Biomedical subjects

P M Dummer

Publications and source records attributed to P M Dummer.

At least 55 records · Page 3Linked to original sources

PubMed1997

A comparison of stainless steel Flexofiles and nickel-titanium NiTiFlex files during the shaping of simulated canals.

The aim of this study was to compare the shaping ability of stainless steel Flexofiles and nickel-titanium NiTiFlex files during the preparation of simulated canals in resin blocks. A total of 80 canals with various angles and position of curvature were prepared by one operator using either Flexofiles or NiTiFlex files in a modified double-flared technique with balanced force method of instrument manipulation. Canal shape was assessed at two stages during the procedure, after apical enlargement to size 30 and subsequently at size 45. Pre- and post-operative images of the canals were taken with a video camera and stored and manipulated in a computer with image analysis software. The presence of canal aberrations and the amount of material removed as a result of preparation were determined from composite images of superimposed pre- and post-operative views. Canal preparation using NiTiFlex files was significantly quicker (P < 0.0001) up to size 30. More instrument failures occurred with Flexofiles (12) compared to NiTiFlex files (7) but there were no statistically significant differences between file type, instrument size or canal shape. Flexofiles created significantly more zips, perforations and ledges; there were no differences in terms of danger zones. Overall, canals prepared with Flexofiles were significantly wider because more material was removed from the outer aspect of the curve at the end-point of preparation and from the inner aspect of the curve at the apex. Under the conditions of this study, preparation with NiTiFlex files was more effective and produced more appropriate canal shapes than Flexofiles.

Analysis of Variance↗

PubMed1997

Comparison of two stainless steel files to shape simulated root canals.

The aim of this study was to compare the shaping ability of two stainless steel files using simulated canals. A total of 80 simulated canals of various angles and positions of curvature were prepared by hand using either Mani K-Files or Micro Mega K-Files. Following orifice enlargement each file type was used to prepare 40 canals employing a linear filing motion and an anticurvature stepback technique. Pre- and post-operative longitudinal images of the canals were taken with a video camera and stored and manipulated in a computer with image analysis software. The presence of canal aberrations and the amount of material removed as a result of preparation were determined from composite images of superimposed pre- and post-operative views. Overall, canal preparation with Mani K-Files was significantly quicker (P < 0.005) and was associated with fewer instrument failures. Zips and elbows were observed in 70% of specimens with significantly more (P < 0.05) occurring following preparation with Micro Mega K-Files. Mani K-Files created significantly more (P < 0.01) danger zones. Micro Mega K-Files created significantly wider (P < 0.001) zips with significantly more (P < 0.01) resin removed from the outer aspect of the curves and, thus, significantly more (P < 0.01) transportation. Canal shape had a significant influence on preparation time (P < 0.001), the incidence of zips (P < 0.05) and danger zones (P < 0.005), the width of zips (P < 0.001) and transportation at the zips (P < 0.001). Under the conditions of this study, Mani K-Files were more effective than Micro Mega K-Files and produced canals with better shapes. Original canal shape had a substantial influence on the outcome of shaping procedures.

Analysis of Variance↗

PubMed1997

Late failure of root canal therapy: a diagnostic and treatment planning challenge. Case report.

This report describes a case in which failure of conventional root canal therapy presented 17 years following initial treatment. The apical pathology was curetted, the tooth root resected and a root-end filling placed. The possible reasons for failure of the initial orthograde root canal therapy are discussed with the conclusion that the cause may not have been addressed fully by surgical intervention. The case highlights the challenge facing clinicians when assessing failed root fillings, not only in determining the exact cause of failure but deciding the appropriate treatment for the individual tooth and patient.

Adult↗

PubMed1997

A split-shank prefabricated post system: a critical multidisciplinary review.

A multidisciplinary panel of senior academics and practitioners has evaluated a system of prefabricated threaded split-shank posts (Flexi-Post/Flexi-Flange) from published research and their own clinical use. These posts have been compared with requirements of an ideal post system in relation to clinical use, stress effects, stress distribution, retention, loosening and displacement, provision for cores, and biocompatibility. The purpose was to provide this critical review to allow interested clinicians to compare this novel design to other available post systems.

Dental Prosthesis Design↗

PubMed1996

Root-end cavity preparation using the MicroMega Sonic Retro-prep Tip. SEM analysis.

