Investigators looking into gifts to Gov. Robert F. McDonnell and his family have asked questions about whether first lady Maureen McDonnell received cosmetic dental work for free, according to two people familiar with the probe.

Federal officials have been investigating allegations that a dentist within the large Richmond-area practice of W. Baxter Perkinson Jr. provided cosmetic dentistry services at no charge to the first lady, according to the two people, who spoke on the condition of anonymity because the investigation is ongoing.

Free dental work would expand the number of gifts that the first family has received and add a new name to what has been a short list of benefactors. It also would fit a pattern of items given to Maureen McDonnell — including designer clothing and accessories — that appear to have been aimed at polishing her image as first lady.

Until now, most of the gifts that investigators were known to be probing were from Jonnie R. Williams Sr., the chief executive of Star Scientific. They include a $15,000 New York shopping spree for the first lady, a $6,500 Rolex watch for the Republican governor and $145,000 in payments and loans to the McDonnells and two of their bride-to-be daughters.

Investigators also have asked about possible gifts from Del. David I. Ramadan (R-Loudoun), a jeweler who confirmed last month that he had been called to appear as a witness before a federal grand jury in the case.

Timeline: Star Scientific and Gov. McDonnell

Perkinson has declined to respond to messages seeking comment, but a woman who returned a call on behalf of his practice and who gave her name only as Marie noted that laws governing the privacy of health-care records would prevent divulging anything about services to anyone.

“We’re not at liberty to discuss anything,” she said.

A well-known dentist with 11 offices in the Richmond area, Perkinson has a $20 million building named after him at the Vir­ginia Commonwealth University School of Dentistry. McDonnell appointed Perkinson to the VCU board of visitors in July 2010. He had previously served as VCU rector and as vice president of the VCU Health Systems board.

Rich Galen, the privately funded spokesman that Gov. McDonnell hired to field questions about the investigation, neither confirmed nor denied that any dental work had been provided for free.

“It wasn’t reported, but it didn’t have to be reported,” Galen said, speaking hypothetically. He was referring to the fact that under Virginia law, elected officials do not have to notify the state about gifts to immediate family members. The officials have to annually disclose any gifts to themselves worth more than $50.

“It may well be that they’ve looked at every gift, but it doesn’t mean there’s any significance,” Galen said. “On the face of it, it’s just not material to everything else we’re talking about.”

The McDonnells have been under scrutiny for gifts since The Washington Post reported in March that they had promoted a nutritional supplement made by Star Scientific around the time that Williams picked up the $15,000 catering tab at the wedding of one of their daughters.

The governor had not reported the gift on the disclosure form he filed the state, but he said he did not have to because it was a present to his daughter, not to him. He has said efforts by himself or his wife to promote the supplement, an anti-inflammatory named Anatabloc, were in line with what they would do to boost any Virginia-based enterprise.