Root resorption before and after orthodontic treatment: a clinical study of contributory factors.

This clinical study evaluated factors related to root resorption before (T1) and after (T2) orthodontic treatment. Ninety-six subjects between 9 and 34 years (34 males and 62 females) who had been treated using fixed appliances for at least 1 year and who had panoramic radiographs at T1 and T2 were selected. The relationship between root resorption at T1 and T2, with regard to gender, age, extraction versus non-extraction patterns, specific teeth and treatment duration was investigated. No statistically significant differences in root resorption were found in relation to gender. Significant differences in root resorption (P = 0.000, P < 0.01) and also in treatment duration (P = 0.036, P < 0.05) were noted between the extraction and non-extraction groups; extraction and treatment duration correlated with T2 mean root resorption. Patient age correlated with root resorption of the upper incisors at T1 and T2. Using multiple regression analysis, age and duration of treatment were found to be more associated with root resorption than with extractions; the presence of root resorption at T1 was associated with T2 root resorption, especially of the anterior teeth.

[Expression of OPG and RANKL at protein level in human periodontal ligament cells and the effect of 1alpha,25(OH)(2) vitamin D(3) on the secretion of OPG protein in vitro].

OBJECTIVE: To study the expression of osteoprotegerin(OPG) and receptor activator nuclear factor kappa B ligand(RANKL) at protein level in human periodontal ligament cells (HPDLCs), and the effect of 1alpha,25(OH)(2) vitamin D(3) [1,25(OH)(2)vitD(3)] on the secretion of OPG protein in vitro. METHODS: HPDLCs were harvested in vitro by sequential digestion with trypsin and collagenase. The expression of RANKL in HPDLCs at protein level was tested by immunocyto-chemistry. Enzyme-linked immunoadsordent assay (ELISA) was used to detect the OPG protein which was secreted into the culture medium by HPDLCs cultured with and without 10(-8) mol/L 1alpha,25 (OH)(2)vitD(3) on the 0, 2nd, 4th, and 6th days, respectively. RESULTS: RANKL protein was detected on the membrane and plasma of HPDLCs, and OPG protein was secreted in the culture medium. The secretion of OPG protein was down-regulated by 10(-8) mol/L 1alpha,25 (OH)(2)vitD(3). CONCLUSION: HPDLCs have the bone metabolism system of OPG/RANKL, which works during the process of 1alpha,25 (OH)(2)vitD(3) inducing HPDLCs. The conclusion has laid the groundwork for the study on bone remodelling mechanisms of HPDLCs.

[Evidence-based quality assessment of 10-year orthodontic clinical trials in 4 major dental journals].

OBJECTIVE: To assess the quality of orthodontic clinical trials published in 4 major dental journals in the past 10 years and establish the reference standard for orthodontic clinical trials and quality control of dental journals. METHODS: All the clinical trials published in Chinese Journal of Stomatology, West China Journal of Stomatology, Journal of Practice Stomatology and Chinese Journal of Orthodontics from 1999 to 2008 were searched. The demographic information of the papers was extracted and the quality of the clinical trials according to the consolidated standards of reporting trials (CONSORT) was assessed. RESULTS: Four hundred and ninety-four clinical trials were retrieved, and 21.3% (105/494) of them were supported by grants. For the study design, only 26.1% (129/494) were prospective studies, and 3.8% (19/494) were randomized clinical trials. It was hard to evaluate precisely due to the lack of information about the details of the study designs. For the randomized clinical trials, the lack of details for randomization, allocation concealment, blinding and intention to treat compromised the quality. CONCLUSIONS: The general quality of clinical trials in orthodontics is poor. It needs to be improved both in the clinical study design and the paper writing.

[Comparison between MLO-Y4 osteocyte and osteoblast to support osteoclast formation in vitro].

