bluuebunny/crossref_metadata_2025 huggingface dataset:
Genioglossus muscle activity during rhythmic open–close jaw movements
Authors: Hiyama S. , Iwamoto S. , Ono T. , Ishiwata Y. , Kuroda T.
Published: March 2003

The purpose of this study was to examine genioglossus muscle activity during rhythmic open–close jaw movements. The electromyographic activity of the genioglossus muscle was recorded with a bipolar fine‐wire electrode in six healthy males. The electromyographic activities of the ipsilateral masseter and digastric muscles were simultaneously recorded with bipolar surface electrodes. The subjects were instructed to perform rhythmic open–close jaw movements in time with a metronome set at 23, 27, 33, 42 and 50 beats/min. In all of the subjects, rhythmic electromyographic activity of the genioglossus muscle was recorded in both the jaw‐opening and jaw‐closing phases. The activity of the genioglossus muscle was predominantly recorded in the jaw‐opening phase in two subjects, and in the jaw‐closing phase in two subjects. The burst duration of the electromyographic activity of the genioglossus muscle changed linearly in accordance with the cycle duration. However, the latency from the onset of the electromyographic activity of the masseter or digastric muscle to that of the genioglossus muscle was almost constant, independent of the cycle duration. Based on these findings, we conclude that the activity of the human genioglossus muscle is closely linked to that of masticatory muscles under the control of a closely related central pattern generator.
Effect of different acid treatments on a porcelain surface1
Authors: Canay Ş. , Hersek N. , Ertan A.
Published: March 2003

The objective of this study was to determine the effect of selected surface treatments on the surface texture of a feldspathic porcelain. The three different etchant treatments were, acidulated phosphate fluoride (APF) applied for 10 min and hydrofluoric acid (HF) applied for 1 and 4 min. After acid treatment, half of the specimens from each group were cleansed with water and others were subjected to ultrasonic cleaning and then dried. Half of the specimens cleansed with two different methods were treated with silane. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the effects of such treatments. Etching with APF displays shallow patterns. Etching for 1 min with HF displays deep channels, pores and precipitates on the surface and as the etching time increased these channels were replaced by larger channels. EDS analyses show that the crystalline precipitates on the etched surfaces, which were not readily soluble in water, were the reaction products of Na, K, Ca, Al, etc. HF displayed a more roughened surface than the APF gel. However, the precipitates remain on the surface after acid application, they can only be removed by ultrasonic cleaning and cannot be removed by rinsing.
Effects of psychological techniques on bruxism in children with primary teeth
Authors: Restrepo C. C. , Alvarez E. , Jaramillo C. , Vélez C. , Valencia I.
Published: March 2003

Four main causes of bruxism have been studied – high anxiety level, malocclusion, temporomandibular disorders (TMD) and oral habits. Effective dental treatment for this problem is unknown in children with primary teeth, although, high prevalence has been reported. The aim of this study was to investigate the effectiveness of psychological techniques in children with bruxism. A total of 33 children, 3–6 years of age with normal occlusal features, without oral habits, rate in the Conners’ parent rating scales (CPRS) and more than 0.75% in Conners’ teacher rating scales (CTRS), and one or more temporomandibular joint (TMJ) disorders registered in the Bernal and Tsamtsouris examination, were selected from 188 children. Two psychological techniques, ’directed muscular relaxation’ and ‘competence reaction’, were applied for 6 months. The results were analysed with a Wilcoxon rank sum test. All patients reduced their anxiety level and TMJ disorders, with statistical significance (P < 0·05). The psychological techniques were effective in the reduction of signs of bruxism in children with primary teeth.
The structure of the bilaminar zone in the human temporomandibular joint: a light and scanning electron microscopy study in young and elderly subjects
Authors: Benigno M. I. M. , Azeredo R. A. , Lemos J. L. R. , König Júnior B. , Liberti E. A.
Published: March 2003

The bilaminar zone (BZ) in the human temporomandibular joint (TMJ) of toothed adults (GI) and toothless, elderly humans (GII) were analysed using light and scanning electron microscopy (SEM). In both groups the BZ consists of an upper and a lower stratum of connective tissue separated by a vascularized middle region. The superior stratum contains bundles of collagen fibres disposed in different directions. The fibres are fairly thick and transversely oriented immediately posterior to the TMJ disc. The initial part of the inferior stratum contains curved bundles of collagen fibres oriented anterio‐posteriorly. From the middle to the posterior part of the inferior stratum, the fibres are right‐aligned in GI and clearly sinuous in nature in GII. In both groups, the middle and posterior portions of the middle region are distinguished by the presence of vessels and vascular spaces. Loosely arranged connective and adipose tissues are also evident. The vascular spaces are wider in GII than in GI. The predominance of type I collagen fibres is clear in all regions of the BZ in both groups. The elastic fibres lie parallel to the collagen fibres in both groups and they are thicker and more abundant in GI, apparently decreasing in GII.
Variation of heads of lateral pterygoid muscle and morphology of articular disc of human temporomandibular joint – anatomical and histological analysis
Authors: Fujita S. , Iizuka T. , Dauber W.
Published: March 2003

