Biomedical subjects

P J Lumley

Publications and source records attributed to P J Lumley.

At least 19 recordsLinked to original sources

PubMed2004

A new insight into the oscillation characteristics of endosonic files used in dentistry.

The aim of this study was to assess the oscillation characteristics of unconstrained endosonic files using a scanning laser vibrometer (SLV). Factors investigated included file vibration frequency and node/antinode location as well as the variation in file displacement amplitude due to increasing generator power setting. A 30 kHz Mini Piezon generator (Electro-Medical Systems, Switzerland) was used in conjunction with a #15 and #35 K-file. Each file was fixed in position with the long axis of the file perpendicular to the SLV camera head. The laser from the SLV was scanned over the length of the oscillating file for generator power settings 1 to 5 (minimum to half power). Measurements were repeated ten times. The fundamental vibration frequency for both files was 27.50 kHz. Scans of each file showed the positions of nodes/anti-nodes along the file length. The #15 file demonstrated no significant variation in its mean maximum displacement amplitude with increasing generator power, except at power setting 5, where a decrease in displacement amplitude was observed. The #35 file showed a general increase in mean maximum displacement amplitude with increasing power setting, except at power setting 4 where a 65% decrease in displacement amplitude occurred. In conclusion, scanning laser vibrometry is an effective method for assessing endosonic file vibration characteristics. The SLV was able to demonstrate that (unloaded) file vibration displacement amplitude does not increase linearly with increasing generator power. Further work is being performed on a greater variety of files and generators. Vibration characteristics of files under various loads and varying degrees of constraint should also be investigated.

Dentistry↗

PubMed2004

Thermal changes and cure depths associated with a high intensity light activation unit.

OBJECTIVES: The objectives of this study were to evaluate the thermal emission and curing characteristics of a high intensity halogen light (Astralis 10-Ivoclar Vivadent, Schaan. Leichtenstein) alone and on curing a conventional and a fast-curing micro-hybrid composite. METHODS: A bead thermistor was placed in the base of a standard model cavity. The cavity was irradiated using the light unit whilst empty, and when filled with either composite. Temperature rises were recorded using the light in four different output modes. Further samples were prepared to assess depth of cure via a digital penetrometer, light transmission using a computer-based radiometer, and microhardness with a Wallace hardness tester. RESULTS: Mean peak temperature rises recorded during polymerisation of the composites ranged from 6.9 degrees C for the product InTen-S cured with the Adhesive programme (Adh) to 11.0 degrees C for the product Tetric Ceram HB cured with the High Power (HI P) programme. A significantly greater depth of cure was obtained for InTen-S in line with the greater light transmission obtained for this material. DISCUSSION: The very high thermal emission characteristics reported in a recently published investigation for this light unit were not confirmed. CONCLUSIONS: As the extent of thermal trauma that can be tolerated by the dental pulp is unknown consideration should be given to the choice of light activation unit and curing programme when polymerising light activated resin based restorations in deep cavities close to the pulp.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2003

Odontoblast morphology and dental repair.

OBJECTIVES: To investigate the changes in morphology and activity of pulp odontoblasts in response to cavity restoration variables and patient factors. METHODS: Class V non exposed cavities were prepared in the intact 1st or 2nd premolar teeth of 27 patients, aged between 9 and 17 years-old. Following tooth extraction, the area of reactionary dentine and the area of the odontoblasts were measured using computerised histomorphometry. RESULTS: The cytoplasm to nucleus ratio of the odontoblasts was found to increase beneath cut dentinal tubules, following the secretion of reactionary dentine. However, none of the patient or preparation variables were found to be correlated with changes in the odontoblast cytoplasm to nucleus ratio. CONCLUSIONS: Morphological changes in human odontoblasts is directly related to their capacity to repair dentine injuries and provide pulp protection. Changes in odontoblast morphology reflect secretory activity.

Adolescent↗

PubMed2002

A pilot investigation of operator variability during intra-oral light curing.

