Differences in craniofacial and dental characteristics of adolescent Mexican Americans and European Americans.

INTRODUCTION: The purpose of this study was to compare the soft-tissue profiles of matched Class I adolescent European Americans and Mexican Americans. The secondary aim was to explain profile differences based on group differences in soft-tissue thickness, skeletal morphology, dental position, and tooth size. METHODS: The study pertained to 207 untreated Class I adolescents, including 93 Mexican Americans and 114 European Americans. Lateral cephalometric and model analyses were performed to quantify morphologic differences. Two-way analyses of variance were used to evaluate ethnicity, sex, and their interaction. RESULTS: Mexican Americans had significantly (P <0.05) greater lip protrusion and facial convexity than did European Americans. Mexican Americans had smaller craniofacial dimensions and larger teeth, resulting in maxillary and mandibular dentoalveolar protrusion. Mexican Americans also had thicker soft tissues and greater maxillary skeletal prognathism than European Americans. The combination of thicker soft tissues, maxillary skeletal prognathism, and dentoalveolar protrusion explained the protrusive lips of Mexican Americans. The greater facial convexity of Mexican Americans was due primarily to maxillary prognathism and mandibular hyperdivergence. Sex differences pertained primarily to size; the linear dimensions of the boys were consistently and significantly larger than those of the girls. CONCLUSIONS: European American normative data and treatment objectives do not apply to Mexican Americans. Knowledge of the soft-tissue, skeletal morphology, and dental position differences should be applied when planning treatment for Mexican American patients.

The identification of a novel locus for mandibular prognathism in the Han Chinese population.

Mandibular prognathism is a common dentofacial phenotype with a substantial genetic component; however, few susceptibility loci have been mapped. Ethnicity is a risk factor for mandibular prognathism, and a relatively high prevalence is observed in Asian populations. The hypothesis of this study suggested that a specific locus for mandibular prognathism exists in the Han Chinese population. So, the authors studied a Han Chinese pedigree in which mandibular prognathism was inherited (11 affected, 10 unaffected) in an autosomal dominant pattern. A genomewide linkage scan was performed with the Illumina Linkage-12 DNA Analysis Kit. Multipoint parametric and nonparametric linkage analyses were performed with MERLIN 1.01. A susceptibility locus was identified on chromosome 14q24.3-31.2, with a nonparametric linkage score of 11.341 (empirical P = .020) and a logarithm of the odds score of 2.032 (empirical P = .008). Haplotype analysis refined the candidate locus to a 10.62-cM interval (72.42 to 83.14 cM; 74.57 to 84.66 Mb) between rs1468507 and rs7141857. Within this interval, the candidate functional genes are TGFB3 and LTBP2. In conclusion, the authors detected a suggestive linkage for mandibular prognathism in a Han Chinese pedigree, and this finding can be combined with previous studies to further understand the genetic basis of mandibular prognathism.

Genome scan for locus involved in mandibular prognathism in pedigrees from China.

BACKGROUND: It is well known that genetic components play an important role in the etiology of mandibular prognathism, but few susceptibility loci have been mapped. METHODOLOGY: In order to identify linkage regions for mandibular prognathism, we analyzed two Chinese pedigrees with 6,090 genome-wide single-nucleotide polymorphism (SNP) markers from Illumina Linkage-12 DNA Analysis Kit (average spacing 0.58 cM). Multipoint parametric and non-parametric (model-free) linkage analyses were used for the pedigrees. PRINCIPAL FINDING: The most statistically significant linkage results were with markers on chromosome 4 (LOD=3.166 and NPL=3.65 with rs 875864, 4p16.1, 8.38 cM). Candidate genes within the 4p16.1 include EVC, EVC2. CONCLUSION: We detected a novel suggestive linkage locus for mandibular prognathism in two Chinese pedigrees, and this linkage region provides target for susceptibility gene identification, a process that will provide important insights into the molecular and cellular basis of mandibular prognathism.

Identification of SNP markers on 1p36 and association analysis of EPB41 with mandibular prognathism in a Chinese population.

