The Effect of Er:YAG Laser on a Shear Bond Strength Value of Orthodontic Brackets to Enamel-A Preliminary Study.

We sought to evaluate the effects of Er:YAG laser (LightTouch, LightInstruments, Israel) conditioning on enamel roughness and shear bond strength of orthodontic brackets on enamel. Eighteen human molars (n = 9) and premolars (n = 9), were divided into 3 groups depending on the enamel conditioning method; Er:YAG laser (G1, n = 6), conventional etching with 37% orthophosphoric acid (G2, n = 6), Er:YAG laser combined with conventional etching (G3, n = 6). Er:YAG laser parameters were as follows: energy: 100 mJ, frequency: 10 Hz, exposure time: 10 s, applicator diameter: 600 µm, fluence: 35.37 J/cm2, distance: 1 mm away from a tooth, cooling: 80%. An MTS 858 MiniBionix® machine was used to determine the shear bond strength (MTS System, Eden Prairie, MN, USA). The enamel structure was assessed using X-ray microtomography (SkyScan 1172, Bruker, Kontich, Belgium). The highest values of shear bond strength were obtained in the G3 group (9.23 ± 2.38 MPa) and the lowest values in the G2 group (6.44 ± 2.11 MPa) (p < 0.05). A significant change in the enamel surface was noted after applying laser, reaching up to 9% of enamel thickness, which was not observed in the etched samples. Moreover, the Er:YAG laser-irradiated enamel surface was characterized by the greatest roughness. The combined use of an Er:YAG laser with a conventional etching improves the adhesion of composite materials to the tooth.

Three-dimensional printing as a technology supporting the treatment of lower limb deformity and shortening with the Ilizarov method.

BACKGROUND: Treatment of multiplanar deformities, especially in younger children, requires construction of a complex Ilizarov fixator, frequently with small dimensions. The aim of this study is to verify clinical application of a3D-printed bone model in treatment with the Ilizarov method. METHODS: The study involved a 6-year-old child in whom clinical and radiological examination revealed multiplanar deformity of the right leg. Then, 3D models of individual bones were printed by means of additive manufacturing and were used as a scaffold to install the Ilizarov apparatus. To compare the expected and factual axial correction and lengthening, we measured spatial orientation of bone fragments three times. The factual axial correction and lengthening were determined with a photometric technique. RESULTS: Ilizarov fixator with a configuration developed using a 3D model of the treated bone was mounted on the patient's leg. Corticotomy was carried out at the proximal metaphysis of the right tibia, along with osteotomy of the right talus. The treatment resulted in a 3.5-cm lengthening of the limb and a 7° correction of valgus angle. The values of actual lengthening and axial correction were 4.1% lower than the expected values of these parameters. INTERPRETATION: Orthopedists should consider differences between the expected and actual lengthening and axial correction in planning treatment with the Ilizarov method. Three-dimensional printing is a useful technology that can be used to support treatment with the Ilizarov method.

The combined impact of mechanical factors on the wall stress of the human ascending aorta - a finite elements study.

BACKGROUND: Biomechanical factors influence stress in the aortic wall. The aim of this study was to assess how the diameter and shape of the vessel, blood pressure and longitudinal systolic aortic stretching (SAS) caused by the contraction of the myocardium influence stress in the aortic wall. METHODS: Three computational models of the non-dilated aorta and aneurysms of the ascending aorta and aortic root were created. Then, finite elements analyses were carried out. The models were subjected to blood pressure (120 mmHg and 160 mmHg) and longitudinal systolic aortic stretching (0 mm, 5 mm, 10 mm and 15 mm). The influence of wall elasticity was examined too. RESULTS: Blood pressure had a smaller impact on the stress than the SAS. An increase in blood pressure from120 mmHg to 160 mmHg increased the peak wall stress (PWS) on average by 0.1 MPa in all models. A 5 mm SAS caused a 0.1­0. 2 MPa increase in PWS in all the models. The increase in PWS caused by a 10mm and 15mmSAS was 0.2 MPa and 0. 4 MPa in the non-dilated aorta, 0.2­0.3 MPa and 0.3­0.5 MPa in the aneurysm of the ascending aorta, and 0.1­0.2 MPa and 0.2­0.3 MPa in the aortic root aneurysm model, respectively. The loss of elasticity of the aneurysmal wall resulted in an increase of PWS by 0.1­0.2 MPa. CONCLUSIONS: Aortic geometry, wall stiffness, blood pressure and SAS have an impact on PWS. However, SAS had the biggest impact on wall stress. The results of this study may be useful in future patient-specific computational models used to assess the risk of aortic complications.

The Use of 3D Printing Technology in the Ilizarov Method Treatment: Pilot Study.

BACKGROUND: Significant developments in additive manufacturing technology have occurred in recent years. 3D printing techniques can also be helpful in the Ilizarov method treatment. OBJECTIVES: The aim of this study was to evaluate the usefulness of 3D printing technology in the Ilizarov method treatment. MATERIAL AND METHODS: Physical models of bones used to plan the spatial design of Ilizarov external fixator were manufactured by FDM (Fused Deposition Modeling) spatial printing technology. Bone models were made of poly(L-lactide) (PLA). RESULTS: Printed 3D models of both lower leg bones allow doctors to prepare in advance for the Ilizarov method treatment: detailed consideration of the spatial configuration of the external fixation, experimental assembly of the Ilizarov external fixator onto the physical models of bones prior to surgery, planning individual osteotomy level and Kirschner wires introduction sites. CONCLUSIONS: Printed 3D bone models allow for accurate preparation of the Ilizarov apparatus spatially matched to the size of the bones and prospective bone distortion. Employment of the printed 3D models of bone will enable a more precise design of the apparatus, which is especially useful in multiplanar distortion and in the treatment of axis distortion and limb length discrepancy in young children. In the course of planning the use of physical models manufactured with additive technology, attention should be paid to certain technical aspects of model printing that have an impact on the accuracy of mapping of the geometry and physical properties of the model. 3D printing technique is very useful in 3D planning of the Ilizarov method treatment.