Showing 6 results for Adaptation
H. Afshar , M Mozafari Kojidi ,
Volume 19, Issue 2 (5-2006)
Abstract
Background and Aim: The need for recrimping precrimped stainless steel crowns by the dentist in clinic is controversial. This study aimed to evaluate the rate of marginal circumference and marginal thickness change of precrimped stainless steel crowns after recrimping.
Materials and Methods: In this experimental study, 30 primary photos were taken from margins of 30 S.S.Cs (3M, Ni-Cr) related to tooth 85 with a digital camera fixed at a determined distance. Margins of crowns were crimped by 114 and 137 pliers with a controlled force (0.2 N) and then 30 secondary photos were taken in the same conditions. The circumference of crown margins in primary (group A) and secondary (group B) photos were assessed by a digitizer system. Comparing the circumferences of crown margins in primary and secondary photos showed a significant decrease after crimping. Thickness of 30 random points on the crown margins of a crown similar to mentioned cases was measured by SEM (×150). Then similar procedures including taking a primary photo, crimping and taking a secondary photo was done for the sample crown. After significant reduction in margin circumference, thickness of 30 other random points on the crown margin were measured by SEM. Data were analyzed by paired sample t-test with p<0.05 as the limit of significance.
Results: The mean marginal circumference of precrimped stainless steel crowns was reduced by 7.3% which was significant (P<0.001). On the other hand the mean marginal thickness of sample stainless steel crown showed 18µ increase.
Conclusion: According to the results of this study, marginal circumference of precrimped stainless steel crowns (3M, Ni-Cr) showed a significant decrease after crimping. It is concluded that crimping the stainless steel crowns even for precrimped ones seems necessary.
E. Jalalian, M. Mirtorabi,
Volume 23, Issue 3 (12-2010)
Abstract
Background and Aims: Marginal adaptation is important for the long-term success of full-coverage restorations. Preparation design is one of the important factors influencing the marginal integrity. Therefore, the purpose of this study was to compare the effect of radial shoulder and chamfer finish line designs on the marginal adaptation of all-ceramic Cercon restorations.
Materials and Methods: This in vitro study was done using single blind experimental technique. One stainless steel die with 7 mm height and 5 mm diameter was prepared by milling machine. The preparation design consisted of half radial shoulder with 1mm depth and half chamfer with 0.8mm depth. All walls had a convergence angle of 10º. Ten stone dies and ten ZrO2 copings of Cercon (Cercon Smart Ceramics, DeguDent, Hanau, Germany) were made and after cementation were ground at buccolingual direction. Then marginal gap of each sample was measured by scanning electron microscopy. Data were then analyzed using t-test.
Result: The mean marginal gap for radial shoulder was 98.4µ and for chamfer was 39.7µ. The difference was statistically significant (P=0.002).
Conclusion: The marginal gap of chamfer preparation is less than that of radial shoulder.
Soudabeh Koulivand, Hakimeh Siadat, Safoura Ghodsi, Marzieh Alikhasi,
Volume 31, Issue 4 (1-2019)
Abstract
Background and Aims: Despite the increasing application of intra-oral scanners, the effect of finish line position on gingival margins adaptation is still discussed. The purpose of this clinical study was to evaluate the fitness of cobalt-chromium copings obtained from intraoral scanning in two depth of finish lines.
Materials and Methods: Thirty teeth prepared for single premolar metal-ceramic crowns were included. Fifteen teeth had supragingival and fifteen had sub-gingival finish lines. Digital impressions were made using an intraoral scanner (Trios-3shape). Computer-aided design and computer-aided manufacture (CAD/CAM) cobalt-chromium copings were fabricated from the scan files. The copings were evaluated intraorally and after adjustments, the internal and marginal discrepancy were measured using silicone replicas and a stereomicroscopy. Internal and marginal discrepancies were analyzed using the Multivariate test (P<0.05).
Results: The mean internal and marginal gap were 52.1 and 56.27μ, for supragingival group and 49.72 and 62.98μ for subgingival group, respectively. The evaluation of finish line position showed no significant effect on obtained results (P>0.05).
Conclusion: CAD/CAM chrome-cobalt copings fabricated by digital impressions provided acceptable marginal and internal precision. However, the finish line position had no significant effect on the internal and marginal adaptation.
Marzieh Alikhasi, Narges Ameri, Hakimeh Siadat, Ahmad Reza Shamshiri, Mohammadreza Nejati,
Volume 32, Issue 1 (7-2019)
Abstract
Background and Aims: Passive fitness of implant frameworks are important factors for long-term success of dental implant restorations. The aim of this in vitro study was to evaluate the dimensional changes of implant supported zirconia frameworks fabricated by Zirkonzahn CAD/CAM system during fabrication stages.
