Τετάρτη, 28 Αυγούστου 2019

Three-dimensional skeletal and pharyngeal airway changes following therapy with functional appliances in growing skeletal Class II malocclusion patients

Abstract

Introduction

To three-dimensionally analyze the skeletal and pharyngeal airway changes induced by Twin Block (TWB) and Forsus Fatigue Resistance Device (FFRD) in skeletal Class II female patients compared with untreated controls.

Materials and methods

The study comprised 62 growing female patients with skeletal Class II malocclusion due to mandibular retrusion treated with either TWB (n = 23) or FFRD (n = 21), or neither (n = 18; controls). Pre- and posttreatment/observational cone beam computed tomography images were used to evaluate the treatment changes.

Results

TWB induced more obvious mandibular skeletal changes and caused significant retrusive effects on the maxilla. Similarly, the sagittal and vertical jaw relationships were affected more obviously with TWB (P <0.001) compared to FFRD. Changes in oropharyngeal volume and minimal axial area were more obvious with TWB.

Discussion

The TWB functional appliance induced significant skeletal and pharyngeal airway changes. These changes were more obvious relative to the slight changes induced by FFRD or by natural growth.

Effect of rapid maxillary expansion on the morphology of spheno-occipital synchondrosis in rats

Abstract

Purpose

Spheno-occipital synchondrosis (SOS) plays a significant role in the anterior growth of the midface. Orthopaedic forces acting during rapid maxillary expansion (RME) are transferred to the skull base and thus could alter the morphology of SOS. The aim of this study was to assess the influence of experimental RME on the rats’ SOS by means of micro-computed tomography (micro-CT).

Methods

In all, 40 male 8‑week-old Wistar rats were enrolled into the study, among which 30 underwent experimental RME for 7, 14 and 21 days by means of custom designed spring-coil expander. Specimens were scanned by micro-CT and median palatal suture area, maxillary skeletal base and SOS width were analysed.

Results

Experimental RME resulted in a significant increase of the median palatal suture space and maxillary skeletal base which was particularly pronounced between day 14 and 21 of expansion. SOS width increased significantly during the first 7 days at the lowest point of the synchondrosis. However, the SOS width assessed at its highest point was temporarily even decreased between days 8 and 14 of therapy.

Conclusions

Early SOS widening could be identified in the lowest part before median palatal suture opening. Similarly, narrowing of the SOS at its top was observed before the most significant median palatal suture expansion. Thus it can be hypothesized that changes within the SOS complex result from the transmission of the orthopaedic forces rather than from a displacement of the maxillary halves.

Is there a relationship between maxillary canine impaction and ocular asymmetry

Abstract

Introduction

Impacted maxillary canines may be in close proximity with related structures, such as the nasal cavity, orbital cavity, and maxillary sinus. The aim of this study was to evaluate the effects of unilateral maxillary canine impaction on ocular asymmetry. The null hypotheses were as follows: (1) there is no difference in the ocular location between the subjects with impacted canines and the control group; (2) there is no difference in the ocular location between the two sides of subjects with impacted canine.

Methods

A total of 50 subjects with unilateral palatally impacted maxillary canines were selected as the study group, and 49 subjects without any impacted teeth were selected as controls. Ocular asymmetry was evaluated on standardized frontal photographs of the subjects in both groups, and the results were statistically compared.

Results

Unilateral impaction of maxillary canines did not have a statistically significant effect on the vertical ocular location, nor did maxillary canine impaction affect the horizontal ocular location on either side of the face within the impacted canine group. There was a statistically significant difference in the horizontal ocular location between the impacted canine group and the control group. Gender differences did not have an effect on the ocular location in either of the study groups.

Conclusions

Both hypotheses were accepted. A relationship between the impacted maxillary canine and ocular asymmetry could not be demonstrated.

Qualitätssicherung in der Kieferorthopädie

Comparison of crevicular fluid cytokine levels after the application of surface sealants

Abstract

Purpose

Surface sealants are widely used in orthodontic practice to avoid enamel decalcifications in patients treated with fixed orthodontic appliances. While their clinical benefit was tested in several studies, their biocompatibility has been evaluated to a lesser extent. Therefore, the aim of this randomized prospective study was to evaluate possible adverse biological effects of three commonly used surface sealants and a bonding primer on gingival tissues by analysing cytokines in crevicular fluid of orthodontic patients after the application of surface sealants.

Methods

A single centre parallel trial was conducted. Using a split-mouth design quadrants of 15 patients requiring orthodontic treatment with fixed appliances were randomized to one of three commonly used surface sealants (Pro Seal®, Opal®Seal™, Protecto®CaF2Nano) and a bonding primer (Transbond™ XT). Interleukin (IL)-8 and IL-10 levels in crevicular fluids of the individual quadrants were assessed at four different time points (before application, and at 30, 60 and 90 min after application).

Results

In all, 60 quadrants of 15 patients were randomized (Pro Seal® n = 15, Opal®Seal™ n = 15, Protecto®CaF2Nano n = 15, Transbond™ XT n = 15) and analysed. No significant changes for IL-8 or IL-10 levels in crevicular fluid after the application of surface sealants or bonding primer were detected. However, interpatient variability was high. No further clinical side effects were detected.

