Force decay of orthodontic power chains during five weeks in artificial saliva: An in vitro study.

Abstract

Orthodontists frequently use elastomeric chains for space closure and incisor retraction, though these chains are prone to force degradation and permanent deformation over time. Initially introduced in the early 20^th century, elastic power chains became more widely adopted in orthodontic practice in the 1960s due to industrial advancements. There are three main types of elastomeric chains: closed (continuous), open (short), and long (broad), available in various colors such as clear and black. Elastomeric chains generate forces for several orthodontic applications, including traction of impacted teeth, space closure, midline correction, retraction of canines and incisors post-extraction, tooth leveling and alignment, mesial displacement in posterior regions, and space closure. However, therapeutic control challenges arise as the force exerted by these chains diminishes over time, with studies indicating a reduction of 50%-75% in the first 24 hours, followed by continued exponential decay.

Objectives: This study aimed to analyze the rate of force decay in closed and open power chains, both black and transparent, from four orthodontic manufacturers (American Orthodontics^®, Ortho Technology^®, Ormco^®, and Orthometric^®). Additionally, we sought to determine any significant differences among brands and colors that could influence the elastics' clinical effectiveness.

Materials and methods: A total of 48 power chain samples were tested for force decay by using a universal orthodontic force gauge. The chains, stretched to 90 mm (twice their original length), were measured at 0 hours, 24 hours, 1 week, 2 weeks, 3 weeks, 4 weeks, and 5 weeks. The samples were stored in artificial saliva within a laboratory water bath at a constant 37°C to simulate the oral environment. Tukey's honestly significant difference (HSD) test was applied to assess differences between brands, colors, types (closed or open), and time intervals.

Results: The study revealed significant differences in force decay among the various orthodontic power chains over the 5-week evaluation period. American Orthodontics^® demonstrated the highest reduction in force, with a decay of 73.42% by week 5, while Ormco^® exhibited the least decay at 48.17%. The black power chains of American Orthodontics^® and Ortho Technology^® showed superior initial force retention compared to their clear power chains counterparts, although all tested materials experienced substantial force decay. Closed power chains consistently retained higher forces than open ones across all brands, highlighting their potential advantage in clinical applications requiring optimal force delivery.

Discussion: The significant differences in decay patterns suggest that clinicians should consider using Ormco^® and Orthometric^® for prolonged applications due to its relative stability, while the black power chains of American Orthodontics^® and Ortho Technology^® may be more suitable for cases requiring immediate, high forces. Additionally, the consistent superiority of closed power chains in force retention emphasizes their potential advantages in optimizing tooth movement, reinforcing the need for orthodontists to align material choices with specific clinical objectives.

Conclusion: This study highlights the significant variability in force decay among different orthodontic power chains, emphasizing the necessity for careful material selection based on both initial strength and long-term performance. The findings advocate for tailored approaches to enhance treatment efficacy and patient outcomes in orthodontic care.