Articles
Permanent URI for this collection
Browse
Recent Submissions
- PublicationOpen AccessThe effect of Er, Cr:YSGG laser debonding on the bond strength of two ceramic materials to dentin(Springer Nature, 2023-01-12)Objectives: Evaluating the bond strength of two ceramic materials to dentin after Er,Cr:YSGG laser debonding. Would laser debonding affect the bond strength of ceramic to dentin? Materials and methods: Recently extracted human molars were ground to expose dentin. Forty square shaped samples were prepared from CAD/CAM ceramic blocks. Samples were divided into two groups according to the type of ceramic material; group E: Lithium disilicate and group T: Ultra-translucent Zirconia (n = 20) Each group was divided into two subgroups (n = 10) according to the laser debonding effect (subgroup B: bonded samples, subgroup R: re-bonded samples after laser debonding). Ceramic samples were bonded to dentin using dual cure self-adhesive resin cement. Laser debonding of ceramic samples of subgroups R using Er, Cr:YSGG laser, were then re-bonded again to dentin surface with same resin cement. The Shear bond strength test using Universal testing machine was done. The failure mode was analyzed. Two-way analysis of variance was used to compare the mean bond strength and re-bond strength of two materials. The significance level was set at ≤ 0.05. Results: Two-Way ANOVA showed that ceramic type had a significant effect on the re-bond strength to dentin. The predominant failure mode was adhesive. Conclusions: Laser debonding of Lithium disilicate and Ultra translucent Zirconia decreased the re-bond strength to dentin. Deterioration in re-bond strength for Lithium disilicate ceramics was more pronounced than for Ultra translucent Zirconia. Clinical Relevance Deterioration in the bond strength between ceramics & dentin after laser debonding still needs improvement to allow its clinical use.
- PublicationOpen AccessComparative evaluation of internal fit and marginal gap of endocrowns using lithium disilicate and polyether ether ketone materials - an in vitro study(Springer Nature, 2023-04-07)Background: The aim of the study was to investigate the effect of material and occlusal preparation design on the internal fit and marginal gap of endocrowns made of Polyether ether ketone (PEEK) and lithium disilicate. Methods: 32 endocrowns were fabricated on prepared mandibular molars and divided into two groups (n = 16) according to the material. Group L: lithium disilicate and Group P: PEEK. Each group was further subdivided into two subgroups (n = 8) according to the occlusal preparation design: full occlusal coverage (LF and PF) and partial occlusal coverage (LP and PP). Samples were analyzed using microcomputed tomography (µCT) with a voxel size of 6 μm to evaluate internal fit, and an optical microscope was used to evaluate the marginal gap. Data were collected, tabulated, and statistically analyzed. Numerical data were described as mean and standard deviation and compared using the ANOVA test. The level of significance was set at α P ≤ 0.05. Results: All groups’ internal fit and marginal gaps values were within the acceptable clinical range. However, the lithium disilicates group recorded statistically significantly higher mean internal gap values than the PEEK groups. Regardless of the material, the difference between the two occlusal designs was not statistically significant in both internal fit and marginal gap records. Conclusion: Within the limitations of this study, PEEK endocrown restorations revealed better internal fit and marginal gap than lithium disilicate endocrown restorations. The marginal and internal fit of both lithium disilicate and PEEK endocrown restorations were within the clinically acceptable range. The occlusal preparation design had no influence on the internal fit and marginal gap of the endocrown restoration.
- PublicationOpen AccessClinical Outcomes of Implant Supported Mandibular Overdenture with Bar and Cantilevered Ball Bar Attachment: Crossover Study(2022-01-01)This study aimed at assessing the maximum bite force (MBF) and the masticatory efficiency (ME) for mandibular implant overdenture (MIOD) assisted by anterior bar versus cantilevered ball (CB) bar. Twenty completely-edentate patients received two inter-foraminal implants. The Patients were divided randomly and equally to ten patients received MIOD assisted with anterior bar, then after one year converted to CB bar for another one year. The rest of patients received MIOD assisted with CB bar then after one year replaced by anterior bar for another one year. MBF and ME were registered for each patient after three months of conventional denture insertion (T1), at insertion of MIOD (T2), after six months of MIOD insertion (T3) and after one year of MIOD insertion (T4). For MBF, there was a significant increase in the recorded MBF within each group between at all intervals (p <0.001). There was a significant difference between both groups at T2 and T3 (p = 0.01 and 0.02 respectively). For ME, There was a significant increase in the recorded ME within during wearing the MIOD with CB bar for all time intervals (p < 0.001). While at using anterior bar, there was a significant difference between T2, T3 and T4 only (p <0.001).There was a significant difference between both groups at T2, T3, and T4 (p <0.001). Within the limitations of the study, patients wearing MIOD assisted by CB bar attachment design revealed superior MBF and ME comparing to anterior bar after one year clinical service.
