Biomedical subjects

M G Hans

Publications and source records attributed to M G Hans.

At least 19 recordsLinked to original sources

PubMed2005

Three-dimensional cone beam computerized tomography in orthodontics.

There has been an escalating interest in three-dimensional imaging devices over the last decade. Orthodontists are beginning to appreciate the advantages that the third dimension gives to clinical diagnosis, treatment planning and patient education. This article focuses on the cutting edge technology of cone beam CT, which utilizes conventional X-ray technology and computerized volumetric reconstruction to reproduce a three-dimensional image. A variety of applications and range of issues associated with this technology will be discussed.

Alveolar Process↗

PubMed2001

Subgrouping persons with snoring and/or apnea by using anthropometric and cephalometric measures.

Craniofacial and anthropometric characteristics are identified risk factors for obstructive sleep apnea syndrome (OSAS). Phase 1 of this study used cephalometric radiographs to record craniofacial measurements from 60 OSAS subjects with a respiratory disturbances index (RDI) of 20 or greater (group A) and 60 subjects with a history of loud snoring and an RDI less than 20 (group B). From this data set, a craniofacial risk index (CRI) was constructed using age, body mass index (BMI), and 14 cephalometric measures previously reported to be associated with OSAS. A separating boundary (CRIS) was established by using discriminant analysis to differentiate between the two groups. All measurements were determined by an investigator who was blinded to the subjects' RDI score. Phase 2 used a second sample of 19 group A and 47 group B subjects to test the ability of the CRI derived from the first sample to classify subjects in this second sample into the correct age group. The CRI was able to classify correctly 72.3% (34 of 47) of the group A subjects when all variables were used in the discriminant model. Using only four variables (age, BMI, hyoid mandibular plane distance, and tongue length) selected by the stepwise method, 72.3% (34 of 47) of the group B subjects and 78.7% of group A subjects were classified correctly. These results suggest that a stepwise CRI could be used to classify heterogeneous groups of individuals with increased RDI into subgroups with varying degrees of anatomic risk for disease. Such subgrouping by anatomic risk could be important in determining the pathophysiology of OSAS because it is likely that differences in upper airway anatomy among individuals interacts with a variety of other factors to produce clinical illness.

Adult↗

PubMed2001

The relationship between craniofacial morphology and obstructive sleep apnea in whites and in African-Americans.

Previous studies of craniofacial risk factors for obstructive sleep apnea (OSA) have been based predominantly on cephalometry. However, differences in head form (measured by the cranial index [CI]) and facial form (measured by the facial index [FI]) are considered by anthropologists to provide a basis for structural variation in craniofacial anatomy. We assessed the association of head and facial form with the apnea hypopnea index (AHI) in 364 white individuals and 165 African-Americans. Data collected included cranial and facial dimensions (using anthropometric calipers), body mass index (BMI), neck circumference, and the AHI. CI and FI differed for whites with OSA (AHI > or = 15) versus those without OSA (AHI < 5) (increased CI and decreased FI in subjects with OSA, p = 0.005 and p = 0.006, respectively). CI and FI did not differ in OSA versus non-OSA groups of African-Americans. In subjects with OSA, the CI in whites was again greater and the FI smaller than those in African-Americans (p = 0.007 and p = 0.004, for CI and FI.) We conclude that brachycephaly is associated with an increased AHI in whites but not in African-Americans. The CI may useful in phenotyping and identifying population subsets with OSA.

Adult↗

PubMed2000

Three-dimensional Bolton-Brush Growth Study landmark data: ontogeny and sexual dimorphism of the Bolton standards cohort.

