scholarly journals Load-Bearing Capacity of Zirconia Crowns Screwed to Multi-Unit Abutments with and without a Titanium Base: An In Vitro Pilot Study

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3056
Author(s):  
Hadas Heller ◽  
Adi Arieli ◽  
Ilan Beitlitum ◽  
Raphael Pilo ◽  
Shifra Levartovsky
Keyword(s):  
Failure Modes ◽  
Load Bearing ◽  
Zirconia Crowns ◽  
Group A ◽  
Monolithic Zirconia ◽  
Loading Tests ◽  
Group B ◽  
Iso 14801 ◽  
Static And Dynamic Loading

The static and dynamic load-bearing capacities and failure modes of zirconia crowns screwed to multi-unit abutments (MUAs) with and without a titanium base (T-base) were determined. Thirty-six monolithic zirconia crowns screwed to straight MUAs torqued to laboratory analogs (30 Ncm) were assigned to two groups (n = 18). In group A, the zirconia crowns were screwed directly to the MUAs; in group B, the zirconia crowns were cemented to the T-base and screwed to the MUAs. All specimens were aged in 100% humidity (37 °C) for one month and subjected to thermocycling (20,000 cycles). Afterwards, the specimens underwent static and dynamic loading tests following ISO 14801. The failure modes were evaluated by stereomicroscopy (20×). There was an unequivocally similar trend in the S-N plots of both specimen groups. The load at which the specimens survived 5,000,000 cycles was 250 N for both groups. Group A failed mainly within the metal, and zirconia failure occurred only at a high loading force. Group B exhibited failure within the metal mostly in conjunction with adhesive failure between the zirconia and T-base. Zirconia restoration screwed directly to an MUA is a viable option, but further studies with larger sample sizes are warranted.

scholarly journals Fracture Strength of Monolithic Zirconia Crowns with Modified Vertical Preparation: A Comparative In Vitro Study

2021 ◽  
Author(s):  
Marwah Ismael Abdulazeez ◽  
Manhal A. Majeed
Keyword(s):  
Fracture Strength ◽  
In Vitro Study ◽  
Fracture Load ◽  
Significant Difference ◽  
Zirconia Crowns ◽  
Group A ◽  
Monolithic Zirconia ◽  
Bonferroni Test ◽  
Group B

Abstract Objective The aim of this study was to evaluate the influence of different marginal designs (deep chamfer, vertical, and modified vertical with reverse shoulder) on the fracture strength and failure modes of monolithic zirconia crowns. Materials and Methods Thirty sound human maxillary first premolar teeth with comparable size were used in this study. The teeth were divided randomly into three groups according to the preparation design (n = 10): (1) group A: teeth prepared with a deep chamfer finish line; (2) group B: teeth prepared with vertical preparation; and (3) group C: teeth prepared with modified vertical preparation, where a reverse shoulder of 1 mm was placed on the buccal surface at the junction of middle and occlusal thirds. All samples were scanned by using an intraoral scanner (CEREC Omnicam, Sirona, Germany), and then the crowns were designed by using Sirona InLab 20.0 software and milled with a 5-axis machine. Each crown was then cemented on its respective tooth with self-adhesive resin cement by using a custom-made cementation device. A single load to failure test was used to assess the fracture load of each crown by using a computerized universal testing machine that automatically recorded the fracture load of each sample in Newton (N). Statistical Analysis The data were analyzed statistically by using one-way analysis of variance test and Bonferroni test at a level of significance of 0.05. Results The highest mean of fracture load was recorded by chamfer (2,969.8 N), which followed by modified vertical (2,899.3 N) and the lowest mean of fracture load was recorded by vertical (2,717.9 N). One-way ANOVA test revealed a significant difference among the three groups. Bonferroni test showed a significant difference between group A and group B, while a nonsignificant difference was revealed between group C with group A and group B. Conclusion Within the limitations of this in vitro study, the mean values of fracture strength of monolithic zirconia crowns of all groups were higher than the maximum occlusal forces in the premolar region. The modification of the vertical preparation with a reverse shoulder placed at the buccal surface improved the fracture strength up to the point that it was statistically nonsignificant with the chamfer group.

