FORCES PRODUCED BY LIP BUMPERS ON MANDIBULAR MOLARS

The purpose of this study was to measure the forces produced by a lip bumper on the mandibular permanent first molars. The forces in a sampl e of 38 patients were measured bilaterally with specially designed gau ges at rest but with their lips lightly touching, speaking the words c hurch, phone, and pop, and swallowing water. Forces were compared betw een two types of lip bumpers, i.e., wire or shield, and between Variou s anteroposterior and vertical positions of the lip bumper. The restin g forces produced by the wire lip bumper 2 mm anterior to the incisors and vertically positioned at the middle of the incisor crown were 5.9 3 +/- 4.84 gm for the left side and 4.66 +/- 4.8 gm for the right. The forces were found to be significantly higher when the wire lip bumper was placed 4 mm anterior to the incisors and at a more gingival posit ion, measuring 16.68 +/- 8.7 gm for the left side and 13.88 +/- 8.28 g m for the right. The shield lip bumper had higher forces both at the c enter of the incisor as well as when it was positioned gingivally. A l arge individual variation was observed. There were no statistically si gnificant differences in force levels between male and female subjects . Speaking the words church, pop, and phone, produced forces between 1 1 and 23 gm, using a wire lip bumper. Swallowing produced the highest forces, between 32 and 36 gm. Lip thickness and height did not appear to affect the force levels.