Evaluation of external apical root resorption and apical root displacement in maxillary molars with different sinus-root relationships by cone-beam computed tomography.

Abstract

Objective: To evaluate the effects of different pretreatment sinus-root relationships on external apical root resorption (EARR) and apical root displacement (ARD) of maxillary molars in maxillary premolar extraction treatment using a split-mouth design.

Materials and methods: Paired palatal roots of maxillary molars with different sinus-root relationships from the same patients were included in groups based on pretreatment CBCT. The relationships were classified as follows: type I, root separated from the maxillary sinus floor (MSF); type II, root contacting MSF; and type III, root protruding into the maxillary sinus. Pretreatment and posttreatment CBCT images were superimposed to quantify three-dimensional ARD. EARR length was measured post-orthodontics. Groups I vs. II and II vs. III were analyzed using paired t-tests/Wilcoxon tests, respectively. Analysis of associated factors was conducted using Generalized Estimating Equations (GEE).

Results: Mean EARR was < 1 mm across all types. Type II roots exhibited greater extrusive displacement in vertical ARD (P < 0.01) and increased EARR (P < 0.001) compared to type I. Type III roots demonstrated reduced mesial ARD compared to type II (P < 0.05), with no significant difference in EARR between types II and III. Type II roots were found to promote more EARR than type I (P < 0.001), while type III roots restricted mesial ARD compared to type II (P < 0.05).

Conclusions: Roots contacting MSF before orthodontic treatment increase EARR of maxillary molars, though the values remain clinically acceptable. Protrusion into the maxillary sinus prior to orthodontic treatment restricts the mesial movement of molar roots in the maxillary premolar extraction treatment, suggesting MSF morphology modulates orthodontic outcomes, duration, and anchorage demands.

Clinical relevance: A pretreatment evaluation of sinus-root relationship is recommended to anticipate the sequelae and biomechanical limitation in maxillary molars. However, complications from MSF proximity rarely necessitate excessive concern from orthodontists clinically.