The Effect of Varying Ferrule Modes on Fracture Resistance of Canines Restored with One-Piece Milled Zirconia Post and Core

2012 ◽  
Vol 624 ◽  
pp. 98-102
Author(s):  
Yao Kun Zhang ◽  
Long Quan Shao ◽  
Ruo Yu Liu ◽  
Lin Lin Wang ◽  
Jun Ai ◽  
...  
Keyword(s):  
Fracture Resistance ◽  
In Vitro Study ◽  
Significant Difference ◽  
Zirconia Crowns ◽  
Group A ◽  
Post And Core ◽  
Resistance Decrease ◽  
Group B ◽  
Group D

The aim of this invitro study was to evaluate the fracture resistance of endodontically treated canines restored with one-piece milled zirconia post and core in the varying ferrule modes. Fifty recently extracted human maxillary canines were endodontically treated and randomly divided into 5 groups of 10 specimens each. According to the defect degree of ferrule, intact ferrule was classified as group A and served as control, 2 mm ferrule height without buccal ferrule was classified as group B, 2 mm ferrule height without mesial and buccal ferrule was classified as group C, 2 mm ferrule height without mesial, buccal and lingual ferrule was classified as group D, no ferrule preparation was classified as group E. All of the teeth were restored with one-piece milled zirconia post and core, and zirconia crowns. The teeth were prepared to standardized specifications. The restored teeth were loaded to fracture at a 135° angle to their long axis, at a cross-head speed 0.5 mm/min, and the load (N) at failure was recorded. Statistical analysis was performed by SNK pairwise multiple comparisons (α=0.05). The mean fracture resistance of five groups as follows: 1019.30±139.01N for group A, 861.20±105.67N for group B, 833.70±100.56N for group C, 733.20±96.91N for group D, 698.00±99.90N for group E. The fracture resistance of restored teeth between group B and group C, group D and group E had no statistically significant difference(P>0.05). The fracture resistance of the rest pairwise group comparisons had statistically significant difference(P<0.05). Increasing the absence degree of ferrule, it was found that the fracture resistance decrease. The buccal and lingual ferrule were more important than mesial ferrule for enhanced fracture resistance. This in vitro study supports evidence that reserving the buccal and lingual ferrule is a key point to increase the fracture resistance of canines restored with one-piece milled zirconia post and core.

scholarly journals In Vitro Fracture Strength of Teeth Restored with Lithium Disilicate Onlays with and without Fiber Post Build-Up

2018 ◽  
Vol 6 (3) ◽  
pp. 35 ◽  
Author(s):  
Nicola Mobilio ◽  
Alberto Fasiol ◽  
Francesco Mollica ◽  
Santo Catapano
Keyword(s):  
Fracture Strength ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Lithium Disilicate ◽  
Fiber Post ◽  
Chi Square ◽  
Human Teeth ◽  
Group A ◽  
Group B

To our knowledge there is no data about the mechanical performance of indirect restoration adhesively cemented on teeth without an adequate build-up to provide the correct geometrical configuration. The aim of this study was to compare the fracture strength of human teeth restored with lithium disilicate onlays, with and without fiber post build-up. Methods: Twenty human mandibular molars were horizontally sectioned and divided into two groups (n = 10). No treatment was applied in group A. Teeth in group B were endodontically treated, built-up using fiber post and composite core and prepared with a circumferential chamfer providing a 1 mm circumferential ferrule. Lithium disilicate onlays were pressed and luted on teeth using dual-curing luting composite. Teeth were tested under static load. Failures were classified as restorable or not restorable. Failure loads were analyzed with one-way analysis of variance. Failure modes were compared using Pearson’s Chi-square tests. Results: The mean fracture loads were 1383.5 N for group A and 1286.3 N for group B. No difference was found (p = 0.6). Ninety per cent of fractures were classified as not restorable in both groups, with no difference (p = 0.8). Conclusions: For teeth restored with adhesive procedures and lithium disilicate onlays, the presence of build-up with fiber post to provide retention and resistance form does not influence the fracture strength.

Factor II Related Antigen and Antithrombin III Levels as Indicators of Liver Failure in Consumption Coagulopathy

1982 ◽  
Vol 47 (03) ◽  
pp. 218-220 ◽  
Author(s):  
P Sié ◽  
E Letrenne ◽  
C Caranobe ◽  
M Genestal ◽  
B Cathala ◽  
...  
Keyword(s):  
Liver Failure ◽  
Antithrombin Iii ◽  
Coagulation Factors ◽  
Consumption Coagulopathy ◽  
Blood Coagulation Factors ◽  
Factor Ii ◽  
At Iii ◽  
Group A ◽  
Group B

