Cytotoxic Effects of Bulk-Fill Composites on L929 Fibroblast Cells

Objective: Unlike traditional composite resins, bulk-fill composite resins could be polymerized as thicker layers. This study aims to contribute to the field by investigating the cytotoxic effects of various bulk-fill composite resins on L929 mouse fibroblast cells in vitro. Material and Methods: In our study, six bulk fill and one conventional composite resin were used. Composite resin samples (8×4 mm) were prepared in a sterile cabinet by using a glass mod and polymerizing with a led light device (DTE LUX E, Germany). Composite samples (n:3) of which surface area was calculated according to ISO 10993-12: 2012 standards (3 cm2/ml), were kept in media for 24 h and 72 h in 37 oC incubator, their extracts were filtered in 1:1 and 1:2 proportion and were added on L929 mouse fibroblast cells. Cell viability was examined by the MTT assay and cell death by the LDH test. Cell viability results were evaluated using one-way analysis of variance (ANOVA) test (p<0.05). Results: When the 1:1 extracts from 4 mm thick bulk-fill composite samples were applied on L929 mouse fibroblast cells, cell viability rates showed significant differences compared to the control group at the end of 24 h and 72 h (except for Estelite Bulk Fill Flow). Although the extracts of the tested composite samples at 1:1 and 1:2 ratio at the end of 72 hours caused a decrease in L929 mouse fibroblast cell viability, the cell viability rate of only PRG-containing bulk fill composite and conventional composite remained below the cell viability ratio (70%) specified in ISO standards. Bulk fill composites did not produce toxic effects (except Beautifil Bulk Restorative) according to the LDH test. Conclusions: Despite decreasing in general the cell viability, bulk-fill composite resins used in 4 mm thick layers provided cell viability rates over the acceptability level, except PRG-containing bulk fill composite (Beautifil Bulk Restorative), which was cytotoxic to L929 mouse fibroblasts. Keywords Bulk fill composite; Cytotoxicity; L929 cells; LDH assay.

The Effect of Mouthrinses on Surface Roughness of Two Nanohybrid Resin Composites

Objective: The aim of this study was to evaluate the effect of four different mouthrinses on the surface roughness of two nanohybrid resin composites. Material and Methods: Fifty samples were prepared for each of the resin composites (2x8 mm) and a profilometer was used to determine the initial surface roughness (Ra) of each sample. Then, they were divided into 5 subgroups (n= 10), and exposed to the following mouthrinses (12h, 37 ºC): containing alcohol and essential oils; alcohol and chlorhexidine; alcohol-free and essential oils; alcohol free and cetil prydinium chlorite; or distilled water (control). The surface roughness of each sample was measured again. Statistical analyses of the data were performed via two-way ANOVA and Bonferroni tests. Results: Overall, statistically significant differences were not found between the resin composites (p> 0.05), but significant differences were found among the mouthrinses (p< 0.05). Interactions between the mouthrinses and the resin composites was statistically significant (p< 0.05). Both of the resin composites had the highest surface roughness after exposure to mouthrinse with alcohol and essential oils (p< 0.05), followed by mouthrinse with alcohol and chlorhexidine. Both alcohol-free mouthrinses caused surface roughness either similar to distilled water (p> 0.05) or lower than distilled water (p< 0.05) on the nanohybrid resin composites used. Conclusion: The mouthrinses affected the surface roughness of the resin composites in different ways. This was dependent on mouthrinse contents and the chemical structure of the resin composites. Alcohol-containing mouthrinses caused the most changes in the surface roughness of both resin composites. Keywords Alcohol; Chlorhexidine; Composite resin; Essential oil; Roughness.

