Brian Barnes of Laurel had not been to a dentist in years. When he developed a toothache a few weeks ago, he knew exactly where he wanted to go for help -- a drugstore in his neighborhood.

"I heard about this place on the radio . . . It is a lot less money and you can just walk in . . . and I did," said Barnes, a writer of technical manuals.

In the last 18 months, six retail dental centers -- a kind of no-frills dentist office usually located in a drugstore or department store . . . have opened in the Washington area. Several more are expected to open in the next few months.

Hailed by their sponsores as a prototype of the future, the retail dental centers offer shopping center hours, immediate appointments if the dentist is free, and savings of about 20 to 50 percent on some -- though not all -- basic dental treatment and examination.

In many cases consumers can save on simple silver filings, simple tooth extractions, full-mouth X-rays and teeth cleaning and examination packages, according to price comparisons made by The Washington Post.

At the same time the claims by some of the retail centers that there are across-the-board savings seem exaggerated. Specifically some centers charge more than private dentists for surgical tooth removal and some types of root canal work.

By locating in areas with high-volume pedestrian traffic, such as shopping malls, the dental center operators hope that their price savings and long hours will attract a heavy flow of customers. All of the centers accept credit cards and stay open later than the usual dentist's office. One center, located at a Zayre's discount store in Wheaton, is open on Sundays.

"It [the development of dentist centers] is a response to the age of consumerism," said Dr. J. William Gallagher, the dentist who operates the center at Zayre's.

As estimated 50 percent of the population does not see a dentist regularly, according to the professional dentist associations. It is this untapped group of patients that the dental centers are particularly eager to reach.

Each center is operated by a dentist who has contracted for the space from the host company. Besides the one at the Zayre's, three are inside Peoples Drug Stores. The other two local centers are operated as retail outlets under the name Sterling Dental Center.

Consumers who walk into the center may see a dentist immediately, if the dentist does not have a patient, but all of the centers encourage people to call ahead for an appointment. The centers, which have one or two full-time dentists on duty and some part-time dentists who can come in if needed, say they often can set up appointments the same day they are called.

The number of persons receiving dental treatments at the centers vary. Dr. Gallagher estimates his Zayre center handles 140 patients a week, for example.

Staff dentists at the center have experience ranging from one year to 31 years.

Patients seek a variety of work, said Dr. Lee Shapiro, 30, who works at the Peoples center in Laurel."They come for fillings, to have missing teeth replaces, to have root canal work," he said. "I get a lot who haven't been to a dentist in years and who need comprehensive care while some others have been to a dentist and just haven't had the work done because it wasn't convenient."

Gale Bernard, who lives near the Laurel center, said she postponed going to a dentist even though she knew her teeth needed some work. "I was scared . . . and I hate dentists," she said. "But somebody at work told me you can just walk in here and see a dentist," she said.

Emerging from the center after her first visit, Bernard said she had not felt a thing when Dr. Shapiro drilled into her tooth. She said she will go back for more work.

Prices at the centers may sometimes exceed those charged by private dentists, and the centers often fall short of price claims, according to a Washington Post comparison of center prices with Blue Cross area averages. Both Peoples and Sterling, for example, say their fees are as much as 50 percent below average. There are actual 47 percent savings on two dental procedures at Sterling. For a simple silver amalgam filing the cost is $9 compared to the area average of $17.13; and for full mouth x-rays $15 rather than $28.27 area average.

In addition, all of the centers except Zayre say their prices are at least 20 percent below average, but The Post comparison found that the centers lived up to that claim only in half of the procedures checked -- the savings was more than 20 percent in 17 of the 30 instances.

There are some savings for consumers who go to the dental centers. They included the simple tooth extraction, which was $12 at Sterling and $15 at Peoples and Zayre, and the examination-cleaning-bitewing x-ray package at Peoples, which was $20 compared to the area average price of $33.71. Those prices represent savings of 29-to-43 percent on extraction and 40 percent on the cleaning package.

Prices vary widely from one center to another. The bill for work on a three-surface silver amalgam filling ranged from a low $24 at Sterlings to a high $36 at Zayre, for example.

In three instances, the center prices were higher than the average charged by private dentists. That $36 three-surface filling at Zayre, for instance, was more than $2 above the area average of $34.73. The surgical single tooth extraction at Peoples was $30, compared to the area average of $29.05. And the work on a molar with three canals was $225 at Peoples, nearly $7 over the area average of $217.95.

Dr. Mark Taff, the Maryland dentist who has the contract to operate the three centers in the Peoples Drug Stores, said the 20- to 50-percent savings claim was based on a comparison of his centers' rates with national dental fee studies published in 1979. "There are some qualifications . . . We are trying to be general and yet as specific as we can."

In addition, Dr. Taff said his centers do not try to be "the cheapest -- we try to offer the best quality for th lowest price."

Another center operator, Dr. Peter Winkelman of the Sterling Dental Center in Landover Hills, said the Blue Cross figures used in comparison are not the only source of average dental fees in the area. "There are a lot of ways to get a representative sample . . . and the one we used is at least as valid as Blue Cross," Winkelman said. He and Dr. Gary Colangelo, who operates the Sterling Dental Center in Wheaton, said they used fee averages from a professional insurance assocation as the basis for their comparison.

Gallagher, the Zayre dentist, is the only one who does not make the claim of offering savings of up to 50 percent. "That probably is true but it is too difficult to substantiate," he said, "so I just say we have substantial savings."

Since the first retail dental center was opened in 1977 in a Sears Roebuch and Co. store in El Monte, Calif., about 45 have sprung up around the country. The majority are in California and New York.

None of the believers in the dental center concept expects the discount dentist to replace the private dentist, but they do expect retail dentistry to grow.

"Fees for the private dentist of necessity have been high . . . because their supplies were purchased and delivered at retail prices," and Dr. Gallagher of the Zayre center. Moverover, the private dentist functioning as a one-person cottage industry has not generally made use of efficiencies available to the high-volume businessman, such as computerized billing, he said.

Gallagher compared the present changes in dental service systems to what has happened in some other businesses. "It's like the movement from the Mom and Pop grocery store to the supermarket," he said. "Now we are moving from the small private dentist office to the larger dental center."