Effects of the headgear-activator Teuscher appliance in the treatment of Class II Division 1 malocclusion: a geometric morphometric study

Biomechanical effects of Teuscher activator in hyperdivergent Class II malocclusion treatment: A finite element analysis

Background

In orthodontic treatment, the combination of an activator with a headgear is commonly used in treatment of the hyperdivergent Class II malocclusion. However, the distribution of stresses transmitted to the maxilla by these appliances has been little studied. This study aimed to compare the biomechanical effects of stresses transmitted to the maxilla and teeth by a Teuscher activator (TA) for different lines of action of extraoral force, using finite element analysis.

Material and Methods

A tridimensional finite element model of the maxilla and teeth was created based on the true geometry of a human skull. The (TA) and the face bow were designed in 3D computer-aided design and fixed in the maxilla model. To study the effects of mechanical stress transmitted to the maxilla in the treatment of hyperdivergent Class II malocclusion with (TA) combined with extraoral forces, five different finite element models were used, considering the centers of resistance of the maxilla and dentition.

Results

The results showed that stresses increased progressively when the force line of action moved in posteroanterior direction. Von Mises equivalent stress was lower in Model 1 (0°) than in Model 5 (60°). In Models 1 (0°) and 2 (15°), molars suffered greater distal displacement and incisors showed extrusion. In Model 3 (30°), the force line of action promoted a distal displacement of molars and incisors. In Models 4 (45°) and 5 (60°), the whole maxillary anterior sector showed counterclockwise displacement.

Conclusions

Different force lines of action influence the intensity and distribution of orthodontic and orthopedic forces in the maxilla. The extraoral force's line of action used in Model 3 (30°) is the most compatible with the objectives of the hyperdivergent Class II malocclusion treatment in growing patients. Key words:Class II, Headgear, Early treatment, FEA.

Evaluation of the Posterior Airway Space Following Biobloc Therapy: Geometric Morphometrics

The aim of this study was to evaluate changes in the posterior airway space in patients following Biobloc therapy, using geometric morphometrics. Pre- and post-treatment lateral cephalographs of 53 children (mean age, 12.9 +/- 1.5 years; mean treatment time, 21.3 +/- 6.2 months) were scanned and 27 landmarks encompassing the airway were digitized. Mean configurations were computed using Procrustes superimposition, followed by principal components analysis (PCA) and finite-element scaling analysis (FESA). Marked shape-changes were identified using PCA for the airway following treatment (p < 0.01). Using pseudo-colored FESA, a relative 31% increase in nasopharyngeal airway area was found above and behind the soft palate. Additionally, a 23% increase in oropharyngeal airway area was located behind the base of the tongue with a 9% increase in hypopharyngeal area near the level of the hyoid bone. Functional airway improvements are associated with Biobloc treatment in actively growing patients.

Successful early neonatal repair of cleft lip within first 8 days of life

OBJECTIVE

In the children born with a cleft lip, surgery is the first step in correcting the inborn anomaly. In comparison with usually made 3-month surgery, benefits of the surgery in neonates have been reported: a very good wound healing, feeding facilitation, and good socialization of a child from neonatal age. The aims of the present study were to perform cheiloplasty in early newborns affected by the total cleft lip and palate (CLP) by the technique modified to search for optimum aesthetic result, and to assess the surgery outcome from qualitative and quantitative aspects.

METHODS

The operations were performed by the same surgeon in 97 neonates 1-8 days old during 2005-2008. The original technique by Tennison was modified and used. Aesthetic outcome of the surgery was evaluated according to scar visibility, and the shape and symmetry of the lip and nose. The effect of cheiloplasty on the formation of the upper jaw segments was evaluated in a sample of unilateral CLP patients using the 3D-finite element scaling analysis (FESA). We compared 3D models of dental plaster casts made prior to lip surgery (in neonates under 8 days of age) and prior to palate surgery (at 12 months of age).

RESULTS

Only the children in excellent health state and without an associated inborn defect were allowed to pass the operation. There were no per-operative complications (except the correction of tracheal tube position in several cases). The parents appreciated bringing home a neonate with no visible cleft. This aspect not only facilitated baby feeding, but had important positive psycho-social impact on the whole family. The wound healing and aesthetic effect of the cheiloplasty were very good. The scar was barely visible and lip and nose were symmetric in majority of children. After lip closure, the growth and approximation of jaw segments was observed. This aspect was also associated with incisors development in the anterior portion of the segment including premaxilla.

