The Effect of Water Coolant and Bur Type on Pulp Temperature When Removing Tooth Structure and Restorative Dental Materials.

OBJECTIVE: The aim was to compare intrapulp temperature (IPT) changes when flat-fissure diamond burs and pear-shaped tungsten carbide burs were used to cut tooth structure, amalgam, and composite resin with and without water coolant. METHODS: Thermocouples were inserted into the pulp chamber of extracted intact mandibular molars. The thermocouples were connected to an electronic thermometer that detects temperature every second to an accuracy of 0.1°C. IPT changes were recorded while using a high-speed handpiece during MOD cavity preparations (n=40), composite resin removal (n=40), and amalgam removal (n=40). A two-way ANOVA was used for each procedure to test for the effect of bur (pear-shaped tungsten carbide vs flat-fissured diamond) and water coolant (on vs off), with significant main effects (α=0.05) further analyzed using Tukey's multiple comparison test. RESULTS: During MOD cavity preparation, water coolant reduced changes in IPT (0.03±0.27°C) compared to no water coolant (1.27±0.29°C) when tungsten carbide burs were used (p<0.05) but not when diamond burs were used. During composite resin removal, tungsten carbide burs had less changes in IPT (0.55±0.18°C) compared to diamond burs (1.66±0.50°C) with no water coolant (p<0.05). Water coolant also reduced changes in IPT (0.09±0.14°C) compared to no water coolant (1.66±0.50°C) when diamond burs were used (p<0.01). Water coolant did not significantly affect IPT when tungsten carbide burs were used. During amalgam removal, tungsten carbide burs had lower changes in IPT (0.56±0.15°C) compared to diamond burs (1.88±0.43°C) with no water coolant (p<0.05). Water coolant also significantly reduced changes in IPT (0.71±0.2°C) compared to no water coolant (1.88±0.43°C) when diamond burs were used (p<0.05) but not when tungsten carbide burs were used. CONCLUSIONS: Water coolant reduced IPT changes when drilling tooth structure with tungsten carbide burs, but not when removing amalgam or composite. Conversely, water coolant reduced IPT changes when drilling with flat fissure diamond burs to remove amalgam and composite, but not when removing tooth structure. When amalgam and composite were removed without water coolant, the tungsten carbide burs resulted in lower IPT changes than when flat fissure diamond burs were used in the same way.

Visualization of airborne droplets generated with dental handpieces and verification of the efficacy of high-volume evacuators: an in vitro study.

BACKGROUND: The COVID-19 pandemic led to concerns about the potential airborne transmission of the virus during dental procedures, but evidence of actual transmission in clinical settings was lacking. This study aimed to observe the behavior of dental sprays generated from dental rotary handpieces and to evaluate the effectiveness of high-volume evacuators (HVEs) using laser light sheets and water-sensitive papers. METHODS: A dental manikin and jaw model were mounted in a dental treatment unit. Mock cutting procedures were performed on an artificial tooth on the maxillary left central incisor using an air turbine, a contra-angle electric micromotor (EM), and a 1:5 speed-up contra-angle EM (×5EM). Intraoral vacuum and extraoral vacuum (EOV) were used to verify the effectiveness of the HVEs. The dynamics and dispersal range of the dental sprays were visualized using a laser light sheet. In addition, environmental surface pollution was monitored three-dimensionally using water-sensitive papers. RESULTS: Although the HVEs were effective in both the tests, the use of EOV alone increased vertical dispersal and pollution. CONCLUSIONS: The use of various types of HVEs to reduce the exposure of operators and assistants to dental sprays when using dental rotary cutting instruments is beneficial. The study findings will be helpful in the event of a future pandemic caused by an emerging or re-emerging infectious disease.

Protein detection by fluorescence of manually cleaned high-speed dental handpieces.

We analyzed the effectiveness of manual cleaning protocols performed on high-speed dental handpieces, using protein identification by fluorescence. Although one protocol was able to able to lower the amount of protein, >40% of the handpieces showed amounts of residual protein at unacceptable levels.

Increased Handpiece Speeds without Air Coolant: Aerosols and Thermal Impact.

This study assessed the impact of increased speed of high-speed contra-angle handpieces (HSCAHs) on the aerosolization of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) surrogate virus and any concomitant thermal impact on dental pulp. A bacteriophage phantom-head model was used for bioaerosol detection. Crown preparations were performed with an NSK Z95L Contra-Angle 1:5 (HSCAH-A) and a Bien Air Contra-Angle 1:5 Nova Micro Series (HSCAH-B) at speeds of 60,000, 100,000, and 200,000 revolutions per minute (rpm), with no air coolant. Bioaerosol dispersal was measured with Φ6-bacteriophage settle plates, air sampling, and particle counters. Heating of the internal walls of the pulp chambers during crown preparation was assessed with an infrared camera with HSCAH-A and HSCAH-B at 200,000 rpm (water flows ≈15 mL min-1 and ≈30 mL min-1) and an air-turbine control (≈23.5 mL min-1) and correlated with remaining tissue thickness measurements. Minimal bacteriophage was detected on settle or air samples with no notable differences observed between handpieces or speeds (P > 0.05). At all speeds, maximum settled aerosol and average air detection was 1.00 plaque-forming units (pfu) and 0.08 pfu/m3, respectively. Irrespective of water flow rate or handpiece, both maximum temperature (41.5°C) and temperature difference (5.5°C) thresholds for pulpal health were exceeded more frequently with reduced tissue thickness. Moderate and strong negative correlations were observed based on Pearson's correlation coefficient, between remaining dentine thickness and either differential (r = -0.588) or maximum temperature (r = -0.629) measurements, respectively. Overall, HSCAH-B generated more thermal energy and exceeded more temperature thresholds compared to HSCAH-A. HSCAHs without air coolant operating at speeds of 200,000 rpm did not increase bioaerosolization in the dental surgery. Thermal risk is variable, dependent on handpiece design and remaining dentine thickness.

