Nearly every tooth in Theresa's mouth is in need of some kind of treatment — from root canals, veneers, and fillings to bridge replacements, whitenings and crowns — if you combine all the recommendations of 20 dentists she visited.

That, despite the fact that dental experts suggested only a few cleanings and possibly a crown.

Theresa, a CBC researcher, went to a mixture of small and large dental offices in Toronto and Vancouver for a Marketplace episode, Money Where Your Mouth Is, airing on Friday.

By the end, the dentists had recommended treatments covering 19 different teeth, ranging from nighttime mouth guards to veneers promising a "complete smile makeover," with cost estimates ranging from $144 to $11,931.

"Some of it I found quite frightening," said dental insurance expert Rick Beyers. "It was actually quite scary that invasive procedures like root canals and bridge replacement would be offered."

Before visiting dental offices, Theresa underwent an examination by two expert dentists — University of Toronto professors Dorothy McComb, a restorative dentistry specialist, and Laura Tam, co-director of the faculty's Comprehensive Care Program.

According to their baseline treatment recommendation, Theresa had no tooth decay, needed several cleanings to fight gum disease and potentially needed a crown on one tooth, at a cost of about $1,800 to $2,000.

Armed with a hidden camera, Theresa went to see 20 dentists, offering them X-rays of her teeth and asking for a treatment plan.

The first dentist, after an 11-minute consultation that did not include looking in Theresa's mouth, agreed with the experts that a cleaning and crown was necessary but also recommended a filling, a mouth guard and a root canal. She also suggested Theresa was suffering from severe bone loss and definitively stated she'd lose one tooth, requiring treatment at a cost of $7,000 to $8,000.

'Easy to abuse' dental plans

Another Toronto dentist raised the possibility of a root canal on another tooth, identified three cavities, recommended two cast metal onlays and the whitening of lower teeth.

Dentists visited by Theresa suggested treatments for 19 of her teeth, plus whitening to target her lower front teeth and a night mouth guard. (CBC)

She also suggested a "complete smile makeover" that included six veneers to correct a cosmetic midline shift, meaning the centerline of her upper and lower teeth don't line up. "It doesn't look nice to me," the dentist concluded. The total treatment cost was $8,622.

Dentist and author of Confessions of a Former Cosmetic Dentist, Dr. Michael Zuk of Red Deer, Alta., says cosmetic dentists often focus on veneers as a cure-all but it can be a costly solution — and one sometimes driven by economics rather than patient interest.

"The teeth are often mutilated in the process and once they are done, the patient is stuck with that treatment," said Zuk. "And they will have to have it redone over the period of their lifetime."

Zuk said some dentists try to push veneers, "trying to make $30,000 to $40,000 in cases that really don't need the treatment."

The issue of dentists crafting treatment plans based on an individual's insurance also arose during Marketplace's undercover dental office visits.

One dentist told Theresa she needed three fillings, but refused to specify the teeth without viewing her insurance plan.

"It's pretty easy to abuse dental plans," says Beyers, a former dentist who now works for companies that investigate misuse of dental insurance plans.

"The joke we make in some cases: They're not treating the patient. They're treating the dental plan," said Beyers. "In other words, they’re reading up on the plan, finding out what it covers."

Dentistry not 'black and white'

The most expensive treatment estimate encountered by Theresa was $11,931, a total that included a root canal, six optional veneers, a crown and cleanings.

The estimate came from a Vancouver-area dentist, who was visited by CBC Marketplace 15 years ago for a similar episode looking at dental costs and came under fire then for providing the highest estimate.

'It depends very much on the dentist’s personal experience.'—University of Toronto professor Dorothy McComb

About three-fifths of the 20 dentists visited by Marketplace offered dental treatment options either in line with the expert opinion or containing what the experts describe as innocuous differences.

Overall, McComb noted that she wasn't concerned with the wide variety of suggested treatments.

"Unfortunately in dentistry more than in medicine, things are not absolutely black and white," says University of Toronto professor McComb. "So [there are] a lot of shades of grey and it depends very much on the dentist’s personal experience."

Other factors that can contribute to dental treatment variation include where a dentist trained, whether they take a wait-and-see or more aggressive approach, and the types of materials used by the dentist.

The patient's own medical history, oral hygiene status as well as their likelihood to follow a treatment plan can also influence the dentist's decisions.

“It’s not that they are basically trying to tell you something different to make more money, but they have different ideas," said Zuk. "And different trainings. And they see things differently. And it’s extremely variable."

Still, some recommendations by the dentists puzzled McComb.

One Vancouver-area dentist suggested replacing two bridges in Theresa's mouth at a cost of $7,013 — bridgework complimented by other dentists visited in the Marketplace test.

McComb says bridges don't typically need replacement unless there's a "real overt reason for it."

Watch Marketplace's Money Where Your Mouth Is on CBC TV at 8 p.m. on Friday (8:30 p.m. in Newfoundland and Labrador).