Biomedical subjects

Peter H Buschang

Publications and source records attributed to Peter H Buschang.

29 records · Page 2Linked to original sources

PubMed2003

Long-term stability of Class I premolar extraction treatment.

This study evaluates Class I, 4-premolar-extraction patients who were treated with the edgewise appliance by 1 practitioner, according to the philosophy of Tweed, and who had been out of retention a minimum of 5 years. The sample includes 32 patients, who started treatment at an average age of 12.8 years and who were examined a mean of 15 years posttreatment (11.7 years postretention). Cephalometric and model analyses were conducted to evaluate treatment and posttreatment tooth movements. The results showed that irregularity, as measured by the irregularity index, decreased 5.3 mm during treatment and increased 0.7 mm (SD 1.1 mm) during the posttreatment period. Eighty percent of the patients had satisfactory (<3.5 mm) mandibular incisor alignment over 10 years postretention, and none was in the severe category (>6.5 mm). Mandibular intercanine width increased (1.7 mm) during treatment, whereas intermolar width decreased (-2.1 mm). Maxillary molar widths remained unchanged posttreatment, and mandibular intercanine width decreased 1.4 mm from immediately posttreatment to postretention. Arch lengths decreased during treatment because of molar protraction and incisor retraction. Mandibular arch length continued to decrease posttreatment (-1.4 mm) because of mesial molar movement rather than distal incisor movement. Satisfactory long-term results can be achieved for most Class I, 4-premolar-extraction patients for whom evidence-based treatment objectives-including minimal alteration of the mandibular arch form and the retraction and uprighting or maintenance of mandibular incisors in their original position-have been met.

Adolescent↗

PubMed2003

Incisor crowding in untreated persons 15-50 years of age: United States, 1988-1994.

The purpose of this study was to (1) describe the prevalence of mandibular incisor irregularity (II) among untreated adults in the United States and (2) evaluate the factors explaining individual differences in II. Data were derived for a random sample of 9044 individuals (49% male and 51% female; 35% Mexican American, 34% black, and 31% white) between 15 and 50 years of age collected as part of the Third National Health and Nutrition Examination Survey. Although the differences were small (0.5 mm), males had significantly greater II than did females; blacks showed less II than did whites (0.9 mm) and Mexican Americans (1.1 mm). Family income was negatively related with II. Incisor irregularity increased in a curvilinear fashion with age, with the greatest increases occurring during early adulthood. Although the number of premolars and molars (first and second) were positively related with II, the presence of third molars had a negative effect on II. Multivariate Poisson regression analyses showed that the ethnicity, the number of first and second molars, sex, and age combined to explain differences in II. Odds ratios were relatively low, indicating that these factors explained relatively small amounts of between-subject variation. We conclude that (1) approximately 50% of individuals in the United States who were 15-50 years of age have little or no II, 23% have moderate II, and 17% have severe irregularity, (2) erupted third molars are not associated with increased crowding, (3) crowding increases most during early adulthood, and (4) although individual differences in crowding are multifactorial, the primary determinants remain unidentified.

Adolescent↗

PubMed2003

Effects of high-speed curing devices on shear bond strength and microleakage of orthodontic brackets.

This study evaluated the shear-peel bond strength and mode of bond failure of 3 curing devices (plasma arc light, argon laser, and conventional halogen light) and 2 orthodontic bracket adhesives with different filler contents (Transbond XT and Adhesive Precoated [APC]). Observations of microleakage were also reported. Ninety human adolescent premolars were randomly divided into 6 groups, and standardized brackets were bonded according to the manufacturers' recommendations. The plasma arc light produced significantly (P =.006) higher bond strength than did the halogen light or the argon laser when Transbond was used. When APC was used, the plasma arc light and the halogen light produced similar results, and they both produced significantly (P =.015) higher bond strengths than did the argon laser. Overall, the APC showed substantially less variation in bond strength than did the Transbond. Although all curing methods showed significant microleakage (P <.001), differences among the 3 curing lights occurred only when APC was used. Microscopic evaluations demonstrated that 95% of the specimens failed for adhesion at the bracket or tooth surface; the argon laser produced the highest adhesive remnant index scores. On the basis of bond strength and microleakage results, the plasma arc light was comparable with or superior to the other curing devices, depending on the adhesive used.

Adolescent↗

PubMed2003

Maximum bite force, muscle efficiency and mechanical advantage in children with vertical growth patterns.

