To achieve effective translation, which condition must be met regarding the moments?

To achieve effective translation in orthodontics, the requirement is that the moments must be equal. This means that when a force is applied to a tooth, the rotational effects (moments) created by that force must be countered, allowing for a purely translational movement without unwanted tipping or rotation.

When moments are equal, the forces applied predominantly create a straight-line movement of the tooth through the center of resistance, enhancing the efficiency of the translation. This balance ensures that the net effect of the force results in the desired direction of movement instead of causing undesirable rotations.

While other conditions regarding moments and forces may play a role in different scenarios, the condition of having equal moments specifically underpins the efficient translational movement sought in orthodontic force systems.