bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charecterization of hydroxyapatite powders and compacts at room temprature and after sintering at 1200°C
Authors: ROOTARE HILLAR M. , CRAIG ROBERT G. 
Published: June 2007

SummarySynthetic HAP made in the laboratory as ‘synthetic bone’ may be a possible replacement or repair material, since the mineral phase of dental hard tissue and bone is essentially hydroxyapatite in form. Hydroxyapatite or modified compositions of HAP appear to offer possibilities as a substitute for the original material provided by nature.A high surface area (70·4 m2sol;g) commercially available hydroxyapatite (HAP) of poor crystallinity was converted to a highly crystalline HAP through sintering at 1200°C in an atmosphere of steam and nitrogen. Compacts were made of the powdered HAP from 500 to 25,000 psi and sintered under the same conditions. The changes in the resulting pore volumes, pore sizes, pore size distributions, densities, and surface areas of the sintered compacts were determined by mercury porosimetry. A 20‐fold reduction in open pore volume for sintered compacts was observed. For compacts made at pressures above 5000 psi, the reduction in open pore volume was compensated for by the formation of closed pore volume. The sintering mechanism was attributed mainly to neck formation, growth between particles, diffusion, and plastic deformation.
Activity of temporal and lip muscles during swallowing and chewing
Authors: INGERVALL BENGT 
Published: June 2007

SummaryThe activity of the anterior and posterior portions of the temporal muscle and in the upper and lower lips were studied electromyographically in 50 girls, aged 9–13 years with normal occlusion.The recordings were made during swallowing of water, saliva, apple and peanuts as well as during chewing of apple and peanuts.The maximal mean voltage amplitudes during swallowing varied notably with the test medium and were larger for solid than for fluid media. The amplitudes were the same for both portions of the temporal muscle, but always greater for the lower lip than for the upper. Many girls swallowed fluid media without demonstrable activity of the anterior portion of the temporal muscle, while absence of demonstrable activity in the lips was rare. No correlation was found between the degree of activity of the lips during swallowing of fluid and solid substances.The amplitudes during chewing were the same for both portions of the temporal muscle, but larger for the lower lip than for the upper.The amplitudes found for the two portions of the temporal muscle and for the upper and lower lips were intercorrelated both during swallowing and chewing.No correlation was found between the amplitudes from the lower lip and from the temporal muscle during swallowing. The amplitude from the upper lip during swallowing was correlated only with that from the posterior portion of the temporal muscle. Palpation of muscular activity of the temporal muscle during swallowing is of little or no value for estimating the degree of activity of the lip during swallowing.
In vitro toxicity tests of zinc phosphate cement
Authors: TYAS M. J. 
Published: June 2007

SummaryBHK‐21 (C‐13) cells were exposed to freshly mixed zinc phosphate cement for 0·5, 1 and 2 h in a simulated cavity apparatus. The effect on the cells was evaluated by quantitative measurement of acid phosphatase and succinic dehydrogenase reaction product in order to determine organelle membrane permeability. After 0·5 h cellmaterial contact there was no significant effect. After 1 h cell‐material contact, there was slight labilization of the lysosomal membranes, and a significant decrease in succinic dehydrogenase activity. The mean overall stain density in the experimental cells was 109% and 57% of the control values for acid phosphotase and succinic dehydrogenase respectively. After 2 h cell‐material contact, there was significant labilization of the lysosomal membranes, and also labilization of the mitochondrial membranes. The mean overall stain densities were 114 % and 75 % of the control values for acid phosphatase and succinic dehydrogenase respectively. The relevance of these findings to the in vivo situation is discussed.
Age changes in the perception of comfortable mandibular occlusal positions
Authors: MCMILLAN D.R. , TRYDE G. , STOLTZE K. , MAEDA T. , BRILL N. 
Published: June 2007

