Treatment change comparisons between skeletal Class I and II white adolescents with 3 different vertical divergencies-Part 2: Holdaway difference.

INTRODUCTION: The Holdaway difference represents the relationship of the NB line to the mandibular incisor (NB-L1) and the bony pogonion (NB-Pog). This study aimed to evaluate treatment changes of NB-L1, NB-Pog, and the Holdaway difference in patients with skeletal Class I and II relationships with 3 different skeletal divergencies. METHODS: This retrospective study was the second part of treatment outcome assessments of 135 white adolescent patients (females, n = 69; males, n = 66; mean age, 12.8 ± 1.4 years pretreatment and 15.0 ± 1.4 years posttreatment). The NB-L1, NB-Pog, and Holdaway differences (NB-L1 - NB-Pog) were measured. The mixed-model analysis of variance was used to assess within- and between-subject effects responding to horizontal and vertical skeletal discrepancies. RESULTS: For the group with favorable profile changes, the means of the Holdaway difference were maintained in the hypodivergent and normodivergent subgroups and reduced in the hyperdivergent subgroups for patients with skeletal Class I and II relationships. The means of NB-L1 and Holdaway difference were significantly larger in the skeletal Class II group and became greater as skeletal vertical divergencies increased. The NB-Pog means were significantly different only between the hypodivergent and hyperdivergent subgroups. CONCLUSIONS: Based on the findings of this study, the Holdaway difference should be adjusted to individualize the incisor positions, considering not only the anteroposterior but also the vertical skeletal relationships of the patients.

Treatment change comparisons between skeletal Class I and II white adolescents with 3 different vertical divergencies-part 1: Frankfort-Mandibular Incisor Angle (FMIA) and soft-tissue profile.

INTRODUCTION: This study investigated the interrelationship between FMIA and soft-tissue profile changes in skeletal Class I and II white adolescents with 3 different vertical skeletal patterns. METHODS: Two hundred seventy cephalometric images were constructed from pretreatment and posttreatment cone-beam computed tomography images of 135 white adolescents (69 females and 66 males with a mean age of 12.8 ± 1.4 years pretreatment and 15.0 ± 1.4 years posttreatment). SNA, SNB, ANB, Frankfort Mandibular Angle [FMA], Incisor Mandibular Plane Angle [IMPA], Frankfort-Mandibular Incisor Angle [FMIA], and Z angle were measured. A mixed-model analysis of variance was performed for patients with an increased posttreatment Z angle to evaluate within-subject and between-subject effects of variables in relation to horizontal and vertical skeletal patterns. Post-hoc tests were conducted to identify statistical significance among the 3 different divergent subgroups. RESULTS: Patients with a skeletal Class I relationship had straighter facial profiles and a larger FMIA than patients with a skeletal Class II relationship before and after treatment. FMA, FMIA, IMPA, and Z angle treatment changes were similar between the skeletal Class I and II groups. The final FMIA means of the 3 divergent subgroups converged at 65° in the skeletal Class I group and 60° in the skeletal Class II group. The mandibular incisors were uprighted during treatment in the hyperdivergent patients whose Z angle values increased after treatment. CONCLUSION: Horizontal skeletal relationships seem more suitable for determining the desired FMIA in Tweed's total space analysis than vertical skeletal divergencies.

A cross-sectional retrospective study of normal changes in the pharyngeal airway volume in white children with different skeletal patterns. Part 2: Cervical vertebral maturation method and hyoid bone.

INTRODUCTION: The purpose of this cross-sectional retrospective study was to evaluate the patterns of pharyngeal airway volume change determined by cervical vertebral maturation (CVM) stage and compare it with that which was characterized by chronological age. Correlations between hyoid bone positions and airway volumes were also examined. METHODS: CVM staging was determined from cone-beam computed tomography scans of 420 white patients aged 9-15 years. Patients were stratified on the basis of sex and skeletal pattern to establish pharyngeal airway volume clusters for each CVM stage. The horizontal and vertical positions of hyoid bones were measured using Hyoidius and Sella. RESULTS: Males had larger pharyngeal airway volumes compared with females. In males, the largest increases in pharyngeal airway volumes occurred at an earlier CVM stage than females. No statistically significant differences in pharyngeal airway volumes were noted in subjects with skeletal Class I, II, and III malocclusion. The hyoid bone in males was more anteriorly and inferiorly positioned compared with females. The Class III group had a further forward position of the hyoid bone than the Class I and II groups. CONCLUSIONS: The patterns of pharyngeal airway change obtained using CVM staging did not correlate well with traditional maturational models for skeletal growth. It implies that chronologic age could be a relatively reliable indicator for the assessment of pharyngeal airway volumes in adolescents, as outlined in part 1 of the present study. Subjects with anteriorly and superiorly positioned hyoid bones exhibited smaller pharyngeal airway volumes, which highlights the role of soft tissue and its influence on airway patency.

Effects of maxillary incisor inclination on dentoalveolar changes in class II division 1 and 2 non-extraction treatment for Caucasian children - A retrospective study using CBCT.

