[Experts consensus on diagnostic and therapeutic strategies for malocclusions at early developing stage].

Early orthodontic intervention remains a controversial notion in current dental care regime. Whilst early orthodontic treatment for children is the province for orthodontic specialists, a growing number of general practitioners, who may not possess sufficient specialty knowledge, are also involved, raising the concerns about the propriety and quality of their treatment modalities. However, orofacial development of children and adolescents is in a very complicated environment. Comprehensive theoretical knowledge and a great wealth of practical experience are required to ensure the final treatment effect. The possible complications should be kept under control and fully informed to patients and their parents. In order to unify and standardize early orthodontic treatment protocol and help to promote healthy and orderly development of early orthodontic treatment, this consensus summarized the practical experience of orthodontic experts from many famous colleges and affiliated hospitals for clinical reference.

Dehiscence and fenestration in anterior teeth : Comparison before and after orthodontic treatment.

BACKGROUND: Previous studies have reported incidence rates of dehiscence (DEH) and fenestration (FEN) as high as 36.51 and 51.09%, respectively. Only a few studies comparing DEH and FEN before and after orthodontic treatment (OT) are available in the literature. PURPOSE: The aim of this study was to evaluate the occurrence of DEH and FEN in anterior teeth, before and after OT, using cone-beam computed tomography (CBCT). In addition, findings may provide a clinical basis for avoiding DEH and FEN during therapeutic tooth alignment. PATIENTS AND METHODS: CBCT images of 21 patients near the end of their peak growth and development were included. DEH and FEN in the anterior teeth and thicknesses of the alveolar bone at the palatal (TP) and labiolingual (LL) sides of each anterior tooth were measured before and after OT. RESULTS: After OT, the incidence rates of mandibular anterior labial DEH, maxillary anterior TP-bone defect, and mandibular anterior lingual bone defect were increased by 20, 19, and 30%, respectively. Assessment of CT images prior to treatment showed that the teeth developing bone defects were significantly different regarding the apical alveolar bone thicknesses compared to the teeth that did not develop bone defects after OT, i.e., the incidence of DEH and FEN after OT was lower if the thickness of the apex to labiolingual alveolar bone before OT was as follows: the apex to labial alveolar bone thickness of the maxillary central incisor and maxillary lateral incisor was >4 mm, the apex to palatal alveolar bone thickness of the maxillary lateral incisor was >3 mm; the apex to labiolingual alveolar bone thickness of the lower incisor was >5 mm. CONCLUSION: The incidence of post-OT DEH at the maxillary anterior and mandibular anterior lingual surfaces were increased significantly compared to before treatment. In general, the smaller the apex to labiolingual alveolar bone thickness, the greater the likelihood of bone defects occurring after OT. Evaluation of the apical position of anterior teeth in alveolar bone can help minimize the occurrence of bone defects after OT.

Novel rechargeable calcium phosphate nanoparticle-containing orthodontic cement.

White spot lesions (WSLs), due to enamel demineralization, occur frequently in orthodontic treatment. We recently developed a novel rechargeable dental composite containing nanoparticles of amorphous calcium phosphate (NACP) with long-term calcium (Ca) and phosphate (P) ion release and caries-inhibiting capability. The objectives of this study were to develop the first NACP-rechargeable orthodontic cement and investigate the effects of recharge duration and frequency on the efficacy of ion re-release. The rechargeable cement consisted of pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol A dimethacrylate (EBPADMA). NACP was mixed into the resin at 40% by mass. Specimens were tested for orthodontic bracket shear bond strength (SBS) to enamel, Ca and P ion initial release, recharge and re-release. The new orthodontic cement exhibited an SBS similar to commercial orthodontic cement without CaP release (P>0.1). Specimens after one recharge treatment (e.g., 1 min immersion in recharge solution repeating three times in one day, referred to as "1 min 3 times") exhibited a substantial and continuous re-release of Ca and P ions for 14 days without further recharge. The ion re-release did not decrease with increasing the number of recharge/re-release cycles (P>0.1). The ion re-release concentrations at 14 days versus various recharge treatments were as follows: 1 min 3 times>3 min 2 times>1 min 2 times>6 min 1 time>3 min 1 time>1 min 1 time. In conclusion, although previous studies have shown that NACP nanocomposite remineralized tooth lesions and inhibited caries, the present study developed the first orthodontic cement with Ca and P ion recharge and long-term release capability. This NACP-rechargeable orthodontic cement is a promising therapy to inhibit enamel demineralization and WSLs around orthodontic brackets.