OBJECTIVE: The results of a genome-wide scan suggested that chromosome locus 1p36 might be linked to the etiology of mandibular prognathism (MP) amongst Asian ethnicities. In this study, we performed a two-stage case-control association study to determine whether one or more genes that confer susceptibility to MP are located within this genomic region. DESIGN: In the first stage of the study, we examined 103 single nucleotide polymorphisms (SNPs) on 1p36 across an 8.6Mb critical region and within four candidate genes in 158 cases and 147 controls to identify genes associated with MP. In the second stage of the study, we examined an additional 23 SNPs within the erythrocyte membrane protein band 4.1 (EPB41) gene in 211 cases and 224 controls. RESULTS: Four SNPs located in the EPB41 gene showed possible allelic and genotypic associations with MP (P<0.03 and P<0.05, respectively) in the first stage. In the analysis of single SNPs in the second stage, the allele of rs4654388 showed the strongest significant association with MP (P=0.008) and the rs4654388 G-allele was associated with a significantly increased risk of MP (OR: 1.78, 95% CI: 1.16-2.74). Haplotype analysis revealed that MP was associated significantly with haplotype GTTCAGGT (P(corrected)=0.031), which included the rs4654388 G-allele. CONCLUSIONS: An association between genetic polymorphisms in the EPB41 gene and MP has been observed. Although the polymorphisms which may contribute to MP have not been determined, the results of our study suggest that the EPB41 gene could confer susceptibility to MP.

Cephalometric norms for saudi adults living in the western region of Saudi Arabia.

European-American norms are still used in the orthodontic treatment of Saudi patients, despite the different ethnic backgrounds of Saudis. The aims of this study were to evaluate the cephalometric features of a Saudi population and to establish cephalometric norms for Saudis living in the western region of Saudi Arabia. Seventy lateral cephalometric radiographs of Saudis (32 females and 38 males; aged 18-28 years) with acceptable profiles and Class I dental relationships were traced and analyzed. The mean value, standard deviation, and range of 16 angular and linear variables were calculated. The resulting norms for Saudis were compared with European-American norms using an independent t-test. Male and female groups were also compared using the t-test. Saudis tend to have an increased ANB angle because of retrognathic mandibles and bimaxillary protrusion as compared with European-Americans. Males tend to have more prognathic mandibles than females as indicated by the statistically significant increase in facial angle (P < .05) and SNB angle (P < .05). Although the anterior lower face height was similar in males and females, males tend to have a steeper mandibular plane angle when related to the anterior cranial base than females (P < .05). Saudis have distinct cephalometric features, which should be used as a reference in treating Saudi orthodontic patients.

Cephalometric evaluation in children presenting adapted swallowing during mixed dentition.

The tongue trust and anterior projection through the dental arcades during swallowing is known as Adapted Swallowing (AS) and is a common finding during mixed dentition. The authors studied the morphologic dentofacial characteristics through cephalometric measures in 38 girls and 35 boys, aged seven to nine years, presenting AS, as determined by the speech therapist evaluation. Cephalometric evaluation was obtained by Radiocef 2.0 software. The measurements studied were the mandibular and maxillary relations to the cranial base, the nasolabial angle, and the upper airway patency, as proposed by McNamara Jr (1984), and the convexity and facial axis angles and maxillary height from Ricketts (1960; 1981). Results, analyzed in relation to sex and racial group, showed an association of Class II facial convexity with the African Brazilian children with dark black skin. This classification does not reflect an abnormality as all African Brazilians studied were classified as class II, due to the fact that the standard measurements are based in the white American population. These findings point to the need of specific racial normative standard for evaluating orofacial and dental structures.

Differences in soft tissue profile changes following mandibular setback in Chinese men and women.

PURPOSE: This study investigated the soft tissue profile changes after surgical correction of mandibular prognathism in Chinese patients and evaluated the sex differences in the ratios of soft tissue to hard tissue change. PATIENTS AND METHODS: Forty-three adult Chinese patients (18 men and 25 women) with mandibular prognathism were treated by intraoral oblique or vertical ramus osteotomy. Lateral cephalometric radiographs were taken presurgically and between 6 to 12 months postsurgically, and specific soft and hard tissue points were digitized and analyzed with a computer-aided system. RESULTS: As a result of surgical setback of the mandible, the soft tissue to hard tissue change ratios were: Li:Ii = 0.71:1, Si:B = 0.90:1, Pg':Pg = 0.94:1 for the males; and Li:Ii = 0.82:1, Si:B = 0.92:1, Pg':Pg = 1.06:1 for the females. CONCLUSION: The changes in soft tissue were closely correlated with the hard tissue movement after surgical setback of mandible. The average ratios of soft tissue to hard tissue change in horizontal direction appear to show a gender difference, which suggests the need for different ratios when predicting the results of orthognathic surgery.

A study of nasal respiratory resistance and craniofacial dimensions in white and West Indian black children.

