bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adaptation of amalgams to cavity walls
Authors: ØILO GUDBRAND 
Published: June 2007

SummaryThe adaptation of amalgam fillings to the cavity walls has been studied. Cavities were made in human teeth and filled with four different amalgams: (1) amalgam with an expansion of approx. 10 μm/cm after 48 h; (2) amalgam with no dimensional change after 48 h (balanced); (3) amalgam with a contraction of approx. 10 μm/cm after 48 h; and (4) amalgam with a contraction of approx. 20 μm/cm after 48 h.The filling surface and parts of the surrounding enamel were planed, polished and studied under the microscope. The degree of contact between the amalgam and the cavity wall and the number and dimensions of the marginal defects were observed.Fillings made from expanding or balanced amalgams mostly had good contact with the cavity wall, and the marginal defects were small and scattered. Around fillings made from contracting material, a slit formation was observed, and in these areas fractures of both the amalgam and the enamel margins had regularly changed the slit to a V‐shaped gap 10–20 μm wide. Greater defects exceeding 50 μm were also frequently observed.The results showed a gradual decrease in the quality of adaptation from fillings made of expanding material to those made of contracting material. It was further shown that the polishing procedure caused fracturing of both the unsupported enamel and amalgam margins thus widening the defects considerably.
Pyruvic acid as an etching agent
Authors: RETIEF D. H. , BISCHOFF J. , VAN DER MERWE E. H. M. 
Published: June 2007

SummaryPhosphoric acid at different concentrations has been extensively used as an etching agent to improve bonding of dental materials to enamel surfaces. Recently attention has been drawn to the possible use of polyfunctional organic acids as conditioning agents.The object of this investigation was to determine the optimal concentration of pyruvic acid as an etching agent. A commercial composite resin with an intermediary bonding system supplied with 37% H3PO4 as an etching agent was used as the control system. In addition, a comparative study was carried out to evaluate 37% H3PO4, 20% lactic acid and the optimal concentration of pyruvic acid as conditioning solutions.Etching enamel surfaces with 10% pyruvic acid resulted in the optimal tensile bond strength of the resin to etched enamel surfaces. The use of 10% pyruvic acid did not adversely affect the bond strength of the resin system when compared to enamel surfaces etched with 37% H3PO4 for the same time period. Significantly lower tensile bond strengths were recorded on enamel surfaces etched with 20% lactic acid. The rate and depth of etching obtained with 37% H3PO4 can be considerably reduced by using 10% pyruvic acid as the conditioning agent.
Assessment of reliability of cineradiographic recording of temporomandibular joint movements
Authors: SAXBY M. S. , FRANKS A. S. T. 
Published: June 2007

SummaryAs part of a cineradiographic study of temporomandibular joint movements, the reliability of the apparatus and techniques has been assessed. The areas of concern were the radiographic procedure, tracing apparatus and tracing technique.To assess the accuracy of the radiographic procedure, anatomical and radiographic measurements of mandibular condyles were compared. A range of variation of 0.46–0.8 mm was found, which compared favourably to the only previously published investigation. The use of mechanical devices simulating the fundamentals of mandibular movements suggested that the cineradiographic record showed paths of opening and closing separated more widely than occurred in vivo.The reliability of the tracing apparatus was assessed by calculated misalignments and found to be acceptable.The subjective error in tracing cineradiographic films by a regular observer was investigated by a point location error method. The error was found to be small and within acceptable limits.
Some morphological aspects of the meatus acusticus externus in connection with mandibular movements
Authors: VAN WILLIGEN J. 
Published: June 2007

SummaryA method is described to measure volumetric variations in the meatus acusticus externus caused by the movements of the mandible. Simultaneous registration of EMG activity and gnatho‐sounds demonstrated that after tooth contact a slight decrease in volume, followed by some increase in volume takes place within 20–30 ms. The fast volume changes, during and after tooth contact, seem to be correlated to the speed of closure.
The fallacy of facial measurements of occlusal height in edentulous subjects
Authors: TRYDE GERD , MCMILLAN D. R. , CHRISTENSEN J. , BRILL N. 
Published: June 2007

