Comparison of two endodontic handpieces during the preparation of root canals in extracted human teeth.

This in vitro study compared and assessed two endodontic handpieces during the preparation of root canals in extracted human teeth. Eighty extracted human teeth, with single root canals, were divided into eight matched groups. They were prepared using Shaper files activated by the MM1500 Sonic Air handpiece (Micro-Mega, Besançon, France) or Excalibur files activated by the W & H Excalibur 969 handpiece (W & H, Bürmoos, Austria). The files were 21 mm or 25 mm in length. When preparing the canals, the files were used either in line with or perpendicular to any canal curvature. Preparation of the canals was carried out using the techniques described in the manufacturers' literature. A variety of parameters were used to compare the handpieces, including canal preparation time, deformation or fracture of instruments, loss of canal length, weight loss from the prepared teeth and the overall postpreparation canal shape. A microradiographic technique was used to produce a tracing record of the pre- and postpreparation canal shape. Both handpieces provided an efficient and easy method of preparing and shaping the root canal with little operator fatigue. The MM1500 Sonic air handpiece took significantly more time (P < 0.001) to prepare the canals than the Excalibur. Few aberrations in the shapes of prepared canals were created by either handpiece. No endodontic file fractured but a few of them were permanently deformed. The effects of two variables--file length and the plane of use of the file--on performance of the handpieces, were also assessed.

Evaluating undergraduate preclinical operative skill; use of a glance and grade marking system.

OBJECTIVES: The purpose of the study was to evaluate the intra- and inter-examiner variability of a panel of examiners using a 'glance and grade' marking system when assessing Class II preparations. METHODS: The examination panel consisted of five university staff with varying clinical and teaching experience. The panel assessed 75 disto-occlusal preparations suitable for restoration with dental amalgam prepared in extracted human premolar teeth. The majority of the preparations were cut by undergraduates in their preclinical year of study and the remainder by an experienced staff member. The panel were blind to the identity of each operator. RESULTS: The study revealed a high degree of both intra- and inter-examiner variability, with some preparations being given a pass on one occasion and a fail on another and vice-versa. In addition, some of the panel, perhaps assuming that the practical exercise had been prepared entirely by undergraduates, were reluctant to award good grades. CONCLUSIONS: The study has highlighted the need for better staff training and a more comprehensive system of assessing preclinical skills.

The polarized light microscopic appearance of caries-like lesions adjacent to restored cavities in the crowns and roots of extracted human teeth.

Longitudinal clinical studies indicate consistently that secondary caries is the major cause of failure of restorations. Recently there has been an increase in the number of fluoride-containing materials coming to the market place and this has renewed the debate about the cariostatic effectiveness of such materials. The present study examined the histologic appearance of caries-like lesions adjacent to a non-fluoride-containing material (amalgam), a low fluoride-containing material (composite) and a moderate fluoride-containing material (glass-ionomer). The artificial caries system used to produce lesions has been previously reported and is a microbial system using Streptococcus mutans NCTC 10832. The lesions produced were similar to naturally occurring lesions in many respects, indicating the usefulness of this in vitro technique. Variations in the appearance of lesions were found adjacent to the different materials and the effect of the fluoride contained within two of the materials is discussed.

Prevalence and depth of artificial caries-like lesions adjacent to cavities prepared in roots and restored with a glass ionomer or a dentin-bonded composite material.

One potential advantage of glass-ionomer materials for the treatment of root caries is their ability to release fluoride and so resist cariogenic attack. A commercially available composite material has also been reported to release fluoride which reduced caries lesions in the tooth tissue adjacent to it. The aim of this study was to assess the effectiveness of a conventional glass-ionomer restoration compared with a dentin-bonded, fluoride-releasing, composite restoration when exposed to a microbial artificial caries system. Artificial caries-like lesions produced in relation to the restorations were examined and classified either as outer (surface) lesions or as wall lesions. A split-unit experimental design allowed for within-tooth comparisons of the 2 experimental restorations at different sites on the root surface. These were either totally within the root surface or positioned at the amelo-cemental junction. Outer lesion depths were significantly (p < 0.001) shallower at all sites adjacent to the glass ionomer when compared with the composite restorations. Wall lesions were significantly (p < 0.01) more prevalent adjacent to the composite material. In addition, the cavity margin position significantly (p < 0.05) affected the incidence of wall lesions, particularly in the composite group. In conclusion, glass ionomer was successful in reducing the caries-like lesion production in the adjacent root surface. This resulted from improved marginal integrity and fluoride release from this material when compared with the composite bonding system used.

