Could various angulated implant depths affect the positional accuracy of digital impressions? An in vitro study.

PURPOSE: The purpose of this in vitro investigation was to assess how implant depth could affect the three-dimensional positional accuracy of digital impressions made from angulated implants. MATERIALS AND METHODS: Four modified maxillary models were printed and divided into four study groups. In each model, two angulated implant analogs were placed at the sites of the first premolar and first molar at four different depths of 1 (G1), 2 (G2), 3 (G3), and 4 (G4) mm from the models' edentate area. Scan bodies were connected to the analogs, and one operator made 10 full-arch scans for each master model using an intraoral scanner. Afterward, the marginal gingival part of all models was removed, and digital scans were performed for each model using a laboratory scanner to achieve a reference STL file as the control group. One-way ANOVA and Leven's tests were used to measure and compare the 3D distance deviations across research groups after the superimposing test and control scans. RESULTS: A significant difference between research groups was revealed by trueness and precision analysis (p < 0.001). The trueness and precision results obtained for G1 and G4 were significantly better than those for G2 and G3 (p < 0.05). CONCLUSION: This study demonstrated that implant depth could affect the digital implant impressions' 3D positional accuracy.

Effect of denture cleansers on color stability and surface properties of denture base material containing titanium dioxide nanoparticles.

PURPOSE: To investigate the effect of different denture cleansers on color stability, surface roughness, and hardness of polymethylmethacrylate (PMMA) infused with titanium dioxide nanoparticles (TiO2 NPs) at concentrations of 1% and 2% by weight on each. MATERIALS AND METHODS: In this in vitro study, 90 disc-shaped specimens (10×10×2 mm) were divided into 3 main groups: the non-containing nanoparticle group (0wt% concentration), 1wt% concentration, and 2wt% concentration TiO2 NPs groups. Each group was further assorted into 3 subgroups (n = 10): immersed in distilled water, oxygenating tablet (Corega), and 0.5% sodium hypochlorite. Color change, surface roughness, and hardness values were assessed after 90 and 180 days of storage. Color changes (∆E) were measured with a spectrophotometer (VITA, Easy Shade V, Germany) and assessed using the CIE L*a*b* colorimetric system and the American National Bureau of Standards (NBS = 0.92×∆E). The surface roughness and surface hardness values were measured using a profilometer device and Vickers hardness tester, respectively. First, ANOVA-repeated measurements were performed, followed by the Tukey test. The significance level in this study was considered 0.05. RESULTS: At all concentrations, there were significant differences in the mean color changes of samples immersed in cleansers compared to distilled water (p < 0.01). Moreover, hypochlorite caused a significant increase compared to Corega at 0wt% concentration after 90 days and at 1wt% concentration after 90 and 180 days. Evaluations also showed that the mean NBS values in all cleanser groups were in the range of appreciable change, except the water group. In addition, only hypochlorite changed the color higher than the clinically acceptable range (∆E >3.7). The mean roughness of samples immersed in hypochlorite at 0wt% concentration was significantly higher than the samples containing TiO2 NPs (p = 0.006). No significant difference was observed in surface roughness of samples containing different concentrations of TiO2 NPs immersed in different cleansers; however, hypochlorite increased the surface roughness of samples without TiO2 NPs compared to samples containing TiO2 NPs after 180 days. The immersion time in cleansers had a significant influence on the surface roughness and hardness while having no effect on the color. CONCLUSION: In general, the cleansers had a significant effect on color change in all groups compared to distilled water. The adverse effect of hypochlorite was more than Corega. The cleansers in the samples containing TiO2 NPs did not make a significant difference in surface roughness in comparison with the distilled water groups. Surface hardness of the samples was not affected in a steady pattern by the cleansers.

Effect of external staining on the optical properties and surface roughness of monolithic zirconia of different thicknesses.

