An in-vitro evaluation of mechanical and esthetic properties of orthodontic sealants.

OBJECTIVE: To evaluate mechanical and esthetic Properties of two commercially available orthodontic sealants: Opal(®)Seal (OS) and L.E.D. Pro Seal (PS). MATERIALS AND METHODS: Discs of each sealant were prepared to test the following properties: Micro hardness, wear resistance and color stability. Samples were randomly selected after the wear test for SEM imaging to analyze surface morphology. RESULTS: OS was significantly harder than PS (P \u3c 0.001). PS was significantly more wear resistant than OS (P \u3c 0.05). PS showed a greater ∆E*ab (increased staining) when placed in wine or coffee showing a significant difference (P \u3c 0.05). SEM showed particle size, shape and distribution were different for PS and OS reflecting the pattern seen on wear surfaces. CONCLUSION: Both orthodontic sealants are beneficial for protecting enamel. However with better wear properties PS was superior in resisting mechanical stresses. OS was more color stable

Upper Airway Flow Dynamics in Obstructive Sleep Apnea Patients with Various Apnea-Hypopnea Index

Background and aim: This study evaluates the upper airway flow characteristics, anatomical features and analyzes their correlations with AHI in patients with varied degrees of OSA severity seeking for discernments of the underlying pathophysiological profile. Materials and Methods: Patient-specific computational fluid dynamics models were reconstructed from high-resolution cone-beam computed tomography images for 4 OSA patients classified as minimal, mild, moderate, and severe according to AHI. Results: The parameters, minimal cross-sectional area (MCA), and the pharyngeal airway volume did not show clear correlations with the OSA severity defined according to AHI. No correlations were found between the classically defined resistance of the airway in terms of pressure drop and AHI. The flow analysis further showed that the fluid mechanisms likely to cause airway collapse are associated with the degree of narrowing in the pharyngeal airway rather than AHI. Results also suggested that some patients classified as severe OSA according to the AHI can show less susceptibility to airway collapse than patients with relatively lower AHI values and vice versa. Conclusions: The relative contribution of anatomical and non-anatomical causes to the OSA severity can significantly vary between patients. AHI alone is inadequate to be used as a marker of the pathophysiological profile of OSA. Combining airflow analysis with AHI in diagnosing OSA severity may provide additional details about the underlying pathophysiology, subsequently improving the individualized clinical outcomes

Three-Dimensional Force Characterizations in Maxillary Molar Distalization: A Finite Element Study

Class II malocclusion is a very common condition in orthodontic patients. The reaction force and moment on the teeth induced by a maxillary segmental distalizer (MSD) are essential for understanding tooth movement, tipping, and rotation. This work quantified the three-dimensional (3D) reaction force and moment on canine and molar teeth induced by three different MSDs: the JVBarre (JVB), Carriere Motion 3D (CM3D), and CM3D Clear. A patient-specific mandibular model was reconstructed based on cone-beam computed tomography (CBCT) images. Each of the three MSDs was implanted using finite element analysis (FEA). The reaction force and moment were obtained. The results show that the JVB induced less extrusion force (15% less), tipping (90% less), and rotational moment (70% less) on the canine, compared with the other two CM3Ds. However, the JVB induced a relatively larger extrusion force, tipping, and rotational moment on the molar due to the hook location changing from the end to the middle of the bar. These observations were consistent with the 3D stress distribution of the MSDs. The mechanical understanding from this work may shed light on the optimal design of MSDs