than the bamboo toothbrush. The bamboo toothbrush was, however, not the most environmentally sustainable toothbrush, contrary to popular belief because using them just stops land from being put to better use such as helping biodiversity, or in growing forests to offset carbon emissions. A plastic manual replaceable head toothbrush was probably the best, according to the study. Optional features Timer Many modern electric toothbrushes have a timer that buzzes, or briefly interrupts power, typically after two minutes, and sometimes every 30 seconds. This is associated with a customary recommendation to brush for two minutes, 30 seconds for each of the four quadrants of the mouth. Display Some electric toothbrushes have LCD screens that show brushing time and sometimes smiley face icons or other images to encourage optimal brushing. These features could encourage people to brush more accurately. Pressure sensor Brushing teeth too hard causes enamel and gum damage. Most modern top-end sonic toothbrushes come with a pressure sensor, which prevents users from brushing too aggressively. There are two types of pressure sensors. Some sensors produce a sound warning and some immediately stop movements of the sonic toothbrush when it is used too aggressively. Some electric brushes, such as the Oral B oscillating rotating brush, simultaneously coach the user to brush with optimal pressure during the brushing experience itself using AI and Bluetooth technology. Ultrasound indicator Because ultrasonic frequencies are beyond the audible range and the amplitude of movement emitted by an ultrasonic toothbrush is typically too small to be perceived, the ultrasound is imperceptible to humans and it may not be apparent that a brush running if pure ultrasound is turned on. Ultrasonic toothbrushes may include an indicator to notify the user that ultrasound is being emitted. Bluetooth Bluetooth connectivity enables data to be transmitted from an electric toothbrush to another Bluetooth device, such as a smartphone. The brush can send data to a mobile app such as how long it has been brushing for and if too much pressure has been applied when brushing. The app can in turn send data back to the brush such as changing the cleaning modes available, and cleaning time. The sharing of data between toothbrush and smartphone is intended to assist the user in creating better brushing technique and habits. This technology enables coaching for the user as it tracks where the user brushes, how long in each area, and consequently, can identify