This study correlated maximum bite force and masticatory muscle electromyography (EMG) activity with craniofacial morphology and mechanical advantage of children with vertical growth patterns. From lateral cephalograms of 30 females and 17 males (9.3 +/- 3.6 years of age), 13 morphological and eight biomechanical measurements were recorded. Two maximum bite forces and 12 submaximal bite forces along with their associated EMG muscle activity were recorded at the right mandibular first molar. Muscle efficiency was evaluated using the relationship between bite forces and EMG activity levels. There were no significant sex differences (P > 0.05) for any of the morphological, functional or biomechanical variables. Factor analyses reduced: (1) the 13 morphological variables to four factors explaining 82.8 per cent of the morphological variance; (2) six functional variables to two factors explaining 68.8 per cent of the functional variance; and (3) 11 biomechanical variables to three factors explaining 90.9 per cent of the biomechanical variance. The vertical size factor was negatively correlated with the muscle efficiency factor (r = -0.39; P = 0.006) and positively correlated with the moment arm factor (r = 0.67; P < 0.001). The morphological divergence factor was negatively correlated with the bite force factor (r = -0.34; P = 0.019) and the mechanical advantage factor (r = -0.32; P = 0.028). The muscle efficiency factor (functional) was negatively correlated with the moment arm factor (r = -0.33; P = 0.023). It is concluded that: (1) independent of chronological age, children with larger faces have larger moment arms and require less muscle activity to attain any given force, and (2) greater hyperdivergence is related to poorer mechanical advantage and lower maximum bite force. These data support the relationships between bite force, muscle strength and morphology in children, similar to those reported for adults.

Adolescent↗

PubMed2002

Masticatory performance and areas of occlusal contact and near contact in subjects with normal occlusion and malocclusion.

This preliminary study evaluated relationships between masticatory performance and areas of interocclusal distance contact (<50 microm) and near contact (50-350 microm) of the buccal segments during maximum intercuspation. The sample included subjects with normal occlusion (n = 18) and Class I (n = 14), Class II (n = 13), and Class III (n = 6) malocclusions. Chewing performance was evaluated on the basis of the breakdown of CutterSil (Heraeus Kulze, South Bend, Ind); chewing ability was assessed by the number of chews necessary to swallow jerky and almonds. Impressions of the buccal segments, taken with Blu Mousse (Parkell Bio-Materials, Farmingdale, NY) impression material, were scanned and enlarged, and each subject's first molars and premolars were manually traced bilaterally to estimate the platform area. The areas of contact and near contact (ACNC) that measured between 0 and 350 microm thick were estimated optically on the basis of the amount of light transmitted through the impression. The results showed no significant differences in platform area between the right and left sides or between the malocclusion groups. ACNC were negatively related to median particle size and broadness of particle distribution. There were no correlations between ACNC and the number of chews necessary to swallow jerky or almonds. Subjects with normal occlusion had significantly larger ACNC than those with Class I, Class II, and Class III malocclusions, in descending order. Subjects with Class III malocclusions had the smallest areas of near contact (<350 microm). We concluded that ACNC are similar on the right and left sides; that subjects with larger ACNC are better able to break down foods; and that subjects with malocclusions have smaller ACNC than those with normal occlusions.

Adolescent↗

PubMed2002

Predicting lower lip and chin response to mandibular advancement and genioplasty.

The purposes of this retrospective study were to examine the multidimensional nature of soft tissue changes associated with mandibular advancement and genioplasty and to develop predictive models. Longitudinal lateral cephalograms of 62 nongrowing patients (27 men and 35 women) were taken in centric relation with the lips in repose within 4 weeks before surgery and at least 6 months postoperatively (median postsurgical duration was 11 months). The mandibular incisor and pogonion were advanced surgically approximately 6 mm and 11 mm, respectively. The lower lip lengthened slightly (2.5 +/- 3.8 mm), and its surface contour straightened because of thinning at labrale inferior (-2.8 +/- 2.0 mm); there was a slight thickening at the labiomental fold (1.0 +/- 2.3 mm) and a slight thinning at soft tissue pogonion (-0.8 +/- 2.2 mm). Multiple regression models (explaining from 80% to 94% and 66% to 82% of the variation for horizontal and vertical movements, respectively) showed that soft tissue response to advancement surgery depended on pretreatment tissue thickness, horizontal skeletal movement, vertical skeletal movement, and the position of the maxillary incisors. Similar amounts of variation were explained when the models were applied to an independent validation sample of 15 subjects. It was concluded that lower lip and chin response to mandibular advancement and genioplasty is multifactorial but can be accurately and reliably predicted.

Adolescent↗

PubMed2002

Mandibular skeletal growth and modelling between 10 and 15 years of age.

This study pertains to a random sample of untreated French-Canadian adolescents (79 females and 107 males) evaluated at 10 and again at 15 years of age. Superimpositions on natural reference structures were performed to describe condylar growth and modelling of 11 mandibular landmarks. Superimpositions on natural cranial/cranial base reference structures were performed to describe mandibular displacement and true rotation. The results showed significant superior and posterior growth/modelling of the condyle and ramus. Males underwent significantly (P < 0.01) greater condylar growth and ramus modelling than females. With the exception of point B, which showed significant superior drift, modelling changes for the corpus landmarks were small and variable. The mandible rotated forward 2-3.3 degrees and was displaced 9.6-12.7 mm inferiorly and 1.9-2.7 mm anteriorly. Individual differences in ramus growth and modelling, both amount and direction, can be explained by mandibular rotation and displacements. Multivariate assessments revealed that superior condylar growth and ramus modelling were most closely associated with forward rotation and inferior mandibular displacement. Posterior growth and modelling were most closely correlated with anterior mandibular displacement and forward rotation. Modelling of the lower anterior border was independent of rotation and displacement.

