Use of electromagnetic stimulation on an Enterococcus faecalis biofilm on root canal treated teeth in vitro.

Root canal disinfection is of utmost importance in the success of the treatment, thus, a novel method for achieving root canal disinfection by electromagnetic waves, creating a synergistic reaction via electric and thermal energy, was created. To study electromagnetic stimulation (EMS) for the disinfection of root canal in vitro, single rooted teeth were instrumented with a 45.05 Wave One Gold reciprocating file. Specimens were sterilized and inoculated with Enterococcus faecalis ATCC 29,212, which grew for 15 days to form an established biofilm. Samples were treated with 6% sodium hypochlorite (NaOCl), 1.5% NaOCl 1.5% NaOCl with EMS, 0.9% saline with EMS or 0.9% saline. After treatments, the colony forming units (CFU) was determined. Data was analyzed by Wilcoxon Rank Sums Test (α = 0.05). One sample per group was scored and split for confocal laser scanning microscopy imaging. There was a significant effect with the use of NaOCl with or without EMS versus 0.9% saline with or without EMS (p = 0.012 and 0.003, respectively). CFUs were lower when using 0.9% saline with EMS versus 0.9% saline alone (p = 0.002). Confocal imaging confirmed CFU findings. EMS with saline has an antibiofilm effect against E. faecalis and can potentially be applied for endodontic disinfection.

Pediatric Phantom Dosimetry of Kodak 9000 Cone-beam Computed Tomography.

PURPOSE: The purpose of the study was to evaluate the radiation dose of the Kodak 9000 cone-beam computed tomography (CBCT) device for different anatomical areas using a pediatric phantom. METHODS: Absorbed doses resulting from maxillary and mandibular region three by five cm CBCT volumes of an anthropomorphic 10-year-old child phantom were acquired using optical stimulated dosimetry. Equivalent doses were calculated for radiosensitive tissues in the head and neck area, and effective dose for maxillary and mandibular examinations were calculated following the 2007 recommendations of the International Commission on Radiological Protection (ICRP). RESULTS: Of the mandibular scans, the salivary glands had the highest equivalent dose (1,598 microsieverts [µSv]), followed by oral mucosa (1,263 µSv), extrathoracic airway (pharynx, larynx, and trachea; 859 µSv), and thyroid gland (578 µSv). For the maxilla, the salivary glands had the highest equivalent dose (1,847 µSv), followed closely by oral mucosa (1,673 µSv), followed by the extrathoracic airway (pharynx, larynx, and trachea; 1,011 µSv) and lens of the eye (202 µSv). CONCLUSION: Compared to previous research of the Kodak 9000, completed with the adult phantom, a child receives one to three times more radiation for mandibular scans and two to 10 times more radiation for maxillary scans.

Antibacterial Effects of Antimicrobials Used in Regenerative Endodontics against Biofilm Bacteria Obtained from Mature and Immature Teeth with Necrotic Pulps.

INTRODUCTION: We investigated the direct and residual antibacterial effects of intracanal antimicrobials against bacterial biofilms obtained from infected mature and immature teeth with necrotic pulps. METHODS: Sterile dentin slabs (n = 100) were inoculated with bacterial biofilms obtained from root canals of an immature or a mature tooth with pulpal necrosis and incubated anaerobically for 3 weeks (n = 50 per biofilm). Dentin infected with each type of biofilm received 1 week of treatment with 1 or 5 mg/mL double antibiotic paste (DAP) in methylcellulose hydrogels, calcium hydroxide, or placebo paste or received no treatment (n = 10). The pastes were removed, and biofilm disruption assays were performed. Additional dentin slabs (n = 100) were pretreated with the same treatments (n = 20). The pastes were rinsed off, and the samples were immersed in phosphate-buffered saline for 1 week. Thereafter, samples from the treatment groups were infected with bacterial biofilm from both clinical sources mentioned earlier (n = 10 per biofilm) and incubated anaerobically for 3 weeks before conducting biofilm disruption assays. Uninfected dentin slabs were used for both antibacterial experiments as negative control groups (n = 20). RESULTS: All antimicrobials showed significant direct antibacterial effects regardless of the biofilm source. Dentin pretreated with 5 mg/mL DAP provided significantly higher residual antibacterial effects in comparison with all other groups regardless of the source of biofilm. Dentin pretreated with calcium hydroxide did not show any residual antibacterial effects. CONCLUSIONS: Tested antimicrobials showed significant direct antibacterial effects. Only 5 mg/mL DAP exhibited significant residual antibacterial effects against bacterial biofilms from an infected root canal of an immature tooth.