Capacidad de sellado apical entre dos técnicas de obturación con instrumentos rotatorios fracturados en tercio apical / Apical sealing capacity between two obturation techniques with rotary instruments broken in third apical

Introducción: La finalidad del tratamiento de conductos es conseguir la máxima desinfección, conformación y sellado tridimensional. Objetivo: Comparar la capacidad del sellado apical entre dos técnicas de obturación en conductos mesiales de molares inferiores con limas fracturadas en tercio apical. Material y métodos: Se utilizaron 60 raíces mesiales de molares inferiores, instrumentados con Protaper Universal, se desgastó 4 milímetros la parte activa del instrumento y se fracturó intencionalmente en tercio apical. Se formaron dos grupos de 30 raíces mesiales (n = 30) cada uno y se utilizaron dos técnicas de obturación: grupo 1: condensación lateral clásica y grupo 2: Obtura II. Las muestras se sumergieron en tubos de ensayo y en su interior contenían 5 mL de tinta china, se diafanizaron y observaron con un microscopio estereoscópico (LEICA, EZ4D) a 35x para medir la penetración de tinta china dentro del conducto radicular. Resultados: Se encontró una mayor microfiltración apical con suficiente evidencia estadística en el grupo de Obtura II comparado con el grupo de condensación lateral clásica (p < 0.002). Conclusiones: Ambos grupos presentaron microfiltración apical; sin embargo, en el grupo que se utilizó el sistema de obturación termoplastificada Obtura II se detectó mayor filtración apical comparada con el grupo de condensación lateral clásica (AU)

Introduction: The purpose of root canal treatment is to achieve maximum disinfection, shaping and three-dimensional sealing. Objective: To compare the apical sealing capacity between two obturation techniques in mesial canals of mandibular molars with broken files in the apical third. Material and methods: 60 mesial roots of lower molars were used, instrumented with Protaper Universal, the active part of the instrument was worn by 4 millimeters and it was intentionally broken in the apical third. Two groups of 30 mesial roots (n = 30) each were formed and two filling techniques were used: group 1: classic lateral condensation and group 2: Obtura II. The samples were immersed in test tubes and contained 5 mL of Chinese ink inside, they were clear and observed with a stereomicroscope (LEICA, EZ4D) at 35x to measure the penetration of Chinese ink into the root canal. Results: A higher apical microfiltration with sufficient statistical evidence was found in the Obtura II group compared to the classic lateral condensation group (p < 0.002). Conclusions: Both groups presented apical microfiltration, however, in the group that used the Obtura II thermoplastic obturation system, greater apical filtration was detected compared to the classic lateral condensation group (AU)

Airborne contamination of the dental operatory during activities performed with open or closed windows.

PURPOSE: To quantify the biological contamination of a dental operatory environment using a biological tracer. METHODS: A Streptococcus mutans suspension was infused into the mouth of a phantom, and an operator performed standardized dental procedures using an air turbine, a contra-angle handpiece, or an ultrasonic scaler either with windows open or closed. The presence of the tracer was measured by placing Petri dishes with a selective medium at 18 sites on the dental unit and 38 sites in the surrounding operatory environment. RESULTS: The contamination was drastically reduced when windows were opened, no matter which handpiece was used. Air turbine spread significantly higher contamination compared to contra-angle and scaler. All tested instruments spread the tracer over the entire dental unit and the surrounding environment, including the walls and ceiling; however, higher contamination levels were detected on the dental unit compared to the operatory surfaces. Opening windows during dental operative procedures greatly reduced contamination levels for all handpieces and can be recommended for reducing airborne contamination levels. CLINICAL SIGNIFICANCE: The significant levels of airborne contamination produced when operating dental handpieces can be significantly reduced by natural ventilation, i.e., simply opening the windows.

Effect of spray air settings of speed-increasing contra-angle handpieces on intrapulpal temperatures, drilling times, and coolant spray pattern.

