bluuebunny/crossref_metadata_2025 huggingface dataset:
Uptake and reversibility of uptake of nickel by human macrophages
Authors: Edwards  , Wataha  , Hanks
Published: March 2003

The use of nickel‐containing alloys in dentistry has been questioned because of the biological liabilities of nickel and the release of nickel ions from dental appliances into the oral cavity. The uptake of nickel by cells in the oral tissues is a critical factor in assessing the biological liabilities of nickel. Nickel uptake by macrophages may be particularly important because of the central role of macrophages in the inflammatory process and the known role of the macrophage in orchestrating the response to biomaterials. The aims of the current study were to assess the reversibility of the uptake of nickel from human macrophages and determine the portion of the nickel which reaches the nuclei as a function of time. Cellular nickel content was measured by means of atomic absorption spectrometry. Nuclear nickel content was assessed after fractionating cells. The results showed that nickel was rapidly taken up by macrophages and that the nickel accumulated in the nucleus in as little as 8 h. After 48 h, over 60% of the cellular nickel was in the nucleus. Once taken up, the nickel was lost at a lower rate. The rate of loss decreased as the initial exposure time to the nickel increased. Thus, the results indicated that macrophages may accumulate nickel if the time between exposures is insufficient to reverse the uptake. Further studies are necessary to correlate the retention of nickel with impaired function of macrophages and to further define the biological risks of using nickel in dental alloys.
Satisfaction with chewing ability in a diverse sample of dentate adults
Authors: Gilbert  , Foerster  , Duncan
Published: March 2003

The Florida Dental Care Study (FDCS) is a longitudinal study of changes in oral health, which included at baseline 873 subjects who had at least one tooth, were 45 years or older, and who participated for an interview and clinical examination. Two objectives of the FDCS were to: (i) describe satisfaction with chewing ability in a diverse sample of dentate adults; and (ii) quantify the associations between satisfaction with chewing ability and other measures of oral health. Approximately 16% of subjects reported that they were dissatisfied or very dissatisfied with their chewing ability. Bivariate and multivariate results provided consistent evidence of the construct validity of a proposed multi‐dimensional model of satisfaction with chewing ability. Multiple regression analysis suggested that dissatisfaction with chewing ability was independently associated with 12 specific clinical and self‐reported measures of oral disease/tissue damage, pain, functional limitation, and disadvantage. The self‐reported measures of oral health and the proposed model of satisfaction with chewing ability improve our understanding of this important oral health outcome in diverse population groups.
Properties of four composite veneering materials polymerized with different laboratory photo‐curing units
Authors: Tanoue  , Matsumura  , Atsuta
Published: March 2003

SUMMARY This study examined properties of four composite veneering materials polymerized with two different photo‐curing units for the purpose of evaluating curing performance of the combination of composite material and curing unit. Two microfilled (Dentacolor® and Thermoresin LC II®) and two hybrid (Cesead II® and Solidex®) composite materials designed for prosthetic veneer were selected. The respective light sources of the units were a xenon (Dentacolor XS®) and a metal halide (Hyper L II®) lamp. The composite materials were exposed with the photo‐curing unit for 60 s on each side (i.e. from top and bottom). Knoop hardness, compressive strength, flexural strength, flexural modulus, water absorption and water solubility were determined according to standardized testing methods. The specimens exposed with the metal halide unit generally exhibited greater Knoop hardness number, and compressive strength and lower solubility than those exposed with the xenon unit. A microfilled material (Thermoresin LC II) cured with the metal halide unit exhibited significantly improved results for all tests as compared with the same material cured with the xenon unit.
Difference in the mechanism of balancing‐side disclusion between 1st and 2nd molars
Authors: Ogawa  , Koyano  , Tsukiyama  , Tsukiyama  , Sumiyoshi  , Suetsugu
Published: March 2003

This study investigates the cusp angle and movement variables related to balancing‐side disclusion and compares the characteristics between the 1st and 2nd molar regions. Fifty‐six normal young adults were divided into two groups according to balancing‐side contact: a disclusion group consisting of 40 subjects (80 excursions), and a non‐disclusion group consisting of 16 subjects (20 excursions). Lateral excursions were measured in six‐degrees of freedom, and the inclinations of the frontal paths were calculated on the working‐side canine, balancing‐side 1st and 2nd molars and balancing‐side condylar point. The cusp angle was measured using a three‐dimensional digitizer. While there were no differences between disclusion and non‐disclusion groups in the inclination of the balancing‐side condylar path, significant differences were found in the cusp angle and the inclination of the working‐side canine path. In the non‐disclusion group, the cusp angle of the 2nd molar was markedly greater than that of the 1st molar. It was concluded that the inclination of the anterior guidance and the cusp angle of related teeth have a great effect on the occurrence of balancing‐side disclusion and that the mechanism of high frequent balancing‐side contacts at the 2nd molar was characterized by its greater cusp angle compared to the 1st molar.
Effect of moisture protective coatings on the strength of a modern metal‐reinforced glass–ionomer cement
Authors: Williams J. A. , Billington R. W. , Pearson G. J.
Published: March 2003

