未熟歯の治癒および根尖形成プロトコルにおけるカルシウム-ケイ酸塩系再生および破折強度への影響

This study aimed to evaluate the impact of MTA- and putty-based regenerative and one-step apexification protocols on the fracture strength and failure patterns of immature teeth.

Seventy-two extracted human maxillary central incisors were decoronated and prepared to simulate immature root morphology. The samples were randomly divided into eight groups (n = 10): negative control (sound teeth), positive control (simulated immature teeth with no intervention), full MTA, full putty, apical MTA barrier + warm vertical compaction (WVC), apical Putty barrier + WVC, regenerative MTA, and regenerative Putty groups. After material placement and restoration, all specimens were embedded in acrylic blocks and loaded at 135° to the long axis using a universal testing machine at a crosshead speed of 0.5 mm/min until fracture occurred. The maximum load at fracture (N/cm) and fracture location (above or below the cementoenamel junction) were recorded. Data were analyzed using the Kruskal-Wallis and Dunn tests, Fisher's exact test, and Weibull analysis (p < 0.05).

Significant differences in fracture strength were observed among the groups (p < 0.05), whereas fracture location did not differ significantly (p > 0.05). The lowest mean fracture strength was found in the regenerative Putty group, while the full MTA group exhibited the highest values. Weibull analysis revealed no significant difference in the shape parameter (p = 0.108), but the scale parameter differed significantly among the groups (p < 0.001), confirming greater reliability and characteristic strength in MTA-based protocols.

Filling immature roots entirely with MTA or using an apical MTA plug followed by WVC provided superior and more consistent fracture resistance compared with putty-based regenerative protocols. Bioceramic Putty may not be a good choice for regenerative applications when the reinforcement of immature teeth is desired.