Three-Dimensional Analysis of Maxillary Dental Casts Using Fourier Transform Profilometry: Precision and Reliability of the Measurement

Morphometric covariation between palatal shape and skeletal pattern in children and adolescents: a cross-sectional study

Objective

To assess shape covariation of the palate and craniofacial complex (CFC) in children and adolescents.

Methods

Pre-treatment lateral cephalometric radiographs and corresponding maxillary casts of 100 children (8-10 years) and 100 adolescents (15-20 years) were digitized. Exclusion criteria were previous orthodontic treatment, craniofacial syndromes, mouth breathing, finger sucking, crossbite, tooth agenesis, and tooth impaction. Palatal shape was described with 239 surface and curve semilandmarks and craniofacial shape with 10 fixed landmarks and 117 curve semilandmarks. Procrustes superimposition and principal component analysis were applied for evaluation of shape variability. Shape covariation between palate and CFC was assessed with partial least squares analysis.

Results

The first five principal components explained 77 per cent (palate) and 60 per cent (CFC) of total shape variability. The palate varied mainly in height (adolescent group) and width-length (both groups), whereas the CFC varied mainly in the vertical dimension. Significant covariation was found between the craniofacial and palatal components (RV coefficient: 0.27, children; RV: 0.23, adolescents). Variation of the CFC in the vertical and anteroposterior direction was mainly related to variation in the height-width and the width-length ratio of the palate, respectively.

Limitations

The use of lateral cephalometric radiographs eliminated the transverse dimension from the craniofacial shape analysis. The study was cross-sectional, so the observed intergroup differences should be interpreted with caution.

Conclusions

Covariation strength and pattern were similar in children and adolescents. The closer a subject was to the high-angle end of the variability spectrum, the higher and narrower was the palate, and conversely.

Multibracket appliance: impression defaults and their reduction by blocking-out - a three-dimensional study

OBJECTIVES

This study examines accuracy of dental impressions and following plaster models taken during treatment with fixed appliances.

MATERIALS AND METHODS

A maxillary typodont was provided with brackets. Three examiners took impressions three times each of the variants: brackets only, archwire fixed by alastics, ligatures or Kobayashi-hooks, and brackets and archwire covered completely or just on the gingival side by protection or impression wax. Casts were scanned using Activity102(®). Virtual models were compared to the scan of the typodont using Comparison(®). Differences were measured and descriptively analyzed. Estimated means with 95% confidence intervals were computed. Significance was assessed using linear mixed models.

RESULTS

While pyramidal reference blocks had a mean difference of 0.019 mm (95% CI = 0.017-0.021 mm) to the master model, teeth without attachments showed 0.097 mm (95% CI = 0.082-0.111 mm), and teeth with brackets 0.169 mm (95% CI = 0.156-0.182 mm) (p < 0.001). Smallest mean was found when using protection wax only on the gingival bracket side (0.152 mm (95% CI = 0.113-0.192 mm)). Incisors deviated most (0.258 mm (95 % CI = 0.239-0.277 mm)).

CONCLUSIONS

Teeth with brackets make impressions more inaccurate because of undercuts. Removing the archwire before taking the impression or covering the brackets on the gingival side shows tendencies toward better precision.

CLINICAL RELEVANCE

Taking impressions during treatment with fixed appliances, some inaccuracy has to be taken into account.

Three-dimensional analysis of palatal shape in patients treated with SARME using traditional and geometric morphometrics

OBJECTIVES

To demonstrate the advantages of dense surface models in the evaluation of surgical-assisted rapid maxillary expansion's effect (SARME) on palatal morphology. Furthermore, we compared the palatal surface before (T1) and after (T2) therapy with controls.

SETTING AND SAMPLE POPULATION

Surgical-assisted rapid maxillary expansion's effect group of 15 adult patients (Le Fort I and midpalatal sagittal osteotomy, hyrax screw) and 50 adult individuals. Patients were treated in General Faculty Hospital, Prague.

MATERIALS AND METHODS

Eighty plaster casts were digitized using a three-dimensional laser scanner and evaluated using traditional and geometric morphometrics.

RESULTS

An unpaired Student's t-test on the controls and the SARME T1 group revealed significant differences in all width measurements. Between the controls and the SARME T2 group, significant differences were only related to the interdental angle between the first molars and particularly to the palatal height. The most remarkable differences between the pre- and post-treatment palatal morphology were a widening of the dental arch and buccal shift of the lateral teeth associated with apparent flattening of the alveolar crest.

