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Introduction: The loss of occlusal support due to tooth loss is associated with systemic diseases. However, there was little about the association between occlusal support and cognitive impairment. The cross-sectional study aimed to investigate their association. Methods: Cognitive function was assessed and diagnosed in 1,225 communitydwelling adults aged 60 years or older in Jing’an District, Shanghai. Participants were diagnosed with mild cognitive impairment (MCI) by Peterson’s criteria, or dementia, according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. We determined the number of functional occlusal supporting areas according to Eichner classifications. We used multivariate logistic regression models to analyze the relationship between occlusal support and cognitive impairment and mediation effect models to analyze the mediation effect of age. Results: Six hundred sixty participants were diagnosed with cognitive impairment, averaging 79.92 years old. After adjusting age, sex, education level, cigarette smoking, alcohol drinking, cardiovascular disease, and diabetes, individuals with poor occlusal support had an OR of 3.674 (95%CI 1.141–11.829) for cognitive impairment compared to those with good occlusal support. Age mediated 66.53% of the association between the number of functional occlusal supporting areas and cognitive impairment. Discussion: In this study, cognitive impairment was significantly associated with the number of missing teeth, functional occlusal areas, and Eichner classifications with older community residents. Occlusal support should be a significant concern for people with cognitive impairment. [ABSTRACT FROM AUTHOR]

Background: This study investigated the characteristics of Monson's sphere in Chinese young adult females with individual normal occlusion to provide a reference for oral rehabilitation in prosthodontic and orthodontic treatments., Methods: Points at the dental cusps and incisal edges were selected from 51 digital mandibular dental models of Chinese young adult females (aged 18-22 years) with individual normal occlusion. Monson's spheres were fitted to the selected points based on the least-squares principle and the radii were calculated. The deviation of each selected point from its relative spherical surface was also calculated. The radii and deviations of these points were examined using conventional descriptive statistics and distributions of the most deviated points inside and outside the spheres were analyzed., Results: The mean radius of Monson's sphere in Chinese young adult females was 79.60 ± 14.13 mm. The deviation of each selected point from its relative sphere surface was 0.38 ± 0.30 mm. The maximum deviations inside and outside the sphere were 0.93 ± 0.25 mm and 0.95 ± 0.30 mm, respectively. The most deviated points outside the spheres were mainly distributed at the distolingual cusps of the mandibular second permanent molars (31.37%), while those inside the spheres were mainly distributed at the mesiolingual cusps of the mandibular first permanent molars (45.10%)., Conclusions: The radius of Monson's sphere in Chinese young adult females was smaller than the classic four-inch value suggested by Monson. Deviation was observed from all selected points to their Monson's sphere surface, with the most deviated points distributed primarily in the molar region., (© 2024. The Author(s).)

Objectives: Tooth loss, which usually leads to malnutrition, is common in the elderly. However, limited information is available regarding its association with sarcopenia. This study aimed to investigate the relationship between loss of occlusal pairs of tooth and sarcopenia. Design: A cross-sectional retrospective study was performed. Setting: The elderly who participated in the National Basic Public Health Project in the Maigaoqiao Community Medical Center in Nanjing, Jiangsu Province, China. Participants: A total of 2850 individuals aged ≥60 years were enrolled. Measurements: Sarcopenia was defined according to the criteria proposed by the Asian Working Group for Sarcopenia. A trained dentist assessed oral health status and counted the number of present teeth. Logistic regression analyses were performed to evaluate the association between the loss of occlusal pairs and sarcopenia. Results: The prevalence of sarcopenia was 7.1% (201/2850). Univariate logistic regression analysis showed that loss of occlusal pairs was associated with sarcopenia [anterior occlusal pairs (AOPs): odd ratio (OR) = 1.292, 95% confidence interval (CI) = 1.158–1.442; posterior occlusal pairs (POPs): OR = 1.147, 95% CI = 1.018–1.221]. Multivariate logistic regression analysis indicated that loss of POPs was still an independent risk for sarcopenia (OR = 1.108, 95% CI = 1.007–1.220) after adjustment for traditional confounders. Subgroup analysis showed that loss of POPs was more significantly linked to sarcopenia in those with advanced age (≥80years) (OR = 1.307, 95% CI = 1.116–1.532) and in females (OR = 1.165, 95%CI = 1.038–1.308). Compared to individuals with ≥5 occluding pairs of POPs, those with <5 occluding pairs of POPs had a higher incidence of sarcopenia. Conclusions: Loss of POPs is associated with an increased risk of sarcopenia in the elderly in a Chinese population. Further research on the mechanism of the observed causal relationship is needed. [ABSTRACT FROM AUTHOR]

Background: The purpose of the present study is to evaluate the prevalence of temporomandibular disorders (TMD) and their associated biological and psychological factors in Chinese university students. Methods: A total of 754 students were included from Zunyi Medical University, each participant completed questionnaires and clinical examinations according to the Diagnostic Criteria for Temporomandibular Disorders. Results: The overall prevalence of TMD was 31.7% among medical students. Subjects with TMD had a high prevalence of bruxism, empty chewing, unilateral chewing, chewing gum, anterior teeth overbite, anterior teeth overjet, depression, anxiety, and sleep disturbance. Moreover, sleep bruxism, empty chewing, unilateral chewing, anterior teeth overbite, depression, and anxiety were the strongest risk factors for TMD. Conclusions: Individuals with TMD have a high prevalence of psychological distress and oral parafunctional habits. Except for the psychological factors associated with TMD, bruxism, abnormal chewing, and malocclusion also shared similar risks for TMD. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to analyze the detailed three-dimensional measurements of temporomandibular joint (TMJ) in Chinese adults with normal occlusion and harmonious skeleton. Methodology: In 51 subjects 102 joints were analyzed using Anatomage Invivo dental 5.4. The measurements include: joints' parameters, position, angulation, and inclination of the condyle and articular fossa as well as 3D volumetric of the joint-spaces. All measurements were statistically analyzed by paired Student's t test to find out the differences between the left- and right sides. Pearson correlation coefficient test was done to figure out the relationship of the TMJ parts in the normal situation. Results: The inter-condyle distances medially, geometrically, and laterally were 90.2 ± 5.2,107 ± 6.1, and 125 ± 5.5 mm, respectively. However, the 102 condyles were angulated on three planes 54.9º ± 11.2, 71.8º ± 7.3, and 12.5º ± 6.3 at vertical-, horizontal-, and midsagittal planes, respectively. The joint spaces measurements were 2.6 ± 0.7 mm, 2.5 ± 0.8 mm, 2.4 ± 0.7 mm, and 3.3 ± 0.7 mm for anterior-, medial-, posterior-, and superior joints, respectively. The total volume of the whole joint-space was 404.3 ± 71mm3. The left condyle position was on the centric position whereas the right condyle was eccentric (slightly anterior). Conclusion: Chinese subjects are characterized by wide inter-fossa distance and inter-condyle distance; however, no significant correlations with joint spaces in normal occlusion were found. The asymmetries between right- and left mandibular condyle were distinguished in angular and linear-vertical measurements. Finally, this study could be considered as reference data for upcoming research in the Chinese population. [ABSTRACT FROM AUTHOR]

