[Histological changes in the circum-maxillary sutures during alternate maxillary expansions and constrictions in a rat model].

OBJECTIVE: To investigate changes in the circum-maxillary sutures during alternate maxillary expansions and constrictions in a rat model. METHODS: Twenty-two male Sprague-Dawley rats (6 weeks old) were used and divided into three groups. In maxillary expansion (ME) group (n=9), an expander was activated for 5 d, and then sacrificed. In alternate maxillary expansions and constrictions (Alt-MEC) group (9 animals), an alternate expansion and constriction protocol (5 d expansion and 5 d constriction for one cycle) was conducted for 2.5 cycles (25 d total), and then sacrificed. The control group comprised 4 animals with no appliances used, each of two sacrificed on day 5 and day 25, respectively. Circum-maxillary sutures (mid-palatal, maxillopalatine, premaxillary, zygomaticotemporal, and frontonasal suture) in each group were characterized histologically. RESULTS: Histological findings of circum-maxillary sutures: in control group, the normal sutures were divided into 5 zones, the center was polygon mesenchyme zone, the lateral was mature chondrocyte zone, the next lateral was bone tissue. In ME group, the mid-palatal suture was expanded after ME, the fibre and connective tissue were extracted and invaded into cartilage zone. Osteoblast hyperplasia and new bone formation occurred. The orientation of the new bone trabecula was consistent with force. The osteoclast appeared in some area. Findings of other sutures were similar with those of control group, osteogenesis was active in some area without obvious reconstruction in Alt-MEC group, mid-palatal suture and other sutures in some area were widened after Alt-MEC with much more osteoblast hyperplasia and new bone formation. Fibre and connective tissue were extracted, distorted or even broken. Sutures in some areas were narrowed with osteoblast cytopenia and osteoclast hyperplasia. Fibre and connective tissue compressed because of the different force and orientation. Osteoclast count results showed that compared with the control group, the number of the osteoclast was increased only in the palatal suture in ME group (P<0.05). Other sutures did not show obvious changes (P>0.05). In Alt-MEC group, the numbers of the osteoclast in circum-maxillary sutures were the most, and had statistical significances (P<0.05). CONCLUSION: These RESULTS suggested that circum -maxillary sutures were actively reconstructed after Alt-MEC. while only midpalatal suture had active reaction after ME.

Comparative characterization of maxillary expansion and alternate maxillary expansions and constrictions in rats.

The purpose of this study was to evaluate whether the cranial and circumaxillary sutures react differently to maxillary expansion (ME) and alternate maxillary expansions and constrictions (Alt-MEC) in a rat model. Twenty-two male Sprague-Dawley rats (6 weeks old) were used and divided into three groups. In ME group (n=9), an expander was activated for 5 days. In Alt-MEC group (9 animals), an alternate expansion and constriction protocol (5-day expansion and 5-day constriction for one cycle) was conducted for 2.5 cycles (25 days total). The control group comprised 4 animals with no appliances used, each of two sacrificed on day 5 and day 25 respectively. Midpalatal suture expansion or constriction levels were assessed qualitatively and quantitatively by bite-wing X-rays and cast models. Distances between two central incisors and two maxillary first molars were measured on cast models after each activation. Circumaxillary sutures (midpalatal, maxillopalatine, premaxillary, zygomaticotemporal and frontonasal suture) in each group were characterized histologically. Results showed that midpalatal suture was widened and restored after each expansion and constriction. At the end of activation, the widths between both central incisors and first molars in Alt-MEC group were significantly larger than those in ME group (P<0.05). Histologically, all five circumaxillary sutures studied were widened in multiple zones in Alt-MEC group. However, only midpalatal suture was expanded with cellular fibrous tissue filling in ME group. Significant osteoclast hyperplasia was observed in all circumaxillary sutures after alternate expansions and constrictions, but osteoclast count increase was only observed in midpalatal suture in ME group. These results suggested that cranial and circumaxillary sutures were actively reconstructed after Alt-MEC, while only midpalatal suture had active reaction after ME.

