Effects of Autoclave Sterilization on Cyclic Fatigue Resistance in 5 Types of Rotary Endodontic Instruments: An In Vitro Study.

BACKGROUND Rotary endodontic instruments are increasingly used in root canal treatment and have replaced stainless steel manual files. Cyclic fatigue is the cyclic loading of stress to produce deformation or fracture. This study aimed to evaluate and compare the effects of autoclave sterilization on cyclic fatigue in 5 types of rotary endodontic instruments. MATERIAL AND METHODS ProTaper Universal, BioRace, ProTaper Next, Twisted File, and HyFlex CM instruments were included in this study. Each type included 96 instruments, divided into 4 groups according to the number of sterilization cycles (0, 1, 3, 5). After sterilization, each group of instruments was divided into 2 subgroups and tested for cyclic fatigue in 2 simulated canals (45 degrees both and 2 radii, 2 mm and 5 mm). The number of cycles to failure (NCF) was calculated, and statistical analyses were carried out using the t test, Mann-Whitney U test, and ANOVA, followed by the Tukey post hoc test (p<0.05). Fracture surfaces were analyzed using scanning electron microscopy (SEM). RESULTS Within the group of non-sterilized instruments, ProTaper Universal showed significantly lower resistance to cyclic fatigue compared to the other types of instruments (p<0.001). After repeated sterilization, a significantly higher mean of NCF was observed for BioRace (p<0.001), ProTaper Next (p<0.001), Twisted File (p<0.001), and HyFlex CM (p<0.001) compared to ProTaper Universal. The resistance of HyFlex CM was significantly higher compared to the other types of instruments (p<0.001). CONCLUSIONS The findings from this study showed that autoclave sterilization of newer rotary endodontic instruments could increase resistance to cyclic fatigue.

Determining the Impact of the COVID-19 Pandemic on Dental Care in the Serbian Adult Population: An Online Questionnaire-Based Study.

BACKGROUND Emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 virus) could lead to an increase in dental anxiety, avoidance of dental visits, and general neglect of oral health. This online questionnaire-based study conducted in April and May of 2021 in Serbia aimed to determine the impact of the coronavirus disease 2019 (COVID-19) pandemic on dental care. MATERIAL AND METHODS The study included 2060 adult citizens of the Republic of Serbia who participated in an anonymous online questionnaire based on a 5-point Likert scale. Data were collected on dental care routine prior to and during the pandemic, and the fear of negative consequences for oral health. The results were statistically analyzed using descriptive statistics, Pearson's correlation coefficient, ANOVA, and the paired t test. RESULTS Approximately one-fifth of the respondents postponed dental visits during the pandemic. Concern about postponing dental treatment was expressed by more than one-half of the respondents (57.1%), while 21.4% thought that they were already experiencing the consequences. Avoidance of preventive examinations and improvement of oral hygiene are more common among the elderly compared to younger respondents (P=.000). CONCLUSIONS The COVID-19 pandemic did not significantly affect the habit of avoiding dental interventions due to fear, but it did lead to part of the population completely avoiding even urgent dental interventions during the peak of the pandemic, and opting for tooth extraction rather than treatment. The strongest impact on dental care in the pandemic was among people over 64 years old.

COVID-19: Another Cause of Dental Anxiety?

BACKGROUND Fear has always been closely linked to dentistry but it could be intensified by the objective risks imposed by the pandemic. The objective of this study was to determine the profile of the frightened dental patient during the COVID-19 pandemic and determine measures taken by dentists to reduce fear and increase security among their patients. MATERIAL AND METHODS An anonymous online survey was conducted between March 15 and April 15, 2021. The respondents were 2060 adult citizens of the Republic of Serbia. In addition to demographic data, data related to the COVID-19 pandemic, dental fear, and attitudes and fear of dental interventions during the ongoing pandemic were compiled. The data were analyzed using descriptive statistics: the chi-square test and Pearson's coefficient. RESULTS Seventy percent of the respondents felt some level of fear of the ongoing pandemic, 50% felt fear of going to a dentist during the pandemic, 20% considered a dental office a hotspot for the transmission of SARS-CoV-2, and 43% would visit their dentist only in the case of emergency. CONCLUSIONS The COVID-19 pandemic has affected the attitudes and behavior of people pertaining to visits to dental offices. Identifying frightened patients and their opinions and fears at this challenging time would make it easier for dentists to include protocols in their everyday practice to increase a sense of security among their patients, such as implementing preventive measures in front of the patients, ensuring an empty waiting room, and providing telephone consultations.