A combined orthodontic/restorative clinic. Rationale, evolution, and experience.

The rationale for running combined clinics between orthodontics and restorative dentistry is given, together with the history of the development and experience of such a clinic at the Dental School and Hospital in Cardiff. Brief details of the organization of the combined clinic and possible future developments are also given.

Comparison of two endodontic handpieces during the preparation of simulated root canals.

The objective of this in vitro study was to compare and assess two endodontic handpieces during the preparation of simulated root canals. One hundred and sixty simulated root canals in clear resin blocks, of two angles and positions of curvature, were prepared using either Shaper files activated by the MM1500 Sonic Air handpiece (Micro-Mega, Besançon, France) or Excalibur files activated by the W & H Excalibur 969 handpiece (W & H, Bürmoos, Austria). Files of 21-mm or 25-mm length were used. When preparing the canals, the files were used either in line with or perpendicular to the canal curvature. Preparation of the canals was carried out using a technique described in the manufacturers' literature. A variety of parameters were used to compare the handpieces, including an assessment of the canal preparation time, the deformation or fracture of instruments, loss of canal length, weight loss from the resin blocks and the overall postpreparation canal shape. Both handpieces provided an efficient and easy method of preparing and shaping the root canal with little operator fatigue. The MM1500 Sonic Air handpiece took significantly more time (P < 0.001) to prepare the canals and was associated with both more loss of working length (P < 0.05) and more loss of weight (P < 0.001). Both handpieces created a high percentage of aberrations in the shapes of prepared canals. The MM1500 Sonic Air handpiece created significantly more aberrations than the Excalibur handpiece (P < 0.05 for zip and elbow, P < 0.05 for danger zone and coronal narrow). The effects of the variables, canal curvature, file length and the plane of use of the file, on the performance of the handpieces, were also assessed.

The sealing ability of Thermafil obturators assessed by four different microleakage techniques.

An in vitro investigation was performed to assess the extent of apical dye leakage in relation to root fillings made by Thermafil obturators and the lateral condensation of gutta-percha in extracted human teeth under conditions of passive dye penetration, centrifugation, a vacuum technique and an increased air pressure technique. One hundred and twenty-eight extracted teeth were selected and prepared. The specimens were allocated into eight closely matched experimental groups. Four groups were obturated with Thermafil obturators and four with the lateral condensation technique. Microleakage was assessed after exposing one group of specimens from each of the obturation techniques to each of the four dye penetration systems using India ink as the leakage detector. The teeth were demineralized and cleared prior to examination and the maximum dye penetration for each specimen was recorded. The statistical analysis on transformed data revealed no significant differences between the four microleakage techniques and no differences between the two obturation techniques.

Variation in the microleakage produced by four different techniques in root fillings in a simulated root canal model.

An in-vitro investigation was performed to assess the extent of apical microleakage in simulated canals in clear resin blocks. Four different methods of producing dye penetration were employed: passive dye penetration alone, centrifugation alone, vacuum plus passive dye penetration, and increased pressure plus passive dye penetration. Forty simulated root canals were prepared and obturated. The specimens were randomly allocated into four groups and each group was subjected to a different leakage technique using methylene blue dye as the detector. The maximum apical dye penetration observed through each of the four faces of the blocks was recorded. There were large variations in the leakage recorded in each individual specimen and between the specimens within each group. There were statistically significant differences between passive dye penetration and each of the other three techniques. There was no significant differences between the centrifugation, vacuum and pressure techniques.

An in vitro study into the effect of a bacterial artificial caries system on the enamel adjacent to composite and amalgam restorations.