SummaryIn order to detect impaired synthesis of blood coagulation factors associated to consumption coagulopathy, a simultaneous evaluation of factor II-related antigen (II rAg) and of antithrombin III (AT III) was carried out in 16 patients affected with severe defibrination. An in vitro preliminary study on plasma and serum demonstrated that the levels of II rAg and of AT III, assessed by the Laurell technique with Behring antisera, were not reduced by the coagulation process. The patients were, a posteriori, classified into two groups according to the absence (group A) or the presence (group B) of factors predisposing to liver failure such as metastasis, cirrhosis, and prolonged shock. II rAg and AT III levels are significantly correlated; they are in the normal range in group A but reduced in group B. Thus II rAg or AT III level determinations are useful markers in the detection of liver failure associated to the consumption phenomenon. These results also suggest that part of the decreased AT III levels reported in severe cases of disseminated intravascular coagulation may be the consequence of an associated liver failure.

scholarly journals The Impact of Left Atrial Size in Catheter Ablation of Atrial Fibrillation Using Remote Magnetic Navigation

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Xiao-yu Liu ◽  
Hai-feng Shi ◽  
Jie Zheng ◽  
Ku-lin Li ◽  
Xiao-xi Zhao ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Catheter Ablation ◽  
Left Atrial ◽  
Magnetic Navigation ◽  
Remote Magnetic Navigation ◽  
X Ray ◽  
Group A ◽  
Group B ◽  
The Impact

Objective. The objective of this study was to investigate the impact of left atrial (LA) size for the ablation of atrial fibrillation (AF) using remote magnetic navigation (RMN). Methods. A total of 165 patients with AF who underwent catheter ablation using RMN were included. The patients were divided into two groups based on LA diameter. Eighty-three patients had small LA (diameter <40 mm; Group A), and 82 patients had a large LA (diameter ≥40 mm; Group B). Results. During mapping and ablation, X-ray time (37.0 (99.0) s vs. 12 (30.1) s, P<0.001) and X-ray dose (1.4 (2.7) gy·cm2 vs. 0.7 (2.1) gy·cm2, P=0.013) were significantly higher in Group A. No serious complications occurred in any of the patients. There was no statistical difference in the rate of first anatomical attempt of pulmonary vein isolation between the two groups (71.1% vs. 57.3%, P=0.065). However, compared with Group B, the rate of sinus rhythm was higher (77.1% vs. 58.5%, P<0.001) during the follow-up period. More patients in Group A required a sheath adjustment (47/83 vs. 21/82, P<0.001), presumably due to less magnets positioned outside of the sheath. In vitro experiments with the RMN catheter demonstrated that only one magnet exposed created the sheath affects which influenced the flexibility of the catheter. Conclusions. AF ablation using RMN is safe and effective in both small and large LA patients. Patients with small LA may pose a greater difficulty when using RMN which may be attributed to the fewer magnets beyond the sheath. As a result, the exposure of radiation was increased. This study found that having at least two magnets of the catheter positioned outside of the sheath can ensure an appropriate flexibility of the catheter.

Salivary oestradiol and progesterone after in vitro fertilization and embryo transfer using different luteal support regimens

1990 ◽  
Vol 2 (4) ◽  
pp. 351 ◽  
Author(s):  
YF Wong ◽  
EP Loong ◽  
KR Mao ◽  
PP Tam ◽  
NS Panesar ◽  
...  
Keyword(s):  
In Vitro Fertilization ◽  
Embryo Transfer ◽  
Luteal Phase ◽  
Biologically Active ◽  
Luteal Support ◽  
Vitro Fertilization ◽  
Group A ◽  
Group B ◽  
Ivf Et

Salivary oestradiol (E2) and progesterone (P) levels have been shown to reflect the biologically active fractions in the serum. The luteal-phase status of stimulated cycles was investigated after in vitro fertilization and embryo transfer (IVF-ET). Thirty patients were randomly allocated to one of three luteal therapy groups: group A had no support, group B had intramuscular P and group C had intramuscular P and human chorionic gonadotrophin (hCG). One pregnancy was achieved in group A, two in group B and three in group C. Significant correlations between salivary and serum levels of E2 and of P in matched samples during luteal phase were found. Salivary E2 levels from luteal day 8 through day 14 and P levels from day 3 through day 14 were significantly higher in the pregnant than in the nonpregnant cycles. Among the nonpregnant cycles, salivary E2 and P levels were significantly higher in group C than in group A or B. These findings suggest that, in stimulated cycles for IVF-ET, determination of salivary E2 and P levels may be used as reliable alternatives to serum concentrations for assessing the luteal phase. Also, the additional hCG has an enhanced luteotrophic effect, as reflected by the higher salivary E2 and P levels, which may lead to a better pregnancy rate.