Aims: To examine the effect of decreased estrogen level and altered diet hardness on condylar cartilage morphology of the rat temporomandibular joint (TMJ) and on the expression of condylar cartilageestrogen receptor alpha (ER?) and matrix metalloproteinase-8 (MMP-8). Methods: A total of 36 female rats was divided into four groups: ovariectomized rats fed a normal diet, non-ovariectomized controls fed a normal diet, ovariectomized rats fed a soft diet, and non-ovariectomized controls fed a soft diet. Ovariectomy was performed at the age of 60 days. Seven days after the operation, the rats were sacrificed. Repeated measures ANOVA and Duncan's multiple comparison tests were used for statistical analysis. Results: The ovariectomized rats had thicker cartilage layers than the controls, both in the normal diet and soft diet groups. The thinnest cartilage layers were found in the control rats fed with the soft diet. The thickness of the chondroblastic layer was significantly higher (P < .001) in the normal-diet rats than in the soft-diet rats in both ovariectomized and non-ovariectomized groups. The thickness of the proliferative layer was significantly higher (P < .001) in the ovariectomized softdiet rats than in the soft-diet control rats. The proportional amount of ER? was statistically significantly higher (P < .001) in the condylar cartilage of the ovariectomized rats than in the non-ovariectomized control rats both in the normal- and soft-diet groups. The proportional amount of ER? was statistically significantly higher (P < .001) in the ovariectomized normal-diet rats than in the ovariectomized soft-diet rats. The proportional number of MMP-8-positive cells was statistically significantly higher (P < .001) in the condylar cartilage of ovariectomized rats fed the soft diet than in non-ovariectomized control rats fed the soft diet. Control rats fed with the normal diet had a higher proportional amount of MMP-8 positive cells than control rats fed with the soft diet (P < .05). Conclusion: The rat TMJ condylar cartilage is sensitive to changes in estrogen levels and altered diet hardness. [ABSTRACT FROM AUTHOR]

'Haramiyidans' are extinct mammaliaforms often clustered with Multituberculata as Allotheria, and with a fossil record extending from the Upper Triassic to possibly the Upper Cretaceous. For many decades, 'haramiyidans' were known only from isolated teeth, and their relationships to other mammaliaforms remain unclear. With the discovery of several euharamiyidans represented by skeletal specimens from the Jurassic Yanliao Biota, north‐western China, our knowledge of this group has significantly advanced. Nonetheless, much morphology, including dentition and occlusal patterns, has only been briefly described for most taxa, and phylogenetic reconstruction and interpretation of the biology of the group still remain unclear or controversial. Here we provide systematic descriptions of the dental wear of shenshouids (Qishou and Shenshou) from the Yanliao Biota. We reconstruct the occlusal mode of shenshouids and compare it with those of other taxa based on our observation of specimens of most known 'haramiyidan' taxa. Several occlusal patterns are recognized. In particular, that of Thomasia, Haramiyavia and Maiopatagium is similar to the multituberculate M1/m1 occlusal relationship and probably represents the primitive occlusal condition in 'haramiyidans'. The occlusal mode of shenshouids resembles the multituberculate M2/m2 occlusion. The double‐engaged mode in Arboroharamiya and Vilevolodon, as well as that of Eleutherodon, represents a more advanced occlusal pattern. The diverse dental occlusions suggest diverse diet adaptations and resource partitioning from co‐existing taxa in the Jurassic forests; they also reflect mosaic evolutionary transformations and complicated phylogenetic relationships within the group. Some aspects of the dental evolution remain challenging and require further vigorous testing. [ABSTRACT FROM AUTHOR]

Worn dentition, often accompanied by occlusion changes such as reduced vertical dimension, poses a big challenge to both diagnosis and treatment. Current established causes fail to explain the observed tooth wearing patterns, and the treatments based on the documented pathogeneses are often unpredictable and require frequent maintenance. From the perspective of stomatognathic system, we postulate that the role of maxillo-mandibular relation is a crucial part in the tooth wear progression patterns, and should be well addressed in treatment planning. Incompatible occlusion with the inherent tendency of maxillo-mandibular relation has a profound effect on either wearing of natural teeth or failures of restorations. With the aid of cephalometrics and analysis of occlusion it is now possible to reduce this fallacy and achieve a harmony by re-designing the occlusion. According to our treated worn dentition cases, the restoring treatment guided by the tendency of maxillo-mandibular relation showed very promising results. [ABSTRACT FROM AUTHOR]

This study investigated the prevalence, risk factors and association of occlusive wear with non-carious cervical lesions ( NCCLs) in the general Chinese population. A total of 1320 subjects were recruited, and multistage and random sampling methods of survey spots were performed. All age groups comprised similar numbers of participants and equal numbers of males and females. Each subject completed a structured interview, and all teeth of each subject were examined by a practitioner to determine NCCLs and occlusive wear. Binary logistic regression was conducted by analysing the association of risk factors with the occurrence of NCCLs. Bivariate correlation analysis was performed by determining the association of NCCLs dimension or depth with the range of occlusive wear facets. Clinical assessment showed that the overall prevalence of subjects diagnosed with NCCLs was 63%. The proportion of subjects or teeth with NCCLs significantly increased with age. Pre-molars were the most commonly affected teeth. Single variables and interactive effects of variables associated with the occurrence of NCCLs include the following: age group, intensity of toothbrushing, frequency of fresh fruit consumption and interactive effect between intensity of toothbrushing and frequency of fresh fruit consumption. A weak positive correlation of the grading index was found between NCCLs dimension, size or depth and range of occlusive wear facets. This study reported the higher prevalence of NCCLs in the general Chinese population. Implementation of a combined strategy to reduce risk factors of NCCLs could be more effective than individual techniques; meanwhile, the occurrence of NCCL could be related to the wear degree of occlusive defects in the population studied. [ABSTRACT FROM AUTHOR]

Treatment outcomes of Angle Class II subdivision malocclusions may be compromised because of the uncertainty of the aetiology. Previous studies have reported controversial ideas about the origins, but the existence of a primary contributor still remains unknown. Functional factors have been mentioned as a probable cause, but until now, there have been no supporting data. This study was a cross-sectional investigation of the characteristics of Angle Class II subdivision malocclusion, including dental, skeletal and functional factors, by comparison of the subdivision group and the normal occlusion group. The evaluations of dental and skeletal asymmetries of both groups were carried out by cone-beam computed tomography ( CBCT) and analysis of dental casts. The functional deviations were evaluated by cast mounting and measuring. In the subdivision group, the asymmetric position of the glenoid fossa was found to be the most significant skeletal asymmetry. No dentoalveolar asymmetry was found in this group. The most important finding was that, in subdivision malocclusions, functional deviation resulting in pseudoasymmetry occurred in 32·86% of the study participants. This deviation is probably related to the disharmonious arch width between maxillary and mandibular dental arches in the premolar section. The origin of Angle Class II subdivision malocclusion is multifactorial, with dental, skeletal and functional factors included. Functional deviation occurs, probably due to dental arch width disharmony. Asymmetric position of the glenoid fossa may account for most of the skeletal asymmetry. [ABSTRACT FROM AUTHOR]

