Biomedical subjects

B J Millar

Publications and source records attributed to B J Millar.

At least 19 recordsLinked to original sources

PubMed2006

Eight year results with direct ceramic restorations (Cerana).

BACKGROUND: Single-visit system ceramic restorations are now in use to provide an alternative to resin-based materials. Inserts have been shown to improve characteristics of composite restorations. OBJECTIVE: To investigate the longevity of Cerana (Nordiska Dental, Sweden) in a prospective clinical trial. METHODS: Cerana restorations use matched drills with pre-etched and silanated leucite inserts cemented using a conventional restorative composite resin material. The results of 33 Cerana restorations up to eight years (25 Class I, eight class II) are presented. Restorations were reviewed and assessed by two examiners using modified USPHS criteria for anatomical form (AF) A-C, marginal adaptation (MA) A-D, surface roughness (SR) A-D, marginal discoloration (MD) A-C, colour match (CM) A-C and discomfort (DT) A-D as well as retention. RESULTS: The percentage of A scores for AF, MA, SR, MD, CM and DT at baseline (n = 33) were: 100, 100, 79, 100, 21, 100; after two years (n = 27) 100, 85, 33, 100, 19, 100 and after four years (n = 24) 96, 75, 17, 96, 25, 100. At six years (n = 20) 95, 70, 10, 95, 15, 100 and finally at the eight year recall (n = 18) 94, 61, 0, 94, 6, 100. AF was maintained in all except for one fractured marginal ridge. MA of the insert was good but composite was lost where exposed. SR increased to a B score for all inserts. MD at B grade was observed in 6% between composite and tooth but none between insert and composite. CM was stable in all cases. DT nil in all. There were no scores less than B. All reviewed restorations were retained, clinically acceptable and in function except for two lost for reasons not directly related to the Cerana insert. One class II restoration had a fractured marginal ridge but otherwise remains satisfactory. CONCLUSIONS: The results suggest that these restorations can be expected to perform well. Cerana is acceptable in terms of aesthetics, patient acceptance, occlusal wear and ease of use and is a good alternative for a single-visit, tooth coloured restoration in suitable cavity shapes.

Aluminum Silicates↗

PubMed2005

Clinical performance of Rochette bridges used as immediate provisional restorations for single unit implants in general practice.

A retrospective clinical audit of the role and survival of 69 Rochette bridges used as immediate provisional restorations for single tooth, implant-retained crowns was carried out over the period between February 1991 and May 2001. In each case the extracted tooth was immediately temporised using a Rochette bridge with a single wing and pontic and cemented to the abutment tooth without any tooth preparation (Phase I). This bridge was removed at the time of implant placement and recemented (Phase II). At the implant exposure stage the bridge was removed and discarded. In Phase I, 15.9% of the bridges required recementation and 27.5% of the bridges required recementations in phase 2; 7.2% of the bridges required recementations in both phases. An 80% probability of survival was noted after an interval of 200 days for phase I and a 78% probability of survival over the same time interval was observed for Phase II. A significant debond rate was observed when the retainer was a canine in comparison to the other bridges in Phase I. In Phase I the spring cantilever debond rate was significantly higher than that observed on the other bridges. More debondings were observed in males (25.8%) compared with females (7.9%) in Phase I. More debondings were noted in the maxilla than in the mandible in Phase II. The performance characteristics of the metal acrylic Rochette bridge observed in this report supports the conclusion that this type of restoration is an effective means of immediate temporisation for patients undergoing single tooth implant retained restorations.

Adult↗

PubMed2001

Effect of curing with a plasma light on the properties of polymerizable dental restorative materials.

Specimens of light-curable dental restoratives have been prepared using either a conventional dental curing lamp (for 20 or 30 s) or a plasma light (for 1 or 2 s). The specimens were then stored in water until their mass equilibrated, then dried to constant mass. Most specimens lost material in this process but the losses in all specimens cured with the plasma light were significantly greater than those cured with the conventional lights (P < 0.05). Longer cure times gave slightly reduced losses in water in most cases. The specimens were then returned to water and allowed to re-equilibrate and their equilibrium water uptake determined. There was no simple trend in this latter property because elution of loosely bound hydrophilic species may have resulted in a less hydrophilic specimen, whose equilibrium water content was therefore correspondingly lower. Overall, the losses through dissolution in water suggest that plasma curing is less effective for these materials than conventional light curing, as it probably results in material with lower molar mass. The losses for the resin-modified glass-ionomer were much greater than for other materials, and it was concluded that the more rapid polymerization with plasma light caused a significant inhibitation of the acid-base part of the setting process. These findings suggest that long-term durability of materials may be compromised by employing plasma light cure rather than a conventional cure system and further studies of this point are recommended.

