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Biomedical subjects

E Ellis

Publications and source records attributed to E Ellis.

At least 19 recordsLinked to original sources
PubMed1995

Structural properties of mandibular bone following application of a bone plate.

PURPOSE: Similarities in strain patterns between long bones and the mandible suggest that plates may induce stress shielding, resulting in deleterious long-term changes. This study is an investigation of the use of bone plates on the mandible in four adult rhesus monkeys. MATERIAL AND METHODS: A stainless steel plate was attached facially along the inferior border of each mandibular corpus. On the left, a thick (2.5-mm) plate was engaged with four screws. On the right, a thin (0.5-mm) plate was attached with one screw. Monkeys were killed a year after plate placement. At the beginning and end of the experiments, bone strain was recorded inferior to each bone plate during evoked maximal incisal clenching. After death, bone was removed from the mandibles around and under the plates and examined. Gross dimensions and density were measured. An ultrasonic technique was used to measure the material properties, including the elastic and shear moduli. RESULTS: Bone strain inferior to the plates was reduced by 34% to 53% after attachment of the thick plates. Little change in strain was found after attachment of the thin plates. However, no significant differences in structural or mechanical measurements, such as density, cortical thickness, elastic and shear moduli, and Poisson's ratios, were detected between the two sides in each monkey. CONCLUSION: Long-term placement of bone plates, and the resulting stress shielding, were found to result in structural changes in the mandibular corpus.

Animals↗
PubMed1995

The effects of orthodontic treatment on isometric bite forces and mandibular motion in patients before orthognathic surgery.

PURPOSE: Little is known about the effects of orthodontic treatment on oral motor function. The objective of this report is to evaluate changes in mandibular motion and maximum bite force that occur between the initiation of presurgical orthodontics and its completion before surgery. PATIENTS AND METHODS: Fifteen patients (9 women, 6 men) with a variety of dentofacial deformities were examined before and after presurgical orthodontics. Mechanical advantage of the muscles and bite points, mandibular range of motion, maximum isometric bite force, and levels of electromyographic (EMG) activity in the anterior and posterior temporalis and masseter muscles during isometric bites were recorded on all subjects over time. Data obtained before and after completion of presurgical orthodontics were statistically compared. RESULTS: Presurgical orthodontics reduced mandibular mobility somewhat, but the amount was not significant. Statistically significant reductions in bite force were noted after orthodontics for incisor, canine, premolar, and molar bite positions. No significant difference in the EMG/bite force slopes was obtained, nor was there any difference in the moment arms of the bite points or the muscles of mastication from orthodontics. CONCLUSIONS: This study showed significant changes in measures of oral motor function resulting from orthodontic treatment. A larger study is needed to confirm that these results will be similar in all orthodontic patients. There is no indication that these changes are the result of physiologic alterations of the muscles of mastication. The best current explanation is that these changes result from the pain and discomfort of the orthodontic appliances and the induced malocclusion.

Adolescent↗
PubMed1995

Functional characteristics of retrognathic patients before and after mandibular advancement surgery.

PURPOSE: The purpose of this investigation was to compare morphologic parameters and functional performance between controls and a sample of patients with mandibular retrognathia prior to surgical correction, and to examine how oral motor function adapts after treatment. PATIENTS AND METHODS: Twenty-four retrognathic female patients were compared with 26 female controls before and up to 3 years after mandibular advancement surgery. Measures of skeletal morphology, mandibular range of motion, maximum isometric bite force, and levels of electromyographic activity in the anterior and posterior temporalis and masseter muscles during isometric bites were made on all subjects over time. One-way analysis of variance was used to compare the controls, the patients before surgery, and the patients after surgery. RESULTS: Surgical lengthening of the mandible averaged 7.3 mm, bringing most skeletal measures into the normal range. There were no significant differences in jaw muscle mechanical advantage between patients and controls before surgery, but surgery significantly reduced mechanical advantage of the anterior temporalis and masseter muscles. Jaw hypomobility was apparent at 6 weeks after surgery, but returned to normal values within 12 to 24 months. Before surgery the patients had maximum isometric bite forces less than half those of controls. Bite forces steadily increased after surgery, approaching normal values within 2 years. Before surgery the patients' muscle activity levels per unit of bite force were equivalent to those of controls or somewhat higher. After surgery some of the patients' muscles had significantly lower levels of muscle activity per unit of bite force than did controls. CONCLUSION: The results of this study suggest that correction of mandibular retrognathia by mandibular advancement surgery produces some significant functional benefits.

Adolescent↗
PubMed1995

A longitudinal study of changes in masticatory performance of patients undergoing orthognathic surgery.