SUMMARY The strength of a modern, low metal : glass ratio, metal‐reinforced glass–ionomer cement was measured evaluating a number of protective barriers: one light‐cured resin, two solvent‐based dental varnishes and petroleum jelly. The cement was exposed to water at 10 and 60 min from start of mix. The results obtained with these protecting agents were compared with those obtained where no protection was applied. A comparison of uniaxial flexural strength and biaxial flexural strength showed the latter to be more discriminating. Proprietary dental varnishes were superior to petroleum jelly, producing similar strengths of 50 MPa. Petroleum jelly was, however, preferable to no protection. Moisture protection during the first 30min was found to be beneficial, thereafter no further strength increase was found. A second material, a cermet which has a high metal : glass ratio, was found to be more moisture resistant but weaker in strength than the modern material, with a biaxial strength of 39 MPa.
Leached components from dental composites in oral simulating fluids and the resultant composite strengths
Authors: Lee  , Huang  , Lin  , Shih
Published: March 2003

The aim of this study was to analyse the leached moieties of dental composites after storage in ethanol and organic acids of plaque and further evaluate the resultant effect on the diametral tensile strength (DTS) of the composites. Three commercial composites were used: Bis‐GMA‐based Z100, Bis‐GMA/UDMA‐based Heliomolar, and Bis‐MPEPP‐based Marathon One. The solutions used were: 99·9% acetic acid, 99% propionic acid and 75% ethanol. Specimens (4 mm diam. × 2 mm thick) were stored at 37°C in 3 mL of solution for up to 30 days. Gas chromatography/mass spectrometry was used to characterize the leached moieties and DTS of the specimens after immersion was evaluated. Data were analysed using ANOVA and Tukey LSD test. The eluted substances were not all the same in different solutions and composites but mostly increased with immersion time, and included diluents (TEGDMA and decamethacrylate) and some additives, such as an ultra‐violet stabilizer (TINUVINP), plasticizers (dicyclohexyl phthalate and bis(2‐ethylhexyl) phthalate), initiator (triphenyl stibine), coupling agent (γ‐methacryloxypropyl trimethoxysilane), and phenyl benzoate. The chief polymerizing monomers were not found. More kinds of components were found in the acetic acid and ethanol groups studied. The fewest kinds and quantities of leached moieties were found for Bis‐GMA specimens and then Bis‐GMA/UDMA ones, most of which are diluent agents. Bis‐MPEPP specimens leached the most substances, which were composed mostly of a short phenyl group chain structure. The BisGMA composite showed the highest DTS (54·8 ± 5·7 MPa), which was not greatly affected by the length of storage. Bis‐GMA/UDMA (36·2 ± 6·8 MPa) and Bis‐MPEPP (26·1 ± 4·5 MPa) composites were significantly reduced (P < 0·05) after 30 days storage in the ethanol (35–50%), in the propionic acid (25–30%), and in the acetic acid (40–60%). Irreversible processes such as the leaching of components occur in fluids simulating an oral environment, which may contribute to irreversible material degradation, especially for non‐Bis‐GMA‐based composites.
Resonant characteristics of the human head in relation to temporomandibular joint sounds
Authors: Prinz J. F.
Published: March 2003

Frequency analysis of the sounds produced by the temporomandibular joint (TMJ) has been claimed to be of diagnostic value. In this study the resonant behaviour of the human skull has been characterized. Assuming that impact is one major mechanism generating the sound, it is shown that the frequencies seen in TMJ sounds relate to the resonant modes of the skull. Where the rise time of the impact is sufficiently short, higher resonant modes are excited.
EMG activity of the orbicularis oris and mentalis muscles in children with malocclusion, incompetent lips and atypical swallowing – Part I
Authors: Tosello D. O. , Vitti M. , Berzin F.
Published: March 2003

The function and the level of activity of the orbicularis oris (upper and lower), and of the mentalis muscles were verified electromyographically in resting position and in several movements and carried out in 18 children aged 8–12 years, divided into three groups: one with normal occlusion, and two with Class II division 1, with atypical swallowing and/or incompetent lips, who had received no orthodontic treatment. It was observed that, in a resting position with the lips separated, there was no activity in any of the muscles. When there was a contact of the lips, action potentials were recorded in the muscles studied, in those individuals with incompetent lips. In the movements of sucking either through a straw or a pacifier and the thumb, there were no differences among the groups. The incompetent lips group presented very marked muscle activity of the lower orbicularis oris and mentalis in the movement of sucking a lollipop. In deglutition of saliva, the orbicularis oris presented slight activity, and the mentalis, moderate. In deglutition of water, the mentalis presented very marked activity, whereas, the upper and lower orbicularis oris presented moderate and marked activities, respectively.
Comparative wear ranking of dental restoratives with the BIOMAT wear simulator
Authors: Yap A. U. J. , Ong L. F. K. L. , Teoh S. H. , Hastings G. W.
Published: March 2003