SummaryIt has been shown that a zone of comfort in maxillo‐mandibular relationships in edentulous subjects can be identified with some precision. Whilst the neurophysiological mechanism involved has not been explained fully, the phenomenon is influenced by starting position and by fatigue. This experiment was set up to test the hypothesis that age is another significant factor in perception of the comfortable zone.A group of seventeen subjects with a mean age of 62 years and an equivalent younger group, the mean age of which was 28 years, were tested with Timmer screw jacks applied using the central approach to record the upper and lower limits of the zone fifteen times in succession for each subject.A linear statistical model was used to analyse the data from upper and lower borders separately. The results showed that the effect of making successive adjustments, whilst not significant statistically in the young group, was significant in the more elderly. Regression lines from the young group data were horizontal signifying the high degree of accuracy with which their perceptual mechanisms worked: the upwards inclination of those from the more elderly was interpreted as showing that initial appreciations were subjected to constant correction.
Comparison of the accuracy of denture bases by a non‐parametric method
Authors: SONI P. M. , POWERS J. M. , CRAIG R. G. 
Published: June 2007

SummaryA comparison of the accuracy of denture bases made from a conventional acrylic and four modified acrylic resins was made with the use of a non‐parametric method. Twenty‐five identical maxillary stone casts were made and five dentures for each resin were processed by conventional compression moulding techniques. The fit of each denture at the molar‐to‐molar region on its cast was evaluated by five evaluators who independently ranked the twenty‐five dentures from best to worst fit after processing, after polishing, and after storage in water at 37°C for 42 days. The ranking data were analysed by Kendall's coefficient of concordance, the Kruskal‐Wallis statistic, and the Mann‐Whitney test. Excellent agreement among observers was obtained. After storage in water, two modified acrylic resins, Hydrocryl and Vitalon II, had a better fit on their casts than the conventional acrylic, Lucitone Hypro. Lucitone 199 had the same and Hircoe had a poorer fit than Lucitone Hypro.
The effect of silicate cement on the mitochondria and lysosomes of cultured cells assessed by quantitative enzyme histochemistry
Authors: TYAS M. J. 
Published: June 2007

SummaryThe cytotoxic effect of the silicate cement ‘Silicap’ was evaluated in an in vitro system which simulates the clinical usage of the material. BHK‐21 (C‐13) cells on cover slips were exposed to the freshly mixed material for 1h, and stained for the demonstration of succinic dehydrogenase and acid phosphatase. The mean stain density for succinic dehydrogenase and acid phosphatase in the experimental cells was 77% and 153% of the control values respectively. The mechanism of cytotoxicity of ‘Silicap’ is discussed.
A clinical study of marginal integrity and tarnish behaviour of three Cu‐rich amalgam systems
Authors: LARSON T. H. , SABOTT D. , COOLEY R. , GREENER E. H. 
Published: June 2007

SummaryThree high Cu‐γ2 free amalgams and one conventional amalgam were used in a clinical study to evaluate degree of marginal integrity and surface discoloration occurring for time periods of up to two years. Two hundred and seventy restorations were placed in Class I and II cavities in sixty‐two paedodontic patients. Amalgams were prepared from conventional alloy, Cu admixed, Dispersalloy and three parts 50Ag‐20 Sn‐30Cu mixed with one part conventional alloy. Restorations were evaluated by three groups of clinicians. Ridit means obtained from all three groups of evaluations were in good agreement. The lower ridits indicate better marginal integrity and less tarnish. Marginal integrity of amalgams prepared from Cu‐admix did not differ appreciably (0.41) from the ridit associated with initial placement (0.39). Conventional amalgams had the highest ridit (0.65) for marginal integrity whereas the ternary/conventional and Dispersalloy restorations were intermediate (0.55 and 0.52). The ridit for tarnish and surface discoloration was decidedly higher for the Cu‐admix (0.73) than for the other systems investigated which had ridits of the order of 0.50 compared to an initial ridit for tarnish of 0.28.
A comparison of two methods of quantifying masticatory pressures developed under dentures with variable occlusal widths
Authors: ROEDEMA WILLIAM H. 
Published: June 2007