PURPOSE: Individuals with developmental deformities of the jaws may be less efficient at chewing food. Previous studies have reported masticatory deficiency in patients with such deformities. This study was designed to detect any changes in masticatory performance that accompany orthognathic surgery. MATERIALS AND METHODS: Masticatory performance was tested in 18 patients with various jaw deformities before application of orthodontic appliances and 2 to 3 years after surgical correction of their malocclusion. A control group was tested at three 6-month intervals. The subjects chewed carrots and masticatory performance was measured using a standard sieve technique. The Rosin-Rammler equation was used to calculate the median particle size and broadness index of each set of carrots. The number of chewing cycles required for each subject to swallow one piece of carrot was also recorded. RESULTS: A statistically significant difference in median particle size between patients and controls was found both preoperatively and postoperatively (P < .05), but no difference in median particle size or broadness index was seen between trials for controls or patients (P > .05). CONCLUSION: It was concluded that before surgery patients have a lower level of performance than controls and surgical correction of the malocclusion does not significantly enhance performance.

Adolescent↗
PubMed1995

Functional and morphologic alterations secondary to superior repositioning of the maxilla.

PURPOSE: The purpose of this investigation was to 1) compare morphological characteristics and functional performance of a sample of patients with vertical maxillary excess (VME) with controls, and to 2) examine how the patients' oral motor function adapts to surgery. MATERIALS AND METHODS: Fifteen female VME patients were compared with 26 female controls before and up to 3 years after maxillary intrusion surgery. Measures of skeletal morphology, mandibular range of motion, maximum isometric bite force, and levels of electromyogram (EMG) activity in some of the muscles of mastication were made on all subjects over time. One-way analysis of variance (ANOVA) was used to compare the controls with the patients before and after surgery. Univariate repeated measures ANOVA was used to study longitudinal changes in the patients. RESULTS: Preoperatively, the patients possessed morphological measurements characteristic of vertical maxillary excess. Superior repositioning of the maxilla averaged 3.3 mm. Concurrently, most skeletal measures were brought closer to normal values. Masseter muscle mechanical advantage was significantly lower in the patients than in controls both before and after surgery (P < or = .05). There was no significant difference between patients and controls for other biomechanical measurements. Mandibular hypomobility was apparent at 6 weeks after surgery, but returned to control values within 6 to 12 months. Before surgery, the patients had maximum isometric bite forces significantly less than those of controls. Bite forces steadily increased after surgery, approaching normal values within 2 years. Before surgery the patients' muscle activity levels per unit of bite forces were equivalent to those of controls or somewhat lower. After surgery some of the patients' muscles had significantly lower levels of muscle activity per unit of bite force than did controls. CONCLUSIONS: The results of this study suggest that correction of vertical maxillary excess with maxillary intrusion surgery improves some characteristic functional deficits.

Adolescent↗
PubMed1995

Breathing patterns during spontaneous speech.

Lung volumes, speech intensity, the linguistic location of inspirations, and the variability of each, were studied during spontaneous speech in 6 healthy young women over 7 to 10 sessions each, using respiratory inductance plethysmography. Although average lung volume levels were within the vital capacity range previously reported for speech (Hixon, Goldman, & Mead, 1973), significant inter- and intrasubject variability was observed. This variability was considerable for some subjects (average initiation lung volume varying between 42 and 63% VC over the sessions) and relatively small for others (between 47 and 53% VC). Some of the lung volume variation was associated with changes in mood state, examined by self-report questionnaire at each measurement occasion. Linguistic factors were important influences in the lung volume variation. The majority of breaths in the conversations and monologues preceded structural (clause) boundaries. The volume of air inspired preutterance was found to be linked to the length of the ensuing breath group in each of our 6 subjects, as longer breath groups, spanning up to seven clauses in the spontaneous speech, were anticipated by inspiring to a higher lung volume. The subjects used a comfortable speaking intensity range, which varied for different individuals and sessions over 4 to 18 dB. Increases in speech intensity within individual ranges were not associated with increased lung volumes. The data provide novel insight into associations between physiological and linguistic factors in the control of speech breathing, and are suggestive of the existence of neural planning of the respiratory system, in anticipation of the demands of the utterance.

Adult↗
PubMed1994

Treatment of mandibular angle fractures using two noncompression miniplates.

PURPOSE: To evaluate treatment with two 2.0-mm noncompression miniplates for patients with angle fractures. PATIENTS AND METHODS: Sixty-seven consecutive patients with 69 fractures of the mandibular angle were treated by open reduction and internal fixation using two noncompression miniplates and 2.0-mm self-threading screws placed through a transoral incision with transbuccal trochar instrumentation. No patient was placed into postsurgical maxillomandibular fixation or elastics. RESULTS: Overall, 19 fractures (28%) experienced complications requiring secondary surgical intervention. Most of the complications were postoperative infections requiring surgical drainage (n = 17) and subsequent hardware removal (n = 16). Of the 17 infected fractures, 11 were healed at the time of hardware removal and required no further treatment. Five were still mobile and required a period of maxillomandibular fixation for healing. One of the fractures did not heal and required bone grafting. CONCLUSION: The use of two noncompression miniplates was found to be relatively easy, but resulted in an unacceptable rate of infection in our patient population when used for treatment of fractures of the mandibular angle.