Effects of Mechanical Stimulation on MMP-2 and TIMP-2 Expression of Scleral Fibroblasts after Posterior Sclera Reinforcement

2014 ◽  
Vol 490-491 ◽  
pp. 867-871
Author(s):  
Guo Hui Wang ◽  
Wei Yi Chen
Keyword(s):  
Mechanical Stimulation ◽  
Sine Wave ◽  
Posterior Pole ◽  
Cyclic Stretch ◽  
Elisa Method ◽  
Band Group ◽  
Group A ◽  
Operation Group ◽  
Group B

To understand the effect of mechanical stimulation on posterior sclera reinforcement (PSR), the rabbit scleral fibroblasts after PSR were subjected to stretch in vitro and MMP-2 and TIMP-2 expression of scleral fibroblasts were evaluated. Three-week-old rabbits were monocularly performed by eyelid suturation randomly to prepare experimental myopia eye. After 60 days, the experimental myopia eyes were treated by PSR. After 6 months, the posterior pole scleral fibroblasts (normal sclera - group A, sclera after operation - group B and fusion region of sclera and reinforcing band group C) were isolated and cultured in vitro. The cells were subjected to cyclic stretch regimens (sine wave, 3% and 6% elongation amplitude, 0.1Hz, 48h duration) by FX-4000 Tension System. The MMP-2 and TIMP-2 expression of scleral fibroblasts were evaluated by ELISA method. The results show that after cyclic stretch to the scleral fibroblasts of the normal sclera and the sclera after operation, the MMP-2 expression was significantly reduced and the TIMP-2 expression was significantly increased, the MMP-2 and TIMP-2 expression of the scleral fibroblasts of the fusion region after operation was no changed. It was indicated that the mechanical stimulation could regulate the MMP-2 and TIMP-2 expression of scleral fibroblasts and play an important role in the process of treating high myopia with PSR surgery.

scholarly journals Photopolymerizable Injectable Cartilage Mimetic Hydrogel for the Treatment of Focal Chondral Lesions: A Proof of Concept Study in a Rabbit Animal Model

2018 ◽  
Vol 47 (1) ◽  
pp. 212-221 ◽  
Author(s):  
Cecilia Pascual-Garrido ◽  
Elizabeth A. Aisenbrey ◽  
Francisco Rodriguez-Fontan ◽  
Karin A. Payne ◽  
Stephanie J. Bryant ◽  
...  
Keyword(s):  
Animal Model ◽  
Chondrogenic Differentiation ◽  
Osteochondral Lesions ◽  
Chondral Defect ◽  
Group A ◽  
Group B ◽  
Safranin O

Background: In this study, we investigate the in vitro and in vivo chondrogenic capacity of a novel photopolymerizable cartilage mimetic hydrogel, enhanced with extracellular matrix analogs, for cartilage regeneration. Purpose: To (1) determine whether mesenchymal stem cells (MSCs) embedded in a novel cartilage mimetic hydrogel support in vitro chondrogenesis, (2) demonstrate that the proposed hydrogel can be delivered in situ in a critical chondral defect in a rabbit model, and (3) determine whether the hydrogel with or without MSCs supports in vivo chondrogenesis in a critical chondral defect. Study Design: Controlled laboratory study. Methods: Rabbit bone marrow–derived MSCs were isolated, expanded, encapsulated in the hydrogel, and cultured in chondrogenic differentiation medium for 9 weeks. Compressive modulus was evaluated at day 1 and at weeks 3, 6, and 9. Chondrogenic differentiation was investigated via quantitative polymerase reaction, safranin-O staining, and immunofluorescence. In vivo, a 3 mm–wide × 2-mm-deep chondral defect was created bilaterally on the knee trochlea of 10 rabbits. Each animal had 1 defect randomly assigned to be treated with hydrogel with or without MSCs, and the contralateral knee was left untreated. Hence, each rabbit served as its own matched control. Three groups were established: group A, hydrogel (n = 5); group B, hydrogel with MSCs (n = 5); and group C, control (n = 10). Repair tissue was evaluated at 6 months after intervention. Results: In vitro, chondrogenesis and the degradable behavior of the hydrogel by MSCs were confirmed. In vivo, the hydrogel could be delivered intraoperatively in a sterile manner. Overall, the hydrogel group had the highest scores on the modified O’Driscoll scoring system (group A, 17.4 ± 4.7; group B, 13 ± 3; group C, 16.7 ± 2.9) ( P = .11) and showed higher safranin-O staining (group A, 49.4% ± 20%; group B, 25.8% ± 16.4%; group C, 36.9% ± 25.2%) ( P = .27), although significance was not detected for either parameter. Conclusion: This study provides the first evidence of the ability to photopolymerize this novel hydrogel in situ and assess its ability to provide chondrogenic cues for cartilage repair in a small animal model. In vitro chondrogenesis was evident when MSCs were encapsulated in the hydrogel. Clinical Relevance: Cartilage mimetic hydrogel may offer a tissue engineering approach for the treatment of osteochondral lesions.