- PublicationMetadata onlyAssociation of CTLA4 c.49A > G (rs231775; p.Thr17Ala) gene variant with the risk of hepatocellular carcinoma and gastric cancer: A meta-analysis and meta-regression(Elsevier, 2022-02-01)Objective: Various reports have examined the contribution of the CTLA4 c.49A > G (rs231775; p.Thr17Ala) gene variant with different cancerous disorders. This meta-analysis was executed to further probe into the involvement of this missense variant with the susceptibility for hepatocellular carcinoma (HCC) and gastric cancer (GC). Methodology: Following a wide-based scrutinized search of the internet done by three independent researchers for the contribution of the CTLA4 c.49A > G (rs231775; p.Thr17Ala) variant with the cancer risk up to February 2021, only 16 case-control studies were found relevant and usable to the analysis out of 575 total retrieved reports. Multiple genetic models were checked for the proposed association through the computation of the odds ratio (OR) in addition to their 95% confidence intervals (95%CIs). Stratification and regression analysis was also carried out for the analyzed reports based on their geographical distributions, genotyping techniques, source of cancer-free controls, genetic equilibrium within cancer-free controls, and quality score. In addition, trial sequential analysis (TSA) was applied to test for the adequacy of the total sample size. Results: This meta-analysis has included 4320 HCC and GC patients in conjunction with 6601 cancer-free controls. This work disclosed a significant association for the CTLA4 c.49A > G (rs231775; p.Thr17Ala) variant with HCC among overall subjects tested by the recessive model [OR = 1.235, 95% CI = 1.050–1.453, P-value = 0.011]. Similarly, an elevated risk of GC was noticed associated with this variant within the overall subjects tested by the allelic model [OR = 1.225, 95% CI = 1.070–1.401, P-value = 0.003], and dominant model [OR = 1.352, 95% CI = 1.081–1.691, P-value = 0.008]. Furthermore, the stratification analysis showed a verification of correlation for this variant with HCC in Asian subjects under the recessive model, while the association was observed to be significant with GC in Asian and Caucasian patients under the dominant model. TSA confirmed that this work had significant findings noting that the collective Z-curve spanned the examining borderlines prior to attaining sample size confirming the acceptability of the study sample size. Conclusion: The CTLA4 c.49A > G (rs231775; p.Thr17Ala) gene variant could be considered as an actual risk factor for the susceptibility of HCC and GC warranting efficient and adequate genetic counseling for this gene variant carriers.
- PublicationOpen AccessUsing Different Low-Profile Abutments for Assisting Mandibular Implant Overdenture: A Split-Mouth Study.(Hindawi, 2022-04-09)Background: Using a pair of different low-profile abutments to assist mandibular implant overdenture (MIOD) in limited restorative space is questionable due to the different morphology. Objective: To investigate the marginal bone level (MBL) change and peri-implant-tissue health (PITH) around a pair of OT Equator® and Locator® suprastructures assisting MIOD. Methods: Seventeen edentulous patients received MIOD assisted by OT Equator® and Locator®. MBL change was investigated at the implant loading (T1), after six months (T2) and twelve months (T3) of implant loading. PITH was evaluated at T2 and T3. Results: There was within abutment significant difference in MBL change after T2 and T3 of loading for Locator (0.05 ± 0.02 and 0.32 ± 0.08, respectively) (P=0.01); and for Equator (0.11 ± 0.08 and 0.21 ± 0.09, respectively) (P=0.01). Also, there was a significant difference between Locator and Equator on the modified plaque index (MPI) after T3 (P=0.01). The significant results were recorded for the MPI at T2 and T3 for Locator (0.92 ± 0.26 and 1.5 ± 0.51, respectively) (P=0.01) and for Equator (0.82 ± 0.26 and 1.42 ± 0.51, respectively) (P=0.003). For modified bleeding index, there was significant difference at T2 and T3 for Locator (0.57 ± 0.19 and 1.14 ± 0.41, respectively) (P=0.03) and for Equator (0.46 ± 0.22 and 1.07 ± 0.41, respectively) (P=0.01). For gingival index, there was significant difference at T2 and T3 for Locator (0.57 ± 0.11 and 1.28 ± 0.35, respectively) (P=0.001) and for Equator (0.35 ± 0.21 and 1.1 ± 0.46, respectively) (P=0.001). Conclusions: Using different pairs of the low-profile OT Equator® and Locator® abutments to assist MIOD is clinically acceptable based on the MBL change and PITH outcomes.