Three-axis load analysis of high-speed handpiece on dental training teeth and computer-aided design/computer-aided manufacturing blocks.

This study aimed to evaluate and compare the mechanical properties of dental training teeth with subtractive and additive computer-aided design/computer-aided manufacturing (CAD/CAM) materials used to fabricate dental simulation models. Therefore, the three-axis load generated during cutting movements, including drilling and milling performed using a dental handpiece, was measured and compared. The samples were cut vertically downward by 1.5 mm, horizontally by 6 mm, and vertically upward at a constant speed (1 mm/s), while the rotational speed of the bur was maintained at 200,000 rotations per minute. A three-axis load cell was used to measure the X-, Y-, and Z-axis loads on the specimen. The median value of the X-, Y-, and Z-axis measurements and the resultant load during the vertical-downward, horizontal, and vertical-upward movements were compared using a one-way analysis of variance and Tukey's post hoc test. For vertical downward movement, the drilling force of the dental training teeth was lower than that of Vita Enamic® and similar to that of Lava™ Ultimate. In contrast to subtractive CAD/CAM blocks, the drilling force of the dental training teeth was higher than that of 3D-printed resin blocks. Regarding horizontal movement, the milling force of dental training teeth was lower than that of Vita Enamic®. In contrast, the milling force of Nissin was similar to that of Lava™ Ultimate, while that of Frasaco was lower. Furthermore, compared to additive CAD/CAM blocks, the milling force of the dental training teeth was higher than that of 3D-printed resin blocks. Regarding vertical upward movement, the resultant loads of dental training teeth was lower than that of Vita Enamic®. Similarly, the resultant load of Nissin was similar to that of Lava™ Ultimate, while that of Frasaco was lower. Additionally, compared to additive CAD/CAM blocks, the resultant loads of the dental training teeth were similar to those of the 3D-printed resin blocks.

Precise control of digital dental unit to reduce aerosol and splatter production: new challenges for future epidemics.

BACKGROUND: During dental procedures, critical parameters, such as cooling condition, speed of the rotary dental turbine (handpiece), and distance and angle from pollution sources, were evaluated for transmission risk of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), simulated by spiking in a plasmid encoding a modified viral spike protein, HexaPro (S6P), in droplets and aerosols. METHODS: To simulate routine operation in dental clinics, dental procedures were conducted on a dental manikin within a digital dental unit, incorporating different dental handpiece speeds and cooling conditions. The tooth model was immersed in Coomassie brilliant blue dye and was pre-coated with 100 µL water spiked-in with S6P-encoding plasmid. Furthermore, the manikin was surrounded by filter papers and Petri dishes positioned at different distances and angles. Subsequently, the filter papers and Petri dishes were collected to evaluate the aerosol splash points and the viral load of S6P-encoding plasmid in aerosols and splatters generated during the dental procedure. RESULTS: Aerosol splashing generated a localized pollution area extended up to 60 cm, with heightened contamination risks concentrated within a 30 cm radius. Significant differences in aerosol splash points and viral load by different turbine handpiece speeds under any cooling condition (P < 0.05) were detected. The highest level of aerosol splash points and viral load were observed when the handpiece speed was set at 40,000 rpm. Conversely, the lowest level of aerosol splash point and viral load were found at a handpiece speed of 10,000 rpm. Moreover, the aerosol splash points with higher viral load were more prominent in the positions of the operator and assistant compared to other positions. Additionally, the position of the operator exhibited the highest viral load among all positions. CONCLUSIONS: To minimize the spread of aerosol and virus in clinics, dentists are supposed to adopt the minimal viable speed of a dental handpiece with limited cooling water during dental procedures. In addition, comprehensive personal protective equipment is necessary for both dental providers and dental assistants.

New aerosol-decreasing dental handpiece functions sufficiently decrease pulp temperature: An in vitro study.

