Scope of Preparation of Oval and Long-Oval Root Canals: A Review of the Literature.

Successful endodontic treatment depends on cleaning and disinfecting the root canals, in order to provide conditions for three-dimensional filling, which should prevent root canal reinfection. However, anatomical complexities pose a challenge during endodontic treatment. The present study was a literature review carried out in the following databases: PubMed, SciELO, and MEDLINE, which were searched for articles published from 2017 to 2021. Micro-CT studies published in English, which analysed the capacity for preparation of oval and long-oval root canals, were included. The following keywords were used: "oval-shaped canals," "long-oval-shaped canals," "endodontics," and "micro-CT." The aim of this study was to carry out a literature review of micro-CT studies on the scope of the capacity for preparation performed in oval and long-oval root canals with rotary and reciprocating instruments.

Instrumentación rotatoria en endodoncia. ¿Qué tipo de lima o procedimiento es el más indicado? / Rotary instrumentation in endodontics: which kind of lime you might use

El objetivo del presente trabajo es realizar una revisión bibliográfica de los últimos diez años a cerca de la instrumentación rotatoria en endodoncia y de los diferentes tipos de limas que se pueden usar, buscando una comparativa de ventajas y desventajas e incluso posibles indicaciones para cada caso y tipo de lima o procedimiento. EL sistema de endodoncia rotatoria ha significado un avance extraordinario en el tratamiento de conductos tanto de dientes anteriores como posteriores. La instrumentación rotatoria permite utilizando un menor número de limas, darle una mayor conicidad que facilite la limpieza del conducto y su posterior obturación. Por ello se pretende explicar la técnica de instrumentación mecánica de los conductos radiculares, exponiendo su diseño, características de composición, forma de uso y las ventajas o inconvenientes respecto a otros sistemas (AU)

The objective of the present work is to perform a literature review of the last ten years about rotary instrumentation in endodontics and the different types of files that can be used, searching for a comparative of advantages and disadvantages and even possible indications for each case. File type or procedure. The rotational endodontic system has meant an extraordinary advance in the treatment of ducts of both anterior and posterior teeth. The rotary instrumentation allows using a smaller number of files, give a greater conicity that facilitates the cleaning of the duct and its subsequent obturation. The aim of this work is to explain the technique of mechanical instrumentation of the root canal, exposing its design, characteristics of composition, form of use and the advantages or disadvantages with respect to other systems (AU)

Durabilidad de las fresas de diamante tras realizar desgastes en dientes naturales, comparando 4 marcas comerciales, analizado en microscopía electrónica / Diomond Burs durability, aer tooth wears, 4 brands compaired. Electronic Microscopy analysis

Antecedentes: Los hallazgos reportados en la literatura no relacionan directamente la efectividad de corte de las fresas de diamante de alta velocidad con la cantidad y calidad de diamantes en la superficie, ni su vida media después de un determinado número de usos. Objetivo: Evaluar la durabilidad de los diamantes de corte de la superficie activa de las fresas después de realizar desgastes en dientes naturales. Métodos: Este estudio ex vivo comparó 4 marcas comerciales de fresas de diamante con granos de 64-126 |zm, de forma troncocónica y punta redonda (norma ISO 850): MDT", Swisstech*, Pointech* y Jota". Se realizaron 5 cortes de 0,16 mm con cada fresa en la corona del diente. Luego se analizaron las fresas en microscopio electrónico de barrido para observar: a) adhesión de diamantes al sustrato en cabeza y cuerpo; b) estado de los diamantes en el sustrato en cabeza y cuerpo, tras los 5 cortes; y c) estadofinal de las fresas. Se realizó un análisis cualitativo y cuantitativo. Resultados: Todas las fresas de las 4 marcas presentaron similar desgaste después de los 5 usos, tanto en la cabeza como el cuerpo. Pese a que todas las muestras presentaban variaciones, en algunas fue más evidente el desalojo y fractura de los diamantes. Conclusión: El estudio sugiere que las fresas deberían cambiarse después de 5 usos clínicos para garantizar un desgaste adecuado y evitar daños pulpares ocasionados por la fricción.