OBJECTIVES: Decreasing aerosol leaks are of great interest, especially in the recent era of COVID-19. The aim was to investigate intrapulpal heat development, coolant spray patterns, and the preparation efficiency of speed-increasing contra-angle handpieces with the spray air on (mist) or off (water jet) settings during restorative cavity preparations. METHODS: Standard-sized cavities were prepared in 80 extracted intact human molar teeth using diamond cylindrical drills with a 1:5 speed-increasing contra-angle handpiece. A custom-made device maintained the standardized lateral drilling force (3 N) and predetermined depth. Temperatures were measured using intrapulpal thermocouple probes. The four experimental groups were as follows: mist cooling mode at 15 mL/min (AIR15), water jet cooling mode at 15 mL/min (JET15), mist cooling mode at 30 mL/min (AIR30), and water jet cooling mode at 30 mL/min (JET30). The coolant spray pattern was captured using macro-photo imaging. RESULTS: The JET15 group had the highest increase in temperature (ΔT = 6.02 °C), while JET30 (ΔT = 2.24 °C; p < 0.001), AIR15 (ΔT = 3.34 °C; p = 0.042), and AIR30 (ΔT = 2.95 °C; p = 0.003) had significantly lower increases in temperature. Fine mist aerosol was formed in the AIR15 and AIR30 preparations but not in the JET15 and JET30 preparations (p < 0.001). The irrigation mode had no influence on the preparation time (p = 0.672). CONCLUSIONS: Water jet irrigation using coolant at 30 mL/min appeared to be the optimal mode. Considering the safe intrapulpal temperatures and the absence of fine mist aerosols, this mode can be recommended for restorative cavity preparations. CLINICAL SIGNIFICANCE: To increase infection control in dental practices, the water jet irrigation mode of speed-increasing handpieces with coolant flow rates of 30 mL/min should be considered for restorative cavity preparations.

Estudio comparativo de los tiempos registrados por los instrumentos TruNatomy y ProTaper Next para alcanzar la longitud de trabajo en conductos curvos simulados obturados con GuttaCore / Comparative study of the times recorded by the TruNatomy and ProTaper Next instruments to reach the working length in simulated curved canals filled with GuttaCore

Objetivo: Comparar el tiempo empleado por los instrumen- tos TruNatomy Medium y ProTaper Next X3 para penetrar hasta la longitud de trabajo la masa de obturaciones realizadas con Gut- taCore Primary y sellador en conductos curvos simulados. Materiales y métodos: Se prepararon 20 conductos curvos simulados con instrumentos rotatorios WaveOne Gold Primary y se obturaron con GuttaCore Primary y AH Plus. Las muestras fueron divididas en dos grupos de 10 cada uno. Grupo 1: El material de obturación fue penetrado hasta la lon- gitud de trabajo con instrumentos TruNatomy Medium. Gru- po 2: El material de obturación fue penetrado hasta la longitud de trabajo con instrumentos ProTaper Next X3. Se registraron los tiempos de penetración requeridos para cada grupo y los valores obtenidos fueron analizados mediante la prueba t de Student. Resultados: Los instrumentos ProTaper Next X3 pe- netraron la masa del material de obturación más rápidamente que los instrumentos TruNatomy MediumTM. Las diferencias observadas entre ambos instrumentos fueron estadísticamente significativas (P <0.01). Conclusión: Si bien los instrumentos ProTaper Next X3 y TruNatomy MediumTM penetraron la masa de Gutta- Core Primary de manera eficiente, ProTaper Next X3 penetró hasta la longitud de trabajo más rápidamente (AU)

Aim: Compare the time required by the instruments TruNatomy Medium and ProTaper Next X3 to penetrate up to the working length the mass of fillings made with GuttaCore Primary and sealant in simulated curved canals. Materials and methods: The simulated canals of 20 EndoTraining Blocks were prepared with WaveOne Gold Pri- mary and obturated with GuttaCore Primary and AH Plus. The sample was divided into two groups of 10 each. Group 1: The sealing material was penetrated up to working length with TruNatomy Medium. Group 2: The sealing material was penetrated up to working length with ProTaper Next X3. The penetration time was recorded in each group and the obtained values were statistically analyzed with the Student's t test. Results: ProTaper Next X3 instruments penetrated the sealing material mass faster than TruNatomy Medium. Statis- tically significant differences were observed between the two instruments (P <0.01). Conclusion: While the ProTaper Next X3 and TruNat- omy Medium penetrated the GuttaCore mass to the working length efficiently, the ProTaper Next X3 did it in less time (AU)

The effect of high-speed dental handpiece coolant delivery and design on aerosol and droplet production.

OBJECTIVES: High-speed dental instruments produce aerosol and droplets. The objective of this study was to evaluate aerosol and droplet production from a novel electric micromotor handpiece (without compressed air coolant) in real world clinical settings. METHODS: 10-minute upper incisor crown preparations were performed in triplicate in an open-plan clinic with mechanical ventilation providing 3.45 air changes per hour. A 1:5 ratio electric micromotor handpiece which allows water coolant without compressed air (Ti-Max Z95L, NSK) was used at three speeds: 60,000 (60 K), 120,000 (120 K), and 200,000 (200 K) revolutions per minute. Coolant solutions contained fluorescein sodium as a tracer (2.65 mmol L - 1). High-speed air-turbine positive control, and negative control conditions were conducted. Aerosol production was evaluated at 3 locations (0.5 m, 1.5 m, and 1.7 m) using: (1) an optical particle counter (OPC; 3016-IAQ, Lighthouse) to detect all aerosol; and (2) a liquid cyclone air sampler (BioSampler, SKC Ltd.) to detect aerosolised fluorescein, which was quantified by spectrofluorometric analysis. Settled droplets were detected by spectrofluorometric analysis of filter papers placed onto a rig across the open-plan clinic. RESULTS: Local (within treatment bay) settled droplet contamination was elevated above negative control for all conditions, with no difference between conditions. Settled droplet contamination was not detected above negative controls outside the treatment bay for any condition. Aerosol detection at 1.5 m and 1.7 m, was only increased for the air-turbine positive control condition. At 0.5 m, aerosol levels were highly elevated for the air-turbine, minimally elevated for 200 K and 120 K, and not elevated for 60 K. CONCLUSIONS: Electric micromotor handpieces which use water-jet coolant alone without compressed air produce localised (within treatment bay) droplet contamination, but are unlikely to produce aerosol contamination beyond the immediate treatment area (1.5 m), allowing them to be used safely in most open-plan clinic settings.

