bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some causes of failure of crowns, bridges and dentures
Authors: PICTON D. C. A. , CREASEY S. J. 
Published: June 2007

SummaryWith increasing emphasis being placed on precision in the construction of prostheses the importance of the visco‐elastic characteristics of tooth support should be understood. Since the tooth returns to its resting position quite slowly, especially when repeated or sustained forces have been applied, an impression prepared prior to full recovery will convey erroneous relationships of the tooth with its neighbours to the working model and, eventually, to the prosthesis.Such an error has been identified in young human subjects when inter‐dental wedges, gingival retraction cord, and rubber dam are placed. The preparation of conventional alginate impressions in special trays can displace abutment teeth to a clinically significant degree as was recorded for seven partially dentate patients. Simple precautions will circumvent these potential sources of error.
The silent period in the masseter and the anterior temporalis muscles in adult patients with mild or moderate mandibular dysfunction symptoms
Authors: ZULQARNAIN B. J. , FURUYA R. , HEDEGÅRD B. , MAGNUSSON T. 
Published: June 2007

SummaryThe electromyographical silent period in the masseter and the anterior temporalis muscles during tooth tapping and jaw jerk were studied in patients with fairly mild temporomandibular joint dysfunction symptoms. The length of the silent periods in the patient group did not differ generally from that in a control group. During tooth tapping, however, patients with distinct muscular disorders had shorter silent period duration (7.7 ms) than patients with other symptoms or when compared with control subjects (10.5 and 11.3 ms, respectively). The duration returned to normal after correction of the muscular disorders. This finding suggests that the duration of the silent period is affected by the muscle condition. Patients with obvious muscular disorders of mild to moderate magnitude, thus, may show a shorter silent period duration during tooth tapping.
The immediate effect of splint‐induced changes in jaw positioning on the asymmetry of submaximal masticatory muscle activity
Authors: McCARROLL R. S. , NAEIJE M. , KIM Y. K. , HANSSON T. L. 
Published: June 2007

SummaryMaxillary full‐arch splints in the retruded position (RP) and in a right lateral occlusion (1.0‐ 1.5 mm to the right of the retruded contact position) were fabricated for ten subjects. Surface electromyography of the masseter and anterior temporal muscles was performed during submaximal clenching in order to investigate the immediate effects of the splints on the activity patterns of these muscles relative to the patterns found with the subjects occlusion in the inter‐cuspal position. The splints in the RP were found to have no effect on the asymmetry of the activity of the masseter and the anterior temporal muscles, while the splints in a right lateral occlusion resulted in relative increases in right anterior temporal muscle activity (P<0.005).
Effects of texture of food on chewing patterns in the human subject
Authors: HORIO T. , KAWAMURA Y. 
Published: June 2007

SummaryTo elucidate the effects of food character on chewing patterns in humans, the electromyographic activity (EMG) of the chewing muscles and also the jaw movements were recorded in twenty‐nine young subjects during ordinary chewing of five different foods.The results obtained were as follows. (a) The harder food materials showed a higher amplitude of the masseter EMG than the softer ones. (b) Concerning the number of chewing strokes and the elapse of time until the last swallowing action, subjects could be divided into two groups. (i) In the first major group, the number of chewing strokes and chewing time until the last swallowing action increased following increase of hardness of the food. This suggests that chewing force and chewing movements may be strongly influenced by the texture of food, especially its hardness. Further, the degree of pulverization of eating materials appears to be the major factor in controlling the swallowing action. (ii) In the second minor group, the chewing strokes and the chewing time were less influenced by the hardness of food. Here, a certain number of chewing strokes could be stimulating the swallowing centre in the brain and so induce swallowing, regardless of the degree of pulverization of the food.
Assessment of occlusal interferences
Authors: VALLON D. , NILNER M. , KOPP S. 
Published: June 2007

