A breakage index for characterizing in vitro nut fragmentation and predicting human oral fragmentation.

Breakage of food influences eating experience and sensory perception. The aims of the study were to identify an appropriate breakage index and to develop an in vitro method for predicting the ease of oral breakage of nuts. Kernels of five types of nuts were fragmented in vitro using a texture analyzer and 12 subjects therefore performed molar bites. In addition, peanuts were differently roasted (over 0, 15, 25, and 35 min) to vary texture within the same nut type. Projected particle areas were determined using imaging. Two Breakage Indices were compared (1) BI-I, the difference, after and before fragmentation, in square root values of ratios between total projected area and volume [Agrawal et al., 1997, Archives of Oral Biology, 42(1), 1-9], and (2) BI-II, the ratio of the total projected area after and before fragmentation. BI-II gives a stronger linear regression than BI-I between in vivo and in vitro index values for different types of nuts; Pearson's r = 0.834 versus 0.499 (12 subjects with all data pooled). Using BI-II, a subject's regression result in fragmentation tests with differently roasted peanuts was as strong as when testing different nut types: Pearson's r = 0.984 versus 0.964. Since the range of the in vitro BI-II values was 5.5 times smaller in the peanut tests, the finding of a similarly strong regression indicates a high sensitivity of BI-II to detect differences in food texture. BI-II is useful for food industry to determine how easily solid foods break down and thereby compare the potential of flavor release between foods during chewing.

Consensus on the terminologies and methodologies for masticatory assessment.

A large number of methodological procedures and experimental conditions are reported to describe the masticatory process. However, similar terms are sometimes employed to describe different methodologies. Standardisation of terms is essential to allow comparisons among different studies. This article was aimed to provide a consensus concerning the terms, definitions and technical methods generally reported when evaluating masticatory function objectively and subjectively. The consensus is based on the results from discussions and consultations among world-leading researchers in the related research areas. Advantages, limitations and relevance of each method are also discussed. The present consensus provides a revised framework of standardised terms to improve the consistent use of masticatory terminology and facilitate further investigations on masticatory function analysis. In addition, this article also outlines various methods used to evaluate the masticatory process and their advantages and disadvantages in order to help researchers to design their experiments.

Optimizing a determination of chewing efficiency using a solid test food.

A test using a solid food is relevant to measure chewing ability (CA) as (a) it includes an integrated functioning of all oral structures involved, (b) an impairment of chewing a solid food causes inevitably diet restrictions, and (c) chewing efficiency (CE) can easily be defined. CE is the number of chewing cycles, N(1/2-Xo), needed to attain a particular chewing outcome (a median particle size, X 50 , which is half the initial particle size Xo) whereas chewing performance (CP) is a state of chewing outcome (X 50 ) at an arbitrary number of chewing cycles. The use of CE is preferable for CA because inter-subject ratios are constant regardless of the initial conditions of the test food. Furthermore, the inter-subject variation is two times larger for CE values than for CP ones, yielding a better inter-subject differentiation of CA. However, a determination of CP needs only one N-value, and that of CE at least two N-values for enabling an interpolation of N(1/2-Xo). Using samples of only two half-cubes (9.6 x 9.6 x 4.8 mm; limiting test load) of Optosil (an artificial test food), and detailed previous information on log(X 50 )-log(N) relationships (Liu et al., Archives of Oral Biology, 2018, 91, 63-77) as a "gold standard," a short procedure has been developed for a priori choosing two appropriate N-numbers, and the subsequent determination of a subject's CE. This procedure has been developed using results from 20 young adults (23.7 years, SD 1.1) and was validated in 10 middle-aged and older adults (52.3 years, SD 10.1), where impairments in the dentition were reflected in the CE-values. Our short procedure to determine CE will improve studies on relationships between CA and food preference, or between CA and dental factors and/or physiological factors. The first type of relationship may be of interest for food industry whereas the second type may be of interest for population studies in rapidly aging societies and for clinical studies in dentistry. Results can be compared between subjects and studies without bias by using CE rather than CP as a measure of CA.

Oral physiological characteristics among Chinese subjects in the eastern region of China.

