The appliance produced an increase in the intermolar width averaging 0.5 mm after 8 days. Tetracycline uptake in the control rats suggested a rapid turnover of bone in both the interradicular domain and the bone–periodontal ligament interface. In the experimental group, however, incorporation of tetracycline into the interradicular domain was reduced and conventional histology revealed evidence of bone loss and osteopenia, in both the experimental and a group of sham-treated positive controls (with inactive, annealed springs). Serum alkaline phosphatase declined significantly in both experimental and sham-treated groups over the 8-day time course, indicating decreased bone formation. Serum acid phosphatase also declined, suggesting a concomitant decrease in bone resorption. Three-dimensional FE analysis of the stresses generated in the bone following occlusal (2 N) and orthodontic loading showed that the orthodontic force created a constant loading condition shielding some areas of bone from mechanical stress. Areas of low mechanical stimulation were coincident with sites of bone loss observed histologically, while bone mass was preserved in areas with higher levels of loading.

These findings suggest that (1) the osteopenia resulted from stress shielding of the interradicular bone by the appliance, and a consequent reduction in occlusal loading below the critical threshold required for maintaining normal osseous architecture and (2) the mechanostat model can be employed to explain, at least in part, the response of the bone to orthodontic loading.

Mobility was detected in three of the 56 (5.4 per cent) MSIs. The mobile implants were all unloaded controls and showed no BIC. All remaining stable MSIs showed some BIC. However, variation in BIC was large, ranging from 2.2 to 100 per cent. There were no significant (P > 0.05) differences in BIC associated with timing of force application, amount of force applied, or implant location. There was a tendency for less BIC at the coronal level, but the differences between levels were not statistically significant. Within the limits of this study, it is concluded that the timing and amount of force at loading and location of implant placement do not affect BIC. Moreover, it appears that only limited amounts of osseointegration are necessary to ensure implant stability.

Pre-treatment digital cephalometric radiographs of 125 patients were traced using Vistadent 2.1 AT and Jiffy Orthodontic Evaluation (JOE) software programs and by hand tracing of the printouts. Twenty-six anatomical landmarks were defined on each radiograph by a single investigator and 28 variables were calculated. Statistical analysis was undertaken using one-way analysis of variance and multiple group comparisons using Duncan's test at a significance level of 0.05.

Low correlation coefficients indicated poor reproducibility for nasolabial angle for each of the three methods (P > 0.05). Most of the variables showed consistency between the three methods except for nasolabial angle, ANS–Me, APFH, L1–NB, Nperp–Pg, Go–Me, and U1–NA measurements. The findings indicated that most of the cephalometric measurements were highly reproducible with direct digital radiographs using Vistadent 2.1 AT as well as with printouts using both JOE software and hand tracing. Despite the low correlation for some measurements between the Vistadent 2.1 AT, JOE, and hand-tracing methods, most of the commonly used measurements were accurate. The user-friendly and time-saving nature of the computerized method using digital radiographs makes it the preferred option.

Pre- and post-surgical lateral cephalographs of 30 adult patients (12 males and 18 females, median age = 25 years, standard deviation = 8.7) who had undergone orthognathic treatment were scanned into a computer. One operator identified 25 landmarks digitally on the computer display and manually on acetate paper. Measurements on the 60 radiographs were duplicated, and measurement error of each method was determined with interclass correlation. A paired t-test was used to detect differences between the manual and digital methods.

Overall, greater variability in digital cephalometric measurements was found. Differences in Gn’, Li, Si, and Ii–Li measurements between the two methods were statistically (P < 0.05), but not clinically significant.

The findings indicate that the results of the two investigated tracing methods are similar and that digital tracing with FACAD® is reliable and can be used routinely.

Significant differences were found between the two methods for SNB, Wits appraisal, Cd–A, Cd–Gn, FMA, SN–PP, U1–NA (mm), U1–FH, L1–NB (mm), and Li–E plane. No significant differences were found between the two methods in the measurement of treatment changes. Cephalometric measurements of most parameters were reproducible for both methods. Despite some discrepancies in measured values between hand-tracing and the computerized method, any differences were minimal and clinically acceptable.

