Parálisis del XI par craneal secundaria a enfisema subcutáneo por uso de pieza de mano de alta velocidad en cirugía de terceros molares / Paralysis of the XI cranial nerve following subcutaneous emphysema by use of high speed handpiece in third molar surgery

Introducción: La cirugía de los terceros molares es el procedimiento quirúrgico más frecuentemente realizado por los cirujanos orales y maxilofaciales, que a pesar de contar con una vasta experiencia y entrenamiento en el área quirúrgica pueden presentarse complicaciones transoperatorias y postoperatorias. Cuando éste es realizado por un cirujano dentista de práctica general las complicaciones pueden aumentar. Presentación de caso clínico: Se trata de un paciente de 25 años de edad sometido a extracción quirúrgica de terceros molares por un dentista de práctica general, el cual realiza procedimiento quirúrgico con uso de pieza de mano de alta velocidad. Tres días posteriores al evento quirúrgico el paciente acude al Departamento de Cirugía Oral y Maxilofacial del Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado por presentar edema, infl amación y crepitación en región bucal, maseterina y submandibular derecha, así como limitación a la apertura bucal de 25 mm. En tomografía computarizada contrastada se obs erva desviación de la vía aérea hacia el lado izquierdo. Se decide manejó del proceso infeccioso y de enfi sema subcutáneo con farmacoterapia y drenaje del mismo. Una vez remitido el enfi sema subcutáneo, en la cuarta semana de evolución el paciente refi ere limitación a la abducción del hombro derecho, observándose atrofi a del músculo trapecio y esternocleidomastoideo ipsilateral, correspondiente a lesión del XI par craneal. Discusión: La lesión del nervio accesorio (XI par craneal) ocasiona parálisis del músculo trapecio, principal estabilizador de la escápula que contribuye en los movimientos de fl exión, rotación y abducción del hombro. El trayecto del XI par craneal es superfi cial en el triángulo posterior del cuello presentando susceptibilidad a ser lesionado de manera iatrogénica, en este caso la utilización de pieza de mano de alta velocidad durante la extracción quirúrgica de los terceros molares generó enfi sema subcutáneo que condicionó la posible compresión del nervio accesorio, lesionando al mismo (AU)

Introduction: The third molar surgery is the most frequent surgical procedure performed by oral and maxillofacial surgeons, who despite their vast experience and training in the surgical area can present transoperatory and postoperative complications. When the oral surgery is done by a general practice dentist the complications can be increased. Case presentation: A 25-year-old male patient undergoing third molar surgery by a general practice dentist who performs a surgical procedure using a high-speed handpiece. Three days after the surgical procedure patient comes to the Department of Oral and Maxillofacial Surgery Institute for Social Security and Services for State Workers by present edema, swelling and crepitus in buccal space, masseteric and right submandibular region and limitation of mouth opening of 25 mm. Contrast computed tomography shows airway deviation to the left side. We decided to manage the infectious process and subcutaneous emphysema with antibiotic therapy and drainage. After subcutaneous emphysema was in remission, in the fourth week of evolution, the patient reported limitation of abduction of the right shoulder, with atrophy of the trapezius muscle and ipsilateral sternocleidomastoid, corresponding to a lesion of the XI cranial nerve. Discussion: Accessory nerve injury (XI cranial nerve) causes palsy of the trapezius muscle, the major stabilizer of the scapula that contributes to the fl exion, rotation and abduction movements of the shoulder. The trajectory of the XI cranial nerve is superfi cial in the posterior triangle of the neck presenting susceptibility to iatrogenic injury, in this case, the use of high-speed handpiece during the surgical extraction of the third molars, caused subcutaneous emphysema that conditioned the possible compression of the spinal nerve (AU)

Quantitative assessment of the enamel machinability in tooth preparation with dental diamond burs.