To grasp the documented evidences available regarding the cause of the anteriorly displaced human temporomandibular joint (TMJ) disc. With 20 specimens of human TMJ from cadavers, at first the number of heads of lateral pterygoid muscle (LPM) bundles were analysed with macroanatomical method. Secondary histological procedure with haematoxyline and eosine staining and orceine staining were carried out for the same specimens. Macroscopically, in 13 specimens an upper and a lower head of the LPM were present. In the other seven specimens, not only an upper and a lower head, but also a third inner head of the LPM covered with a separate fascia was observed. Histochemically, the specific localization of certain bundles of thick elastic fibres in the antero‐medial parts of the anteriorly displaced deformed TMJ disc were observed.
Quantitative study of bite force during sleep associated bruxism
Authors: Nishigawa K. , Bando E. , Nakano M.
Published: March 2003

Nocturnal bite force during sleep associated bruxism was measured in 10 subjects. Hard acrylic dental appliances were fabricated for the upper and lower dentitions of each subject. Miniature strain‐gauge transducers were mounted to the upper dental appliance at the right and left first molar regions. In addition, thin metal plates that contact the strain‐gauge transducers were attached to the lower dental appliance. After a 1‐week familiarization with the appliances, nocturnal bite force was measured for three nights at the home of each subject. From the 30 recordings, 499 bruxism events that met the definition criteria were selected. The above described system was also used to measure the maximum voluntary bite forces during the daytime. The mean amplitude of detected bruxism events was 22·5 kgf (s.d. 13·0 kgf) and the mean duration was 7·1 s (s.d. 5·3 s). The highest amplitude of nocturnal bite force in individual subjects was 42·3 kgf (15·6–81·2 kgf). Maximum voluntary bite force during the daytime was 79·0 kgf (51·8–99·7 kgf) and the mean ratio of nocturnal/daytime maximum bite force was 53·1% (17·3–111·6%). These data indicate that nocturnal bite force during bruxism can exceed the amplitude of maximum voluntary bite force during the daytime.
A histomorphometric analysis on bone dynamics in denture supporting tissue under continuous pressure in streptozotocin‐induced diabetic rat
Authors: Okamoto M. , Sato T. , Shirai H. , Imai Y.
Published: March 2003

The purpose of this study was to investigate bone dynamics in denture supporting tissue under continuous pressure in the diabetic condition by using bone histomorphometry in relation to initial intensity of continuous pressure exerted through the denture base. The experimental denture base, which was designed to load initial continuous pressure of 0·0, 1·0, 10·0 or 20·0 kPa to the denture supporting tissue, was applied to the molar region of hard palate of streptozotocin‐induced diabetic rats. Fluorescent labelled palatal bone tissue was stained with Villanueva bone stain and was prepared for the undecalcified grinding section. In 0·0 kPa group, no bone resorption was observed and bone formation was transiently inhibited after the denture insertion. In 1·0 kPa group, although no bone resorption was observed, the beginning of bone formation after the inhibition of bone formation was later than that in 0·0 kPa group and bone formation dynamics after the resumption of bone formation was similar to that in 0·0 kPa group. In 10·0 and 20·0 kPa groups, bone resorption was observed until 3 and 4 weeks, respectively, and the amount of bone resorption for each group was 60 ± 16 and 87 ± 18 μm, respectively. The resumption of bone formation in 10·0 and 20·0 kPa groups were observed at the same stage with 1·0 kPa group, and the bone formation dynamics after the resumption of bone formation in 10·0 and 20·0 kPa groups were also similar to that in 0·0 kPa group. From the results of this study, it was revealed that bone formation following bone resorption did not cause equivalent recovery of the bone surface level to the level observed in the case without bone resorption in the diabetic condition.
Survival rate and fracture strength of incisors restored with different post and core systems after exposure in the artificial mouth
Authors: Strub J. R. , Pontius O. , Koutayas S.
Published: March 2003

Survival rate and fracture strength of incisors restored with different post and core systems after exposure in the artificial mouth. The survival rate and fracture resistance of 40 decapitated endodontically treated maxillary central incisors using four different post and core systems covered with all‐ceramic copings was evaluated after exposure in the artificial mouth. Ten samples of the following post and core systems were investigated: high precious metal post (Permador®) and core (Olympia®) (A), zirconia post (Cerapost®) with a pre‐fabricated bonded ceramic core (Ceracap®) (B), resin‐ceramic post (experimental) with a pre‐fabricated bonded ceramic core (Ceracap®) (C) and a zirconia post (Cerapost®) with a custom made ceramic core (Cosmo Ingots®) (D). The all‐ceramic copings (Procera®) were cemented using Panavia TC®. The survival rates after 1 200 000 cycles in the artificial mouth are as follows: 90% (A), 80% (B), 60% (C) and 100% (D). The results of the means and standard deviations (s.d.) of the fracture resistance during static loading are: 1270 ± 312·5 (A), 1494·5 ± 333·5 (B), 1146·7 ± 182·6 (C) and 463·3 ± 46·2 (D). There are statistically significant differences between all groups with the exception of A and B, and A and C (Wilcoxon test). None of the zirconia posts with custom made ceramic cores covered with all‐ceramic copings fractured during dynamic loading in the artificial mouth. The mean fracture strength during static loading was less favourable than that of groups A, B and C but above the clinical necessary level.
Multifactorial analysis of an MOD restored human premolar using auto‐mesh finite element approach
Authors: Lin Chun‐Li , Chang Chih‐Han , Ko Ching‐Chang
Published: March 2003

