Assessment of Microhardness of Conventional and Bulk-Fill Resin Composites Using Different Light-Curing Intensity.

(1) Background: This study evaluates the effect of a conventional/low-voltage light-curing protocol (LV protocol) (10 s with 1340 mW/cm2) and high-voltage light-curing protocol (HV protocol) (3 s with 3440 mW/cm2) on the microhardness (MH) of dental resin-based composites (RBCs). Five resin composites were tested: conventional Evetric (EVT), Tetric Prime (TP), Tetric Evo Flow (TEF), bulk-fill Tetric Power Fill (PFL), and Tetric Power Flow (PFW). (2) Materials and Methods: Two tested composites (PFW and PFL) were designed for high-intensity light curing. The samples were made in the laboratory in specially designed cylindrical molds; diameter = 6 mm and height = 2 or 4 mm, depending on the type of composite. Initial MH was measured on the top and bottom surfaces of composite specimens 24 h after light curing using a digital microhardness tester (QNESS 60 M EVO, ATM Qness GmbH, Mammelzen, Germany). The correlation between the filler content (wt%, vol%) and the MH of the RBCs was tested. For the calculation of depth-dependent curing effectiveness, the bottom/top ratio for initial MH was used. (3) Conclusions: MH of RBCs is more dependent on material composition than on light-curing protocol. Filler wt% has a greater influence on MH values compared to filler vol%. The bottom/top ratio showed values over 80% for bulk composites, while for conventional sculptable composites, borderline or suboptimal values were measured for both curing protocols.

The Influence of Different Occlusal Loading on Six Restorative Materials for Restoration of Abfraction Lesions-Finite Element Analysis.

OBJECTIVES: The aim of the study was to analyze the occurrence of stress on teeth with abfraction lesions restored with six different restorative materials, and by introducing the tensile strength parameters to calculate the safety factor of the material under the load (ratio between the strength of the material and the maximum stress). MATERIALS AND METHODS: Three-dimensional models of the mandibular premolar are created from a microcomputed tomography images. An abfraction lesion is modeled on the tooth. The stress of the dental tissues and six restorative materials under functional and nonfunctional occlusal loading of 200 (N) are analyzed by finite element method. STATISTICAL ANALYSIS: CTAn program 1.10 and ANSYS Workbench (version 14.0) were used for analysis. Results are presented in von Mises stress. RESULTS: Oblique loads caused ≈ four times higher stress in restorative materials than the axial ones. It is noticeable that high values of von Mises stress are measured at the bottom of the sharp lesion, even up to 240 MPa, that are significantly reduced after the restoration. The highest stresses at the restorative material are present at the lower (gingival) margin of the restoration. The highest stresses under both types of loads are measured in nanohybrid composite (Tetric EvoCeram, Ivoclar Vivadent). The lowest values of the stress are measured in the flowable composite (Tetric Flow, Ivoclar Vivadent), but at the same time, the highest value of the stress is measured in the surrounding dental tissues on the tooth restored with the flowable composite. The microhybrid composite (Herculite XR, Kerr), with the highest safety factor, is the material that best withstands the stresses it is exposed to. The obtained safety factor did not exceed the critical limit, except for the glass ionomer cement, with the safety factor lower than 1. CONCLUSION: The type of tooth loading has the greatest influence on the intensity of stress. The value of the obtained stresses in the restorative material and dental tissues differ due to the different mechanical properties of the materials. Restoration of noncarious lesions significantly reduces extremely high stress values at their bottom.

Prevalence of TMD among Children Provided with Fixed Orthodontic Treatment.

BACKGROUND: According to available scientific references and textbooks, there are contradictory views concerning the etiology of signs and symptoms of TMD. OBJECTIVES: The aim of this study was to determine a correlation between the incidence of signs and symptoms of TMD in children aged 12-18 who do not wear a fixed orthodontic appliance and the incidence of signs and symptoms of TMD in children who wear a fixed orthodontic appliance. MATERIAL AND METHODS: The total number of 120 subjects were included in this survey and divided into two groups. There were 60 respondents in the experimental group that consisted of 30 boys and 30 girls with different types of malocclusion, who were treated with a fixed orthodontic straight wire technique. The remaining 60 respondents, which was a group that also consisted of 30 boys and 30 girls, were patients with neutroclusion. RESULTS: The results of the study have shown that the TMJ clicking sound symptom, the most common symptom of TMD, occurs with almost equal prevalence in both groups of respondents; specifically, 56.4% in orthodontic patients, and 46.6% in the control group respondents. A statistically significantly higher percentage of female respondents in both groups have experienced headache problems (p <0.03). CONCLUSION: On the basis of the statistics obtained as a result of this research, we can come to the conclusion that there is no correlation between the fixed orthodontic treatment and the development of signs and symptoms of TMD.

Evaluation of Solubility of Luting Cements in Different Solutions.

OBJECTIVE: To evaluate and compare the solubility of three luting cements in three different solutions: distilled water and artificial saliva with different pH values (7.4 and 3.0). MATERIALS AND METHODS: Resin-modified glass-ionomer cement (GC Fuji Plus) and two resin cements (Multilink Automix and Variolink II) were used. A total of 45 specimens, 15 specimens (15x1 mm) for each cement, were prepared according to ISO standard 4049:2009. The solubility of the cements was calculated by weighing the specimens before and after immersion and desiccation. Values of solubility in water (Wsl) in microgram/mm3 for each of the five specimens were calculated using the following formula (ISO 4049:2009): Wsl=(m1-m3)/V. The Mann-Whitney U nonparametric statistical method and Post hoc sample comparisons were applied. RESULTS: GC Fuji Plus showed statistically significant higher solubility in comparison with Variolink II and Multilink Automix in all three solutions. In acidic artificial saliva (pH 3.0) Multilink Automix showed significantly higher values of solubility compared to Variolink II (P<0.016). By studying the effect of pH value on the solubility of GC Fuji Plus cement, significantly higher values of solubility in pH 3.0 artificial saliva were confirmed (P<0.009). The influence of the surrounding pH value on the solubility of the resin cements Multilink Automix and Variolink II was researched. No statistically significant difference was found. CONCLUSION: Solubility values were mainly influenced by the proportion of hydrophilic matrix, the type and composition of filler, and the pH value of the solutions.