A microbial artificial caries system was used to produce caries-like lesions adjacent to amalgam and composite restorations. Polarised microscopy allowed measurement of outer and wall lesions depths. Comparison was made of the depths found in relation to the restorative materials, margin finishing procedures (composite group), varnish application (amalgam group) and thermal stressing. It was found that differences were detectable between the different restorative materials and the type of margin finishing procedure used in the composite group. Varnish application and thermal stressing had little effect. Some comparison is made between this microbial technique, other artificial caries techniques, and other methods of assessing marginal leakage.

Root canal retained restorations revisited.

The authors published a series of articles which extensively reviewed the current situation in root retained restorations in 1990. This article is intended to update the reader on the advances in this area since the publication of the series.

The production of secondary caries-like lesions on cavity walls and the assessment of microleakage using an in vitro microbial caries system.

The aim of this study was to assess microleakage along restored cavity walls using a new in vitro microbial technique. Extracted human teeth containing cavities restored with a microfine posterior composite were incubated in broth inoculated with a single strain of Streptococcus mutans for 10 days, using a sequential batch culture technique. Each margin of the cavities was finished in one of three ways: butt joint and etching; butt joint and no etching, or; bevel joint and etching. The assessment of microleakage was achieved by examining sections of the teeth histologically using polarized light for the presence or absence of caries-like cavity wall lesions. Outer (surface) lesions were also examined and displayed the characteristic zones of early natural caries lesions. The cavity wall lesions were observed as a translucent zone in 31% of butt and unetched margins, 16% of butt and etched margins, and 5% of bevelled and etched margins.

Root canal retained restorations: 3. Root-face attachments.

It has been common practice for many years to use retained roots to provide support and stability for partial or full dentures. The retention of such overdentures is greatly enhanced if the remaining roots are modified and restored with posts and root-face attachments. The final article in this series on root canal retained restorations classifies and describes some of the root-face attachments currently available, and also describes a number of prefabricated post systems with integral overdenture attachments. Guidelines for clinical and laboratory procedures are given.

Root canal retained restorations: 1. General considerations and custom-made cast posts and cores.

The first article in this series reviews general considerations relating to the use of root canal retained restorations. The authors discuss factors affecting retention, the arguments for cast versus wrought posts, reinforcement of the tooth, and treatment planning. Clinical procedures for constructing custom-made cast posts and cores, using direct and indirect techniques, are also described. The three subsequent articles will deal with threaded and unthreaded prefabricated post-and-core systems, and root-face attachments for the retention of complete and partial overdentures.

Sealing ability of amalgam used as a retrograde root filling in endodontic surgery.

A dye penetration technique was used to investigate the sealing ability of amalgam retrograde root fillings in vitro. A factorial design was employed to determine the effect of amalgam fillings of 1, 2 and 4 mm in length with and without prior filling of the canals with gutta-percha. The results were compared with a group of teeth filled with laterally condensed gutta-percha alone and another with laterally condensed gutta-percha plus root resection but with no retrograde filling. It was concluded that increasing the length of the amalgam filling did not improve the seal, that prior filling of the canal did not improve the seal, that retrograde root fillings were no worse than laterally condensed gutta-percha alone and that root resection of teeth filled with laterally condensed gutta-percha without retrograde filling was no worse than those filled with laterally condensed gutta-percha without root resection or retrograde root filling.

Sealing ability of materials used as retrograde root fillings in endodontic surgery.

The sealing ability of retrograde root fillings of amalgam plus cavity varnish, EBA cement, glass ionomer cement, light-cured composite resin, dentine bonding agent, and light-cured composite resin plus dentine bonding agent were compared with laterally condensed conventional root fillings. A dye penetration technique was used to assess microleakage and it was concluded that none of the materials produced a perfect seal but that glass ionomer cement, light-cured composite resin, light-cured composite resin plus dentine bonding agent and dentine bonding agent alone produced better seals than conventional laterally condensed gutta-percha, amalgam plus cavity varnish and EBA cement.

Management of anxiety in dental practice in the UK.

A postal questionnaire was sent to a random sample of dentists in the United Kingdom. The response rate was 59.9%. Anxiety was reported as a significant problem by 66% of dentists and information was gained regarding the techniques used to manage this anxiety. 'Patient management' and general anaesthesia were the techniques most commonly employed. The frequency of usage of intravenous and inhalational sedation varied according to the age of the patient. Only 55.3% of dentists in general practice had any training in a sedative technique.