bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of oxygen on the corrosion of dental amalgam
Authors: GREENER E. H. , MATSUDA K. 
Published: June 2007

SummaryThe anodic and cathodic polarization of five dental amalgams were determined as a function of oxygen concentration in Ringer's solution and artificial saliva. The results indicate an anodic polarization behaviour dependent on Cl ion concentration and a corrosion potential determined primarily by oxygen concentration. At high oxygen concentrations the corrosion rates of traditional and copper enriched amalgams were equivalent.
A long‐term prognosis for the free‐end saddle‐bridge
Authors: IZIKOWITZ LENNART 
Published: June 2007

SummaryA consecutive series of eighty‐seven saddle‐bridges with free‐end saddles, executed by the author during the years 1958‐72, was investigated in 1982. The aim was to assess the long‐term prognosis.Five years after application 98% of the bridges were still functioning. The corresponding percentage after 10, 15 and 20 years was 82, 69 and 49%, respectively. The risk that saddle‐bridges cease to function is very low during the first 5‐year period but significantly higher thereafter.Soldering fractures constitute an important cause of the removal of appliances during the first 8 years following application. After this time the most frequent causes are caries and loosening of the teeth.Factors such as sex, time of application, patient's age, length of saddle and whether the bridges were fitted in the mandible or maxilla, have not had a significant influence on the prognosis. Furthermore, no statistically significant difference has been found between the long‐term prognosis for full and partial saddle‐bridges. On the other hand, patients with a removable full denture in the opposing jaw show a significantly worse prognosis (P<0.05) than patients without a denture in this jaw.The results of the present study indicate that the short‐term prognosis for saddle‐bridges is very favourable and that the long‐term prognosis is so good that saddle‐bridges can constitute an alternative therapy even in jaws with as few as three remaining teeth.
An experimental comparison of vertical tooth movement of 33† and 0† teeth after denture processing procedures
Authors: CARR L. , CLEATON‐JONES P. , FATTI P. , WOLFAARDT J. 
Published: June 2007

SummaryMovement of teeth during denture processing is an unsolved problem. This study investigates the amount of vertical tooth movement during controlled processing of acrylic, using 33° and 0° teeth invested in specific mixes of plaster of Paris or dental stone.Forty sample set‐ups each containing four posterior teeth were processed under strictly controlled laboratory conditions. Twenty of these samples carried 33° teeth and the other twenty carried 0° teeth. Each group of twenty samples was randomly divided on a factorial design into batches of ten for investment in plaster of Paris or stone. The vertical movements were measured with a greater degree of accuracy than is required for clinical application. All results were analysed statistically.Significantly greater movement occurred with teeth invested in stone than those invested in plaster of Paris. Whereas, for teeth invested in stone, significantly greater movement occurred with 33° than with 0° teeth, no such effect was found with teeth invested in plaster of Paris.
Automated thermatic condensation of gutta‐percha root fillings in teeth with open (immature) apices
Authors: DUMMER P. M. H. , DAVIES J. , HARRIS M. 
Published: June 2007

SummaryForty upper human premolar teeth with open (immature) apices were root filled by one of three methods, namely lateral condensation with sealer, automated thermatic condensation with sealer, and automated thermatic condensation without sealer. The completed root fillings were then assessed for apical defects, apical extrusions, radiographic voids, apical seal and surface adaptation. The majority of the results indicate that the automated thermatic technique without sealer produces marginally better root fillings in teeth with open apices than the other two methods. However, it is impossible to say whether this would confer any clinical advantage on the technique.The authors recommend that clinicians who wish to use the automated thermatic technique for condensing gutta‐percha become highly proficient before its use on patients.
Temporomandibular joint abnormalities and bite force in a group of adults with rheumatoid arthritis
Authors: LARHEIM T. A. , FLÖYSTRAND F. 
Published: June 2007

