Tungsten Carbide Bur Research Articles

Evaluation of enamel surface roughness using different types of polishing system after orthodontic bracket debonding

Background: returning surface of the enamel to its pre-orthodontic state after debonding of brackets without any damage to the texture of enamel is a clinical contest. removal of Residual adhesive using correct and suitable tools and methods ensures a smooth surface and healthy plaque-free environment. Therefore; the study aims to determine the safest method to finish enamel surface after bracket debonding using three different methods. Method: Thirty premolars extracted for orthodontic purposes were selected for this study. The samples were coded 1-30 randomly and surface roughness was measured before bracket placement using profilometer. Then bracket bonded in the middle third of the buccal surface of the premolars and then debonded using debonding plier. The sample was divided into three groups, 10 for each group (group 1: 18-flute tungsten carbide bur, group 2: 12- flute tungsten carbide bur, group 3: adhesive removing plier). Then the second roughness measurement was recorded. Result: It is found that debonding with adhesive removing plier was the least efficient method followed by 12-fluted tungsten carbide bur, so the best clean-up method in this study achieved is by using 18-fluted tungsten carbide bur. Conclusion: The 18-fluted flame-shaped tungsten carbide bur at high speed for orthodontic adhesive removal demonstrated more favorable results in our hands, as it resulted in the smoothest enamel surface and could reasonably be used as a standard by which future other burs or other procedures are compared.

Comparison of enamel surface roughness and color alteration after bracket debonding and polishing with 2 systems: A split-mouth clinical trial

This split-mouth randomized clinical trial aimed to compare the enamel surface roughness (SR) and color alteration after bracket debonding and polishing using 2 systems. After removal of excess adhesive using a 12-blade tungsten carbide bur on a low-speed handpiece, a randomized polishing procedure using Sof-Lex discs was applied on 1 side (n=36) and Sof-Lex Spiral Wheels on the contralateral side (n=36). Dental replicas were obtained with epoxy resin before bracket bonding and after tooth polishing. The SR was evaluated using a profilometer. The color was assessed using an Easyshade spectrophotometer before bracket bonding, immediately after tooth polishing, and 30days after polishing. Two-way analysis of variance and t tests were applied for statistical analysis. The SR of enamel showed similar results between the polishing systems (P=0.309) and between moments (before bracket bonding and after tooth polishing) (P=0.317). The color change was also similar between the polishing systems (P>0.05). The Sof-Lex discs and Sof-Lex Spiral Wheel polishing systems used after removal of excess adhesive using a 12-blade tungsten carbide bur on a low-speed handpiece did not appear to significantly damage the enamel surface, and the color change was similar between them.

Assessement of Pain Response during Caries Removal using Conventional Tungsten Carbide Bur and a Chemomechanical Caries Removal Agent (Brix Gel) : An In Vivo Study

Aim: The present study aimed to assess the pain response during caries removal using conventional tungsten carbide bur and a chemomechanical caries removal agent(CMCR) – Brix 3000 gel using Wong Baker Faces pain scale. Materials and methods: In this study twenty patients in the age group of 20 to 50 years with site 1 size 2 and 3(Mount and Hume’s classification) dentinal caries in the permanent maxillary and mandibular molars were randomly selected and distributed to 2 experimental groups. In Group A Tungsten carbide round burs was used while in Group B Brix 3000 gel was applied into the cavity for caries excavation. Dentin excavation was stopped until a hard dentin was detected with nonflexible blunt probe. Finally a caries detector dye is used to assess complete removal of infected dentin. Results: The scores obtained from the scale was analysed using Mann whitney U test which didn’t show any significant difference between the two methods of caries excavation. Conclusion: Although the results did not indicate marked difference in the pain perception, carious tissue removal using Brix 3000 gel can be used as an alternative to conventional drilling method as it removes only the carious dentine with less application of pressure. Key Words Caries Detector, Chemomechanical, Dental anxiety, Pain Perception, Papain, Tungsten Carbide.

Assessement of Pain Response during Caries Removal using Conventional Tungsten Carbide Bur and a Chemomechanical Caries Removal Agent (Brix Gel) : An In Vivo Study

Aim: The present study aimed to assess the pain response during caries removal using conventional tungsten carbide bur and a chemomechanical caries removal agent(CMCR) – Brix 3000 gel using Wong Baker Faces pain scale. Materials and methods: In this study twenty patients in the age group of 20 to 50 years with site 1 size 2 and 3(Mount and Hume’s classification) dentinal caries in the permanent maxillary and mandibular molars were randomly selected and distributed to 2 experimental groups. In Group A Tungsten carbide round burs was used while in Group B Brix 3000 gel was applied into the cavity for caries excavation. Dentin excavation was stopped until a hard dentin was detected with nonflexible blunt probe. Finally a caries detector dye is used to assess complete removal of infected dentin. Results: The scores obtained from the scale was analysed using Mann whitney U test which didn’t show any significant difference between the two methods of caries excavation. Conclusion: Although the results did not indicate marked difference in the pain perception, carious tissue removal using Brix 3000 gel can be used as an alternative to conventional drilling method as it removes only the carious dentine with less application of pressure. Key Words Caries Detector, Chemomechanical, Dental anxiety, Pain Perception, Papain, Tungsten Carbide.

Effect of different resin removal methods on enamel after metal and ceramic bracket debonding : An in vitro micro-computed tomography study.

The aim of this study was to conduct an in vitro evaluation of the effects of different adhesive debonding and polishing techniques performed after metal and ceramic bracket removal on enamel using micro-computed tomography (micro-CT). This study was performed on 42 extracted maxillary first premolars divided into 2main groups and 6subgroups as follows: metal (group1) or ceramic (group2) brackets were bonded to the teeth, then, after debonding, one of three different methods was used to remove the residual adhesive: tungsten carbide burs with pumice(A), fiber-reinforced composite burs and polishing paste(B), or Sof-Lex discs(C; 3M Dental, St Paul, MN, USA). The samples were evaluated by micro-CT before bracket bonding (T0) and after resin removal (T1). Demineralization area, demineralization depth, demineralization volume, mineral density, and mineral volume were measured. At T1, demineralization area was significantly larger in groups1A and2A compared to groups1B, 1C, 2B, and2C (P = 0.001). Group2A (ceramic bracket/tungsten carbide-pumice) had the highest demineralization volume (P = 0.001). When the groups were compared in terms of change from T0 to T1, groups1A and2A showed significantly larger changes in demineralization area compared to the other 4groups (P = 0.001). The increase in demineralization volume was larger in group2A compared to all other groups (P = 0.001). All resin removal methods damaged the enamel surface to varying degrees. Regardless of bracket type, the use of tungsten carbide and pumice should be avoided when cleaning the tooth surface after debonding. Use of composite burs and Sof-Lex discs in particular after the debonding of ceramic brackets will help minimize damage.

Chemical vapor deposition diamond dental burs for high speed air turbine handpieces

Abstract Background The objectives were, establishment of diamond coating using Chemical Vapor Deposition (CVD) on tungsten carbide burs and, assessment of diamond film adherence at 250,000 rpm after cavity preparations on teeth. Methods Hot Filament CVD (HFCVD) was used to deposit a thin diamond film on tungsten carbide burs using 1–1.5% methane in excess hydrogen at 1800–2200 °C and 2700 - 6700 Pa pressure. Consistent and repeated film deposition of Microcrystalline diamond (MCD) and Nano crystalline diamond (NCD) could be achieved. Raman spectrometry and scanning electron microscopy (SEM) were used to confirm diamond deposition. Adherence of the films was checked after cavity preparations on human teeth at speeds of ~250,000 rpm, and flank wear was determined using SEM. Results SEM images confirmed presence of microcrystalline and nanocrystalline forms. MCD had a 3–7 μm cubo-octahedral crystal formation. NCD was seen as 25–50 nm cuboidal facets in columnar formation. Raman spectrometry corroborated these findings. SEM of NCD showed no loss of diamond film or blunting of blades after three cavity preparations followed by a maximum loss of 33 μm after nine repeated cavity preparations. MCD showed partial loss of diamond film after third cavity with a maximum loss of 91 μm after nine repeated cavities. Conclusion Successful deposition of uniform diamond coating on tungsten carbide burs that remain adherent even at high rotational speeds was achieved and NCD coating adhered better compared to MCD. Practical implication The newly developed dental bur which combines the cutting action of bladed instruments and the hardness of diamond and provides a new area of clinical application.

Flexural Properties and Polished Surface Characteristics of a Structural Colored Resin Composite.

The aim of this study was to determine the flexural properties and surface characteristics of a structural colored resin composite after different finishing and polishing methods, in comparison to those of conventional resin composites. A structural color resin composite, Omnichroma (OM, Tokuyama Corp, Chiyoda City, Tokyo, Japan), and two comparison resin composites, Filtek Supreme Ultra (FS, 3M, St Paul, MN, USA) and Tetric EvoCeram (TE, Ivoclar Vivadent, Schaan, Liechtenstein), were used. The flexural properties of the resin composites were determined in accordance with the ISO 4049 specifications. For surface properties, 70 polymerized specimens of each resin composite were prepared and divided into seven groups of 10. Surface roughness (Sa), gloss (GU), and surface free energy (SFE) were investigated after the following finishing and polishing methods. Three groups of specimens were finished with a superfine-grit diamond bur (SFD), and three with a tungsten carbide bur (TCB). After finishing, one of the two remaining groups was polished with a one-step silicone point (CMP), and the other with an aluminum oxide flexible disk (SSD). A group ground with SiC 320-grit was set as a baseline. The average flexural strength ranged from 116.6 to 142.3 MPa in the following order with significant differences between each value: FS > TE > OM. The average E ranged from 6.8 to 13.2 GPa in the following order with significant differences between each value: FS > TE > OM. The average R ranged from 0.77 to 1.01 MJ/mm3 in the following order: OM > FS > TE. The Sa values of the OM groups polished with CMP and SSD were found to be significantly lower than those of the other resin composites, regardless of the finishing method. The GU values appeared to be dependent on the material and the finishing method used. The OM specimens polished with SSD showed significantly higher GU values than those polished with CMP. Most of the resin composites polished with SSD demonstrated significantly higher γS values compared to the other groups. Extremely strong negative correlations between Sa and GU in the combined data from the three resin composites and each resin composite and between Sa and γS in the OM specimens were observed; GU showed a strong positive correlation with γS in the same material. These findings indicate that both flexural and surface properties are material dependent. Furthermore, the different finishing and polishing methods used in this study were observed to affect the Sa, GU, and SFE of the resin composites.

Comparison of the enamel surface roughness before bonding and after debonding by diamond, tungsten carbide and fiber reinforced composite burs under AFM an in-vitro study

Introduction: The bonding of orthodontic attachments directly to etched enamel surface is an example of clinical application of a simplified procedure. With modifications of the acid etch technique and resin systems, the removal of the directly bonded attachments and finishing of the underlying enamel have become an acute clinical problem. Aims and Objectives: To evaluate the enamel surface roughness observed under atomic force microscope (AFM) in following methods: 1. Before bonding; 2. Removal of residual resin after debonding with 3 different burs. Fine diamond bur Tungsten carbide bur Fiber reinforced composite bur Materials and Methods: Sixty premolar teeth were divided into 3 equal groups and the buccal surface were subjected to AFM to obtain Ra, Rq, Rmax initial roughness values. The brackets were bonded with a light-cured adhesive and debonded with posterior debonding plier. Residual resin was removed with different burs in 3 groups respectively and subjected to final AFM measurements. Results of roughness were analysed with the use of repeated measurement analysis of variance and independent t-test respectively. Results: It was found out that parametric values were statistically insignificant with P value >0.001 in prebond condition & statistically significant after resin removal with P value Conclusion: Fiber reinforced composite bur created smoother surface after debonding when compared to diamond and tungsten carbide bur. Keyword: Fine diamond bur, Tungsten carbide bur, Fiber reinforced composite bur, Residual resin, AFM.

Temperature and time variations during apical resection

Objective The aim of this study was to investigate temperature and time variations during root-end resection. Material and methods Sixty human premolars were selected. The root canals were enlarged up to ProTaper X3 rotary instrument. A thermocouple was placed into the root canal 1 mm behind the resection line. The teeth were randomly divided into six groups according to the apical resection method: steel bur, tungsten carbide bur, Lindeman bur, diamond bur, laser and ultrasonic surgical piezo with a diamond tip. The root ends were resected 3 mm away from the root apex. The temperature of the root dentine during resection was recorded as maximum temperature, mean temperature and temperature change. The time required for apicectomy was recorded for each group. The Kruskal–Wallis method was used to analyse the differences between temperature changes during apical resections. The significance level was set at 5%. Results There was no significant difference between bur groups in terms of temperature increase. The maximum temperature in piezo surgery was significantly higher than the Lindeman, tungsten and steel burs (p < .001). In addition, the maximum temperature in laser surgery was higher than the Lindeman bur (p < .05). An increase in the temperature was mostly seen in piezo surgery and the least temperature change occurred in the Lindeman bur. Mean time stayed under 1 min in each group. Conclusions Although piezo caused the highest temperature increase, the measured temperature increase was within physiological limits in all tested techniques.

A base-line study of the wear of burs used for chairside milling of ceramic crowns of different hardness: effect on internal fit and surface roughness

INTRODUCTION: Wear of milling burs may affect the internal fit and surface roughness of the milled crown. AIM: To assess the wear of diamond and tungsten carbide (TC) burs from milling ceramic materials and the effect on internal fit and surface roughness. METHODS: Thirty crowns of each of the two materials were milled from the same standard preparation. Diamond burs were used for a feldspathic ceramic and TC burs for zirconia. Before and after the 10th, 20th and 30th milling, diamond particle loss was counted and cutting blade changes of the TC burs measured. Internal fit was measured using a silicone replica technique and surface roughness by 3D laser microscope. RESULTS: An average 26% loss of diamond particles occurred after 30 crowns, resulting in a 6% decrease in internal luting space and a 21% decrease in surface roughness. Wear of the TC burs resulted in a 13% decrease in the luting space, and a 16% increase in surface roughness. CONCLUSION: The wear of milling burs reduces the luting space, and the milling parameters must be adjusted to compensate for this. Surface roughness is affected by bur type: with diamond burs it decreased, and increased with TC burs.

Tooth color alteration after debonding in orthodontic patients with adhesive removal using composite bur or tungsten carbide bur: a single center, randomized controlled clinical trial

Introduction: The objective of this study was to determine whether recently developed fiber reinforced composite burs provided better results by comparing tooth discoloration after debonding of orthodontic brackets.Methods: A split-mouth, randomized controlled trial was carried out in one orthodontic office; including 23 patients with intact, vital and caries-free four upper incisors aged 12 to 30 years who completed their fixed orthodontic treatment. For each patient, upper central and lateral incisors on each side of the mouth were randomly selected to remove the adhesive with either a tungsten carbide bur (TC) (n = 46) or a fiber-reinforced composite bur (FC) (n=46). Color evaluation of each tooth was conducted at two time points: immediately after finishing and polishing procedure and two months afterwards. The primary outcome would be the amount of color change in each group during the post treatment phase. The participants, the person assessing the color change and the statistician were blinded to TC group assignment. Color changes in each group were analyzed with the Paired T-test. The color change corresponding to the resin removal method was also statistically analyzed with the Independent T-test at ?=0.05 as the level of significance.Results: 86 teeth, 43 in each group, were analyzed. The ?E value was 3.713±1.161, for teeth finished TC and 2.114±0.514 for teeth finished with FC (p&lt;0.01).Conclusion: adhesive removal with FC bur results in a more color-resistant tooth surface in comparison with tungsten carbide bur.

Effects of Orthodontic Adhesives on Dental Enamel Color Alteration Using Chemically Cured and Light-Cured Composites.

Objectives:The purpose of this investigation was to evaluate the color alteration of dental enamel following the use of light-cured and chemically cured composites for bonding of metal brackets.Materials and Methods:Sixty extracted human premolars divided into five groups (n=12) were included in this study. Metal brackets were bonded using chemically cured (System 1+ and Unite) and light-cured (Transbond XT and Grengloo) composites. The control group remained untreated. After 72 hours of immersion in a staining solution and 24 hours of photoaging, the brackets were debonded, and adhesive remnants were cleaned using a 12-blade tungsten carbide bur and polished with Sof-Lex discs. The color was assessed at the baseline and after cleaning procedures in accordance with the CIE L*a*b (lightness, red/green, blue/yellow) color system. Statistical analyses were performed using paired sample t-test and one-way analysis of variance (ANOVA).Results:The L*, a*, and b* parameters showed a significant increase in all adhesive groups (P<0.001). The experimental groups showed significant color changes (P<0.05), and the mean ΔE ranged from 2.46 to 3.15 units. No significant difference was found between the ΔE of the adhesive groups (P>0.05).Conclusion:The enamel color change is influenced by bonding and debonding procedures. Chemically cured and light-cured composites have similar effects on dental enamel color alterations.

Effects of polishing with paste containing surface pre-reacted glass-ionomer fillers on enamel remineralization after orthodontic bracket debonding.

Surface pre-reacted glass-ionomer (S-PRG) technology allows for the release of multiple ions. This study was performed to investigate the remineralization of etched enamel after removal of the bracket using a novel paste containing S-PRG filler. Surfaces of polished enamel were etched with phosphoric acid and then subdivided into two regions. Bracket bonding resin was thinly applied to one region. After 24-hr immersion in artificial saliva, the bonding resin on the enamel surfaces was removed by grinding with tungsten carbide bur at low-speed, followed by polishing with one of four different polishing systems: (a) nonfluoridated paste (NF); (b) fluoridated paste (F); (c) S-PRG filler-containing paste (S-PRG); or (d) nonfluoridated plus S-PRG filler-containing paste (NF + S-PRG) (n = 15). The polished specimens were then immersed in an artificial saliva solution for 7 days. Nanoindentation testing of enamel surfaces was performed and their mechanical properties were compared. Representative specimens were examined with scanning electron microscope. In all specimens, the mechanical properties of the enamel surfaces were markedly degraded by acid etching. However, the mechanical properties of both regions (etched and resin-infiltrated enamels) showed recovery after polishing and 7-day immersion. Polishing with NF + S-PRG paste led to significant recovery of mechanical properties compared to polishing with NF or S-PRG paste alone, and remineralization was equivalent to that seen with F paste. Porous etched enamel surfaces were filled with a remineralization layer after each polishing procedure and 7-day immersion in all polishing groups. Polishing using NF + S-PRG paste can facilitate enamel remineralization after bracket removal.

Effect of bur selection on machining damage mechanisms of polymer-infiltrated ceramic network material for CAD/CAM dental restorations

The surface and edge quality of polymer-infiltrated ceramic network material (PICN) in CAD/CAM milling and clinical adjusting is crucial to restorative successes. The paper reports on PICN responses to diamond and tungsten carbide machining with respect to machining forces and frictions, material removal mechanisms, surface quality and edge integrity. A force sensor together with a high-speed data acquisition system was used to measure machining forces. Scanning electron microscopy was applied to reveal bur wear and debris adhesion, and machining-induced surface and edge chipping damage. The results show two distinct removal mechanisms of PICN in which tungsten carbide machining was dominated by friction-induced ductile deformation and normal pressing of the material while diamond machining was controlled by the penetration-induced fracture. These mechanisms were reflected by significantly higher tangential (or frictional) forces and coefficients of friction in tungsten carbide machining than in diamond machining (p < 0.05). The ductile removal in tungsten carbide machining yielded more smoother areas and much less edge chipping damage in PICN. The fracture mode in diamond machining broke the ceramic and polymer networks in PICN, resulting in more fractured and pulverized areas with 6–7 times higher roughness and much more severe edge chipping damage in PICN. Thus, for better surface and edge quality, tungsten carbide burs are superior than diamond burs and recommended for surface finishing and adjusting while diamond burs are the good choice for rapid material removal in both CAD/CAM milling and clinical adjusting. However, high material removal rate-induced high tangential (or frictional) forces in tungsten carbide machining limited the bur usage for rapid oral adjusting. This paper also compared the influence of PICN microstructure on the machinability with CAD/CAM glass ceramics.

In vitro evaluation of enamel surface roughness and morphology after orthodontic debonding: Traditional cleanup systems versus polymer bur

The primary aim of this randomized in vitro study was to compare the effectiveness of carbide, fibreglass and polymer burs on resinous remnant removal after bracket debonding, by the evaluation of enamel surface roughness and morphology. The secondary objective was to compare the time dispended on the procedures. The buccal surfaces of 28 bovine incisors were analysed by a profilometer to initial roughness measurement (Ra-T1). Brackets were bonded with a light-cured resin and debonded with a debonding plier. The samples were randomly divided into four groups, according to the bur used (n=7): A-Tungsten carbide; B-Fibreglass; C-Polymer; D-Polymer with 75% ethanol pre-treatment. The second roughness measurements were made after resin removal (Ra-T2). Time for removal procedures was also recorded. The third measurements were made after polishing (Ra-T3). Scanning Electronic Microscopy was performed in two samples of each group: after resin removal and after polishing. Results of roughness and time measurements were statically analysed by analysis of variance with post-hoc Bonferroni. After polishing, tungsten carbide (P=0.1555) and fibreglass burs provided final surface roughness statistically similar to the baseline condition (P=1.0000). Yet, polymer burs, associated (P<0.0001) or not to alcohol (P<0.0001), provided surface roughness significantly higher when compared to baseline values. Polymer burs were more time-consuming on resinous remnant removal than tungsten carbide and fibreglass burs (P<0.05). Polymer burs were less effective and more time-consuming to remove the remaining resin than tungsten carbide and fibreglass burs. The polishing step created smoother surfaces regardless of the burs used for resin removal.

Effects of toothbrushing on surface characteristics of microhybrid and nanofilled resin composites following different finishing and polishing procedures

ObjectivesTo evaluate the effects of simulated tooth brushing (STB) on the surface roughness of microhybrid and nanofilled resin composites following different finishing and polishing procedures. Materials and methodsNinety cylindrical-shaped specimens of Filtek Supreme XT (a universal nano resin composite) and Filtek Z250 (a universal microhybrid resin composite) were prepared. The specimens were allocated at random into 9 paired groups each of 10 specimens. The finishing and polishing systems included were Tungsten Carbide bur (TC); Diamond bur (Db); Sof-Lex discs (S); PoGo discs (PG); TC + S; Db + S; TC + PG; Db + PG. Polymerisation against a Mylar strip without finishing and polishing acted as the control. Surface roughness was measured using a 3D non-contact optical profilometer and surface morphology was examined by scanning electron microscopy. Specimens were subjected to the equivalent of four years STB and surface roughness was measured again. ResultsMylar formed surfaces were the smoothest for both composites before and after STB. Finishing with the diamond finishing bur caused significantly greater surface irregularity (p < 0.0001) before and after STB compared to the tungsten carbide bur. The surface treatment with Db + PG resulted in significantly greater surface roughness following STB than all other regimes of finishing and polishing (p < 0.01). ConclusionWhere indicated clinically, finishing is better conducted using a tungsten carbide bur rather than a diamond finishing bur. The combination of tungsten carbide bur/Enhance PoGo and tungsten carbide bur/Sof-Lex surface protocols produced a similarly smooth finish for both composites. The composite surfaces in all groups increased in surface irregularity following STB. Clinical significanceWhilst finishing using a tungsten carbide finishing bur followed by either the Sof-Lex or PoGo polishing system may be found to result in a smooth surface finish, all the surfaces investigated increased in surface roughness following toothbrushing.

Comparison of the Enamel Surface Roughness from Different Polishing Methods: Scanning Electron Microscopy and Atomic Force Microscopy Investigation.

Objective This study aimed to compare the enamel surface roughness created by four polishing methods after debonding, by using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Materials and Methods Four experimental polishing groups (Sof-Lex disc, SD; sandblaster, SB; tungsten carbide bur, TB; and white stone bur, WB) and one control group were selected from 100 premolars ( n = 20/group). The experimental teeth were bonded with a bracket, thermocycled, and debonded. Residual adhesive was removed by either of the respective methods. Pre and postdebonding root mean square (Rq) values were obtained from AFM evaluations. All specimens were examined and evaluated with SEM using a modified enamel surface index (modified ESI). Statistical Analysis Differences among the polishing methods were compared with analysis of variance and Fisher’s least significant difference test at p < 0.05. Results Both microscopic evaluations indicated that the surface with the greatest roughness herein belonged to the SD group, followed by that for SB, TB, and WB groups. AFM measurements indicated a maximum postdebonding Rq herein for the WB group and a significantly greater surface roughness for the TB and WB groups than for the SD and SB groups. Among the experimental groups, SEM followed by modified ESI evaluations revealed similar data to those obtained with AFM. Significant differences were seen among all paired groups, except for that between the SB and TB groups. Conclusion Within the limitations of this study, all four polishing methods were concluded to be clinically acceptable for removing residual orthodontic adhesives.