STATEMENT OF PROBLEM: The effect of the number of external staining applications on the color, translucency, and surface roughness of monolithic zirconia is not known. PURPOSE: The purpose of this in vitro study was to investigate the effect of glazing and repeated external staining on the color, translucency, and surface roughness of 2 types of monolithic zirconia with 2 different thicknesses. MATERIAL AND METHODS: Thirty-two 10×10-mm monolithic zirconia blocks, of which 16 were super high translucent and 16 were high translucent, were milled. The thickness of half the blocks was 0.7 mm, and the others were 1.2-mm thick. Four specimens in each subgroup were colored with value stain, and the other half with yellow stain. Staining was repeated twice for each specimen. The color and translucency of each specimen were measured before overglazing as the baseline, after overglazing, and after each staining process by using a spectrophotometer. The surface roughness (Ra) was measured after overglazing, the first staining, and the second staining. Data were analyzed by using repeated measures ANOVA and the independent t test (α=.05). RESULTS: The number of coloring, type of coloring, and thickness changed the optical properties of monolithic zirconia. a∗, b∗, L∗ Value and ΔE were affected by the stage of firing (glazing, first staining, and second staining) (P<.001). ΔE Increased after the first and second staining in each type and thickness of monolithic zirconia and each type of stain. The amount of ΔE change was more for the first staining stage. The color difference (ΔE) after overglazing ranged from 3.08 to 3.75. The highest changes in color were related to the first staining with yellow colorant of super-high-translucent monolithic zirconia (cubeX²) with 0.7-mm thickness (ΔE=17.62). The surface roughness of the specimens was affected by the number of colorings (P<.001). In all groups, the first staining increased the surface roughness, and the second staining decreased the surface roughness. The type of monolithic zirconia (P=.756), thickness (P=.735), and type of stain (P=.239) had no significant effect on the surface roughness. CONCLUSIONS: The first stage of staining with both stains caused more color change in all types and thicknesses of monolithic zirconia. Translucency increased after glazing and decreased after the first and second staining. The first staining increased the surface roughness, and the second decreased the surface roughness.

Upregulation of serum vascular endothelial growth factor and matrix metalloproteinase-3 in patients with oral squamous cell carcinoma.

Vascular endothelial growth factor (VEGF) is known as a fundamental regulator of angiogenesis that accelerates cellular proliferation, vascular permeability, and endothelial cell migration and is an inhibitor of apoptosis. Extracellular matrix degradation by matrix metalloproteinase (MMP) is necessary for endothelial cell proliferation, migration, and metastasis. Accordingly, the objective of the present study was to determine the circulating levels of VEGF and MMP3 and their relation in patients with oral squamous cell carcinoma. Using an ELISA kit, the circulating levels of VEGF and MMP-3 in the sera of 45 patients with oral squamous cell carcinoma (OSCC) and 45 healthy controls were assessed. Mean VEGF levels in the sera of patients with OSCC (122.4 ± 36.1) were significantly higher than those in controls (65.3 ± 23.4); however, no relation was found between VEGF levels and clinicopathologic factors. The serum MMP-3 level in OSCC patients was significantly higher (9.45 ± 4.6 ng/ml, n=45) than that in healthy controls (5.9 ± 3.6 ng/ml, n=45). There was no correlation in serum MMP-3 concentration with clinicopathologic features such as tumor stage, tumor size, nodal status, and histological grade. A significant relationship was found between serum levels of VEGF and MMP3. This study concludes that VEGF and MMP3 may have a potential role in the pathogenesis of OSCC but cannot be used as a tool for monitoring tumor progression. Moreover, the role of VEGF in the regulation of angiogenesis is in part due to activation of MMP-3.

Evaluation of the effect of surface roughness and modification of implant abutment axial wall on the retention of zirconium oxide copings before and after thermocycling.

Background: The purpose of this study was to determine the effect of one-wall elimination of the abutment and also the surface treatment of the abutment on the retention of cement-retained, implant-supported zirconium oxide copings. Material and Methods: In this experimental study, four straight abutments were connected to four implant analogs (DIO, UF, Busan, Korea) with 35 Ncm torque. They are mounted vertically in resin blocks. Abutments were prepared as following groups: A) abutment was used in its intact standard form as a control group. B) 4 mm of the flat wall was removed to produce an abutment with 3 walls. C) The abutment surface was abraded with 50 µm AL2O3 powder. D) 4 mm of a flat wall of the abutment was removed, then the abutment surface was abraded with 50 µm AL2O3 airborne particle.10 zirconium oxide copings were made. Samples were cemented with temp bond NE to abutments. The retention of copings was measured before and after incubation using the universal testing machine. T-test, one-way ANOVA, and Post Hoc Tukey Test were used for statistical analysis of data. Results: In all groups, retention was decreased after thermocycling (P ≤0.001). 3 wall abutments had less retention than the control group before thermocycling. A significant difference was detected between 3 wall abutments and 4 walls of sandblasted abutments before thermocycling. After thermocycling, no difference in retention was seen between groups. Conclusions: Thermocycling significantly reduces the retention of implant-supported ceramic copings. Sandblasting abutments with 50 µm AL2O3 air-borne particles did not increase the retention of ziconium oxide copings which were cemented with temp bond NE. One wall elimination of abutment decreased the retention of zirconia copings. Key words:Retention, crown, abutment, zirconia coping, sandblasting.

Evaluation of the effect of different core substrates on the accuracy of intraoral scanners.