The use of an mesial‐occlusal‐distal (MOD) restoration in repairing a large carious lesion depends on many factors. Biomechanical performance is one of the most important. It has been recognized that resistance to restoration failure is not solely a biological concern (e.g. toxicity), but that the cavity shape, dimensions, and the state of stress must all be taken into account. In the present study, a newly developed auto‐mesh program was used to generate 30 three‐dimensional (3D) finite element (FE) models simulating the biomechanics for multiple factorial design of the MOD gold restoration in a maxillary second premolar. Stress levels were related to individual design factors (e.g. pulpal wall depth [P], isthmus width [W] and interaxial thickness [T]) and to their interactions under the worst physiological scenario: a concentrated bite force acting on lingual cusp with debonded interfaces between cavity walls and restorations. The results showed that enlarging the volume of the MOD cavity significantly increased stresses in enamel but did not intentionally affect stresses in dentin. The alternation of individual design parameters significantly changed the peak stresses (P < 0·05). For all three parameters, except for the width, the peak stress increased as the cavity dimension increased. Stress elevation rate (termed as ‘volumetric stress rate’– stress elevation by increasing one unit volume of the restored materials) was different among three design factors. Depth was the most critical factor governing the stress elevation in enamel (1·76 MPa mm−3) while length (interaxial thickness) was the most important parameter in dentin (0·49 MPa mm−3). Width was the least compromising factor to the remaining tooth, 0·32 MPa mm−3 for enamel and −0·23 MPa mm−3 for dentin. The findings, at its core, did not fully agree with the traditional concept that the preservation of tooth substances will reduce risk of tooth fracture. This study leaves open possibility for the structural optimization of the MOD restoration.
Surface roughness and wettability of enamel and dentine surfaces prepared with different dental burs
Authors: Al‐Omari W. M. , Mitchell C. A. , Cunningham J. L.
Published: March 2003

The aim of dental adhesive restorations is to produce a long lasting union between the restoration and the tooth structure. This bond depends on many variables including the geometry of the preparation and the type of bonding agent or luting cement. It is therefore suggested that the topography of the tooth surface may influence the wettability and the bonding quality of adhesive systems. This study measured the surface roughness and wettability of enamel and dentine after preparation with different dental burs. The mesial and distal surfaces of 15 extracted sound human premolar teeth were prepared with a tungsten carbide crown bur, a diamond bur and a tungsten carbide finishing bur and finished in enamel or dentin, respectively. The prepared surfaces were analysed with a surface profilometer and scanning electron microscopy (SEM). The contact angle of distilled water on each of the prepared surfaces was used as the measure of wettability. The differences in average surface roughness (Ra) were significant between the rotary instrument groups, as revealed by a two‐way ANOVA test. No differences were detected between enamel and dentine surfaces prepared with the same type of dental bur. The smoothest surfaces were those completed with tungsten carbide finishing burs. The diamond bur preparations were intermediate in the roughness assessment and the tungsten carbide crown burs gave the roughest surfaces. There were no significant differences in the contact angle measurements for the various groups. It was concluded that the surface roughness of enamel and dentine prepared by different rotary instruments had no significant influence on the wettabilty of distilled water on these surfaces.
Maxillary central incisor with two root canals: an unusual presentation
Authors: Cabo‐Valle M. , González‐González J. M.
Published: March 2003

An unusual case is presented, underlying the rarity of the presence of two canals in a maxillary central incisor associated with macrodontia.
Maintenance of condylar position using an occlusal splint after mechanical vibrating‐traction of the TMJ
Authors: Minagi S. , Natsuaki N. , Sato T. , Akamatsu Y. , Shimamura M.
Published: March 2003

Although adequate relief of excess mechanical loading to the joint has been accepted as one of the important treatment concepts in the orthopaedic field, a treatment method for the temporomandibular joint (TMJ) to relieve excess mechanical loading has not yet been established. This study aimed to clarify the effect of an occlusal splint on the maintenance of the distracted condylar position achieved by vibrating‐traction method. Vibrating dynamic traction force was applied for 5 min to the right TMJ using vibrating‐traction apparatus. A flat stabilization splint was adjusted to keep the mandibular position and the condylar displacement was evaluated for 6 h after the dynamic traction procedure. Mean vertical displacement of the mandibular right first molar immediately after the vibrating‐traction for the six subjects was 156 μm (ranging from 141 to 179 μm). The calculated mean condylar displacement immediately after the traction was 480 μm and could be kept to be 381 μm even after 6 h by wearing the flat stabilization splint. From the results of this study, it was revealed that the mechanically tracted condylar position could be maintained by a flat occlusal splint. It was suggested that the vibrating‐traction method followed by the provision of occlusal support might have a possibility to work as a mechanical relieving procedure for the TMJ.
Viability of fibroblasts in cell culture after treatment with different chemical retraction agents
Authors: Kopač I. , Batista U. , Cvetko E. , Marion L.
Published: March 2003

