Evaluation of dentin microroughness and composite bond strength after multiple uses of diamond burs / Evaluación de la micro rugosidad dentinaria y la resistencia adhesiva de composites tras múltiples usos de fresas de diamante

Abstract Using a bur multiple times to prepare dental structure may produce a smoother final surface on dentin than a new one. This superficial roughness may affect adhesion with resin-based materials by modifying the substrates' characteristics. The aim of this study was to evaluate the effect of multiple uses of diamond burs on dentin's superficial microroughness and bond strength with resin composite when using a self-etch adhesive. Diamond dental burs were used to simulate a preparation (dentin flat surface) on extracted third molars. Samples were distributed into groups according to burs' number of previous uses as follows: 0, 1, 5 and 10. Scanning electron microscopy images at 70x, 350x, and 1000x were used to illustrate burs' deformation. Each specimen's dentin microroughness was measured three times to compare between experimental groups and the micro-shear bond strength test (n=15) was performed for the 0 and 10 uses groups using a universal adhesive in a self- etching mode. Diamond crystals wear and dislodgements were evident among groups where the burs were used more times. As the number of uses increased the mean microroughness of the dentin surface decreased with significant differences between the 0 and 10 uses groups. No statistical differences between experimental groups resulted from bond strength tests. When using a universal adhesive in a self-etching mode, the number of previous uses of a diamond bur seems to have no significant effect on dentin/resin composite bond strength.

Resumen El uso de una fresa múltiples veces para preparar la estructura dental puede producir una superficie final más lisa en la dentina que una fresa nueva. Esta rugosidad superficial modifica las características del sustrato y puede afectar la adhesión con materiales resinosos. El objetivo de este estudio fue evaluar el efecto de los múltiples usos de las fresas de diamante sobre la micro rugosidad superficial de la dentina y la resistencia adhesiva con la resina compuesta cuando se utiliza un adhesivo de autograbado. Se utilizaron fresas dentales de diamante para simular una preparación (superficie plana de la dentina) en terceros molares extraídos. Las muestras se distribuyeron en grupos según el número de usos previos de las fresas de la siguiente manera: 0, 1, 5 y 10. Se utilizaron imágenes de microscopía electrónica de barrido a ×70, ×350 y ×1000 para ilustrar la deformación de las fresas. Se midió la micro rugosidad de la dentina de cada espécimen tres veces para comparar entre los grupos experimentales y se realizó la prueba de resistencia a la adhesión por micro cizallamiento (n=15) para los grupos de 0 y 10 usos utilizando un adhesivo universal en modo de autograbado. El desgaste de los cristales de diamante y los desprendimientos fueron evidentes entre los grupos en los que las fresas se utilizaron más veces. A medida que aumentaba el número de usos, la micro rugosidad media de la superficie de la dentina disminuyó, con diferencias significativas entre los grupos de 0 y 10 usos. En las pruebas de resistencia adhesiva no se observaron diferencias estadísticas entre los grupos experimentales. Cuando se utiliza un adhesivo universal en modo de autograbado, el número de usos previos de una fresa de diamante no parece tener un efecto significativo en la resistencia de la unión dentina/resina del composite.

Precision Dermabrasion of Small Areas of Vitiliginous Skin Using Dental Diamond Burs.

Dermabrasion is important step in any vitiligo surgery. Unfortunately, it is not possible to derma abrade very small area with conventional burs available. The present paper highlights the use of dental burrs in such situations.

Quantifying machining outputs of pristine human teeth relevant to dental preparation procedures.

Minimally-assisted tooth repair (MaTR) systems are envisioned to be capable of substituting for the skill of a dentist. If successfully developed, MaTR systems could enable lower-skilled dental technicians to provide dental care at a fraction of the overall medical cost. This paper explores a key initial step towards the development of such systems by quantifying the machining responses of pristine human teeth relevant to dental preparation procedures. The working hypothesis of the study is that such findings will enable the benchmarking of key process planning and control metrics relevant for the future development of MaTR systems. To this end, pristine human cadaver teeth were cut using a computer-controlled motion platform and dental hand-piece. Relevant cutting responses, such as cutting forces, in-process rotational speed of the dental bur, teeth morphology, and bur wear were captured. The trends in cutting forces show the potential for implementing region-specific process parameters for cutting the enamel and dentin regions of the tooth. A feed-per-tooth value of 0.1 µm at rotational speeds of 8 krpm and 50 krpm is seen to cut both the enamel and dentin regions at cutting forces lower than patient discomfort thresholds identified in literature. Cutting force signals were also successfully mapped against the CT-scan data of the tooth. This mapping indicates a clear identification of the enamel/dentin regions, and a transition region that is dependent on cutting parameters, tooth/tool geometry and tool pose. The trends in the in-process rotational speed of the dental bur indicate that stalling of the dental bur occurs at feed per tooth values greater than 0.25 µm. The evidence of stalling can be detected by both a drop in the cutting force signal and by surface morphology changes on the cut surface of the tooth. MaTR systems should be designed to avoid bur stalling regions by either operating at feed per tooth values ≤ 0.25 µm or by the use of dental spindles with higher torque capacity. Lastly, the type of fit present on the shank of the bur is seen to result in differences in the cutting force signals and wear of the cutting edges (flutes) of the dental bur. In general, a right-angle (RA) fit on the shank of the dental bur results in a larger tool runout leading to uneven loads on the flutes and increased tool wear. The friction grip (FG) fit avoids these problems and may be more suited for MaTR systems.

Evaluation of Efficiency of Different Decontamination Methods of Dental Burs: An In vivo Study.

INTRODUCTION: Infection control is very important in dentistry. Both dentist and patients are at risk of communicating diseases during treatment procedures. Dental burs have been identified as a source of cross-contamination between patient and dental personnel. AIM: The present study was done to quantitatively and qualitatively assess the pathogenic contamination of dental burs used for tooth preparation and to determine the effective method of sterilization(autoclave, glass bead sterilizer, hot air oven and surgical spirit immersion) of burs used for crown preparation. METHODOLOGY: Dental burs were assessed before and after tooth preparation, also after sterilization burs were evaluated. CONCLUSION: Findings of our study revealed that among the experimental groups used in the present study, Autoclave and Hot air oven was found to be the relatively best method to sterilize burs. Proper cleaning and sterilization of burs should be strictly employed to prevent cross contamination in clinical practice.

Influence of reused dental burs on bond strength to dentin

AIM: this study evaluated the bond strength of an adhesive system to human dentin prepared with reused diamond burs. MATERIAL AND METHODS: five molars (G1) were prepared in a standardized way with five diamond burs. Flat deep dentin surfaces were etched, received adhesive and received composite build-ups. The same burs were cleaned and reused on another five teeth groups (G2 until G8). After 24-hours storage and thermocycling, 50 dentin-resin sticks per group were obtained and subjected to microtensile bond strength test (µTBS). RESULTS: analysis of variance (ANOVA) and Tukey test were applied to identify differences between groups (p<0.05). The reuse of a diamond bur for more than two preparations resulted in significantly lower µTBS values (G1 = G2 > G3 = G4 = G5 = G6 = G7 = G8). CONCLUSION: Reuse of diamond burs interfered on adhesion between dentin and resin.

Comparative study of the cutting efficiency and working life of carbide burs.

PURPOSE: The aim of this study was to establish the wear and cutting efficiency of tungsten carbide burs from different manufacturers by performing cutting tests with machinable glass ceramic. MATERIALS AND METHODS: Cutting tests were performed with 70 tungsten carbide burs from seven manufacturers: (A) Coltene/Whaledent, (B) CEI, (C) Meisinger, (D) Axis, (E) Komet, (F) Kerr, (G) Edenta. All groups were examined under scanning electron microscope (SEM) before and after the cutting efficiency test for similarities and differences. A specially designed cutting device was used. An electric handpiece was operated at 200,000 rpm with a 120 ml/min coolant water supply rate. The burs were tested under a 165 g constant load using 3 mm wide Macor ceramic as substrate. For each bur the cutting procedure involved a total of five cuts of 3 minutes on every cut, with a total cutting time for each bur of 15 minutes. Data were analyzed using one-way ANOVA at 95.0% confidence level. RESULTS: Significant differences (p < 0.05) were found in the mean cutting rates of the different groups. Groups A and B showed the highest cutting rates. Higher cutting rates were associated with a longer bur lifespan. SEM photomicrographs of the burs and substrates revealed significant changes on the surfaces after the cutting process. CONCLUSIONS: The morphology characteristics of tungsten carbide burs are related to their effectiveness. The group that presented the worst working life also showed substantial wear on its surface according to the results of SEM.