ABSTRACT
ABSTRACT The purpose of this preliminary study is to evaluate the push-out bond strength (PBS) of experimental dentin posts (EDPs) obtained from human and bovine teeth sterilized by autoclaving and gamma radiation. Eighty-four mandibulary premolars were obturated and divided into three post groups: the glass fiber group (Fb) human EDP group (Hm) and the bovine EDP group (Bv). Three subgroups (n=12) were obtained for each EDP groups according to the sterilization methods; no sterilization (Cnt), steam autoclaving (Aut), and gamma radiation (Rad) a total dose of 25 kGy. All posts were cemented to root canals using a dual cured resin cement (Panavia SA). After the micro slices (1mm in thickness) were obtained of each subgroup, PBS test was performed. Data were analyzed using two-way ANOVA and Tukey's multiple comparison tests (α=.05). The post type and sterilization method was significantly effective on the PBS values according to the ANOVA (P<.001). No sterilization apllied EDP groups showed significantly higher PBS values than the sterilized groups (P<.001). Bv_Cnt (9.42 ±1.31) showed significantly lower PBS values than both Fb (12.36 ±1.54) and Hm_Cnt (11.06 ±1.38) groups (P<.001). Both steam autoclaving and gamma radiation affect the PBS values and fracture modes of EDPs negatively. The bovine EDPs are not as effective as human EDPs with regard to the PBS to the root dentin.
RESUMEN El propósito de este estudio preliminar es evaluar el push-out bond strength de los postes de dentina experimentales (PDE) obtenidos de dientes humanos y bovinos esterilizados por autoclave y radiación gamma. Ochenta y cuatro premolares mandibulares fueron obturadores y se dividieron en tres grupos experimentales de postes: el grupo de fibra de vidrio (Fb) grupo PDE humano (Hm) y el grupo PDE bovino (Bv). Se obtuvieron tres subgrupos (n=12) para cada grupo de PDE según los métodos de esterilización; sin esterilización (Cnt), autoclave a vapor (Aut) y radiación gamma (Rad) con una dosis total de 25 kGy. Todos los postes se cementaron a los conductos radiculares utilizando un cemento de resina de curado doble (Panavia SA). Después de que se obtuvieron las micro rebanadas (1 mm de espesor) de cada subgrupo, se realizó una prueba de push-out bond strength. Los datos se analizaron utilizando ANOVA de dos vías y las pruebas de comparación múltiple de Tukey (α=.05). El tipo de poste y el método de esterilización fueron significativamente efectivos en los valores de push-out bond strength según el ANOVA (P <.001). Los grupos de PDE no aplicados a la esterilización mostraron valores de push-out bond strength significativamente mayores que los grupos esterilizados (p <0,001). Bv_Cnt (9.42 ±1.31) mostró valores de push-out bond strength significativamente más bajos que los grupos Fb (12.36 ±1.54) y Hm_Cnt (11.06 ±1.38) (P <.001). Tanto el autoclave al vapor como la radiación gamma afectan negativamente los valores de push-out bond strength y los modos de fractura de los PDE. Los PDE bovinos no son tan efectivos como los PDE humanos con respecto a la fuerza de adhesión a la dentina de la raíz.
