Aim: The treatment of patients with mixed dentition, with inferior moderate dental crowding (the so-called borderline cases, between extraction and expansion) is not yet clear. Two examples of widely used appliances for increasing lower dental arch dimensions are the Schwarz's appliance and lip bumper. The aim of this prospective study was to compare dental crowding and arch dimensions from pre- to post-treatment with lip bumper versus Schwarz's appliance. Subjects and Methods: Pre- and post-treatment orthodontic records of twenty subjects (10 males and 10 females) were analyzed in the present study. Inclusion criteria were: first/second molar class malocclusion; crowding of the mandibular arch, from mild to moderate (4-6 mm); mixed dentition; age ≤ 9 years at the beginning of the treatment; stage CS1 or CS2 of maturation of the cervical vertebrae analysis (CVM) at the beginning of the treatment. Ten subjects were treated with a lip bumper, and ten with the removable Schwarz appliance. The primary outcomes were the variations in dental crowding and arch dimensions from pre- to post-treatment. Results: Both the two appliances caused a statistically significant mean improvement/reduction in crowding, of 3.5 mm and 2.9 mm, for the Schwarz appliance and lip bumper, respectively. The Schwarz appliance resulted more effective in increasing arch dimension at the intercanine level, and arch perimeter, while the lip bumper achieves a higher increase in arch length. Conclusions: A lip bumper and Schwarz appliance are both useful in reducing crowding in mixed dentition. This improvement is due to the increase in dental arch dimensions, although the distribution of space resulted slightly differently between the two appliances.
Keywords: corrective orthodontics; dental arch; interceptive orthodontics; mandible; mixed dentitions; preventive orthodontics.