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Phenotypic switching and beta-N-acetylhexosaminidase activity of the pathogenic yeast Trichosporon asahii.

The pathogenic yeast Trichosporon asahii is the major causative agent of deep-seated trichosporonosis in immunocompromised patients. Although infection by this microorganism is becoming increasingly frequent, information related to its pathogenicity and virulence factors is still limited. Therefore, we investigated phenotypic switching in colony morphology, and the production of extracellular enzymes as a virulence factor. Sixty-one clinical isolates of T. asahii produced four different morphological types on Sabouraud dextrose agar (SDA): 69% WF (white farinose), 18% WP (white pustular), 10% Y (yellowish white), and 3% WC (white cerebriform). Strains of the three major types (WF, WP, and Y) produced two to five colony types when cultured on SDA at 37 C. The frequency of switching between colony types was 10(-2) to 10(-4), as in Candida albicans and Cryptococcus neoformans. Notably, most of the colonies switched to the smooth (S) type irreversibly, at frequencies of 10(-2) to 10(-3). No secreted aspartic proteinase or phospholipase activity was detected in T. asahii, while beta-N-acetylhexosaminidase activity, which catalyzes the hydrolysis of terminal nonreducing N-acetyl-D-hexosamine residues in N-acetyl-beta-D-hexosaminides, was found. Furthermore, enzymatic activity of the S type was significantly greater than that of the parent type in all strains. No other clinically relevant Trichosporon species (T. mucoides, T. inkin, and T. ovoides ) produced this enzyme. These results provide basal information for understanding the pathogenic potential of T. asahii.

Culture Media↗

Effects of prosthetic treatment for shortened dental arches on oral health-related quality of life, self-reports of pain and jaw disability: results from the pilot-phase of a randomized multicentre trial.

A multi-centre randomized clinical trial is under way at 14 university dental schools in Germany to compare prosthodontic treatments for the shortened dental arch (SDA). One of the aims of this pilot-study was to measure the effect of two treatment options of the SDA on oral health-related quality of life and on the Research Diagnostic Criteria (RDC) for temporomandibular disorders (TMD). Thirty-four patients participated in the pilot-study. Inclusion criteria were: all molars were missing and the presence of at least both canines and one premolar in each quadrant. Participants were randomly assigned to receive either removable partial dentures including molar replacement (RPD_group) or retain a premolar occlusion (PROC_group). The Oral Health Impact Profile (OHIP-49) and the RDC for TMD were completed by participants before treatment (pre-treatment), 6 weeks (6 wks), 6 months (6m) and 12 months (12 m) after treatment. At the 12-month follow up, data of 10 women and 11 men (mean age: 62 +/- 10 years) were available. Medians of the OHIP total-scores were as follows: RPD (n = 10), 43.5 (pre-treatment), 18.2 (6 wks), 13.3 (6m), 14.7 (12 m). PROC (n = 11): 31.8 (pre-treatment), 27.1 (6 wks), 8.8 (6m), 8.3 (12 m). Significant differences were shown for RPD_group between pre-treatment and 6m/12 m and for PROC_group between pre-treatment and 6m. There were no significant differences between treatment groups at any time. Within each group, an improvement of life-quality was observed. No significant difference could be reported between the two therapy concepts. This may be due to the low sample size within the pilot study.

Aged↗

Molds in onychomycosis.

BACKGROUND: Onychomycosis is a major cause of nail dystrophy. The causative organisms in onychomycosis are dermatophytes, Candida and molds. A variety of molds have been isolated from nails. METHODS: Nail scrapings and clippings were collected from 100 cases and inoculated on slants containing SDA with cycloheximide 0.5 mg/mL, chloramphenicol 0.05 mg/mL, and SDA with chloramphenicol 0.05 mg/mL. RESULTS: The culture positivity rate for molds was 22%. The predominant mold isolates were Aspergillus species (86.4%, Fusarium oxysporum (4.5%), Curvularia species (4.5%) and Penicillium species (4.5%). CONCLUSION: Primary invasion of nails by molds can cause onychomycosis.

Female↗

Modulation of water activity on fungicide effect on Aspergillus niger growth in Sabouraud dextrose agar medium*.