Acids↗

PubMed1999

Storage of polyacid-modified resin composites ("compomers") in lactic acid solution.

OBJECTIVES: The aim of this study was to determine the interaction of four polyacid-modified resin composites with aqueous lactic acid solutions, and to compare changes with those for a glass-ionomer cement and a conventional resin composite. METHODS: For each material, namely Compoglass F, Dyract AP, Hytac and Ana Compomer, plus AquaCem (glass-ionomer cement) and Pekafil (conventional composite resin), five cylindrical specimens of 4 mm diameter x 6 mm height were prepared and weighed. They were stored individually in 2.0 cm3 of 0.02 mol l-1 lactic acid solution for 1 week then the pH was determined and the specimens reweighed. The lactic acid solution was replenished, and the specimens were stored for a further week, after which the pH and specimen weights were again measured. This was repeated at 1 week intervals until the specimens were 6 weeks old. Differences were analysed by ANOVA followed by Newman-Keuls post hoc analysis. RESULTS: All four polyacid-modified composites increased the pH of the solutions at all time intervals by at least 0.26 pH units (significant to at least p < 0.01). This effect was similar to that of the glass-ionomer (but significantly less, p < 0.05) while significantly greater (p < 0.05) than that for the composite, Pekafil, which, by contrast, had no effect on pH. The observed rise in pH reduced significantly over time (ANOVA, p < 0.05). After 1 week, all pH changes were accompanied by net reductions in specimen mass, indicating susceptibility to acid erosion. Hytac was significantly more resistant to this erosion than the other materials; conversely, it had the least effect on solution pH. SIGNIFICANCE: These results show that polyacid-modified resin composites neutralise lactic acid in vitro but suffer erosion in the process.

Analysis of Variance↗

PubMed1999

Mesencephalic innervation of the vibrissal follicle-sinus complex in the mouse embryo.

Peripheral projections of neurones whose cell bodies lie in the mesencephalic nucleus of the fifth cranial nerve, situated between the central grey and mesencephalic reticular formation, were studied in mouse embryos aged between day 9 and 15 and in postnatal day 1 mice. Nonspecific neural antibody staining allowed visualisation of the developing cranial nerves, in particular the descending mesencephalic tract. This facilitated successful dissection of the descending mesencephalic tract and trigeminal ganglion in the heads of fresh mouse embryos and postnatal mice. The fluorescent dye, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil), was injected into the descending mesencephalic tract in mouse embryos aged 12.5, 13.5 and 15 days of gestation and also into postnatal day 1 mice. Following a period of incubation, 100 microm sections were viewed under visible light and episcopic fluorescence. Mesencephalic neurones were observed to pass superiorly over the trigeminal ganglion and enter the maxillary division to innervate vibrissal follicle-sinus complexes, whilst none was observed innervating mandibular and maxillary intraoral structures. There was no fluorescent labelling in non-Dil injected control specimens. Using a highly specific neuronal tracer, this study shows that mesencephalic neurones in the periphery project exclusively to follicle sinus complexes in the developing mouse embryo and remain at least until postnatal day 1. These observations, contrary to those made in other animals, indicate a species specificity of mesencephalic peripheral projections.

Animals↗

PubMed1999

Cerana--a direct ceramic inlay technique.

Ceramic materials provide aesthetic restorations which are able to withstand the oral environment but two appointments are needed to fabricate ceramic restorations by means of an indirect technique. However, single-visit systems are becoming available and a recent development, Cerana, utilises matched drills with pre-etched and silanated leucite inlays. The cavity is refined using one of three conical burs and a size- and shaped-matched conical inlay is cemented using a conventional restorative resin material. The final restoration consists of a leucite inlay surrounded by a small amount of composite resin. The exposed resin, being a restorative composite resin, has a higher filler loading than that of a luting cement and an overlap technique can be used to reduce the area of exposed surface resin. This paper describes the technique and illustrates some cases. The initial results are promising in terms of aesthetics, patient acceptance, occlusal wear and ease of use. The major clinical application of this new technique is the ability to restore a cavity with a leucite inlay at a single visit thereby offering a cost-saving alternative to current aesthetic restorations. The technique requires only a little more time than a direct placement composite restoration yet reduces polymerisation contraction, and the occlusal contacts can be placed on the ceramic surface, rather than on the composite resin, for longer-term stability.

