Showing papers in "The European journal of prosthodontics and restorative dentistry in 2003"

A comparison of three hard chairside denture reline materials. Part I. Clinical evaluation.

Abstract: Three chairside reline materials were each used to reline ten complete dentures. Comfort, fit, colour change, staining and integrity were assessed at 3, 6, and 12 months post-placement. Working and setting times were obtained using an oscillating rheometer. Tokuso Rebase Fast Set had the shortest working and setting times. It was the most colour stable, stain resistant and durable. Coe Kooliner was difficult to use due to high flow. Total Hard had the longest working and setting times, and the poorest stain resistance and durability. Severe loss of reline materials only occurred 12 months after placement, and then mostly from within lower dentures. No differences between the materials were noted for the other parameters investigated.

Quality of materials supplied to dental laboratories for the fabrication of cobalt chromium removable partial dentures in Ireland.

Abstract: The adequacy of prescription for fabrication of cobalt chromium removable partial dentures is often regarded as being less than ideal. This study examines the nature and quality of written instructions and master impression sent to dental laboratories in Ireland for fabrication of cobalt chromium removable partial denture frameworks. Questionnaires were issued to dental laboratories seeking specific information relating to the materials (impression materials and trays) and written instructions supplied, as well as the technicians' opinion regarding the suitability of these materials. One hundred completed questionnaires were returned. One-third of master impressions were made using a plastic stock tray and alginate; technicians felt that one-fifth of master impressions were unsuitable; almost three-fifths of written instructions were inadequate. The quality of clinical information examined was found to be less than adequate.

A comparison of three hard chairside denture reline materials. Part II. Changes in colour and hardness following immersion in three commonly used denture cleansers.

Abstract: This study investigated the effects of daily use of three denture cleansers on three hard chairside reline materials over a 6-month period. Two controls were used; one dry and one involving storage in water. Colour and hardness were measured at 0 (baseline) and 6-months. There was no significant colour change with Tokuso Rebase Fast Set. Coe Kooliner and Total Hard changed colour more with the short acting peroxide cleanser (Steradent 3 Minutes) than with the overnight peroxide cleanser (Steradent Fresh) and the hypochlorite cleanser (Dentural). The hardness of all materials remained unchanged over the whole test period.

Safety issues when using carbamide peroxide to bleach vital teeth--a review of the literature.

Abstract: Hydrogen Peroxide is used to bleach discoloured teeth but since its introduction in the late nineteenth century there have been concerns about its safety and efficacy. This paper reviews the literature on hydrogen peroxide and carbamide peroxide and assesses if these products can be recommended for clinical use. The authors used a Medline search to find the literature for review and from these the findings were divided into laboratory, animal and human studies. In conclusion no dental treatment is without risk but from the evidence it seems that bleaching teeth is comparatively safe.

A laboratory investigation of the accuracy of the repositioning impression coping technique at the implant level for single-tooth implants.

Abstract: This study investigated the accuracy of the repositioning impression technique at the implant level using vinyl polysiloxane impression material. Three groups each of ten senior dentists, postgraduate students and technicians were asked to use this technique to record the position of an implant in a master model. The Reflex Microscope was used to measure variations between the resulting casts and the master model. Significant difference between the casts and the master model in the X and Y-axes (p < 0.01) was recorded. Alarming inclinational and rotational errors for the implant analogue position were measured with all groups of operators. Similar distortion in the Z-axis was recorded.

Potential for temperature change during application of ultrasonic vibration to intra-radicular posts.

Abstract: The aim of this study was to assess the potential for heat production when intra-radicular posts were subjected to ultrasonic vibration. Thirty zirconium ceramic posts and thirty stainless steel posts were luted into canine roots. Ultrasonic vibration was applied to the top of each post for thirty minutes and temperature change on the root surface was measured. The mean peak temperature rise from baseline was 18.7 degrees C. Post type had no influence on peak temperature. Temperature increase on the external root surfaces increased as the thickness of dentine between post and root surface reduced.

