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This study aimed to assess the impact of occlusal loading on secondary tooth eruption and to determine the extent to which altering the occlusal loading influences the magnitude of secondary eruption through an experimental rat model. The present sample consisted of 48 male Wistar rats. At the onset of the experiment, 24 rats were 4 weeks old (young rats) and 24 rats were 26 weeks old (adult). Within each age group, the rats were further divided into two equal subgroups (12 rats each), receiving either a soft- or hard-food diet for the 3-month duration of the experiment. The primary outcome was the tooth position changes relative to stable references in the coronal plane by evaluating the distance between the mandibular first molars and the inferior alveolar canal. Microcomputed tomography scans were taken from all rats at three standardized intervals over the 3-month study period. Descriptive statistics were calculated by age and diet over time, and the evolution of the outcomes were plotted by age and diet over time. Longitudinal data analysis via generalized estimating equations was performed to examine the effect of age, diet and time on the primary outcomes. Secondary tooth eruption was observed in all age groups (young and adult) regardless of diet consistency (soft or hard food). In young rats, the secondary eruption was greater in the animals fed a soft diet than those fed a hard diet. In adult rats, minimal difference in secondary tooth eruption were found between different diet consistencies. Occlusal loading influences secondary tooth eruption in teeth with an established occlusal contact. The quantity of eruption in growing rats is higher when occlusal loading is less, providing a certain amount of secondary tooth eruption occurs. This difference, however, is not evident in adult rats, at least during the given 3-month time frame., (© 2024 The Author(s). Journal of Morphology published by Wiley Periodicals LLC.)

Mesiodens is the most common type of supernumerary tooth, located between the maxillary central incisors. A young man was referred by his orthodontist for management of a supernumerary tooth located in quadrant I, superposed to the bottom of the right maxillary sinus, distally orientated with the crown in contact with the apex of the palatal root of the maxillary first molar. The tooth was found on a panoramic radiography before starting his orthodontic treatment. To remove it and in order to study, its relationship to the anatomical structures a cone-beam CT examination was performed. This revealed the presence of a mesiodens located on the right paramedian maxillary area. Pericoronal tissue submitted for histopathological examination showed an uninflamed dental follicle. Healing was uneventful. This case shows that mesiodens outside the arch, located in the posterior palate, may be not discovered in a panoramic radiograph., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: To evaluate the potential influence of muscular capacity and facial morphology on facial expressions in children., Materials and Methods: A cross-sectional study was carried out on 40 healthy children (ages 9-13), without previous orthodontic treatment. Masseter muscle thickness and anthropometric facial proportions were measured using ultrasound and digital calipers respectively. A three-dimensional infrared face-tracking system was used to register facial expressions. The maximal amplitude of smile and lip pucker (representing maximal lateral and medial commissure movement) were used for analysis. Stepwise regression was used to investigate whether muscle thickness or anthropometric facial proportions were associated with the quantity of commissure movement., Results: When performing maximal smile, children with thicker masseter muscles were found to have more limited displacement of the commissures (R = 0.39; p = 0.036). When performing lip pucker, children with thicker masseter muscles were found to have greater commissure movement (R = 0.40; p = 0.030). No significant associations were found between anthropometric facial proportions and facial expressions., Conclusion: Masseter muscle thickness seems to be associated with facial expressions in children. Those with thicker muscles show more limited commissure movement when smiling, but greater movement with lip pucker. This indicates that masticatory muscles may serve as a surrogate for mimic muscle activity. Facial morphology of the subjects does not seem to be associated with facial expression., (© 2021 The Authors. Clinical and Experimental Dental Research published by John Wiley & Sons Ltd.)

Objective: The aim of this study was to quantify changes in facial expressions in children with Class II division 1 malocclusion treated with functional appliances., Materials and Methods: A prospective controlled study was carried out evaluating 20 children with Class II division 1 malocclusion (ages 9-13) treated with a functional appliance for 12 months (treatment group). Age- and gender-matched children without immediate orthodontic treatment need were followed up without treatment for 12 months (control group). A frame-mode video sequence was taken of each subject at the beginning and end of the 12-month study period, during which 5 distinct facial expressions (posed smile, spontaneous smile, aggressive smile, lip pucker, and maximal mouth opening) were recorded. Frames at which each facial expression was at its peak were analysed. Changes in horizontal and vertical facial anthropometric distances brought about by performing each facial expression were measured. Intragroup differences following treatment were assessed using paired t-tests, whereas intergroup differences were assessed using unpaired t-tests., Results: All treated children showed an improvement in dentoalveolar relationships. Initial facial expressions differed between groups, with the treatment group showing less marked changes during lip pucker and more marked changes during maximal mouth opening. In contrast, no statistically significant differences were found between groups for the final facial expressions., Conclusions: This study suggests that functional appliance use in growing children with Class II division 1 malocclusion tends to normalize soft-tissue movements during facial expressions., (© The Author(s) 2018. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.)