OBJECTIVES: With an increasing number of elderly in China, it becomes imperative to establish a comprehensive understanding of their physiological capabilities and investigate fundamental mechanisms underpinning the discrepancies between Chinese individuals and other ethnical groups, which will facilitate government policymaking, design and development of special food products. DESIGN: In this study, 100 healthy Chinese subjects in the eastern region of China (22-89 years old) were recruited with full consent, then divided into young adult, middle-aged and elderly groups. Subjects' maximum biting force (MBF), maximum tongue pressure (MTP), maximum oral volume (MOV), and saliva flow rate were recorded. Unstimulated (US) and stimulated (SS) saliva were collected. Subjects were then objectively clustered into 3 different levels of oral processing capability. A total of 10 young subjects from two different clusters were selected for chewing efficiency (CE) determination. CONCLUSIONS: With increased age, there is a decline in subject's dental status, MBF and MTP. Gender affects greatly on MOV; males have larger MOV. No significant effects on SS and US flow rate were found with age and gender. The finding of a similar CE and differences in overall capability in relevant physiological variables (MBF and MOV in young adults) suggest that the degree of CE is not determined by a total capability of various oral physiological variables. In contrast, the findings suggest that CE will be non-impaired as long as each of the relevant physiological variables (i.e. dental status, MBF) operates at a supra-threshold level.

Locking up of food between posterior teeth and its influence on chewing efficiency.

OBJECTIVES: Food particles are intra-orally locked up between antagonistic posterior teeth, during each chewing cycle. Food locking up (FL) may enhance selection of particles for subsequent breakage, hence chewing efficiency (CE). The two aims were to determine FL, and to examine the relationship between FL and CE. DESIGN: A spherical gum bolus (volume: 1.3 cm3) that undergoes plastic deformation rather than breakage, was used to determine FL in 20 young adults. Chewing such a bolus with initially a width-length ratio of 1, decreases this ratio, the more locking up elongates the bolus to a greater extent by pressing from the tongue, teeth, and a cheek. Before and after chewing randomly for 2-6 cycles (3 trials each), the bolus was scanned and its width-length ratio was determined using imaging. The number of chewing cycles needed to attain a width-length ratio of 0.5, N(0.5 W-L ratio) was a measure of FL. CE corresponded with the number of cycles needed to halve the initial particle size, N(1/2-Xo), when chewing samples of 2 half cubes (9.6 × 9.6 × 4.8 mm; sample volume: 0.88 cm3) of a solid artificial model food. CONCLUSIONS: N(0.5 W-L ratio) and N(1/2-Xo) were on average 3.21 cycles (SD 1.14) and 4.04 cycles (SD 1.87) respectively. Whereas a relationship between CE and FL was lacking for subjects whose CE was worse than the median, a pronounced quadratic U-shaped relationship (R2 = 0.75; p < 0.01) occurred for subjects whose CE was better. This relationship might reflect an interaction between two tongue functions: transport and subsequently FL of particles.

Determining chewing efficiency using a solid test food and considering all phases of mastication.

OBJECTIVES: Following chewing a solid food, the median particle size, X50, is determined after N chewing cycles, by curve-fitting of the particle size distribution. Reduction of X50 with N is traditionally followed from N ≥ 15-20 cycles when using the artificial test food Optosil®, because of initially unreliable values of X50. The aims of the study were (i) to enable testing at small N-values by using initial particles of appropriate size, shape and amount, and (ii) to compare measures of chewing ability, i.e. chewing efficiency (N needed to halve the initial particle size, N(1/2-Xo)) and chewing performance (X50 at a particular N-value, X50,N). DESIGN: 8 subjects with a natural dentition chewed 4 types of samples of Optosil particles: (1) 8 cubes of 8 mm, border size relative to bin size (traditional test), (2) 9 half-cubes of 9.6 mm, mid-size; similar sample volume, (3) 4 half-cubes of 9.6 mm, and 2 half-cubes of 9.6 mm; reduced particle number and sample volume. All samples were tested with 4 N-values. Curve-fitting with a 2nd order polynomial function yielded log(X50)-log(N) relationships, after which N(1/2-Xo) and X50,N were obtained. CONCLUSIONS: Reliable X50-values are obtained for all N-values when using half-cubes with a mid-size relative to bin sizes. By using 2 or 4 half-cubes, determination of N(1/2-Xo) or X50,N needs less chewing cycles than traditionally. Chewing efficiency is preferable over chewing performance because of a comparison of inter-subject chewing ability at the same stage of food comminution and constant intra-subject and inter-subject ratios between and within samples respectively.

