bluuebunny/crossref_metadata_2025 huggingface dataset:
Comments on standardization of reflex measurements in human masseter muscle, including silent periods
Authors: VAN DER GLAS H. W. , VAN STEENBERGHE D.
Published: June 2007

The following comments are given on the guidelines suggested by Türker (1988) for studies on oral reflexes using the surface EMG of the masseter muscles in man, including the silent period.

(i) Attention should not be confined to electrical stimulation since mechanoreceptors in the periodontium, especially in the periodontal ligament, can only be activated by mechanical stimulation of a tooth. Furthermore, different modes of stimulation and stimulation sites do not yield equivalent reflex complexes. Weak and transient mechanical stimulation of a tooth while clenching at a low level of 5 or 10% MVC is a selective model (89%) to study the influence of periodontal receptors.

(ii) Statistical criteria should be applied on rectified and averaged EMG records to prevent any subjective bias in the measurements of reflex variables. Whether a period of increased EMG activity is due to clustering of action protentials of motor units firing of which was delayed by a preceding inhibition, or to a real excitatory influence, can be assessed by applying statistical criteria on averaged and subsequently rectified records.

(iii) The clenching level should be less than 25% of MVC to avoid muscle fatigue, and to elicit pronounced reflexes with a weak and therefore more selective stimulus.

(iv) The stimulus intensity should be much less than six times the threshold if selectivity for mechanoreceptors is desired. Furthermore, periods of increased activity in surface EMG resulting from a weak stimulus are probably due to real excitatory influences and not to clustering of motor unit action potentials after an inhibition.

(v) Jaw separation and the use of a force transducer are not always advantageous. If mechanical stimulation is applied to a tooth, clenching in full habitual occlusion causes a complete suppression of the influence of muscle spindles. A shift in activity between the various elevator muscles, and hence a change in activity of the muscle studied, may occur during an experimental session if biting force is used as a feedback. Such a shift is not relevant if feedback is carried out on rectified and lowpass filtered (1.6 Hz) EMG of the muscle studied.
Correlation between clinical and histological evaluations of the peri‐implant gingiva around the single‐crystal sapphire endosseous implant
Authors: AKAGAWA YASUMASA , TAKATA TAKASHI , MATSUMOTO TOSHIKADO , NIKAI HIROMASA , TSURU HIROMICHI
Published: June 2007

The correlation between clinical periodontal parameters and histological structure of the gingiva around a single‐crystal sapphire implant has been evaluated in two volunteer subjects. The implants had functioned after 6 years as the distal abutment of implant bridges in the Kennedy class II mandible. First, clinical evaluation was performed (gingival bleeding index, crevicular fluid volume, plaque index and probing depth) of the gingiva around the implant and natural teeth abutments and then a small piece of peri‐implant gingiva was excised from the lingual site of the implant of each subject for histological evaluation. The clinical evaluation using the periodontal parameter indices corresponded with the histological evaluation of the peri‐implant gingiva. The result suggests that it is possible for such parameters to be used in practice for judging the success of an implant.
Conditioning of root canals prior to dowel cementation with composite luting cement and two dentine adhesive systems
Authors: LIBERMAN R. , BEN‐AMAR A. , URSTEIN M. , GONTAR G. , FITZIG S.
Published: June 2007

Two hundred and forty root canals of extracted single‐rooted teeth were prepared to the same dimension, and Dentatus posts of equal size were cemented without screwing them into the dentine. Five cleansing solutions and two dentine adhesive systems were evaluated prior to post‐cementation using chemical‐cure composite resin.‘Pull‐out' tests were then conducted in order to evaluate the bond strength of these intra‐pulpal posts. The use of Conclude (composite luting cement) alone, with or without the cleansing solutions, resulted in significantly lower pull‐out forces. Scotchbond Dental Adhesive gave significantly better results, regardless of the cleansing solution used. Gluma Dentine Adhesive significantly increased the pullout forces only when used with its supplied cleanser or Tubulicid.
The radiopacity of glass ionomer dental materials
Authors: WILLIAMS J.A. , BILLINGTON R.W.
Published: June 2007

Although some glass ionomer dental materials are described as radiopaque by the manufacturer, it is rare for the actual degree of radiopacity to be specified. Using a technique previously described for measurement of the radiopacity of enamel, dentine and composite resin dental materials, the radiopacity of a number of glass ionomer materials, including restorative, lining and luting cements, was determined.
The influence of spacers on forces exerted on the abutment teeth of complete mandibular overdentures
Authors: OGATA K. , AOKI T.
Published: June 2007

The avoidance of lateral forces on overdenture retainers is essential to prevent pathological change in the supporting tissues of the root abutment. In this study, the influence of spacer thickness on the vertical and lateral forces exerted on overdenture abutments was examined clinically.