OBJECTIVE: The treatment of craniofacial reconstructive surgery patients may benefit from comparison to average referent three-dimensional landmark data. These data may be useful for diagnosis, treatment planning, prosthetic design, or outcomes assessment. With regard to subadult patients, we hypothesize that the pattern of ontogenetic shape change of same sex, same ethnicity, referent populations will show gross uniformity. We present a preliminary shape analysis of 50 three-dimensional landmarks derived from 317 Bolton-Brush Growth Study biorthogonal image pairs. We determine which landmarks can be collected from scanned radiographs reliably by four operators for the precisely locatable points, ontogenetic trends in landmark configuration shape change, and patterns of sexual dimorphism. PARTICIPANTS: Participants were Bolton standards individuals (16 male and 16 female) who contributed biplane cephalograms seven or more times with annual or greater spacing between ages 3 and 18 years. DESIGN: After removing outliers, we searched for ontogenetic heterogeneity, including sexual dimorphism and within sex-specific Procrustes coordinate shape spaces. RESULTS: A cut-off of 4.3-mm interoperator error left 32 landmarks in our analysis. Three different approaches (principal component analysis, age-trend analysis, and principal components of age residuals) all found no patterns of individual variation around sex-specific average trends of shape change. Male shape change peaks at age 15, a correlate of the growth spurt. CONCLUSIONS: Simultaneous frontal and lateral anatomic landmark identification improves three-dimensional localization reliability. Three-dimensional craniodental shape change from ages 8 to 18 within the Bolton standards presents little heterogeneity. Considerations of ethnicity aside, these may be initial grounds for use of these data as a normative referent.

Adolescent↗

PubMed1999

Recognition of malocclusion: an education outcomes assessment.

The purpose of this study was to assess the outcome of predoctoral orthodontic dental education in an American dental school. A test was used that measured the clinical abilities of dental students in the diagnosis of malocclusion in children, as well as their didactic abilities in answering select questions from recent national board examinations in orthodontics. The records of 7 children with different types of malocclusion were selected from the practice of a board-certified orthodontist. These cases were presented to dental students who were asked to make diagnoses and recommendations for treatment. The results of the didactic and clinical tests were used to assess the outcome of the predoctoral dental curriculum in imparting orthodontic knowledge to future general dentists. Didactic knowledge increased over the 4 years of dental education. First year students answered 30% of the questions correctly, whereas fourth year students answered 59% correctly. The relationship between clinical diagnostic skills and dental education, however, was not as strong. The fourth year students answered 70% of questions concerning the 7 cases correctly. These results indicate that fourth year dental students demonstrated only slight improvement compared with first year students, who answered 65% of the questions correctly. Thus, this study indicated that orthodontic diagnostic skills, as measured by the clinical test used, did not improve substantially during 4 years of undergraduate dental education.

Analysis of Variance↗

PubMed1999

Condylar cartilage response to continuous passive motion in adult guinea pigs: A pilot study.

This article reports on the development and testing of a continuous passive motion device suitable for experimental animals and on the effect of 1 week of continuous passive motion on the thickness of the condylar cartilage in adult guinea pigs. Continuous passive motion is currently used for postsurgical joint therapy and consists of moving a synovial joint passively and constantly through its normal range of motion. In this study continuous passive motion was applied to the temporomandibular joints of two experimental animals for 7 hours per day for 5 days. Two animals were restrained for the same amount of time that the experimental animals were on the continuous passive motion machines (control group 1), and two animals were allowed normal cage activity (control group 2). Six weeks later all animals were sacrificed. Each mandibular condyle was sectioned sagitally, and routine histologic sections were prepared with hematoxylin-eosin stain. Microscopic examination of the mandibular condylar cartilage of the animals placed on continuous passive motion showed a marked increase in thickness compared with the condylar cartilage found on the control animals. The condylar cartilage of the animals placed on continuous passive motion averaged 345 microm, and the controls averaged 232 microm. These findings demonstrate the application of continuous passive motion in an experimental model and provide interesting information regarding the response of the mandibular condyle to increased motion. More studies are necessary to further investigate the effect of continuous passive motion on the condylar cartilage.

Animals↗

PubMed1999

Evidence of correction of open bite malocclusion using active vertical corrector treatment.