The objective of this laboratory study was to compare root-end cavities prepared with sonic Retro-prep tips in a MM1500 Sonic Air handpiece with those created by burs in a conventional handpiece. A total of 80 single-rooted extracted human teeth with mature apices and straight canals were included in the study. Four groups of 20 extracted teeth were prepared as follows: I, a 3-4 mm root-end resection perpendicular to the long axis of the root, with a size 40 sonic Retro-prep tip creating an apical cavity 3 mm into root canal system; II, a 45 degrees bevel of the root-face removing a 3-4 mm root segment and root-end preparation as per group I; III, root-end resection as per group I, with an apical cavity prepared using a size 010 inverted cone bur 3 mm down the long axis of the root; IV, resection as per group II, followed by an apical cavity preparation with a size 010 inverted cone bur 3 mm into the root canal system. The apical root portion and root-end cavities were replicated and prepared for SEM analysis at x 20 and x 80 magnification. The degree of chipping associated with the margin of the root-end cavities, as evaluated with a standard grading system, and the incidence of root-face cracks were noted. Marginal chipping of root-end cavities prepared using sonic instrumentation was significantly worse than that produced by burs (P < 0.001). Perpendicular root-end resections showed significantly better scores than bevelled root-end resections (P < 0.005). The incidence of root-face cracking was low with no significant difference between the experimental groups.

Dental Instruments↗

PubMed1995

Canal blockage and debris extrusion with eight preparation techniques.

The objective of this study was to assess and compare canal blockages and apical extrusion of dentin debris during canal shaping with eight preparation techniques. A total of 208 canals in extracted human teeth were prepared by one operator using one type of file. The techniques included were standardized, stepback with reaming, stepback with circumferential filing, stepback with anticurvature filing, double-flare, stepdown, crown-down pressureless, and balanced force. Records were kept of the number of canals that became permanently blocked with debris at some stage during preparation. Dentin debris extruded apically was collected in preweighed containers and the dry weight of debris determined to 10(-5) g precision. Blockages varied significantly among techniques (p < 0.001) and occurred most frequently in canals prepared with the stepback techniques with anticurvature (n = 19) and circumferential filing (n = 16) and least in the balanced force technique (n = 0). Apical extrusion occurred in 169 of the 208 roots, but there were no significant differences in the incidence of extrusion among techniques. The weight of extruded dentin did vary significantly among techniques (p < 0.05), with most extrusion occurring with the stepback techniques with circumferential (0.71 mg) and anticurvature (0.69 mg) filing and the least extrusion with the balanced force (0.38 mg) and crown-down pressureless (0.46 mg) techniques. Under the conditions of this study, it is concluded that techniques involving a filing (linear) motion caused significantly more blockages and extruded significantly more apical dentin debris.

Chi-Square Distribution↗

PubMed1995

Sealability of the Trifecta technique in the presence or absence of a smear layer.

The aim of this in vitro study was to assess the sealability of a recently introduced thermoplasticized gutta-percha technique (Trifecta, Hygenic Corp., OH, USA) in the presence or absence of a smear layer. A total of 100 teeth with single straight root canals were included in the study. The teeth were decoronated and the canals prepared with a modified double-flared technique under constant irrigation with 2.5% sodium hypochlorite solution. The apical matrix was prepared to size 40 and apical patency subsequently confirmed with a size 10 file. Four teeth were discarded for technical reasons and the remaining 96 allocated randomly into two groups of 44 teeth and a group of eight teeth which acted as controls. Canals in group 1 were obturated randomly with either cold lateral condensation of gutta-percha or with the Trifecta technique. Canals in Group 2 were rinsed with 17% REDTA to remove the smear layer and then obturated with lateral condensation or the Trifecta technique. All teeth were suspended in India ink for 9 days, demineralized, and rendered transparent prior to the assessment of apical linear dye penetration. Apical extrusion of sealer and gutta-percha occurred commonly but there was no significant difference between the four obturation groups. However, overall, there was significantly more extrusion of sealer with the Trifecta technique compared with lateral condensation (P < 0.05). The majority of canals (79 out of 88) had no evidence of apical leakage and there was no significant difference between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Hydroxide↗

PubMed1995

Assessing the shape of root canals: an in vitro method using microradiography.

