Abstract
Purpose :
Light contact with dental floss on the cornea is a common method to assess corneal sensation, critical in the diagnosis of neurotrophic keratopathy. However, the mechanical characteristics of dental floss impacting the cornea are not understood, making the test difficult to interpret. This study is intended to quantify forces associated with light touch by dental floss.
Methods :
Two kinds of experiments were conducted. In each, dental floss was fixed to a vertical micrometer (+0.001 mm), at various initial lengths (1 cm, 3 cm, and 5 cm) was advanced perpendicularly to a Sartorious laboratory scale (0.0001 gm + 0.0003 gm).
In the first experiments, force was recorded at impact (n =15 at each length) and then at 10 second intervals over 3 minutes while concomitantly recording floss displacement from no contact to first contact on the scale. A one-sided ANOVA was used to assess difference between impact forces associated with length of dental floss. Ordinary least squares were used to compare the force vs. the time of force application. Second, initial impact forces for different brands of dental floss (waxed EquateTM and ReachTM, and unwaxed GlideTM)) were measured at 3cm floss lengths. Variation in impact forces between brands were evaluated by descriptive statistics.
Results :
Statistically significant differences between contact forces varied inversely with floss length (average force 0.2892 gm @1 cm, 0.1606gm @ 3cm and 0.0735 gm @ 5 cm). The force applied was insensitive to floss displacement in the range of 0.2 to 0.9 mm, regardless of length. The force of dental floss also decreased over time for 1cm and 3cm floss lengths (~30-50% well fit by a parabolic curve), but not for the 5cm length. Mean forces between brands of dental floss 3 cm long were similar.
Conclusions :
The force applied by dental floss is important to quantify to validate tests of corneal sensation and in comparison to the Cochet-Bonnet Esthesiometer. Longer initial lengths of dental floss reduced the vertical force applied, implying longer length may detect subtle decreases in corneal sensation. Prolonging contact of dental floss on the eye may decrease applied forces, so specifying the contact time with the eye may be useful when characterizing corneal sensitivity. Laboratory measurement of forces may inform clinical assessments in ophthalmology for different lengths of dental floss or when there are changes to a brand’s materials, structure or manufacturing methods.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.