Endodontics and new graduates, Part 2: Undergraduate experience and course evaluation.

Abstract: A postal survey of recent United Kingdom dental graduates was undertaken to establish the amount of their undergraduate endodontic experience and their opinions of their training. A 75% response was achieved from all but two schools. Recent graduates had generally undertaken fewer cases as students than older graduates. Several had undertaken very few endodontic procedures as students. Differences and trends were seen in the opinions of students and their experiences among the schools, and between the two year groups studied. Most students were not very confident to undertake molar endodontics. Many felt they needed more practical experience as students and training in newer techniques and instrumentation.

Posterior occlusal support and bite force influence on the mandibular position.

Abstract: Three-dimensional mandibular displacement related to loss of posterior occlusal support was investigated. Five subjects, whose mandibular premolars and molars needed to be restored, were selected. Their experimental prostheses were removed in sequence from the most posterior to anterior. The more the absence of posterior occlusal support increased, the more condylar displacements were increased. On the other hand, maximum bite forces were decreased, by removing each prosthesis in sequence from posterior to anterior. These results suggest that condylar position would be easily displaced with low level bite force following loss of posterior occlusal support.

Case report: management of the flabby ridge: re-visiting the principles of complete denture construction.

Abstract: Displaceable tissue on edentulous ridges may present a considerable clinical challenge to dental practitioners when providing complete dentures. Surgical excision techniques or use of dental implants has provided clinicians with methods of addressing this particular difficulty. However careful consideration and application of the principles of complete denture construction can provide a less invasive and less complex form of treatment. This article describes one such clinical scenario, and demonstrates the use of a suitable impression technique that is based on successful manipulation of the thermoplastic nature of the impression material.

Reducing microleakage in composite resin restorations: an in vitro study

Abstract: The purpose of this in vitro study was to evaluate the effect of a resin lining on microleakage around composite resin restorations. Standard slot cavities were prepared on the approximal surfaces of 48 extracted human molar teeth. The cavities were restored with two conventional or two condensable composite resins, placed with or without a flowable composite resin lining. The teeth were subjected to thermal stress and immersed in dye solution. Dye penetration was viewed with both a stereomicroscope and a scanning electron microscope. Flowable resin lining material under condensable composites may be beneficial in reducing microleakage around cervical margins.

Bonding of silicone extra-oral elastomers to acrylic resin: the effect of primer composition.

Abstract: Silicone elastomer is bonded to acrylic resin in many facial or oro-facial prostheses. The silicone elastomer/acrylic resin bond has been reported to be insufficient and primers have been used to enhance the bond. This study investigated the bond strength of silicone elastomer to acrylic resin using different types of primers. The extra-oral silicone elastomers studied were Cosmesil and Ideal. The "overlap-joint" model was used to evaluate the bond strength and the samples were stretched until fracture. The bonding surfaces were treated with a primer. The control primer was Cosmesil and the others a mixture of Cosmesil/Z-6020 and Cosmesil/A-174 in 50/50 v/v ratio. The bond strength ranged from 0.026 MPa to 0.219 MPa. The results obtained in this work led to the conclusion that the most critical parameter allowing the efficient performance of a primer is the compatibility and affinity of its composition with the selected silicone elastomer.

Rehabilitation of occlusal support by removable partial dentures with free-end saddles.

Abstract: This study aimed to assess the level of restored occlusal support by removable partial dentures with free-end saddles. The maximal clenching force of 61 subjects was measured using pressure sensitive film with and without their dentures. The restored level of occlusal support was estimated from the shift of the occlusal load centre. In comparison with previous results of experimental occlusions using splints for eight normal dentate subjects, the restored level using dentures ranged from 40-60% of that of natural teeth. The analysis of the shift of the occlusal load centre could reasonably evaluate the prostheses from the standpoint of occlusal support.

The effect of the addition of different fibres on the transverse and impact strength of acrylic resin denture base material.

