Residents’ journal review

Orthopedic prevention of asymmetry in unilateral temporomandibular joint arthritis

Stoustrup P, Küseler A, Kristensen KD, Herlin T, Pedersen TK. Orthopaedic splint treatment can reduce mandibular asymmetry caused by unilateral temporomandibular involvement in juvenile idiopathic arthritis. Eur J Orthod 2013;35:191-8

Between 20% and 70% of patients with juvenile idiopathic arthritis demonstrate involvement of the temporomandibular joint. Among these, 40% to 50% experience unilateral temporomandibular joint involvement. The purpose of this study was to evaluate the effects of an orthopedic splint in mitigating the effects of unilateral juvenile idiopathic arthritis on mandibular growth and dentoalvelolar development. Twenty-two patients were treated with a distraction splint. This appliance is an acrylic splint that covers the occlusal surfaces of the mandibular teeth; the posterior height on the arthritic side is gradually increased to prevent eruption of the mandibular first molar while allowing eruption of the maxillary first molar. The treatment objectives were to correct the cant of the occlusal plane, gradually unload the joint, and guide the mandible into the normal anterior rotational growth pattern. Condylar height, ramus height, and total mandibular vertical height were measured on panoramic views constructed from cone-beam computed tomography images before and after treatment. A ratio between the affected and unaffected sides was calculated for each variable of interest to measure mandibular asymmetry. The results showed that the distraction splint decreased mandibular asymmetry for ramus height and total vertical mandibular height. Mandibular growth rates on the affected and unaffected sides were comparable in most patients. Although the unaffected side was used as a control, both the possible subsequent juvenile idiopathic arthritis of the normal temporomandibular joint and the effects of appliance therapy on dentoalveolar development on this side make the suitability of this internal control questionable. Because no control group was used, it is difficult to conclude whether or which of the outcomes were due to treatment. Nevertheless, the findings on the possible effects of this splint therapy and future studies with appropriate controls could provide valuable information on the efficacy of splint therapy in the management of this complex disorder.

Reviewed by Mona Bajestan

Nickel-free titanium-niobium material for orthodontic wires

Arciniegas M, Manero JM, Espinar E, Llamas JM, Barrera JM, Gil FJ. New Ni-free superelastic alloy for orthodontic applications. Mater Sci Eng C Mater Biol Appl 2013;33:3325-8

The low magnitude and continuous forces generated by superelastic nickel-titanium wires are optimal for orthodontic tooth movement. However, nickel-containing wires can cause contact dermatitis in patients with a nickel allergy. The authors of this study evaluated the superelasticity, corrosion resistance, and cytotoxicity of Ti19.1Nb8.8Zr, a new nickel-free titanium alloy that might be suitable for orthodontic applications. Phase transition and superelasticity were measured by calorimetry and by subjecting wire specimens to 150 load-unload cycles in artificial saliva at 37°C. Corrosion of the titanium alloy with specific measurements of open circuit potential, corrosion potential, and corrosion current density were compared with 6 commonly used nickel-titanium orthodontic archwires. The cytotoxicity of the titanium alloy was measured by immersing it and the controls in DMEM media at 37°C, followed by culturing of MG63 cells in this media and counting live cells. The results of the calorimetry tests showed reversible austenitic-martensitic phase transformations with martensite start-finish at 45°C to 14.8°C, and austenite start-finish at 46°C to 87°C. Repeated load and unload cycles indicated typical superelastic behavior in the titanium alloy with a mechanical phase transformation plateau from 0.5 to 8 mm of deflection. After 150 cycles, there was approximately 0.2 mm of residual elongation of the wire after deflection. The nickel-free archwire had the best resistance to corrosion among all the wires investigated. The titanium-alloy wires showed favorable cytotoxicity values, with 100% of the cells remaining viable at 72 hours; this was not significantly different relative to the controls. The nickel-free Ti19.1Nb8.8Zr alloy demonstrates superelastic behavior, better corrosion resistance compared with common nickel-titanium wires, and excellent biocompatibility. Since the authors used a 2.5-mm diameter wire, which is substantially larger than those used in orthodontic practices, further investigations are recommended with wire sizes more typically used for orthodontic treatment to derive clinically relevant information.

Reviewed by Adam Donnell

Nickel-free titanium-niobium material for orthodontic wires

Arciniegas M, Manero JM, Espinar E, Llamas JM, Barrera JM, Gil FJ. New Ni-free superelastic alloy for orthodontic applications. Mater Sci Eng C Mater Biol Appl 2013;33:3325-8

The low magnitude and continuous forces generated by superelastic nickel-titanium wires are optimal for orthodontic tooth movement. However, nickel-containing wires can cause contact dermatitis in patients with a nickel allergy. The authors of this study evaluated the superelasticity, corrosion resistance, and cytotoxicity of Ti19.1Nb8.8Zr, a new nickel-free titanium alloy that might be suitable for orthodontic applications. Phase transition and superelasticity were measured by calorimetry and by subjecting wire specimens to 150 load-unload cycles in artificial saliva at 37°C. Corrosion of the titanium alloy with specific measurements of open circuit potential, corrosion potential, and corrosion current density were compared with 6 commonly used nickel-titanium orthodontic archwires. The cytotoxicity of the titanium alloy was measured by immersing it and the controls in DMEM media at 37°C, followed by culturing of MG63 cells in this media and counting live cells. The results of the calorimetry tests showed reversible austenitic-martensitic phase transformations with martensite start-finish at 45°C to 14.8°C, and austenite start-finish at 46°C to 87°C. Repeated load and unload cycles indicated typical superelastic behavior in the titanium alloy with a mechanical phase transformation plateau from 0.5 to 8 mm of deflection. After 150 cycles, there was approximately 0.2 mm of residual elongation of the wire after deflection. The nickel-free archwire had the best resistance to corrosion among all the wires investigated. The titanium-alloy wires showed favorable cytotoxicity values, with 100% of the cells remaining viable at 72 hours; this was not significantly different relative to the controls. The nickel-free Ti19.1Nb8.8Zr alloy demonstrates superelastic behavior, better corrosion resistance compared with common nickel-titanium wires, and excellent biocompatibility. Since the authors used a 2.5-mm diameter wire, which is substantially larger than those used in orthodontic practices, further investigations are recommended with wire sizes more typically used for orthodontic treatment to derive clinically relevant information.

Reviewed by Adam Donnell

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Apr 7, 2017 | Posted by in Orthodontics | Comments Off on Residents’ journal review
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