Fundamental in vitro wear tests are important for the study of wear mechanisms, provision of data during material development and screening of materials prior to clinical trials. The aim of this project was to compare the wear of six dental restoratives using the BIOMAT wear simulator which was developed to simulate jaw movements and stresses generated in the occlusal contact areas during the chewing process. The correlation of wear to hardness of the restoratives was also assessed. Wear ranking from the least to the most volumetric wear was as follows: high copper unicompositional alloy, Tytin® (T) < high copper admixed alloy, Valiant PhD® (V) < microfilled composite resin, Silux Plus® (S) < gallium alloy, Galloy® (G) < heavily filled composite resin, Z100® (Z) < hybrid composite resin, P50® (P). The high copper amalgam alloys had significantly greater wear resistance when compared with all the composite resins. The gallium alloy, microfilled and heavily filled composite resins also exhibited significantly less wear than the hybrid resin. Wear ranking with the BIOMAT simulator was similar to that obtained in vivo. Ranking from the hardest to softest material: high copper unicompositional alloy, T < gallium alloy, G < high copper admixed alloy, V < hybrid composite resin, P < heavily filled composite resin, Z < microfilled composite resin, S. The amalgam alloys were significantly harder than the heavily filled and microfilled composite resins. There was no apparent correlation between wear performance and material hardness.
Long‐term survival characteristics of 832 resin‐retained bridges and splints provided in a post‐graduate teaching hospital between 1978 and 1993
Authors: Djemal S. , Setchell D. , King P. , Wickens J.
Published: March 2003

The clinical performance of 832 resin‐retained bridges and splints provided in the adult fixed prosthodontic clinic of a post‐graduate teaching hospital was reviewed. Recall data was available for 58·4% of cases and the median survival was 7 years and 10 months. Analysis of clinical variables influencing survival revealed that the design and retainer coverage were significant factors. The experience of the operator carrying out treatment also had a pronounced effect which was not readily explained in terms of the distribution of other significant factors. Resin‐retained restorations made with minimal tooth preparation are shown to be capable of extended clinical service and their failure rarely resulted in adverse consequences for the patient. Patient satisfaction with their treatment was reportedly high.
Curing depth of prosthetic composite materials polymerized with their proprietary photo‐curing units
Authors: Tanoue N. , Matsumura H. , Atsuta M.
Published: March 2003

This study examined curing depth of eight prosthetic composite materials polymerized by means of six photo‐curing units for the purpose of evaluating the curing performance of material‐curing unit combinations. Each composite material was exposed with a photo‐curing unit recommended by the manufacturer. The light sources of the units were halogen/fluorescent, xenon, metal halide, fluorescent, and halogen lamps, and exposure periods were 20, 30, 60, and 90 s. Curing depth of the materials was determined according to the method described by the International Organization for Standardization (ISO 4049). The results were analysed by factorial analysis of variance (
anova) and multiple comparison intervals. Two‐factor
anova revealed that the depth of cure was influenced both by the material‐unit combination and by the exposure period (P=0·0001). Among the eight combinations, a hybrid composite material (Prywood color®) polymerized with a metal halide curing unit (Hyper LII®) exhibited the greatest depth of cure after 90‐s exposure. For all combinations, longer exposure increased the depth of cure.
Evaluation of biting performance with standardized test‐foods
Authors: Shiau Y. Y. , Peng C. C. , Hsu C. W.
Published: March 2003

Human masseter muscle is the main power source used for crushing or grinding the foods. Its size is regarded as an determining factor of chewing force and function. A system of measuring the masseter muscle volume from MR images was developed in this study. For a better understanding of the masseter muscle function, a standardized test‐food developed in our laboratory was used. Twelve male subjects having complete dentition and healthy masticatory function were used to chew the test‐foods. The EMG muscle activity of the masseter muscle during breaking and chewing the test‐foods was observed. It was found that the muscle volume was positively related to the body size. The increase of the muscle activity during breaking and chewing was almost parallel to the increase of the test‐food hardness, and the increase was mostly in the duration of muscle contraction. It was concluded that the measurement of masseter muscle volume is possible, and our test‐foods can be used for chewing function examination with high reliability. Within a certain level of hardness, harder food requires longer muscle contraction time instead of stronger muscle force to break and chew the food.
Wear of composite resin veneering materials in a dual‐axis chewing simulator
Authors: Kern M. , Strub J. R. , Lü X.‐Y.
Published: March 2003

The attritional wear of human enamel and four different composite resins for the veneering of crowns was evaluated in a dual‐axis chewing simulator over up to 1 200 000 loading cycles. Enamel showed less wear than the composite resins. However, an ultrafine compact‐filled composite resin (Targis®) showed a wear not statistically significantly different from that of enamel. The other composite resins showed a statistically significantly higher wear than enamel regardless whether microfine, ultrafine midway‐filled or ultrafine compact‐filled.
Electrognathographic and electromyographic observations on jaw depression during neck extension
Authors: Mckay D. C. , Christensen L. V.
Published: March 2003

Albeit never substantiated through experimental and clinical evidence, the theoretical linchpin of the mechanics of a so‐called whiplash injury of the temporomandibular joint (TMJ) is the postulate that a pre‐existing depressor force (continual anchoring force), generated by the anterior suprahyoid (SH) muscles, will always act on the mandible and cause traumatic mouth opening (anterior acceleration of the TMJ condyles) when the neck is extended (posterior acceleration of the head). To test aspects of this postulate, six subjects assumed the positions of neutral (0°), medium (32°) and maximum (58°) neck extension while the mandible was in its postural positions of rest and light centric occlusion. By means of surface electromyography, it was shown that the relative contractile activities of the anterior SH muscles never exceeded 7·3% of the contractile activity required to anchor the mandible in a position of maximum depression. By means of electrognathography, it was shown that the maxillary and mandibular incisors were never separated by more than 2·6 mm during neutral, medium, and maximum extension of the neck. In other words, during neck extensions there was no evidence of a continual or induced voluntary or involuntary depressor force that would and could anchor the mandible in a position of traumatic mouth opening. Accordingly, and in agreement with other biophysical and biomedical evidence, it was concluded that there is no foundation for the pseudoscientific speculations and unsubstantiated opinions offered in support of a concept and diagnosis of a so‐called TMJ whiplash injury. Additionally, this study found co‐activation of cervical flexor muscles and mandibular elevator as well as depressor muscles.
Effects of the solvents on bond strength of resin bonded porcelain
Authors: Barghi N. , Chung K. , Farshchian F. , Berry T.
Published: March 2003

