A comprehensive review on nanocomposite biomaterials based on gelatin for bone tissue engineering.

The creation of a suitable scaffold is a crucial step in the process of bone tissue engineering (BTE). The scaffold, acting as an artificial extracellular matrix, plays a significant role in determining the fate of cells by affecting their proliferation and differentiation in BTE. Therefore, careful consideration should be given to the fabrication approach and materials used for scaffold preparation. Natural polypeptides such as gelatin and collagen have been widely used for this purpose. The unique properties of nanoparticles, which vary depending on their size, charge, and physicochemical properties, have demonstrated potential in solving various challenges encountered in BTE. Therefore, nanocomposite biomaterials consisting of polymers and nanoparticles have been extensively used for BTE. Gelatin has also been utilized in combination with other nanomaterials to apply for this purpose. Composites of gelatin with various types of nanoparticles are particularly promising for creating scaffolds with superior biological and physicochemical properties. This review explores the use of nanocomposite biomaterials based on gelatin and various types of nanoparticles together for applications in bone tissue engineering.

Gelatin-Curcumin Nanocomposites as a Coating for Implant Healing Abutment: In Vitro Stability Investigation.

Regarding the importance of preventing peri-implantitis in dental implants, the current study aimed to coat a healing abutment with gelatin−curcumin nanocomposites, and the stability of this coating on the healing abutment was evaluated. A cell viability measuring test was used to determine the cytotoxicity of nanocomposites against dental pulp stem cells. To show the pattern of curcumin release from nanocomposites, drug dissolution apparatus two was applied. Then, 16 healing abutments were examined in vitro. Titanium healing abutments were coated with the gelatin−curcumin nanocomposite. The dip coating method was applied for coating and the consistency of coated cases was evaluated at intervals of one, 30, and 60 days after coating inside the simulated body fluid (SBF) solution. A scanning electron microscope (SEM) was used for investigating the microstructure and morphology of coatings, and an energy dispersive X-ray (EDX) was applied for determining the combination of the coating. Moreover, the healings were weighed before and after coating via an accurate digital scale with an accuracy of 0.0001. Finally, the data were analyzed using SPSS software. The prepared nanocomposite was non-cytotoxic against tested cells. The nanocomposite showed a relatively rapid release pattern in the first 10 days for curcumin. The release of curcumin from the nanoparticles continued slowly until the 30th day. The weight changes were statistically significant (p-value < 0.001) during this time. Based on the post hoc test, the weight between two times immediately after coating and 30 days after coating, and also one day after coating and 30 days after coating, was statistically insignificant. The results revealed that the coating of the gelatin−curcumin nanocomposite on the healing was successful and this consistency was kept for at least one month. It is necessary to investigate more evaluations in different fields of physicochemical, mechanical, and antimicrobial aspects for coated healing abutments.

Prevalence of proximal contact loss between implant-supported fixed prosthesis and adjacent teeth and associated factors: A systematic review and meta-analysis.

Background. This systematic review and meta-analysis investigated the prevalence of proximal contact loss and its associated factors. Methods. A bibliographic search was conducted in June 2021 with no limitation in the article date or language and updated in January 2022 by hand searching. There was no time limit on the search to retrieve all studies. The search included randomized controlled trials or quasi-experiments, and cross-sectional or cohort studies were included in the absence of these studies. Two authors screened the title and abstract. After evaluating the full texts of selected articles, irrelevant studies and or non-English papers that were impossible to translate were excluded. Disagreements between the re-viewers' selection process were resolved by debate on the eligibility of studies. Standardized critical appraisal instruments from the Joanna Briggs Institute for different types of studies were used to assess the studies' quality. Comprehensive Meta-Analysis (CMA) software (Version 2.2; Biostat, Englewood, NJ) was used for data analysis. Results. The proximal contact loss (PCL) frequency was %29. According to the results, the frequencies of PCL for the distal and mesial aspects were %7 and %21, respectively. The meta-analysis results showed that the contact loss events on the mesial aspect were statistically higher than on the distal aspect (P<0.0001). There were no significant differences between other associated factors such as the mandibular or maxillary arch, retention type, opposing dentition, implant type, molar or non-molar, parafunction behaviors, and vitality of adjacent teeth. There was a significant association between bone loss and PCL, and in individuals with bone loss >%50, the proximal contact loss was higher (OR: %95[ 2.43 CI: 4.03‒1.47], P=0.0006). The PCL in the anterior area was lower than in the posterior area (P=0.004). Although the frequency of contact loss in females was higher than in males, this rate was not statistically significant. Conclusion. The PCL on the mesial aspect and the posterior area was high. In individuals with bone loss >%50, the proximal contact loss was higher than in others.

Effect of different geometric changes in the dental implant abutment body on the amount of residual excess cement and retention in a cemented implant-supported prosthesis.