Comparison of the biological response of osteoblasts after tension and compression.

The aim of this study was to investigate the difference in the biological response of osteoblasts when stretched and compressed. A cellular cyclic tension and compression apparatus (CCTCA) was designed to stretch and compress cells under the same conditions. After stretching or compressing MC3T3-E1 with continuously increased strain for 5 hours, cellular cytoskeletal modulation was detected by immunohistochemical assay with actin antibody. Real-time polymerase chain reaction was performed at 1, 3, and 5 hours to detect local factors related to bone remodelling. Statistical analysis was undertaken with analysis of variance and the Kruskal-Wallis. Following stretching or compression for 5 hours, MC3T3-E1 attached to the culture dishes grew well. Compared with the control, the microfilaments orientated parallel with each other and were clearly observed by laser scanning confocal microscope after 5 hours of stretching. The morphology of MC3T3-E1 cells was thinner and longer than the control. However, microfilaments presented a disordered arrangement after 5 hours of compression, and the MC3T3-E1 cells decreased in size. Gene expression of Wnt10b and Lrp5 increased during tension but more in the compression groups at 1, 3, and 5 hours. The ratio of osteoprotegerin to receptor activator for nuclear factor kappa B ligand increased in the tension group compared with the control but decreased in the compression group at 5 hours.

Intrusion of overerupted maxillary molars with miniscrew implant anchorage: a radiographic evaluation.

The aim of this retrospective study was to quantitatively evaluate the treatment effects of intrusion of overerupted maxillary molars using miniscrew implant anchorage and to investigate the apical root resorption after molar intrusion. The subjects included 30 patients whose average ages were 35.5±9.0 years. All patients had received intrusion treatments for overerupted maxillary molars with miniscrew anchorage. There were 38 maxillary first molars and 26 maxillary second molars to be intruded. Two miniscrews were inserted in the buccal and palatal alveolar bone mesial to the overerupted molar. Force of 100-150 g was applied by the elastic chains between screw head and attachment on each side. Lateral cephalograms and panoramic radiographs taken before and after intrusion were used to evaluate dental changes and root resorption of molars. Only 6 of the 128 miniscrews failed. The first and second molars were significantly intruded by averages of 3.4 mm and 3.1 mm respectively (P<0.001). The average intrusion time was more than 6 months. The crown of the molars mesially tilted by averages of 3.1 degrees and 3.3 degrees (P<0.001) for first and second molars. The amounts of root resorption were 0.2-0.4 mm on average. The intrusion treatment of overerupted molars with miniscrew anchorages could be used as an efficient and reliable method to recover lost restoration space for prosthesis. Radiographically speaking, root resorption of molars was not clinically significant after application of intrusive forces of 200 to 300 g.

[Influence of the mandibular second premolar extraction on the angulation of the mandibular third molar].

OBJECTIVE: To compare the angular changes in the developing mandibular third molars in the mandibular second premolar extraction and non-extraction cases and to determine whether the mandibular second premolar extraction causes favorable rotational changes in the angulations of the developing mandibular third molars and benefits its later eruption. METHODS: Pretreatment and posttreatment panoramic radiographs were taken from 45 subjects who had been treated by the extraction of the mandibular second premolars and 48 subjects who had been treated without extraction. The horizontal reference plane was used to measure and compare the changes in the angulations of the developing mandibular third molars. RESULTS: The mean uprighting of the mandibular third molars seen in the extraction group was (5.9±2.5) degrees on the right side and (8.0±3.4) degrees on the left side following treatment. For the nonextraction group the mean uprighting was (1.8±2.4) degrees on the right side and (1.5±2.1) degrees on the left side. There was a statistically significant difference between the groups (P<0.05). CONCLUSION: Mandibular second premolar extraction might be a helpful procedure on the angulations of the developing mandibular third molars.

