Background: The objective of this study was to evaluate and compare the validity and accuracy of the Willems, Demirjian and Nolla methods in predicting chronological age in a Spanish ethnicity population. Methods: A sample of 604 orthopantomographs of Spanish children aged 4 to 13 years was evaluated by two independent evaluators. Descriptive statistics were applied to calculate the chronological age and dental age, presenting the mean and standard deviation. The difference between dental age and chronological age was calculated for each method. A positive result indicated an overestimation and a negative figure indicated an underestimation. The Wilcoxon test for paired data and Spearman’s correlation coefficient were applied by age groups and sex to compare the chronological age and dental age of each method (that of Willems, Demirjian and Nolla). Statistical tests were performed at a 95% confidence level. Results: The interexaminer agreement was 0.98 (p = 0.00), and the intraexaminer agreement was 0.99 (p = 0.00). The Willems method significantly overestimated the age of boys (0.35 years (0.93)) and girls (0.17 years (0.88)). The Demirjian method significantly overestimated the age of boys (0.68 years (0.95)) and girls (0.73 years (0.94)). The Nolla method significantly underestimated age in boys (0.44 years (0.93)) and girls (0.82 years (0.98)). Conclusions: In the Spanish population, the use of the Demirjian method for legal and medical purposes is frequent. This study reveals that the Willems method is more appropriate due to its greater precision in estimating dental age.

The use of orthodontic aligners has increased significantly due to their convenience and esthetic advantages. However, understanding their microbiological behavior and cytotoxicity is essential. This study aimed to evaluate the metabolic activity (MA) and proliferation of different bacterial strains—assessed through colony-forming unit (CFU) counts—as well as the cytotoxicity of three widely used aligner systems: Spark, Invisalign, and Smile. Wettability and surface free energy (both dispersive and polar components) were determined using the sessile drop technique. The bacterial strains Streptococcus oralis, Actinomyces viscosus, Streptococcus gordonii, Enterococcus faecalis, and Porphyromonas gingivalis were cultured, and their behavior on the aligner surfaces was assessed under simulated oral cavity conditions in both aerobic and anaerobic environments using a bioreactor. Cytocompatibility was evaluated with HFF-1 human fibroblasts. Distinct strain-specific behaviors were observed. For Spark aligners, the contact angle was 70.5°, Invisalign 80.6°, and Smile 91.2°, and the surface free energy was 60.8, 66.7, and 74. 2 mJ/m², respectively, highlighting the high polar component of the Spark aligner of 31.9 mJ/m² compared to 19.3 and 20.2 mJ/m² for Invisalign and Smile, respectively. The Spark aligner exhibited the lowest metabolic activity for Streptococcus oralis (23.1%), Actinomyces viscosus (43.2%), Porphyromonas gingivalis (17.7%), and biofilm formation (2.4%), likely due to its higher hydrophilicity. The Smile aligner showed the lowest metabolic activity for Streptococcus gordonii (23.6%) and Enterococcus faecalis (51.1%), attributed to its low polar surface free energy component. CFU counts were minimal for all aligners and bacterial strains, including biofilm. All aligners demonstrated cytocompatibility above 70% (Spark: 71.0%, Invisalign: 75.7%, and Smile: 75.6%). These findings highlight the importance of considering aligner material properties in clinical practice and underscore the need for proper oral hygiene and aligner maintenance.

The aim of this study was to evaluate the comfort of children and adolescents with conventional full-arch dental impression methods compared to two intraoral scanners (iTero^TM and Primescan^TM). Methods: A monocentric, analytical, controlled crossover study was designed to compare conventional impression and digital impression with two intraoral scanners (iTero^TM and Primescan^TM) in children and teenagers. Patient comfort was evaluated using a 100 mm VAS scale adapted to Spanish and for children. A descriptive and analytical statistical method was conducted with a confidence level of 95% (p ≤ 0.05) and asymptotic or bilateral significance. Results: A total of 51 subjects were enrolled in the study (mean age = 12.35 years). Although the group of 10–14-year-olds was the most numerous, gender was equally distributed among the age groups. None of the variables on the VAS scale showed differences between the gender categories (p > 0.05). There were differences (p < 0.05) with respect to the age categories, as the middle adolescent group showed the worst general perception and total comfort during the conventional impression. Statistically significant differences were found between all VAS scale items and the three impression methods (p < 0.05). Conclusions: The digital impression technique is superior in terms of total comfort to the conventional alginate impression in children and adolescents.

The mechanical properties of polyurethane dental aligners have been studied in an oral environment at 37°C and subjected to thermal cycling between 5°C and 55°C for long periods of time at different mechanical stresses. The aim is to determine the efficacy of the orthodontic aligner at different stress levels, the effect of thermal cycling with therapy time on tooth position correction. Sixty aligners with the same design were studied applying tensions of 0, 3 and 30 N and determining the deformation at different times from 1 to 760 h. Half of these aligners were subjected to stresses submerged in artificial saliva at 37°C and the other half were subjected to thermal cycles between 2°C and 55°C in salivary medium. Deformation was determined using a high-resolution stereo magnifier and ImageJ image analysis software. Water adsorption by the polyurethane was determined at the different test times. The results showed that in the unloaded aligners there is no appreciable deformation, but with thermal cycling there is a light shrinkage of the aligner due to the semi-crystallization process (ordering of polymeric chains) of the polyurethane. When applying loads of 3 and 30 N, creep curves with constant deformation transition zones can be seen. The transition zones decrease as the applied mechanical load increases. In addition, the significant effect of thermal cycling on the reduction of the transition zone of the aligners has been demonstrated. The transition zones are optimal for dental correction as constant stresses are exerted for tooth movement. The effect of thermal cycling shortens the constant deformation zone and reduces tooth alignment time. It was observed that the absorption of water in the aligner is constant after 1 h of immersion and does not exceed 0.4% by weight of absorbed water.

Background: The association between dental anomalies has been studied, giving rise to the concept of Dental Anomaly Pattern (DAP). Tooth agenesis has been associated with alterations such as molar infracclusion, taurodontism and delayed dental development. The aim of this study was to evaluate the dental development pattern in patients with non-syndromic dental agenesis, in comparison with a control group. Methods: Dental and chronological age was analysed in a sample size of 204 orthopantomographs divided into a study group (n = 104) and a control group (n = 100) with the Demirjian Method. Intra and intergroup differences in chronological and dental age, and the correlation between them were calculated by statistical analysis with a 95% confidence level (p < 0.05). Results: Dental age exceeded chronological age both in the control group and in the study group. Statistically significant differences (p = 0.004) were found when comparing the difference between chronological and dental age in the study (-0.16 ± 1.12) and control group (-0.58 ± 0.90). Regarding sex and age intergroup differences, the results were only statistically significant in the girls’ group (p = 0.017), and the age over 8 years old (p < 0.05). There were no significant differences in tooth development depending on the number of missing teeth or the affected tooth group, but there was a delay in the development of the homologous tooth contralateral to the absent one in 14.9% of patients. Conclusions: The difference between chronological and dental age in permanent dentition is significantly lower in Spanish children with non-syndromic agenesis compared to a control group, presenting a lower dental age than chronological age than children without non-syndromic agenesis.