Background: Outcomes reported in the literature do not relate cutting effectiveness of high-speed diamond drills directly to the diamond surface amount and quality, not either their average life after a specific number of uses. Objective: To evaluate the durability of diamond burrs in the drill active surface after doing removal in natural teeth. Methods: This ex vivo study compared dental drills of four different brand names with 64-126 pm, round tip, conical-trunk diamond grit (ISO 850): MDT", Swisstech", Pointech* and Jota". Five 0.16 mm cuts were carried out using each dental drill on a tooth crown. The dental drills were then analyzed under the scanning electron microscope in order to observe: a) any adhesion of diamond to substrate in the head and body; b) condition of the diamonds in the substrate, in head and body, after 5 cuts; and c) final condition of the dental drills. Then a qualitative and quantitative analysis was carried out. ResuJts: The four different dental drills showed a similar worn condition after five uses, both in the head and body. Despite all the samples showed variations, some of them had greater evidence of diamond fracture and displacement. Conclusion: This study suggests that the dental drills should be changed over after 5 clinical uses in order to ensure a desirable worn condition and prevent pulpal damage due to the friction.

Do the ball-ended probe cause less damage than sharp explorers?-An ultrastructural analysis.

BACKGROUND: No evidence about damage caused by ball-ended probes on tooth is available. No study compared probing defects caused by ball-ended probes with sharp explorers during tactile examinations of primary teeth. This exploratory study aimed to compare ultrastructural defects caused by ball-ended probes with sharp explorers during tactile examinations of primary teeth. METHODS: Forty-nine primary extracted teeth were tactile examined as performed for caries activity assessment. Surfaces were randomly divided into groups based on probe type (ball-ended probe or sharp explorer). Two examiners probed different surfaces using the sharp explorer and the ball-ended probe. The order for examination was randomly determined. Images were captured using environmental scanning electron microscopy (ESEM) before and after probing. Two external examiners evaluated independently the ESEM images and scored them as: 0) no damage, 1) slight marks, 2) distinct marks, 3) marks with discontinuity, 4) enamel break-offs. Multilevel Poisson regression models were used to analyze associations between probing ultrastructural damage and surface type, baseline condition and probe type. Prevalence ratios (PR) were calculated with 95 % confidence interval (CI). RESULTS: The most common defects observed on the dental surfaces were probing marks without discontinuity (scores 1 and 2). Ball-ended probes caused significantly less severe damage than sharp explorers (PR: 0.28; CI: 0.11-0.76, p = 0.01). CONCLUSION: Ball-ended probes cause less damage than sharp explorers when probing gently dental surfaces of primary teeth.

Análise comparativa da eficiência de corte de instrumentos rotatórios de níquel-titânio ProTaper NEXT e ProTaper Universal / Comparative analysis of the cutting efficiency of rotational instruments of nickel-titanium ProTaper NEXT and ProTaper Universal

Os instrumentos rotatórios fabricados em Níquel-Titânio possuem características geométricas e dimensionais que influenciam sua eficiência de corte. Torque e força apical exercidos durante o preparo de canais radiculares são parâmetros que definem esta propriedade mecânica. Neste estudo avaliou-se o torque e a força apical exercidos por instrumentos ProTaper Universal (PTU) S2 e F1 e ProTaper NEXT (PTN) X1 e X2, que apresentam diâmetros semelhantes e geometrias diferentes. Os ensaios foram realizados em dispositivo de bancada, onde 10 instrumentos de cada tipo foram testados em blocos de acrílico préfabricados, contendo um canal artificial previamente explorado com limas rotatórias PathFile #13 e #16. Acionados por um motor endodôntico com velocidade de 300 rotações por minuto (rpm) e torque de 4,0 Newton por centímetro (Ncm), os instrumentos foram inseridos no canal a uma velocidade constante de 0,09 mm/seg. Enquanto uma célula de carga registrou a força axial exercida, um multímetro acoplado ao motor endodôntico registrou o torque requerido pelo instrumento durante seu deslocamento ao longo do canal. Os ensaios foram realizados utilizando um bloco novo para cada sistema, na sequência de S2 e F1 para PTU, e X1 e X2 para PTN. Os resultados mostraram que os instrumentos do sistema PTU apresentaram menores valores de força apical e torque, quando comparados com PTN