BACKGROUND: The aim of this study was to determine if different types of core substrates have any effect on the trueness and precision of digital intraoral impressions. MATERIAL AND METHODS: A customized typodont with four similar cores of natural dentine, composite, metal (Ni-Cr), and zirconia in the position of premolars was fabricated. The study model was scanned five times with two types of intraoral scanners (Carestream 3600 and 3Shape Trios 3), and a reference standard scan was obtained using a laboratory scanner (3shape D1000). A metrology software (Geomagic X) was used to align the data of experimental scans and the reference scan to determine deviation values (trueness). Precision values were calculated with random superimposition in each intraoral scanner group. The Kruskal-Wallis test was used to compare differences between different substrates, and the Mann-Whitney test was used to compare the average values between the two scanners. RESULTS: Trios 3 was found to be significantly truer and more precise than Carestream 3600 (p value = .005, <0.001). There were no significant differences in the trueness of different substrates when they were scanned by Trios 3, while different materials showed significantly different trueness values in the Carestream 3600 group (p value = .003). Dentin showed the best trueness, and zirconia performed worse than other substrates. Regarding the precision of the scanners, neither of the scanners was affected by the type of scanning substrate. CONCLUSION: For Carestream 3600, substrate type did impact the trueness of intraoral scans, with dentin and zirconia showing the highest and lowest accuracy, respectively, while Trios 3 was similarly accurate across all substrates. Trios 3 had both higher trueness and precision than Carestream 3600.

Oral rehabilitation with dental implants in patients with systemic sclerosis: A systematic review.

OBJECTIVE: To assess the influence of systemic sclerosis (SSc) on the survival rate of dental implants in SSc patients receiving implant-supported treatments. METHODS: The Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) Statement and the Cochrane Collaboration's guiding principles were followed during the study's execution. The data from three databases, PubMed, Google Scholar, and Scopus, available until January 2023, were used to compile the material for our research. Only English-language publications were submitted for this research and evaluated based on their titles, abstracts, and full texts. For performing a quality assessment, quality scores were calculated. RESULTS: The total number of patients and implants studied were 37 and 153, respectively, all having had scleroderma. The patients' ages ranged from 28 to 77 years old, with a mean (SD) age of 58.16 (12.88). All the patients in the case reports and most in the case series study were female. The range of follow-up duration was from 1 to 10 years. In case report studies, the survival rate was 100%; in case series, it was 89.2%. CONCLUSION: The SSc status had no discernible impact on the implant survival rate. Implant-based treatments in SSc patients should not worsen the overall morbidity and should not conflict with systemic treatments. Before starting implant therapy, a thorough risk assessment is essential, though.

Comparing Castability of Nickel-Chromium, Cobalt-Chromium, and Non-Precious Gold Color Alloys, Using two Different Casting Techniques.

Statement of the Problem: The castability of nonprecious gold color alloy using torch/ centrifugal and induction/vacuum-pressure casting techniques has not been studied yet. Purpose: This study was conducted to compare the castability of nickel chromium, cobalt-chromium and nonprecious gold color alloy using torch/centrifugal and induction/ vacuum-pressure casting techniques. Materials and Method: In this in vitro study, a total number of 54 identical acrylic wax meshes were prepared and divided into 6 different groups of 9 each. Group 1: nickel-chromium alloy, which was casted with induction technique. Group 2: nickel-chromium alloy was casted with centrifugal technique. Group 3: cobalt-chromium alloy was casted with induction technique. Group 4: cobalt-chromium alloy was casted with centrifugal technique. Group 5: nonprecious gold color alloy was casted with induction technique. Group 6: nonprecious gold color alloy was casted with centrifugal technique. Then castability of specimens was measured using modified Whitlock's method. The results were analyzed using two way ANOVA and post hoc tests. Results: ANOVA test revealed no statistically significant difference between different alloys with a p Value of 0.313. Moreover, it represented no significant differences within the groups regarding alloy types and casting techniques with a p Value of 0.511 and 0.682, respectively. Conclusion: No significant difference was found in the castability value of nickel-chromium, cobalt-chromium, and nonprecious gold color alloys. In addition, the castability value of three alloys tested in this study was not different by using torch/centrifugal or induction/vacuum-pressure casting machines.

A Special Design to Facilitate Retrieval of Cement-Retained Zirconia-Based Implant-Supported Restorations.