SummaryMaximal mouth opening, translatory condylar motion (radiographically assessed) and bite force in sixteen adults with rheumatoid arthritis and radiographic temporomandibular joint abnormalities were compared with data from sixteen individuals without joint disease. Mean mouth opening in the arthritis group was reduced, but not statistically significant. Condylar translation and bite force showed significantly lower values than in the healthy individuals. Maximal mouth opening seemed to be the most uncertain parameter for the estimation of jaw function. In seven patients with a normal mouth opening (40–46 mm), both the condylar translation and the bite force were significantly impaired.
An evaluation of crowns and bridges in a general dental practice
Authors: LEEMPOEL P. J. B. , ESCHEN S. , DE HAAN A. F. J. , VAN'T HOF M. A. 
Published: June 2007

SummaryIn this article the results are presented of an evaluation of crowns and bridges in a general practice. The study includes 601 solitary crowns, 213 crowns on bridge abutments and 103 crowns on RPD abutments. In total eighty‐four bridges were examined. All these restorations were constructed during a period of 11.5 years. By means of the Kaplan‐Meier method a prognosis is given of the life span of the different solitary crown‐types over periods between 1 and 11 years. The total amount of failures and follow‐up treatments on bridge and RPD abutments was very small. The authors also examined whether the bridges were constructed according Ante's law. A follow‐up of this study in other Dutch general practices in combination with experimental clinical trials is under way.
Lateral preference in mastication: a feasibility study
Authors: CHRISTENSEN L. V. , RADUE J. T. 
Published: June 2007

SummaryTo study lateral bolus placement during mastication, referred to as masticatory lateral preference, fifteen males and ten females chewed sugarless gum for 15, 20 and 25 s, and visual inspections were done of either right or left side bolus placements. In each of three series of observations, there were no significant differences between right or left side bolus placements. Three consecutive spot checks, in single subjects, showed that lateral preference occurred at random. However, information on a favoured chewing side predicted fairly reliably the side of observed masticatory lateral preference. Observed lateral preference could not be predicted from hand laterality. Consistent and predominant right or left lateral preference was, presumably, an expression of mainly motivational chewing behaviour.
A photogrammetric method for monitoring changes in the residual alveolar ridge form
Authors: ADAMS L. P. , WILDING R. J. C. 
Published: June 2007

SummaryResorption of the residual alveolar ridge calls for regular attention to the fitting surface of a denture. In the case of distal extension partial dentures, changes which occur in less than a year may require attention. These changes are apparent, though difficult to measure using radiographic techniques. Stereopho‐togrammetry is a means of recording and measuring contours of land masses. A short focus non‐metric camera was used in this study to produce stereoscopic paired pictures of four casts of the same partial dentition. Additional casts were made 2 and 12 months after a partial denture had been made. A stereophoto‐grammetric plotting instrument was used to map the alveolar ridge area of each cast. A prescribed area for each map was traced out and the volume above a reference height was calculated. The percentage error between the four columns for the pretreatment casts was _t2%. A 10% loss of ridge volume was observed after wearing a partial denture for.2 months. The same area observed 12 months later revealed an 18% volume reduction. Short range stereophotogrammetry may be applied to study changes in alveolar ridge morphology which may result from wearing a partial denture.
Prediction of the shape and size of the maxillary anterior arch in edentulous patients
Authors: PRETI G. , PERA P. , BASSI F. 
Published: June 2007

SummaryThe aims of the study were to examine the morphometric and angular relationships between the interincisive papilla and the maxillary anterior teeth, and to describe a clinical method derived from this analysis useful in siting the upper front teeth.Plaster casts of upper jaws of adult patients with complete dentition, were selected. Two measurements were taken: (i) the distance from the centre of the papilla to the most vestibular part of the labial surface of the anterior teeth; and (ii) the angles between the perpendicular to the median line and the line from the centre of the papilla to the most vestibular part of each tooth.The equation of the resulting parabola, corresponding to the upper frontal arch, can be applied to every maxillary dimension. Parabolas were divided into small, medium, and large, using the mean and standard deviations. Each curve was traced on a transparent base‐plate shaped for intra‐oral placement. In individuals with complete dentition the closest parabola to the maxillary frontal arch was selected and the distance between the lateral frenula measured.Statistical study demonstrated a correspondence between the interfrenulum distance and the parabolas. In edentulous patients the interfrenulum distance thus provides a curve useful in siting the maxillary anterior arch.
An assessment of visible‐light polymerizing sources
Authors: MOSELEY H. , STRANG R. , STEPHEN K. W. 
Published: June 2007