PURPOSE: To assess the changes in intrapulpal temperature between electric high-speed handpieces of different coolant functions ('Water Jet' and 'Water Spray'), coolant port designs (1- and 4-port), suction use, and bur and tooth types using an experimental in vitro setup. MATERIALS AND METHODS: Forty-four extracted anterior and posterior teeth were collected. A total of 18 groove cuts (n = 18/coolant port spray design, bur and tooth type group) and 12 groove cuts (n = 12/tooth type and suction use) were completed, with a total of 264 groove cuts. Real-time temperature and duration were recorded at 1-s intervals throughout the preparation process using a thermocouple and digital data logger setup (GFX Data Logger Series and EL USB-TC; Lascar Electronics Inc., USA), and the data retrieved using EasyLog Software (EasyLog USB; Lascar Electronics Inc., USA). Statistical analysis was performed (SPSS V.27) for the change in temperature using the analysis of variance and post hoc analysis. RESULTS: The majority of the specimen cuts, regardless of tooth (anterior or posterior) and bur (diamond or carbide) types, handpiece coolant port design, and suction use showed an overall decreasing trend in intrapulpal temperature. No cuts caused a mean temperature change that reached the critical temperature of 42.5°C or resulted in an overall increase in intrapulpal temperature when the 60-s duration was completed. CONCLUSIONS: The tested electric handpieces efficiently reduced intrapulpal temperature, with the majority displaying a decreasing trend. A greater decrease in intrapulpal temperature was observed in canines compared to premolars; carbide burs compared to diamond; and with no suction preparations compared to when suction was used.

[Occupational protection effect of two protective devices for manual cleaning and oiling of dental handpieces on operators].

Objective: To explore the occupational protective effect of different protective devices on the operators during manual cleaning and oiling of dental handpieces, and to provide a basis for the selection of appropriate protective methods. Methods: From November 2020 to December 2021, 20 high-speed dental handpieces of the same brand were selected and randomly divided into disposable protective bag group and small aerosol safety cabinet group by drawing lots, with 10 in each group. After recording the model, they were distributed to the clinical fixed consulting room for use, and were collected by specially-assigned personnel every day for manual cleaning under the protection of the two devices. By measuring the number of airborne colonies, the concentrations of particulate matter and the satisfaction of operators, the occupational protection effect of the two protective devices on operators was evaluated. Results: Under the protection of the two devices, the average number of airborne colonies after operation was less than 1 CFU/ml. When no protective device was used, the number concentration of particulate matter produced during operation was (21595.70±8164.26) pieces/cm(3). The number concentrations of particles produced by disposable protective bag group [ (6800.24±515.05) pieces/cm(3)] and small aerosol safety cabinet group [ (5797.15±790.50) pieces/cm(3)] were significantly lower than those without any protective device (P<0.001). The number concentration of particle matter of small aerosol safety cabinet group was significantly lower than that of disposable protective bag group (P<0.001). In the satisfaction evaluation of operators, small aerosol safety cabinet group [ (3.53±0.82) points] was significantly better than disposable protective bag group [ (2.23±1.10) points] (P<0.001) . Conclusion: The use of small aerosol safety cabinet during manual cleaning and oiling of dental handpieces has good protective effect, superior safety performance and strong clinical applicability, and has advantages in occupational protection of clinical operators.

Occupational protection effect of two protective devices for manual cleaning and oiling of dental handpieces on operators / 中华劳动卫生职业病杂志

Objective: To explore the occupational protective effect of different protective devices on the operators during manual cleaning and oiling of dental handpieces, and to provide a basis for the selection of appropriate protective methods. Methods: From November 2020 to December 2021, 20 high-speed dental handpieces of the same brand were selected and randomly divided into disposable protective bag group and small aerosol safety cabinet group by drawing lots, with 10 in each group. After recording the model, they were distributed to the clinical fixed consulting room for use, and were collected by specially-assigned personnel every day for manual cleaning under the protection of the two devices. By measuring the number of airborne colonies, the concentrations of particulate matter and the satisfaction of operators, the occupational protection effect of the two protective devices on operators was evaluated. Results: Under the protection of the two devices, the average number of airborne colonies after operation was less than 1 CFU/ml. When no protective device was used, the number concentration of particulate matter produced during operation was (21595.70±8164.26) pieces/cm(3). The number concentrations of particles produced by disposable protective bag group [ (6800.24±515.05) pieces/cm(3)] and small aerosol safety cabinet group [ (5797.15±790.50) pieces/cm(3)] were significantly lower than those without any protective device (P<0.001). The number concentration of particle matter of small aerosol safety cabinet group was significantly lower than that of disposable protective bag group (P<0.001). In the satisfaction evaluation of operators, small aerosol safety cabinet group [ (3.53±0.82) points] was significantly better than disposable protective bag group [ (2.23±1.10) points] (P<0.001) . Conclusion: The use of small aerosol safety cabinet during manual cleaning and oiling of dental handpieces has good protective effect, superior safety performance and strong clinical applicability, and has advantages in occupational protection of clinical operators.