Materials and Methods: The master model of 3-unit FDP was made of two implant abutments. The master model was scanned 12 times and data were saved as STL files (scanning groups). Using semi-sintered zirconia,
12 real-size frameworks (milling groups) and 12 enlarged frameworks which were then sintered (sintering group) were made in this system. Dimensions of master model and specimens of each stage were measured. The dimensional changes in respect to master model were calculated. Data were analyzed using Repeated measures ANOVA, independent t-test, and paired sample t-test at α=0.05 of significance.
Results: The milling stage showed greater dimensional changes comparing to the other stages (P<0.05). At all stages, the dimensional changes of premolar abutment height were greater than canine (P<0.001).
Conclusion: Within the limitations of this study, the results suggested that the fabrication stages and size of abutments had significant effects on the dimensional changes of zirconia frameworks.
Pooya Jannati, Mohammad Ebrahimi Saravi, Tahmineh Bamdadian, Farhad Sobouti, Sahar Cheperli, Jamshid Yazdani Charati, Nasrin Khaki, Sahba Amini, Abbas Mesgarani,
Volume 32, Issue 4 (1-2020)
Abstract
Background and Aims: One of the most important challenges for dentists is providing a crown with appropriate marginal fit and gap. The 135-degree tooth preparation found to have some advantages such as technical ease and appropriate finish line record. Despite the advantages of 135-degree tooth preparation, scant research has been done in this area. Therefore, the aim of this study was to compare 135-degree and deep chamfer tooth preparation on the marginal fit and marginal gap of posterior metal-ceramic crowns.
Materials and Methods: Deep chamfer and 135-degree tooth preparation were performed on the two first mandibular molars with healthy coronal tissue and similar size. Impression was taken from each tooth and 30 crowns were made on each die. The sample plastered with fit checkers were pressed under the force of 40 N for 3 min in a universal testing machine. They were measured and recorded under a loop with 40x power in three points on each aspect. Data were analyzed by Wilcoxon and Kolmogorov-Smirnov tests using SPSS version 24.
Results: The mean marginal fit values in deep chamfer and 135-degree were 48.5417µm and 55.3333 µm, respectively with no statistically significant difference (P>0.05). While the mean marginal gap in deep chamfer (2.4833 µm) was significantly higher (P<0.05) than 135-degree (1.0083).
Conclusion: It can be concluded that the marginal gap by 135-degree’s tooth preparation was lower than that of deep chamfer in metal-ceramic crowns. However, no significant difference in the marginal fit between the deep chamfer and 135-degree tooth preparation was found.
Robab Farhang, Mehrnoosh Kaviani, Maedeh Aminian, Aziz Kamran, Mahdi Fathi, Zahra Heidarpour,
Volume 38, Issue 0 (4-2025)
Abstract
Background and Aims: The foundations of a successful root canal treatment are adequate adaptation of the gutta-percha to the canal wall and the establishment of an impermeable apical seal. Despite the common use of M3 and Neoniti rotary files by dentists, no study has been conducted to examine the compliance of gutta-percha in curved canals prepared with M3 and Neoniti files using CBCT. The present study was designed and compiled with the aim of investigating the adaptation of gutta-percha in curved canals prepared with M3 and Neoniti files by CBCT.
Materials and Methods: This randomized controlled laboratory study was conducted ex vivo on 30 permanent human first molar teeth. The teeth were randomly divided into two groups (the first group with M3 and the second group with neoniti), after finding and fixing the appropriate canal path with the examined rotary files. All groups were filled with Single Cone method using F2 gutta-percha and AH26 sealer. Then, the gutta adaptation was assessed using clinical criteria (visual and radiographic) and after the specimens were evaluated using CBCT. All the images obtained from CBCT were converted into the JPEG format and then entered into image J software. The gap between the canal walls and gutta was measured in each canal, and the obtained data were analyzed using the Mann–Whitney U test.
Results: The results showed that the average and standard deviation of gap in M3 files (0.181 ± 0.089) was higher than that of Neoniti file (0.173 ± 0.033). However, no significant difference in the gutta-percha adaptation in curved canals prepared between the M3 and Neoniti files was observed (P>0.05).
Conclusion: Considering the acceptable adaptation of gutta-percha in canals prepared with M3 and Neoniti files, the use of these two files is recommended in curved canals.