This study used a cephalometric analysis that isolated tipping and bodily tooth movements of the upper and the lower incisors and measured vertical skeletal changes in the anterior region of the maxilla and mandible to evaluate the outcome of two-phase nonextraction treatment for open bite malocclusion. Twenty-nine subjects treated with an active vertical corrector (AVC) followed by fixed 022 orthodontic appliances were selected by one orthodontist from his private practice. All subjects lacked vertical incisor contact at the start of treatment and had adequate initial, end of phase 1, and deband lateral cephalograms. Each subject in the treated group was matched by age and sex with an untreated subject from the Broadbent Bolton Collection, Cleveland, OH. Data were collected for three time intervals; phase 1 treatment with the AVC (T1 to T2), phase 2 fixed-appliance treatment (T2 to T3), and over the total treatment period (T1 to T3). Analysis of the data showed no statistically significant (P < or = .002) changes between treated subjects and controls for any variables during the phase 1 (T1 to T2) or phase 2 (T2 to T3) treatment intervals. However, overbite was significantly improved compared with controls (P < or = .002) during the T1 to T3 time interval. It was concluded that two-phase treatment with the AVC followed by fixed orthodontic appliance treatment results in a statistically significant increase in incisor overbite. The observed increase in overbite was the result of small but clinically significant changes in relative mandibular vertical growth, bodily incisor movement toward the occlusal plane, and lingual tipping of the lower incisors.

Adolescent↗

PubMed1998

An assessment of extraction versus nonextraction orthodontic treatment using the peer assessment rating (PAR) index.

The extraction of teeth for orthodontic purposes has always been a controversial subject in the specialty. The purpose of this study was to assess the outcome of orthodontic treatment in 100 patients treated with the extraction of four premolars and compare it with the outcome of 100 patients treated without extractions, using the peer assessment rating (PAR) index. Records were selected from 1,198 consecutively completed cases treated by a single provider (MGH) between 1981 and 1995. We chose the first 100 finished patients in each group (extraction and nonextraction) who were under the age of 16 and had no deciduous teeth at the start of treatment. The results of this study show that average treatment time for the extraction group was 29.7+/-6.1 months compared with 26.0+/-7.2 months for the nonextraction group. The extraction group had significantly higher initial PAR scores (T1-PAR ext = 30.01+/-8.20 vs. T1 PAR nonext = 25.21+/-8.55), with greater initial maxillary anterior crowding (PAR ext value = 6.05+/-3.85 vs. PAR nonext value = 4.21+/-2.90) and greater initial overjet (PAR ext value = 1.82+/-1.01 vs. PAR nonext value 1.28+/-1.04). All pretreatment differences were significant at the p < or = 0.0001 level. Although significantly different at the beginning of treatment, both groups were statistically identical at the end (PAR T2 ext = 6.18 + 3.04% reduction = 79.4% compared with PAR T2 nonext = 5.64 + 3.08% reduction = 77.6%). In conclusion, the results demonstrate that, given an additional 3 months of treatment, it is possible for an orthodontist to produce dento-occlusal relationships in extraction patients that are as good as those achieved in nonextraction cases.

Adolescent↗

PubMed1997

Comparison of two dental devices for treatment of obstructive sleep apnea syndrome (OSAS).

Previous case reports have indicated dental devices can be an effective nonsurgical treatment for snoring and obstructive sleep apnea. This pilot study evaluated the effectiveness of two intraoral devices in reducing the Respiratory Disturbance Index (RDI) and Epworth Sleepiness Scale (ESS) scores in a group of 24 adult volunteers with a history of loud snoring. Subjects were randomly assigned to two groups. Twelve subjects were fitted with a dental device designed to increase vertical dimension and protrude the mandible (device A). The other 12 subjects received a different device designed to minimally increase vertical opening without protruding the mandible (device B). Unattended home sleep monitoring (Edentrace II Digital Recorder, Edentech Corp.) was used to compute RDI at two time periods: (T0) before using any dental device and (T1) while using a dental device 2 weeks after the initial delivery date. The mean RDI and ESS scores at T0 for subjects in the device A group were 35.6 +/- 28.4 and 12.0 +/- 3.9, respectively. Means for the same measures at T1 were 21.1 +/- 21.4 and 8.2 +/- 4.0. For subjects in the device B group, means for RDI and ESS scores at T0 were 36.5 +/- 43.7 and 13.0 +/- 4.5, the means at T1 were 46.8 +/- 47.0 and 12.5 +/- 5.7. The effectiveness of the two devices was estimated by comparing the difference in RDI scores from T0 to T1 for the 10 subjects who were using device A and completed the study and the 8 subjects who were using device B and completed the study. Six subjects withdrew for various reasons. From T0 to T1, device A reduced RDI scores in 9 of 10 subjects, with a mean reduction in RDI of 14.5 (p < or = 0.05) and in ESS score of 3.8 (p < or = 0.005). Device B showed no change or an increased RDI score in 8 of 8 subjects. Seven of the eight subjects who showed no improvement in RDI with device B were then fitted with device A. Four of these seven subjects showed a reduction in RDI and five showed a reduction in ESS after using device A for 2 weeks. The mean reduction in RDI and ESS was 2.4 +/- 19.8 and 2.4 +/- 3.0, respectively. Hence, we conclude that a dental device that advances the mandible and increases the vertical dimension to open the upper airway is more effective in reducing the number of apneic and snoring events during sleep than one which does not.

