- Email: [email protected]
Force degradation characteristics of orthodontic colored elastomeric chains—a comparative study
American Journal of Orthodontics and Dentofacial Orthopedics Volume 105, No. 4
the artificial carious lesion. Labiolingual sections of 100 I-tm were immediately obtained from each tooth and photographed with polarized light microscopy in imbibition media of water and Thoulet's (R.I." 1.41, 1.47), resperesenting a minimum of 5%, 10%, and 25% pore volume, respectively. The sections were varnished so that only the external surface of the section remained exposed and were placed into separate closed environments of a nonfluoridated artificial saliva for 3 months. Using a sonic digitizer, the area of the body of the lesion was measured in each imbibition medium, comparing the experimental lesions adjacent to the fluoride releasing resin to the control lesions. Results demonstrated a statis-
tically significant reduction hi the body of the lesion (p < 0.05) for those exposed to the fluoride releashlg reshz.
Force degradation characteristics of orthodontic colored elastomeric chains - a comparative study. J.C. Annello. San Francisco:
University of the Pacific, 1993 The present investigation was designed to compare the force degradation of colored elastomeric chains with those of grey and of clear elastomerie chains. Four manufacturer's products were evaluated. Grey, clear, pink, purple, and green elastomeric chains were obtained from Ormco, Unitek, A-Co., and Rocky Mountain. An acrylic jig with two parallel rows of embedded dowel pins allowed attachment and simultaneous testing of 50 chains. The jig and elastics remained submerged in synthetic saliva, pH 6.75, at 37 ~ C at all times, except when force measurements were taken. Force produced by the stretched elastomeric chains was measured through a calibrated spring-tension gauge. Force measurements were made at time of placement, at 1 hour, 8 hours, 24 hours, 2, 3, 4, 5, 6, 7 days and then weekly to 5 weeks. Two hundred specimens were tested with a total of 2800 force measurements. Starting with a mean force of 377 --- 11 gm there was a 19% loss in tension after the first hour. At 1 week, 64% of the initial force remained, after which the elastics maintained a reasonably constant tension over the following 5 weeks, bz general, the grey,
clear, phzk, purple, and green elastomeric chabzs behave similarly. The products of all companies do not behave sbnilarly. Compared to the other manufacturers, Rocky Mountain's elastomeric chahls displayed the most ideal forces for physiologic tooth movement. (Duncan Multiple Range Test p < 0.05).
Reviews and abstracts
423
Development-age: Test of x-ray methods and assessment of criteria. G.D. Richards, and A.C. Watrous. San Francisco and Berkeley: Unirersity of the
Pacific, School of Dentistry and University of California at Berkel~; 1993 Accurate assessments of developmental-age are central to research in growth and development. Dental calcification and eruption sequences and x-rays are usually used to generate ages. To evaluate this method's accuracy and determine predictive limits for the procedure, we compare three radiographic methods and evaluate sources of intra- and inter-observer error. A mixed geographic sample of skulls (n = 40) from the Atkinson Collection, UOP, were examined. All skulls had a mixed developing dentition and normal craniofa~ cial development. Lateral and panorex (n = 10) x-rays were taken with the mandible in functional occlusion. Twelve periapical x-rays were taken for each individual. A g e determinations were made by comparison of the x-rays with Schour and Massler's, Standards for Development of the Human Dentition (Am. Dent.Assoc., 2 ed., 1944). Radiographs were evaluated separately by each author. Teeth were scored separately and solely on the basis of their developmental stage. Relative to periapical and panorex films, lateral radiographs ( 1 ) l a c k appropriate image quality to fully evaluate crown and root development, (2) have extensive overlapping which results in fewer ageable teeth, and (3) produce ages with high intra- and inter-observer, error. Radiographic technique clearly sets confidence limits on age assessments. Equally important, however, is the confidence level generated by the 'standard' aging chart, criteria application, andobserver ability. Significant inter-study error is introduced due to random errors in chart reproduction. Furthermore, .assessment criteria are broadly defined which results in wide variation in their application and in the addition of undocumented criteria. Thus the accuracy of age determinations are extensively affected by expert knowledge. Our work demonstrates that this agittg
method is highly affected by radiographic method, chart used, and 'expert knowledge" The method also lacks strict guidelines for its application. Results from growth and development studies using this method should, therefore, be cautiously evahtated.