Water jet as a novel technique for enamel drilling ex vivo.

To investigate the usage of a water jet for enamel drilling ex vivo, 210 individual extracted molars without lesions or fillings were collected. Then, the specimens were drilled by a water jet or a high-speed dental drill. The cavities of 50 teeth were reconstructed digitally by micro-computed tomography (micro-CT) to measure the height and width. The cavities of 10 teeth were longitudinally incised and their surfaces were observed by scanning electronic microscopy (SEM). After the cavities were filled, 50 fillings were vertically incised. The bonding interface between tooth and filling was observed by SEM. 50 teeth with fillings were stained in 0.1% rhodamine B solution, and then the dye penetration between tooth and filling was observed under the stereomicroscope and confocal laser scanning microscopy (CLSM). The bonding strength between enamel and filling of 50 teeth was simulated and predicted with finite element analysis (FEA). At 140-150 MPa and for 2-3 s, cavities were made with a depth of approximately 764 µm in each tooth. SEM showed the cavity surface in the water jet group had a more irregular concave and convex structure than that in the high-speed dental drill group. There was a trend that the microleakage and bonding width was smaller in the water jet group than in the high-speed dental drill group. FEA indicated that the stress on the resin surface was greater than on the enamel surface in the water jet group. Compared with the tooth drilled by a high-speed dental drill, the tooth drilled by a water jet gained better retention of the filling material and suffered less bonding strength on the enamel surface. Water jet drilling is effective for enamel drilling.

Comparison of crown fit and operator preferences between tooth preparation with electric and air-turbine handpieces.

STATEMENT OF PROBLEM: Tooth preparations for ceramic crowns require precision and accuracy, which may be influenced by the choice of dental handpiece. However, comparisons of the accuracy of tooth preparations made with traditional air-turbine handpieces and electric handpieces are lacking. PURPOSE: The purpose of this in vitro study was to evaluate operator preferences and tooth preparation performance by using electric and air-turbine handpieces with self-reported preferences, sound levels, surface roughness, and the fit of the crown produced. MATERIAL AND METHODS: Twenty dentists were asked to use the air-turbine or the electric handpiece. Feedback on the noise, weight, feel of grip, flexibility, and tooth preparation in general was scored according to a visual analog scale (VAS). Additionally, the dentists were asked to complete a questionnaire on their handpiece preference. The noise of the 2 handpieces was measured by using a precision sound level meter. The surface roughness of 10 teeth was measured by using a profilometer. The other 18 teeth were prepared to measure the marginal and internal fit of ceramic crowns by the replica technique. The VAS scores of operator preferences were analyzed with the Wilcoxon signed ranks test. Decibel levels were analyzed with the Mann-Whitney U test. The McNemar test was used to compare the ratio of preferred handpiece. The surface roughness and marginal and internal fit were analyzed with the independent t test to determine significant differences (all α=.05). RESULTS: The electric handpiece was heavier, had a poorer grip feel, was less flexible (P<.001), produced lower noise and better feeling of the tooth preparation in general (P<.001), and was preferred in the finishing stage for its greater smoothness (P<.05). The noise produced by the electric handpiece was lower during both idling and tooth preparation at 15-cm, 30-cm, and 45-cm distances (P<.01). The electric handpiece produced surface roughness values (Sa) similar to those of the air-turbine handpiece (P>.05). No significant differences were noted for the marginal and internal crown fit between the air-turbine handpiece and electric handpiece groups (P>.05). CONCLUSIONS: Despite its heavier weight, poorer grip feel, and less flexibility, the electric handpiece emitted lower noise, produced better feeling of the tooth preparation in general, and was preferred in the finishing step of tooth preparation for its greater smoothness than the air-turbine handpiece. The surface roughness of the prepared teeth and the crown fit between the tooth and ceramic crown were not affected by the air-turbine or electric handpiece.

Influencia del tallado en la lisura superficial del esmalte / The influence of carving on surface smoothness of enamel

Al momento de realizar una preparación dental existen diferentes alternativas. Dentro del instrumental rotatorio hay dos opciones: la turbina dental (ultra-velocidad) y el micromotor acoplado a un contra-ángulo multiplicador (alta velocidad). El propósito de este estudio fue evaluar cualitativamente la diferencia en la lisura superficial sobre esmalte, que se genera al desgastarlo, utilizando para esto, una turbina dental y un micromotor eléctrico acoplado a un contra-ángulo multiplicador 1:5 (anillo rojo). Se realizó un análisis cualitativo sobre una muestra de 24 superficies de esmalte obtenidas de 12 premolares extraídos por indicación ortodóntica, los cuales fueron preparados y observados al microscopio óptico. Luego de observar las 24 superficies al microscopio se pudo constatar una mayor lisura superficial sobre el esmalte al utilizar micromotor eléctrico acoplado a contraángulo multiplicador en comparación con turbina (AU)

Topographic aspects of airborne contamination caused by the use of dental handpieces in the operative environment.

