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Updated: Feb 3, 2026
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Measuring the Complete-arch Distortion of an Optical Dental Impression
Published on: May 30, 2019
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Second molar intrusion: Continuous arch or loop mechanics?
Renato Parsekian Martins1, Ricardo Lima Shintcovsk2, Luegya Knop Shintcovsk3
1Private practice, Araraquara, São Paulo, Brazil; Faculdade de Odontologia de Araraquara, Universidade Estadual Paulista, Araraquara, São Paulo, Brazil.
Summary
Rectangular loops and continuous arch mechanics both intrude maxillary second molars. Continuous arch offers better intrusion with less tipping, especially for smaller movements.
Area of Science:
- Orthodontics
- Biomaterials Science
Background:
- Maxillary second molar intrusion is a complex orthodontic challenge.
- Comparing load systems from different mechanics is crucial for treatment planning.
Purpose of the Study:
- To compare the load systems produced by rectangular loops and continuous arch mechanics.
- To evaluate their effects on maxillary second molar intrusion.
Main Methods:
- Utilized a force tester with a passive orthodontic appliance (second molar to second molar).
- Compared beta-titanium rectangular loops and super-elastic nickel-titanium continuous arch mechanics.
- Measured vertical (Fz) and mesial (Fy) forces, and tipping moments (Mx) at various deactivation levels.
Main Results:
- Significant differences in forces and moments were observed between the two mechanics at the molar tubes and centers of resistance.
- Continuous arch produced greater vertical forces (Fz) but lower mesial forces (Fy) compared to rectangular loops.
- Both mechanics achieved molar intrusion, with continuous arch showing reduced tipping moments in the second molar.
Conclusions:
- Both rectangular loops and continuous arch mechanics can intrude maxillary second molars.
- Continuous arch mechanics are preferable for achieving intrusion with minimal tipping, particularly when less intrusion is needed.
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