Selection in mixtures of food particles during oral processing in man.

OBJECTIVES: Two processes underlie food comminution during chewing: (1) selection, i.e. every particle has a chance of being placed between the teeth and being subjected to (2) breakage. Selection decreases with particle number by saturation of breakage sites, and it depends on competition between smaller and larger particles for breakage sites. Theoretical models were tested which describe competition between various sizes X. In the one-way model, small particles cannot compete with larger ones because of their smaller height. In the two-way model, small particles may compete when piled between antagonistic teeth. DESIGN: Five subjects participated in one-chew experiments on cubes made of Optosil®. The critical particle number (nc(X)) at which saturation starts, and the number of breakage sites (nb(X)) were determined by varying particle numbers (nX) for single-sized cubes of 1.7-6.8mm. Using nc(X) and nb(X), the models predicted relationships between number of selected particles (ns(X)) and nX in one-chew experiments using simple mixtures with only two sizes. A fixed number (mean 6 or 26) of larger cubes (X=6.8 or 3.4mm) was mixed with various numbers (16-1024) of smaller cubes (X=4.8, 2.4 or 1.7mm), thus varying the factors X, nX, and possible particle piling (for X<4mm). RESULTS: The one-way model was largely followed with small numbers of smaller particles and the two-way model with large numbers. CONCLUSIONS: The two-way model applies to chewing a food which yields a loose aggregation of different-sized particles following an initial phase, whereas other circumstances may be favourable for the one-way model. As conditions of a food bolus can be approached by embedding hard Optosil particles in a soft medium, the models will, apart from dentistry, be of interest for controlling flavour release in food engineering.

Towards an optimal therapy strategy for myogenous TMD, physiotherapy compared with occlusal splint therapy in an RCT with therapy-and-patient-specific treatment durations.

BACKGROUND: Temporomandibular Disorders (TMD) may be characterized by pain and restricted jaw movements. In the absence of somatic factors in the temporomandibular joint, mainly myogenous, psychobiological, and psychosocial factors may be involved in the aetiology of myogenous TMD. An occlusal appliance (splint) is commonly used as a basic therapy of the dental practice. Alternatively, a type of physiotherapy which includes, apart from massage of sore muscles, aspects of cognitive-behavioural therapy might be a basic therapy for myogenous TMD. Treatment outcome of physiotherapy (Ph-Tx) was evaluated in comparison to that of splint therapy (Sp-Tx), using the index Treatment Duration Control (TDC) that enabled a randomized controlled trial with, comparable to clinical care, therapy-and-patient-specific treatment durations. METHODS: Seventy-two patients were randomly assigned to either Ph-Tx or Sp-Tx, with an intended treatment duration between 10 and 21 or 12 and 30 weeks respectively. Using TDC, the clinician controlled treatment duration and the number of visits needed. A blinded assessor recorded anamnestic and clinical data to determine TDC-values following treatment and a 1-year follow-up, yielding success rate (SR) and effectiveness (mean TDC) as treatment outcomes. Cohen's d, was determined for pain intensity. Overall SR for stepped-care was assessed in a theoretical model, i.e. a second of the two studied therapies was applied if the first treatment was unsuccessful, and the effect of therapy sequence and difference in success rates was examined. RESULTS: SR and effectiveness were similar for Ph-Tx and Sp-Tx (long-term SR: 51-60%; TDC: -0.512- -0.575). Cohen's d was 0.86 (Ph-Tx) and 1.39 (Sp-Tx). Treatment duration was shorter for Ph-Tx (on average 10.4 weeks less; p < 0.001). Sp-Tx needed 7.1 less visits (p < 0.001). CONCLUSIONS: Physiotherapy may be preferred as initial therapy over occlusal splint therapy in stepped-care of myogenous TMD. With a similar SR and effectiveness, physiotherapy has a shorter duration. Thus patients whose initial physiotherapy is unsuccessful can continue earlier with subsequent treatment. The stepped-care model reinforces the conclusion on therapy preference as the overall SR hardly depends on therapy sequence. TRIAL REGISTRATION: isrctn.com/ISRCTN17469828 . Retrospectively registered: 11/11/2016.

The index 'Treatment Duration Control' for enabling randomized controlled trials with variation in duration of treatment of chronic pain patients.