AIMS: To examine whether water activity (aw) in combination with low concentration of fungicides can be used to effectively control Aspergillus niger van Tieghem growth in cultural medium, the Sabouraud dextrose agar (SDA). The data would be used as baseline information for reducing A. niger contamination in insect artificial diets. METHODS AND RESULTS: Aspergillus niger was isolated from an insect artificial diet. Four concentration levels (i.e. 0, 1, 10 and 20 micromol) of two fungicides (i.e. amphotericin B and itraconazole) were tested against A. niger under four aw levels (i.e. 0.994, 0.961, 0.921 and 0.859) adjusted by including 0, 12.5, 25 and 38% of glycerol in the medium mixture. Aspergillus niger growth was significantly reduced at low fungicide concentration (1 micromol), and at reduced aw. The spore germination was prevented with either higher fungicide concentration (>10 micromol), or low aw in the medium (aw < 0.921). The two ecological determinants (fungicides and aw) showed a significant impact on A. niger survival in the medium (P < 0.0001). Itraconazole is more effective than amphotericin B in controlling A. niger contamination in the agar medium. CONCLUSION: Adjustment of aw (with 12.5% of glycerol) in combination with 1 mumol of itraconazole can effectively prevent A. niger growth in the SDA cultural medium. SIGNIFICANCE AND IMPACT OF THE STUDY: Aspergillus niger contaminations have frequently affected the quality of insects produced from mass rearing facilities. Low aw in combination with low fungicide concentration has the potential to become one of the most cost-effective management strategies to prevent A. niger contamination in insect artificial diets. The effect of fungicides and low aw in artificial diets on insect biology needs to be further examined.

Antifungal Agents↗

The mechanism of the inhibitory effect of polyamines on the induction of nitric oxide synthase: role of aldehyde metabolites.

1. We have recently found that in the presence, but not in the absence, of foetal calf serum, spermine inhibits the production of nitric oxide (NO) in cultured J774.2 macrophages stimulated with bacterial endotoxin (lipopolysaccharide; LPS) or with gamma-interferon (IFN), showing that polyamines may act as suppressants of NO-mediated immune functions. Here, we have studied the mechanisms and the specificity of this inhibitory action. 2. Other polyamines, as well as spermine, inhibit the formation of NO in cultured J774.2 macrophages, with the order of potency being spermine > spermidine >> putrescine = cadaverine. This inhibition of NO formation is not due to any cytotoxic effect of these agents for they neither reduced mitochondrial respiration nor increased the release of lactate dehydrogenase into the supernatant. 3. Spermine is not a direct inhibitor of the activity of iNOS in induced J774.2 cells as measured by its lack of effect on the conversion of L-arginine to L-citrulline in homogenates. Neither spermine, nor its metabolites, interfere with the production of nitrite from NO or act as scavengers of NO. Thus, spermine is an inhibitor of the induction of iNOS. 4. Spermine inhibits nitrite formation in the presence of foetal, newborn or adult bovine serum, but not rat or human serum. 5. The effect of sper mine on nitrite production can be prevented by isoniazid, hydrazine or hydroxylamine, inhibitors of spermine oxidase, as well as by phenylhydrazine, an aldehyde inhibitor. We have, therefore, tested the effects of spermine dialdehyde or malon dialdehyde on the induction of iNOS. Spermine dialdehyde (SDA, 10(-5) M) inhibits nitrite formation by IFN-activated J774.2 cells in the absence of serum when given as a pretreatment but not when given 6 h after stimulation. In contrast, malon dialdehyde was ineffective. Thus, aldehyde metabolites of spermine, such as SDA, account for the inhibitory effect of polyamines on the induction of NOS in vitro. 6. The inhibitory effect of polyamines on iNOS induction appears to be fairly specific to iNOS, for spermine does not inhibit LPS-induced production of prostaglandin F2 alpha or tumour necrosis factor.

Aldehydes↗

AIDS risk among students attending Seventh-day Adventist school, in North America.

In 1995, a survey was conducted among students attending 69 Seventh-day Adventist (SDA) high schools within the United States and Canada. The survey assessed the extent that these students practiced sexual and drug-use behaviors which place them at risk for contracting or transmitting the human immunodeficiency virus (HIV). A total of 1,748 respondents enrolled in grades 9 through 12 completed questionnaires similar to the instrument used in the 1993 Youth Risk Behavior Survey (YRBS). Data were collected and compared to results from the 1993 YRBS. Students who attended SDA parochial schools reported lower rates of sexual intercourse compared to YRBS school counterparts (16.3% vs. 53.1%) and lower rates of all substances measured. Furthermore, respondents were more likely to engage in substance use and sexual intercourse if they had at least one parent who used tobacco, alcohol, or marijuana, as reported by the students.