[Dental changes of patients with obstructive sleep apnea and hypopnea syndrome treated by oral appliance for more than 6 years].

OBJECTIVE: To investigate dental changes in long-term oral appliance treatment of obstructive sleep apnea and hypopnea syndrome(OSAHS). METHODS: A total of 7 patients were included in the study. The three-dimensional (3D) model study was used to investigate the delicate changes of dentition. RESULTS: The 7 patients who had been treated with an oral appliance for a mean duration of 8.5 years were recruited. The arch widths increased in the molar area. The distance between the distobuccal cusps of the left and right upper second molar increased (2.11 ± 2.14) mm, P=0.040. The distance between the distobuccal cusps of the left and right upper first molar increased (0.56 ± 0.61) mm, P=0.049. The distance between the distobuccal cusps of the left and right lower first molar increased (1.25 ± 0.93) mm, P=0.040. Several molar and premolar cusps were depressed. Other teeth had no change statistically. CONCLUSION: The orthodontic side-effects on the teeth are small during the treatment of patients with OSAHS.

A comparison study of upper airway among different skeletal craniofacial patterns in nonsnoring Chinese children.

OBJECTIVE: Patients with OSAS (obstructive sleep apnea syndrome) demonstrate decreased upper airway dimension and craniofacial skeletal abnormalities. The study was performed to analyze whether upper airway dimensions differed among Chinese nonsnoring children of different sagittal and vertical skeletal facial morphologies. MATERIALS AND METHODS: Lateral cephalometric records were used to measure the dimensions of the upper airway. Two groups of subjects were studied. A group of subjects with a normodivergent facial pattern (n = 190; FH-MP angle between 23.5 degrees and 30.5 degrees ) was divided into three subgroups according to ANB angle (Class I, II, or III). A second group of subjects with a normal sagittal facial pattern (n = 180; ANB angle between 0.7 degrees and 4.7 degrees ) was divided into three subgroups according to the FH-MP angle (low angle, normal angle, or high angle). All subgroups were matched for age and sex. RESULTS: In the group of subjects with a normodivergent facial pattern, a significant tendency for reduced upper airway dimension in the inferior part (palatopharyngeal and hypopharynx) was found in the Class III, Class I, and Class II subgroups, in that order. In the group of subjects with a normal sagittal facial pattern, the superior part of the airway (nasopharyngeal and palatopharyngeal) decreased with increasing mandibular plane angle. CONCLUSION: The sagittal and vertical skeletal patterns may be contributory factors for the variation of the inferior and superior part of the upper airway, respectively. Skeletal deficiency of nonsnoring Chinese children may predispose them to upper airway obstruction.

[Relationship between craniofacial and airway structure and pediatric obstructive sleep apnea and hyponea syndromes: a case-control study].

OBJECTIVE: The children obstructive sleep apnea and hyponea syndromes has become a global research hot spot, but the research of craniofacial features in obstructive sleep apnea and hyponea syndromes (OSAHS) children was scarce. To evaluate the craniofacial features of obstructive sleep apnea and hyponea syndromes children. METHODS: The subjects involved in this study fell into two groups: the patient group and the control one. The patients and controls were strictly matched by age and sex. Lateral head radiographs and cephalometric measurements were obtained and then compared between the two groups. RESULTS: The findings demonstrated marked differences in terms of SNB, PG-NB, lower facial height, H-C3Me and A&T/P. The SNB angle (75.8±4.3) in the patient group was smaller than that in the control one (78.7±2.6) and the P value was 0.035; the PG/NB value in the patient group (1.3±0.8) mm was higher than that in the control one (0.6±0.6) mm and the P value was 0.02. The anterior face height was (65.1±5.9) mm in the patient group (P=0.04), while the anterior face height in the control group was (61.5±3.2) mm. The position of hyoid was lower in the patient group(5.3±3.7) mm, compared with the control one (2.6±2.6) mm, and the P value was 0.03. Furthermore, the patients of OSAHS had more swelled adenoids and tonsils than the controls. CONCLUSION: The patient group differed from the control group in the length of mandible, lower facial height, position of hyoid and the chin, and the size of the adenoids and tonsils.