the artificial carious lesion. Labiolingual sections of 100 I-tm were immediately obtained from each tooth and photographed with polarized light microscopy in imbibition media of water and Thoulet's (R.I." 1.41, 1.47), resperesenting a minimum of 5%, 10%, and 25% pore volume, respectively. The sections were varnished so that only the external surface of the section remained exposed and were placed into separate closed environments of a nonfluoridated artificial saliva for 3 months. Using a sonic digitizer, the area of the body of the lesion was measured in each imbibition medium, comparing the experimental lesions adjacent to the fluoride releasing resin to the control lesions. Results demonstrated a statis-
tically significant reduction hi the body of the lesion (p < 0.05) for those exposed to the fluoride releashlg reshz.
Force degradation characteristics of orthodontic colored elastomeric chains - a comparative study. J.C. Annello. San Francisco:
University of the Pacific, 1993 The present investigation was designed to compare the force degradation of colored elastomeric chains with those of grey and of clear elastomerie chains. Four manufacturer's products were evaluated. Grey, clear, pink, purple, and green elastomeric chains were obtained from Ormco, Unitek, A-Co., and Rocky Mountain. An acrylic jig with two parallel rows of embedded dowel pins allowed attachment and simultaneous testing of 50 chains. The jig and elastics remained submerged in synthetic saliva, pH 6.75, at 37 ~ C at all times, except when force measurements were taken. Force produced by the stretched elastomeric chains was measured through a calibrated spring-tension gauge. Force measurements were made at time of placement, at 1 hour, 8 hours, 24 hours, 2, 3, 4, 5, 6, 7 days and then weekly to 5 weeks. Two hundred specimens were tested with a total of 2800 force measurements. Starting with a mean force of 377 --- 11 gm there was a 19% loss in tension after the first hour. At 1 week, 64% of the initial force remained, after which the elastics maintained a reasonably constant tension over the following 5 weeks, bz general, the grey,
clear, phzk, purple, and green elastomeric chabzs behave similarly. The products of all companies do not behave sbnilarly. Compared to the other manufacturers, Rocky Mountain's elastomeric chahls displayed the most ideal forces for physiologic tooth movement. (Duncan Multiple Range Test p < 0.05).
Reviews and abstracts
423
Development-age: Test of x-ray methods and assessment of criteria. G.D. Richards, and A.C. Watrous. San Francisco and Berkeley: Unirersity of the
Pacific, School of Dentistry and University of California at Berkel~; 1993 Accurate assessments of developmental-age are central to research in growth and development. Dental calcification and eruption sequences and x-rays are usually used to generate ages. To evaluate this method's accuracy and determine predictive limits for the procedure, we compare three radiographic methods and evaluate sources of intra- and inter-observer error. A mixed geographic sample of skulls (n = 40) from the Atkinson Collection, UOP, were examined. All skulls had a mixed developing dentition and normal craniofa~ cial development. Lateral and panorex (n = 10) x-rays were taken with the mandible in functional occlusion. Twelve periapical x-rays were taken for each individual. A g e determinations were made by comparison of the x-rays with Schour and Massler's, Standards for Development of the Human Dentition (Am. Dent.Assoc., 2 ed., 1944). Radiographs were evaluated separately by each author. Teeth were scored separately and solely on the basis of their developmental stage. Relative to periapical and panorex films, lateral radiographs ( 1 ) l a c k appropriate image quality to fully evaluate crown and root development, (2) have extensive overlapping which results in fewer ageable teeth, and (3) produce ages with high intra- and inter-observer, error. Radiographic technique clearly sets confidence limits on age assessments. Equally important, however, is the confidence level generated by the 'standard' aging chart, criteria application, andobserver ability. Significant inter-study error is introduced due to random errors in chart reproduction. Furthermore, .assessment criteria are broadly defined which results in wide variation in their application and in the addition of undocumented criteria. Thus the accuracy of age determinations are extensively affected by expert knowledge. Our work demonstrates that this agittg
method is highly affected by radiographic method, chart used, and 'expert knowledge" The method also lacks strict guidelines for its application. Results from growth and development studies using this method should, therefore, be cautiously evahtated.