SummaryA controlled trial was made using fifteen subjects and making 120 measurements with a caliper gauge between marks disposed on the upper lip and the point of the chin when maxillo–mandibular relationships were altered vertically by known amounts within a range of 6 mm. It was found that mean facial measurements could account for only half of the skeletal movement involved. The variability of soft tissue translation in relation to skeletal movement led to the conclusion that such facial measurements are inappropriate to clinical practice.
The linear model: a statistical tool applied to psychophysical research in dental prosthetics
Authors: STOLTZE K. , TRYDE GERD , MCMILLAN D.R. , MORIMOTO T. , SPANNER O. , BRILL N. 
Published: June 2007

SummaryThe construction of a linear model is described, and its function in analysing variations in the perception of comfortable mandibular occlusal positions is explained. In principle, the model combines analyses of variance and regression in a number of simple computer operations. Data from a clinical study were used to demonstrate the analytical capacity of a specific model, designed to estimate the effect of factors, which were supposed to influence the perception of comfortable mandibular positions.
Long‐term changes in the perception of comfortable mandibular occlusal positions
Authors: TRYDE GERD , STOLTZE K. , MORIMOTO T. , SALK D. , BRILL N. 
Published: June 2007

SummaryThe aim of this study was to disclose, whether use of a screw jack device to set the distance between the jaws, would contribute towards a stabilization of the magnitude and position of a comfortable zone of mandibular positions or even eliminate it. Thirteen subjects participated in each of fifteen experimental sessions distributed over a 3‐week period. Throughout the investigation the zone prevailed at an average width of 1.3 mm. The gap shrank 0.08 mm on average per experimental session. Although this latter value was found to be significant statistically, it can hardly be of clinical importance, considering the time needed for a total contraction of 0.8 mm to develop.
The variation in contact angle of a fissure sealant on enamel surfaces
Authors: BREAKSPERE ROBERT J. , WILTON ALLAN 
Published: June 2007

SummaryFor strong adhesion of ultraviolet initiated polymeric fissure sealants to dental enamel, a well‐formed tag structure is necessary. This requires that the unpolymerized sealant must be able to flow quickly into the etched surface before polymerization is initiated. The variation in contact angle, θ, with time (the spreading ability) of unpolymerized Nuva‐Seal has been measured on unetched, etched and moist enamel surfaces. This spreading ability varies with the condition of the surface. It is estimated that, in the system investigated, the roughness of the enamel surface is increased by up to 13% on etching, but is reduced again if moisture is present, due to condensation into the etch pits. An etched, moisture free enamel surface is therefore necessary for strong adhesion of polymeric materials.
A comparative study of three different approaches to the comfortable zone
Authors: FUJII H. , STOLTZE K. , TRYDE GERD , McMILLAN D. R. , BRILL N. 
Published: June 2007

SummaryBy means of a screw jack device, applied to thirteen edentulous subjects, the comfortable zone was approached in three different ways, by the central, the internal and the external approaches. Correspondingly, the zonal borders behaved differently. Applying the central approach it was found that the initial height of the screw jack had a lingering effect upon subsequent adjustments of the screw. Moreover, lower border data collected by the external approach distinguished themselves form other zonal border data by showing a signifincantly lower susceptibility to successive adjustments. The study suggests that muscle activity is a factor on which the perceptual mechanism relies, when a zonal border is assessed subjectively by a patient.
Polymer adhesion to enamel
Authors: CATE J. M. TEN , KEIZER S. , ARENDS J. 
Published: June 2007

SummaryFor a four‐component acrylate adhesive system the influence of viscosity and penetration on adhesion to enamel was investigated. While low viscous monomer adhesives yield both inter‐ and intraprismatic penetration in enamel after polymerization, highly viscous adhesives result in the former type only. This difference in penetration of the adhesive in enamel is reflected quantitatively in the tensile strength values. Scanning electron microscopic measurements on the tag formation under various circumstances have been carried out. The SEM experiments show, e.g. that at polymerization times less than 1·5–2 min (a clinical necessity) polymer‐tags were usually fractured from the bulk material due to stresses generated.
Dimension discrimination at two different degrees of mouth opening and the effect of anaesthesia applied to the periodontal ligaments
Authors: CHRISTENSEN JOHN , MORIMOTO TOSHIFUMI 
Published: June 2007