Acquired Immunodeficiency Syndrome↗

The shortened dental arch--an assessment of patients' dental health state utility values.

OBJECTIVES: The aim of this study was to determine how patients value the potential outcomes from different treatments for the shortened dental arch (SDA). METHODS: 110 partially dentate patients were interviewed and presented with illustrative models as well as a description of the process and likely outcome of six possible treatments for the shortened dental arch. The patients were asked to indicate on a standardised visual analogue scale how they would value the health of their mouth if they had received each of the treatments described. RESULTS: With a utility value of 0.0 representing the worst possible health state for a mouth and 1.0 representing the best, the mean utility value for 'no treatment' for a SDA was 0.28 (sd=0.29). For a cobalt-chromium based removable partial denture, an acrylic-resin based removable partial denture, implant treatment, a resin-bonded cantilevered bridge and a conventional cantilevered fixed bridge the utility values were 0.42 (sd=0.3), 0.49 (sd=0.31), 0.53 (sd=0.35), 0.63 (sd=0.26) and 0.64 (sd=0.28) respectively. CONCLUSIONS: The treatment outcome from a cantilevered bridge attracted the highest mean utility value. Participants did not value implant treatment as highly as fixed bridgework, but they did rate the utility of implants more highly than the utility value of removable dentures. However, the patients placed a very low value on the outcome from 'no' treatment. Thus, the appropriateness of the shortened dental arch as an oral health goal can be questioned.

Dental Arch↗

Investigation of light propagation models to determine the optical properties of tissue from interstitial frequency domain fluence measurements.

Four models, standard diffusion approximation (SDA), single Monte Carlo (SMC), delta-P1, and isotropic similarity (ISM), are developed and evaluated as forward calculation tools in the estimation of tissue optical properties. The inverse calculation uses the ratio of the fluences and phase difference at two locations close to an intensity modulated isotropic source to recover the reduced scattering coefficient mus' and the absorption coefficient mua. Diffusion theory allows recovery of optical properties (OPs) within 5% for media with mus'mua>10. The performance of the delta-P1 model is similar to SDA, with limited enhanced accuracy. The collimation approximation may limit the use of the delta-P1 model for spherical geometry, and/or the fluence may not be accurately calculated by this model. The SMC model is the best, recovering OPs within 10% regardless of the albedo. However, the necessary restriction of the searched OPs space is inconvenient. The performance of ISM is similar to that of diffusion theory for media with mus'mua>10, and better for 1 5.

Algorithms↗

Use of a synthetic peptide epitope of Asp f 1, a major allergen or antigen of Aspergillus fumigatus, for improved immunodiagnosis of allergic bronchopulmonary aspergillosis.

Allergic bronchopulmonary aspergillosis (ABPA) is an immunologically complex allergic disorder caused by the fungal pathogen Aspergillus fumigatus. Elevated levels of total immunoglobulin E (IgE), specific IgE, and IgG antibodies in sera are important immunodiagnostic criteria for ABPA. International reference standards or standardized immunodiagnostic assays are not available due to a lack of well-defined diagnostic antigens. The present study was carried out to identify and evaluate the immunodiagnostic relevance of synthetic epitopic peptides of Asp f 1, a major allergen, antigen, or cytotoxin of A. fumigatus. Five overlapping peptides were synthesized from the N terminus of Asp f 1, one of the potential immunodominant regions predicted by algorithmic programs. The 11-amino-acid synthetic peptide (P1) significantly inhibited both IgG binding (89.10% +/- 4.45%) and IgE binding (77.32% +/- 3.38%) of the standardized diagnostic antigen (SDA) (a well-defined pool of diagnostically relevant allergens and antigens of A. fumigatus). With a panel of sera of ABPA patients, allergic patients with skin test negativity to A. fumigatus, and healthy individuals, P1 showed a higher diagnostic efficiency than SDA (specific IgG, 100%; specific IgE, 98.3%). The diagnostic efficiency of P1 could be attributed to the presence of homologous epitopes in various immunodominant allergens or antigens of A. fumigatus. The ability of P1 to induce histamine release from sensitized mast cells and a Th2 type of cytokine profile in peripheral blood mononuclear cells of ABPA patients suggests its potential for use in intradermal testing. P1 could be further explored for development of a standardized, specific, and sensitive immunodiagnostic test for aspergillosis.