BACKGROUND: Treatment duration varies with the type of therapy and a patient's recovery speed. Including such a variation in randomized controlled trials (RCTs) enables comparison of the actual therapeutic potential of different therapies in clinical care. An index, Treatment Duration Control (TDC) of outcome scores was developed to help decide when to end treatment and also to determine treatment outcome by a blinded assessor. In contrast to traditional Routine Outcome Monitoring which considers raw score changes, TDC uses relative change. METHODS: Our theory shows that if a patient with the largest baseline scores in a sample requires a relative decrease by treatment factor T to reach a zone of low score values (functional status), any patient with smaller baselines will attain functional status with T. Furthermore, the end score values are proportional to the baseline. These characteristics concur with findings from the literature that a patient's assessment of 'much improved' following treatment (related to attaining functional status) is associated with a particular relative decrease in pain intensity yielding a final pain intensity that is proportional to the baseline. Regarding the TDC-procedure: those patient's scores that were related to pronounced signs and symptoms, were selected for adaptive testing (reference scores). A Contrast-value was determined for each reference score between its reference level and a subsequent level, and averaging all Contrast-values yielded TDC. A cut-off point related to factor T for attaining functional status, was the TDC-criterion to end a patient's treatment as being successful. The use of TDC has been illustrated in RCT data from 118 chronic pain patients with myogenous Temporomandibular Disorders, and the TDC-criterion was validated. RESULTS: The TDC-criterion of successful/unsuccessful treatment approximated the cut-off separating two patient subgroups in a bimodal post-treatment distribution of TDC-values. Pain intensity decreased to residual levels and Health-Related Quality of Life (HRQoL) increased to normal levels, following successful treatment according to TDC. The post-treatment TDC-values were independent from the baseline values of pain intensity or HRQoL, and thus independent from the patient's baseline severity of myogenous Temporomandibular Disorders. CONCLUSIONS: TDC enables RCTs that have a variable therapy- and patient-specific duration.

Selective stimulation of human tooth-pulp with a new stable method: responses and validation.

INTRODUCTION: The aims of this study were to establish a safe technique for selective stimulation of nerves in human tooth-pulp during long experiments and to validate its use even with stimuli of high intensities. METHODS: A custom-made veneer containing 2 silver wire-conductive cream electrodes was attached with cement to the labial surface of an upper central incisor tooth. A variety of stimulus intensities were applied, and sensory and reflex responses from jaw-closing muscles were recorded. RESULTS: In 15 participants, the stimuli evoked predominantly sharp or painful sensations and reflex inhibitions of activity in the jaw muscles. Stimulation of 3 non-vital teeth evoked no sensations or reflexes, even at intensities that evoked maximal reflexes in vital teeth. The electrodes had reasonably stable resistances throughout experiments lasting up to 90 min. CONCLUSION: The method described enables responses to low- or high-intensity stimulation of human pulpal nerves to be investigated in long experiments.

The influence of auditory and visual information on the neuromuscular control of chewing crispy food.

The influence of auditory and/or visual information on the neuromuscular control of chewing a crispy food was investigated. Participants chewed biscuits of three different levels of crispness under four experimental conditions: no masking, auditory masking, visual masking, and auditory plus visual masking. The order of the four masking condition blocks was randomized. The sound of chewing was masked by loud sounds on a headphone, and visual masking of the food was achieved by closing the eyes. Mechanical tests were performed on the biscuits to determine their characteristics, yield force, and sound production. Skull vibration, jaw-muscle activity, and jaw movement were measured while the subjects chewed and swallowed the food. Auditory and/or visual masking did not have a significant effect on skull vibration, muscle activity, and number of chewing cycles until swallowing. However, auditory and/or visual masking significantly increased the chewing cycle duration, but only for the participants who started the experiments with auditory and/or visual masking. The other participants were not influenced by masking. The memory of the unmodified stimuli helped these subjects to maintain their habitual chewing rate in later trials.

Oral function after oncological intervention in the oral cavity: a retrospective study.