Aerosol concentrations and size distributions during clinical dental procedures.

Background: Suspected aerosol-generating dental instruments may cause risks for operators by transmitting pathogens, such as the SARS-CoV-2 virus. The aim of our study was to measure aerosol generation in various dental procedures in clinical settings. Methods: The study population comprised of 84 patients who underwent 253 different dental procedures measured with Optical Particle Sizer in a dental office setting. Aerosol particles from 0.3 to 10 µm in diameter were measured. Dental procedures included oral examinations (N = 52), restorative procedures with air turbine handpiece (N = 8), high-speed (N = 6) and low-speed (N = 30) handpieces, ultrasonic scaling (N = 31), periodontal treatment using hand instruments (N = 60), endodontic treatment (N = 12), intraoral radiographs (N = 24), and dental local anesthesia (N = 31). Results: Air turbine handpieces significantly elevated <1 µm particle median (p = 0.013) and maximum (p = 0.016) aerosol number concentrations as well as aerosol particle mass concentrations (p = 0.046 and p = 0.006) compared to the background aerosol levels preceding the operation. Low-speed dental handpieces elevated >5 µm median (p = 0.023), maximum (p = 0.013) particle number concentrations,> 5 µm particle mass concentrations (p = 0.021) and maximum total particle mass concentrations (p = 0.022). High-speed dental handpieces elevated aerosol concentration levels compared to the levels produced during oral examination. Conclusions: Air turbine handpieces produced the highest levels of <1 µm aerosols and total particle number concentrations when compared to the other commonly used instruments. In addition, high- and low-speed dental handpieces and ultrasonic scalers elevated the aerosol concentration levels compared to the aerosol levels measured during oral examination. These aerosol-generating procedures, involving air turbine, high- and low-speed handpiece, and ultrasonic scaler, should be performed with caution. Clinical significance: Aerosol generating dental instruments, especially air turbine, should be used with adequate precautions (rubber dam, high-volume evacuation, FFP-respirators), because aerosols can cause a potential risk for operators and substitution of air turbine for high-speed dental handpiece in poor epidemic situations should be considered to reduce the risk of aerosol transmission.

Effective cleaning and decontamination of the internal air and water channels, heads and head-gears of multiple contra-angle dental handpieces using an enzymatic detergent and automated washer-disinfection in a dental hospital setting.

BACKGROUND: Dental handpieces (DHPs) are reusable invasive medical devices that must be cleaned, decontaminated, lubricated and steam sterilized after use. DHPs have a complex internal design including narrow channels, contamination of which can compromise sterilization. DHPs are not designed for routine disassembly, making cleaning/decontamination efficacy difficult to monitor. Washer-disinfection is the preferred method of decontaminating DHPs, but few studies have investigated its direct effectiveness at reducing microbial contamination internally. AIMS: To use contra-angle DHPs as a model system to investigate the effectiveness of washer-disinfection at reducing microbial contamination of internal components of multiple DHPs. METHODS: The air and water channels and heads of 10 disassembled contra-angle DHPs (BienAir, Biel/Bienne, Switzerland) were inoculated separately with 108 colony forming units (cfu) of Pseudomanas aeruginosa, Staphylococcus aureus, Enterococcus hirae or Candida albicans in the presence of 0.3% bovine serum albumin (BSA) (clean conditions), 3.0% BSA or 10% artificial test soil (dirty conditions). After reassembly, all 10 DHPs underwent washer-disinfection simultaneously in a Míele (Míele Ireland Ltd., Dublin, Ireland) PG8528 washer-disinfector and were tested for reductions in micro-organisms and protein. Additional experiments were undertaken with three lubricated DHPs inoculated with S. aureus and 10% test soil. All experiments were repeated in triplicate. FINDINGS: On average, an approximate 5 log or greater reduction in microbial cfu and a >93% reduction in protein from DHP heads and channels was consistently recorded following washer-disinfection for all DHPs under all conditions tested. CONCLUSIONS: The internal components of multiple DHPs can be effectively cleaned and decontaminated by washer-disinfection.

Bacterial Contamination of Equine Dentistry Equipment-Effect of Cleaning and Disinfection.

