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PubMed2004

Ability of restorative and fluoride releasing materials to prevent marginal dentine demineralization.

The study aimed to define the in vitro secondary caries inhibiting potential of restorative materials currently used in dental practice. Class V restorations were prepared in extracted human third molars and immersed in a demineralizing solution (lactic acid, pH 4.5) at 37 degrees C for 2 days to simulate secondary caries formation. The bonding and the restorative systems tested in the study were: Scotchbond 1+Z 250 (Group A), Scotchbond 1+F 2000 (Group B), ABF+APX (Group C), ABF+F2000 (Group D). Perimarginal dentine, immediately close to the margin of the restoration, and exposed dentine, at approximately 0.5 mm from the margins of the restoration, after exposure to the acid solution, were investigated; protected dentine, at approximately 4 mm from the margin in a varnish-covered area, was analysed as control. Polarized light microscopy and contact transverse microradiography (TMR) were employed. The output parameters were lesion shape and size (depth in microm) of the exposed dentine, dentine mineral volume%, and integrated mineral loss (Delta Z, in %volmicrom) of the lesions. Compomers (Groups B and D) showed a thinner demineralization of the outer lesions, a less demineralization along the perimarginal dentine (inner lesion) and more caries inhibition zones or CIZs (Delta Z positive values) compared to composites (Groups A and C). In conclusion, Groups B and D materials seemed to partially counteract the marginal demineralization induced by an acid solution and favourably influence the formation of CIZs along the restorations. On the contrary, composites did not show a protective effect, probably due to an insufficient marginal seal and the lack of fluoride release.

Absorptiometry, Photon↗
PubMed1998

Fluoride release and uptake by glass-ionomers and related materials and its clinical effect.

The anticariogenic effect of silicate cement is well known and considered a result of fluoride release. In several studies a similar fluoride release from conventional glass-ionomer cement (GIC) has been established. Therefore, an anticariogenic effect may be predicted from the GICs too. In my studies the fluoride release was studied by exposing the test specimens to a continuous flow of running tap water. At certain time periods the specimens were transferred for 1 week in a small amount of deionized water (5 ml). The determination of the fluoride content of the solution showed the fluoride release of the material at that time. There was an initial 'burst' effect of fluoride release and then the release gradually decreased, settling at a constant level. The long-term release from conventional GICs was shown to remain on the same level for at least 8 years. The amount of the constant release did not differ much between different brands. Resin-modified GICs released fluoride to the same extent and in the similar way as conventional GICs whereas polyacid-modified composites ('compomers') did not show an initial fluoride 'burst' effect. To study the fluoride binding ability of GICs, specimens which had been exposed to running water for different periods of time were treated with a 50 ppm fluoride solution. After this 'recharging' GIC and resin-modified GIC specimens released more than twice the amount of fluoride released before the treatment. The fluoride treatment had no effect on polyacid-modified composites or on fluoride-containing composites or on the amalgams. To get an impression of the clinical effect of GICs a questionnaire was handed out to practitioners attending courses in the Nordic countries and in Australia during the period 1991-1992 which resulted in 954 answers. Among other questions, the dentists were asked if they had observed caries and gingival inflammation in association with GIC and composite fillings. According to the opinion of most dentists caries and gingival inflammation had never or only seldom been observed in association with GIC fillings whereas most dentists had observed these complications often in connection with composite restorations.

Biocompatible Materials↗
PubMed1998

Water sorption in resin-modified glass-ionomer cements: an in vitro comparison with other materials.

