bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental studies on masseter muscle grafts in rats: comparison of donor muscles
Authors: MONG F. S. F. 
Published: June 2007

SummaryExperimental studies were performed in rats to explore the feasibility of using limb muscles to replace masticatory masseter muscles. The results showed that if several small fusiform muscles such as the extensor digitorum longus (EDL), soleus (SOL) and plantaris (PLT) were used for the grafting, the graft regenerated and matured fully in the masseter bed, although the weights were lower than those of contralateral control masseter muscles. If a multipennate muscle such as the gastrocnemius was used for the grafting, the graft also regenerated but later degenerated due to the lack of innervation. This is probably due to the excessive amount of connective tissue in the multipennate muscle. The connective tissue proliferates faster than the regeneration of muscle fibres and, thus, renders the innervation of muscle fibres difficult. Other factors pertinent to the possible clinical application of muscle transplantation in oral region are discussed.
A laboratory and clinical evaluation of three dental luting cements
Authors: KNIBBS P. J. , WALLS A. W. G. 
Published: June 2007

SummaryThe loss of material from specimens of three luting cements was measured after continuous erosion cycling in the laboratory. The glass ionomer luting cement showed significantly less material loss than the zinc polycarboxylate and zinc phosphate luting cements.Two hundred and fifty restorations cemented with one of the three materials were studied clinically for marginal integrity and retention over 3–5 years. The data were tested using survival analysis. Zinc phosphate cement gave the best clinical performance. Possible explanations for the poor correlation between the findings in the laboratory and clinical study are discussed.
Increase in compressive strength of glass ionomer restorative materials with respect to time: a guide to their suitability for use in posterior primary dentition
Authors: WILLIAMS J. A. , BILLINGTON R.W. 
Published: June 2007

SummaryGlass ionomer restorative cements have been used in anterior restorations for a number of years but have not been considered strong enough for use in posterior restorations. The compressive strengths of a number of materials currently available were measured at 30min, 1 hour and 24 hours. It was concluded that some of the materials might be considered for posterior restorations in deciduous teeth where no other considerations, such as radiopacity, apply.
Effect of substrate age on microleakage of dentine adhesive agents
Authors: CRIM G. A. 
Published: June 2007

SummaryThe present investigation was performed to determine the effect of substrate age on the microleakage of two new dentine adhesive agents. Class 5 preparations were placed at the cemento‐enamel junctions of two groups of extracted human molar teeth which had been stored in water for less than 3 months or for approximately 18 months. Silux Plus was used to restore cavities that had been primed with either Scotchbond 2 or GLUMA. The restored teeth were thermally stressed for 100 temperature cycles and placed in a dye solution for 24 h. Leakage was measured under a microscope at ×50 magnification. Under the experimental conditions, there was no significant difference in microleakage which could be attributed to the two different post‐extraction tooth storage periods.
Studies in oral galvanism: mercury and copper levels in urine, blood and saliva in submerged electrically cutting divers
Authors: ÖRTENDAHL T. W. , HOLLAND R. I. , RÖCKERT H. O. E. 
Published: June 2007

SummaryThe aim of the study was to analyse the concentration levels of mercury and copper in urine, blood/blood plasma and saliva in relation to intra‐oral electrical activity. Five Swedish Navy divers took part in the study in order to determine whether working submerged with electrical cutting equipment produced changes in the presence and level of oral galvanism and whether this posed a serious occupational health risk.The investigation concluded that the risk of seriously increased intra‐oral electrical activity during welding or cutting activities was small. Development of the study is suggested, with long‐term sampling of urine and blood samples of divers supported.
Finite element analysis of three‐ and four‐unit bridges
Authors: FARAH J. W. , CRAIG R.G. , MEROUEH K. A. 
Published: June 2007

