The dentine-removing characteristics of an ultrasonically energized K-file

This in vitro study evaluated the pattern of dentine removal when an ultrasonically energized file (Cavi-Endo-size 25 file) was applied to flat surfaces of dentine under standardized conditions. The influences of power setting, interfacial force between file and dentine, direction of file oscillation and operator-assisted movement were examined. Impressions of the instrumented surfaces revealed characteristic patterns consisting of a series of oblique crests, each one parallel to the next and separated by a constant distance along the line of contact with the file. Determination of height, width and separation of these crests with a Reflex microscope aided objective assessment. The simplest pattern was formed when the energized file was held against the dentine (power setting = 1; interfacial force = 30 g). Increasing the power setting to 8 caused deeper troughs over the apical 5 mm. The width of the crests corresponded to the taper of the file except at the apical tip where the crests were relatively wider. However, increasing the interfacial force to 60 g reduced the efficiency of the apical part of the file. The superimposition of operator-induced movement greatly increased the extent of dentine removal, resulting in a tapering groove with a persistent crestal pattern. Oscillation of the file perpendicular to the dentine surface had a significantly greater influence on dentine removal, producing a deeper groove than was obtained with oscillation parallel to the surface. These findings may be of relevance in aiding controlled root canal preparation when using the Cavi-Endo instrument.     

Survival against the odds: microbiology of root canals associated with post‐treatment disease

Most periapical lesions resolve after root canal treatment of teeth with primary infections. Over the last decade there has been a renewed focus on post‐treatment apical periodontitis and its etiology. This review describes the microbiota associated with persistent post‐treatment infection, including microbial identification, ecology, and environmental selection. Compared with untreated teeth, the infection pattern in root canals with post‐treatment disease shifts to a resistant, mainly Gram‐positive community. The main challenge in root canal re‐treatment is access to the residual apical infection. Elimination of the microbial flora, or a dramatic reduction and sufficient ecological shift to allow host tissue healing, remains the biological goal.     

Outcome of non‐surgical re‐treatment

The purpose of this review was to critically analyze the relevant literature in order to synthesize an overview on the clinical outcomes (radiographically judged periapical healing and tooth survival) following root canal re‐treatment and the factors influencing them. A further aim was to explain the findings on the basis of current knowledge and understanding. The relevant literature was captured and critiqued using the principles of a systematic review. The data were classified into a coherent structure for analyses and presentation but are not presented as a systematic review; rather, the authors have chosen a narrative style to enable integration of the clinical outcomes with relevant findings from laboratory and animal studies. Overall, the outcomes were similar to those for teeth undergoing primary treatment with common factors influencing the outcomes. The major differences between the outcomes of primary and secondary root canal (re‐)treatment reside only in the ability to predictably access and negotiate the root canal system to the (residual) apical infection. The data offer a very favorable prognosis for non‐surgical root canal re‐treatment performed to guideline standards.     

Clinical diagnosis of internal resorption: an exception to the rule

This paper describes a case in which the radiographic appearance of a resorptive lesion in a mandibular incisor tooth posed difficulty in the diagnosis of its origin. The lesion did not conform to the normally accepted criteria for diagnosis of internal resorption. Clinical examination did not support the diagnosis of external cervical resorption. Serial histological section of the extracted tooth subsequently confirmed the diagnosis of internal resorption. The criteria for differential diagnosis of resorptive lesions with smooth outlines in the cervical regions of teeth are discussed together with the rationale for their management.     

The effect of retrograde cavity design on microleakage of amalgam fillings

A phantom head model was modified to simulate as closely as possible the limited access encountered during periapical surgery on maxillary anterior teeth. Extracted human maxillary anterior and mandibular canine teeth were placed in this model in a standardized position for root resection, retrograde cavity preparation and filling with amalgam. Three different designs of retrograde cavities were evaluated: the conventional class 1 cavity, the slot cavity and a previously unreported approach, the funnel cavity. Upon completion of the retrograde filling, the teeth were removed from the model and subjected to microleakage tests by placing radiolabelled lipopolysaccharide in a reservoir created coronal to the retrograde fillings. Leakage was quantified by measurement of radioactivity in scintillation counter. It was found that the retrograde fillings in the funnel cavity leaked significantly less than those in the other two cavity designs. There was no statistically significant difference in leakage between the conventional class 1 and the slot cavities up to the thirtieth day 30.     