PURPOSE: To assess self-perceived oral function of patients with oral cavity cancer at different stages of treatment, ie, before oncologic intervention, 5 weeks after intervention, and 5 years after intervention. PATIENTS AND METHODS: A cohort of 158 patients with malignancy in the oral cavity treated by surgery in 1999 or 2000 was included. From this cohort we interviewed 69 patients by telephone in 2005 and collected data on dental status, disorders of chewing and swallowing, xerostomia, preference of food consistency, tube nutrition, weight loss, and speech for different stages of treatment. RESULTS: For patients treated in the maxilla region we observed a significant (P < .05) recovery of perceived chewing ability after 5 years to the level experienced before oncologic intervention. Patients treated in the mandible region reported a deteriorated dental state, chewing ability, lip competence, and xerostomia after 5 years. Patients treated in the tongue and mouth-floor region experienced deterioration for dental state, chewing ability, and xerostomia after 5 years compared with the level before the oncologic intervention. CONCLUSIONS: Our telephone interview on oral function provided supplementary information on how patients experienced their problems with oral function during various phases of oncologic treatment. A retrospective interview may thus help to add information to incomplete retrospective data.

Statistically and clinically important change of pain scores in patients with myogenous temporomandibular disorders.

A within-patient change in pain score after treatment is statistically 'reliable' when it exceeds the smallest detectable difference (SDD). The aims of the present study were (i) to determine SDD for scoring pain behavior on a 0-5 point adjectival scale, and (ii) to explore the relationship between SDD, clinically important difference (CID) and effect size (ES) following treatment of known efficacy, and to compare these parameters of pain behavior with those of VAS-scores of pain intensity [van Grootel RJ, van der Bilt A, van der Glas HW. Long-term reliable change of pain scores in individual myogenous TMD patients. Eur J Pain 2007;11:635-43]. SDD was determined using duplicate scores on pain behavior from a pre-treatment diary that was completed by 118 patients with myogenous temporomandibular disorders (TMD). CID was determined as the mean change in score following treatment, and Cohen's ES as the ratio between mean change and SD of baseline values. The SDDs were 2-3 units (40-60% of the scale range) for test-retest intervals of 1-13 days. CID was 1.13 units (22.6%) and ES was 1.38. The normalized SDD and CID values and ES were similar for VAS-scores of pain intensity, i.e., 38-49% (SDD), 24.2% (CID) and 1.09 (ES). Because reliable change (change>SDD) exceeds CID, the responsiveness of scoring of pain variables is low for detecting CID. The finding of ES values that are larger than 0.5 (ES for patients with chronic degenerative diseases [Norman GR, Sloan JA, Wyrwich KW. Interpretation of changes in health-related quality of life. The remarkable universality of half a standard deviation. Med Care 2003;41:582-92]) suggests that for myogenous TMD (chronic pain not caused by somatic disease and with a large chance on recovery following treatment), there are higher expectations of what constitutes important change.

Dissociation of nociceptive modulation of a human jaw reflex from the influence of stress.

In human beings, inhibitory jaw reflexes can be depressed by painful stimulation of remote parts of the body. Since similar effects can be produced by the stress of anticipating pain, we wished to investigate whether the effects of remote painful stimuli are dependent on stress. EMG recordings were made from a masseter muscle while subjects maintained activity in the muscle at approximately 12.5% of maximum using visual feedback. The protocols involved three sequences: (1) "standard controls" in which reflexes were evoked by electrical test stimuli applied to the upper lip; (2) "standard conditioning" in which painful electrical conditioning stimuli were applied over the sural nerve 100 ms before the test stimuli; (3) "random sequences" in which test-only and conditioning-test combinations were employed in a double-blind, random, order. Data are presented as means +/- SEMs. In the standard controls, the stimuli evoked clear inhibitory reflexes (latency 37 +/- 1.3 ms, duration 62 +/- 5.6 ms; n = 10) in all the subjects. During standard conditioning, the reflex magnitude was reduced significantly (by 50.0 +/- 8.5%, P = 0.0002, one-sample t-test). When the test-only and conditioning-test responses were extracted from the random sequences, there was also a significant reduction in the reflex magnitude following conditioning (by 34.6 +/- 5.5%, P = 0.0002, one-sample t-test) albeit less so than between the standard sequences (P = 0.03, paired t-test). A second series of experiments suggested that these lesser effects during the random sequences were not substantially due to any loss of temporal summation of the conditioning mechanisms. The evidence for this was that application of pairs of conditioning stimuli did not produce a significantly greater effect than single conditioning stimuli within a random sequence (39.9 +/- 9.6% as opposed to 32.7 +/- 9.1% reductions in the reflex, P = 0.117, paired t-test). Therefore since any stress in the random sequences would not have been "tied" to the conditioned responses alone, the effects of remote painful stimuli on this inhibitory jaw reflex cannot be entirely secondary to stress.