Adolescent↗

PubMed2002

The effect of the amount of limb lengthening on skeletal muscle.

The adaptation of tibialis anterior muscles after 20% and 30% gradual limb lengthening was evaluated. Eight skeletally mature neutered male goats had 20% (n = 4) or 30% (n = 4) tibial distraction at a rate of 0.25 mm three times per day. Muscles from lengthened and contralateral control limbs were harvested on completion of distraction. Fiber length and sarcomere length were measured followed by calculation of sarcomere number and muscle fiber-to-bone lengthening ratio. Fiber length and sarcomere number after 20% and 30% limb lengthening were significantly greater in the distracted muscles, whereas no difference in sarcomere length was detected. The difference in muscle fiber length and sarcomere number between distracted and control limbs was greater in the 30% than in the 20% group. The disproportion between the amounts of muscle fiber and bone length increase was similar after 20% and 30% lengthening. The results show that muscular adaptation continues during 20% to 30% limb lengthening by increasing fiber length. It seems that this increase occurs through serial sarcomere addition rather than sarcomere length alteration. The higher rate of musclerelated clinical complications after limb lengthening beyond 20% does not seem to be related to a failure of muscle fiber contractile elements to adapt to increasing limb length.

Animals↗

PubMedDate not supplied

Midsagittal facial soft-tissue growth of French Canadian adolescents.

This study examines changes in 12 midline soft-tissue thicknesses from the forehead, nose, lip, and chin regions in girls and boys from 10 to 16 years of age. The soft-tissue changes are compared to changes in two hard-tissue distances (sella-nasion and nasion-menton). The subjects are from a mixed-longitudinal sample studied at the Montreal Human Growth Research Center in the 1960s and 1970s. Total sample size is 242 (from lateral cephalographs of 124 males and 118 females), with numbers varying by age and measurement. For hard-tissues, boys show clearly defined adolescent spurts, while girls display small velocity increases indicative of only very minor spurts. Forehead tissue thicknesses for both sexes change little and show no demonstrable growth spurts. For the nose and philtrum region, which have the greatest absolute soft-tissue growth changes, both boys and girls show adolescent spurts. Peak velocities are attained between 13 and 14 years in boys and between 11.9 and 12.5 years in girls. Boys appear to have small adolescent spurts for upper (13.7 years) and perhaps lower lip thicknesses. Neither sex displays clear evidence for adolescent spurts in the chin region.

Adolescent↗

PubMedDate not supplied

Variation in longitudinal diaphyseal long bone growth in children three to ten years of age.

Data from the Child Research Council (Denver, CO) were analyzed to model longitudinal growth changes in the humerus, radius, femur, and tibia in 31 boys and 36 girls between 3 and 10 years of age. Multilevel modeling of growth changes allowed efficient estimates of bone size and bone growth variation to be obtained as well as comparisons of growth patterns within and between limbs. The long bones displayed decelerating growth through time, with greater velocities for the larger lower limb (vs. smaller upper limb) bones and the larger proximal (vs. smaller distal) elements within limbs. Coordination for bone size and growth velocity is good both within and between limbs, suggesting a common growth control mechanism that should make growth prediction possible. Adjusted for size, the tibia appears to be the most variable of these four long bones, which may be due to a combination of environmental effects and flexible growth potential.

Age Factors↗

PubMedDate not supplied

Longitudinal models of long bone growth during adolescence.

Data from the Child Research Council (Denver, CO) were utilized to model longitudinal adolescent growth of the humerus, radius, femur, and tibia for 36 girls (10-16 years) and 33 boys (10-17 years). Multilevel modeling procedures were used to estimate variation, covariation, and the polynomial parameters necessary for generating growth curves. At age 10, long bone lengths for girls and boys are similar; by age 16, each of the boys' arm bones is about 20 mm longer and each of their leg bones is about 30 mm longer. Due to the earlier maturation of girls, the models show the length of each of their long bones exceeding that of boys to some degree during some period of adolescence. Peak velocities for leg bones are attained earlier than those for arm bones; in both sexes, age at humeral peak velocity coincides with age at peak height velocity (PHV). At age 13, correlations among lengths and among velocities of bones are strong to moderate, and girls consistently display higher variation than do boys for both long bone length and growth velocity. Considered relative to the average velocity of each bone's growth, the tibia is the most variable of the four long bones at age 13 years.

Adolescent↗