For guidance on when particular dental procedures are appropriate, no appropriate, preferred, etc., see the "Practice Guidelines," "Standards" promulgated by the various associations such as the American Dental Association, the American Association of Endodontics, the Academy of Operative Dentistry, the American Academy of Pediatric Dentistry. To find them, you can (a) look on the relevant Association web site, (b) search PubMed, limiting your results to the Article Type "Practice Guidelines" and (b) search the web with Google or another good search engine.
As of 2012 there was no broad encyclopedia covering the entire field of dentistry (i.e., no Am Jur of dentistry). Rather, dental treatises generally cover one practice area (e.g., Pathways of the Pulp is the leading treatise for endodontics.
Journal articles on dentistry are indexed in and often available through PubMed.