SEARCH METHODS:
We searched the Cochrane Oral Health Group's Trials Register (to 1 November 2012); the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 7); MEDLINE via OVID (1946 to 1 November 2012); EMBASE via OVID (1980 to 1 November 2012); SCISEARCH, CAplus, INSPEC, NTIS and PASCAL via STN Easy (to 1 September 2012); and DARE, NHS EED and HTA (via the CAIRS web interface to 29 March 2012 and thereafter via Metaxis interface to September 2012). There were no language or publication restrictions. We also searched for ongoing trials via ClinicalTrials.gov (to 23 July 2012).