Biomedical subjects

P H Buschang

Publications and source records attributed to P H Buschang.

At least 55 records · Page 3Linked to original sources

PubMed1997

Orthognathic surgery effects on maxillary growth in patients with vertical maxillary excess.

This study assesses the effects of superior repositioning of the maxilla by LeFort I osteotomy on adolescent maxillary growth. A total of 48 patients, 23 who were stabilized with rigid fixation (RF) and 25 stabilized with wire fixation (WF), were compared with closely matched unoperated controls. Comparisons were made for the presurgical intervals (2.3 years for RF and 1.3 years for WF groups) and postsurgical intervals (1.9 years for RF and 2.3 years for the WF groups). Lateral cephalograms were evaluated to describe the presurgical and postsurgical spatial changes of the maxilla. During the presurgical interval, there were no significant differences in vertical or horizontal maxillary growth between the WF group and their controls. Although vertical growth changes were similar, the RF group showed slightly more than expected posterior movement of the upper incisor during the presurgical interval. During surgery, the maxilla was advanced approximately 2 mm and impacted approximately 2 mm. After surgery, there were no statistically significant differences in vertical maxillary growth between the two surgical and control groups. Horizontally, the RF group showed maxillary stability, whereas the WF groups showed posterior movement. It is concluded that multiple piece LeFort I osteotomy has little or no effect on vertical maxillary growth; rigid fixation provides superior long-term anteroposterior stability compared with wire fixation.

Adolescent↗

PubMed1997

The effects of bolus size and chewing rate on masticatory performance with artificial test foods.

To better understand 'within subject' variability in masticatory performance of artificial food, this study evaluates the effects of bolus size and chewing rate. Twenty young adult male subjects each participated in two experiments evaluating their ability to process an artificial food (CutterSil). Based on the frequency distributions for the weights of the chewed particles, median particle size and broadness of the particle distribution were estimated. Controlling for the number of chews, the effect of (1) bolus size was evaluated by having each subject chew one whole tablet, four quarters, three quarters or two quarters; (2). chewing rate was evaluated by having the subjects chew first habitually, then at slow (40 cycles/min) and fast (100 cycles/min) rates. The results showed that median particle sizes decreased and the distribution of particles widened with decreasing bolus size. The slow chewing rate produced the smallest particles with the widest distributions, followed by the habitual and fast rates, respectively. The study has shown that bolus size and chewing rate are important source of variation which must be considered in studies of masticatory performance.

Adult↗

PubMed1997

Differential growth and maturation in idiopathic growth-hormone-deficient children.

This study describes and compares the growth and maturation of idiopathic growth hormone deficiency (IGHD) and evaluates the potential effects of growth hormone therapy. The sample includes 40 idiopathic growth-hormone-deficient children grouped according to duration of growth hormone replacement therapy. Somatic and craniofacial development, skeletal maturation and dental maturation were evaluated and compared. The results showed consistent delays in the maturity indices for IGHD children. Height age displayed the greatest delay (3 years) followed by skeletal age (2.2 years) and dental age (0.8 years). Overall craniofacial growth deficiencies were also demonstrated. Anterior cranial base and mandibular length were most affected; posterior cranial base length and facial heights were least affected. Analysis of covariance, controlling for the starting age of therapy, showed significant differences between children grouped according to duration of growth hormone therapy. Catch-up growth with hormonal therapy was established for height, facial height, skeletal age and posterior cranial base length. It was concluded that the various craniofacial skeletal components have different potentials for growth retardation with IGHD; catch-up growth following growth hormone replacement therapy was greatest for the components with the greatest initial (or baseline) growth potential.

Adolescent↗

PubMed1996

Normal masticatory performance in young adults and children.

Previous studies have paid little attention to either the development or sexual dimorphism of masticatory performance. The aim of this study was to measure and compare the masticatory performance of adults and children. Forty-seven healthy and normal individuals (15 adult men, 15 adult women, 15 young girls and 2 young boys) were selected, based on their occlusion, temporomandibular joint function, skeletal classification, and the state of their dentition. Masticatory performance was evaluated by the individual's ability to break down a standardized bolus. Cuttersil impression material was chewed for 20 strokes, spat out, dried, and passed through a series of seven sieves. The Rosin-Rammler equation was used to calculate the median particle size and broadness of particle distribution. Measurements of dentitional surface area, contact area, bite force, mandibular morphology, and body size were also taken as covariates. The results showed significant differences in masticatory performance among the three larger groups; men performed best, followed by women then girls. Multiple regression analyses showed that body size was the most important variable associated with differences in masticatory performance. Adjusting for weight eliminated the group differences. Body size, together with the occlusal contact area of the posterior teeth and the bite force, explained 60-72 percent of the variation in performance. Contact area, posterior ramus height, and bite force explained differences between men and women, but differences between adults and children remained.

