Dental Research Journal
Volume:18 Issue: 1, Feb 2021

The “All‑on‑four” concept for treatment of edentulous arches incorporates four implants that are placed in between mental foramina in the mandible. The prosthetic framework is an important parameter in stress/strain concentration at the implants, prosthesis, and the underlying bone. Materials such as titanium, zirconia, and carbon fibers have been used for fabrication of framework in the past. The aim of this study was to analyze the effect of framework materials in the “All‑on‑four” implant system.

Finite element three‑dimensional (3D) model of edentulous mandible was simulated using a computerized tomographic scan data of an edentulous patient. Threaded implants were replicated along with the abutments using 3D modeling software and the framework was designed and simulated using material properties of titanium, zirconia, and polyetheretherketone (PEEK). Axial and nonaxial load of 200 N was applied at the abutment region of right distal implants. The computer‑generated numerical values were tabulated and analysed by ANSYS software.

Principal strain, von Mises stress and micromotion were assessed in the peri‑implant bone region to evaluate its stress condition. Zirconia framework showed the least stress/strain values at axial and oblique loading. Maximum strain values were seen at the PEEK framework material. Zirconia framework in all models showed the least micromotion/displacement.

The stress distribution pattern at implant–bone interface was influenced by the framework material used. The framework material, loading site, and direction of forces influenced the stresses and displacement at the bone–implant interface.

The purpose of this study was to compare the microhardness values of ProRoot mineral trioxide aggregate (MTA), Biodentine, and total fill root repair material (TF‑RRM) Putty at varying pH and times.

In this laboratory experiment, materials were mixed and placed in cylinder blocks with internal dimensions of 6 mm × 4 mm. Ten samples of each material were soaked in buffered solutions of butyric acid with 4.4, 5.4, 6.4, and 7.4 pH values and stored at 37°C in 100% humidity. The samples were submitted to the microhardness test at the end of 1 week and then 1 month. Multivariate analysis of variance and Tukey honestly significant difference tests were carried out to compare the mean values at a significance level of P < 0.05.

Low pH caused a significant decrease in the microhardness values of all samples. Surface microhardness increased with time (P < 0.0001). The microhardness values of Biodentine were significantly greater than those of ProRoot MTA and TF‑RRM putty (P < 0.0001). The lowest microhardness values were recorded for TF‑RRM putty groups regardless of the pH of the environment and the evaluation time.

An acidic environment impaired the surface microhardness of all root repair materials tested. Overall, the mean surface microhardness of TF‑RRM Putty was lower than those of ProRoot MTA and Biodentine. Biodentine showed the greatest microhardness values at all pH values, regardless of the evaluation time.

This study assessed the antimicrobial activity of Biodentine, mineral trioxide aggregate (MTA), and calcium‑enriched mixture (CEM) cement against Enterococcus faecalis, Streptococcus mutans , and Candida albicans.

In this in vitro study, microbial suspensions were inoculated onto agar plates. The antimicrobial effects of MTA, Biodentine and CEM cement were assessed against E. faecalis, S. mutans, and C. albicans by the agar diffusion test. In each experimental group, 7 plates containing 3 wells were prepared and immediately filled with freshly mixed cements. Positive and negative control plates were prepared with/without the bacterial suspension, respectively. After 2 h of preincubation at room temperature, the plates were incubated at 37°C for 24 h. The diameter of growth inhibition zones was measured after 24 h. Data were analyzed using ANOVA and Tukey’s test (α = 0.05).

Biodentine showed strong antimicrobial activity against all three microorganisms with an average inhibition zone of 9.10 mm. The inhibitory effect of Biodentine on E. faecalis and C. albicans was significantly superior to that of the other two cements (P < 0.05). MTA and CEM cement showed significantly higher antimicrobial activity against S. mutans (P < 0.05). The antimicrobial effects of Biodentine on S. mutans and E. faecalis were significantly greater than on C. albicans (P < 0.05).

All cements revealed antimicrobial properties against the tested microbial strains. Biodentine had stronger antimicrobial effects against E. faecalis and C. albicans compared with MTA and CEM cement. Furthermore, the largest inhibition zones around all three cements belonged to S. mutans.

Various systemic diseases can cause oral manifestations, such as inflammatory bowel disease (IBD). This study is designed to investigate the frequency of oral manifestations in patients with IBD referred to health centers and offices in Isfahan in 2018.

This cross‑sectional study was done among 161 patients suffering from IBD in Isfahan, Iran. They were chosen by the systematic randomized sampling. Finally, the data were analyzed using the logistic regression test in the SPSS software. Significance was assigned at P < 0.05.

