Molecular identification and quantification of bacteria from endodontic infections using real-time polymerase chain reaction

Introduction:  It was the aim of the present study to evaluate root canal samples for the presence and numbers of specific species as well as for total bacterial load in teeth with chronic apical periodontitis using quantitative real-time polymerase chain reaction (PCR).
Methods:  Forty adult patients with one radiographically documented periapical lesion were included. Twenty teeth presented with primary infections and 20 with secondary infections, requiring retreatment. After removal of necrotic pulp tissue or root canal filling, a first bacterial sample was obtained. Following chemo-mechanical root canal preparation a second sample was taken and a third sample was obtained after 14 days of intracanal dressing with calcium hydroxide. Analysis by real-time PCR enabled the quantification of total bacterial counts and of nine selected species.
Results:  Root canals with primary infections harbored significantly more bacteria (by total bacterial count) than teeth with secondary infections ( P  < 0.05). Mean total bacterial count in the retreatment group was 2.1 × 10⁶ and was significantly reduced following root canal preparation (3.6 × 10⁴) and intracanal dressing (1.4 × 10⁵). Corresponding values for primary infections were: 4.6 × 10⁷, 3.6 × 10⁴, and 6.9 × 10⁴. The numbers of the selected bacteria and their detection frequency were also significantly reduced.
Conclusion:  Root canals with primary infections contained a higher bacterial load. Chemo-mechanical root canal preparation reduced bacterial counts by at least 95%.     

Effect of root canal procedures on endotoxins and endodontic pathogens

BACKGROUND/AIMS: The purpose of this study was to determine the amount of endotoxin (lipopolysaccharide) and cultivable bacteria in human necrotic root canals before (S1) and after chemo-mechanical preparation using chlorhexidine (CHX) gel as auxiliary chemical substance (S2), and after 7 days of intracanal dressing (S3) in order to evaluate the anti-endotoxin and antimicrobial effects of endodontic procedures. METHOD: Twenty-four teeth were selected for the present study. Chemo-mechanical preparation was performed using 2% CHX gel and three different intracanal medicaments [CaOH2 paste; 2% CHX gel; and CaOH2 + 2% CHX gel]. A quantitative chromogenic Limulus amoebocyte lysate assay was used to measure the amount of endotoxin. Aerobic and anaerobic techniques were used to isolate and identify bacteria, and to determine the bacterial reduction by counting colony-forming units (CFU). RESULTS: Endotoxins and bacteria were present in 100% of the initial samples, with endotoxin concentration ranging from 62.93 to 214.56 UE/ml and CFU ranging from 4 x 10(5) to 2.6 x 10(6). After chemo-mechanical preparation a mean endotoxin reduction of 44.4% was found. Eight (33.3%) root canals were still positive by culture analysis with a mean reduction of bacteria (CFU) of 99.96%. After 7 days of intracanal dressing, endotoxin concentration decreased by only 1.4% compared with S2, and residual bacteria were recovered by culture analysis in 13 cases (54.1%). No significant difference was found among different intracanal medicaments. CONCLUSION: Relatively high values of endotoxin were still present in the root canal after chemo-mechanical preparation although the majority of bacteria were eliminated. No improvement was achieved by 7 days of intracanal dressing.     

Bacterial quantification in teeth with apical periodontitis related to instrumentation and different intracanal medications: a randomized clinical trial

The antibacterial efficacy of intracanal medication with calcium hydroxide [Ca(OH)2], 2% chlorhexidine gel (CHX), and a combination of both [Ca(OH)2/CHX] was assessed in teeth with chronic apical periodontitis. Thirty-three canals were instrumented, randomly divided into three groups, and medicated with either Ca(OH)2, CHX, or Ca(OH)2/CHX. Bacteriological samples obtained from the operative field and the root canals before (S1) and after instrumentation (S2) in the first treatment session, and after medication (S3) in the second session 1 week later, were assessed for bacterial growth, observed by turbidity and in agar plates, and viable colony-forming unit (CFU) counts. Bacterial growth and CFU counts decreased significantly from S1 to S2 (Mann-Whitney, p<0.05). Differences in growth and counts between S2 to S3 were not statistically significant for all three intracanal medication groups. It was concluded that the antibacterial efficacy of Ca(OH)2, CHX, and Ca(OH)2/CHX was comparable.     

