Fabricio B. Teixeira

An Evaluation of Microbial Leakage in Roots Filled with a Thermoplastic Synthetic Polymer-Based Root Canal Filling Material (Resilon)

The purpose of this study was to compare bacterial leakage using Streptococcus mutans and Enterococcus faecalis through gutta-percha and a thermoplastic synthetic polymer-based root filling (Resilon) using two filling techniques during a 30-day period. Teeth were decoronated, roots prepared to a length of 16 mm, and instrumented to ISO sizes 40 to 50. A total of 156 roots were randomly divided into 8 groups of 15 roots (groups 1-8) and 3 control groups (12 roots each). Roots were filled using lateral and vertical condensation techniques with gutta-percha and AH 26 sealer (groups 1 and 2) or with gutta-percha and Epiphany sealer (groups 3 and 4). Groups 5 and 6 were filled with Resilon and Epiphany sealer using the lateral or vertical condensation techniques. A split chamber microbial leakage model was used in which S. mutans placed in the upper chamber could reach the lower chamber only through the filled canal. Groups 7 and 8 were identical to groups 5 and 6 respectively; however, E. faecalis was used to test the leakage. Positive controls were filled with Resilon (12 roots) and gutta-percha (12 roots) without sealer and tested with bacteria, whereas negative controls (12 roots) were sealed with wax to test the seal between chambers. All but one positive control leaked within 24 h, whereas none of the negative controls leaked. Resilon showed minimal leakage (group 8: one leakage; groups 5-7: each with two leakages), which was significantly less than gutta-percha, in which approximately 80% of specimens with either technique or sealer leaked. Kruskal-Wallis test showed statistical significance when all groups were compared (p < 0.05). Mann-Whitney U test compared the respective groups and found Resilon groups superior to gutta-percha groups (p < 0.05).

In vitro assessment of the antimicrobial action and the mechanical ability of chlorhexidine gel as an endodontic irrigant.

The objective of this study was to assess the chlorhexidine gluconate gel as an endodontic irrigant. First the ability of chlorhexidine gel to disinfect root canals contaminated in vitro with Enterococcus faecalis was investigated. A scanning electron microscope was also used to evaluate its cleansing ability compared with endodontic irrigants commonly used, such as sodium hypochlorite and chlorhexidine gluconate liquid. The results indicated that the chlorhexidine gel produced a cleaner root canal surface and had an antimicrobial ability comparable with that obtained with the other solutions tested. It was concluded that chlorhexidine gluconate in gel form has potential for use as an endodontic irrigant.

Direct effect of intracanal medicaments on survival of stem cells of the apical papilla

INTRODUCTION Regenerative endodontic procedures are an alternative treatment for immature teeth with necrotic pulps. Typically, intracanal medicaments such as triple antibiotic paste (TAP) or double antibiotic paste (DAP) and calcium hydroxide (Ca[OH](2)) are used for disinfection. However, their effect on human stem cells of the apical papilla (SCAPs) is unknown. We hypothesized that intracanal medicaments at high concentrations are toxic to SCAPs. To test this hypothesis, a cell culture assay was used. METHODS Briefly, SCAPs were cultured and subjected to either no drug treatment or various concentrations including TAP, DAP, modified TAP (ciprofloxacin, metronidazole and cefaclor), Augmentin (Champs Pharmacy, San Antonio, TX), or Ca(OH)(2). Viable stem cells counts were obtained using an automated method of detecting trypan blue dye at 3 days after treatment. RESULTS All 4 antibiotics significantly reduced SCAP survival in a concentration-dependent fashion. Interestingly, Ca(OH)(2) was conducive with SCAP survival at all concentrations. CONCLUSIONS Collectively, our data show that high concentrations of antibiotics have a detrimental effect on SCAP survival, whereas lower concentrations as well as Ca(OH)(2) at all tested concentrations are conducive with SCAP survival and proliferation. These studies highlight the clinically important point that intracanal medicaments must be used at concentrations that are bactericidal while having minimal effects on stem cell viability.

Treatment Options: Biological Basis of Regenerative Endodontic Procedures

Dental trauma occurs frequently in children and often can lead to pulpal necrosis. The occurrence of pulpal necrosis in the permanent but immature tooth represents a challenging clinical situation because the thin and often short roots increase the risk of subsequent fracture. Current approaches for treating the traumatized immature tooth with pulpal necrosis do not reliably achieve the desired clinical outcomes, consisting of healing of apical periodontitis, promotion of continued root development, and restoration of the functional competence of pulpal tissue. An optimal approach for treating the immature permanent tooth with a necrotic pulp would be to regenerate functional pulpal tissue. This review summarizes the current literature supporting a biological rationale for considering regenerative endodontic treatment procedures in treating the immature permanent tooth with pulp necrosis.