scholarly journals In vitro Comparison of Apically Extruded Debris during Root Canal Retreatment with Rotary and Reciprocating Systems

2019 ◽  
Vol 13 (1) ◽  
pp. 488-492
Author(s):  
María J. Burbano Balseca ◽  
Silvana B. Terán Ayala ◽  
Fábio D. da Costa Aznar ◽  
Adriana R. de Freitas-Aznar ◽  
Guillermo M. Aguirre Balseca ◽  
...  
Keyword(s):  
Similar Amount ◽  
Hybrid Technique ◽  
Significance Level ◽  
Sealing Material ◽  
Apical Extrusion ◽  
Root Canal Retreatment ◽  
Group A ◽  
Group B ◽  
Reciprocating Systems

Introduction: The extrusion of apical detritus during the retracting procedure is very important, as, besides eliminating materials of radicular obturation, aggressive agents and products such as the remains of dentin taken out, and microorganisms are generally located in tissue around the roots, producing undesired effects, such as inflammation, acute pain, post-operatory pain and delays in the periapical treatment. Objective: To determine the amount of apically extruded detritus using rotary and reciprocating retreatment systems. Methodology: An experimental comparative study as conducted in which 40 single-rooted human first premolars were analyzed. The instruments used were ProTaper Universal files up to F3 and sodium hypochlorite, and the sealing was made through the hybrid technique Tager. They were then kept at 37ºC and 100% of humidity for 15 days so that the sealing material would seal. For the retracting procedure, experimental tubes previously weighted were used. The sample was divided randomly into two groups of 20 pieces. Group A: ProTaper R, and group B: Reciproc. Then, the irrigating material (distilled water) was evaporated from the tubes for 12 hours in a stove at 105ºC, and the experimental tubes were weighted in an analytical precision weighing scale 10-5g. The data was analyzed through the T Student with a significance level of 5%. Results: Results indicated that groups A and B, retreatment with rotational ProTaper R and reciprocating retreatment system (Reciproc) showed a similar difference of initial and final weights, indicating similar apical extrusion of detritus. Conclusion: Both systems extruded a similar amount of detritus during the retreatment procedures.

scholarly journals Frictional Characteristics of the Newer Low-friction Elastomeric Ligatures

2016 ◽  
Vol 6 (1) ◽  
pp. 19-23
Author(s):  
Amol Mhatre ◽  
VK Ravindranath ◽  
Sachin Doshi ◽  
Girish Karandikar ◽  
PS Vivek
Keyword(s):  
Testing Machine ◽  
Frictional Resistance ◽  
Minimal Amount ◽  
New Delhi ◽  
Low Friction ◽  
Significant Difference ◽  
Group A ◽  
Group B ◽  
New Generation

ABSTRACT Aim The aim of this in vitro study was to investigate the efficiency of the new generation of elastomeric ligatures with innovative designs (SlideTM and AlastiKTM Easy-to-Tie) in reducing frictional resistance (FR) during sliding mechanics as compared with conventional ligatures. Materials and Methods Sixty ligature samples divided into four groups were used for the study. Group A: QuiK-StiK™ (3M Unitek, Monrovia, CA, USA), Group B: AlastiK™ Easy-to-Tie (3M Unitek, Monrovia, CA, USA), Group C: Slide™ (Leone, Firenze, Italy), and Group D: SS ligatures 0.010” (Libral Traders, New Delhi, India). Universal Testing Machine, Instron was used for measuring FR at the bracket-wire interface. Results There was statistically significant difference in FR among all the four groups of ligatures tested (p < 0.001). Slide ligatures produced the least amount of FR followed by SS ligatures, Easy-to-Tie, and QuiK-StiK in the increasing order of the FR values registered. Conclusion SlideTM ligatures may represent a valid alternative to passive self-ligating brackets when minimal amount of friction is desired. Angulation introduced into the elastomeric ligatures reduces the friction in comparison to conventional elastomeric ligatures. How to cite this article Vivek PS, Ravindranath VK, Karandikar G, Doshi S, Mhatre A, Sonawane M. Frictional Characteristics of the Newer Low-friction Elastomeric Ligatures. J Contemp Dent 2016;6(1):19-23.

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