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Biomedical subjects

J L McDonald

Publications and source records attributed to J L McDonald.

At least 19 recordsLinked to original sources
PubMed2001

Effect of molar rotation on arch length.

The aim of this study was to evaluate the effect of maxillary first molar rotation on arch length in patients whose Class II, division 1 malocclusion was treated with a straight-pull headgear. The sample included 19 children who represent a subset of a population enrolled for 2 years in a prospective clinical trial of Class II treatment. The inner bow was adjusted at monthly visits and the average distalizing force was 14-16 oz per side. Measurements were made with digital calipers on casts obtained at baseline and at a time point averaging 16 months (SD 3 months) into treatment. Molar movement was related to a coordinate system referenced to the midpalatal raphae and the occlusal plane through a palatal plug that could be transferred to successive casts of the same patient. Distances from the cusp tips were measured to the reference system. The distal and lateral displacement, and the rotation of the molars over time were then computed. High correlations were observed between molar rotation and tooth displacement (that is the net differential movement between the mesiobuccal - MB - and mesiopalatal - MP - cusps): r=0.9, p=0.0001 (left side); r=0.8, p=0.0001 (right side). The average rotation of the molar was 15.4 degrees (SE+/-3.80) on the left side and 10.8 degrees (SE+/-2.20) on the right side. The average differential displacements between the MB and MP cusps were 1.04 mm (SE+/-0.29) (left) and 0.73 mm (SE+/-0.23) (right). The differences between the two sides were not statistically significant. The molar rotation did not correlate with any of the following parameters: initial tooth position; initial distance between the MB and MP cusps as a correlate of molar anatomy; transverse (mostly buccal) movement of the MB and MP cusps; distal movement of the tooth, as measured by the total displacement of the MB and MP cusps. This study qualifies the relationship between molar rotation and increase in arch length. The mean total distal movement of the molar was larger (nearly 3 mm) than the average contribution of molar rotation to space gain (about 1 mm), suggesting that the distal movement of the tooth was a combination of rotation and translation (or tipping). The contribution of the molar rotation is more significant with a smaller total displacement of the tooth.

Journal Article↗
PubMed2001

Nonmainstream dialect use and specific language impairment.

Most work looking at specific language impairment (SLI) has been done in the context of mainstream dialects. This paper extends the study of SLI to two nonmainstream dialects: a rural version of Southern African American English (SAAE) and a rural version of Southern White English (SWE). Data were language samples from 93 4- to 6-year-olds who lived in southeastern Louisiana. Forty were classified as speakers of SAAE, and 53 were classified as speakers of SWE. A third were previously diagnosed as SLI; the others served as either age-matched (6N) or language-matched (4N) controls. The two dialects differed in frequency of usage on 14 of the 35 coded morphosyntactic surface patterns; speakers of these dialects could be successfully discriminated (94%) from each other in a discriminant analysis using just four of these patterns. Across dialects, four patterns resulted in main effects that were related to diagnostic condition (SLI vs. 6N), and a slightly different set of four patterns showed effects that were related to developmental processes (4N vs. 6N). More interestingly, the surface characteristics of SLI were found to manifest in the two dialects in different ways. A discriminant function based solely on SAAE speakers tended to misclassify SWE children with SLI as having normal language, and a discriminant function based on SWE speakers tended to misclassify SAAE unaffected children as SLI. Patterns within the SLI profile that cut across the two dialects included difficulties with tense marking and question formation. The results provide important direction for future studies and argue for the inclusion of contrastive as well as noncontrastive features of dialects within SLI research.

Child↗
PubMed2001

Retroactive interference from translation equivalents: implications for first language forgetting.

First language vocabulary is vulnerable to forgetting after massive exposure to a second language. Two possible factors responsible for the forgetting are degree of semantic overlap between concepts in the two languages and amount of second language exposure. In a laboratory simulation of the language forgetting situation, participants received 10 exposures to a list of words in a foreign language, followed by 2, 5, 10, or 15 exposures to a list in a second foreign language. The second list consisted of either translation equivalents or new concepts. Participants were then tested for retention of the first list. More retroactive interference was found for translation equivalents than for new concepts and for higher degrees of exposure to the second list. When retention of the first list was broken down in terms of gains and losses, effects of both similarity of the second list to the first and amount of exposure to the second list were found only for losses--a fact that points to lack of discriminability as one of the underlying causes of forgetting. Overall, the experimental paradigm proved useful for exploring and developing theories about the causes of first language forgetting.