Allergens↗

Vulvovaginal-swab or first-catch urine specimen to detect Chlamydia trachomatis in women in a community setting?

Screening for chlamydia in women is widely recommended. We evaluated the performance of two nucleic acid amplification tests for detecting Chlamydia trachomatis in self-collected vulvovaginal-swab and first-catch urine specimens from women in a community setting and a strategy for optimizing the sensitivity of an amplified enzyme immunoassay on vulvovaginal-swab specimens. We tested 2,745 paired vulvovaginal-swab and urine specimens by PCR (Roche Cobas) or strand displacement amplification (SDA; Becton Dickinson). There were 146 women infected with chlamydia. The assays detected 97.3% (95% confidence interval [CI], 93.1 to 99.2%) of infected patients with vulvovaginal-swab specimens and 91.8% (86.1 to 95.7%) with urine specimens. We tested 2,749 vulvovaginal-swab specimens with both a nucleic acid amplification test and a polymer conjugate-enhanced enzyme immunoassay with negative-gray-zone testing. The relative sensitivities obtained after retesting specimens in the negative gray zone were 74.3% (95% CI, 62.8 to 83.8%) with PCR and 58.3% (95% CI, 46.1 to 69.8%) with SDA. In community settings, both vulvovaginal-swab and first-catch urine specimens from women are suitable substrates for nucleic acid amplification tests, but enzyme immunoassays, even after negative-gray-zone testing, should not be used in screening programs.

Adolescent↗

Comparison of the BACTEC MYCO/F Lytic bottle to the isolator tube, BACTEC Plus Aerobic F/bottle, and BACTEC Anaerobic Lytic/10 bottle and comparison of the BACTEC Plus Aerobic F/bottle to the Isolator tube for recovery of bacteria, mycobacteria, and fungi from blood.

The BACTEC MYCO/F Lytic blood culture bottle (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) is designed to optimize the recovery of fungi and mycobacteria; however, this bottle also supports the growth of most aerobic bacteria. We compared the MYCO/F Lytic bottle with two other BACTEC bottles and the Isolator system for the recovery of bacteria as well as fungi and mycobacteria from blood. A total of 6,108 blood culture sets were inoculated with blood obtained from adult patients. Twenty-five to 28 ml of blood collected by a phlebotomy team for each blood culture set was randomly distributed into each of four blood culture receptacles: the Isolator tube (Wampole Laboratories, Cranbury, N.J.) and three BACTEC bottles: the MYCO/F Lytic bottle, the BACTEC Plus Aerobic/F bottle, and the BACTEC Anaerobic Lytic/10 bottle. The sediment from the Isolator tube was inoculated onto chocolate agar (CA), brain heart infusion agar (BHI), and Sabouraud dextrose agar (SDA) and into a BACTEC 13A bottle. Incubation durations were as follows: MYCO/F Lytic bottle, 42 days; Plus Aerobic/F bottle, 5 days; Anaerobic Lytic/10 bottle, 5 days; sediment from Isolator tube on CA, 3 days; sediment from Isolator tube on BHI, 30 days; sediment from Isolator tube on SDA, 30 days; and sediment from Isolator tube in a BACTEC 13A bottle, 42 days. Two isolates of Histoplasma capsulatum were recovered from the Isolator tube only. Three isolates of Mycobacterium tuberculosis complex were recovered: two isolates from the MYCO/F Lytic bottle only and one isolate from the Isolator tube (whose sediment was inoculated into the BACTEC 13A bottle) only. Two isolates of Cryptococcus neoformans were recovered: one from the MYCO/F Lytic bottle only and the other from the MYCO/F Lytic bottle and the Isolator tube (whose sediment was inoculated into the BACTEC 13A bottle). For potential pathogens overall, there was a statistical difference in recovery that favored the Isolator system over the MYCO/F Lytic bottle (P = 0.0015), including statistically significant differences for Staphylococcus aureus (P = 0.0001) and Streptococcus pneumoniae (P = 0.0313). However, there was no statistically significant difference between the two blood culture systems when detection of bloodstream infection was considered. The time to detection for all potential pathogens combined was less for the MYCO/F Lytic bottle than for the Isolator system (P = 0.0004). Overall, the potential pathogen recovery was greater for the BACTEC Plus Aerobic/F bottle than for either the Isolator system (P = 0.0003) or the MYCO/F Lytic bottle (P = 0.0001). However, the BACTEC Plus Aerobic/F bottle did not recover M. tuberculosis, H. capsulatum, or C. neoformans isolates. The combination of the Isolator system and MYCO/F Lytic bottle may be useful as a selective blood culture method to optimize the recovery of fungi and mycobacteria from blood. Compared with the manual Isolator system, the MYCO/F Lytic system has the advantage of less preanalytic processing and continuous automated monitoring of bottles for growth by the BACTEC 9240 instrument.