OBJECTIVE: To compare between MLO-Y4 osteocyte and osteoblast to support osteoclast formation in co-culture system. METHODS: MLO-Y4 cells and murine osteoblast cells were co-cultured with bone marrow cells with or without vitamin D3 presence.Bone marrow cells were as control group. Tartrat resistant acid phosphatase (TRAP)+ giant cells with three or more nuclei were counted and compared under a microscope at day 9. RESULTS: In the absence of vitamin D3, (1963.3 ± 93.1)/plate osteoclasts were observed when MLO-Y4 cells co-cultured with bone marrow cells in 24-well plate.While only (12.7 ± 5.5)/plate osteoclasts were found in the osteoblast group, and (6.0 ± 1.0)/plate in control group. The statistical difference occurs for any two groups (P < 0.05). Vitamin D3 could significantly increase osteoclast formation in the three groups. CONCLUSIONS: Osteocytes could induce osteoclastogenesis without the presence of vitamin D3 and vitamin D3 could enhance the induction effects of MLO-Y4 and osteoblast cells.

[A retrospective study for vertical control with high-pull headgear in the treatment of high angle cases].

OBJECTIVE: To assess the effectiveness of vertical control with high-pull headgear in the treatment of high angle cases. METHODS: Forty high angle cases (MP-SN >40 degrees) were included in this study and all the patients were treated with extraction. Twenty patients in the study group and control group, respectively. Totally 14 cephalometric measurements were selected for the assessment Paired t-test and independent t-test were used in the analysis. RESULTS: No significant differences were found between the two groups (P > 0.05). In the study group, after treatment Y angle, MP-SN angle, MP-FH angle and U6-PP distance increased 1.9 degrees, 1.5 degrees, 2.3 degrees and 1.1 mm, respectively (P < 0.01). CONCLUSIONS: High-pull headgear could not provide effective vertical control in high angle cases.

[Non-extraction treatment with self-ligating and conventional brackets].

OBJECTIVE: To compare the dental change and the mechanism after non-extraction treatment between passive self-ligating and conventional bracket systems. METHODS: Twenty-six non-extraction crowding cases were selected. Half of them were treated with Damon3 self-ligating brackets and the others were treated with conventional brackets. The results were compared. Stepwise regression analysis was performed for the two groups. RESULTS: There were no statistically significant differences in the changes of the intercanine and interpremolar widths and L1-MP angle (P > 0.1). In the self-ligating bracket group, the intermolar width increased by 1.42 mm and the L1-APo increased by 2.66 mm. In the conventional appliance group, the intermolar width increased by 0.65 mm and L1-APo increased by 1.57 mm. The differences were statistically significant between the two groups (P < 0.1). Stepwise regression analysis showed that in self-ligating bracket group, the coefficient of determination for the changes of L1-MP was 96.6%. CONCLUSIONS: In crowding cases treated with non-extraction, there were an overall increase in the proclination of the mandibular incisors and the arch width in both bracket groups. Compared with cases treated with conventional appliances, the cases treated with Damon3 brackets resulted in greater intermolar width increases; In Damon3 bracket group, the change of the lower incisor inclination was influenced not only by the mandibular crowding and the intermolar width before treatment but also by the patient's skeletal pattern and the changes of the arch width during treatment.

[Changes of Streptococcus mutans concentration of plaque during fixed appliance treatment].

OBJECTIVE: To evaluate the dynamic changes of Streptococcus mutans concentration of plaque during fixed appliance treatment and the effects of two materials of ligation on Streptococcus mutans concentration. METHODS: Twenty-eight patients undergoing fixed appliance treatment were observed. Ligature wire and elastomeric rings were applied on one side of arches, stochastically. The dynamic changes on the quantity and percentage of Streptococcus mutans were observed before and after fixed appliance bonding. RESULTS: Statistically significant increase of the quantity and percentage of Streptococcus mutans was found after fixed appliance bonding, and the percentage of Streptococcus mutans in the plaque around the brackets ligated with elastomeric rings was more than that of ligature wire at the beginning of fixed appliance bonding, statistically. CONCLUSIONS: The finding suggested that the caries-associated capability of the plaque increased after bonding and there was greater caries-associated capability of the plague on the teeth when elastomeric rings was used than that of the plague when ligature wire was used at treatment beginning. The ligature wire is recommended in the fixed appliance treatment.