Effects of quaternary ammonium chain length on the antibacterial and remineralizing effects of a calcium phosphate nanocomposite.

Composites containing nanoparticles of amorphous calcium phosphate (NACP) remineralize tooth lesions and inhibit caries. A recent study synthesized quaternary ammonium methacrylates (QAMs) with chain lengths (CLs) of 3-18 and determined their effects on a bonding agent. This study aimed to incorporate these QAMs into NACP nanocomposites for the first time to simultaneously endow the material with antibacterial and remineralizing capabilities and to investigate the effects of the CL on the mechanical and biofilm properties. Five QAMs were synthesized: DMAPM (CL3), DMAHM (CL6), DMADDM (CL12), DMAHDM (CL16), and DMAODM (CL18). Each QAM was incorporated into a composite containing 20% NACP and 50% glass fillers. A dental plaque microcosm biofilm model was used to evaluate the antibacterial activity. The flexural strength and elastic modulus of nanocomposites with QAMs matched those of a commercial control composite (n = 6; P > 0.1). Increasing the CL from 3 to 16 greatly enhanced the antibacterial activity of the NACP nanocomposite (P < 0.05); further increasing the CL to 18 decreased the antibacterial potency. The NACP nanocomposite with a CL of 16 exhibited biofilm metabolic activity and acid production that were 10-fold lesser than those of the control composite. The NACP nanocomposite with a CL of 16 produced 2-log decreases in the colony-forming units (CFU) of total microorganisms, total streptococci, and mutans streptococci. In conclusion, QAMs with CLs of 3-18 were synthesized and incorporated into an NACP nanocomposite for the first time to simultaneously endow the material with antibacterial and remineralization capabilities. Increasing the CL reduced the metabolic activity and acid production of biofilms and caused a 2-log decrease in CFU without compromising the mechanical properties. Nanocomposites exhibiting strong anti-biofilm activity, remineralization effects, and mechanical properties are promising materials for tooth restorations that inhibit caries.

Mechanical Properties of Orthodontic Thermoplastics PETG/ PC2858 after Blending.

OBJECTIVE: To characterise and compare the tensile characteristics after multi-proportional blending, to determine the proper blending ratio for new thermoplastic material and to compare its mechanical performance with commercial thermoplastics. METHODS: PETG and PC2858 aggregates were blended in five different ratios. Standard specimens of each ratio were molded and tested to determine their mechanical performance. Then the new material with the proper blending ratio was chosen and compared against commercial thermoplastics. RESULTS: With the increase of PC2858 content, the tensile and impact strength increased but elongation at break decreased. When blending ratio (wt %) was 70/30, the PETG/PC2858 exhibited optimal mechanical properties, with a tensile strength of 63.42 ± 1.67 MPa, and a stress relaxation rate of 0.0080 ± 0.0005 N/s, which exceeded those of Erkodur and Biolon. CONCLUSION: By blending PETG and PC2858 at the weight ratio 70/30, we obtained new thermoplastic material which outperformed commercial products.

Integrated three-dimensional digital assessment of accuracy of anterior tooth movement using clear aligners.

OBJECTIVE: To assess the accuracy of anterior tooth movement using clear aligners in integrated three-dimensional digital models. METHODS: Cone-beam computed tomography was performed before and after treatment with clear aligners in 32 patients. Plaster casts were laser-scanned for virtual setup and aligner fabrication. Differences in predicted and achieved root and crown positions of anterior teeth were compared on superimposed maxillofacial digital images and virtual models and analyzed by Student's t-test. RESULTS: The mean discrepancies in maxillary and mandibular crown positions were 0.376 ± 0.041 mm and 0.398 ± 0.037 mm, respectively. Maxillary and mandibular root positions differed by 2.062 ± 0.128 mm and 1.941 ± 0.154 mm, respectively. CONCLUSIONS: Crowns but not roots of anterior teeth can be moved to designated positions using clear aligners, because these appliances cause tooth movement by tilting motion.