Setting up an MSc programme in endodontics

The course has been designed to provide a suitable foundation for academic and general practice careers. Emphasis has been placed on developing diagnostic and practical skills. Students are encouraged to review their clinical practice critically in the light of recent advances in knowledge. The course begins with an intensive period of lectures and seminars covering general aspects of endodontics, and is generously supplemented by practical demonstrations and classes on a variety of procedures performed on laboratory models. The course continues with lectures and seminars designed to stimulate group discussion. These are complemented by supervised clinical sessions encompassing assessment, planning and treatment of a comprehensive range of conventional and surgical endodontic problems. The syllabus includes relevant basic sciences, pathology, differential diagnosis, pharmacology and therapeutics. The biological basis for endodontics is stressed and covers the following: maintenance of pulp vitality; effects of pulp capping pulpotomy and pulpectomy; the management and treatment of traumatic injuries to teeth; the management of medically compromised patients; the effect of various methods of instrumentation of root canals; radiology; restorative treatment of the endodontically treated tooth; the interface between endodontics and periodontics, prosthetics or orthodontics. Each student is required to undertake a research project and write a report.     

Cryoablation with an 8‐mm Tip Catheter for Pediatric Atrioventricular Nodal Reentrant Tachycardia Is Safe and Efficacious with a Low Incidence of Recurrence

Background: Cryoablation with 4‐ and 6‐mm tip ablation catheters has been demonstrated to be safe and effective in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT) in pediatric patients, albeit with a higher rate of clinical recurrence. Limited information is available regarding efficacy, mid‐term outcomes, and complications related to the use of the 8‐mm Freezor Max Cryoablation catheter (Medtronic, Minneapolis, MN, USA) in pediatric patients. Methods: We performed a retrospective review of all pediatric patients with normal cardiac anatomy who underwent an ablation procedure for treatment of AVNRT using the 8‐mm tip Cryoablation catheter at three large pediatric academic arrhythmia centers. Results: Cryoablation with an 8‐mm tip catheter was performed in 77 patients for treatment of AVNRT (female n = 40 [52%], age 14.8 ± 2.2 years, weight 62.0 ± 13.9 kg). Initial procedural success was achieved in 69 patients (69/76, 91%). Transient second‐ or third‐degree atrioventricular (AV) block was noted in five patients (6.5%). There was no permanent AV block. Of the patients successfully ablated with Cryotherapy, there were two recurrences (2/70, 2.8%) over a follow‐up of 11.6 ± 3.3 months. Conclusion: Cryoablation with an 8‐mm tip ablation catheter is both safe and effective with a low risk of recurrence for the treatment of AVNRT in pediatric patients. (PACE 2010; 33:681–686)     

Diagnostic dilemma: an unusual presentation of an infected nasopalatine duct cyst

The pertinent literature on nasopalatine duct cysts is reviewed. A case is reported in which a nasopalatine duct cyst infected by Actinomyces presented clinically with unusual features. The clinical findings could have been confused with an early acute periapical abscess arising from an incisor tooth. The relevant aspects of diagnosis are discussed.     

Dentine-removing characteristics of K-files energized by the Piezon-Endo

This in-vitro study evaluated the pattern of dentine removal when a size 25 K-file energized by the Piezon-Endo was applied to flat surfaces of dentine under standardized conditions. The effects of power setting, interfacial force between file and dentine, direction of file oscillation and operator-assisted movement were examined. Vinyl polysiloxane impressions of the instrumented surfaces revealed characteristic patterns consisting of a series of oblique crests, similar to those observed in a previous study using the Cavi-Endo. Each crest was parallel to the next and separated by a relatively constant distance. These crests were disposed along the line of contact with the file. The Reflex microscope was used to determine the height, width and separation of these crests. There were differences in the amount and pattern of dentine removal compared with the study on the Cavi-Endo. When the file was held against the dentine surface using the minimum power setting and an interfacial force of 30 g, the pattern of dentine removal was very similar to that produced by the Cavi-Endo. Increasing the power setting to the maximum recommended for endodontics produced a slight but statistically non-significant increase in dentine removal. Further increase of the power setting to the absolute maximum produced significantly deeper and wider areas of dentine removal by the apical part of the file.(ABSTRACT TRUNCATED AT 250 WORDS)