Effects of fluorides on Candida albicans

Aims:  To assess whether a short exposure of Candida albicans to commonly used fluorides would affect growth, cell surface hydrophobicity, and adherence to buccal epithelial cells.
Methods:  Candida albicans ATCC 90028 and 11 clinical isolates were used. Minimal inhibitory concentrations (MICs) of sodium fluoride (NaF) and of an amine fluoride / stannous fluoride combination (AmF / SnF₂) were determined. Yeasts were exposed to MICs of tested agents for 1 h. Subsequently, their growth was recorded spectrophotometrically. Their cell surface hydrophobicity was assessed with n -hexadecane. Adherence to buccal epithelial cells was determined microscopically. Phosphate buffered saline (PBS) and chlorhexidine digluconate (CHX) served as controls. All results were analyzed by one-way ANOVA.
Results:  MICs of AmF / SnF₂ and CHX varied between 1 and 4  μ g ml⁻¹, whereas those of NaF were 15 000  μ g ml⁻¹. Statistically significant growth inhibition was detected after AmF / SnF₂ (OD_24 h ± SD 0.457 ± 0.059) and CHX (0.175 ± 0.065) in comparison with PBS (0.925 ± 0.087) and NaF (0.813 ± 0.081). All strains demonstrated uniform behavior. Only minor changes in cell surface hydrophobicity and adherence to buccal epithelial cells (BEC) were detected.
Conclusion:  Growth inhibition of AmF / SnF₂ was comparable with that of CHX whereas NaF had a weaker effect. Exposure to the fluorides did not seem to alter the cell surface hydrophobicity nor adherence to BEC.     

Increased number of CD25+ FoxP3+ regulatory T cells in oral squamous cell carcinomas detected by chromogenic immunohistochemical double staining

Background:  The role of tumor-infiltrating regulatory T cells (Treg) compromising antitumor effects of immune cells in oral squamous cell carcinoma (OSCC) is largely unknown.
Purpose:  The presence of CD25⁺ FoxP3⁺ Treg as well as of CD3⁺ FoxP3⁺ and of CD8⁺ FoxP3⁺ tumor-infiltrating lymphocytes (TIL) was verified in OSCC and compared with non-cancerous lymphoepithelial tissue.
Method:  Three double stainings (CD3/FoxP3, CD8/FoxP3 and CD25/FoxP3) were performed on tissue sections of 15 OSCC and compared with 15 human tonsils.
Results:  OSCC biopsy samples provide evidence for a strong infiltration of TIL, in particular, naturally occurring CD25⁺ FoxP3⁺ Treg. Whereas a comparison of OSCC and control tissue did not show significant changes in the number of CD3⁺ FoxP3⁺ TIL and of CD8⁺ FoxP3⁺ TIL, a significantly higher frequency of CD25⁺ FoxP3⁺ TIL (Treg) could be observed in OSCC ( P  < 0.001, two-sided t -test). Given the small number of specimens, a significant correlation with tumor stage could not be verified.
Conclusion:  Chromogenic double staining of CD4/FoxP3 is a promising tool for the detection of Treg in paraffin-embedded tissue of OSCC.     

Systemic treatment of anti-CD4+CD25+ T cell monoclonal antibody exacerbates sialoadenitis in submandibular glands during the early life in lupus-prone female NZB × NZWF1 mice

Background:  The maintenance mechanisms of peripheral tolerance by CD4⁺CD25⁺ T cells before the development of sialoadenitis in secondary Sjögren's syndrome (sSS) are not well understood. The aim of the present study is to examine the effect of reduction of CD4⁺CD25⁺ T cells on the development of sialoadenitis during the early life in female NZB × NZWF₁ (B/WF₁) mice, a model for human sSS.
Methods:  Female B/WF₁ mice at 3 days after birth were treated with either anti-mouse CD4⁺CD25⁺ T cells rat IgG₁ monoclonal antibody (mAb) or Rat IgG₁(control). At 25 weeks of age, autoantibodies against nucleus and cytoplasm of ductal epithelial and myoepithelial cells, and histpathology of submandibular glands were examined in the mAb-treated and control groups. Also the development of anti-Ro/SS-A antibodies was examined until 25 weeks of age in both groups.
Results:  The mAb-treated group showed severe lesions with the development of autoantibodies compared to the control group.
Conclusions:  The present results suggest that peripheral CD4⁺CD25⁺ T cells may, at least in part, contribute to down-regulate the development of sialoadenitis in submandibular glands of lupus-prone female B/WF₁ mice during their early life.     

