Endotoxin affinity for orthodontic brackets.

Endotoxin, cell envelope lipopolysaccharide produced by gram-negative bacteria can activate an immune response through a variety of pathways. In addition, it can stimulate bone resorption and reduce the periodontal tissue's healing capacity. Previous studies have documented the affinity of lipopolysaccharide for restorative materials. This study evaluated the affinity of lipopolysaccharide for commercially available orthodontic brackets. Stainless steel, ceramic, plastic, and "gold" brackets were exposed to 10 EU/mm2radiolabeled Porphyromonas gingivalis or Escherichia coli lipolpoysaccharide in water and incubated for 24 hours at 37 degrees C. Brackets were then transferred to fresh lipopolysaccharide-free water and incubated for 24 hours at 37 degrees C to evaluate elution. This elution transfer was continued up to 96 hours total incubation. Lipopolysaccharide adherence and elution levels were calculated after treatment, and elution solutions were evaluated through liquid scintillation spectrometry. Mean initial lipopolysaccharide adherence ranged from 2.42 +/- 0.26 EU/mm2(E. coli, plastic) to 6.75 +/- 0.34 EU/mm2 (P. gingivalis, stainless steel). P. gingivalis lipopolysaccharide adherence was significantly greater than E. coli lipopolysaccharide adherence for all bracket types. Moreover, for each lipopolysaccharide type, stainless steel brackets exhibited significantly greater lipopolysaccharide adherence. Regarding elution, only the P. gingivalis lipopolysaccharide-exposed ceramic and plastic brackets at 24 hours and the stainless steel and ceramic brackets at 48 hours eluted measurable lipopolysaccharide. Results from this study demonstrate that P. gingivalis and E. coli LPS exhibit a high affinity for orthodontic brackets. In vivo, this affinity could affect the concentration of LPS in the gingival sulcus, thereby contributing to inflammation in tissues adjacent to the brackets.

A comparison of the effects of first premolar extractions on third molar angulation.

The effect of third molars on the stability of orthodontic treatment has been studied extensively. Yet the effect of orthodontic treatment, particularly premolar extractions, on third molars has not been substantially studied. The purpose of this investigation was to compare the changes in third molar angulation in patients treated with and without extractions. Records of 45 Class I, nonextraction and 33 Class I, first premolar extraction patients were examined. The pretreatment and posttreatment pantographs were digitized, and the angles between the third molar long axes and the occlusal plane were measured. Changes in third molar angulation from pretreatment to posttreatment for the two groups were compared for statistical differences using a Student's t-test. Statistical analysis revealed there were no significant differences in the change in third molar angulation in either group. On average, the maxillary and mandibular third molars showed an improvement in angulation relative to the occlusal plane. The results suggest that factors other than first premolar extractions may influence third molar angulation.