Two subjects with an edentulous maxilla, two canines and a left first premolar remaining in the mandible were selected for the experiment. The anchor type attachment was embedded in the left canine portion of the denture base. The transducer used for the previous study (Ogata et al., 1990), was embedded in this left canine portion. The transducer could detect the magnitude and direction of lateral forces exerted on an abutment tooth parallel to the Camper's plane. The other transducer was embedded in the left first mandibular premolar area, and could detect vertical forces exerted on the abutment tooth perpendicular to the Camper's plane. Furthermore, the transducer could change the space between a denture base and an abutment tooth to 1.5 mm, 0.6 mm or 0.3 mm. Therefore measurements could be made in the same way as if three experimental dentures had been used with a different thickness spacer. Recordings of forces were taken during food chewing, using each spacer on the day of denture insertion and twice at intervals of 1–2 weeks thereafter.

The results demonstrated that as spacer thickness decreased, the magnitude of the lateral forces decreased, while the magnitude of the vertical forces increased. These findings suggest that a large part of the lateral component of forces exerted on an abutment tooth could be converted into a vertical component by using a thinner spacer.
Assessment of adverse reactions to prosthodontic materials
Authors: DAHL B. L. , HENSTEN‐PETTERSEN A. , LYBERG T.
Published: June 2007

In 1978 five cases of so‐called hypersensitivity reactions to Scutan® and two to Impregum® were reported (Dahl, 1978). The aim of the present study was to assess whether hypersensitivity or cell‐mediated immune reactions were associated with the adverse clinical reactions in these patients or in others who had experienced the same reactions. Epicutaneous patch testing and lymphocyte transformation tests were carried out in a total of 13 individuals. The findings were difficult to interpret, because there was no consistent association between skin reactions and cell‐mediated immune responses in subjects with suspected allergies. Other possible reasons for the reactions originally recorded were therefore discussed. It was concluded that adverse reactions associated with immune‐mediated, delayed type hypersensitivity reactions may be elicited by prosthodontic materials, but other pathogenic mechanisms and aetiological factors responsible for the reactions observed should also be considered.
The unreliability of facial measurements in the determination of the vertical dimension of occlusion in edentulous patients
Authors: CAROSSA S. , CATAPANO S. , SCOTTI R. , PRETI G.
Published: June 2007

The aim of this research was to test the reliability of skin markers in the determination of the V.D.O. in edentulous patients during prosthetic rehabilitation. Two resin baseplates were constructed; on the upper one a modified pin of the Central Bearing Point registration device was fixed with impression compound. The height of the pin could be altered by rotating the pin directly in the patient's mouth with a probe. Two lead spheres were inserted on the resin base‐plate as bone markers, and two others were fixed to the skin as markers, one above (end of nose) and one below (point of chin) the oral commissure. Five lateral cephalometric radiographs were exposed for each patient, raising the V.D.O. by 1.2 mm on each occasion. Statistical analysis of measurements made on the resulting radiographs showed a very strong correlation between bone markers and pin position, whereas great variation and considerable differences were found between skin markers and bone as well as measurements.
An investigation into the microhardness of a light cured composite when cured through varying thicknesses of porcelain
Authors: WARREN K.
Published: June 2007

An investigation was carried out to measure the completeness of cure of samples of a composite resin, light cured for 40s and 60s through porcelain discs of varying thickness. Once cured, each specimen was subjected to Vickers microhardness testing to assess the completeness of cure. Composite resin specimens cured without an intervening porcelain disc were used to establish a baseline. The results showed that increasing the thickness of the porcelain disc produced a statistically significant decrease in microhardness of the composite resin. Increasing the cure time from 40s to 60s produced a significant increase in microhardness. The increase in microhardness with increased cure time was more pronounced when the discs of thickness 1 mm and 2 mm were used, and when there was no overlying porcelain disc.
A clinical evaluation of conventional bridgework
Authors: CHEUNG G.S.P. , DIMMER A. , MELLOR R. , GALE M.
Published: June 2007

The present study evaluated the incidence and causes of failure of conventional bridgework provided in the Prince Philip Dental Hospital, Hong Kong. Any bridge that utilized resin‐bonded (Maryland) retainers was excluded from this study. All patients with bridges fitted between 1981 and 1987 were recalled for review, and 143 patients attended, a response rate of 77%. A total of 169 bridges were examined, their mean length of service being 35 months. Thirty‐five bridges were deemed to have failed. The most frequent cause was endodontic, followed by loss of retention, then persistent pain and sensitivity. Failures of endodontic origin affected mostly anterior bridges, which could be attributed to the over‐sized pulp of anterior teeth and the amount of tooth reduction required for the ceramometal retainer. All of the bridges that failed because of endodontic problems had had ceramometal retainers. Taking posterior bridges alone, the failure rate was 4.4% per year. From the evidence of this study, the replacement of the maxillary canine with a cantilever bridge appears to be contra‐indicated.
Wear of teeth in a mentally retarded population
Authors: ØILO G. , HATLE G. , GAD A‐L. , NIOM B.L. DAHL
Published: June 2007

The study includes an evaluation of dental wear in 69 individuals, 44 men and 25 women, of mean age 35 years and range 18–59 years, living in a home for mentally retarded persons. Wear was evaluated with a newly developed index based on Ryges' system, where the need for treatment is the key issue. The index consisted of three categories representing clinical situations from no wear to moderate, age dependent wear without problems for the patient, and two categories in which treatment was found to be necessary either to prevent future problems or to improve the present situation.

