Wei-Shao Lin

The Effect of Core Material, Veneering Porcelain, and Fabrication Technique on the Biaxial Flexural Strength and Weibull Analysis of Selected Dental Ceramics

PURPOSE The objective of this study was to compare the effect of veneering porcelain (monolithic or bilayer specimens) and core fabrication technique (heat-pressed or CAD/CAM) on the biaxial flexural strength and Weibull modulus of leucite-reinforced and lithium-disilicate glass ceramics. In addition, the effect of veneering technique (heat-pressed or powder/liquid layering) for zirconia ceramics on the biaxial flexural strength and Weibull modulus was studied. MATERIALS AND METHODS Five ceramic core materials (IPS Empress Esthetic, IPS Empress CAD, IPS e.max Press, IPS e.max CAD, IPS e.max ZirCAD) and three corresponding veneering porcelains (IPS Empress Esthetic Veneer, IPS e.max Ceram, IPS e.max ZirPress) were selected for this study. Each core material group contained three subgroups based on the core material thickness and the presence of corresponding veneering porcelain as follows: 1.5 mm core material only (subgroup 1.5C), 0.8 mm core material only (subgroup 0.8C), and 1.5 mm core/veneer group: 0.8 mm core with 0.7 mm corresponding veneering porcelain with a powder/liquid layering technique (subgroup 0.8C-0.7VL). The ZirCAD group had one additional 1.5 mm core/veneer subgroup with 0.7 mm heat-pressed veneering porcelain (subgroup 0.8C-0.7VP). The biaxial flexural strengths were compared for each subgroup (n = 10) according to ISO standard 6872:2008 with ANOVA and Tukeys post hoc multiple comparison test (p≤ 0.05). The reliability of strength was analyzed with the Weibull distribution. RESULTS For all core materials, the 1.5 mm core/veneer subgroups (0.8C-0.7VL, 0.8C-0.7VP) had significantly lower mean biaxial flexural strengths (p < 0.0001) than the other two subgroups (subgroups 1.5C and 0.8C). For the ZirCAD group, the 0.8C-0.7VL subgroup had significantly lower flexural strength (p= 0.004) than subgroup 0.8C-0.7VP. Nonetheless, both veneered ZirCAD groups showed greater flexural strength than the monolithic Empress and e.max groups, regardless of core thickness and fabrication techniques. Comparing fabrication techniques, Empress Esthetic/CAD, e.max Press/CAD had similar biaxial flexural strength (p= 0.28 for Empress pair; p= 0.87 for e.max pair); however, e.max CAD/Press groups had significantly higher flexural strength (p < 0.0001) than Empress Esthetic/CAD groups. Monolithic core specimens presented with higher Weibull modulus with all selected core materials. For the ZirCAD group, although the bilayer 0.8C-0.7VL subgroup exhibited significantly lower flexural strength, it had highest Weibull modulus than the 0.8C-0.7VP subgroup. CONCLUSIONS The present study suggests that veneering porcelain onto a ceramic core material diminishes the flexural strength and the reliability of the bilayer specimens. Leucite-reinforced glass-ceramic cores have lower flexural strength than lithium-disilicate ones, while fabrication techniques (heat-pressed or CAD/CAM) and specimen thicknesses do not affect the flexural strength of all glass ceramics. Compared with the heat-pressed veneering technique, the powder/liquid veneering technique exhibited lower flexural strength but increased reliability with a higher Weibull modulus for zirconia bilayer specimens. Zirconia-veneered ceramics exhibited greater flexural strength than monolithic leucite-reinforced and lithium-disilicate ceramics regardless of zirconia veneering techniques (heat-pressed or powder/liquid technique).

The use of a scannable impression coping and digital impression technique to fabricate a customized anatomic abutment and zirconia restoration in the esthetic zone.