SummaryA two‐dimensional finite element model of a mandibular quadrant was used to examine differences in magnitude of the principal stresses from the placement of three‐ and four‐unit bridges. The area of interest spanned the first premolar to the second molar. Loading conditions were (i) vertical and distributed and (ii) 30° to the vertical and concentrated. The principal stresses were calculated and compared for: (i) the first molar removed with the remaining bone either cancellous or cancellous surrounded by a cortical shell; (ii) as in (i) but with the second premolar and first molar removed; (iii) a three‐unit bridge spanning the second premolar to the second molar; and (iv) a four‐unit bridge spanning the first premolar to the second molar. Each tooth was supported by periodontal ligaments, cortical and cancellous bone with each assigned the appropriate physical constants. Removal of the first molar resulted in considerable variation of the stresses especially when the cortical shell was replaced by cancellous bone. Because of the lower modulus of cancellous bone and its lower load‐bearing capabilities the stresses were three to ten times lower and more uniform within the cancellous bone. Generally, the addition of a bridge resulted in lower and better distributed σmin stresses. The bridge also resulted in higher tensile stresses distal to the abutment teeth which theoretically could result in bone deposition. No significant differences in magnitude were observed between the three‐ and four‐unit bridge. From a stress standpoint the bridges resulted in more uniform stress distribution around the abutments and an increase in the tensile stresses distal to the abutments. Such findings support the placement of a fixed bridge to maintain bone in an edentulous area.
A laboratory examination of the behaviour of cast cobalt‐chromium clasps
Authors: GHANI F. , MAHOOD M. 
Published: June 2007

SummaryCast cobalt‐chromium clasps, long and short, tapered and untapered, were studied. It is shown that the behaviour of apparently identical clasps is inconsistent. Permanent deformation appears to commence during the first month of wear, and after 6 months' wear the retentive quality of almost all of the clasps is impaired.
A preliminary electromyographic study of bite force and jaw‐closing muscle fatigue in human subjects with advanced tooth wear
Authors: LYONS M.F. , BAXENDALE R.H. 
Published: June 2007

SummaryThe maximum bite force was recorded in five experimental volunteers with advanced tooth wear and five control volunteers who showed no abnormal wear. All subjects were then asked to maintain a force of 50% of the maximum for as long as possible while surface electromyograms from the masseter and temporalis muscles were recorded. The bite force and endurance time were found to be slightly increased in the experimental group, but no conclusions could be drawn regarding the state of fatigue. Two significant problems with regard to fatigue studies of the jaw‐closing muscles emerged from the study, namely the use of the canine position for recording of the force, and the thickness of the force meter.
Occlusal force distribution in lower complete overdentures
Authors: OGATA K. , AOKI T. , MATSUNAGA T. , UCHIDA K. 
Published: June 2007

SummaryA space between the denture base and a root cap can effectively control the distribution ratio of occlusal force to abutment teeth and an alveolar ridge. The purpose of this study on abutments was to analyse the effect of variation in space (0 mm (no space), 0–3 mm and 0–6 mm) on the above ratio.Six subjects, 38–65 years of age, each with an edentulous maxilla and several teeth remaining in the mandible, were selected for this experiment. The lower experimental denture had embedded a transducer which could detect a change in the vertical force applied to the experimental tooth. This transducer was capable of changing the vertical space between a denture base and an experimental tooth. Each subject was asked to increase the occlusal force applied to the denture from zero to the maximum loading rate of 5 kgf s−1. The occlusal force and the force exerted on the experimental tooth were recorded in each space 1 month after insertion of new dentures. The following results were obtained: (i) when the occlusal force was applied to the artificial tooth just above the abutment tooth, the mean ratio in the 0 mm space was 60% of the force applied to the denture, the ratio in the 0–3 mm space was 50%, and the ratio in the 0–6 mm space was 30%; (ii) if the occlusal force was applied to the point 10 mm distant from the point just above the experimental tooth, the magnitude of the ratio was decreased by 60–80%.
The prevalence of sensitivity to constituents of dental alloys
Authors: NAMIKOSHI T. , YOSHIMATSU T. , SUGA K. , FUJII H. , YASUDA K. 
Published: June 2007

