1,354,065 research outputs found
Comparison of the suitability of intra-oral scanning with conventional impression of edentulous maxilla in vivo. A preliminary study
No full textAim According to recent literature, the accuracy of digital impression can be compared with traditional impressions for most indications. However, little is known about their suitability in digitizing edentulous jaws in view of mobile prosthetic rehabilitation. The aim of this study was to compare in vivo an intra-oral scanner with conventional impression in case of maxillary edentulous jaws. Material and methods Four (1 male, 3 female) subjects who had no previous experience with either conventional or digital impression participated in this study. Digital impression were taken using an intra-oral scanner. After that conventional impressions of maxillary edentulous jaws were taken with an irreversible hydrocolloid impression material. Then all IOSs datasets were loaded in a three-dimensional evaluation software (3DReshaper 2017, Hexagon), where they were superimposed on the model obtained using conventional impression and compared. Results The mean value of difference between the two impression techniques ranged from 219 to 347 μm. The comparison of models obtained with the two techniques showed that the compression given by the impression material on the peripheral areas, such as oral vestibule and soft palate, determined the most important differences recorded. Conclusion Digitizing edentulous jaws with the use of IOS appeared to be feasible in vivo, although peripheral tissue were not effectively reproduced. On the basis of the results of this study, the authors could not recommend the use of IOS for digitization of edentulous jaws in vivo in view of mobile prosthetic rehabilitation, until it will be found a way to give a selective pressure in peripheral areas as occurs during edging of impression tray
Smile analysis: The buccal corridor | [Valutazione del corridoio vestibolare nell'analisi del sorriso]
No full textIn questa analisi del sorriso si è preso in esame il corridoio vestibolare per valutare e quantificare con metodo scientifico la sua presenza e metterla in correlazione con altre strutture.
Obiettivo del lavoro è analizzare i rapporti tra porzione più vestibolare del canino e rima labiale; presenza del corridoio vestibolare, distanza tra la linea mediana incisiva e la rima labiale. È stata effettuata un’analisi statistica dei dati raccolti in un campione di 79 soggetti tra 20 e 25 anni. È risultato negativo il Coefficiente di correlazione di Pearson per la correlazione tra: 1) canino rima labiale - corridoio vestibolare, 2) distanza del piano occlusale dell’incisivo laterale dal piano occlusale dell’incisivo centrale - corridoio vestibolare, 3) corridoio vestibolare - distanza tra la linea mediana e la rima labiale. Si può quindi concludere che sia la distanza dal canino alla rima labiale sia il corridoio vestibolare sono da ritenersi una pura sensazione clinica
Effect of storage time on the accuracy of casts made from different irreversible hydrocolloids
No full textAIM: Several new irreversible hydrocolloid formulations have recently become available with claims of an improved dimensional stability by the manufacturers. The aim of this study was to evaluate the accuracy of casts made from alginate impression materials poured immediately and after specific storage periods.
METHODS AND MATERIALS: Five alginates were tested: CA 37 (Cavex); Jeltrate (Dentsply Caulk); Jeltrate Plus (Dentsply Latin America); Hydrogum 5 (Zhermack); and Alginoplast (Heraeus Kulzer). A master model was mounted on a special device and used to obtain the impressions. These impressions were stored at 23 degrees C and 100% relative humidity, then poured with gypsum immediately, and again after 24, 72 and 120 hours. The casts were measured and the data were analyzed by one way analysis of variance (ANOVA) and Tukey test at p<0.05.
RESULTS: The dimensional stability of the alginate impressions was both material and time dependent (p<0.05). After 24 hours of storage, only Alginoplast and Hydrogum 5 comply with the master model (p>0.05). After 72 and 120 hours, only Hydrogum 5 was dimensionally stable (p>0.05).
CONCLUSION: The dimensional stability of the alginate impressions is influenced by the selected material and the storage time.
CLINICAL SIGNIFICANCE: Alginate impressions should generally be poured immediately. However, some new types of alginate may have the pouring delayed
SEM evaluation of the cement layer thickness after luting two different posts
No full textPurpose: To verify with SEM the cement layer thickness and uniformity of resin-relined translucent fiber posts (anatomic posts) and standard translucent fiber posts. Materials and Methods: On 20 extracted maxillary anterior teeth, the roots were endodontically treated and prepared for the insertion of a fiber post. Translucent fiber posts (DT) were luted with a dual-curing resin cement (Duo-Link) in 10 specimens (group 1) after the canal walls had been treated with the One-Step bonding system. In the other 10 specimens (group 2), experimental anatomic posts (Anatomic Post'n Core) were tested. To these posts, a layer of light-curing resin is added to allow for a pre-cementation relining of the post, aimed at improving its fit into the endodontic space. For luting, the same adhesive-resin cement combination of group 1 was used. All the roots were sectioned and prepared for SEM observations. At the 1-mm, 4.5-mm, and 8-mm level of each root, cement thickness was measured, and the presence of gaps or voids within the luting material or at its interfaces was evaluated. A statistical analysis was performed to test the significance of differences in the cement layer thickness around the two types of post and at different levels of the same type of post. Results: In the presence of anatomic posts, the cement layer was significantly thinner and more uniform at the coronal and middle level of the root. In both groups, voids and bubbles were detected within the luting material, within the abutment material, and between fiber post and cement. Gaps were also visible between post and relining material. Conclusions: The resin cement thickness was significantly lower in the anatomic post group than in the control group (standardized posts), except at the apical third of the canal, where there was no statistically significant difference. A good adaptation of anatomic posts was evident in all of the specimens
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