Clinical trials of porcelain veneers for chairside colour modifications may require the use of a trial resin with various colours of tints. The bond strength effects of four different solvents used for removal of trial resin from etched porcelain specimens were investigated. Fifty‐six porcelain specimens were fabricated, flattened by a metallurgically standard method, etched with hydrofluoric acid and silane treated. The specimens were divided into four groups at random. The trial resin material was cleaned with different solvents prior to bonding of a dual cure resin composite button. After bonding the specimens were stored in water at 37 °C for 7 days. Shear bond strength results were as follows: acetone (control) group, 12·9±2·9 MPa; ethanol group, 15·1±4·6 MPa; methanol group, 11·5±2·9 MPa; methylene chloride group, 11·3±2·4 MPa. No significant differences were measured ( anova, P>0·05). The results indicated that the resin–porcelain bond strengths were not affected by the type of solvent used to remove trial resin. This procedure is recommended for clinical cases when resin composite is used for the try‐in of etched porcelain bonded restorations.
Occlusal contact area, occlusal pressure, bite force, and masticatory efficiency in patients with anterior disc displacement of the temporomandibular joint
Authors: Sato S. , Ohta M. , Sawatari M. , Kawamura H. , Motegi K.
Published: March 2003

The occlusal contact area, occlusal pressure, bite force, and masticatory efficiency were measured in 48 patients with anterior disc displacement (ADD) of the temporomandibular joint (TMJ). The results were compared with those of 30 normal controls without TMJ dysfunction. The values of occlusal contact area, bite force, and masticatory efficiency measured in patients with ADD were significantly smaller than those measured in the controls, although there was no difference in occlusal pressure between the two groups. The results of the measurements of 22 patients with ADD with reduction were also compared with those of 26 patients with ADD without reduction. There was no difference in any measurement between these patients subgroups. The analysis of occlusal contact area, bite force, and masticatory efficiency appeared to be useful methods in documenting the fact that masticatory function was impaired in patients with ADD of the TMJ.
Normal side‐to‐side variation of the exteroceptive suppression of masseter muscle in young dentate adults
Authors: Karkazis H. C. , Kossioni A. E.
Published: March 2003

Previous studies have shown that various stimuli applied in the orofacial region, evoke bilateral inhibitory responses in the jaw elevator muscles. The exteroceptive supression (ES) of the masseter muscle after electrical stimulation of the mental nerve, often appears as a double phase of inhibition interrupting the voluntary sustained contraction of the muscle. The aim of the present study was to investigate the normal bilateral variation of the masseteric ES in a control group of 20 healthy dentate adults, and to determine the range of its boundaries. The reflex was elicited by electrical stimulation of the mental nerves, during maximum intercuspal clenching. Generally, the overall mean values for the latencies and durations were in line with those reported in previous investigations, while no significant differences were found between the left and the right masseter muscles, regardless of the side of stimulation. However, in the intra‐individual analysis, significant bilateral variation was occasionally recorded, particularly in the latency and duration of the late exteroceptive suppression. It was concluded that the exteroceptive suppression of the masseter muscle is a repeatable and clear bilateral reflex response, although an increased number of observations is recommended in normal subjects, before its use could be extended for diagnostic purposes.
Buffering capacities of soft drinks: the potential influence on dental erosion
Authors: Edwards M. , Creanor S. L. , Foye R. H. , Gilmour W. H.
Published: March 2003

The pH of fruit juices and carbonated drinks are known to be low and have, therefore, been implicated in the increasing incidence of erosion. The ability of a drink to resist pH changes brought about by salivary buffering may play an important part in the erosion process. The aims of this study were to measure the initial pH of several widely available soft drinks and determine their buffering capacities. As part of a larger study, the following groups of drinks were tested: pure fruit juices, non‐fruit‐based carbonated drinks, fruit‐based carbonated drinks, flavoured spring waters, and plain carbonated mineral waters as positive controls with still water as the negative control. The measurement of pH was carried out using a pH electrode connected to an Orion EA940 Ionanalyser. One hundred millilitres of each drink was then titrated with 1 m sodium hydroxide, added in 0·5 mL increments, until the pH reached 10. Each titration was repeated three times. The average initial pH was lowest for the non‐fruit‐based drinks (2·81±0·274) and highest for plain mineral water (7·4±0·1002). The buffering capacities can be ordered as follows: fruit juices>fruit‐based carbonated drinks and flavoured mineral waters>non‐fruit‐based carbonated drinks>sparkling mineral waters>still mineral water. It is concluded that fruit juices and fruit‐based carbonated beverages, with their increased buffering capacities, may induce a prolonged drop in oral pH.
The post‐orthodontic prevalence of temporomandibular disorder and functional occlusion contacts in surgical and non‐surgical cases
Authors: Milosevic A. , Samuels R. H. A.
Published: March 2003