SummaryMeasurements were made of the spectral distribution of light emitted from five commercially available visible‐light polymerization units. All emissions peaked between 400 and 500 nm but the ‘functional’ irradiance varied by a factor of 20 for the sources investigated. Timer checks revealed errors of up to 20%. Light output was plotted as a function of time and, after 60 s, varied from −15% to +38% of the initial level. The decrease in irradiance with distance from the end of the guide was such that irradiance at 20 mm was between 20% and 40% of that at 2 mm. The light distribution across the face of each light guide was investigated and significant inhomogeneities discovered. An ultraviolet light (UV) hazard assessment was performed and it was concluded that none of the light sources presented a hazard to the operator in normal use.
An examination of the surface corrosion state of dental fillings and constructions
Authors: HÅKANSSON B. , YONTCHEV E. , VANNERBERG N.‐G. , HEDEGÅRD B. 
Published: June 2007

SummaryElectrochemical measurements on amalgams and gold alloys in natural saliva and saline solutions have been performed.The results show strong inhibiting effects of some components in natural saliva on the surface corrosion behaviour of amalgams.For the gold alloys the cathodic reduction of oxygen was notably lower in natural saliva than in saline solutions.For galvanic combinations of gold and amalgams substantially lower currents than those calculated from thermodynamic data can be expected in natural saliva.
Creep versus marginal fracture of amalgam restorations
Authors: VRIJHOEF M. M. A. , LETZEL H. 
Published: June 2007

SummaryIn the literature there is controversy over the existence of a correlation between creep and marginal deterioration of amalgam restorations. It was the aim of this study to re‐investigate this correlation. In five clinical trials, 2068 amalgam restorations were made of six conventional alloys and ten high copper systems. The results show a correlation between creep and marginal fracture in the conventional, low copper amalgams. No correlation could be found for the group of high copper, non‐gamma‐2, amalgams. It is emphasized that dental practitioners should not buy their amalgam alloy on the basis of creep data, because wrong decisions might be taken. Evidence from a controlled clinical study is a more reliable criterion.
Particle and pore size distributions of investments
Authors: MUELLER H. J. 
Published: June 2007

SummaryThe particle‐size distributions of investment powders and the pore‐size distributions of set‐fired investments were investigated by electrozone size analysis, and by mercury intrusion scanning porosimetry, respectively, for a number of different investments, representing all three types available, namely: the gypsum‐, phosphate‐ and silicate‐bonded. The pore volume (V), the pore surface area (S), and their first derivatives with respect to radius, r, dV/dr and dS/dr, were obtained with pressures up to 414 MPa corresponding to spherical pores of 0.0018 μm radius if the Washburn equation is to apply. Results distinguished pores with a range of different sizes. Besides the porosity due to the matrix binder, porosity was also attributable to the refractory components. This latter type of porosity occurred with pore radii below about 0.03 μm, whereas matrix porosity occurred above this pore size. Matrix porosity for the phosphate materials was smallest at about 0.03 to 0.5 μm in radius, followed by the gypsum materials at about 0.3 to 0.6 μm, and by the silicate materials at about 1 to 10 μm. The particle‐size distribution of the investment powders may affect both types of porosities, whereas the setting chemistries of the particular investment types may affect matrix porosity, by the generation of gaseous by‐products. No major distinctions in pore size and distributions occurred between air‐set and hygroscopic‐set materials. This study emphasizes that at present, knowledge of the total pore volume only is inadequate for characterizing porosity distribution and hence investment permeability.
The mechanical advantage of biting with the posterior teeth
Authors: DEVLIN H. , WASTELL D. G. 
Published: June 2007