Abstract: The aim of the present study was to investigate the effect of the addition of different types of fibres on the transverse and impact strength of acrylic resin denture base material. The addition of glass fibres (strand) and polyethylene fibres produced a non significant increase in the modulus of elasticity, compared with the control of conventional heat-cured acrylic resin. The addition of glass fibres (woven and strand), polyethylene and carbon fibres to acrylic resin produced a non significant increase in the modulus of rupture. The addition of carbon, glass (strand) and polyethylene fibres produced a significant increase in the impact strength. Within the limitations of this study the addition of silk fibres did not produce an improvement in the mechanical properties.

Comparison of bond strengths between adhesive and conventional acrylic resins to cobalt chromium denture base alloy.

Abstract: In removable partial dentures there is normally no chemical bonding between the cast alloy and the poly(methylemethacrylate). Mechanical retention of the resin to the casting is required and presents a significant challenge during the design of partial dentures. Recently developed adhesive denture base resins which contain the monomer 4-methacryloxyethyl trimellitate anhydride can create a chemical bond to partial denture alloys. This study investigated the bond strength of adhesive denture base resin (Metafast) and conventional acrylic resin (Croform x 10) to partial denture alloy (CoCr) under three different storage conditions (dry, water, water with thermocycling). The results showed that the bond strength of the conventional acrylic resin (Croform x 10) was less than the bond strength of the adhesive denture base resin (Metafast) and the storage environment had a significant effect upon the bond strength of both resins.

Case report: management of tooth tissue loss from intrinsic acid erosion.

Abstract: Acid erosive tooth wear is increasingly being reported in many western countries, and is also being recognised as a significant cause of tooth destruction in persons with xerostomia. The primary aetiology is related to a high consumption of dietary sources of acids and also to an increasing awareness of gastric acid as a significant factor in both children and adults. Recommended preventive dental treatments aim to neutralise the effects of acids, reduce the severity of xerostomia, stimulate salivary flow and buffering capacity, and increase the acid resistance of tooth substance. Initial restorative treatments should be conservative, using adhesive dentistry techniques. This treatment approach is illustrated by the oral rehabilitation of a severe erosion case using adhesive onlays, veneers and all ceramic crowns.

Dimensional changes and water sorption of two acrylic polymer materials reinforced with glass fibres.

Abstract: The purpose of this study was to examine the effect of glass fibre reinforcement on the dimensional changes and water sorption of a heat-polymerising denture acrylic polymer and a microwave-polymerising denture acrylic polymer. Fifteen specimens from each group were prepared with 2% by weight (18 mg) E-glass fibre and 15 without glass fibre. The dimensional change measurements were made at three different stages on the 60 specimens. The water sorption calculations were made on specimens immersed in distilled water at 37 degrees C +/- 1 degree C for 0, 1 and 7 days. Glass fibre reinforcement and processing method do not affect the dimensional change of test specimens, but as the time increased the dimensional change decreased. The glass fibre reinforcement decreased water sorption, but the two processing methods failed to show a significant difference.

A study of the relationship between lateral guidance and temporomandibular joint internal derangement.

Abstract: The aim of this study was to examine the relationship between lateral retrusive and lateral protrusive tooth guidance and temporomandibular joint disc displacement. The control group comprised 55 symptomless students and dental nurses. The patient group consisted of 117 patients (90 women and 27 men). Fifty-four patients had temporomandibular joint clicking on the right side and 63 patients had clicking on the left side. The incidence of ipsilateral lateral retrusive tooth guidance was significantly higher in the patient group (87%) than in the control group (18.5%).

Comparison of restorative dentistry referrals to a district general hospital and to a teaching hospital using a pilot Index of Restorative Dental Treatment Need.

Abstract: The purpose of this study was to identify differences between referral patterns and the clinical conditions of patients referred to consultant-led Restorative Dentistry clinics in a district general hospital and a London dental teaching hospital. The Index of Restorative Dental Treatment Need was used to classify patients into those patients whose treatment was appropriate for any dental graduate in general practice, for an experienced dentist in general practice, and for a dentist with specialist training. Demographic and clinical details were recorded for one hundred patients at each hospital. The results of the study showed that the proposed treatment of 21% of the patients seen at the district general hospital and 16% of the patients seen at the teaching hospital was appropriate for specialist care. The results support the expansion of specialist restorative dentistry services in district general hospitals.