Orofacial and gastrointestinal hyperplasia and neoplasia in smad4+/− and elf+/−/smad4+/− mutant mice

Background:  Smad4 is vital to the roles of Smads 2 and 3 in transforming growth factor-beta (TGF)-β signal transduction, and inactivated Smad4 is common to human gastrointestinal cancers. The embryonic liver fodrin (ELF) is a β-spectrin that facilitates the nuclear translocation of activated Smad4.
Methods:  Smad4 ^+/− mice, known to develop gastrointestinal cancer, were crossbred with elf ^+/− mice. The smad4 ^+/− and smad4 ^+/−/ elf ^+/− offspring were autopsied as abnormalities developed.
Results:  In addition to polyps and adenocarcinomas of the stomach and duodenum, the smad4 ^+/− mice developed squamous cell carcinomas of the skin, oral mucosa and forestomach, benign neoplasms of connective tissue and lacrimal gland, and a lymphoma. The smad4 ^+/−/ elf ^+/− mice developed extensive hyperplasia and neoplasia of the gastric mucosa.
Conclusion:  These findings indicate that investigating interactions among smad4 , elf , and other genes involved in TGF-β signaling should be useful in further delineating the processes of neoplasia in a wide variety of tissues.     

FOXP3+ T regulatory cells in lesions of oral lichen planus correlated with disease activity

Objective:  The aim of this study was to determine the correlation between the number of FOXP3⁺ T cell in lesions and the disease activity of patients with oral lichen planus (OLP).
Materials and Methods:  The expression of FOXP3 was investigated using immunohistochemical staining and real-time RT-PCR in 23 OLP lesions and 12 controls. Changes of FOXP3⁺ Treg in peripheral blood from three patients' pre and post-treatment were assessed using flow cytometry.
Results:  Few FOXP3⁺ cells were detected in controls, but an increased number of FOXP3⁺ cells were observed in lesions ( n  = 20, 40.99 ± 24.68 cells per high-power field – hpf). Furthermore, the frequency of FOXP3⁺ Treg in reticular OLP ( n  = 7, 63.6 ± 23.2 cells per hpf) was significantly higher than that in erythematous/erosive OLP ( n  = 13, 28.8 ± 16.8 cells per hpf, P  = 0.001). In addition, negative correlation was found between the number of FOXP3⁺ Treg and disease activity (correlation oefficient = −0.557, P  = 0.013). The proportion of FOXP3⁺ Treg showed remarkable increase in peripheral blood from patients after treatment (1.39 ± 0.71% vs 4.91 ± 1.59%).
Conclusions:  These data indicated that FOXP3⁺ Treg were involved in the pathogenesis of OLP and correlated with disease's subtype and activity.     

The effects of lavender scent on dental patient anxiety levels: a cluster randomised-controlled trial

Kritsidima M, Newton T, Asimakopoulou K. The effects of lavender scent on dental patient anxiety levels: a cluster randomized-controlled trial. Community Dent Oral Epidemiol 2010; 38: 83–87. © 2009 John Wiley & Sons A/S   Abstract – 
Objectives:  To review the effect of lavender scent on anticipatory anxiety in dental participants.
Methods:  In a cluster randomized-controlled trial, patients' ( N  = 340) anxiety was assessed while waiting for a scheduled dental appointment, either under the odor of lavender or with no odor. Current anxiety, assessed by the brief State Trait Anxiety Indicator (STAI-6), and generalized dental anxiety, assessed by the Modified Dental Anxiety Scale (MDAS) were examined.
Results:  Analyses of variance ( anova s) showed that although both groups showed similar, moderate levels of generalized dental anxiety (MDAS F _(1,338) = 2.17, P  > 0.05) the lavender group reported significantly lower current anxiety (STAI: F _(1,338) = 74.69, P  < 0.001) than the control group.
Conclusions:  Although anxiety about future dental visits seems to be unaffected, lavender scent reduces state anxiety in dental patients.     