SummaryThe dimension discrimination ability of twenty‐five young persons was tested at two different degrees of mouth opening. One reference stick of 10·0 mm and another of 45·0 mm was placed between the teeth, alternating with test sticks of different heights. The subjects were asked to assess whether a test stick felt higher or lower than the reference stick. The experiment was performed with and without anaesthesia applied to the periodontal ligaments.Anaesthesia did not impair the discrimination ability. At dimensions in the region of the 10.0 mm stick the incorrect assessments occurred predominantly among sticks higher than the reference stick. Around the 45.0 mm stick incorrect assessments were distributed evenly detween dimensions higher or lower than the reference stick.
Tooth tapping ability of young and elderly males and females
Authors: WIDMALM SVEN‐ERIK 
Published: June 2007

SummaryThe ability to perform high frequency tooth tapping movements was studied in young dentulous, elderly dentulous and elderly edentulous subjects of both sexes as a possible test of the overall efficiency of the masticatory motor apparatus and related structures.Tapping frequency was measured during a test period of 90 s by counting the number of taps per 5 s intervals. It was found that observed values of tapping frequency could be fitted to an exponential equation with a high degree of fit for 90% of the young subjects and for 60% of the elderly subjects. The values of the remaining elderly subjects were best fitted to straight lines. The elderly subjects could thus be regarded as belonging to two different populations which were differently affected by advanced age and loss of teeth regarding their tooth tapping ability.Young dentulous subjects had the highest starting frequency (6·1 Hz) followed by elderly dentulous (5·5 Hz) and elderly edentulous subjects (4·9 Hz). The lower limits were 4·6 Hz for young dentulous subjects, 4·1 Hz for elderly dentulous and 3·7 Hz for elderly edentulous subjects.The average group means pointed all in the same direction that increased age and loss of teeth change the functional ability by deteriorating it.
The performance of ultraviolet lights used to polymerize fissure sealants
Authors: YOUNG K. C. , HUSSEY M. , GILLESPIE F. C. , STEPHEN K. W. 
Published: June 2007

SummaryThe performances of ultraviolet (uv) lights used to initiate polymerization in fissure sealant systems were studied with a view to establishing recommendations for improving clinical results. The relationship between the setting time of an uv polymerized sealant (Nuva‐seal) and the intensity of radiation applied was first established. This was compared with the intensity and distribution of radiation from seven Nuva‐lites and one Quartzlite. It was found that some of the Nuva‐lites did not produce an average intensity of uv radiation sufficient to completely polymerize Nuva‐seal within the manufacturer's recommended exposure times. It is suggested that this may be a factor contributing to the large variation in sealant retention found in the different clinical trials with Nuva‐seal. Finally, a number of recommendations are made to ensure that sufficient uv radiation is applied to all sealant surfaces when Nuva‐seal system is used.
Preparation areas resisting displacement of artificial crowns
Authors: HEGDAHL T. , SILNESS J. 
Published: June 2007

SummaryThe areas of luting cement resisting rotation of artificial full crowns subjected to non‐axial forces were calculated for varying values of preparation diameter, height, and convergence angle. The calculations were performed for regular conical and pyramidal preparations.The results showed that the resisting areas are larger in pyramidal than in conical preparations. Increasing the convergence angle resulted in an almost linear reduction in resisting area. The reduction was particularly pronounced for preparations of large diameters.
Occlusion between removable dentures and natural teeth
Authors: PIETROKOVSKI JAIME , MEJIAS JUDITH E. 
Published: June 2007