Adult↗

PubMed1996

Improvement of maximum occlusal forces after orthognathic surgery.

PURPOSE: A number of studies have reported that maximum voluntary bite forces increase after orthognathic surgery. This study determined rates of long-term improvement in bite forces and looked for both sex-related differences in improvement and for any differences among surgical procedures. PATIENTS AND METHODS: The study tested 117 patients before surgery and between 6 months and 3 years after surgery. At each trial, unilateral maximum voluntary bite force was measured at four different tooth positions using a standard transducer. Forty-three control subjects were similarly tested. The rate of increase in maximum bite force was calculated separately for male and female patients in various groups of patients and the controls. RESULTS: The patients had significantly lower maximum bite forces than the controls before surgery and for as long as 2 years after surgery. Within 6 months after surgery, patients' bite forces were already greater than their pre-surgical forces. Patients generally showed steady improvement in bite force thereafter, with male patients improving more quickly than female patients. There were no clear differences among surgical procedures. CONCLUSIONS: Any temporary reduction in maximum voluntary bite force disappears less than 6 months after orthognathic surgery. Orthognathic surgery improves patients' bite forces, but this improvement may be gradual, requiring many months.

Analysis of Variance↗

PubMed1996

Long-term stability of Class II, Division 1, nonextraction cervical face-bow therapy: II. Cephalometric analysis.

The long-term stability of Class II, Division 1 nonextraction therapy, using cervical face-bows with full fixed orthodontic appliances was evaluated for 42 randomly selected patients. Part 1, a study model analysis, was published in the March 1996 issue of the JOURNAL. Each patient was treated by the same practitioner, with the same techniques, and the treatment goals had been attained for all patients. Pretreatment records were taken at a mean age of 11.5 years; the posttreatment and postretention records were taken 3.0 and 11.6 years later, respectively. The results showed that the ANB angle decreased 2 degrees during treatment, most of which was due to the 1.6 degree decrease of the SNA angle. The mandibular plane angle was not changed significantly during treatment. Although upper incisor inclination was maintained during treatment, the lower incisor was proclined 2.3 degrees and the lower molar was tipped back 4 degrees. Of the 22 cephalometric measures evaluated, only four indicated relapse related with the treatment change. Three of the four measures pertain to lower incisor retroclination subsequent to excessive proclination. The ratio of treatment proclination of incisors to posttreatment retroclination is approximately 5:1. Similarly, for every 3 degrees of molar tip back, there was approximately 1 degree of relapse. It is concluded that nonextraction therapy for Class II malocclusion can be largely stable when the orthodontist ensures proper patient selection and compliance and attains treatment objectives.

Adolescent↗

PubMed1996

Long-term stability of Class II, Division 1, nonextraction cervical face-bow therapy: I. Model analysis.

The long-term stability of Class II, Division 1 nonextraction therapy remains poorly described. This study evaluates the face-bow therapy, in conjunction with full-fixed appliance therapy, of 42 patients (34 females and 8 males) who were treated by the same practitioner. Treatment goals had been attained for all patients. The pretreatment, posttreatment, and postretention records were taken at 11.5, 14.5, and 23.1 years, respectively. The results showed that mandibular and maxillary arch widths were increased significantly during treatment. Mandibular intercanine width decreased 0.3 mm during the postretention period; the remaining width measures increased or remained stable. Arch length, which did not change during treatment, decreased 1.0 mm after treatment. Overjet and overbite decreased 4.4 mm and 2.5 mm, respectively, during treatment. Both overjet (0.5 mm) and overbite (0.4 mm) showed small increases after retention. Mandibular incisor irregularity was decreased 2.7 mm during treatment and increased only 0.4 mm after treatment. Within the limits of this study, it is concluded that, when the described techniques are used, nonextraction therapy for patients with Class II malocclusion is largely stable.

