Table 4.

Association between dental erosion extent (mean number of affected surfaces) and explanatory variables in univariable and multivariable Poisson regression analyses

Characteristic	Univariable			Multivariable
	RR	95% CI	P	RR	95% CI	P
Sociodemographics
Gender
Girls	Ref.			Ref.
Boys	1.68	1.26–2.23	<0.001	1.66	1.28–2.17	<0.001
Socio-economic status
High	Ref.
Mid–high	1.03	0.73–1.45	0.87
Mid–low	0.89	0.77–1.02	0.09
Low	0.66	0.29–1.51	0.33
School
Public	Ref.			Ref.
Private	1.84	1.59–2.13	<0.001	1.89	1.53–2.35	<0.001
Dietary habits
- Soft drinks
Rarely/never	Ref.			Ref.
Sometimes	4.33	1.24–15.15	0.022	5.27	1.46–19.05	0.01
Daily	5.97	1.26–28.33	0.025	6.82	1.39–33.50	0.02
Orange
Rarely/never	Ref.
Sometimes	0.93	0.56–1.54	0.77
Daily	0.91	0.60–1.39	0.67
Lemon
Rarely/never	Ref.			Ref.
Sometimes	0.88	0.68–1.14	0.34	0.92	0.69–1.24	0.60
Daily	1.36	1.15–1.60	<0.001	1.49	1.11–2.00	0.007
General health
Gastro-oesophageal disorders
Absent	Ref.
Present	1.43	0.96–2.12	0.08
Asthma
Absent	Ref.
Present	1.27	0.70–2.30	0.42
Weight status
Normal	Ref.
Overweight	0.99	0.83–1.17	0.87
Obese	1.01	0.77–1.34	0.92
Controlling variables
Brushing frequency
≤1 time/day	Ref.
2 times/day	1.23	0.83–1.81	0.30
≥3 times/day	1.22	0.83–1.77	0.31
Bruxism
Absent	Ref.
Present	0.90	0.66–1.24	0.54

95% CI, 95% confidence interval; Ref., reference category; RR, rate ratio.