Some Washington area dentists charge nearly 2 1/2 times as much as others for such common procedures as routine cleaning with X-rays, simple extractions and simple root canal work, according to a new consumer study.

The Washington Consumers' Checkbook, a nonprofit group that rates services, provided these examples of the wide variation in dental charges, based on a survey of about 200 of the Washington area's 2,000 dentists:

* Routine adult cleaning, with two bitewing X-rays, ranged from $27 for the lowest priced dentists to $70 for the highest priced dentists.

* Simple extraction, from $20 to $53.

* Simple root canal, from $118 to $278.

At the same time, the researchers "found little, if any, correlation between patient satisfaction and price." They said that seven dentists who were among the lowest priced of those surveyed were rated "superior" on doing work properly by 95 percent or more of their patients in the survey.

In addition, 11 of the highest priced dentists received the same 95 percent rating from their patients who were queried.

The study, which is featured in the latest Checkbook magazine, said that dental fees generally are higher in Washington than in the suburbs and that the dental services available in retail stores are 18 to 20 percent less expensive than the average private practitioner.

The magazine did not speculate on the reason for the wide variation in prices.

"We have no data on that," said Robert Krughoff, Checkbook president.

In addition to showing prices by area, the magazine lists the prices for about 200 individual dentists for a market basket of 20 dental procedures, including examinations, X-rays, extractions, root canals and porcelain crowns.

The magazine said that the lowest prices found were charged by Frank J. Trachtman, Springfield Medical Arts Building, and the highest were charged by Alan L. Book, 1601 18th St. NW.

Both dentists said yesterday that they were surprised by their ranking in the price survey.

"I knew I was low, but I didn't know I was that low," Trachtman said. He said he had no idea why his prices were so much less than other dentists.

"But don't tell my partner," he said.

Book said that he usually charges a higher fee for an initial examination of a new patient because he spends more time with that person.

But, he said, his prices for crowns generally are lower than his colleagues charge, while his prices for root canal work are about the same as their rates.

"So I would say the survey is very misleading," Book said, adding: "I don't make any more money."

The price information is part of a 33-page report that provides consumer information on what is new in the dental business, how to care for your teeth, how to choose a dentist, how to keep dental costs down, and where to complain.

C.J. Brown, executive director of the D.C. Dental Society, said that the report offered a "fairly good representation of the clinical aspects of dentistry."

But he was critical of the price survey of dental services because, "To rate professional services the same way as you would rate TV shops is unwise . . . . There is more to choosing and rating a dentist than a TV."