The Arduino UNO operates at 5V logic, if the DS18B20 VDD is connected to 3.3V and Pin DQ is connected directly to the Arduino UNO then damage may occur as these pins need to be within 0.3V of one another at maximum. Connect VDD to the 5V pin of the Arduino UNO to prevent this issue, or use a 3.3V microcontroller for data and power.