The lower lip bumper is a simple habit correction appliance and is usually well tolerated by the young patient. In orthodontics, the applications of lip bumpers were reported for molar anchorage control,4 correction for lower lip habit,5,6 and space gaining for alignment of mild to moderate crowding in lower dentitions.7,8
The patient in this case had protrusive upper anterior teeth, caused by the lower lip trapping between the space of upper and lower anterior teeth that related to the lower lip biting habit. This habit was regarded as the primary etiology of malocclusion, which cause a big overjet with flaring out in upper anterior teeth. In this case, a lower lip bumper appliance was used to eliminate the lower lip biting habit and improve mentalis muscle activity. The correction of biting habit came from the reminder of the labial shield in the appliance.
The lip bumper used in this case was made of stainless-steel wire with a diameter 0.040 inches. It was placed on the lower arch from the right primary second molar to the left primary second molar. The curve of this lip bumper was located in apically to lower gingival margin and 3 mm away from the labial teeth surface. The anterior wire was covered by acrylic shield which functions as to improve the adaptation of lip and cheeks muscles. This appliance had an adjustable loop located in front of primary second molar in each side. The lip bumper appliance was suggested to wear full day for a period from 6 to 18 months, based on the different level of tooth movement and treatment goal.
After lip bumper treatment, the outcome demonstrated upper incisors inclined palatally, lower incisors inclined labially, and the large overjet was corrected because of the elimination of the mentalis muscle forces which altering the equilibrium between cheeks, lips, and tongue.
According to Murphy et al., most of the expansion of lip bumper occurs at the beginning of treatment and then faded with time.13 About 50% of the total expansion occurs in the first 100 days of treatment and 90% of the total expansion was achieved within the first 300 days. In this case, lower lip bumper was used for the initial four months. Once the lower biting habits was eliminated, the second phase of lower fixed 2x4 appliance could be continued. From the model analysis, the irregularity index was decreased largely from 4.15 to 2.82 and total arch length increased from 63.06 mm to 65.14 mm. These results were similar with the reported literatures.9,13
Lip bumper treatment along with fixed appliances is an effective treatment to obtain long-term increases in arch width and decreases in the irregularity index.14 The lip biting habit could be controlled earlier in the mixed dentition, and the dental space was gained for crowding relief by the appliance. Since the patient was still in mixed dentition, further dental development and skeletal growth should be monitored to make sure the long-term stability.