OBJECTIVE: To test the hypothesis that operator experience influences the efficacy of light curing in a typical posterior intra-oral location. To investigate whether short cure cycles affect performance. DESIGN: A cross-sectional single-centre study designed to assess the efficacy of experienced and inexperienced operators when undertaking simulated intra-oral curing. SETTING: An in vitro laboratory based investigation conducted in a dental school during 2001. MATERIALS AND METHODS: A computer-based technique was used to monitor light intensity in a clinical simulation. Dentists and student operators were tested for their ability to cure a posterior restoration effectively. Relative light intensity was assessed against time for each operator and test run. RESULTS: Experienced (qualified) operators produced more effective and consistent cure results than less experienced undergraduate students. Operator performance was not affected by variations in irradiation time. CONCLUSIONS: This cross-sectional pilot investigation demonstrates that operator experience is a factor in successful clinical photo-curing of posterior restorations. Stable and accurate light guide positioning are required throughout the entire irradiation cycle to optimise intra-oral cure of light-activated restorations. Further investigations are planned to assess the potential of this novel method of assessment for use as a routine teaching aid in clinical practice.

Analysis of Variance↗

PubMed2002

Evaluation of smear layer removal by EDTAC and sodium hypochlorite with ultrasonic agitation.

AIM: To evaluate smear layer removal by different irrigating solutions under ultrasonic agitation. METHODOLOGY: Twenty recently extracted mandibular incisors with a single root canal were divided into four equal groups. Three groups were instrumented using the modified double-flared technique, the fourth remained unprepared. Each group was irrigated with either distilled water, 1.0% sodium hypochlorite alone or associated with 15% EDTAC between each file size. The final group was not instrumented but irrigated with 1.0% sodium hypochlorite and 15% EDTAC. A size 15 file energised by ultrasound was used with small amplitude filing movements against the canal walls in all groups. The teeth were split longitudinally and the roots measured to provide three sections of the same size (cervical, middle and apical). Samples were examined under the scanning electron microscope and assessed for the amount of smear layer by three independent and calibrated examiners. The scoring system ranged from 1 (no smear layer) to 4 (all areas covered by smear layer). Due to the non-parametric nature of the data, Friedman's test was used for statistical analysis. RESULTS: Canal walls were covered with smear layer in the group irrigated with 1% sodium hypochlorite alone and the group irrigated with distilled water. Canals irrigated with 1.0% sodium hypochlorite associated with 15% EDTAC had less smear layer throughout the canal (P < 0.001). There were no statistical differences for the amount of smear layer found on the cervical, middle and apical thirds when each group was analysed separately. CONCLUSIONS: Under ultrasonic agitation, sodium hypochlorite associated with EDTAC removed the smear layer from root canal walls, whereas irrigation with distilled water or 1.0% sodium hypochlorite alone did not remove smear layer.

Dental Pulp Cavity↗

PubMed2001

Effect of exposure intensity and post-cure temperature storage on hardness of contemporary photo-activated composites.

OBJECTIVES: The effect of variation in post-exposure storage temperature (18 vs. 37 degrees C) and light intensity (200 vs. 500mW/cm(2)) on micro-hardness of seven light-activated resin composite materials, cured with a Prismetics Mk II (Dentsply) light activation unit, were studied. METHODS: Hardness values at the upper and lower surfaces of 2mm thick disc shaped specimens of seven light-cured resin composite materials (Herculite XRV and Prodigy/Kerr, Z100 and Silux Plus/3M, TPH/Dentsply, Pertac-Hybrid/Espe, and Charisma/Kulzer), which had been stored dry, were determined 24h after irradiation with a Prismetics Mk II (Dentsply) light activation unit. RESULTS: Hardness values varied with product, surface, storage temperature, and curing light intensity. In no case did the hardness at the lower surface equal that of the upper surface, and the combination of 500mW/cm(2) intensity and 37 degrees C storage produced the best hardness results at the lower surface. CONCLUSIONS: Material composition had a significant influence on surface hardness. Only one of the seven products (TPH) produced a mean hardness values at the lower surface >80% of the maximum mean upper surface hardness obtained for the corresponding product at 500mW/cm(2) intensity/37 degrees C storage temperature when subjected to all four test regimes. Despite optimum post-cure storage conditions, 200mW/cm(2) intensity curing for 40s will not produce acceptable hardness at the lower surface of 2mm increments of the majority of products tested.

Analysis of Variance↗

PubMed2000

Tooth slice organ culture for cytotoxicity assessment of dental materials.

