At up to $100 in supermarkets, the Oral-B electric toothbrush is widely marketed as "the brand more dentists and hygienists use".
But dentists and therapists have broken ranks with their professional associations - one of which receives sponsorship from Oral-B - to say the clean provided by electric toothbrushes is no better than a manual toothbrush.
The Herald on Sunday canvassed 30 independent dentists and discovered a level of discomfort with their profession's close relations with dental product marketing companies.
Wrigley also claims the professional endorsement of dentists. Its advertisements say "dentists recommend chewing Extra sugarfree gum after eating and drinking".
Others to market themselves as having dentists' endorsement have included Philips Sonicare electric toothbrushes and Colgate Total toothpaste.
Supermarket shoppers can pay between $39 and $100 for an Oral-B electric toothbrush.
But many dentists argue a manual brush would do the same job.
Auckland cosmetic dentist Clarence Tam said: "It's all the same. What is important is the technique you use."
Wrigley said its advertising was supported by 2011 research, which showed 87 per cent of dentists in New Zealand agreed with the claim. The benefits of chewing its gum, specifically Extra, were recognised by the World Dental Federation, Australian and New Zealand Dental Associations, said the company.
Oral-B did not respond to calls about its advertising - and the professional associations ducked for cover.
New Zealand Dental Association executive director David Crum declined to comment on the claims "because of other commitments".
Gillian Tahi, president of the New Zealand Dental Therapists Association, said she was unable to comment because of "sponsorship reasons".
"Both those companies are very good sponsors of our associations and conferences," she said.
Of the 30 dentists canvassed this week, 20 said they used Oral-B brand products. But they were split 50-50 about whether an electric toothbrush gave a better clean. Some argued a manual toothbrush gave a superior clean, but others said an electric toothbrush could reach where a manual brush couldn't.
New Plymouth dentist Vaibhav Balesara said electric toothbrushes were best in rare situations such as when someone struggled with dexterity.
But most people didn't need to spend lots of money for a good clean. "In the end it comes down to how well you brush. It doesn't matter about the toothpaste or toothbrush," he said.
Another dentist, who did not wish to be named, expressed "extreme frustration" that companies made such claims without asking most dentists what they recommended.