PubMed Health⌕ Search

Biomedical subjects

Peter H Buschang

Publications and source records attributed to Peter H Buschang.

At least 19 recordsLinked to original sources
PubMed2006

Craniofacial dimensions in children in rural Oaxaca, southern Mexico: secular change, 1968-2000.

The objective of this investigation was to analyze the underlying cause(s) of secular changes in craniofacial dimensions among indigenous children in an isolated community in Oaxaca, southern Mexico, between 1968-2000. Subjects were schoolchildren resident in a rural, agrarian, Zapotec-speaking community in the Valley of Oaxaca, previously characterized as mildly-to-moderately undernourished with growth-stunting in 1968 and 1978. In 2000, children had experienced a secular increase in height compared with two prior growth surveys. Four craniofacial dimensions (head length, head breadth, and bizygomatic and bigonial breadths) were measured during anthropometric surveys of schoolchildren aged 6-13 years in 1968, 1978, and 2000. Cephalic and zygomandibular indices were calculated. Samples by survey were: 1968, 151 males and 157 females; 1978, 179 males and 184 females; and 2000, 180 males and 186 females. The analysis was based on a total of 1,037 children. Multivariate analysis of covariance was used to assess secular trend effects, with height, age, and age2 as covariates by sex. Over the interval of 32 years, significant secular changes occurred in craniofacial dimensions and one index: 1) head length was shorter in boys and girls; 2) bizygomatic breadth was narrower in boys and girls; 3) head breadth increased over time only among girls; 4) brachycephalization increased significantly in a linear manner among both sexes; and 5) the zygomandibular index decreased significantly only in boys. Thus, the cranial complex remodeled to a shorter head length, both relatively (brachycephalization) and absolutely. Remodeling over time also resulted in a narrower face, with the midface changing at about the same rate as the lower face (i.e., mandible). Secular changes are generally recognized as multifactorial. Changes in the cephalic index and cranium over time in schoolchildren in an isolated rural agrarian Zapotec-speaking community in the Valley of Oaxaca suggest that the underlying forces for the secular change are associated: 1) decreased food (maize) coarseness or grit content (masticatory stress), and 2) relaxed natural selection, resulting in 3) a greater role for developmental plasticity.

Adolescent↗
PubMed2006

Craniofacial growth in growth hormone-deficient rats after growth hormone supplementation.

INTRODUCTION: Growth hormone (GH) supplementation is an established therapy to increase stature in GH-deficient or short-for-age children, but comparatively little is known of its effects on the craniofacial skeleton. METHODS: Using a mutant strain of Lewis rats (dw/dw) in which GH levels were 6% to 10% of normal, but other trophic hormones were unaffected, we investigated the differential susceptibility of craniofacial measures to GH supplementation, characterized their potential for partial or complete catch-up growth, and compared their growth changes with those in long bones. At 24 days of age and for 3 subsequent weeks, radiographs of the lateral head, upper limb, and lower limb were obtained from 3 groups of growing rats (n = 8-9 in each group): dwarf (experimental) with GH injection, dwarf (sham) with vehicle injection, and wild type (control) with vehicle injection. The x-ray images were scanned, standardized points digitized, and linear distances measured. Absolute growth curves were generated for each group by using multilevel modeling procedures and iterative generalized least-squares curve fitting. RESULTS: For every measure, growth differences were evident between the experimental and the sham groups, but the treatment effect varied inversely with relative maturity of the measure. Although all craniofacial measures showed some catch-up growth, only 31% of craniofacial measures had complete catch-up compared with all limb measures. The percentage of catch-up varied inversely with relative maturity of the measure. Our results suggest that the effects of GH supplementation vary considerably, so that measures with the lowest relative maturity (greatest baseline potential) show the greatest treatment effect and catch-up, whereas more mature measures show less growth response to GH replacement. CONCLUSIONS: These results suggest that, depending on the timing of GH supplementation, there is potential for change in proportions or shape of the craniofacial complex.

Age Factors↗
PubMed2006

Orthodontic treatment changes of chin position in Class II Division 1 patients.