The purpose of this work was to develop a tooth slice organ culture method to assess the response of the cells of the dental pulp to commonly used dental materials and products. Wistar rat tooth slices were grown in culture for two and ten days in the presence of dental materials. After culture, the tooth tissues were processed and the responses of the pulpal cells were analysed histomorphometrically. Cytotoxic cell destruction was observed following the direct application of test materials to tooth slices (n = 298) after 10 days in culture (MANOVA, P = 0.0001), whilst the restoration of prepared deep dentine cavities (n = 30), with test products, did not result in a significant amount of pulpal injury (MANOVA, P = 0.287). In rank order of causing pulpal injury, the test materials from the most to the least cell destructive, was; Salicylic acid. Calcium hydroxide, Kalzinol zinc oxide eugenol, high-mercury Amalgam, Prime & Bond, Dycal, Barium sulphate, Hypocal, Scotchbond, Calasept, Life and One-step. Tooth slice organ culture, provided a cytotoxicity screening method for dental materials, bearing a closer physiological resemblance to the clinical situation than cell culture screening methods. Tooth slice culturing may have the potential to replace some types of in vivo animal experimentation, as there is a clear need to reduce this form of testing.

Animals↗

PubMed2000

Human odontoblast cell numbers after dental injury.

OBJECTIVES: The purpose of this study was to measure the changes in odontoblast cell numbers in response to cavity restoration variables and patient factors, and the effect these factors have on dental repair by tertiary dentinogenesis. The number of vital odontoblasts is a critical factor for pulpal repair following restorative surgery, and yet little information is available on these cell numbers. METHODS: Class V non-exposed cavities were prepared in the buccal surface of intact first or second premolar teeth of 27 patients, between 9 and 17 years of age. Following tooth extraction (28-163 days) the area of reactionary dentine and the area of the odontoblasts were measured histomorphometrically. RESULTS: Patient factors, as well as cavity preparation and restoration variables, had little effect on the numbers of odontoblasts per pulpal unit area. However, the age of the patient did appear to have an effect on the reactionary dentine secretory capacity of odontoblasts per unit area, and on the relative number of odontoblasts beneath cut dentinal tubules. CONCLUSIONS: Odontoblast cell numbers were maintained following the preparation of cavities cut into dentine with a 0.5mm residual dentine thickness. The repair capacity of the pulp-dentine complex would appear to be age dependent, this may explain differences in the success of various restorative treatments between patients.

Adolescent↗

PubMed2000

Ultrastructural localisation of TGF-beta exposure in dentine by chemical treatment.

Transforming growth factor-beta (TGF-beta) sequestered in dentine matrix has an important role in dental tissue repair after injury and its exposure at sites of injury may stimulate tertiary dentinogenesis. This study aimed to investigate the expression of TGF-beta isoforms in mature human dentine matrix and the ability of chemical treatments to expose TGF-beta on the cut surface of dentine using gold immunolabelling and subsequent scanning electron microscopy examination. TGF-beta1 was the only isoform that could be detected in human dentine and the nature of the chemical treatment of the tissue influenced its detection. EDTA treatment provided good exposure of TGF-beta1 on the dentine surface, whilst citric acid and sodium hypochlorite treatments revealed lesser amounts of this isoform. Only minimal staining for TGF-beta1 was observed in samples treated with phosphate-buffered saline. TGF-beta2 and -beta3 could not be detected in the specimens with any of the treatments. This study suggests that TGF-beta1 is the only TGF-beta isoform expressed by human odontoblasts to be sequestered in dentine implying that differences in isoform-extracellular matrix interactions may exist. Information on chemical treatment of tissue specimens for immunostaining may provide a useful basis for selection of tissue preparation techniques for clinical restorative treatment procedures to facilitate TGF-beta mediated reparative processes at sites of dental injury.

Citric Acid↗

PubMed2000

An in vitro investigation into the cutting action of ultrasonic radicular access preparation instruments.

The aim of this study was to investigate the dentine cutting action of a CT4 and SJ4 radicular preparation inserts (Excellence in Endodontics/Analytic Technology, Orange, CA, USA) used in a Piezon Master 400 ultrasonic handpiece (Electro Medical Systems SA, Nyon, Switzerland). Calibration of the ultrasonic inserts was carried out at minimum, medium and maximum power settings using light microscopic measurement of the tip displacement amplitudes (x120 mag). Polished dentine samples were instrumented, at monitored loads, at the three chosen power settings, to produce uniform dentine cuts. The resultant dentine debris was collected for SEM analysis, and comparison with that produced by rotary instruments. The depth of dentine cut was measured at x30 magnification. Fracture of the SJ4 insert was noted at medium power setting. Results revealed a significant increase in both displacement amplitude and depth of dentine cut with power setting (ANOVA P < 0.001). Dentine chip size increased with power, and differed in structure and appearance from those produced by rotary instruments. In conclusion, ultrasonic cutting is influenced significantly by power setting, and dentine chip formation is fundamentally different to rotary instrumentation.

