BackgroundAngulated implants may result in inaccurate impressions, and the impression technique may affect the accuracy of the definitive cast. This study was designed to compare the dimensional accuracy of casts obtained from three impression techniques for three definitive lower casts with implants at different angulations.MethodsThree Osseolink implants were placed in three reference models with different angles (parallel, 15° and 30°). Impressions of each model were made with three techniques (n = 10 per group): indirect, unsplinted direct, and acrylic resin-splinted direct technique. Impressions were poured with type IV dental stone. Inter-implant distances were measured for casts using a coordinate measuring machine, and the deviations from the reference models (Δr) were calculated. Data were analyzed using one-way ANOVA followed by post hoc tests to detect significance between groups (α = 0.05).ResultsThis study showed that the deviations in micrometers from the reference model were the least for acrylic resin-splinted direct technique (Δr1 = 49.96, Δr2 = 50.36) versus indirect (Δr1 = 93.8, Δr2 = 90.9) and unsplinted direct techniques ((Δr1 = 67.07, Δr2 = 68.66) in 30° angulated implant situation (p value < 0.0001* for both Δr1 and Δr2). In 15° angulated implants, both the acrylic resin-splinted direct (Δr1 = 44.64, Δr2 = 45.58) and unsplinted direct techniques (Δr1 = 47.39, Δr2 = 55.28) were more accurate than indirect technique (Δr1 = 64.8, Δr2 = 68.3) (p value < 0.0001* for both Δr1 and Δr2). While in parallel condition, no difference was found between all three techniques (p value = 0.085, 0.056 for Δr1 and Δr2, respectively).ConclusionsThe impression technique affected the accuracy of definitive casts. The acrylic resin splinted direct technique produced the most accurate casts, followed by direct unsplinted and indirect techniques. Furthermore, implant angulation affected the impression accuracy. When implant angulation increased from parallel implants to 30°, the forces of deformation increased, which resulted in increased distortion.

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Purpose Evaluate microstrains on peri-implants tissue of different designs of maxillary complete overdenture assisted by different number of implants. Methods Two maxillary epoxy resin models used, for the first model two implants with 4.5 mm diameter and 13 mm length installed in the canine area and two implants with 4.5 mm diameter and 10 mm length installed in the second premolar area and two designs of maxillary overdenture used: group I maxillary implant overdenture (MIOD) assisted by four implants and Group (II) palateless maxillary implant overdenture assisted by four implants, for the second model two implants with 4.5 mm diameter and 13 mm length installed in the canine area and two designs of maxillary over denture used: group III MIOD assisted by two implants and group IV palateless implant overdenture assisted by two implants, four strain gauges used around each implant, bilateral static 100 N vertical load and 65 N oblique load applied on the occlusal surface of each MIOD. Stress meter used to measure the microstrains using software (ED × 10 A). Results The least stress found related to group I under 100 N vertical loading and the highest readings found related to group IV under 65 N oblique loading, under vertical loading stresses recorded in group III was greater than group I, stress in group IV was greater than group II, stress in group II was greater than group I, stress in group IV was greater than group III, under oblique loading, stress in group III was greater than group I, stress in group IV was greater than group II, stress in group II was greater than group I, stress in group IV was greater than group II. Conclusion Removing the palatal part from MIOD could be done in case of using four implants without damaging the prei-implants tissues.