Prevalence of Human Cytomegalovirus and Epstein-Barr Virus in Chronic Periapical Lesions.

OBJECTIVE: The aim of this study was to investigate the presence of human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) in the tissue of chronic periapical lesions, and to compare the results in relation to the symptoms of patients and the size of the lesion. METHODS: Periapical lesions analyzed in the study were collected from the roots of the teeth indicated for extraction. Samples were divided according to the symptoms into groups of symptomatic and asymptomatic, and according the size into groups of small and large lesions. Polymerase chain reaction was used to detect HCMV and EBV. The amplification was performed in a DNA Thermal Cycler (Hybaid). RESULTS: Symptomatic lesions were 7.68 times more likely to be infected with HCMV than asymptomatic lesions (p < 0.001). Large symptomatic lesions were 73.50 times more likely to harbor HCMV than small symptomatic lesions (p < 0.001). Large symptomatic lesions were 7.64 times more likely to be infected with EBV than small symptomatic lesions (p = 0.05). Large symptomatic lesions were 5.38 times more likely to harbor dual HCMV/EBV infection than small symptomatic lesions (p = 0.115). CONCLUSION: Detection of HCMV and EBV in the samples of periapical lesions suggests an important role of herpesviruses in periapical tissue destruction.

Erosive Effect of Different Soft Drinks on Enamel Surface in vitro: Application of Stylus Profilometry.

OBJECTIVE: To assess the erosive potential of various soft drinks by measuring initial pH and titratable acidity (TA) and to evaluate enamel surface roughness using different exposure times. MATERIALS AND METHODS: The initial pH of the soft drinks (group 1: Coca-Cola; group 2: orange juice; group 3: Cedevita; group 4: Guarana, and group 5: strawberry yoghurt) was measured using a pH meter, and TA was measured by titration with NaOH. Enamel samples (n = 96), cut from unerupted human third molars, were randomly assigned to 6 groups: experimental (groups 1-5) and control (filtered saliva). The samples were exposed to 50 ml of soft drinks for 15, 30 and 60 min, 3 times daily, during 10 days. Between immersions, the samples were kept in filtered saliva. Enamel surface roughness was measured by diamond stylus profilometer using the following roughness parameters: Ra, Rq, Rz, and Ry. Data were analyzed by one-way ANOVA, Tukey's post hoc and Student-Newman-Keuls post hoc tests. RESULTS: The pH values of the soft drinks ranged from 2.52 (Guarana) to 4.21 (strawberry yoghurt). Orange juice had the highest TA, requiring 5.70 ml of NaOH to reach pH 7.0, whereas Coca-Cola required only 1.87 ml. Roughness parameters indicated that Coca-Cola had the strongest erosion potential during the 15 min of exposure, while Coca-Cola and orange juice were similar during 30- and 60-min exposures. There were no significant differences related to all exposure times between Guarana and Cedevita. Strawberry yoghurt did not erode the enamel surface regardless of the exposure time. CONCLUSION: All of the tested soft drinks except yoghurt were erosive. Erosion of the enamel surfaces exposed to Coca-Cola, orange juice, Cedevita, and Guarana was directly proportional to the exposure time.

In vitro effect of beer, red and white wine on the morphology and surface roughness of human enamel.

