Bleaching effect on bonding performance of composite to enamel.

This study aimed to assess the effects of dental bleaching on the immediate shear bond strength (SBS) of composite to enamel. Different bleaching methods and time intervals between bleaching and composite restoration were examined. A total of 45 enamel specimens were divided into three groups (n = 15) based on the applied bleaching protocol: in-office (A), at-home (B), and unbleached control (C). Groups A and B were then subdivided into three time intervals until bonding: 1, 3, and 7 days. The composite was bonded to enamel using self-etch adhesive technique and submitted to SBS testing. The enamel surface and adhesive interface were observed under scanning electron microscope (SEM). The highest average SBS was measured in the control (unbleached) group (31.1 ± 3.4). A significant difference in SBS was found between the control and in-office bleaching (p < .001), as well as between control and at-home bleaching (p = .034), while the difference between in-office and at-home bleaching methods was insignificant. In relation to the waiting period, a significant reduction in SBS (p < .001) was found 1 day post-bleaching. The weakest marginal sealing to enamel under SEM was observed also 1 day after bleaching. Both bleaching methods significantly reduced the SBS of composite to enamel, especially immediately after the bleaching procedure. Reduction in SBS is temporary and 3-day waiting period seems to be sufficient to reverse the adverse effects of bleaching. RESEARCH HIGHLIGHTS: SBS of composite to enamel is significantly reduced by bleaching procedures, especially immediately after bleaching. The reduction in SBS is temporary and reversible by delaying the restoration for a minimum of 3 days.

Influence of etching mode and composite resin type on bond strength to dentin using universal adhesive system.

Adhesive bond strength at the composite/dentin interface is influenced by various factors, including the etching mode and composite resin type. The purpose of this study was to evaluate the influence of the total-etch and self-etch mode on the microtensile bond strength (µTBS) of conventional and bulk-fill composite to dentin, using the universal adhesive system. Sixty non-carious human teeth were sectioned parallel to their longitudinal axis, using a low-speed diamond saw to obtain a flat dentin surface. According to the etching technique and composite resin type used, teeth were randomly divided into four different groups (n = 15): TC (total-etch/conventional composite), TB (total-etch/bulk-fill composite), SC (self-etch/conventional composite), and SB (self-etch/bulk-fill composite). Cylindric composite build-ups were made with 3M Filtek Z250 and 3M Filtek Bulkfill Posterior, using a plastic mold, 4 mm in diameter and 4 mm in height. The specimens were subjected to the µTBS test in a universal testing machine and failure force was recorded. Failure modes were determined using stereoscopic and scanning electron microscopy. Data were analyzed using the two-way ANOVA and Student's t test. The µTBS was significantly affected by the etching technique. A significant statistical difference was determined between total-etch and self-etch groups, irrespective of the composite resin type used. Higher bond strength was obtained in total-etch groups. The µTBS was not affected by the composite resin type. No significant statistical difference was determined between the conventional and bulk-fill groups, irrespective of the etching-mode.

Dental care during the Covid-19 pandemic - To treat or not to treat?

The recent spread of COVID-19 presents a huge public health concern. Clinical presentations of COVID-19 range from asymptomatic cases to severe pneumonia that can lead to death. Drastic measures were necessary to prevent the disease from spreading and protect the most vulnerable groups in the general population. The rapid reorganization of the healthcare system and great efforts made by medical staff were needed to admit to hospitals and then treat a progressively growing number of patients. The predominant route of virus transmission is through direct contact with an infected individual or respiratory droplets, therefore, all dental procedures with aerosol-formation pose an extremely high risk for the spread of infection. The aim of this article is to provide an overview of the current epidemiological situation, routes of transmission, and specific recommendations for dental practices including patient screening and triage, infection control, and treatment protocols. In this situation, it is essential that all dental healthcare workers make wise clinical decisions and educate themselves and their patients on how to prevent the spread of infection.

Marginal adaptation of composite resins under two adhesive techniques.

In the present research, different adhesive techniques were used to set up fillings with composite resins. After the application of etch and rinse or self etch adhesive technique, marginal adaptation of composite fillings was estimated by the length of margins without gaps, and by the microretention of resin in enamel and dentin. The study material consisted of 40 extracted teeth. Twenty Class V cavities were treated with 35% phosphorous acid and restored after rinsing by Adper Single Bond 2 and Filtek Ultimate-ASB/FU 3M ESPE composite system. The remaining 20 cavities were restored by Adper Easy One-AEO/FU 3M ESPE composite system. Marginal adaptation of composite fillings was examined using a scanning electron microscope (SEM). The etch and rinse adhesive technique showed a significantly higher percentage of margin length without gaps (in enamel: 92.5%, in dentin: 57.3%), compared with the self-etch technique with lower percentage of margin length without gaps, in enamel 70.4% (p < .001), and in dentin-22.6% (p < .05). In the first technique, microretention was composed of adhesive and hybrid layers as well as resin tugs in interprismatic spaces of enamel, while the dentin microretention was composed of adhesive and hybrid layers with resin tugs in dentin canals. In the second technique, resin tugs were rarely seen and a microgap was dominant along the border of restoration margins. The SEM analysis showed a better marginal adaptation of composite resin to enamel and dentin with better microretention when the etch and rinse adhesive procedure was applied.