A relatively large number of teeth showed considerable wear in the 20–29 year age group. Wear was observed predominantly in incisors and canines. Only 1 % of cases were considered to require treatment. Wear increased with age, and more than 5% of teeth were diagnosed as needing treatment in the 30–39 year and 40–49 year age groups.

Wear in the studied population was found to be more severe than that observed in an urban population from the same area in a parallel study.
Clinical performance of resin‐bonded bridges: a 5‐year prospective study. Part III: failure characteristics and survival after rebonding
Authors: CREUGERS N.H.J. , SNOEK P.A. , VAN'T HOF M.A. , KÄUYSER A.F.
Published: June 2007

A total of 203 resin‐bonded bridges were inserted under controlled clinical conditions and evaluated over a period of 5 years. During the evaluation period there were 47 dislodgements and 30 pontic fractures. The majority of the failures were retreated successfully. Dislodgement was in most cases due to fracture at the resin/retainer interface. The small number of fractures at the resin/tooth interface indicate that the clinical procedures, as used in this study, were satisfactory. Dislodged and rebonded resin‐bonded bridges had a lower retention than original bonded bridges, indicating that patients with a dislodged bridge are a risk group for the retention of rebonded bridges. However, possible factors that may be responsible for this higher risk could not be demonstrated. The bridges which were removed for repair of the pontics and rebonded showed an acceptable retention. There was no relationship between the failure characteristic and the retainer type or the cementation material used.
Nocturnal bruxing events in healthy geriatric subjects
Authors: OKESON J.P. , PHILLIPS B.A. , BERRY D.T.R. , COOK Y. , PAESANI D. , GALANTE J.
Published: June 2007

Thirty healthy geriatric subjects were studied during a single night of sleep in a sleep laboratory. Unilateral masseter muscle activity was recorded in addition to the standard polysomnographic study. The geriatric subjects in this study exhibited fewer bruxing events than other subjects reported in the literature. Certain conditions that have not been previously investigated, such as sleep position, type of bruxing event, and relationship to the state of the dentition, are reported.
Current views on biological testing of restorative materials*
Authors: NIOM I. A. MJÖR
Published: June 2007

It is anticipated that biological testing in Europe after 1 January 1993 will be based on European Standards (EN) common to all biomaterials. No details regarding the future certification programmes are yet available.

In vitro cytotoxicity, tissue reactions to implanted materials and pulp studies (‘usage tests’) represent three levels commonly used for biological testing of restorative dental materials. Considerable variation in test methodology exists, and no universal agreement prevails with regard to which test or tests are most appropriate for evaluation of the biological effects of restorative materials. The latter also include a number of allergens, but few biological side‐effects have been noted in clinical practice.
Dental materials science — the maintenance of standards
Authors: TYAS M. J.
Published: June 2007

Standards for dental materials are available for both biological and chemical/physical properties. In order to predict the clinical performance of a material by means of standard tests, both the test and the method used in the test should ideally simulate clinical usage. However, owing to lack of knowledge with regard to intra‐oral failure modes, and technical considerations in the performance of tests, this ideal may not always be achieved.
Postural contractile activities of human jaw muscles following use of an occlusal splint
Authors: CARR A.B. , CHRISTENSEN L.V. , DONEGAN S.J. , ZIEBERT G.J.
Published: June 2007

As induced by an occlusal splint over a period of 1 week, this study monitored surface electromyographic changes in the postural contractile activities of jaw elevator and depressor muscles in six healthy adults. The immediate effect of the occlusal splint was to increase the postural contractile activities of the suprahyoid muscles. All postural muscle activities showed wide‐ranging biological variation, but the activities induced by the splint tended to stabilize within 1 week, with decreased postural activities in the masseter and anterior temporalis muscles, and increased postural activities in the suprahyoid muscles.
Porosity of pit and fissure sealants
Authors: LEKKA M. , PAPAGIANNOULIS L. , ELIADES G.
Published: June 2007

The aim of this study was to investigate the bulk porosity of a range of pit and fissure sealants. The following materials were included in the study: Concise White Sealant and Delton (chemically cured); Delton (visible light‐cured); Helioseal, Visioseal and Prolite (visible light‐cured with delivery from the bottle via cannule): Delton, Luma Seal and Prisma Shield (visible light‐cured with syringe‐type direct delivery systems). Five cylindrical samples, 7 mm in diameter and 1 mm in thickness, were prepared from each sealant and the following parameters were analysed in a computer‐controlled mercury porosimeter: (i) total cumulative pore volume; (ii) specific surface area of pores; (iii) percentage total porosity (iv) bulk density; and (v) pore radius distribution. According to the results, the chemically cured sealants exhibited total cumulative pore volume, specific surface area of pores and total porosity. Significant differences were detected within the group of visible light‐cured materials. The visible light‐cured sealants with syringe‐type delivery exhibited the lowest porosity.
Wedges in restorative dentistry: principles and applications
Authors: ELI I. , WEISS E. , KOZLOVSKY A. , LEVI N.
Published: June 2007

Overhanging margins of proximal restorations are a well‐known, iatrogenic cause of periodontal pathology. The high incidence of such findings in Western societies should arouse the concern of the dental community. However, overhanging margins represent only part of the iatrogenic problem created by the misuse of wedges in restorative procedures. Other causes include incorrect proximal contouring, inadequate contact points and under‐ or overfilling the restorative material.