The NiTi instruments have geometrical and dimensional characteristics that could play an important hole in the cutting efficiency. Torque and apical force exerted during the root canal preparation are parameters that define this mechanical property. This study evaluated the apical force and torque required by the instruments ProTaper Universal (PTU) S2 and F1, and ProTaper NEXT (PTN) X1 and X2, with similar diameters and different geometries, to penetrate standardized acrylic blocks containing an artificial canal previously explored with rotary instruments Pathfile #13 and #16. The parameters were determined using a bench-testing machine, where the instruments were set to move against the artificial canal in a constant speed of 0.09 mm/sec. The X-Smart Plus motor, with a rotational speed of 300 rpm and torque limitation of 4N.cm, was employed to drive the instruments and the load cell of the machine recorded the apical force exerted, while a digital multimeter attached to the endodontic motor recorded the torque required during the work of the instrument along the canal. Ten instruments of each type were tested using a new acrylic block for each system, in a sequence of S2 and F1 for PTU, and X1 and X2 for PTN. The results showed that the instruments of the PTU system displayed lower torque and apical force during the test, when compared to PTN instruments

Influence of cyclic flexural deformation on the torsional resistance of CM files in comparison to conventional NiTi instruments

As propriedades mecânicas dos instrumentos endodônticos são afetadas por fatores como microestrutura, diâmetro, geometria, composição química, e tratamentos termomecânicos aplicados durante o processo de fabricação. Os instrumentos de NiTi com Memória Controlada (CM) sofrem um tratamento térmico especial que os tornam mais flexíveis e resistentes à fadiga que instrumentos de NiTi convencional. O objetivo deste estudo é avaliar como a fadiga influencia nas propriedades torcionais dos instrumentos CM, quando comparados com instrumentos superelásticos (SE) com geometria e características dimensionais similares. Instrumentos novos Hyflex CM (HF; Coltene/ Whaladent Inc.), Typhoon CM (TYP; Clinician´s Choice Dental Products), RaCe (RC; FKG, La-Chaux De Fonds, Switzerland) e Protaper Universal F2 (F2; Dentsply Maillefer, Ballaigues, Switzerland), todos de calibre e conicidade 30/.06, foram avaliados. Características geométricas e dimensionais como o diâmetro, comprimento de pitch e ângulo helicoidal foram medidos ao longo da parte ativa dos instrumentos. A fadiga flexural (Nf) e a resistência torcional para cada instrumento (n=10) foram determinadas de acordo com a especificação ISO-3630. Dez novos instrumentos de cada sistema foram fadigados a 3/4 de Nf e depois submetidos à torção até a ruptura. Os dados foram analisados utilizando o teste ANOVA (α=.05). A superfície longitudinal, bem como a superfície de fratura após a fadiga foi examinada com um microscópio eletrônico de varredura (MEV). Os resultados mostram que os instrumentos CM tiveram valores de Nf significativamente maiores quando comparados aos instrumentos SE, com HF exibindo o maior Nf (P = .001). Os valores de torque médio para F2 foram os mais elevados (P = .001), seguido de TYP, HF e RC. Instrumentos CM pré-carregados a 3/4 de Nf e submetidos à torção até a ruptura tiveram valores de torque menores quando comparados aos instrumentos não carregados (HF P = .003; TYP P =.001), enquanto os instrumentos SE não apresentaram diferenças significativas (F2 P = .059; RC P =.079). A superfície de fratura dos instrumentos CM mostraram maiores superfícies lisas de fraturas e menores regiões de dimples, em relação aos instrumentos SE. Conclui-se que a vida em fadiga dos instrumentos CM foi significativamente maior quando comparada aos instrumentos SE, com o instrumento HF apresentando o valor de Nf maior. Os valores de torque para F2 foram maiores entre todos os instrumentos. Portanto a resistência torcional dos instrumentos CM pode ser comprometida após o pré carregamento em fadiga