Adult↗

PubMed1997

The demographics of Dr. Geoffrey Walker's cephalometric collection.

The Bolton-Brush Growth Study Center (BBGSC) at Case Western Reserve University recently acquired the radiographic collection of Geoffrey F. Walker, an orthodontist, anthropologist, and pioneer computer expert. Dr. Walker's culturally diverse collection on more than 1500 persons has added lateral and frontal cephalograms to the Bolton-Brush collection. In contrast to the longitudinal Bolton-Brush study, the Walker collection contains predominantly cross-sectional samples of various tribes and ethnic groups around the world. A computerized index (similar to the Bolton-Brush index) has been created for efficient access. The addition of this unique collection enhances the BBGSC's ability to serve as a resource for orthodontic students, researchers, and practitioners, as well as the physical anthropology community.

Adolescent↗

PubMed1997

Racial differences in sleep-disordered breathing in African-Americans and Caucasians.

In this case-control family study of sleep-disordered breathing (SDB), we describe the distributions of SDB and SDB risk factors in African-Americans and Caucasians. A total of 225 African-Americans and 622 Caucasians, ages 2 to 86 yr, recruited as members of families with an individual with known sleep apnea (85 index families) or as members of neighborhood control families (63 families) were studied with an overnight home sleep-study, questionnaires, and physical measurements. A subsample underwent cephalometry. Outcome measures were the respiratory disturbance index (RDI) and a binary variable indicating the presence of increased apneic activity (IAA). In both races, a strong relationship was demonstrated between the (log transformed) RDI and age and age2. African-Americans with SDB were younger than Caucasians with SDB (37.2 +/- 19.5 versus 45.6 +/- 18.7 yr, p < 0.01). In subjects < or = 25 yr, RDI level and IAA prevalence were higher in African-Americans (odds ratio, adjusted for obesity, sex, proband sampling, and familial clustering, 1.88, 1.03 to 3.52, 95% CI). In this age group, racial differences also were observed in the relationship between RDI and age (p < 0.001 for the RDI-age interaction). This suggests that young African-Americans may be at increased risk for sleep apnea.

Adolescent↗

PubMed1996

The effects of antirat nasal septum cartilage antisera on facial growth in the rat.

Antirat nasal septum cartilage antisera (RNS-IgG) produced in rabbits by injection of crude antigens derived from rat nasal septum cartilage was cytotoxic for rat chondrocytes in vitro. The effect of this antisera on rat facial growth was tested by injecting three groups of growing rats at 4-day intervals from birth to 30 days. The treatment group (n = 19) received injections of RNS-IgG, one control group (n = 11) received injections of the IgG fraction of preimmune rabbit sera (PI-IgG) and a second control group (n = 16) received injections of normal saline. All animals were killed at the conclusion of the experiment, and lateral and dorsoventral cephalometric radiographs were taken. Statistical difference between treatment and control groups were found for 15 cephalometric measurements. Specifically, snout length (as measured from the intersphenoidal synchondrosis to the upper incisors (is-i) was reduced in animals treated with RNS-IgG compared with both PI-IgG and saline injected controls (p < 0.06, p < 0.005, respectively). In addition, premaxillary length, premaxillary displacement, and bimaxillary width were significantly reduced (p < 0.05) in RNS-IgG treated animals compared with saline injected controls. Bimolar width was reduced (p < 0.05) between RNS-IgG and PI-IgG groups. These results demonstrate that injection of antinasal septum antisera reduces midfacial dimensions in experimental rats and that nonimmune rabbit antisera may have an effect on the growth process. In summary, the results of this pilot study suggest the possibility for using more specific antinasal cartilage antibodies to effect dose-dependent, tissue specific, modulation of facial growth.