Prior to fixed prosthodontic impression procedures, temporary horizontal retraction of the free gingival tissue should be accomplished apically to the preparation finishing line. The mechanical–chemical method using cotton retraction cords of various sizes impregnated with various retraction chemicals is the most commonly employed retraction technique. Most retraction agents have pH values from 0·8 to 0·3, and are therefore hazardous to the cut dentine and periodontal tissues. Sympathomimetic vasoconstrictors introduced recently have a pH of 5·6, and are free of systemic side‐effects. The present study using the dye exclusion test, colony forming ability test and colorimetric assay was undertaken to evaluate cytotoxic effects of four chemical retraction agents on cultured V‐79 fibroblasts, and the dependence of cytotoxicity on the agent concentration and time of exposure. Original concentrations of retraction agents produced stronger cytotoxic effects than dilutions of 1:1 and 1:10. The most aggressive agent, 25% aluminium chloride, took only 1 min to damage all cell cultures. The proportion of cells damaged after 10 min of exposure to tetrahydrozoline was 60%, which was significantly less compared with other chemicals tested. With the colony forming ability test using retraction agents diluted to 1:10 the greatest number of colonies emerged in samples treated with tetrahydrozoline (statistical significance: P < 0·01). The colorimetric assay showed equal cytotoxic effects for 25% aluminium sulphate and tetrahydrozoline. The colorimetric test used in the study has proved an ergonomic, accurate and reliable test for cytotoxicity determination.
Sites of dental erosion are saliva‐dependent
Authors: Young W. G. , Khan F.
Published: March 2003

Acid demineralization of teeth causes occlusal erosion and attrition and associated non‐carious cervical lesions at sites relatively unprotected by saliva. Associations of occlusal pathology and cervical lesions were looked for in 450 patients with toothwear, and 174 subjects with cervical lesions were identified. Associations of occlusal attrition, or erosion, or no wear, with cervical lesions at 72 buccal and lingual sites were recorded from epoxy resin replicas of the subjects’ dentitions (3241 teeth). Criteria used to discriminate occlusal erosion from attrition; and shallow from grooved and wedge‐shaped cervical lesions were delineated by scanning electron microscopy (SEM). In the absence of occlusal pathology, cervical lesions were very rare (<1%). In the presence of occlusal pathology, cervical lesions were present in 27·71% of buccal sites as opposed to 2·61% of lingual sites. The commonest site of cervical lesions was the facial of maxillary incisors (36% of sites). The least common site was the lingual aspect of mandibular molars (1·7% of sites). These differences may reflect the normal protective role of serous saliva and salivary pellicle in a site‐specific manner, on the lingual surfaces of mandibular teeth particularly, and do not support abfraction as the prime aetiology of cervical lesions.
Effect of calcium supplementation on bone dynamics of the maxilla, mandible and proximal tibia in experimental osteoporosis
Authors: Shirai H. , Sato T. , Oka M. , Hara T. , Mori S.
Published: March 2003

The effect of calcium supplementation on the bone dynamics in the hard palate of the molar region (maxilla), mandible and proximal tibia in experimental osteoporotic rats was examined. Ninety ovariectomized (OVX) and 45 sham‐OVX Wistar female rats were used in this study. All the rats received surgical operation at 6 weeks of age. Ovariectomized rats were fed on a low calcium diet (0·02%) for 12 weeks post‐operation, and then randomly divided into the two following groups. One group was fed on high calcium diet (2·30%) (OVX‐HCa) and the other group was remained on the low calcium diet (OVX‐LCa). Sham‐OVX rats were fed on regular calcium diet (1·15%) during the experimental period (Sham‐OVX). Histomorphological analysis was carried out from 12 to 32 weeks post‐operation. On undecalcified thin section, bone volume, eroded surface, osteoid surface and bone formation rate were calculated for cortical bone of the maxilla, and for cancellous bone of the mandible and proximal tibia. In the OVX‐LCa group, compared with the Sham‐OVX group, decrease of the bone volume and increase of the bone resorption and formation parameters were detected throughout the observation periods. In the OVX‐HCa group, compared with the OVX‐LCa group, increase of the bone volume and temporarily increased parameters of bone formation at 1 week after feeding on high calcium diet were observed in the maxilla, but these changes were not observed in the mandible and proximal tibia. Moreover, the bone resorption and formation parameters in the maxilla, mandible and proximal tibia in the OVX‐HCa group became equivalent to the Sham‐OVX levels with the passage of time.
Clinical TMD, pain‐related disability and psychological status of TMD patients
Authors: Yap A. U. J. , Chua E. K. , Hoe J. K. E.
Published: March 2003

