The evaluation of surface sealants? effect on the color stability of Nano-hybrid composite after polishing with One-Step system (in-vitro)

The clinical use of composite resins has increased substantially over the past few years due to increased esthetic demands by patients, improvements in formulation, and simplification of bonding procedures. An alternative for preventing or reducing composite discoloration is using of composite surface sealant. The purpose of this study was to determine the effect of surface sealant on color-stability of Nano-hybrid composites after polishing with one-step system. 56 disk-shaped specimens (10*2 mm) of a Nano-hybrid composite resin (VOCO,Cuxhaven,Germany) were prepared. The specimens were randomly divided in to 2 groups of 28 specimens each. The surfaces of specimens were polished with One-step system (Dimanto,VOCO,Germany ). one group of specimens assigned as control group and received no more surface treatment .surface sealant (PermaSeal,Ultradent,USA) was applied on the surface of specimens of the other group as experimental group .specimens were stored in Ringer?s solution for 24 hours at 37oC. The specimens were subjected to artificial aging with thermocycling method between coffee solution at 55°C and Ringer?s solution at 5°C for 3000 cycles. CIE L*a*b color coordinates were established using a spectrophotometer for each specimen. Statistical significance was set at p 3.3) and there was no significant difference between the two groups in ?E. Surface sealant was not effective in improving color stability

Effects of Diode and Nd:YAG Laser Irradiation on Friction Forces Between Two Types of Ceramic Brackets and Rhodium-Coated Archwires

Introduction: Ceramic brackets have gained increasing popularity among dental clinicians and orthodontic patients but friction is a major concern when using them. This study sought to assess the effects of diode and Nd: YAG (neodymium-doped yttrium aluminum garnet) laser irradiation on friction forces between two types of ceramic brackets and rhodium-coated esthetic archwires.Methods: Thirty polycrystalline and 30 poly-sapphire brackets were divided into 6 groups (n=10) as follows: (I) control polycrystalline brackets (no laser irradiation), (II) polycrystalline brackets subjected to diode laser irradiation, (III) polycrystalline brackets subjected to Nd: YAG laser irradiation, (IV) control poly-sapphire brackets (no laser irradiation), (V) poly-sapphire brackets subjected to diode laser irradiation, and (VI) poly-sapphire brackets subjected to Nd: YAG laser irradiation. The bracket slots were laser-irradiated on a custom-made table. Sixty 5-cm pieces of rhodium-coated archwires were used for the friction test in a universal testing machine at a speed of 10 mm/min. Ten brackets from the six groups underwent scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX).Results: The frictional resistance value of polycrystalline brackets was significantly higher than that of poly-sapphire brackets, irrespective of laser type (P < 0.05). Irradiation of diode and Nd: YAG lasers, compared with the control group, had no significant effect on friction, irrespective of bracket type (P> 0.05).Conclusion: It appears that diode and Nd: YAG laser irradiation cannot significantly decrease friction. Future studies are warranted on different laser types with variable exposure. DOI: 10.34172/jlms.2021.1

The Effect of Remineralizing Agents With/Without CO2 Laser Irradiation on Structural and Mechanical Properties of Enamel and its Shear Bond Strength to Orthodontic Brackets

Introduction: Remineralizing agents may be used for the treatment of white spot lesions (WSLs) prior to bracket bonding. However, some concerns exist regarding their possible interference with the etching and bonding process, negatively affecting the bond strength. This study aimed to assess the effect of two remineralizing agents with/without CO2 laser irradiation on the mechanical properties and shear bond strength (SBS) of demineralized enamel to the orthodontic bracket.Methods: This study evaluated 60 premolar teeth in 6 groups (n=10) as follows: (I) sound enamel, (II) demineralized enamel, (III) Nupro remineralizing agent (N), (IV) Nupro and CO2 laser (N/L), (V) Teethmate remineralizing agent (T), and (VI) Teethmate and CO2 laser (T/L). The remineralizing agents were applied to the enamel surfaces after their immersion in a demineralizing solution for 5 days. In groups IV and VI, the CO2 laser with a 10.6 μm wavelength, 10 ms pulse duration, a 50 Hz repetition rate, 0.3 mm beam diameter and 0.7 W power was irradiated after applying the remineralizing agents. Brackets were bonded to the enamel surfaces and SBS was measured by a universal testing machine. For the assessment of enamel microhardness, 20 sections of molar teeth were divided into 4 groups (n=5; N, N/L, T, T/L) and their microhardness was measured before demineralization, after demineralization and after remineralization. X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FESEM) and energy-dispersive spectrometry (EDS) were carried out to assess the formation of hydroxyapatite. The atomic percentages of the C, O, P, Ca, Na, Si, F and Ca/P ratio were determined by EDS analysis.Results: The SBS significantly decreased in group II (P < 0.001). There was no significant difference among the groups I, III, IV, V and VI (P < 0.05). This finding was similar to the microhardness results, which showed an increase in microhardness after remineralization (P < 0.05), with no difference among the remineralizing agents. The Ca/P ratio was the highest in the Nupro group and the lowest in the demineralized group.Conclusion: Remineralizing agents can significantly improve the microhardness and structural properties of demineralized enamel to a level similar to that of sound enamel with no adverse effect on SBS to orthodontic brackets

Evaluation of the theoretical and clinical methods for reducing marginal leakage in resin-based composite restorative materials: A review

Resin-based composite restorative materials  have a substantial share in dental treatments. Their esthetic has made them patients’ first choice as restorative materials. Marginal leakage is one of their problems which leads to recurrent caries and post-operative hypersensitivity. Our aim was to evaluate the theoretical and clinical methods that have been proposed in the dental literature. Around 50 articles from Pubmed, SCOPUS and google scholar were selected and categorized in 4 groups based on the selected keywords. All the studies discussed in this paper have emphasized that there is no way to eliminate the microleakage but it can be reduced by means of some approaches. On the other hand, due to the multifactorial nature and difference of oral environment and laboratory conditions, there isn’t any certain way to define precisely. It seems that there is an absolute need for more research in this field to make the relation of theoretical results and clinical findings possible

Correlation of EGFR Expression with Survival Rate in Patients with Oral Squamous Cell Carcinoma

Background and Aim: This study aimed to indicate the role of epidermal growth factor (EGF) in proliferation and growth of epithelial tissue and to determine the correlation be-tween the frequency of expression of EGF receptor (EGFR) by means of immunohistochemistry with survival rate in oral squamous cell carcinoma (OSCC). Materials and Methods: Thirty-eight cases of OSCC diagnosed by hematoxylin and eo-sin (H&E) staining were included in this prospective study, and immunohistochemistry for EGFR was applied using antibodies against EGFR. The total score of stained cells and the correlation between the total score and survival rate of patients were recorded. The data were analyzed by Kaplan-Meier, Spearman and the log rank tests using SPSS software version 20. Results: The mean age of patients was 71.8±1.09 years. The follow up range was 25-86 months. The mean survival time for EGFR score 3 (51±9.32 months) was significantly higher than that for score 4, (28.64±4.1 months) (P=0.002) and overexpression of EGFR was correlated with poor prognosis. A significant correlation was found between the grade of tumor and EGFR scale (P=0.049, R=0.318). There was no significant correlation between EGFR overexpression and OSCC stage (P>0.05). Conclusion: EGFR is probably an independent prognostic factor for assessment of survival rate. A correlation also exists between the grade of tumor and expression of EGFR