Adolescent↗

PubMed1996

Masticatory function in patients with xerostomia.

The effects of reduced salivary output in patients suffering from xerostomia on masticatory function has not been previously studied. This study compares masticatory performance and kinematic activity of patients suffering from xerostomia with age-, sex-, and number of occluding pairs-matched healthy controls. Masticatory function was evaluated by assessment of chewing motion and muscle activity during chewing an artificial food (CutterSil), chewing gum and swallowing a bolus of almond. Chewing motion was recorded with the Optotrak computer system. Bilateral muscle activity of both masseter and anterior temporalis was recorded using surface electrodes. Results of this study revealed significant differences between patients and controls in their ability to process food and masticatory muscle activity. The majority of patients could not break down the artificial food, others had a larger median particle size than the controls. A significant difference was also observed in the number of chewing cycles required to swallow almonds, the patients required more than twice as many chews as the controls, P < 0.001. The right masseter muscle displayed significantly less activity for the patient than the controls. These findings suggest that patients with xerostomia exhibit reduced ability to process food. The observed decline in masticatory performance is probably due to reduced activity of the muscles of mastication.

Aged↗

PubMed1994

Occlusal plane alteration in orthognathic surgery--Part II: Long-term stability of results.

Alteration of the occlusal plane may be indicated in patients who present with either low occlusal plane (LOP) facial type or the high occlusal plane (HOP) facial type. Surgical alteration with double jaw surgery to increase or decrease the occlusal plane angulation may be required to achieve optimal functional and esthetic results. This study evaluated the stability of results in two groups of patients. Group 1 consisted of 14 patients who underwent surgical increase of the occlusal plane angulation with a postsurgical follow-up average of 23 months. The average surgical increase in occlusal plane angulation was 5.6 degrees. Several anatomic landmarks were evaluated relative to stability of results. Postsurgical changes that were statistically significant included a postsurgical anterior facial height change (-0.8 mm), ramus height change (-0.3 mm), and a change in mandibular plane angle (-0.5 degrees). These changes were due, in part, to the removal of the occlusal splint allowing some autorotation of the mandible superiorly and settling in of the occlusion. There was no significant change in any of the other parameters evaluated. Group 2 consisted of 27 patients, with a mean follow-up of 21 months, that had an average surgical decrease in occlusal plane angulation of 8.8 degrees with double jaw surgery. There was an 8 mm advancement of the mandible at point B, and a 10 mm advancement at pogonion. The maxilla was moved 3 mm superiorly at point A, and the maxillary first molar showed no significant vertical movement. The postsurgical changes demonstrated no statistically significant horizontal movement of the mandible.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Quantitative evaluation of craniofacial changes with Jasper Jumper therapy.

Although the Jasper Jumper is becoming a widely accepted orthodontic appliance, no quantitative guidelines exist for therapy. The purpose of this investigation was to describe the orthopedic and orthodontic changes associated with Jasper Jumper therapy. A sample of 31 consecutively treated Class II patients was collected from three orthodontic practitioners who were using the same procedures and methods. Lateral cephalograms were taken immediately before appliance placement and immediately after appliance removal (mean interval of 0.4 years). The sample was case matched to untreated controls based on age, sex, and mandibular plane angle. The cephalograms were superimposed using anterior cranial base, maxillary, and mandibular reference structures to distinguish between growth/displacement and tooth movement. The results show that the majority of Class II correction was due to dental, rather than skeletal change. The maxilla underwent significant posterior displacement. The maxillary incisors retroclined and the maxillary molars tipped distally. Clockwise or backwards rotation was evident for the mandible. The mandibular incisors proclined significantly and the mandibular molars translated and tipped mesially. Jasper Jumper therapy is a valuable procedure for the correction of Class II dental malocclusions. Like all other treatment modalities, there are both indications and contraindications for its use.

Activator Appliances↗

PubMed1994

Face mask therapy of preadolescents with unilateral cleft lip and palate.

