摘要:

SUMMARYThe release of elements from dental casting alloys is a continuing concern because of the potentially harmful biological effects the elements may have on local tissues. The surfaces of the alloys appear to be most important in controlling the release of these elements. In the current study, the surfaces of high‐, reduced‐, and no‐gold dental alloys were analysed by X‐ray photoelectron spectroscopy before and after they were exposed to a biological medium for up to 96 h. The goal was to relate the release of elements from these alloys to their surface composition, and to determine the depth of the effect of the medium. The depth of the effect of the exposure was determined by argon milling of the alloy surface after exposure to the medium. Elements that were released into the medium were measured by means of atomic absorption spectroscopy. The release of elements from alloys was greater when the atomic ratio of noble to non‐noble elements at the surface was less than 1. The depth of the effect of the medium varied with the alloy, but was always less than 100 Å. The surface composition was significantly different from layers only 5 Å below. It was concluded that the surface concentration of noble elements is important in controlling the release of non‐noble elements from these alloys, and the surface composition appeared to be only one or two atomic layers thick. of the three types of alloys, the high‐gold alloy appeared to develop the most stable surface composition which released the lowest lev

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00896.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SUMMARYIn order to determine the feasibility of constructing fixed partial dentures using glass‐ceramic materials, the flexural strength and marginal fit of three experimental glass ceramic materials, and DICOR® as control, were studied. The flexural strength ranged from 1058 MPa to 1295 MPa. Ceramic and alumina addition provided significant strength as tested by ANOVA and multiple range tests (P<0.05). The range for the cemented bridge margins was from 48.9 μm to 80.4 μm. The tested ceramics had no statistically significant differences in margin openings for the same sites (P<0.05). However, the openings on the mesial side of the premolar abutment and the distal end of the molar abutment of the fixed partial denture did have statistically significant differences (P<0.01). Appropriate addition of alumina led to an increase in bending strength. The alumina stabilizes and strengthens the glass‐ceramic material by incorporation into the silicone n

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00897.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SUMMARYThe periodontal regeneration of interproximal bone defects of the posterior teeth produced by guided tissue regeneration (GTR), with expanded Polytetrafluoroethylene barrier membranes and conventional therapy, was clinically evaluated in 20 intrabony periodontal defects in 10 patients. The material included the presence of at least two proximal angular lesions for the same patient, probing pocket depth ≥ 6 mm, bone defect depth ≥ 3 mm, and 2‐wall defects with crestal involvement relative to the tooth circumference ranging from 90 to 270°. Healing was clinically evaluated by surgical re‐entry of GTR‐treated sites (10 sites) and debridement only sites (10 sites) 1 year after initial surgery following a strict plaque control regimen. A significant correlation was observed between probing depth reduction, attachment gain and defect depth (test sites); there was increased bone fill in GTR‐treated lesions of 2.95 ± 1.3 mm corresponding to a 69.4% improvement compared to control sites, and 1–3 ± 1.0 mm corresponding to a 32% improvement (P<0.0039). The results demonstrated that bone regeneration is highly reliable, as compared to conventional therapy, in cases of severe periodontal bone loss from posterior teeth provided that the principles of

