摘要:

summaryTo facilitate the detection of overhangs and defects adjacent to a filling, restorative materials should have a radiographic density higher than or at least similar to that of enamel. In the present study the density of 21 glass ionomer materials was measured and compared with the density of enamel, dentine, amalgam and aluminium. Most materials were more radiopaque than enamel, thereby satisfying the requirements as proposed by several investigators. The materials with lower density were mainly types intended for use in anterior teeth where the entire filling can more easily be examined clinically. They should not be used as a base under approximal fillings in order to avoid a false positive diagnosis of recurrent caries.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00803.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

summaryThe aim of the study was to compare the masticatory pattern and the activity of the masticatory muscles of a group of myotonic dystrophy patients with those of a group of healthy individuals. The electromyographic (EMG) activity of the temporal and the masseter muscles was measured in the resting position, during maximal clenching, and while the patient was chewing five peanuts until swallowing. It was found that the patients had approximately 3 times less EMG activity in the masticatory muscles during maximal clenching. During chewing the patients had approximately half the activity in the anterior temporal and the masseter muscles, while the activity of the posterior temporal muscle did not differ significantly from that in healthy individuals. No differences were found in the muscle activity in the resting position or in the speed of chewing between the groups. The patients needed more time and more chewing cycles to bring the five peanuts to the swallowing threshold, but possibly this was an effect of the lower number of antagonizing teeth. Myotonic dystrophy thus influences the masticatory muscles, reducing their activity both at a maximal and a functional level.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00804.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

summaryOn account of its tissue resolution capacity, computed tomography (CT) is an excellent method for the examination and quantitative analysis of the masticatory muscles. The aim of the present study was to evaluate the influence of the long edentulous period by CT on the structure of the main masticatory muscles in 10 edentulous patients and to study their functioning by electromyography (EMG) in connection with the renewal of the dentures. CT scanning was performed before prosthodontic treatment and EMG recordings of the masseter and temporal muscles before treatment and 4 weeks and 6 months after insertion of the new dentures. The results suggest, however, that a long edentulous period is visible not only in the functioning of the masticatory muscles, in terms of decreased EMG activity, but also as decreased density of the muscles which implies muscle atrophy, as seen by CT in the masseter and medial pterygoid muscles.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00805.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

summaryThe aim of this study was to observe the tissue responses to a number of membrane materials processed for use in guided tissue regeneration at different time periods. Non‐degradable Gore‐Tex° PTFE membrane and degradable polylactic acid (PLA) membranes were placed transcutaneously in surgical incisions made in the dorsum of rats. The tissue responses to these materials were observed histologically at 3 days, 1 week and 4 weeks after placement. A wide variation in the tissue responses to both materials was evident at each time period. These variations could not be attributed to different rates of healing over time, but rather to more complex factors. These factors may include differences in host responses between different animals, local factors pertaining to specific site variations, physical characteristics of the materials like surface texture, and contamination from the wound surface. Neither membrane material was found to be totally satisfactory. The PLA membranes were well tolerated by the tissues but they were unevenly absorbed within 2 weeks of placement. The Gore‐Tex PTFE membranes, however, were associated with prolonged acute inflammatory infiltrate throughout the duration of the study, indicating that they were less well tolerated by the tissues than the PLA materials. As the healing characteristics of tissues are complex and highly variable, and as neither the non‐degradable PTFE or degradable PLA membranes demonstrated ideal tissue responses, it is concluded that variations in clinical responses to these materials used in regeneration techniques must be ant

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00806.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

summaryThe purpose of this study was to investigate the correlation between maximal mouth opening and size of the skeleton. The subjects were dental students at the Dental School of the Health Sciences University of Hokkaido with no functional disorders of the masticatory system. The stature and maximal mouth opening were recorded in 29 males and 31 females. These subjects agreed to have a lateral cephalogram taken at the closed and maximal mouth opening positions. The correlations between the maximal mouth opening and the body height, mandibular length and mandibular angle were significant. The correlation between the maximal mouth opening and the movement of the condyle was also significant.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00807.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

summaryIt is necessary to visualize and reconstruct tissue anatomic surfaces accurately for a variety of oral rehabilitation applications such as surface wear characterization and automated fabrication of dental restorations, accuracy of reproduction of impression and die materials, etc. In this investigation, a 3‐D digitization and computer‐graphic system was developed for surface characterization. The hardware consists of a profiler assembly for digitization in an MTS biomechanical test system with an artificial mouth, an IBM PS/2 computer model 70 for data processing and a Hewlett‐Packard laser printer for hardcopy outputs. The software used includes a commercially available Surfer 3‐D graphics package, a public domain data‐fitting alignment software and an inhouse Pascal program for intercommunication plus some other limited tasks. Surfaces were digitized before and after rotation by angular displacement, the digital data were interpolated by Surfer to provide a data grid and the surfaces were computer graphically reconstructed: Misaligned surfaces were aligned by the data‐fitting alignment software under different choices of parameters. The effect of different interpolation parameters (e.g. grid size, method of interpolation) and extent of rotation on the alignment accuracy was determined. The results indicate that improved alignment accuracy results from optimization of interpolation parameters and minimization of the initial misorientation between the digitized surfaces. The method provides important advantages for surface reconstruction and visualization, such as overlay of sequentially generated surfaces and accurate alignment of pairs of surfaces with small m