[Current research of dentistry on obstructive sleep apnea hypopnea syndrome].

Obstructive sleep apnea hypopnea syndrome (OSAHS) has been the main research area of the Dental Therapy Center for Sleep Apnea, Peking University School and Hospital of Stomatology. The basic research in the center includes: epidemic survey of OSAHS and snoring in a Beijing population, setting up the cephalometric and MRI standard of airway and surrounding structures for non-snoring Chinese, aetology exploring OSAHS from views of airway size, craniofacial form, neck circumference and genioglossus muscle activity. Clinically, different dental appliances were developed. The treatment effects of the oral appliances for OSAHS patients were evaluated quantitatively. Two and three dimension changes of the airway and surrounding structures, genioglossus muscle activity, as well as snoring loudness following mandible advancing and opening were studied. Besides, research was expended to OSAHS in children recently. Under the support of National Nature Science Foundation 7 PhD and 3 MS students have graduated. More than 60 papers were published domestically and abroad and two awards were received from the National Ministry of Education and Chinese Medical Association in the past 10 years. This paper is a review of the past and current situation of dental research on OSAHS in China.

[Study on periodontal disease in Chinese in Xia Dynasty].

OBJECTIVE: To study the teeth of the ancients in Xia Dynasty, the first dynasty in Chinese history about 4 000 years ago, and acquaint ourselves with their incidences of periodontal disease,and the evolution of oral diseases. METHODS: The teeth and jaws excavated in Erlitoou, Henan Province and Youyao, Shanxi Province were observed with clinical methods. The specimens totaled 56 individuals (male 38, and female 18), including 894 teeth, and 86 dental arches. The objects were all permanent teeth. The major observation items were periodontal disease. The prevalence of periodontal disease of the people in Chinese Xia Dynasty were outlined. RESULTS: The prevalence rate of periodontal disease was 19.80% in the 894 teeth, while prevalence rate was about 42.86% among the individuals. The premortal tooth loss rate was 7.45% in the observed teeth. CONCLUSION: Periodontal disease is an age-related disease without sex difference and commonly seen in the mandible, which is quite similar to the situation at present. The periodontal disease was the main reason for tooth loss in people of Xia Dynasty.

[A magnetic resonance imaging research of upper airway and surrounding tissues of 83 non-snoring males].

OBJECTIVE: To obtain the data about morphology of upper airway and surrounding tissues of non-snoring males from three age groups. METHODS: Through questionnaires and clinic examinations, 83 non-snoring males (20-60 years) were selected from 453 volunteers and involved in the following research. There were 30 volunteers aged from 22 to 29 (mean 23.60+/-2.58 years), 31 volunteers aged from 36 to 45 (mean 40.10+/-2.64 years) and 22 volunteers aged from 46 to 57 (mean 49.55+/-3.45 years). Magnetic resonance imaging (MRI) of upper airway of each volunteer was acquired under strict posture-control conditions. The dimensions and cross-section area of nasopharynx, velopharynx, glossopharynx, hypopharynx and whole upper airway with its surrounding tissues were measured with MRI intrinsic software. Volumes of upper airway and surrounding tissues were also calculated. RESULTS: There were 93 items about morphology of the upper airway and surrounding tissues of non-snoring males from the three age groups. With increase in age, some nasopharynx items showed increase tendency, while little change showed in velopharynx, glossopharynx and hypopharynx. Fat volume, tongue volume, anterior and posterior pharyngeal dimension showed age-related increase tendency, but fat deposition rate slowed down in elder age in non-snoring males, which supplies the reason why non-snoring males avoided becoming sleep apnea patients. CONCLUSION: We provide age-related reference data of upper airway and its surrounding tissues for further sleep and respiration research.