Adult↗

Use of CHROMagar Candida for genital specimens in the diagnostic laboratory.

OBJECTIVE: To evaluate CHROMagar Candida (CA), a new yeast differential medium, for yeast isolation in a clinical laboratory for the routine examination of high vaginal swabs. METHODS: Results of high vaginal swab cultures processed in a standard manner on plates containing equal halves of Sabouraud dextrose agar (SDA) and CA were compared. Non-Candida albicans yeast isolates were further speciated with API 20C AUX or API 32C. To assess the ease of use of CA, laboratory staff lacking in experience of the medium were asked to identify 23 unlabelled yeast cultures on CA by referring to six labelled reference plates. RESULTS: Of the 1784 swab cultures processed, yeasts were isolated from 373 SDA and 368 CA. Of the 78 non-albicans isolates further speciated, CA identified correctly all cultures of C krusei and C tropicalis, and 82% of C glabrata. All the 38 inexperienced laboratory staff achieved 100% accuracy for C albicans and over 90% for C krusei and C tropicalis. CONCLUSIONS: CA is a satisfactory isolation medium for genital specimens, allowing immediate and correct identification of the commonly encountered yeasts and easy recognition of mixed cultures.

Candida↗

Plastic specula: can we ease the passage?

BACKGROUND: For many years, genitourinary physicians have taught that specula should be used without lubrication other than water, as it was assumed that gel would interfere with the processing of samples, but there seems little evidence to support this. Many clinics are now using plastic specula to avoid reusable instruments, and one of the commonest problems with such specula is increased friction. METHODS: We looked at the effect of Aquagel on the culture of different dilutions of Neisseria gonorrhoeae on three standard laboratory media. The effect of Aquagel on the chlamydial strand displacement assay (SDA) test was also assessed by mixing different amounts of Aquagel with the positive and negative control and processing in the usual way. RESULTS: There was found to be no inhibition of culture following emulsification of N gonorrhoeae in Aquagel at any concentration. All the results for the chlamydial SDA test were satisfactory following mixing with Aquagel. CONCLUSION: We think that the clinician should now be more confident that if a difficult examination requires the use of a lubricant, the test results will not be compromised.

Chlamydia Infections↗

Chlamydia trachomatis and Neisseria gonorrhoeae infection and the sexual behaviour of men who have sex with men.

BACKGROUND: Rates of bacterial sexually transmitted infections (STIs) continue to rise among men who have sex with men (MSM) in the UK. OBJECTIVE: To evaluate factors associated with Chlamydia trachomatis and Neisseria gonorrhoeae among MSM attending a genitourinary medicine clinic in inner London. STUDY DESIGN: 599 MSM undergoing testing for STIs were recruited. Specimens for ligase chain reaction (LCR), strand displacement amplification (SDA) assay and culture were collected from the pharynx, urethra and rectum for the detection of C trachomatis and N gonorrhoeae. Details regarding demographics, symptoms, signs and sexual behaviour were recorded. Associations of these factors with each infection were tested, adjusting for other risk factors. RESULTS: The prevalence of C trachomatis and N gonorrhoeae was 11.0% and 16.0%, respectively. LCR and SDA performed well for the detection of C trachomatis and N gonorrhoeae from urethra and rectum. Using either method, compared with our current testing policy, over 18% of those with C trachomatis and N gonorrhoeae would not have had their infection diagnosed or treated. Age, sexual behaviour, urethral and rectal symptoms and signs were strongly associated with both infections. A total of 33.7% of men reported at least one episode of unprotected anal intercourse in the previous month. Men reporting multiple episodes were markedly more likely to be HIV positive. CONCLUSION: The prevalence of infection, rates of partner acquisition and unprotected anal intercourse reported among these MSM are alarming. Improved detection of C trachomatis and N gonorrhoeae using nucleic acid amplification tests has major public health implications for STI and possibly HIV transmission in this population.