The purpose of this study is to examine the relationship between molar intrusion efficiency and bone density in patients with different vertical facial morphology. Thirty-six female patients, with overerupted upper first molars, were divided into two groups according to mandiblular plane angle ( FH- MP): hyperdivergent, FH- MP>30° (G1), hypodivergent, FH- MP<22° (G2). Mini-screw implants with elastic chains were used to intrude upper first molars. Spiral CT was used to measure the intrusion degree of upper first molar and bone density, and molar intrusion efficiency was calculated as amount/duration (mm month−1). In addition, each tooth was divided into three portions (cervical, furcation and apical) to measure the bone density. It was found in this study that treatment duration was 3·13 and 4·71 months in G1 and G2 and that the intrusion efficiency was 1·57 and 0·81 in G1 and G2 with significant difference ( P < 0·05). There were significant differences in cervical, furcation and apical bone density between two groups ( P < 0·05). The bone density was significantly reduced after molar intrusion. In addition, the bone density change was greater in G1 than in G2 ( P < 0·05). It was concluded that molars were more easily to be intruded in hyperdivergent than in hypodivergent patients. The difference of bone density and bone density changes during intrusion may account for the variation of molar intrusion efficiency. [ABSTRACT FROM AUTHOR]

To assess associations between occlusal tooth wear and shortened dental arches ( SDA) in Chinese 40 years and older subjects. From a sample of 1462 urban and rural adults, those presenting with SDA ( n = 150) were compared with a control group of 65 randomly selected subjects with complete dentitions ( CDA). Occlusal wear was assessed using a modified Smith and Knight index - the occlusal tooth wear index ( OWTI) - and analysed using multivariate (logistic) regression. There was no significant effect from SDA on severe occlusal wear ( OTWI score 3 or 4: OR = 2·016; 95% CI = 0·960-4·231; P = 0·064). Higher age was associated with severe occlusal wear ( P values ≤0·007) and with higher mean OTWI scores; urban had less often severe occlusal wear than rural residents ( OR = 0·519; P = 0·008). Higher mean OTWI scores were associated with rural residents, except for anterior teeth. Females had lower mean OTWI score for anterior teeth (effect = −0·153; P = 0·030). Premolars in SDA had higher mean OTWI scores compared with those in CDA (effect = +0·213; P = 0·006). In SDA, more posterior occluding pairs ( POPs) were associated with lower mean OTWI sores for anterior teeth (effect: −0·158; P = 0·008) and higher scores for molars (effect: +0·249, P = 0·003). Subjects with SDA or CDA presented comparable occlusal wear, but premolars in SDA tend to have higher probability for having occlusal wear. Fewer numbers of POPs were associated with more wear in anterior teeth. [ABSTRACT FROM AUTHOR]

PURPOSE: To obtain the reference value of centrographic analysis of Shanghai adults with normal occlusion. METHODS: Seventy five subjects of Han nationality at permanent dentition with normal occlusion were selected from Shanghai region (34 males, 41 females, age rang:18-21 years). Centrographic analysis was conducted on the basis of the lateral cephalograms, and the obtained data was compared with that of Caucasian. SAS9.2 software package was used for statistical analysis. RESULTS: The reference value of centrographic analysis in Shanghai adults with normal occlusion was established. The facial centroid was located on the Ba-A plane; the upper centroid was positioned on the centroid plane; the lower centroid was positioned anterior to the centroid plane within 0.92~1.29mm; the long axis of lower incisor was positioned posterior to 1/3 Ba-Gn plane symphysis intersection; the long axis of upper incisor was positioned posterior to orbitale and the upper incisor was positioned in proper occlusion with the lower incisor. The lips were positioned on the outer profile plane. There was no significant difference between male and female adults (P>0.05). CONCLUSIONS: Compared with that of Caucasians, mandibular position of adults in Shanghai was in a relative forward position, the incisor was labially inclined and the soft tissue in the lower 1/3 of the face was convex slightly. [ABSTRACT FROM AUTHOR]

Objective: To test the null hypothesis that there is no effect of maxillary incisor labiolingual inclination and anteroposterior (AP) position on smiling profile esthetics in young adult females. Materials and Methods: A facial smiling profile photograph of a Chinese woman with a normal profile, a Class I occlusion, and a Class I skeletal pattern was digitized. The digital image was modified to obtain four series comprising 29 smiling profiles. The sample of individuals rating these pictures comprised 21 orthodontic professionals and 66 undergraduates. Post hoc tests were done with the Student Newman Keuls method to analyze the data. Results: Significant differences (P < .001) were detected when each photograph's ratings were compared. The smiling profile with the highest score was the one with 5° lingual inclination, while the ones with 15° labial inclination or 4-mm retrusion had lower scores than the others. Maxillary incisor protrusion and lingual inclination were preferable compared with retruded or flared incisors. There was no significant discrepancy between the professional and nonprofessional groups in terms of their assessments. Conclusions: The hypothesis is rejected. Both maxillary incisor labiolingual inclination and AP position play an essential role in the esthetics of the smiling profile. However, when formulating treatment plans, dentists should never underestimate the labiolingual inclination's influence on the smiling profile. [ABSTRACT FROM AUTHOR]

PURPOSE: The aim of this study is to evaluate the vertical relationship of maxilla and mandible with overbite depth indicator (ODI) in order to help diagnose and treat skeletal Class III malocclusion. METHODS: 100 adults and adolescents were divided into 5 groups according to age and occlusion. It consisted of 20 eases of adult normal occlusion, 20 youngster normal occlusion, 28 adult skeletal Class III malocclusion, 24 early skeletal Class III malocclusion, 8 early skeletal Class III malocclusion with treatment failure. Cephalometrie analysis was taken on lateral cephalograms including FH-PP, MP-AB, ODI. The data were analysed with SAS6.12 software package for grouped t test. RESULTS: The mean value of ODI in normal occlusion was above 70°. The average value of Class III malocclusion was less than 63°. All measurements in teenager were lower than those in adult. Severe malocclusions who need surgical treatment showed lower ODI value less than 53°. ODI displayed significant difference between groups, P<0.001. CONCLUSIONS: There is high correlation between ODI and severity of malocclusion. The results of this study demonstrate that ODI is an efficient index for evaluation of the vertical position of the skeletal Class III malocclusion. Supported by Shanghai Leading Academic Discipline Project (Grant No.Y0203). [ABSTRACT FROM AUTHOR]