Subject(s)
Sterilization/methods , Dentin/drug effects , Tooth/radiation effects , Dental Materials , Radiation Equipment and SuppliesABSTRACT
ABSTRACT: Cochlospermum regium roots are used in popular medicine and its extract has diverse phytochemical molecules some with antimicrobial activity, consequently exposing this specie to genetic erosion risks. Thus, the objective of this study was to develop an in vitro multiplication protocol using chemical sterilization of culture medium. Therefore, explants obtained from apical buds of C. regium seedlings were inoculated into with 0.05mg L-1 NAA and 1mg L-1 BAP sterilized by chemical agent sodium hypochlorite (NaOCl) at 0.001%, 0.003% and 0.005% of active chlorine (Cl). Autoclaved culture medium was used as control. Result showed that the contamination by bacterial at 91 days of cultivation was significantly (P<0.05) controlled by autoclaving, 0.001% and 0.005% Cl. Moreover, the callus induction in the culture medium with 0.001% and 0.005% Cl was, respectively, 30% and 20% major than autoclaving sterilization. There was not significant (P<0.05) in the percentage of shoot induction among the sterilization preparations methods, and 65% of the explants survived in the presence of culture medium with 0.005% Cl. Histological analyses indicated that the Cl did not have any deleterious effects on morphogenic events. These results indicated that the chemical sterilization using 0.001% - 0.005% Cl controlled the fungal and bacterial multiplication in the culture medium and no affected the C. regium explants development, becoming it an alternative to autoclaving method.
RESUMO: As raízes de Cochlospermum regium são usadas na medicina popular, pois seu extrato apresenta diversas moléculas fitoquímicas, algumas com atividade antimicrobiana, que, consequentemente, expõe esta espécie ao risco de erosão genética. Assim, o objetivo deste estudo foi elaborar um protocolo de multiplicação in vitro para explantes de C. regium usando esterilização química do meio de cultura. Gemas apicais obtidas de plântulas de C. regium germinadas in vitro foram inoculadas em meio de cultivo MS suplementado com 0,05mg L-1 de ANA e 1mg L-1 de BAP e esterilizado pela adição do agente químico hipoclorito de sódio (NaOCl) nas concentrações de cloro ativo de 0,001%, 0,003% e 0,005%. O meio autoclavado foi utilizado como controle. Os resultados mostraram que a contaminação por bactérias aos 91 dias de cultivo foi significativamente (P<0,05) controlada pela autoclavagem, 0,001% e 0,005% de cloro ativo. Além disso, a indução de calos no meio de cultura com 0,001% e 0,005% de cloro ativo foi, respectivamente, 30% e 20% maior do que na esterilização por autoclavagem. Não houve diferença significativa (P<0,05) da porcentagem de indução de brotos entre os métodos de esterilização e 65% dos explantes sobreviveram na presença de 0,005% de cloro ativo. Análises histológicas indicaram que o cloro ativo não afetou os eventos morfogênicos. Os resultados indicaram que a esterilização química por meio do uso de 0,001% - 0,005% de cloro ativo auxiliou no controle da proliferação de bactérias e fungos no meio de cultura e não afetou o desenvolvimento dos explantes de C. regium, tornando-a uma alternativa em relação a autoclavagem.
ABSTRACT
Aim: The purpose of this study was to evaluate the effect of multiple root canal usage on the surface topography and fracture of Twisted File (TF) and ProTaper (PT) rotary Ni-Ti file systems, using scanning electron microscope (SEM). Materials and Methods: Ten sets of PT and TF instruments were used to prepare the mesial canals of mandibular first molars. TF 25, 0.06 taper and PT F1 instruments were analyzed by SEM when new and thereafter every three root canal usages. This sequence was repeated for both the TF and PT groups until 12 uses. Two images of the instrument were recorded, one of the instrument tip and the other 5 mm from the tip, both at ×100 magnification. The sequential use was continued till the instrument fractured and the number of root canal usages for the file to fracture was noted. All fracture surfaces were examined under the SEM. Results: Fresh TF instruments showed no surface wear when compared to PT instruments (P < 0.05). Spiral distortion scores remained the same for both the groups till the 6 th usage (P > 0.05), while at the 9 th usage TF showed a steep increase in the spiral distortion score when compared to PT (P < 0.05). PT instruments fractured at a mean root canal usage of 17.4, while TF instruments showed a mean root canal usage of 11.8. Fractographically, all the TF instruments failed due to torsion, while all the PT instruments failed because of cyclic fatigue. Conclusion: PT instruments showed more resistance to fracture than TF instruments.