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00898.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SUMMARYSugar and agar balls containing barium were made for the fluoroscopic observation of the bolus position during habitual side chewing in 13 adult males (aged from 20 to 28 years) who had a complete dentition and healthy masticatory system. The test foods had constant size, shape, weight and known hardness, i.e. type 1, 20 kg; type 2, 40 kg; type 3, 1.0 kg and type 4, 0.5 kg. These four types of test foods were chewed randomly in a fluoroscopic room. The jaw separation distance and the bolus position during first bite and crushing bite were observed. The influence of the chewing order of four types of test foods on the bolus position was also recorded. It was found that both hard and soft test foods were most often crushed at the first molar area, and the separation distance during the crushing bite was only slightly wider than the diameter of the food. The first bite jaw separation distance for hard food chewing was significantly wider than soft food chewing and the later in the chewing order the wider the separation distance. The effect of chewing order was not significant on the position and jaw separation distance of the crushing bite.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00899.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SUMMARYThe occlusal conditions of periodontitis patients were investigated by using a computerized monitoring device. Thirty‐three mild to severe periodontitis patients were enrolled in the study and they were categorized into three groups by their periodontitis severity. Each subject answered a preliminary questionnaire, received routine dental examinations, and underwent MKG/EMG tests using the K6 Diagnostic System. Clinical manifestations of periodontitis were confirmed by the questionnaire and the routine clinical examinations. According to the MKG tests, the traces of maximum opening distance and vertical freeway space showed no significant statistical difference among the groups. However, the velocity of terminal tooth contact was significantly delayed in the severe periodontitis group. According to the EMG tests, there was no significant difference in the rest mode EMG activities, but the function mode EMG activities significantly weakened in the severe periodontitis group. These results showed that severe periodontitis patients had poor occlusal conditions that might have been triggered by the instability of centric occlusion due to attachment los

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00900.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SUMMARYExperimental equipment for recording mandibular excursive position during nocturnal bruxism has been devised. The equipment consists of chromium‐cobalt alloy cast frameworks for each upper and lower dental arch and two pairs of tiny magnetic sensors and magnets, capable of electromyographic (EMG) recordings of the bilateral masseter muscles and simultaneously recording mandibular position. The two subjects tested were confirmed to be bruxing during sleeping. Although EMG records for the two subjects showed a common EMG pattern as a bruxer, the sensor records revealed that one subject was a bilateral bruxer and the other bruxed almost unilaterally. The present study demonstrated that this newly devised equipment is practical for studying mandibular position during nocturnal bruxis

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00901.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SUMMARYThe occurrence of canine tooth dimorphism in Indian subjects has been investigated and the use of two statistical methods of evaluation compared. These were the methods of N.G. Rao and co‐workers published in 1988 and quadratic discriminant analysis for correct classification of sex. Parameters considered were (i) the mesiodistal width of maxillary and mandibular canines, (ii) the maxillary canine arch width (intercanine distance) and (iii) the mandibular canine arch width. The results indicated significant dimorphism of the maxillary and mandibular canine teeth. When the results of the arch widths were subjected to the two statistical methods, differing results were obtained in the accuracy of sex classification. The percentage of correct classifications of sex was higher when using quadratic discriminant analysi

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00902.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SUMMARYThe utility of the amide II absorption band at 1537 cm−1as internal reference for calculation of monomer conversion in urethane dimethacrylates (UDMA)‐based dental restorative materials and sealants by means of Fourier transform infrared spectroscopy (FTIR) is demonstrated in this pa

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00903.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00904.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SUMMARYTwelve healthy subjects performed 10 s, 15 s, 20 s, and 25 s of right‐sided and, subsequently, left‐sided gum chewing. The contractile activities of the ipsilateral (chewing side) and contralateral (non‐chewing side) masseter muscles, mainly the concentric contractions of the phase of jaw closing and the isometric contractions of the phase of dental occlusion, were recorded through cumulative surface electromyography (EMG). A linear function (y = ax + b) described the association between an increase in the duration (x) of unilateral gum chewing and the cumulative EMG (y) of both the ipsilateral and the contralateral masseter muscle, and because of different slopes (a) of the two straight lines a geometric function (y = aqx) described the progressively larger differences between the paired and straight lines. When differential calculus was applied to the exponential functions, it became evident that the chewing forces generated by the ipsilateral masseter muscle continually exceeded those generated by the contralateral masseter muscle, and that the positive work (force x distance) produced by the concentric contractions of the ipsilateral masseter muscle continually exceeded that produced by the concentric contractions of the contralateral masseter muscle. It was inferred that mechanophysical work plays a major role if clinical muscle fatigue develops during prolonged unilateral gum ch

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00905.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY