Relationship between the polymerization distance of monowave and polywave light-curing units and the irradiance and physical properties of dental resin-based composites.

PURPOSE: To evaluate the influence of the polymerization distance of monowave and polywave light curing units (LCUs) on the measured irradiance relative to the value reported by the manufacturer in relation to the physical properties of resin-based composites (RBCs). METHODS: Four LCUs were used: one monowave and three polywave. The irradiance was measured with a digital radiometer. Depth of cure (DC) and flexural strength (FS) tests were performed according to ISO 4049:2019 at polymerization distances of 0 mm and 5 mm. RESULTS: The irradiance of all LCUs was higher than that reported by the manufacturer (>25-64%). The irradiance of the four LCUs was reduced when polymerization was performed at between 0 to 5 mm (paired t-test, P < 0.001). The DC at 0 mm was similar in all groups but was significantly decreased at 5 mm distance (ANOVA P < 0.001). FS showed differences among the LCUs at 0 mm (ANOVA P < 0.001) and was affected by the polymerization distance. The elastic modulus was unaffected by the LCU used or the distance (ANOVA P > 0.001). CONCLUSIONS: The LCU must be positioned as near as possible to RBCs during the polymerization process, as increased distance negatively affects the depth of cure and flexural strength.

Mesialización del sector posterior por la ausencia del primer molar mediante el uso de microimplantes / Mesialization of the posterior sector due to the absence of the first molar through the use of micro-implants

Se presenta un caso clínico de paciente femenina de 16 años, la cual reportó haber perdido su primer molar superior izquierdo por caries dos años atrás. Es una paciente con maloclusión clase II esquelética, mesofacial, perfil recto, clase I molar derecho, ausencia del diente 26, clase I canina derecha y tendencia a clase II canina izquierda, con apiñamiento leve superior e inferior y línea media dental inferior desviada a la izquierda. Se trató mediante el uso de microimplante, con el objetivo de mesializar los dientes 27 y 28 así como mejorar el asentamiento de la clase canina izquierda. Se finalizó de manera exitosa la mesialización de los dientes posteriores superiores izquierdos, estableciendo una adecuada oclusión, eliminando el apiñamiento, logrando una buena guía anterior con líneas medias dentales coincidentes, proporcionando una sonrisa funcional y armoniosa. El propósito de este caso es demostrar que con las herramientas y mecánicas adecuadas además de una buena planificación, se puede lograr el control del anclaje en el movimiento de cierre posterior a falta de un molar ausente, y así lograr establecer una adecuada oclusión.

A clinical case of a 16-year-old female patient is presented, who reported having lost her upper left first molar due to caries two years ago is presented. She is a patient with class II skeletal, mesofacial malocclusion, straight profile, class I right molar, absence of tooth 26, class I right canine and tendency to class II left canine, with mild upper and lower crowding and lower dental midline deviated to the left. It was treated through the use of a microimplant, with the objective of mesializing teeth 27 and 28 as well as improving the settlement of the left canine class. The mesialization of the upper left posterior teeth was successfully completed, establishing adequate occlusion, eliminating crowding, achieving good anterior guidance with coincident dental midlines, providing a functional and harmonious smile. The purpose of this case is to demonstrate that with the appropriate tools and mechanics in addition to good planning, control of the anchorage in the posterior closing movement can be achieved in the absence of an absent molar, and thus achieve adequate occlusion.

Physical properties, marginal adaptation and bioactivity of an experimental mineral trioxide aggregate-like cement modified with bioactive materials.

PURPOSE: To evaluate the effect of adding wollastonite and bioactive glass to an experimental mineral trioxide aggregate-like cement (MTA) on the dimensional stability, compressive strength, solubility, bioactivity, and marginal adaptation by scanning electron microscopy (SEM) and X-ray diffraction (XRD). METHODS: Four groups were evaluated at 7, 14, and 21 days: MTA Angelus, experimental MTA-like cement (MTA Exp), BG10 (MTA Exp+10 wt% bioactive glass), and WO20 (MTA Exp+20 wt% wollastonite). To evaluate marginal adaptation, extracted teeth were endodontically obturated and root-end cavities were prepared and filled with the tested materials. RESULTS: Cements with bioactive materials showed minimal dimensional changes. Adding wollastonite or bioactive glass to MTA Exp reduces the compressive strength but does not affect solubility. Bismite (Bi2O3), larnite (Ca2SiO4), calcite (CaCO3) and carbonated hydroxyapatite (Ca5[PO4,CO3]3[OH]) were identified in the four cements; ettringite (Ca6Al2[SO4]3[OH]12·26H2O) and bismutite ([BiO]2CO3) were only observed in MTA Exp, BG10, and WO20. Cement-dentin interfaces were not observed after 14 days on the BG10 and WO20 cement composites due to the ettringite formation. CONCLUSION: Acicular growing crystals typical of hydroxyapatite were found on the surfaces of all cements. An improved marginal adaptation was observed with the addition of wollastonite or bioactive glass.

Theoretical method for a radiopacifier proportion calculation in MTA type cements.

This article deals with the problem of determining the proportion by weight of radiopacifying material needed to add to a cement clinker of mineral trioxide aggregated (CE) to comply with ISO 6876/2001 and ANSI-ADA 57 regulations for radiopacity. With this aim, CE was synthesized and mixed experimentally with 5, 10, 15, and 20 wt% of ZrO2 as radiopacifying material. Radiographic images were taken so that radiographic density was obtained and related to the mmAl scale by using an aluminum step wedge. From a theoretical point of view, absorbed intensity given by the Lambert-Beer law was calculated using mass attenuation coefficients (NIST database) for each chemical element included in each component of the cement samples. In this way, we predicted that by adding above 10 wt% of ZrO2 to the CE, the requirements stipulated by ISO 6876 for radiopacity were satisfied with discrepancies around 1 mmAl. This theoretical method gives an excellent approximation to determine the amount of radiopacifying material needed to meet the requirements stipulated by ISO.

Cell viability and physicochemical effects of different concentrations of bismuth trioxide in a mineral trioxide aggregate cement.

PURPOSE: To evaluate the effect of three concentrations of bismuth trioxide (Bi2O3) on the biological and physicochemical properties of an experimental mineral trioxide aggregate-type (MTA-type) cement at different time points. METHODS: Three experimental groups with white Portland cement containing 15, 20, or 25 wt% of Bi2O3 were assessed. Cellular proliferation in human periodontal ligament fibroblasts was evaluated with an MTT assay. Radiopacity, dimensional stability, pH, and compressive strength were evaluated at different time points. RESULTS: Bismuth trioxide induced cell proliferation in the Bi15 and Bi25 groups in a time-dependent manner; pH was similar in all groups. Compressive strength was associated with time and bismuth concentration. Bi25 had significantly contracted at day 7 and expanded at day 14 (ANOVA P < 0.05, post hoc Tukey test P < 0.05). CONCLUSION: A higher Bi2O3 concentration had a negative effect on the physical properties of the cement at all time points.

Association Between Self-Reported Health and Education with Past-year Dental Visits among Older Mexican Adults: Results of the Mexican Health and Aging Study 2018.

PURPOSE: To explore the relationship between of self-reported health (SRH) and educational attainment with pastyear dental visits in older adults in México. MATERIALS AND METHODS: For this cross-sectional study, data were derived from the Mexican Health and Aging Study 2018 (MHAS-2018), which used a nationally-representative sample of older adults (50 years or older) in Mexico (n = 14,085). Variables taken from the MHAS questionnaire included residence (rural/urban), years of education, SRH, multimorbidity, pain severity, and past-year dental visits. A logistic regression model was used to identify the association between the variables and past-year dental visits. RESULTS: While the percentage of past-year dental visits reported was 39.8%, this number declined with age [OR=0.76, p < 0.001], with older adults living in rural areas 34% less likely to report past-year dental visits than older adults living in urban areas. Older adults with no formal education were 73% less likely (OR=0.27; p < 0.001) to report past-year dental visits than older adults ≥10 years education. Older adults with poor SRH were 32% less likely (OR=0.68; p < 0.001) to report past-year dental visits than older adults with good/very good/excellent SRH. Sex, degree of multimorbidity, and pain level ([OR=1.37; p < 0.001] [OR=1.37; p < 0.001] and [OR=1.17; p < 0.001]) were all found to be positively associated with past-year dental visits in the study population. CONCLUSION: The present study highlights the association between poor SRH, a low level of educational attainment, and less frequent past-year dental visits, as well as the finding that past-year dental visits declined with age in the older adults sampled.

Correlation between dental enamel chemical composition and bracket debonding, comparing adhesive systems through a scanning electron microscope.

Literature reports indicate that during bracket removal there can be enamel damage. We compare the shear bond strength (SBS) and tooth enamel loss of four adhesive systems and identify the Ca/P ratio. Then a total of 20 premolars were divided into four groups of five each. After prophylaxis, photographs were taken at 35× with a scanning electron microscope (SEM) and analyzed with X-ray spectroscopy (EDS) at 250×. Brackets were bonded with Transbond™ MIP(G1), Transbond™ PLUS SEP(G2), Enlight(G3) and Stylus®(G4) adhesives, 24 h after were debonded with a Instron universal testing machine at 1 mm/min. All the brackets were photographed with the SEM. The amount of lost enamel was measured with AutoCad. All the results were measured with a significance level p < .05. The SBS general average at debonding was 7.94 ± 2.26 MPa, meanwhile the SBS for G1, G2, G3 and G4 was 9.38 ± 1.46, 6.28 ± 0.69, 9.08 ± 2.45 and 7.04 ± 2.64 MPa respectively. 90% of the samples had no enamel loss, 10% had enamel loss. Only two samples in G1 presented an enamel loss area of 0.34mm2 and 0.80mm2 respectively. From EDS analysis, the Ca/P ratio was 1.6 ± 0.05, 1.61 ± 0.03, 1.64 ± 0.83 and 1.59 ± 0.07 for G1, G2, G3 and G4 respectively; no statistically significant differences were found. We conclude that no association was found between the Ca/P ratio and enamel damage when brackets are removed. HIGHLIGHTS: Where enamel is lost, we observe fractures, steps, horizontal and vertical enamel loss. There is a loss of tooth enamel from 0.34 to 0.80 mm2 with Transbond PLUS SEP. Structural loss of enamel is almost inevitable during the separation of the bracket.

Evaluation of enamel loss by scanning electron microscopy after debonding brackets place with four different adhesives.

The clinically adequate shear bond strengths (SBS) should be from 2.8 to 10 MPa. The aim of this research is to observe tooth enamel loss through a scanning electron microscope (SEM) during the debonding of braces of four adhesive systems. Then, 100 premolars were used in 4 groups of 25 specimens each, for Transbond MIP (G1), Enlight (G2), Stylus (G3), and Transbond Plus SEP (G4). The research was done under the NOM ISO/TS 11405:2015. Gemini 3M were placed under the manufacturer's recommendations. The SBS test was done at 24 hr in an Instron electromechanical universal testing machine at 1 mm/1 min. Adhesive remnant index (ARI) was measured, all of the brackets where examined in the SEM. For the shear bonding strength G1 = 10.09 ± 2.73 MPa, G2 = 9.27 ± 3.99 MPa, G3 = 7.83 ± 4.46 MPa, and G4 = 6.40 ± 2.85 MPa statistically significant differences were found when comparing the four groups (p = .002). In the Tukey post hoc test, G1 versus G4 and G2 versus G4, statistically significant differences were found. For the ARI a value of 1 in 46%, followed by a value of 2 in 38%, a value of 3 in 13% and a value of 0 in 3% of the total samples, finding statistically significant differences (p < .001). In relation to the tooth enamel loss due to SBS, statistically significant differences were found (p = .326). G1 and G4 had not statistically significant differences. Even though our results concur with the appropriate clinical values, we observed tooth enamel loss with Transbond Plus SEP and Stylus.