SummaryThe variability in the assessment of occlusal variables was investigated in eight subjects by the repeated registrations of four observers. The following variables were investigated in three different ways: sliding between the RCP (retruded contact position) and the ICP (inter‐cuspal contact position) in the sagittal, vertical and lateral plane. Interferences during lateral movements on the working and balancing sides as well as interferences causing deviation of the mandible during protrusive movements were recorded.The intra‐ and inter‐observer error for the measurement of sagittal and vertical distance RCP‐ICP was within acceptable limits. There was no significant difference between the three methods used. The intra‐ and inter‐observer agreement between duplicate recordings of the lateral distance RCP‐ICP was high and there were no differences between the different measurement modalities.The inter‐observer agreement was lower than the intra‐observer agreement concerning presence/absence of balancing side interferences, and positive interobserver agreement was only found on lateral movement more than 3 mm from the RCP or the ICP.The observer error for the variable working side interferences should be acceptable for future research, while the observer error for measurement of lateral deviation of the mandible upon protrusion was somewhat larger.
A comparative in vitro study of visible light‐cured sealants
Authors: LEKKA M. P. , PAPAGIANNOULIS L. , ELIADES G. C. , CAPUTO A. A. 
Published: June 2007

SummaryThe introduction of visible light polymerization in dentistry led to the development of a new generation of pit and fissure sealants. The purpose of this study was an overall evaluation of some in vitro characteristics of four new sealants (Delton LC, Helioseal, Pentra‐Seal and Visioseal) in comparison with a chemically cured control (Delton). The results indicate that the monomer systems utilized in the new materials have already been used in dental polymer technology. The relatively new monomers TCDDMA/TCDMA were identified in one product. Camphoroquinone is used as a photoinitiator in all the light‐cured systems which, after 40 s exposure, present better conversion than the control. The extent of oxygen inhibition was considerably reduced in the new sealants and the surface hardness was enhanced. Great differences were obtained in the penetration coefficient values; these, however, did not affect the enamel retention capacity of the materials tested. Consequently, light‐cured sealants should be considered to be strongly compatible with the conventional chemically cured sealants from a laboratory aspect until more clinical evidence is available for their effectiveness in the prevention of pit and fissure decay.
Joint strength between two layers of different amalgam types condensed successively
Authors: GORDON M. , LIBERMAN R. , BEN‐AMAR A. , ELDAR S. 
Published: June 2007

SummaryThe flexure strength of the joint between layers of different types of amalgam condensed consecutively one on to the other was evaluated in vitro. The data indicated no statistical differences in flexure strength between the combined samples (single composition spherical and lathe‐cut eutectic amalgams) and the control (homogeneous lathe‐cut eutectic amalgam).
Investigation of the surface texture of hydroxylapatite‐coated dental implants by means of SEM
Authors: VAN ROSSEN I. P. , DE PUTTER C. , DE GROOT K. 
Published: June 2007

SummaryIn this experiment hydroxylapatite‐coated dental implants were submitted to a wear test in order to study their resistance to toothbrushing. After 20,000 double brush strokes the coating had disappeared in some places. It was concluded that the wear resistance of the coating was not good enough to withstand longer brushing periods.
The gothic arch tracing and the upper canine teeth as guides in the positioning of upper posterior teeth
Authors: EL‐GHERIANI A. S. , DAVIES A. L. , WINSTANLEY R. B. 
Published: June 2007

SummaryThe relationship between the position of the buccal cusps of the natural upper posterior teeth and the distance between the lateral arms of the Gothic arch tracing or the distance between the upper canine teeth has been found to be constant to within ±2mm. This may be of value when setting up artificial teeth for denture patients, enabling them to be positioned close to the natural predecessors.
Cyclic fatigue of composite restorative materials*
Authors: DRUMMOND JAMES L. 
Published: June 2007

SummaryThe purpose of this project was to investigate and evaluate dental composite restorative materials classified according to filler particle size (microfill, small particle, hybrid) regarding fracture characteristics and susceptibility to stress corrosion. The composite materials were tested by cyclic fatigue in distilled water at 37°C. No trend was observed between the number of cycles to fracture and the cycling load as a percentage of the modulus of rupture. Linear regression analysis correlation was weak for most of the composites used to determine the stress corrosion resistance constant, which ranged from 0.80 to 12.05.Observation of the fracture interface revealed inter‐ and intraparticle fracture for the small particle and hybrid composites. The microfills fractured between and through the prepolymerized particles.
A mechanistic study of the electrochemical corrosion of the γ2 phase in dental amalgams. I. Evaluation of the measurements
Authors: LEMAITRE L. , MOORS M. , VAN PETEGHEM A. P. 
Published: June 2007