PURPOSE: The purpose of this study is to investigate the outcome and stability of combined surgical anti orthodontic treatment of severe maxillary anterior teeth and dentoalveolar bone protrusion. METHODS: Twenty-eight adults with severe bimaxillary protrusion were included. Presurgical orthodontic treatment coordinated axis of upper anteriors and dentoalveolar bone. Maxilla was impacted and set back by Le Fort I osteotomy and maxillary anterior segmental osteotomy, while upper anteriors and dentoalveolar bone were uprighted and retracted. Post-surgical orthedontic treatment detailed the occlusion. Each patient underwent X ray examination at five time points including pre-treatment, pre-surgery, one month after surgery, three months after surgery and post-treatment. Hard tissue and soft tissue changes were investigated by cephalometric analysis. The data were analyzed by paired t tests with SPSS12.0 software package. RESULTS: It was observed that upper anteriors were uprighted and retracted (11.77±9.9)° (P<0.001) after treatment while dentoalveolar bone was uprighted (6.24±3.9)°(P<0.001). UI-LI angle increased (19.4±8.6)°(P<0.001), UI-Apog distance decreased (6.62±2.2)mm (P<0.001). The thickness of alveolus on anterior teeth labial side showed no change (P>0.05). The treatment outcome demonstrated a significant improvement in soft tissue profile. Nasolabial angle increased (11.06±11.8)° (P<0.001), upper and lower lips moved backword, and pog' moved forward. Most measurements showed no significant difference from surgery time to post treatment. CONCLUSIONS: Combined surgical and orthodontic treatment is a very effective procedure in treatment of severe maxillary anterior teeth and dentoalveolar bone protrusion and gummy smile. It remains the thickness of alveolus on anterior teeth labial side. It shows big improvement in soft tissue profile and great stability. Supported by Shanghai beading Academic Discipline Project (Grant No.Y0203). [ABSTRACT FROM AUTHOR]

PURPOSE: To investigate the size of tooth, dental arch, dental base bone and palate on normal permanent occlusion of Yizu persons in Yunnan province and characterize the morphology of tooth, dental arch and base bone of Yizu persons. METHODS: 186 normal dentognathic models of permanent dentition from healthy Yizu persons were obtained and measured. Group t test, correlation analysis and linear regression analysis were used for data analysis with SPSS12.0 software package, the data was also compared with that from different regions and nationalities. RESULTS: There were significant differences in tooth size, width of dental arch and basal bone between males and female, where those from males showed higher mean values. The size of tooth and dental dimensions from Yizu persons was bigger (P<0.05) than that from Chinese Han's persons in Yunnan province. CONCLUSIONS: The results of current investigation are of value to orthodontist on diagnosis, design and orthodontic treatment. The tooth size and dental dimensions are different between different race, region and sex. [ABSTRACT FROM AUTHOR]

The objectives of this analysis were to describe the numbers of teeth lost and those indicated for extraction, dental prosthetic status, and occluding tooth pairs among adults in Southern China and to investigate factors affecting tooth mortality. A sample consisting of 1573 35- to 44-year-old and 1515 65- to 74-year-old urban and rural Chinese was examined clinically by calibrated examiners. Teeth not present for any reason were defined as missing (MT). The sum of MT and teeth indicated for extraction (IMT) was defined as adjusted missing teeth (AMT). Only 4.4% of the urban and 3.400 of the rural 65- to 74-year-olds were edentulous. MT were not significantly different between urban and rural residents, but more IMT were found in rural residents. Women, those who had a lower education level, and those who were less wealthy had more AMT in both age groups. Smoking was found to be associated with AMT in the 35- to 44-year-olds. Eighteen percent of the urban and 27% of the rural elderly had no occluding tooth pairs after IMT were accounted for, and only 38% and 30%, respectively, had 10 or more occluding pairs. Fifty-one percent of the urban and 43% of the rural elderly were found to have some form of dental prostheses in either jaw. A partial denture was more common in urban residents in both age groups. [ABSTRACT FROM AUTHOR]

BACKGROUND Proximal contact loss (PCL) is very common between implant-fixed prostheses (IFPs) and adjacent teeth and leads to a high incidence of food impaction. Our aim was to determine if the mesio-distal adjustable (MDA) crown prostheses introduced in this study could easily establish new contacts intraorally without the intervention of prostheses retrieval. MATERIAL AND METHODS The MDA crown requires casting in the inlay framework at the proximal contact area. If PCL occurred, the resin in the inlay framework could be easily removed and refilled chairside. This single-center prospective study aimed to investigate the use of a resin inlay dental implant-fixed prosthesis for the closing proximal contact loss in 93 patients who were recruited from April 2017 to December 2017. Four patients dropped out during the 3-year follow-up; therefore, 89 patients were included. The effect of this technique was assessed by the implant mucosal status and follow-up investigations of food impaction. RESULTS PCL occurred in 29.21% (26 prostheses) of the IFPs. The PCL rate at the mesial contact surfaces (n=24, 26.97%) was significantly higher than that at the distal contact surfaces (n=5, 8.33%) (P<0.01); however, the incidence of PCL was greater at adjacent teeth with significant bone resorption (P=0.00). After readjusting the resin inlay and closing the clearance, implant mucosal status and food impaction were significantly reduced (P<0.01). CONCLUSIONS The findings of this study showed that use of the MDA crown for closing PCL was time-saving and effective with satisfactory results at 3-year follow-up.

Purpose: To study the effect of adolescent premolar scissor bite on the sagittal position of mandible and provide proper reference for correct orthodontic diagnosis and right time to treatment. METHODS： One hundred adolescents (54 females, 46 males) with scissor bite of premolars(70 were unilateral,30 were bilateral) were selected as experimental group between 2004 to 2017 from the Department of Orthodontics, Stomatological Hospital of China Medical University. Among them, 54 females served as female group, 46 males served as male group; 30 were bilateral and 70 were unilateral. Lateral cephalograms were recorded before treatment. 16 sagittal hard tissue variables on maxilla and mandible were measured cephalometrically by Winceph 9.0 software, and the cephalometric data were analyzed statistically by using SPSS 21.0 software package., Results: Compared with normal occlusion, Beta angle, SNB, SND, ANB, AB-Plane angle, APDI, convexity angle, facial angle, Wits, Co-Po showed statistically significant difference in both unilateral group and bilateral group (P<0.05). In addition, Go-Pog showed statistically significant difference between normal occlusion and unilateral group(P<0.05)., Conclusions: Adolescents with premolar scissor bite restricts the sagittal position of mandible and tend to have skeletal Ⅱ sagittal jaw relationship. Scissor bite affects the growth of mandible and makes mandibular body length and mandibular length less than normal. More attention should be paid to scissor bite as early as possible to decrease the harmful effects on growth of mandible and sagittal jaw relationship.