Two studies have shown that there are morphologic differences in the nasopharynx between the major racial groups. This investigation was conducted to see whether these morphologic differences affected nasal respiration. Twenty-two West Indian and 24 white children (mean age of 13 years 11 months) were studied to examine the relationship between nasorespiratory function and nasopharyngeal and dentofacial structure. The nasorespiratory function was measured in terms of nasal respiratory resistance, NRR, (Pascals/cm3 per second), both by anterior and posterior methods, with a computerized rhinomanometer. Nasopharyngeal structure was described in terms of cephalometric variables. The West Indian cephalometric profile generally conformed to its existing description in the literature including prognathic jaws and bimaxillary proclination; in addition, the West Indians were found to have a greater bony nasopharyngeal width (posterior nasal spine-basion) and shallower nasopharyngeal roof angle (posterior nasal spine-hormion-basion). All rhinomanometric measurements were significantly lower in the West Indian group, especially when posterior rhinomanometry was used. The correlation coefficients between the cephalometric and the rhinomanometric measurements were statistically significant but low. In addition, the measure of mandibular prognathism (angle SNB) was also found to be significantly correlated with the nasorespiratory resistance.

A study of nasal respiratory resistance and craniofacial dimensions in white and West Indian black children

Two studies have shown that there are morphologic differences in the nasopharynx between the major racial groups. This investigation was conducted to see whether these morphologic differences affected nasal respiration. Twenty-two West Indian and 24 white children (mean age of 13 years 11 months) were studied to examine the relationship between nasorespiratory function and nasopharyngeal and dentofacial structure. The nasorespiratory function was measured in terms of nasal respiratory resistance, NRR, (Pascals/cm3 per second), both by anterior and posterior methods, with a computerized rhinomanometer. Nasopharyngeal structure described in terms of cephalometric variables. The West Indian cephalometric profile generally conformed to its existing description in the literature including prognathic jaws and bimaxillary proclination; in addition, the West Indians were found to have a greater bony nasopharyngeal width (posterior nasal spine-basion) and shallower nasopharyngeal roof angle (posterior nasal spine-hormion-basion). All rhinomanometry were significantly lower in the West Indian group, especially when posterior rhinomanometry was used. The correlation coefficients between the cephalometric and the rhinomanometric measurements were statistically significant but low. In addition, the measure of mandibular prognathism (angle SNB) was also found to be significantly correlated with the nasorespiratory resistance (AU)

[Factorial analysis of the "proper" angles involved in ethnic prognathism]. / Analyse factorielle d'angles "propres" intervenant dans le prognathisme ethnique.

This work rest on 10 populations, chiefly arising from "musée de l'Homme" (Paris). 9 angles was considered in squeletal profile, and "reciprocal averaging" analysis was made. It shows the main function of peri-buccal segments situation, relatively to palatal and mandibular planes, as well as participation of facial whole situation relatively to anterior neurocranium. This analysis confirm the peculiar position of leucoderm men with reference to other groups.

The significance of the integumentary profile.

Profile analysis was performed on 180 Thai female subjects with ages ranging from 16 to 21 years. Seventy were of Chinese origin. The determination of the profile analysis mean values was based on the methods of Schwarz, Subtelny, Ricketts, Burstone, and Schwartz. The results were compared to Caucasian standards and to the findings of our previous study on a Javanese population. For the profile forms, our investigated groups showed mainly prognathic faces (75% to 84%). A "shift backward" profile flow dominated. We found a "prognathic face" combined with a "shift backward" in 50% to 60% of the Asian subjects analyzed. Our soft-tissue profile results (approximately 165 +/- 6 degrees) showed less convexity than that of the Caucasians and there was no significant difference in overall profile between the 2 Thai groups (approximately 134 +/- 5 degrees); this is in the range given by Subtelny (141 degrees to 131 degrees) except for that of the Javanese subjects. For the lip analysis, we listed a posterior position or a lip position upon the esthetic line between 60% to 70% of both Thai groups with respect to the upper lip and only 28% to 33% for the lower lip. The Javanese group, however, showed 90% anterior position of the upper lip and 93% of the lower lip to this line. It is significant that proper blending of the integumentary profile produces an esthetically pleasing face and this varies in different ethnic groups. A good combination could even make a "prognathic face shift backward" very acceptable as illustrated by a profile analysis of Miss Thailand, 1984.(ABSTRACT TRUNCATED AT 250 WORDS)