مجله دندانپزشکی دانشگاه علوم پزشکی تهران
سال سی‌ام شماره 4 (پیاپی 93، زمستان 1396)

For the clinical success of implant-retained prostheses, fitness of matching components and stability of the applied torque to the implant-abutment assembly under dynamic occlusal loading is essential. The aim of this study was to evaluate the torque loss in Co-Cr castable abutments after cyclic loading.
10 castable abutments were cast in Co-Cr alloy with similar size and height. Each specimen was mounted vertically on a separated implant using a 30 Ncm tightening torque. The detorque values of the abutments were evaluated after 10 min. The same tightening torque was applied to the abutments on their corresponding implants and cyclic loading was applied for 500,000 cycles to the implant-abutment assembly. The torque values after cyclic loading were recorded for each specimen. T-test analysis was conducted on scores from the groups.
Resultes: The results of this study showed that the percentage of torque loss in castable abutments was significantly increased after cyclic loading (P Misfit between the castable implant components can cause torque loss before and after cyclic loading. However, it is more appropriate to relate the results of this study to the screw loosening of the above mentioned abutments than judging their clinical performance.

Microhardness, sorption, and solubility are useful predictors of a resin composite’s clinical success. This study aimed to evaluate the effect of 60 days of water storage on the microhardness, sorption, and solubility of 3 commercial nanohybrid resin composites.
Three nanohybrid composites were evaluated: GC Kalore (GC), Aura (SDI), and G-ænial Universal Flo Universal Flo (GC). Ten disc-shaped samples were prepared for each material. After baseline weight measurement, the specimens were stored in distilled water for a period of 60 days, and then in desiccators for another 60 days. Specimens were weighed at 24 hours, 7 and 60 days of water storage and desiccation. For the microhardness test, 24 were prepared for each material and divided into 6 groups based on storage media (dry and wet) and storage time (24 hours, 7 days, and 60 days). Specimens were tested by a digital Vickers microhardness tester after storage and data were analyzed using SPSS software.
G-ænial Universal Flo Universal Flo showed the highest sorption and solubility and the lowest microhardness after 60 days of water storage. GC Kalore showed lower sorption and solubility compared to Aura. Also GC Kalore had higher microhardness than Aura after 60 days of storage in water, while Aura had higher microhardness in dry storage.
Composites with lower sorption and solubility showed higher microhardnss in wet conditions. Flowable composite resin showed the lowest microhardness and the highest sorption and solubility values. Therefore, the negative effect of water sorption and solubility on Surface microhardness should be considered in clinical decisions.

Marginal gap measurement in all ceramic restorations they are of fundamental important for the successful used. As some studies led to contradiction results, yhe aim of this study is to compare marginal gap restorations between 4 kinds of ceramic restorations Inceram, IPS-e.max Press, Zirconia (CAD/CAM) and PFM.
In this In-vitro experimental research, one stainless steel die with deep chamfer finish line design (1 mm depth) was prepared on a maxillary premolar. 40 epoxy resin dies were made, dies were divided in to 4 groups (n=10), Zirconia, IPS e.max press, Inceram, Mental Ceramic systems (MC). Then, the prepared crowns were put on the stainless steel die and observed their marginal mismatch under sterio microscope before cementation. Data were analyzed by One- way ANOVA, and one sample kolmogorosmirnov tests.
Resultes: There was significant difference in the marginal gaps between (MC) (102.92±28.7), Inceram (98.41±24.91), IPS e.max press (128.22±25.48), and Zirconia (69.5±10.9) (P=0.0001).
The comparison of marginal gap for the four groups was significant test. Therefore, it can be concluded that marginal gap, the probability of leakage and recurrence of caries in Zirconia systems is the least and in the IPS e.max press systems is the most.

According to many uses of MTA in different treatments, studying about its properties like the setting time, is of great importance. The aim of this study was to compare the initial and final setting time of an Iranian MTA and a foreign MTA.
Seven samples were in each group; for measurement of initial and final setting time of MTAs, a mold with dimension of 2×10 mm was prepared. The cements after mixation were put into an incubator with temperature of 37ₒC and humidity of 90%. After mixing of cements, a Gilmore needle with a weight of 100 gr and active tip of 2 mm was used vertically on the surface of MTA for measurement of the initial setting time. Setting was measured by the start of cement mixation to the time the tip of the needle didn’t penetrate to the surface of MTA. For measurement of the final setting time a Gilmore needle with a weight of 456 gr and active tip of 1mm was used vertically on the surface of MTA. The ANOVA test followed by Tukey test was used for comparison of the mean setting time between an Iranian and foreign MTA. The statistical difference was considered significant at the level of 0.05.
Resultes: The mean initial setting time Angelus and Root MTAs were 13.57±0.91 and 11.14±0.92 min, the mean final setting of Angelus and Root MTA, were 48.93±1.54 and 37.86±1.5 min while the initial setting time of Angelus MTA lasted for 0.53±43.2 more min than Root MTA (P=0.001). The final setting time of Angelus MTA took longer for 110.7±0.82 min than Root MTA (P=0.001).
The initial and final setting time of the Iranian MTA was shorter than the foreign one and thus it could a more alternative option in this respect.