Determination of vertical dimension of occlusion by using the phonetic vowel "O" and "E".

BACKGROUND/AIM: The vertical dimension of occlusion is a very important parameter for proper reconstruction of the relationship between the jaws. The literature describes many methods for its finding, from the simple, easily applicable clinically, to quite complicated, with the use of one or more devices for determination. The aim of this study was to examine the possibility of determining the vertical dimension of occlusion using the vocals "O" and "E" with the control of values obtained by applying cognitive functions. METHODS: This investigation was performed with the two groups of patients. The first group consisted of 50 females and 50 males, aged 18 to 30 years. In this group the distance between the reference points (on top of the nose and chin) was measured in the position of the mandible in the vertical dimension of occlusion, the vertical dimension at rest and the pronunciation of the words "OLO" and "ELE". Checking the correctness of the particular value for the word "OLO" was also performed by the phonetic method with the application of cognitive exercises when the patients counted from 89 to 80. The obtained difference in the average values in determining the vertical dimension of occlusion and the "OLO" and "ELE" in the first group was used as the reference for determining the vertical dimension of occlusion in the second group of patients. The second group comprised of 31 edentulous persons (14 females and 17 males), aged from 54 to 85 years who had been made a complete denture. RESULTS: The average value obtained for the vertical dimension of rest for the entire sample was 2.16 mm, for the word "OLO" for the entire sample was 5.51 mm and for the word "ELE" for the entire sample was 7.47 mm. There was no statistically significant difference between the genders for the value of the vertical dimension at rest, "ELE" and "OLO". There was a statistically significant difference between the values f or the vertical dimension at rest, "OLO" and "ELE" for both genders. There was a statistically significant correlation between the value for the vertical dimension at rest, "OLO" and "ELE", for both groups of subjects. CONCLUSION: Determining the vertical dimension of occlusion requires 5.5 mm subtraction from the position of the mandible in pronunciation of the word "OLO" or 7.5 mm in pronunciation of the word "ELE".

[Scanning electron microscopy analysis of marginal adaptation of composite resines to enamel after using of standard and gradual photopolimerization].

INTRODUCTION: Bonding between composite and hard dental tissue is most commonly assessed by measuring bonding strength or absence of marginal gap along the restoration interface. Marginal index (MI) is a significant indicator of the efficiency of the bond between material and dental tissue because it also shows the values of width and length of marginal gap. OBJECTIVE: The aim of this investigation was to estimate quantitative and qualitative features of the bond between composite resin and enamel and to determine the values of MI in enamel after application of two techniques of photopolymerization with two composite systems. METHODS: Forty Class V cavities on extracted teeth were prepared and restored for scanning electron microscope (SEM) analysis of composite bonding to enamel. Adhesion to enamel was achieved by Adper Single Bond 2 - ASB (3M ESPE), or by Adper Easy One--AEO (3M ESPE). Photopolymerization of Filtek Ultimate--FU (3M ESPE) was performed using constant halogen light (HIP) or soft start program (SOF). RESULTS: Quantitative and qualitative analysis, showed better mikromorphological bonding with SOF photopolymerization and ASB/FU composite system. Differences in MI between different photopolymerization techniques (HIP: 0.6707; SOF: 0.2395) were statistically significant (p < 0.001), as well as differences between the composite systems (ASB/FU: 0.0470; AEO/ FU: 0.8651) (p < 0.001) by two-way ANOVA test. CONCLUSION: Better marginal adaptation of composite to enamel was obtained with SOF photopolymerization in both composite systems.

Stromal reaction and prognosis in acinic cell carcinoma of the salivary gland.

INTRODUCTION: Primary acinic cell carcinoma (ACC) is an uncommon malignant neoplasm of the salivary gland (SG), which usually presents as slow growing tumor. CASE REPORT: We reported a 69-year-old woman with tumor in the right parotid gland with a 5-year progress. Biopsy sections revealed a hybrid form of ACC with a low- and high-grade component and prominent lymphoid tissue in tumor stroma. Immunohistochemistry was performed to define the molecular profile of this unusual ACC, with special interest for stromal influence on to the proliferative activity of ACC with dedifferentiation. We detected that the level and the type of stromal lymphoid reaction (particularly CD8+/CD4+ ratio) had a significant influence on to Ki-67 index in the high-grade component of ACC, as well as the involvement of the CXCR4 signaling axis in the stromal reaction influence. CONCLUSION: We suggest that tumor stroma may be a source of potential new tumor biomarkers which can determine the aggressivity of this tumor.

[SEM investigation of composite restoration adaptation to enamel after use of total etch and self etch adhesive system].