The aim of this paper is to describe an in vitro method which provides clear and accurate details of root canal shape. The method utilizes the technique of contact microradiography to produce high resolution, two-dimensional, real-size images of canals in a longitudinal plane. Specimens can be accurately rotated through 90 degrees allowing images to be produced in a bucco-lingual and mesio-distal direction. The method is simple, relatively rapid and can process large numbers of teeth without the need for complicated and expensive mounting blocks or film holders. The technique can be used to produce pre- and post-operative images of canal shape which can be superimposed to delineate the dentine removed during canal preparation. The method is thus suitable for the evaluation of the shaping ability of endodontic instruments and preparation techniques.

Dental Pulp Cavity↗

PubMed1995

An assessment of approximal bone height in the posterior segments of 15-16-year-old children using bitewing radiographs.

The alveolar bone height in a total of 713 15-16-year-old children consisting of 364 males and 349 females was assessed using posterior bitewing radiographs. The distance between the alveolar crest (AC) and amelo-cemental junction (ACJ) on all molar and premolar teeth was determined from magnified images of the radiographs. Analyses of variance models were fitted in order to assess the dependence of the overall ACJ to AC distance on the inter-subject variables of gender and social class and the intrasubject variables of site, missing adjacent tooth, condition of the approximal tooth surface, and for mesial surfaces, gingivitis and pocket depth. The overall geometric mean for bone height for the whole population was 0.542 mm. The ACJ to AC distance for the vast majority of sites was below 2 mm. Site had a highly significant effect on bone height (P < 0.001): ACJ to AC distances were greater in the maxilla compared to the mandible (P < 0.001), greater for distal sites compared to mesial (P < 0.001) and significantly affected by tooth type (P < 0.001). Sites with missing adjacent teeth also had significantly increased distances (P < 0.001). The condition of the approximal tooth surface and the presence of pocketing or gingivitis did not have a significant association with bone height. The geometric mean AC to ACJ distance, adjusted for subject, site and social class was 0.577 mm for males and 0.506 mm for females (P < 0.001), but the main effect of social class was not significant.

Adolescent↗

PubMed1995

A laboratory model for dental radiographic studies.

Though a number of laboratory models have been developed to study the effects of X-ray geometry on the appearance and relative positions of anatomical landmarks, such as the amelocemental junction and alveolar crest, many have failed to take into account the three-dimensional nature of the alveolus and its spatial relationships with the teeth. As a result, the findings of many ex vivo investigations must be questioned. The aim of this investigation was to develop and refine a new laboratory method for experimental dental radiography utilizing a series of anatomical radio-opaque acrylic models containing extracted teeth. The method allows adjustment of the beam-object relationship through the use of precision-made wedges, which are able to tilt the models through a series of angles thus simulating in vivo changes in both vertical and horizontal X-ray beam angulation. The technique is capable of being used in studies involving assessment of alveolar bone height or the depth of carious lesions. The precision of the method was tested by radiographing in nine different positions a test device consisting of four small amalgam fillings embedded in a perspex sheet. Following removal and replacement, exposures of the test device were repeated for each position. Five linear distances between pairs of fillings were selected and measured on each radiograph to give a total of 45 measurements per set of films. There was exact agreement in 39 of the measurements recorded and a discrepancy of +/- 0.1 mm in the remaining six. The estimated standard deviation for variation on repeat radiography was 0.258 and the 95% confidence interval 0.214 to 0.325. The precision of the apparatus was thus found to be adequate for the measurement of differences in small distances.

Acrylic Resins↗

PubMed1995

Radiographic amelocemental junction and alveolar crest: effect of X-ray beam angulation.

The effect of X-ray beam angulation on the radiographic images of the amelocemental junction (ACJ) and alveolar crest (AC) and their positions relative to one another were assessed using a new laboratory model for radiographic studies. A total of 39 teeth with 62 usable approximal surfaces were included in the investigation. When all tooth types were combined, changes in vertical or horizontal angulation from baseline through 20 degrees had no significant effect on the distance between the marked (true) ACJ and marked (true) AC. However, the distance between the apparent (radiographic) ACJ and apparent (radiographic) AC was significantly reduced by varying the beam angulation in either a vertical or horizontal direction. Results for individual tooth types were qualitatively similar but larger discrepancies were found in molars followed by premolars and incisors. The results emphasize the importance of maintaining the ideal X-ray beam, tooth, bone, film relationship when taking radiographs for the assessment of periodontal destruction.

Acrylic Resins↗

PubMed1995

Radiographic alveolar bone loss from posterior teeth in young adults over a 4-year period.

