Comparative analysis of flexural strength of 3D printed and milled 4Y-TZP and 3Y-TZP zirconia.

STATEMENT OF PROBLEM: The mechanical properties of 3 dimensionally (3D) printed zirconia have been reported to be comparable with those of milled zirconia, except for the flexural strength. However, most previous studies tested 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), making it necessary to study 3D printed zirconia with 4 mol% yttria content (4Y-TZP). PURPOSE: The purpose of this in vitro study was to compare the flexural strength of 3D printed 4Y-TZP with 3Y-TZP materials and milled 4Y-TZP. MATERIAL AND METHODS: A total of 80 disk specimens (Ø15×1.5 mm) were fabricated and divided into 4 groups (n=20) using the fabrication method and yttria content: milled 3Y-TZP (Katana HT; Kuraray Noritake), 3D printed 3Y-TZP (TZ-3Y-E; Tosoh), milled 4Y-TZP (Katana STML; Kuraray Noritake), and 3D printed 4Y-TZP (3DMAT; Genoss). The biaxial flexural strength was determined with a piston-on-3-ball test (n=15). The flexural strength of each specimen was measured, and the Weibull modulus (m) and characteristic strength (σ0) were estimated from the fracture load distribution. Two intact and fractured specimens were examined with scanning electron microscopy (SEM). The crystalline phase of the specimens in each group was identified through X-ray diffraction (XRD) analysis (n=5). A 1-way ANOVA was used to compare the flexural strength among different groups. Subsequently, pairwise comparisons were conducted with the Tukey post hoc method (α=.05). RESULTS: The flexural strength of 3D printed 4Y-TZP was significantly higher than that of milled 4Y-TZP (P<.001). In contrast, the flexural strength of 3D printed 3Y-TZP was significantly lower than that of milled 3Y-TZP (P<.001). X-ray diffraction (XRD) analysis revealed that the tetragonal phase was the dominant phase in all groups, with the identification of some cubic phase peaks. CONCLUSIONS: Three dimensionally printed 4Y-TZP showed significantly higher flexural strength than milled 4Y-TZP and exhibited a clinically acceptable flexural strength exceeding 800 MPa.

Precise implant placement with a computer-assisted surgical guide in cleft lip and palate patients.

It is very common for cleft lip and palate patients to have congenitally missing teeth. Insufficient buccopalatal bone volume, a shallow vestibule, and lack of soft tissue resulting from previous surgical scarring render it difficult for clinicians to place implants in the missing area. This report describes guide surgery that represents a treatment option for cases in which implants need to be placed in tight spaces with minimal bone space, to minimize as far as possible manual placement errors.

Precise Implant Placement With a Computer-Assisted Surgical Guide in Cleft Lip and Palate Patients.

It is very common for cleft lip and palate patients to have congenitally missing teeth. Insufficient buccopalatal bone volume, a shallow vestibule, and lack of soft tissue resulting from previous surgical scarring render it difficult for clinicians to place implants in the missing area. This report describes guide surgery that represents a treatment option for cases in which implants need to be placed in tight spaces with minimal bone space, to minimize as far as possible manual placement errors.

The study of anatomic structures in establishing the posterior seal area for maxillary complete dentures.

STATEMENT OF PROBLEM: The spatial relationship between the foveae palatinae and vibrating lines varies among individuals; such variability could be related to the contour of the palate. PURPOSE: The purpose of this study was to investigate the relative location of the foveae palatinae and vibrating lines and to determine the correlation between the seal area of the posterior palate and the palatal contour with lateral cephalogram radiography. MATERIAL AND METHODS: Fifty participants were examined. The Valsalva maneuver was used to determine the anterior vibrating line, and the phonation ('ah') method was used to detect the posterior vibrating line. The distance from the anterior to the posterior vibrating line and the distances between the foveae palatinae and the anterior and posterior vibrating lines were measured. A lateral cephalogram was made to trace the hard and soft palate contour, and the angle of the palatal contour was measured with the V-ceph program. Correlation analysis was conducted with statistical software to examine the relation between the distance from the anterior to the posterior vibrating line and the angle of the palatal contour at the junction of the hard and soft palate. RESULTS: The anterior vibrating line was located approximately 2.58 ±1.19 mm anterior to the foveae palatinae, and the posterior vibrating line was located 0.71 ±0.68 mm posterior. A positive correlation was found between the distance from the anterior to the posterior vibrating line in the lateral sagittal plane and the angle of the palatal contour at the junction of the hard and soft palate. Correlation coefficients were 0.495 in the left sagittal plane and 0.560 in the right sagittal plane (P<.05). CONCLUSIONS: Considering their proximity to the posterior vibrating line, the foveae palatinae could be reliable reference points for locating the posterior border of the maxillary denture. The results of this study also suggest that a wider posterior palatal seal area could be obtained if the patient has a gentle palatal contour at the junction of the hard and soft palate.