Peter Cathro

Efficacy of low concentrations of sodium hypochlorite and low-powered Er,Cr:YSGG laser activated irrigation against an Enterococcus faecalis biofilm.

AIM To establish the antibacterial efficacy of low concentrations of sodium hypochlorite with and without Er,Cr:YSGG laser activation on Enterococcus faecalis biofilms in extracted teeth. METHODOLOGY The root canals of 96 decoronated single-rooted extracted human teeth were prepared to a size 40, 0.06 taper 1 mm beyond the apex. They were mounted within a flow cell, which was sterilized before pumping a nutrient media through the root canals. The flow cell was inoculated with E. faecalis (ATCC 700802) and cultivated for 4 weeks. The root-ends were sealed, and the roots were then subjected to one of six treatment groups: group 1: syringe irrigation (SI) with saline (control) using a 27 -gauge Monoject needle 1 mm from the apex for 2 min; group 2: as for group 1 but with 1% NaOCl; group 3: as for group 1 but with 4% NaOCl; group 4: 0.5% NaOCl irrigation for 15 s followed by laser-activated irrigation (LAI) with four 15-s cycles replenishing the irrigant between cycles; group 5: as for group 4 but with 1% NaOCl as the irrigant; group 6: as for group 4 but with 4% NaOCl as the irrigant. Following treatment, teeth were crushed and viable bacteria were quantitated by serial dilution and plating. The colony-forming unit values were compared between groups using one-way anova and Tukey-adjusted post hoc tests. A two-tailed P value of <0.05 was considered statistically significant. RESULTS The mean number of cells recovered from the 1% NaOCl SI group was significantly higher than that from the 4% NaOCl LAI group (P = 0.02). CONCLUSION Within the limitations of this laboratory study, low-powered (0.5 W) Er,Cr:YSGG laser activation did not improve the antibacterial effect of low concentrations of sodium hypochlorite.

Fracture resistance and pattern of the upper premolars with obturated canals and restored endodontic occlusal access cavities

We studied whether obturing canals and restoring endodontic occlusal access cavities on upper premolars could provide acceptable resistance and pattern to fracture. Eighteen upper premolars were divided equally into 3 groups. Group 1 consisted of intact controls; group 2 had access cavities and root canal preparations; group 3 as in group 2 but obturated with gutta-percha and AH26, and the access cavity restored with glass ionomer and composite. Specimens were submitted to compressive strength testing using the Hounsfield Universal H50KM testing machine with a load cell of 2000 Newtons and a crosshead speed set at 1.0 mm/min until fracture. The results from the compressive strength tests showed that intact controls (1105.83±90.93 MPa) and restored premolars (936.67±44.67 MPa) were significantly different from premolars with unrestored access cavities 568.33±105.49 MPa. There was no significant difference between intact controls and restored premolars. The predominant fracture pattern for intact teeth was an oblique fracture. For premolars that had endodontic access cavities, restored or unrestored, the most common fracture pattern was a vertical fracture. The restoration of occlusal access cavities with glass ionomer and composite provided fracture resistance close to that of intact controls, but when restored teeth fractured, they were predominantly non-restorable.

Endodontic sequelae of miniplate bone fixation

Various techniques of rigid internal fixation have evolved to achieve skeletal stability during healing. Although the miniplates and screws currently used have many advantages, their placement and presence may present significant difficulties for clinicians subsequently providing treatment. Problems with both endodontic diagnosis and treatment after miniplate fixation are illustrated with three case reports.

Isolation and identification of Enterococcus faecalis membrane proteins using membrane shaving, 1D SDS/PAGE, and mass spectrometry

Enterococcus faecalis is a significant nosocomial pathogen, which is able to survive in diverse environments and resist killing with antimicrobial therapies. The expression of cell membrane proteins play an important role in how bacteria respond to environmental stress. As such, the capacity to identify and study membrane protein expression is critical to our understanding of how specific proteins influence bacterial survival. Here, we describe a combined approach to identify membrane proteins of E. faecalis ATCC V583 using membranes fractionated by either 1D SDS/PAGE or membrane shaving, coupled with LC‐ESI mass spectrometry. We identified 222 membrane‐associated proteins, which represent approximately 24% of the predicted membrane‐associated proteome: 170 were isolated using 1D SDS/PAGE and 68 with membrane shaving, with 36 proteins being common to both the techniques. Of the proteins identified by membrane shaving, 97% were membrane‐associated with the majority being integral membrane proteins (89%). Most of the proteins identified with known physiology are involved with transportation across the membrane. The combined 1D SDS/PAGE and membrane shaving approach has produced the greatest number of membrane proteins identified from E. faecalis to date. These protocols will aid future researchers investigating changes in the membrane proteome of E. faecalis by improving our understanding of how E. faecalis adapts and responds to its environment.