[Stability of upper molars with the application of implant anchorage].

OBJECTIVE: To investigate the stability of upper molars with the application of micro-screw implant anchorage during orthodontic treatment. METHODS: Fifteen adult patients with severe maxillary protrusion were included. Upper first premolars were extracted and upper posterior anchorage was reinforced with micro-screw implant in all patients. The average treatment period to close the extraction space was 10.5 months. Cephalometric and cast analysis were carried out. RESULTS: During the treatment, the micro-screw implants kept stable in sagittal plane; neither the mesial-distal movement nor the rotation or tipping of the upper molars during the treatment was of statistic significance (P > 0.05); the edge of upper incisors was retracted by 6.99 mm on average, and no significant vertical change was observed (P > 0.05). CONCLUSIONS: Micro-screw implant could provide good anchorage control in the orthodontic treatment.

[Condylar lateral movements in patients with mandibular deviation].

OBJECTIVE: To record condylar movements of patients with mandibular deviation and analyze their characteristics. METHODS: Computer aided diagnosis axiography (CADIAX III) was used to record and analyze condylar lateral movements in 31 patients (9 males, 22 females and the age range 12 - 26, mean age 18 years old) with mandibular deviation. Paired-t test and rank sum test were used to compare condylar movements. Multinomial logistic analysis was used to clarify the relationship between condylar movement and mandibular deviation. RESULTS: The condylar lateral movements in patients with mandibular deviation were asymmetric. The tracing of the shifted side was longer than the contralateral side (P < 0.01). The transverse inclination of the shifted side was smaller than the contralateral side (P < 0.01). With the increase of deviation, the movement length difference between the two sides increased and the length of contralateral side decreased (P < 0.01). CONCLUSIONS: The patients with mandibular deviation not only have morphological asymmetry but asymmetric condylar movement length and inclination in lateral movements. There is specific relationship between condylar movement and mandibular deviation.

[Posttreatment stability of four first bicuspid extraction cases treated with the Alexander technique--model analysis].

OBJECTIVE: To evaluate the posttreatment stability of four first bicuspid extraction cases with the Alexander technique. METHODS: Fifteen patients, 8 males and 7 females in the permanent dentition were selected. The age range of the patients was 10.3 to 16.2 years old. Four first bicuspids of every patient were extracted and all patients were treated with the Alexander technique. The study casts were taken before (T(1)), after treatment (T(2)) and 27.8 months averagely follow-up (T(3)). Data were correlated by means of paired t tests. RESULTS: Although maxillary and mandibular intercanine widths were increased by 0.98 mm and 0.87 mm, respectively, during treatment, they were decreased by 0.37 mm and 0.72 mm, respectively, during follow-up period. Maxillary and mandibular crowding were increased by 0.53 mm and 0.98 mm, respectively, during follow-up period. No statistical significance were found. Upper and lower arch depth were decreased significantly due to retraction of anterior teeth and remained stable during follow-up period. CONCLUSIONS: According to this study, the design of the Alexander appliance and the Alexander technique are helpful for stability of extraction therapy. Follow-up is still necessary to evaluate the long-term stability.

[Treatment of OSAS with modified twin-block advancement appliances].

OBJECTIVE: To introduce a new modified twin-block advancement appliance and investigate the effects on respiratory variables in patients with OSAS. METHODS: 29 patients with OSAS participated in the study and were fitted with modified twin-block appliances to hold the mandible in an anterior and inferior position. Polysomnography was performed with and without appliance insertion. And questionnaires were used for registration of patients subjective symptoms. Pair-t analysis was used to evaluate the effects of appliances in patients with OSAS. RESULTS: 26 patients responded to the appliance therapy. Apnea-hypopnea index, apnea index and hypopnea index were reduced significantly (P < 0.01). Lowest arterial oxygen saturation improved significantly (P < 0.01). Discomfort with mandibular advancement disappeared within one week. CONCLUSIONS: Modified twin-block advancement appliance is a conservative, successful treatment alternative that could benefit patients suffered from OSAS.

