Margareta Bendeus

Virtual model analysis as an alternative approach to plaster model analysis: reliability and validity

The objective of this study was to assess the feasibility of virtual models as an alternative to orthodontic plaster models. Virtual dental models (obtained from OrthoCAD) and corresponding plaster models of 80 patients in the permanent dentition were randomly selected from patients seeking orthodontic care. Inter-examiner error was assessed by measuring tooth width, overjet, overbite, intermolar width, intercanine width, and midline discrepancy. Criterion validity of virtual model analysis was determined by the agreement between the measurements from virtual and plaster models. Test-retest reliability was determined by remeasuring 10 virtual models 1 week later. Comparison analysis was assessed by calculating the mean directional differences and standardized directional differences. Correlation analysis was determined by calculating the intraclass correlation coefficients (ICCs). Both intra- and inter-examiner reliability and test-retest reliability of virtual model analysis were acceptable in measuring intercanine, intermolar, overjet, overbite, midline discrepancy, space analysis, and tooth width (ICC > 0.7). Good criterion validity was indicated by agreement between the results from the plaster and virtual models (ICC > 0.8). There were substantial agreements for canine and molar relationship classifications (κ > 0.70). The results suggest that analysis performed on virtual models is as valid as traditional plaster models for intra- and inter-arch relationship.

A Follow-up Study of Early Treatment of Pseudo Class III Malocclusion

This study investigated the long-term outcome of 27 consecutive young patients diagnosed with pseudo Class III malocclusion treated with simple fixed appliance (2 x 4 appliance), which resulted in a positive overjet in all cases. Of the original sample of 27 patients, 25 patients (93%) were examined at the five-year follow-up. Two patients dropped out soon after the active treatment was completed. Of the remaining 25 patients, 20 patients had had no other treatment other than treatment with 2 x 4 appliance, and the other five patients had undergone additional comprehensive fixed appliance therapy because of crowding. Lateral cephalograms were obtained before and after active treatment with the 2 x 4 appliance and at five-year follow-up. The long-term results showed that at the five-year follow-up all 25 patients still maintained a positive overjet. The immediate treatment outcome in the sagittal plane was the same for those who had had 2 x 4 appliance treatment only and those who had had additional treatment with comprehensive fixed appliance treatment, but lower face height increased (P < .01) and the mandibular plane angle opened (P < .05) more in those who had had additional treatment, comprehensive fixed appliance treatment. During the five-year follow-up period, the dental compensation and the growth of the jaw were similar in both groups. In conclusion, in young patients diagnosed with pseudo Class III malocclusion and treated early with a 2 x 4 appliance, the overjet was corrected, and the treatment result was maintained in the long term.

Condylar growth and mandibular positioning with stepwise vs maximum advancement

INTRODUCTION The aim of this study was to compare the effects of several Class II malocclusion treatments on condylar growth and positioning of the mandible. METHODS The material comprised series of lateral cephalograms obtained at the start, after about 6 months, and after about 12 months of treatment from 3 groups of consecutively treated patients who used a headgear-activator with stepwise mandibular advancement (HGA-S), a headgear-activator with maximum jumping of the mandible (HGA-M), and a headgear-Herbst appliance with stepwise advancement (HGH-S), respectively. Six-month growth data from matched controls were used to calculate the net treatment effects. RESULTS Mandibular prognathism was enhanced after stepwise advancement but not after maximum jumping, and only during the initial phase of therapy; the effect was significantly greater for the fixed functional appliance than for the removable functional appliance. Lower-facial height was increased by the HGA-S, unchanged by the HGA-M, and restrained by the HGH-S. The low construction bite of the HGH-S meant that the extent of bone apposition on the posterior and superior parts of the condyle was similar, whereas the high construction bite of the HGA-S and the HGA-M meant that the effect on the superior part was greater, but only significantly so after stepwise advancement. CONCLUSIONS The mode of jumping, the vertical opening, and whether the functional appliance is fixed or removable affect the amount and pattern of condylar growth, and the position of the mandible.

Anteroposterior dental arch and jaw-base relationships in a population sample.

OBJECTIVE To determine the association between the anteroposterior relationship of the dental arch and the anteroposterior relationship of the jaw-base in a Chinese population sample. MATERIALS AND METHODS Orthodontic casts and lateral cephalograms were obtained from a random sample of 405 twelve-year-old Chinese children from a population survey in Hong Kong. Angles classification was used to assess the dental arch relationship from orthodontic casts. The jaw-base relationship was assessed from the lateral cephalograms using angular (ANB angle) and linear (Wits analysis) measurements. The correlation between the anteroposterior dental arch and jaw-base relationships was assessed. RESULTS The anteroposterior dental arch did coincide with the jaw-base relationships, as expressed by the ANB angle in 61%, the Wits analysis in 67%, and with both in 53%. The jaw-base relationship assessed with the Wits analysis was more significantly associated with the dental arch relationship (P < .001) than that assessed with the ANB angle (P < .01). The correlation coefficient between the ANB angle and the Wits appraisal was .65 for the combined sample, and .60, .64, and .67 for Class I, II, and III dental arch relationships. CONCLUSION In this population, the anteroposterior relationship of the dental arch and jaw-base fail to match in at least one out of every three individuals. Linear measurement of anteroposterior jaw-base relationships is a more valid reflection of the dental arch relationship than angular measurements.

Digital images as an alternative to orthodontic casts in assessing malocclusion and orthodontic treatment need

Objective. To investigate the potential use of two-dimensional digital images as an alternative to orthodontic casts in the assessment of malocclusion and orthodoantic treatment need. Material and Methods. Assessment of malocclusion (Angles classification of molars, overjet, and overbite) and orthodontic treatment need (Index of Orthodontic Treatment Need (IOTN): Dental Health Component (DHC) and Aesthetic Component (AC)) was conducted on 313 study casts and their images by two trained and calibrated examiners. Agreement of orthodontic treatment need and Angles molar classification was assessed employing Kappa statistics (κ). Agreement of overjet and overbite (measured in mm) was assessed in comparison and correlation analyses. Inter- and intra-examiner reliability of assessment was investigated. Results. There was substantial agreement of the molar relationship classifications (κ >0.70), orthodontic treatment need as assessed by IOTN-DHC (κ =0.79) and IOTN-AC (κ =0.56) between measurements obtained from orthodontic casts and their images. There was also substantial agreement of measurements of overjet and overbite as obtained from orthodontic casts and their images. The standardized directional differences of overjet and overbite were ≤0.2. The intra-class correlation coefficients of assessments of overjet and overbite obtained from orthodontic casts and their images were >0.90. Inter- and intra-examiner reliability for the assessment of malocclusion and orthodontic treatment need was acceptable. Conclusion. Two-dimensional digital images can be used as an alternative to casts in assessment of malocclusion and orthodontic treatment need.