Purpose: To measure and analyze the teeth surfaces in 90 Chinese Han young adults with normal occlusion from one university in Shanghai, and to provide data for straight wire appliance system for Chinese patients., Methods: 90 volunteers with normal occlusion were selected from 9000 college freshmen in Shanghai，whose dental impression with normal occlusion were scanned into digital models. Crown angulation, crown inclination, buccal(labial) crown facial prominence were measured and analyzed by Smartee Ortho（A）software. SPSS 17.0 software package was used for statistical analysis., Results: The mean values of the teeth surfaces in normal occlusion were obtained, including crown angulation, crown inclination, buccal (labial) crown facial prominence. Crown angulations were leaning toward the middle line except upper second molars. Compared with west Caucasian, angulations were smaller in incisors and canines, and crown inclinations were larger in incisors and canines, especially the upper and lower canines. The upper and lower molars were inclined more to the lingual side. Crown facial prominence differences between upper first and second incisor were smaller, while the differences were larger between lower second incisor and canine, lower first and second molar., Conclusions: There are differences between Chinese and west Caucasian with normal occlusion. It is necessary to invent a kind of straight wire appliance system for Chinese patients.

Objective: To explore the influence of gender and age on the measurement of cone beam CT (CBCT) in normal and occluded craniofacial hard tissues for Han nationality in Changsha area.
 Methods: A total of 80 CBCT data of normal and occluded craniofacial hard tissues for Han nationality in Changsha area were collected, including 40 adults [16 males and 24 females, aged (17.57±1.83) years] and 40 children[16 males and 24 females, age (11.50±1.26) years]. Three-dimensional cephalometric measurements were carried out by Dolphion Imaging software, and the influence of gender and age was compared.
 Results: The symmetry of craniofacial hard tissues in male and female in the adults was good (the maximum asymmetric rate R was 6.39% and the minimum asymmetric rate R was 0.08%). There was no significant differencein the anterior palatal width, palatal width, the upper incisor protrusion distance, the lower incisor protrusion distance, hyoid-mandibular plane, basal epiglottis width, and palatal plane airway width between the males and females (all P>0.05); while the remaining indicators were significantly higher in males than those in females (all P<0.05). There was no significant gender difference in angle indicators (all P>0.05). There were significant differences in the posterior height, the maxillary length, the lower incisor protrusion, and the mandibular plane angle between the adults and the children(all P<0.05); but the rest of indicators were not significant difference (all P>0.05).
 Conclusion: The symmetry of craniofacial hard tissues for Han nationality in Changsha area is good. The gender and age affect the line space measurements but not affect the most of the angle measurements.

A calendar of meetings and courses on dentistry from March 29 to October 17, 1998 is presented, including the 4th Endodontic World Congress in Jerusalem, Israel, the 1st Chinese International Conference on Comprehensive Orthodontics in Nanjing, China, and the Designing the Esthetic Occlusion and Cultivating Natural Esthetics in Winnipeg, Manitoba.

Objective: To investigate the internal regularities and symmetry of craniofacial structures from adults with normal occlusion in North China., Methods: The study consisted of 60 volunteers who were examined with spiral 3D computed tomography (CT). The axial images of craniofacial structure were reconstructed into 3D models and analyzed by using Proplan 1.2 software to measure the internal regularities and symmetry of craniofacial structures., Results: All the linear measurement's value of the males were bigger than those of the females (P<0.05). There were no significant differences in the ratio measurements between the males and the females(P>0.05). Facial asymmetry was less than 10% in all the images., Conclusion: CT is an effective method for three-dimensional analyses of craniofacial structure and symmetry. There are certain and harmonious regularities in normal 3D craniofacial structures. The 3D craniofacial structure database of people with normal occlusion can provide standards and references for diagnosis and treatment planning of craniofacial deformities.

Purpose: To assess the relationships between occlusal tooth wear and occlusal conditions, chewing side preference, and occlusal guidance scheme., Materials and Methods: A total of 257 Chinese adult dental school patients were categorized according to a hierarchical functional classification system. Occlusal tooth wear was assessed using a modified Smith and Knight index. Occlusal tooth wear index (OTWI) scores were analyzed using multivariate regression models, including four specific occlusal conditions (≥10 teeth in each arch, complete anterior regions, sufficient premolar regions, and sufficient molar regions) adjusted for age and sex., Results: Occlusal tooth wear was observed in all participants; older participants and men had significantly higher mean OTWI scores. The occlusal condition of having fewer than 10 teeth in each arch was significantly associated with occlusal tooth wear; participants with fewer than 10 teeth in each arch had higher mean OTWI scores in anterior and premolar teeth. OTWI scores for the different tooth types were highly correlated with chewing side preference. OTWI scores for the molar region (including third molars) were significantly higher at the preferred chewing side. The same effect was seen for OTWI scores of all teeth combined. OTWI scores were not associated with occlusal guidance scheme., Conclusions: The occlusal condition of having fewer than 10 teeth in each arch appears to be a risk factor for increased occlusal tooth wear. Occlusal wear was more severe at the chewing side. Occlusal tooth wear was significantly associated with the nondental factors of age and sex.

Objective: To evaluate the impact of the incisor position on the self-perceived psychosocial impacts of malocclusion among Chinese young adults., Materials and Methods: This cross-sectional study included a convenience sample of 17.1- to 22.3-year-old young adults (n = 1005). The five groups represented were normal occlusion as well as incisor Class I, Class II/1, Class II/2, and Class III malocclusion. For clinical assessment, the incisor relationship was evaluated according to the British Standards Institute Incisor Classification, and the self-perception of dental esthetics was assessed using the Psychosocial Impact of Dental Aesthetics Questionnaire (PIDAQ). Statistical analysis involved the analysis of variance and Tukey multiple-comparison post hoc tests., Results: Psychosocial impacts were different among the five groups for the four PIDAQ domains (P < .001 for all four domains). Statistically significant differences were found between the four malocclusion groups and the normal occlusion group in all four domains (P < .001 for all four domains). Furthermore, statistically significant differences were found between four malocclusion groups., Conclusions: All four malocclusion groups had more severe psychosocial impacts than the normal occlusion group in the four PIDAQ domains. Statistically significant differences were also found between the four malocclusion groups; these malocclusion groups ranked by score, highest to lowest, were Class III, Class II/1, Class II/2, and Class I.

Purpose: To obtain the reference value of centrographic analysis of Shanghai adults with normal occlusion., Methods: Seventy five subjects of Han nationality at permanent dentition with normal occlusion were selected from Shanghai region (34 males, 41 females, age rang:18-21 years). Centrographic analysis was conducted on the basis of the lateral cephalograms, and the obtained data was compared with that of Caucasian. SAS9.2 software package was used for statistical analysis., Results: The reference value of centrographic analysis in Shanghai adults with normal occlusion was established. The facial centroid was located on the Ba-A plane; the upper centroid was positioned on the centroid plane; the lower centroid was positioned anterior to the centroid plane within 0.92-1.29mm; the long axis of lower incisor was positioned posterior to 1/3 Ba-Gn plane symphysis intersection; the long axis of upper incisor was positioned posterior to orbitale and the upper incisor was positioned in proper occlusion with the lower incisor. The lips were positioned on the outer profile plane. There was no significant difference between male and female adults (P>0.05)., Conclusions: Compared with that of Caucasians, mandibular position of adults in Shanghai was in a relative forward position, the incisor was labially inclined and the soft tissue in the lower 1/3 of the face was convex slightly.