The number of patients with ulcerative colitis and Crohn’s syndrome was, respectively, 119 persons (73.9%) and 42 persons (26.1%). Oral manifestations were seen among 52 (32.3%) of the samples. The frequency of oral manifestations was 35.6% (31 cases) in males and 28.4% (21 cases) in females. Oral manifestations were seen in 29.4% of patients with ulcerative colitis and 40.5% of patients with Crohn’s disease. Based on the logistic regression, there was a statistically significant relationship between the use of azathioprine and mesalazine with oral manifestations (P < 0.05), whereas the severity of disease and smoking were not statistically significantly related to oral manifestations (P > 0.05).

The severity of the disease was not significantly correlated with oral manifestations, which are in agreement with the results of previous studies. It was also found that among patients with IBD, the oral aphthous ulcers can appear 1–3 years before the diagnosis of the disease. Besides that, some of the drugs used to treat the disease have a significant relationship with oral manifestations.

Nickel‑titanium (NiTi) open coils are common tools in fixed orthodontic treatments to apply light and continuous forces. Their favorable mechanical properties and their relatively high cost have prompted many clinicians to decide to reuse them.

The present study aimed to evaluate the effect of 10% hydrochloric acid (HCl) and 5.25% sodium hypochlorite (NaClO) solution and sterilization, on the unloading force of NiTi open‑coils.

This experimental in vitro study consisted of 160 NiTi open coils from two brands of Highland Metals and Masel were provided. Each group was randomly divided into four subgroups: control, three rounds of immersion, three rounds of autoclave sterilization, and three rounds of immersion and autoclaving. Each round of immersion process included 1 min in 10% HCl, followed by 5 min in 5.25% NaClO. Spring was compressed for 4 mm. Then, the unloading forces of each spring were recorded at 4, 3, 2, and 1 mm of compression, respectively. The data were analyzed with SPSS (P < 0.05), using one‑way ANOVA and independent t‑test.

One‑way ANOVA showed a significant difference in the 2‑mm compression of Group 1 and 3‑mm compressions of Groups 1 and 2 compared to the control group in the Highland metals brand (P < 0.04, P < 0.014, and P < 0.007, respectively). There was no significant difference between the different compressed lengths and groups in the Masel brand.

One‑minute immersion in 10% HCL and 5‑min immersion in 5.25% NaOCl, followed by autoclave sterilization, even after repeating the process three times, did not significantly change the force properties of NiTi open springs. Therefore, the re‑use of these springs with the above‑mentioned method as preparation can be recommended.

Most parents believe that teething is associated with some symptoms and commonly use Internet to gain more information about the health of their children. Pediatricians can also serve as a source of information for health‑related requirements of parents. This study aimed to compare the information provided by pediatricians regarding tooth eruption and the information available in Persian‑language websites.

This descriptive, analytical, cross‑sectional study was performed in two phases. In the first phase, the questionnaire was designed by 85 pediatric pediatricians in Isfahan about children’s dental eruption and internet resources. The second phase was the study of 22 Persian websites about children’s tooth eruption using Google search engine and the keywords “tooth eruption,” “tooth eruption symptoms.” Then a checklist was prepared to evaluate the quality and completeness of the content. Data were analyzed by the Chi‑square test and Fisher’s exact test using SPSS (P < 0.05).

None of the retrieved websites had the health on the net code of conduct. The most common symptoms of teething reported by both pediatricians and websites included irritability, drooling, gingival tenderness, chewing tendency, decreased appetite and sleep disturbances. In non‑pharmacological methods to control the symptoms related to tooth eruption in both groups, embracing the baby (P < 0.001), using soft tooth ring (P = 0.049) and chewing hard foods (0.016 P = significant. Use of oral pain medication (P = 0.01) and sedatives and medications (P = 0.04) were significant in the medication method.

None of the websites reviewed had a valid source code and author. Although websites cannot replace the instructions of pediatricians regarding growth and development of children and their teething, supplementary information can be acquired from high‑quality websites because there seems to be no significant difference between these two information sources regarding tooth eruption symptoms and their management.

Various iron drops are prescribed to children to prevent iron‑deficiency anemia. The current study aimed to evaluate and compare the physicochemical profile of iron drops and the effect of these medicines on the color of primary teeth.

On the commencement of this experimental study, the pH and viscosity of five types of iron drops were measured. For the purpose of the current study, sixty healthy anterior deciduous teeth were provided; thereafter, they were assigned to five groups and then exposed to iron drops. The color and color difference of each specimen were measured by VİTA Easyshade Compact after 2 weeks. The amount of absorbed iron was determined by atomic absorption. The data were analyzed using two‑way ANOVA and Tukey’s test (P < 0.05).

As evidenced by the obtained results, all medications demonstrated acidic pH and discoloration. The viscosity values of iron drops were reported to be within the range of 2.07–33.58 cP. Based on the results of Pearson’s correlation coefficient test, discoloration showed a correlation with pH and atomic absorption (P < 0.05).