Aluminum Silicates↗

PubMed1998

Focus on loupes.

This article aims to introduce the reader to the use of magnification in clinical dentistry and describes the lens systems available. The main principles of dental loupes are discussed and some of the potential problems outlined in order to help clinicians choose a magnification suited to their needs, provide years of service, and reduce the risk of eye, neck and back strain. The additional benefits and disadvantages of adding supplementary illumination, and the options available, are also considered.

Dentistry, Operative↗

PubMed1998

In vitro study of the number of surface defects in monophase and two-phase addition silicone impressions.

STATEMENT OF PROBLEM: Monophase addition-cured silicone impression materials in stock trays are considered to be alternatives to two-phase systems used with custom trays. PURPOSE: This study compared the number of surface defects in addition-cured silicone impressions recorded with monophase materials in stock trays and two-phase impressions in custom trays. METHODS: The number of voids visible on the surface of impressions recorded in vitro were counted. Two monophase impression materials. (President Monobody system 75, Bayer Cutter) in stock trays were compared with impressions recorded with two-phase addition silicone materials (President Plus light-body/regular-body and Zhermack Elite light-body/medium-body) in custom trays. A total of 200 automixed impressions, 50 with each material, were recorded of 50 dentoform molar teeth prepared for full veneer crowns. Impressions were examined for surface voids anywhere on the prepared part of the tooth by a trained examiner. RESULTS: Mean number of voids observed for the monophase impressions were 3.0 +/- 2.2 for President Monobody system and 3.4 +/- 2.0 for Bayer Cutter system. Mean number of voids for the two-phase materials were 0.8 +/- 1.0 for President Plus, and 1.0 +/- 1.1 for Zhermack Elite. No significant differences were observed for number of voids between the monophase materials or between the two-phase systems (ANOVA and Neuman-Keuls p > 0.05). However, both two-phase materials in custom trays had significantly fewer surface voids than the two-monophase materials (ANOVA and Neuman-Keuls, p < 0.001) used in stock trays. CONCLUSION: Monophase addition-cured impression materials in stock trays carries an increased risk of void formation on the surface of the impression when compared with two-phase addition silicone materials in custom trays.

Analysis of Variance↗

PubMed1998

In vitro caries inhibition by polyacid-modified composite resins ('compomers').

OBJECTIVES: The aim of this study was to compare the in-vitro caries inhibition of two polyacid-modified composite resins (PMCRs). METHODS: Three standardized class V cavities were prepared in eight extracted human molar teeth. Two of these cavities in each tooth were restored with Compoglass and Dyract according to manufacturers' guidelines. A conventional glass-ionomer cement restoration (Chemfil II) was placed in the third cavity in each tooth as a control. The teeth were submerged in an acid gel (lactic acid, gelatin, thymol, pH 4.5) for 28 days and then resin embedded. Ground sections were examined at x 160 magnification for enamel surface lesion depth, dentine surface lesion depth, wall lesions and evidence of caries inhibition. RESULTS: There was no significant difference between the depths of enamel or dentine surface lesions between the two compomer and conventional glass-ionomer materials. However, both PMCRs exhibited greater wall lesions than the conventional glass-ionomer material indicating less caries inhibition. CONCLUSIONS: These results suggest that PMCRs provide less caries inhibition than glass-ionomer cements.

Anti-Infective Agents, Local↗

PubMed1997

Clinical evaluation of an anterior hybrid composite resin over 8 years.

AIM: To evaluate the performance of an anterior hybrid composite resin restorative material (Opalux). DESIGN: Single-centre clinical trial. MATERIALS AND METHODS: Scores were obtained based on USPHS criteria for marginal adaptation, anatomic form, colour match, surface roughness and marginal discolouration. INTERVENTIONS: The restorative material was evaluated in suitable cavities in 24 patients (12 male, 12 female). Ethical permission and consent were obtained. MAIN OUTCOME MEASURES: Baseline data was collected on 44 restorations (25 Class III, 3 Class IV, 16 Class V) and reviewed independently by two of the three clinicians who contributed to the study who then reached a consensus score. Restorations were reviewed and scored in the same way at 3 months and 1, 2, 3 and 8 years. RESULTS: The total number of alpha ratings at baseline and review (3 months and 1, 2, 3 and 8 years) appointments for the following parameters were: marginal adaptation (33, 28, 29, 27, 12, 17), anatomic form (39, 30, 32, 26, 17, 15), surface roughness (34, 26, 24, 23, 11, 4), colour match (24, 25, 26, 24, 15, 12) and marginal discolouration (39, 31, 30, 25, 10, 9). The incidence of secondary caries was very low. Life table analysis suggests a 73% survival, with no scores below B, at 8 years. CONCLUSIONS: The majority of these restorations continued to perform satisfactorily. Although this particular material is no longer available, these results may be applicable to currently available similar materials.