BACKGROUND: The use of dental handpieces produces aerosols containing microbial agents, bacteria, and viruses representing a high-risk situation for airborne cross infections. The aim of this study was to map and quantify the biological contamination of a dental operatory environment using a biological tracer. METHODS: Streptococcus mutans suspension was infused into the mouth of a manikin, and an operator performed standardized dental procedures using an air turbine, a contra-angle handpiece, or an ultrasonic scaler. The presence of the tracer was measured at 90 sites on the dental unit and the surrounding surfaces of the operatory environment. RESULTS: All tested instruments spread the tracer over the entire dental unit and the surrounding environment, including the walls and ceiling. The pattern and degree of contamination were related to the distance from the infection source. The maximum distance of tracer detection was 360 centimeters for air turbine, 300 cm for contra-angle handpiece, and 240 cm for ultrasonic scaler. No surface of the operative environment was free from the tracer after the use of the air turbine. CONCLUSIONS: Attention should be paid to minimize or avoid the use of rotary and ultrasonic instruments when concerns for the airborne spreading of pandemic disease agents are present. PRACTICAL IMPLICATIONS: This study supports the recommendations of dental associations to avoid treatments generating aerosols, especially during pandemic periods. Guidelines for the management of dental procedures involving aerosols, as well as methods for the modification of aerosols aimed to inactivate the infective agent, are urgently needed.

Eficacia del instrumento XP-endo Finisher y del sistema EndoActivator en la reducción/eliminación del biofilm bacteriano: un ensayo ex vivo / Ability of the XP-endo Finisher instrument and the EndoActivator system to reduce/eliminate of the bacterial biofilm: an ex vivo assay

Objetivos: Comparar ex vivo la eficacia del instrumento XP-endo Finisher y del sistema EndoActivator en la reducción/eliminación del biofilm microbiano en conductos radiculares infectados. Materiales y métodos: Se utilizaron 23 premolares inferiores humanos extraídos cuya longitud fue estandarizada en 17 mm. Todos los conductos se prepararon con el sistema WaveOne Gold Medium (#35.06). Los dientes se esterilizaron, se inocularon con Enterococcus faecalis y se separaron en dos grupos experimentales de 10 piezas cada uno. De los 3 dientes remanentes, 1 fue utilizado como control positivo y 2, como controles negativos. En el grupo 1, las soluciones irrigantes se agitaron con XP-endo Finisher. En el grupo 2, se utilizó EndoActivator. Se tomaron muestras antes de la contaminación, luego de esta y después de la agitación de los irrigantes mediante conos de papel estériles. La carga microbiana fue sembrada en agar sangre y los conos se cultivaron en caldo tripteína de soja. La remoción de la carga microbiana se determinó por la presencia o ausencia de turbiedad del medio. Las unidades formadoras de colonias (UFC) remanentes se cuantificaron y los resultados se categorizaron como R1 (≤10 UFC) o R2 (>10 UFC). Los datos fueron analizados mediante la prueba de Fisher. Resultados: No hubo diferencias significativas entre XP-endo Finisher y EndoActivator (P>0,05). El número de usos no influyó sobre la capacidad operativa de ambos instrumentos (AU)

Aim: To compare ex vivo the effectiveness of the XP-endo Finisher and the EndoActivator in biofilm reduction/ removal from infected root canals. Materials and methods: Twenty three extracted human single-rooted lower premolars were selected and standardised to 17 mm in length. All the canals were prepared with WaveOne Gold Medium reciprocating files (#35.06). The teeth were autoclaved and inoculated with Enterococcus faecalis. The infected teeth were then assigned to 2 experimental groups of 10 teeth each according to the final irrigation/agitation protocol. Of the three remaining teeth, one was used as a positive control, and the other two were used as negative controls. In Group 1 the irrigating solutions were agitated with XP-endo Finisher while in Group 2 the EndoActivator was used. All root canals were sampled before and after contamination, and again after irrigant agitation with sterile paper points. The microbial load was spread on blood agar plates and the paper points were cultured in sterile trypticase soy broth. The removal of the microbial load was determined by visual observation of the turbidity of the media and by quantification of the number of colony-forming units (UFC). The results were categorized as R1 (≤10 UFC) or R2 (>10 UFC). Data were analysed by the Fisher's exact test at P<0.05. Results: No significant differences was found between XP-endo Finisher and EndoActivator (P>0.05) regarding their effectiveness in the reduction/removal of the microbial biofilm. The number of uses of both instruments did not affect their operative performance (AU) Conclusion: XPF and EA were both equally effective for microbial biofilm reduction/removal from ex vivo infected root canals (AU)

Evaluación radiográfica de la capacitación preclínica de alumnos de grado en el uso del sistema ProTaper Next en endodoncia / Radiographic evaluation of the preclinical training of undergraduate students in the use of ProTaper Next system in endodontics