The pattern of water uptake into a polyacid-modified composite resin (compomer), Dyract (D), was assessed using gravimetric analysis and tritiated water absorption. The results were compared with a resin composite, Herculite (H), a resin-modified glass-ionomer, Fuji II LC (FL), and a conventional glass-ionomer, Fuji II (F). Samples were stored in tritiated water for periods varying between 6 h and 6 months. The resulting change in gravimetric weight and dimensions was recorded. The tritiated water content was then assessed using liquid scintillation counting and this was compared to the gravimetric changes. The inherent water content of each material was also established. D and H showed a slow steady net uptake to 3% and 1.3% weight by volume (WV) respectively at 6 months. FL showed a rapid uptake reaching 8.9% WV at 7 days and 9.3% WV at 6 months. F showed a steady, less dramatic water uptake reaching 5.3% WV by 6 months. For the glass-ionomer materials, values for gravimetric water uptake and tritium release differed due to the ongoing acid base reaction and an increase in firmly bound water. This phenomenon was noted in D suggesting evidence of a similar reaction in this material.

Absorption↗
PubMed1999

Cuspal deflection during polymerisation of composite lutes of ceramic inlays.

OBJECTIVE: The purpose of this study was to measure the cuspal deflection that occurs in teeth as a result of the dimensional changes of resin-based lutes during polymerisation. METHODS: Standardised MOD cavities were cut in 15 intact human premolar teeth using a custom paralleling device. A ceramic inlay was machined by the CEREC 2 system for each tooth ensuring an interface width of 50 microns (SD = 17.5) at the cavity margin. The 15 teeth were divided into three groups of five according to the cementation system employed: a microfilled hybrid posterior composite; a compomer restorative; a dual-cure luting composite. The inter-cuspal tooth dimension was recorded continuously with a laser micrometer assembly during a 2 min photoactivation period and a further 30 min post-activation period. RESULTS: A clear overall reduction in tooth dimension was detectable for the first 10 min of polymerisation. The mean changes ranged from -0.02% to -0.06% depending on the nature of the luting material. In addition, all samples exhibited a slight expansion of 0.03% during the time of light-activation. CONCLUSIONS: The dimensional changes that teeth experience during the polymerisation of resin-based lutes are clearly detectable. It can be postulated that an increase in the dimensions of the teeth during photoactivation occurs as a result of expansion of the lute due to the thermal energy delivered.

Analysis of Variance↗
PubMed1999

Solid state spatially resolved 1H and 19F nuclear magnetic resonance spectroscopy of dental materials by stray-field imaging.

As part of a program to evaluate the use of stray-field magnetic resonance microimaging (STRAFI) in dental materials research spatially resolved nuclear magnetic resonance (NMR) for solid dental cements has been investigated. By applying a quadrature echo pulse sequence to a specimen positioned in the stray-field of a NMR spectrometer superconducting magnet the magnetic resonance within a thin slice was obtained. The specimen was stepped through the field in 500 microm increments to record 1H and 19F profiles and T2 values at each point. The specimens were fully cured cylinders made from four types of restorative material (glass ionomer, resin modified glass ionomer, compomer, composite). The values for 1H T2 varied with material type and reflected the nature of the matrix structure. For all materials containing 19F in the glass two values were calculated for 19F T2, one short and one long. These were relatively invariant. Solid state magic angle spinning (MAS)-NMR showed that they came from the glass. This suggests that a proportion of the element is relatively mobile (in a glass phase) and the remainder is more tightly bound (in a compound dispersed in the glass). This demonstration, that NMR microimaging of both 1H and 19F in solid dental cements is possible, opens up exciting new possibilities for investigating the distribution of these elements (in particular fluorine) in solid dental materials.

Journal Article↗
PubMed2003

Time-dependent strength and fatigue resistance of dental direct restorative materials.

