[Checking the dimensional stability and accuracy from casting material copies (author's transl)].
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The burgeoning popularity of motion pictures in dental education, despite the absence of supporting data, presents the possibility that the medium is being used uncritically. Assumptions underlying the choice and production of dental films are enumerated and critiqued. The assumption that the typical dental procedure film provides a useful model of dental motions is seriously questioned. Potentially superior alternatives are proposed.
The quality of clinical decision making is limited by the performance of human cognitive processing of complex visual information. In the field of oral implantology, treatment planning is still based on the holistic interpretation and mental reconstruction of cross sectional 2d-image data. This surpasses widely human cognitive competence and hampers treatment planning in three dimensions that are essential in implantology. To overcome these problems, a virtual reality environment for enhanced treatment planning in oral implantology is presented, which provides a fully three-dimensional perception of an individual clinical situation. It enables the clinician to perceive and handle the objects of her work in a virtual world as needed for the task of diagnosis and treatment. Human visual decoding effort is thus reduced, and estimating the real position and orientation of implants during planning is enabled in any direction. Immersive three-dimensional perception is achieved by hybrid stereoscopic rendering techniques combined with large screen projections. The virtual world in which treatment planning takes place allows the clinician to move and interact with the individual anatomy simultaneously with three degrees of freedom. A set of virtual tools enables the clinician to perform a virtual treatment "in advance." The design and placement of implants, as it is interactively controlled by the clinician, is simulated in real-time. Thus the results of actions become immediately visible and provide visible feedback for interactive adjustment. In addition, the presented virtual reality environment for oral implant treatment planning includes algorithms for detection of inappropriate treatment in the concerned bone regions, according to the current design of the implant. These algorithms take both the individual properties of a patient's bone and the type of implants used into account.
Three impression techniques were assessed for accuracy in a laboratory cast that simulated clinical practice. The first technique used autopolymerizing acrylic resin to splint the transfer copings. The second involved splinting of the transfer copings directly to an acrylic resin custom tray. In the third, only impression material was used to orient the transfer copings. The accuracy of stone casts with implant analogs was measured against a master framework. The fit of the framework on the casts was tested using strain gauges. The technique using acrylic resin to splint transfer copings in the impression material was significantly more accurate than the two other techniques. Stresses observed in the framework are described and discussed with suggestions to improve clinical and laboratory techniques.
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BACKGROUND: Having laboratory technicians prepare soft-tissue casts and implant abutments with or without concomitant removable temporary prostheses during the restorative phase of single-tooth replacement is an accepted practice. It can, however, result in functional and esthetic intraoral discrepancies. CASE DESCRIPTION: Single-tooth implants can be restored with crowns (like those for natural teeth) fabricated at a dental laboratory on casts obtained from final impressions of prepared implant abutments. In the case reported, the restorative dentist restored the patient's single-tooth implant after taking a transfer impression. He constructed a cast simulating the peri-implant soft tissue with final impression material and prepared the abutment on this model. His dental assistant then fabricated a fixed provisional restoration on the prepared abutment. At the patient's next visit, the dentist torqued the prepared abutment onto the implant, took a final impression and inserted the provisional restoration. A crown was made conventionally at the dental laboratory and cemented in place at the following visit. CLINICAL IMPLICATIONS: This alternative method for restoring single-tooth implants enhances esthetics by more accurately simulating marginal gingival architecture. It also improves function by preloading the implant through fixed temporization after the dentist, rather than the laboratory technician, prepares the abutment to the dentist's preferred contours.
The morphology of dental arch has been studied in representatives of 11 contrast (by anthropological characteristics) ethnic groups from regions of their compact residence. The sampling from each ethnic group consisted of 200 subjects (100 male and 100 female) aged 13-20 years. A total of 4,500 plaster models of dental arches were examined. The results were statistically processed using factor, canonical, discriminant analyses, and multidimensional scanning. The data on the variability and sex dimorphism in the size and shape of dental arches in subjects belonging to different ethnic groups may be practically significant in forensic medical personality identification.
INTRODUCTION: Study models provide invaluable information in treatment planning. Digital models have proved to be an effective measurement tool, but their use in treatment planning has not been studied. METHODS: Ten sets of records of Class II malocclusion subjects (dental study models, lateral cephalograms/tracings, panoramic radiographs, intraoral and extraoral photographs) were used for treatment planning by 20 orthodontists on 2 separate occasions. Digital models were used to evaluate the patients at 1 session and plaster models were used at the other session. Treatment recommendations were scored and compared for agreement. Eleven orthodontists served as the control group, looking at the records on 2 occasions with plaster models for agreement. RESULTS: Good agreement was noted for surgery (P = 1.00, kappa = 0.549), extractions (P = .360, kappa = 0.570), and auxiliary appliances (P = 1.00, kappa = 0.539) for the digital/plaster group. Agreement in the plaster/plaster group for surgery (P = 1.00, kappa = 0.671), extractions (P = 1.00, kappa = 0.626), and auxiliary appliances (P = .791, kappa = 0.672) was also good. Overall proportions of agreement ranged between 0.777 and 0.870 for digital/plaster and 0.818 and 0.873 for plaster/plaster. CONCLUSIONS: There was no statistical difference in intrarater treatment-planning agreement for Class II malocclusions based on the use of digital models in place of traditional plaster models. Digital orthodontic study models (e-models) are a valid alternative to traditional plaster study models in treatment planning for Class II malocclusion patients.
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The aim of this retrospective study was to describe the use and reliability of a numerical scoring system (modified Huddart/Bodenham) for the measurement of maxillary arch constriction in patients born with unilateral cleft lip and palate (UCLP), and to compare and contrast the new scoring system with the current methods of measuring treatment outcome, the Goslon and 5-year-old indices. Dental study models of 50 patients aged 5 years, and 50 patients aged 10 years, were scored using the 5-year-old and Goslon indices, respectively. Four examiners scored each set of models using the modified Huddart and Bodenham system, and repeated the scoring one month later. The intra- and inter-rater reliability of the numerical scoring system was assessed using the Kappa (kappa) statistic. The scores using the new method were correlated with the 5-year-old and Goslon scores using Spearman's (rho) and Kendall's (tau) rank correlation coefficients. There was a high level of intra-rater reliability for both the 5 (0.87: incisors, 0.91: canines, 0.88: molars) and 10 (0.9: incisors, 0.84: canines, 0.78: premolars/molars) year models. The weighted kappa values measuring inter-rater reliability were above 0.85 and 0.74, respectively, for all examiners. There was a statistically significant correlation between the modified Huddart/Bodenham scores and both the 5-year-old and Goslon scores in all cases (P < 0.001). It is concluded that the modified Huddart/Bodenham system provides an objective and reliable assessment of maxillary arch constriction. It has a high degree of correlation with the recommended standards, but is more versatile and sensitive to inter-arch discrepancies.