• Warintra Udtamapanya D.D.S. (Hons)
• Vachara Phetcharakupt D.D.S., Dip. In Orthodontics (Bergen), Thai Board of Orthodontics
• Nushanad Na Ranong Ph.D.

Objective To compare the static frictional forces between stainless steel wire and bracket ligated with
elastomeric ligatures fabricated from 4 formulations of epoxidized natural rubber, and 3 different cross
section configurations.

Materials and methods The 0.016 x 0.022 inch stainless steel wire was used with the 0.018 x 0.025
inch slot first premolar standard edgewise stainless steel bracket, and ligated with elastomeric ligatures
fabricated from 4 formulations of epoxidized natural rubber, which were epoxidized natural rubber
without silica, with 30% silica, with 45% silica, and with 55% silica. Each formulation had 3 different
cross section configurations, which were round, eclipse and rectangular. The static frictional force was
measured by using the Shimadzu Universal Testing Machine. One-way analysis of variance and
multiple comparisons with Tamhaneûs T2 were used to analyze the difference of the static frictional
force between groups at the statistically significant level of 0.05

Results Elastomeric ligature fabricated from epoxidized natural rubber without silica group showed
the lowest static frictional force followed by the 30% silica, 45% silica, and 55% silica groups respectively.
For the cross section configuration, the round groups showed the lowest static frictional force followed
by the eclipse and rectangular groups respectively. There were statistically significant differences of
static frictional force among all groups at the significance level of 0.05, except for the round and
eclipse groups.

Conclusion The static frictional force was significantly greater when the percentage of silica in
elastomeric ligature fabricated from epoxidized natural rubber increased. For cross section configuration,
the rectangular groups produced significantly higher static frictional force than the eclipse and round
groups. However, there was no statistically significant difference between the eclipse and the round
groups.

(CU Dent J. 2013;36:21-30)