[Microbial Diversity and Community Analysis of Dental Plaques in Orthodontic Patients Wearing Invisible Appliances and Fixed Appliances].

Objective: To explore the microbial diversity and community structure of dental plaques in orthodontic patients with invisible appliances and fixed appliances and to study the differences. Methods: Ten orthodontic patients wearing invisible appliances (I) and ten wearing fixed appliances (F) were recruited. Dental plaques were collected from both buccal (B) and lingual (L) sides. Based on 16S rDNA, 40 dental plaque samples were analyzed after Illumina sequencing. Results: The microbial diversity, abundance and evenness of the FB group were significantly higher than those of the IB and IL groups (P<0.05), while the FL group showed substantial individual differences. The community structures were generally similar among the four groups, but significant differences in the relative abundance of some bacteria were found. The IB group showed higher abundances of Actinomycetes and Rosella (P<0.05), which were considered to be involved in dental caries and periodontal diseases. Some key communities showing significant differences were significantly enriched in the FB group, including Coprobacillus, Bifidobacterium, Enterobacterium, Lactobacillus, etc.. Conclusion: Dental plaques in patients wearing invisible appliances and fixed appliances showed significantly different microbial abundance, diversity and composition, which may be involved in orthodontic complications such as dental caries and periodontal diseases. Orthodontic patients need strengthened measures for oral hygiene maintenance, no matter what kind of appliances they wear.

[Histological study of miniscrew implanted in lower mandibles of juvenile and adult Beagle dogs].

OBJECTIVE: To examine the histological discrepancies between juvenile and adult Beagle dogs at different concrescence times after miniscrew implants. METHODS: Miniscrew implants were performed in six juvenile Beagle dogs and six adult Beagle dogs. The space between the fourth premolar root and first molar root, and the spaces in distal and mesial of M1 root were picked up for the implants of the 48 miniscrews. The lower jaw specimens including the miniscrews were harvested 3 and 12 weeks after the implants for the histological examinations and bone implant contact (BIC) calculations. RESULTS: There was no miniscrew falling off or becoming loose. The miniscrews had favorable biological consistencies with the tissues around them. The osteoblasts and osteoclasts showed active functions in the peri-bones of the minisrews. The BIC became higher when the healing time was prolonged. The juvenile Beagle dogs had lower BIC than the adults 3 weeks after the implants. But the BIC of the juvenile dogs surpassed the adults 12 weeks after the implants. CONCLUSION: The osseointegration of the miniscrews is hindered by the poorer bone quality of the juvenile Beagle dogs. But the early osseointegration deficiency can be made up by the rapid development and growth of the bones of the juvenile dogs.

Morphologic Analysis of the Temporomandibular Joint Between Patients With Facial Asymmetry and Asymptomatic Subjects by 2D and 3D Evaluation: A Preliminary Study.

Signs and symptoms of temporomandibular joint (TMJ) dysfunction are commonly found in patients with facial asymmetry. Previous studies on the TMJ position have been limited to 2-dimensional (2D) radiographs, computed tomography (CT), or cone-beam computed tomography (CBCT). The purpose of this study was to compare the differences of TMJ position by using 2D CBCT and 3D model measurement methods. In addition, the differences of TMJ positions between patients with facial asymmetry and asymptomatic subjects were investigated. We prospectively recruited 5 patients (cases, mean age, 24.8 ±â€Š2.9 years) diagnosed with facial asymmetry and 5 asymptomatic subjects (controls, mean age, 26 ±â€Š1.2 years). The TMJ spaces, condylar and ramus angles were assessed by using 2D and 3D methods. The 3D models of mandible, maxilla, and teeth were reconstructed with the 3D image software. The variables in each group were assessed by t-test and the level of significance was 0.05. There was a significant difference in the horizontal condylar angle (HCA), coronal condylar angle (CCA), sagittal ramus angle (SRA), medial joint space (MJS), lateral joint space (LJS), superior joint space (SJS), and anterior joint space (AJS) measured in the 2D CBCT and in the 3D models (P < 0.05). The case group had significantly smaller SJS compared to the controls on both nondeviation side (P = 0.009) and deviation side (P = 0.004). In the case group, the nondeviation SRA was significantly larger than the deviation side (P = 0.009). There was no significant difference in the coronal condylar width (CCW) in either group. In addition, the anterior disc displacement (ADD) was more likely to occur on the deviated side in the case group. In conclusion, the 3D measurement method is more accurate and effective for clinicians to investigate the morphology of TMJ than the 2D method.