Animals↗

PubMed1996

Cephalometric assessment in obstructive sleep apnea.

It is reported that some specific craniofacial characteristics are associated with obstructive sleep apnea syndrome (OSAS). To test this finding, the present study developed and assessed the feasibility of a craniofacial index score (CIS) in differentiating patients with OSAS from habitual snorers. Anthropometric measurements and lateral head radiographs were obtained on 24 male and 4 female patients with OSAS who had physician-diagnosed OSAS (respiratory disturbance index (RDI) >20), and 25 male and 5 female habitual snorers (RDI <20). Thirteen cephalometric and four anthropometric measure- ments were used in a discriminant model to construct the CIS. The model was able to correctly classify 82.1% of the OSAS group and 86.7% of the snoring group. In addition, variables that were related to the soft tissues, hyoid bone to mandibular plane, Body Mass Index, and soft palate length had the highest predictive value. These findings indicate that a CIS constructed from cephalometric and anthropometric measurements can be used to identify subjects with and without OSAS.

Anthropometry↗

PubMed1996

Soft tissue growth of the oropharynx.

The purpose of this study was to describe the pattern of bony and soft tissue growth of the oropharynx in a sample of healthy, orthodontically untreated children. The sample consisted of 16 males and 16 females with lateral cephalograms at 6, 9, 12, 15, and 18 years of age, for a total of 160 lateral cephalometric radiographs. All subjects were enrolled in the Broadbent Bolton Study and their radiographs were used to produce the Bolton Standard Templates. Each radiograph was traced by hand and the tracings were paired and averaged to create a standard template for pharyngeal tissues at each age. In addition, all 160 tracings were digitized and means and standard deviations were calculated for 29 hard and 7 soft tissue measurements. Four linear (Ar-H,S-H,Go-H, Gn-H) and three angular (N-S-H, SN-ArH,GoGn-H) measurements demonstrated that the hyoid bone descends and moves slightly anteriorly up to age 18. The soft palate (PNS-P) increased 1 mm in length and 0.5 mm in thickness every 3 years after age 9. The distance between the anterior border of the atlas (ATA) and PNS did not change after age 12, while two soft tissue measurements (PNS-pharyngeal wall [PhW2] and posterior soft palate to pharyngeal wall [psp-PhW3]) increased. In general, two periods of accelerated change (6-9 years and 12-15 years) and two periods of quiescence (9-12 years and 15-18 years) were identified for the pharyngeal soft tissues. Further studies are needed to determine in soft tissues in the oropharynx continue to change after age 18.

Adolescent↗

PubMed1996

The association of sudden unexpected infant death with obstructive sleep apnea.

We studied the relationship of sudden unexpected infant death/apparent life-threatening events (ALTE) to obstructive sleep apnea (OSA) in 74 index probands who had either sleep-laboratory-confirmed OSA or a clinical diagnosis of OSA requiring treatment, 62 matched control probands, and their spouses and first- and second-degree relatives. Sleep was monitored in the home overnight, and OSA was defined by respiratory disturbance indices (number of apneas/hypopneas per hour of sleep) corrected for normal increases with age. Information on sudden unexpected infant death/ALTE was obtained by questionnaire and was corroborated. For living relatives, data were obtained by questionnaire, examination, or study (cephalometric radiographs, ventilatory responsiveness to hypercapnia and hypoxia). Eight index families had 10 infants with sudden unexpected infant death/ALTE; two control families had three infants with sudden death (p = 0.11). All told, 91 of the 136 families (index plus control) included members with OSA, and all 10 infant death/ALTE families were among these (versus zero of 45 families with no OSA; p = 0.03). The sudden infant death/ALTE families had a greater frequency of two or more members with OSA (p = 0.06), reported more respiratory disease or allergy, were more frequently brachycephalic (p = 0.05), and had a smaller mean posterior nasal spine-basion distance (p = 0.0001) and ratio of anterior mandibular/anterior maxillary dental height (p < 0.05). Ventilatory responses to hypoxia were reduced in members of families with OSA (p = 0.008), with a trend toward the greatest blunting in subjects from families with OSA plus sudden unexpected infant death/ALTE. Thus, OSA in adults and sudden unexpected infant death/ALTE in their biologic relatives appear to be related. Familial factors influencing this association may include the degree of the predilection for OSA, liability for respiratory illness or allergy, dimensions of the oral-pharyngeal airway, and ventilatory response to hypoxia.