BACKGROUND: Fixed implant-supported restorations are mainly used in dental implantology. In comparison with screw-retained implants, cement-retained prostheses have the following advantages: the ease of splinting implants; increased passive casting; and procedural similarity to conventional tooth-supported fixed partial dentures. Furthermore, they show reduced fracturing of components with better esthetic outcomes and an improved force direction, along with a reduced cost and less chairside time. OBJECTIVES: The aim of this study was to evaluate the effect of different geometric changes in the dental implant abutment body on the amount of residual excess cement (REC) and the retention of cemented implant-supported prostheses. MATERIAL AND METHODS: Seventy-two straight abutments were categorized into 4 groups: vertical groove; 1 horizontal groove; 2 horizontal grooves; and ccontrol (with no geometric changes in the abutment). The access hole was partially filled and the cast copings were cemented using Temp-Bond™ NE, a non-eugenol cement. The difference in weight before and after removing the excess cement was considered as REC. Furthermore, the retention of the cast coping was measured as the force that was required to separate the cemented cast coping from the abutment. RESULTS: The mean REC values of the groups with 1 and 2 horizontal grooves were significantly different as compared to the control group (p < 0.05). CONCLUSIONS: This study shows that the presence of 1 or 2 horizontal grooves in the abutment body significantly reduces the amount of REC in comparison with control.

The Effect of in Vitro Sample Preparation Methods on Bond Strength of Mineral Trioxide Aggregate to Root Dentin.

Introduction: The aim of this study was to compare the effect of sample preparation methods on push-out bond strength of mineral trioxide aggregate (MTA). Methods and Materials: Twenty-four extracted human mandibular premolars with single root canal were selected for this in vitro study. After instrumentation, irrigation and drying of root canals, they were randomly divided into two experimental groups (n=12). Group 1: After removing the 3 mm of root ends, 2 mm thick sections were established from the remaining roots. MTA was mixed following the manufacturers' recommendations and root sections were filled. Group 2: The whole root canal was used for filling and packing of MTA and like group 1, after removing the 3 mm of root ends, root sections were provided. Push-out bond strength was measured and analyzed by the independent t-test. Level of statistical significance was set at 0.05. Results: The highest mean push-out bond strength was in apical section of group 2 (4.86±1.31) and the lowest value was in coronal section of group 2 (3.05±1.15). The results of the independent t-test showed a significant difference between two groups only in the apical section (P=0.02). Conclusion: Based on the results of this in vitro study, the highest mean push-out bond strength was in apical section of group 2. It seems that using the whole root canal for MTA application is better for MTA in vitro analysis of bond strength to root dentin because it is more similar to the clinical conditions.

Comparison of stress in implant-supported monolithic zirconia fixed partial dentures between canine guidance and group function occlusal patterns: A finite element analysis.

Background. Monolithic zirconia is an emerging material for crowns and bridges. The possibility of full digital design has made it an attractive alternative material for implant-supported prostheses. A proper design is vital in the success of such a prosthesis like any other. This study, in the shortage of scientific evidence, has tried to assess the stress distribution of occlusal forces inside the implant-prosthesis system of a 3-unit bridge made of monolithic zirconia. Methods. A 3-unit monolithic zirconia bridge supported by two implant fixtures placed on the teeth #13 and #15 was digitalized. It was converted to a mesh of 59000 nodes and 34000 elements. Five types of occlusal forces (one as vertical centric, two at 15º and 30º simulating canine pattern of lateral movement, and two at 15º and 30º simulating group function pattern) were applied. The stress distribution among all the components of the implant-bridge system was assessed using Ansys Workbench 14 software and finite element analysis. Results. The maximum stress was between 286 and 546 MPa, which were found in either the fixture‒abutment screw area or in the upper part of the pontic connector between the canine and first premolar. The maximum pressure increased with an increase in the angle of occlusal force. Significantly higher stress was recorded in the group function occlusal pattern. Conclusion. Monolithic zirconia can be promising in designing bridges in the canine‒premolar area. However, proper design is necessary with more attention to the connectors and types of occlusal forces.

Investigating the effect of abutment-implant connection type on abutment screw loosening in a dental implant system using finite element methods.

Background. The most common problem associated with dental implants is the abutment screw loosening. This research aimed to investigate the effect of the type of connection on screw loosening, using a finite element method (FEM). Methods. Periosave system and different types of the implant-abutment connection were used for modeling. After being measured, CAD files were modeled using CATIA software and imported to the ANSYS analysis software, and the model was loaded. Results. A force of 100 N was applied at 0.1 second, and no force was applied at 0.42 second. The screw head deformation at 0.1 and 0.42 seconds was 8 and 3.8 µm, and 7.6 and 2.8 µm at morse taper and octagon dental implant connections, respectively. The displacement rate of the internal surface of the abutment at 0.1 and 0.42 seconds was 10.7 and 8.4 µm, and 5.7 and 5.6 µm in the octagon and morse taper dental implant connections, respectively. The displacement of the implant suprastructure-abutment interface from the screw head at 0.1 and 0.42 seconds was 9 and 7 µm, and 7 and 6 µm in the morse taper and octagon dental implant connections, respectively. At intervals of 0 to 0.1 seconds and 0.6 to 0.8 seconds, the octagon connection was separated at the maximum screw head displacement and the internal part of the abutment, but the morse taper connection did not exhibit any separation. In the above time intervals, the results were similar to the maximum state in case of the minimum displacement of the screw head and the internal part of the abutment. Conclusion. Screw loosening is less likely to occur in the morse hex connection compared to the octagon connection due to the lack of separation of the screw from the internal surface of the abutment.