The Influence of Gender on the Cortical Width of the Lower Border of the Mandible and the Mandibular Cortical Index.

OBJECTIVE: To evaluate the influence of gender on the mental index (MI) and the mandibular cortical index (MCI). METHODS: In this study, there were 120 subjects (43 male and 77 female subjects), who had undergone a dental panoramic radiograph examination for the needs of diagnosis and future treatment planning. MI and MCI were determined by orthopantomograph. RESULTS: There was a statistically significant difference in MI dependent on gender. Male patients demonstrated significantly higher values for MI than female patients (right: t=4.127; P=0.0001, left: t=3.110; P=0.002). No statistically significant difference was observed for MCI dependent on gender (right: χ²=2.36 P=0.308, left: χ²=3.85 P=0.146). CONCLUSION: MI is affected by gender, but MCI is not.

Comparison of Results of Measurement of Dimensions of the Placed Dental Implants on Cone Beam Computed Tomography with Dimensions of the Producers of the Implants.

INTRODUCTION: One of the most frequently used method for scanning patients with indication for dental implantation in dentistry is cone beam computed tomography. Implantation, CBCT imaging and implant programme are inevitable when planning a successful replacement of lost teeth. CBCT offers exact information about available bone and its density, adjacent tooth roots, the place of mandibular canal and maxillary sinus and adjacent anatomical structure. AIM: The goal of this study is to estimate accuracy of measurements on CBCT images ofpatients who have implants of different producers and determine if there is any statistically significant correlation between four test groups regardless of the alloy of which implants are made. MATERIAL AND METHODS: The study was a prospective-comparative, and included fifteen patients with hundred dental implants divided in four groups depending on the producer. RESULTS: Over dimensioning in the gained measurements of the whole sample on CBCT images in relation to dimensions of producers is between 0.1006mm and 0.368mm. Even though over dimensioning is measured in millimetres, it has to be taken into consideration in clinical practice when planning an implant placement, and we can recommend safety zone of 0.5mm. There have been no statistically significant differences in the gained results in over dimensioning of implants of different alloys for horizontal and vertical measurements on CBCT images of Astra Tech, Brendet titanium implants and Straumann titanium-zirconium implants. Based on the goals of the study there have been confirmed statistically significant correlations of great value (from 0.841 to 0.936) of high level of importance between manufactured value of dimensions and average dimensions values gained through CBCT imaging in four types of implants (four test groups). The total exactness of measurements on CBCT scan in this research is 96.66% for horizontal measuring and 96.92% for vertical measuring. Therefore, we can conclude that CBCT as radiological method has an unavoidable importance in planning and successful realisation of dental implant procedure. CONCLUSION: Cone Beam Computed Tomography provides exact measurements of dimensions of placed dental implant in relation to dimensions of the producers of the implant because the material from which dental implants have been made does not significantly affect the precision of the measurement.

Evaluation of the water sorption of luting cements in different solutions.

OBJECTIVE: To evaluate and compare the water sorption of three luting cements in three different solutions: distilled water and artificial saliva with different pH values (7.4 and 3.0). MATERIALS AND METHODS: Resin-modified glass-ionomer cement (GC Fuji Plus) and two resin cements (Multilink Automix and Variolink II) were used. A total of 45 specimens - 15 specimens (15x1 mm) for each cement were prepared according to ISO standard 4049:2009. The water sorptions of the cements were calculated by weighing the specimens before and after immersion and desiccation. RESULTS: . Nonparametric statistic methods were applied. GC Fuji Plus cement showed significantly higher values of water sorption in all three solutions of both resin cements (p<0.009) and significantly higher values of sorption in artificial saliva pH 3.0. Multilink Automix showed significantly higher values of water sorption compared with Variolink II in artificial saliva pH 7.4, and higher values of sorption in this solution compared with pH value 3.0. CONCLUSION: Water sorption values are mainly influenced by the proportion of hydrophilic matrix, the type and composition of filler, and the pH value of solutions.

Radiographic Evaluation of Crestal Bone Loss Around Dental Implants in Maxilla and Mandible: One Year Prospective Clinical Study.

PURPOSE: The aim of the study was to analyze the amount of maxillary and mandibular crestal bone loss around Bredent Sky Blue type of implants of different dimensions one year after implantation. MATERIALS AND METHODS: 36 implants of diameter 3.5 x 10 mm were inserted in the maxilla and 12 in the mandible. 52 implants of diameter 4.0 x 8 mm were inserted in the maxilla, and 61 in the mandible (two-stage implant surgery). RESULTS: No statistically significant differences were found between the right and left side of the maxilla and between the right and left side of the mandible at the implant sites regarding distal and mesial bone losses as shown by analysis of variance (ANOVA). CONCLUSION: Statistically significant differences were found between anterior maxilla, posterior maxilla and anterior mandible and posterior mandible at implant sites regarding distal and mesial bone losses as shown by analysis of variance (ANOVA).