Fish Oil Supplements Lower Serum Lipids and Glucose in Correlation with a Reduction in Plasma Fibroblast Growth Factor 21 and Prostaglandin E2 in Nonalcoholic Fatty Liver Disease Associated with Hyperlipidemia: A Randomized Clinical Trial.

UNLABELLED: Fish oil has been used effectively in the treatment of cardiovascular disease via triglyceride reduction and inflammation modulation. This study aimed to assess the effects of fish oil on patients with nonalcoholic fatty liver disease (NAFLD) associated with hyperlipidemia. Eighty participants with NAFLD associated with hyperlipidemia were randomly assigned to consume fish oil (n=40, 4 g/d) or corn oil capsules (n=40, 4 g/d) for 3 months in a double-blind, randomized clinical trial. Blood levels of lipids, glucose and insulin, liver enzymes, kidney parameters and cytokines at baseline and the end of the study were measured. Seventy people finished the trial. Plasma concentrations of eicosapentaenoic acid and docosahexaenoic acid significantly increased in the fish oil group after intervention. After adjustment for age, gender and BMI, fish oil significantly decreased fasting serum concentrations of total cholesterol, triglyceride, apolipoprotein B and glucose (by (mean±SD) 0.49±0.43 mmol/L, 0.58±0.89 mmol/L, 0.28±0.33 g/L and 0.76±0.56 mmol/L, respectively, P<0.05), as well as alanine aminotransferase and γ-glutamyl transpeptidase levels (by (median (interquartile)) 9.0(0.5, 21.5) and 7.0(2.2, 20.0) IU/L, respectively, P<0.05), significantly increased serum adiponectin levels (by 1.29±0.62 µg/mL, P<0.001), and reduced serum levels of tumor necrosis factor α, leukotrienes B4, fibroblast growth factor 21 (FGF21), cytokeratin 18 fragment M30 and prostaglandin E2 (by 1.70±1.18 pg/mL, 0.59±0.28 ng/mL, 121±31 pg/mL, 83±60 IU/L and 10.9±2.3 pg/mL, respectively, P<0.001). Corn oil had no effect except for increasing serum creatinine concentrations by 7.7±8.9 µmol/L (P=0.008). The effects of fish oil on lipids, glucose and γ-glutamyl transpeptidase were positively correlated with the reductions of serum FGF21 and prostaglandin E2 concentrations after adjustment for age, gender and BMI (r = 0.275 to 0.360 and 0.261 to 0.375, respectively, P<0.05). In conclusion, our findings suggest that fish oil can benefit metabolic abnormalities associated with NAFLD treatment. TRIAL REGISTRATION: ChiCTR-TRC-12002380.

[Histological changes of craniofacial sutures after retractive forces with zygomatic implant anchorage to the maxilla of rhesus monkeys].

PURPOSE: To demonstrate the histological changes of the maxilla-facial sutures caused by retractive forces of a zygomatic implant anchorage to the maxilla of rhesus monkeys. METHODS: Four young male rhesuses were employed, 3 in the experimental group (1 was been distracted for 1.5 months and 2 for 3 months), and 1 as control. HE staining and vital fluorescent were used to observe histological changes in the circum-maxillary sutures (i.e. zygomaticomaxillary suture, transverse palatine suture, frontomaxillary suture and pterygopalatine suture) and the posterior sutures (i.e. zygomaticotemporal suture and sphenozygomatic suture, sphenozygomatic suture) of zygoma bone caused by retractive forces of zygomatic implant to the maxilla of rhesus monkeys. RESULTS: Obvious reactions of compressive stress and bone resorption were observed around the 4 circum-maxillary sutures. There were 3 patterns of sutural reactions, indicating the direction of sutural stress influenced by sutural position and morphology. Reactions of interdigitate wedging were observed in the transverse palatine suture and frontomaxillary suture, showing a bony collision that the tip of bony process and the hollow were resorbed markedly. Phasic reactions were found in the pterygopalatine suture reaction, representing a bony sliding that one side of a bony surface was deposited while the opposite side was resorptive. Both reactions were observed in the zygomaticomaxillary suture. Tensile stresses were observed in the 3 sutures around anchoraged zygoma bone (i.e. zygomaticotemporal suture, sphenozygomatic suture and sphenozygomatic suture) with similar three-pattern reactions. CONCLUSIONS: Histologically, significant changes differing from physiological remodeling are observed in the circum-maxillary sutures and posterior sutures of zygoma bone, but no destructive changes are found. These findings demonstrate that bone resorptions are major reactions caused in the 4 circum-maxillary sutures. Different sutures respond slight histological differences. The maxillary complex is retracted distally with some rotation. Tensile stress occured in the posterior sutures around zygoma bone with a zygomatic implant anchorage, which is different from the effect with a headgear. Supported by Science and Technology Plan Project of Yunnan Province (2007C0029R).