BACKGROUND: Beer, red and white wine are acidic drinks whose frequent consumption can increase the risk of dental erosion. OBJECTIVES: To establish the effect of beer, red and white wine on the morphology and surface roughness (SR) of human enamel using different exposure times in a cyclic deand remineralization model in vitro. MATERIAL AND METHODS: The experiment included 33 surgically extracted impacted human third molars from patients aged 18-25 years. Enamel samples obtained by cutting crowns (n = 132) were submitted to alternate cycles of demineralization in (1) beer, (2) red wine, (3) white wine, (PC) positive control (orange juice), and remineralization in artificial saliva, which also represented a medium for negative control (NC). The experiment included cycles with different exposure times in alcoholic beverages and orange juice of 15, 30 and 60 min. Thus, 12 groups were formed (for each drink and each exposure time) containing 10 samples each, while the NC group consisted of 12 samples. Experiments were repeated 3x/day for 10 days. Enamel surface alterations were determined by stylus profilometry (average surface roughness (Ra)) and scanning electron microscopy (SEM). The Shapiro-Wilk test, independent samples Kruskal-Wallis test and multiple comparisons (all pairwise) were performed. RESULTS: With increasing exposure time, there was a positive correlation with Ra for white wineand orange juice-immersed samples (60 min compared to 15 min), which was also observed using SEM. There was no significant difference in the Ra between the other experimental samples for the same exposure time. CONCLUSIONS: This study confirms a certain erosive potential of beer, red and white wine, and a significant relationship with pH, titratable acidity (TA) and SR, but not with the exposure time for all tested alcoholic beverages. Moreover, differences among the ultrastructural patterns caused by alcoholic beverages over the enamel surface were observed.

Ultrastructural changes in the cemento-enamel junction after vital tooth bleaching with fluoride and fluoride-free agents - a pilot study.

BACKGROUND: The impact of bleaching on the cemento-enamel junction (CEJ) is not well known. Due to frequent sensitivity of the cervical region of teeth after the vital bleaching, the aim of the present study was to evaluate the morphological features of the CEJ of human teeth after application of fluoridated and fluoride-free bleaching agents, as well as post-bleaching fluoridation treatment, by scanning electron microscopy (SEM) analysis. MATERIAL/METHODS: Thirty-five extracted permanent human teeth were longitudinally cut, yielding 70 specimens. Thirty specimens were randomly divided into the 3 experimental groups, and 20 specimens, were used as (2) control groups, each: negative (untreated) control group; positive control group treated with 35% hydrogen peroxide; experimental group 1, bleaching with 10% carbamide peroxide (CP); experimental group 2, treatment with a mixture of 10% CP and fluoride; and experimental group 3, treatment with 10% CP and 2% sodium fluoride gel applied 30 minutes after bleaching. Experimental groups were treated 8 h per day for 14 days. The samples were examined by SEM. RESULTS: The bleaching materials tested caused morphological changes to the surface of the CEJ. There was a statistically significant difference between experimental groups (Kruskal Wallis Test chi-square=11,668; p<0.005). Mean value of experimental group 2 scores showed statistically significant difference from groups 1 and 3. CONCLUSIONS: Bleaching gel with fluorides does not significantly change morphological appearance of the CEJ and represents a better choice than the hard tissue fluoridation process after bleaching.

Poloxamer-188 Exacerbates Brain Amyloidosis, Presynaptic Dystrophies, and Pathogenic Microglial Activation in 5XFAD Mice.