SummaryThe greater forces generated between posterior teeth compared with between anteriors, may be explained by interpreting the behaviour of the mandible as a lever system, with the condyle as a fulcrum. This study used a semi‐conductor strain gauge transducer to measure load, and EMG activity to index muscular effort. A posterior and an anterior load position were compared by using parallel metal platforms which maintained the occlusal vertical dimension for different biting positions. Reductions in muscular effort were observed for the posterior position of a magnitude that was consistent with the greater mechanical advantage predicted by the lever model.
Occlusal interferences analysed in patients treated with fixed prosthesis four years earlier
Authors: ETTALA‐YLITALO U.‐M. , MARKKANEN H. , YLI‐URPO A. 
Published: June 2007

SummaryThis study consists of 147 subjects treated with fixed prostheses 4 years previously. Occlusal analyses were made, and the fillings, crowns, and pontics on the occlusal surfaces were recorded. Occlusal interferences were found in 42.6% of the fillings, in 34.9% of the crowns, in 27.0% of the pontics, and in 24.6% of the intact surfaces. The most common interference types were intercuspidation, retrusion and mediotrusion in the fillings, as well as intercuspidation, retrusion, and laterotrusion interferences in the crowns. In pontics interferences appeared mostly in intercuspidation and retrusion. When adjustment was made for preprosthetic occlusion, the number of interferences on all types of occlusal surfaces considerably decreased.
Composite versus amalgam restorations
Authors: HENDRIKS F. H. J. , LETZEL H. , VRIJHOEF M. M. A. 
Published: June 2007

SummaryIn a clinical study the behaviour of posterior composite restorations was evaluated. For the study, 232 Class I or II restorations in premolars and molars were made by three operators in a group of forty‐nine adult patients. Each patient underwent one or two series of four restorations. The materials within a series were a strontium glass filled composite (Profile), a microfilled composite (Estic MF), a macrofilled composite (Adaptic Radiopaque) and a high copper amalgam (Dispersalloy). The last two materials served as a negative and positive controls respectively. For a period of 3 years the clinical behaviour was evaluated yearly with the USPHS criteria (anatomic form, marginal adaptation, colour match, marginal staining and caries). Differences in the ratings of the criteria between materials, tooth type and evaluation year were tested statistically for significance. The number of restorations replaced after 3 years in clinical service was eight (=3.6%). The results showed that the material, tooth type and evaluation year all have an influence on the anatomic form and the colour match of the restoration. The behaviour of the three composites with respect to colour match, marginal adaptation and marginal staining was acceptable. For anatomic form, however, only the behaviour of the microfilled composite Estic MF was still acceptable after 3 years.
Retentive and stress characteristics for a magnetically retained partial overdenture
Authors: HIGHTON R. , CAPUTO A. A. , MATYAS J. 
Published: June 2007

SummaryThe retentive and stress characteristics of a magnetically retained partial overdenture were studied. The retentive properties were compared to those of an I‐bar and Zest Anchor retained overdenture.The magnetically retained partial denture uniformly distributed stress to the supporting structures and exhibited significantly greater retention than that of the I‐bar, but less than that of the Zest Anchor. Based on these observations, the magnetically retained denture should be considered as an option to be used instead of or in conjunction with other types of partial overdentures.
An application of impedance techniques to corrosion research on dental amalgam
Authors: LEMAITRE L. , MOORS M. , VAN PETEGHEM A.P. 
Published: June 2007

SummaryAC impedance techniques are finding increasing application in corrosion research. It was our aim to introduce them as a method for the evaluation of the electrochemical behaviour of dental amalgam. The complex plane plots are large depressed semicircles representing the frequency dependence of the impedance and measured at the corrosion potential. Conventional dental amalgams, in a chloride medium, exhibit a current peak in the proximity of –250 mV (vs. SCE). The corresponding impedance spectra are rather complex and difficult to interpret. The high frequency part, however, can be fitted to a semicircle with its centre lying below the real axis. An evaluation of the corresponding ‘charge transfer resistance’ shows that it is inversely proportional to the corrosion current density.
Comparison of the strengths of aluminous porcelain fired on to platinum and palladium foils
Authors: PIDDOCK V. , MARQUIS P. M. , WILSON H. J. 
Published: June 2007