A novel protein-repellent dental composite containing 2-methacryloyloxyethyl phosphorylcholine.

Secondary caries due to biofilm acids is a primary cause of dental composite restoration failure. To date, there have been no reports of dental composites that can repel protein adsorption and inhibit bacteria attachment. The objectives of this study were to develop a protein-repellent dental composite by incorporating 2-methacryloyloxyethyl phosphorylcholine (MPC) and to investigate for the first time the effects of MPC mass fraction on protein adsorption, bacteria attachment, biofilm growth, and mechanical properties. Composites were synthesized with 0 (control), 0.75%, 1.5%, 2.25%, 3%, 4.5% and 6% of MPC by mass. A commercial composite was also tested as a control. Mechanical properties were measured in three-point flexure. Protein adsorption onto the composite was determined by the microbicinchoninic acid method. A human saliva microcosm biofilm model was used. Early attachment at 4 h, biofilm at 2 days, live/dead staining and colony-forming units (CFUs) of biofilms grown on the composites were investigated. Composites with MPC of up to 3% had mechanical properties similar to those without MPC and those of the commercial control, whereas 4.5% and 6% MPC decreased the mechanical properties (P<0.05). Increasing MPC from 0 to 3% reduced the protein adsorption on composites (P<0.05). The composite with 3% MPC had protein adsorption that was 1/12 that of the control (P<0.05). Oral bacteria early attachment and biofilm growth were also greatly reduced on the composite with 3% MPC, compared to the control (P<0.05). In conclusion, incorporation of MPC into composites at 3% greatly reduced protein adsorption, bacteria attachment and biofilm CFUs, without compromising mechanical properties. Protein-repellent composites could help to repel bacteria attachment and plaque build-up to reduce secondary caries. The protein-repellent method might be applicable to other dental materials.

Reliability assessment and correlation analysis of evaluating orthodontic treatment outcome in Chinese patients.

This study aimed to assess the reliability of experienced Chinese orthodontists in evaluating treatment outcome and to determine the correlations between three diagnostic information sources. Sixty-nine experienced Chinese orthodontic specialists each evaluated the outcome of orthodontic treatment of 108 Chinese patients. Three different information sources: study casts (SC), lateral cephalometric X-ray images (LX) and facial photographs (PH) were generated at the end of treatment for 108 patients selected randomly from six orthodontic treatment centers throughout China. Six different assessments of treatment outcome were made by each orthodontist using data from the three information sources separately and in combination. Each assessment included both ranking and grading for each patient. The rankings of each of the 69 judges for the 108 patients were correlated with the rankings of each of the other judges yielding 13 873 Spearman rs values, ranging from -0.08 to +0.85. Of these, 90% were greater than 0.4, showing moderate-to-high consistency among the 69 orthodontists. In the combined evaluations, study casts were the most significant predictive component (R(2)=0.86, P<0.000 1), while the inclusion of lateral cephalometric films and facial photographs also contributed to a more comprehensive assessment (R(2)=0.96, P<0.000 1). Grading scores for SC+LX and SC+PH were highly significantly correlated with those for SC+LX+PH (r(SC+LX)vs.(SC+LX+PH)=0.96, r(SC+PH)vs.(SC+LX+PH)=0.97), showing that either SC+LX or SC+PH is an excellent substitute for all three combined assessment.

[Bond strengths of customized titanium brackets manufactured by selective laser melting].

OBJECTIVE: To investigate the bond strengths of customized titanium bracket manufactured by selective laser melting. METHODS: Eighty human premolars which had been extracted for orthodontic purpose were collected and divided randomly (by random table) into two groups (customized bracket group and 3M bracket group, 40 molars in each group). The 35% phosphoric acid was used for etching and the brackets were bonded with 3M Unitek bonding adhesive. All bonded specimens were placed in saline for 24 hours at room temperature and were tested on DWD3050 electronic testing machine to determine the shear bond strength and tensile bond strength. After debonding, the adhesive remnant indexes (ARI) were recorded. RESULTS: The shear bond strengths of customized brackets was 6.80 (6.20, 8.32) MPa, which was significantly lower than that of the 3M brackets [10.46 (9.72, 11.48) MPa] (Z = -3.463, P < 0.05). And the tensile bond strengths of customized brackets was (6.93 ± 1.21) MPa, which was significantly higher than that of the 3M brackets [(5.88 ± 1.23) MPa] (t = 2.81, P < 0.05). No significant difference was found in the ARI between two different kinds of the brackets. CONCLUSIONS: The shear bond strength and tensile bond strength of both kinds of brackets were enough for clinic application.

