No matter what you find that he will drink from (bottle, sippy cup or straw) there is no need to wean at all... When you are around your little one, then continue to breastfeed. When he is away, you can provide a bottle or sippy cup of pumped milk (or formula if you absolutely are against pumping)...The AAP (American Academy of Pediatrics) recommends breastfeeding for 1 year and the WHO (World Health Organization) recommends 2yrs. At only 6 mo old he is still a baby and is benefiting TREMENDOUSLY from your breastmilk. He is not only benefiting from all the nutrition, but he is also benefiting from the bond, comfort and security that nursing gives him while he continues to mature and develop.
There are certain bottles that work more like the breast...I think one is even called the 'breast bottle' You may be able to search something online about best bottles for breastfed babies...I know some are best to AVOID, such as Dr.Brown's because they work exactly opposite the breast and sometimes cause nursing problems.
I don't know if you are getting pressured by well-meaning family, your pediatrician or someone else to wean, but I highly recommend NOT weaning while he is only 6 mo old...hang in there, you can do it! Especially since he will only need a pumped bottle once a week, that's no big deal. Find some good support through a Yahoo group or local nursing support group to give you encouragement and sound advice.
As for teething - it usually is NO issue at all, but sometimes it may be uncomfortable for a short time right when their gums are sore from getting a tooth and they have a hard time sucking the milk out. They sometimes nurse differently or make it a little uncomfortable for you but it is VERY TEMPORARY....nothing bad enough to wean them over :-)
Best wishes to you and your little one! Hang in there...