Direct and indirect antibacterial effects of various concentrations of triple antibiotic pastes loaded in a methylcellulose system.

We investigated the direct and indirect (residual) antibacterial effects of various concentrations of triple antibiotic paste (TAP) loaded into a methylcellulose system. Enterococcus faecalis (E. faecalis) was grown on sterilized dentin blocks (n = 60) and treated with clinically used TAP (1,000 mg/mL), low concentrations of methylcellulose-based TAP (100, 10, and 1 mg/mL), placebo paste, or 1.5% NaOCl (n = 10). The pastes were then removed, and biofilm disruption assays were performed. Additional dentin blocks (n = 120) were pretreated with the same experimental groups (n = 20). The pastes were rinsed off, and the samples were immersed independently in phosphate-buffered saline for 2 and 4 weeks (n = 10). E.faecalis was then grown on the dentin blocks, and biofilm disruption assays were performed. Fisher's Exact and Wilcoxon rank sum tests were used for statistical analyses. With regard to direct antibacterial effects, all treatment groups demonstrated complete eradication of biofilms in comparison to placebo paste, while 10 mg/mL of TAP or higher provided substantial residual antibacterial effects. However, dentin treated with 1 mg/mL of TAP or 1.5% NaOCl did not provide substantial residual antibacterial effects. Dentin pretreated with 10 mg/mL of TAP or higher exhibited extended residual antibacterial effects and can thus be used during endodontic regeneration.(J Oral Sci 58, 575-582, 2016).

Residual antibiofilm effects of various concentrations of double antibiotic paste used during regenerative endodontics after different application times.

OBJECTIVE: We investigated the residual antibiofilm effects of different concentrations of double antibiotic paste (DAP) applied on radicular dentin for 1 or 4 weeks. DESIGN: Dentin samples were prepared (n=120), sterilized and pretreated for 1 or 4 weeks with the clinically used concentration of DAP (500mg/mL), low concentrations of DAP (1, 5 or 50mg/mL) loaded into a methylcellulose system, calcium hydroxide (Ca(OH)2), or placebo paste. After the assigned treatment time, treatment pastes were rinsed off and the samples were kept independently in phosphate buffered saline for 3 weeks. Pretreated dentin samples were then inoculated with Enterococcus faecalis and bacterial biofilms were allowed to grow for an additional 3 weeks. Biofilms were then retrieved from dentin using biofilm disruption assays, diluted, spiral plated, and quantified. Fisher's Exact and Wilcoxon rank sum tests were used for statistical comparisons (α=0.05). RESULTS: Dentin pretreatment for 4 weeks with 5, 50 or 500mg/mL of DAP demonstrated significantly higher residual antibiofilm effects and complete eradication of E. faecalis biofilms in comparison to a 1 week pretreatment with similar concentrations. However, dentin pretreated with 1mg/mL of DAP or Ca(OH)2 did not provide a substantial residual antibiofilm effect regardless of the application time. CONCLUSIONS: Dentin pretreatment with 5mg/mL of DAP or higher for 4 weeks induced significantly higher residual antibiofilm effects in comparison to a 1 week pretreatment with the same concentrations.

The effects of radicular dentine treated with double antibiotic paste and ethylenediaminetetraacetic acid on the attachment and proliferation of dental pulp stem cells.

AIM: This study explored the effects of dentine treated with two concentrations of double antibiotic paste (DAP) and ethylenediaminetetraacetic acid (EDTA) on the attachment and proliferation of dental pulp stem cells (DPSCs). MATERIALS AND METHODS: Radicular dentine samples were prepared with identical dimensions and randomized into six groups (n = 4). Four groups were treated with double antibiotic paste (DAP) at concentrations of 500 mg ml(-1) or 1 mg ml(-1) with or without EDTA. The other two groups were treated with EDTA only or received no treatment. DPSCs were seeded on each dentine sample (10 000 cells per sample). Lactate dehydrogenase activity assays were used to calculate the attached DPSCs after 1 day of incubation. Water soluble tetrazolium assays were performed to investigate DPSCs proliferation on the treated dentine samples after three additional days of incubation. Two-way anova followed by Tukey-Kramer tests was used for statistical analyses (α = 0.05). RESULTS: Dentine treated with 1 or 500 mg ml(-1) of DAP followed by EDTA caused significant increases in DPSCs attachment compared to the dentine treated with the DAP alone. The 500 mg ml(-1) of DAP with or without EDTA caused significant reductions in DPSCs proliferation. However, the treatment of dentine with 1 mg ml(-1) of DAP did not have significant negative effects on DPSCs proliferation regardless of the use of EDTA. CONCLUSION: The use of 1 mg ml(-1) of DAP followed by 10 min of irrigation with EDTA in endodontic regeneration procedure may have no negative effects on the attachment and proliferation of DPSCs.