[Repeatability of three-dimensional measurements based on cone-beam CT images].

OBJECTIVE: To investigate the repeatability of three-dimensional (3-D) cephalometric measurements for the clinical application of 3-D cephalometry. METHODS: Forty-nine measurements that widely used in traditional cephalometric analyses were defined in 3-D cone-beam CT (CBCT) images. Three examiners identified landmarks on CBCT images of 17 subjects with normal occlusion, respectively, and 3-D measurements were exported automatically by software SimPlant. Inter-examiner reliability correlation coefficients (ICC) were obtained for all measurements. RESULTS: Repeatability of 36 measurements was high (ICC value greater than 0.9), including SNA, SNB. Repeatability of 11 measurements was moderate (ICC value between 0.8 and 0.9), including CoL-GoL, CoL-MSP. Repeatability of 2 measurements was low (ICC value lower than 0.8), including Gn-MSP and MPR-MSP. CONCLUSIONS: Most 3-D cephalometric measurements based on CBCT had high repeatability. However, some 3-D cephalometric measurements had limited repeatability.

Validation of the American Board of Orthodontics Objective Grading System for assessing the treatment outcomes of Chinese patients.

INTRODUCTION: Orthodontics in China has developed rapidly, but there is no standard index of treatment outcomes. We assessed the validity of the American Board of Orthodontics Objective Grading System (ABO-OGS) for the classification of treatment outcomes in Chinese patients. METHODS: We randomly selected 108 patients who completed treatment between July 2005 and September 2008 in 6 orthodontic treatment centers across China. Sixty-nine experienced Chinese orthodontists made subjective assessments of the end-of-treatment casts for each patient. Three examiners then used the ABO-OGS to measure the casts. Pearson correlation analysis and receiver operating characteristic curve analysis were conducted to evaluate the correspondence between the ABO-OGS cast measurements and the orthodontists' subjective assessments. RESULTS: The average subjective grading scores were highly correlated with the ABO-OGS scores (r = 0.7042). Four of the 7 study cast components of the ABO-OGS score-occlusal relationship, overjet, interproximal contact, and alignment-were statistically significantly correlated with the judges' subjective assessments. Together, these 4 accounted for 58% of the variability in the average subjective grading scores. The ABO-OGS cutoff score for cases that the judges deemed satisfactory was 16 points; the corresponding cutoff score for cases that the judges considered acceptable was 21 points. CONCLUSIONS: The ABO-OGS is a valid index for the assessment of treatment outcomes in Chinese patients. By comparing the objective scores on this modification of the ABO-OGS with the mean subjective assessment of a panel of highly qualified Chinese orthodontists, a cutoff point for satisfactory treatment outcome was defined as 16 points or fewer, with scores of 16 to 21 points denoting less than satisfactory but still acceptable treatment. Cases that scored greater than 21 points were considered unacceptable.

[Effect of orthodontic force on expression of Asporin after tooth auto-transplantation: an experimental study in Beagle dogs].

OBJECTIVE: To evaluate the effect of orthodontic light force on the expression of Asporin, bone morphogenetic proteins-2 (BMP-2) and alkaline phosphatase (ALP) after auto-transplantation. METHODS: Thirty-two maxillary and mandibular incisors in four 13 month-old male Beagle dogs were auto-transplanted to the other side of the same jaw. The teeth were all endodontically treated and divided into four groups, control (group 1) and three experimental groups (groups 2, 3 and 4).In control group, the teeth were unloaded. In the other three experimental groups, continuous force was applied in the 1st week (group 2), 2nd week (group 3) and 4th week (group 4) after auto-transplantation, respectively. The dogs were sacrificed in the 8th week. The mRNA expressions of Asporin,BMP-2 and ALP were examined by real time PCR. The expression of periodontal ligament associated protein-1 (PLAP-1) was examined by Western blotting. The data were statistically analyzed using SPSS 17.0 and one-way analysis of variance (ANOVA). RESULTS: In group 3, the expression of Asporin mRNA (2.047 ± 0.281) was higher than that in the other three groups, while the expression of BMP-2 (1.358 ± 0.095) was lower than that in group 2 and control group (P < 0.05). The expression of PLAP-1 (1.054 ± 0.113) in group 3 was higher than other groups, while significant difference was found between any two groups. CONCLUSIONS: Orthodontic force could stimulate the expression of Asporin and PLAP-1. The orthodontic force applied in the 2nd week after the tooth auto-transplantation, the expression of Asporin and PLAP-1 reached the highest level.

