A new orthodontic force simulation system with a simulated periodontal ligament to measure the delivered force at the root apex.

OBJECTIVE: To develop a new orthodontic force simulation system with a simulated periodontal ligament (PDL) that enables measurement of the delivered force at the root apex and to clarify the relationship between the applied orthodontic force and the delivered force at the root apex. DESIGN: In vitro study. SETTING: Orthodontics department of a university, Tokyo, Japan. METHODS: A new orthodontic force simulation system that enables measurement of the force at the root apex of the maxillary central incisor, was developed. Lingual and intrusion movements were simulated with applied orthodontic force at three levels: 50, 100 and 200 gf. The delivered forces at the root apex were compared between the two movements. Furthermore, the ratio of delivered force at the root apex to the applied orthodontic force (the apex force ratio) was calculated. RESULTS: The magnitudes of delivered forces at the root apex were significantly greater in intrusion movement than in lingual movement (P < 0.01). The apex force ratios were in the range of 47.3%-56.2% for lingual movement and 85.6%-86.2% for intrusion movement. CONCLUSION: The present study, of a newly developed orthodontic force simulation system, showed that the characteristics of the delivered force at the root apex differed according to the direction of tooth movement.

Impact of the prefabricated forms of NiTi archwires on orthodontic forces delivered to the mandibular dental arch.

BACKGROUND: Although preformed archwires with a variety of arch forms are currently commercially available, the effects of variation in the shape of these archwires on the orthodontic force at each tooth are not well understood. Therefore, we evaluated the forces delivered by various types of commercially available preformed nickel-titanium alloy (NiTi) archwires in a simulated mandibular dental arch. METHODS: Sixty-three types of 0.019 × 0.025-inch preformed NiTi archwires from 15 manufactures were selected for analysis. The intercanine width (ICW) and intermolar width (IMW) of each archwire were measured at the mean canine and first molar depths of 30 untreated subjects with normal occlusions. Each archwire was placed in a multi-sensor measurement system simulating the mandibular dental arch of subjects with normal occlusions, and orthodontic forces in the facial-lingual direction at the central incisors, canines, and first molars were measured. Correlations between the ICW, IMW, and ICW/IMW ratio of archwires and the delivered forces were analyzed. The archwires were classified into the following four groups according to the ICW and IMW: Control group, ICW and IMW are within the means ± standard deviations of the normal ranges; Ovoid group, narrow ICW and IMW; Tapered group, narrow ICW; and Square group, narrow IMW. The forces were compared among these groups for each tooth. RESULTS: Significant correlations between the measured archwire width and force to each tooth were found, except between IMW and forces at the central incisors and canines. Significant differences in the forces were found among all groups, except between the Ovoid and Tapered groups at all teeth and between the Ovoid/Tapered and Control groups at the first molar. Significantly greater orthodontic forces in the facial direction were delivered at the central incisors by the archwires in the Ovoid and Tapered groups when compared with the archwires in the other groups. CONCLUSION: These findings suggest that there is a possible risk of a clinically significant level of unfavorable orthodontic force being delivered to the mandibular incisors in labial inclination when using a preformed archwire with an ICW that is narrower than the dental arch.

Impact of passive self-ligation and conventional elastic ligation on orthodontic force in the simulation of a mandibular lateral incisor linguoversion.

INTRODUCTION: This study compared three-dimensional forces delivered to the displaced tooth and its adjacent teeth between passive self-ligation (PSL) and conventional elastic ligation (CL) in simulation of mandibular lateral incisor linguoversions. METHODS: A multisensor system was used to measure three-dimensional forces delivered to brackets attached to the mandibular left central incisor, lateral incisor, and canine (FDI tooth numbers 31, 32, and 33, respectively). Two ligation methods (PSL and CL), 3 nickel-titanium (0.014-inch) archwires similar to the arch form of normal occlusion, and 2 displacements (1 and 4 mm) were tested. RESULTS: In 1-mm displacement, forces were significantly smaller in CL than in PSL at 32 in the labial direction and larger at 31 in the mesial direction for all 3 types of archwires (P <0.01 for both). For 2 of 3 archwires, forces were larger in CL than in PSL at 33 in the lingual direction (P <0.01). In 4-mm displacement, forces were significantly larger in CL than in PSL at 31 in the mesial direction and significantly smaller in CL than in PSL at 33 in the distal direction for all 3 archwires (P <0.05 and P <0.01, respectively). Mean forces in the vertical direction were small, ranging from -0.05 to 0.05 N. CONCLUSIONS: Under a small amount of displacement, force magnitude in PSL was smaller than that in CL at the displaced tooth in labial-lingual directions. Under a large amount of displacement, a more "open coil spring effect" was significantly obtained in CL than PSL at both adjacent teeth of the displaced tooth.

Influences of archwire size and ligation method on the force magnitude delivered by nickel-titanium alloy archwires in a simulation of mandibular right lateral incisor linguoversion.

The present study investigated the influence of archwire size and ligation method on the force magnitude delivered by nickel-titanium alloy archwires to 4 incisor brackets (42, 41, 31, and 32) in a simulation of mandibular right lateral incisor linguoversion. The force delivered by 0.014 and 0.016 inch nickel-titanium alloy archwires was measured using a newly developed multi-sensor measuring system and the mean force magnitudes were compared between different archwire sizes when using conventional ligation (CL) with elastic modules or self-ligating (SL) brackets by three-way ANOVA and post-hoc Bonferroni's tests. The mean force magnitudes for the brackets were significantly decreased in the order of 42, 41, 31, and 32 (p<0.01). The force magnitude was significantly larger in CL than SL at 42, 31, and 32 (p<0.05). In conclusion, the ligation method affected the force magnitude at 4 incisor brackets. Despite the ligation method, archwire size affected the force magnitude from 42 to 31.