Bite Force, Occlusal Contact and Pain in Orthodontic Patients during Fixed-Appliance Treatment

Orthodontic maxillary molar movement-induced zygomatic pillar remodeling and its consequences on occlusal characteristics and stress distribution

OBJECTIVE

We aimed to evaluate changes in the zygomatic pillar during orthodontic treatment involving premolar extraction, analyze the effects of maxillary first molar movement on zygomatic pillar remodeling, and examine occlusal characteristics and stress distribution after remodeling.

METHODS

Twenty-five patients who underwent premolar extraction were included in the study. The zygomatic pillar measurement range was defined, and cross-sectional areas, surface landmark coordinates, alveolar and cortical bone thicknesses, and density changes were assessed using Mimics software based on the cone-beam computed tomography scans taken before (T0) and after the treatment (T1). Multiple linear regression analysis was performed to determine the correlation between changes in the zygomatic pillar and maxillary first molar three-dimensional (3D) movement and rotation. Additionally, the correlation between pillar remodeling and occlusal characteristics was analyzed by Teetester. Pre- and post-reconstruction 3D finite element models were constructed and loaded with an average occlusal force of two periods.

RESULTS

The morphological and structural remodeling of the zygomatic pillar after orthodontic treatment involving premolar extraction showed a decreased cross-sectional area of the lower segment of the zygomatic pillar. The zygomatic process point moved inward and backward, whereas the zygomatico-maxillary suture point moved backward. The thicknesses of the zygomatic pillar alveolar and cortical bones were thinner, and reduced alveolar bone density was observed. Simultaneously, the movement and angle change of the maxillary first molar could predict zygomatic pillar reconstruction to a certain extent. With decreasing the total occlusal force and the occlusal force of the first molar, occlusal force distribution was more uniform. With zygomatic pillar remodeling, occlusal stress distribution in the zygomatic alveolar ridge decreased, and occlusal stress was concentrated at the junction of the vertical and horizontal parts of the zygomatic bone and the posterior part of the zygomatic arch.

CONCLUSIONS

Orthodontic treatment involving premolar extraction led to zygomatic pillar remodeling, making it more fragile than before and reducing the occlusal force of the maxillary first molar and the entire dentition with stress concentrated in weak areas.

CLINICAL RELEVANCE

No other study has focused on the effects of orthodontics on pillar structures. The present study indicates that the mesial movement of the maxillary first molar weakened the zygomatic pillar and reduced occlusal function, thereby providing insights for inserting anchorage screws and facial esthetics.

Predictors of Analgesic Consumption in Orthodontic Patients

During orthodontic treatment, pain is a subjective experience influenced by several factors. Orthodontic patients consume analgesics at different rates to alleviate this pain. Correlations between orthodontic pain and analgesic consumption were analyzed. Predictive factors to analgesics consumption were not statistically analyzed. This study was conducted to identify the predictive factors for analgesic consumption after initiation of orthodontic treatment with fixed appliances. Two hundred and eighty-six patients involved in this study kept a seven-day diary in which they recorded pain intensity (using a 0–10 numerical rating scale), analgesic consumption, localization of pain, pain triggers, and pain characteristics. Univariable analyses identified potential predictive factors: age, gender, pain intensity, pain localization, pain while chewing, pain at rest, night pain, headache, pulsating pain, sharp pain, dull pain, and tingling. Logistic regression was conducted to create a model that could predict analgesic consumption. Multivariate analyses demonstrated that analgesic consumption was increased by increased age, increased intensity of pain, and presence of a headache. Overall, the model explained 33% of analgesic requirement variability. Age, intensity of pain, and headache proved to be predictors of analgesic consumption. Knowledge of such factors may help clinicians identify orthodontic patients who will consume analgesics on their own.