A Novel Technique for the Connection of Ceramic and Titanium Implant Components Using Glass Solder Bonding.

Both titanium and ceramic materials provide specific advantages in dental implant technology. However, some problems, like hypersensitivity reactions, corrosion and mechanical failure, have been reported. Therefore, the combining of both materials to take advantage of their pros, while eliminating their respective cons, would be desirable. Hence, we introduced a new technique to bond titanium and ceramic materials by means of a silica-based glass ceramic solder. Cylindrical compound samples (Ø10 mm × 56 mm) made of alumina toughened zirconia (ATZ), as well as titanium grade 5, were bonded by glass solder on their end faces. As a control, a two-component adhesive glue was utilized. The samples were investigated without further treatment, after 30 and 90 days of storage in distilled water at room temperature, and after aging. All samples were subjected to quasi-static four-point-bending tests. We found that the glass solder bonding provided significantly higher bending strength than adhesive glue bonding. In contrast to the glued samples, the bending strength of the soldered samples remained unaltered by the storage and aging treatments. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses confirmed the presence of a stable solder-ceramic interface. Therefore, the glass solder technique represents a promising method for optimizing dental and orthopedic implant bondings.

High-frequency ultrasound as an option for scanning of prepared teeth: an in vitro study.

Because of its ability to non-invasively capture hard structures behind soft tissue, high-frequency ultrasound (HFUS)-assisted microscanning could be a patient-friendly and promising alternative for digitization of prepared teeth. However, intra-oral HFUS microscanners for taking digital impressions of prepared teeth are still not available in the clinical setting. Because working range, scanner size, scanning time, surface reconstruction accuracy and costs are major factors in such a system, our overall objective is to minimize hardware efforts and costs while maintaining the accuracy of the surface-reconstructed tooth model in the range 50 µm. In the work described here, we investigated the accuracy of tooth impression taking using a single-element HFUS microscanner with only three translational degrees of freedom under the restriction that only one occlusal scan is performed per tooth. As in favor of time and scanning efforts the data density is expected to be low, the surface reconstruction process is linked to a model-based surface reconstruction approach using a thin spline robust point matching algorithm to fill data gaps. A priori knowledge for the model is generated based on the original HFUS measurement data. Three artificial teeth and one human molar were prepared and scanned using an extra-oral HFUS laboratory microscanner that was built to test and evaluate different scanning setups. A scanner with three translational degrees of freedom was used to scan the teeth from an occlusal direction. After application of the proposed thin-spline robust point matching algorithm-based reconstruction approach, reconstruction accuracy was assessed by comparing the casts with a control group scanned with an extra-oral laser-scanning system. The mean difference between the reconstructed casts and the optical control group was in the range 14-53 µm. The standard deviation was between 21 and 52 µm. This let us assume that the suggested approach can help to decrease hardware efforts while maintaining the robustness of the 3-D surface reconstruction process for future HFUS-based intra-oral scanners.

Soft tissue-preserving computer-aided impression: a novel concept using ultrasonic 3D-scanning.

Subgingival preparations are often affected by blood and saliva during impression taking, regardless of whether one is using compound impression techniques or intraoral digital scanning methods. The latter are currently based on optical principles and therefore also need clean and dry surfaces. In contrast, ultrasonic waves are able to non-invasively penetrate gingiva, saliva, and blood, leading to decisive advantages, as cleaning and drying of the oral cavity becomes unnecessary. In addition, the application of ultrasound may facilitate the detection of subgingival structures without invasive manipulation, thereby reducing the risk of secondary infection and treatment time, and increasing patient comfort. Ultrasound devices commonly available for medical application and for the testing of materials are only suitable to a limited extent, as their resolution, precision, and design do not fulfill the requirements for intraoral scanning. The aim of this article is to describe the development of a novel ultrasound technology that enables soft tissue-preserving digital impressions of preparations for the CAD/CAM-based production of dental prostheses. The concept and development of the high-resolution ultrasound technique and the corresponding intraoral scanning system, as well as the integration into the CAD/CAM process chain, is presented.

Recent advances of ultrasound imaging in dentistry--a review of the literature.

Ultrasonography as an imaging modality in dentistry has been extensively explored in recent years due to several advantages that diagnostic ultrasound provides. It is a non-invasive, inexpensive, painless method and unlike X-ray, it does not cause harmful ionizing radiation. Ultrasound has a promising future as a diagnostic imaging tool in all specialties in dentistry, for both hard and soft tissue detection. The aim of this review is to provide the scientific community and clinicians with an overview of the most recent advances of ultrasound imaging in dentistry. The use of ultrasound is described and discussed in the fields of dental scanning, caries detection, dental fractures, soft tissue and periapical lesions, maxillofacial fractures, periodontal bony defects, gingival and muscle thickness, temporomandibular disorders, and implant dentistry.