CONCLUSIONS

Dense surface model provided descriptive visualization of the treatment effect and was helpful in the evaluation of palatal shape variability including detection of the most difficult patients. Correction of the dental arch width discrepancy by SARME was successfully achieved. After therapy, palatal shape variability of most of the patients was comparable to the variability of the control group.

Three-dimensional morphology of the palate in patients with bilateral complete cleft lip and palate at the stage of permanent dentition

OBJECTIVE

Three-dimensional analysis of palate size and shape in 30 patients with complete bilateral cleft lip and palate (BCLPc) at the stage of permanent dentition.

DESIGN

Cross-sectional study based on laser scanning.

SUBJECTS

Thirty dental casts of boys approximately 15 years old with BCLPc and 28 dental casts of healthy boys of the same age.

INTERVENTIONS

Arched-lip suture with periosteoplasty and push-back of the palate with pharyngeal-flap surgery.

MAIN OUTCOME MEASURES

Data on palate height in the 210 defined locations and on palate widths and profile area in 10 transverse sections.

RESULTS

The palate in patients with BCLPc was conical and narrower than in control study subjects, much more anteriorly than posteriorly. From the canines posteriorly, the palate was of almost constant height of 10 mm in the midline, being higher than in control study subjects at this location and lower more posteriorly (by 24% to 29% between molars). The area of transverse sections was reduced as compared with control study subjects from the first premolars posteriorly and reached more than 40% between molars. The length of the palate up to the first molars was not changed.

CONCLUSION

BCLPc subjects exhibited narrow, low, and flat palate. Palate size and shape differences indicate a substantial reduction of the space for the tongue.

Three-Dimensional Palatal Development between 3 and 6 Years

Objective: To measure palatal landmarks of healthy nonpatient children aged 3 to 6 years with a normal deciduous dentition and to evaluate palatal shape independent of size.

Materials and Methods: Fifty-eight dental casts of children with a normal and complete deciduous dentition were obtained and digitized with a computerized 3D instrument. At all ages, male and female data did not differ (Student's t-test), so the pooled values were considered. Dimensions were compared between ages by analyses of variance.

Results: Palatal slope and height increased significantly as a function of age (P &lt; .001). Palatal length did not change with age (average: 23.1 mm). In the frontal plane, the intermolar width increased slightly with age by about 1.8 mm at the second molars, 1.1 mm at the first molars, and 0.9 mm at the canines. Palatal height in the frontal plane did not change in the posterior part of the palate, but decreased anteriorly. The intercanine distance increased by 0.9 mm with age. However, this change did not reach statistical significance.

Conclusions: Between 3 and 6 years of age, palatal shape changed and became proportionally higher in both the frontal and sagittal planes.

Objective growth monitoring of the maxilla in full term infants

OBJECTIVE

To develop a non-invasive method for longitudinal maxillary volume measurements and to provide first normative data.

DESIGN

Thirty-four healthy infants served as a gold standard for a growing population sample. Alginate impressions were taken of the upper jaw within the first week after birth, and consecutively at different stages of development. The plaster casts were digitised by an optical scanner generating a high resolution polygon mesh of each object. The digital models were aligned to a reference coordinate system with an iterative, landmark-independent procedure. Biometric linear and volume measurements were obtained by using feature-dependent calculations independent of landmark placements. Intra-investigator reproducibility was tested by repeated alignments and measurements of 30 randomly selected casts. To assess the effect of mesh resolution, the reproducibility test was repeated with low resolution models. The method was proved to be valid on the defined gold standard consisting of 96 consecutive edentulous casts.

RESULTS

Feature-dependent, linear distances are less error prone (0.56-2.66%) compared to subjectively determined measurements (0.88-3.65%). The same applies to feature-dependent volume calculations (4.34%) compared to subjectively determined volumes (4.95%). Mesh resolution shows an effect (p<or=0.001) only on two linear measurements: palatal depth and palatal length. Growth of the individuals in the population sample was evidently confirmed by the maxillary volume measurements (asymptotic pattern) and by comparisons of head circumference (proportional pattern).

CONCLUSION

The described method is non-invasive, precise and without any risk for the infant. Maxillary volume calculation could serve as an important biometric measurement for bone growth evaluation.