Malocclusions in Xia Dynasty in China.

BACKGROUND: The prevalence of malocclusion in modern population is higher than that in the excavated samples from the ancient times. Presently, the prevalence of juvenile malocclusion in the early stage of permanent teeth is as high as 72.92% in China. This study aimed to observe and evaluate the prevalence and severity of malocclusions in a sample of Xia Dynasty in China, and to compare these findings with the modern Chinese population. METHODS: The material consisted of 38 male and 18 female protohistoric skulls of Xia Dynasty 4000 years ago. Of 86 dental arches, 29 cases had the jaw relationships. Tooth crowding, diastema, individual tooth malposition and malocclusion were studied. RESULTS: Of the samples, 23.3% showed tooth alignment problems including crowding (8.1%), diastema (9.3%), and individual tooth malposition (5.8%). The prevalence of malocclusion was 27.6%, mainly presented as Angle Class I. CONCLUSIONS: It is indicated that over thousands of years from Neolithic Age (6000 - 7000 years ago) to Xia Dynasty (4000 years ago), the prevalence of malocclusion did not change significantly. The prevalence of malocclusion of Xia Dynasty samples was much lower than that of modern population.

[Changes of blood flow volume in dog's mental artery after mandible osteocompression].

OBJECTIVE: To observe the changes of blood flow volume in mental artery of dog before and after osteocompression. METHODS: 16 adult dogs were selected and the osteocompressors were fixed on the right buccal side of the mandible. The osteocompressor was used to compress the mandible 1.0 mm per 3 days for totally 15 days. On the 1st, 15th, 45th and 90th day after osteocompression, the 4 MHz prober of color Doppler flow imaging machine was put on the surface of the mucosa below which there was the mental artery. The color Doppler flow imaging was used to measure the blood flow volume in the mental artery of both experimental and control sides. RESULTS: 1) The blood flow value in the mental artery was the lowest on the 15th day after osteocompression, however there was not significantly different before and after osteocompression. 2) Compared with the control, the blood flow value of the mental artery on the 1st day after experiment was significantly decreased. 3) Compared with the data before experiment, the deduction of the blood flow values between experimental side and control on the 1st, 15th and 45th day after osteocompression had significant differences. On the 90th day, the deduction of the blood flow value was similar to normal. CONCLUSION: The osteocompression influences blood flow volume in mental artery temporarily, however, the influence is reversible and can be recovered by times after osteocompression.

[Induction of human dental pulp stem cells of premolars into osteoblast-like cells by mineralizing culture medium].