Elastic modulus (EM), initial fracture strength (FS) and flexural fatigue limit (FFL) of dental restorative materials were measured in a simulated oral environment to correlate mechanical response under the influence of water with the chemical nature of the test materials under investigation. One resin composite (RC; Tetric Ceram, Ivoclar-Vivadent Corp., Liechtenstein), an ion-leaching resin composite (ILRC; Ariston pHc, Ivoclar-Vivadent Corp., Liechtenstein) a compomer (CO; Dyract AP, Dentsply Corp., USA) and a glass-ionomer cement (GIC; Ketac Molar, 3MEspe Corp., Germany) were tested. Static EM, FS and dynamic FFL experiments were performed. The FFL was determined under cyclic loading for 10(5) cycles in terms of a staircase approach. The materials were stored for 1, 8, 30, 90 and 180 days in 37 degrees C distilled water, respectively. The RC degraded over time due to water adsorption followed by failure within the resin matrix. The ILRC suffered from a pronounced decrease in FS as well as in FFL due to a constant ion-leaching and macroscopic crack growth. CO failed over time due to resin-filler interface cracking. The GIC exhibited improved mechanical performance over time due to a post-hardening mechanism. The results reveal the necessity for substantial preclinical evaluation of direct restorative materials. The material parameters under investigation are capable of predicting clinical performance over time.

Journal Article↗
PubMed2004

The role of the ionomer glass component in polyacid-modified composite resin dental restorative materials.

In order to model the processes that occur within polyacid-modified composite resin ("compomer") dental restoratives, a series of experiments has been carried out with silanated and silane-free ionomer glass G338, and silanated and silane-free unreactive glass (Raysorb T-4000). In an acid-base reaction with dental grade aqueous maleic acid-acrylic acid copolymer solution, the setting time of the silanted G338 was found to be 9 min, compared with 5 min for the silane-free glass. Inclusion of each glass in an experimental composite resin system showed that the formulations which contained G338 absorbed more water than the formulations which contained Raysorb T-4000, regardless of whether or not the glass was silanted. Biaxial flexure strength was superior for experimental composites containing Raysorb T-4000, with highest results being obtained with the silanated glass. Overall these results demonstrate that silanation of the filler is essential for optimal physical properties but that, for the ionomer glass, it inhibits the acid-base reaction. The presence of ionomer glass led to an increase in water uptake compared with the unreactive glass, regardless of the presence of silane.

Composite Resins↗
PubMed2002

Influence of the method of funding on the age of failed restorations in general dental practice in the UK.

OBJECTIVE: This study examined the effect of the method of funding treatment on the age of restorations at the time of replacement. METHOD: A group of general dental practitioners were recruited to take part in the study. Each participant was asked to record the reason for placement and replacement of restorations. The age and class of the restoration being replaced was also recorded, together with details of the material being used and the material being replaced. Details of the method of payment of the failed restoration were recorded. RESULTS: Details of the reason for placement/replacement were received for 3,196 restorations from 32 GDPs. Of the restorations placed, 54% were amalgam, 32% composite, 8% compomer and 7% glass ionomer. The age of restorations at the time of replacement was significantly associated with the method of payment for the restoration, with restorations placed in the Armed Forces having been in service significantly longer at the time of their replacement than restorations placed under NHS regulations. CONCLUSION: Statistical analysis indicated that restorations placed within the NHS regulations were replaced at a significantly lower age than restorations placed under the other funding arrangements investigated.

Age Factors↗
PubMed1997

The future of dental amalgam: a review of the literature. Part 7: Possible alternative materials to amalgam for the restoration of posterior teeth.

This is the last in a series of articles on the future of dental amalgam. It considers possible alternative materials to amalgam for the restoration of posterior teeth. The materials discussed are gold inlays, gold foil, gallium alloys, and tooth coloured non-metal alternatives including glass-ionomer cements, composite resins, glass-ionomer-resin hybrids, compomers and ceramics. The clinical indications for these restorations are first described along with their potential clinical problems and their mean survival rates in comparison with dental amalgam. Secondly, the safety of composite resins is considered and potential toxic and hypersensitive effects of these materials are discussed. Finally, it is concluded that the present evidence does not appear to demonstrate that dental amalgam is hazardous to the health of the general population. It does, however, recommend that in continuing to use amalgam dentists must use strict mercury hygiene procedures to avoid risk to their staff and contamination of the environment. It seems that mercury contamination of the environment is likely to be the main reason for any future government action against the continued clinical use of dental amalgam.