This study investigated the clinical temporomandibular disorders (TMD), pain‐related disability and psychological status of TMD patients using a computerized on‐line TMD diagnostic system (NUS TMD v1·1). A total of 107 patients (32 male, 75 female) referred to the TMD clinics at the National Dental Centre and National University Hospital participated in this study. The mean age of the predominantly Chinese population (82·2%) was 30·8 years (range from 12 to 64 years). The history questionnaire and clinical examination were input directly into computers by patients and clinicians. A `Summary of Findings' was then immediately generated by the program based on Axis I and II rules. The data was subsequently exported to SPSS for statistical analysis. About 20·6% of the patients had myofascial pain but only 7·5% experienced limited mandibular opening associated with myofascial pain. The majority of patients (> 80%) did not suffer from disc displacements (right and left joints). The frequency of arthralgia was also low (right joint 8·4%; left joint 7·5%) and only one patient had osteoarthosis of the TMJ. About 78·5% of the patients had low disability with almost equal distribution between low and high intensity pain, 27·1% of the patients were moderately depressed and 11·2% had severe depression. No significant difference in limitations related mandibular functioning scores was observed between normal/depressed patients and between patients with the different graded chronic pain severity classification. The three most frequent jaw disabilities were: eating hard foods (77·6%), yawning (75·7%) and chewing (64·5%). NUS TMD v1·1 is an extremely useful tool in the diagnosis/research of clinical TMD.
Influence of removable partial denture on periodontal indices and microbiological status
Authors: Vanzeveren C. , D'hoore W. , Bercy P.
Published: March 2003

Thirty patients (19 men and 11 women) were provided with a removable partial denture (RPD) and assigned randomly to two groups: 15 patients were called back twice a year for plaque control, reinforcement of instructions, denture hygiene control and professional prophylaxis; the other 15 were not called back. The 30 patients were examined after 2–3 weeks following the end of the prosthetic treatment, after 1 and 2 years. At each examination, the following parameters were recorded [gingival inflammation, plaque index (Pl I), tooth mobility, attachment level, pocket depth] and a bacteriological examination of subgingival plaque was carried out. Few differences appeared between the two groups; the values observed show a relatively low level of hygiene and but little motivation with regard to prophylaxis techniques.
Relationship between The flow of bolus and occlusal condition during mastication – computer simulation based on the measurement of characteristics of the bolus
Authors: Amemiya K. , Hisano M. , Ishida T. , Soma K.
Published: March 2003

The purpose of the present study was to clarify the relationship between the flow of a bolus and occlusal condition during mastication. First, the characteristics of a bolus under mastication was measured in subjects having different occlusal conditions. Secondly, the flow of a bolus between the upper and lower first molars under mastication was simulated using finite element non‐linear dynamic analysis. Measurement of the elasticity of the bolus clarified the phenomenon of its communition. The measurement of the viscosity of the bolus clarified the phenomenon of its mixing with saliva. In addition, a relationship between the elasticity and the viscosity of the bolus at the point of just before swallowing was investigated. The flow of the bolus under mastication was revealed to vary according to the occlusal condition. These results suggest a close relationship between the occlusal condition, the flow of the bolus and its characteristics.
Digital acoustic analysis of five vowels in maxillectomy patients
Authors: Sumita Y. I. , Ozawa S. , Mukohyama H. , Ueno T. , Ohyama T. , Taniguchi H.
Published: March 2003

The aim of the study was to characterize the acoustics of vowel articulation in maxillectomy patients. Digital acoustic analysis of five vowels, /a/, /e/, /i/, /o/ and /u/, was performed on 12 male maxillectomy patients and 12 normal male individuals. A simple set of acoustic descriptions called the first and second formant frequencies, F1 and F2, were employed and calculated based on linear predictive coding. The maxillectomy patients had a significantly lower F2 for all five vowels and a significantly higher F1 for only /i/ vowel. From the data plotted on an F1–F2 plane in each subject, we determined the F1 range and the F2 range, which are the differences between the minimum and the maximum frequencies among the five vowels. The maxillectomy patients had a significantly narrower F2 range than the normal controls. In contrast, there was no significant difference in the F1 range. These results suggest that the maxillectomy patients had difficulty in controlling F2 properly. In addition, the speech intelligibility (SI) test was performed to verify the results of this new frequency range method. A high correlation between the F2 range and the score of SI test was demonstrated, suggesting that the F2 range is effective in evaluating the speech ability of maxillectomy patients.
Use of woven glass fibres to reinforce a composite veneer. A fracture resistance and acoustic emission study
Authors: Vallittu P. K.
Published: March 2003