INTRODUCTION: Because most patients with skeletal Class II malocclusions also have mandibular deficiencies, treatment plans should include improvement in chin projection. On that basis, the purposes of this study were to (1) determine how Class II treatment affects anteroposterior (AP) chin position in growing subjects and (2) ascertain the most important determinants of AP chin position. METHODS: Pretreatment and posttreatment lateral cephalograms of 67 treated patients (25 extraction headgear and Class II elastics, 23 nonextraction headgear, and 19 Herbst) were collected, traced, and digitized. The average pretreatment age was 12.2 years (range, 9-14 years), and the average treatment duration was 30.2 months (range, 17-65 months). Cephalometric changes were compared with 29 matched untreated Class II controls. Mandibular superimpositions were used to evaluate condylar growth and true mandibular rotation. RESULTS: All 3 treatment methods produced normal dental relationships and restricted or inhibited AP maxillary growth, with no significant improvement of AP chin position. Differences between changes in vertical position of the maxilla, maxillary and mandibular molars, and condylar growth could not reliably predict changes in chin position. Analyses demonstrated that true mandibular rotation was the primary determinant of AP chin position. Stepwise multiple regression showed that, combined with true mandibular rotation, condylar growth and movements of the glenoid fossa accounted for 81% of the variation in AP changes of pogonion. CONCLUSIONS: Contemporary treatments do not adequately address mandibular deficiencies. Future treatments must incorporate true mandibular rotation into Class II skeletal correction.

Adolescent↗
PubMed2006

Postsurgical stability of oropharyngeal airway changes following counter-clockwise maxillo-mandibular advancement surgery.

PURPOSE: This study evaluated oropharyngeal airway changes and stability following surgical counter-clockwise rotation and advancement of the maxillo-mandibular complex. METHODS AND PATIENTS: Fifty-six adults (48 females, 8 males), between 15 and 51 years of age, were treated with Le Fort I osteotomies and bilateral mandibular ramus sagittal split osteotomies to advance the maxillo-mandibular complex with a counter-clockwise rotation. The average postsurgical follow-up was 34 months. Each patient's lateral cephalograms were traced, digitized twice, and averaged to estimate surgical changes (T2-T1) and postsurgical changes (T3-T2). RESULTS: During surgery, the occlusal plane angle decreased significantly (8.6 +/- 5.8 degrees ) and the maxillo-mandibular complex advanced and rotated counter-clockwise. The maxilla moved forward (2.4 +/- 2.7 mm) at ANS and the mandible was advanced 13.1 +/- 5.1 mm at menton, 10 +/- 4.4 mm at point B, and 6.9 +/- 3.7 mm at lower incisor edge. Postsurgical hard tissue changes were not statistically significant. While the upper oropharyngeal airway decreased significantly (4.2 +/- 3.4 mm) immediately after surgery, the narrowest retropalatal, lowest retropalatal airway, and the narrowest retroglossal airway measurements increased 2.9 +/- 2.7, 3.7 +/- 3.2, and 4.4 +/- 4.4 mm, respectively. Over the average 34 months postsurgical period, upper retropalatal airway increased 3.9 +/- 3.7 mm, while narrowest retropalatal, lowest retropalatal airway, and narrowest retroglossal airway remained stable. Head posture showed flexure immediately after surgery (4.8 +/- 5.9 degrees ) and extension postsurgically (1.6 +/- 5.6 degrees ). CONCLUSION: Maxillo-mandibular advancement with counter-clockwise rotation produces immediate increases in middle and lower oropharyngeal airway dimensions, which were constrained by changes in head posture but remain stable over the postsurgical period. The upper oropharyngeal airway space increased only on the longest follow-up.

Adolescent↗
PubMed2006

Evaluation of preemptive valdecoxib therapy on initial archwire placement discomfort in adults.

The purpose of this randomized, double-blinded, placebo-controlled prospective clinical trial was to compare the efficacy of preemptive and postoperative administration of valdecoxib in reducing discomfort caused by initial archwire placement in adults. A total of 56 orthodontic patients aged 18-54 years who were to begin treatment were randomly assigned to one of three groups: (1) placebo, (2) those who received preemptive valdecoxib 40 mg at least 30 minutes before initial archwire placement, or (3) those who received postoperative valdecoxib 40 mg two hours after initial archwire placement. Patients in the active treatment groups also received continuous valdecoxib therapy for an additional 48 hours. Discomfort levels were recorded on a visual analog scale at zero, two, six, 24, and 48 hours after initial archwire placement. At baseline, no significant differences were detected between the three groups. In the preemptive valdecoxib group, there was no significant increase (P > .05) in discomfort from baseline at any time point. The placebo and postoperative valdecoxib groups showed significant (P < .05) increases in discomfort after six hours, with the peak discomfort at 24 hours. The postoperative group showed a tendency toward decreased discomfort over time, but the changes were not significantly different from the placebo or the preemptive group. Preemptive analgesia with nonsteroidal anti-inflammatory drugs may be an approach to prevent discomfort associated with initial archwire placement in healthy adults.