SummaryStudy casts of thirty‐five partially edentulous patients were analysed at their arch level and at the interarch levels. At the arch level the crest of the residual ridge is located lingually to the position of the remaining teeth in the maxilla as well as in the mandible.The spatial interarch relationship between the residual edentulous ridge and the antagonist natural teeth in the buccolingual plane indicated that the crest of the residual ridge is lingual to the occlusal surfaces of the antagonist teeth.In the maxilla the positioning of the artificial teeth in the area previously occupied by the natural extracted teeth will place the denture teeth far buccal as well as away from the crest of the residual ridge. Other possibilities are to place the artificial teeth in a cross bite relation or to eliminate the buccal cusps of the replacement teeth. In the mandible the denture teeth can be placed at the position occupied formerly by the natural teeth.
An overhead projection aid for teaching the principle of occlusion
Authors: WISE MICHAEL D. 
Published: June 2007

SummaryA technique has been presented whereby models which can be animated are used to form a projected image on a screen and thereby demonstrate the principles of occlusion together with principles of articulators. The system can be used alone or in conjunction with clinical slides interjected at relevant places in the discussion. This technique has been found to be a very useful aid in the teaching of occlusion to both graduate and undergraduate students.
Biological testing of dental restorative materials
Authors: TYAS MARTIN J. , BROWNE R. M. 
Published: June 2007

SummaryThe problems discussed are those inherent in standardizing test procedures for dental materials, where the pulp response is studied after the materials have been placed in cavities in teeth. The advantages of cell culture methods are stressed. Standardization is only possible with in vitro methods and the development of these methods is advocated.
A colorimetric study of coffee and tea staining of four composite resins
Authors: GROSS M. D. , MOSER J. B. 
Published: June 2007

SummaryColorimetric measurements were made on four composite resins before and after controlled immersion treatments. The four composite resins were: Adaptic (Johnson and Johnson), Prestige (Lee Pharmaceuticals), Addent XV (3M Mfg. Co.) and Smile (Kerr Mfg. Co.).Specimens of each material were prepared with mylar surfaces and with abraded finished surfaces. Separate groups of specimens of the four materials were immersed in three separate solutions for 12 days at 55°C. The three solutions used were: a control solution of distilled water, a solution of distilled water and coffee and a solution of distilled water and tea.For all materials and surface finishes, immersion in coffee and tea produced significantly greater colour changes than distilled water. Coffee produced significantly greater colour changes than tea with the exception of ‘Prestige’ and ‘Addent XV’ with finished surfaces. When immersed in a tea solution, speciments of the same material with differing surface finishes showed greater differences in colour change than when immersed in control and coffee solutions. The relative colour changes of the four materials due to the immersion procedures were as follows: ‘Adaptic’ showed the least colour changes and ‘Smile’ showed the most. ‘Addent XV’ and ‘Prestige’ tended to vary between the former two. Comparison and correlation of colorimetry results with visual assessment scores allowed for the expression of the objective measures in subjective terms suitable for clinical purposes.
Tissue reactions to implanted vitreous carbon and high purity sintered alumina
Authors: HOBKIRK J. A. 
Published: June 2007

SummaryVitreous carbon and high purity sintered alumina implants were inserted into the iliac crests and mandibles of rabbits. The reactions of the tissues were assessed after periods up to 2 years using resin embedded histological sections.Both types of material were well tolerated, although the alumina excited a slightly greater tissue response than did the vitreous carbon.Electron microprobe analysis of the bone around the implants failed to show the movement of known contaminants from the alumina and vitreous carbon into the surrounding tissue.Observations are made on the reactions of the tissues to the implants and the effect of cortical penetration and implant movement.
The development of an artificial saliva for in vitro amalgam corrosion studies
Authors: DARVELL B.W. 
Published: June 2007

SummaryPublished data, consideration of chemical and physical properties and the requirements of amalgam corrosion testing were used to formulate an artificial saliva. A previously described method was used to determine the relevance of a number of human saliva constituents. Some results of those tests are described. Practical problems are discussed, and necessary further developments outlined. A number of other applications are suggested.
Mechanism of adhesion of polymers to acid‐etched enamel
Authors: SOETOPO  , BEECH D.R. , HARDWICK J.L. 
Published: June 2007