Air Pollutants, Occupational↗
PubMed2005

Contemporary dental practice in the UK: indirect restorations and fixed prosthodontics.

OBJECTIVES: To investigate, by questionnaire, the use and selection of materials and techniques for indirect restorations and fixed prosthodontics by dental practitioners in the North West of England and Scotland. METHODS: A questionnaire was sent to 1,000 general dental practitioners selected at random from dentists in Scotland and the North West of England. Non-responders were sent another questionnaire after a period of 4 weeks had elapsed. RESULTS: A total of 701 usable questionnaires were returned, giving a response rate of 70%. When selecting a material for the core build-up of vital teeth, practitioners used the following materials (%): amalgam (60), dual and light-cured resin composite (54), glass-ionomer cements (47), compomer (29) and resin-modified glass-ionomer cements (24). Where the use of a post was indicated indirect posts of both precious (67) and non-precious (37) alloys were preferred to prefabricated posts by the majority of practitioners for the restoration of root filled teeth. Direct titanium (14) and stainless steel (14) posts were not used extensively. Impression materials used by the practitioners were as follows: addition-cured silicone (70), condensation-cured silicone (20), polyether (9) and polysulphide (2). Traditional glass-ionomer cements (59) were used for the luting of single and multiple porcelain fused to metal units, with zinc phosphate and polycarboxylate cements (33) being the preferred alternatives. CONCLUSIONS: The majority of the practitioners surveyed in this study used: amalgam for core build-ups; indirect posts; addition-cured silicone for impressions; and glass-ionomer cements for luting procedures.

Crowns↗
PubMed2006

What is the most effective adhesive for attaching orthodontic bands?

DATA SOURCES: The Cochrane Oral Health Group's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), Medline and Embase were used and a search of the internet also undertaken. There was no restriction with regard to publication status or language of publication. STUDY SELECTION: Randomised controlled trials (RCT) and controlled clinical trials (CCT), including split-mouth studies, of adhesives used to attach orthodontic bands to molar teeth were selected. DATA EXTRACTION AND SYNTHESIS: All review authors were involved in study selection, validity assessment and data extraction without blinding to the authors, adhesives used or results obtained. All disagreements were resolved by discussion. RESULTS: Five RCT and three CCT were identified as meeting the review's inclusion criteria. All the included trials were of split-mouth design. Four trials compared chemically cured zinc phosphate and chemically cured glass ionomer; three trials compared chemically cured glass ionomer cement with light-cured compomer; one trial compared chemically cured glass ionomer with a chemically cured glass phosphonate. Data analysis was often inappropriate within the studies that did meet the inclusion criteria. CONCLUSIONS: There is insufficient evidence to determine the most effective adhesive for attaching orthodontic bands to molar teeth in patients with full-arch fixed orthodontic appliances.

Comment↗
PubMed2003

Fluoride release and uptake by four new fluoride releasing restorative materials.

The present study compared the initial fluoride release and release following refluoridation of a conventional glass-ionomer Ketac-Molar (ESPE), a resin-modified glass-ionomer, Vitremer (3M), and two compomers F-2000 (3M) and Hytac (ESPE). Fifteen test specimens were prepared for each brand and immersed in deionized water. The fluoride released was measured every 2 days for 22 days. Refluoridation of the test specimens was done with solutions of 0.02, 0.04 and 0.2% NaF for 5 min on days 22, 30, 38 and 46. The fluoride released from recharged specimens was measured every 2 days until day 54. The fluoride release was highest during the first days after preparation, after which it decreased sharply and then more slowly. The four materials became 'recharged' with fluoride following repeated fluoride exposure in solution, the 0.2% solution being the most effective. From a clinical point of view, the results from this study imply that all the restorative materials tested may act as intra-oral devices for the controlled slow release of fluoride at sites at risk of recurrent caries. Fluoride release and uptake by four new fluoride releasing restorative materials.

Cariostatic Agents↗
PubMed1995

Damage to dental composite restorations following exposure to CO2 laser radiation.