Objetivo: Evaluar radiográficamente 162 tratamientos endodónticos realizados ex vivo en premolares inferiores y superiores humanos mediante el empleo del sistema ProTaper Next por parte de alumnos de grado de una cátedra de endodoncia de una universidad argentina. Materiales y métodos: Se evaluaron 162 tratamientos endodónticos realizados ex vivo durante los años 2017, 2018 y 2019 (54 por cohorte) en premolares inferiores y superiores humanos por alumnos de grado de la cátedra de Endodoncia I de la Escuela de Odontología de la Universidad del Salvador / Asociación Odontológica Argentina. Para la instrumentación fue empleado el sistema ProTaper Next. La muestra se tomó de forma aleatoria. En un programa de presentación de computadora se incluyeron las radiografías periapicales pre- y posoperatoria para su evaluación. Un evaluador externo analizó las imágenes radiográficas de los tratamientos y los categorizó como correctos o incorrectos teniendo en cuenta tres requisitos excluyentes: la conformación de la preparación quirúrgica, el límite apical y la homogeneidad de la obturación. Para el análisis estadístico, se utilizó la frecuencia relativa (intervalo de confianza 95%) y la prueba de chi-cuadrado. Resultados: La evaluación radiográfica de los tratamientos endodónticos realizados mostró un número considerable de tratamientos correctos. Los resultados para cada cohorte (años 2017, 2018 y 2019) fueron del 96,3% (87,2- 99,5%), el 94,4% (84,6-98,8%) y el 98,2% (90,1-99,9%) respectivamente. El porcentaje global de tratamientos correctos fue del 96,3% (92,1-98,6%). La diferencia entre las cohortes no fue estadísticamente significativa (P>0,05). Conclusión: El empleo del sistema ProTaper Next por parte de estudiantes de grado evaluados mostró resultados radiográficamente satisfactorios en la instrumentación ex vivo de conductos radiculares de premolares inferiores y superiores humanos (AU)

Aim: To evaluate radiographically, 162 endodontic treatments performed ex vivo by three cohorts of students from a school of dentistry in Argentina, using ProTaper Next rotatory system in mandibular and maxillary human premolars. Materials and methods: 162 mandibular and maxillary human premolars received endodontic treatment by undergraduate students from the Department of Endodontics I of the School of Dentistry USAL/AOA. The treatments were performed ex vivo during the academic years 2017, 2018 and 2019 (54 teeth were chosen for each cohort) using the rotatory system ProTaper Next. The samples were taken randomly. Pre and postoperative radiographs were included in a computer presentation program for its evaluation. An external examiner analysed the radiographic images by the shape of the preparation, the apical limit, and the homogeneity of the obturation, considering the treatments well obturated (correct) or ill obturated (incorrect). To be considered correct the case had to meet all the requirements. The statistic calculations used in this study were: relative frequency (confidence interval 95%) and the chi-square test. Results: The radiographic evaluation showed a considerable number of endodontic treatments correctly done using ProTaper Next system. The percentages for each cohort were 96.3% (87.2-99.5%), 94.4% (84.6-98.8%) y 98.2% (90.1-99.9%) for years 2017, 2018 y 2019 respectively. Global percentage of correctly endodontic treatments was 96.3% (92.1-98.6%). The difference between the cohorts was not statistically significant (P>0.05). Conclusion: The use of ProTaper Next by the dental students evaluated showed satisfactory results in the ex vivo instrumentation of mandibular and maxillary human premolar root canals (AU)

Actualización acerca del riesgo de pérdida auditiva inducida por ruido en el personal odontológico / Upgrade about the risk of hearing loss in the dental personal

La relación entre la exposición a los ruidos y la pérdida auditiva se considera desde hace muchos años. La comunidad odontológica no está exenta de este problema, ya que los profesionales trabajan a diario, y durante tiempos prolongados, con instrumentos ruidosos. Esta revisión bibliográfica tiene como propósito realizar una actualización acerca del riesgo de pérdida auditiva inducida por ruido en el personal que trabaja en la clínica odontológica. En la actualidad, se afirma que los odontólogos y el personal en la clínica dental corren el riesgo de contraer diversas patologías auditivas ­como es el caso de la hipoacusia­ debido al ruido que producen los equipos de alta velocidad. Las enfermedades profesionales del tipo auditivas que se abordan en este trabajo constituyen factores que comprometen no solo el buen estado de salud de los odontólogos y demás profesionales, sino su calidad de vida (AU)

The relationship between noise exposure and hearing loss has been known for many years. The dental community is not exempt from this problem, because they work every day and for long periods of time with noisy instruments. This literature review aims to update the risk of noise-induced hearing loss in personnel working in the dental clinic. The risk to which dentists and staff in the dental clinic are subjected to the high-speed and other noisy equipment is well known, and that can cause various auditory problems such as hearing loss. The occupational diseases of the auditory type that were addressed in this article constitute factors that compromise not only the good state of health of dentists and other professionals who work in similar conditions, but also in their quality of life (AU)

Cytotoxic and genotoxic potential of respirable fraction of composite dust on human bronchial cells.