The aim of this study was to investigate the possibility to reinforce the mechanically interlocked veneer of a porcelain‐fused‐to‐metal (PFM) crown by woven glass fibre. A simulated situation to repair a fractured porcelain veneer was used in the experimental test set‐up. A brass jig made into the shape of a framework of PFM maxillary central incisor crown with a retentive area at the palatal side of the incisal edge was used. A veneer were made with a restorative hybrid composite on the brass jig (control group). In the test groups, one or two layers of woven polymer pre‐impregnated glass fibres (thickness: 0·06 mm/layer) were used by pressing the fibre weaves to the surface of the brass jig. Restorative hybrid composite was applied on the glass fibre weaves. Five veneers were made for all groups and the veneers were not cemented on the test jig. The veneers were loaded from the incisal edge until fracture occurred. The force was measured simultaneously with an acoustic emission analysis (AE) of the fracture propagation. Fracture force values for control veneers were 121 N and for those reinforced with one layer of glass fibres 399 N and for those reinforced with two layers of glass fibres 744 N ANOVA revealed significant difference between the mean values (P=0·003). The AE analysis showed different fracture propagation for the unreinforced and glass fibre reinforced veneers. The results of this study suggests that by placing two layers of woven glass fibres on the retentively shaped metal framework of the PFM crown before applying the restorative composite, considerably higher fracture resistance for the veneer could be obtained.
Immediate effect of a stabilization splint on masticatory muscle activity in temporomandibular disorder patients
Authors: FERRARIO V. F. , SFORZA C. , TARTAGLIA G. M. , DELLAVIA C.
Published: March 2003

Summary Surface electromyography (EMG) allows the quantification of the occlusal equilibrium in dysfunctional patients, for instance in those with temporomandibular disorders (TMD). Fourteen patients (ten women, four men) with internal derangement type I were selected among the TMD patients referred to a private practice in Milan. A stabilization splint with posterior contacts was made for each patient. To verify the static neuromuscular equilibrium of occlusion, EMG activity of left and right temporal and masseter muscles was recorded in all patients and the activity (ratio between the activities of the temporal and masseter muscles) index was computed over a maximum voluntary clench test of 3 s. Muscular waveforms were also analysed by computing a percentage overlapping coefficient (POC, an index of the symmetric distribution of the muscular activity determined by the occlusion). The total electrical activity was measured by calculating the area under the entire muscular waveforms. In all patients EMG was performed just before and immediately after the insertion of the splint and data were compared by paired Student's t‐tests. Overall, the splint reduced the electrical activity of the analysed muscles (P < 0·005) and made it more equilibrated both between the left and right side (larger symmetry in the masseter muscle POC, P < 0·05) and between the temporal and masseter muscles (activity index, P < 0·01).
Electromyographic activity of the jaw‐closing muscles during jaw opening – comparison of cases of masseter muscle contracture and TMJ closed lock
Authors: Yamaguchi T. , Satoh K. , Komatsu K. , Kojima K. , Inoue N. , Minowa K. , Totsuka Y.
Published: March 2003

SUMMARY  Contracture of jaw‐closing muscles is one of the causes of limitations of jaw opening. In contracture patients who have no history of trauma or infection, it is not easy to distinguish contracture from temporomandibular joint (TMJ) closed lock (TCL). The purpose of this study was to clarify whether there is any difference between electromyographic (EMG) activities of jaw muscles during jaw opening in patients with TCL and patients with masseter muscle contracture (MMC). The MMC‐patient group consisted of one male and 11 females with no history of trauma or infection. The TCL‐patient group consisted of one male and 11 females. Ten of the MMC patients showed certain types of EMG activities in masseter muscles (and eight in temporal muscles) during jaw opening. However, particular EMG activities were not observed in most of the TCL patients. The integral values in masseter muscles and in temporal muscles at the maximum opening position were significantly higher in the MMC‐patient group than those in the TCL‐patient group. These findings demonstrate that the EMG pattern of MMC patients without a history of trauma or infection is different from that of TCL patients. Therefore, EMG analysis of jaw‐closing muscles during jaw opening is expected to be useful for differential diagnosis between MMC and TCL.
Comparison of microleakage properties of three different filling materials. An autoradiographic study
Authors: Hersek N. , Canay S¸. , Akça K. , Çiftçi Y.
Published: March 2003

summary  The aim of this study was to compare the microleakage behaviour of three restorative materials using the autoradiographic method. The study was accomplished in vitro using freshly extracted human molars and a Ca45 radioisotope and autoradiography. Twenty‐seven molar teeth were divided into three experimental groups of seven specimens each. Class II cavities were prepared at the mesio‐occlusal aspect and restored with amalgam and two different composite resins. The restorations were finished, thermocycled and tested for microleakage, using the Ca45 radioisotope. The results were analysed using the Kruskal–Wallis analysis test. Amalgam exhibited more leakage compared with composite resins. However the differences among the leakage behaviours of three filling materials were not statistically significant (P=0·064).
Clinical and SEM evaluations of three compomer systems in Class V carious lesions
Authors: Abdalla A. I. , Mahallawy S. EL. , Davidson C. L.
Published: March 2003