The understanding of the variables associated with wedge selection and positioning has a major role to play in the prevention of iatrogenic periodontal pathology associated with restorative procedures. It is concluded that:

(i) the occlusion of the matrix band to the remaining healthy tooth structure of the gingival cavosurface line angle should be achieved solely by the correct application of the wedges;

(ii) the effect of the wedges on the proximal contour and contact area should be carefully re‐evaluated prior to insertion of the restorative material;

(iii) various sizes and shapes of wedges and a sharp knife for carving must be readily available.
Chewing and swallowing activity of masticatory muscles in patients with a complete upper and a partial lower denture
Authors: TALLGREN A. , TRYDE G.
Published: June 2007

The chewing and swallowing activity of jaw‐closing muscles was studies longitudinally in 30 partially edentulous subjects who were provided with an immediate complete upper and a partial lower denture. Electromyographic recordings of the anterior temporal and masseter muscles were obtained during habitual chewing of apple and during swallowing of saliva and water, before final extractions and 7 weeks, 6 months, 1 year and 2 years after denture insertion.

At the pre‐treatment stage, when the patients were chewing with a residual anterior dentition, the mean voltages showed low values compared to findings reported in subjects with a complete natural dentition. After 6 months of denture use, the chewing forces showed significant increases in amplitude, and the increased force of contraction persisted to the 2‐year stage.

The recordings of swallowing revealed no significant changes in maximal mean voltage during the observation period. However, there was a significant increase in the duration of the swallows after 1 year of denture wearing, which might be related to stabilization of the complete upper denture due to continuing resorption of the maxillary ridge.
The masseteric reflex evoked by tooth and denture tapping
Authors: BRODIN P. , FLØYSTRAND F. , ØRSTAVIK J.
Published: June 2007

The characteristics of the masseter reflex evoked by tapping a maxillary incisor were compared with the reflex pattern evoked by tapping a corresponding denture tooth after insertion of an immediate denture. Up to three inhibitory phases (I‐1, I‐2 and I‐3), followed by excitation, were found on an averaged EMG. The tapping force threshold for the early inhibitory phase was lower than for the late phases. The pattern of the reflex was generally the same before and after insertion of the denture, but the threshold values increased. After insertion of the denture, the threshold for I‐1 increased from 1±0.3N to 2.2±0.4N, the threshold for I‐2 increased from 2.4±0.8N to 3.8±0.9N, and the threshold for I‐3 increased from 5.1±0.6N to 8.3±0.9N. The latency period for I‐1 also increased from 12.3±0.5 ms to 13.1±0.3 ms after insertion of the denture. After relining, the threshold for evoking I‐1 decreased from 2.7±1.2N to 1.2±0.6N. It was assumed that the mechanoreceptors situated in the mucosa under the denture base could take over the functional role of the periodontal mechanoreceptors for evoking the masseter reflex during tapping, and that these afferents probably had connections to the same interneurones.
Effect of occlusal bite‐raising splint on electromyogram, motor unit histochemistry and myoneuronal dimensions in rats
Authors: YAFFE A. , TAL M. , EHRLICH J.
Published: June 2007

Composite resin bite‐raising splints were fabricated on both sides of the upper jaw in rats. EMG activity of the deep masseter muscle was monitored continuously for 24 h before and up to 4 weeks after treatment. Together with the EMG activity, measurements of the neuromuscular junction area and muscle fibre histochemistry were made. EMG activity showed great variability immediately after splint fabrication. Some of the animals showed increased EMG activity, while others exhibited less activity 48 h after splint application. Overall, the fluctuation lasted for about 4 days, and after approximately 7 days all the animals exhibited decreased EMG activity, followed by a gradual increase in activity towards baseline levels. The neuromuscular junction territory increased significantly 5–10 days after splint application. Histochemical characterization of the deep masseter muscle revealed that it contained the three main types of muscle fibre: slow oxidative (SO), fast‐oxidative‐glycolytic (FOG) and fast glycolytic (FG). The frequency distribution of fibre types did not change after bite‐raising splint treatment. These findings indicated that splint treatment in rats is effective in reducing EMG activity, while the muscle type characteristics remain stable. The effect of lower activity on the motor end‐plates suggested that the neuromuscular junctions are quite sensitive to functional changes.
The relationship between failure and design in conventional bridgework from general dental practice
Authors: FOSTER L.V.
Published: June 2007