This study aimed to assess mandibular mobility and the prevalence of functional occlusal contacts in subjects treated to a Class 1 incisor relationship by fixed orthodontic appliance therapy. Two hundred and thirty subjects participated (mean age=18 years) of whom 42 underwent orthognathic surgery. All subjects were in retention with a mean time of 7 months between debond and examination. Maximal mandibular opening, lateral and protrusive excursions were all significantly reduced in the surgical cases compared to the non‐surgical group. Centric and eccentric non‐ideal occlusal contacts were not different between surgical and non‐surgical groups. Non‐working side contacts occurred in 30% of subjects, posterior contacts on protrusion in 20% and RCP‐ICP prematurities in 18% of subjects. Non‐working side contacts were significantly more frequent in post‐graduate cases compared to staff cases (P<0·05). An overbite less than the mean of 2·4 mm resulted in a reduced likelihood of canine guidance on the working side (P<0·001) and an increased frequency of non‐working side contacts and posterior contacts on protrusion (P<0·001).
Intercondylar width as a guide to setting up complete denture teeth
Authors: Keshvad A. , Winstanley R. B. , Hooshmand T.
Published: March 2003

A clinical study was designed to investigate the relationship between intercondylar width (ICW) and inter‐dental widths of the upper and lower canines and first molars to aid in denture teeth positioning. The study was divided into two parts so that the results of the first part could be verified in the second part. In the first part, 27 adult subjects were selected according to the exclusion criteria of the study. A kinematic hinge axis locator was used to locate the true point of condylar rotation. The distance between these points was considered to be the ICW. A strong correlation was found between ICW and inter‐dental measurements, with ICW and upper first molars being the strongest (r=0·612, P=0·004). A set of indices developed from the results was recommended for the positioning of complete denture teeth. In the second part of the study, inter‐dental measurements were estimated using the indices obtained in the first part. The estimated inter‐dental widths showed no significant differences compared with the real widths (P=0·109, P=0·849, P=0·353, P=0·41). Based on the results of this study, ICW measurements can be used for setting up canines and first molars in complete dentures.
Influence of formaline cresol on bond strength of adhesive luting agents to dentin
Authors: Soeno K. , Taira Y. , Atsuta M.
Published: March 2003

The present study investigates the influence of the pulpotomy agent formaline cresol (FC) on bond strength between dentin and five adhesive systems (Super‐Bond C&B, Bistite II, Imperva Dual Set, Panavia 21, and Panavia 21 with AD Gel). After the dentin surfaces of 75 bovine teeth (including 25 control samples) were exposed by grinding, 25 of the samples were soaked in FC for 2 days, and 25 samples were soaked for 7 days. Samples were bonded to acrylic rods using five adhesive systems, and tensile bond strengths were determined after 1‐day immersion in water. Data were analysed by analysis of variance and Duncan's new multiple range test, and the fractured surfaces were observed through a scanning electron microscope. The bond strengths were found to be influenced by the type of system, soaking period, and their combination. The bond strength values of three adhesive systems (Super‐Bond C&B, Imperva Dual Set Bistite II, and Panavia 21 with AD Gel) decreased after soaking in FC. After 7 days of FC exposure, the highest bond strength (9·8±2·9 MPa) was obtained with the Super‐Bond C&B system.
In vitro dentin demineralization inhibition effects of an experimental fluoridated HEMA and water wetting agent
Authors: Segura A. , Donly K. J. , Quackenbush B.
Published: March 2003

The ability of fluoride‐releasing resins to inhibit dentin demineralization remains controversial. The purpose of this study was to evaluate the caries inhibition of resin composite restorations with an experimental fluoridated hydroxyethyl methyl methacrylate (HEMA) and water wetting agent. Standardized Class V preparations were placed in 40 molars, the gingival margin placed below the cementoenamel junction. Two dentin primers (sodium fluoride, HEMA and water; HEMA and water) were placed in equal numbers of 20 preparations, then One‐Step® Dental Adhesive (Bisco) was applied as recommended by the manufacturer, followed by the placement of a resin composite restoration. Amalgam restorations with no primer/adhesive were placed in 10 preparations and 10 preparations were restored by placing One‐Step® Dental Adhesive, then resin composite. All teeth were subjected to an artificial caries challenge (pH 4·4) for 5 days. Results demonstrated the mean areas (μm2±s.d.) of demineralization 100 μm from the restoration/dentin margin to be: amalgam 5570±873; One‐Step® 7038±2099; HEMA and water 6126±634; fluoridated HEMA and water 3411±593.
anova and Duncan's test (P<0·05) demonstrated the fluoridated HEMA and water wetting agent to have significantly less adjacent dentin demineralization than the other three groups. Eighty percent of HEMA and water wetting agent, 80% of One‐Step® Dental Adhesive and 100% of amalgam restorations demonstrated wall lesions. One hundred percent of restorations with fluoridated HEMA and water wetting agent demonstrated inhibition zones in adjacent dentin.
A clinical diagnosis of diurnal (non‐sleep) bruxism in denture wearers
Authors: Piquero K. , Sakurai K.
Published: March 2003