Damage to tooth structure is a major hazard in the use of infrared lasers for oral surgical procedures. While the effects of laser exposure on dental enamel and dentine are well characterized, there are no data on the effects of laser exposure on dental composite materials, which are widely used in tooth-colored restorations. This study examined surface changes in several dental composites exposed to CO2 laser radiation for 200 msec. Surface changes, such as ablation, combustion, and melting, occurred even at relatively low power densities (340 W/cm2), with greater effects occurring in composites than in "compomers" (glass iomomer-composite mixtures). These findings indicate that nonmetallic dental restorations are prone to damage from inadvertent laser exposure. Clinicians must be aware of this hazard and employ measures to protect both natural tooth structure and restorations when performing intraoral laser surgery.

Carbon Dioxide↗
PubMed2006

Acceptance and efficiency of Er:YAG laser for cavity preparation in children.

OBJECTIVE: To evaluate the clinical efficiency and patient acceptance during cavity preparation in children, a direct comparison was made between Er:YAG laser preparation and conventional mechanical preparation of caries using a split-mouth design. BACKGROUND DATA: The Er:YAG laser system was developed for cutting dental hard tissue and has been approved as a useful alternative method for cavity preparation. METHODS: Children with previously unrestored and matched carious cavities in non-pulpally involved anterior teeth were selected, and the sequential order of treatment was randomized. In total, 40 children from 4 to 12 years old took part in the study. Two teeth each in the 40 patients were prepared without anesthesia and restored with a light-cured compomer following application of a bonding agent. The time spent on cavity preparation and the behavior of the patients during cavity preparation were recorded; finally, a modified face scale was used for pain assessment. In addition, the children were asked to indicate whether they found the laser or the mechanical approach more uncomfortable, and their preferred treatment when undergoing future caries therapy. RESULTS: The analysis of pain indicated that 82.5% of children felt no pain at all with the laser preparation, and they also showed much more body and head movement with the conventional mechanical preparation. Although the Er:YAG laser took about 2.35 times longer to prepare the same type of cavity, 92% of the children said that they would prefer laser preparation for further caries therapy. CONCLUSION: Cavity preparation with the Er:YAG laser would seem to be an option for fearful children, since it produces less pain and has acceptable efficiency compared to the conventional mechanical preparation.

Child↗
PubMed2004

A standard for radiopacity of root-end (retrograde) filling materials is urgently needed.

AIM: To assess the radiopacity of materials used, or recommended for use, as apical root-end (retrograde) fillings. METHODOLOGY: The radiopacity of 14 materials falling into the category of root-end filling materials was measured in equivalent millimetres of aluminium (mm Al) using a new computerized method. These included temporary or intermediate sealing materials; composite, compomer and GIC filling materials; EBA-derived cements; amalgam, etc. Gutta-percha cone material was added as a control. Samples of 1 mm thickness were radiographed on periapical film alongside an aluminium step wedge calibrated in millimetres, and the opacity of the materials, in greyscale or pseudo-colour, was compared with the equivalent step. RESULTS: The radiopacity ranged from 1.75 mm Al to >10 mm Al. The lower range appears insufficient for routine clinical detection when it is compared with the minimal requirement for intracanal fillings. CONCLUSIONS: Because of the proliferation of root-end filling materials with a broad range of radiopacity, an international standard stipulating the required minimal radiopacity, as well as other properties, is needed urgently. It should be based on in vitro results and on large-scale clinical radiographic surveys.

Contrast Media↗
PubMed2004

Undergraduate experience of clinical procedures in paediatric dentistry in a UK dental school during 1997-2001.