Enamel cutting using dental handpieces is a critical process in tooth preparation for dental restorations and treatment but the machinability of enamel is poorly understood. This paper reports on the first quantitative assessment of the enamel machinability using computer-assisted numerical control, high-speed data acquisition, and force sensing systems. The enamel machinability in terms of cutting forces, force ratio, cutting torque, cutting speed and specific cutting energy were characterized in relation to enamel surface orientation, specific material removal rate and diamond bur grit size. The results show that enamel surface orientation, specific material removal rate and diamond bur grit size critically affected the enamel cutting capability. Cutting buccal/lingual surfaces resulted in significantly higher tangential and normal forces, torques and specific energy (p<0.05) but lower cutting speeds than occlusal surfaces (p<0.05). Increasing material removal rate for high cutting efficiencies using coarse burs yielded remarkable rises in cutting forces and torque (p<0.05) but significant reductions in cutting speed and specific cutting energy (p<0.05). In particular, great variations in cutting forces, torques and specific energy were observed at the specific material removal rate of 3mm(3)/min/mm using coarse burs, indicating the cutting limit. This work provides fundamental data and the scientific understanding of the enamel machinability for clinical dental practice.

Assessment of Er:YAG laser for cavity preparation in primary and permanent teeth: a scanning electron microscopy and thermographic study.

PURPOSE: Most studies of cavity preparation using Er:YAG lasers have employed permanent teeth. This study's purpose was to compare the cutting efficiency of an Er:YAG laser versus diamond burs in primary and permanent teeth in order to measure thermal effects on the pulp and evaluate lased surfaces using scanning electron microscopy (SEM). METHODS: A total of 80 primary and permanent teeth were used. Crater depths and mass loss were measured after delivering laser pulses at varying energies onto sound or carious enamel or dentin using the Key-3 laser. Control samples were cut using diamond burs in an air turbine handpiece. Thermal changes were measured using miniature thermocouples placed into the pulp chamber. Lased surfaces were evaluated using SEM. RESULTS: Laser ablation crater-like defects were deeper in dentin than enamel at the same pulse energy. Greater ablation rates for dentin and enamel and significantly more efficient removal of carious tooth structure by laser was present in primary teeth. Temperature rises in the pulp did not exceed the 5.5 degrees Celsius threshold in any teeth during laser ablation. CONCLUSIONS: The Er:YAG laser is an efficient device for cavity preparations in primary teeth, with no unacceptable increases in temperature detected in this model.

Theoretical evaluation of nickel-titanium MTWO series rotary files

Las limas rotatorias de níquel-titanio son un avance tecnológico que permite al odontólogo llevar a cabo tratamientos en conductos con morfologías irregulares Lamentablemente, estos instrumentos pueden fracturarse sin presentar señales visibles que permitan prevenir este accidente. Por lo tantoel objetivo del presente estudio fue evaluar teóricamente el comportamientomecánico de las limas rotatorias de Níquel-Titanio para uso en endodoncia Mtwo® para determinar cuál de losinstrumentos de la serie básica es el que presenta mayor probabilidad de fractura. Con este fin se realizó un análisis por medio del método de los elementos finitos utilizando modelos matemáticos de los instrumentos de la serie básica de las limas Mtwo®. Aestos instrumentos se les aplicaron cargas de flexión y torsión en condiciones normales y en condiciones extremas, para determinar cuáles presentaban los esfuerzos de Von Mises más altos. En una aproximación similar al uso normal, ninguno de los modelosde las limas alcanzó el limite máximo de falla por fractura. Ante un uso inadecuado, los modelos de las limas 10/0.04 y 25/0.06 mostraron los esfuerzos de Von Mises más altos tanto a flexión como a torsión respectivamente, por lo tanto se recomienda dar un solo uso a la lima 10/0.04 y a la lima 25/0.06 de Mtwo® para prevenir la fractura de estos instrumentos.

Nickel-Titanium rotary files are a technological development thatenables dentists to prepare irregularly shaped root canals withoutaltering them. Unfortunately, these files may fracture without anyprior visible warning signs. The aim of this study was to perform atheoretical evaluation of the mechanical behaviour of Mtwo®Nick-el-Titanium rotary files for endodontics, in order to determinewhich of the files in the basic series are most likely to fracture.Mathematical models of the Mtwo®basic file series were analyzedusing the finite elements method. Bending and torsion loads wereapplied to the files both under normal conditions and under extremeconditions, to determine which of them had the highest Von Misesstresses. When the approximation was similar to normal use, noneof the file models reached the maximum limit of failure by fracture.When used inadequately, file models 10/0.04 and 25/0.06 had thehighest Von Mises stresses for bending and torsion, respectively.Thus, it is recommended that Mtwo®files10/0.04 and 25/0.06should be used once only, to prevent fractures.