OBJECTIVE: To determine the cytotoxic and genotoxic potential of the respirable fraction of composite dust (<4 µm) on human bronchial epithelial cells. METHODS: Composite sticks of three commercial dental composites (Filtek Supreme XTE, Grandio, Transbond XT) were ground in an enclosed plexiglass chamber with a rough dental bur (grain-size 100 µm) and the generated airborne respirable dust was collected in a personal cyclone on a teflon filter (pore size 5 µm). Immediately after particle collection, the dust was quantified gravimetrically and the particles were suspended in cell culturing medium. Next, human bronchial epithelial cells (16HBE14o-) were exposed to the suspensions (3 µg/ml-400 µg/ml). After 24 h, cell viability (WST-1 assay) and membrane integrity (LDH assay) were evaluated. Furthermore, the genotoxic effect of a sub-cytotoxic concentration (50 µg/ml) of composite dust was evaluated by the comet assay after 3 h exposure and cell cycle disturbances were analyzed by flow cytometry. Cellular uptake of particles was evaluated by transmission electronic microscope (TEM). RESULTS: For all three tested composite materials, a decrease in metabolic activity of 10-35% was observed when the cells were exposed to the highest concentrations (100 µg/ml-400 µg/ml). Toxicity was partially linked to membrane disruption especially after 72 h exposure. All tested composites provoked a mild genotoxic effect after short-term exposure compared to the control groups. TEM revealed that respirable particles of all tested composites were taken up by the cells. SIGNIFICANCE: The respirable fraction of composite dust only showed cytotoxic effects at the highest concentrations, whereas mild genotoxicity was observed after exposure to a sub-cytotoxic concentration.

Efeito do uso de dispositivos auxiliares na precisão do retratamento de facetas diretas / Effect of the use of auxiliary devices on the accuracy of retreatment of direct veneers

A remoção de facetas de resina composta quando o retratamento se faz necessário representa um desafio ao clínico no sentido de preservação do remanescente dental. Sendo assim, o objetivo deste estudo foi avaliar dispositivos auxiliares na precisão dos retratamentos de facetas diretas, por meio de escaneamento digital. Setenta e cinco espécimes de dente bovino (10 x 8 mm ­ cor A1) foram selecionados, e então foi realizado o escaneamento inicial (T0). Em seguida, os espécimes foram preparados para faceta de resina composta e novamente escaneados (T1) para verificação da padronização dos preparos. As superfícies dentárias foram então restauradas com sistema adesivo e resina composta. Os espécimes foram divididos em 5 grupos (n=15): remoção sem dispositivo auxiliar (CN ­ grupo controle), remoção com alta rotação com LED branco (AL), remoção com alta rotação com luz ultra-violeta (UV), remoção com motor elétrico e multiplicadora 1/5 (MT) e remoção com uso de lupa de aumento 2,5x (MN). A remoção das facetas e o re-preparo dos espécimes foi feito por outro operador, sendo então realizado um novo escaneamento (T2). A alteração volumétrica entre T2 e T1, assim como, as áreas de desgaste dentário e/ou presença de resíduos de resina composta foram avaliados. A média entre desgaste e presença de resíduos entre T2 e T1 foi também realizada. Os dados foram submetidos aos testes estatísticos de Kruskal-Wallis e pós teste de Dunn ao nível de significância de 5%. Não foi encontrada diferença estatística entre os grupos entre T1 e T0, com uma média de desgaste de 0,28 mm (± 0,07), p ≥ 0.05. Somente houve diferença entre os grupos para as análises referentes às áreas de desgaste e de presença de resíduos (p ≤ 0,05). Ocorreu maiores áreas de desgaste para o grupo MN, sendo estatisticamente superior aos grupos CN e MT (p≤ 0,05). O oposto ocorreu para áreas de resíduos, sendo que o grupo MN apresentou as menores áreas de resíduos, sendo estatisticamente inferior aos grupos CN e MT (p≤ 0,05). Considerando a média entre desgaste e resíduos, ocorreu um desgaste adicional após o re-preparo, indepedente do grupo (p≥ 0,05). Apesar do uso de lupa odontológica ser mais efetivo para remoção da resina composta durante o retratamento de faceta direta, este proporciona maior desgaste da estrutura dentária. A similaridade da fluorescência entre a resina composta e o substrato dentário minimizou os benefícios do dispositivo com luz UV(AU)

The removal of direct composite veneers when the retreatment is necessary represents a challenge to the clinician in the sense of dental preservation. Thus, the aim of this study was to evaluate auxiliary devices, in the precision of direct composite veneers retreatments, through digital scanning. Seventy-five bovine tooth specimens (10 x 8 mm - A1 shade) were selected and the initial scanning (T0) was performed. Then, the specimens were prepared for direct composite veneer and rescanned (T1) to verify the standardization of the preparations. The dental surfaces were then restored with adhesive system and composite resin. The specimens were divided into 5 groups (n=15): removal without auxiliary device (CN - control group), removal with a hand piece with a white LED (WL), removal with a hand piece with an UV light source (UV), removal with electric motor and multiplier 1/5 hand piece (MT); and removal with the use of a 2.5x dental loupe (MN). The removal of the restorations and the re-preparation of the specimens were done by another operator, and a new scanning (T2) was performed. The volumetric change between T2 and T1, as well as the areas of additional dental wear and presence of composite resin residues were evaluated. The mean considering additional wear and the presence of residues between T2 and T1 were also performed. The data were submitted to Kruskal-Wallis and Dunn's as post-test, at significance level of 5%. No statistical difference among the groups were found between T1 and T0 with a wear mean of 0.28 mm (±0.07), p≥ 0.05. There were only statistical differences between the groups for the analyses related to the areas of wear and presence of residues (p≤ 0.05). There were greater areas of wear for MN group, being statistically superior to CN and MT groups (p≤ 0.05). The opposite occurred for areas of presence of residues, with the MN group presenting smaller areas of residues, being statistically lower than the CN and MT groups (p≤ 0.05). Considering the average between wear and residues, additional wear occurred after re-preparation, regardless of the group (p≥ 0.05). Although the use of dental loupe is more effective for removal of composite resin during the retreatment of direct composite veneers, it provides greater wear of the dental structure. The fluorescence similarity between the composite resin and the dental substrate minimized the benefits of UV light device(AU)

