Dental fluorosis: variability among different inbred mouse strains.

Concurrent with the decline in dental caries has been an increase in the prevalence of dental fluorosis, a side-effect of exposure to greater than optimal levels of fluoride during amelogenesis. The mechanisms that underlie the pathogenesis of dental fluorosis are not known. We hypothesize that genetic determinants influence an individual's susceptibility or resistance to develop dental fluorosis. We tested this hypothesis using a mouse model system (continuous eruption of the incisors) where genotype, age, gender, food, housing, and drinking water fluoride level can be rigorously controlled. Examination of 12 inbred strains of mice showed differences in dental fluorosis susceptibility/resistance. The A/J mouse strain is highly susceptible, with a rapid onset and severe development of dental fluorosis compared with that in the other strains tested, whereas the 129P3/J mouse strain is least affected, with minimal dental fluorosis. These observations support the contribution of a genetic component in the pathogenesis of dental fluorosis.

Vital capacity following traumatic brain injury.

This study was designed to describe lung volume subdivisions in individuals with traumatic brain injury. Records were reviewed for 114 consecutive referrals for motor speech evaluations in a community re-entry residential rehabilitation programme. Obtained measures were vital capacity, inspiratory capacity, and expiratory reserve volume at the time of evaluation. Seventy-nine per cent of subjects evidenced at least moderate deficits in expiratory reserve volume, with 60% evidencing severe deficits. Inspiratory capacity was the least affected, with 61% of subjects evidencing values within normal limits. Possible contributors to reduced expiratory reserve volumes include expiratory muscle weakness due to physical inactivity, inability to voluntarily perform the task, or perceived effort.

Aerodynamic, acoustic, and perceptual measures of nasality following traumatic brain injury.

Data were obtained from 31 subjects who had incurred a traumatic brain injury (TBI). Two expert listeners judged nasality using direct magnitude estimation with a referent. They rated samples of the first sentence of the Rainbow Passage, played backwards, with all pauses removed. Sensitivity was good for nasalance, velopharyngeal airway resistance, and velopharyngeal orifice area, indicating that these measures would accurately identify an individual as nasal. Specificity was reduced, and was adequate only for nasalance. The reduced specificity was due to a high number of false positives, i.e. perceived nasality in the absence of objective corroboration. Analysis of the false positives revealed that a slow speaking rate could mislead a listener's perception of nasality. Overall, for individuals with dysarthria following TBI, the measure of nasalance may most accurately reflect listener perception of nasality.

Age-related changes in orofacial force generation in women.

OBJECTIVES: This study was designed to assess the effect of age on orofacial force generation. STUDY DESIGN: Forty women participated in a cross-sectional design, with 10 in each age group from 20 to 39, 40 to 59, 60 to 79, and 80 to 100 years of age. METHODS: Measures of force generation were obtained for the upper lip, lower lip, tongue, and jaw. RESULTS: There were no statistical differences among age groups, probably because of large individual variability within groups. Trends indicated a decline, particularly after age 80 years. CONCLUSION: Although trends in the data suggest some decline in the function of orofacial structures with age, it is unlikely that these changes would noticeably affect functional communication.

Velopharyngeal airway resistance disorders after traumatic brain injury.

OBJECTIVE: Disorders affecting velopharyngeal port closure may result in the perception of hypernasality. This study was designed to determine (1) the incidence of velopharyngeal airway resistance deficits after traumatic brain injury, (2) the relation between velopharyngeal airway resistance and dysarthria severity, and (3) the relation between velopharyngeal airway resistance and perceived hypernasality. DESIGN: Case series. SETTING: Community re-entry residential rehabilitation program. PATIENTS: Eighty-three consecutive referrals for speech production evaluations. MAIN OUTCOME MEASURES: Velopharyngeal airway resistance at the time of the evaluation. RESULTS: About half the patients evidenced reduced velopharyngeal airway resistance. Subjects who evidenced mild or absent dysarthria typically had no velopharyngeal deficits, while subjects who evidenced severe dysarthria had very low velopharyngeal airway resistance. With few exceptions, the severity of the velopharyngeal airway resistance deficit was associated with perceived hypernasality. CONCLUSIONS: Velopharyngeal airway resistance disorders after traumatic brain injury are common. Discrepancies between velopharyngeal airway resistance and perceived hypernasality may be caused by intelligibility, speaking style, or nonrepresentative sampling.