Assessment of noise levels of the equipments used in the dental teaching institution, Bangalore.

CONTEXT: In dental practical classes, the acoustic environment is characterized by high noise levels in relation to other teaching areas, due to the exaggerated noise produced by some of these devices and use of dental equipment by many users at the same time. AIMS: To measure, analyze and compare noise levels of equipments among dental learning areas under different working conditions and also to measure and compare noise levels between used and brand new handpieces under different working conditions. MATERIALS AND METHODS: Noise levels were measured and analyzed in different dental learning areas that included clinical, pre-clinical areas and laboratories selected as representatives of a variety of learning-teaching activities. The noise levels were determined using a precision noise level meter (CENTER® 325 IEC 651 TYPE II) with a microphone. The mean of the maxima was determined. The data were collected, tabulated, and statistically analyzed using t tests. RESULTS: The noise levels measured varied between 64 and 97 dB(A).The differences in sound levels when the equipment was merely turned on and during cutting operations and also between used and brand new equipments were recorded. The laboratory engines had the highest noise levels, whereas the noise levels in high-speed turbine handpieces and the low-speed contra angle handpieces were decreased. CONCLUSION: The noise levels detected in this study are considered to be close to the limit of risk of hearing loss.

In-process assessment of dental cutting of a leucite-reinforced glass-ceramic.

This paper reports an in-process assessment of the dental cutting of a leucite-reinforced glass-ceramic with a high-speed dental handpiece under clinical operating conditions. The dental cutting was performed using a computer-controlled 2-degrees-of-freedom (2-DOF) testing regime and a coarse diamond bur of 106-125 microm grit size. Dynamic forces were monitored during the cutting process using a piezoelectric force dynamometer and a data acquisition system in both time and frequency domains. Bur speeds were found to decrease with the depth of cut and with the feed rate, by a maximum of 10.5% from the free-running speed of 322.2 krpm (1 krpm=1,000 rpm) to 288.4 krpm at the highest feed rate of 60mm/min and depth of cut of 50 microm. Both the tangential and normal forces increased with the depth of cut and the feed rate, in the ranges of 0.24-1.77 N and 0.60-2.93 N respectively. The torque increased with the depth of cut and feed rate. The specific cutting energy generally decreased with the depth of cut or the feed rate with the exception of a small-scale fluctuation at the higher depth of cut and feed rate. The dental cutting characteristics for the leucite glass-ceramic were similar to those for the feldspathic porcelain but had higher magnitudes.

Histomorphometric assessment in human cadavers of the peri-implant bone density in maxillary tuberosity following implant placement using osteotome and conventional techniques.

OBJECTIVE: To evaluate and compare peri-implant bone condensation in the maxillary tuberosity of human cadavers following the osteotome and standard drilling techniques, and to determine whether peri-implant bone condensation following the osteotome technique is localized or homogeneous. MATERIAL AND METHODS: Twenty-four cylinder-threaded titanium implants (12 on each side) were placed in the left (standard technique) and right (osteotome technique with tapered osteotomes for bone condensation, Straumann) maxillary tuberosities of 12 edentulous posterior maxillae of deceased people who had bequeathed their bodies to the University of Santiago de Compostela for medical-scientific research. After surgery, the implants were removed with the surrounding bone, prepared using sawing and grinding technique and examined histomorphometrically. The bone density (bone area/analyzed area) of the entire, periapical (fifth apical) and pericylinder peri-implant areas was calculated, statistically analyzed and compared with the bone density of the host cancellous maxillary bone. RESULTS: The bone density of the entire peri-implant area was statistically found to be greater with the osteotome technique (39.38 +/- 9.67) than with conventional drilling technique (31.06 +/- 5.9). This difference was greatest for the periapical zone (53.32 +/- 12.26 vs. 34.18 +/- 6.34). Nonetheless, in the pericylinder area no significant difference was found between the two techniques (32.30 +/- 8.74 vs. 30.34 +/- 7.2). CONCLUSION: Peri-implant bone condensation following the osteotome technique is not homogeneously observed through the entire peri-implant area. A greater bone density was achieved only in the fifth apical peri-implant area.

