Alok Ranjan; Anil Kumar Biradar; Ankita Patel; Vanessa Varghese; Ankita Pawar; Rohit Kulshrestha
Abstract
Objectives: This studied aimed to measure the yield strength and stress relaxation properties of three commercially available thermoplastic aligner materials.
Methods: The three different thermoplastics aligner materials Duran (Scheu, Iserlohn, Germany), Erkodur (Pfalzgrafenweiler, Erkodent, Germany) ...
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Objectives: This studied aimed to measure the yield strength and stress relaxation properties of three commercially available thermoplastic aligner materials.
Methods: The three different thermoplastics aligner materials Duran (Scheu, Iserlohn, Germany), Erkodur (Pfalzgrafenweiler, Erkodent, Germany) and Track (Forestadent, Germany) were selected. A three-point bending test was carried out via the universal testing machine to measure their yield strength and stress relaxation properties. An independent t-test was performed for intergroup comparison. P-value < 0.05 was set as the level of significance. Results: All the selected three polymers liberate a notable amount of stress during 24 hours. The highest stress release was observed in Duran i.e. 18.96 N/cm2 as compared to Erkodur, which was 13.96 N/cm2 and Track, which was 13.18 N/cm2. The yield strength of Duran was the highest (75.85 Mpa) compared to Track and Erkodur with the yield strength of 52.75 Mpa and 55.86 Mpa, respectively.
Conclusions: Tooth movement is influenced by the composition of aligner material and its thickness. Duran had the highest stress release and yield strength. Stress released by different aligners exceeds around half of the initial stress value, which directly affects the orthodontic force application and subsequent tooth movement.
Giulia Gay; Serena Ravera; Tommaso Castroflorio; Francesco Garino; Giovanni Cugliari; Andrea Deregibus
Abstract
Background: Existing literature indicates that orthodontics patients are more likely to have severe apical root shortening, interesting mostly maxillary, followed by mandibular incisors.
Objectives: The aim of the present study was to investigate the incidence and severity of root resorption (RR) in ...
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Background: Existing literature indicates that orthodontics patients are more likely to have severe apical root shortening, interesting mostly maxillary, followed by mandibular incisors.
Objectives: The aim of the present study was to investigate the incidence and severity of root resorption (RR) in mandibular incisors of adult patients treated with aligners.
Methods: The study group consisted of 71 adult healthy patients (mean age 32.8 ± 12.7) treated with aligners (Invisalign®, Align Technologies, San Jose, CA, USA) for the intrusion of the lower incisors. Root and crown lengths of a total of 279 lower incisors were measured in panoramic radiographs at the beginning (T0) and at the end (T1) of aligner therapy. Individual root-crown-ratio (RCR) of each tooth and therefore the relative changes of RCR (rRCR) were determined. Results: 44% of the 279 measured teeth presented a reduction of the pre-treatment root length. A reduction in percentage of > 0% up to 10% was found in 26.76% (n = 76), a distinct reduction of > 10% up to 20% in 12.32% (n = 35) of the sample. 4.58% (n = 13) of the teeth were affected by a clinically relevant reduction (> 20%).
Conclusions: Orthodontic treatment with Invisalign® aligners could led to RR in cases in which intrusion of the lower incisors is planned. However, the incidence of RR is comparable to data described in case of application of light forces with fixed appliances, and considerably lower than what has been described for traditional comprehensive orthodontic treatments.