SummaryPressures developed during mastication with removable dental prostheses have beer quantified by two methods. This pilot study (1) compares the peak pressure method of pressure quantification with the integrated curve method of quantification and (2) continues the exploration of the effect of the width of the occlusal table on pressures developed under dentures.A set of specially designed experimental dentures was constructed for one individual. The mandibular experimental denture contained a series of pressure transducers by which masticatory pressures were recorded. These pressures were monitored between the denture base and the residual ridge tissues. Several interchangeable posterior occlusal segments, varying only in the width of the occlusal table, were fabricated for the opposing maxillary denture.Masticatory pressure and total ridge pressure were quantified by the integrated curve method and the peak pressure method. Both methods indicated a direct relationship between masticatory pressures produced and the width of the occlusal table. A similar direct relationship between total ridge pressure and occlusal width was suggested statistically by the integrated curve method, and graphically by both methods.
The Langerhans cell density of palatal epithelium in denture and non‐denture wearers, as correlated with other parameters of the palatal mucosa
Authors: VAN MENS P. R. , JAMES J. 
Published: June 2007

SummaryA quantitative histological investigation was carried out on biopsy specimens taken from patients suffering from denture sore mouth. The results were compared with those obtained in investigations on denture and non‐denture wearers. The sections were studied by standardized quantitative morphometric methods. After 4 years the denture bearing palatal epithelium from both groups, normal denture wearers and the patients suffering from denture sore mouth did not show changes in mean thickness of the epithelium as compared with the controls. The mitotic index in denture bearing epithelium from patients suffering from denture sore mouth was three times lower than in the epithelium of the normal denture wearers. The number of Langerhans cells correlated with the mitotic indices of the group of denture wearers and nondenture wearers. The group of denture sore mouth patients showing a low mitotic index showed a high number of Langerhans cells in their palatal epithelium. The three groups of patients investigated did not show differences in density of mast cells in the lamina propria of their palatal epithelium.
Evaluation of endosseous implant abutments as a base for fixed prosthetic appliances. A preliminary clinical study
Authors: WIE H. , LARHEIM T. A. , KARLSEN K. 
Published: June 2007

SummaryIn the present 2‐year report nineteen Linkow blade implants with a total of twentyseven perforating posts were assessed. All implants included were considered functionally successful and served as abutments for fixed prosthetic appliances. Periodontal probe and radiographic measurements of bone loss around the perforating implant posts, and registratration of plaque and gingival index scores were performed every 6 months.During the first 4–6 weeks after implantation a vertical bone loss approximating an average of 1–2 mm occurred in the neck area of the implants. After this initial resorption, bone loss proceeded at a slower rate. The mean annual crest reduction was approximately 0.1 mm from the first to the fourth examination, as assessed from radiographic measurements.Periodontal probe measurements, showing a mean annual crest reduction of 0.2 mm, usually exhibited higher values than corresponding radiographic measurements at both implants and abutment teeth.At implants there was a significant positive correlation between plaque and gingivitis after 18 and 24 months, but not before that time. No correlation was seen between gingival index scores and the degree of bone resorption.
Book Reviews and Notices
Authors: Rock W. P. , Foster T. D. 
Published: June 2007

Books reviewed in this article.Preventive Dentistry By Leon Silverstone.The European Journal of Orthodontics Vol. 1 No. 1 January 1979.Textbook of Oral Biology Ed. by J. H. Shaw E. A. Sweeney C. C. Cappucino and S. M. Meller..Sectional Dentures By E. Pullen‐Warner and P. R. L'Estrange.Elements of Dental Materials By R. W. Phillips.
Short term evaluation of counselling and occlusal adjustment in patients with mandibular dysfunction involving the temporomandibular joint
Authors: KOPP S. 
Published: June 2007