The purpose of this study was to establish a clinical method for diagnosing diurnal bruxism in denture wearers by recording masseter and anterior temporal electromygraph (EMG) activity. Seven suspected bruxists and five normal patients who wore complete dentures and/or distal extension base removable partial dentures were selected for participation. EMG activity in both the masseter and the anterior temporal muscles was recorded bilaterally during silent reading (10 min), maximal voluntary clenching (MVC), tapping in centric occlusion, lateral movements, chewing and swallowing. No significant differences of EMG activity were found between the groups during tapping, lateral movement, chewing and swallowing (P>0·05). However, during 10 min of silent reading, a significant difference was found between the groups when comparing masseter muscle activity (P<0·05). A threshold of 10% of MVC of at least 3‐s duration was used to define an individual bruxism event. When the muscle activity recorded during silent reading was further analysed using these criteria, the control group displayed no bruxing activity while the suspected bruxist group displayed a mean frequency of six bruxism events (range 2–10). It was concluded that: (a) masseter muscle activity recorded during 10 min of silent reading showed significant difference between the groups; (b) the criteria selected in this study for the detection of sleep bruxism can also be used to assess diurnal bruxism; and (c) it is possible to diagnose diurnal bruxism in denture wearers by measuring the masseter EMG activity during 10 min of silent reading.
Analysis of stiffness and stress in I‐bar clasps
Authors: Sato Y. , Tsuga K. , Abe Y. , Asahara S. , Akagawa Y.
Published: March 2003

An I‐bar clasp is one of the most popular direct retainers for distal‐extension removable partial dentures. However, no adequate information is available on the shape associated with biomechanics. This study aimed (1) to establish a three‐dimensional (3D) finite‐element modelling method of I‐bar clasps, and (2) to clarify the effect of the shape on the stress and stiffness of I‐bar clasps. 3D computer models of I‐bar clasps were created with vertical and horizontal straight sections connected with a curved section with six parameters: thickness of the clasp tip (T), width of the clasp tip (W), radius of the curvature (R), horizontal distance between the base and the vertical axis (H), vertical dimension between the tip and the horizontal axis (V), taper (change of width per unit length along the axis)(Tp). Stress decreased as T, W, R and Tp increased, and as V decreased. Stiffness (which is proportional to retention) increased as T, W, R and Tp increased, and as H and V decreased. In both stress and stiffness, the effects of T and Tp were especially large. From the results, a systematic formula between the clasp shape and the stiffness was derived.
A long term study of fluoride release from metal‐containing conventional and resin‐modified glass–ionomer cements
Authors: Williams J. A. , Billington R. W. , Pearson G. J.
Published: March 2003

The objective of this study was to determine long term release of fluoride from a resin‐modified glass–ionomer cement (RMGIC) (Fuji II LC (FLC)) compared with that from two conventional acid–base setting cements (HiDense (HD) and KetacSilver (KS)) marketed for similar restorative purposes. Fluoride release from discs of cement immersed in water or artificial saliva was measured for 2·7 years using an ion selective electrode technique. The RMGIC was affected by water if immersed immediately after setting. This is similar to conventional acid–base cements and the experimental method was designed to allow for this. Over the 2·7‐year period, the RMGIC and HD released similar amounts of fluoride into both water and artificial saliva. In water, the RMGIC released the most fluoride, while in artificial saliva the highest release was from HD. KS released the least amount of fluoride in both immersing liquids. In artificial saliva, release was reduced to 17–25% of that found in water, with the RMGIC showing the greatest reduction. Both acid–base cured cements showed changes in colour over the 2·7‐year span, while the colour of the RMGIC was stable. It was concluded that the RMGIC released equivalent or greater amounts of fluoride than the two acid–base cure glass–ionomers over a period of 2·7 years.
Treatment need for fixed metal ceramic bridge prostheses in patients treated by dental students in 1984–1996
Authors: Näpänkangas R. , Salonen M. A. M. , Raustia A. M.
Published: March 2003

Even if implant therapy is very common nowadays, treatment with conventional fixed bridge prosthesis still has indications and cannot be forgotten. Because of improved dental health more teeth can be preserved and more fixed prostheses are prepared also for the elderly. The aim of this study was to discuss the future of treatment need in fixed metal ceramic bridge prostheses based on the analysis of distribution of pontics in dentition in four different age groups during the years 1984–1996. Data were collected from the patient files. The numbers of upper lateral incisors, upper first premolars and lower first molars were analysed in years 1984–1987, 1988–1992 and 1993–1996 between and within age groups of under 34, 35–49, 50–64 years and over 65 years. As a conclusion, in the future the treatment need for fixed bridge prostheses will be highest among patients over 50 years and their most replaced teeth are, besides lower first molars, the upper first premolars.
Environmental damage and occlusal contact area wear of composite restoratives
Authors: Yap A. U. J. , Chew C. L. , Ong L. F. K. L. , Teoh S. H.
Published: March 2003