Pulp and plaque microbiotas of children with severe early childhood caries.

BACKGROUND AND OBJECTIVE: Bacterial invasion into pulps of primary teeth can lead to infection and premature tooth loss in children. This pilot study aimed to explore whether the microbiota of carious exposures of dental pulps resembles that of carious dentin or that of infected root canals. DESIGN: Children with severe early childhood caries were studied. Children were consented and extent of caries, plaque, and gingivitis measured. Bacteria were sampled from carious lesion biofilms and vital carious exposures of pulps, and processed by anaerobic culture. Isolates were characterized from partial sequences of the 16S rRNA gene and identified by comparison with taxa in the Human Oral Microbiome Database (http://www.HOMD.org). The microbiotas of carious lesions and dental pulps were compared using univariate and multivariate approaches. RESULTS: The microbiota of cariously exposed pulps was similar in composition to that of carious lesion biofilms except that fewer species/taxa were identified from pulps. The major taxa identified belonged to the phyla Firmicutes (mainly streptococci) and Actinobacteria (mainly Actinomyces species). Actinomyces and Selenomonas species were associated with carious lesions whereas Veillonella species, particularly Veillonella dispar was associated with pulps. Other bacteria detected in pulps included Streptococcus mutans, Parascardovia denticolens, Bifidobacterium longum, and several Lactobacillus and Actinomyces species. By principal, component analysis pulp microbiotas grouped together, whereas those in caries biofilms were widely dispersed. CONCLUSIONS: We conclude that the microbiota of cariously exposed vital primary pulps is composed of a subset of species associated with carious lesions. Vital primary pulps had a dominant Firmicutes and Actinobacteria microbiota which contrasts with reports of endodontic infections which can harbor a gram-negative microbiota. The microbiota of exposed primary pulps may provide insight into bacterial species at the forefront of caries invasion in dentinal lesions that can invade into the pulp and the nature of species that need suppressing for successful pulp therapy.

Effects of two combinations of triple antibiotic paste used in endodontic regeneration on root microhardness and chemical structure of radicular dentine.

We investigated the effects of triple antibiotic paste (TAP) and modified triple antibiotic paste (MTAP) concentrations on the microhardness and chemical structure of radicular dentine. Human root cylinders were instrumented and randomized into four treatment groups and an untreated control group. Two treatment groups received 1 g/mL TAP or MTAP, and the other two treatment groups received 1 mg/mL methylcellulose-based TAP or MTAP. Cylinders were stored at 100% relative humidity for 4 weeks. Each root cylinder was subjected to a microhardness test before and after treatment. Different sets of radicular dentine specimens were treated as mentioned previously, and were examined using attenuated total reflection Fourier transform infrared spectroscopy. All treatment groups showed significant reductions in microhardness of roots when compared to untreated control roots at 1,000 and/or 500 µm from the pulp-dentine interface. However, 1 mg/mL methylcellulose-based antibiotics caused significantly less reduction in microhardness when compared to 1 g/mL antibiotics. In addition, 1 g/mL TAP and DAP caused significantly lower phosphate/amide I ratios when compared to other groups. The use of 1 mg/mL methylcellulose-based TAP and MTAP may minimize the reduction in microhardness of roots compared with the currently used 1 g/mL concentration of these antibiotics.

Susceptibility of methacrylate-based root canal filling to degradation by bacteria found in endodontic infections.

OBJECTIVES: To present a case of endodontic failure obturated with a methacrylate-based root filling material, Resilon/RealSeal (RS). To determine if RS is susceptible to biodegradation by endodontically relevant microbes by a method known to show RS degradation. METHOD AND MATERIALS: Emulsions of RS were dispersed in agar with minimal bacterial nutrients in culture plates. Lipase PS served as a positive control. Pseudomonas aeruginosa, Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas gingivalis, Porphyromonas asaccharolytica, Enterococcus faecalis, Streptococcus sanguis, Streptococcus mutans, Staphylococcus aureus, and Staphylococcus epidermidis were tested for their ability to biodegrade RS. The bacteria were inoculated in the plates and examined daily for RS degradation for 7 days. RESULTS: Degradation of the emulsified RS manifested in the formation of clear zones around P aeruginosa, P intermedia, P asaccharolytica, S aureus, and S epidermidis. No degradation was seen with the other tested bacteria or in plates that did not contain RS emulsion. CONCLUSION: Endodontic pathogenic bacteria can degrade RS. These findings complement other work and suggest that the seal and integrity of root canal fillings obturated with RS may be impaired by a microbial insult.