SummaryThe effect of counselling and occlusal adjustment was investigated in thirty patients with mandibular dysfunction involving the temporomandibular joint (TMJ). The patients were examined at three visits 6 weeks apart. At the first visit all patients received counselling. At the second visit they were divided into two groups, one receiving occlusal adjustment and the other not receiving treatment. The degree of mandibular dysfunction was assessed by the patients according to a five grade scale and by the clinical dysfunction index according to Helkimo (1974a). The score of subjective dysfunction was reduced significantly during the period following counselling and 60% of the patients improved. No effect was found on the clinical dysfunction score. The score of clinical dysfunction was reduced significantly during the period following occlusal adjustment and 67% of the patients improved. No further effect could be detected on the subjective dysfunction score. The correlation between changes in subjective and clinical dysfunction was poor, but changes in the subjective score were generally associated with changes in the clinical score. It was concluded that counselling may reduce the subjective symptoms; and occlusal adjustment the clinical signs of mandibular dysfunction involving the TMJ, but that the individual variation in response is substantial.
Roentgenological detection of casting defects in cobalt‐chromium alloy frameworks
Authors: WICTORIN L. , JULIN P. , MÖLLERSTEN L. 
Published: June 2007

SummaryA method for non‐destructive X‐ray investigation of casting defects in cobalt‐chromium prosthetic frameworks has been developed and tested. The attenuation properties of a cobalt‐chromium alloy were studied. A dental X‐ray machine with a tube voltage working at 70 kVp and a focus‐film distance of 45–50 cm on dental ultraspeed film made it possible to detect defects representing 10% or less of the thickness of cobalt‐chromium details with dimensions between 0.6 and 3.0 mm.The frequency and site of internal defects in sixty‐six frameworks were investigated. Of the sixty‐six frameworks only two were without roentgenologically visible defects. In the other sixty‐four frameworks 294 pores or cracks were recorded. The defects were mostly situated in the saddles. Porosities occurred in 53% of the saddlebar regions. The results confirmed the need for a non‐destructive routine test of prosthetic frameworks.
Diametral tensile strength of twenty‐three hardened commercial amalgams
Authors: VRIJHOEF M. M. A. , VERMEERSCH A. G. , SPANAUF A. J. 
Published: June 2007

SummaryIn view of the ever increasing number of high copper alloys, it was the aim of this study to investigate the tensile strength property of some of the new alloy systems. The factors alloy system and heat treatment were investigated in relation to the tensile strength. The factors alloy system as well as the heat treatment turned out to be significant. The study suggests that the introduction of ‘dispersion’ alloys did not change the dental picture as to the property of the tensile strength. The selection of strength values in the range of 35–55 MN/m2 for the diametral tensile strength probably have no clinical relevancy as to the prevention of bulk fractures of amalgam restorations under oral conditions.
Influence of muscle pain tolerance on muscle pain threshold in experimental tooth clenching in man
Authors: CHRISTENSEN L. V. 
Published: June 2007

SummaryTen adults and ten children exercised maximal voluntary tooth clenching until pains appeared in the jaw muscles, i.e. the muscle pain threshold of tooth clenching was determined. Subsequently, the subjects were instructed to exercise tooth clenching until they were forced to stop because of intolerable pains and exhaustion of the contracting muscles, i.e. the muscle pain tolerance of tooth clenching was recorded, and during these bouts of clenching the pain threshold was also determined. In adults, determination of the pain tolerance decreased the pain threshold by 19%, and in children it either decreased the pain threshold by 20%, or increased it by 56%. It is proposed to introduce the muscle pain tolerance of tooth clenching as an adjunct in the clinical examination of cases of facial pains presumed to originate from the jaw muscles, but the test should be interpreted with caution.
Investigation of the strain produced in maxillary complete dentures in function
Authors: STAFFORD G. D. , GRIFFITHS D. W. 
Published: June 2007

SummaryAn experiment has been completed to investigate the strain levels obtained on polymethylmethacrylate dentures in function when biting and swallowing. The use of stacked, rosette strain gauges enabled the magnitude of strain in the material underlying the gauge to be calculated and, in addition, the direction of the principal maximum and minimum strain was also calculated.Strain in the denture base was measured in biting and swallowing with a normal occlusion, when the occlusal contact area was narrowed, and with the rosette gauges.
Tensile strength of the bond between resin to enamel etched with phosphoric acid containing fluoride
Authors: GRAJOWER R. , GLICK A. , GEDALIA I. , KOCHAVI D. 
Published: June 2007