STATEMENT OF THE PROBLEM: Retrieval of cement-retained implant-supported restorations is challenging in cases of screw loosening or periodontal problems. PURPOSE: The purpose of this study was to evaluate the effect of the screw access hole on the fracture resistance of zirconia-based cement-retained restorations with and without an access opening. MATERIALS AND METHOD: In this in vitro study thirty-three cement-retained implant-supported zirconia-based molar crowns were fabricated and divided into 3 groups (n=11). As the control group, group 1 consisted of conventional cement-retained crowns. Group 2 comprised conventional cement-retained crowns in which a hole was created in the location of the screw. Group 3 consisted of cement-retained crowns in which a ledge was created in the location of the screw access channel. The specimens were cemented to their abutments and their access openings were filled with composite resin. A compressive load was applied to the specimens using a universal testing machine until they fractured. The mean fracture resistance values of the samples were compared by using the one-way ANOVA and Tamhane post-hoc test (a=0.05). RESULTS: The mean fracture resistance values were 1270.18± 12.67 N in group 1 (the control group), 960.09±210.67 N in group 2 (conventional), and 1357.81±361.68 N in group 3 (the special design). The fracture resistance value was higher in the special design group than that of the conventional design (p= 0.018) and the fracture resistance value of the conventional design group was less than that of the control group (p= 0.042). No statistically significant difference was detected between the control group and the special design group in fracture resistance values. CONCLUSION: Preparing a screw access hole in cement-retained implant-supported zirconia-based crowns decreased the fracture resistance of the restoration. Designing a ledge in the zirconia framework around the access hole may increase the fracture resistance of the restoration.

Comparison of temporomandibular disorders between menopausal and non-menopausal women.

OBJECTIVES: Hormonal changes during menopause alter a woman's susceptibility to some disorders. Information regarding the prevalence of temporomandibular disorder (TMD) in menopausal women is limited in the literature. In this study, the prevalence and severity of TMDs were compared between menopausal and non-menopausal women. MATERIALS AND METHODS: The study included 140 women (69 premenopausal and 71 postmenopausal) 45 to 55 years of age that were examined in Shiraz Dental School, Shiraz in Iran. The Helkimo clinical dysfunction index (Di) was used to evaluate temporomandibular joint (TMJ) dysfunction. The data were analyzed using chi-square and Fisher's exact tests. RESULTS: Occurrence of TMD was significantly higher in menopausal than non-menopausal women (P<0.001). All the TMD criteria based on Helkimo Di except range of mandibular movement were significantly more common in menopausal women. The range of mandibular movement was not significantly different between menopausal and non-menopausal women (P=0.178). CONCLUSION: The results from this study show that TMD can be considered more common and severe in menopausal than non-menopausal women. This finding indicates that, similar to other conditions in menopausal women such as arthritis and osteoporosis, TMD should be taken into consideration by dental and medical professionals.

The effect of various veneering techniques on the marginal fit of zirconia copings.

PURPOSE: This study aimed to evaluate the fit of zirconia ceramics before and after veneering, using 3 different veneering processes (layering, press-over, and CAD-on techniques). MATERIALS AND METHODS: Thirty standardized zirconia CAD/CAM frameworks were constructed and divided into three groups of 10 each. The first group was veneered using the traditional layering technique. Press-over and CAD-on techniques were used to veneer second and third groups. The marginal gap of specimens was measured before and after veneering process at 18 sites on the master die using a digital microscope. Paired t-test was used to evaluate mean marginal gap changes. One-way ANOVA and post hoc tests were also employed for comparison among 3 groups (α=.05). RESULTS: Marginal gap of 3 groups was increased after porcelain veneering. The mean marginal gap values after veneering in the layering group (63.06 µm) was higher than press-over (50.64 µm) and CAD-on (51.50 µm) veneered groups (P<.001). CONCLUSION: Three veneering methods altered the marginal fit of zirconia copings. Conventional layering technique increased the marginal gap of zirconia framework more than pressing and CAD-on techniques. All ceramic crowns made through three different veneering methods revealed clinically acceptable marginal fit.

Serum level of MMP-3 in patients with oral squamous cell carcinoma--lack of association with clinico-pathological features.

BACKGROUND: MMP-3 is a proteolytic enzyme of the matrix metalloproteinase family. Protein degradation which is their fundamental action regulates different activities of tumor cell such as their growth, differentiation, apoptosis, migration, invasion, angiogenesis as well as their resistance to the immune system. AIM: The aim of this study was to determine MMP-3 serum levels in patients with OSCC and investigate if they correlate with clinicopathological features. METHOD AND MATERIALS: Using an ELISA kit, we assessed and compared the circulating levels of MMP-3 in blood serum of 45 oral squamous cell carcinoma patients with 45 healthy control samples. RESULTS: The serum MMP-3 level in OSCC patients was significantly higher (9.45±4.6 ng/ml) than healthy controls (5.9±3.6 ng/ml, p<0.001), especially in females and in older patients. However, there was no apparent correlation in serum MMP-3 concentration with the clinico-pathological features such as tumor location, stage, tumor size, nodal status, distant metastasis, histological grade and smoking. DISCUSSION: This result suggests that the measurement of serum MMP-3 concentration might be helpful to diagnose OSCC but not to predict prognosis.