OBJECTIVE: The objective of this study was to investigate the effects of maxillary central incisor (U1) inclination changes on alveolar bone and root length in the 20 Class II division 1 and 20 Class II division 2 (CII div1, CII div2) Caucasian adolescents treated without extraction. MATERIAL AND METHODS: Forty U1s from each group were assessed for root length and alveolar variables at the crestal, mid-root, and apical levels using sagittal sections obtained from CBCT images pre- and post-treatment. Mixed MANOVAs, Repeated measures MANOVAs, Pearson correlations, and regression analyses were performed. RESULTS: The facial bone height did not change significantly after an average of 15 degrees of proclination in the CII div2 group, whereas a statistically significant decrease in the palatal bone height was noted. However, in the CII div1 group, a statistically significant reduction in the facial and palatal bone height was observed with mild crown retroclination. Both groups had a significant decrease in total bone thickness at all levels, more decrease in the CII div2 group after treatment. No statistically significant difference in root length was observed between the groups during treatment. CONCLUSIONS: The findings support that the flaring of retroclined U1s as a process for normalizing U1 inclination did not harm the facial alveolar bone height in the CII div2 non-extraction treatment. Crown proclination itself was not correlated to the amount of root resorption in Class II div1&2 non-extraction treatments in adolescents.

A cross-sectional retrospective study of normal changes in the pharyngeal airway volume in white children with 3 different skeletal patterns from age 9 to 15 years: Part 1.

INTRODUCTION: This study investigated correlations between airway size and age, sex, and skeletal patterns; identified airway change trends; and measured volumetric norms in children via cone-beam computed tomography. METHODS: Four hundred twenty nontreated white patients were stratified by age, sex, and anteroposterior skeletal pattern. The nasopharyngeal airway (NPA), oropharyngeal airway (OPA), and total pharyngeal airway (TPA) volumes were delineated on 3-dimensional digital cephalograms. SPSS (SPSS, Chicago, Ill) was used to run an analysis of variance and post-hoc analyses. RESULTS: The Class III group had significantly larger OPA volumes than Class I and II groups. Male subjects had considerably larger NPA volumes than female subjects. Age was significantly associated with all 3 airway volumes (P <0.05). The young cohort (ages, 9-10 years) had a mean TPA of 11,435.34 ± 484.45 mm3, the middle cohort (ages, 11-13 years) had a mean TPA of 14,152.07 ± 395.46 mm3, and the older cohort (ages, 14-15 years) had a mean TPA of 18,057.99 ± 484.25 mm3. CONCLUSIONS: An effect of skeletal classification on OPA and a sex effect on NPA were observed. The annual change in the mean of TPA volume decreased in subjects aged 10-12 years, then rebounded until 14 years. TPA change peaked in female subjects 1 year before male subjects.

Comparison of early treatment outcomes rendered in three different types of malocclusions.

OBJECTIVE: To evaluate the outcome of early treatment in Class I, II, and III malocclusions based on the reduction of weighted Peer Assessment Rating (PAR) scores. MATERIALS AND METHODS: Two hundred thirty subjects (female = 105; male = 125) selected from 400 cases were divided into three groups based on their malocclusions (Class I, II, and III). The PAR index was evaluated prior to early treatment (T0), at the end of phase I (T1), and after completion of phase II therapy (T2). The reliability of overall PAR scores was assessed by Bland-Altman plot and intraclass correlation coefficient. The starting age, total weighted PAR scores and their changes after phase I and II treatments, treatment time, and the percentage of correction in the three different malocclusions were assessed by repeated-measures analysis of variance with post hoc analysis. The level of significance was set at P < .05. RESULTS: More than 30% reduction of the weighted PAR scores and less than 10 points of the remaining weighted PAR scores were observed in all malocclusion groups at T1. The Class III group had the highest percentage of correction during phase I treatment. CONCLUSIONS: Early treatment effectively reduced the complexity of Class I, II, and III malocclusions and accounted for 57%, 64%, and 76% of the total correction, respectively, after phase I treatment, as indicated by an overall reduction in weighted PAR scores. The Class III group responded most favorably to early treatment followed by the Class II group.

Laser-treated stainless steel mini-screw implants: 3D surface roughness, bone-implant contact, and fracture resistance analysis.

BACKGROUND/OBJECTIVES: This study investigated the biomechanical properties and bone-implant intersurface response of machined and laser surface-treated stainless steel (SS) mini-screw implants (MSIs). MATERIAL AND METHODS: Forty-eight 1.3mm in diameter and 6mm long SS MSIs were divided into two groups. The control (machined surface) group received no surface treatment; the laser-treated group received Nd-YAG laser surface treatment. Half in each group was used for examining surface roughness (Sa and Sq), surface texture, and facture resistance. The remaining MSIs were placed in the maxilla of six skeletally mature male beagle dogs in a randomized split-mouth design. A pair with the same surface treatment was placed on the same side and immediately loaded with 200 g nickel-titanium coil springs for 8 weeks. After killing, the bone-implant contact (BIC) for each MSI was calculated using micro computed tomography. Analysis of variance model and two-sample t test were used for statistical analysis with a significance level of P <0.05. RESULTS: The mean values of Sa and Sq were significantly higher in the laser-treated group compared with the machined group (P <0.05). There were no significant differences in fracture resistance and BIC between the two groups. LIMITATION: animal study CONCLUSIONS/IMPLICATIONS: Laser treatment increased surface roughness without compromising fracture resistance. Despite increasing surface roughness, laser treatment did not improve BIC. Overall, it appears that medical grade SS has the potential to be substituted for titanium alloy MSIs.