Differences in the mandibular premolar positions in Angle Class I subjects with different vertical facial types: A cone-beam computed tomography study.

OBJECTIVE: To compare the positions of the mandibular premolars in Angle Class I subjects according to vertical facial type. The results will provide a theoretical basis for predicting effective tooth movement in orthodontic treatment. METHODS: Cephalometric parameters were determined using cone-beam computed tomography in 120 Angle Class I subjects. Subjects were categorized as short, normal, and long face types according to the Frankfort mandibular angle. Parameters indicating the position of the mandibular right premolars and the mandible were also measured. RESULTS: The angle between the mandibular first premolar axis and buccal cortex, the distance between the root apex and buccal cortex, angle of vestibularization, arc of vestibularization, and root apex maximum movable distance were significantly greater in the short face type than in the long and norm face types. The angle between the mandibular second premolar axis and buccal cortex, the distance from root apex to buccal cortex, and the arc of vestibularization were significantly greater in the short face type than in the normal face type. CONCLUSIONS: There are significant differences in the mandibular premolar positions in Class I subjects according to vertical facial type.

[Establishment of malodor model and its effects on identifying the halitosis-related bacteria].

OBJECTIVE: To establish a salivary sediment malodor system, and to evaluate the effect of several kinds of bacteria dedicated to the halitosis formation, hence to identify halitosis-correlated bacteria. METHODS: The proportion of the supernatant and sediment, gained from centrifugal whole saliva, was adjusted to establish a salivary sediment malodor system incubated in facultative aerobic environment under 37 degrees C for 7 hours. The halitosis indexes in both gaseous phase and liquid phase were checked by direct sniffing, and volatile sulphur compounds (VSCs) and pH were determined by halimeter and glass electrode respectively between hours to evaluate the malodor formation. The suspended fluid of suspicious halitosis-correlated bacteria and non-halitosis-correlated bacteria and water control were introduced into the salivary sediment system incubated for 1 hour. The five groups were incubated in facultative aerobic environment under 37 degrees C in the residual hours. The halitosis indexes, VSCs and pH changes were recorded between hours. RESULTS: The salivary sediment malodor system can simulate the metabolism of halitosis formation to produce halitosis. The odors of the suspicious halitosis-correlated bacteria introduced groups were higher than the non-halitosis-correlated bacteria and water control group. CONCLUSION: With its simple but fundamental manipulations, incubated whole saliva is a powerful model for study of the metabolism of the oral mixed microbial flora, malodor formation, and other oral diseases-related processes.

[Time varied stress effects on the shape-alteration of myoblast in rats].

OBJECTIVE: To investigate the effects of time varied stress on the shape-alteration of myoblast in rats and to provide a theoretic base to determine the mechanics of myoblast in orthodontic therapy. METHODS: Based on the pulsatile mechanical system our group founded, this study loaded different strain (2.5 kPa, 5.0 kPa and 10.0 kPa) to the myoblast of lateral pterygoid muscle. The alterations in shape under time varied stress of 6 h and 12 h were assessed by phase-contrast microscopy, scanning electron microscope. RESULTS: The orientation of myoblast seemed no obvious orderliness before loading. But after loading the lower time varied strain (2.5 kPa, 5.0 kPa), they were changed their orientation to paralel with the direction of strain along with the membrane. Meanwhile, there had one trend to set the shape of myoblast more upright along with the membrane after loading the higher time varied stress (10.0 kPa). CONCLUSION: It was proved that the different time varied stress in vitro expressed the different influence on the remolding of myoblast.