Saeid Mahmoudian, Sareh Farhadi, Maryam Hosseinzadeh,
Volume 8, Issue 2 (4-2023)
Abstract
Background and Aim: Multiple studies have shown the common co-occurrence of tinnitus and temporomandibular disorders (TMDs). This study assessed the effectiveness of a conservative treatment for TMD signs and symptoms of six patients with tinnitus-related complaints.
Materials and Methods: Six patients with persistent non-pulsatile tinnitus were evaluated in this case series. The tinnitus characteristics evaluated included pitch and loudness matching (PMT-LMT), minimum masking level (MML), and residual inhibition (RI). In addition, the Persian versions of the 52-item Tinnitus Questionnaire (TQ), the Tinnitus Handicap Inventory (THI), and the Steigerwald/Maher TMD Disability Index (SMTDI) were used. The corresponding TMD treatment plan was subsequently implemented, taking into account the subtype of the disease. The data were statistically analyzed at 0.05 level of significance.
Results: The mean SMTDI score significantly decreased after treatment (P=0.0001) and the symptoms of TMD effectively resolved. Comparison of visual analog scale (VAS) scores of tinnitus patients before and after TMD therapy indicated statistically significant changes (P<0.05) in intensity, irritation, and awareness. Comparison of the mean tinnitus evaluation test scores before and after TMD therapy in tinnitus patients indicated a significant change only in PMT (P=0.039). Comparison of THI and TQ scores before and after TMD therapy revealed significant changes in tinnitus patients (P<0.05). |
Conclusion: In case of correct selection of patients with concurrent somatosensory tinnitus and TMD signs and symptoms, TMD therapy might alleviate this condition, according to the present findings. Consequently, a multidisciplinary approach may be useful in treatment of such cases.
Faranak Zolfagharloo, Neda Nasr, Omid Tavakkol, Marzieh Momayezinejad,
Volume 8, Issue 2 (4-2023)
Abstract
Background and Aim: This study assessed the effect of crown dimensions on stress distribution in the abutment screw upon loading using three-dimensional (3D) finite element analysis (FEA).
Materials and Methods: Eighteen finite element models were designed using Mimics, 3D-Matic, Catia, and ANSYS software programs. Implant models were designed with 8.5-, 10- and 11.5-mm fixture heights, three different vertical cantilever heights of 8, 10, and 12 mm, and two horizontal cantilever lengths of 7 and 14 mm for the mandibular first and second molars. The interaction effect of of 120 N and 20 N loads on the implant and implant crown at the site of first molar, and the interaction effect of 150 N and 25 N loads on the cantilever at the site of second molar were analyzed.
Results: By an increase in horizontal cantilever length, stress in the abutment screw, abutment, and fixture increased in all models. Stress decreased in the abutment screw and increased in the abutment and fixture by an increase in vertical cantilever. Minimum screw stress was recorded in implants with 8.5 mm fixture height, 7 mm horizontal cantilever, and 12 mm vertical cantilever. Maximum screw stress was noted in implants with 11.5 mm fixture height, 14 mm horizontal cantilever, and 8 mm vertical cantilever.
Conclusion: According to FEA, increasing the horizontal and vertical cantilever length may result in an increased risk of screw loosening and fatigue fracture due to increased stress values in the screw or in other components (abutment and fixture), respectively. |
Arezu Babasafari, Ezatollah Jalalian, Arash Zarbakhsh, Abdolkarim Rostamian, Shaghayegh Golalipour, Sotoudeh Khorshidi,
Volume 8, Issue 3 (8-2023)
Abstract
Background and Aim: This study aimed to assess the effect of horizontal cantilever on microgap and microleakage at the implant-straight abutment interface in cement-retained crowns.
Materials and Methods: In this experimental study, 12 implant-abutment assemblies and 12 cement-retained crowns were evaluated. The implant fixtures were bone-level, and had 10 mm length and 4 mm diameter. Straight titanium abutments had 7 mm length, 4 mm diameter, and 1 mm gingival height with Morse-Taper connection. Two groups were evaluated: 6 cement-retained crowns with a horizontal cantilever (test group) and 6 cement-retained crows without a horizontal cantilever (case group). The assemblies underwent load cycling in a chewing simulator. Cyclic load (75 N) with 1 Hz frequency was applied along the longitudinal axis of each specimen to the triangular ridge between the mesiobuccal and mesiolingual cusps of the crown. The amount of microgap before and after cyclic loading, and the microleakage score after immersion in fuchsine were evaluated under a light microscope. Data were compared by t-test (alpha=0.05).
Results: The change in microgap after cyclic loading compared with before was not significant in the control group (P=0.724). However, in the case group, the amount of microgap significantly increased after cyclic loading compared with before (P=0.000). Microleakage in the case group was significantly greater than that in the control group (P=0.019).
Conclusion: Horizontal cantilever caused horizontal microgap and increased the microleakage at the implant-straight abutment interface. |
Sarira Mehraban Jahromi, Mohammad Alidad Naeeni, Reza Mostafa Pour, Reza Nahidi, Ali Kaboudanian Ardestani,
Volume 8, Issue 3 (8-2023)
Abstract
Background and Aim: This study compared the flexural strength (FS) of heat-cure acrylic resin following one- and two-step processing techniques in dry and wet conditions.
Materials and Methods: In this in vitro study, 60 acrylic specimens (3×10×65 mm) were fabricated (ISO20795-1) and flasked using a type III dental stone. The specimens were heated to 70°C for one hour and baked for 30 minutes at 100°C. After cooling and polishing, 30 specimens were randomly selected; of which, 15 were stored in 37°C water, and 15 in dry condition for one month. The remaining 30 were flasked again, baked, and divided into two subgroups for storage in dry and wet conditions. The FS of specimens was measured by a universal testing machine. Data were analyzed by one-way ANOVA and Tukey's post-hoc test (α=0.05).