Tissue Engineering Strategies for Immature Teeth with Apical Periodontitis

INTRODUCTION Regenerative endodontic treatment on immature teeth with apical periodontitis is promising but still not well-established. The purpose of this study was to explore novel strategies to engineer a vital support structure within a root canal space by a combination of induced blood clot, exposure of dentin matrix, and a cross-linked collagen scaffold. METHODS Apical periodontitis was induced in 6 dogs with immature teeth (n = 64). After disinfection, the following groups were randomly assigned: blood clot (BC) alone, BC with a cross-linked collagen scaffold (CCS), BC with exposure of dentin matrix by ethylenediaminetetraacetic acid (EDTA), and BC with CCS and EDTA. Positive (infected only) and negative controls (untreated) were also included. The dogs were followed up for 3.5 months and killed. Periradicular healing and root wall thickening were radiographically analyzed and statistically evaluated. The jaws were then fixed, demineralized, and subjected to histologic analyses. Newly formed mineralized tissues were histomorphometrically analyzed, quantified, and statistically evaluated. RESULTS Radiographically there was significant difference in periradicular healing and root wall thickening (P < .05). Histomorphometric analysis showed significantly more mineralized tissue formation in the groups containing the scaffold (P < .05). Exposure of the dentin matrix by EDTA appeared to increase the adherence of the newly formed mineralized tissue to the root walls. CONCLUSIONS The use of cross-linked collagen scaffold and exposure of dentin matrix combined with blood clot might provide an efficient approach to generate a vital support structure for the treatment of immature teeth with apical periodontitis.

Concentration-dependent effect of sodium hypochlorite on stem cells of apical papilla survival and differentiation.

INTRODUCTION Intracanal disinfection is a crucial step in regenerative endodontic procedures. Most published cases suggest the use of sodium hypochlorite (NaOCl) as the primary irrigant. However, the effect of clinically used concentrations of NaOCl on the survival and differentiation of stem cells is largely unknown. In this study, we tested the effect of various concentrations of NaOCl on the stem cells of the apical papilla (SCAPs) survival and dentin sialophosphoprotein (DSPP) expression. METHODS Standardized root canals were created in extracted human teeth and irrigated with NaOCl (0.5%, 1.5%, 3%, or 6%) followed by 17% EDTA or sterile saline. SCAPs in a hyaluronic acid-based scaffold were seeded into the canals and cultured for 7 days. Next, viable cells were quantified using a luminescence assay, and DSPP expression was evaluated using quantitative real-time polymerase chain reaction. RESULTS There was a significant reduction in survival and DSPP expression in the group treated with 6% NaOCl compared with the untreated control group. Comparable survival was observed in the groups treated with the lower concentrations of NaOCl, but greater DSPP expression was observed in the 1.5% NaOCl group. In addition, 17% EDTA resulted in increased survival and DSPP expression partially reversing the deleterious effects of NaOCl. CONCLUSIONS Collectively, the results suggest that dentin conditioning with high concentrations of NaOCl has a profound negative effect on the survival and differentiation of SCAPs. However, this effect can be prevented with the use of 1.5% NaOCl followed by 17% EDTA. The inclusion of this irrigation regimen might be beneficial in regenerative endodontic procedures.

Microbial Susceptibility to Calcium Hydroxide Pastes and Their Vehicles

The aim of this study was to investigate the susceptibility of some microorganisms commonly isolated from root canals to calcium hydroxide in combination with several vehicles by the agar diffusion method. Stainless-steel cylinders were placed on each inoculated agar medium. The test medications and their controls were placed inside the cylinders. The zones of growth inhibition were measured and recorded after the incubation period for each plate, and the results were analyzed statistically. Enterococcus faecalis was most resistant, whereas the anaerobic Porphyromonas endodontalis was more susceptible to all medications, followed by P. gingivalis and Prevotella intermedial intermedia. Ca(OH)2 + CMCP + glycerin showed significantly larger mean zones of inhibition when compared with the other medications. We conclude that anaerobic Gram-negative bacteria are more susceptible to calcium hydroxide pastes than facultative Gram-positive microorganisms.