Summary The aim of this study was to evaluate the clinical performance of three compomer systems: Compoglass F, Dyract AP and F2000 in Class V carious lesions. In addition, some restorations were placed in teeth scheduled for extractions in order to evaluate the compomer/dentin interface with the scanning electron microscope (SEM). A total of 175 Class V carious lesions having the gingival margins extending into cementum were restored with the tested materials. Each restoration was clinically evaluated immediately after placement, after 1 year and after 2 years using the USPHS criteria. After 1 year no loss of restoration was recorded. No significant difference between the materials was observed for any evaluation category. After 2 years, one Compoglass and two Dyract restorations were lost. No loss of F2000 was reported. No significant difference was reported between the tested materials and between the 2‐year data and baseline ones. A well‐defined hybrid layer as well as resin tags was seen at the interface between the tested materials and vital dentin.
Validation of the clinical diagnostic criteria for temporomandibular disorders for the diagnostic subgroup – disc derangement with reduction
Authors: Emshoff R. , Brandlmaier I. , Bo¨sch R. , Gerhard S. , Rudisch A. , Bertram S.
Published: March 2003

summary  Research is needed to assess the validity of the clinical diagnostic criteria for temporomandibular disorders (CDC/TMD). The purpose of this study was to test the reliability of the clinical diagnosis of temporomandibular joint (TMJ) internal derangement type (ID)‐I as compared with the magnetic resonance imaging (MRI) ‘gold standard’. The study comprised 168 TMJs in 84 patients, who were assigned a clinical TMJ‐related diagnosis of ID‐I (disc displacement with reduction) in at least one TMJ. Bilateral sagittal and coronal MR images were obtained subsequently to establish the corresponding diagnosis of the disc–condyle relationship. For the CDC/TMD interpretations, the positive predictive value (PPV) of ID‐I for disc displacement with reduction (DDR) was 44%, and for the presence of an ID 69%. The overall diagnostic agreement for ID‐I was 47·6% with a corresponding K‐value of 0·05. Most of the disagreement was the result of the false‐positive interpretations of ID‐I, and false‐negative interpretations of an ‘absence of ID’. The results suggest CDC/TMD for ID‐I to be insufficient reliable for determination of ID and/or DDR. Patients assigned a clinical TMJ‐related diagnosis of ID‐I may need to be supplemented by evidence from MRI to determine the functional ‘disc–condyle relationship’.
Hormone‐dependent fluctuations of pressure pain threshold and tactile threshold of the temporalis and masseter muscle
Authors: Drobek W. , Schoenaers J. , De Laat A.
Published: March 2003

SUMMARY  In order to better objectify reported pain and disturbed sensation, psychophysical parameters as pressure pain threshold (PPT) and tactile threshold (TT) have been introduced in pain research. The present study evaluated fluctuations of these parameters, obtained using an algometer (PPT) and von Frey hairs (TT), in relation to fluctuations in female reproductive hormones. Ten students not using oral contraceptives and eight students using oral contraceptives participated in the study. In addition, seven male students served as a control group. During two menstrual cycles, the PPT and TT of the masseter and temporalis muscles, as well as from the hand, were obtained twice per week. At the end of the study the values were evaluated in relation to the different phases of the menstrual cycle, by means of a linear mixed model. The TT appeared very reproducible within subjects and did not fluctuate over time. Scores on the left temporalis muscle appeared significantly higher than that on the right side. In all subjects the PPT tended to be higher on the left side, while in students using oral contraceptives, the PPT values of the temporalis muscle were significantly higher in the menstrual phase, and lower in the follicular phase. A significant correlation between the PPT of the temporalis muscle and the TT of the overlying skin was observed.
Quid test and clinical findings in a TMD treatment‐seeking population
Authors: MAURO G. , TAGLIAFERRO G. , MONTINI M. , MACALUSO G. M.
Published: March 2003

The aim of the present study was to investigate the response pattern to ‘QUID test’ (Italian analogue of the ‘McGill Pain Questionnaire’) and the clinical aspects of a TMD seeking care population.

A total of 229 consecutive patients (mean age 35·9 years) completed the QUID test and underwent a complete clinical examination. An analysis of pain descriptors was also performed. This population was divided in six groups according to their clinical characteristics: 1. TMD: pain at the moment of the examination, positive findings for TMD. 2. eTMD: history of TMD, episodic pain, no clinical findings at present. 3. Headache (H): main complaint. 4. Neck pain (N): main complaint. 5. Atypical Facial Pain (AFP): facial pain not fulfilling other criteria (IHS 12·8). 6. No Orofacial Pain (NOFP): no pain disturbances. Statistical analysis was performed using t and chi‐squared tests. Significance level was set to 0·05. The percentages of the six groups were: TMD 53·71%, eTMD 9·17%, H 4·80%, N 1·31%, AFP 6·11%, NOFP 24·89%. Significant differences were found in: – pain intensity between H and TMD (P=0·034), and between AFP and eTMD (P=0·027); – hypermobility and cervical problems between NOFP and TMD (P=0·021 and 0·0001, respectively); – presence of psychobehavioural factors (axis II) between eTMD and AFP (P=0·05); – type and distribution of words chosen: particularly five descriptors showed a significantly different pattern of distribution; – affective component of pain experience (PRIrcA): highest for the AFP group.
Biofeedback experiments with a submaximal jaw closing force
Authors: JAKSTAT H. A.
Published: March 2003

Temporomandibular disorders are often accompanied with pain in the elevator muscles such as Mm. Masseterici and Mm. Temporales. In most experiments measurement of the closing force of these muscles was conducted with maximum bite force using EMG‐devices.

The experiments presented here were conducted using visual or audible biofeedback using force transducers. Visual feedback was presented on a computer screen using geometrical graphics. Audible feedback used two different signals, the frequency of these audio signals was modulated. The force was chosen between 5 and 30 N, which is near the forces actually used for chewing, but far less than maximum clenching force. The persons chosen for the experiments were divided into two groups: A group of younger persons did not wear any removable dentures, a group of older persons was wearing a total prosthesis of the upper and lower jaw. The results were processed statistically and graphically.