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00808.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

summaryTemporomandibular joint (TMJ) sounds were recorded in 98 orthodontic retention patients, mean age 19 ± 8–6 (s.d.) years, by interview, auscultation and electronic recording. Sounds were found by auscultation in 41% and by interview in 32% of the subjects, more often in females than in males (P ≤ 0.05). A new method for time‐frequency analysis, the reduced interference distribution (RID), was used to classify the electronic sound recordings into five subclasses, RID types 1–5, based upon location and number of their energy peaks. RID types 1–3 had a few energy peaks close in time. RID types 4–5, typical of subjects with crepitation, had multiple energy peaks occurring close in time for a period of 20–300 ms. RID type 1, found in 45% of the subjects, typical of patients with clicking, had its dominant energy peak located in a frequency range ≤600 Hz and was significantly more common in the female than in the male subjects (P≤ 0.01). RID type 2, found in 68% of the subjects, with the dominant peak in the range 600–1200 Hz, and RID type 3, found in 38% of the subjects, with the peak in the frequency range>1200 Hz, were found to have a similar gender distribution. RID type 4, found in 49% of the subjects, had the energy peaks distributed in the frequency range ≤600 Hz. RID type 5, found in 43% of the subjects, more often in females than in males (P≤ 0.05), had the peaks distributed over the whole frequency range from about 30 Hz up to about 3000 Hz. In conclusion, a more detailed classification could be made of the TMJ sounds by displaying the RIDs than by auscultation. This suggests that RID classification methods may provide a means for differentiating sounds indicating diff

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00809.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

summaryThe aim of the present study was to determine the sound wave forms which correspond to auscultatory findings of temporomandibular joint (TMJ) clicking and crepitation. Such knowledge is important when selecting parts of digital recordings for spectral analysis. Electronic digital recordings were made with a sampling rate of 44 100 Hz from 60 subjects, including 51 patients referred for suspected rheumatological disease and nine healthy subjects. Accelerometers with the bandwidth 20–3600 Hz were used for all subjects and complementary recordings were made from a subgroup of nine subjects using a measurement microphone with the bandwidth 20–20 000 Hz. The clicking sounds could be classified into different types according to differences in temporal period duration (T) as measured on the analogue display. One type of clicking, found in 51% of the patients, had aTof 2–20 ms. Another type, found in 70% of the subjects, had a T of less than 1 ms, often as low 0.2 ms. This type of clicking was not seen at all in the analogue display if the sampling rate was below 3 000 Hz. The character of the two types of clicking differed: the short duration sounds had a very high pitch, while the pitch of the longer duration sound was lower. Crepitation was found in 63% of the subjects and was observed to be composed of a series of short duration sounds, occurring with brief (less than 10 ms) intervals. It is concluded that the accelerometer (or microphone) bandwidth should cover the entire audible range (20–20 000 Hz), and that sampling rates must be much higher than 3000 Hz, and preferably greater than 10 000 Hz, before the true significance of electronically recorded joint sounds/vibrations can be det

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00810.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

summaryThe relationship between a removable partial denture (RPD) and damage caused to residual oral structures is the subject of on‐going research. A group of patients wearing RPD, treated in the same way in the same department, were recalled to evaluate their oral hygiene and to compare the clinical condition of abutment teeth with that of non‐abutment teeth. The study shows that most patients were unable to maintain high standards of oral hygiene. In the group of patients with non‐optimal hygiene the clinical condition of abutment teeth was worse than that of non‐abutment teeth. In the group of patients with optimal oral hygiene the condition of abutment teeth and non‐abutment teeth was almost identical. To increase the standards of oral hygiene it is strongly advisable to recall and follow up patients on a regu

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00811.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

summaryThe influence of the experimental occlusal discrepancy on masticatory muscle activity was investigated on 12 subjects. Specially designed occlusal interferences were fabricated and various occlusal states were simulated with their aid. Subjects were asked to carry out eccentric clenching efforts and electromyographic activity of the masseter plus the anterior and posterior temporal muscles was measured. When compared with clenching on the unaltered natural dentition, clenching on the experimental interferences resulted in distinct patterns in the jaw elevator muscles, and the most characteristic change was observed when clenching effort was exerted on the experimental non‐working side interference. Electromyographic activity in the anterior and posterior temporal muscles was decreased on the working side and increased on the non‐working side and originally unilateral activity pattern with clear dominance on the working side was altered to a bilateral pattern, while that of the masseter muscles remained uninfluenced. Resultant bilateral activity in the anterior and posterior temporal muscles is thought to cause a superior movement of the working side condyle and an inferior movement of the non‐working side co

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1996.tb00812.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY