RESUMEN
Various applications of dental lasers on dental materials have been proposed for surface modifications. This study evaluated whether laser etching could be an alternative to hydrofluoric acid (HF) etching. One hundred and ten lithia-based all-ceramic specimens (Empress 2) (R: 4 mm, h: 4 mm) were prepared and divided into five groups (n = 22/group). The untreated specimens served as the control, while one of the experimental groups was treated with 9.5% HF for 30 seconds. Three remaining test groups were treated with different laser (Er:YAG laser wavelength:2940 nm, OpusDent) power settings: 300 mJ, 600 mJ and 900 mJ. Ten specimens in each group were luted to the other 10 specimens by a dual-curing cement (Variolink II), and shear-bond strength (SBS) tests were performed (Autograph, crosshead speed: 0.5 mm/minute). The results were statistically analyzed (Kruskal Wallis and Mann Whitney-U, alpha = .05). Mean SBS (MPa) were 31.9 +/- 4.0, 41.4 +/- 4.3, 42.8 +/- 6.2, 29.2 +/- 4.5 and 27.4 +/- 3.8 for the control and HF, 300, 600 and 900 mJ groups, respectively. SEM evaluations revealed different surface morphologies depending on the laser parameters. The differences between HF acid and 300 mJ, when compared with the control, 600 and 900 mJ groups, were significant (p < .05). The 300 mJ laser group exhibited the highest shear-bond strength values, indicating that laser etching could also be used for surface treatments.
Asunto(s)
Grabado Ácido Dental/métodos , Recubrimiento Dental Adhesivo , Grabado Dental , Porcelana Dental/química , Rayos Láser , Silicatos de Aluminio , Erbio , Humanos , Ácido Fluorhídrico/química , Compuestos de Litio/química , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Cementos de Resina/química , Resistencia al Corte , Estrés Mecánico , Propiedades de Superficie , ItrioRESUMEN
This study presents the stress analysis of the mandibular first premolar tooth restored with an all-ceramic crown under thermal loading as a result of hot/cold liquid intake to the mouth using the three-dimensional (3D) finite element analysis (FEA). In the first step of the study, the temperature changes as a result of hot/cold liquid intake were calculated. The thermal stress distributions because of the temperature changes were then obtained. Thermal loads ranging from 60 to 15 degrees C were applied on all prepared models. The distribution of temperature and stress were plotted for some critical points which were the transition points of strain to tension or tension to strain when hot or cold liquids were consumed. The changes in oral temperature cause thermal fatigue and the material stability might be negatively affected. According to the thermal tension results in the present study, IPS Empress, Carrara press ceramic and Ceramco FAC all-ceramic materials exhibited different values while IPS Empress 2 material showed similar properties to that of enamel.
Asunto(s)
Temperatura Corporal , Cerámica , Coronas , Diente Premolar , Análisis de Elementos Finitos , Humanos , Modelos Dentales , Boca/fisiología , Estrés MecánicoRESUMEN
The aim of this study was to determine the values of the retentive forces of the telescopic crowns. At the first step of the study, the samples having different heights and angles were compared in relation to retentive force. At the second step, the samples were subjected to removal procedures having a pre-determined speed, force and number. The obtained retention values were compared. Ninety dies were prepared in order to measure the retention of the conus crowns. The removal tests were performed with the insertion/separation device. The speed of the test device was 100 cm min(-1) providing the placement of the pieces with 5 kgf in 100, 200, 300, 500, 1000, 5000 and 10 000 cycles. The mean of the retention values of the changes of the angles were found to be statistically different (P < 0.01). According to the results of the variant analysis, the differences in the changes of the height were statistically significant (P < 0.01). The differences between the changes of the number of procedures of all groups were statistically significant (P < 0.01). The number of procedures, height and angle interactions were statistically insignificant (P = 0.758). According to the results of this study, the effect of the angle and height factors in terms of retention among the groups were not independent of each other. In equal angles, as the height increased, increased retention measurements were obtained. In more acute angles, the increase in retention was more obvious. It was also found that an accessory device was necessary to maintain retention capabilities after a long-term use.
Asunto(s)
Coronas , Retención de Prótesis Dentales/métodos , Dentadura Parcial Removible , Diseño de Prótesis Dental , Análisis del Estrés Dental/métodos , Humanos , Preparación Protodóncica del Diente/métodosRESUMEN
The removable partial dentures supported by the telescopic crowns are an alternative for directly retained removable partial dentures. The stress distribution on the retainers and the surrounding tissues created by the telescopic and conus crowns of different sizes (4, 5, 6 mm) and taper (0 degrees, 2 degrees, 4 degrees, 6 degrees ) was investigated with the finite element analysis (FEA) method. The stress values obtained were evaluated either as strain or tensional forces. The loosening force of the secondary crown being determined as 5 N, the increase in tension of the dentine, metal structure, alveolar bone, periodontal ligament and the pulp were determined by the increasing height and taper. The reason for the increase in tensional forces with increasing taper was the result of the constant loosening force of 5 N applied in all experimental models. The strain was more effective than the tension with the highest stress being in the cervical region of the metal structure. The aim of this study was to determine the force exerted on the teeth and surrounding tissues by the loosened secondary crown.