In vitro evaluation of the effectiveness of irrigants and intracanal medicaments on microorganisms within root canals

AIM: To evaluate in vitro the effectiveness of sodium hypochlorite (NaOCl), chlorhexidine (CHX) and five intracanal medicaments on microorganisms within root canals. METHODOLOGY: Ninety-six human single-rooted extracted teeth were used. After removing the crowns, canal preparation was completed and the external root surfaces were coated with epoxy resin. Following sterilization, the teeth were contaminated with Candida albicans and Enterococcus faecalis, and were incubated at 37 +/- 1 degrees C for 7 days. The teeth were divided according to the irrigant solution or intracanal medicament: group 1, sterile physiologic solution (SPS) and calcium hydroxide (Ca(OH)2) paste; group 2, SPS and camphorated paramonochlorophenol (CPMC); group 3, SPS and tricresol formalin; group 4, SPS and CaOH2 + CPMC paste; group 5, SPS and PMC furacin; group 6, 2.5% NaOCl without intracanal medication; group 7, 2.0% CHX without intracanal medication and group 8, SPS without intracanal medication (control group). Microbiological samples were collected with sterile paper points, and bacterial growth was determined. The data were submitted to the analysis of variance (anova, P = 0.05). RESULTS: For C. albicans, groups 3 and 8 were statistically less effective than groups 1, 2, 4 and 5 (Kruskal-Wallis (K-W) = 65.241; gl = 7; P = 0.001). For E. faecalis, groups 6 and 8 were statistically less effective than groups 1-4 and 7 (K-W = 61.048; gl = 7; P = 0.001). CONCLUSIONS: Ca(OH)2 + CPMC paste was the most effective intracanal medicament for the elimination of the two microorganisms; 2.0% CHX solution was more effective than 2.5% NaOCl against E. faecalis.     

Partial pulpotomy on caries-free teeth using enamel matrix derivative or calcium hydroxide: a randomized controlled trial

Aim  To compare the effect of enamel matrix derivative (EMD) and calcium hydroxide [Ca(OH)₂] on exposed human pulp.
Methodology  Fifteen pairs of human contralateral premolars were intentionally and partially pulpotomized. The exposed pulps were randomly capped with either EMDgel (Emdogain^®) or a mix of Ca(OH)₂ and sterile water. The subjects recorded pain or discomfort during the first 10 days and were also interviewed and examined by a blinded examiner at 1 day, 2 weeks, 3 and 6 months post-operation. Periapical radiographs were taken prior to the operation, and 3 and 6 months post-operation. After 6 months, the teeth were extracted and processed for histological evaluation. The data were described and analysed using McNemar test and Kaplan–Meier survival analysis.
Results  The EMDgel-treated teeth had significantly less tooth hypersensitivity than the Ca(OH)₂-treated teeth during the first 2 weeks ( P  =   0.031) but were not significantly different after 2 weeks ( P  =   0.125). No detectable periapical radiographic changes were observed in any teeth and radiographic evidence of dentine bridge formation from both groups were not significantly different during the follow-up periods ( P  >   0.05). Histological evaluation demonstrated that the Ca(OH)₂-treated teeth had less inflammation and more dentine bridge formation than those in the EMDgel-treated teeth.
Conclusions  After 6 months, healthy pulps capped with Ca(OH)₂ had more favourable results than counterparts capped with EMDgel. However, similar clinical and radiographic results were seen in both groups.     

Oral ulcers in HIV-positive Peruvian patients: an immunohistochemical and in situ hybridization study