Five-year clinical evaluation of all-ceramic posterior FDPs made of In-Ceram Zirconia.

The aim of this prospective study was to evaluate the clinical outcomes of three and four-unit posterior fixed dental prostheses (FDPs) made of In-Ceram Zirconia. Twenty FDPs were inserted in 15 patients. Over a mean observation period of 74.6 months, the survival rate was 85%. Sixty-five percent of cases did not allow for connector dimensions that met the manufacturer's recommendations without the use of surgical procedures (eg, crown lengthening). Posterior all-ceramic FDPs made of In-Ceram Zirconia appear to be a viable prosthetic treatment option to replace a missing tooth.

In vitro study of adhesive polymethylmethacrylate bone cement bonding to cortical bone in maxillofacial surgery.

PURPOSE: In the treatment of midface fractures, the fragments are immobilized using screws and plates for osteosynthesis until reunion has occurred. This method involves drilling holes for the insertion of the screws, which can be associated with additional fracturing of the corresponding bone owing to the complex architecture and thin layers of facial bone. To alleviate this problem, new adhesive techniques for fixing the plates for osteosynthesis have been investigated, mitigating the detrimental effects of screw hole drilling. In the present experimental study, the strength of this adhesive bond and its resistance to hydrolysis were investigated. MATERIALS AND METHODS: To determine the adhesive bonding strength, a tension test was implemented. Osteosynthesis plates with screw holes 1.3 mm in diameter were fixed to cortical bone samples of bovine femur using ultraviolet (UV) light-curing polymethylmethacrylate bone cement. To facilitate bonding, the surface of the bone was conditioned with an amphiphilic bonding agent before cementing. UV light curing was implemented using either a conventional UV unit, such as is used in dentistry, or with a specialized UV unit with a limited emission spectrum but high luminosity. Reference control samples were prepared without application of the bone bonding agent. After this procedure, the samples were stored for 1 to 7 days at 37°C submerged in 0.9% saline solution before being subjected to the tension test. RESULTS: Without the bone bonding agent, the bonding strength was 0.2 MPa. The primary average bonding strength at day 0 was 8.5 MPa when cured with the conventional UV unit and 14 MPa for the samples cured with the specialized UV unit. An almost constant average bond strength of 8 and 16 MPa was noted for all samples stored up to 7 days after curing with the conventional and specialized UV unit, respectively. CONCLUSION: With the development of a new bone bonding agent, a method is now available to promote the bonding between the hydrophilic bone surface and the hydrophobic polymethylmethacrylate bone cement by creating an interlayer that is beneficial for adhesion. In the present in vitro study, the strength of this bond and its resistance to hydrolysis were investigated. This new method could have clinical bearing in cases in which conventional fixation with screws and plates is limited, such as can occur in comminuted fractures. The observed average bonding strengths of 8 to 16 MPa support the implementation of this technique in nonload-bearing regions such as the midface, facilitating immobilization until the bone reunion is complete.

Clinical behavior of zirconia-based fixed partial dentures made of DC-Zirkon: 3-year results.

PURPOSE: The aim of this prospective study was to evaluate the clinical performance of anterior and posterior fixed partial dentures (FPDs) with frameworks made using DC-Zirkon after a mean observation time of 3 years. MATERIALS AND METHODS: Forty-six patients with 1 to 3 missing anterior or posterior teeth were included in this study. All abutment teeth were prepared for full crowns with a chamfer preparation of 0.6 to 0.8 mm. The zirconia frameworks were produced with the Precident DCS system and veneered with veneering porcelain (Vita D). A self-curing resin cement was used for the anterior FPDs and a conventional zinc oxide phosphate cement was used for the posterior FPDs. RESULTS: Fifteen anterior FPDs and 50 posterior FPDs were recalled at least once a year after cementation. The mean observation period was 38 (+/- 18.0) months for the anterior FPDs and 37 (+/- 15.5) months for the posterior FPDs. Within the observation time, no remakes were necessary, but in 4 cases a small chipping of the veneering material occurred in the posterior region. Two FPDs were recemented after decementation, and 3 teeth needed endodontic treatment. No negative influences at the gingival margin were observed. CONCLUSIONS: Within the mean observation time of 3 years, zirconia-based FPDs demonstrated a sufficient success rate under clinical conditions. However, special attention should be paid to designing the zirconia framework to ensure a sufficient veneering layer thickness with a range between 1 to 2 mm.