The chemical environment is one aspect of the oral environment, which could have an appreciable influence on the in‐vivo degradation of composite resins. The resin matrix can be softened and fillers constituents can be leached out when composites are exposed to certain chemicals/food‐simulating liquids (FSLs). A reciprocal compression sliding wear device was used to study the effects of the chemical environment on occlusal contact area (OCA) wear of four composite restoratives (Silux Plus, Z100, Ariston pHc and Surefil). The effects of FSL on hardness was also investigated and correlated to wear. Thirty‐six hardness/wear specimens of each material were made and stored in artificial saliva at 37 °C for 24 h. The specimens were then divided into six groups of six specimens and stored in the following FSL for 1 week at 37 °C: distilled water (W), 0·02 N citric acid (C), 0·02 N lactic acid (L), heptane (H) and 75–25% ethanol–water solution (E). Conditioning in artificial saliva (S) was used as control. After conditioning, the specimens were wear tested at 20 MPa contact stress against SS304 counter‐bodies in the respective FSL/artificial saliva up to 20 000 cycles. Wear depth (lm, n=6) was measured using profilometry. Change in hardness (ΔKHN, Knoop hardness number) was determined by microhardness testing pre‐ and post‐conditioning. Results of statistical analyses (ANOVA/Scheffe’s at significance level 0·05) of wear data were as follows: Silux – S, W > L, H, E and C, L > H; Z100 – S, W > all other mediums and E > H; Ariston – all other mediums > H; Surefil – W, C > S, L, H, E (> indicates significantly more wear). With the exception of Surefil, the greatest wear was observed with conditioning and wear testing in water. This ranged from 93·18 ± 21·96 lm for Z100 to 31·43 ± 2·80 lm for Surefil. For all materials, conditioning in heptane resulted in the least wear. This ranged from 8·9 ± 2·2 μm for Ariston to 16·5 ± 5·9 lm for Silux. The effects of the different FSL on OCA wear were material dependent. No correlation was observed between ΔKHN and wear.
Marginal adaptation of partial crowns cast in pure titanium and in a gold alloy – an in vivo study
Authors: Stoll R. , Fischer C. , Springer M. , Stachniss V.
Published: March 2003

The aim of the present study was to assess in vivo the marginal integrity of partial crowns cast in pure titanium and in a gold alloy. For this purpose, two groups of 25 molars were prepared for partial crowns and then restored with partial crowns cast in Degulor M® gold alloy and in pure titanium. At a subsequent session, replicas were produced using a special impression‐taking technique. The scanning electron microscope (SEM) technique was used to perform quantitative margin analysis (Tiffmess 1·8 program). The gold alloy partial crowns displayed significantly (P < 0·05) more continuous margin (marginal quality A, <50 μm), and the titanium partial crowns significantly more marginal quality B (50–100 μm) and C (>100 μm). The results show that better marginal integrity can be achieved with gold alloy than with titanium partial crowns. However, in practical terms the difference in marginal quality is only slight, so that the use of pure titanium for single‐tooth restorations is justified.
Influence of visible‐light exposure on colour stability of current dual‐curable luting composites
Authors: Koishi Y. , Tanoue N. , Atsuta M. , Matsumura H.
Published: March 2003

This study was conducted to evaluate influence of visible‐light exposure on colour stability of dual‐curable luting composite. Using six dual‐curable luting composites [Bistite II (BI), Clapearl DC (CL), Dicor Light Activated Cement (DI), G‐Cera Cosmotech II (GC), Lute‐It (LU) and Variolink II (VA), disk specimens were prepared with the following two methods: (i) dual‐cured specimens, exposure with visible‐light from a photo‐curing unit for 120 s and (ii) chemical‐cured specimens, chemically cured without exposure. Five specimens were produced for each material and curing mode. After 24 h, all specimens were immersed in distilled water at 37 °C for 24 weeks, during which colour accuracy was measured with a dental colorimeter. The colours characterized in the Commission Internationale d'Eclairage (CIE) L*a*b* colour space were first determined 24 h after preparation (baseline colour evaluation), and again after 1, 2, 3, 4, 8, 12, 16 and 24 weeks. The colour difference (ΔE*) values between 24 h and the other immersion periods were calculated, and then analysed by repeated measure analysis of variance (ANOVA). In addition, the ΔE* values after 24 weeks for dual‐cured specimens were compared with those for chemical‐cured specimens by one‐way ANOVA and by contrasts for each composite (P < 0·05). The ΔE* values were influenced by the material and curing mode as well as immersion period (P=0·0001). After 24 weeks the dual‐cured specimens showed significantly lower ΔE* values than the chemical‐cured specimens, except for the VA material. The CL material exhibited the least colour change (1·9 ± 0·2) among the dual‐cured specimens, and the VA material showed the least (4·5 ± 0·9) among the chemical‐cured specimens after 24 weeks. Dual‐curable luting composites should be polymerized with the dual modes to ensure colour stability.
Usage and status of cobalt–chromium removable partial dentures 5–6 years after placement
Authors: Yeung A. L. P. , Lo E. C. M. , Clark R. K. F. , Chow T. W.
Published: March 2003