Adolescent↗
PubMed2005

Masticatory performance in children and adolescents with Class I and II malocclusions.

It is not fully understood whether masticatory performance is compromised in individuals with the more common forms of malocclusion (i.e. Class I and Class II). The aim of this prospective investigation was to establish the relationships between masticatory performance, malocclusion (type and severity), age, body size and gender, in children and adolescents. A total of 335 individuals were examined at the average ages of 6, 9, 12 and 15 years. Each subject's occlusal status was described by Angle classification and by the Peer Assessment Ratio (PAR) index. Masticatory performance was quantified by the median particle size (MPS) and the broadness of particle distribution using artificial food. Masticatory performance improved significantly with age. The 6-year-old children were less able to break down the food particles (MPS 4.20 mm2) than the 15 year olds (MPS 3.24 mm2). Analysis of covariance showed that age differences in performance are related to an increase in body size. There were statistically significant differences in masticatory performance between children with normal occlusion and those with a Class I malocclusion; no differences were found between normal occlusion and Class II malocclusion. Gender differences did not explain the variation in masticatory performance. It is concluded that occlusal indices are not reliable predictors of masticatory performance. Traditional descriptors of malocclusion type and severity apparently cannot explain most of the variation in masticatory performance in children and adolescents.

Adolescent↗
PubMed2005

Effect of an auditory cue on chewing cycle kinematics.

OBJECTIVES: This study analysed the systematic and random effects of a rhythmic auditory cue on chewing cycle kinematics. METHODS: The chin movements of 25 subjects (19-35 years of age) with normal class I occlusion were recorded at 100Hz (Optotrak) Northern Digital) during two natural gum chewing (2.5 g) sequences to determine the chewing rate of each subject. Another sequence was recorded with the subjects chewing at their natural rate following an audible cue. Multilevel modeling procedures were used to evaluate differences between natural chewing with and without an audible cue. RESULTS: Differences were found between experimental conditions for excursions, velocities and cycle shape. When chewing with the audible cue velocities were slower and there was less excursion of the chin marker, with the exception of initial lateral movements toward the balancing side. No differences in between-subject variability were found when chewing with or without an audible cue. Within-subject variability was 44% smaller for total cycle duration and 53% smaller for total 3D excursion when chewing with the auditory cue. CONCLUSIONS: Chewing at one's normal rate while following an auditory cue produces more consistency in chewing cycle kinematics. This method may be applicable, with some limitations, to reduce within-subject variability in chewing cycle kinematics.

Adult↗
PubMed2005

Ethnic differences in upper lip response to incisor retraction.

INTRODUCTION: The purpose of this retrospective longitudinal study was to investigate the response of the upper lip to incisor retraction and to ascertain the effect of ethnicity on this response. METHODS: Pretreatment and posttreatment lateral cephalograms of 88 postpubertal female patients (44 black and 44 white; mean age, 18.45 years) were evaluated. The groups were matched by age and the amount of incisor retraction at incisor superius. RESULTS: Although significant pretreatment differences existed between the groups in some cephalometric measurements, analysis of the treatment changes demonstrated significant differences only in incisor inclination. Hard and soft tissue changes of the black group were more downward, whereas changes in the white group were more backward. Multivariate regression analysis showed that the horizontal response of the upper lip to hard tissue changes at subnasale and superior labial sulcus was different in whites than in blacks. At subnasale, stepwise multivariate regression analysis showed that ethnicity contributed to the upper lip response to incisor retraction and was significantly greater in the white group. CONCLUSIONS: The hard and soft tissue treatment changes of the black group were more downward, and those of the white group were more backward. Ethnic differences exist in the soft tissue response to hard tissue changes in the upper lip, and at subnasale and the superior labial sulcus; however, these response differences at superior labial sulcus can be explained by the ethnic differences in initial lip thickness and incisor inclination; they are not due in and of themselves to ethnicity. The change at prosthion was significantly correlated with the response of the upper lip at labrale superius to incisor retraction. Ethnicity added no increase to the predictability of the response. When incisor retraction was performed, the final horizontal upper lip position could be accurately and reliably predicted.

