Time efficiency of self-ligating vs conventional brackets in orthodontics: effect of appliances and ligating systems.

OBJECTIVES: The aim of the present study was to compare the speed of archwire change between self-ligating (SL) brackets and conventional brackets with elastic and stainless steel (SS) ligatures. MATERIAL AND METHODS: Fifty orthodontic patients, divided into five groups according to the type of fixed appliance and ligating system used (10 subjects=Time 2 SL brackets; 10 subjects = SmartClip SL brackets; 10 subjects = In-Ovation SL brackets; 10 subjects = conventional brackets with SS ligatures, 10 subjects = conventional brackets with elastic ligatures) were included in the study. The clinical phases were carried out by a unique operator experienced in both conventional and SL brackets techniques. Aligning and levelling were completed for each subject. The time needed to remove and ligate .019 x .025 SS archwires in both dental arches was measured for the 5 groups of patients. Independent sample t-test and ANOVA analyses were used. RESULTS: SL brackets had a significantly shorter mean archwire ligation and removal times when compared with conventional brackets with elastic and SS ligatures. The ligation time in the lower arch was affected by the type of SL appliance used. Systems with elastic ligatures had a shorter mean archwire ligation time than systems with SS ligatures. No differences were found between maxillary and mandibular arches in wire ligation and removal times. CONCLUSIONS: The type of bracket has influence on chairside time. SL systems showed a quicker and more efficient wire removal and placement for late orthodontic treatment phases.

Masseter thickness, endurance and exercise-induced pain in subjects with different vertical craniofacial morphology.

The aim of the study was to compare neuromuscular features of the masseter muscle in subjects with different vertical craniofacial morphology. Fifteen short-faced (mandibular plane-Frankfurt plane angle < 15 degrees) and 15 normal- to long-faced (mandibular plane-Frankfurt plane angle > or = 23 degrees) male students participated. The thickness of the masseter was assessed by ultrasonography. Onset and endurance of exercise pain were recorded during sustained biting at a level of 15% of maximum voluntary contraction and 30 micro V electromyographic activity. Pain and fatigue was measured on visual analog scales before and after the biting, as well as before and after 10 min chewing. Statistical comparison showed that the masseter muscle was significantly thicker (+15%) in the short-faced than the normal- to long-faced subjects. The pain onset time and endurance time were also consistently shorter in short-faced subjects, whereas the intensity of pain and fatigue did not differ significantly between the two groups. Multiple stepwise regression showed positive influence from the mandibular plane inclination and the masseter thickness on the pain onset time and endurance time. The present findings support the concept that subjects with different craniofacial morphology show neuromuscular differences.