The as-received wires exhibited an inhomogeneous surface with different surface irregularities resulting from the manufacturing process. For the in vivo archwires, an increase in the variety, type, and number of surface irregularities were observed. Crevice corrosion occurred not only at surface irregularities formed during manufacturing and orthodontic handling but also at the bracket-archwire-contacting surfaces and at the archwire surfaces coated with plaque and food remnants. This corrosion may be linked to the formation of a micro-environment at these locations. In addition, a limited number of signs of degradation induced during in vivo testing due to wear and friction were observed.

Non-parametric tests (Mann–Whitney U) indicated significant differences between the two groups (P < 0.009). Lower bond strengths were found for the silanated group implying that silane agents may be an unnecessary step. However, both groups had a clinically acceptable mean SBS [silanated group = 13.1 megapascals (Mpa), non-silanated group = 19.4 MPa]. Bond failure occurred at the bracket–adhesive interface in both groups. There would appear to be no advantage in using a silane agent when bonding metal orthodontic brackets to filled RCs.

The differences between SBSs analysed at 12 and 24 hours were not significantly different. Although a significant difference (P < 0.01) was observed with conventional and self-etching primer (SEP) adhesive systems, SEP revealed bond strengths higher than clinically accepted limits (6–8 MPa). SEP systems can achieve successful orthodontic bond strengths. The rate of development of the bond strength must be determined to ensure sufficient maturation of orthodontic adhesives before functional loading.

Forty-five (30 fluorosed and 15 non-fluorosed) non-carious fresh human premolar teeth, extracted for orthodontic reasons and without any caries or visible defects, were used in this study. The fluorosed teeth were selected according to the modified Thylstrup and Fejerskov index, which is based on the clinical changes in fluorosed teeth. In groups 1 (fluorosed teeth) and 3 (control), the brackets were bonded with Light Bond composite resin and cured with a halogen light. In group 2, Enhance LC was applied to fluorosed enamel before bonding. After bonding, the SBS of the brackets was tested with a universal testing machine. One-way analysis of variance and Tukey multiple comparison tests were used to compare the SBS of the groups. Any adhesive remaining after debonding was assessed and scored according to the modified adhesive remnant index.

The results showed that while fluorosis significantly reduced the bond strengths of the orthodontic brackets (mean 13.94 ± 3.24 MPa; P < 0.01), Enhance LC significantly increased bond strength on fluorosed enamel (mean 18.22 ± 5.97 Mpa; P < 0.05). Groups 1 and 3 had greater bond failures at the composite–bracket interface, whereas group 2 showed bond failure primarily at the enamel–composite interface.

The values for reliability of the total and weighted ICON scores were generally high for the T₀ sample (range 0.83–0.95) but less high for the T₁ sample (range 0.55–0.85). Differences in total ICON score between plaster and digital models resulted in mostly statistically insignificant values (P values ranging from 0.07 to 0.19), except for observer 1 in the T₁ sample. No statistically different values were found for the total ICON score on either plaster or digital models.

ICON scores performed on computer-based models appear to be as accurate and reliable as ICON scores on plaster models.

In the early group, 70 per cent, and in the late group 42 per cent, of adolescents had a history of orthodontic treatment. General dentists carried out 90 per cent of the treatment in the early group and specialists every third treatment in the late group. An early start resulted in more frequent visits (P = 0.004) and a longer treatment duration (P < 0.001), while later timing resulted in an increase in the number of appliances (P < 0.001).

Overjet exhibited an extreme range between –2 and 12 mm (median values 3–3.5 mm). An increased overjet was more prevalent than a reduced or reverse overjet, and a severely increased overjet greater than 6 mm was a common finding affecting around 5–10 per cent of the children. Similarly, overbite showed considerable variations of between –1 and 9 mm (medians 3–3.5 mm) and males exhibited a significantly larger overbite than females. In Class II malocclusion subjects, overbite was significantly enlarged (on average between 0.5 and 1 mm) when compared with those with a Class I malocclusion. Traumatic contact of the gingiva affected every 14th child. A Class II molar relationship of three-quarter units or more was a frequent finding affecting more than one child in five. In addition, at 9 years of age, 3 per cent of the children exhibited a Class III molar relationship of at least a half unit. The wide range of orthodontically relevant occlusal traits found in the present study underlines the need for orthodontic screening at 9 years of age (or earlier).