PURPOSE: To induce human dental pulp stem cells(HDPSCs) of premolars into osteoblast-like cells by mineralizing culture medium. METHODS: HDPSCs of premolars were induced by mineralizing culture medium for 28 days.The activity of ALP was examined by enzyme histochemical staining on the 7th and 28th day. The ability of mineralization of HDPSCs was detected by Alizarin-red staining on the 14th, 21st and 28th day. The gene expression of ALP, DSPP, BSP, OCN on day 0, 3, 5, 7, 14, 21 and 28 was evaluated by RT-PCR. The protein expression of BSP, OCN was analyzed by Western blotting and immunocytochemistry. RESULTS: ALP was expressed and mineralized nodules were observed after induction of HDPSCs. ALP mRNA was detected since the 3rd day, while no expression of DSPP mRNA. The gene of BSP, OCN was expressed from the 5th day and exhibited increment with time. The expression trend of BSP protein was consistent with BSP mRNA. OCN stained positive since the 5th day. CONCLUSIONS: HDPSCs of premolars could be induced to differentiate into osteoblast-like cells,which suggests that HDPSCs of premolars may be a potential source of cells used for bone-tissue engineering in the future. Supported by National Natural Science Foundation of China (Grant No.30772452).

[Z2 appliance: the pre-adjusted appliance based on Chinese normal occlusion].

Z2 appliance is the pre-adjusted appliance designed for Chinese orthodontic patients. The prescription of the appliance is based on Chinese normal occlusion, which is much different from the West in the first and the second orders as well as the third one. The appliance routinely includes 20 brackets and 8 molar buccal tubers with 3 standard arch forms. Clinically, continued light force is used in whole treatment. The side-effects such as forward tipping of incisors, bite deepening and loss of molar anchorage are reduced further due to fewer tips built into the anterior brackets as well as lower friction elastometric modules used during aligning and leveling. In condition of arch are leveled completely, 0.48 mm x 0.64 mm stainless steel archwire with 1.47 N retraction force is the best combination for sliding mechanics, which is proved by 3D nonlinear finite element study. Self drilling micro-screw is used for maximum anchorage. In finishing stage 0.53 mm x 0.64 mm NT arch wire is added in order to get full torque expressing. The research of Chinese pre-adjusted appliance has been lasted for more than 10 years in the department and clinical studies on Z2 appliance show that with minimal wire bending, treatment is more efficient and result is high quality and more consistent for Chinese orthodontic patients.

[Dental caries in ancient Chinese in Xia Dynasty].

OBJECTIVE: To study the ancient teeth helped us to acquaint with the evolution of oral diseases. METHODS: Teeth and jaws excavated in Erlitou, Henan province and Youyao, Shanxi province were observed clinically with care. The total specimens included 56 individuals (38 males and 18 females, including 894 permanent teeth and 86 dental arches). The dental caries were observed. The incidence of dental caries was calculated. RESULTS: The rate of dental caries was 6.9% in 894 observed teeth. The prevalence was 39% among individuals. CONCLUSIONS: The rate of dental caries in ancient Chinese in Xia Dynasty was lower than that in modem people. There were more caries in elderly people while no sex difference was found in Chinese in Xia Dynasty, which was similar to the situation in modern society. Cervical caries was more common than occlusal caries. The second molars and the third molars were frequently involved, which was different from the phenomenon nowadays.

[Clinical evaluation of preadjusted appliance based on Chinese normal occlusion].

OBJECTIVE: To evaluate the effect of the preadjusted appliance (Z1 appliance) based on Chinese normal occlusion. METHODS: Thirty non-extraction patients were treated with Z1 appliance. No wire bending was made during treatment. The results of these 30 cases had been evaluated by five senior orthodontists. Models were analysed quantitatively to testify and evaluate the efficiency of the appliance. RESULTS: The average score for post-treatment models was 91.2 (total score was 100). The model measurements indicated that average projective distance on occlusal plane between proximal contact points of adjacent teeth was less than 0.3 mm, which demonstrated good alignment. The prominence of crowns was almost coincident with the data of Chinese normal occlusion. For the average tip of most teeth, there was no statistical difference between the study group and the normal control group. The crown torque variation tendency from anterior to posterior was similar to that in the subjects with normal occlusion. However, the cases treated with Z1 appliance achieved more negative torque in the lower posterior segment. CONCLUSIONS: The result of the non-extraction patients treated with Z1 appliance was quite satisfied. Wire bending could be reduced during treatment. It was necessary to adjust the crown torque values for lower posterior teeth.