Introduction: To evaluate the influence of cyclic deformation on the torsional resistance of NiTi controlled memory (CM) files, when compared to superelastic (SE) instruments with similar geometric and dimensional characteristics. Methods: New 30/.06 HyFlex (HF; Coltene/Whaledent,Inc, Cuyahoga Falls, OH), Typhoon (TYP; Clinician's Choice Dental Products, New Milford, CT), RaCe (RC; FKG, La-Chaux De Fonds, Switzerland), and ProTaper Universal F2 instruments (F2; Dentsply Maillefer, Ballaigues, Switzerland) were assessed. Diameter, pitch length and helical angle were measure along the active part of the instruments. Flexural fatigue and torsion to failure tests for each file (n = 10) were carried out. Ten new instruments of each type of file were fatigued to 3/4 of their fatigue life and then submitted to torsion until rupture. The longitudinal surface, as well as the fracture surface after fatigue was examined with a scanning electron microscope. Data were analyzed using one-way analysis of variance (α = .05). Results: CM files had a significantly higher mean number of cycles to fracture (Nf) when compared to SE instruments, HF exhibiting the highest Nf (P = .001). The mean torque value for F2 was the highest (P = .001). CM files pre-cycled to 3/4 Nf had a significantly lower torque than the new files (HF P = .003, TYP P = .001), whereas the SE instruments displayed no significant differences (F2 P = .059, RC P = .079). The surface fracture of CM files displayed larger smooth areas and smaller dimple region than SE instruments. Conclusion: Fatigue life of CM instruments was significantly higher than SE instruments, with HF displaying the highest mean Nf values. Torque value for F2 was significantly higher among all of the instruments. Cyclic flexural loading significantly reduced the torsional resistance of CM instruments

Adaptación de conos de gutapercha en conductos radiculares instrumentados hasta una lima ProTaper Universal F3 / Guttap-percha cones adaptation to instrumented root canals up to a ProTaper Universal F3 file

Objetivo: evaluar la adaptación, en longitud de trabajo, de conos de gutapercha F3 a las paredes dentinarias en conductos mesiales de molares inferiores instrumentados con el sistema rotatorio ProTaper Universal, hasta una lima F3. Materiales y métodos: 60 conductos radiculares de las raíces mesiales de 30 molares inferiores humanos, fueron instrumentados con el sistema rotatorio ProTaper Universal, hasta una lima F3. En cada cambio de instrumento, fueron irrigados con 5 ml de una solución de hipoclorito de sodio al 2, 5 por ciento. Luego, fueron secados y se realizó la conometría con conos de gutapercha F3. La condición fue que llegaran a la longitud de trabajo y que tuvieran tug bag, ajuste y adaptación radiográfica con proyecciones de frente y perfil. Luego, se incluyeron en moldes de acrílico y se realizaron cortes transversales de cada raíz, aproximadamente a 1,5, 5 y 9 mm desde el ápice, con un micrótomo de tejidos duros. Todos los cortes de los especímenes fueron rotulados, observados a 40x y fotografiados. Se midió el área del cono de gutapercha en el conducto radicular instrumentado y se estableció el porcenaje ocupado por él. Los datos fueron analizados estadísticamente con ANOVA. Resultados: los resultados de la prueba de ANOVA multivariada mostraron que no hubo una influencia significativa del factor en el tercio (cervical, medio y apical), ni diferencias entre los conductos vestibulares y linguales. La interacción entre ambos factores no fue significativa. Conclusiones: si bien no se observaron diferencias estadísticamente significativas en las variables evaluadas, el porcentaje del área ocupada por el cono de gutapercha y el contacto con las paredes radiculares en los niveles de corte evaluados podrían ser clínicamente aceptables.