The goal for the persons conducting the experiments was to select a closing force as near as possible to the given force which was shown using the biofeedback. The actual force used by the person was also shown.

There were no statistically significant differences in the results using 5, 10 or 30 N as given force. Results showed that older edentulous patients can modulate the chewing force not as exactly as younger persons. Especially when using low closing forces (5 N) the edentulous persons showed less exactness in reaching the given closing force.

The results of the experiments may be used to develop a test to determine the capability of older patients to perform exact closing (and chewing) movements.
Twitch forces in human masseter during experimental muscle pain
Authors: SVENSSON P. , SOHN M. K. , GRAVEN‐NIELSEN T. , ARENDT‐NIELSEN L.
Published: March 2003

Motor control strategies in relation to pain are not completely understood. Decreased firing rates of single motor units (SMU), but with a constant bite force have recently been demonstrated in the presence of masseter pain suggesting the existence of compensatory mechanisms (Sohn et al., 2000). The aim of this study was to describe twitch force characteristics of masseter SMU using spike triggered averaging (STA) before and during experimental muscle pain. Ten healthy subjects (20–29 years) participated. Fine wire electrodes were inserted into the masseter to record SMU activity. Subjects performed an isometric contraction on a force transducer (Kistler, Switzerland) with their incisor teeth to keep the SMU steady firing. A template‐matching procedure was used to identify SMU and the corresponding force was determined with STA. One‐min test series were recorded before 1, 4, 7, 10, 15 and 20 min after injection of 0·2 mL 100 µg mL−1 capsaicin into the masseter. Pain was continuously scored on 10‐cm visual analogue scales (VAS). The amplitude of twitch force and contraction time was measured. Injection of capsaicin into the masseter caused a deep, painful sensation with a VAS peak of 5·5 ± 0·6 cm. Twitch amplitudes were significantly influenced by pain (anova: P < 0·001) with higher amplitudes during pain‐1‐min (56·1 ± 10·7 mN) and pain‐4‐min (53·5 ± 11·9 mN) compared with before pain (33·9 ± 11·6 mN; P < 0·05). The contraction time (51·6 ± 4·4 ms) was not significantly changed during pain (anova: P > 0·429). The present study suggests that increased twitch force during painful muscle contraction could compensate for decreased firing rates of SMU.
Handy measurement for tongue motion and coordination with laryngeal elevation at swallowing
Authors: TSUGA K. , HAYASHI R. , AKAGAWA Y.
Published: March 2003

In managing elderly people's quality of life, dysphagia is a critical problem because of its presumable relation to pneumonia. In the oral stage of swallowing, the tongue involves profoundly and its proper performance is necessary for bolus forming and transferring to the pharynx. In this regard, informative videofluorography, however, requires special facilities and inevitable exposure to radiation. For the present study we prototyped a device for a safe and handy objective estimation of tongue motion and its coordination with laryngeal elevation at swallowing.

Ten healthy subjects were asked five times to swallow 5 mL of water. The tongue pressure was recorded by means of two strain gauge pressure transducers aligned in 20 mm distance on a brass strap placed along the palatal midline. Laryngeal vibration was recorded with piezo‐electric acceleration transducer. Time difference between each pressure onset of the anteriorly/posteriorly located transducers and impulsive output of laryngeal vibration were measured.

Pressure onset of the anteriorly located transducer preceded posterior one for 294 ± 164 ms. Considering the distance of transducers, tongue squeezed at 93 ± 60 mm s−1 speed. Laryngeal vibration occurred 671 ± 175 ms after the anterior pressure onset. There was a large variation in these parameters between subjects. The total recording time for each subject was <10 min. Although the information is limited, the developed device could handily describe some aspects of tongue motion and its coordination with laryngeal elevation.
Treatment received, treatment demand and treatment need for temporomandibular disorders in 35‐year‐old subjects
Authors: MAGNUSSON T. , EGERMARK I. , CARLSSON G. E.
Published: March 2003

An epidemiology sample of 114 subjects was followed longitudinally from the age of 15–35 years concerning received treatment, treatment demand and treatment need for temporomandibular disorders (TMD). Some kind of TMD treatment had been provided to 18% of the subjects during the 20‐year follow‐up period. Eighty‐five per cent of those who had received TMD treatment previously reported that the treatment had a positive effect on their symptoms. The estimated present need of treatment was 11%, but, in line with several other investigations, the active demand for such treatment was much less (3%). From 15 to 25 years of age, a small but gradual increase in clinical signs of dysfunction was found. From the age of 25–35 years, however, a significant reduction of such signs was noted. One explanation to this reduction of clinical signs of TMD might be the stomatognathic treatment performed. It was concluded that 18% had received some TMD treatment during the 20‐year follow‐up period. Only 3% had a demand for such treatment at 35 years of age.

This study was supported by the Research Council, County of Halland, Sweden, and the Swedish Dental Society.