The aim of this study was to describe the usage of cobalt–chromium (Co–Cr) removable partial dentures (RPDs) by patients 5–6 years after denture insertion and to find out the factors that affected their denture usage. A random sample of patients provided with Co–Cr RPDs from a dental teaching hospital in Hong Kong was selected. Patients were interviewed using a structured questionnaire concerning their assessment and use of the dentures. Those who had been constantly wearing their original RPDs were examined by one calibrated examiner under optimal clinical conditions. The response rate of the patients who could be contacted was 98%. The results from 189 patient interviews showed that usage of the RPDs declined with time and that half of the dentures had been discarded or replaced 5–6 years after insertion. These discarded RPDs had been in use for an average of 19·5 months. The main reason given by the patients for not using the RPDs was general dissatisfaction with the dentures in various combinations of comfort, fit and chewing ability and, less importantly, with food trapping and appearance. No statistically significant association between denture usage and their respective Kennedy classification was found. The status of the Co–Cr RPDs that had been constantly used for 5–6 years was generally good. The majority of these RPDs demonstrated fair to good cleanliness, stability and retention and had no defect of any sort.
Effect of disinfectants containing glutaraldehyde on bonding of a tri‐n‐butylborane initiated resin to dentine
Authors: Baba N. , Taira Y. , Matsumura H. , Atsuta M.
Published: March 2003

The purpose of this study was to evaluate the effects of disinfectants on the bond strength of resin to dentine. The surface of bovine dentine was exposed to formaldehyde (FA) aqueous solutions, glutaraldehyde (GA) aqueous solutions, 2‐hydroxyethyl methacrylate aqueous solutions (HEMA), a commercially available dentine primer (Gluma CPS desensitizer, GLUMA), isotonic sodium chloride solution (IS), and distilled water (DW), and placed in a humidor (HU) at 37 °C, or non‐stored (baseline). All dentine surfaces were conditioned with a 10% citric acid and 3% ferric chloride solution (10‐3 liquid), and then bonded to an acrylic rod with a self‐curing adhesive resin (Super‐Bond C&B). The mean tensile bond strengths determined 24 h after bonding were compared by analysis of variance (ANOVA) and Fisher's protected LSD test (n=5, P ≤ 0·05). The exposure of dentine to IS, DW and HU for both 48 and 168 h resulted in a decrease in bond strength when compared with the baseline. The highest bond strengths after 168 h of exposure were obtained with 5% GA, 10% HEMA, and GLUMA, the values of which were equivalent to baseline and were significantly higher than that of FA. It is concluded that disinfectant pre‐treatment with 5% GA or GLUMA stabilizes the bonding of tri‐n‐butylborane (TBB) initiated luting agent to bovine dentine conditioned with 10‐3 liquid.
The effect of bleaching agents on the microhardness of dental aesthetic restorative materials
Authors: Türker S. B. , Biskin T.
Published: March 2003

This study investigated the effects of three home bleaching agents on the microhardness of various dental aesthetic restorative materials. The restorative materials were: feldspatic porcelain, microfilled composite resin and light‐cured modified glass–ionomer cement and the bleaching agents Nite‐White (16% carbamide peroxide), Opalescence (10% carbamide peroxide and carbapol jel) and Rembrandt (10% carbamide peroxide jel). A total of 90 restorative material samples were prepared 1 cm diameter and 6 mm thick and kept in distilled water for 24 h before commencing bleaching which was carried out for 8 h day–1 for 4 weeks. Microhardness measurements were then made using a Tukon tester. Statistically significant differences with respect to unbleached controls were found only for the feldspatic porcelain and microfilled composite resins (P <0.05) for Nite‐White and Opalescence. All the bleaching agents decreased the microhardness of the porcelain and increased that of the light cured modified glass–ionomer cement. For the composite resin, whereas Nite‐White increased its microhardness, the other bleaching agents decreased it. There were no significant differences between the bleaching agents for any of the restorative materials.
Influences of social support on the oral health of older people in Britain
Authors: McGrath Colman , Bedi Raman
Published: March 2003

summary  A national UK study involving a random sample of 876 non‐institutionalized older people (aged 65 or older) were recruited, to identify the association between social support (living alone), self‐reported oral health status and oral health behaviour (use of services). Home interviews were undertaken exploring oral health behaviour (time and reason for last dental visit) and oral health status measures (self‐reported number of teeth possessed and denture status). In addition, socio‐demographic characteristics were collected. Bivariate analysis identified that social support was associated with time since last dental visit (P < 0·01), reason for last dental visit (P < 0·01), self‐reported number of teeth possessed (P < 0·01) and denture status (P < 0·01). In regression analysis, social support emerged as an important predictor of reason for last dental visit and denture status having accounted for other factors in the model (age, gender, social class and educational attainment). Social support is associated with oral health status and oral health behaviour of older people in Britain and is likely to influence both the decision making process of when to seek dental care and what type of treatment to opt for.
Microfracture behaviour of composite resins containing irregular‐shaped fillers
Authors: Kim K.‐H. , Okuno O.
Published: March 2003

summary  Microfracture behaviour of composite resins containing irregular‐shaped fillers was understood by filler morphology observation, fracture toughness test and acoustic emission (AE) detecting method. The fracture toughness (KIC) was obtained by using single edge notched specimens. AE, the elastic wave due to the debonding of filler from the resin matrix or the fracture of filler itself, was detected during fracture toughness test. The reasons for the different fracture toughness values of composite resin, in spite of having almost the same morphology and filler content, were understood by the results of fracture surface finding and AE releasing behaviour during fracture toughness test.