Aim: To compare the dentofacial characteristics of southern and northern Chinese adolescents., Methods: A southern Chinese sample comprised 70 males (Mean age 12.4 +/- 0.60 years) and 60 females (Mean age 12.5 +/- 0.4 years), and a northern Chinese sample consisted of 50 males (Mean age 12.8 +/- 1.8 years) and 50 females (Mean age 12.4 +/- 1.2 years). All subjects had a Class I molar relationship with no or minimal crowding, a well balanced cephalometric profile, and no history of orthodontic treatment. Patient cephalograms were traced and digitized and McNamara's analysis applied., Results: A smaller midface and a shorter overall mandibular length were observed in southern Chinese, whereas significantly increased vertical dimension and a retrusive chin were noted in northern Chinese. Protrusive upper and lower incisors and a protrusive upper lip were found in southern Chinese., Conclusions: There were significant differences in dentofacial morphology between southern and northern Chinese adolescents. It is suggested that separate cephalometric norms be used for patients originating from different parts of China.

Purpose: The aim of this study was to investigate the occlusion, the demand for orthodontic treatment and the reasons for this among Chinese young adults in Hong Kong., Materials and Methods: A questionnaire was used to study previous orthodontic experience and to evaluate the orthodontic treatment demand and the reasons for this in Chinese university students. Among those who had no orthodontic treatment, 120 participants were invited for an occlusal assessment. Their treatment need was graded using the index of orthodontic treatment need., Results: A total of 240 students, aged 18 to 27 years, completed the questionnaire survey. Thirty-one students (13%) had orthodontic treatment. Sixty-seven (28%) students had orthodontic treatment demand, and their common reasons were to improve appearance (78%), self-image (36%), self-confidence (34%) as well as to follow parental advice (24%). The reasons for those students who would not consider having orthodontic treatment included no perceived need (64%), long treatment time (18%) and high treatment fee (14%). All 120 invited participants who had no orthodontic treatment attended the occlusal assessment. One-fifth had a normal occlusion. Most malocclusions were manifested as Angle Class I (48%) followed by Class III (21%) malocclusion. Fifty-six students (47%) had moderate and 40 students (33%) had 'great' or 'extremely great' treatment need., Conclusions: The most prevalent malocclusion among this group of Chinese young adults was Angle Class I malocclusion. Although the majority of the Chinese young adults had malocclusion with a high treatment need, their demand for orthodontic treatment was relatively low. Apart from consideration of dental health needs, the common reasons for orthodontic treatment demand were influenced by the desire for improvement in appearance.

Purpose: To investigate the size of tooth, dental arch, dental base bone and palate on normal permanent occlusion of Yizu persons in Yunnan province and characterize the morphology of tooth, dental arch and base bone of Yizu persons., Methods: 186 normal dentognathic models of permanent dentition from healthy Yizu persons were obtained and measured. Group t test, correlation analysis and linear regression analysis were used for data analysis with SPSS12.0 software package, the data was also compared with that from different regions and nationalities., Results: There were significant differences in tooth size, width of dental arch and basal bone between males and female, where those from males showed higher mean values. The size of tooth and dental dimensions from Yizu persons was bigger (P<0.05) than that from Chinese Han's persons in Yunnan province., Conclusions: The results of current investigation are of value to orthodontist on diagnosis, design and orthodontic treatment. The tooth size and dental dimensions are different between different race, region and sex.

This study investigated the relationship between clinical dental status and eating difficulty in a sample of older Chinese people in Guangxi, China. Sample was selected from people aged 55 years and older who had routine annual health check-ups at a large hospital health centre. The sample consisted of 1,196 dentate people who had clinical oral examinations and face-to-face interviews. Different measures, namely the Index of Eating Difficulty, dissatisfaction with chewing ability and ease of eating certain foods were used to measure eating difficulty. Multiple logistic regression analysis showed that after controlling for the effects of age, sex, occupation, self-assessed social class and self-perceived general health, increased eating difficulty was significantly related with having fewer teeth, fewer posterior and anterior occluding pairs of teeth (both natural teeth only and natural plus replaced teeth), more unfilled posterior spaces, more unfilled anterior spaces, mobile teeth, decayed teeth and roots. In conclusion, clinical dental status was strongly related with eating difficulty in a sample of older Chinese dentate people.

The objective of this study was to evaluate long-term dentofacial changes in Chinese obstructive sleep apnea (OSA) patients treated with a mandibular advancement device (MAD). Lateral cephalograms in natural head posture were obtained from 67 consecutive OSA patients (mean age = 46.9 +/- 8.9 years) treated with an MAD. The cephalograms were obtained at start of treatment (T0), after 1 year (T1), 2 years (T2), and 3 years (T3) of treatment. The lateral cephalograms were digitized twice, and the average of two readings was used for statistical analyses. Small, but statistically significant changes occurred in some dentofacial variables. The lower anterior facial height steadily increased during the observation period, and this increase was significant for the T0-T1 and T1-T2 periods and marginally significant for the T2-T3 period. A significant increase in the mandibular plane angle was observed during the T0-T1 and T2-T3 periods only. Significant reductions in the overjet and overbite were observed for the T0-T1 period but not thereafter. Statistically significant dentofacial changes were observed in this study, but they were of small magnitude. The overjet and overbite changes observed mainly occurred at the initial stage of treatment.

Objective: To reveal malocclusion of primary dentition in the suburb of Chengdu., Methods: Cross-section survey and malocclusion rate calculation were performed., Results: There are 491 children with malocclusion from total 1 279 children; the rate of malocclusion is 38.38%. The most important malocclusion in primary dentition are over bite (III degrees), anterior cross bite, edge to edge bite, early loss of deciduous teeth, fused teeth., Conclusion: The rate of malocclusion of primary dentition in the suburb of Chengdu is a little bit light. Much work should be done to prevent or treat the malocclusion of primary dentition.

Objective: The purpose of this study was to obtain the normal value of McNamura analysis for Chengdu adolescents with normal occlusion of early permanent dentition., Methods: McNamara analysis was conducted on the basis of the lateral cephalograms of 67 Chengdu adolescents with normal occlusions, and the obtained data was compared with that of Shanghai adolescents and McNamara., Results: There was no difference in the normal value of McNamara analysis between male and female Chengdu adolescents. The Comparative results between Chengdu and Shanghai adolescents indicated significantly larger values of Shanghai adolescents in effective middle facial lengths, mandibular lengths and lower anterior facial heights. The vertical distances from the upper incisor to point A and, from the lower incisor to A-Po line of Chengdu adolescents were larger than those of white adolescents., Conclusion: There is significantly difference in values of normal occlusions of McNamara analysis among different regions and different races.