An assessment of the effect of sound produced in a dental clinic on the hearing of dentists.

OBJECTIVE: To assess the effect of sound produced in a dental clinic on the hearing of dentists in a dental school. MATERIALS AND METHODS: Thirty-two dentists were evaluated for changes in their hearing thresholds at the Speech and Audiology Department, Manipal College of Allied Health Sciences, Manipal, India. Middle Ear Analyser (MEA), Pure Tone Audiometry (PTA) and Oto-Acoustic Emission (OAE) were used to evaluate changes in the hearing thresholds. RESULTS: There was a change in distortion product (DP) amplitude (temporary shift) in all frequencies. Statistically significant changes were found in the 6 kHz and 4 kHz ranges in the left ear and 6 kHz in the right ear. There was a larger DP shift in the left ear than in the right ear. A comparison of the hearing thresholds of males and females showed a significant difference of 3 kHz in the left ear, where males had a higher hearing loss. CONCLUSION: There were shifts of hearing threshold at 6 kHz and 4 kHz. The danger to hearing from dental clinic working environment in a dental school cannot be underestimated.

In vitro assessment of temperature change in the pulp chamber during cavity preparation.

STATEMENT OF PROBLEM: Tooth preparation with a high-speed handpiece may cause thermal harm to the dental pulp. PURPOSE: This in vitro study evaluated the temperature changes in the pulp chamber during 4 different tooth preparation techniques and the effects of 3 different levels of water cooling. MATERIAL AND METHOD: The tip of a thermocouple was positioned in the center of the pulp chamber of 120 extracted Shuman premolar teeth. Four different tooth preparation techniques were compared: (1) Low air pressure plus low load (LA/LL), (2) low air pressure plus high load (LA/HL), (3) high air pressure plus low load (HA/LL), and (4) high air pressure plus high load (HA/HL) in combination with 3 different water cooling rates. Control specimens were not water cooled; low water cooling consisted of 15 mL/min, and high water cooling consisted of 40 mL/min. Twelve different groups were established (n=10). An increase of 5.5 degrees C was regarded as critical value for pulpal health. The results were analyzed with a 3-factor ANOVA and Bonferroni adjusted Mann Whitney U test (alpha=.004). RESULTS: For all techniques without water cooling (LA/LL/0, LA/HL/0, HA/LL/0, and HA/HL/0), the average temperature rise within the pulpal chamber exceeded 5.5 degrees C during cavity preparation (7.1 degrees C; 8.9 degrees C; 11.4 degrees C, and 19.7 degrees C, respectively). When low water cooling was used with high air pressure and high load technique (HA/HL/15), the average temperature rise exceeded 5.5 degrees C limit (5.9 degrees C). However, when high water cooling (LA/LL/40, LA/HL/40, HA/LL/40, and HA/HL/40) was utilized, the critical 5.5 degrees C value was not reached with any air pressure or load (3.1 degrees C, 2.8 degrees C, 2.2 degrees C, and -1.8 degrees C, respectively). CONCLUSION: Within the limitations of this in vitro study, the results indicate that reducing the amount of water cooling or increasing air pressure and load during cavity preparation increased the temperature of the pulp chamber in extracted teeth.

Thermographic assessment of dentine pin placement.

