Evaluation of surface characteristics of Ti-6Al-4V and Tilite alloys used for implant abutments.
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The aim of this study was to evaluate surface free energy (SFE), surface roughness (SR) and surface hardness (SH) of two commercially available materials for fabricating dental implant abutments. In addition, the specimens were investigated by scanning electron microscopy (SEM) to determine the surface morphology. Twenty five discs (5 x 2 mm) of Ti-6Al-4V and Tilite (Ni-Cr-Ti) alloys were used in this study. Surface free energy was determined by the contact angle formed between a drop of distilled, deionized water and the surface of the specimen of each material. The surface roughness was measured with a mechanical profilometer and the surface hardness was evaluated by means of the Vickers hardness micro indentation test. SFE, SR and SH data were analyzed using one-way ANOVA (p < 0.05). Statistical differences (p < 0.05) were found between Ti-6Al-4V (36.2 erg x cm(-2); 0.2 microm) and Tilite (30.9 erg x cm(-2); 0.16 microm) for SFE and SR. However, the differences between the surface hardness values of Ti-6Al-4V (325.0 kg/mm(2)) and Tilite (324.3 kg/mm(2)) were not statistically significant (p > 0.05). Evaluations by SEM revealed different surface morphology. Within the limits of this study, it can be concluded that the Ti-6Al-4V and Tilite alloys showed differences in surface properties, except for surface hardness, suggesting that both alloys may be considered appropriate for producing abutments. Further studies are, however, necessary to elucidate the biological responses to implant abutments made with these alloys. (+info)
Evaluation of the marginal gingival health using laser Doppler flowmetry.
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The purposes of this study were to compare the gingival blood flow (GBF) in test sites (teeth retaining fixed partial dentures) and control sites (contralateral natural teeth) and investigate whether there is any relationship between clinical indices and GBF values. Twelve healthy subjects (6 females and 6 males) aged 20 to 54 years were enrolled this study. The GBF was measured from the middle point of the marginal gingiva in the test and control sites using laser Doppler flowmetry (LDF). Additionally, plaque index, gingival index and probing depth measurements were recorded. Statistically significant difference (p<0.05) was found between the test and control sites for marginal GBF. In contrast, no significant difference (p>0.05) was found between test and control sites with respect to the clinical indices, except for plaque index. The findings of this study suggest that there is a significant relation between resin-bonded fixed partial dentures with margins located subgingivally and marginal GBF. Clinical indices are helpful to collect information about the clinical health status of gingival tissues, but GBF is a good tool to measure gingival tissue blood flow and assess periodontal health. In conclusion, laser Doppler flowmetry can be used together with clinical indices to evaluate the marginal gingival health. (+info)
The correlation of student performance in preclinical and clinical prosthodontic assessments.
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Tracking student performance in preclinical and clinical courses can be helpful in developing and refining a curriculum. Our objective was to correlate student performance on three fixed prosthodontic examinations taken by eighty junior dental students. Examinations included a knowledge-based objective structured clinical examination (OSCE), a manual skills exercise completed on a typodont (Typodont), and a competency casting exam (Casting CE) on a patient. Multiple regression analysis indicated that the OSCE and Typodont exam scores, as independent variables, were not statistically significant predictors (P=0.07; P=0.87, respectively) of Casting CE exam performance, which was the dependent variable. Correlations were weak for the OSCE (r=0.21) and nearly nonexistent for the Typodont exam(r=0.03) when compared to the Casting CE. Our results indicate a weak correlation between an OSCE-based knowledge exam measuring students' knowledge of critical errors in preparations and castings and a competency exam involving the preparation of a full veneer crown. Results also indicate virtually no correlation between a typodont preparation examination designed to provide a measure of students' clinical skill and a clinical competency exam involving the preparation of a full crown. (+info)
Stabilization of an abutment under a rigidly fixed bridge by holographical-speckle interferometry.
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OBJECTIVE: There are no detailed reports of three-dimensional measurement of abutment teeth in mastication, because it is knotty to observe the rotation in chewing directly, and inexact to estimate indirectly. This work studies the three-dimensional stability of rigidly fixed bridge under the stresses of distributed loads and concentrated loads by optical method that gives the tip angle and rotation angle calculated directly based on measurement data. METHODS: The specimen, taken from a 25-year-old male, was a left mandible without the second premolars and the first molars. As abutments, first premolar and second molar have complete periodontium. The specimen was soaked in formaldehyde solution. The bridge was fixed between two abutment teeth (first premolars and second molars), and the mandible was cemented in a steel box. The load was increased from 0 kg to 23 kg. Laser holographic technique was used to measure the three-dimensional bit shift of the dens, both buccolingual bit shift and mesiodistal bit shift, and determine tip angle and rotation angle. RESULTS: The effects of stress distribution on the rigidly fixed bridge were evaluated, and stabilization of the bridge under the stresses of distributed loads and concentrated loads, respectively, were analyzed. The results showed that the tips of two abutments were very similar, and no distinct difference was observed between the distributed load and the concentrated load. However, the maximum rotation angle for the distributed load was two to four times as large as that for the concentrated load. In the experiment, the tip angle of the abutment teeth was no more than 0.65 degree, and the rotation angle was no more than 0.60 degree. All maximum angles occurred in the second molar. CONCLUSION: The fixed bridge is considered to be safe. In addition, a method for measuring the rotation angle was provided effectively. (+info)
Clinical assessment of primary stability of endosseous implants placed in the incisor region, using resonance frequency analysis methodology: an in vivo study.