[Application of integrated digital maxillodental model in computer aided design of individualized lingual brackets].

OBJECTIVE: To create an integrated digital maxillodental model and to apply it in computer aided design (CAD) of individualized lingual brackets in order to align both crowns and roots without fenestration and dehiscence. METHODS: Cone-beam computerized tomography (CBCT)-based maxillodental model and laser-scanned dental model were integrated by auto registration in 10 patients with malocclusions. The registration error was calculated automatically. Three observers tested the method independently. The inter-observer difference was investigated. An integrated model was selected randomly and the setup was created with roots and jaws in good relationship without fenestration and dehiscence. The individualized lingual brackets were designed by CAD on the setup. RESULTS: No significant difference was found in inter observers (P > 0.05). The registration errors of maxilla and mandible were (0.144 ± 0.020) mm and (0.141 ± 0.022) mm, respectively. The digital individualized lingual brackets based on the virtual treatment in integrated digital maxillodental model were produced. CONCLUSIONS: An integrated digital maxillodental model was created in good accuracy. By applying the integrated model, individualized lingual brackets were designed.

[Research on Chinese orthodontic specialists' subjective evaluation of orthodontic treatment outcome].

OBJECTIVE: To analyze the results of multiple Chinese orthodontic specialists' subjective evaluation of orthodontic treatment outcome, to investigate the relevance of different experiment items and to explore the weight of each monomial material. METHODS: As a randomized clinical trial, with six orthodontic treatment centers and Angle's classification being regarded as two stratification factors, it contained 108 cases with integrity data, which was random extracted from 2383 cases that received orthodontic treatment in six orthodontic treatment centers during the past five years, gathering post-treatment study casts, cephalometrics and photographs of 48 cases as the research subject. Similarly taking Angle's classification as a stratification factor, 108 cases were randomly divided into 9 groups. The randomization of sampling and grouping were both generated by a pseudo-random number generator. According to the monomial and combined subjects, 69 orthodontic specialists were regarded as the raters to rank the 12 cases in each group, and to judge whether the case was qualified. RESULTS: Correlation analysis: the Spearman r between Post-M + C and Post-M + C + P and the Spearman r between Post-M + P and Post-M + C + P were both greater than 0.950. The Spearman r between Post-M and Post-P and the Spearman r between Post-M and Post-C were about 0.300. The Spearman r between Post-P and Post-C was 0.505. Regression analysis: the linear regression results: M + C = 0.782M + 0.308C - 0.150, M + P = 0.804M + 0.233P - 0.091, M + C + P = 0.764M + 0.243P + 0.131C - 0.291. The r(2) of above three models was greater than 0.9. CONCLUSIONS: It was applicable to use M + C and M + P instead of M + C + P. Study casts could not replace cephalometrics or photographs when doing subjective evaluation. Cephalometrics and photographs could not substitute for each other either. In the combined materials evaluation, model accounted for the largest percentage. Based on the regression model, for the greater part, the integration of several monomial materials could replace the combined material assessment effectively.

[Effect of orthodontic force on periodontal healing after autotransplantation: an experimental study].