Análise da eficiência de corte de instrumentos de NiTi em movimento recíproco / Evaluating the cutting efficiency of NiTi instruments in reciprocating motion

A habilidade de corte de instrumentos endodônticos é complexa e está relacionada a parâmetros como geometria da seção transversal, ângulos de corte, comprimento de pitch, ângulo helicoidal, propriedades metalúrgicas e tratamento de superfície dos instrumentos. Este trabalho tem como objetivo, avaliar a eficiência de corte, bem como as características dimensionais e geométricas de instrumentos endodônticos, por meio dos parâmetros diâmetro a cada milímetro da ponta, comprimento de pitch, ângulo helicoidal, geometria e área da seção transversal e ângulo de corte dos instrumentos Reciproc - RC (VDW, Munich, Germany) e WaveOne - WO (Dentsply Maillefer, Ballaigues, Switzerland) de calibre de ponta 25 e conicidade .08. Dez instrumentos de cada sistema foram fotografados de forma padronizada utilizando uma câmera digital Canon EOS 20D e a análise das imagens foi realizada utilizando o software ImagePro Plus 6.0. Os ensaios de eficiência de corte foram realizados em dispositivo de bancada, consistindo na peça de mão de um motor X-SmartR Plus , presa à uma base de acrílico fixado na base da máquina de teste NA8032. Blocos de acrílico pré-fabricados, foram previamente explorados. Cada bloco foi fixado em outra base menor, também acrílica, presa à máquina de testes, que se movimentava no sentido vertical a uma velocidade constante de 0,09 mm/seg. Para simular a condição clínica, a formatação do canal foi realizada em dois momentos: os instrumentos prepararam inicialmente 13,5 mm do canal, e em seguida, os 3 mm finais. Foi observado que o diâmetro aumentou progressivamente ao longo da parte ativa nos dois sistemas analisados e que o diâmetro a 3mm da ponta (D3) não apresentou diferença estatisticamente significativa entre os instrumentos (p = 0,521). Os valores médios dos comprimentos de pitch nos instrumentos RC foram superiores àqueles nos WO, embora a variação não tenha apresentado diferença significativa (p = 0,489). Os instrumentos WO apresentaram maiores valores médios de ângulos helicoidais na parte ativa que os RC, mas também sem diferença significativa entre eles (p = 0,135). A geometria da seção transversal, bem como a área a 3 mm da ponta (A3) variou entre os instrumentos analisados...

The cutting ability of endodontic instruments is complex and related to parameters such as cross-sectional geometry, cutting angles, pitch length, helical angle, metallurgical properties in addition to surface treatment. This study aimed to evaluate the cutting efficiency taking into account dimensional and geometric features of Reciproc - RC (VDW , Munich, Germany ) and WaveOne - WO ( Dentsply Maillefer , Ballaigues , Switzerland ), 25/.08 size instruments. Measurements of diameter at each millimeter from the tip, pitch length, helical angle, cross-sectional area and cutting angles were assessed. Samples of each system (n = 10) were photographed in a standardized manner using a Canon EOS 20D digital camera and image analysis was performed using ImagePro Plus 6.0 software. The cutting efficiency tests were carried out on a specific bench device by measuring the torque required during shaping of artificial canals. Ten instruments of each type were tested in prefabricated acrylic blocks containing an artificial canal previously explored with manual K-files. The motor was set at a speed of 300 rpm and torque 5 Ncm and the instruments were inserted into the canal at a constant speed of 0.09 mm/sec. In order to simulate the clinical condition, the shaping of the artificial canal was performed in two stages: initial instrument penetration through 13.5 mm, and then a second penetration until reach the full length, i.e., 16.5 mm. Statistical analysis was done with one-w y AN VA (α . ). A increase in diameter throughout the active part was observed in the two systems analyzed showing no statistically significant difference between RC and WO instruments (P = 0.521) in relation to the diameter at 3 mm from the tip (D3). The mean values of pitch lengths for RC were higher than those presented by WO instruments, although the difference was not statistically significant (P = 0.489). WO instruments had higher mean values of helical angles in comparison to RC instruments, but without statistically significant difference (P = 0.135). The cross section geometry as well as the area at 3 mm from the tip (A3) varied between the analyzed instruments. The RC samples showed slightly larger A3 mean value than WO instruments, but also without statistically significant difference (P = 0.521). The average of the two cutting angles on RC and WO instruments were similar. However, the five WO cutting angles were all significantly different when compared with each other. WO instruments in the first insertion depth and RC in the second stage of insertion required higher torque values respectively. The Reciproc and WaveOne instruments analyzed showed similar dimensional characteristics with RC presenting higher torque values in the second shaping stage.