[An adjustable appliance in treatment of obstructive sleep apnea-hypopnea syndrome].

OBJECTIVE: The research tended to approach applying of adjustable appliance in the treatment of obstructive sleep apnea-hypopnea syndrome (OSAHS). METHODS: 30 OSAHS patients (24 males and 6 females) participated in the adjustable group, with a mean age of (49.9 +/- 9.9) years old. AHI was (33.1 +/- 22.7) per hour. The control group consisted of 30 OSAHS patients wearing ordinary mandibular advancing appliance in the corresponding period, with age, weight and AHI at the same level. Monoblind way was designed to obtain and analyze the therapy differences. Differences in changes of upper airway, mandible and hyoid bone were also analyzed among the doctor-experience position, final adjusted position and original position. RESULTS: AHI decreased by 85.5% in the adjustable appliance group. The change in AHI was greater significantly (P = 0.025) in the adjustable group than in the control group. In the final adjusted position, the amount of mandibular advancement was (5.8 +/- 1.4) mm [(71 +/- 26)% of the maximum range of protrusion] and that of bite opening (the distance between upper and lower incisor edges) was (4.6 +/- 1.1) mm. CONCLUSIONS: The adjustable appliance had shown better therapy effect in OSAHS patients. The final adjusted position provided useful information on determining mandibular position using other appliances.

[A factors study of root resorption after orthodontic treatment].

OBJECTIVE: To investigate the factors relating to root resorption after orthodontic treatment. METHODS: 96 cases treated with fixed appliances were selected. The panoramic radiographs before and after treatment were examined. The relationship between root resorption after treatment (RRAT) and the variables including sex, age, extraction or nonextraction approach, tooth location, treatment duration and the root resorption before treatment (RRBT) were analyzed by multiple variance analysis and stepwise multivariate linear regression analyses. RESULTS: (1) There were statistically significant differences in root resorption in relation to gender (estimate of RRAT for female: 0.41, that for male: 0.34), extraction (estimate of RRAT for the extraction group: 0.43, that for non-extraction: 0.31), anterior or posterior teeth (estimate of RRAT for the anterior teeth: 0.59, that for the posterior teeth: 0.12). (2) The estimate of RRAT for the upper teeth was 0.40, and that for the lower teeth was 0.37. There were no statistically significant differences. (3) Using multiple regression analysis, age, duration and RRBT were associated with RRAT (R = 0.59, R(2) = 0.35). CONCLUSIONS: (1) Factors including gender, extraction or not and anterior or posterior teeth have influences on the RRAT. More root resorption was found in female or extraction cases. Anterior teeth were more susceptible to root resorption relative to posterior teeth. (2) Age, treatment duration and RRBT can explain approximately 35% of the RRAT. Root resorption aggregated when it was present before treatment. The age and treatment duration were lightly related to the root resorption.

[The effect of pre-surgical orthodontics on secondary alveolar bone grafting in the patients with complete cleft lip and palate].

OBJECTIVE: To examine the effect of pre-surgical orthodontics on the outcome of the secondary alveolar bone grafting in the patients with complete cleft lip and palate. METHODS: Sixteen complete cleft lip and palate patients (9 males and 7 females) with collapsed upper arch or severe mal-positioned upper incisors were selected. The cleft was not easily grafted because of the poor access. The total cleft sites were 22 (10 patients with UCLP and 6 patients with BCLP). The age range of the patients was from 8 to 22 years. Pre-surgical orthodontic treatment was mainly to expand the collapsed upper arch and correct the mal-positioned upper incisors. After the secondary alveolar bone grafting, the patients were followed up and anterior occlusal radiograph/intraoral panograph were taken regularly. The observation period was from 6 months to 4 years. Bergland criteria were used to evaluate the interdental septal height. RESULTS: Upper arch expansion and the correction of the mal-positioned upper incisors done by the orthodontic treatment made the bone grafting procedure easier. The clinically successful rate reached 86%. CONCLUSION: The severe upper arch collapse and mal-positioned upper incisors in the patients with complete cleft lip and palate should be corrected orthodontically before the secondary alveolar bone grafting.

