RESUMEN
The current study evaluated the bracket bond strength of hypomineralized teeth with and without acid etching. Twenty premolar teeth extracted for orthodontic purposes were used in this study. Hypomineralization was induced in all experimental teeth using a cariogenic solution. Then the teeth were divided into two groups. In the first group, orthodontic brackets were bonded by orthodontic adhesive (Green Gloo, Ormco, USA) without etching, while in the second group, further etching was used before bonding. All specimens were examined for morphological changes in the enamel surface after demineralization and debonding using a scanning electron microscope. The shear bond strength was also measured, and the recorded values of bond strengths were collected and statistically analyzed. All massed results were statistically evaluated via an independent t-test to equate Group 1 (G1) and Group 2 (G2). A p-value of < 0.05 is deemed to be statistically substantial. The shear bond strength of groups interacted by orthodontic adhesive with etching (Group 2) was considerably greater than that of groups bonded by orthodontic adhesive without etching. The etching indicates considerably greater tackiness rates compared to bonding without etching, although it leaves more destructed cores, which may need further treatment.
RESUMEN
Background This study aims to evaluate the accuracy of volumetric measurements of three-dimensional (3D)-printed human condyles from cone-beam computed tomography (CBCT) in comparison to physical condyles using a water displacement test. Methodology A sample of 22 dry condyles was separated from the mandibular body by disc, mounted on a base made of casting wax, and scanned using the SCANORA (Scanora 3DX, Soredex, Finland) CBCT scanner. Subsequently, the projection data were reconstructed with the machine-dedicated OnDemand 3D (Cybermed Co., Seoul, Korea). The Standard Tessellation Language file was prepared for 3D printing using chitubox slicing software v1.9.1. Frozen water-washable gray resin was used for 3D printing. All condyles were printed using the same parameters and the same resin. The volumetric measurements were then performed using a customized modified pycnometer based on water volume and weight displacement. Volumetric measures were performed for both the physical human condyles and the 3D-printed replicas and the measurements were then compared. Results The volume of dry condyles using the water displacement method showed an average (±SD) of 1.925 ± 0.40 cm3. However, the volume of 3D-printed replicas using the water displacement method showed an average (±SD) of 2.109 ± 0.40 cm3. The differences in measurements were insignificant (p > 0.05), as revealed by an independent t-test. Conclusions Highly precise, accurate, and reliable CBCT for volumetric mandibular condyle was applied for measurements of a human condyle and 3D-printed replica. The modified pycnometer for volumetric measurements presented an excellent volumetric measure based on a simple water displacement device. The tested modified pycnometer can be applied in volumetric measurements in both 3D-printed and mandibular condyle. For best accuracy, the highest scanning resolution possible should be used. As it directly handles irregularly shaped solid objects in a non-destructive manner with a high level of precision and reliability, this 3D scanning approach may be seen as a superior alternative to the current measurement methods.