ABSTRACT
BACKGROUND: Mechanotransduction plays a pivotal role in remodeling and repair of skeletal tissues. This mechanism has been widely used in bone tissue engineering especially under in vitro conditions. To date, various stem cells have been used for this purpose. The present study was the first to evaluate the effect of mechanical loading on differentiation of human endometrial stem cells (hESCs) to osteoblasts. MATERIALS AND METHODS: Adhesion of endometrial stem cells after isolation and culture on a silicone membrane covered with collagen was evaluated under scanning electron microscope (SEM). Twenty-four hours after cell culture on the membrane and ensuring appropriate cell adhesion, a group of cells in a conventional culture medium received 3% static uniaxial strain. In the positive control group, cells cultured on the membrane were placed in an osteogenic medium without receiving any mechanical strain. The negative control group was placed in a regular medium and received no strain either. Two weeks later, cultured cells were evaluated for expression of osteogenic markers using immunofluorescence staining and real-time polymerase chain reaction (PCR). Data of real-time PCR was analyzed by ANOVA. P < 0.05 was considered statistically significant. RESULTS: SEM analysis revealed adequate cell adhesion to the membrane after 24 h. Two weeks after loading, expression of markers in the positive control group was significantly higher compared to test group. CONCLUSION: We can conclude that static uniaxial strain exerted on hESCs results in their differentiation to osteoblasts. However, this magnitude of static strain in the tested time period cannot yield excellent differentiation when compared to the osteogenic medium.
ABSTRACT
AIM: To determine the strength of attachment between plain stainless steel band material and glass ionomer cement. METHODS: Seventy-five extracted upper premolars, free of visible structural defects, were used. The teeth were divided randomly into three groups and embedded in acrylic resin blocks. A short length of plain, stainless steel band material with a welded stainless steel standard edgewise 0.022 inch bracket was adapted to the buccal surface of each tooth. The bracket-stainless steel pads were then cemented to the teeth with either Bandtite (Group 1), Granitec (Group 2) or Ariadent (Group 3) glass ionomer cement and stored in an incubator at 37 degrees C for 30 days. The shear bond strengths of the specimens were measured and compared. RESULTS: The mean shear bond strengths (SBS) were significantly different: Bandtite 0.7331 +/- 0.056 Mpa; Granitec 0.3869 +/- 0.047 Mpa; Ariadent 0.2931 +/- 0.033 Mpa (ANOVA, p < 0.001). Tukey HSD post-hoc tests also showed significant differences between Bandtite and Granitec, Bandtite and Ariadent, and Granitec and Ariadent (p < 0.001). All specimens failed at the band-cement interface. CONCLUSION: The highest and lowest SBS were related to Bandtite and Ariadent cements, respectively. All cements had bond strengths less than the range of bond strengths considered to be clinically acceptable for bonded orthodontic attachments. Mechanical factors are important for band retention.