Polywave And Monowave Light-Curing Units Effects On Polymerization Efficiency Of Different Photoinitiators

Objective: of this study was to characterize and correlate the absorption spectra of three photoinitiators [camphorquinone (CQ), diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) and phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO)], using second or third-generation light curing units (LCU), and to evaluate the degree of conversion and the physical properties of an experimental resin adhesive. Material and methods: Second-generation (Radii-cal® and Emitter D®) and third-generation (Valo® Cordless and Bluephase N®) LCU were assessed regarding spectrum and irradiance rate of emitted light. Also, the photoinitiators (CQ, TPO and BAPO) were characterized by a light absorption spectrum assessed by UV-Vis spectroscopy, degree of conversion and yellowing effect. Statistical analyzes considered two-way ANOVA and post-hoc Tukey test. Results: BAPO presented higher reactivity compared to TPO. Regarding degree of conversion of the photoinitiators activated by different light-curing units, the Emitter D® device promoted a high degree of conversion. BAPO presented the highest yellowing effect values. Conclusions: The emission and absorption characteristics of the photoinitiators were different. The polymerization reaction activated by the second-generation light-curing unit was reduced when using an experimental resin with photoinitiator TPO, and the third-generation light-curing unit showed a higher polymerization potential regardless of the photoinitiator. Keywords Light-curing of dental adhesives; Photoinitiators dental; Curing lights dental.

Fracture Resistance of Primary Molars Restored with Endocrowns Versus Zirconia Crowns (An in Vitro Study)

Objective: This study aimed to assess the fracture resistance of primary molars restored with endocrowns compared to prefabricated zirconia crowns. Methods: Twelve sound, defect-free primary second molars were selected and divided into two groups: group I included 6 molars restored with zirconia crowns, while group II included 6 teeth restored with endocrowns. For both groups access cavity was prepared for the teeth to open pulp chamber. Fracture resistance of both groups was tested using a universal testing machine. Results: Zirconia crown showed statistically significantly higher mean fracture resistance than Endocrown (P-value = 0.001, Effect size = 2.72). Conclusion: Pulpotomized primary molars restored with Zirconia crowns showed significantly higher mean fracture resistance compared to primary molars restored with endocrowns, meanwhile both restorations have shown higher mean fracture resistance than the maximum biting force in children. Keywords Composite resins; Endocrown; Fracture strength; Zirconia crowns.

Awareness of medical emergencies among dental practitioners in three Egyptian Dental Schools: A cross-sectional study

Objectives: To evaluate the awareness of medical emergencies among dental practitioners in three dental schools. Material and methods: The study group included 384 dental practitioners, including dental staff members, post-graduate students, and dental interns. These professionals were attending three dental educational institutions in Egypt. Two of them were governmental and one was a private school. The educational model is almost the same in most Egyptian dental schools. Results: The response rate was 100%. Most of the participants worked in private academia (44.16%) or practice (42.34%) and 65.20% of them were females. The participants recorded medical history and filled a form (91.17%, 80.52 % respectively) while only 41.82% obtained the vital signs. Among the participants, 48.57 % were confident about handling medical emergency and 74.29 % reported their capability of intramuscular injection while only 25.71 % for intravenous injection and 49.35% knew about emergency kits. Management knowledge of airway obstruction and prosthetic heart valve patients was reported by 80.27 % and 71.94 % respectively, while less percentage for activation of EMS, chest compression, CPR ratio, and infant rescue breathing. The mean preparedness percent score was 54.57% and it was inversely correlated to the years of experiences and directly correlated to the degree of confidence in their ability to manage the dental emergency. Conclusion: The current study results reflected a deficiency in the dental practitioner awareness about the medical emergency especially the practical part. Keywords Dentists; Cross-sectional studies; Emergencies; Educational models; Dental schools.