Adolescent↗

PubMed1997

Preliminary investigation of a novel retentive system for hydrofluoric acid etch-resistant dental ceramics.

STATEMENT OF PROBLEM: A potential limitation to clinical use of In-Ceram and In-Ceram Spinell dental ceramics has been the inability to etch fit surfaces. PURPOSE: This study investigated a novel retentive system for In-Ceram and In-Ceram Spinell ceramics. MATERIAL AND METHODS: The system, Bateman etch retention system, relies on incorporation of plastic chips on the surface of a specimen. The plastic chips were subsequently burnt-out to leave pits on the fitting surface of the ceramic restoration. The effect of these surface pits on flexural strength of test specimens was compared with unetched and sandblasted samples. Shear bond strengths between clean and saliva contaminated samples and Panavia TC resinous cement were also determined. RESULTS: The Bateman etch retention system significantly reduced the flexural strength of both In-Ceram and Spinell ceramic specimens compared with unetched and sandblasted samples (p < 0.05). No significant differences were discovered between shear bond strengths of uncontaminated Bateman etch retention system and sandblasted samples. However, mean shear bond strengths of saliva-contaminated Bateman etch retention system In-Ceram samples were substantially greater than those of saliva contaminated sandblasted samples (p < 0.05). CONCLUSION: The Bateman etch retention system method should be the subject of additional investigation.

Aluminum Oxide↗

PubMed1997

The effect of a surface wetting agent on void formation in impressions.

STATEMENT OF PROBLEM: Impressions free from voids are important for the fabrication of accurate restorations. Any material or technique that reduces the incidence of bubbles is welcome. PURPOSE: The aim of this study was to determine whether the use of a surfactant designed for clinical use (Hydrosystem) reduced the number of visible air bubbles on the surface of a range of impression materials. MATERIAL AND METHODS: The surfactant was used before impressions were recorded with one of the following: a putty-wash condensation silicone, four polyvinyl siloxane materials, a polyether, a polysulfide, and an irreversible hydrocolloid impression material. Impressions recorded without the use of Hydrosystem acted as controls. Impressions were made of two prepared acrylic resin teeth in vitro and examined for surface voids by an examiner who was blind to whether the surfactant was used. RESULTS: Hydrosystem surfactant significantly reduced the number of surface voids when it was used with low-viscosity addition-cured silicone material but not when used with irreversible hydrocolloid, polysulfide, a hydroactive monophase addition-cured silicone, or a putty-wash condensation silicone. CONCLUSION: The use of Hydrosystem surfactant may result in a clinically significant improvement in impression quality.

Alginates↗

PubMed1997

Strength of secondary-cured resin composite inlay repairs.

A study was designed to simulate the repair of an indirect resin composite restoration with conventionally cured resin composite. Two-part specimens were prepared to test the diametral tensile strength of the repair interface between the base material of an indirectly cured resin composite (Herculite XRV) and repairs carried out with three directly cured materials (Herculite XRV, TPH, and Charisma). The repairs were carried out with and without use of the bonding resin for the repair material. The diametral tensile strengths of all repaired specimens were significantly less than those of bulk unrepaired specimens. There were no significant differences between the diametral tensile strengths of repaired blocks when the repair materials were used without bonding resin. The use of an intermediate layer of bonding resin significantly increased the bond strengths obtained when Herculite XRV and TPH were used for repair. There was no significant difference between the strength values of Herculite XRV and TPH, but Charisma exhibited the lowest strengths of repaired specimens.

Acrylic Resins↗

PubMed1996

A survey of the effectiveness of dental light-curing units and a comparison of light testing devices.