The objective of this study was to determine alveolar bone loss from premolar and molar teeth in young adults over a 4-year period between the ages of 15-16 years and 19-20 years. Pairs of posterior bitewing radiographs from 382 subjects aged 15-16 years were examined and the height of the alveolar bone adjacent to mesial and distal tooth surfaces recorded. Repeat radiographs of the same individuals taken 4 years later were then examined and the height of the alveolar bone remeasured. Change in bone height over the study period was computed for individual sites. Clinical data for the cohort were also obtained at both examinations and included plaque score, bleeding on probing and probing depth. Of the 3314 sites, 16.7% exhibited bone gain, 4.5% exhibited no change whilst 78.8% demonstrated bone loss. The overall mean bone loss for all sites combined was 0.407 mm. Bone loss than 0.5 mm was found in 36% of sites, bone loss between 0.5 and 0.99 mm in 33% of sites whilst only 0.5% of sites had bone loss greater than 2 mm. Only one site had bone loss greater than 3 mm. Bone loss was affected significantly by subject (p < 0.001) and by site (p < 0.05) but there was no significant effect for tooth type, whether the surface was mesial or distal or between quadrants. There was significantly more bone loss from around maxillary teeth than mandibular (p < 0.05). There were no significant associations between bone loss and plaque score, bleeding on probing, pocket depth, gender or social class.

Adolescent↗

PubMed1995

Reproducibility of repeat bitewing radiographs determined by measurement of the distance between the amelocemental junction and the alveolar crest: an ex vivo study using human skulls.

OBJECTIVE: To assess the reproducibility of repeat bitewing radiographs. METHODS: Five right and left pairs of posterior bitewing radiographs were taken without the use of beam-aiming or film-holding devices in five dry skulls with complete dentitions. The amelocemental junction (ACJ) and alveolar crest (AC) of every interdental site was traced on projected radiographs and the linear distance between the ACF and AC determined. RESULTS: There was close concordance between the ability to read the ACJ on the approximal tooth surface and the AC. The overall readability of interdental sites was 71% although sites at the extremities of radiographs were often unreadable. Kappa analysis of the readability of alveolar bone height from repeat radiographs was 0.52. There were significant differences in the reproducibility of ACJ and AC measurements from repeated radiographs (p<0.001). Intra-examiner variability was significantly less (p<0.001) than that due to repeat radiography with no significant differences between sites. The standard deviation for all surfaces from repeat readings of the same radiographs was 0.12 mm compared with 0.51 mm from repeat radiography. CONCLUSIONS: In this study a freehand technique produced a degree of imprecision in readings of alveolar bone height from successive films of the same site. In clinical terms, a difference of more than 1.4 mm between pairs of serial measurements from the same site would have to occur in order to be certain that the difference was not measurement error but real bone loss.

Alveolar Bone Loss↗

PubMed1995

Root resorption of a partially erupted tooth: a case report.

This article reports a case of a maxillary second premolar which on presentation was partially erupted, and which resisted attempts at orthodontic extrusion. The crown of the tooth was eventually restored using an adhesive composite onlay technique. The patient subsequently complained of pain and the root of the tooth showed radiographic evidence of resorption. The root of the extracted tooth had a vital pulp but massive external resorption was evident, with repair with bone-like material.

Adolescent↗

PubMed1994

A laboratory study of root fillings in teeth obturated by lateral condensation of gutta-percha or Thermafil obturators.

The aim of this in vitro study was to assess the quality of root canal obturation and degree of apical dye penetration in teeth root-filled with either laterally condensed cold gutta-percha or Thermafil obturators. A total of 144 extracted teeth with single roots were included in the study. All canals were prepared with a standard technique using a sonic handpiece with copious irrigation. Radiographs taken of the teeth to show the maximum degree of canal curvature were then exposed and the angle, radius and position of curvature determined. This information about the canals, together with their working length and diameter at end-point was used to divide the teeth into two experimental and two control groups. A total of 71 teeth were filled with Thermafil obturators, 69 with lateral condensation while four teeth remained unfilled and acted as controls. Following obturation, the teeth were radiographed in two planes and the technical quality of fill assessed on a four-point scale. All access cavities were then sealed and the teeth immersed in dye for 48 h before being split longitudinally. Linear dye penetration via the apical foramen was then assessed. In both straight and curved canals obturation with Thermafil obturators was significantly quicker (P < 0.001) then lateral condensation. Apical extrusion of gutta-percha occurred significantly more often in straight canals obturated with lateral condensation (P < 0.005) but there was no difference in curved canals. There was little difference in the radiographic quality of fill in the apical halves of the root fillings but Thermafil obturators were significantly better in the coronal halves when viewed from the proximal.(ABSTRACT TRUNCATED AT 250 WORDS)

Chi-Square Distribution↗

PubMed1994

An 8-year study of changes in oral hygiene and periodontal health during adolescence.