Effect of Dentin Conditioning with Intracanal Medicaments on Survival of Stem Cells of Apical Papilla

INTRODUCTION Regenerative endodontics is a valuable treatment modality for immature teeth with pulpal necrosis. A common feature in regenerative cases is the use of intracanal medicaments. Although these medicaments are chosen because of their antibacterial properties, their enduring effect on dentin (conditioning) and the subsequent impact on stem cell survival has never been evaluated. In this study, we hypothesized that triple antibiotic paste (TAP), double antibiotic paste (DAP), or Ca(OH)2 has an indirect adverse effect on the survival of stem cells of apical papilla (SCAP) by dentin conditioning. METHODS Human dentin disks were created with a standardized root canal diameter of 3.2 mm. The disks were then exposed to either TAP or DAP (at concentrations of 1 mg/mL or 1000 mg/mL), Ca(OH)2 (Ultracal), or Hanks balanced salt solution for 7 or 28 days. Next, the medicaments were removed with copious irrigation, followed by placement of SCAP in a Matrigel scaffold in the lumen of the disks. The bioengineered constructs were cultured for 7 days, followed by determination of cellular viability by using the CellTiter-Glo luminescence assay. Data were analyzed using 1-way analysis of variance with Bonferroni post hoc test. RESULTS Exposure of dentin to TAP or DAP at 1000 mg/mL resulted in no viable SCAP, whereas the use of these medicaments at 1 mg/mL had no adverse effect on cell viability. In contrast, Ca(OH)2 treatment significantly increased SCAP survival and proliferation when compared with the control group. CONCLUSIONS Dentin conditioning with TAP and DAP at commonly used clinical concentration (approximately 1000 mg/mL) alters dentin in such a way as to prevent SCAP survival. This lethal indirect effect of both TAP and DAP can be largely avoided if these medicaments are used at the 1 mg/mL concentration. Conversely, dentin conditioning with Ca(OH)2 promotes SCAP survival and proliferation.

In vitro antimicrobial activity of calcium hydroxide pastes and their vehicles against selected microorganisms

The aim of this study was to investigate in vitro the antimicrobial activity of calcium hydroxide in combination with several vehicles against some microorganisms commonly isolated from root canals. Antimicrobial activity was determined by the agar diffusion method. Stainless-steel cylinders were placed on each inoculated agar medium. The test medicaments and their controls were placed inside the cylinders. The zones of growth inhibition were measured and recorded after incubation for each plate and the results were analyzed statistically (ANOVA). The in vitro antimicrobial effects of the medications were ranked from strongest to weakest as follows: Ca(OH)2 + CMCP + glycerine, Ca(OH)2 + CMCP, Ca(OH)2 + glycerine, Ca(OH)2 + anesthetic, Ca(OH)2 + saline, Ca(OH)2 + H2O, Ca(OH)2 + polyethyleneglycol. The pastes with oily vehicles showed significantly larger mean zones of inhibition compared to those with aqueous or viscous vehicles. It was concluded that diffusion and antimicrobial activity of calcium hydroxide were affected by the type of vehicle used.

Comparative study of the antimicrobial efficacy of chlorhexidine gel, chlorhexidine solution and sodium hypochlorite as endodontic irrigants

The purpose of this study was to assess the in vitro the antimicrobial efficacy of chlorhexidine gluconate gel as an endodontic auxiliary chemical substance compared to sodium hypochlorite (NaOCl) and chlorhexidine gluconate solution. The antimicrobial efficacy of the tested substances was evaluated using the agar diffusion test. The growth inhibition zones produced by 0.2%, 1% and 2% chlorhexidine gel were evaluated against 5 facultative anaerobic bacteria and 4 pigmented Gram-negative anaerobes, and compared to the results obtained by NaOCl and chlorhexidine solution. The largest growth inhibition zones were produced when the test bacteria were in contact with 2% chlorhexidine gluconate gel (11.79 mm), being significantly different (p<0.05) from the growth inhibition zones produced by all NaOCl concentrations, including 5.25% (9.54 mm). However, there was no statistically significant difference (p>0.05) between the growth inhibition zones obtained with equal concentrations of chlorhexidine solution and gel. The results of this study indicate that, as far as its antimicrobial properties are concerned, chlorhexidine gel has a great potential to be used as an endodontic auxiliary chemical substance.