Conventional vs figure-8 ligation
Little RA, Spary DJ. The effect of conventional versus figure-of-eight module ligation on mandibular incisor alignment: a randomized controlled trial. J Orthod 2017;18:1-10
Reduced frictional resistance during tooth movement is believed to increase the efficiency of the orthodontic force system. The method of ligation contributes to the amount of frictional force between the archwire and bracket. Studies have shown that elastomeric ligatures tied in a figure-8 pattern had significantly more friction than conventional elastomeric or stainless steel ligation. The authors tested whether figure-8 elastomeric modules affect the rate of mandibular incisor alignment and whether there was a difference in the number of bracket failures between figure-8 and conventional groups. There were 120 patients with mandibular incisor irregularity of 5 to 10 mm as measured by Little’s irregularity index. Patients were randomly divided into a conventional module or the figure-8 module group with further subdivisions into extraction and nonextraction groups. Victory Twin brackets were bonded, and the initial 0.014-in nickel-titanium wire was placed. Unstretched Super Slick (TP Ortho) grey elastomeric ligatures were applied. After 6 weeks, the wire was changed to the largest round nickel-titanium wire that would fully engage the bracket slots. Incisor irregularity was measured at the start of treatment and at 6 and 12 weeks into treatment. The results showed no significant difference concerning the rate of alignment between conventional and figure-8 pattern modules. In both groups, lower alignment rates were faster in extractions patients. The rate of bracket failure was similar for both groups. In clinical applications, early use of figure-8 modules will not slow or accelerate tooth alignment. Future studies could include a broader comparison of ligation types such as self-ligating brackets.
Reviewed by Cayce Cloud
Neural effects of obstructive sleep apnea treatment
Lu H, Wang W, Zhou Z, Liu C, Liu Y, Xiao W, et al. Treatment of obstructive sleep apnea-hypopnea syndrome by mandible advanced device reduced neuron apoptosis in frontal cortex of rabbits. Eur J Orthod 2017;39 Sept 23 [Epub ahead of print]
Prevalence of obstructive sleep apnea-hypopnea syndrome (OSAHS) is on the rise. A known danger of OSAHS is oxygen desaturation and the associated negative sequela, including damage to the brain’s frontal cortex, the region responsible for cognitive function such as short-term memory and attention. Treatment approaches often advance the mandible, opening the obstructed upper airway, thus improving oxyhemoglobin saturation and relieving symptoms. Little is understood regarding the mechanism by which OSAHS induces cognitive impairment. Thirty male rabbits were randomly divided into 3 groups; OSAHS was induced in 2 groups, and the third group acted as the control. Of the 2 OSAHS groups, 1 was left untreated, and the other wore a mandibular advancement device (MAD) guiding the mandible forward 3 to 4 mm. All rabbits were induced into a supine sleep position each day, and pulse, nasal air flow, blood oxygen saturation, computer tomography of the upper airway, polysomnography recordings, and other data were collected. After the 8-week observational period, the frontal cortices were dissected and evaluated for neuron apoptosis and AchE activity. No statistically significant differences were observed between the control and MAD groups; however, the untreated OSAHS group demonstrated significant increases in the apnea-hypopnea index, neuron apoptosis, and respiratory effort with decreased AchE activity, oxygen saturation, and nasal airflow. The MAD group’s apoptosis rates were slightly, although not significantly, higher compared with the control group. Results in this animal model suggest that MAD treatment may be an affordable, mildly invasive, yet effective treatment to improve neuron damage and improve the functional deficits of OSAHS caused by a narrowed airway.
Reviewed by Rebekah Goforth