Exhibit 99.1

American Dental Partners, Inc.

401 Edgewater Place, Suite 430

Wakefield, MA 01880

Phone: 781/224-0880                     Fax: 781/224-4216

For Immediate Release

AMERICAN DENTAL PARTNERS REPORTS

FIRST QUARTER 2011 FINANCIAL RESULTS

WAKEFIELD, MASSACHUSETTS – April 27, 2011 – American Dental Partners, Inc. (NASDAQ: ADPI) announced financial results today for the quarter ended March 31, 2011.

Comparing results for the first quarter of 2011 with results for the first quarter of 2010:

For the quarter, patient revenue of the Company’s affiliated dental group practices and Arizona’s Tooth Doctor for Kids was $117,590,000 and same market patient revenue increased 1.7%.

Cash flow from operations was $13,532,000 for the quarter. Amounts paid for acquisitions amounted to $150,000 during the quarter. The Company completed two in-market acquisitions during the quarter. Capital expenditures were $2,371,000 for the quarter. The Company completed one de novo facility during the quarter.

The Company recognized $388,000, $232,000 net of tax or $0.01 per diluted share, of stock-based compensation expense during the quarter, as compared to $391,000, $238,000 net of tax or $0.01 per diluted share, for the same quarter last year.

In March 2011, Dental Associates, P.C., the affiliated practice at Redwood Dental Group, filed a lawsuit against the Company and its subsidiary, American Dental Partners of Michigan, LLC in the Wayne County Circuit Court in Michigan. The complaint alleges, among other things, breach of the service agreement between the subsidiary and Dental Associates, breach of fiduciary duty and tortious interference with relationships. The complaint seeks, among other things, monetary damages and termination of the service agreement. For the year ended December 31, 2010 and the quarter ended March 31, 2011, the service fees the Company received under the service agreement with Dental Associates represented approximately 2% of the Company’s net revenue for both periods and approximately 3% and 2%, respectively, of the Company’s earnings before interest, taxes, depreciation and amortization. The Company and its subsidiary intend to defend themselves vigorously with respect to this matter.

Patient Revenue of the Affiliated Practices

The Company does not consolidate the financial statements of the practices affiliated with the Company by means of service agreements with its financial statements. Patient revenue of the affiliated practices is, however, a financial measure used by the Company’s management to monitor operating performance and to help identify and analyze trends of the affiliated practices that may affect the Company’s business. Most of the operating expenses incurred by the Company, pursuant to the service agreements, are on behalf of the affiliated practices in the operation of dental facilities. These expenses are significantly affected by the patient revenue of the affiliated practices.

Use of Non-GAAP Financial Measures

Adjusted net earnings and adjusted net earnings excluding service agreement amortization are non-GAAP financial measures. In accordance with the requirements of Regulation G of the Securities and Exchange Commission, please see the attached financial tables for a presentation of the most comparable GAAP measures, the reconciliation to those GAAP measures and all additional reconciliations required by Regulation G.

The Company believes non-GAAP financial measures, such as adjusted net earnings and adjusted net earnings excluding service agreement amortization, are important financial measures for understanding its financial performance. Amortization expense of intangible assets related to service agreements with the affiliated practices is presented separately and excluded from the Company’s adjusted net earnings excluding service agreement amortization, a non-GAAP financial measure, due to its magnitude and non-cash impact on the Company’s ongoing operations and because, unlike depreciation of the Company’s dental facilities, it requires no recurring capital investment. The primary limitations associated with the Company’s use of non-GAAP measures are that these measures may not be directly comparable to the amounts reported by other companies. Management compensates for these limitations by providing a detailed reconciliation of the non-GAAP financial measures to the most directly comparable GAAP measures in this press release.

Conference Call

For further discussion of these events and a comprehensive review of the quarter ended March 31, 2011, the Company will host its previously announced conference call on Thursday, April 28, 2011 at 9:00 a.m., EDT, which will be broadcast live over the Internet at www.amdpi.com. The call will be hosted by Gregory A. Serrao, Chairman, President and Chief Executive Officer. To access the webcast, participants should visit the Investors section of the website at least 15 minutes prior to the start of the conference call to download and install any necessary audio software. A replay of the webcast will be available at www.amdpi.com approximately two hours after the call through 6:00 p.m., EDT, Thursday, May 5, 2011.

About American Dental Partners, Inc.

American Dental Partners is one of the nation’s leading business partners to dental group practices. The Company is affiliated with 26 dental group practices, which have 278 dental facilities with approximately 2,390 operatories located in 21 states.

Use of Forward-Looking Statements

“Safe Harbor” Statement under the Private Securities Litigation Reform Act of 1995: With the exception of the historical information contained in this press release, the matters described herein contain “forward-looking” statements that involve risk and uncertainties that may individually or collectively affect the matters herein described, including but not limited to the Company’s risks associated with overall or regional economic conditions, dependence upon affiliated dental practices, contracts the affiliated practices have with third-party payors, government regulation of the dental industry, impact of health care reform, dependence upon service agreements and the impact of any terminations or potential terminations of such contracts, business interruptions, the outcome of pending litigation and the

Company’s acquisition and affiliation strategy, which are detailed from time to time in the “Risk Factors” section of the Company’s filings with the Securities and Exchange Commission, including its annual report on Form 10-K and quarterly reports on Form 10-Q.

AMERICAN DENTAL PARTNERS, INC.

FINANCIAL HIGHLIGHTS

(in thousands, except per share amounts)

(unaudited)

AMERICAN DENTAL PARTNERS, INC.

FINANCIAL HIGHLIGHTS

(in thousands)

(unaudited)

AMERICAN DENTAL PARTNERS, INC.

SUPPLEMENTAL OPERATING DATA

(unaudited)

Selected statistical data

Patient revenue and same market patient revenue growth (c)

(in thousands)

AMERICAN DENTAL PARTNERS, INC.

SUPPLEMENTAL OPERATING DATA

(in thousands)

(unaudited)

Components of same market patient revenue growth

Reconciliation of GAAP net earnings, as reported, to non-GAAP adjusted net earnings

(in thousands, except per share amounts)