By the end of the year, you may be able to choose a dentist in Washington the same way you look for a supermarket special - by sitting through the newspaper ads.

The city's corporation counsel has ruled that a U.S. Supreme Court decision allowing advertising by lawyers applies to dentists as well, ending the traditional prohibition here on dental advertising.

In a memorandum to Dr. Montague Cashman, secretary of the D.C. Board of Dental Examiniers, Acting Corporation Counsel Louis P. Robbins has held that most of the antiadvertising provisions of the city's Dental Practice Act may no longer be enforced.

"There can be no serious question, as the professional dental societies have apparently recognized," wrote Robbins, "that the rationale expressed by the court . . . would apply to the dental profession."

Cashman said members of the board, which licenses dentists and regulates the practice of dentisty in the District, want to "control the men who (are) planning to advertise to keep it modest and tasteful.

"We hope we can keep the people who do advertise, and there are very few so far" - he estimates about four dentists have begun advertising - from advertising on radio or television, or from having great big ads," Cashman continued.

"Advertising in any form was against the code of ethics," he said. "We just felt that dentists should earn their livings on the basis of their reputation, and shouldn't seek out patients by any advertising whatsoever. That's the way it's been for 30 to 40 years, but the Supreme Court's thrown that out."

Proposed regulations printed in the D.C. Register, would still prohibit advertising on radio and television and any advertising that uses "showmanship, puffery, self-laudation or hucksterism, including the use of slogans, jingles, garish displays or sensational language."

The new rules also forbid promises of superior service or painless dental work, testimonials, or data about past successes or performance.

Advertising that is intended or "is reasonably likely to create unjustified expection in the mind of the layman" would also be prohibited.

Dentists would be allowed to advertise prices, services and the "availability of credit arrangements."

In is memo to the board, Robbins said he believes there will be some criticism of the proposed ban on television and radio advertising, because "many professional groups, including the D.C. Bar, have decided to permit use of electronic media."

The new regulations are available for publice comment until Nov. 27. Cashman said be expects the board to approve them and put them into effect shortly after that.

The board might consult with other licensing agencies "and professional societies" to decide how to handle the electronic media question, said Cashman.

The "great majority of dentists resent" advertising, said Cashman. "It's against tradition. It's unprofessional. It's unbecoming to the conduct of a professional man. We just don't feel you should get your patients by advertising your fees."

Cashman said he believes advertisements of denture prices are deceptive, because the final charge, including x-ray and fittings, is invariably higher than the advertised price.