SummaryThe tensile bond strengths of composites to enamel etched with various concentrations of phosphoric acid have been shown to correlate closely with the phase diagram for the system Ca(OH)2/H3PO4/H2O. Bond strengths were independent of the adhesive used and were a maximum when using ∼20% phosphoric acid as etchant. High bond strengths were obtained with 2% phosphoric acid etchant without ‘tag’ formation, after short term water immersion. Washing the enamel for 60 s instead of 15 s after etching significantly increased the bond strengths obtained with 16 and 30% acid but not with 2%. Etching enamel with phosphoric acid results in deposition of calcium phosphates, which must be removed to give optimal bonding.
Dynamic and static recordings of the comfortable zone
Authors: BRILL N. , FUJII H. , STOLTZE K. , TRYDE G. , KATO H. , Møller E. 
Published: June 2007

SummaryA dynamic and a static method of assessing the comfortable zone by means of a screw jack were compared in 12 subjects. Recorded under dynamic conditions the average width of the comfortable zone was approximately 3·0 mm, and under static conditions approximately 5·0 mm (P < 0·0001). It is suggested that in the dynamic experiments the larger output from receptors in the chewing system was responsible for the narrower zone, i.e. the more precise assessments of the comfortable zone.
Effect of the curing cycle on some properties of a polymethylmethacrylate denture base material
Authors: JAGGER R. G. 
Published: June 2007

SummaryThe properties of a denture base material may be modified by altering both the temperature and the time of heating during the curing cycle. In this study a polymethylmethacrylate denture base containing no crosslinking agent was polymerised using four different curing cycles. The structure of the materials so obtained was investigated by an acid etching technique. The materials were characterized with respect to degree of cure, strength and water sorption.It was concluded that: 1. No correlation was observed between the curing cycles and polymer structure.2. The curing cycle of 7 h at 70°C plus 1 h at 100°C produced best indentation strength and tensile strength.3. A correlation was observed between residual monomer, indentation resistance, tensile strength and water sorption. This suggested that residual monomer concentration is the most important parameter in the determination of the properties of the material investigated in this study.
The clinical significance of median occlusal position
Authors: MCNAMARA DAVID C. 
Published: June 2007

SummaryThe harmony of the occlusal components of the teeth, mandibular joint and muscles, were investigated in 180 human subjects by clinical, dental articulator, radiographic and electrodiagnostic methods. Significant correlations were found between disharmony of these components at median occlusal position (MOP), and with pain‐dysfunction of the masticatory system. Using the standardized stimuli of opening the jaw wide and snapping it shut automatically into MOP, temporalis and masseter muscle co‐ordination and somesthetic reflex effects were quantified. The interval from tooth contact (s) to reinstitution of EMG activity (x), and the EMG silent‐period duration (SP), were prolonged in the patients but returned to within the control range with elimination of the pain‐dysfunction. Muscle incoordination with mandibular dysfunction was prevalent in the patients, and the incidence of osteoarthritis was greatest in those with persistent symptoms. The hypothesis was supported that disharmony of MOP exists in pain‐dysfunction patients—while successful occlusal therapy leads to the restoration of the harmony within the biologic range. This implies physiological significance to this hitherto clinically neglected occlusal position.
Microhardness studies on the setting characteristics of fissure sealants
Authors: YOUNG K.C. , CUMMINGS A. , MAIN C. , GILLESPIE F.C. , STEPHEN K.W. 
Published: June 2007

SummaryThe hardness of five fissure sealants was measured using a Wallace Microhardness Tester and found to continue to increase long after the initial setting. The effect of the intensity of radiation and exposure time on the setting of two u.v. activated sealants (Nuva‐seal and Alphaseal) was also investigated, with higher intensities producing both a more rapid set and greater final hardness. Alphaseal required longer exposure at a given intensity of u.v. radiation to achieve the same hardness as Nuva‐seal, and displayed relatively slow setting in depth, which could give rise to incomplete polymerization during clinical use, resulting in early sealant loss. Thus special care must be taken to ensure that Alphaseal receives an adequate exposure to u.v. radiation, and sources which are suitable for setting Nuva‐seal may not be sufficiently powerful when applying Alphaseal.