A total of 142 failed bridges constructed in general dental practice were assessed for design factors that might relate to failure. The overall mean age of the bridges at failure was 6.2 years; anterior and complex bridgework had a mean age of about 5 years, compared with 7.5 years for posterior bridges. The lifespan of the bridgework was significantly correlated with the number of retainers but not with the number of units. Bridges with one or two retainers had an average lifespan of just over 7 years, whilst those with three or more retainers had been in service for, on average, only 4 years. The practical difficulties of constructing multi‐abutment bridgework could account for this difference. One hundred and ninety‐one of the 346 retainers were porcelain bonded to semi non‐precious metal crowns, and had a mean lifespan of 3.7 years, whilst those that were gold based lasted at least twice as long. Post crowns as retainers survived on average for 6.2 years.
Orthognathic diagnosis and treatment planning: a cephalometric approach
Authors: CHACONAS S.J. , FRAGISKOS F.D.
Published: June 2007

Cephalometric analyses have long been important diagnostic tools for the orthodontic specialist. Such analyses, as they pertain to adult skeletal problems and their consequent therapy, should also be a valuable adjunct for various dental specialties, e.g. the oral surgical clinician. However, because of the complexity of most analyses, it is difficult to glean the important values needed for most orthognathic cases. In this article an analysis is presented to aid the clinician in surgical diagnosis and treatment planning.
Activity index and isometric contraction velocity of human jaw muscles
Authors: CHRISTENSEN L. V. , KUNDINGER K.K.
Published: June 2007

To determine the relative contribution of the masseter and anterior temporalis muscles to global isometric bite force, activity indices were constructed on the basis of the peak mean voltage (μV) and the integrated voltage (μV.s) of bipolar surface electromyograms obtained during brief maximum voluntary teeth clenching (MVC). The index that was based on integrated myoelectrical activity showed that the masseter muscle contributed the major part of the isometric MVC force. The index that was based on instantaneous peak myoelectrical activity also showed that activity in the masseter muscle predominated over that in the anterior temporalis muscle. In addition, the latter index showed a negative linear association with the initial (0–50% MVC) isometric contraction velocities of the masseter and anterior temporalis muscles. Both indices appear to be promising clinical diagnostic tools.
Use of shell crowns in Hong Kong dental hospital attenders
Authors: CORBET E.F. , HOLMGREN C.J. , PANG S.K.
Published: June 2007

In 1984 an oral health survey of Hong Kong adults aged 35–44 years revealed that 15% of subjects presented with metal shell crown restorations, often as components of fixed‐bridge reconstructions. The aim of this study was to describe the patterns and means of use of shell crowns, and to describe the patterns of tooth loss in patients who presented with such restorations, attending for treatment at the dental teaching hospital in Hong Kong over a 2‐year period. A total of 1563 such patients attended. The records, which included radiographs, of 165 of these patients aged 35 years and above, obtained by means of a systematic sampling frame, were studied by one trained examiner. On initial presentation each patient was found to have a mean of 4.0 shell crowns, 77% of these being components of bridge restorations. The bridges involved a mean of only 3.9 units (retainers and pontics). The tooth type most commonly replaced by a bridge of this type was the first molar. It was concluded that most shell crowns used in this patient group are abutment retainers for predominantly short‐span bridge restorations.
Microleakage studies comparing a one‐visit indirect composite inlay system and a direct composite restorative technique
Authors: CASSIN A.M. , PEARSON G.J.
Published: June 2007

Problems related to leakage have been observed with direct‐filled composite restorations. The development of indirect system of fabrication followed by cementation should theoretically reduce this phenomenon. The present study compares the leakage around directly placed composites with composite inlays prepared by a surgery‐based system. The results indicate that the amount of leakage is reduced with the inlay system, but that it is not eliminated.
Non‐cast titanium restorations in fixed prosthodontics
Authors: BOENING K.W. , WALTER M.H. , REPPEL P.‐D.
Published: June 2007

The problems encountered in casting titanium in dentistry have not been completely resolved. The Procera system forms crowns by means of a combination of spark‐erosion and milling. The accuracy of fit was examined before and after ceramic veneering both in vitro and in vivo. Before veneering, on conical surfaces space widths were approximately 53 μm in vitro and 69 μm in vivo. At shoulders and occlusal surfaces, spaces of about 430 μm were measured in vitro and of about 500 μm were measured in vivo. After ceramic veneering, slight increases in space widths could be observed. The metal‐ceramic compound was tested by the 3‐point bending test (DIN) and the bending test (ISO). The DIN test was satisfactory, but not the ISO test. It is concluded that titanium crowns processed by the Procera System are suitable for clinical usage, if the space widths at shoulders and the occlusal surface and the special requirements of tooth preparation are taken into account.
Maximum jaw opening capacity in adolescents in relation to general joint mobility
Authors: WESTLING L. , HELKIMO E.
Published: June 2007

Mandibular jaw opening was related with general joint mobility in a non‐patient adolescent group. The angular rotation of the mandible at maximum jaw opening was slightly larger in females than in males and significantly larger in hypermobile individuals. No significant relationship between linear measuring of maximal mandibular opening capacity and peripheral joint mobility was found either at active (AROM) or at passive range of mandibular opening (PROM). PROM was strongly correlated to the mandibular length. Clinical signs in the great jaw closer muscles could not be associated to decreased AROM. The mean value of the difference between PROM‐AROM (DPA) was 1.2mm. Frequent clenching and/or grinding was correlated to increased DPA only in hypermobile adolescents (r=0.49***). Those with DPA exceeding 5 mm had all reciprocal clicking.
Electromyographic parameters related to clenching level and jaw‐jerk reflex in patients with a simple type of myogenous cranio‐mandibular disorder
Authors: BUCHNER R. , VAN DER GLAS H.W. , BROUWERS J.E.I.G. , BOSMAN F.
Published: June 2007

