Search

(1) This study aimed to evaluate the influences of differences in denture teeth shade on harmony ratings and esthetic quality. Particular attention was paid to the question of how the overall variance of shade differences in the dental arch influences the perception of shade differences between adjacent teeth. (2) A total of 51 pictures of upper front teeth with standardized different colors of the left central incisor and different color variance of the dental arch were created. Eighty participants without dental knowledge and of different age, sex and educational level rated the pictures on a visual analogue scale from 0 (strongly disagree) to 100 (strongly agree) with regards to esthetic and color equality. (3) Results: The color differences between two teeth were judged in a negative linear correlation to the evaluation of color and esthetic quality. There was a sex- and education-specific difference in color and harmony ratings. In relation to the age of the participants, there was a significant difference in the color rating (p = 0.01) but not in the harmony rating (p = 0.27). Lower rating of color difference and harmony was found for a color difference in the dental arch up to ΔE = 3.1. In contrast, higher color differences resulted in higher ratings. (4) There is an influence of personal parameters on color perception. Color inhomogeneity in a dental arch leads to significant differences in color and harmony rating in a non-linear relation. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the retentive behavior of the Locator legacy and Novaloc attachment systems with different retention inserts both within and across systems under cyclic load. Materials and methods: Three retention inserts of each system (green, yellow, and white for Novaloc; green, orange, and red inserts for extended range for legacy Locator) were tested on abutments of both systems with a sample number of 10 per force and 10,000 cycles of insertion and removal. The loading was applied in the axial direction of the abutments, which were placed in artificial saliva. The retention force was measured in each cycle. The results were compared with the manufacturer's specifications and evaluated for a simulated period of use of 10 years. Characteristic time constants were determined, and subsequently, the two systems were compared regarding their wear behavior. Results: The manufacturer's specifications could only be confirmed for the green Novaloc retention insert on a Novaloc abutment (t‐test: p = 0.50); for all other inserts, the baseline exceeded the manufacturer's specifications by 30%–75% (Novaloc; t‐test: p < 0.001) and 75%–550% (Locator; t‐test: p < 0.001). After 10,000 cycles performed, the manufacturer's specifications were confirmed on a Novaloc abutment for the white Novaloc retention insert (t‐test: p = 0.86) and on a Locator abutment for the green Novaloc retention insert (t‐test: p = 0.32). Both systems lost retention force during the experiment. Overall, Novaloc inserts on both abutments showed less wear (decrease to 56%–85% of initial force) and a slower decrease in retention force compared to Locator inserts (decrease to 6%–31% of initial force). Conclusions: In both systems, wear leads to a varying loss of retention; therefore, regular checks with possible replacement of the inserts are necessary in clinical use. Novaloc attachments seem to be more resistant to the loss of retention than Locator attachments. A cross‐combination may be clinically useful in some cases. [ABSTRACT FROM AUTHOR]

Digital holography enables a multifocus quantitative phase microscopy for the investigation of reflective surfaces and for marker-free live cell imaging. For digital holographic long-term investigations of living cells an automated (subsequent) robust and reliable numerical focus adjustment is of particular importance. Four numerical methods for the determination of the optimal focus position in the numerical reconstruction and propagation of the complex object waves of pure phase objects are characterized, compared, and adapted to the requirements of digital holographic microscopy. Results from investigations of an engineered surface and human pancreas tumor cells demonstrate the applicability of Fourier-weighting- and gradient-operator-based methods for robust and reliable automated subsequent numerical digital holographic focusing. OCIS codes: 090.1995, 180.0180.