Adolescent↗

Therapeutic embolization of bronchial artery: a successful treatment in 209 cases of relapse hemoptysis.

Still today bronchial artery embolization (BAE) is an important procedure in the management of hemoptysis, as an alternative to, or in association with, surgical or medical therapy. From 1974 to 1990, BAE was performed in 209 patients who suffered from hemoptysis with different etiopathogeneses and severity. Bronchiectasis were the most frequent indication (46%) followed by tuberculosis (31%), cystic fibrosis (16%), lung cancer (4%), and aspergillosis (3%). BAEs were performed by means of polyvinyl alcohol particles and absorbable gelatin sponge. In a few cases complete occlusion of the main truncus of particularly large bronchial arteries was obtained by use of Gianturco steel coin (5 mm o) technique. In the last seven years, together with the traditional angiographic techniques, selective digital angiography (SDA) was performed, above all in preliminary control phases, to evaluate occlusion during embolization. SDA reduced catheterization time and the mean quantity of contrast administered, decreasing side effects; 98% of hemoptysis was controlled in the first twenty-four hours, the other 2% in the following forty eight hours; 16% relapses occurred within the first year; 27 patients needed reembolization (15 patients twice, 11 patients three times, 1 patient five times). No complications were seen. If diagnosis, therapeutic indications, operative technique, and equipment selection are adequate, BAE has a high reliability in patients affected by relapsing hemoptysis, which is difficult to resolve.

Angiography, Digital Subtraction↗

Use of the structured descriptive assessment with typically developing children.

To date, only a limited number of studies have focused on functional assessment with typically developing populations. The most commonly reported method of functional assessment with this population seems to be descriptive assessment; however, the methods used in the descriptive assessment often are unclear. This is unfortunate as researchers and practitioners often are left with little guidance as to how to conduct a functional assessment with typically developing children. The purpose of this study was to determine whether the structured descriptive assessment (SDA) might be used with typically developing children. Four children with problem behavior participated in the study, and hypotheses about functional relations were developed for all children. Furthermore, efficacious interventions were developed and implemented for 2 children based on the results of the SDA.

Aggression↗

Irregular patterns in the daily weight chart at night predict body weight regain.

This study examined whether charting daily weight patterns can predict weight regain in obese patients. The subjects were 98 moderately obese Japanese women aged 23 to 66 years who were obliged to precisely record their daily weights during the initial 4-month education period, but not thereafter. The patients were followed up at 8, 12, and 16 months. Abdominal fat areas and blood samples were assessed in the outpatient clinic at 0, 4, and 16 months. The standard deviations (SDs) of the differences in body weight between "after waking up" and "after breakfast" (SDa), "after dinner" (SDb), and "before going to bed" (SDc) were calculated, which were parameters reflecting the fluctuations in the daily weight patterns during the first 4 months. SDc, but not SDa or SDb, was correlated positively with weight regain at 8, 12, and 16 months (P = 0.049, P = 0.002, and P = 0.001, respectively). There were significant differences in temporal change in body weight and abdominal visceral fat between the small SDc group (SDc </=25th percentile) and the large SDc group (SDc >75th percentile), but not for subcutaneous abdominal fat or the serum concentrations of glucose, insulin, or lipids. The results indicate that fluctuation of body weight immediately before going to bed is useful for predicting the rebound in body weight.

Adult↗

Occlusal and TMJ loads in subjects with experimentally shortened dental arches.

To determine whether shortened dental arches (SDAs) cause functional overloading of the teeth and the temporomandibular joints, which has been implicated in periodontal diseases and temporomandibular disorders, we investigated the influences of SDA on occlusal and joint loads. Bite force and masticatory muscle electromyograms were recorded in five dentate subjects who clenched maximally on intra-oral appliances, creating symmetrical SDAs experimentally. Muscular forces estimated from the recorded electromyograms were fed into a finite element jaw model for calculating bite forces and joint loads. Comparison between the measured and the calculated bite forces ensured that the joint loads were representative. The bite force on each tooth increased with missing molar occlusions, while joint loads decreased. The bite force per root surface area was always greatest on the most posterior tooth, and these values were most constant. The findings provide no evidence that SDA causes overloading of the joints and the teeth, which suggests that neuromuscular regulatory systems are controlling maximum clenching strength under various occlusal conditions.

Adaptation, Physiological↗