Heike Korbmacher-Steiner

Therapeutic effects of functional orthodontic appliances on cervical spine posture: a retrospective cephalometric study

IntroductionInteractions between the cervical spine and the stomatognathic system have been discussed in literature. The present study was conducted to investigate whether, and to what extent, orthodontically induced mandibular advancement produces changes in cervical spine posture. Furthermore, possible appliance-specific effects should be distinguished.Material and methodsThe cephalograms of 64 patients with skeletal class II were analysed before and after mandibular advancement. Linear and angular cephalometric parameters were identified to define the position of the atlanto-occipital and atlantoaxial joints. The total example was divided into two subgroups (comprising 32 individuals each) according to the employed appliance: activator versus bite-jump appliance (BJA). Students t-test and analysis of covariance were used for statistical analysis.ResultsOverall, a significant straightening of the cervical spine was observed during the treatment. This conclusion is based on changes of Chamberlain (p = 0.0055), CVT (p = 0.0003), OPT (p < 0.0001), Redlund-Johnell/Petersson (p < 0.0001), McGregor-mC2 (p = 0.0333) and AT-FH (p = 0.0445). Improvements in occipitoatlantal dislocation were also observed in the total sample. Appliance-specific changes were found in the activator subgroup for a number of linear parameters (Chamberlain, McGregor, CVT, OPT, Redlund-Johnell/Petersson). In contrast, only two linear parameters (OPT and Powers ratio) revealed statistically significant changes in the BJA subgroup.ConclusionsDuring skeletal class II treatment the position of upper cervical spine changes. In the activator subgroup the observed effects were more pronounced than those in the BJA subgroup. Further studies including a control group comprised with non-treated class II patients are needed to assess whether these effects may be caused directly by the appliances irrespective of growth.

445-nm diode laser-assisted debonding of self-ligating ceramic brackets

Abstract Objectives: This study determined the influence of irradiation on aesthetic ceramic brackets with a novel 445-nm diode laser prior to debonding on the bracket failure mode. Materials and methods: Thirty ceramic brackets (In-Ovation® C, GAC) were standard-bonded to the oral and buccal planed and polished enamel surfaces of 15 caries-free human 3rd molars. Prior to study-blinded debonding, the brackets in the laser group were irradiated with the diode laser (SIROLaser Blue®, Sirona), while the irradiation was simulated within the conventional group. To determine the degree of enamel fractures and the adhesive remnant index (ARI) before debonding (T0), after debonding (T1) and after removal of the remaining composite using a rotating fraise (red ring, Comet) (T2), micrographs of the enamel surface at 10-fold and 20-fold magnifications were taken. Additionally, the enamel surface was investigated using seven randomly chosen samples from each group at every time point by SEM at 200-fold and 500-fold magnifications. Results: In the laser group, the ARI-score was statistically significantly reduced (p<0.05) at 10-fold and 20-fold magnifications compared to the conventional group, while enamel fractures were not found at any magnification in either group at T1. Enamel fractures and grinding marks were increasingly found in the conventional group by SEM at T2. Conclusion: Irradiation with the novel diode laser prior to debonding of ceramic brackets significantly changes bonding failure in terms of less remaining adhesive. This is of clinical importance as the risk of enamel fractures and chair time can be reduced.

Shear Bond Strength of Three Orthodontic Bonding Systems on Enamel and Restorative Materials

Objective. The aim of this in vitro study was to determine the shear bond strength (SBS) and adhesive remnant index (ARI) score of two self-etching no-mix adhesives (iBond™ and Scotchbond™) on different prosthetic surfaces and enamel, in comparison with the commonly used total etch system Transbond XT™. Materials and Methods. A total of 270 surfaces (1 enamel and 8 restorative surfaces, n = 30) were randomly divided into three adhesive groups. In group 1 (control) brackets were bonded with Transbond XT primer. In the experimental groups iBond adhesive (group 2) and Scotchbond Universal adhesive (group 3) were used. The SBS was measured using a Zwicki 1120™ testing machine. The ARI and SBS were compared statistically using the Kruskal–Wallis test (P ≤ 0.05). Results. Significant differences in SBS and ARI were found between the control group and experimental groups. Conclusions. Transbond XT showed the highest SBS on human enamel. Scotchbond Universal on average provides the best bonding on all other types of surface (metal, composite, and porcelain), with no need for additional primers. It might therefore be helpful for simplifying bonding in orthodontic procedures on restorative materials in patients. If metal brackets have to be bonded to a metal surface, the use of a dual-curing resin is recommended.