Análisis bacteriológico de piezas de mano de alta velocidad utilizadas en la práctica clínica / Bacteriological analysis of high speed handpieces used in clinical practice

Los profesionales de la salud están expuestos a una gran variedad de microorganismos desde esporas, bacterias, hongos, virus y protozoarios que pueden encontrarse en la sangre y/o saliva de los pacientes. Cualquiera de estos microorganismos puede causar una enfermedad infectocontagiosa a través de pinchazos y/o salpicaduras producidas por el aerosol durante la práctica dental. Objetivo: Determinar la presencia bacteriana en las piezas de alta velocidad utilizadas en la práctica clínica. Material y métodos: Es un estudio experimental, observacional y transversal en el que se evaluó la contaminación de 30 piezas de alta velocidad utilizadas en la práctica clínica. Previo al estudio se efectuó una estandarización obteniendo una kappa del 0.85. Se realizó una base de datos en el programa SPSS versión 22, con el que se llevó a cabo el análisis descriptivo para determinar medidas de tendencia central. Resultados: 73.3% de las muestras analizadas tuvieron crecimiento bacteriano, entre las bacterias que se encontraron resultó que 54.5% de ellas fueron bacterias Gram positivas y el resto Gram negativas. La bacteria con mayor presencia en la muestra fue el Bacillus en 45.5% seguida del Streptococcus en 27.3%, el restante 27.2% fue Staphylococcus, Coccus y Streptobacillus. Conclusiones: El uso correcto de las piezas de alta, así como su desinfección en la consulta dental es de suma importancia, ya que nos ayudan a evitar contaminaciones cruzadas y a prevenir que dentro del área de trabajo se formen focos de infección (AU)

Health professionals are exposed to a wide variety of microorganisms from spores, bacteria, fungi, viruses and protozoa that can be found in the blood and/or saliva of patients. Any of these microorganisms can cause an infectious disease through punctures and / or splashes produced by the aerosol during dental practice.1,2 Objective: To determine the bacterial presence in the high-speed pieces used in clinical practice. Material and methods: It are an experimental, observational and transversal study; where the contamination of 30 high-speed pieces used in clinical practice was evaluated. Prior to the study, a standardization was made obtaining a kappa of 0.85. A database was made in the program SPSS version 22, with which the descriptive analysis was carried out to determine measures of central tendency. Results: 73.3% of the analyzed samples showed bacterial growth, among the bacteria that were found, 54.5% of them were gram-positive bacteria and the rest were gram-negative. The bacterium with the highest presence in the sample was for Bacillus in 45.5% followed by Streptococcus in 27.3%, the remaining 27.2% was for Staphylococcus, Coccus and Streptobacillus. Conclusions: The correct use of the discharging parts, as well as their disinfection in the dental practice is of the utmost importance as they help us to avoid cross contamination and to prevent foci of infection from forming within the work area (AU)

A novel technique to develop thoracic spinal laminectomy and a methodology to assess the functionality and welfare of the contusion spinal cord injury (SCI) rat model.

This study reports the advantage of a novel technique employing a motorised dental burr to assist laminectomy over the conventional manual technique at T10-T11 vertebra level in a rat model of spinal cord injury. Twenty-four female rats were randomly assigned to four groups: (1) conventionally laminectomised, (2) dental burr assisted laminectomised, (3) conventionally laminectomised with spinal cord contusion and (4) dental burr assisted laminectomised with spinal cord contusion. Basso Beattie Bresnahan (BBB) score, postoperative body weights, rat grimace scale (RGS), open cage activity and rearing was studied at 1, 7, 14, 21 and 28 days postoperatively, and area of spinal tissue affected was evaluated histologically. Laminectomised and spinal cord injured rats from dental burr groups showed significantly more weight gain and less weight loss respectively in comparison with respective conventionally laminectomised groups at various time points. Significantly higher RGS score was noticed in conventionally laminectomised animals on Day 1 in comparison to burr assisted laminectomy and presence of pain was evident until Day 7 in the conventionally spinal cord injured group. BBB score did not differ between techniques, whereas laminectomy groups showed more resting time than spinal injury groups. High rearing score was significantly higher in groups which underwent dental burr assisted technique at various time points with respect to their conventional counterparts. This study suggests that the use of dental burr assisted technique to perform laminectomy will bring refinement by producing less pain, aiding in better recovery, removing procedural artefacts without affecting the outcome of the model.