SummaryConventional dental amalgams are prone to corrosion of the γ2 phase. In an anodic polarization experiment the presence of γ2 causes a current peak in the proximity of −250mV vs. SCE. Electrochemical impedance measurements carried out at this potential indicate the occurrence of an impedance curve in two parts. The high frequency part is a semi‐circle with its centre below the real axis. Apart from the faradaic impedance and the double layer capacitance, the high frequency part is dominated by the behaviour of the corrosion products layer on the amalgam surface. The low frequency part has the form of a diffusion‐like curve. However, since the phase angle is smaller for the above‐mentioned case than for a free diffusion, this phenomenon is ascribed to diffusion in a porous layer at the interface between amalgam solution.
A mechanistic study of the electrochemical corrosion of the γ2 phase in dental amalgams. II. Introduction of a model
Authors: LEMAITRE L. , MOORS M. , VAN PETEGHEM A. P. 
Published: June 2007

SummaryElectrochemical impedance measurements on conventional dental amalgams at an anodic polarization potential of −250 mV vs. SCE were performed. An initial evaluation was given in part I of this study; in the second part the results are interpreted in terms of a model. The latter, characterized by an equivalent circuit, is a parallel combination of a flat surface and a pore. The selection of appropriate values for the elements of the equivalent circuit leads to a better insight into the corrosion process. Although no simple relationship exists between the circuit elements and the impedance curves, an explanation was found for some typical features of these curves. As an application, the influence of the anodic polarization potential on the impedance curves was studied. Evaluation by means of the model demonstrated the importance of the characteristics of the corrosion products.
In vitro acid decalcification of human surface enamel pretreated with toothpaste slurries
Authors: TADMOR E. , POITOU P. , GEDALIA I. 
Published: June 2007

SummaryAn in vitro caries‐like challenge of human tooth enamel treated with inorganic fluoride (NaF) and organic fluoride (aliphatic and aromatic amine fluorides) toothpaste slurries has been investigated. The results revealed that the organic fluoridecontaining toothpastes affected positively the resistance of tooth enamel to demineralization.
The anatomical effects of surgically repositioning the disc in the temporomandibular joint of rats. An experimental study.
Authors: LEKKAS C. , HONEE G.L.J.M. 
Published: June 2007

SummaryA sample of 16 rats was used as experimental material to evaluate the effect of surgical repositioning of the disc of the temporomandibular joint according to the technique described by McCarty and Farrar (1979) and its variation according to Leopard (1984). The animals were killed 6 weeks postoperatively. Macroscopic and microscopic examination revealed that in all rats treated according to the procedure of McCarty and Farrar (1979) the disc had completely disappeared. The underlying condyle was deformed to a mushroom shape and the cartilage of the condyle was thickened. In seven of eight rats operated on according to the technique of Leopard, the same results were observed. It is concluded that surgical repositioning of the disc according to these techniques represents a method of disc removal.
Mucosal reactions to amalgam restorations
Authors: JAMESON M.W. , KARDOS T.B. , KIRK E.E.J. , FERGUSON M.M. 
Published: June 2007

SummaryAmalgam restorations have been implicated both in contact sensitivity reactions and in lichenoid reactions. This appears to be related principally to the mercury content, although other metals cannot be discounted. The cases of two patients are reported who showed features of lichenoid reactions of the oral mucosa, in addition to features of a contact hypersensitivity to mercury. The mucosal lesions resolved following replacement of the amalgams with non‐metallic restorations. Consideration is given to the selection of materials and procedures currently available for treatment of these patients. This paper supports the view that sensitivity to heavy metals must be considered as a possible cause of erythematous and lichenoid reactions of the oral mucosa.
Accuracy of impression materials measured with a vertical height gauge
Authors: LEWINSTEIN I. , CRAIG R.G. 
Published: June 2007