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AIM: To evaluate the effect of immediate loading on the primary stability of endosseous implants placed in the anterior incisor region by mapping the stability, using resonance frequency analysis, over a period of time. MATERIALS AND METHODS: A total of eight implants (Zimmer Screw-Vent) were placed in four patients. The Osstell resonance frequency analyzer was used to determine the primary stability at baseline (day 1), 15 th day, 30 th day, 60 th day, and 90 th day for each of the eight implants. Analysis of data was done using SPSS (Statistical Package for Social Science; version 4.0.1). RESULTS: All implants showed adequate initial stability at baseline with an ISQ > 50. Implant nos. 1, 3, 4, 7, and 8 showed a high initial stability at baseline (ISQ > 65), following which a decrease in the stability was recorded during the 15 th day, 30 th day, and 60 th day. By the 90 th day, the stability values were nearly equivalent to those obtained at baseline. The highest mean stability value was recorded on the day of implant placement. The lowest mean stability recording was obtained on the 30 th day after implant osteotomy. By the 90 th day, the mean stability value was nearly equivalent to that obtained at baseline. CONCLUSIONS: Within the limitations of this study, it can be concluded that immediate loading of implants placed in the maxillary and mandibular incisor region does not seem to have an adverse effect on the osseointegration of implants, which achieved a high primary stability. The use of the resonance frequency analyzer as a tool to monitor the variation in the stability of the implants over a period of time has been validated. (+info)
Prosthetic laboratory influence on the vertical misfit at the implant/UCLA abutment interface.
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An inadequate fit at the abutment/implant interface can generate mechanical and biological problems. The laboratorial stages could induce misfit in such interface when the castable UCLA abutment type is used. The purpose of this study was to comparatively evaluate the performance of three prosthetic laboratories (Labs A, B and C) by vertical fit analysis of castable UCLA abutments on the casting and soldering stages of the same prosthesis. Four fixed prostheses were built by each laboratory using castable UCLA abutments. The evaluation was made by scanning electron microscopy under 500x magnification in the mesial and distal regions of each element of the prosthesis, totalizing 24 measurements per laboratory. The results were analyzed statistically by Kruskal-Wallis test (p<0.05). In the casting process, the values presented by the laboratories differed significantly to each other (p=0.004). After soldering, the values presented by the laboratories showed no significant difference (p=0.948). It may be concluded that the fit values obtained in the casting stage of UCLA abutments can be influenced when processed by different laboratories, and that conventional soldering itself increased the degree of framework misfit, regardless of which laboratory made it. (+info)
Effect of sintering on the marginal and internal fit of CAD/CAM-fabricated zirconia frameworks.
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The aim of this study was to investigate the effect of post-machining sintering on marginal and internal fit of CAD/CAM-fabricated zirconia frameworks. Single crown copings (A: abutment), three-unit bridge frameworks (APA, P: pontic), four-unit bridge frameworks (APPA), and five-unit bridge frameworks (A1P1A2P2A3) were fabricated with raw-stage zirconia blanks using a commercial CAD/CAM system (KATANA, Noritake Dental Supply Co. Ltd., Aichi, Japan). Crown copings and frameworks were cemented to their respective master abutment models, and thickness of the cement layer was measured at specific measuring points. Marginal and internal fit of both APA and APPA were within clinical acceptance. However, the marginal gap and thickness of the cement layer on the axial surface of the pontic side of APA and APPA were slightly higher than those of the non-pontic side. As for the marginal gap of A1P1A2P2A3 framework, it was superior to those of APA and APPA because the center abutment supported the framework to prevent distortion. (+info)
BACKGROUND AND OBJECTIVE: Dentists often question the use of resin-bonded fixed partial dentures (RBFPDs) for reliable restoration of tooth-bound edentulous spaces. Initial attempts at bonding fixed partial dentures on teeth resulted in early failure due to debonding. In the 1980s and 1990s, improvements in preparation methods, metal alloys and bonding techniques made the RBFPD a more predictable option. In this paper, we summarize recent information concerning its success and failure. METHODS: A MEDLINE search using key words describing RBFPDs was carried out to identify pertinent English articles appearing in peer-reviewed journals since 2000. RESULTS: The principle reason for failure of RBFPDs remains debonding of the framework from the abutment teeth. Selection of nonmobile abutment teeth, preparation to enhance retention and resistance form, choice of the appropriate alloy and metal, and tooth bonding technique are the keys to success. The use of cantilever and nonrigid attachments may decrease interabutment forces and reduce debonding of retainers. CONCLUSIONS: The survival rate of RBFPDs is still considerably lower than that of conventional fixed partial dentures. Although RBFPDs can be used in both the anterior and posterior regions of the mouth to replace 1 or 2 missing teeth, careful abutment selection, tooth preparation, alloy selection and bonding technique are critical for clinical success. (+info)