Adolescent↗
PubMed1994

Masticatory performance, muscle activity, and occlusal force in preorthognathic surgery patients.

Previous studies have indicated that patients scheduled for orthognathic surgery tend to have lower maximum bite forces and exert lower forces during mastication. The effect of these deficits on masticatory performance have not been previously assessed. Masticatory performance was analyzed in four groups: male and female orthognathic surgery patients prior to presurgical orthodontics (n = 12 and 23), and male and female controls (n = 27 and 31). Mastication performance was analyzed by having the subjects chew 5-g pieces of carrot for 20 cycles and measuring the resulting median particle size with a standard sieve method. Masticatory performance showed the same trends as maximum bite force and masticatory forces: male controls had the best and patients the poorest masticatory performance. There was a weak correlation between masticatory performance and maximum bite force at the molar positions. Masticatory performance also weakly correlated to electromyographic signals during mastication of a constant bolus (gummy bears) for all muscles except the left posterior temporalis. Correlations were generally not present or were very weak between masticatory performance, estimated masticatory forces, and muscle efficiency, suggesting that muscle efficiency and forces generated during mastication are not the primary factors that determine masticatory performance. Other factors contributing to a person's ability to chew food might include occlusal relationships and mechanical advantage.

Adolescent↗
PubMed1994

Estimated masticatory forces in patients before orthognathic surgery.

There has been relatively little study of masticatory forces in dentofacial deformity patients before orthognathic surgery. This study used a mathematical equation based on electromyographic activity (EMG) during mastication and forces obtained during isometric bites to estimate masticatory forces in 55 control subjects and 48 patients. Subjects chewed on a constant bolus while EMG recordings were made bilaterally from the superficial masseter, anterior temporalis, and posterior temporalis muscles. Unilateral isometric bite forces in the first molar position and simultaneous EMGs were recorded in these same subjects. Superficial masseter muscle activity and isometric bite forces were strongly correlated. The slope of masseter EMG versus isometric force was used to estimate the masticatory forces. Males were found to have significantly higher estimated masticatory forces than females.

Adult↗
PubMed1994

Bite forces in patients treated for mandibular angle fractures: implications for fixation recommendations.

Voluntary bite forces were recorded at varying periods in 35 males treated with rigid internal fixation for fractures of the mandibular angle. Bite forces were also obtained in 29 male controls for comparison. It was found that molar bite forces in patients were significantly less than in controls for several weeks after surgery. Further, molar bite forces on the side of the fracture were significantly less than on the nonfractured side. The results of this study indicate that recommendations for the amount of fixation required for a given fracture may be reduced.

Adolescent↗
PubMed1994

Connective tissue forces from mandibular advancement.

PURPOSE: To quantify the connective tissue forces generated during surgical lengthening of the mandible. PATIENTS AND METHODS: Sixty-three patients who had mandibular advancements by sagittal ramus osteotomy were used in this study. Prior to sectioning the rami, the overjet was recorded. After sectioning the rami, a spring-gauge was attached to the mandibular orthodontic wire and pulled anteriorly to determine how much force was necessary to bring the mandibular incisors into a Class I relationship with the maxillary incisors. Aggressive stripping of the perimandibular periosteum and connective tissues on the distal segment was then performed. The amount of force was again recorded. RESULTS: The mean preoperative overjet in the 63 patients was 6 mm (range, 3 to 11 mm). The mean amount of force required to advance the mandible prior to stripping the tissues was 1,498 g compared with a mean of 787 g after stripping (P < .001). There were statistically significant correlations between the preoperative overjet and the prestripping and poststripping force levels (P < .001). There was also a significant relationship between prestripping and poststripping values (P < .001). CONCLUSION: The results of this study indicate that orthopedic forces are generated by the perimandibular connective tissues following advancement by the mandible. The effect of these forces on the temporomandibular joint should be evaluated in future studies.

Bone Resorption↗
PubMed1994

Variability and consistency in speech breathing during reading: lung volumes, speech intensity, and linguistic factors.

