Based on the input from our experts, and our research, we came up with a method to test the cleaning power of each model. Our experts felt that the different cleaning modes were mainly unnecessary features, with the exception of a gentle mode for users with sensitive gums. None of our testers were in this situation, so we used the standard mode on each toothbrush. We procured identical brush heads for each of our 5 testers, for each model that we tested, and the group would use a different model of electric toothbrush each day. We used the stock brush head type that came with each toothbrush model, and brushed with each model for 2 minutes, using a stopwatch to regulate our pace and brush in a quadrant method.
Our cleaning test was split into two components: the plaque disclosing tablet and whitening test. The procedure for the plaque test was quite simple; each member of our testing panel would skip brushing in the morning, and would chew a plaque disclosing tablet before brushing with the electric toothbrush. They were also instructed to eat as many sugary foods as possible. This, combined with the lack of brushing for around 16 hours would lead to a sizeable buildup of visible plaque. We would then take before and after pictures, and score the results.
This test was based on the idea that your electric toothbrush cannot clean where it cannot reach. A common misconception is that sonic toothbrushes use sonic waves to actually blast plaque off of your teeth, when in reality "sonic" is just referring to how fast the bristles are vibrating (Sonic and ultrasonic toothbrushes do have a proven fluid dynamics effect, where they are able to disrupt bacteria up to 4mm away from the actual brush head in certain circumstances, but 4mm isn't very far, still requiring you to effectively move the toothbrush into all the cracks and crevices of your mouth).
Our test highlights which toothbrushes were the most intuitive to use while brushing, the most maneuverable, and the models that most people will miss the least number of spots in their mouth, based on our group of testers. Each tester used each toothbrush model only once, to use each model in a "worst case scenario" as each user would miss the most spots when the brush was the most unfamiliar. We also had each tester bring in their manual toothbrush and complete the test with that, to act as a control.
We also looked at the ability of these toothbrushes to remove surface stains. Our expert dentist told us that toothbrushes can not actually whiten teeth, which is only possible with a prolonged chemical-based treatment, but they can possibly remove surface stains. We utilized eggshells as a facsimile of teeth, leaving them soaking in black coffee for 4 days. We then ran each toothbrush on a tooth-sized section of the shell for a full 2 minute cycle, and evaluated performance based on before and after photos. This would equate to a little over 4 weeks of brushing, using the recommended 2 minutes of brushing, twice a day. Any models that had a specific whitening mode were run in that mode, otherwise the normal setting was used. Our scores were based on comparing before and after photos. As this test is somewhat subjective, and brushing an egg is not necessarily a perfect analog for brushing your teeth, this test made up a relatively small portion of our cleaning score.
We then scored the before and after photos, with this aspect making up a much smaller portion of the score than the plaque test
When it came to evaluating comfort, we assessed three categories: holding comfort, brushing comfort, and noise level. Our panel ranked the holding comfort while blindfolded, and had not previously seen the toothbrushes. The same panel ranked the brushing comfort after having used them multiple times, over a period of two weeks. We also had them rate the level of irritation the noise of each model caused them. This captures what the the person brushing would actually hear, as their are some interesting effects due to bone conduction that affect the sound. We also measured the sound output of each model with an SPL meter at 2" away, for how vexing the sound may be to anyone else that is around when you are brushing.
The ease of use metric looked at the aesthetics of each product, the maintenance and day to day use. A group of people independently ranked the look of each toothbrush, and drew very similar conclusions. Below is the order of toothbrushes, from least to most visual appeal, based on our tests.
For maintenance, we looked at the difficulty and dexterity required to swap out a toothbrush head, as well as clean each brush. We sprayed each model with a solution of water and toothpaste, and saw how long it took to clean each model, as well as if there were any spots we missed or that were exceptionally difficult to reach.
Day to day use was measured by the number of cleaning modes each toothbrush had, as well as the interface necessary to access those various modes. We also looked at the stability of each product, both on and off the base, as it can be somewhat frustrating to knock these over — who really want to keep using that brush head after it has been on the bathroom floor? this was accomplished by setting each model up, and hitting the table with impacts of progressively larger magnitude until there was one left standing.
Battery life was easy to test, as we simply charged each model fully per the manufacturer's instructions, and then ran each one repeatedly until it died, taking note if there was a low battery indicator present, and if so, when it turned on. Below is a chart showing the time each toothbrush ran, and the equivalent number of days it would function when using the recommended brushing amount.