A discriminant analysis has been applied on several electromyographic (EMG) parameters of the masseter and the anterior temporal muscles, related to clenching and the jaw‐jerk reflex, to characterize jaw muscle function of patients with craniomandibular disorder (CMD) with respect to controls. The subject samples, matched for age, consisted of 20 females with myogenous CMD, and 20 symptom‐free females. The jaw‐jerk reflex was elicited by a downward‐directed mandibular load, transmitted by a bite‐fork causing a similar occlusion and bite‐rise as a splint. The patients differed mainly from the controls by smaller maximum EMG activity in both muscle groups (P<0.05 with the bite‐fork inserted). This finding was related to a smaller muscle strength as the EMG level did not improve with pain‐free jaw muscles after therapy using a relaxation splint. Discriminating factors of secondary importance were an enhanced bilateral asymmetry in the muscle activity of the patients, and in the reflex amplitude normalized for background EMG activity. In all subject samples, the activity of the anterior temporal muscles decreased with respect to the masseter muscles when the bite‐fork was inserted (P<0.05–0.001). The therapeutic effect of a relaxation splint may, in part, be related to a relief of the temporal muscles.
Shrinkage of tissue conditioners with time — effect of the particle size in powder and the EtOH content in liquid
Authors: MURAKAMI S. , MURATA H. , SADAMORI S. , SHIGETO N. , HAMADA T.
Published: June 2007

The dimensional change of tissue conditioners with time was measured until 4 weeks after mixing. Shrinkage of the materials was evaluated in relation to particle size in powder and the EtOH content in liquid. The dissolution of EtOH and plasticizer were also measured to investigate the relation to dimensional change. Shrinkage with time was recorded. The smaller the particle size in powder and the more EtOH in liquid, the greater the shrinkage rate. The smaller the particle size in the powder and the more EtOH contained in the liquid, the greater the dissolution of EtOH. The dissolution of BPBG was below 1/100 comparing that of EtOH and no difference was recognized by particle size and EtOH content.

On the basis of these results it is suggested that the dissolution of EtOH is related to shrinkage of tissue conditioners with time and that the component particle size in the powder and EtOH content in the liquid have a significant influence on dissolution of EtOH associated with shrinkage.
Relationship between autoregressive model coefficients of EMG and its potentials of jaw closing muscles at rest position and clenching
Authors: SHI C.‐S. , HUA Z. Y.
Published: June 2007

At rest position and varied clenching levels at intercuspal position, autoregressive (AR) models of myoelectrical activities of both masseter and anterior temporal muscles of 11 healthy subjects with intact natural dentitions were established. The relationship between the AR model coefficients of surface EMGs and their potentials was analyzed by multiple linear regression. It was found that the fourth order coefficient of AR had the greatest effect on the EMG potential levels and their relationship was positive in all recorded muscles. The results indicate the AR coefficients may become a characteristic parameter to describe myoelectrical activity of jaw closing muscles.
The ‘temporomandibular pain dysfunction syndrome’ personality: fact or fiction?*
Authors: MARBACH J.J.
Published: June 2007

It is widely accepted that abnormal personality traits are important factors in the aetiology and maintenance of the temporomandibular pain and dysfunction syndrome (TMPDS). However, the foundation upon which this paradigm rests is largely based on clinical lore rather than evidence. The continued belief in the stress theory has onerous implications. First of all, clinicians could be lulled into a false sense of security about the efficacy of traditionally sanctioned treatments. Second, and potentially more important is the chilling effect on research that results from the premature and unsupported conclusions voiced by many, that certain issues regarding the diagnosis and treatment of TMPDS are solved. Such conclusions will lead not only to problems of patient care but may forge an unstable foundation for future research. Three theories are examined for convergent evidence in support of the putative relationship between personality and TMPDS. They are the 1) psychosomatic 2) coping and 3) psychophysiological theories. Currently evidence lacks for all three theories although there is partial support for the latter. It has not been demonstrated that TMPDS cases are characterized by a specific premorbid personality.
Level of accuracy and degree of precision in attempting to maintain steady levels of biting force
Authors: WILLIAMS W.N. , COFFEY J. , TURNER G.E. , CRARY M.E. , CAPEN R. , WHARTON P.W.
Published: June 2007