Differential activity of the pars recta and pars oblique in fundamental frequency control.

This study was designed to determine if differences exist in pars recta and pars oblique muscle activity during speech and singing. Hooked wire electrodes were implanted in the muscle bundles under direct vision during thyroid surgery in two men and three women. It was found that the pars recta and pars oblique do not function in a similar manner across fundamental frequencies (fo's), tasks, or subjects. Large inter- and intrasubject variability was evident in the contribution of the cricothyroid bundles to fundamental frequency (fo) control. It is speculated that the effect of pars recta and pars oblique contraction may be a function of individual anatomic variations.

Comparison of direct and indirect calculations of laryngeal airway resistance in connected speech.

Direct measures of subglottal pressure obtained through a tracheal puncture were used to calculate laryngeal airway resistance. Six subjects completed tasks including syllable trains and more natural speech samples produced at three loudness levels. Direct calculations of natural speech resistance values were compared with indirect estimates obtained during syllable train production. The degree of correspondence between direct and indirect calculations varied by subject. Overall, the smallest relative errors among calculations occurred for syllable trains, with higher relative errors for the monologue and sentence. For loudness conditions, the smallest and largest relative errors occurred for soft and loud productions, respectively. The clinical utility of indirect estimation is questioned and suggestions for improving its validity are provided.

Intelligibility and nonspeech orofacial strength and force control following traumatic brain injury.

Objective measures of nonspeech orofacial strength and force control were obtained for 20 individuals with traumatic brain injury. The dynamic and static force generating abilities of the upper lip, lower lip, tongue, and jaw were assessed. Based on sentence intelligibility scores, the subjects were divided into two groups, more and less intelligible. Force measures included reaction time, slope, derivative, peak overshoot, and first- and second-half mean hold and standard deviation. Groups differed only in the ability to sustain the 2 N force level with the tongue. Other potential contributors to the differences in intelligibility are discussed.

Estimating respiratory volumes from rib cage and abdominal displacements during ventilatory and speech activities.

This methodological study examined the predictive strength associated with modeling respiratory volumes from chest-wall movements during selected ventilatory and speech activities. A linearized magnetometry system transduced the anterior-posterior diameters of the rib cage and abdomen, supplying kinematic data that were used to estimate respiratory volumes. Kinematic and airflow measures were acquired during (a) tidal ventilation, (b) vital capacity maneuvers, (c) Rainbow Passage reading at customary loudness, (d) Rainbow Passage reading at twice-customary loudness, (e) extemporaneous speech, and (f) /a/ prolongation. Multiple-regression statistics were applied to the body surface and integrated airflow data to obtain (a) intercepts, (b) volume-motion coefficients for the rib cage and abdomen, and (c) coefficients of determination. Volumes estimated by applying regression-derived intercepts and volume-motion coefficients to the respiratory kinematic data were then compared to integrated airflow signals. Two magnetometer-based, volume-estimation strategies were contrasted for the speech tasks, one based on volume-motion coefficients derived from that particular speech activity and one based on volume-motion coefficients derived from tidal ventilation. Regression-derived intercepts and volume-motion coefficients for the abdomen varied significantly across subjects but not tasks. Volume-motion coefficients for the rib cage varied significantly across both subjects and tasks. Coefficients of determination for the magnetometer-based volume estimates were affected significantly by subjects and tasks but not by volume-estimation strategies. The calibration, use, and potential limitation of respiratory kinematic devices for speech research are discussed.

Factors associated with dysphonia in high school cheerleaders.

Questionnaire responses that encompassed the severity of acute, cheering-related dysphonia, typical vocal use, vocal history, medical history, smoking and drinking behaviors, and A-Scale personality characteristics were obtained from 146 female high school cheerleaders. Multiple-regression analysis was chosen to examine the degree to which the dysphonia severity items could be associated with the remaining items. The results indicated that acute, cheering-related dysphonia may be preceded or accompanied by a compact set of clinical signs that could be incorporated easily into a screening protocol for prospective cheerleaders.