BACKGROUND: Alzheimer's disease (AD) is initiated by aberrant accumulation of amyloid beta (Aß) protein in the brain parenchyma. The microenvironment surrounding amyloid plaques is characterized by the swelling of presynaptic terminals (dystrophic neurites) associated with lysosomal dysfunction, microtubule disruption, and impaired axonal transport. Aß-induced plasma membrane damage and calcium influx could be potential mechanisms underlying dystrophic neurite formation. OBJECTIVE: We tested whether promoting membrane integrity by brain administration of a safe FDA approved surfactant molecule poloxamer-188 (P188) could attenuate AD pathology in vivo. METHODS: Three-month-old 5XFAD male mice were administered several concentrations of P188 in the brain for 42 days with mini-osmotic pumps. After 42 days, mice were euthanized and assessed for amyloid pathology, dystrophic neurites, pathogenic microglia activation, tau phosphorylation, and lysosomal / vesicular trafficking markers in the brain. RESULTS: P188 was lethal at the highest concentration of 10mM. Lower concentrations of P188 (1.2, 12, and 120µM) were well tolerated. P188 increased brain Aß burden, potentially through activation of the γ-secretase pathway. Dystrophic neurite pathology was exacerbated in P188 treated mice as indicated by increased LAMP1 accumulation around Aß deposits. Pathogenic microglial activation was increased by P188. Total tau levels were decreased by P188. Lysosomal enzyme cathepsin D and calciumdependent vesicular trafficking regulator synaptotagmin-7 (SYT7) were dysregulated upon P188 administration. CONCLUSION: P188 brain delivery exacerbated amyloid pathology, dystrophic neurites, and pathogenic microglial activation in 5XFAD mice. These effects correlated with lysosomal dysfunction and dysregulation of plasma membrane vesicular trafficking. P188 is not a promising therapeutic strategy against AD pathogenesis.

Ultrastructural changes in the cemento-enamel junction caused by acidic beverages: An in vitro study.

The present in vitro study was aimed at evaluating the morphological changes in the cemento-enamel junction (CEJ) after exposure to acidic beverages using the scanning electron microscopy (SEM). The initial pH and titratable acidity (TA) was analyzed from follow groups: (I) Coca cola, (II) orange juice, (III) Cedevita, (IV) Red Bull, (V) Somersby cider, and (VI) white wine. The CEJ samples (n = 64), obtained from unerupted third molars, were allocated to one control (artificial saliva, n = 16) and six experimental groups (n = 8). The experimental samples were immersed in beverages (50 ml) for 15 min, three times daily, 10 days, and in artificial saliva between immersions. SEM analysis was performed in a blind manner, according to scoring scale. One-way ANOVA and Tukey's post hoc tests, as well as Kruskal-Wallis and Mann-Whitney U test used for statistical analysis. The pH values of the acidic beverages ranged from 2.65 (Coca cola) to 3.73 (orange juice), and TA ranged from 1.90 ml (Coca cola) to 5.70 ml (orange juice) of NaOH to reach pH 7.0. The SEM analysis indicated statistically significant differences between the control samples and those immersed in acidic beverages. The Groups IV, I, and II, showed the highest CEJ damage grade while those of the Group VI were the lowest. All the tested acidic beverages caused morphological changes in the CEJ with a smaller or larger exposure of dentine surface, and were not always related to the pH or TA of acidic beverages.

[Analysis of antimicrobial effect of MTAD solution in infected root canal system using PCR technique].

INTRODUCTION: Clinically acceptable antiseptic should possess organolithic-mineralolithic properties and antimicrobial efficacy, and should be non-toxic. OBJECTIVE: The aim of the paper was to assess the presence of genomes of the most common microorganisms (Porphyromonas gingivalis, Agregatibacter actinomycetemcomitans, Tanerella forsythensis, Prevotella intermedia, Treponema denticola and Enterococcus faecalis) in infected tooth root canals before and after rinsing with solution of doxycycline, citric acid and detergent Tween-80 (MTAD) in patients with clinically diagnosed primary apex periodontitis. METHODS: The content of primarily infected canals before and after using the MTAD solution was used as a biological material in which the presence of microorganisms DNA was proved. For the detection of bacterial genome the multiplex PCR technique was applied. RESULTS: The percentage of positive samples before canal treatment was 100%. In infected root canals E. faecalis was most dominant (37%). In a relatively high percentage we detected P. intermedia (25%), A. actinomycetemcomitans (20%), T. denticola (17%), T. forsythensis (15%) and P. gingivalis (10%). After rinsing the canal system using MTAD solution, there was a statistically significant decrease in E. faecalis (12%), P. intermedia (0%), T forsythensis (0%) and P. gingivalis (0%). The presence of other bacteria was also diminished but not statistically significantly. CONCLUSION: With the application of multiplex PCR technique which provided a simultaneous amplification of various genomic sequences, using several pairs of primers, the most dominant in infected root canals were E. faecalis. P. intermedia, A. actinomycetemcomitans, T. denticola, T. forsythensis and P. gingivalis. After mechanic treatment and irrigation of root canals with MTAD solution, P. intermedia, P. gingivalis and T forsythensis were not found. The presence of E. faecalis, A. actinomycetemcomitans and T. denticola was diminished, however, not statistically significantly.