Long-term reliable change of pain scores in individual myogenous TMD patients.

A within-patient change in pain score after treatment is statistically 'reliable' when it exceeds the smallest detectable difference (SDD). The aims of the present study were to: (i) determine SDDs for VAS-scores of pain intensity, for sufficiently long test-retest intervals to include most biological fluctuations, (ii) examine whether SDD is invariant to baseline score, and (iii) discuss the value of reliable change (RC) for detecting clinically important difference (CID) or as a possible indicator of successful treatment. SDDs were determined using duplicate data from 118 patients with myogenous Temporomandibular disorders: (1) VAS-scores of pain intensity from the masticatory system in a pre-treatment diary, and (2) VAS-scores of pain intensity from the hand (cold-pressor test). RC was determined in VAS-scores from a pre- and post-treatment questionnaire. The long-term SDD was 49mm. A regression analysis on duplicate VAS-scores showed that SDD was largely invariant to the baseline level. Because RC (change>SDD) exceeded CID, it might serve as an indicator of successful treatment. However, only 17% of the patients showed RC after treatment, mainly because the baseline was smaller than SDD in 67% of the patients thus making detection of any treatment effect impossible. For patients with possible detection (33%), the frequency of RC was 51%. If the detection threshold would be avoided by provoking pain in patients with a low baseline, a long-term RC in VAS-scores might occur in about half of all myogenous TMD patients and might then serve as an indicator of cases of treatment success.

Functional roles of oral reflexes in chewing and biting: phase-, task- and site-dependent reflex sensitivity.

Because loading during chewing is not totally predictable and jaw-closing muscles are strong and act over short distances, feedback from oral receptors is important in the control of mastication. Information on such feedback can be obtained by studying reflexes in jaw muscle EMGs. This review will deal with the contribution of reflex mechanisms to modifying motor neuron activity during chewing, and the dependency of reflex sensitivity on motor task, phase of movement, and site of stimulation.

Differentiation of nociceptive- from stress-induced modulatory influences on human reflexes.

This paper describes a new protocol that addresses the question of whether, in human experiments, modulatory effects of remote nociceptive conditioning stimuli on reflex responses are mediated by the stress induced by the conditioning stimuli. The protocol has been illustrated by a study into the effect of a remote nociceptive conditioning stimulus on an inhibitory jaw reflex. Electromyograms were recorded from an active masseter muscle and inhibitory reflexes were evoked by applying electrical stimuli to the upper lip. This protocol utilised the application of discrete electrical conditioning stimuli applied to the sural nerve prior to the test stimulus. A preliminary experiment determined that the optimal interval between the conditioning and test stimuli, which produced modulatory effects was 100 ms. In the definitive study, computer software was used to deliver control and conditioned sweeps in a double-blind randomised sequence. This resulted in a "stress-equal" protocol in which the level of stress would be the same for both control and conditioned sweeps. Therefore any observed modulatory effects on the reflexes could not have been wholly secondary to stress. This protocol could be adapted to the study of the modulation of other reflexes or evoked sensations by nociceptive conditioning stimuli.

Patterns of pain variation related to myogenous temporomandibular disorders.

OBJECTIVES: Myogenous temporomandibular disorders are characterized by jaw muscle pain. The aims were: 1) to characterize this pain generally in terms of intensity, frequency, duration, and behavior across a period of 2 weeks; 2) to identify main intraday pain patterns and to examine whether subgroups of patients in this respect differed in clinical, demographic, pain and sleep variables, psychosocial factors, and use of medication; and 3) to investigate some possible interday trends of pain intensity at a group level. METHOD: One hundred thirty-three patients with myogenous temporomandibular disorders completed a 2-week diary, rating pain intensity (100 mm Visual Analog Scale [VAS]), duration, behavior (verbal 6-point scale), and medication use on 4 times of the day. Furthermore, questionnaires were completed to score pain period before seeking treatment, spread of pain, and demographic, psychosocial, and sleep variables. RESULTS: In the diary, pain intensity, frequency, daily pain duration, and the score of pain behavior were on average 29.1 mm, 69% of the scoring times, 5.5 hours, and 1.8 points (approaching "pain present, but I can ignore it at times"), respectively. Pain intensity was, on average, maximal late in the day (before dinner or bedtime) for the majority of patients (79%) and early in the day (before breakfast or lunchtime) for the minority (21%). The larger subgroup had a significantly higher daily pain intensity, more frequently a widespread pain and problems with falling asleep at bedtime, agreed more about the role of a physician as an external health locus of control, and had a more distancing coping style. Both subgroups were similar for other variables, most notably in the level of state anxiety and depressive mood, and in a sparse use (7.8% of all possible times) of over-the-counter medication. Daily mean VAS scores, averaged across patients, were approximately constant for the various diary days. Both the daily mean and maximal VAS score were not related to a specific day of the week. CONCLUSIONS: Two main daily pain patterns occur in patients with myogenous temporomandibular disorders (79%: maximal pain late in the day; 21%: early in the day), which might be related to differences in processes that influence pain sensitivity and patterns of jaw muscle activation. The interday similarities in pain level suggest that a sustained influence of counseling after the intake or an influence of a common behavioral pattern with a cycle duration of a week are not involved.