SummaryNinety‐five participants were epicutaneous patch tested in order to determine the prevalence of sensitivity to components of dental alloys. Seventeen individuals (17.9%) developed allergic reactions, which were caused by mercury (10.5%), copper (2.1%), nickel, cobalt, tin, gold and zinc (1.1%). Eight of 17 allergic responders had a history of dermatitis from metal contact. The results show that there is a need for careful immunological considerations during the selection of suitable alloys, particularly in the case of patients with lesions suspected of being caused by dental alloys.
Human jaw‐opening muscle responses elicited by multiple‐site electrical stimulation
Authors: YAMADA YOSHIAKI , HARAGUCHI NAOHISA , OI KUMIKO , ASH MAJOR M. 
Published: June 2007

SummaryElectrical stimuli were applied to subjects' upper and/or lower gingivae around the right canines; (i) during maintained relaxation of masticatory muscles; (ii) at an active opening position; (iii) while clenching in an incisal edge‐to‐edge contact (IEC) position; and (iv) at the wide‐open position. Reflex responses of the suprahyoid and jaw‐closing muscles were obtained using surface electrodes. The electrical stimulation produced segmented reflex excitation(s) in the suprahyoid muscle and conventional reflex excitation and/or inhibition in the jaw‐closing muscles when some background activity was maintained in the muscle(s). The excitatory reflex in the suprahyoid muscle responded to multiple site electrical stimulation which was delivered on both the upper and lower jaw simultaneously rather than to single site stimulation. Also, the responses depended on the intensity of the electrical stimulation. In particular, stronger intensities resulted in longer latencies. The results support the suggestions in our previous studies with mechanical stimuli, i.e. that the human jaw‐opening reflex can be obtained only when some background activity is maintained in the jaw openers, perhaps due to low threshold afferent input, and that spatial summation may be effective for the reflex.
Etched glass ionomer liners: surface properties and interfacial profile with composite resins
Authors: PAPAGIANNOULIS L. , ELIADES G. , LEKKA M. 
Published: June 2007

SummaryThe purpose of this study was to assess the surface alterations induced by acid etching on two glass ionomer lining cements (Ketac Bond, G‐C lining cement) and to evaluate their interface with a composite resin (Herculite XR) following various surface treatments. The changes in the surface composition and topography of the etched liners were studied by electron microprobe and ESCA analyses. The interfacial treatments performed on the ionomer surfaces were: (i) application of a bonding resin; (ii) 20‐s acid etching and application of a bonding resin; (iii) application of a dental adhesive based on a chlorophosphate ester of BisGMA (Scotchbond LC), without acid etching. The interfacial sealing efficiency of these treatments was studied by the silver nitrate microleakage technique combined with optical and electron microscopy. According to the results the etched surfaces of both the liners present excessive porosity with glass and matrix dissolution. Significant changes in the surface chemistry of the liners were detected indicating severe degradation. The microleakage study revealed interfacial gaps and fractures in the etched samples. The best results were obtained from the non‐etched ionomer liners which were subjected to the adhesive treatment. The efficiency of acid etching as a necessary step in the ‘layered’ technique is seriously questioned.
The effect of sustained release application of chlorhexidine on salivary levels of Streptococcus mutans in partial denture wearers
Authors: ZYSKIND D. , STEINBERG D. , STABHOLZ A. , FRIEDMAN M. , SELA M. N. 
Published: June 2007

SummaryThe effect of a slow‐releasing dosage (SRD) coating of chlorhexidine on the salivary levels of Streptococcus mutans and on plaque index scores in patients with removable partial dentures (RPD) was tested. The SRD proved to be effective in maintaining a low level of S. mutans counts after mechanical cleaning, as compared to a baseline established during the control period. Plaque index scores were lower following the treatment and correlated with the microbiological results. Our findings indicate that a single application of sustained‐release chlorhexidine to removable partial dentures effectively maintains S. mutans levels as well as reducing the plaque score for a minimum period of 1 week.
Evaluation of the properties of a new pour denture base material utilizing a modified technique and initiator system
Authors: FRANGOU M. , HUGGETT R. , STAFFORD G. D. 
Published: June 2007

