Herbst appliance shows larger improvement in sleep apnea than twin block in small trial

The Herbst group showed statistically significant improvements: AHI decreased by an average of 1.08 events per hour (p=0.031), supine AHI fell by 3.29 events per hour (p=0.001), and ODI dropped by 2.09 events per hour (p=0.013). The Twin Block group did not achieve statistical significance on AHI or supine AHI changes. Both groups showed significant improvements in subjective sleep quality on the PSQI and in skeletal measurements of jaw position (SNB, ANB, and Wits angles), confirming that the orthodontic treatment successfully repositioned the jaw. Minimum oxygen saturation did not change significantly in either group. The study suggests functional orthodontic treatment may offer adjunctive benefit for OSA, though sample size was small and follow-up was modest at 8 months.

The absolute reductions in AHI and ODI observed with the Herbst appliance—roughly 1–2 events per hour—are clinically modest; a typical OSA patient might start with an AHI of 15–30 and would still retain significant apnea burden after treatment. Supine AHI showed the largest effect (3.29-event reduction), suggesting the appliance works partly by changing sleep position or airway mechanics in supine posture. Both appliances produced similar improvements in subjective PSQI scores and jaw positioning, hinting that the mechanical benefit of moving the jaw forward may matter more than the appliance type for quality of life, even if objective respiratory events favored Herbst. The study was limited by small sample size, lack of a control (untreated) arm, relatively short 8-month follow-up, and polygraphy (less sensitive than polysomnography). Subgroup analyses by baseline OSA severity, age, or BMI were not reported, so it remains unclear who benefits most.