Antibacterial Effect of Two Nano Zinc Oxide Gel Preparations Compared to Calcium Hydroxide and Chlorhexidine Mixture.

INTRODUCTION: The aim of this study was to compare the antibacterial effects of two gels containing zinc oxide and zinc oxide/silver nanoparticles and a mixture of calcium hydroxide and 0.12% chlorhexidine as intracanal medicaments in root canals contaminated with Enterococcus faecalis (E. faecalis) at different time intervals. METHODS AND MATERIALS: After preparation and culturing of E. faecalis in 132 single root teeth, the initial count of bacteria was performed. Then, different materials as intracanal medicaments were used in periods of 3, 7 and 14 days (group 1: calcium hydroxide with 0.12% CHX paste; group 2 zinc oxide nanoparticles gel; group 3: zinc oxide/silver nanoparticles gel; group 4: normal saline as the control group). After the specified time, intracanal medicament was removed and the final count of bacteria was performed. Antibacterial effect of materials was counted by measuring the percentage reduction in the colony counts (RCC). Data were analyzed using the descriptive statistics (Mean±SD) and multi-factorial analysis of variance (by taking into account the effect of the time factor on the dependent variable). RESULTS: There were no statistically significant differences among mean RCC of different time intervals in each group (P=0.09). However, the differences in mean RCC of different dressing materials were significant (P<0.001). The effect of interaction between time and materials was significant (P=0.015). Comparison of the antibacterial effects of experimental agents at different time intervals showed that the mean RCC in group 1 was higher than other groups (P<0.001). The difference in antibacterial effect between groups 2 and 3 was not significant (P>0.05). The minimum antibacterial effect was observed in group 4 (P<0.0001). CONCLUSIONS: The mixture of calcium hydroxide/chlorhexidine as an intracanal medicament was more effective than zinc oxide and zinc oxide/silver nanoparticles gels.

Comparative CBCT evaluation of the efficacy of Nd:YAG laser and K3 rotary system in non-surgical root canal retreatment.

BACKGROUND: The aim of the present study was to compare the efficacy of Nd:YAG laser and K3 rotary system in the non-surgical root canal retreatment. METHODS: Sixty-one rooted human teeth were divided into two groups of 30 after root canal therapy. In groups 1 and 2 root canal retreatments were carried out using K3 rotary system and Nd:YAG laser, respectively. CBCT images were used to evaluate canal transportation and root canal debridement at coronal, middle and apical canal cross-sections. In addition, the time necessary for canal debridement and the temperature on the external root surface were calculated. Mann-Whitney U test was used for statistical analysis of data with SPSS 17 after means ± SD were calculated. Shapiro-Wilk test was used to evaluate normal distribution of data. Statistical significance was defined at P<0.05. RESULTS: The mean time necessary for the debridement of root canals in the laser group was significantly shorter than that in the K3 group (P=0.001). However, there were no significant differences in external root surface temperatures between the two groups (P=0.17). The coronal third of the canals was cleaner in the laser group significantly (p=0.01). Less canal transportation was seen in the laser group compared to the K3 group, significantly (P=0.04). CONCLUSIONS: Nd:YAG is superior to K3 rotary system in the non-surgical root canal retreatment because it is faster and results in less canal transportation in the middle and apical thirds of the canals.

Sealing Efficacy of Single-cone Obturation Technique with MTA and CEM Cement: An in Vitro Bacterial Leakage Study.

Background and aims. Various materials and methods have been introduced for obturating cleaned and shaped root canal systems. This in vitro study aimed to evaluate the sealing ability of single-cone obturation technique with mineral trioxide aggregate and calcium-enriched mixture based on bacterial leakage approach. Materials and methods. Sixty-four single-canal teeth were prepared and randomly divided into 5 groups, consisting of three experimental groups (n = 16) and two control groups (n = 8).In group 1, root canal obturation was performed using gutta-percha with 0.02 taper and AH26 sealer by lateral compaction technique. In groups 2 and 3, single Protaper gutta-percha cone was used for obturation with MTA and CEM cement, respectively. A bacterial leakage apparatus was utilized for leakage assessment for 60 days. Leakage comparison between the experimental groups was performed by one-way ANOVA using SPSS 16 statistical software. Results. The mean bacterial leakage intervals in groups 1, 2 and 3 were 33.68 ± 9.39, 40.68 ± 11.03 and 39.56 ± 9.03 days, respectively. One-way ANOVA indicated no significant differences in bacterial leakage between the three experimen-tal groups (P = 0.109). Conclusion. Single-cone obturation with well-fitted gutta-percha and MTA and CEM cement is an appropriate alternative for traditional lateral compaction technique.