Background:  This study describes the histopathological, immunohistochemical (IHC) and in situ hybridization (ISH) data of 25 cases of oral ulcers in HIV-positive patients, with clinical and microscopical features similar to ulcers not otherwise specified (NOS)/necrotizing ulcerative stomatitis (NUS).
Methods:  Sex, age and clinical history were obtained from the clinical records. Histological analysis for H&E, Gomori–Grocott and Ziehl–Neelsen stains, IHC analysis to detect infectious agents and to characterize inflammatory cellular infiltrate, and ISH for cytomegalovirus (CMV) and EBER1/2 were performed.
Results:  Twenty-one patients were men and four were women (mean age of 34.6 years). The tongue was preferentially affected. Microscopically, the lesions showed extensive necrosis, leukocytoclasia, vasculitis with luminal fibrin clots and an intense inflammatory cellular infiltrate predominated by CD68⁺ atypical large cells, normal-sized and crescent-shaped nuclei macrophages, interspersed by CD8⁺ T lymphocytes. Mast cells were also observed in all samples studied. CD4⁺ T lymphocytes, CD20⁺ B lymphocytes and VS38c⁺ plasma cells were practically absent. CMV and EBER1/2 were identified in scarce cells of 3 and 16 of 25 cases respectively.
Conclusion:  These results show that CD68⁺ macrophages, followed by CD8⁺ T lymphocytes, were the predominant inflammatory cells, indicating they are relevant to the pathogenesis of the ulcers, possibly reflecting an abnormal immune response in the oral mucosa. The clinicopathological and immunoprofile features of the present cases are similar to NOS ulcers/NUS in HIV-positive patients.     

The changes in the T-lymphocyte subsets in a population of Turkish children with puberty gingivitis

Objective.   The aim of the study was to investigate the number of CD4 and CD8 T lymphocytes, analyse subjects with gingivitis and those without, and determine the role of T lymphocytes in the pathobiology of puberty gingivitis.
Material and methods.   Fifty individuals with and without puberty gingivitis were recruited for this study. The CD4⁺ and CD8⁺ T-lymphocyte counts were determined using flow cytometry on the biopsy samples, and the CD4⁺/CD8⁺ ratio was calculated. At the same time, periodontal index scores were recorded to assess the periodontal status. Acquired data were analysed statistically using a paired t -test to compare laboratory values obtained before and after the treatment in individuals with puberty gingivitis and disease-free individuals. In addition, Pearson's correlation analysis was performed to investigate the relation between laboratory values and clinical measurements.
Results.   The CD4⁺/CD8 ratio in gingival tissues obtained from test group was significantly higher ( P <  0.05) than that found in the gingival tissue obtained from control group. We found that the CD4⁺ and CD8⁺ lymphocyte counts continued to increase significantly ( P <  0.001) and the CD4⁺/CD8⁺ ratio continued to drop significantly ( P <  0.05) after treatment in test group.
Conclusions.   T lymphocytes could play a significant role in the pathobiology of puberty gingivitis     

Microbial analysis of endodontic infections in teeth with post-treatment apical periodontitis before and after medication

This study aimed to determine the intraradicular microbiota of previously root canal-treated teeth with apical periodontitis and to investigate the antibacterial effectiveness of different intracanal medicaments. Sixteen patients with post-treatment apical periodontitis were allocated into two groups according to the intracanal medicament used: calcium hydroxide (CH) and 2% chlorhexidine gluconate gel (CHX) group. Total bacterial loads, as well as the amount of Enterococcus faecalis (E. faecalis) were determined before (S1) and after (S2) chemomechanical preparation and finally, after intracanal medication (S3) by means of ddPCR. The unpaired t test was used to compare parametric. S3-total bacteria copy number of the CH group was lower than the CHX group (p < 0.05). There was no statistical difference between the CHX- and the CH groups in terms of E.faecalis copy number (p > 0.05). But in terms of total bacteria, CH is better than CHX. Consequently, CH can be used to optimise the antibacterial efficiency of chemomechanical preparation in previously root canal-treated teeth with apical periodontitis.     

Effect of immediate intracanal placement of Ledermix Paste® on healing of replanted dog teeth after extended dry times

Abstract  – Ledermix Paste^® is a paste containing triamcinolone and demeclocycline with demonstrated anti-inflammatory activity that may slow down resorptive processes after severe traumatic injuries to the dentition. A total of 29 premolar roots of six mongrel dogs were extracted and instrumented with rotary nickel titanium files. Fifteen of these roots were then filled with a calcium hydroxide (Ca(OH)₂) slurry and 14 roots were filled with Ledermix Paste^® paste. All accesses were sealed with glass ionomer and the roots replanted after an extraoral dry time of 60 min. After 4 months, the dogs were killed and the roots prepared for histological evaluation. Five-micrometer thick cross-sections of the root and surrounding tissue taken every 90 µm were evaluated for healing. In addition, residual root mass was also measured to determine the extent of root structure loss for each treatment method. The Ledermix Paste^®-treated roots had statistically significantly more healing and less resorption than the roots treated with Ca(OH)₂. Root filling with Ledermix Paste^® also resulted in significantly less loss in root mass due to resorption compared to those roots filled with Ca(OH)₂. Immediate intracanal placement of Ledermix Paste^® at the emergency visit after an avulsion injury appears to decrease resorption and increase favorable healing.     