OBJECTIVE: To investigate the effect of the continuous light force to the donor teeth on the periodontal healing after transplantation. METHODS: Thirty-two maxillary and mandibular incisors in four 10-month-old male Beagle dogs were autotransplanted. The pulps were removed in all teeth. The teeth were divided into four groups, one control and three experimental groups. In control group (group 1), the teeth were unloaded. In the other three experimental groups, continuous force (0.49 N) was applied in the 1st (group 2), 2nd (group 3) and 4th (group 4) week, respectively. The dogs were sacrificed in the 8th week. The tissue blocks were demineralized and sectioned perpendicular to the long axis of the teeth. The histological analysis was made. RESULTS: Histomophometric analysis revealed a significantly lower occurrence of replacement root resorption in the group 3 (2.1%) than in the control group (12.5%, P < 0.05). The significant lower incidence of replacement root resorption, and a higher surface and inflammatory root resorption were found in group 2 (6.3% and 68.8%) than in the control group (12.5% and 41.7%, P < 0.05). No significant difference was found between group 4 and control group (P > 0.05). CONCLUSIONS: The orthodontic force promoted the regeneration of the periodontal ligament and prevented dentoalveolar ankylosis, whereas excessive initial force might cause root and bone resorption.

[Three-dimensional analysis of craniofacial growth in adolescents with normal occlusion in Beijing].

OBJECTIVE: To analyze craniofacial growth three-dimensionally for adolescents with normal occlusion in Beijing. METHODS: One hundred and twenty-six adolescents with normal occlusion were selected according to the criteria. The sample was divided into four age groups (53 within 4 years, 30 within 7 years, 27 within 10 years and 16 within 13 years). Information of growth was collected. Three-dimensional cephalometric system based on cone-bean CT was established. RESULTS: From 4 to 13 years Co-A increased (14.55 ± 1.15) mm on average on the left and (13.66 ± 1.14) mm on the right, and Co-Gn increased (22.89 ± 1.40) mm on the left and (22.82 ± 1.38) mm on the right; and U1-NA increased (2.20 ± 0.44) mm on the left and (1.60 ± 0.46) mm on the right; and CoL-CoR and GoL-GoR increased (13.31 ± 1.21) mm and (18.59 ± 1.40) mm, and N-Me increased (18.03 ± 1.32) mm.SN-PP and SN-MPL basically remained unchanged. CONCLUSIONS: Adolescents with normal occlusion in Beijing grew obviously in three-dimensions and developed harmoniously.

[A comparative study of mechanical properties of commercialized dental thermoplastic materials].

OBJECTIVE: To compare the mechanical properties of different dental optimal material selection for orthodontic appliance. METHODS: Four commercialized thermoplastic products under different test conditions, and provide the suggestion of thermoplastic products were tested. The tear strength, elongation at break and stress relaxation of these materials were measured under different test conditions. RESULTS: The tear strength declined after thermoforming, and rose again after 2 weeks of distilled water immersion. The elongation at break rose after thermoforming, and declined after 2 weeks of distilled water immersion. No significant changes were observed for brand A under different test conditions. Brand A showed the slowest stress relaxation of 0.0148 N/s. CONCLUSIONS: The mechanical properties of thermoplastic materials were influenced by environmental factors. Brand A exhibited optimal comprehensive properties.

[Evaluation of periodontal tissue during orthodontic tooth movement in rats: a micro-computed tomography study].

OBJECTIVE: To observe the microstructure changes of rat alveolar bone around tooth root under orthodontic force loading. METHODS: Ten 10-week-old rats were included in the study. Upper first molars were moved mesially with 0.196 N of force. The alveolar bone around the root of upper first molar was scanned by a micro-computed tomography scan system (SkyScan-1076) in different period after the initiation of orthodontic force loading (on the 3rd, 7th, 14th day after force loading) and analyzed by a specially-designed software to measure the microstructure parameters of alveolar bone (bone volume fraction, bone surface to volume ratio, structure model index, trabecular thickness, trabecular separation, trabecular number). RESULTS: From the 7th day, bone volume fraction [(41 ± 14)%], structure model index (1.51 ± 0.52) and trabecular separation [(90 ± 30) µm] changed significantly in the compressive area compared with those [(64 ± 15)%, (0.51 ± 0.85), (56 ± 10) µm] on the 3rd day. From the 14th day, bone volume fraction [(78 ± 14)%], structure model index (0.28 ± 0.20) and trabecular separation [(29 ± 13) µm] changed significantly in the tension area compared with those [(67 ± 14)%, (0.40 ± 0.41), (48 ± 15) µm] on the 7th day. No difference on trabecular number was found between the compressive area and tension area (P > 0.05). CONCLUSIONS: The significant resorption of the alveolar bone was observed on the 7th days in the compressive area and the deposition of the alveolar bone was observed on the 14th day in the compressive area after orthodontic force loading.