Effects of Diode and Nd:YAG Laser Irradiation on Friction Forces Between Two Types of Ceramic Brackets and Rhodium-Coated Archwires

Introduction: Ceramic brackets have gained increasing popularity among dental clinicians and orthodontic patients but friction is a major concern when using them. This study sought to assess the effects of diode and Nd: YAG (neodymium-doped yttrium aluminum garnet) laser irradiation on friction forces between two types of ceramic brackets and rhodium-coated esthetic archwires.Methods: Thirty polycrystalline and 30 poly-sapphire brackets were divided into 6 groups (n=10) as follows: (I) control polycrystalline brackets (no laser irradiation), (II) polycrystalline brackets subjected to diode laser irradiation, (III) polycrystalline brackets subjected to Nd: YAG laser irradiation, (IV) control poly-sapphire brackets (no laser irradiation), (V) poly-sapphire brackets subjected to diode laser irradiation, and (VI) poly-sapphire brackets subjected to Nd: YAG laser irradiation. The bracket slots were laser-irradiated on a custom-made table. Sixty 5-cm pieces of rhodium-coated archwires were used for the friction test in a universal testing machine at a speed of 10 mm/min. Ten brackets from the six groups underwent scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX).Results: The frictional resistance value of polycrystalline brackets was significantly higher than that of poly-sapphire brackets, irrespective of laser type (P < 0.05). Irradiation of diode and Nd: YAG lasers, compared with the control group, had no significant effect on friction, irrespective of bracket type (P> 0.05).Conclusion: It appears that diode and Nd: YAG laser irradiation cannot significantly decrease friction. Future studies are warranted on different laser types with variable exposure. DOI: 10.34172/jlms.2021.1

La eficacia o ineficacia de la evidencia digital como elemento probatorio en el juzgamiento de los delitos informático

El presente trabajo de investigación gira en torno a la evidencia digital que es la información utilizada en investigaciones y procesos legales para los casos de delitos informáticos ha sido sometido al análisis documental misma que permitió comprender los principios de donde parte el conocimiento de la evidencia digital en la investigación necesaria y útil para la prueba y de esta manera conocer y comprender cuál será aceptado o no en las cortes. En el tratamiento de la información se consideró el uso de técnicas de instrumentalización como la entrevista, lo que evaluar las respuestas de la muestra probabilística por conveniencia que afirma la idea a defender en la que denota la falta de expertos en la pericia (perito informático) lo que vuelve ineficaz el tratamiento de la evidencia y por ende la determinación de la prueba por ello cuando se denuncia este tipo de acciones antijurídicas, muchos entes del sistema penal no cuenta con el personal capacitado para las investigaciones necesarias, como es el caso de la provincia de Santa Elena, en la no existe una unidad de investigación especializada que se dedique específicamente al estudio de los elementos probatorios derivados de la evidencia digital obtenida por medios informáticos, electrónicos y telemáticos, para que dado el caso sea la información validada como medio de prueba pertinente dentro de los procesos judiciales y en su determinación sancionar a los responsables

The Effect of Remineralizing Agents With/Without CO2 Laser Irradiation on Structural and Mechanical Properties of Enamel and its Shear Bond Strength to Orthodontic Brackets

Introduction: Remineralizing agents may be used for the treatment of white spot lesions (WSLs) prior to bracket bonding. However, some concerns exist regarding their possible interference with the etching and bonding process, negatively affecting the bond strength. This study aimed to assess the effect of two remineralizing agents with/without CO2 laser irradiation on the mechanical properties and shear bond strength (SBS) of demineralized enamel to the orthodontic bracket.Methods: This study evaluated 60 premolar teeth in 6 groups (n=10) as follows: (I) sound enamel, (II) demineralized enamel, (III) Nupro remineralizing agent (N), (IV) Nupro and CO2 laser (N/L), (V) Teethmate remineralizing agent (T), and (VI) Teethmate and CO2 laser (T/L). The remineralizing agents were applied to the enamel surfaces after their immersion in a demineralizing solution for 5 days. In groups IV and VI, the CO2 laser with a 10.6 μm wavelength, 10 ms pulse duration, a 50 Hz repetition rate, 0.3 mm beam diameter and 0.7 W power was irradiated after applying the remineralizing agents. Brackets were bonded to the enamel surfaces and SBS was measured by a universal testing machine. For the assessment of enamel microhardness, 20 sections of molar teeth were divided into 4 groups (n=5; N, N/L, T, T/L) and their microhardness was measured before demineralization, after demineralization and after remineralization. X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FESEM) and energy-dispersive spectrometry (EDS) were carried out to assess the formation of hydroxyapatite. The atomic percentages of the C, O, P, Ca, Na, Si, F and Ca/P ratio were determined by EDS analysis.Results: The SBS significantly decreased in group II (P < 0.001). There was no significant difference among the groups I, III, IV, V and VI (P < 0.05). This finding was similar to the microhardness results, which showed an increase in microhardness after remineralization (P < 0.05), with no difference among the remineralizing agents. The Ca/P ratio was the highest in the Nupro group and the lowest in the demineralized group.Conclusion: Remineralizing agents can significantly improve the microhardness and structural properties of demineralized enamel to a level similar to that of sound enamel with no adverse effect on SBS to orthodontic brackets