In a cross-sectional analytical study, the craniofacial structure and profile based on two-dimensional lateral cephalograms of Southern Chinese hypodontia patients (n = 49, 24 males, 25 females, mean age 16.4 years) and a comparison group without hypodontia (n = 41, 15 males, 26 females, mean age 16.7 years) were compared. The hypodontia patients were divided into three subgroups according to the severity of hypodontia (mild: ≤5, moderate: 6–9, and severe: ≥10 congenitally missing permanent teeth).

All hypodontia patients had a significantly reduced mandibular plane, ANB, and face height compared with the control group (P < 0.05). A significant increase in chin thickness was also observed in the hypodontia patients (P < 0.05). As the severity of hypodontia increased from moderate to severe, a tendency to develop a retrognathic maxilla and a Class III skeletal relationship was noted in addition to the above features, making the already thick chin even more prominent. Statistically significant correlations (Pearson's correlation coefficient) were found between the number of missing teeth and SNA, NAFH, and ANB angles, the mandibular plane, chin thickness, and face height.

In Southern Chinese subjects, hypodontia was associated with a shorter face, a flatter mandibular plane, a more pronounced chin, and a Class III skeletal profile. In severe hypodontia subjects, the maxilla was more retrognathic with a greater predilection to a Class III skeletal relationship.

The results showed some correlation between morphology and muscle function (at a confidence level of 95 per cent). However, as the values of the correlation coefficient (r) were too low to establish associations between variables, it was concluded that the dimensions of the upper lip are not correlated with muscle activity.

In the first experiment, a force of 20 cN was applied to eight canines in five volunteers. The mean tooth movement during 10 weeks was 2.4 mm. In the second experiment, two forces of 20 or 200 cN were applied to maxillary premolars in 12 male subjects (aged 24–31 years) to measure pain intensity for 7 days. Spontaneous and biting pain were recorded every 2–4 hours on a 100 mm visual analogue scale (VAS). Wilcoxon signed-rank test was used for statistical analysis.

Comparing the VAS score at force initiation with the other time points, there was no significant difference in spontaneous pain for either group, or in biting pain for the light-force group. However, biting pain in the heavy-force group during the time period from 6 to 156 hours was significantly (P < 0.05) greater than that at force initiation. Comparing the VAS scores between the light- and heavy-force group, VAS scores for biting pain in the heavy-force group during the time period from 8 to 100 hours was significantly (P < 0.05) greater than that in the light-force group.

A force of 20 cN can move teeth, but pain intensity while biting may be greater approximately 8 hours to 5 days following the application of heavy continuous force compared with light force.

SNA, ANB, OcP-NL, OcP-ML, upper space balance, overbite, overjet, bilateral molar relationship, and L1-NB changed significantly (P ≤ 0.05) during treatment. The changes in overbite, overjet, spatial conditions, and molar relationship were in line with the targeted treatment objectives and within the normal range. Although the change in L1-NB was probably due to treatment, it was not clinically relevant given that the mean final values were close to normal at 22.8 degrees (SD 5.8°) for L1-NB and 95 degrees (SD 8°) for L1-ML.

Isolated orthodontic space closure for bilateral upper lateral incisor aplasia using PPM can be regarded as a valid alternative to prosthetic solutions. Long-term use of Class III elastics does not lead to significant changes in relevant orthodontic parameters.

The addition of RME to fixed appliance therapy caused a change in transverse measurements between the medial aspects of the bilateral rugae. There was no change in antero-posterior measurements (APM). The transverse changes were more marked for the third, less for the second rugae, and the least for the first rugae. The medial aspects of the third rugae cannot be considered as stable reference landmarks for dental cast analysis when RME is performed in addition to fixed appliance therapy.

The findings demonstrated that the two maxillary premolar extraction protocol provided the occlusal outcomes in a shorter time (group 1: 45.7 months, group 2: 23.01 months) and, therefore, demonstrated greater treatment efficiency than the pendulum appliance.