Equine dentistry has developed immensely and human dental equipment, such as handpieces, are often used. Measures to avoid the spread of infectious microorganisms are important, but this is challenging since handpieces are difficult to decontaminate. Thus, it is necessary to develop effective IPC measures in equine dentistry. The aim of this study was to contribute to the evidence needed for future evidence-based guidelines on IPC by investigating hygiene in equine dentistry. Used handpieces and dummies (i.e., handpieces not used during dental procedure, reflecting environmental bacterial contamination) and the head support were sampled each day before the first patient, for each patient after treatment, and after decontamination. All equipment was sampled with 3M TM Swab Samplers and the head support additionally sampled with dip slides. After dental procedures, the detected bacterial load was often high on used handpieces, dummies, and the head support. After decontamination, handpieces did not meet the criteria for high-level disinfected equipment. In all but one case decontamination of the head support resulted in a lowered bacterial load. There is a great need for evidence-based guidelines on hygiene in equine dentistry, including IPC measures, to decrease the risk of spreading infectious microorganisms between patients, facilities, and stables.

Measuring tooth vibrations induced during cavity preparation with time-averaged holography and its influence on near vision acuity in dentists.

The aim of this study was to quantify vibrations and their influence on visual acuity. The study consisted of two parts, laboratory and clinical. Time-averaged holographic interferometry (TAHI) method was used in laboratory for measuring the amplitude of tooth vibrations induced by dental handpiece. The amplitudes of tooth vibrations were measured for the three diameters and three speeds. The larger diameter coupled with increasing speed resulted in greater vibration amplitudes, whereby a maximum amplitude of less than one micrometer was detected. For quantifying the natural visual acuity for the corresponding tooth vibrations, we have used the clinical condition approach with miniaturized Snellen optotype as an assessing tool. Central visual acuity did not display variance in visual acuity at rest or under load. Results indicate that the vibrations induced during cavity preparation are not sufficient to negatively affect visual acuity of dentists.

Autoclave sterilization of dental handpieces: A literature review.

PURPOSE: The present review aimed to investigate autoclave sterilization of dental handpieces based on available studies. STUDY SELECTION: The sterilizing efficiency of dental handpieces with autoclave is mainly affected by the types of apparatus (N, B, and S), the packaging with sterilizing pouch, cleaning, and lubrication. These subjects were reviewed based on the in vitro experimental studies. RESULTS: Dental handpieces can be sterilized, including inactivation of heat-resistant bacterial spores, with type B or type S sterilizers, regardless of the use of a sterilization pouch. In contrast, although type N autoclaves are capable of sterilization of general bacteria such as Streptococcus salivarius even in a sterilization pouch if instruments are washed beforehand, complete sterilization of the wrapped handpiece is not always achieved. Therefore, to achieve sterilization efficiency with type N autoclaves, processing without any packaging is recommended. As regards cleaning of handpiece, although contamination decreases with irrigation and wiping of handpieces, all reports concluded that these treatments alone do not achieve complete decontamination of reusable handpieces. CONCLUSION: Although type B and type S autoclaves allow us to sterilize the dental handpieces, it is important to realize that complete sterilization of the handpiece is not always achieved by type N autoclave. Understanding autoclave processing of handpieces is essential for dental practice to deliver the safe dental care.

The cooling efficiency of different dental high-speed handpiece coolant port designs.

The study investigated the cooling efficiency of different numbers of water coolant ports on high-speed handpieces (HSH) under cooling conditions used in clinical practice. Twenty-four groove cuts with water on and nine cuts without water were made on extracted human premolars using three HSHs with different port configurations. Thermocouples were placed in the pulp chambers and temperature changes were recorded with 1-, 3- and 4-coolant port handpieces. Cooling rate was calculated for each coolant port design system. Temperature changes were statistically analysed with Kruskal-Willis Test. All three sample groups resulted in a net temperature decrease during the cutting period with water turned on. There was a pattern of increased cooling rate with increasing number of coolant ports (1-port: -4.27 (±0.94) °C, 3-port: -4.66 (±2.90) °C, 4-port: -5.03 (±1.08) °C). The difference was not statistically significant (p = 0.681). Calculations of cooling rate showed a higher cooling rate with an increase in the number of ports (1-port: 46.13 × 10-4 K-1, 3-port: 51.36 × 10-4 K-1, 4-port: 56.32 × 10-4 K-1). In the dry tooth preparation samples, all resulted in a net increase in temperature (1-port: 4.43 (±3.30) °C, 3-port: 5.13 (±3.27) °C, 4-port: 2.87 (±2.97) °C). All the three water coolant port configurations showed effective cooling of the tooth during cutting and decreased pulpal temperature with no statistical difference. There are HSH designs with varying numbers of coolant ports available in the market for clinicians. The results of the current study could potentially aid clinicians in making a decision while choosing between different dental handpieces.

