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1979 United States Experimental The services provided by expanded-function dental hygienists can be of high quality. Jones et al. 1981 United Kingdom Empirical No specific conclusions reported with regard to technical competence (it was not the main focus of the study). Lewis 1981 Canada Empirical The economies of scale in terms of cost per child were not accomplished at the expense of lower quality. Barmes 1983 Australia Empirical The data do not support the charges of inferior quality in the SDS. The quality of care that has been provided by the SDS can only be described as excellent, both clinically and in the social sense. Crawford & Holmesa 1989 Canada Empirical Therapists play a very important role, and should be expanded, rather than replaced by contract dentists. Fiset 2005 United States Empirical The performance of the DHATs met the standards of care established. Bolin 2008 United States Empirical No significant evidence was found to indicate that irreversible dental treatment provided by DHATs differed from similar treatment provided by dentists. Calache et al. 2009 Australia Empirical The standard of restorations provided by dental therapists newly trained to provide care to adults was at least similar to that expected of newly graduated dentists. Bader et al.b 2011 United States Empirical DHATs are performing at what must be considered an acceptable level. a These same data were also analyzed by Trueblood (undated). b These same data were also reported in Wetterhall et al. (2010). Downloaded from jdr.sagepub.com at UNIV OF MICHIGAN on May 24, 2013 For personal use only. No other uses without permission. © International & American Associations for Dental Research 4 JDR Clinical Research Supplement Month 2013 based program. The team examined a “representative” number of children, and while overall just 7% of restorations were judged unsatisfactory, they nevertheless concluded that “[a]n attempt to solve the weaknesses in the California public and private dental care systems by establishing a New Zealand dental nurse type of technician is unwarranted” (Redig et al., 1973). Though quite different methodologically, all but 2 of the 13 non-experimental empirical studies involved direct clinical evaluations; the 2 that did not (Lewis, 1981; Bolin, 2008) relied on chart reviews. In these 2 cases, as well as in a chart review conducted by Bader et al. (2011), random or quasi-random samples of therapists’ patients’ charts were examined for either post-procedure complications or failed restorations. In all cases, the rates of these problems were very low (less than 3%), and in the one study that directly compared therapists’ complication rates with those of their supervising dentists, no significant difference was found (Bolin, 2008). Half of the studies that involved clinical examinations also used control groups, and in most cases blinded examinations were performed. Three of these studies took place in South Australia, where children served by the SDS (the vast majority of whose restorations would have been placed by therapists) were compared with non-participants (all of whose restorations were placed by dentists). The restorations in SDS children were judged either to be no different from those in non-participants (Roder, 1976) or to be somewhat superior (Roder, 1973; Barmes, 1983). In Canada, Ambrose et al. (1976) compared restorations in children treated by the Saskatchewan Dental Plan (which employed therapists) with those performed by dentists, and Crawford and Holmes (1989) compared restorations in both children and adults in Baffin Island, some of whom had been treated by therapists, and some by dental residents or dentists. In both cases, the work of therapists was judged, overall, to be superior to that of dentists, though Ambrose et al. found no significant differences with respect to stainless steel crowns. Finally, Bader et al. (2011) compared the work of Alaskan DHATs with that of their supervising dentists and found that, on 2 of 3 measures, the DHATs outperformed the dentists. The remainder of the studies