SummaryA new denture base system, Provac, has been developed for complete and partial dentures, and for relining. The Provac material is methyl methacrylate, which cures with the aid of barbituric acid. In this study the physical and mechanical properties of the new resin were investigated and compared with those of a conventional autopolymerizing material (Croform) and a conventional heat polymerizing material (Trevalon).It was found that the dimensional accuracy of Provac was better than that of the conventional heat‐curing material, Trevalon, and the denture was finished more easily and quickly. The physical and mechanical properties of Provac resin were found to be similar to those of the other two materials, and conformed to the International Specifications for denture base materials. The residual monomer levels in Provac material were always higher than the minimal obtainable values associated with conventional heat‐cured materials when these were polymerized with a terminal boil during the curing cycle.
Studies on the temporomandibular joints of an eighteenth‐century London population (Spitalfields)
Authors: WHITTAKER D. K. , JONES J. W. , EDWARDS P. W. , MOLLESON T. 
Published: June 2007

SummaryThe mandibular condyles and glenoid fossae of 93 adult skulls of known age at death were studied in skeletons exhumed from the crypt of Christ Church, Spitalfields, London. Antero‐posterior and mesio‐lateral dimensions were recorded, as were the shapes together with form and surface changes. In addition, the teeth present and the extent of occlusal attrition were noted.There was sexual dimorphism in the mesio‐lateral size of the condyle, and although ante‐mortem tooth loss was higher than in previously studied Romano‐British skulls, form and surface changes of the condyle were less marked. It is concluded that tooth loss is not the main factor involved in remodelling of the condyle.
Wear of prosthodontic materials—an in vivo study
Authors: EKFELDT A. , ÖILO G. 
Published: June 2007

SummaryThe aim of this investigation was to study quantitative and qualitative aspects of the wear process of some prosthodontic materials in three different persons in vivo. The in vivo models combined two methods: removable double crowns and a replica technique. The wear resistance of gold (types III and IV), porcelain and a microfilled resin was studied opposing metal ceramic crowns and in one person when opposing all four materials. All three persons had earlier histories of occlusal wear of teeth and/or restorations.The wear rate of gold and porcelain showed equal values antagonizing metal ceramic crowns in all three persons. The microfilled resin had a wear rate three or four times higher in the same situations. No significant difference in wear resistance could be found between type III and type IV gold alloys. The wear mechanism seemed to be a fatigue type in porcelain, and in gold a combined fatigue and abrasive type of wear. The microfilled resin showed mainly a fatigue type of wear but some observations indicating a tribochemical reaction were also made.
Determination of occlusal vertical dimension by means of controlled pressure against tissues supporting a complete denture
Authors: MUNAKATA Y. , KASAI S. 
Published: June 2007

SummaryIn order to establish the vertical dimension (VD) of a complete denture prosthesis, a new method of determining a comfortable mandibular position was tested using a recently designed hydraulic jack (hydraulic vertical displacement meter) in five edentulous patients. The device was designed so as to vary occlusal height by means of an extraoral jig connected to intra‐oral hydraulic jacks, and to distribute the bite pressure applied against the denture‐supporting tissue in approximately the same pattern as that produced by a denture with a VD preferred by the patient. The most comfortable mandibular position determined by this method coincided remarkably with the preferred VD of each patient in our study, indicating that the new device may be used to establish VD for complete denture construction.
Clinical compliance of two resilient denture liners
Authors: GRAHAM B.S. , JONES D.W. , THOMSON J.P. , JOHNSON J.A. 
Published: June 2007

SummaryAlthough intra‐oral‐setting resilient denture liners have been used for 30 years to treat the severely resorbed residual ridges of elderly patients, their clinical physical properties are not well understood.The effect of clinical usage on the compliance (compressibility, flexibility) of two intra‐oral‐setting resilient denture liners was measured in 10 patients, for up to 30 days. The clinical compliance of Material B (Coe‐Comfort®) was found to be significantly greater than Material A (Veltec®) for up to 14 days. At 24 h both materials had significant compliance reductions from the original 1 h measurement. These compliance reductions continued throughout the testing period. For up to 14 days of clinical usage there were no significant differences between the compliance reductions of the two materials. The study suggests that (i) Material B would provide more effective tissue conditioning of abused residual ridge mucosa than Material A; and (ii) a functional impression made with these materials should be left in the mouth for at least 24 h before the cast is poured.
The effects of an occlusal splint on the electromyographic activities of the temporal and masseter muscles during maximal clenching in patients with a habit of nocturnal bruxism and signs and symptoms of craniomandibular disorders
Authors: HOLMGREN K. , SHEIKHOLESLAM A. , RIISE C. , KOPP S. 
Published: June 2007