Second Molar Uprighting with Temporary Anchorage Devices: A Finite Element Study

BACKGROUND AND OBJECTIVE: Premature loss of mandibular first molar is a common problem in adults. Mesial tipping of second molar may occur in this situation. Various orthodontic mechanics have been proposed for molar uprighting. The aim of this study was to compare four methods of molar uprighting using Finite Element Analysis(FEM). METHODS: In first model of this finite element study, a 0.019×0.025 inch beta-titanium segmental arch wire with a T-loop was used. In second model a miniscrew was inserted in retromolar space and force was applied using elastomeric chain. The third model was a piece of 0.016×0.022inch beta-titanium wire with a bend which was placed more occlusal than the screw. The fourth model contained a mesially inserted miniscrew with an angle of 70 degrees to bone surface and a 0.018×0.025inch beta-titanium wire with helix. Extrusion, center of rotation and stress distribution in PDL during movement was compared between methods. FINDINGS: Buccal cusp extruded 1.36E-03, 1.13E-03, -9.74E-04 and 1.49E-03 mm in first, second, third and fourth model, respectively. Similarly, in lingual cusp, the amount of vertical displacement was at least in third model (-6.83E-04 mm). This amount in second and first method was 1.12E-03 and 4.05E-04 mm, respectively. The maximum amount of extrusion of lingual cusp occurred in fourth model (9.01E-03 mm). Mesial and distal cusps extruded 2.12E-04 and 1.58E-03 mm in first model, -1.14E-03 and 3.80E-03 mm in second method, -2.37E-03 and 7.04E-04 mm in third design and, 1.88E-03 and 8.57E-03 mm in the fourth model. The center of rotation was located at molar bifurcation in third model. CONCLUSION: The maximum amount of extrusion in both mesiodistal and buccolingual path was seen in fourth model. The best type of movement was found in third model, in which minimum extrusion occurred and center of rotation located at molar bifurcation

The effect of fixed orthodontic treatment with first premolar extraction on mandibular third molars angulation and retromolar space

Introduction: In most orthodontic patients, mandibular 3rd molars are in early stages of calcification, and prediction of eruption status would be difficult during the course of orthodontic treatment. The aim of this study was to evaluate the effect of first premolar extraction with moderate anchorage on angular changes of third mandibular molar after orthodontic treatment. Materials & Methods: Panoramic radiographs of 50 skeletal class I patients with normal facial height were selected. The patients were divided into two groups of extraction and non-extraction treatments. The angle between 2nd and 3rd molars and 3rd molar angle to mandibular plane were evaluated. Space for eruption of 3rd molar and 3rd molar position relative to ramus were evaluated with regard to Pell and Gregory classification. Paired T-test was used to compare the changes after treatments. Results: In both groups, 3rd molar angle relative to mandibular plane was increased after the treatment but the difference was not significant. M2-M3 angle changed during the treatments but it was not significant (P>0.05). The retromolar space had significantly higher amounts in extraction groups after the treatment (P<0.001). In non-extraction group, there was significant increase in stage I of Pell and Gregory classification (P<0.001). In extraction group, counts of patients with no space for eruption of M3M were decreased and the difference was significant (P<0.001). Conclusion: Extraction of premolars did not have any significant positive effect on mandibular 3rd molar angulation but it can increase the posterior space for eruption of wisdom teeth

Numerical study of effect of elastomeric stress absorbers on stress reduction in bone-dental implant interface

Objective This paper focused on optimal stress distribution in the mandibular bone surrounding a dental implant and is devoted to the development of a modified Osteoplant® implant type in order to minimize stress concentration in the bone-implant interface. Material and Methods This study investigated 0.4 mm thick layers of two elastomeric stress barriers incorporated into the dental implant using 3-D finite element analysis. Results Overall, this proposed implant provoked lower load transfer in bone-implant interface due to the effect of the elastomers as stress absorbers. The stress level in the bone was reduced between 28% and 42% for three load cases: 75 N, 60 N and 27 N in corono-apical, linguo-buccal and disto-mesial direction, respectively. Conclusion The proposed model provided an acceptable solution for load transfer reduction to the mandible. This investigation also permitted to choose how to incorporate two elastomers into the Osteoplant® implant system