A new adhesive technique for internal fixation in midfacial surgery.

BACKGROUND: The current surgical therapy of midfacial fractures involves internal fixation in which bone fragments are fixed in their anatomical positions with osteosynthesis plates and corresponding screws until bone healing is complete. This often causes new fractures to fragile bones while drilling pilot holes or trying to insert screws. The adhesive fixation of osteosynthesis plates using PMMA bone cement could offer a viable alternative for fixing the plates without screws. In order to achieve the adhesive bonding of bone cement to cortical bone in the viscerocranium, an amphiphilic bone bonding agent was created, analogous to the dentin bonding agents currently on the market. METHODS: The adhesive bonding strengths were measured using tension tests. For this, metal plates with 2.0 mm diameter screw holes were cemented with PMMA bone cement to cortical bovine bone samples from the femur diaphysis. The bone was conditioned with an amphiphilic bone bonding agent prior to cementing. The samples were stored for 1 to 42 days at 37 degrees C, either moist or completely submerged in an isotonic NaCl-solution, and then subjected to the tension tests. RESULTS: Without the bone bonding agent, the bonding strength was close to zero (0.2 MPa). Primary stability with bone bonding agent is considered to be at ca. 8 MPa. Moist storage over 42 days resulted in decreased adhesion forces of ca. 6 MPa. Wet storage resulted in relatively constant bonding strengths of ca. 8 MPa. CONCLUSION: A new amphiphilic bone bonding agent was developed, which builds an optimizied interlayer between the hydrophilic bone surface and the hydrophobic PMMA bone cement and thus leads to adhesive bonding between them. Our in vitro investigations demonstrated the adhesive bonding of PMMA bone cement to cortical bone, which was also stable against hydrolysis. The newly developed adhesive fixing technique could be applied clinically when the fixation of osteosynthesis plates with screws is impossible. With the detected adhesion forces of ca. 6 to 8 MPa, it is assumed that the adhesive fixation system is able to secure bone fragments from the non-load bearing midfacial regions in their orthotopic positions until fracture consolidation is complete.

Lifetime of alumina- and zirconia ceramics used for crown and bridge restorations.

The lifetime of a ceramic is dependent on the presence of incidental cracks and their gradual propagation under the conditions of the oral cavity. The objective of this study was to examine the long-term strength of glass-infiltrated alumina- and various zirconia ceramics currently used in CAD/CAM systems to manufacture crown and bridge frameworks. Fracture mechanics were applied to determine characteristic strength (sigma(omicron)), Weibull modulus (m), fracture toughness (K(Ic)), and the subcritical crack growth parameters n and B. Based on these parameters, lifetime diagrams were generated which allowed the evaluation of the long-term behavior. The results showed that in a moist environment, the glass-infiltrated alumina- and some zirconia ceramics have a high susceptibility to subcritical crack growth. Zirconia ceramics with an alumina oxide content of 0.25 wt %, however, exhibited the highest initial and most favorable long-term strength, and should therefore be suitable for crown and bridge restorations.

Spectroscopic analysis of polymer-ceramic dental composites after accelerated aging.

PURPOSE: The aim of the study was to determine the color and surface chemistry changes of two fiber-reinforced composites and one "advanced composite" as a function of an accelerated aging process by light exposure and water spray. MATERIALS AND METHODS: Three composites (Artglass, Targis, and Conquest Sculpture) were assessed for color evaluation in three different shades and with XPS analysis. Four specimens of each shade were analyzed with the UV/VIS/NIR Spectrophotometer in reflectance to determine the baseline color for the CIE L*a*b* system. XPS spectra were obtained from three specimens for each material group. All sample disks were artificially aged in a weathering machine and exposed to water spray and a controlled irradiance xenon arc of 0.55 W/m2/nm measured at 340 nm for a total exposure time of 122 hours. L*a*b* and XPS analyses were repeated after the aging process for all specimens. RESULTS: Artglass had "just perceptible," changes, with deltaE* between 1.8 and 2.7, while Conquest Sculpture showed, in all shades, "visually perceptible" changes from deltaE* 5 to 9. Targis had just perceptible as well as visually perceptible changes after aging. All materials showed decreased Ba and Si on the aged samples, while carbon increased. CONCLUSION: All materials tested underwent a surface change after the aging process. Artglass and Targis changed minimally into whitish/reddish and yellowish appearances, respectively. An organic-rich surface was produced by a combination of washout of filler particles and rearrangement of polymer molecules through diffusion.