Abstract The aim of this study was to determine the clinical experience of undergraduate students in paediatric dentistry. This was a prospective study in a clinic teaching paediatric dentistry to undergraduates within a UK dental school. Students who graduated between 1997 and 2001 at King's Dental Institute, London, were required to complete a quantitative record of their clinical activity. The mean undergraduate intake for the 5-year period was 58. Thirty-six (36) sessions each of 2-2 1/2 h duration were available in the course for the clinical treatment of children (one half day per week), a total of 81 h. The undergraduates assessed and planned treatment for 13.4 patients, 3.6 emergency patients and administered 10.4 local analgesics. The mean number of inhalation sedation administrations increased (1.5-3.3) per student during the 5-year period. The mean number of procedures performed by undergraduates for primary teeth was 8.1 restorations in glass ionomer or compomer and 1.9 in amalgam, 1.6 pulpotomies and 0.2 preformed crowns. The mean number of procedures for permanent teeth was 24.5 fissure sealants, 2.6 preventive resin restorations, 1.5 amalgams, 1.7 composites, 1.4 incisal edge restorations and 0.8 root canal treatments. For permanent teeth, the trend was towards an increase in the number of preventive resin restorations (1.9-2.8) and composite restorations (1.4-1.9) but a decrease in the number of amalgam restorations (2.1-0.9) during the 5-year period. Individual students' clinical experience was very variable. Procedures that were performed more than 10 times were experienced by every student. A procedure performed on average two to four times within a year group would be experienced by only 80-90% of the group and less frequently performed procedures would only have been experienced by a minority of graduates. A large number of patients failed to attend or cancelled appointments representing a loss of 21 h of clinical treatment time per student, about 25% of the total time available for the treatment of children in the clinical course.

Child↗
PubMed1996

Restorative therapy for erosive lesions.

More needs to be learned about the etiology of erosion lesions before they can be accurately diagnosed, confidently treated and, more importantly, prevented. The treatment is dependent on the location and the degree of erosion. The decision to treat an erosion lesion should be based on careful consideration of the etiology and progression of the condition. Reasons for restoring noncarious enamel/dentin lesions are discussed and various therapeutic measures are provided. Preventive and restorative therapeutic measures for noncarious abrasive/ erosive lesions are proposed such as: a change of dietary or behavior patterns; application of desensitization products; intensive fluoride therapy with or without iontophoresis; brushing with desensitizing dentifrices; adhesive penetration with dentin bonding agents; glass ionomers and compomers; resin composites; composite or porcelain veneers; crown and bridge work; occlusal adjustments and nightguard fabrication if the abfraction factor coincides. The clinical durability of restorative therapy and important clinical factors related to the restoration of multifactorial defects are discussed.

Composite Resins↗
PubMed1999

Clinical evaluation of glutaraldehyde with calcium hydroxide and glutaraldehyde with zinc oxide eugenol in pulpotomy of primary molars.

The objectives of this study were to clinically evaluate the effectiveness of 2% buffered glutaraldehyde in pulpotomies of human primary molars and to compare the success rate of glutaraldehyde with calcium hydroxide and glutaraldehyde with zinc oxide eugenol as dressing material on the radicular pulp. Pulpotomies were completed on 61 primary molars in 19 children. The teeth were divided into two groups by random allocation. One group had a dressing of zinc oxide-eugenol base (IRM) incorporated with one drop of 2% buffered glutaraldehyde while the other group had a dressing of calcium hydroxide base incorporated with one drop of 2% buffered glutaraldehyde after the initial placement of 2% buffered glutaraldehyde on cotton pellet for 3 min. All teeth had light-curing compomer (Dyract) placed over the dressing material followed by a stainless steel crown restoration within 1 or 2 weeks after the pulpotomy. Blind clinical and radiographic evaluations of 57 teeth available after 12 months showed a success rate of 92.9% and 73.6% respectively. The clinical and radiographic success rates for glutaraldehyde/zinc oxide eugenol pulpotomies were 96.5% and 75.8% respectively while those for glutaraldehyde-calcium hydroxide were 89.2% and 71.4%. There was no statistically significant difference between the two groups either clinically or radiographically. The overall clinical success rate suggested that 2% buffered glutaraldehyde was an effective agent in the pulpotomy of human primary molars.

Calcium Hydroxide↗