This report described the fabrication of a customized anatomic abutment and zirconia restoration in the esthetic zone with a digital pathway. The implant level impression was made with a scannable impression coping and intraoral digital scanner. The milled definitive polyurethane cast with corresponding implant analog, customized anatomic abutment, and definitive zirconia restoration were made with a computer-aided design and computer-aided manufacturing (CAD/CAM) process.

Use of digital data acquisition and CAD/CAM technology for the fabrication of a fixed complete dental prosthesis on dental implants

The work flow in this report describes a metal-resin fixed complete dental prosthesis fabricated by using digital data acquisition at the implant fixture level with a computer-aided design and computer-aided manufacturing (CAD/CAM) fabricated tissue-colored anodized titanium framework.

A retrospective study of complications associated with 100 consecutive maxillary sinus augmentations via the lateral window approach.

PURPOSE To report the complications encountered during 100 consecutive maxillary sinus augmentations via the lateral window approach and to propose solutions to manage these complications. MATERIALS AND METHODS Pretreatment residual bone heights and the presence of septa were recorded. The incidences of any intraoperative or postoperative sinus complications such as excessive bleeding, membrane perforation, infection, wound dehiscence, sinusitis, loss of bone graft, and implant success were reported. results: This study evaluated 42 men and 44 women requiring 100 consecutive sinus elevation procedures between March 2008 and February 2011. Five intraoperative membrane perforations were noted, and one subsequently developed an active infection (2 weeks after surgery). Eight instances of suppuration were noted, while 10 sites presented with wound dehiscence 1 to 2 weeks after surgery. One example of partial loss of the bone graft 6 months after surgery was identified. Of a total of 151 implants placed in 97 sinuses (one patient with bilateral sinuses and one with unilateral sinus did not complete implant placement), 2 implants presented excessive bone loss prior to uncovering. One implant was removed and one was left submerged. conclusions: Sinus floor elevation utilizing the lateral window approach is a predictable approach to manage bone volume deficiency in the posterior maxilla for patients seeking dental implant-based treatment. However, complications may include membrane tear, infection, wound dehiscence, loss of graft, and implant failure. It is vital for the clinician to understand how to recognize and solve these complications.

Use of implant-supported interim restorations to transfer periimplant soft tissue profiles to a milled polyurethane definitive cast.

A customized impression coping is often used in conjunction with conventional implant impression techniques to transfer a well-defined periimplant soft tissue profile resulting from an implant-supported interim restoration to the definitive cast with a removable gingival replica and achieve the desired esthetic outcome of the definitive restorations. However, a direct line of sight between the intraoral scanner and the periimplant soft tissue is needed during the data acquisition of the digital impression techniques, and it is not possible to use customized scannable impression copings to support periimplant soft tissue. This study describes a clinical technique with implant-supported interim restorations to transfer desired periimplant soft tissue profiles to the milled definitive polyurethane cast with a removable periimplant soft tissue replica to maximize the esthetic outcome of the definitive restorations.

Use of intraoral digital scanning for a CAD/CAM-fabricated milled bar and superstructure framework for an implant-supported, removable complete dental prosthesis.

This report describes a clinical technique for fabricating a maxillary implant-supported, removable complete dental prosthesis by using an intraoral digital scanner to register implant positions and soft tissue morphology. The presented technique uses computer-aided design/computer-aided manufacturing (CAD/CAM) technology with a subtractive manufacturing process to fabricate a milled bar (infrastructure framework) and an additive process to fabricate a friction fit, superstructure framework. This digital restorative pathway may decrease patient discomfort and reduce the labor associated with fabricating implant-supported, removable complete dental prostheses.