Team training at an outreach dental unit.

Abstract: A cohort of eighty nine undergraduate dental students worked for one year on two clinics completing a total of 3901 days work. Most of this time (63%) was spent at a site with shared nursing support, but despite this another site with dedicated nursing support produced approximately the same output. Students and nurses preferred working as a team rather than sharing; 98% of the students completed a questionnaire on the role of dental nurses and the majority identified chairside assistance as being the most important contribution to the increased throughput of patients.

Case report: differential pressure impressions for complete dentures.

Abstract: A method of producing a differential pressure, secondary impression of a lower arch with a sharp bony ridge is described. The use of this technique allows the clinician to dictate where the load is to be borne by the mucosa.

Prevention of bone loss for edentulous patients.

Abstract: This paper examines the consequences of being edentulous particularly on the intra-oral hard tissues. Short, medium and long-term studies of the overall post-extraction changes are reviewed and the bone loss that might be anticipated quantified. Following on from this, means by which bone loss may be prevented are reviewed. The bone-preserving potential of conventional and implant-retained overdentures is presented, advantages and potential problem areas highlighted.

Influence on dimensional accuracy of volume of wash material introduced into pre-spaced putty/wash impressions.

Abstract: This study compared the accuracy of stone models obtained from two-stage, pre-spaced putty/wash impressions under conditions in which known volumes of wash material were introduced during the second stage of the impression: Group I, a quantity of wash material corresponding to the space provided; Group II, double the quantity of wash material as the space provided; Group III, double the quantity of wash material, but with V-shaped vents in the putty for escape of excess material. Percentage deviations of the vertical dimensions of stone dies with respect to the master model were significantly different between Groups I and II (the latter being shorter) (p < 0.05). For horizontal dimensions, differences were less consistent, although the deviations for Groups I and II and Groups II and III, with respect to the master model, were significantly different from each other for two of the three dimensions measured (Group II inter-abutment distances were generally larger) (p < 0001 and p < 0.05, respectively). It is concluded that putty recoil, resulting from compression by excess wash material, plays a significant role in the undersizing of working dies, although the level of clinical relevance is less clear.

Satisfaction with dento-facial appearance in the eating disorders.

Abstract: This study aimed to determine if satisfaction with dento-facial appearance is related to body image distortion and estimation in subjects with an eating disorder. Body Image Distortion, both perceived and desired, was measured with the Anamorphic Micro body image assessment software. The Body Satisfaction Scale and the Eastman Esthetic Index were used to determine satisfaction or otherwise with appearance. A convenience sample of fifteen subjects participated of whom nine were diagnosed with bulimia nervosa, two with binge eating disorder and four with eating disorder not otherwise specified. The group overestimated their body image by a mean of 28% and desired to be a mean 25% thinner. Of the 16 anatomical areas assessed on the Body Satisfaction Scale, the face was the only area associated with the over-estimate of body image (Spearman's rho = +0.52, p < 0.05). The teeth were not associated with body image.

Events in the mould during heat processing of poly(methyl methacrylate).

Abstract: Recordings of temperature and pressure in the mould have raised questions concerning the flow of poly(methylmethacrylate) during heat processing. Three simple experiments investigated flow of polymerised and partly polymerised poly(methylmethacrylate). Flow was not observed at normal processing temperatures. These results, combined with the results of previous work, suggest that as the mould heats up, thermal expansion of the dough exceeds polymerisation contraction, causing increase in pressure rather than flow. Maximum pressure occurs at maximum temperature. Thereafter, thermal expansion is reduced, polymerisation contraction increases and pressure in the mould drops. When the lowest pressure is reached the poly(methylmethacrylate) is polymerised.