Purpose: Computer-aided technologies have been recently employed for use in extracorporeal bone tissue engineering strategies. In this pilot animal experimental study, the intention was to test whether autologous osteoblast-like cells cultured in vitro on individualized scaffolds can be used to support bone regeneration in a clinical environment. Materials and Methods: For this purpose, mandibular bone defects were surgically introduced into the mandibles of minipigs and the scaffold of the defect site was modeled by computer-aided design/computer-aided manufacturing technique. Autologous bone cells from porcine calvaria were harvested from minipigs and grown in culture. Cells were seeded on scaffolds generated by rapid prototyping of polylactic acid/polyglycolic acid copolymers. The defects were then reconstructed by implanting the tissue constructs. Results: The intraoperative sites as well as the postoperative computerized tomographic scans demonstrated an accurate fit in the defect sites. The implanted scaffold constructs enriched with osteoblast-like cells were well tolerated and appeared to support bone formation, as revealed by histologic and immunohistochemical analyses. Discussion: These results indicated that in vitro expanded osteoblast-like cells spread on a resorbable individualized scaffold can be capable of promoting the repair of bony defects in vivo. Conclusion: These results warrant further attempts to combine computer modeling and tissue engineering for use in bone reconstructive surgery. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the study was to measure the influence of the maxillary central incisors free from adaptation phenomena using spectral analysis. Materials and Methods: The maxillary dentures of 18 subjects were duplicated. The central incisors were fixed in a pivoting appliance so that their position could be changed from labial to palatal direction. A mechanical push/pull cable enabled the incisor section to be handled extraorally. Connected to the control was a sound generator producing a sinus wave whose frequency was related to the central incisor angulation. This acoustic signal was recorded on one channel of a digital tape recorder. After calibration of the unit, the denture duplicate was inserted into the subject's mouth, and the signal of the /s/ sounds subsequently produced by the subject was recorded on the second channel during alteration of the inclination angle simultaneously with the generator signal. Spectral analysis was performed using a Kay Speech-Lab 4300B. Results: Labial displacement in particular produced significant changes in spectral characteristics, with the lower boundary frequency of the /s/ sound being raised and the upper boundary frequency being reduced. Conclusion: Maxillary incisor position influences /s/ sound production. Displacement of the maxillary incisors must be considered a cause of immediate changes in /s/ sound distortion. Therefore, denture teeth should be placed in the original tooth position as accurately as possible. Our results also indicate that neuromuscular reactions are more important for initial speech sound distortions than are aerodynamic changes in the anterior speech sound-producing areas. [ABSTRACT FROM AUTHOR]

Purpose: The conventional impression technique for manufacturing facial prostheses has the disadvantage of deforming the soft tissues because of the tension caused by the impression material, as well as causing discomfort to the patient. The purpose of this study was to establish a system that allows contact-free reproduction of the facial surface combined with computer-assisted design and fabrication of facial prostheses. Materials and Methods: Three-dimensional data of the facial surface were obtained using an optical acquisition system based on the method of phase-measuring profilometry. A sensor head with a fringe projector and two CCD cameras for photogrammetric triangulation were used in connection with a PC for measurement control and data evaluation. Software for computer-assisted design of the facial surface to be reconstructed was developed. A prototype facial prosthesis was fabricated using stereolithography. The system was tested using a modified puppet head. First clinical tests were performed with a patient who had undergone maxillofacial surgery including the resection of one eye. Results: Three dimensional data acquisition and imaging allow visualization of a whole face without causing tension or neuromuscular reaction. As surface brightness is also part of the digital model, it is even more realistic than a plaster cast. The stereolithographic object showed good marginal fit and satisfactory shape. Conclusion: The presented technique allows three-dimensional data reproduction of the facial surface, computer-assisted design of a facial prosthesis, and transfer to a rapid prototyping unit. The system has obvious advantages over conventional impression techniques. Further clinical trials are planned to evaluate the clinical success of the technique. [ABSTRACT FROM AUTHOR]

Purpose: The risks of radiotherapy to normal tissues are well known. In many cases, a tumor patient suffering a relapse cannot undergo radiotherapy a second time. One exception may be the local application of brachytherapy. Afterloading devices allow the position of radiating materials near the site for treatment exactly according to three-dimensional treatment planning. This report shows the technical procedure for the fabrication of an intracavitary afterloading radiation device. Materials and Methods: A 48-year-old woman who had received neutron radiotherapy and tumor surgery for adenoid cystic carcinoma had to be treated for relapse. The mouth opening was limited to 15 mm. The mixing tip of a silicone impression system was used as an axis for a pivoting appliance. Results: Two years after reradiation, the patient was free of relapse symptoms, although an increased limitation of mouth opening was recorded. Conclusion: Even if the mouth opening is severely limited after tumor surgery and/or radiation, intracavitary brachytherapy still can be performed in edentulous patients using a pivoting device. [ABSTRACT FROM AUTHOR]