Eficiência de corte de diferentes sistemas endodônticos de NiTi / Cutting efficiency of rotary NiTi instruments

As características geométricas dos instrumentos de NiTi influenciam diretamente a sua eficiência de corte. Neste estudo avaliou-se o corte de instrumentos rotatórios de NiTi de calibre 20, taper .06, dos sistemas EndoSequence (ES), Mtwo, GT, GTX, K3, RaCe e ProTaper F1 (F1). Inicialmente, os instrumentos foram caracterizados com relação ao diâmetro da parte ativa, geometria da seção transversal e ãngulos helocoidais e de corte. Os ensaios de eficiência de corte foram realizados em dispositivo de bancada, onde 5 instrumentos de cada tipo foram testados em blocos de acrílico pré-fabricados, contendo um canal artificial previamente explorado com limas manuais #10 e #15...

Shaping canals with ProFiles and K3 instruments: does operator experience matter?

OBJECTIVE: The aim of this study was to determine the influence of operator experience on the shaping ability of ProFile and K3 nickel-titanium rotary instruments in simulated root canals. STUDY DESIGN: One hundred sixty simulated canals consisting of 4 different shapes in terms of angle and position of curvature were prepared by experienced and inexperienced operators. One experienced operator prepared 80 canals and 2 inexperienced operators prepared 80 canals with a crown-down technique using either ProFile or K3 .06 taper instruments. Images of the canals were taken, using a camera attached to a computer with image analysis software, before surgery and after preparation to sizes 20, 25, and 30 to working length. Postoperative images were combined with the preoperative image to highlight the amount and position of material removed during preparation as well as the shape of the prepared canal. RESULTS: Overall, there was a highly statistically significant difference (P<.001) between the instruments for the time taken to prepare the canals, with K3 instruments taking a mean of 4.9 minutes and ProFile 6.0 minutes. Six instruments fractured (3 in each operator category); 4 were ProFile instruments. Four instruments deformed, all with the inexperienced operators; 3 were K3. No perforations or zips were observed; however, 1 danger zone (created by the experienced operator using K3 instruments) and 1 ledge (created by an inexperienced operator using K3 instruments) were created. Twelve outer widenings were created with a highly significant difference (P<.001) between the operator and instrument used. There was a highly significant difference by instrument (P<.001), and experience (P=.008) regarding absolute transportation at the beginning of the curve and a statistically significant difference (P=.031) for the instrument used regarding absolute transportation half way to the orifice. CONCLUSION: The experienced operator prepared canals more quickly and safely than the inexperienced operators when using K3 instruments; both used ProFile instruments quickly and safely. Inexperienced operators would be advised to train using less aggressive instruments and when confident could progress to other instrument designs.

Preliminary study to establish a relationship between tactile sensation and surface roughness.

