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.

Reflective practice in the teaching of conservative dentistry to undergraduate dental students - perceptions derived from a pilot study using personal development diaries.

The aim of this study was to explore final-year student perceptions to the use of personal development diaries (PDDs) and to compare the findings with an established system of competitive continuous assessment, using open display of score ratings displayed on a clinic notice board. Focus groups in conjunction with personal development diaries (PDDs) were used to investigate the teaching of conservative dentistry to senior dental undergraduates. Thirty per cent of the statements made reference to the positive aspects of PDDs, while a small percentage (6%) was negative. Nineteen per cent of the comments derived from the focus groups showed that the undergraduates disliked the open display of their marks on the conservation clinic notice board. This compared with only 2% who claimed that they enjoyed the competitive method. A further 22% of the comments related to the fact that open display of marks was stressful, whereas 3% were unaffected. Eighteen per cent of the responses indicated that clinical conservative dentistry was a stressful experience.

The use of real time video magnification for the pre-clinical teaching of crown preparations.

OBJECTIVE: To investigate the effect on the undergraduate learning process of using an alternative method designed to enhance the visual demonstration of taper on full veneer crown preparations (better understanding of the value of taper on preparations early in the teaching programme in restorative dentistry). DESIGN: A comparison between the conventional teaching of full veneer crown preparations and the same teaching with the additional use of a magnified real time video display using a surgical microscope was investigated in this study. OUTCOME MEASURES: The degree of taper was measured for replica full crown preparations and results compared between different cohorts of undergraduates and experimental conditions. RESULT: Undergraduates taught using the real time video produced more accurately tapered preparations. This ability was retained over one year. CONCLUSIONS: A possible explanation for the result was that the use of magnification improved the undergraduates' precise understanding of taper by enhancing their ability to evaluate this critical measurement during the teaching process.

Three-dimensional finite element analysis of thermal shock in a premolar with a composite resin MOD restoration.

A three-dimensional finite element model of a human premolar with a composite resin Class II MOD has been used to investigate the temperature changes and induced thermal stresses associated with the imbibing of a hot liquid. Regions of high tensile stress were revealed and their possible clinical significance with respect to microleakage and failure in the approximal region of the restoration are discussed.

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.

Endodontic radiography.

The ability to take radiographs of good diagnostic quality is an essential prerequisite for successful root canal therapy. However, the operator also has a responsibility to limit the radiation dose to the patient. This article reviews the radiography required for root canal treatment with these criteria in mind.

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.

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.

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.

Maintaining the quality of dental undergraduates for general dental practice: a performance management study.

An investigation and survey explored the effect of the display of dental undergraduates clinical performance by a process termed silent monitoring. The study measured the effect of silent monitoring on the quality of patients' treatment and the frequency of non-attendance at appointments for patients arranged by undergraduates. A cross-sectional study also estimated the impact of silent monitoring on undergraduates' clinic time use. Both enquiries revealed that silent monitoring motivated students. It significantly increased the number of patients treated and reduced the non-attendance of appointments. However, there was an increase in the incidence of patients informing undergraduates that they could not attend appointments. This phenomenon allowed the rescheduling of appointments and better use of clinic time. Silent monitoring increased the time undergraduates spent preparing for the patients' treatment. it also improved the patients punctuality. Evaluation of the procedure by questionnaires showed approval of the method, although some undergraduates felt that aspects of their assessment were unfair. A survey revealed that other United Kingdom dental schools do not use silent monitoring. If they adopted such a method, it could have similar positive influences on their undergraduates' management of clinical practice and improve the quality for dental practice.

The durability of ceramic coated dental instruments.

This study investigates the hardness, structure, composition, and thickness of coatings on two dental instruments and the changes which occurred when the instruments were subjected to conditions that closely match their clinical use. One group of instruments had a titanium nitride coating that was approximately 8 micrometers thick and had a hardness of 19.5 GN/m2. The coating on the other instrument was alumina (aluminium oxide) and contained some microcracks even when new; this coating was thicker (approximately 30 micrometers) and had a hardness less than the titanium nitride coating (15.8 GN/m2). The results showed that the titanium nitride coating was structurally superior compared with the aluminium oxide coating. Laboratory wear tests against composite resin showed that the wear resistance of titanium nitride was superior to that of stainless steel whether assessed in terms of weight or volume loss.

