Objective: To investigate the age- and gender-related changes in upper and lower incisors' position and inclination in different vertical craniofacial relationships. Materials and Methods: A retrospective study on patients' records of age 8-48 years. The sample was divided based on Frankfort mandibular plane angle into three groups; normal, high, and low angle groups. It was then subdivided according to age. Upper and lower incisors' inclinations and positions were assessed from lateral cephalometric radiographs. Gender and age associations and effects size were calculated using two-way ANOVA tests. Significance level was set at P < 0.05. Results: Four hundred and twenty records (F = 272, M = 148) were included; 115 had normal, 81 low, and 250 had high vertical relationships with no significant age and gender distribution differences (P > 0.05). All significant associations and effects were found in the low angle group only. A significant association was found between gender and upper incisor inclination (P < 0.05) with medium effect size (0.13 ≤ ηp ² < 0.26). An association is also found between age × gender interaction and upper incisor inclination and lower incisor position (P < 0.05) with large effect size (0.26 ≤ ηp ² ). Conclusion: Age- and gender-related upper and lower incisor changes were found to be significant in subjects with decreased vertical skeletal pattern only. The upper incisor inclination and the lower incisor position were the most affected variables with age and gender.

Objective: To investigate the influence of silver (Ag), zinc oxide (ZnO), and titanium dioxide (TiO ₂ ) nanoparticles on shear bond strength (SBS). Materials and Methods: One hundred and twenty extracted premolars divided into four groups with thirty specimens in each group. Group 1 (control): brackets (American Orthodontics) were bonded with Transbond XT primer. Groups 2, 3, and 4: brackets (American Orthodontics) were bonded with adhesives incorporated with Ag, ZnO, and TiO ₂ nanoparticles in the concentration of 1.0% nanoparticles of Ag, 1.0% TiO ₂ , and 1.0% ZnO weight/weight, respectively. An "Instron" universal testing machine AGS-10k NG (SHIMADZU) was used to measure the SBS. The data were analyzed by SPSS software and then, the normal distribution of the data was confirmed by Kolmogorov-Smirnov test. One-way ANOVA test and Tukey's multiple post hoc procedures were used to compare between groups. In all statistical tests, the significance level was set at 5% (P < 0.05). Results: A significant difference was observed between control (mean [standard deviation (SD)] 9.43 [3.03], confidence interval [CI]: 8.30-10.56), Ag (mean [SD]: 7.55 [1.29], CI: 7.07-8.03), ZnO (mean [SD]: 6.50 [1.15], CI: 6.07-6.93), and TiO ₂ (mean [SD]: 6.33 [1.51], CI: 5.77-0.89) with SBS (F = 16.8453, P < 0.05) at 5% level of significance. Conclusion: Incorporation of various nanoparticles into adhesive materials in minimal amounts may decrease SBS and may lead to the failure of bracket or adhesive. The limitation of this study is that it is an in vitro research and these results may not be comparable to what the expected bond strengths observed in vivo. Further clinical studies are needed to evaluate biological effects of adding such amounts of nanoparticles and approve such adhesives as clinically sustainable.

Objectives: The aim of this study was to investigate the effects exerted by the acidulated fluoride gel on stainless steel and nickel-titanium (Ni-Ti) orthodontic wires. Materials and Methods: Sixty stainless steel and Ni-Ti orthodontic archwires were distributed into forty archwires used for in vitro study and twenty for in situ study. Fluoride was applied for 1 h in the in vitro experiment while it was applied for 5 min in the in situ experiment. The friction resistance of all wires with ceramic brackets before/after topical fluoride application was measured using a universal testing machine at 1 min intervals of moving wire. Moreover, surface properties of the tested wires before/after fluoride application and before/after friction test were examined by a scanning electron microscope (SEM). Dunnett's t-test was used to compare frictional resistance of as-received stainless steel wires and Ni-Ti wires to the wires treated by fluoride in vitro and in situ (P < 0.05). Two-way ANOVA was used to compare the effect of fluoride application and type of wire on friction resistance in vitro and in situ (P < 0.05). Results: Ni-Ti wires recorded significantly high friction resistance after fluoride application when compared to stainless steel wires in vitro, P < 0.05. Fluoride application did not significantly affect the friction resistance of the tested wires in situ, P < 0.05. SEM observation revealed deterioration of the surface texture of the Ni-Ti wires after fluoride application in vitro and in situ. Conclusions: The in vitro fluoride application caused an increase in friction resistance of Ni-Ti wires when compared to stainless steel wires. In vitro and in situ fluoride application caused deterioration in surface properties of Ni-Ti wires.

Aims: This study is conducted to determine the amount of distortion of digital panoramic radiographs. Materials and Methods: Panoramic radiographs of all patients who received dental implants in the years 2012 and 2013 were selected from the records at the faculty of dentistry, King Abdulaziz University. Radiographs were analyzed using the R4 Kodak Software for linear measurements of implants length and width. The measurements were compared to the actual size of the implant, and the amount of distortion was calculated. Results: A total of 169 implants were analyzed. Horizontally, there was a statistically significant increase of 0.4 mm in width in the radiographic measurement compared to the actual size in the incisor region. Vertically, the sample overall exhibited a decrease by 0.4 mm compared to the actual size. Incisors had the highest difference with a decrease of 1.7 mm in the radiographic measurements compared to actual size. The highest distortion was found in the incisor region for both diameter and length (1.1 and 0.86), respectively. Conclusion: Digital panoramic radiographs show minimal to no distortion. The highest distortion is found in the anterior area.

Introduction: Archwires act as gears to move teeth with light, continuous forces. However, the intraoral use of orthodontic archwires is liable to surface deposits which alter the mechanical properties of archwires, causing an increase in the friction coefficient. Objectives: To evaluate the surface changes of the stainless steel archwires after 6 weeks of intraoral use and its influence on frictional resistance during sliding mechanics. Materials and Methods: As-received rectangular 0.019" × 0.025" stainless steel orthodontic archwires (control) were compared with the archwires retrieved after the final phase of leveling and alignment stage of orthodontic treatment collected after 6 weeks of intraoral exposure (test samples) from 10 patients undergoing treatment. The control and test samples were used to evaluate surface debris using Scanning Electron Microscopy, surface roughness was assessed using Atomic Force Microscope and frictional forces were measured using Instron Universal Testing Machine in the buccal inter-bracket region that slides through the molar tube for space closure. Unpaired t-test and Pearson correlation tests were used for statistical analysis (P < 0.05 level of significance). Results: Significant increase was observed in the level of debris (P = 0.0001), surface roughness (P = 0.0001), and friction resistance (P = 0.001) of orthodontic archwires after their intraoral exposure. Significant positive correlations (P < 0.05) were also observed between these three variables. Conclusion: Stainless steel test archwires showed a significant increase in the degree of debris and surface roughness, increasing the frictional forces between the archwire-bracket interfaces which would considerably reduce the normal orthodontic forces. Thus, continuing the same archwire after levelling and alignment for space closure is not recommended.