Preschool children (n=721) aged between 4 and 5 years were examined and 60 were selected. Two pairs of dental casts were obtained for each child. The first pair was from primary dentition before eruption of permanent first molars; the second pair had the permanent first molars in occlusion. The sample was divided into 3 groups, according to the terminal plane. The findings indicate that 55% of the group with flush terminal plane developed into Class I, 40% into Class II, and 5% into Class III molar relationship in the permanent dentition. The group with mesial step, 70% progressed to Class I, 25% to Class II, and 5% to Class III molar relationship in the permanent dentition. Finally, the group with distal step developed into Class II in the permanent dentition. It can be concluded that the terminal relationship of deciduous second molars was associated with the permanent first molars occlusion.

Background:Molar incisor hypomineralization (MIH) is a change in the formation of dental enamel of systemic origin that affects at least one of the first 4 permanent molars and usually affects incisors. During the eruption, the affected surfaces tend to fracture, exposing the dentin, which causes excessive sensitivity in addition to making the region very susceptible to the appearance of carious lesions. The objective of this research will be to evaluate the clinical effect of antimicrobial photodynamic therapy (aPDT) in permanent teeth with severe and sensitive MIH.Methods:The methodology will be based on the selection of patients from 6 to 12 years of age with permanent molar teeth, randomly divided in 2 groups. The selected teeth should have MIH on the occlusal surface, indicated for clinical restorative treatment. In Group 1, aPDT will be applied for the treatment of infected dentin. Afterward, the teeth will be restored with high viscosity glass ionomer cement. In Group 2, the removal of the softened dentin around the side walls of the cavity with sharp dentine curettes and posterior restoration with high viscosity glass ionomer cement will be performed. All patients will have clinical and radiographic follow-up with a time interval of 6 and 12 months. The data obtained will be submitted to descriptive statistical analysis to evaluate the association of categorical variables. Chi-square test and Fisher exact test will be applied, to analyze the correlation between the continuous variables, Pearson correlation test will be applied. For the analysis of dentin density in the scanned radiographic images and the microbiological results for colony-forming units, ANOVA and Kruskal–Wallis will be applied.Discussion:Often in the presence of severe MIH, the presence of dentin sensitivity is also associated with caries lesion, making it even more necessary to respect the principles of minimal intervention.Trial registration:NCT03904641.