Table 4.

Study design of selected articles.

Articles	Study Design
Bukhari et al. [10] (2018)	R, CCT, UC
Ugolini et al. [24] (2015) and Cerruto et al. [25] (2017)	P, RCT
Wong et al. [7] (2011)	R, CCT, NC
Petrén et al. [5,26] (2011), (2013)	P, RCT, NC
Petrén and Brondemark [8] (2008)	P, RCT, UC
Weyrich et al. [27] (2010)	P, CT
Lippold at al. [18] (2013)	P, RCT, UC
Primozic et al. [28] (2011)	P, CCT, UC, NC
Godoy at al. [9] (2011)	P, RCT, UC

P, prospective study; R, retrospective study; L, longitudinal study; RCT, randomized clinical trial; CCT, controlled clinical trial; CT, clinical trial, i.e., comparison at least two treatment modalities without any untreated or normal group involved; UC, untreated control group; and NC, normal control group.