The aims of this study were to: 1. survey the light output from 49 light-curing units in clinical use; 2. measure the effect on depth of cure of composite resin caused by a range of light outputs; 3. assess the relationship between radiometer meter readings and depth of cure of composite resin in a human tooth model and a Heliotest. The mean meter reading produced by the 49 lights surveyed using a lampChecker radiometer was 4.4 (+/-2.4 SD), range 0.3 to 10.0. The manufacturer of the radiometer considers optimal light output to provide a meter reading within the range 5.0 to 7.0. Lights of very low output (0.7 +/- 0.1 SD) were found to be capable of curing, after 20 seconds, a 1.9 (+/-0.3 SD) mm thickness of composite resin. However, only approximately 50% of this thickness can be considered fully cured. Increasing the cure time from 20 seconds to 60 seconds increased the mean depths of cure by a factor of approximately 1.4. The mean depths of cure of composite resin placed in the Heliotest were greater than those observed in the natural tooth model, by a factor of approximately 1.3. Correlation coefficients of meter readings and depth of cure were greater for the Efos Cure Rite and Demetron 100 radiometers than the lampChecker unit.

Chemical Phenomena↗

PubMed1996

An assessment of the reliability of pulp testing deciduous teeth.

The aim of this study was to assess the reliability of children's responses to pulp testing of deciduous teeth. The maxillary canine was chosen as the test tooth. One hundred children aged 7-10 years were selected who had at least one non-carious maxillary canine with an intact root showing only early radiographic signs of resorption. Using a minimization sampling technique, the children were allocated to one of two groups, for pulp testing with ethyl chloride (EC) or with an electric pulp tester (EPT). True and sham tests for both pulp testing methods were applied. The tests were repeated following an application of 5% lignocaine paste to the gingival margin around the tooth to prevent gingival detection of the stimulus. Children were asked to record their responses to each of the four tests on a visual analogue scale (VAS) of 1-10. Significantly higher mean scores were obtained with true tests than with sham tests, for both EC and EPT. The application of lignocaine to the gingival margin did not significantly affect the responses to either EC or EPT. It was concluded that pulp testing of intact maxillary deciduous canines with no or only early signs of radiographic root resorption, using EC or EPT, results in reliable responses in 7-10-year-olds, suggesting that pulp testing is valid in the deciduous dentition. The VAS was a useful tool for the evaluation of the children's responses.

Child↗

PubMed1996

A survey of dental airlines and an examination of tooth-drying techniques.

The aims of this study were: 1. To assess the prevalence and severity of water and oil contamination in 20 dental airlines in clinical use, using a commercial test kit, LP Aerotest. 2. To determine the effect, in vitro, of such contamination on the shear bond strengths to etched bovine enamel, of composite resin and a dedicated bonding agent. The enamel was dried using either an oil-and-water-contaminated 3-in-1 syringe, a warm-air tooth-dryer, silica gel-dried air or blotting paper, prior to bonding. A total of 11 (5 mm diameter) composite discs were bonded in each group. The samples were shear tested 72 hours later at a cross-head speed of 50 mm/min. All airlines had > 100 mg/m3 water and traces of oil (< 0.5 mg/m3) were present in 50% of samples. The mean shear bond strengths (MPa) for the 3-in-1 syringe, tooth-dryer, dried air and blotting paper-dried teeth were 14.5 +/- 3.8, 19.0 +/- 2.6, 19.6 +/- 4.2 and 19.7 +/- 1.9 respectively. The differences between the values for the tooth dryer, dry air and blotting paper were not significant (P > 0.01) but a significant difference (P < 0.01) was observed between these and the 3-in-1 syringe.

Air↗

PubMed1996

Assessment of a prototype battery operated wax-knife for domiciliary and surgery use.

The aims of this study were to examine a prototype battery operated wax-knife, assess the extent to which manufacturer's claims have been achieved and determine its potential for clinical use. The mean time required for the wax-knife to achieve an operating temperature of 150 degrees C was 20.2(+/-4.3) s. The mean operating temperature of the ceramic blade was 155.4(+/-3.9) degrees C, range 150 degrees C to 162 degrees C. The mean usage time following full battery recharge was 42 (+/-2) minutes. The wax-knife provided a direct heating tool which retained many of the characteristics of the traditional wax-knife and was suitable for use in the surgery and in domiciliary situations.

Burns↗

PubMed1996

An in vivo study of a clinical surfactant used with poly(vinyl siloxane) impression materials.

The aim of this study was to determine whether the use of a topical surfactant (Hydrosystem), designed for clinical use, improved the quality of the impression surface of two poly(vinyl siloxane) materials used in vivo. Before impressions were taken, Hydrosystem was applied to the maxillary left or right premolar teeth, allocated at random, in 50 subjects. The untreated side acted as a control for each subject. The impressions were examined for quality of reproduction and number of surface defects. Hydrosystem was found to significantly improve the quality of reproduction.

Bicuspid↗