This study evaluates 21 children treated with maxillary expansion and protraction appliances for skeletal discrepancies associated with unilateral cleft lip and palate (UCLP). The subjects were treated by the same orthodontist, using the same techniques and appliances. Mean pre- and posttreatment ages were 7.3 and 8.7 years, respectively. Each child was matched by ethnicity, sex, age, and the SN/MP angle to an untreated (non UCLP) control. Stable cranial and cranial base reference structures were used for superimposing serial cephalograms. The results showed definite protraction of the maxilla for the UCLP group. The posterior maxilla of the UCLP group underwent anterior displacement; the posterior maxilla of the control group displayed posterior growth changes. The maxillary incisor tips of the UCLP group demonstrated greater anterior movement than expected for untreated controls. Vertical changes of the maxilla showed no significant group differences. The mandible of the UCLP group was rotated inferiorly and posteriorly; the control group showed inferior/anterior changes. The lower incisor of the UCLP and control groups remained stable and moved anteriorly, respectively. The UCLP group showed significantly greater inferior movements of the anterior mandible than the control group. We concluded that differences between the control and UCLP groups are primarily related to mandibular clockwise rotation and secondarily to anterior maxillary repositioning.

Analysis of Variance↗

PubMed1994

Differences in dental arch morphology among adult females with untreated Class I and Class II malocclusion.

The purpose of the study was to evaluate differences in dental arch morphology among an orthodontic sample of 386 untreated adult females between 17 and 68 years of age, categorized by age group (17-25 years, 26-35 years, or 35+ years) and malocclusion (Class I, Class II division 1, or Class II division 2). The results show that both maxillary and mandibular dental arch size were significantly larger for the younger age group. Arch shape was relatively shorter and wider for the oldest age group. Palatal height was greatest for the youngest age group and least for the oldest group. Subjects with Class II malocclusion had significantly smaller arches, greater maxillary incisor irregularity, and less mandibular incisor irregularity than patients with Class I malocclusion. Subjects with Class II division 1 malocclusion had greater palatal heights and relatively longer/narrower maxillary dental arches than subjects with Class II division 2 malocclusion.

Adolescent↗

PubMed1994

Craniofacial morphology of spinal muscular atrophy.

Spinal muscular atrophy (SMA) is the second most common neuromuscular disease of childhood. It is the most common fatal recessive neuromuscular disease. This study is the first to evaluate the craniofacial growth of SMA patients. The results pertain to a sample of 25 SMA patients, between 5 and 32 y of age, who were case matched with unaffected normal controls. Group differences for 25 measures, derived from tracings of standardized cephalometric radiographs, were evaluated using multivariate analysis of variance. The SMA group showed excessive vertical development, particularly of the lower face. They demonstrated relatively larger anterior than posterior facial heights, due in part to a smaller cranial base angulation and a more anteriorly positioned mandibular ramus. Anteroposterior skeletal discrepancies of SMA patients, due to the combined effects of a protrusive maxilla and a retrusive mandible, were moderate. The interincisal angle of the SMA group was smaller than normal, due primarily to proclined maxillary incisors. Relative to palatal length, the SMA group had smaller anterior cranial base and mandibular corpus lengths. These results suggest abnormal craniofacial growth patterns of SMA patients. The etiology of the observed abnormalities seems to be complex and multifaceted, but attention to the treatment of malocclusion may be important for optimal nutrition and respiratory function.

Adolescent↗

PubMed1994

Sexual dimorphism in mesiodistal dentin and enamel thickness.

This study evaluates sexual dimorphism in mesiodistal diameter, enamel thickness and dentin thickness of the permanent posterior mandibular dentition in order to gain a better understanding of variation in mesiodistal tooth size. The results relate to a sample of 59 males and 39 females, 20-35 years of age. Bitewing radiographs of the right permanent mandibular premolars and molars were illuminated and transferred at a fixed magnification to a computer via a video camera. Enamel and dentin landmarks were identified and digitized on the plane representing the maximum mesiodistal diameter of each tooth. The results showed significant sex differences (p < 0.01) in mesiodistal diameter favouring males over females. Dimorphism was more pronounced for the molars than for the premolars. Enamel thickness, which is 0.4-0.7 mm greater for the molars than premolars, shows no significant sex differences. Dentin is significantly thicker in males than females, and is 3.5-4.0 mm thicker in molars than premolars. It is concluded that sexual dimorphism in mesiodistal tooth sizes is due to differences in dentin thickness and not enamel thickness.

Adult↗

PubMed1993

Longitudinal shape changes of the nasal dorsum.