SummaryThe disc strengths of aluminous porcelain fired on to both platinum and palladium foil matrices have been determined. Also, the effect on strength of removing the matrices has been measured. The appearance of the separated metal and porcelain surfaces has been studied using scanning electron microscopy, and energy dispersive X‐ray analysis has been used to evaluate the chemical composition of these surfaces. Reasons for the increase in strength observed when the matrix is left intact are discussed. Practical suggestions for obtaining stronger jacket crowns are presented.
The role of personality in the management of partial dentures
Authors: WATSON C. L. , REEVE P. E. , BARNES E. , LANE A. E. , BATES J. F. 
Published: June 2007

SummaryA sample of fifty‐three partially dentate subjects who had had partial dentures provided in the last 3 years completed a personality questionnaire (Cattell's 16 PFQ). At the same time they completed a clinical questionnaire and were examined by two of the authors. The purpose of this was to assess the patients' satisfaction with their partial dentures.The results of the personality questionnaire showed that this group of partial denture wearers differed from the general population on only two factors. They were less intelligent and more self‐sufficient. Interestingly they differed from a similar group of complete denture wearers on a further three factors. The partial denture group were more self‐assured, self‐sufficient and more relaxed. On the basis of the clinical questionnaire and examination, five partially dentate patients were found to be dissatisfied. Their personality scores were significantly more unstable than the satisfied group of partial denture wearers.Although based on a relatively small group, the results do suggest that personality may have a marked effect on the patients' adaption to partial dentures. When compared to a similar group of edentulous patients, marked differences were found, suggesting that the loss of the natural teeth in some individuals affects behaviour.
The metal post and composite core combination
Authors: KÄYSER A. F. , LEEMPOEL P. J. B. , SNOEK P. A. 
Published: June 2007

SummaryRestoring broken down non‐vital teeth implies in general the provision of a post and core foundation. Many materials and techniques have been introduced for this purpose in recent years. In this article the advantages and disadvantages of the cast and the non‐cast post and core are discussed. The problems involved with the application of the post and core are reviewed. An efficient procedure for restoring a broken down tooth with a prefabricated post in combination with a composite core is presented.
The air‐powder dental abrasive unit—an evaluation using a model system
Authors: WALMSLEY A. D. , WILLIAMS A. R. , LAIRD W. R. E. 
Published: June 2007

SummaryAir‐powder abrasive systems are used in dentistry to remove dental plaque, calculus and stain from the surfaces of teeth. A model system consisting of a thin layer (14 μm) of vacuum‐deposited aluminium was used to demonstrate the effectiveness of such a system. Photomicrographic analysis showed two distinct areas of removal: an inner area where removal of aluminium was complete, surrounded by an area where removal was incomplete.With the aid of a relocation pin attached to the nozzle of the instrument it was demonstrated that nozzle–target distance, the air pressure input, the flow of water and the time of operation were all factors which affected the clinical efficiency of the instrument.
Adaptation of dental amalgam to the cavosurface margin of Class I cavity preparations
Authors: SYMONS A. L. , WING G. , HEWITT G. H. 
Published: June 2007

SummaryThe adaptation of a range of amalgam alloys to the cavosurface margin of Class I cavity preparations was examined for two condensation techniques. The marginal contour of amalgam condensed into the cavity preparation and packed approximately 1 mm past the cavosurface margin was compared with amalgam margins of restorations which were packed to final contour with minimal carving. The effect of burnishing and/or polishing the cavosurface margin was compared with carving the amalgam to the cavosurface margin. Specimens were sectioned, metallographically polished and examined using a light microscope.The technique of overpacking amalgam produced a greater number of acceptable amalgam margins at the cavosurface margin than the condensation technique of packing to final contour, the best cavosurface margin was produced when specimens were burnished and polished, the carved margin being the least desirable. The cuspal incline also influenced the quality of the marginal finish with the difficulty of marginal finishing increasing with the steepness in cuspal incline.