[The inhibitory effect of glass ionomer cement for orthodontic bonding on bacteria].

OBJECTIVE: To prove the inhibitory effect of glass ionomer cement for orthodontic bonding on bacteria. METHODS: Twenty-two persons were chosen randomly. In vivo, with the split-mouth technique, brackets were bonded with glass ionomer cement or composite resin respectively. Plaque samples were taken from the area of the adhesive one month after the placement of brackets and incubated for microbiologic analysis. RESULTS: There was no significant difference in the amount of total anaerobic bacteria with the two materials. There were also no obvious reduction of the numbers of S. mutans (the composite: 2.4 x 10(10) CFU/L, the glass ionomer cement: 2.8 x 10(10) CFU/L, P = 0.673) and its proportion (percentage of total CFU) with the use of glass ionomer cement compared with the composite. CONCLUSIONS: There was no long term inhibitory effect on bacteria adjacent to glass ionomer cement for orthodontic bonding.

[Combined orthodontic-periodontal treatment on periodontal patients with anterior displaced incisors].

OBJECTIVE: Combined orthodontic-periodontal treatment with supracrestal fiberotomy was undergone on the periodontal patients with anterior displacement of incisors. Evaluate of the changes before and after treatment. METHODS: Periodontal indices, periapical x-ray analysis, and model analysis were used for investigating the changes of alveolar bone height and periodontal health by orthodontic treatment following supracrestal fiberotomy of anterior displaced incisors on periodontal patients. RESULTS: Alveolar bone height was increase by 1.2 mm in fiberotomy patients. The overjet was reduced from 7.0 mm to 2.0 mm, while the overbite was decreased from 4.0 mm to 2.0 mm, and the periodontal health maintained as well. CONCLUSION: Combined orthodontic periodontal treatment with supracrestal fiberotomy could correct the malpositioned teeth, and improve the periodontium conditions and gain the crest bone.

[Application of straight wire appliance for pre- and post-surgical orthodontics].

OBJECTIVE: To analyze the surgical patients treated with straight wire appliance for guidelines of clinical using of the appliance. METHODS: Totally 51 patients from Joint Clinic of Orthodontic Surgery, Peking University School of Stomatology with dentofacial deformities treated with straight wire appliance were analyzed. The patients were aged from 15 years to 34 years 5 months, average 18 years 9 months. Among whom, 16 are males, while the other 35 are females. RESULTS: Eighteen patients were treated with extraction of teeth, while other 33 cases were nonextraction case. The duration of average presurgical orthodontic treatment was 13.3 months, and 10.4 months was for postsurgical orthodontic treatment, totally active treatment time was 25.5 months. CONCLUSIONS: Straight wire appliance would benefit a lot for three dimensional control of teeth when doing pre- and post-surgical orthodontic treatment. Good results could be achieved without wire bending.

[The three-dimensional nonlinear finite element analysis of force system of the "rocking-chair archwire"].

OBJECTIVE: The purpose of this study was to qualitatively and quantitatively analyze the initial force system of "rocking-chair archwire" on every tooth. METHODS: Three-dimensional finite element model of "rocking-chair archwire" was set up, and nonlinear method was used to analyze the force system. RESULTS: The archwire exerted intruding force, labial force, lingual-root torque and mesial-labial moment on incisors; Extruding force, lingual-root torque and mesial-labial moment were applied on canines and premolars; The archwire also created intruding force, buccal force, buccal-root torque and mesial-labial moment on molars. CONCLUSIONS: "rocking-chair archwire" produced a complicated force system. While intruding incisors, molars and extruding premolars. It has a tendency to induce tooth rotation and tipping.