Proliferative activity of cells from remaining dental pulp in response to treatment with dental materials

Background:  The biological examination of pulp injury, repair events and response of dental pulp stem cells to dental restorative materials is important to accomplish restorative treatment, especially to commonly used dental materials in paediatric dentistry, such as glass ionomer cement (GIC) and calcium hydroxide (Ca(OH)₂) lining cement.
Methods:  Healthy patients aged between 9 to 11 years with carious primary molars without pulp exposure were selected and divided into two groups: Group 1 (teeth restored with GIC) and Group 2 (teeth lined using Ca(OH)₂ and restored with GIC). The proliferative activity of stem cells of teeth between these two groups was compared using colourimetric cell proliferation reagent, alamarBlue. Immunocytochemistry and flow cytometry confirmation were performed using mesenchymal stem cell markers, CD105 and CD166.
Results:  The proliferative activity using alamarBlue™ assay showed that cells derived from the remaining dental pulp of exfoliated deciduous teeth were positive for CD105 and CD166 and exhibited no difference between the two groups.
Conclusions:  It can be concluded that the use of Ca(OH)₂ or GIC as a lining material in indirect pulp capping procedures has the same effect on cells derived from the remaining dental pulp of exfoliated deciduous teeth which have responded favourably to the restorative treatments.     

Porphyromonas gingivalis fimbriae induce unique dendritic cell subsets via Toll-like receptor 2

Backgound and Objective:  Dendritic cells (DCs) play a critical role in the activation of T cells as well as in shaping immune responses. We have reported previously that Porphyromonas gingivalis lipopolysaccharides ( Pg LPS) induced a CD14⁺CD16⁺ DC subset with a weak immuno-stimulatory activity. In contrast, Escherichia coli LPS ( Ec LPS) induced fully matured DCs with strong immunostimulatory activities. Since Pg LPS as well as Pg fimbriae have been indicated to work as Toll-like receptor (TLR) 2 ligands, we speculate that the TLR usage of bacterial antigens may be critical for DC maturation.
Material and Methods:  We investigated the effect of Pg fimbriae on the phenotype and function of human peripheral blood DCs in comparison with a TLR2 ligand, peptidoglycan, and a TLR4 ligand, Ec LPS.
Results:  Flow cytometry revealed that Pg fimbriae and peptidoglycan but not Ec LPS induced CD14 and CD16 expression on peripheral blood DCs (CD14⁻CD16⁻). A monoclonal antibody against TLR2 abrogated this induction, but an antibody against TLR4 had no effect. Dendritic cells stimulated with Pg fimbriae had a weaker capability to induce allogenic T cell proliferation and exhibited a weaker production of interleukin-8 and regulated upon activation, normal T cell expressed and secreted (RANTES) than DCs stimulated with Ec LPS.
Conclusion:  These results indicate that different TLR usage affects mature DC phenotype and function and is thus crucial to the regulation of immunity to the pathogen.     

Trans-enamel and trans-dentinal cytotoxic effects of a 35% H2O2 bleaching gel on cultured odontoblast cell lines after consecutive applications