Exostoses on the mandible and maxilla is a frequently observed bone growth of controversial aetiology. The aim of this study is to analyse environmental factors that may stimulate the formation of exostoses on different regions of the maxilla and mandible. Sixty-six well-preserved crania from Neolithic China were studied for the presence of buccal exostoses on the maxilla (BE) and lingual exostoses on the mandible (LME). Other oral health indicators, such as occlusal wear on molars, pathology of temporomandibular joint (TMJ), carious lesions, calculus accretion, periodontal disease, and antemortem tooth loss were recorded. Buccal maxillary exostosis was unusually common on the Neolithic skulls from China, which thus resemble the Sinantropus crania described by Weidenreich (1943). We report a significant Spearman correlation between BE and LME (rho = 0.54, P < 0.00001), suggesting a partially shared aetiology of these two types of exostoses. The highest correlations between either form of exostoses and any oral indicator of stress were found for pathology at TMJ (rho = 0.46, P < 0.0001 for both types of exostoses). Smaller but significant correlations were observed between LME and the age adjusted wear rate on lower molars, as well as between BE and indicators of oral/dental pathology, e.g. caries, calculus, periodontoses, and antemortem tooth loss. Both types of exostoses tended to increase in frequency with age, although a significant trend was observed only for BE. We conclude that formation of exostoses is a complex process that can be invoked by any agent causing damage and inflammation of gingival tissue. However, severe occlusal stress, which is often manifested in TMJ disorder, is the main environmental factor leading to exostosis development in genetically pre-disposed individuals.

In this paper we discuss diet and health changes of millet agriculturists in Northern China, Shaanxi province, during the period 7,000-4,000 BP. An episode of intensive climatic oscillations that preceded the onset of colder climate circa the fifth millennium BP divides the period (Shi et al. [1993] Global Planet. Change 7:219-233). The onset of the cooler climate marks the decline of the egalitarian society of Yangshao and the rise of the chiefdom-like society of Longshan. Skeletal materials from the two sites of Beiliu and Jiangzhai are from the earlier phases of Yangshao culture (7,000-6,000 BP), while remains from the Shijia site were excavated from the terminal phase of Yangshao culture (6,000-5,000 BP), a phase that would be expected to show adjustments to strong climatic fluctuations. Human remains from the Longshan culture (5,000-4,000, BP) were found at the Kangjia site. In order to investigate whether the trajectory of diet and health changes persisted beyond the Longshan, a skeletal sample from the Xicun site of the Western Zhao Dynastic period (3,800-2,200 BP) is included in our analyses. All Yangshao sites in our study are characterized by low frequencies of anemia and carious lesions. Some subsistence changes probably occurred during the later phase of Yangshao culture that resulted in elevated masticatory stress and occlusal macrowear among the Shijia people. However, deterioration of community health did not begin until the Longshan, when increased occurrence of porotic hyperostosis and caries is accompanied by decreased adult stature. The transition to softer, more extensively processed food during Longshan is evident in decreased rates of occlusal wear. Increased population density and diminished food values were most likely responsible for these changes. Poor health persisted into the subsequent Dynastic period of Western Zhao., (Copyright 2002 Wiley-Liss, Inc.)

This investigation utilized a manipulated digital video imaging model to elicit profile facial esthetics preferences in a lay population of native Chinese participants from Beijing. A series of 4 distinct digitized distortions were constructed from an initial lateral cephalogram. These images represented skeletal or dental changes that differed by 2 standard deviations from the normative values for Chinese adults. Video morphing then created soft-tissue profiles. A series of nonparametric tests validated the digitized distortion model. The native Chinese participants in this sample found that the profile distortions most acceptable were the "flatter", or bimaxillary retrusive distortion, in the male stimulus face and the "anterior divergent", or maxillary deficiency, in the female stimulus face.

Objective: To study the intrinsic compensative mechanism of craniofacial soft and hard tissue structures of Uygur adults with normal occlusion and establish standard cephalometric values to evaluate craniofacial soft and hard tissue structures of normal Uygur adults., Methods: Lateral cephalometric radiographs of 93 Uygur adults with normal occlusion (43 men and 50 women) were evaluated with the same standard. Their age ranged from 18 to 25 years old, and they had normal and well-balanced faces without receiving any orthodontic treatment. Based on the study of craniofacial soft and hard tissue structures with normal occlusion, the horizontal tendency, the vertical tendency pattern and the medial pattern of craniofacial soft and hard tissue structures were compared, and the intrinsic compensative mechanism in the inner structures of the horizontal and the vertical tendency patterns was investigated. Finally 21 indexes were analysed by mean squar deviation and Newman-Keuls test., Results: The obvious compensative changes in the horizontal and vertical tendency patterns were found in teeth, skeleton and soft-tissues. 1. When the horizontal tendency was compared with the medial pattern, the value of ODI and angles of FH-NA and FH-NB increased (P < 0.01), while the angle of SN-PP decreased (P < 0.01). It showed that the anterior maxilla rotated in the counter-clockwise direction, and the anterior mandible rotated in the clockwise direction. The angle of U1-L1 increased (P < 0.01), which meant that the inclination of anterior teeth decreased. 2. When the vertical tendency was compared with the medial pattern, the value of ODI decreased (P < 0.01), while the height of ANS-Me, U1-PP, L1-MP, and the thickness of LL-SnPg increased (P < 0.01); The angle of L1-MP decreased (P < 0.05), while the length of Sn-Stms increased (P < 0.05). These results showed that there was an obvious positive relationship between hard and soft tissues. The soft tissue thickness could compensate the changes of hard tissues to keep the facial patterns harmony., Conclusion: Normal occlusion depends on the homeostasis of teeth, skeleton and soft tissues, but doesn't only depend on the normal craniofacial soft and hard tissue structures respectively. The intrinsic compensative mechanism plays an important role in forming normal occlusion, therefore, doctors should choose the best treatment to obtain optimal individual intrinsic compensative mechanism and achieve an optimal balance between the craniofacial structures and the occlusion.