This investigation quantifies childhood and adolescent growth changes of the upper and lower nasal dorsum and evaluates various aspects of the persons' morphology that relate to shape changes of the dorsum. A longitudinal sample of 37 French-Canadian girls, each having cephalograms at 6, 10, and 14 years of age, was evaluated. The 6- to 10-year interval was chosen to represent childhood growth; the 10- to 14-year interval represented adolescent growth. The upper dorsum rotates upward and forward (counterclockwise) approximately 10 degrees between 6 to 14 years of age. The lower dorsum shows both downward and backward (clockwise) and upward and forward (counterclockwise) rotation average childhood and adolescent changes in angulation were not significant. The results clearly indicate that changes in the nasal dorsum are most closely related to angulation changes of the lower dorsum, particularly during adolescence. The lower dorsum rotates downward and backward in persons who show greater vertical and less horizontal growth changes. Rotational changes of the lower dorsum are most closely related with vertical changes at pronasale.

Adolescent↗

PubMed1993

Relationships between mandibular canine calcification stages and skeletal maturity.

Hand wrist radiographs and dental panoramic radiographs of 200 boys and 215 girls were assessed to determine the relationship between the developmental stages of the mandibular canine and skeletal maturity indicators of the pubertal growth spurt. Chi-square and Kendall's tau statistics demonstrated significant (P < 0.001) relationships between skeletal maturity indicators. Associations between canine development and skeletal maturity ranged from 0.53 to 0.85. Most children having attained canine stage G showed the presence of the adductor sesamoid (81%), capping of the diaphysis of the third middle phalanx (77%), and capping of the fifth proximal phalanx (87%). Growth reference data for American children suggest that stage G occurred approximately 0.4 years and 1.3 years before peak height velocity for girls and boys, respectively. It is indicated that canine calcification could serve as a useful tool for evaluating childrens' skeletal maturation and, by association, somatic maturity.

Adolescent↗

PubMed1993

Physiologic drift of the mandibular dentition following first premolar extractions.

A retrospective study of two groups of patients was conducted to evaluate the physiologic drift, or "driftodontics", of the mandibular teeth following the extraction of four first premolars. Group 1 included 32 patients who underwent early extraction in the mixed dentition stage at a mean age of 10.4 years; they were followed for approximately 2.5 years postextraction. Group 2 included 20 patients whose premolars were extracted after the permanent dentition had fully erupted. Their mean age at the time of extraction was 14.2 years, followed by a 0.8 year observation period. Except for the extractions, no other mandibular therapy was rendered. The results show no differences in rates of molar movements between groups. The molar apex moved mesially approximately 0.6 mm/yr; the molar cusp moved mesially approximately 1.2 mm/yr. In contrast, there were marked group differences in movements of the mandibular incisors and canines; rates of change were significantly greater in Group 2 than in Group 1. The canines drifted laterally and distally into the extraction sites while the incisors became more upright over basal bone and less crowded. Incisor irregularity decreased 1.3 mm/yr in Group 1 and 5.5 mm/yr in Group 2. The group differences in amounts of tooth movement were accounted for by changes in incisor crowding.

Adolescent↗

PubMed1992

Childhood and pubertal growth changes of the human symphysis.

Longitudinal growth changes of the human symphysis were evaluated for 75 children (37 males and 38 females) between 6 and 15 years old. Childhood growth was described by mean yearly rates of change between 6 and 10 years for females and between 7 and 11 years for males; pubertal changes pertain to growth between 10 and 14 for females and between 11 and 15 for males. Cephalometric tracings of the mandible were superimposed using stable reference structures. Vertical growth changes, particularly for landmarks located in the upper 20% of the symphysis, were most pronounced. Annual rates of vertical growth ranged between 0.9 mm/yr for the lingual incisor contact point to -0.2 mm/yr for gnathion. Males showed significantly greater rates of vertical growth than females, especially for the upper half of the symphysis. Vertical growth rates were also greater during puberty than during childhood. The horizontal growth changes indicated lingual movement of most symphyseal landmarks. Annual rates of growth were greatest for landmarks located in the upper half of the symphysis. B-point showed the greatest lingual drift. During puberty, the mandibular incisors in females moved lingually as the upper anterior half of the symphysis remodeled; in males, the incisors maintained their horizontal position as the labial sulcus developed.

Adolescent↗