SummaryThe effects of a full arch maxillary plane occlusal splint on the level of electromyographic (EMG) activity in the anterior temporal and masseter muscles during maximal clenching were studied in 31 patients with a habit of nocturnal bruxism and signs and symptoms of craniomandibular disorders, before and after occlusal splint therapy. The results showed, before treatment, that the occlusal splint changed significantly (in 71% of patients) the level of EMG activity during maximal clenching. However, these changes were not consistent and differed between patients and even, in some patients, between muscles. After long‐term occlusal splint therapy and improvement of the signs and symptoms of craniomandibular disorders, the number of patients who had an identical level of EMG activity during maximal clenching in the intercuspal position and on the occlusal splint tended to increase. Moreover, in these patients the level of symmetry of action in pairs of muscles during maximal clenching was strong, and the splint did not change this level of symmetry.
Correlation between degree of conversion, filler concentration and mechanical properties of posterior composite resins
Authors: CHUNG K.‐H. , GREENER E. H. 
Published: June 2007

SummaryThe degree of conversion, filler concentration and mechanical properties of seven proprietary light‐cured posterior composite resins were investigated. The degree of conversion of composites ranged from 43.5–73.8%. The weight fraction of filler that was obtained was in the range 66.4–85.2%. The volume fraction varied from 58.2–74.2%. The mean values of the observed compressive and diametral tensile strengths ranged from 242.3–324.7 MPa and from 39.8–62.6 MPa, respectively. The Knoop hardness numbers ranged from 41.8–81.9. Significant correlations were observed between the volume fraction of filler and the diametral tensile strength (r=0.89), and between the volume fraction of filler and the Knoop hardness number (r=0.89). No correlation was found between the degree of conversion and any of the mechanical properties of the composite resins tested. Because of the positive correlations between the volume fraction of filler and the diametral tensile strength, and between the volume fraction of filler and the Knoop hardness numbers, it is concluded that the filler concentration plays a prominent role in determining the properties of contemporary posterior composite resins.
An electromyographic study of aspects of ‘deprogramming’ of human jaw muscles
Authors: DONEGAN S. J. , CARR A. B. , CHRISTENSEN L. V. , ZIEBERT G. J. 
Published: June 2007

SummarySurface electromyograms from the right and left masseter and anterior temporalis muscles were used to detect peripheral correlates of deprogramming, also known as programming and reprogramming, of jaw elevator muscles. Putative deprogramming was attempted through the clinically recommended use of a leaf gauge, placed for 15 min between the maxillary and mandibular anterior teeth and disoccluding the posterior teeth by about 2 mm. Studied contractile activities were those of postural activity (subconscious, semi‐isometric, minimal activity) and intercuspal teeth clenching (conscious, isometric, maximal activity). Use of the leaf gauge did not affect normalized postural activity (about 4%), the duration (about 900 ms) and static work efforts of clenching (about 1200 μV.s), the time to peak mean voltage of clenching (about 400 ms), and the peak mean voltage of clenching (about 300 μV). Activity and asymmetry indices showed that the studied motor innervation patterns were not changed by the leaf gauge.
Effects of lesions to the trigeminal motor nucleus on temporomandibular disc morphology
Authors: BYRD K. E. , STEIN S. T. 
Published: June 2007

SummaryStereotaxic surgery was performed on the trigeminal motor nuclei (TMNu) of 47 actively growing rats in order to test the effects of neuromuscular alterations on TMJ disc morphology. Lesioned animals received a small electrolytic lesion to their leftside TMNu, while shams had their TMNu stimulated without an actual lesion being produced. Both lesioned and sham‐lesioned animals demonstrated significant (P<0.05; P<0.01) morphological alterations of their discs 28, 56, and 84 days postoperatively. Data indicated that (i) TMNu lesions do indeed affect disc morphology, and (ii) even subtle damage to trigeminal motoneurones can influence TMJ disc morphology. It is therefore suggested that at least some TMJ disease processes have a neuromuscular basis.