Adolescent↗
PubMed2005

Development and testing of multilevel models for longitudinal craniofacial growth prediction.

INTRODUCTION: The aims of this study were to (1) develop longitudinal growth curves that would allow individual variations to be accurately modeled and (2) use these models to predict craniofacial growth changes in children with varying amounts of longitudinal data available. METHODS: Based on a sample of 159 girls (994 cephalograms) and 128 boys (947 cephalograms), multilevel population models were derived. Polynomial models of the population's growth curve were derived for the measurements MPA, Me-X, Me-theta, Me-Y, and Me-R. Angular and horizontal measures (MPA, Me-X, and Me-theta) were described by simpler, second-order models, and vertical measures (Me-Y and Me-R) were described by more complex, fifth-order models. RESULTS: Decreases in MPA during childhood and increases in Me-theta during adolescence could be explained by the relative contributions of the horizontal (Me-X) and vertical (Me-Y) movements of menton. There was greater anterior movement of menton during childhood and greater inferior movement during the adolescent growth spurt. By using varying numbers of longitudinal cephalograms between 6 and 10 years of age, the models were used to predict subjects' craniofacial growth changes from ages 10 to 15. Based on correlations, root mean squared error, and percent accuracy, individual growth predictions for the various measures were found to be highly accurate on an independent subsample drawn from the larger sample and on an independent validation sample. Correlations between predicted and actual values on the sample used to develop the models ranged from 0.81 to 0.95. Accuracy was best for the measurements that changed the most during the prediction period (Me-Y and Me-R), with accuracies between 83% and 90%. More longitudinal data did not increase the predictive accuracy for all measurements. The models that were least accurate (Me-X, MPA, and Me-theta) showed the greatest improvement in prediction accuracy with more longitudinal data. These improvements ranged from 1.6% to 15%. CONCLUSIONS: Longitudinal growth curves based on multilevel procedures can accurately describe population and individual growth curves, and 5-year predictions with this method are highly accurate and externally valid.

Adolescent↗
PubMed2005

Long-term profile changes in extraction and nonextraction patients.

INTRODUCTION: The purpose of this investigation was to determine the long-term differences in soft tissue profile changes between extraction and nonextraction patients who had been treated to the same incisor position and lip line. METHODS: Twenty extraction and 20 matched nonextraction patients, with posttreatment and long-term follow-up (average 15 years) records, were selected from a single private orthodontic practice. Posttreatment and long-term follow-up profile photos of the patients' nose, lip, and chin areas were evaluated by 105 orthodontists and 225 laypeople, who indicated their preferences and the amount of change they perceived among the 40 profiles. The patients had similar dental protrusion, soft tissue profile measurements, and ages at the posttreatment observation. RESULTS: No significant cephalometric differences between the extraction and nonextraction groups were found at long-term follow-up; both groups showed similar long-term changes. Significant (P < .05) differences were found between males and females at long-term follow-up; male lips became relatively more retrusive, and their profiles became flatter. Significant (P < .05) changes in the profiles were also perceived over time, but there was no relationship between the amount of change perceived and profile changes measured cephalometrically. There were also no significant (P < .05) differences in preferences between orthodontists and laypeople, between extraction and nonextraction patients, or between males and females. CONCLUSIONS: If extraction and nonextraction patients are treated to the same incisor position and lip line, the treatment modality does not affect long-term soft tissue profile changes. Furthermore, the amounts of change perceived by either orthodontists or laypeople were not related to the amount of change measured cephalometrically.

Bicuspid↗
PubMed2005

Tooth shape preferences in an esthetic smile.