Humans↗
PubMed2001

Problem-based learning and the dental school library.

A major curriculum revision involving the utilization of problem-based learning was implemented at Indiana University School of Dentistry in the summer of 1997. Two of the main goals of this new student-centered curriculum were to promote critical thinking skills and to encourage a desire for lifelong learning, both of which were anticipated to increase student use of the library. This study examined circulation at the library for three years immediately prior to, and for three years immediately following, the curricular change. Results show that library circulation has increased significantly since the pedagogical change. This suggests that students in the new curriculum place more emphasis on the library as a learning resource than did their traditional curriculum counterparts.

Analysis of Variance↗
PubMed1997

Language acquisition: the acquisition of linguistic structure in normal and special populations.

This review examines how language learners master the formal structure of their language. Three possible routes to the acquisition and mastery of linguistic structure are investigated: (a) the use of prosodic and phonological information, which is imperfectly correlated with syntactic units and linguistic classes; (b) the use of function words to syntactically classify co-occurring words and phrases, and the effect of location of function-word processing on structural mastery; and (c) the use of morphology internal to lexical items to determine language structure, and the productive recombination of these subunits in new items. Evidence supporting these three routes comes from normal language acquirers and from several special populations, including learners given impoverished input, learners with Williams syndrome, specific language-impaired learners, learners with Down syndrome, and late learners of first and second languages. Further evidence for the three routes comes from artificial language acquisition experiments and computer simulations.

Adolescent↗
PubMed1993

Word and world order: semantic, phonological, and metrical determinants of serial position.

Animacy, word length, and prosody have all been accorded prominent roles in explanations for word order variations in language use. We examined the sequencing effects of these factors in two types of tasks. In recall tasks designed to simulate language production, we found selective effects of animacy. Animate nouns tended to appear as subjects in transitive sentences, but showed no special affinity for initial position in conjunctions within sentences, but showed no special affinity for initial position in conjunctions within sentences, suggesting a stronger involvement of animacy in grammatical role assignment than in word ordering. Word length had no significant impact: Shorter words did not appear earlier than longer words within sentences or within isolated conjunctions of nouns. Prosody had a weak effect on word order in isolated conjunctions, favoring sequences with alternating rhythm, but only in the absence of an animacy contrast. These results tend to confirm a hypothesized role for conceptual (meaning-based) accessibility in grammatical role assignment and to disconfirm a hypothesized role for lexical (form-based) accessibility in word ordering. In a judgment task, forms with animate nouns early were preferred across all constructions, and forms with short words early were often preferred both in sentences and in conjunctions. The findings suggest a possible asymmetry between comprehension and production in functional accounts of word order variations.

Concept Formation↗
PubMed1990

The smokeless tobacco 'time bomb'.

All healthcare professionals need to become aware of the extent and seriousness of smokeless tobacco use. In this article, the authors briefly review the current status of smokeless tobacco and describe its usage patterns and practices, pharmacologic (addictive) aspects, and associated health problems. They also suggest ways that primary care physicians can discover or prevent smokeless tobacco use in their patients.

Adolescent↗
PubMed1990

How-to-do-it quit-smoking strategies for the dental office team: an eight-step program.

Dental personnel have an ethical responsibility to inform their patients about the hazards of tobacco use. Because oral health team members generally see their patients on a frequent and recurring basis, these treatment providers have unparalleled opportunities to educate and help those who smoke to adopt a smokefree lifestyle. Dental practitioners can readily incorporate smoking cessation efforts into their routine dental practices by using an eight-phase smoking intervention program. The overall focus of this program is to: "Ask" patients about smoking or smokeless tobacco usage; "Advise" tobacco-using patients to quit; "Assist" interested patients in quitting; and "Arrange" for supportive follow-up. By providing these services, dental professionals can do their part to help create a smokefree America by the year 2000.

