, with no significant difference among coronal, middle, and apical third. Mtwo and Revo-S rotary instruments seem to be effective in removing smear layer from canal walls.

Microorganism penetration in dentinal tubules of instrumented and retreated root canal walls. In vitro SEM study

Objectives

This in vitro study aimed to investigate the ability of Candida albicans (C. albicans) and Enterococcus faecalis (E. faecalis) to penetrate dentinal tubules of instrumented and retreated root canal surface of split human teeth.

Materials and Methods

Sixty intact extracted human single-rooted teeth were divided into 4 groups, negative control, positive control without canal instrumentation, instrumented, and retreated. Root canals in the instrumented group were enlarged with endodontic instruments, while root canals in the retreated group were enlarged, filled, and then removed the canal filling materials. The teeth were split longitudinally after canal preparation in 3 groups except the negative control group. The teeth were inoculated with both microorganisms separately and in combination. Teeth specimens were examined by scanning electron microscopy (SEM), and the depth of penetration into the dentinal tubules was assessed using the SMILE view software (JEOL Ltd).

Results

Penetration of C. albicans and E. faecalis into the dentinal tubules was observed in all 3 groups, although penetration was partially restricted by dentin debris of tubules in the instrumented group and remnants of canal filling materials in the retreated group. In all 3 groups, E. faecalis penetrated deeper into the dentinal tubules by way of cell division than C. albicans which built colonies and penetrated by means of hyphae.

Conclusions

Microorganisms can easily penetrate dentinal tubules of root canals with different appearance based on the microorganism size and status of dentinal tubules.

A theoretical model of dentinogenesis: dentin and dentinal tubule formation

INTRODUCTION

Dentinogenesis, odontoblast dentin formation, includes dentinal growth, mineralization and dentinal tubule formation. Odontoblasts synthesize collagen resulting in collagen apposition contributing to dentinogenesis. Furthermore, within the tubule, they express non-collagenous proteins, such as dentin phosphoprotein (DPP), associated with hydroxyapatite crystal formation and growth. The aim of this work was to determine patterns of growth and dentin formation and quantification of its mineralization. Findings from our work are relevant to endodontics for future regenerative treatment.

METHODS

We formulated a 3D domain mathematical model, which recreates the events that lead to dentinal tubule mineralization. As reference we used collagen apposition and DPP activity.

RESULTS

We obtained a model depicting predentin's mineralization distribution during dentin development. Furthermore, we verified different DPP diffusion coefficients to test the model's sensitivity.

CONCLUSIONS

We present a model to shed light on the process of dentin and dentinal tubule formation, and its relation to diffusion and mineralization processes.

Effect of Duration of Irrigation with Sodium Hypochlorite in Clinical Protocol of MTAD on Removal of Smear Layer and Creating Dentinal Erosion

Background and aims

The aim of the present study was to compare 1.3% sodium hypochlorite (NaOCl) in MTAD (mixture of tetracycline isomer, acid, and detergent) for the removal of the smear layer and induction of canal erosion.

Materials and methods

38 maxillary incisors were divided in three experimental groups of 10 and two positive and negative control groups of each 4 teeth, and prepared using rotary files. In test groups, 1.3% NaOCl was used for 5, 10 and 20 minutes during preparation followed by MTAD as the final rinse. In negative control group, 5.25% NaOCl was used for 10 minutes followed by 17% Ethylenediamine Tetra-Acetic Acid (EDTA) as the final rinse. In positive control group, dis-tilled water was used for 10 minutes during preparation and then as the final rinse. The samples were examined under scan-ning electron microscope, and the smear layer and dentinal erosion scores were recorded.

Results

Five and 10 min groups had significant differences with 20 min group (p < 0.05). In apical third, 5 and 10 min groups had also significant differences with 20 min (p < 0.05). In the coronal thirds, when the time of irrigation with 1.3% NaOCl increased from 5 min to 20 min, erosion also increased significantly. However, 5 and 10 min groups had no signifi-cant differences with negative control group.

Conclusion

The use of 1.3% sodium hypochlorite for 5 and 10 minutes in the MTAD protocol removes the smear layer in the coronal and middle thirds but does not induce erosion.

Effect of 808nm diode laser irradiation on root canal walls after smear layer removal: A scanning electron microscope study

INTRODUCTION

This study was carried out to investigate the effect of 808nm diode laser irradiation on dentinal tubules of root canal wall.

MATERIALS AND METHODS

Twelve single-rooted teeth were used. After cleaning and shaping with rotary instruments by the crown down technique, the smear layer was removed by alternating irrigation with EDTA and sodium hypochlorite. The teeth were then randomly divided into experimental and control groups of six teeth each. In experimental group, laser irradiation was activated inside the canal and the teeth of the other group served as controls. Kruskal-Wallis and Friedman tests were used for comparing occluded dentinal tubules in different part of the roots.

RESULTS

Scanning electron microscopy showed that occluded dentinal tubules could be observed in all laser irradiated teeth; however, none of the control teeth showed occluded dentinal tubules. The Friedman test showed that in the laser irradiated group the best result was achieved in the apical third of the root canals compared with the middle (p<0.005) and cervical third (p<0.002). Dentinal tubules of the middle third were also significantly different from the cervical third as well (p<0.005).

CONCLUSION

Laser radiation after removing smear layer could successfully occlude dentinal tubules and the best results was achieved at the apical part of the canal.