Standardisation of sheep model for endodontic regeneration/revitalisation research

OBJECTIVE Different endodontic regeneration/revitalisation protocols have been suggested for the treatment of immature permanent teeth with pulp necrosis. Many aspects of these protocols require further investigating necessitating a suitable standardised animal model for research purposes. The focus of this study was to examine the anatomy and histology of sheep teeth at different stages of development to find an appropriate dental age for endodontic regeneration/revitalisation research. DESIGN Sheep teeth at mature and immature dental ages were investigated. Standardized radiography, computed tomography, and histology were used to measure root length, apical-third dentine thickness and apex diameter, and to evaluate tissue development stages. RESULTS A mature sheep tooth has an apical area which consists of a major foramen, intermediate dilatation and minor foramen. From the time of eruption to maturation no major changes occur in the incisor root lengths, but the apical foramen width decreases and the dentinal wall thickness increases. The two-tooth age exhibited the most similar features to that of an immature permanent human tooth. CONCLUSION Sheep appears to be an appropriate animal model for endodontic regeneration/revitalization research with similar dimension and characteristics to human anterior teeth. Each dental age has its advantages and disadvantages. The two-tooth age showed the most favourable criteria making this age the most suitable for in vivo regeneration/revitalisation research.

Comparative efficacy of endodontic medicaments and sodium hypochlorite against Enterococcus faecalis biofilms

BACKGROUND Many studies have investigated the effectiveness of root canal irrigants and medicaments against Enterococcus faecalis. The aim of this study was to compare the efficacy of commonly used medicaments against E. faecalis cultured as a biofilm on dentine substrate. METHODS An E. faecalis biofilm was established on human dentine slices using a continuous flow cell. Each test medicament (Ledermix, Ca(OH)2 , Odontopaste, 0.2% chlorhexidine and 50:50 combinations of Ledermix/Ca(OH)2 and Odontopaste/Ca(OH)2 ) was introduced into the flow cell and biofilms were harvested and quantitated by determining cellular protein. Cellular viability was determined using serial plating and the number of colony-forming units was normalized against cellular protein to allow treatment protocols to be compared. Qualitative scanning electron microscopy analyses of the biofilm were performed after a 48-h exposure to each test agent. RESULTS Sodium hypochlorite achieved total bacterial elimination. Ledermix and Odontopaste had no significant effect on the E. faecalis biofilm. Ca(OH)2 and 50:50 combinations of Ca(OH)2 /Ledermix or Ca(OH)2 /Odontopaste reduced the viability by more than 99% while 0.2% chlorhexidine reduced bacterial numbers by 97%. CONCLUSIONS Sodium hypochlorite remains the gold standard for bacterial elimination in root canal therapy. However, Ca(OH)2 in isolation and combined with Ledermix, and Odontopaste was highly effective in reducing bacterial viability.

Investigation of the effect of rapid and slow external pH increases on Enterococcus faecalis biofilm grown on dentine.

BACKGROUND Calcium hydroxide is a common endodontic medicament and has an antimicrobial effect by increasing the localized pH within the root canal. However, Enterococcus faecalis has shown some resistance to calcium hydroxide. METHODS A flow cell apparatus was used to grow an E. faecalis biofilm on dentine discs. Following 4 weeks growth in Todd Hewitt Broth, flow cells were exposed to either a rapid or slow increase to pH 11.5 or 12.5. Cellular viability was determined using serial plating and the number of colony-forming units was normalized against the cellular protein content. Scanning electron microscopy was carried out to qualitatively observe the effects of the different rates of pH increase. RESULTS A significant difference in viability between the pH rapid and slow groups was not shown in this study. Compared with pH 11.5 solutions, pH 12.5 solutions were more effective at killing bacteria although some E. faecalis still survived. CONCLUSIONS Enterococcus faecalis did not adapt and develop a greater resistance to high pH following a slow rise in pH compared with a rapid rise in pH. As expected, pH 12.5 was more effective in reducing bacterial numbers compared with pH 11.5 although E. faecalis was not completely eliminated.