Analysis of Variance↗

PubMed2000

The influence of sample dimensions on hydroxyl ion release from calcium hydroxide products.

The purpose of this study was to compare the rate of hydroxyl ion release from commercially available setting and non-setting calcium hydroxide products. The rate of hydroxyl ion release is important, as this has been suggested to be the main factor in the therapeutic activity of these products. In total, hydroxyl ion release was measured from 1104 samples of Dycal, Life, Calasept and Hypocal in solution using in vitro titration. The rate of hydroxyl ion release was measured for up to 14 days, using two sizes of sample surface area. The dimensions of the exposed sample surface area was found to be an important physical constraint to the hydroxyl ion release from non-setting calcium hydroxide products, whereas this was not found to be the case with setting products. The range in hydroxide activity between products was found to be 298%. In rank order of hydroxide ion release, from the most to the least active was: Hypocal, Calasept, Life and Dycal. The differences in the rate of hydroxyl ion release from these products may have some implications for their clinical applications. It is suggested that in cases where the oral healing responses have been poorer than expected, the size and seal of prepared cavities could have negatively influenced the therapeutic release of hydroxyl ions from non-setting calcium hydroxide products.

Analysis of Variance↗

PubMed2000

Cleaning efficacy of two apical preparation regimens following shaping with hand files of greater taper.

AIM: The aim of this investigation was to assess canal cleaning following shaping with hand files of greater taper. METHODOLOGY: Thirty mesial canals and 30 distal canals in mandibular molars were prepared with .08 and .10 hand files of greater taper, respectively. Following initial preparation, 0.02 instruments were used incrementally shorter in a stepback manner. In half the canals instrumentation was performed to size 35 1 mm short of the canal terminus. In the other half the series was continued through to size 60 using stepback increments of half to one millimetre as appropriate (foramen size was maintained at size 20 in all groups). Sodium hypochlorite (4.5%) and REDTA (17%) were used as irrigants for all groups. Cleaning efficacy was evaluated by scoring the amount of remaining debris using a light microscope (x50) and calibrated eyepiece micrometer (range 0-3). RESULTS: Canals stepped back through to a size 60 were significantly cleaner than those instrumented to a size 35 only (Mann-Whitney P < 0.05). CONCLUSION: Refining the apical region of canal preparation by stepping back through to a size 60 reduced remaining debris following shaping with files of greater taper.

Dental Instruments↗

PubMed2000

Postoperative pulpal and repair responses.

BACKGROUND: Each year in the United States, the success of 10 million surgically restored carious lesions depends on a favorable tertiary dentin repair response to preparation, restoration and patient factor variables. The authors investigated the relationship between these variables and dentinal response. METHODS: Standardized rectangular Class V restoration preparations were cut into the buccal dentin of intact first or second premolars of 27 patients without exposing the pulp and were restored. The patients were between 9 and 17 years of age. The treated teeth were scheduled for extraction for orthodontic reasons. After tooth extraction, the tertiary dentin was analyzed histomorphometrically. RESULTS: The area of tertiary reactionary dentin was found to be correlated using linear regression analysis of variance with restoration residual dentin thickness (P = .0024), age of the patient (P = .0045), restoration floor surface area (P = .0266) and restoration width (P = .0415). The authors did not find a correlation with the premolar position (P = .0594), sex of the patient (P = .650), pulpal inflammatory reaction (P = .613) or the time elapsed since surgery (P = .531). Restoration with zinc oxide eugenol was found to negatively influence tertiary dentin matrix secretion (post hoc analysis of variance, P = .030). CONCLUSIONS: The age of a patient at treatment, the choice of restorative material and the size of the restoration preparation are all factors that can positively or negatively affect the pulpal repair response. CLINICAL IMPLICATIONS: Age of the patient affects dentin repair capacity and may be a factor in treatment planning decisions. Minimizing the cutting of dentin, especially the width and base of the preparation, reduces the probability of recurrent pulpal complications.

Adolescent↗

PubMed1999

Protection against Helicobacter pylori infection by intestinal immunisation with a 50/52-kDa subunit protein.