A suitable restorative material must have acceptable mechanical properties. The aim of this study was to evaluate the effect of conventional acidic drinks on the micro-hardness of two dental resins.
48 samples of each of P60 and G-aenial composites were prepared and randomly divided into six groups: Coca-Cola, Fanta, yoghurt drinks, soft beer, Sprites and control groups. The study was in 3 steps: after one day in distilled water and after one day and one week of immersion in beverages per day (6 hours). The Vickers micro-hardness was then evaluated. Finally, data were analyzed by, t-tests, ANOVA and Tukey tests.
Resultes: Comparing the results between the two groups, a significant difference between the two composite was found. After one day in the water, the average micro-hardness for P60 was of 27.12 (kgf/mm2) and 16.51 (kgf/mm2) for G-aenial amount and these differences were found statistically significant (P=0.0001). For the 6-hour maintenance interval, the average micro-hardness between P60 and G-aenial was statistically significant (P=0.0001). For 42 hours, the average micro-hardness ranged between P60 and G-aenial that were statistically significant (P=0.0004). The stiffness of the P60 composite after 42 hours’ storage in soft beer significantly decreased compared with the control group (P=0.03). G-aenial composite hardness after 42 hours of soaking in the Coca-Cola was reduced significantly compared to yogurt drinks (P=0.02).
As a result, the hardness of P60 composite was higher than that of G-aenial. The hardness of both composites reduced in acidic drinks after one week.

While there are a lot of information about an illness risk factors, there are still some gaps in understanding factors influencing the progression of disease. Given the important role of psychological factors in physical conditions, the purpose of this study was to compare the cognitive emotion regulation, stress, depression, anxiety, and stress related to life events in people with and without periodontal disease.
The type of this study was causal comparative. Research society was all clients referred to dental clinics in Lamerd and Mehr cities, then 50 people with and 50 people without periodontal disease (male and female, 15-49 years old) were selected using purposive sampling. The group without periodontal disease was matched with patient group in terms of demographic characteristics. Both groups completed cognitive emotion regulation questionnaire (CERQ), Depression Anxiety Stress Scale (DASS), and life events questionnaire. Data analysis was conducted with SPSS version 17 using multivariate analysis of variance (MANOVA).
Resultes: Data analysis showed that people with periodontal disease had more stress, depression, anxiety, and stress related to life events than matched control group. The groups had significant differences in the components of self-blame, rumination, positive attention to evaluation and catastrophizing (P The results showed people who were vulnerable to stressfull situations, depression, and anxiety during their lives, and also use maladaptive emotion regulation strategies, were more susceptible to periodontal disease.

FTIR spectroscopic imaging is a chemical imaging method that can be employed to a broad range of applications. This powerful technique is suitable for determining the functional groups and chemical structures of the samples. The advantage of infra-red spectroscopy is that it can be used for various modes of physical samples. The aim of the current paper was to review the recent advances and the potential uses of Fourier Transform Infra-red Spectroscopy in dentistry via exploring related literature during 1960 till 2017 in Science Direct and PubMed databases. One of the most popular applications of infrared spectroscopy is to calculate the degree of conversion in the resin based dental materials. It has also been used to investigate the chemical structure of the teeth and bones, synthesis calcium phosphate, the diagnosis of microorganisms, and pathological conditions. In this paper, we mentioned the principles of this technique and recommend this method as a simple and fast way to determine the structure of the materials and their alteration.

Loss of retention is one of the main reasons of failure in teeth restored with post and core. Several factors, including the type of cement can influence the retention of the posts. As zinc phosphate cement is considered as the standard for comparison this study performed to review articles evaluating the retention of cast posts cemented with zinc phosphate.
This systematic review was performed based on the PRISMA (Transparent Reporting of Systematic Reviews and Meta-analyses) guide. The question of this study was that how much is the amount of retention of cast posts cemented with zinc phosphate. Hence, a literature search was done in PubMed and Medline databases as well as Google scholar search engine using relevant keywords until 2016 limited to the English language. Articles were selected based on the inclusion and exclusion criteria, and were evaluated qualitatively.
Resultes: Internet search resulted in 1141 articles. Following the application of inclusion and exclusion criteria, 6 studies were included in this systematic review. The most common post material was nickel-chromium alloy. Retention of casting posts cemented by zinc phosphate was from 8.76 to 34.2 Kg and from 91 to 192.2 N.
Our review showed that the retention of cast posts cemented with zinc phosphate in controlled condition is moderate and factors including post material and length could influence the retention of the post.