CONCLUSIONS

Our results show, that early neonatal lip surgery of CLP is promising technique with very good aesthetic results and important positive psychological impact on the child and its family.

Surface facial modelling and allometry in relation to sexual dimorphism

Sexual dimorphism is responsible for a substantial part of human facial variability, the study of which is essential for many scientific fields ranging from evolution to special biomedical topics. Our aim was to analyse the relationship between size variability and shape facial variability of sexual traits in the young adult Central European population and to construct average surface models of adult males and females. The method of geometric morphometrics allowed not only the identification of dimorphic traits, but also the evaluation of static allometry and the visualisation of sexual facial differences. Facial variability in the studied sample was characterised by a strong relationship between facial size and shape of sexual dimorphic traits. Large size of face was associated with facial elongation and vice versa. Regarding shape sexual dimorphic traits, a wide, vaulted and high forehead in combination with a narrow and gracile lower face were typical for females. Variability in shape dimorphic traits was smaller in females compared to males. For female classification, shape sexual dimorphic traits are more important, while for males the stronger association is with face size. Males generally had a closer inter-orbital distance and a deeper position of the eyes in relation to the facial plane, a larger and wider straight nose and nostrils, and more massive lower face. Using pseudo-colour maps to provide a detailed schematic representation of the geometrical differences between the sexes, we attempted to clarify the reasons underlying the development of such differences.

Effects of activator and high-pull headgear combination therapy: skeletal, dentoalveolar, and soft tissue profile changes

The aim of this study was to evaluate skeletal, dentoalveolar, and soft tissue profile changes with activator and high-pull headgear combination therapy in patients with Class II malocclusions caused by maxillary prognathism and mandibular retrognathism. The subjects, all in the mixed dentition, were selected from a single centre and were divided into two groups: 28 patients were treated with an incisor double capping activator and a high-pull headgear combination appliance (13 girls, 15 boys mean chronological age 11.7 +/- 1.2 years, skeletal age 12.1 +/- 1.4 years) and an untreated group of 28 subjects (14 girls, 14 boys mean chronological mean age 11.9 +/- 1.1 years, skeletal age 12.3 +/- 1.3 years). The skeletal, dentoalveolar, and soft tissue profile changes that occurred were compared on lateral cephalograms taken before treatment (T0) and after 1.1 +/- 0.3 years when the combination appliance was removed (T1). In the control group, the radiographs were obtained at the start (T0) and after an observation period 1.2 +/- 0.4 years (T1). Statistical analysis was undertaken with Wilcoxon's ranked-sum test for intra-group comparisons and differences between groups with t-test and Bonferroni's test at a level of significance of P < 0.05. Activator and high-pull headgear combination treatment in these growing patients resulted in a correction of the skeletal Class II relationship (ANB -3.4 degrees), a restriction of maxillary growth (SNA -2.0 degrees, OLp-A -2.3 mm), an advancement of the mandibular structures (SNB +2.6 degrees, FH-NPg +2.3 degrees, OLp-B +2.7 mm, OLp-Pg +2.2 mm), an increase in lower face height (ANS-Me +3.9 mm), a correction of the overjet (-5.4 mm), an improvement in overbite (-2.2 mm), uprighting of the maxillary incisors (U1-FH -5.3 degrees, OLp-U1 -2.5 mm), protrusion of the mandibular incisors (IMPA +2.0 degrees, OLp-L1 +2.7 mm), and a correction of the dental Class II malocclusion (OLp-L6 +3.5 mm). The soft tissue profile changes were a correction of facial convexity (G'-Sn-Pg' angle 2.3 degrees, Mlf-Li-x-axis angle 9.1 degrees), and an increase in lower antero-posterior (Mlf-y-axis 5.6 mm, Pg'-y-axis 5.3 mm), and lower vertical (Sls-x-axis 3.8 mm, Pg'-x-axis 3.8 mm, Me'-x-axis 5.1 mm) soft tissue dimensions. The mentolabial fold depth (Mlf-E line) also significantly decreased, -0.8 mm in the treated group. The activator and high-pull headgear combination appliance was effective in treating growing patients with maxillary prognathism, mandibular deficiency, and facial convexity by a combination of skeletal and dentoalveolar changes and improvement in the soft tissue facial profile.