SummaryThe objectives of this study were to introduce a different method for evaluating the accuracy of impression materials using a vertical height gauge, and to determine the vertical (axial) and horizontal (transversal) changes of four impression materials. Comparison of means demonstrated the changes for addition and condensation type silicones, and larger changes for the agar/alginate combination and the visible light cured (polyetherurethanedimethacrylate) impression material. The results were in agreement with an earlier study of the agar/alginate combination, and the values for the condensation and addition silicones were about half those reported in previous studies. These small changes might indicate the use of a mandibular stock tray for the upper jaw when a putty/wash technique is employed. The findings suggest that, when the horizontal changes (ΔX) of impressions taken with a mandibular stock tray have a negative sign (contraction), then the vertical changes (ΔL) will have a positive value (expansion), and vice versa. Thus the pattern of distortion can be formulated as δXδL<0.
The effectiveness of dentine adhesives as demonstrated by dye penetration and SEM investigations
Authors: HEGARTY S.M. , PEARSON G.J. 
Published: June 2007

SummaryA previous investigation identified three types of cuspal movement that occur as a result of polymerization shrinkage when extracted molar teeth are filled with a microfine or hybrid composite used in conjunction with a dentine adhesive. That investigation was extended further by dye penetration and SEM studies of the margin, involving assessment of the degree of dye penetration and marginal integrity around the restoration. These studies indicate that there may be a failure of the adhesive bond between tooth and composite/adhesive complex which correlates with little or no cuspal movement. Failure within the tooth structure itself was also observed in a number of cases.
Viscoelastic properties of tissue conditioners — stress relaxation test using Maxwell model analogy
Authors: MURATA H. , SHIGETO N. , HAMADA T. 
Published: June 2007

SummaryIn order to measure the viscoelastic properties of tissue conditioners, a series of stress relaxation tests was carried out using poly ethyl methacrylate polymer powders and liquids composed of butyl phthalyl butyl glycolate/ethyl alcohol mixtures, respectively. The analysis method using the Maxwell model analogy is discussed. The results may be summarized as follows.(i) In this study it was feasible to make the stress relaxation curves for 30min analogous to the Maxwell model, using a model with a maximum of 5 elements.(ii) The elastic modulus E1, the coefficient of viscosity ν, and relaxation time tj, for each element, and the instantaneous modulus Eo, tended to increase with time. These values in the element of the longest relaxation time were most marked in the increase among those in all the elements. Furthermore, in every element the rate of increase of ν was greater than that of E1.The method described is considered to be one of the most useful techniques available for the study of the viscoelastic properties of tissue conditioners.
The effect of posterior composite restorations on the resistance of cavity walls to vertically applied occlusal loads
Authors: LIBERMAN R. , BEN‐AMAR A. , GONTAR G. , HIRSH A. 
Published: June 2007

SummaryThe resistance of the cavity walls of non‐vital premolars to vertically applied occlusal forces was studied. Standardized MOD cavities were prepared, restored, and vertical forces were applied to each of the cuspal tips by the Instron machine.Results suggest that bevelled etched‐enamel margins and dentine‐bonded posterior composite resin restorations significantly improved (by 33%) the resistance of the remaining cavity walls compared to amalgam restorations. In a control group, in which no restorations were carried out in the prepared cavities, the resistance of the walls was significantly smaller than in both restored groups.
Radiographic inhomogeneity of posterior composites
Authors: WATTS D.C. , WILSON N.H.F. , OMER O.E. 
Published: June 2007

SummaryA radiographic technique has been devised for determining the structural inhomogeneity between successive specimens fabricated from any given dental composite. This has been applied to nineteen composites currently recommended for the restoration of Class I and Class II cavities. The inhomogeneity data fell within clearly defined bands, with some light‐cured posterior composites exhibiting an inhomogeneity parameter of zero. Other hands had average inhomogeneities of 1.5%, 2.5%, 3.8% and 6.8%. The level of inhomogeneity exhibited by a composite system may be an important factor in material selection and in long‐term clinical performance.
The temporomandibular joint in rheumatoid arthritis—a comparative clinical and tomographic study pre‐ and post‐prosthesis
Authors: SATO H. , FUJII H. , TAKADA H. , YAMADA N. 
Published: June 2007

