Silicone replacement brush heads are the best choice.  With silicone you will receive a much better circulatory response, and the brush is antimicrobial.  The silicone can be cleaned and serilized where-as the brisstle brush heads can only be cleaned, but not sterilized.  You can wash your silicone brush head in the dishwasher, or with soap, & you can soak it in Alcohol for 20 minutes to sterilize it.  If cared for properly this head should last you a year or more, where-as the brisstle brushes need to be replaced every 3 months to protect against bacteria and because they break down with each use.