Effect of Sodium Fluoride Mouthwash on the Frictional Resistance of Orthodontic Wires.

OBJECTIVES: The friction between the brackets and orthodontic wire during sliding mechanics inflicts difficulties such as decreasing the applied force and tooth movement and also the loss of anchorage. Therefore, many studies have focused on the factors that affect the friction. The purpose of this study was to assess the effect of 0.05% sodium fluoride mouthwash on the friction between orthodontic brackets and wire. MATERIALS AND METHODS: Four types of orthodontic wires including rectangular standard stainless steel (SS), titanium molybdenum alloy (TMA), nickel-titanium (NiTi) and copper-nickel-titanium (Cu-NiTi) were selected. In each group, half of the samples were immersed in 0.05% sodium fluoride mouthwash and the others were immersed in artificial saliva for 10 hours. An elastomeric ligature was used for ligating the wires to brackets. The frictional test was performed in a universal testing machine at the speed of 10 mm/minute. Two-way ANOVA was used for statistical analysis of the friction rate. RESULTS: The friction rate was significantly higher after immersion in 0.05% sodium fluoride mouthwash in comparison with artificial saliva (P=0.00). Cu-NiTi wire showed the highest friction value followed by TMA, NiTi and SS wires. CONCLUSIONS: According to the results of the current study, 0.05% sodium fluoride mouthwash increased the frictional characteristics of all the evaluated orthodontic wires.

Optimization of unilateral molar rotation correction by a trans-palatal bar: a three-dimensional analysis using the finite element method.

OBJECTIVE: The main goal of this study was to optimize unilateral molar rotation correction by modifying a trans-palatal arch (TPA) design using the finite element method. DESIGN: Three-dimensional analysis of different TPA designs was carried out using the finite element method. SETTING: Department of Orthodontics, Tehran University of Medical Sciences, Iran. MATERIAL AND METHODS: For this investigation, 13 three-dimensional finite element models were produced for different TPA designs without pre-activation bends. Each model contained a palatal bar and two tubes. Optimizing unilateral molar rotations was achieved by five separate different paths: incorporating U-loop(s), 'R' loop(s) or helix/helices, a reverse action of the helix/helices and adding a straight wire to the design. The mesial part of the left side tube was displaced 0·1, 0·25, 0·5 and 1 mm, successively towards the midline, simulating palatal bar tab engagement in a mesio-palatal rotated maxillary left molar. The mesio-distal force, moment and energy produced in the normal side (right) molar were recorded for each of the models. RESULTS: Findings showed that in all designs, the associated mesializing force was lower than that seen in the traditional design and the moment showed an increasing pattern when compared with a simple palatal bar. Regarding energy levels, the same increasing pattern was observed in the designs between activations of 0·1 and 1·0 mm. CONCLUSION: According to our optimized system, the TPA design with the highest energy and moment, but the lowest mesializing force associated with derotating a maxillary molar tooth was a parallel wire II design (i.e. adding a straight wire).

The effect of celecoxib on orthodontic tooth movement and root resorption in rat.

OBJECTIVE: Inhibition of prostaglandin (PGs) production leads to decrease in orthodontic tooth movement (OTM). It is not known whether inhibition of cyclooxygenase-1 (COX-1) or cyclooxygenase-2 (COX-2) is the key mechanism for this effect. In this study, the effect of celecoxib, a highly-selective COX-2 inhibitor, was investigated on OTM in rats. MATERIALS AND METHODS: Four groups of male rats (seven animals in each goup) were used in the study. A 5mm-long nickel-titanium closed-coil spring was ligated between the right maxillary incisor and the first molar of each rat to deliver an initial force of 60g. All four groups recieved orthodontic appliances, group 1 received no injections, group 2 received celecoxib injections (0.3 mg in 0.1 ml saline solution), group 3 recieved normal saline injections (0.1 ml saline solution), and group 4 recieved needle penetration without injecting any solution. The local injections were carried out every 3 days for 18 days. All injections were subperiosteal and given in the upper right first molar mucosa. The animals were sacrificed 21 days after appliance insertion and OTM was measured. RESULTS: In the animals treated with celecoxib a statistically significant decrease in OTM was observed compared with the other groups. Histological findings revealed that osteoclast count was significantly lower in group 2 compared with the other groups (P<0.05). The amount of root resorption showed a slight, but nonsignificant decrease in group 3. CONCLUSION: This study suggests that celecoxib decreases OTM and osteoclast count. This might be the result of COX-2 enzyme inhibition and subsequent decrease in prostaglandin production.

Correlation between dental arch width and sagittal dento-skeletal morphology in untreated adults.

OBJECTIVE: Dental arch form is one of the most important characteristics of dentition. However, this dimension usually receives less attention in diagnosis or treatment planning and orthodontic patients are traditionally classified with regard to their sagittal characteristics. The objectives of this study were to investigate if a relationship exists between the dental arch width (transverse dimension) and sagittal skeletal and dental parameters in orthodontic patients. MATERIALS AND METHODS: Dental casts and lateral cephalograms of 108 consecutive untreated Iranian patients (47 males and 61 females) between 16 and 31 years of age were evaluated. Arch width (AW) parameters including upper and lower inter-molar width (UIMW and LIMW) and upper and lower inter-canine width (UICW and LICW) were measured by a digital caliper. Sagittal parameters included SNA and SNB angle and Wits' appraisal obtained from lateral cephalograms in addition to upper and lower arch length (UAL and LAL) obtained from dental casts. The correlation between the aforementioned parameters was evaluated applying Pearson correlation coefficients. Molar and canine relationship according to Angle's classification was also recorded and the means of all parameters were compared between three occlusal relationship classes and two gender groups by means of two-way ANOVA. RESULTS: According to statistical analysis a significant positive correlation between sagittal parameters and arch width measures exists between SNA and UICW and between LICW and LAL. Upper and lower ICW were significantly correlated, the relationship between upper and lower IMW and between UAL and LAL were significant. Among sagittal measures, both UAL and LAL were correlated with the ANB angle. The means of arch width parameters in three occlusal classes were not significantly different. CONCLUSION: The only significant correlation between arch width and sagittal parameters existed between UICW and SNA angle and between LICW and LAL. No significant difference of the arch width parameter was observed between the three occlusal classes.