Case-Control Studies↗

PubMed1995

Age-related differences in mandibular ramus growth: a histologic study.

Histologic reconstructions of remodeling variations of the mandibular ramus are demonstrated. This is significant because morphogenic relationships between the ramus and corpus establish mandibular arch position. Ground and polished microscopic sections were obtained from the ramus of 30 well-preserved human mandibles, dental age 1 to 13 years. The distribution of the various types of endosteal and periosteal bone tissues and resorptive versus depository surfaces was recorded. Fourteen of the 30 specimens and the majority of the mandibles at all ages examined exhibited the classic pattern of deposition and resorption (Type A or classic pattern) described by Enlow. Nine mandibles followed a second variation (Type B or vertical variation) involving a gonial angle alignment change. Seven followed a pattern of deposition and resorption similar to what Björk might have called a forward rotating pattern (Type C or rotation variation). The differences in these patterns are large enough to suggest that a common description of one pattern of remodeling for all mandibles is incomplete. Unfortunately, the process of mandibular growth and remodeling does not appear to correlate well with dental age and the basis for changes in patterns may be more complex than first imagined. If temporal differences exist, they are not related directly to dental development. In theory, the differences in pattern are great enough to influence the outcome of mandibular orthopedic treatment.

Adolescent↗

PubMed1995

Malocclusion in Labrador Inuit youth: a psychosocial, dental and cephalometric evaluation.

Epidemiological studies of malocclusion of world populations have been previously limited to dental parameters. This cross-sectional study examined the prevalence of malocclusion in the dentitions of Inuit (Eskimo) youth aged between 5-22 years from Labrador, Canada, using psychosocial, dental and skeletal (radiographic) parameters. Data were obtained from two communities, Nain (population 1079) and Hopedale (population 534). About 82% (n = 363) of the Inuit youth and 50% (n = 222) of their parents responded to the psychosocial questionnaires. In total, 78% (n = 348) of the Inuit youth were examined intraorally to determine the prevalence of malocclusion using the Treatment Priority Index (TPI), and 23% (n = 100) had cephalometric radiographs taken using a portable cephalometer. The results indicated that 95% of the Labrador Inuit youth examined had some degree of malocclusion, 10-16% were aware of their occlusal disharmonies, 55-65% wanted to have their teeth straightened, and 5% were teased by others because of their malocclusions. In addition, 63% of the parents seemed to be aware of their child's occlusal problems and 70% wished their children to wear orthodontic appliances if they were needed. Prevalence and awareness to malocclusion were positively correlated. According to the TPI, 18% had "severely handicapping" and 20% had "very severely handicapping" malocclusions. The TPI score increased with age from 5.25 in the young group to 8.05 in the older age group (mean 6.7). There were high prevalences of crowded anterior teeth, upper lingual posterior crossbites, and open or edge to edge bites. A prevalence of 35% Angle Class I, 49% Angle Class II and 16% Angle Class III molar relationships were observed. Cephalometric analysis demonstrated a mean wits measurement of -2.0 mm, a mean ANB angle of 4.7, a mean lower face height of 68.3 mm, a mean interincisal angle of 125 degrees and a mean frankfort mandibular plane angle of 31.3 degrees. A need for orthodontic care and further education were clearly indicated and highly recommended.

Adolescent↗

PubMed1994

The Broadbent-Bolton Growth Study--past, present, and future.

A computerized database of 14 textual elements has been created to describe the 4309 subjects enrolled in the Broadbent-Bolton Growth Study. The database can be searched by using Boolean operators to select subsets of subjects matched on the 14 data elements. The structure of the database, along with representative tables and charts of the data, is presented to aid researchers contemplating use of the collection for scientific investigation.

Adolescent↗