Aim  To evaluate the trans-enamel and trans-dentinal cytotoxic effects of a 35% H₂O₂ bleaching gel on an odontoblast-like cell lines (MDPC-23) after consecutive applications.
Methodology  Fifteen enamel/dentine discs were obtained from bovine central incisor teeth and placed individually in artificial pulp chambers. Three groups ( n  = 5 discs) were formed according to the following enamel treatments: G1: 35% H₂O₂ bleaching gel (15 min); G2: 35% H₂O₂ bleaching gel (15 min) + halogen light (20 s); G3: control (no treatment). After repeating the treatments three consecutive times, the extracts (culture medium + gel components that had diffused through enamel/dentine discs) in contact with the dentine were collected and applied to previously cultured MDPC-23 cells (50 000 cells cm⁻²) for 24 h. Cell metabolism was evaluated by the MTT assay and data were analysed statistically (α = 5%; Kruskal–Wallis and Mann–Whitney U -test). Cell morphology was analysed by scanning electron microscopy.
Results  Cell metabolism decreased by 92.03% and 82.47% in G1 and G2 respectively. G1 and G2 differed significantly ( P  < 0.05) from G3. Regardless of halogen light activation, the application of the bleaching gel on the cultured odontoblast-like cells caused significantly more severe cytotoxic effects than those observed in the nontreated control group. In addition, significant morphological cell alterations were observed in G1 and G2.
Conclusion  After three consecutive applications of a 35% H₂O₂ bleaching agent, the diffusion of the gel components through enamel and dentine caused severe toxic effects to cultured pulp cells.     

Effect of Three Methods for Cleaning Dentures on Biofilms Formed In Vitro on Acrylic Resin

Purpose: The aim of this study was to evaluate the effect of three denture hygiene methods against different microbial biofilms formed on acrylic resin specimens.
Materials and methods: The set (sterile stainless steel basket and specimens) was contaminated (37°C for 48 hours) by a microbial inoculum with 10⁶ colony-forming units (CFU)/ml (standard strains: Staphylococcus aureus , Streptococcus mutans , Escherichia coli, Candida albicans, Pseudomonas aeruginosa , and Enterococcus faecalis ; field strains: S. mutans , C. albicans , C. glabrata , and C. tropicalis ). After inoculation, specimens were cleansed by the following methods: (1) chemical: immersion in an alkaline peroxide solution (Bonyplus tablets) for 5 minutes; (2) mechanical: brushing with a dentifrice for removable prostheses (Dentu Creme) for 20 seconds; and (3) a combination of chemical and mechanical methods. Specimens were applied onto a Petri plate with appropriate culture medium for 10 minutes. Afterward, the specimens were removed and the plates incubated at 37°C for 48 hours.
Results: Chemical, mechanical, and combination methods showed no significant difference in the reduction of CFU for S. aureus , S. mutans (ATCC and field strain), and P. aeruginosa . Mechanical and combination methods were similar and more effective than the chemical method for E. faecalis , C. albicans (ATCC and field strain), and C. glabrata . The combination method was better than the chemical method for E. coli and C. tropicalis , and the mechanical method showed intermediate results.
Conclusion: The three denture hygiene methods showed different effects depending on the type of microbial biofilms formed on acrylic base resin specimens.     

Human cytomegalovirus in peripheral giant cell granuloma

Background:  The peripheral giant cell granuloma is a relatively common non-neoplastic inflammatory lesion of gingiva, but the etiopathogeny remains unknown. This study aimed to evaluate the importance of human cytomegalovirus and Epstein–Barr virus in a peripheral giant cell granuloma of a 47-year-old female.
Methods:  The lesion was studied clinically, histopathologically, immunologically and virologically using established procedures.
Results:  The gingival growth was located at the mesial surface of the maxillary left canine having a vital pulp. The mass was 12 × 21 mm in size and exhibited a smooth surface with no evidence of fluctuation on palpation. An excisional biopsy revealed giant cells in a fibrohistiocytic stroma with areas of haemorrhage. Serum protein levels and lymphocyte subsets were within normal limits, except CD3⁺ and CD4⁺ cells were below normal ranges. Polymorphonuclear leukocytes expressed p150,95 (CD11c/CD18) and CXCR-2 receptors within normal ranges, but the CXCR1 receptor showed decreased density, and CD15 were below normal range. A virological sample of the tooth surface adjacent to the gingival swelling yielded 7.6 × 10³ copy-counts of cytomegalovirus and 4.3 × 10³ copy-counts of Epstein–Barr virus.
Conclusions:  The clinical and histological findings were consistent with the diagnosis of peripheral giant cell granuloma. Cytomegalovirus has the potential to induce multinucleated giant cells, and the possibility that the virus contribute to the development of peripheral giant cell granuloma merits further study.