Time-dependent behavior of porcine periodontal ligament: A combined experimental, numeric in-vitro study

Introduction: The aim of this study was to analyze the time‐dependent in‐vitro behavior of the periodontal ligament (PDL) by determining the material parameters using specimens of porcine jawbone. Time‐dependent material parameters to be determined were expected to complement the results from earlier biomechanical studies. Methods: Five mandibular deciduous porcine premolars were analyzed in a combined experimental‐numeric study. After selecting suitable specimens (excluding root resorption) and preparing the measurement system, the specimens were deflected by a distance of 0.2 mm at loading times of 0.2, 0.5, 1, 2, 5, 10, and 60 seconds. The deflection of the teeth was determined via a laser optical system, and the resulting forces and torques were measured. To create the finite element models, a microcomputed tomography scanner was used to create 3‐dimensional x‐ray images of the samples. The individual structures (tooth, PDL, bone) of the jaw segments were reconstructed using a self‐developed reconstruction program. A comparison between experiment and simulation was conducted using the results from finite element simulations. Via iterative parameter adjustments, the material parameters (Youngs modulus and Poissons ratio) of the PDL were assessed at different loading velocities. Results: The clinically observed effect of a distinct increase in force during very short periods of loading was confirmed. Thus, a force of 2.6 N (±1.5 N) was measured at the shortest stress duration of 0.2 seconds, and a force of 1.0 N (±0.5 N) was measured at the longest stress duration of 60 seconds. The numeric determination of the material parameters showed bilinear behavior with a median value of the first Youngs modulus between 0.06 MPa (2 seconds) and 0.04 MPa (60 seconds), and the second Youngs modulus between 0.30 MPa (10 seconds) and 0.20 MPa (60 seconds). The ultimate strain marking the transition from the first to the second Youngs modulus remained almost unchanged with a median value of 6.0% for all loading times. Conclusion: A combined experimental‐numeric analysis is suitable for determining the material properties of the PDL. Microcomputed tomography allows high‐precision recordings with only minimum effort. This study confirms the assumption of time dependency and nonlinearity of previous studies. HighlightsTime‐dependent behavior of the PDL was evaluated with an experimental numeric method.Combined analysis was suitable for determining material properties of the PDL.Time‐dependency and nonlinearity and results from previous studies were confirmed.

Three-Dimensional Quantification of the Effects between Different Types of RME

Objectives: To analyse if Hybrid-RME has different effects on skeletal, dental and periodontal aspects when compared with those of Hyrax-RME or Hyrax-SARME. Methods: In this retrospective multicentre-study 28 patients with a severe nasomaxillary constriction were treated either with a Hyrax-type RME (6 patients, 13.92 ± 0.36 years), with a Hybrid-RME (7 patients, 17.20 ± 2.80 years) or with a surgical assisted Hyrax-SARME (15 patients, 30.58 ± 9.26). This study was performed in analogy to the method published by Garib, et al. using the freeware OsiriX 4.0. All measurements were performed twice with an interval of two weeks and the calculated mean value of both measurements was used for statistical evaluation, which was performed using SPSS 21 for Mac. Results: The age differences between all groups were significant (p<0.001). All appliances led to a significant skeletal and dental expansion while the buccal bone lamella reduced in dependence of the employed appliance. Effects on the suture were comparable at the canine region while they were significantly differences at the molar region, where Hyrax-RME scored first, Hybrid-RME scored second and Hyrax-SARME had the least effects. While Hyrax-RME led to the greatest, Hyrax-SARME showed the least dental expansion at premolar and molar level. Hyrax- and Hybrid-RME showed significantly enhanced skeletal effects on the maxillary base and the skeletal nose than Hyrax-SARME. Hyrax- SARME had significantly less (more than half that much) molar tilting as Hybrid-RME (0.84° vs. 1.74°/ mm activation). Hybrid-RME tended to show the least bone loss (4-12%) while Hyrax-SARME tended to show the most (20-30%). Conclusions: In patients with a borderline-age (17-20 years) Hybrid-RME might be a promising alternative for Hyrax-RME or Hyrax-SARME to gain skeletal and dental expansion while maintaining the surrounding periodontal bones. Future studies are necessary to investigate if also a surgically assisted Hybrid-SARME might be beneficial in older patients (20+) to combine the parallel dental expansion with the pronounced skeletal effects while maintaining the surrounding bones.

Hexe Wackelzahn, Zahnfee & Co

ZusammenfassungDer Überwachung des Zahnwechsels bei Kindern kommt erhebliche präventive Bedeutung zu. Dafür ist es notwendig, den regelrechten Zahnwechsel zu kennen. Unterschieden werden drei Phasen der postnatalen Entwicklung: Milchgebiss, frühes und spätes Wechselgebiss sowie das permanente Gebiss. Im Beitrag werden die physiologischen Veränderungen während der unterschiedlichen Entwicklungsstadien beleuchtet sowie Informationen gegeben über notwendige Maßnahmen zur Vermeidung von Komplikationen beim Zahnwechsel.