Three key factors influencing the bacterial contamination of dental unit waterlines: a 6-year survey from 2012 to 2017.

BACKGROUND: The contaminated output water from dental unit waterlines (DUWLs) is a potential risk to both patients and dental personnel who are frequently exposed to this water or aerosols. AIM: The purpose was to evaluate the contamination level and prevalence of bacteria in the output water of DUWLs, and to identify key factors to provide technical support for formulating relevant policies. METHODS: We developed a special sampling connector designed for collecting dental handpiece output water and a measurement device to assess retraction of a dental chair unit (DCU). Output water from dental handpieces and air/water syringes were collected as representative of DUWLs. Water samples were tested with reference to China's national standard. FINDINGS: From 2012 to 2017, 318 DCUs were randomly selected from 64 hospitals in Tianjin, China. Of these DCUs, 78.93% had no disinfection to prevent DUWL contamination. Three-hundred and forty-three (56.14%) samples complied with the guidelines on DUWL output water. The highest concentration of bacteria was 1.8 × 106  colony-forming units (CFUs)/mL. The three key factors of influence were as follows: daily or weekly disinfection of DUWLs; water supply source being hospital self-made purified water or purchased purified bottled water; and DCU with a valid anti-retraction valve. Potential infectious agents, including Bacillus cereus, Burkholderia cepacia and Pseudomonas aeruginosa, were isolated. CONCLUSION: There was a high rate of contamination in DUWLs. This highlights the need to develop national standards. There is a need to disinfect the DUWLs periodically and use a cleaner source of water; more attention should be paid to the efficacy of DCU anti-retraction valves.

Application of high-speed dental handpiece and original luxator in impacted wisdom tooth extraction / 第二军医大学学报

Objective To explore the application of high-speed dental handpiece and original luxator in the impacted wisdom tooth extraction. Methods Seventy patients with impacted wisdom teeth, who underwent impacted wisdom tooth extraction between Dec. 2016 and Dec. 2017, were selected. The patients were divided into control group (n=35) and minimally invasive group (n=35) according to the surgical options. The patients in the control group received conventional tooth extraction, and the patients in the minimally invasive group received tooth extraction using high-speed dental handpiece and original luxator. The surgical parameters (extraction integrity, mouth restriction, swelling and operation time), pain extent, complications and the quality of life after operation (psychological function, physiological function, physical pain, vitality) were compared between the two groups. Results The surgical parameters, including extraction integrity, mouth restriction, swelling and operation time, were significantly better in the minimally invasive group than those in the control group (all P0.05). After extraction, the VAS score was significantly lower in the minimally invasive group than that in the control group (P<0.05). The incidence of complications in the minimally invasive group was 11.43% (4/35), which was significantly lower than that in the control group (34.29% [12/35], P<0.05). At 3 months after extraction, the scores of psychological function and the other quality of life scores were significantly higher in the minimally invasive group than those in the control group (all P<0.05). Conclusion Application of high-speed dental handpiece and original luxator in impacted wisdom tooth extraction can significantly improve the treatment efficacy and reduce complication incidence.

Effects of four drying methods after mechanical cleaning of dental handpiece / 中华护理杂志

Objective To compare drying methods for dental handpiece,and to provide references and guidance for choosing appropriate handpiece drying methods.Methods Four groups were established according to different methods of drying:vacuum drying,compressed air dryer drying,entire automatic hot cleaner drying,and sterilizing machine drying.Four types (with 50 in each type)of handpieces with the same brand were selected:low-speed straight (EX-6C),low-speed bender (NAC-EC),high speed turbine fast handset,and high speed turbine four hole handset.After cleaning and disinfection,each handpiece was subjected to the aforementioned four drying methods,and the mass was recorded before and after drying.SPSS software was used to calculate and compare the drying rate among these drying methods by analysis of variance.Results There were significant differences in the drying rate among four drying methods(P＜0.01).The drying efficiency with vacuum drying was higher than the other three methods.The mean drying efficiency for four types of dentistry handset with vacuum drying method were as follows:low-speed straight(EX-6C)69.93％,low-speed bender(NAC-EC)93.21％,high speed turbine fast handset 92.70％,and high speed turbine four hole handset 94.27％.Conclusion The drying efficiency of vacuum drying method for handset is superior to the other three drying methods.