The adverse effects of tungsten carbide grinding on the strength of dental zirconia

ObjectivesThis study investigated the effects of tungsten-carbide grinding on the surface characteristics and mechanical strength of dental 3 mol% yttria-stabilized zirconia (3Y-TZP). MethodsTwo types of tungsten-carbide burs (TC), 6-blade (TC1) and 8-blade (TC2) were used to grind 3Y-TZP, in a dental air-turbine handpiece with water-cooling and were also subjected to air-particle abrasion (APA): TC1 + APA and TC2 + APA; and rubber polishing (RP): TC1 + RP and TC2 + RP; one group received only rubber-polishing RP. The control group received no treatment. Surface characterization was examined by surface roughness (Ra) and atomic force microscopy. Specimens were also observed with scanning electron microscopy (SEM) and X-ray-diffraction (XRD) for microstructure and crystalline phases. A piston-on-three-balls biaxial-flexural strength (BFS) test was performed with 15 samples-per-group and the broken specimen were observed under SEM to investigate the fracture origin pattern. One-way ANOVA, Kruskal–Wallis test and Weibull analysis were performed at α = 0.05. ResultsGroups TC1 and TC2 had the lowest mean BFS (p < 0.05) with up to 74 % reduction in strength. APA and RP both significantly increased the mean BFS after tungsten-carbide grinding but was still less than the control (p < 0.05). Compared to the control, the mean BFS was significantly reduced for all groups except for the RP group (p < 0.05). APA and rubber-polishing following TC2 grinding had significant higher mean BFS than those following TC1 grinding respectively (p < 0.05). SEM revealed distinct micro-cracks after tungsten-carbide grinding. SignificanceTungsten-carbide burs (6- and 8-blade) are not recommended for zirconia grinding due to the significant reduction of biaxial-flexural strength and observed micro-structural surface and subsurface damage.

Evaluation of enamel surface after bracket debonding and adhesive removal with six different methods

Introduction/Objective. After an orthodontic brackets debonding procedure it is necessary to remove any residual adhesive from the tooth surface, as this is a common cause of enamel damage. The aim of this study is to evaluate the enamel surface after the application of six different methods of adhesive removal following brackets debonding, as well as to compare the duration of these procedures. Methods. For the purpose of this study, 245 human premolars were extracted as part of the orthodontic treatment. Metal brackets were bonded to 210 human premolars with the Aspire adhesive system. After the debonding of brackets, the samples were divided into six groups according to the adhesive removal method applied: tapered fissure tungsten carbide bur, round tungsten carbide bur, composite bur, abrasive disc, adhesive removing pliers, and ultrasonic scaler. Out of 245 premolars, 35 served as a control group. The duration of adhesive removal was recorded. Enamel damages were estimated according to the enamel surface index on the scanning electron microscopy images. Results. Maximum preservation of the enamel surface was accomplished by using a composite bur (1.08). The application of abrasive disc was significantly less time-consuming in comparison to the application of a composite bur (p &lt; 0.01) and an ultrasonic scaler (p &lt; 0.01). Conclusion. The most harmful for the enamel surface was the use of an ultrasonic scaler as well as a round tungsten carbide bur. Adhesive removal done by an abrasive disc thus proved one of the least damaging and the least time-consuming methods.

Evaluation and Comparison of Caries Excavation Efficacy of Three Different Burs: A Micro-computed Tomographic-assisted Study.

ABSTRACTAims and Objectives:The aim of this study was to evaluate the effectiveness of three different caries excavation methods using micro-computed tomography (micro-CT).Materials and Methods:Fifteen freshly extracted human molar teeth with occlusal dentinal caries were selected. The teeth were sectioned longitudinally into two halves and were randomly divided into three groups (n = 10) depending on the caries removal technique: Group 1: tungsten carbide (TC) bur, Group 2: cerabur (CB), and Group 3: Excavus (EX) tipEX). A preoperative micro-CT scan of all the samples was taken. The caries excavation procedures were carried out followed by postoperative micro-CT scan. The preoperative and postoperative scans of each tooth were analyzed for caries removal effectiveness (CRE), mineral density (MD), and minimal invasiveness potential (MIP) using Avizo 9.4 software (Thermo Fisher Scientific, Germany). Statistical analysis was conducted by applying three-way analysis of variance and independent sample t-test using the Statistical Package for the Social Sciences software, version 20.0 (IBM Corporation, USA).Results:Among the three groups, the TC group had the smallest RC/IC (residual caries/initial caries) ratio, highest mean MD at the cavity floor, and highest MIP. The EX group significantly had the highest RC/IC, lowest mean MD, and lowest MIP. Both the CRE and MIP parameters of CB group were acceptable (RC/IC = 0.08, mean MD = 1.09g/cm3, and MIP = 1.09).Conclusion:As compared with the three excavation methods, CBs can be considered as an alternative to TC burs because of its MIP and complete removal of infected carious dentin.