Conclusions

Commonly used pre-bonding surface sealants (Pro Seal®, Opal®Seal™) do not appear to have a significant impact on inflammatory cytokines levels of crevicular fluid and do not appear to contribute to sensitization or hypersensitivity events.

Mitteilungen der DGKFO

Experimental friction and deflection forces of orthodontic leveling archwires in three-bracket model experiments

Abstract

Objective

In vitro testing of archwires in a multibracket model may provide estimates of force–moment (F/M) systems applied to individual teeth in a realistic geometry. Such investigations have mostly been performed by continuous wire deflection, leading to frictional forces biasing the pure deflection forces. Aim of this study was to quantify this bias and the pure deflection forces for leveling archwires.

Materials and methods

Three nickel–titanium (NiTi) and two multistranded wires were tested in a three-bracket model simulating vertical movement of an upper incisor with a typical interbracket distance of 8 mm (intercenter). To determine pure deflection forces, the middle bracket was first leveled incrementally from its vertical malposition to neutral position with repeated wire insertion at each step (so-called “static leveling mode”). For comparison, forces at the middle bracket were also determined during dynamic leveling with or without ligation of the wire at the lateral brackets by either elastic, tight or loose steel ligatures.

Results

The dynamic mode resulted in significantly lower mean leveling forces for all the tested wires (ANOVA [analysis of variance], p < 0.01) compared to the static mode. Expressed in numbers, dynamic wire unloading resulted in mean force underestimation of 53 ± 9% (loose steel ligatures), 56 ± 11% (elastic ligatures) or 91 ± 29% (tight steel ligatures).

Conclusions

Orthodontic tooth movement is quasi-static. This concerns the initial hyalinization phase in particular. Thus, especially static testing of archwires provides valid reference data for the peak forces exerted directly after clinical insertion of a leveling wire. In dynamic wire testing, significant underestimation of actual forces exerted on individual teeth may occur due to experimental friction, which might considerably differ from that occurring during clinical therapy. This aspect has to be taken into account in the interpretation of published stiffness values for orthodontic wires, and in the selection of the appropriate archwire for leveling of the present tooth malposition, respectively.

Influence of the three-dimensional printing technique and printing layer thickness on model accuracy

Abstract

Objective

The accuracies of three-dimensional (3D) printed dental models using various digital light processing (DLP) and stereolithography (SLA) printers at different thicknesses were compared.

Materials and methods

Based on digital dental models (originally digitized using R700; 3Shape, Copenhagen, Denmark), physical dental models were printed using three types of DLP printers: (1) EvoDent (UnionTec, Shanghai, China) with layer thicknesses of 50 μm and 100 μm; (2) EncaDent (Encashape, WuXi, China) with layer thicknesses of 20, 30, 50 and 100 μm; (3) Vida HD (Envisioned, Dearborn, MI, USA) with layer thicknesses of 50 and 100 μm. Models with the SLA printer Form 2 (Formlabs, Somerville, MA, USA) were printed with layer thicknesses of 25, 50 and 100 μm. All 22 printed models were converted to digital dental models using a D2000 model scanner (3 Shape, Copenhagen, Denmark) and compared three-dimensionally to the source files using Geomagic Qualify 12.0 (3D Systems, Rock Hill, SC, USA).

Results

The printing accuracy of all printers was higher at 50 μm. When the layer thickness was set at 100 μm, the printing speed and printing accuracy of DLP printer were both superior to those of the SLA printer. In all groups, the EvoDent 50 μm group had the highest consistency with the source files (mean absolute deviation of 0.0233 mm in the maxilla and 0.0301 mm in the mandible). While the accuracy of Form 2 100 μm group was the lowest (mean absolute deviation of 0.0511 mm in the maxilla and 0.0570 mm in the mandible).

Conclusion

For the 3D printers studied, 50 μm was the optimum layer thickness for DLP technology, and the printing accuracy using SLA technology increased with decreasing layer thickness. The DLP technology also had higher printing accuracy at a layer thickness of 100 μm. EvoDent 50 μm had the highest and Form 2 100 μm the lowest printing accuracy.

Gender-dependent impact of aging on facial proportions

Abstract

Purpose

Facial proportions in younger people have been evaluated in several studies. However, the number of older people who need orthognathic surgery is growing steadily. The aim of this study was to evaluate facial morphology in Caucasians accounting for age and gender.

Methods

Three-dimensional facial scans of 240 healthy volunteers were taken. The subjects were divided into males and females, then into three groups by age (21–35, 36–50 and 51–65 years). Landmarks and artificial planes were placed in the scans. Distances, relations and angles between them and the artificial frontal plane were recorded.

Results

Nearly all distances between the tragion and the landmarks in the middle of the face increased with the age of the volunteers. Therefore, the soft tissue of the face grows horizontally with increasing age. Also, the length of the upper lip increased with age. The percentage of subnasale-stomion and stomion-menton distances of the total subnasale-stomion-menton measurement changed significantly (men: p = 0.149; women: p < 0.001) during aging in females but not in males. The landmarks in the upper and middle third of the face were closer to the frontal plane in women than in men.

Conclusion

Using the created frontal plane for evaluating landmarks in the sagittal plane facilitates measuring positions of soft tissue. There are significant changes in distances, angles and relations during aging which can be very important for planning orthognathic surgery.

Mitteilungen der DGKFO

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