Relevant influential factors for cleaning quality of dental handpieces / 中国感染控制杂志

Objective To understand the cleaning quality of dental handpieces in Suzhou City, analyze the relevant factors that influencing cleaning effect.Methods A cross-sectional study was performed with the proportional system sampling method, questionnaires were adopted to investigate the cleaning location, cleaning method and process of dental handpieces, the ATP fluorescence detection method was conducted to detect cleaning quality.Results In 10 administrative regions of this city, a total of 72 medical institutions were selected, 25 were public medical oral diagnosis and treatment institutions, 47 were private clinics.Cleaning effect of automatic handpiece cleaning machine was better than traditional manual cleaning (unqualified rate :3.95% vs 11.96%, P0.05).The quality of cleaning of handpieces could be improved if waiting time of cleaning ≤30 minutes, enzymes were used during cleaning, and purified water was used at the end rinse(all P<0.05);whether there was drying process and used lubricant, difference were both not significant.Conclusion Using automatic handpiece cleaning machine, cleaning personnel with adequate knowledge, cleaning waiting time ≤30 minutes, enzyme use during the cleaning process, and purified water use at the end rinse can improve the quality of cleaning of dental handpieces.

Cross-sectional survey and analysis of cleaning quality of dental handpieces in Suzhou City / 中国感染控制杂志

Objective To explore the cleaning status and cleaning quality of dental handpieces in various types of medical institutions in Suzhou City.Methods On October 26-31, 2015, dental clinics in the whole city were sampled according to cross-sectional survey and proportional sampling method, the cleaning quality of dental handpieces in each clinic was detected by ATP bioluminescence assay.Results 72 medical institutions, 201 handpieces, 402 samples in 10 administrative regions of the city were sampled, 42 samples was unqualified, unqualified rate was 10.45％, unqualified rate of cleaning of dental handpiece surface was higher than waterline of dental handpiece(17.91％ vs 2.99％, P<0.05).Cleaning quality of dental handpieces in different grades of medical institutions was different(P<0.05), tertiary medical institutions were all ualified, medical institutions without grade was 14.45％.According to the classification based on name of different medical institutions, cleaning quality of handpieces was statistically significant(P<0.05), cleaning efficacy of dental handpieces in department of stomatology of public hospitals was best(unqualified rate was 4.31％), while private dental clinics had the worst cleaning efficacy(unqualified rate was 13.81％).Conclusion Education and training of dental handpieces cleaning in the whole city should be strengthened, especially the management of cleaning of dental handpieces in low grade and private dental clinics.

Conocimientos y actitudes de estudiantes de estomatología sobre esterilización de piezas de mano dentales / Knowledge and attitude of stomatology students regarding the sterilization of dental handpieces

Objetivos: Fue determinar el grado de conocimiento y el grado de actitud de los estudiantes de pre-grado de la Facultad de Estomatología de una universidad privada peruana, sobre la forma de esterilización de las piezas de mano dentales de alta y baja velocidad. Materiales y Métodos: Mediante una encuesta, se desarrolló un cuestionario de 24 preguntas que fue aplicada a un total de 144 estudiantes de tercer, cuarto y quinto año de dicha facultad que estuvieron estudiando los cursos de Clínica Integral del Adulto y Clínica Integral Pediátrica. El grado de conocimiento fue clasificado como alto, medio y bajo y el grado de actitud se clasificó como positivo, regular y negativo. Así mismo, se evaluó la relación entre el grado de conocimiento y actitud mediante la prueba de Chi cuadrado de Pearson. Resultados: El 43,8% de los estudiantes poseen un grado de conocimientos medio y el 61,8% mostró una actitud regular sobre la forma de esterilización de las piezas dentales de alta y baja velocidad. Conclusiones: No se encontró relación estadísticamente significativa entre el conocimiento y actitud de los estudiantes regulares; sin embargo, la relación entre la actitud y el llevar dos o más veces los cursos de clínica, si fue estadísticamente significativa.

