Magda Trinajstic Zrinski

Machine-driven Versus Manual Insertion Mode: Influence on Primary Stability of Orthodontic Mini-implants

Purpose:The study aimed to explore the effect of the insertion method on maximal insertion torque as a measure of primary stability while controlling for the effect of cortical bone thickness, mini-implant length and diameter, and vertical insertion force on insertion torque. Methods:Six types of mini-implants (Dual Top; Jeil Medical, Corp.) with diameters of 1.4, 1.6, and 2.0 mm and lengths of 6 and 8 mm were inserted manually and in a machine-driven mode into pig rib bone samples, and experiments were repeated 10 times, which totaled 120 tested implants in 120 pig rib samples. Cortical bone thickness was measured with a sliding caliper, whereas insertion torque and vertical insertion forces were recorded with a specially designed device. Results:Significant predictors of better primary stability are thicker cortical bone (explaining 24.2% of variability), wider diameter (20.6%), manual insertion (9.9%), greater length (3.7%), higher maximal vertical insertion force (2.2%), and lower vertical force at maximal insertion torque (1.4%). Conclusions:Manual insertion is associated with higher primary stability of orthodontic mini-implants than mechanical insertion, but thicker cortical bone and larger implant diameter seem to be stronger predictors of primary stability.

Mediation and moderation effect of the big five personality traits on the relationship between self-perceived malocclusion and psychosocial impact of dental esthetics

OBJECTIVE To explore the mediation and moderation effects of personality traits on the relationship between self-perceived malocclusion and the psychosocial impact of dental esthetics. MATERIALS AND METHODS The sample included 252 subjects (62% female) aged 12-39 years. Self-perceived malocclusion was estimated using the 10-point scale Aesthetic Component of the Index of Orthodontic Treatment Need. The Psychosocial Impact of Dental Aesthetics Questionnaire was used to assess the psychological impact and the Big Five Inventory for personality traits. Moderation and mediation effects were evaluated with Pearson correlations and stepwise regression analysis, respectively. RESULTS Self-perceived malocclusion ranged from 1 to 8 and was the most significant predictor of psychosocial impact of dental esthetics, whose unique contribution accounted for 11%-36.4% of variability, while age and sex accounted for 1.2%-2.5%. Personality traits had no mediating effect on this relationship. The moderating effect of agreeableness was present in the relationship between self-perceived degree of malocclusion and Social Impact (SI), Psychological Impact (PI), and Aesthetic Concern (AC) (ΔR2  =  0.035, 0.020, and 0.013, respectively; P < .001), while conscientiousness affected the relationship between perception of malocclusion and SI and PI (ΔR2  =  0.018 and 0.016, respectively; P < .05). In people with lower agreeableness and conscientiousness, increasing the severity of self-perceived malocclusion leads to less increase in SI and PI. In people with lower agreeableness, the increase influences AC in a similar manner. Extraversion, neuroticism, and openness do not have a moderating effect. CONCLUSIONS The relationship between self-perceived malocclusion and the psychosocial impact of dental esthetics appears to be moderated and not mediated by personality traits. Adolescents and young adults with lower agreeableness and conscientiousness seem to be less affected by the increased severity of self-perceived malocclusion, as demonstrated in reporting some psychosocial impacts.

Influence of Manual Screwdriver Design in Combination With and Without Predrilling on Insertion Torque of Orthodontic Mini-Implants

Purpose: The study focused on the influence of screwdriver design in combination with and without predrilling a pilot hole of inner implant diameter on insertion torque of orthodontic mini-implants, controlling for cortical thickness and vertical insertion force as cofactors. Methods: One hundred twenty mini-implants (Forestadent) of 1.7 mm in diameter and 6 and 8 mm in length were manually inserted into 120 swine rib bone samples. Maximal insertion torque as a measure of primary stability and vertical force were measured. The study included procedures with and without pilot hole and different screwdriver handles and shaft length and 2 implant lengths. Results: Design of manual screwdriver does not modify insertion torque to a significant extent. In multiple linear regression model, significant predictors of insertion torque are thicker cortical bone (explaining 16.6% of variability), higher vertical force at maximal torque (13.5%), 6-mm implant length (2.5%), and the presence of pilot hole (2.3%). Conclusions: Handle type and shaft length of manual screwdriver do not significantly influence insertion torque, whereas predrilling a pilot hole has low impact on torque values of manually inserted self-drilling orthodontic mini-implants.

Changes of bite force and occlusal contacts in the retention phase of orthodontic treatment: A controlled clinical trial

Introduction: We aimed to determine whether appliance type affects changes in maximum voluntary bite force (MVBF) and the number of occlusal contacts (NOC) during retention, controlling for sex, age, and body mass index. Methods: The sample comprised 176 examinees (70 male, 106 female) aged 14 to 20 years: 30 had maxillary and mandibular Essix retainers, 30 had wrap‐around retainers, and 30 had a combination of fixed mandibular canine‐to‐canine retainers bonded on each tooth separately (double twisted, 0.254 mm in diameter, stainless steel ligature wire) and Essix retainer in the maxillary arch; 86 with normal occlusion were not treated. MVBF and the NOC were measured immediately after removal of preadjusted edgewise appliances (Roth prescription), 6 weeks after that, and after the next 4 weeks. Results: Increases in MVBF and the NOC were demonstrated, but subjects with 2 Essix retainers showed lower values than did the others. Changes were related to type of appliance, sex, and age (P <0.05) but not to body mass index. The increase in NOC occurred faster than the increase of MVBF, more and sooner with the wrap‐around retainer and in male subjects than with the Essix and in female subjects. MVBF and NOC nearly reached the values of the control subjects. Conclusions: Settling of the occlusion depends on appliance type: it takes longer in female patients and with Essix in both dental arches than with the other tested appliances. HighlightsMaximum voluntary bite force and number of occlusal contacts increase during the first 10 weeks of retention.Settling occurs sooner with the wrap‐around retainer and in males than with the Essix and in females.Body mass index is not related to changes in maximum voluntary bite force and number of occlusal contacts.