Objective: To study craniofacial structures of Uygur adults with normal occlusion and establish the standard cephalometric values to evaluate the craniofacial soft and hard tissue structures of normal Uygur adults., Methods: Lateral cephalometric radiographs of 93 Uygur adults with normal occlusion (43 men and 50 women) were evaluated with the same standard. Their age ranged from 18 to 25 years old, and they had normal and well-balanced faces without receiving any orthodontical treatment. The lateral cephalogram of each normal adult was traced digitized and measured by the same computer system, then the indexes of craniofacial structures were analyzed by multifactor cluster analysis. 18 typical items were chosen to analyze the characters of the craniofacial structures of Uygur adults with normal occlusion. At the same time, Bayers discriminant analysis was used to identify and evaluate the cluster results., Results: Uygur adults with normal occlusion were divided into three patterns according to the multifactor cluster analytic results: horizontal tendency pattern (40%), medial pattern (43%) and vertical tendency pattern (17%). When the horizontal tendency pattern was compared with the medial pattern, it showed that the height of S-Go increased (P < 0.05), while the height of ANS-Xi-Pm decreased (P < 0.05); The proportion of S-Go/N-Me increased (P < 0.01). The angle of Ar-Go-Me and Y axis decreased (P < 0.05), which meant that the mandible rotated in the counter-clockwise direction. SN-MP, PP-MP, OP-MP, MP-FH all decreased (P < 0.01), which meant that the SN plane, the PP plane, the occlusion plane and the MP plane all had the trend of hypodivergence. When the vertical tendency pattern was compared with the medial pattern, the height of Ar-Fo decreased (P < 0.01), while the height of ANS-Me increased (P < 0.01); The angle of Ar-Go-Me, Y axis, SN-MP, PP-MP, OP-MP and MP-FH all increased (P < 0.01). These results showed that the mandible rotated in the clockwise direction and the SN plane, the PP plane, the occlusion plane, and the MP plane all had the trend of hyperdivergence. At last, according to the different skeletal patterns, the normal cephalometric values of Uygur adults with normal occlusion were established., Conclusion: Significantly craniofacial structure difference exist in the adults with normal occlusion. Therefore, it is necessary to establish the normal cephalometric values of Uygur adults with normal occlusion according to different skeletal patterns.

The Dental Aesthetic Index (DAI) is an orthodontic index based on socially defined aesthetic standards. The primary aim of this study was to compare the prevalence of malocclusion using the DAI among three ethnic groups of Asian origin; Japanese, Chinese in Taiwan and Native Americans with white Americans. A secondary goal was to consider the possibility that genetic factors might be the cause of the characteristics of malocclusion in the ethnic groups of Asian origin. Malocclusion was evaluated in 1029 Japanese and 176 Chinese in Taiwan students utilising the DAI, and the findings were compared with those of Native Americans and white Americans. The DAI values of Japanese and Native Americans were significantly higher than those of Chinese in Taiwan and white Americans. The mean DAI values showed no common tendency among the three ethnic groups. The characteristics of malocclusion in each ethnic group were also evaluated by analysis of each of the 10 DAI component scores. The results revealed common characteristics of malocclusion in the three ethnic groups of Asian origin using white Americans as the standard. The findings in the present study suggest the possibility that genetic factors might have an influence on the characteristics of malocclusion.

Cleft lip and palate patients often develop maxillary retrusion after cleft repair. Maxillary protraction treatment during early childhood helps to achieve more favorable occlusion with positive overjet and overbite and allows a more normal growth pattern to occur. The purpose of this study was to investigate the skeletal and dental changes during reverse headgear treatment in a homogeneous group, i.e., Chinese boys born with unilateral complete cleft lip and palate. The results showed that after 7.8 months of reverse headgear wear, normalization of the sagittal maxillomandibular relationship (ANB angle) was achieved. Significant skeletal changes included anterior position of the maxilla and posterior position of the mandible. Dental changes within the respective skeletal units were not significant except for the mandibular molar.

The aim of this study was to investigate the prevalence of temporomandibular joint dysfunction (TMJD) in Chinese children and adolescents, and the relationship between TMJD and type of occlusion. The sample consisted of 3105 Chinese children, 3-19 years of age, divided into four groups by the stage of dental maturation. The prevalence of TMJD for the entir group was 17.9 per cent and there was no significant sex difference. TMJD increased in the mixed and early permanent dentitions, but decreased in the permanent and deciduous dentitions. In the subjects with TMJD, the most common sign was sound (87.7 per cent), followed by abnormal jaw movement (23.6 per cent), but pain was registered in 0.6 per cent only. A single sign was registered in 88.5 per cent, a combination of sound and abnormal jaw movement in 11.0 per cent, and combinations of other signs in less than 1.0 per cent. Sound as a single sign increased with the specific stages of dental development (P < 0.001).

The Standard DAI is an orthodontic index based on perceptions of dental aesthetics in the USA. The Standard DAI is a regression equation linking perceptions of the social acceptability of dental aesthetics with the objective intraoral measurements of ten occlusal traits. Since the Standard DAI is based on perceptions of dental aesthetics in the USA it can be used without modification only where perceptions of dental aesthetics are similar to those in the USA. This study was designed to determine whether perceptions of dental aesthetics of students in eleven diverse ethnic groups are similar to those of students in the USA. The same 25 stimuli (photographs of dental configurations, a subset of the 200 stimuli used in deriving the Standard DAI equation) were rated for dental aesthetics by Australian, Chinese, German, Japanese, Korean, Latvian, Native American, Singaporean Chinese, Singaporean Indian, Singaporean Malay, and Thai students. Their ratings were compared with the ratings of the same 25 stimuli by students in the USA. Spearman rank-order correlations ranged from 0.84 to 0.94. These correlations are sufficiently high to show that perceptions of dental aesthetics in all eleven ethnic groups are very similar to the perceptions of USA students. Therefore the Standard DAI can be used without modification in all eleven ethnic groups.

The molar relations, overjet and overbite of 201 Hong Kong Chinese adults of mean age 20 years were studied. It was found that 63.7 per cent had Angle Class I, 16.4 per cent had Class II and 19.9 per cent had Class III molar relations. Of the sample studied, 69.7 per cent had normal overjets of two to four mm, 14.9 per cent had increased overjets and 15.4 per cent had reduced or reversed overjets. The most prevalent overbite was zero to one-third of the mandibular central incisor crown length (63.2 per cent of the sample); 31.3 per cent had overbites of one to two thirds of mandibular central incisor crown length; four per cent had overbites of more than two thirds of mandibular incisor crown length; and 1.5 per cent only had open bites.

The Standard DAI is an orthodontic index based on public perceptions of dental aesthetics in the USA and is a regression equation linking the relative social acceptability of dental appearance and the objective, physical measurements of ten occlusal traits. It can be used in surveys of need for orthodontic treatment and as a screening tool in public programmes providing orthodontic care. To determine if the Standard DAI could be used internationally, 200 stimuli (photographs of dental configurations) were rated for dental aesthetics by 413 Chinese students, 418 Latvian students and 428 Native Americans. To develop ethnic group-specific DAI equations these ratings were linked by regression procedures to the occlusal trait measurements available for each of the 200 stimuli. Using these equations, group-specific DAI scores were calculated for the 200 stimuli. At all levels on the DAI scale the percentage agreements, sensitivities and specificities ranged from 73 to 100 per cent indicating that the Standard DA can be used without modification to calculate DAI scores among Chinese, Latvians and Native Americans.

The prevalence of malocclusion and treatment need amongst young Chinese adults has not previously been documented in Hong Kong. One-hundred-and-eight Chinese male first year dental students were assessed using the Occlusal Index. It was found that 41.7 per cent of the 108 needed orthodontic treatment and 24.1 per cent needed comprehensive orthodontic treatment to correct major malocclusions. The most commonly occurring feature was crowding (38.9 per cent), followed by Class II malocclusion (21.3 per cent), and Class III malocclusion (14.8 per cent).