A mouse model of Helicobacter pylori infection was used to evaluate the vaccine antigen potential of the citrate synthase homologue protein purified from the H. pylori NCTC 11637 strain. Mice were immunised with the protein by intra-Peyer's patch immunisation. This route gives maximal intestinal immunisation and was used to screen oral vaccine candidate antigens without the added complication of simultaneously testing oral delivery systems. Two weeks post-immunisation mice were infected with Sydney strain H. pylori and 4 weeks after infection the mice were killed and the level of H. pylori infection in the stomach determined. Pre-immunisation with the 50/52-kDa protein led to a 84-91% reduction in H. pylori infection compared to unimmunised controls.

Animals↗

PubMed1999

The periodontal-endodontic interface.

The periodontal tissues and the pulp-dentine complex form an intimate continuum through which pathological changes of either one may lead to infection of the other, and whose management can be fraught with diagnostic and therapeutic difficulty. The purpose of this review paper is to explain the nature of that relationship and to provide pointers which may assist in the diagnostic process and thus enable appropriate management from the outset. Traditional classifications of lesions affecting the periodontal-endodontic complex have caused confusion by attempting to form diagnoses which indicate the putative primary source of infection. We would suggest that the origin of the infection is irrelevant to the management process, and that what is important is whether either, or indeed both, of the tissues are viable or not. Successful therapy will only result from the establishment of an accurate diagnosis, and forming such a diagnosis requires a methodical multi-staged approach.

Dental Pulp Diseases↗

PubMed1998

An in vitro evaluation of canal preparation using Profile .04 and .06 taper instruments.

A model system involving a double radiographic exposure technique was developed in order to evaluate maintenance of the original canal path of curved root canals. The mesiobuccal roots of 30 maxillary molars were prepared using one of three techniques (n = 10 in each group). One group was instrumented using rotary Profile .04 tapers and a second group was prepared using orifice openers, rotary Profile .04 and .06 tapers. The final group was prepared using Profile hand files .02 taper and Gates-Glidden drills. Canal transportation was evaluated in the apical, middle and coronal regions from the double-exposed radiographs. Canal shape was determined by the ease with which a D11T spreader passed to within 1 mm of the working length. Time of instrumentation was also recorded. The results showed no significant difference between the techniques in canal transportation in the apical, middle or coronal regions (P > 0.05). It was significantly easier to place the D11T spreader in the .06 taper group (P < 0.05). Canal preparation was significantly quicker in the .04 taper group (P < 0.05). In conclusion, the use of .06 taper files improved canal shape and did not increase transportation. The additional file changes, however, increased the instrumentation time.

Dental Instruments↗

PubMed1998

The external and internal anatomy of human mandibular canine teeth with two roots.

This study investigated the internal anatomy of 65 human mandibular canines with two well-defined roots. The teeth were decalcified and injected with gelatin coloured with india ink. Diaphanization was carried out using clear resin to allow permanent preservation. It was found that all mandibular canines with two roots had two root canals. Lateral canals were found in 68.9% of teeth and 19.7% had lateral canals at the bifurcation. The results of the external measurements (cusp tip to root apex) showed that the average buccal root length was 23.0 mm and the average lingual root length was 22.7 mm. The maximum and minimum buccal lengths were 26.7 mm and 17.9 mm respectively and the maximum and minimum lingual lengths were 27.2 mm and 17.1 mm respectively. The buccal root was the larger of the two in 47.7% of teeth and 43.1% had roots of equal size. The lingual root was larger than the buccal root in 9.2% of cases. Clinicians should be aware of the anatomical variation that exists for mandibular canines.

Cuspid↗

PubMed1997

Cutting ability of Heliosonic, Rispisonic, and Shaper files.

The aim of this study was to investigate the cutting ability of the Heliosonic, Rispisonic, and Shaper files supplied with the MM 1500 sonic handpiece. A model system was used and the following variables evaluated; file type (Heliosonic, Rispisonic or Shaper), power (air inlet ring opening of half, three quarters or fully open), width (15, 25 or 35), and load (25, 50 or 100 grams). A 3(4) full factorial analysis with two replications was performed. A new file with water irrigation was used for each cut. The substrate used was 1 mm thick sections of bovine bone. The differences between the variables were significant (ANOVA, p < 0.001). The most significant variable to affect cutting was load, followed by file type, power, and width. It is suggested that operators should select the file type for use appropriately and press the file against the root canal wall for optimum cutting.

Analysis of Variance↗