An in vitro study of a surface wetting agent for addition reaction silicone impressions.

The aims of this study were to determine whether the use of a topical surfactant (Hydrosystem) reduced the number of air bubbles visible on the surface of polyvinyl siloxane impressions and stone dies. The impressions exhibited a mean of 1.4 +/- 2.1 bubbles when Hydrosystem wetting agent was used, which was significantly less (p < 0.001) than when it was not used (mean 5.5 +/- 4.7 bubbles). Dies prepared with Hydrosystem surfactant contained a mean of 0.4 +/- 0.8 bubbles, which was significantly (p < 0.001) less than when Wax-Mate surface agent was used (mean 3.5 +/- 5.2 bubbles). In conclusion, in vitro use of Hydrosystem surfactant reduced the number of air bubbles on the surface of silicone impressions and stone dies.

Effects of the removal of composite resin restorations on Class II cavities.

Composite resin has such good aesthetic qualities that it is often difficult to identify the tooth-restoration interface, yet this is particularly important should the material require complete removal. Following the in-vitro removal of direct and indirect composite resin restorations from Class II cavities significant changes in cavity size and shape were recorded. Thirty-eight cavities were studied from both occlusal and proximal aspects and the final cavity size was compared to the original cavity. There was a significant increase in cavity size with a mean increase of 37% for the direct composite cavities and 35% for the indirect cavities, although the range of values is large. Following restoration removal, occlusal surfaces were seen to increase in 71% of teeth and proximal surfaces in 75% of teeth. There was no significant difference between the results for direct and indirect composite restorations. Occlusal dovetails and cavity undercuts were created in cavities which did not contain these features initially.

Tooth root resorption induced in rats by diphenylhydantoin and parathyroidectomy.

Changes in bone, cartilage and the dentition in animals and man following the administration of anticonvulsant drugs resemble those seen in hypoparathyroidism and pseudohypoparathyroidism. Groups of 21-day-old rats were treated with diphenylhydantoin, parathyroidectomized, or made hypocalcaemic with a calcium-deficient diet. Histological examination revealed extensive resorption of cementum and dentine in the molars of the drug-treated and parathyroidectomized rats, but not in the hypocalcaemic or control groups. Localization of injected tetracycline by fluorescence showed that the resorption affected the distal side of the tooth roots and had occurred after root formation. No changes in cementum formation on the mesial side of the roots had occurred in any of the experimental groups. These results suggest that diphenylhydantoin induces a condition similar to pseudohypoparathyroidism in which the resistance of tooth roots to resorption is reduced.

Inhibition of cartilage growth by the anticonvulsant drugs diphenylhydantoin and sodium valproate.

Anticonvulsant-treated epileptic children have reduced growth and show skeletal deformities similar to those seen in hypoparathyroidism. In view of the crucial role of chondrocytes in endochondral bone growth we investigated the effects of anticonvulsant drugs on cartilage growth in rats. Rats were injected i.p. with diphenylhydantoin (PHT) or sodium valproate (dipropyl acetate; DPA), or were thyroparathyroidectomized (TPX) to render them deficient in parathyroid hormone (PTH). Cartilage growth, measured as the increase in thickness and cross-sectional area of the femoral epiphysis and the mandibular condyle cartilage, was significantly reduced in the PHT and TPX groups compared with control animals receiving the drug vehicle alone or a 'sham' TPX operation. The cellularity of the cartilage was reduced in all three treatment groups, but DPA had less effect than PHT or TPX. The similarity in effect between TPX and anticonvulsant treatment suggest the drugs may also interfere with the regulation of chondrocyte activity proliferation and matrix synthesis are reduced by anticonvulsant therapy, and that this contributes to the pathogenesis of abnormal skeletal growth in anticonvulsant-treated children.