Prevalence and Configuration of C-shaped Canals in Lower Molars from a Chilean Subpopulation

Objective: To determine the prevalence of C-shaped canals in lower molars (first and second molars) in a Chilean subpopulation, and to identify root configuration and demographic characteristics using cone beam tomography. Materials and method: 912 molars (456 first and 456 second molars) resulting from the analysis of 228 mandibular CBCT scans (89 men and 139 women between 15 and 80 years old) were evaluated. Through panoramic reconstruction and axial tomographic sections, the root configuration was established, and the presence and type of C-shaped canal were classified, analyzing 5 levels along the root canal. Data were statistically analyzed with a 5% significance level. Results: Of the 912 molars analyzed, 69 were classified as C-shaped (7.57%), constituting 65.72% of those molars that presented fused roots. 100% of this configuration of canals was observed in lower second molars, presenting a higher prevalence in women (n = 49, 71.01%). 40.82% of the cases that presented a C-shaped configuration manifested bilaterally. The most frequent C-shaped canal configuration was C3 (n = 347, 66.10%), according to Melton's classification. Conclusion: The C-shaped canals in the studied population were observed entirely in lower second molars, showing a clear predilection for the female sex and a high rate of bilaterality. Keywords Anatomy; Cone beam computed tomography; Dental pulp cavity; Endodontics.

Fracture Resistance and Strain Analysis of Zirconia Copings With Vertical Knife Edge and Three Horizontal Finish Line Designs; Chamfer, Deep Chamfer and Shoulder With Two Cementation Techniques

Objective: The purpose of this in vitro study is to evaluate the effect of four finish line configurations and two cement types on the fracture resistance of zirconia copings. Material and Methods: Forty yttrium tetragonal zirconia polycrystals copings were manufactured on epoxy resin dies with four preparation designs: knife edge, chamfer, deep chamfer 0.5, 1 mm and shoulder 1 mm. The copings were cemented with two cement types (glass ionomer and resin cement); (n = 5). Two strain gauges were attached on each coping before they were vertically loaded till fracture with a universal testing machine. Data were analyzed by 2-way analysis of variance ANOVA (p < .05). Fractured specimens were examined for mode of failure with digital microscope. Results: Knife edge showed the highest mean fracture resistance (987.04 ± 94.18) followed by Chamfer (883.28 ± 205.42) followed by Shoulder (828.64 ± 227.79) and finally Deep chamfer finish line (767.66 ± 207.09) with no statistically significant difference. Resin cemented copings had higher mean Fracture resistance (911.76 ± 167.95) than glass ionomer cemented copings (821.55 ± 224.24) with no statistically significant difference. Knife edge had the highest strain mean values on the buccal (374.04 ± 195.43) and lingual (235.80 ± 103.46) surface. Shoulder finish line showed the lowest mean strain values on the buccal (127.47 ± 40.32) and lingual (68.35 ± 80.68) with no statistically significant difference. Resin cemented copings had higher buccal (295.05 ± 167.92) and lingual (197.38 ± 99.85) mean strain values than glass ionomer copings (149.14 ± 60.94) and (90.27 ± 55.62) with no statistically significant difference. Conclusion: Vertical knife edge finish line is a promising alternative and either adhesive or conventional cementation can be used with zirconia copings. KEYWORDS Cementation; Flexural strength; Prosthodontics; Tooth preparation; Zirconium.

Reconstruction of extensive sequel of frontal fracture: optimizing results

Introduction: Fractures of the frontal bone correspond to 5 to 15% of all facial fractures. This type of fracture can lead to difficulties in restoring bone congruence and to postoperative secondary aesthetic problems. Objective: This paper aims to present a clinical case report of frontal bone fracture where a late reconstruction was performed using a titanium mesh with the aid of stereolithographic model prototyping. Case report: Female patient, 26 years old, with aesthetic sequelae in the upper third of the face after a motorcycle accident. The imaging exams showed a comminuted frontal bone fracture, as well as upper edge and right orbit ceiling involvement. The planning consisted of reconstruction of the affected area with the use of a titanium mesh pre-shaped in a stereolithographic model. The procedure was performed under general anesthesia and coronal access. After installation of the fixation material, pericranial flap rotation and suture of the surgical wound were performed. The patient progressed well, with considerable improvement in facial aesthetics. Conclusion: This paper reports the importance of good planning in cases of frontal bone fracture sequel, in which the use of model-shaped mesh in a stereolithographic model tends to optimize surgery, bringing aesthetic and psychosocial benefits. Keywords Frontal bone; Titanium; Craniocerebral trauma.