This study evaluated the ability of tactile sensations to distinguish roughness. Five examiners experienced in visual examination participated. Tactile sensation was assessed by 3 standard references, the average roughnesses 0.49, 0.92 and 1.54 mum. The examiners evaluated the roughness using 2 different ends of sharp explorers (TU 17 SE and 23 SE), each with 2 different handles (Standard Handle and No. 6 Handle-Satin Steel), and 1 WHO probe using a 5-point response score. The examiners performed 3 evaluations to establish repeatability. Using the 23 SE explorer with the steel handle was the best option to distinguish between 3 roughnesses (p < 0.05). The intraexaminer intraclass correlation coefficients (ICC) were between 0.90 and 0.98, but the interexaminer ICC were only between 0 and 0.04, indicating that, although trained examiners could repeat their own scores, they were not consistent with each other in grading roughness.

Efficacy of Profile .04 taper series 29 in removing filling materials during root canal retreatment--an in vitro study.

OBJECTIVE: The aim of this study was to compare Profile .04 taper series 29 instruments and hand files for gutta-percha removal. STUDY DESIGN: Twenty maxillary central incisors with a single straight canal were instrumented and filled. The teeth were divided into 2 groups of 10 specimens each, according to gutta-percha removal techniques: Group 1- Profile series 29 and Group 2- hand files and solvent. The amount of time for gutta-percha removal and the number of fractured instruments were evaluated. Radiographs were taken and the teeth were grooved longitudinally and split. The area of residual debris was measured using computer software. RESULTS: The time for filling material removal was significantly shorter when Profile series 29 was used (P = .00). Regarding cleanliness, there were no statistical differences in the teeth halves evaluations (P > .05). Hand instruments cleaned the canals significantly better than Profiles, in the radiographic analysis considering the whole canal. Overall, the radiographic analysis showed a smaller percentage of residual debris than the teeth halves analysis. CONCLUSION: The Profile series 29 instruments proved to be faster than hand instruments in removing root filling materials; however, hand instruments yielded better root canal cleanliness. Some residual debris was not visualized by radiographs.

Dental devices: classification of dental amalgam, reclassification of dental mercury, designation of special controls for dental amalgam, mercury, and amalgam alloy. Final rule.

The Food and Drug Administration (FDA) is issuing a final rule classifying dental amalgam into class II, reclassifying dental mercury from class I to class II, and designating a special control to support the class II classifications of these two devices, as well as the current class II classification of amalgam alloy. The three devices are now classified in a single regulation. The special control for the devices is a guidance document entitled, "Class II Special Controls Guidance Document: Dental Amalgam, Mercury, and Amalgam Alloy." This action is being taken to establish sufficient regulatory controls to provide reasonable assurance of the safety and effectiveness of these devices. Elsewhere in this issue of the Federal Register, FDA is announcing the availability of the guidance document that will serve as the special control for the devices.

A preliminary survey of impression trays used in the fabrication of fixed indirect restorations.

PURPOSE: A variety of impression trays are used in the fabrication of fixed indirect restorations. Impressions used in the construction of fixed indirect restorations were examined for tray type, manner of use, and overall impression quality. MATERIALS AND METHODS: A commercial dental laboratory provided 1403 impressions used to fabricate fixed indirect restorations during a 3-month period. Impressions were examined for tray type, quantity and type of recorded abutments, the impression of intact teeth adjacent to and opposing the abutment, the presence of the canine in the impression, and an assessment of the quality of the impression. RESULTS: A majority of trays examined were plastic (864, or 61.6%). Dual-arch trays comprised 73.1% of the total. Most of these were metal posterior (n = 499) or plastic posterior (n = 280). Among partial dual-arch impressions, 561 (55.7%) were for the single abutment restoration, bounded by intact teeth anterior and posterior, and with an intact opposing tooth. Eleven percent of plastic dual-arch impressions failed to register the canine. Regarding restoration type, there were 955 impressions for the single-tooth crown, 46 for implant-supported restorations, and 11 for veneers. Twenty impressions were for posts, inlays, or onlays. Impressions for multiple single-tooth crowns and fixed partial dentures comprised the remainder. In terms of overall quality, 85.3% of impressions were excellent or good. The lowest performance in terms of excellent quality was in the anterior plastic single-arch impression (44.8%), whereas the best rate of excellent quality noted was for the posterior dual-arch impression (82.4%). CONCLUSIONS: Within the limitations of this study, dual-arch trays were the most commonly used tray. Recommendations for the use of the dual-arch tray were not followed in a substantial number of impressions examined.