Lung volumes during reading and associated factors such as speech intensity and linguistic influences were studied in six healthy young women over 7 to 10 sessions, using respiratory inductive plethysmography. Intrasubject variability of lung volumes over the sessions was almost as great as the intersubject variability. Some of the intrasubject variability was associated with natural variations of speech intensity within a "comfortable loudness" range. The lung volume variability during reading is contrasted with high degrees of both inter- and intrasubject consistency in the location of inspirations, which occurred almost exclusively at grammatically appropriate places in the texts (paragraph, sentence, clause, and phrase boundaries). Within each reading passage, lung volumes were significantly increased for (a) louder utterances, (b) inspirations at sentence and paragraph boundaries compared to inspirations at other locations within sentences, (c) longer utterances compared to shorter utterances, and (d) initial breaths compared to final breaths. The implications of these findings for the neural control of breathing during speech are considered.

Adult↗
PubMed1994

Small, blue collar work site hypertension screening: a cost-effectiveness study.

This study determined the cost-effectiveness of one- versus two-stage hypertension screening at small to medium-sized blue collar, multicultural work sites using voluntary health organization and public health unit personnel. Workers with diastolic blood pressure (DBP) > or = 90 mm Hg were randomly allocated to one- or two-stage screening with differing physician referral protocols based on blood pressure level and treatment status. At first screening of 7856 workers, 12.5% had DBP > or = 90 mm Hg or < 90 and on medication with 64% aware of having hypertension, 42% on medication and 30% controlled (DBP < 90 mm Hg). One year later, there were no significant differences in effects or cost-effectiveness between groups. Both had significant DBP decrease (8.5 mm Hg), 54% had seen a physician within the recommended time, and 50% were controlled on medication or any treatment. One-stage screening, being easier to implement, is the preferred option.

Adult↗
PubMed1993

Rigid fixation of mandibular condyle fractures.

This article reviews the anatomy and surgical approaches for treating fractures of the mandibular condyle with plate and screw fixation. Advantages and disadvantages of the preauricular, submandibular, intraoral, retromandibular, and rhytidectomy approaches are presented.

Bone Plates↗
PubMed1993

Tuberculosis in Canada: a focal disease requiring distinct control strategies for different risk groups.

Cases of new or reactivated tuberculosis (TB) reported in Canadian residents during 1985-1987 (1984-1988 in the province of Quebec) were analyzed by geographic region relative to the geographic distribution of groups known to be at high risk. The crude incidence rate (per 100,000 population) of TB was calculated by census division (or Région socio-sanitaire in Quebec). Rates of TB by census division ranged from 0 to over 200 per 100,000 population; the average rate for Canada was 8.3 per 100,000. Census divisions with very high rates (over 20 per 100,000) were concentrated in the northern regions, with 80% or more of TB cases occurring among aboriginal persons. Census divisions with moderately high TB rates of 10-19 per 100,000 were located either in northerly regions or in major metropolitan areas; reported TB cases in these areas occurred disproportionately in the aboriginal or immigrant populations. Tuberculosis continues to become more geographically focused and limited to aboriginal Canadians, immigrants and the urban poor. Priority must be given to full implementation of effective prevention and control methods in geographic areas with higher incidence rates. Different methods will be required for different areas depending upon the risk groups present.

American Indian or Alaska Native↗
PubMed1993

Treatment of mandibular angle fractures using two 2.4-mm dynamic compression plates.

Sixty-five consecutive patients with fractures of the mandibular angle were treated by open reduction and internal fixation using two dynamic compression plates placed through a transoral incision using transbuccal trochar instrumentation and 2.4-mm screws. In the first 20 cases, the screws were inserted without tapping the drill holes. In the remaining 45 cases, the drill holes were tapped. No patient was placed into postsurgical maxillomandibular fixation or training elastics. Overall, 21 fractures (32%) developed infections requiring secondary surgical intervention. The infection rate was higher in those fractures where the holes were not tapped (40%) than those cases when the holes were tapped (29%). Of the 21 fractures that required hardware removal, 9 fractures were healed and required no further treatment; 12 had no firm bony union and required postsurgical maxillomandibular fixation. Only one case resulted in a malunion with resulting malocclusion. The use of two dynamic compression plates was found to be relatively easy, but resulted in an unacceptable rate of infection.

Adolescent↗
PubMed1993

The second Chalmers J. Lyons Academy study of fractures of the edentulous mandible.

A review of 167 fractures in 104 edentulous mandibles treated by several surgeons using a variety of methods was undertaken. Most patients (81.5%) had open reduction and internal fixation using bone plates. Problems in healing, either delayed or fibrous union, occurred in 21 of 167 fractures (12.6%) in 16 of 104 patients (15%). One fourth of patients treated by closed reduction techniques had problems with union, whereas extraoral open reduction with bone plate fixation produced very good results. The factors involved in treating these challenging fractures is discussed and comparisons are made with the previous Chalmers J. Lyons Academy study.

Adult↗