Ultrastructural analysis of the root canal walls after simultaneous irrigation of different sodium hypochlorite concentration and 0.2% chlorhexidine gluconate.

To determine whether sodium hypochlorite (NaOCl) with 0.2% chlorhexidine gluconate (CHX) leads to colour change and precipitate formation, and to ultrastructurally analyse the dentine surface after simultaneous irrigation with 0.5% NaOCl and 0.2% CHX. Four tubes in which 5ml of different NaOCl concentrations and 5ml 0,2% CHX were placed, were observed every 15 minutes in the first two hours and after 7 days. Mixture solutions were centrifuged at 800 rpm/4 min. A precipitate is observed under light-microscopy. Thirty-five single-rooted teeth were instrumented using crown-down technique with irrigation: Positive control: distilled water, Negative control: 0,5% NaOCl+15% EDTA, Experimental group: identical to the negative control, then canals were treated with 0.5% NaOCl+0.2% CHX. The longitudinal root sections were observed under scanning-electron-microscopy. The amount of debris was assessed with 5/score-system, and the results were analysed using the Mann-Whitney U test (p < 0.001). Change in colour was noticed immediately after the merger and it did not change with time. Mixture solutions showed considerable turbidity, but precipitate was observed only after centrifugation. Statistical analysis showed a significant difference in the dentinal wall purity when comparing the cervical and middle root canal thirds between the experimental and negative control group. The difference was also observed between the cervical and middle thirds compared to the apical third of the root canal within these groups. Interaction between NaOCl and CHX, as well as the creation of precipitates, depends not only on the concentration of NaOCl, but also on the concentration of CHX.

[The investigation of ultrasound efficacy in cleaning the surface of new endodontic instruments]. / Ispitivanje efikasnosti ultrazvuka y ciscenju povrsina novih endodontskih instrumenata.

INTRODUCTION: Active parts and tips of various new stainless steel and nickel-titanium endodontic instruments can be coated with fragments or metal residues, which can become detached during endodontic treatment. These fragments may obstruct the root canals or even reach the periapical tissue during biomechanical preparation and should be removed before clinical use. OBJECTIVE: The aim of this study was to evaluate the presence of metal residues on both new stainless steel and nickel-titanium endodontic instruments, and to determine the cleaning efficacy of ultrasound using distilled water or disinfectant solution for removing these residues. METHODS: Forty-eight stainless steel and nickel-titanium instruments were carefully removed from their original packages with dental tweezers, in order to avoid any contact with the cutting flutes and tips. The instruments were evaluated in term of metal debris presence, using scanning electron microscopy (SEM) and x-ray energy-dispersive spectroscopy (EDS). The instruments were then removed from the electron microscopy analysis stubs and placed in an ultrasonic bath for 15 minutes at a frequency of 28 kHz, using distilled water or disinfectant solution. The surfaces of the instruments were re-evaluated after cleaning. RESULTS: Before ultrasound cleaning, a larger amount of metal debris was observed on the nickel-titanium endodontic instruments when compared to those made of stainless steel. The presence of metal particles on the instruments was evaluated by using EDS analysis. The use of ultrasound was effective in removing the metal residues from both types of endodontic instrument surfaces. CONCLUSION: The use of ultrasound proved to be an efficient method for the removal of metal particles from the surface of new stainless steel and nickel-titanium endodontic instruments.