INTRODUCTION: The purpose of this study was to evaluate the contributions of tooth shape to the esthetic smile. METHODS: Restorative dentists (120), laypeople (102), and orthodontists (113) evaluated a series of color photographs of men's and women's smiles. The photographs were randomly presented to test the effects of 3 different shapes of maxillary incisors and canines on the same patient. RESULTS: For women, orthodontists preferred round and square-round incisors (P < .01), and restorative dentists preferred round incisors (P < or = .03). Laypeople did not discriminate between incisor shapes. For men, all 3 groups preferred square-round incisors (P < or = .042). There was also a tendency for male judges to rate female images more attractive than did female judges. CONCLUSIONS: Restorative dentists, orthodontists, and laypeople share similarities and display differences when considering esthetic preferences in tooth shape. Although there was no consensus in preference among the laypeople as a group, their preferences differed from those of the dental professionals.

Adult↗
PubMed2005

Long-term stability of combined rapid palatal expansion-lip bumper therapy followed by full fixed appliances.

INTRODUCTION: The purpose of this study was to evaluate the long-term postretention stability of rapid palatal expansion-lip bumper therapy followed by full fixed appliances. METHODS: The sample included 20 treated patients (11 women and 9 men) who were recalled to obtain postretention records. The subjects were out of retention for a minimum of 4 years and an average of 7.9 years. They had begun treatment in the late mixed dentition at a mean age of 11.1 with considerable incisor crowding but, on average, no tooth size-arch length discrepancies. Pretreatment, posttreatment (mean age, 13.6 years), and postretention (mean age, 24.3 years) models were digitized, and the computed measurements were compared with untreated reference data. RESULTS: The majority of treatment increases in maxillary and mandibular arch dimensions were statistically significant (P < .05) and greater than expected for untreated controls. Although many measurements decreased postretention, net gains were maintained for 21 of the 30 measurements evaluated. The notable exception was arch perimeter, which decreased to less than pretreatment values. Postretention incisor irregularity increased 0.5 +/- 1.2 mm in the maxillary arch and 1.1 +/- 1.5 mm in the mandibular arch. CONCLUSIONS: Based on the good long-term stability observed in this study, we concluded that use of rapid palatal expansion-lip bumper expansion therapy in the late mixed dentition followed by full fixed appliances is an effective form of treatment for patients with up to moderate tooth size-arch length discrepancies.

Child↗
PubMed2004

Craniofacial growth in growth hormone-deficient rats.

Although supplementation with growth hormone (GH) is an accepted treatment for children who are GH-deficient or very small in stature, its effect on the craniofacial skeleton has been little studied. The goal of this study was to compare the absolute and relative growth of the craniofacial skeleton in GH-deficient dwarf rats to that in wild-type rats of the same strain, using a mixed-longitudinal radiographic design. Lateral and dorsoventral X-rays of the head and hindlimb were obtained weekly in dwarf and wild-type female Lewis rats from 4 to 9 weeks of age (n = 14 for each time interval). The X-rays were scanned, 27 cephalometric points were digitized, and selected linear distances were measured between points. Multilevel statistical procedures were used to model growth changes in different regions of the head. Among craniofacial measures, growth curves of the two groups differed greatly in the magnitude of initial size differences and the effect of GH deficiency on growth velocity. Considerable variation (65-97%) also existed among craniofacial measures with regard to relative maturity (i.e., the percentage of growth completed between the first and last time intervals). The deficiency effect (a quantitative estimate of the extent to which growth velocity was affected by GH) was negatively correlated (r = -0.52, P < 0.01) with relative maturity of a particular measure. The dependence of the GH effect on relative maturity suggests that different craniofacial morphologies may result depending on the timing of GH supplementation therapy.

Animals↗
PubMed2004

Variation in Class II malocclusion: comparison of Mexican mestizos and American whites.

This study compared the skeletal and dental characteristics of Class II Division 1 white Americans and Mexicans. It was designed specifically to the evaluate ethnic, age, and sex differences of 101 whites and 107 Mexican mestizos, with approximately equal numbers in each subgroup. Three-way analyses of variance were used to simultaneously evaluate the effects of age, sex, ethnicity, and their interactions. Although Mexicans and whites in the United States had similar maxillomandibular relationships, Mexicans showed greater protrusion of the jaws and teeth. Mexican subjects with Class II malocclusions also showed less divergence of the cranial base (SN-FH angle) and greater vertical tendencies (MPA, Y-axis, and palatal plane angle) than their white counterparts. In comparison with children (mean age 9.0 years), young adults (mean age 20.1 years) had significantly larger craniofacial dimensions, jaws that were positioned more forward, and teeth that were more protruded. Sex differences pertained only to size (men were larger) and maxillary incisor angulation (men were more protrusive). The findings pertaining to the ethnic differences have important clinical implications regarding treatment decisions for Mexican and white patients. In addition, this study provides a foundation for future studies pertaining to Class II malocclusion in Mexicans.