Dentist-Patient Relations↗
PubMed1989

Smokeless tobacco addiction: a threat to the oral and systemic health of the child and adolescent.

The use of smokeless tobacco (ST) within the United States has increased greatly in recent years, especially among adolescent boys and young men. Recent national data completed from several large scale studies indicate that 10-12 million Americans use some form of ST. Representing a significant systemic and oral health risk, ST usage can produce a wide range of negative effects on both soft and hard oral tissues. These oral conditions include bad breath, discolored teeth and restorative materials, excessive tooth surface wear (abrasion), decreased ability to taste and smell, gingival (gum) recession, advanced periodontal soft and hard tissue destruction, tooth loss, soft tissue erythema and leukoplakia. Long-term ST usage is directly correlated to an increased risk of cancer of the mouth, larynx, throat and esophagus. Much of the destruction of oral tissues is related to the localization of the tobacco quid; i.e., it is habitually held in only one spot in the mouth. Nicotine from ST can activate the sympathetic nervous system thereby significantly increasing heart rate, blood pressure, cardiac stroke volume and output and coronary blood flow. A common misconception is that ST is a 'safe' alternative to smoking cigarettes. Several recent Surgeon General's Reports list ST as being addictive. It is highly possible that ST users will 'graduate' to cigarettes if they eventually conclude that these products are socially unacceptable, inconvenient or out of vogue. Health professionals, educators, parents and schoolchildren need to be informed about the significant health risks associated with ST use.

Adolescent↗
PubMed1988

Overreporting of smokeless tobacco use by adolescent males.

This study evaluates the impact of a pipeline assessment (salivary cotinine determination) on the accuracy of self-reported use of cigarettes and smokeless tobacco by 160 rural seventh- and eighth-grade males ranging in age from 12 to 16. Half of them were randomly assigned to complete a questionnaire on tobacco use prior to revealing the biochemical validation materials and collecting samples. The others had the samples collected prior to receiving and completing the questionnaires. The questionnaire-first group reported significantly greater smokeless tobacco use than did the pipeline-first group. Only for the latter were their self-reports significantly corroborated by the cotinine results. These results suggest that the utilization of a biochemical pipeline not only can improve self-reported tobacco use but also may help identify perceptions about the social desirability of using harmful substances.

Adolescent↗
PubMed1986

Role of aerobic exercise in reduction of stress.

During the past several years, excessive stress has come to be recognized as a threat not only to quality but also to length of life. There is increasing evidence that the emotionally distressed individual may have an increased susceptibility to a number of pathologic conditions. Physical activity, in the form of aerobic exercise, is a very fruitful means for coping with stress. The popular forms of aerobic activities that are most often pursued in order to help general cardiovascular condition may, in effect, improve the mental health of the individual. There are no guarantees that if you follow these recommendations you will live longer. However, the life you live will be healthier, happier, more productive, and less stressful.

Aerobiosis↗
PubMed1985

Effects of nicotine-containing chewing gum on oral soft and hard tissues: A clinical study.

A double-blind clinical trial was conducted to determine whether the use of a chewing gum containing 2.0 mg nicotine (as an adjunct to a stop-smoking program) had any effects upon oral health. A total of 193 adults who smoked cigarettes volunteered with informed consent, were given routine dental prophylaxes, and were examined for the presence of plaque, stained pellicle, gingivitis, calculus, and general oral pathosis. The subjects were then randomly assigned to use either a nicotine-containing or a placebo chewing gum. After 15 weeks the subjects were recalled and re-examined. Smoking cessation was determined through questionnaire and analysis of the carbon monoxide content of alveolar air. At the completion of the study, 79 subjects had used the placebo gum and 78 had used the nicotine gum. Data analysis indicated that the nicotine chewing gum had no significant influence on any of the oral health parameters graded, as compared to the placebo gum. The continuation of smoking, however, was associated with significant increases in gingivitis and calculus rates.

Carbon Dioxide↗