Which statement best explains tipping tendencies during space closure if the force system is not properly controlled?

Which statement best explains tipping tendencies during space closure if the force system is not properly controlled?

• A. If the line of action passes exactly through the center of resistance.
• B. If the line of action does not pass through the center of resistance or the moment-to-force ratio is not properly controlled.
• C. If a pure moment is applied with no linear force.
• D. If forces are applied only when the patient is seated.

Answer: (B)

The movement type you get during space closure hinges on where the resultant force acts relative to the tooth’s center of resistance and on the moment-to-force ratio of the applied forces. The center of resistance is the point inside the root such that a single force through it would move the tooth bodily without tipping. If the force line passes through that point, the tooth translates with minimal tipping. If the line of action does not pass through the center of resistance, a rotational tendency is created, causing tipping as the crown moves while the root resists with a counter moment. The moment-to-force ratio determines how much rotation versus translation occurs; an improper ratio means tipping dominates instead of controlled bodily movement. A pure moment would rotate the tooth with little or no linear translation, which isn’t the typical mechanism described for tipping during space closure, and forces applied only when the patient is seated don’t address the force system’s effectiveness. Thus, tipping tendencies arise when the line of action misses the center of resistance or when the moment-to-force ratio isn’t properly controlled.

The movement type you get during space closure hinges on where the resultant force acts relative to the tooth’s center of resistance and on the moment-to-force ratio of the applied forces. The center of resistance is the point inside the root such that a single force through it would move the tooth bodily without tipping. If the force line passes through that point, the tooth translates with minimal tipping. If the line of action does not pass through the center of resistance, a rotational tendency is created, causing tipping as the crown moves while the root resists with a counter moment. The moment-to-force ratio determines how much rotation versus translation occurs; an improper ratio means tipping dominates instead of controlled bodily movement. A pure moment would rotate the tooth with little or no linear translation, which isn’t the typical mechanism described for tipping during space closure, and forces applied only when the patient is seated don’t address the force system’s effectiveness. Thus, tipping tendencies arise when the line of action misses the center of resistance or when the moment-to-force ratio isn’t properly controlled.