Microstructural Evaluation of the Mineralized Apical Barrier Induced by a Calcium Hydroxide Paste Containing Iodoform: A Case Report

Ultrastructural evaluation of adverse effects on dentine formation from systemic fluoride application in an experimental mouse model

AIM

Fluoride is widely used in dentistry for its caries prevention. To reduce dental caries, the optimal fluoride concentration of public water supplies in the United States is 0.7 ppm. However, excessive systemic fluoride consumption can lead to dental/enamel fluorosis. Numerous studies have explored the effects of fluoride on enamel and enamel-forming cells. However, research on systemic fluoride's impact on dentine is limited, particularly the effect of fluoride on the structure of the dentine-pulp complex. Therefore, this study aimed to identify how excessive fluoride affects dentine microstructure using an experimental mouse model.

METHODOLOGY

C57BL6/J male mice (6-9 weeks old) were randomized into four groups (Fluoride at 0, 50, 100, or 125 ppm in drinking water) (n = 4/group). Mice were provided water ad libitum for 6 weeks along with fluoride-free food. Thereafter, mandibular incisors were analysed. Enamel phenotypes were evaluated using light microscopy and quantitative light-induced fluorescence (QLF) to measure fluorosis levels. Dentine morphology was evaluated using micro-CT, scanning electron microscopy (SEM), SEM-EDX (energy-dispersive X-ray), microhardness test and histological imaging. Data were analysed using one-way ANOVA with Dunnett's multiple comparisons as a post hoc test and the Kruskal-Wallis test with Dunn's multiple comparisons post hoc test (p < .05).

RESULTS

Mice treated with fluoride at 50-125 ppm developed enamel hypoplasia in their erupting incisors and micro-CT imaging revealed that fluoride 125 ppm caused external resorption of the growing incisor. Dentine mineral density, dentine volume decreased compared with the 0 ppm control, while pulp volume increased compared with the 0 ppm control group. SEM showed wider predentine layer and abnormalities in calcified matrix vesicles derived from odontoblasts in fluoride 100 and 125 ppm groups. Vickers microhardness of dentine significantly decreased in the high-dose group. Fluoride-induced dentine hypoplasia in a dose-dependent manner. Histological evaluation showed excessive fluoride 125 ppm induced micro abscess formation and inflammatory cell infiltration. Fluoride induced dentine dysplasia with a dentine microstructure resembling hypophosphatasia.

CONCLUSIONS

High doses of systemic fluoride can cause dentine dysplasia. Both three-dimensional and microstructural analyses showed the structural, chemical and mechanical changes in the dentine and the mineralized tissue components, along with external resorption and pulp inflammation.

Nonsurgical root canal treatment of an Oehlers type IIIa maxillary central incisor with dens invaginatus: a case report

Dens invaginatus has a complex anatomy, making endodontic treatment challenging. We report the case of a 11-year-old girl who presented with radiolucency at the apex of the maxillary central incisor; she was diagnosed with symptomatic apical periodontitis. Cone-beam computed tomography (CBCT) revealed dens invaginatus. The invagination and root canal were observed using a dental operating microscope, and nonsurgical root canal treatment was performed. The invagination was connected to the periodontal tissue, and the tooth was classified as Oehlers type IIIa. Root canal preparations were performed using NiTi files and an ultrasonic device. A calcium hydroxide paste was used as an intracanal dressing. The root canal was filled using a single-cone hydraulic condensation technique with a highly fluid calcium silicate-based sealer. At the 2-year follow-up, no clinical symptoms were observed, and CBCT images revealed no radiographic lesions. Nonsurgical endodontic treatment using CBCT imaging, dental microscope, effective cleaning systems, and a highly fluid sealer facilitated the successful treatment of apical periodontitis attributed to dens invaginatus. The single-cone hydraulic condensation technique using a bio-ceramic sealer is considered effective even in cases with a complex morphology and open apex.