INTRODUCTION: Quality and durability of enamel/composite interface essentially depend on an adhesive restorative system. OBJECTIVE: The aim of this study was to evaluate the quality of marginal adaptation of composite adhesive systems to enamel by scanning electron microscopy (SEM), and to analyse the morphology of the enamel surface along margins of composite restorations, following exposure to cariogenic solution. METHODS: The study material included 56 extracted human third molars. Class V cavities were prepared with margins at enamel. Cavities were restored with Single Bond/Z250 and Single Bond/Filtek flow, using the total etch adhesive system, and Prompt-L-Pop/Z250 and Prompt-L-Pop/Filtek flow, using the self etch adhesive system. After the restorative procedure, the restorations were submitted to demineralization during 7 and 28 days. Samples were stored in a cariogenic solution (lactic acid, pH 4.5; 0.1 M) at 37 degrees C or in deionized water (the control group). The margins of restorations and perimarginal enamel were examined by scanning electron microscope (SEM). The gap formations around restoration were measured on cervical, occlusal and approximate margins. RESULTS: The usage of the total etch adhesive system showed statistically significant lower marginal gap width around composite restoration, compared with the self etch system (p < 0.01). The SEM examination also showed perimarginal enamel zones presenting several signs of demineralization and erosion (alteration of rods, porosities) after acting of a cariogenic solution, in both adhesive methods. Less alteration was found on the enamel surfaces not included in the perimarginal zone. CONCLUSION: Treating the cavity with 35% phosphoric acid in the total etch system significantly improved the adaptation of the composite resins to enamel, compared with the self etch treatment. Stronger demineralization of the perimarginal enamel in a cariogenic solution was observed around all restorations in both adhesive systems.

[Efficiency of final irrigation of root canal in removal of smear layer].

INTRODUCTION: A smear layer forms on the root canal walls as the consequence of root instrumentation. The smear layer formed in such a way considerably influences the quality of root obturation and endodontic treatment outcome. OBJECTIVE: The aim of this study was to ultrastructurally analyse the surface of intracanal dentine after removal of the smear layer by the solution of doxycycline, citric acid and detergent Tween-80 (MTAD). METHODS: The study involved 60 single-rooted, extracted, human teeth divided into four groups. All samples were instrumented by a step-back technique and manual K-files, and rinsed during instrumentation by 2% CHX and H2O2. The first group of samples was exclusively rinsed by CHX and H2O2; in the second group, besides using CHX and H2O2, MTAD solution was used for the final irrigation. The samples which were rinsed by distilled water (+ control) and the samples rinsed by 5.25% NaOCI and 17% Na EDTA (-control) served as control groups. All samples were observed under the scanning electronic microscope JEOL-JSM-5300. The coronary, middle and apex thirds of the radix region were analysed. RESULTS: The obtained results of the SEM analysis showed that the application of 2% chlorhexidine and hydrogen peroxide did not give clear dentine walls, and the smear layer could not be removed completely. The application of the same combination (CHX and H2O2), added by the final MTAD irrigation solution, led to the efficient removal of the smear layer, while the morphological structure of dentine surface remained unchanged. Statistical analysis showed that canal walls in the experimental group with MTAD as the final irrigation were significantly clearer compared to the control group (p < 0.001). CONCLUSION: Based on the obtained results, it can be concluded that MTAD is an efficient solution for the final irrigation of the canal system.

[The resistence of conditioned enamel to the effect of cariogenic solution].

INTRODUCTION: Enamel surface around restoration is very sensitive to the effect of cariogenic solution. It is the consequence of the manner the cavity is prepared before restoration, the existence of marginal cracks around restoration, that is, irregular polishing of filling. OBJECTIVE: The aim of this study is to analyze the morphology of the marginal enamel surface around composite fifth class restoration after the application of cariogenic solution. METHOD: In this study 28 extracted molars were used. After the V class preparation of the buccal crown surface, teeth samples were divided into two groups. The first group was restored with the composite system Single Bond +Z250, applying the total etching technique. The second group was restorated with Prompt L-pop +Z250 and by applying self-etching primers. After the cavity restoration, teeth samples were kept in demineralising solution (lactic acid, pH 4.5, 0.1 M) at the temperature of 37 degrees C during 7 and 28 days. Control group samples were kept in distilled water during the experiment. The marginal enamel surface analysis was done by a scanning electron microscope. RESULTS: The achieved results showed that there was a denivelation and severe demineralization of the perimarginal enamel zone after 7 and 28 days, while on the remaining enamel there were some minor changes. Along the marginal composite/enamel joint there was the central type of demineralization of enamel prisms and preserved inter prismatic enamel.The existence of pores of different sizes and scattered enamel fractures was established. The marginal joint was mostly without any gaps in the first group samples, while in the second group samples there were narrow or wider edge gaps. CONCLUSION: After the application ofcariogenic solution, perimarrginal enamel showed conspicuous morphological damage in comparison to the remaining enamel surface.