Evaluation of diagnostic agreement among cephalometric measurements for determining incisor position and inclination / Evaluación de la concordancia diagnóstica entre mediciones cefalométricas para la determinación de la posición e inclinación de los incisivos

SUMMARY: The incisors are a key factor in dental occlusion and dentofacial aesthetics; therefore, the sagittal position and inclination of the incisors is a key parameter in diagnosis and orthodontic treatment planning. In some cases, the orthodontist will use more than one cephalometric analysis, and thus different results can be obtained. The aim of this study was to establish the diagnostic agreement among the different cephalometric measurements used to determine the anteroposterior position and the inclination of the incisors. Lateral cephalometric radiograms of patients between 18 and 59 years old were measured (n=260). Digital cephalometric measurements were made with Dolphin Imaging software, by a single calibrated operator. Here, a specific cephalometric analysis was designed in the software analysis editor. The results for each variable and each measurement were registered and compared. Fleiss's Kappa statistical tests, Cohen's Kappa, and Kendall's coefficient were used to determine the strength of agreement using the Minitab software. The results showed diagnostic strength agreement between slight and moderate among measurements of the same variable. This indicates that same diagnosis might not be obtained when using different approaches to measure the anteroposterior position and inclination of the incisors. It was concluded that there is a difference in the diagnosis between one measurement and another because the results showed slight or moderate strength of agreement. However, in some cases, better agreement was found when the measurements were compared as a function of the diagnostic response.

RESUMEN: Los incisivos son un factor clave en la oclusión dental y la estética dentofacial; por lo tanto, la posición sagital y la inclinación de los incisivos es un parámetro clave en el diagnóstico y la planificación del tratamiento de ortodoncia. En algunos casos, el ortodoncista utilizará más de un análisis cefalométrico y, por lo tanto, se pueden obtener resultados diferentes. El objetivo de este estudio fue establecer el acuerdo de diagnóstico entre las diferentes mediciones cefalométricas utilizadas para determinar la posición anteroposterior y la inclinación de los incisivos. Se midieron radiografías cefalométricas laterales de pacientes entre 18 y 59 años (n = 260). Las mediciones cefalométricas digitales se realizaron con el software Dolphin Imaging, por un solo operador calibrado. Aquí, se diseñó un análisis cefalométrico específico en el editor de análisis de software. Los resultados para cada variable y cada medición se registraron y compararon. Las pruebas estadísticas Kappa de Fleiss, Kappa de Cohen y el coeficiente de Kendall se usaron para determinar la fuerza del acuerdo utilizando el software Minitab. Los resultados mostraron un acuerdo de fuerza diagnóstica entre leve y moderado entre las mediciones de la misma variable. Esto indica que no se puede obtener el mismo diagnóstico cuando se utilizan diferentes enfoques para medir la posición anteroposterior y la inclinación de los incisivos. Se concluyó que existe una diferencia en el diagnóstico entre una medición y otra porque los resultados mostraron una fuerza de acuerdo leve o moderada. Sin embargo, en algunos casos, se encontró un mejor acuerdo cuando se compararon las mediciones en función de la respuesta de diagnóstico.

Comparative study of dental enamel loss after debonding braces by analytical scanning electron microscopy (SEM).

Clinical procedures when shear forces are applied to brackets suggest adhesion forces between 2.8 and 10.0 MPa as appropriate. In this study dental enamel was evaluated by scanning electron microscopy (SEM) before and after removing the brackets. Thirty bicuspids (previous prophylaxis) with metallic brackets (Roth Inovation 0.022 GAC), Transbond Plus SEP 3M Unitek adhesive and Transbond XT 3M resin were used. The samples were preserved to 37°C during 24 hr and submited to tangential forces with the Instron Universal machine 1.0 mm/min speed load strength resistance debonding. Also the Adhesive Remanent Index (ARI) test was made, evaluating the bracket base and the bicuspid surface. All the bracket SEM images were processed with AutoCAD to determine the enamel detached area. The average value was 6.86 MPa (SD ± 3.2 MPa). ARI value 1= 63.3%, value 2= 20%, value 3= 13.3% and 33% presented value 0. All those samples with dental enamel loss, presented different situations as fractures, ledges, horizontal, and vertical loss in some cases, and some scratch lines. There is no association between the debonding resistance and enamel presence. Less than half of the remanent adhesive on the dental enamel was present in most of the samples when the ARI test was applied. When the resin area increases, the debonding resistance also increases, and when the enamel loss increases, the resin free metallic area of the bracket base decreases in the debonding.