The effect of temperature on the mechanical behavior of nickel-titanium orthodontic initial archwires

Luca Lombardo; Giorgia Toni; Filippo Stefanoni; Francesco Mollica; Maria Paola Guarneri; Giuseppe Siciliani

Angle Orthod. 2013;83:298–305.

Objectives: To investigate and compare the characteristics of commonly used types of traditional and heat-activated initial archwires at different temperatures by plotting their load/deflection graphs and quantifying three parameters describing the discharge plateau phase.
Materials and Methods: Forty-eight archwires of cross-sectional diameters ranging from 0.010 inches to 0.016 inches were obtained from seven different manufacturers. A modified three-point wire-bending test was performed on three analogous samples of each type of archwire at 55uC and 5uC, simulating an inserted archwire that is subjected to cold or hot drinks during a meal. For each resulting load/deflection curve the plateau section was isolated and the mean value of each parameter for each type of wire was obtained.
Results: Permanent strain was exhibited by all wires tested at 55uC. Statistically significant differences were found between almost all wires for the three considered parameters when tested at 55uC and 5uC. Loads were greater at 55uC than at 5uC. Differences were also found between traditional and heat-activated archwires, the latter of which generated longer plateaus at 55uC, shorter plateaus at 5uC, and lighter mean forces at both temperatures. The increase in average force seen with increasing diameter tended to be rather stable at both temperatures. Conclusions: All nickel-titanium wires tested showed a significant change related to temperature in terms of behavior and force for both traditional and heat-activated wires. Stress under high temperatures can induce permanent strain, whereas the residual strain detected at low temperatures can be recovered from as temperature increases. (Angle Orthod. 2013;83:298–305.)

KEY WORDS: NiTi archwire; Load deflection characteristics; Mechanical behavior


Di |2019-11-13T08:14:48+00:00Gennaio 2nd, 2014|Uncategorized|0 Commenti

Changes in the oral environment after placement of lingual and labial orthodontic appliances

Luca Lombardo, Yildiz Öztürk Ortan, Özge Gorgun, Chiara Panza, Giuseppe Scuzzo and Giuseppe Siciliani

Progress in Orthodontics 2013, 14:28


Background: This study compared the oral hygiene and caries risk of patients treated with labial and lingual orthodontic appliances throughout a prospective evaluation of the status of the oral environment before and after bracket placement.

Methods: A total of 20 orthodontic patients aged 19 to 23 years were included in the study and were divided into two groups: 10 patients wore Roth labial appliance (American Orthodontics, Sheboygan, WI, USA) and 10 patients wore STb lingual appliance (Ormco Corporation, Glendora, CA, USA). Plaque index (PI), gingival bleeding index (GBI), salivary flow rate, saliva buffer capacity, salivary pH, and Streptococcus mutans and Lactobacillus counts in saliva were determined at three time points: before orthodontic appliance placement (T0), 4 weeks after bonding (T1), and 8 weeks after bonding (T2). After appliance placement, all patients were periodically educated to the oral hygiene procedures. Wilcoxon rank and Mann-Whitney U tests were used to determine intragroup and intergroup differences as regards qualitative data. To compare quantitative data between the groups, chi-square and Fisher’s exact tests were undertaken, while intragroup differences were tested with McNemar test. The level of statistical significance was set at p < 0.05.

Results: Statistical analysis of the data obtained revealed a statistically significant difference between the data of T0 and T1 and the data of T0 and T2 of the PI scores and between T0 and T2 of the GBI scores in the group treated with the lingual appliance. The GBI value increased significantly between T0 and T1 but decreased significantly between T1 and T2 (p < 0.01) in the group treated with labial appliance. S. mutans counts increased significantly between T0 and T2 in the saliva samples of patients treated with lingual appliance. No statistically significant differences were found between S. mutans and Lactobacillus counts at the three terms of saliva collection in patients treated with labial appliance. No statistically significant differences were found between the two groups at the three time points as regards the salivary flow rate and saliva buffer capacity.

Conclusions: Lingual and labial orthodontic appliances showed a different potential in modifying the investigated clinical parameters: patients wearing STb lingual orthodontic appliance had more plaque retention 4 and 8 weeks after bonding, while there were more gingival inflammation and more S. mutans counts 8 weeks after bonding. No differences were found between the two groups as regards the Lactobacillus counts, the salivary flow rate, and saliva buffer capacity.

Keywords: Oral hygiene habits; Orthodontic treatment; Salivary test; Lingual appliance; Labial appliance

Di |2019-11-13T08:14:49+00:00Gennaio 2nd, 2014|Uncategorized|0 Commenti

Frictional resistance exerted by different lingual and labial brackets: an in vitro study.

Luca Lombardo, Weronika Wierusz, Dominique Toscano, Roberto Lapenta, Andrea Kaplan and Giuseppe Siciliani

Progress in Orthodontics 2013, 14:37


Background: Although much has been written on the implications of friction generated between orthodontic archwires and labial brackets, information on lingual brackets is still limited. Hence, we set out to investigate the frictional resistance exerted by different lingual and labial brackets, including both conventional and self-ligating designs. The effect of various factors, namely bracket/base width, slot size, inter-bracket distance, and first- (ΘcI) and second-order (ΘcII) critical contact angles were evaluated and compared.

Methods: A plaster model of a pretreatment oral cavity was replicated to provide 18 (9 upper and 9 lower) identical versions. The anterior segments of each were taken, and the canine and lateral and central incisors were mounted with either lingual (7th Generation, STb, New STb, In-Ovation L, ORJ) or labial (Mini-Mono, Mini Diamond, G&H Ceramic) brackets. Mechanical friction tests were performed on each type of bracket using a universal testing machine. The maximum force necessary to displace NiTi wires of two different diameters (0.012, 0.014) was measured, using both elastic and metal ligatures with conventional brackets.

Results: The frictional force necessary to displace the wires increased as the diameter of the wire increased in all tested brackets (p < 0.01). Friction was significantly higher (p < 0.001) with elastic ligatures, as compared with metal ones, in all conventional brackets. In the lower lingual group, significantly lower friction was generated at conventional lingual New STb brackets (p < 0.01) and ORJ lingual brackets (p < 0.05) than at self-ligating In-Ovation L lingual brackets. A significant statistical correlation between (ΘcI) and friction was detected in the lower labial bracket group.

Conclusions: Friction resistance is influenced not only by the bracket type, type of ligation, and wire diameter but also by geometric differences in the brackets themselves.

Di |2019-11-13T08:14:50+00:00Gennaio 2nd, 2014|Uncategorized|0 Commenti
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