The primary purpose of this study was to assess the level of accuracy (bias) and degree of precision for a group of 24 normal subjects attempting to maintain a contsant biting force at levels of 100 gm. 500 gm, 100 gm and 2000 gm for a period of 10s each. Accuracy is defined as the difference between subjects actual level of biting force and the target value they were trying to achieve. Precision is the level or range of variability demonstrated by the subjects while attempting to bite with a constant level of force. Subjects performance relative to accuracy and precision was also compared when using the central incisors vs. the first permanent molars. Assessment of bite force was measured using a specially designed strain gauge scale which permitted subjects to visually monitor when their biting force equalled a preset resistance. Each subject was instructed to bite on the end of a plastic sheathed steel beam with enough foree to activate the indicator needle on the voltage meter to its central position and to try to maintain a constant level of biting foree (by attempting to keep the indicator needle steady in its central position). No significant (P > 0.05) differences were found in mean accuracy in bite force for gendeer or specific teeth used in the biting task. However, a significant difference (P < 0.0001) in mean accuracy in bite force was found to exist between the target elvels. At the lowest standard force (100 gm) there was a mean group bias of +17 gm while at the highest standard (2000 gm) the mean group bias was −103 gm. Analysis of subjects precision in biting force revelaed significant differences in performance relative to gender (P <0.0001), teeth (P > 0.01) and target levels (P < 0.0001).
Swallowing activity of lip muscles in patients with a complete upper and a partial lower denture
Authors: TALLGREN A. , TRYDE G.
Published: June 2007

Summary In 30 partially edentulous subjects provided with an immediate complete upper and a partial lower free‐end denture the lip activity in swallowing was studied before and after denture treatment and during a 2‐year period of denture wearing. Electromyographic recordings of the right side upper and lower orbicularis oris, mentalis and anterior temporal muscles were obtained during swallowing saliva and during swallowing of water with and without the dentures in the mouth.

In the different types of swallows recorded, the lower lip and mentalis muscles showed much stronger activity than the upper lip and anterior temporal muscles and also initiated the swallowing activity. No significant changes in mean voltages of the swallowing activity were observed during the 2‐year observation period. On the other hand, the durations of the swallows showed marked increases after 1 year of denture use, when no further rebasings of the complete upper denture had been made.
Signs and symptoms of temporomandibular joint dysfunction in a Saudi Arabian population
Authors: JAGGER R.G. , WOOD C.
Published: June 2007

Summary The signs and symptoms of temporomandibular joint dysfunction present in 219 Saudi Arabians attending a dental clinic for routine dental treatment are described. Joint sounds (36%) and muscle tenderness to palpation (34%) were common findings. Of the subjects examined, 31% reported suffering from frequent headaches.

The study demonstrated a high incidence of signs and symptoms of temporomandibular joint dysfunction. Findings were similar to those of a previous study of an investigation in a bedouin community in Western Egypt (Abdel‐Hakim, 1983).
The masticatory pattern as an adjunct for diagnosis and treatment
Authors: EHRLICH J. , HOCHMAN N. , YAFFE A.
Published: June 2007

Summary The sagitally‐viewed masticatory pattern was investigated in 125 dentate patients. In 25 patients, the phenomenon of an incisal guided phase during mastication was observed. Clinical examination of these cases revealed slight to severe incisal attrition or various degrees of flaring. The hypothesis that the incisal guided phase contributes to this phenomenon and should therefore be taken into consideration during treatment is put forward.
Methodological observations on positive and negative work (teeth grinding) by human jaw muscles
Authors: CHRISTENSEN L.V. , HUTCHINS M.O.
Published: June 2007

Summary Through electrognathography and surface electromyography of the right and left masseter muscle (MM), this methodologic study examined the excentric (lengthening) and concentric (shortening) contractions of brief (2000ms) voluntary teeth grinding performed through canine as well as group function of the opposing teeth. We inferred that the most anterior and superior portions of the right and left MM were lengthened and shortened by at least 4.23 mm (right MM) and 4.82 mm (left MM). For the negative work efforts (excentric contractions) of canine function, the tensions of the ipsilateral MM ranged from 10 to 20% MVC and those of the contralateral MM from 4 to 14% MVC. For the positive work efforts (concentric contractions) of canine function, the tensions of the ipsilateral MM ranged from 11 to 44% MVC and those of the contralateral MM from 20 to 41% MVC. A comparison between canine and group function showed that the negative as well as positive work efforts of group function exceeded those of canine function.
A comparative study of two methods for the orientation of the occlusal plane and the determination of the vertical dimension of occlusion in edentulous patients
Authors: KOLLER M.M. , MERLINI L. , SPANDRE G. , PALLA S.
Published: June 2007

Summary The aim of this study was to compare two methods used to orientate the occlusal plane (OP) and to determine the vertical dimension of occlusion (VDO). In method A the VDO was established by means of the rest position, the minimal speaking distance, and the patient's profile. Method B used a newly developed registration pin assembly. The VDO was registered using a silicone occlusion rim and the swallowing technique. The results were compared to the values of the new dentures.

Three standardized lateral radiographs were taken at the VDO obtained with methods A, B, and at that of the final dentures. On each radiograph the orientation of the OP to the Camper plane and the VDO were measured by two investigators independently. The results indicated no statistically significant differences between the mean VDO with method A and B compared with the new dentures (P>0.05).

With both methods it was not possible to orientate the OP parallel to the Camper plane. None of the occlusal planes of the new dentures were parallel either. Their OP diverged on average by 7° dorso‐caudally.

