Table 2.

Summary of risk of bias of included studies

	Study design	Randomisation	Allocation concealment	Masking of participants	Masking of outcome assessors	Incomplete outcome reporting	Selective reporting	Other bias
Hoerman [16]	RCT	Unclear	High risk	unclear	Unclear	Low risk	Low risk	Low risk
Hildebrandt and Sparks [17]	RCT	Unclear	Unclear	Unclear	Low risk	Unclear	Unclear	Unclear
Thaweboon et al. [18]	Other	Unclear [1]	Unclear	Unclear	Unclear	Unclear	Unclear	Unclear
Makinen et al. [19]	RCT	Unclear	Unclear	Low risk	Low risk	High risk	Unclear	Unclear
Wang et al. [20]	RCT	Low risk	Unclear	Unclear	Unclear	Low risk	Unclear	Unclear
Haresaku et al. [20]	Patient preference non-randomised trial	High risk [2]	Unclear	Unclear	Low risk	High risk	Unclear	Unclear
Calgar et al. [22]	RCT	Low risk	Unclear	Low risk	Low risk	Unclear	Unclear	Low risk
Campus et al. [23]	RCT	Low risk	Low risk	Low risk	Low risk	Unclear	Unclear	Low risk
Hildebrandt et al. [24]	RCT	Low risk	Unclear	High risk	Low risk	Low risk	Unclear	Unclear
Seki et al. [25]	RCT	Low risk	Low risk	Low risk	Unclear	High risk	Unclear	High risk
Alamoudi et al. [26] Hanno et al. [27]	RCT	Unclear	High risk	High risk	Unclear	Unclear	Unclear	Unclear
Al-haboubi et al. [28]	RCT	Low risk	Low risk	High risk	Low risk	Unclear	Unclear	Low risk
Ghassemi et al. [29]	RCT	Unclear	Unclear	Low risk	Unclear	Low risk	Unclear	Unclear

Participants were divided into three groups which were balanced according to their S. mutans counts at baseline: one control group (no supervised gum use), and two xylitol groups (supervised 55% and 100% xylitol gum use). It is unclear whether they were or not randomised after stratification

Participants’ preference for the flavour of gum was taken into account at allocation in an effort to enhance adherence to the chewing regimen