SummaryThe tensile bond strength of Epoxylite 9075 and Enamelite to enamel treated with NaF and SnF2, at two concentrations, in the etching acid (H3PO4) was determined. The average fracture stress of those samples in which fracture occurred in the resin only, may be considered as the tensile strength of the resin, 69·8 + 5·6 kg/cm2. The mean fracture stresses of the Epoxy 9075 systems etched with pure phosphoric acid or with acid solutions containing 0.5 % F salts were significantly higher than those treated with acid solutions containing 2 % F salts. Incorporation of NaE or SnF2 in the etching solutions highly increased the fluoride concentration of enamel. The fluoride increase depended on the fluoride concentration of the etching solution and was greater for NaF than SnF2.
Effect of toothbrush stimulation on temperature of gingival and alveolar mucosae
Authors: KROONE H. , MAEDA T. , STOLTZE K. , BRILL N. , Tryde Gerd 
Published: June 2007

SummaryThermometry was used to study the effect of applying a toothbrush to three types of oral mucosae, in forty dental students. Brushing with an electric tooth brush resulted in an immediate fall in temperature, but 3 min later the temperature was significantly higher than before stimulation. The temperature changes were greater in gingival crevice and attached gingiva compared with alveolar mucosa. Moreover, it was found that a static application of the toothbrush produced temperature changes which were equal to those following a dynamic application.
Fluoride uptake by cavity walls following application of Duraphat® around amalgam restorations
Authors: BJØRGTVEIT ANNE 
Published: June 2007

SummaryThis study aimed to assess possible fluoride uptake by cavity walls following a single application of Duraphat® around class V or I amalgam restorations which were inserted in seventeen human premolars in vitro and in vivo. Six cavities were lined with one layer of Copalite® insertion of the restorations.After a week in vivo and 12–24 h in vitro, 200–300 μm thick longitudinal sections passing through the cavities were prepared. By electron probe microanalysis F concentrations ranging from 2000 to 6000 ppm were measured near the surface of the cavity walls. Copalite seemed to inhibit F uptake. The study indicates that F ions released from the Duraphat varnish have been taken up by the cavity walls. Such uptake may influence development of secondary caries (wall lesions) in connection with amalgam restorations.
Concatenation of variations in plaque formation with variations in crevicular temperature
Authors: MAEDA T. , KROONE H. , STOLTZE K. , RUNOV J. , El GHAMRAWY E. , BRILL N. , Tryde Gerd 
Published: June 2007

SummaryThe hypothesis was tested that variations in the temperature of gingival crevices are linked to variations in plaque formation. Fifty‐nine abutment teeth to removable partial dentures were studied during four experiments, under various conditions of plaque formation, i.e. not brushing the teeth whilst wearing and not wearing dentures, and performing ordinary and then specialized tooth brushing whilst wearing dentures. The collation of temperature curves with plaque curves revealed a proportional relationship between the rate and magnitude of plaque formation and the rate and magnitude of the recorded temperature changes. Furthermore, the removal of plaque resulted in a reversal of induced temperature rises. The lowest crevicular temperatures were obtained with the practice of the specialized tooth brushing.
Some subjective‐experiential parameters of experimental tooth clenching in children
Authors: CHRISTENSEN L. V. 
Published: June 2007

SummaryTwelve children, aged 9–14 years, exercised maximal voluntary tooth clenching until facial pains were experienced and could no longer be endured. The pains were localized in the masseter and temporalis muscles and, occasionally, in the supra‐orbital region. After onset of clenching pains appeared, on average, in 49 s (pain threshold) and they could, on average, be endured for 118 s (pain tolerance). The pain threshold varied significantly between individuals, but not within individuals. The number of pain sites, and the number of teeth in contact during clenching, did not determine the moment of onset of pains, nor the ability to endure pains. The pain tolerance did not seem to be influenced by the pain threshold.
Continuing changes in the contour of the maxillary residual alveolar ridge
Authors: JACKSON R. A. , RALPH W. J. 
Published: June 2007

SummaryUsing a cast measuring technique, the change in contour of the residual maxillary alveolar ridge of patients who have worn dentures for a number of years and are then fitted with new dentures, has been investigated. The study confirmed that even after 30 years of denture wearing, further bone resorption may occur beneath new dentures.