Table 2. Mean wear and the standard deviation in parentheses (µm) of the hemiarch and selected 1 mm² area of the restorations.

Selected area of 1 mm2
Analysis time	GIC + Petroleum jelly	GIC + NPC
6 months	535 (91)a,A	315 (134)b,A
12 months	600 (98)a,A	364 (135)b,A
24 months	610 (93)a,A	370 (142)b,A
36 months	630 (82)a,A	440 (118)b,A
Hemi-arch
Analysis time	GIC+ Petroleum jelly	GIC + NPC
6 months	86 (29)a,A	106 (48)a,A
12 months	149(44)a,A,B	158 (56)a,A
24 months	176 (40)a,B	185 (52)a,A
36 months	180 (36)a,B	182 (32)a,A

Different lower cases indicate statistically significant difference between the columns (p<0.05)

Different upper cases indicate statistically significant difference between the rows (p<0.05)

GIC=glass ionomer cement; NPC=Nanofilled self-adhesive light-cured protective coating