Assessment of the influence of metal ions released from the fixed orthodontic appliances on the static friction and surface topography of stainless steel and I archwires: An in-vitro study.

BACKGROUND: Static friction force between the orthodontic brackets and wire impacts the sliding mechanics that affect teeth movements and treatment duration. This sliding media is jam-packed with released metal ions from the fixed appliances. This study aimed to assess the static frictional force and surface topography of stainless steel (SS) and I archwires in dry conditions and in media fully with metal ions that were released from fixed appliances. METHODS: In this research study, a set of 60 as-received straight archwires specimens (5 cm wire) were employed and categorized into two groups based on the material type [30 super elastics new I archwires gauge (0.018 × 0.014 inch) and 30 SS archwires 0.018 × 0.022" as a control]. The archwires' static friction force was measured while sliding a loaded Roth SS brackets (0.018") on the archwire using a universal tensile testing machine in dry and metal ions released media, while the surface topography was assessed using a noncontact AFM machine. RESULTS: The static friction of I archwire was significantly lower than the SS wire in dry condition. Metal ions media released from fixed appliances significantly reduced the Static friction compared to dry and wet conditions with deionized water for both wires. An Atomic Force Microscope machine surface roughness reports revealed that the highest mean of all three roughness parameters was found in the SS group, followed by I archwires in descending order. Additionally, metal ions media significantly reduce all roughness parameters.

Effects of fluoridated tooth paste on medically erosive enamel in bonded primary teeth during maxillary arch expansion in cleft palate patient: An in vitro study.

AIMS: This study searched the effects of fluoridated toothpaste on the enamel surface of deciduous molars eroded by different pediatric liquid medicaments which were encircled by orthodontic bands by gravimetric analysis method. MATERIALS AND METHODS: A suitable orthodontic band was used to band each of the 110 non-carious exfoliated deciduous molars, and stored in artificial saliva. These teeth were divided randomly into fluoridated and non-fluoridated groups (50 teeth each), and 10 teeth were used as negative controls. The enamel surface of the fluoridated group was swabbed with fluoridated toothpaste for 5 minutes twice daily. Each group was subdivided into five clusters of 10 teeth each according to the type of medication used which included paracetamol, Adol, amoxicillin, Medazole (ME), and Viton (VI) according to a specific immersion cycle. The erosion induced in the enamel for all the teeth was evaluated by gravimetric analysis for different intervals. RESULTS: The results showed that the weight loss increased with increasing exposure to liquid medication for all groups, but this increase was smaller in the fluoridated group. The highest mean weight loss after 28 days was in VI, and the lowest was in ME (0.145 [0.005] mg; 0.08 [0.008] mg), respectively. CONCLUSION: The fluoridated toothpaste significantly reduced medically eroded enamel by oral medical syrups. The gravimetric method is valid for the detection of erosion on banded deciduous molars.

Does the flatting of the curve of spee affect the chewing force distribution in the mandible? (3D finite element study).

OBJECTIVE: To search the effects of Curve of Spee (COS) flatting on the stresses and displacement on the different mandible landmarks and lower teeth during posterior teeth loading using three-dimensional (3D) finite element analysis. MATERIALS AND METHODS: Three-dimensional hemi mandibular model was created from real selected mandible. The lower teeth was aligned originally in a curved form with 2.4 mm depth at the cusp tip of the second premolar. Another replica with flat aligned teeth was formed to confirm the analysis by up righting premolars and molars. A load was applied at mesio-buccal cusp of the lower first molar on both models, and the resultant stresses and displacements on the mandibular landmarks and the lower teeth were tested. RESULTS: Von mises over the mandible was higher in flat than in curve model. The highest stress levels were detected at the Mesio-buccal cusp tip of first molar for flat and curved simulation (5053, 3304) Mpa respectively. Mesio-distally, the teeth displacement was higher in curve model than in flat one. The maximum distal displacement, in flat model, was seen in central and lateral incisors. While, in curve model, the maximum distal displacement was grasped within first and second premolars. CONCLUSIONS: Flatting the COS magnify the stresses over whole mandible and reduce lower teeth displacement mesio-distally. We speculated that the readjustment of the COS after orthodontic treatment could reduce the stress and displacements on the lower anterior teeth and decrease the lower anterior teeth crowding relapse.

The anterior component of occlusal force revisited: direct measurement and theoretical considerations.

BACKGROUND: The anterior component of occlusal force (ACF), considered to result from the mesial inclination of teeth relative to the occlusal plane, has been estimated by indirectly measuring contact point tightness (CPT) through interproximal insertion of metal strips. ACF has been observed concurrently with a posterior component, whose theoretical origin is difficult to explain. OBJECTIVES: Evaluate ACF by measuring CPT directly, and integrate current data to propose a theoretical basis for ACF. MATERIALS AND METHODS: The sample comprised 14 females (age: 22.3±2.8) and 16 males (age: 20.8±2.5). Our device consisted of two force sensors: one for measuring maximum bite force (MBF) (overall thickness: 4mm), and one for measuring CPT directly (0.2mm thick), inserted between the lower first molar and second premolar. ACF was computed as the difference in CPT between the biting (at 75 per cent of MBF) and non-biting conditions. RESULTS: Averages of MBF, CPT, and ACF were 666.67 [standard deviation (SD): 36.06], 6.74 (SD: 1.17), and 20.59 (SD: 4.60) N, respectively. ACF, CPT, and MBF were higher in males by approximately 28, 18 and 7 per cent, respectively. A positive correlation was observed between ACF and MBF (R (2): 0.64). CPT was also significantly correlated to MBF (R (2): 0.40). Biomechanical analysis indicates that previously offered explanations do not unriddle the concurrent increase of CPT at anterior and posterior contact points. CONCLUSIONS: ACF was related to bite force by a logarithmic model. We speculate that CPT increases during biting through a combination of mesial tipping of teeth and mandibular bending.