Little is known about whether the misfit level of implant-supported screw-retained prostheses can be tolerated when different combinations of engaging and nonengaging titanium bases are used.
The ...purpose of this in vitro study was to simulate prosthetic workflow distortions (horizontal and vertical) and to evaluate the fit (passive and active) of 2-implant-supported screw-retained zirconia frameworks with 3 different combinations of abutments: both engaging, engaging and nonengaging, and both nonengaging.
The fit of both engaging (n=10), engaging and nonengaging (n=10), and both nonengaging (n=10) 2-implant-supported zirconia frameworks was evaluated on control and definitive casts simulating 50-, 100-, and 150-μm vertical and 35-, 70-, 100-μm horizontal misfit levels. Stereomicroscopy was used to assess the passive fit (1 screw tightened) and active fit (both screws tightened) of the zirconia frameworks. Vertical deviations in the implant and abutment connection (the implant-abutment gap measured vertically) between the implant platform and reference line on the titanium base were measured. The Kruskal-Wallis and Mann-Whitney U tests (α=.05) were used to compare different implant-supported zirconia specimens on each definitive cast.
When 1 screw was tightened, both engaging specimens had higher vertical deviations (ranging from 40.1 to 131.1 μm) in 35- and 70-μm horizontal misfit levels, as compared with engaging and nonengaging (19.8 to 85.1 μm) and both nonengaging (6.6 to 14.3 μm) specimens. Comparing medians of the 100-μm misfit in horizontal (engaging and nonengaging 140.4 μm; both nonengaging 151.6 μm) and vertical (engaging and nonengaging 49.8 μm; both nonengaging 42.6 μm) directions, the horizontal misfits caused larger vertical deviations. When both screws were tightened in 50-, 100-, and 150-μm vertical misfit groups, the vertical gap increase in the engaging and nonengaging specimens was significantly higher than that in both the nonengaging specimens (P<.001).
As the level of simulated misfit increased, the vertical gap between the implant and abutment increased. Horizontal misfits were less tolerated than vertical ones and may be more detrimental. Both nonengaging 2-implant-supported zirconia frameworks were found to tolerate the different misfit levels better, followed by engaging and nonengaging and both engaging frameworks.
To evaluate deviation propagation from data acquisition with an intraoral scanner to additive manufacturing of complete-arch dentate models.
A reference (Ref) mandibular dentate model having 5 ...precision spheres was scanned with a coordinate measurement machine equipped with a laser scanning head (ALTERA; Nikon) producing a Ni reference data set (n = 1). Digital impressions were taken of the Ref model with intraoral scanner (IOS) (Trios4; 3Shape) with Insane (T4_Imo) and Classic (T4_Cmo) scanning modes (each n = 10). T4_Imo scans were used as a second reference data set and to produce test models with two additive manufacturing (AM) devices (each n = 10): MAX UV385 (Asiga) and NextDent 5100 (3DSystems). As for the control group, dual viscosity vinyl polysiloxane impressions were taken of the Ref model and poured with Type IV dental stone (n = 10). All AM and stone models were scanned with a laboratory scanner (E4; 3Shape). Trueness and precision of linear (intermolar and intercanine width, arch length) and surface deviations were measured between reference (Ni, T4_Imo), test (T4_Cmo, AM), and control (stone) groups using best-fit alignments (Geomagic Control X; 3D Systems). The normality of data and differences between the groups were analyzed using Shapiro-Wilk, Levene's, Mann-Whitney U, Welch's t-test statistical analysis (p<0.05).
The accuracy of the IOS impression was not significantly affected by the scanning mode (p>0.05). Stone models showed significantly better trueness than IOS impressions (p<0.05). AM models had higher trueness than IOS Imo digital impressions (p<0.05). The precision of AM models was comparable (linear, p>0.05) or lower (surface, p<0.05) than of IOS Imo digital impressions. Trueness was insignificantly different among the stone and AM models (p>0.05). Higher trueness was achieved by Max UV385 than with Nextdent 5100 (p<0.05). The majority of linear and all surface deviations of IOS impressions and AM models were below 200 μm.
Within the limitations of this in vitro study, digital IOS impressions and AM models using the aforementioned equipment have acceptable accuracy for orthodontic and prosthodontic applications when complete-arch dentate records are used.
IOS and AM devices can have a significant influence on error propagation when applying digital workflow with complete-arch dentate models
Chondrosarcoma is among the most common primary bone tumors in adults. In the mandible, chondrosarcoma is a very uncommon malignant cartilage-producing tumor. This case report shows how virtual ...planning combined with other digital technologies may improve masticatory function rehabilitation in patients with enlarged mandibular chondrosarcoma. The present study reports a case of a 52-year-old male patient who was initially diagnosed with a mandible chondroma, which was successfully excised with no evidence of malignant transformation. Nevertheless, the patient's symptoms recurred after 10 years, and a subsequent diagnosis of mandible chondrosarcoma was established, prompting the need for subtotal mandible resection and reconstruction with a fibula-free flap. Following a healing period, the patient underwent dental implant surgery to restore the mandibular dental arch, which was performed utilizing computer-aided design and computer-aided manufacturing technology, with fully guided implant placement facilitated by virtual planning. In this case report, the implant position data merging process is described from the digital impression and control model to ensure optimal passive fit of the full-arch zirconia prosthesis and discuss the importance of occlusal adjustments to avoid technical and biological complications. Virtual planning and digital technologies are crucial for the effective management of mandibular defects, allowing for accurate treatment and complete restoration of mandibular function. Their use leads to improved patient outcomes and quality of life. As technology advances, their importance in treating complex medical conditions is only expected to grow.
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