U.S. Dental Museums and Collections:

National Museums:
National Museum of Dentistry, Baltimore, MD 

University-Affiliated Museums and Collections:
School of Dental Medicine's Dental Museum, University of Pittsburgh
Bibby Library Archives, Dentistry Exhibits, Eastman Institute for Oral Health, University of Rochester
Artifacts from the Harvard School of Dental Medicine, Harvard University
Out of the Past Dental History, University of Texas, San Antonio Dental School
Macaulay Museum of Dental History, The Medical University of South Carolina
Kottemann Gallery of Dentistry, University of Illinois at Chicago
Medical Museum, College of Dentistry, University of Iowa
Pierre Fauchard Academy Dental Museum, Community College of Southern Nevada
A.W. Ward Museum of Dentistry Collection, University of the Pacific School of Dentistry
Photographs from the Historical Museum of Medicine and Dentistry, Collected by the Hartford Medical Society & the Hartford Dental Society
Dental Historic Collection, University of Michigan Library. This collection of important and unusual dental publications is comprised of both books and journals.
 

International Dental Museums and Collections:

Dentistry Museum Collection, University of Alberta, Edmonton, Alberta, Canada
British Dental Association Museum, London, England
Henry Forman Atkinson Dental Museum, University of Melbourne, Victoria, Austrailia
The Lyon Dental Museum, Université Claude Bernard Lyon 1, Lyon, France
Seoul National University School of Dentistry Museum of Dentistry, Seoul, Korea 
Chonnam National University School of Dentistry Museum of Dentistry, Gwangji, Korea
History of the Royal Army Dental Corps, Army Medical Services Museum

Additional Research Links:

American Academy of the History of Dentistry: Dentistry Collections Database
This browseable, searchable database site is the result of our ongoing survey of museums, libraries, archives and private collections regarding artifacts and materials relevant to the history of dentistry.
Want to join the dental history listserv?
Want to join a Flickr group related to history of dentistry? Check out this group: History & Art of Dentistry  and then check Flickr pro, Rosefirerising’s dentistry collections of images
Journal of the History of Dentistry (issues available to read online)
Dental Cosmos, a Monthly Record of Dental Science (1859-1936). 
Digital version of the original classic professional journal. All pages scanned, including advertisements.
Google Patent Search. 
Research the function or inventor of dental tools and devices by searching this database of scanned US Patent records including drawings and descriptions.
The Medical Heritage Library is a digital curation collaborative among some of the world’s leading medical libraries, and promotes free and open access to quality historical resources in medicine.

Directories:
Directory of History of Medicine Collections, National Library of Medicine, National Institutes of Health, Washington, DC 
University Museums Collections Worldwide Database Directory, quick search: “dentistry museum”