Creation of a 3-dimensional virtual dental patient for computer-guided surgery and CAD-CAM interim complete removable and fixed dental prostheses: A clinical report

This clinical report proposes a digital workflow using 2-dimensional (2D) digital photographs, a 3D extraoral facial scan, and cone beam computed tomography (CBCT) volumetric data to create a 3D virtual patient with craniofacial hard tissue, remaining dentition (including surrounding intraoral soft tissue), and the realistic appearance of facial soft tissue at an exaggerated smile under static conditions. The 3D virtual patient was used to assist the virtual diagnostic tooth arrangement process, providing patient with a pleasing preoperative virtual smile design that harmonized with facial features. The 3D virtual patient was also used to gain patients pretreatment approval (as a communication tool), design a prosthetically driven surgical plan for computer-guided implant surgery, and fabricate the computer-aided design and computer-aided manufacturing (CAD-CAM) interim prostheses.

The influence of digital fabrication options on the accuracy of dental implant-based single units and complete-arch frameworks.

PURPOSE To compare the accuracy and reproducibility of digital versus conventional dental impressions and fabrication techniques for single units and full-arch implant frameworks. MATERIALS AND METHODS A total of 24 samples, divided into four groups, were created using conventional and digital implant impression/fabrication techniques: group 1 (conventional single implant), group 2 (digital single implant), group 3 (conventional complete arch), and group 4 (digital complete arch). All impressions were made at the abutment level. Marginal fit measurements were made using an optical microscope at two points (buccal and lingual) for each sample. Statistical analysis was performed using F and t tests (α = .05). RESULTS For single implants, the conventional impression/fabrication pathway resulted in a mean marginal discrepancy of 24.1 μm compared to 61.43 μm for the digital impression/fabrication pathway. For full-arch frameworks, the conventional impression/fabrication pathway resulted in a mean marginal discrepancy of 135.1 μm compared to 63.14 μm for the digital technique. CONCLUSION The conventional pathway resulted in a smaller marginal discrepancy for single-implant frameworks. In contrast, the digital pathway resulted in a smaller marginal discrepancy for full-arch implant frameworks.

Effect of Implant Divergence on the Accuracy of Definitive Casts Created from Traditional and Digital Implant-Level Impressions: : An In Vitro Comparative Study

PURPOSE The purpose of this research was to compare the accuracy of definitive casts created with digital and conventional methods for implants with internal-octagon connections placed parallel or at different angles (15, 30, or 45 degrees). MATERIALS AND METHODS Four customized epoxy resin master casts were fabricated with two-implant analogs placed in the posterior mandible with different degrees of divergence. For the conventional (control) group, 10 traditional impressions were taken on each master cast with custom trays, open-tray impression copings, and polyvinyl siloxane; definitive stone casts were poured with type IV dental stone. For the digital group, 10 digital impressions were taken on each master cast with two-piece scannable impression copings and an intraoral digital scanner; definitive milled polyurethane casts were fabricated by the manufacturer. All four master casts and 80 control and test casts were scanned and digitized, and the data sets were compared. Any deviations in measurements between the definitive and corresponding master casts were analyzed statistically. RESULTS The amount of divergence between implants did not affect the accuracy of the stone casts created conventionally; however, it significantly affected the accuracy of the milled casts created digitally. A decreasing linear trend in deviations for both distance and angle measurements suggested that the digital technique was more accurate when the implants diverged more. At 0 and 15 degrees of divergence, the digital method resulted in highly significantly less accurate definitive casts. At 30 and 45 degrees of divergence, however, the milled casts showed either no difference or marginal differences with casts created conventionally. CONCLUSION The digital pathway produced less accurate definitive casts than the conventional pathway with the tested two-implant scenarios. To ensure passive fit of definitive prostheses, verification devices and casts may be used when materials are produced digitally.

Maxillary rehabilitation with a CAD/CAM-fabricated, long-term interim and anatomic contour definitive prosthesis with a digital workflow: A clinical report

The digital workflow in this clinical report describes a maxillary rehabilitation with an articulator-free and definitive cast-free treatment protocol for computer-aided design and computer-aided manufacturing (CAD/CAM) fabricated long-term interim and anatomic contour monolithic lithium disilicate definitive restorations.