Instruct: Classify a given Amazon review into positive or negative sentiment.
Query: Good while it lasted; Won't be buying another.

Our family has used the Oral-B power toothbrushes for several years now. The original model lasted a good 3+ years with heavy use. We bought this model as a replacement, but it lasted not much more than a year. It simply stopped working one day. Judging by the moisture that was getting into the LED screen, I suspected that it suffered a short. Thinking that it was just a defective unit, we went out and bought the same model. This time, it came with two of the power toothbrushes. In less than 6 months use, one of the brushes has already died. It suffered the same problem as the first, with moisture getting inside the brush. One would expect a toothbrush to be waterproof. It's very apparent that these brushes are not. It's a shame because they do a very effective job of cleaning teeth. I will be looking at alternatives now.