A novel simplified numbering system for dental burs.

A universally accepted standardization is of great value for any material or equipment that is used globally. A single number or name should represent the particular material or instrument throughout the world. Since the dental burs are used worldwide, a single standard numbering system, which gives a unique specification for each bur in any part of the world, is mandatory. Though the existing systems have tried to attain this goal, they have their own advantages and limitations that are explained in detail in this article. So, the idea of proposing a novel system is to formulate a simple way of mentioning each bur with its dimension and composition without the need for memorizing the numbers.

Consistency of labial finish line preparation for metal ceramic crowns: an investigation of a new bur.

PURPOSE: Previous studies have reported on the difficulties inherent in preparing the labial aspect of teeth for metal ceramic crowns with consistency and also the implications for the definitive restoration of underprepared and overangled finish lines. In this study, a bur designed to prepare a 1.2-mm deep chamfer was tested and compared with two other bur kits. MATERIALS AND METHODS: Seventy-two teeth were prepared to receive metal ceramic crowns in vitro by students using one of the two bur kits or the new bur. Using a coordinate measuring machine (CMM), replicas of the prepared teeth were scanned in the mid-labial plane, and shoulder width and cavosurface angles were measured. RESULTS: The new bur produced preparations with a mean shoulder width and cavosurface angle of 1.146 +/- 0.241 mm and 108 +/- 11 degrees, respectively, compared with 0.626 +/- 0.234 mm and 128 +/- 14 degrees produced by a commercially available standardized crown cutting bur system and 0.626 +/- 0.218 mm and 124 +/- 15 degrees produced by the bur kit in use at our center at the time of the study. These differences were statistically significant at the 5% level, using Tukey's comparison of means. CONCLUSIONS: Teeth prepared by the new bur had wider shoulders and lower cavosurface angles than teeth prepared either with a standardized crown cutting system or locally selected bur kit. The quality of labial preparations produced by the new bur in terms of closeness to the postulated "ideal" width and angulation warrants further investigation.

Características físicas, estruturais e mecânicas de instrumentos endodônticos de NiTi ProTaper / Physical, structural and mechanical characteristics of ProTaper nickel-titanium endodontic instruments

Neste trabalho foi realizado um estudo das características estruturais, físicas e mecânicas de instrumentos endodônticos de NiTi ProTaper. As características geométricas e dimensionais dos instrumentos foram analisadas utilizando microscópio óptico. Canais curvos em blocos de acrílico formatados por estes instrumentos foram analisados utilizando um programa de análise de imagens com o intuito de verificar a geometria. As características topográficas foram avaliadas por microscopia eletrônica de varredura (MEV), a composição química foi analisada semi-quantitativamente por espectrometria de energia de raio-X (EDS), a estrutura cristalina da liga identificada por difração de raio-X (DRX), enquanto que as temperaturas de transformação foram determinadas por calorimetria exploratória diferencial (DSC). O comportamento mecânico foi avaliado através de ensaios de torção e flexão, de acordo com a especificação ISO 3630-1. A resistência à fadiga foi avaliada em um dispositivo de bancada utilizando um canal artificial com raio de curvatura de 5 mm e ângulo de 45°. Foi também avaliada a influência da deformação cíclica em torção nas propriedades torcionais e na resistência à fadiga flexural. Os instrumentos apresentaram boa padronização geométrica, características superficiais aceitáveis, adequada razão estequiométrica, predominância de fase B e temperaturas de transformação favoráveis à ocorrência de superelasticidade. Os diâmetros obtidos nos canais de acrílico foram fortemente relacionados com as dimensões do último instrumento empregado na formatação. Todos os instrumentos exerceram trabalho na ponta e ao longo das hastes cortantes...