Analyzed iron drops displayed low pH and discoloration higher than 3.3 which can be easily distinguished with naked eyes. Medicine labels should include warning statements on the feasibility of dental discoloration and erosion.

There is little information concerning the biocompatibility of mouthwashes containing metal nanoparticles. This study was conducted to assess the biocompatibility of colloidal solutions containing zinc oxide (ZnO), copper oxide (CuO), titanium dioxide (TiO2), and silver (Ag) nanoparticles compared with chlorhexidine (CHX) in a culture of human gingival fibroblasts (HGFs).

This was an in vitro, experimental study. Nanoparticles, including ZnO, CuO, TiO2, and Ag, were purchased and added to a water‑based solution to produce mouthwashes. The colloidal solutions and CHX were prepared at the minimum inhibitory concentration (MIC) against Streptococcus mutans and Streptococcus sanguis. Cytotoxicity was determined by 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyl tetrazolium bromide (MTT) assay on HGFs at the concentrations of MIC, 0.1 MIC, and 0.01 MIC. To determine apoptosis, DNA fragmentation was assessed as “sub‑G1” peak on DNA content histogram. The data were analyzed using repeated measures analysis at P < 0.05.

At all concentrations, the highest and lowest mean of cell viability was related to TiO2 and ZnO groups, respectively. At MIC, the mean cell viability was significantly greater in the TiO2 group than the other groups (except the Ag group) (P < 0.05). At the concentration of 0.01 MIC, the mean cell viability in the colloidal solution containing ZnO nanoparticles was significantly lower than the other solutions (P < 0.05). The CHX and CuO‑containing solution displayed the highest rate of apoptosis among the groups.

The TiO2‑containing solution can be suggested as a suitable alternative to CHX to provide antiseptic effects with minimal toxicity.

This study was conducted to compare the shear bond strength (SBS) of orthodontic brackets to amalgam surfaces by two surface treatment methods, two different adhesives, and one intermediate resin and also to evaluate surface roughness after two preparation methods as well as bond failure mode.

In this in‑vitro study forty‑eight amalgam samples were randomly allocated to four groups. In Groups 1–3, specimens were sandblasted with 50 μm aluminum oxide, followed by application of Alloy primer in Groups 1 and 2. In Group 3 Alloy primer had not used. In Group 4, samples were prepared by silica coating using a silane coupling agent. Surface roughness analysis was performed in 10 additional samples after two surface treatments. The brackets in Group 1 were bonded with Transbond XT and those in other groups were bonded with Panavia V5. All specimens were examined for SBS following 5000 times thermocycling at 5°C–50°C. Modified adhesive remnant index was utilized for the bond failure mode. Data analysis was done by one‑way analysis of variance, post hoc Tukey, Kruskal–Walli and Mann–Whitney U tests. Statistical significance was set at P < 0.05.

The findings indicated the mean SBS were low (ranged from 0.19 to 4.66 MPa) and significantly lower in Group 3 than in Group 4 (P = 0.009). Bond failure occurred in adhesive/ amalgam interface in nearly all samples. Silica coating produced significantly lower roughness than sandblast (P = 0.009).

Silica coating had a significant higher bond strength than sandblast without application of Alloy primer. However compared to sandblast with Alloy primer, silica coating did not significantly improve the bond strength. Chemical bond between PanaviaV5 and sandblasted amalgam was not considerable.

Glass fiber posts, along with their esthetic properties, may have a better stress distribution than cast posts, Therefore, the aim of the present study was to investigate the effect of glass fiber, casting, titanium, and zirconia posts on stress distribution in maxillary central tooth treated with different amounts of ferrule using finite‑element analysis.

In this experimental study, three‑dimensional models of maxillary central incisors that have undergone root canal treatment were designed. Then, the models were divided into four groups according to the type of post (Ni‑Cr casting, glass fiber, titanium, and zirconia) used. Zirconia monolithic crowns were used in all the four groups. Ferrule heights were repeated at 0 and 2 mm in all models. Models were entered into COMSOL Metaphysics software. Then, the force of 100 N with the angle of 135° on the palatal surface was applied to the longitudinal axis of the tooth, and the stress distribution in the models was investigated.

Maximum stress was observed in the middle third of posts. Stress distribution in glass fiber post was better than zirconia and casting posts. Stress accumulation in models with zirconia, titanium, and casting posts was also found in the site between the middle third and coronal third, whereas in models with glass fiber post, stress accumulation was found between the crown and the cemento‑enamel junction. In models without ferrule, stress accumulation was observed in one‑third of the coronal, especially in glass fiber posts.

The post material and ferrule height affected stress concentration. The stress in the cervical area of the dentin was more for glass fiber post when compared to other posts. The use of glass fiber post in teeth with no ferrule results in lower stress along the post, but greater stress in the simulated tooth region.