Objectives: To determine the degree of knowledge and attitude of the students of the Faculty of Stomatology of a private peruvian university regarding the sterilization of high and low speed hand-pieces. Material and Methods: A questionnaire with 24 questions was applied to the students of third, fourth and fifth year who were taking the subjects of Integral Adult Clinic and Pediatric Clinic. The knowledge was classified as high, medium and low, and the attitude as positive, regular and negative. Chi-square test was used to evaluate the relation between knowledge and attitude. Results: 43.8% of the students had a medium level of knowledge, and 61.8% had a regular attitude regarding the sterilization of high and low hand-pieces. Conclusions: No statistically significance relationship between knowledge and attitude was found, however, the relationship between attitude and the fact if a student repeat a subject showed statistically significance.

Relationships between tissue properties and operational parameters of a dental handpiece during simulated cavity preparation.

A preliminary study was conducted on the development of an intelligent dental handpiece with functionality to detect subtle changes in mechanical properties of tooth tissue during milling. Such equipment would be able to adopt changes in cutting parameters and make real-time measurements to avoid tooth tissue damage caused by overexertion and overextension of the cutting tool. A modified dental handpiece, instrumented with strain gauges, microphone, displacement sensor, and air pressure sensor, was mounted to a linear movement table and used to mill three to four cavities in >50 bovine teeth. Extracted sound frequency and density were analyzed along with force, air pressure, and displacement for correlations and trends. Experimental results showed a high correlation (coefficient close to 0.7) between the feed force, the rotational frequency, and the averaged gray scale. These results could form the basis of a feedback control system to improve the safety of dental cutting procedures. This article is written in memory of Dr Hongyan Sun, who passed away in 2011 at a young age of 37.

Evaluation of three instrumentation techniques at the precision of apical stop and apical sealing of obturation

OBJECTIVE: The aim of this study was to investigate the ability of two NiTi rotary apical preparation techniques used with an electronic apex locator-integrated endodontic motor and a manual technique to create an apical stop at a predetermined level (0.5 mm short of the apical foramen) in teeth with disrupted apical constriction, and to evaluate microleakage following obturation in such prepared teeth. MATERIAL AND METHODS: 85 intact human mandibular permanent incisors with single root canal were accessed and the apical constriction was disrupted using a #25 K-file. The teeth were embedded in alginate and instrumented to #40 using rotary Lightspeed or S-Apex techniques or stainless-steel K-files. Distance between the apical foramen and the created apical stop was measured to an accuracy of 0.01 mm. In another set of instrumented teeth, root canals were obturated using gutta-percha and sealer, and leakage was tested at 1 week and 3 months using a fluid filtration device. RESULTS: All techniques performed slightly short of the predetermined level. Closest preparation to the predetermined level was with the manual technique and the farthest was with S-Apex. A significant difference was found between the performances of these two techniques (p<0.05). Lightspeed ranked in between. Leakage was similar for all techniques at either period. However, all groups leaked significantly more at 3 months compared to 1 week (p<0.05). CONCLUSIONS: Despite statistically significant differences found among the techniques, deviations from the predetermined level were small and clinically acceptable for all techniques. Leakage following obturation was comparable in all groups.

Contamination of dental unit water and air outlets following use of clean head system and conventional handpieces.

BACKGROUND AND AIMS: Dental handpiece is a source of contamination because it is in constant touch with the oral cavity. Sterilization does not seem to be sufficient to prevent penetration of microorganisms into air and water lines of the unit, because negative pressure developed by valves (which are placed in water outlets) and post shut-off inertial rotation of handpiece result in water and debris being sucked into air and water outlets of dental unit. The aim of this study was to compare dental unit contamination following use of clean head system handpieces and conventional handpieces. MATERIALS AND METHODS: Twenty-two dental units in the Department of Pediatric Dentistry in Shahid Beheshti Faculty of Dentistry were used for the purpose of this study. A 1.5×108 cfu/mm3 concentration of Staphylococcus epidermis (SE) was used to contaminate the air and water outlets of dental units. Ten clean head system handpieces and 10 conventional handpieces were used for 30 seconds in the above-mentioned suspension. Microbial samples were collected from the air and water lines. Culturing and colony counting procedures were carried out. Data was analyzed by t-test; a value of p<0.01 was considered significant. RESULTS: Results demonstrated a significantly lower SE contamination in water outlets following the use of clean head system (p<0.01). CONCLUSION: A lower tendency of clean head system handpieces to transmit SE compared to conventional system makes them a better choice for infection control.