Background. There are several invasive dental procedures that require local anesthetics. However, its infiltration is usually associated with anxiety and fear, increasing the perception of pain in pediatric patients. For this reason, it is important to evaluate different strategies for its application. We compared the anesthetic effect of the administration of 2% lidocaine with epinephrine 1:80000 non-alkalized at slow speed and alkalized at fast speed to block the inferior alveolar nerve in deciduous molars. Methods. A crossover clinical trial was carried out whose sample consisted of 38 patients between 6-10 years who required bilateral pulp treatment in their first mandibular primary molars. At the first appointment, they received 2% lidocaine with 1:80000 alkalinized epinephrine administered at a fast rate, and at the second appointment, 2% lidocaine with 1:80000 non-alkalized epinephrine administered at a low speed. We evaluated the onset of action, duration of the anesthetic effect, and intensity of pain during its infiltration. Results. We found that non-alkalized lidocaine at slow speed had a shorter onset time of action (57.21±22.21 seconds) and longer duration of effect (170.82±43.75 minutes) compared to administration of alkalinized lidocaine at fast speed (74.03±22.09 seconds, 148.24±36.24 minutes, respectively). There was no difference in the level of pain intensity. Conclusion. In this study, the slow administration of the non-alkalized local anesthetic showed a shorter onset time of action and a longer duration of the anesthetic effect in comparison with the alkalized local anesthetic administered at a rapid rate in the blockade of the inferior alveolar nerve in deciduous molars.

Congenital third molar (3M) agenesis is a common dental anomaly associated with genetic, epigenetic, and craniofacial growth factors. Evidence regarding its prevalence across populations and its relationship with sagittal and vertical growth patterns remains limited. This study aimed to compare the prevalence of 3M agenesis in Spanish and Peruvian samples and analyze its association with craniofacial growth patterns. A multicenter cross-sectional study was conducted in 1191 patients aged 10–14 years (348 Spanish, 843 Peruvian). 3M agenesis was assessed on digital panoramic radiographs. Sagittal and vertical growth patterns were evaluated using Steiner’s cephalometric analysis (ANB and GoGn–SN angles). Overall, 3M agenesis prevalence was 25.1%, with no difference between the Spanish (25.0%) and Peruvian (25.15%) groups. A non-significant trend toward higher prevalence was observed in Spanish females. 3M agenesis was more frequent in maxillary than mandibular 3M (16.8% vs. 10.2%; p < 0.001). Growth patterns differed between populations, with Class I and normodivergent patterns predominating in Spanish subjects, and Class II and hyperdivergent patterns in Peruvians (p < 0.001). No significant associations were found between 3M agenesis and sagittal or vertical growth patterns (p > 0.05), although Class II patients exhibited a higher prevalence of mandibular 3M agenesis (14.8% vs. 10.8%; p = 0.04). 3M agenesis showed similar prevalence in both populations and was not associated with craniofacial growth patterns, except for mandibular 3M agenesis in Class II patients, suggesting a multifactorial etiology driven by genetic and developmental factors rather than demographic or skeletal variables. It should be noted, however, that the cross-sectional nature of the study, the recruitment of patients from university dental clinics, and the absence of multivariate regression analysis limit both the generalizability and the causal interpretation of the findings.