Adolescent↗
PubMed2004

Transverse skeletal base adaptations with Bionator therapy: a pilot implant study.

The purpose of this randomized, controlled trial was to evaluate transverse skeletal base adaptations to Bionator therapy. The sample included 25 patients (15 male, 10 female) aged 6.9 to 11.2 years with Class II Division 1 malocclusion. The patients were randomly allocated to either a control (n = 11) or treatment (n = 14) group and followed longitudinally for approximately 12 months. Treatment consisted of a Bionator only, constructed to remain approximately 2 mm from the buccal dentition. Transverse maxillary and mandibular changes were evaluated cephalometrically according to 4 bilateral maxillary and 2 bilateral mandibular implants. Untreated Class II controls exhibited significant increases between posterior maxillary implants but no significant changes between the anterior maxillary or mandibular implants. There were no significant width differences between the control and treated groups before treatment. Posterior maxillary implant widths increased significantly (P < .05) in both groups, but the treated group showed significantly greater width increases than the control group. The treated group also showed greater increases between mandibular implants, but the differences were not statistically significant. These results suggest that transverse skeletal base adaptations occur as a result of Bionator therapy.

Activator Appliances↗
PubMed2004

Absolute and relative growth of the rat craniofacial skeleton.

UNLABELLED: Growth of the craniofacial region involves a mosaic of intramembranous and endochondral growth sites that grow at varying rates and mature at different times. OBJECTIVE: The goal of this study was to compare absolute and relative growth of the craniofacial skeleton in wild-type Lewis rats to measures of somatic growth. DESIGN: Lateral and dorsoventral X-rays of the head as well as the hindlimb were obtained weekly from 4 to 9 weeks of age. The X-rays were scanned, digitized, and selected linear distances were measured between points. Multilevel statistical models were used to generate absolute growth curves. RESULTS: Although most growth curves were linear, several were quadratic (exhibiting a deceleration with age), and one displayed a third-order curve. Considerable variation in relative maturity was evident at the first time interval, ranging from 42% of mature (9 week) size (weight) to 97% of mature size (cranial width). Tibial length and body weight were less mature than most, but not all, craniofacial measures. With one exception (bizygomatic width), width measures were relatively more mature than vertical or depth measures. Vertical measures tended to be among the least mature of the craniofacial dimensions. Among the depth (length) measurements, there was a trend of higher maturity for cranial vault/cranial base measures and lower maturity for facial measures. CONCLUSIONS: The wide spectrum of relative and absolute growth potentials demonstrated in this study indicate that the rodent craniofacial complex is amenable to testing the hypothesis that a component's response potential is related to its growth potential.

Animals↗
PubMed2004

Adaptive condylar growth and mandibular remodelling changes with bionator therapy--an implant study.

The purpose of this study was to describe condylar growth and mandibular remodelling changes associated with bionator therapy. Twenty-five patients (15 males and 10 females) between 6.9 and 11.2 years of age with Class II division 1 malocclusions were randomly allocated to either control (n = 11) or treatment (n = 14; bionator only) groups and followed longitudinally for approximately 1 year. Treatment consisted of a bionator only, constructed to clear the buccal dentition by 2 mm and to position the mandible into an edge-to-edge incisor relationship. Using metallic implants for superimposition, mandibular growth, displacement, and true rotation were evaluated cephalometrically. The results showed significant changes in the direction (more posterior) but not in the overall amount of condylar growth. The bionator appliance produced greater than expected posterior drift of landmarks in the condylar and gonial regions. Cranial base superimposition showed greater than expected anterior mandibular displacement, but little or no true mandibular forward rotation with bionator therapy. The bionator appliance alone produced changes in condylar growth direction and remodelling changes associated with mandibular rotation and displacement.

Activator Appliances↗