The relationship of facial two-point discrimination to applied force under clinical test conditions.

When an interside comparison is hampered, for example, in cases of bilateral trauma, normal threshold values of two-point discrimination from healthy subjects might be used to delineate abnormal from normal sensory function in patients. To determine threshold pin distances, two devices, the Disk-Criminator and the Aesthesiometer, have often been applied in a clinical setting. Because these devices are hand-operated, the force of applying a device might vary considerably. The general applicability of normal threshold values from the literature may therefore be questioned. Five subjects participated in experiments with two observers, in which a hand-operated device with a constant pin distance (5 or 10 mm) was pushed on a facial site, until the point at which blanching of the skin started, and the applied force was recorded. To that end, the devices were modified by providing them with force transducers. These recordings revealed a considerable variation in force variables (level, duration, and rate). Significant differences in mean force level, duration, and rate occurred, particularly between devices, pin distances, and/or sites (cheek, upper and lower lips, and mental region) and also in mean duration between observers (p < 0.01 to 0.001, analysis of variance). However, the observed force levels were always at an extremely supra-threshold stimulus intensity. The threshold pin distances in subsequent experiments (four subjects, the two devices and two sites: cheek and mental region) were therefore almost invariant to the difference in the extreme low and high force levels that were applied, using acoustic feedback on the force signal. Furthermore, these thresholds were also similar when one or two observers performed repeated measures on groups of 15 to 18 subjects under the influence of a usual variation of force level, using an interval of at least 1 week and both nonmodified devices. Because of invariance, normal values of threshold pin distance are generally applicable to any well-trained observer and are related to the density of afferent nerve fibers. In contrast, recently reported force thresholds determined at a constant pin distance might not be related to fiber density only. The findings regarding dependency on site and pin distance of the force level suggest that force thresholds will also be related to tissue stiffness and to the extent to which a pair of pins co-operate mechanically.

Remote noxious stimuli modulate jaw reflexes evoked by activation of periodontal ligament mechanoreceptors in man.

The purpose of the study was to investigate whether jaw reflexes evoked by selective stimulation of periodontal ligament me canoreceptors are susceptible to modulation by remote noxious stimulation. Experiments were performed on 10 volunteer subjects. Skin surface recordings were made from the jaw-closing masseter muscle. The subjects activated the muscle to approximately 10% of maximum by biting on a rubber impression of their molar teeth while they received visual feedback of the electromyogram (EMG) of the muscle. Reflexes were produced by the application of gentle mechanical stimuli to an upper central incisor tooth. The stimuli were in the form of 'ramp and hold' forces with a 5 ms rise-time and a 1.5 N plateau which lasted 350 ma. The resulting reflexes were recorded both under control conditions and while the subjects received a remote noxious stimulus (immersion of a hand in water at 3 degrees C). In all 10 subjects, the stimuli produced a single period of inhibition of masseteric activity (latency, 12.8 t 04 ms; duration, 18.1+/-1.3 ms; means +/- S.E.M.), which was usually followed by a period of increased masseteric activity. The period of inhibition constituted a downward wave in full-wave rectified, averaged signals. The integrals of such waves were significantly smaller (by 17+/- 6.5 %; P = 0.027; Student's t test) when the reflex was evoked during remote noxious stimulation rather than under control conditions. As such reflexes are beLieved to play a modulatory role during normal oral function this finding maybe relevant to disorders of mastication associated with pain.