OBJECTIVE: This in-vitro study aimed to examine the change in surface temperature induced by the actions of drills for the placement of dentine pins. METHODS: Ten decoronated extracted premolar teeth were embedded by the apical tip of their roots in orthoresin. They were held in a bench vice and allowed to reach the ambient temperature of 24 degrees C. A thermal imaging camera, Agema Thermovision 900 series, was positioned 0.05 m perpendicular to the decoronated surface. Sequential recording of a series of images was stored at a rate of three per second during each stage of the pin placement procedure. This included a pilot drill, a channel cutting drill and the pin placement. All pins were 0.675 mm diameter x 2 mm in length and were placed 1 mm from the amelo-dentinal junction using a Kavo handpiece rotating at 4000 rpm. RESULTS: The mean baseline temperature for the thermally stabilized teeth was 23.9 degrees C. The action of the round pilot drill changed the temperature from baseline by 25 degrees C. The action of the channel drill generated the greatest heat, with a mean maximum temperature recorded during these procedures of 94 degrees C +/- 9 degrees C. The pilot drill produced a mean change from baseline of 31.3 degrees C +/- 17.7 degrees C during pin placement. CONCLUSIONS: The placement of dentine pins produced a high temperature increase on the surface of the dentine. All stages of pin placement gave rise to an increased temperature, but this was maximal with the channel drill. Further studies are required to determine whether these surfaces temperatures are transferred to the pulpal chamber.

Temperature changes in bovine mandibular bone during implant site preparation: an assessment using infra-red thermography.

OBJECTIVES: Changes in bone temperature during the sequence of drilling for implant site preparation using the Branemark technique were monitored using infra-red thermography. METHODS: Bovine mandibles were used to provide cortical bone of a similar quality to human mandibular bone. To ensure the consistency in the drilling procedure, one operator used a conventional dental handpiece with a motor provided by Nobelpharma. The manufacturer's specifications were followed during the implant site preparation, except that no irrigation was employed since infra-red radiation does not transmit through water. Thermal images were recorded using the Thermovision 900 system. A sequence of images was recorded during implant site preparation. Three drills were examined in terms of temperature changes during drilling over the entire area involved. The three drills used were a round bur, which determines the site of the fixture, a spiral drill (2 mm twist drill) which establishes the direction of the implant and finally a pilot drill (3 mm) which progressively increases the diameter of the site. RESULTS: Average values (n = 10 drill sequences) for maximum recorded temperature (Max T degrees C), change in temperature (delta T degrees C) from baseline and the area of involvement (mm2) for each drill in the 10 drill sequences were as follows: round, spiral (2 mm) and pilot (3 mm) drills gave maximum temperatures of 82.7 degrees C, 130.1 degrees C and 126.3 degrees C, respectively. The changes in temperature, delta T degrees C, were 45.7 degrees C, 79.0 degrees C and 78.9 degrees C for the round, 2 mm twist and 3 mm pilot drill, respectively. The average areas recorded for the round, spiral and pilot drills were 49 mm2, 140.1 mm2 and 273.0 mm2, respectively. CONCLUSIONS: It is concluded that the methodology employed accurately recorded temperature changes at and around the dental implant site, and provided preliminary baseline data against which the cooling efficacy of different irrigant systems may be compared.

Handpiece sterilization: is it really necessary?

Sterilization of air-driven dental handpieces between patients is an integral component of dental instrument sterilization-asepsis protocols. This article explores some technical aspects of handpiece operation and provides suggested protocols for proper sterilization of the instrument.

Using air-abrasive technology to diagnose and restore pit and fissure caries.

National Institute of Dental Research surveys indicate that the incidence of pit and fissure caries constitutes a higher proportion of the total caries incidence among U.S. teens and children than in the past. Air-abrasive technology may provide a more conservative alternative in the diagnosis and treatment of pit and fissure caries than traditional techniques using handpieces. The authors review characteristics of pit and fissure lesions and discuss methods for diagnosing and treating these lesions using air-abrasive technology.

Risk perception and risk communication: benefits of dentist-patient discussions.

Experts in risk communication have encouraged dentists to initiate discussions about dental office-related risks with their patients. However, little is known about how often these discussions occur--and even less about their consequences. A survey of 4,061 dental patients explored patients' concerns, the frequency of risk-related discussions and their correlates. Patients who discussed concerns were less fearful about dentistry and more likely to receive dental care often. The study findings highlight the complexities of risk communication.

Controversies in cross-infection control.

The following article is intended to question certain procedures designed to prevent cross-infection. It is the first of a series of occasional articles describing new techniques, research, and new products, which it is hoped, may enable dental practitioners to update their knowledge of this rapidly changing subject.