SummarySix partially or fully edentulous rheumatoid patients participated in the study. By comparing the clinical symptoms and tomograms of the temporomandibular joints (TMJS) pre‐prosthesis with those post‐prosthesis, this report assesses whether dental treatment could provide positive help for TMJS in patients with rheumatoid arthritis (RA).Among the clinical symptoms of TMJ dysfunction, pain from the TMJ region and limitations of movement were improved in all the patients post‐prosthesis. Tomographic evidence of desirable remodelling of the condylar heads was observed in two cases.
Effect of undercut placement on crown retention after thermocycling
Authors: ARCORIA C.J. , DEWALD J.P. , VITASEK B.A. , WAGNER M.J. 
Published: June 2007

SummaryThe aim of this study was to examine the effect of undercuts in castings and/or tooth structure on the retention of crowns luted with glass ionomer cement. After routine full‐crown preparations had been made in 48 human premolars, wax patterns were fabricated for each tooth. Retentive coves were then produced with a round bur in either the tooth structure or the wax patterns, or in both. One group of teeth and patterns did not receive any undercuts; this was the control group. Castings were made in non‐precious metal. All crowns were luted with glass ionomer cement. Half of the samples were thermocycled, and the remainder were kept at 37°C. Crowns were removed using tension (0.012 cm min−1) and the mean bond strengths calculated. The differences in retentive strengths were tested for statistical significance using anova and Scheffe's test. The presence of coves in castings and/or tooth structure significantly increased the retentive strength of castings cemented with glass ionomer, as compared with conventional crown preparations without retentive undercuts. The effect of thermocycling on the retentive strength of castings cemented with glass ionomer was not statistically significant.
Retention of denture adhesives—an in vitro study
Authors: CHEW C. L. 
Published: June 2007

SummaryDenture adhesives are being used by patients to aid the retention and stability of their dentures. A number of laboratory and clinical investigations have been conducted to study the effects of such adhesives. This study describes a simple in vitro method for measurement of their retentive effect and its relation to loss of adhesive. The results show that there is a reduction in the effectiveness of adhesives, and that there is also an increase in adhesive loss, with time. There appears to be a correlation between these two properties.
Observations in the time and frequency domains of surface electromyograms of experimental brief teeth clenching in man
Authors: CHRISTENSEN L. V. , DONEGAN S. J. 
Published: June 2007

SummaryMaximum voluntary teeth clenching was performed for about 1 s to study the interactions between subjective sensory‐motor events and changes in the time and frequency domains of surface electromyograms of the masseter and anterior temporalis muscle. Isometric jaw muscle contractions were examined for their speeds of contraction, the total energy content and median frequency of their power density spectra, and for the specific rate of change and the efficiency of their voluntary and involuntary activation efforts. The observations suggested that, in general, brief maximum isometric contractions were not preprogrammed, but rather were regulated by a subconscious proprioceptive feedback mechanism; the mechanism, possibly a transcortical loop, appeared to have a low gain and to be based on recruitment/decruitment of motor units.
Prosthetic treatment for speech disorders due to surgically acquired maxillary defects
Authors: YOSHIDA H. , MICHI K. , OHSAWA T. 
Published: June 2007

SummaryTo evaluate speech following prosthetic obturation of surgically acquired maxillary defects, the speech intelligibility of eight patients was measured preoperatively and postoperatively, with and without prostheses. Oro‐nasal separation and velopharyngeal function were also evaluated by use of a specially designed spirometer and endoscope. Following placement of maxillary obturator prostheses, four patients achieved dramatic improvement in speech intelligibility, while four patients did not. In the latter, insufficient improvement in speech intelligibility was attributed to velopharyngeal incompetence or unstable prosthesis. Two of three patients with velopharyngeal incompetence did achieve adequate improvement in speech following placement of a speech appliance in combination with maxillary obturator prostheses.