What happens to the center of resistance in a single-rooted tooth with bone loss?

In a single-rooted tooth, the center of resistance refers to the hypothetical point where forces can be applied for effective tooth movement. When bone loss occurs, typically due to periodontal disease or other factors, the attachment of the tooth to the bone is compromised. This results in a shift of the center of resistance downward.

The reason the center of resistance moves down is primarily due to the reduction of the alveolar bone around the root. With less bone support, the root of the tooth has less resistance to movement, effectively lowering the point around which the tooth can be stabilized during orthodontic treatments. Thus, as bone loss occurs, the tooth’s biomechanical characteristics shift, causing the center of resistance to migrate in a downward direction, reflecting the reduced support of the tooth in the alveolar process.