Purpose: The aim of this study was to assess the influence of several variables in the frequency of prosthetic teeth fractures in fixed full-arch implant-supported acrylic resin prostheses. Materials and Methods: The influence of each variable was determined after analyzing the results obtained from 161 prostheses after a mean follow-up period of 39.69 months. All patients were treated with standard Nobel Biocare and Biomet 3i implants, and followed a strict prosthodontic protocol. Results: A total of 155 fractures were recorded, all of which took place in 60 prostheses (40% of the total). Statistically significant differences were found among several variables: the arch the prosthesis was on, patient sex, opposing arch characteristics, length of the cantilevers, and whether the structure had mechanical retention. The prostheses that suffered a greater number of fractures were those that had been placed in men, opposing a natural arch, with cantilevers shorter than 10 mm and without mechanical retention. Patient age and presence or absence of a cantilever were not determinants. Conclusion: Tooth fractures in fixed full-arch implant-supported metalacrylic prostheses are a common complication. Several factors are linked more directly with the need for mechanical maintenance. The design and indications of this type of prosthesis should be carefully considered.