In the femtosecond laser group , no significant differences in pH were observed between the three subgroups after docking and the femtosecond laser surgical procedure : low ( @ @ -LSB- range : @ to @ -RSB- ) , medium ( @ @ -LSB- range : @ to @ -RSB- ) , and high ( @ @ -LSB- range : @ to @ -RSB- ) level of gas bubbles .