The time spent with method B to orient the OP and to determine the VDO was significantly lower than with method A (17–50min).
Long‐term follow‐up of patients with orofacial discomfort complaints
Authors: YONTCHEV E. , CARLSSON G.E.
Published: June 2007

To a group of 113 patients who exhibited wide variation in orofacial and general complaints, which they related to the effects of dental material, a new questionnaire was sent 8‐10 years after the first examination. Eight patients had died, and 23 individuals could not be contacted. Of the remaining 82 patients, 62 (76%) individuals completed the questionnaire.

Almost two‐thirds (29%) of the responding patients reported that they were now free from the previous symptoms, or that these symptoms were alleviated (35%). Dryness of the mouth and smarting tongue were the most frequent symptoms at the follow‐up. Half of the patients (52%) thought they still needed treatment for their complaints, and several of them had visited many other therapists after the end of the treatment period at the Department. The treatment outcome and symptom development may be regarded as acceptable with regard to the severity and long duration of the original complaints. However, the prognosis was poor in a substantial proportion of the patients, and this group continued to be a high consumer of health‐care resources.
The influence of surface finish and in‐vitro pellicle on contact‐angle measurement and surface morphology of three commercially available composite restoratives
Authors: MILOSEVIC A.
Published: June 2007

Three commercially available composites (Concise, Occlusin and Heliomolar) had surface finishes of varying roughness. Concise and Occlusin were cured against glass and Mylar, or were polished with a white stone or Soflex discs, producing four different surface finishes. Heliomolar was cured against glass or finished with a Vivadent polisher. Each specimen was immersed in water (without pellicle) or artificial saliva (with pellicle) and photographed with a captive air bubble. The influence of pellicle on contact‐angle measurements and hence adhesiveness was determined. Scanning electron microscopy of pellicle‐free and pellicle‐conditioned surfaces was also performed.

The effect of the pellicle on all Concise specimens was profound, tending to increase adhesiveness of the smooth (glass and Mylar) surfaces and decrease adhesiveness of the toughened (white stone and Soflex disc) polished surfaces. The pellicle‐conditioned smooth Occlusin surfaces behaved similarly, but not the polished specimens, having similar contact‐angle measurements after pellicle deposition. Heliomolar had significantly reduced contact‐angle measurements after pellicle formation, and thus increased adhesiveness.

The influence of the pellicle on surface finish characteristics may be significant, and may vary according to the composite used.
Thermal diffusivity of glass ionomer cement systems
Authors: BRANTLEY W.A. , KERBY R. E.
Published: June 2007

The thermal diffusivity has been measured for 10 glass ionomer and resin‐based materials: three conventional (water‐hardened) glass ionomer cements, two silverreinforced glass ionomers, an experimental stainless steel‐reinforced glass ionomer, three visible light‐cured (VLC) glass ionomer‐resin hybrid materials, and a VLC resin‐based product developed for the same clinical uses as the hybrid materials. Cube‐shaped specimens, c. 10 × 10 × 10 mm, initially at room temperature were immersed in mercury surrounded by an ice‐water bath. From the experimental cooling curve a semi‐log plot of relative temperature decrease vs. time yielded a straight line whose slope is proportional to the thermal diffusivity. The values ranged from 1.74–5.16 × 10−3 cm2 s−1, and all of the materials tested would have adequate insulating properties provided normal clinical thickness levels for lining materials are maintained. It was found that the thermal diffusivities for the three metal‐reinforced glass ionomers, where composition information is avaiable, do not follow a rule of mixtures applied to the individual components.
The properties of metal‐reinforced glass ionomer materials
Authors: CHUNG K.‐H.
Published: June 2007

The physical properties and bond strengths of two glass ionomer materials reinforced with silver and amalgam alloy powders were compared with those of a conventional material from the same manufacture as well as two commercially available products. The diametral tensile strength, hardness and bonding strength are improved with the addition of either commercial available silver particles or fabricated high‐copper amalgam alloy powders to the glass. Simple mixture of the metal or alloy powders with the glass ionomer cement seems to be feasible to improve the properties of the regular cement. However, further studies in formulating an optimal composition of metal or alloy, setting characteristics and long‐term clinical evaluation are necessary before proposing uses for this new material.
Comminution of two artificial test foods by dentate and edentulous subjects
Authors: SLAGTER A.P. , BOSMAN F. , VAN DER BILT A.
Published: June 2007

An experimental artificial test food with low fracture strength (Optocal) was compared with Optosil® with respect to the comminution during mastication by complete denture wearers and subjects with natural dentitions. The comminution of both test foods revealed large differences between the denture wearers and the dentate subjects. These differences were larger with Optosil® than with Optocal. The differences in comminution between Optocal and Optosil® were larger in the denture wearers than in the dentate subjects. The differences in comminution between the denture wearers and the dentate subjects as well as the differences in comminution between Optocal and Optosil® within each group were largely established in less than 20 chewing strokes. The results indicate that differences in selection contributed substantially to the differences in comminution. Since Optocal appeared to be much easier to chew than Optosil®, it may be preferred to Optosil® for measuring masticatory performance in complete denture wearers.