Results: The mean FS was 57.5±4.8 MPa and 61.7±4 MPa for specimens subjected to one-step processing and stored in wet and dry conditions, respectively. These values were 56.6±4 MPa and 64.7±2.9 MPa for specimens subjected to two-step processing and stored in wet and dry conditions, respectively (P<0.05). The difference in FS of specimens stored in dry and wet conditions was significant (P<0.05).
Conclusion: The two-step processing technique increased the FS while water storage decreased the FS of acrylic resin. FS of specimens subjected to one-step processing with water storage was slightly higher than that of specimens subjected to two-step processing with water storage. FS experienced a greater reduction following two-step processing in a wet environment compared with one-step processing. |
Gholamreza Esfahanizadeh, Reza Kooshki, Hamed Karimipoor, Verishe Rastin,
Volume 9, Issue 1 (3-2024)
Abstract
Background and Aim: This study aimed to assess the effects of chlorhexidine (CHX) and Listerine mouthwashes on color stability of glazed bilayer zirconia and IPs e.max ceramics.
Materials and Methods: This in vitro experimental study was conducted on 36 glazed bilayer zirconia and IPS e.max ceramic specimens. The baseline CIE L*a*b* color parameters of specimens were measured by a spectrophotometer. The bilayer zirconia and IPS e.max ceramic specimens were then randomly assigned to two subgroups for immersion in 10 mL of 0.2% CHX (n=9) and 10 mL of Listerine (n=9). The specimens were immersed in the respective solutions for 2 minutes daily for 7 days. Next, their color parameters were spectrophotometrically measured again. The color change (∆E) of ceramics in the three groups was calculated and compared by the Kruskal-Wallis test and two-way ANOVA (alpha=0.05).
Results: The L*, a*, and b* color parameters of glazed bilayer zirconia and IPs e.max ceramic specimens were not significantly different at baseline (P=0.8) or after the intervention (P=0.6). The ∆E of the subgroups was not significantly different either (P>0.05).
Conclusion: Both glazed bilayer zirconia and IPs e.max ceramics showed clinically acceptable color stability (∆E<3.3) following immersion in CHX and Listerine mouthwashes.
Zahra Jaberi Ansari, Azam Valian, Anahit Afrasiabi, Parisa Amdjadi,
Volume 9, Issue 4 (12-2024)
Abstract
Background and Aim: Hybrid ceramics are gaining popularity for cosmetic dental restorations due to their advantageous mechanical properties and optimal esthetic results. However, the potential effects of bleaching on their color stability are still a subject of interest. This study aimed to assess the effect of bleaching on stained hybrid ceramics in comparison with IPS e.max.
Materials and Methods: This in vitro study was conducted on 48 specimens fabricated from IPS e.max CAD, Vita Enamic, and Cerasmart (n=16) ceramics. The baseline color coordinates of the specimens were measured by a spectrophotometer. Eight specimens from each ceramic type underwent accelerated aging, and their color coordinates were measured again to calculate the color change (ΔE1). The remaining 8 specimens in each ceramic group were immersed in tea solution, and their ΔE was calculated (ΔE2). Subsequently, all specimens were exposed to 20% carbamide peroxide for 8 hours/day for 10 days, and ΔE3 and ΔE4 were calculated. Data were analyzed by two-way ANOVA and Tukey’s test (alpha=0.05).
Results: Type of ceramic, type of intervention (aging, immersion in tea solution, bleaching), and their interaction significantly affected the ΔE (P=0.0001). The maximum and minimum ΔE values were recorded for Cerasmart and IPS e.max ceramic, respectively.
Conclusion: Both accelerated aging and immersion in tea solution caused staining of hybrid ceramics. The minimum ΔE after bleaching occurred in aged ceramics. Bleaching of stained ceramics improved their color.
Vamsee Priya Golla, Satyanarayana Raju Mantena, Rama Krishna Alla, Vineeth Guduri, Suresh Sajjan Mc, Bheemalingeswara Rao D, Deepika Kandukuri,
Volume 10, Issue 1 (3-2025)
Abstract
Background and Aim: Several studies have investigated the effect of addition of fillers on mechanical strength of denture base materials. This study aimed to evaluate the mechanical properties of heat-cure denture base materials incorporated with different concentrations of zirconia nanotubes (ZNTs).
Materials and Methods: In this in vitro study, 90 specimens were fabricated from each denture base resin material (Trevlon and DPI) and divided into three groups (n=30) based on the mechanical properties to be tested (flexural strength, impact strength, and surface hardness). Thirty specimens in each group were further subdivided into 5 subgroups (n=6) based on the weight percentage (wt%) of ZNTs (0.0wt%, 0.5wt%, 1.0wt%, 2.0wt%, and 5.0wt%). The specimens were subjected to flexural strength, impact strength, and surface hardness testing using a universal testing machine, IZOD impact testing machine, and Vickers hardness tester, respectively. One-way ANOVA and post-hoc tests were used for statistical analyses (alpha=0.05).
Results: The maximum flexural strength was observed following the inclusion of 2.0wt% and 1.0wt% ZNTs in Trevlon and DPI, respectively. The maximum impact strength was obtained with the addition of 1.0wt% ZNTs to both Trevlon and DPI. The surface hardness of Trevlon and DPI increased significantly with an increase in the concentration of ZNTs (P=0.005). Flexural strength (P=0.000) and surface hardness (P=0.005) were significantly different among various concentrations of Trevlon and DPI, but the impact strength (P=0.013) was significantly different only in DPI.
Conclusion: The optimal concentration of ZNTs to obtain enhanced mechanical properties of denture base resins was found to be 1.0wt%.