This study reports data collected from a cohort of 405 South Wales adolescents examined at the ages of 11-12, 15-16 and 19-20 years. Dental plaque and gingivitis scores decreased markedly between the ages of 11-12 and 15-16 years, and to a lesser extent between 15-16 and 19-20 years. There was a decrease in the mean depth of the gingival sulcus between the ages of 11-12 and 15-16 years, perhaps reflecting a decrease in false pocketing and gingival oedema associated with puberty and tooth eruption. Conversely, there was an increase in the mean depth of the gingival sulcus between the ages of 15-16 and 19-20 years, possibly indicating the initiation of periodontal breakdown and the appearance of true pocketing. Gender was found to be an important determinant of the level of oral hygiene practised, the boys having consistently poorer oral hygiene than did the girls. At the commencement of adolescence this was not reflected in higher gingivitis scores, but by the age of 15-16 years the boys exhibited significantly more gingivitis than did the girls.

Adolescent↗

PubMed1993

An in vitro study of the quality of root fillings in teeth obturated by lateral condensation of gutta-percha or Thermafil obturators.

The aim of this in vitro study was to assess the quality of root canal obturation and degree of linear apical dye penetration in teeth root filled with either laterally condensed gutta-percha or Thermafil obturators. A total of 150 teeth with single roots were included in the study. All canals were prepared using a standard step-back technique with anticurvature filing. Radiographs taken of the teeth to show the maximum degree of canal curvature were then exposed and the angle, radius and position of curvature determined. This information about the canals, together with their working length and diameter at end-point, was used to divide the teeth into two experimental and two control groups. A total of eight teeth were excluded because of technical difficulties, 65 were filled with Thermafil obturators, 63 were filled with laterally condensed gutta-percha whilst 14 teeth remained unfilled and acted as controls. Following obturation, the teeth were radiographed in two planes and the technical quality of fill assessed on a four-point scale. All access cavities were then sealed and the teeth immersed in dye for 48 h before being split longitudinally. Linear dye penetration via the apical foramen was then assessed. Canal obturation with Thermafil obturators (0.7 min) was significantly quicker (P < 0.001) than lateral condensation (6.4 min). Apical extrusion of sealer and gutta-percha occurred significantly more often with Thermafil obturators but there was little difference in the technical quality of the fillings and no significant difference in dye penetration. Under the conditions of this study. Thermafil obturators proved a satisfactory alternative to lateral condensation of gutta-percha.

Chi-Square Distribution↗

PubMed1993

The effect of using files with altered tips in a sonic handpiece: an in vitro study.

The objective of this study was to establish the effect of altering the non-cutting tips on Shaper files during canal preparation with the MM1500 Sonic Air handpiece. A total of 90 simulated canals in clear resin blocks of various angles and positions of curvature were prepared using Shaper files activated by an MM1500 Sonic Air handpiece. Thirty canals were prepared with unmodified files having non-cutting tips, 30 canals were prepared with files which had their tips removed completely and a further 30 canals were prepared with files which had tips reduced by half. All canals were prepared using an identical preparation procedure which involved a linear filing motion and an anticurvature technique in curved canals. The parameters investigated included loss of canal length, weight loss from the blocks, smoothness of canal walls, transportation and overall shape of the prepared canals. The effect of altering the file tips was to increase significantly the loss of working distance and the prevalence of canal aberrations such as zips and danger zones. Altering the tips also had a detrimental effect on the pattern and extent of transportation as well as widening canals excessively in their apical third. Overall, under the conditions of this study, alterations to the non-cutting tips of Shaper files was counterproductive and resulted in canals displaying many adverse features. Conversely, retention of the non-cutting tips allowed canal preparation to proceed rapidly and effectively producing canal shapes which displayed many desirable features.

Chi-Square Distribution↗