Diamond Bur Research Articles

Effect of various porcelain surface treatment methods on shear bond strength of orthodontic adhesive

Objective: to evaluate the effect of different treatment methods of porcelain surfaces before bonding on the shear bond strength of orthodontic adhesive. Material and methods: This study was conducted on a sample of sixty feldspathic porcelain cylinders stored in artificial saliva for a week. The sample was divided into five equal groups twelve each according to the applied surface treatment, Gp1 diamond bur roughening, and Gp2 etching 37% phosphoric acid GP3 Laser etching Gp4 9% hydrofluoric acid etching Gp5 sandblasting 50 micron aluminum oxide particles. Randomly one specimen from each group was scanned by electron microscope while the other specimens were bonded to metal brackets and stored in artificial saliva for one week then mounted in acrylic blocks to allow measuring the shear bond strength using Instron universal testing machine. Results: Diamond bur group showed significant difference with all other groups. There is significant difference between phosphoric acid and laser on one hand and sand blasting and hydrofluoric on the other hand. But for both phosphoric acid and laser groups there is no significant difference and for both sand blasting and hydrofluoric acid groups there is no significant difference. Conclusion: The diamond bur group showed the highest bond strength, while phosphoric acid showed the least one.

Evaluation of three methods of surface treatment for bonding orthodontic metal brackets to resin composite in vitro

Objective: The aim of this study is to compare shear bond strength of orthodontic stainless steel brackets to resin composite surfaces In vitro using three different methods of surface treatment. Materials and methods: 60 composite resin discs, 6 mm in diameter and 2 mm in height, were prepared and aged by immersion in water for 4 weeks. After ageing, the specimens were randomly assigned to one of the following groups: (1) Control with no surface treatment, (2) 99 per cent Acetone, (3) methyl methacrylate monomer, (4) Diamond bur. The metal brackets were bonded to composite surfaces by means of an orthodontic adhesive. All specimens were stored in water for 1 week. Shear Bond Strength values were tested using a universal testing machine at a crosshead speed of 1 mm/minute, the brackets bases and corresponding RC discs were examined under stereomicroscope at 10X magnification for adhesive remnant evaluation. Shear bond strength values were analyzed using 1-way analysis of variance (ANOVA)), Adhesive remnant index scores were analysed using Chi-square test using Monte Carlo correction. Significance of the obtained results was judged at the 5% level (P ≤ 0.05). Results: The results of 1-way ANOVA for SBS means showed no statistical significant difference among the 4 groups (P = 0.564). The result of Chi-square test for ARI scores between the four groups showed a statistically significant difference (MCp = 0.039). Chi square comparisons of ARI scores showed statistically significant difference only between group 1 (control) with groups 3 (P1= 0.003) and group 4 (P1= 0.046)

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.

EFFECT OF DIFFERENT DENTIN TREATMENT PROTOCOLS ON SURFACE ROUGHNESS AND COMPOSITE BONDING

Introduction: With advances in technology, other options besides the traditional cavity preparation with diamond and carbide burs have emerged; among them are laser and sono-abrasive systems. Objectives: The aim of this study was to compare in vitro the effect of (Er:YAG) laser with different radiation distances, sono-abrasion and rotary cutting on the surface roughness of dentin and the shear bond strength of resin composite to dentin using self-etching adhesive system. Materials and methods: 50 extracted human molars were randomly divided into 5 groups (n=10) received the following treatments. Group 1: carbide bur, Group 2: diamond bur, Group 3: sono-abrasion, Group 4: contact Er:YAG laser, Group 5: non-contact Er:YAG laser. Average surface roughness (Ra) was determined with a profilometer. Specimens in all groups were treated with self-etching adhesive system and composite build ups were done with Filtek Z-250. Bonding of resin composites to the dentine specimens was tested in shear mode. For morphological analysis; two extra teeth from each group were examined using a scanning electron microscope (SEM). Results:The shear bond strength of composite to the laser irradiated dentine (contact and non-contact) ranged from 6.64 ± 5.24 MPa and 6.29 ± 2.08 MPa respectively, and were significantly lower than the bond strength seen in other groups. However, the surface roughness of the laser irradiated dentine was significantly higher than that of the sono-abraded dentine and bur-cut dentine. SEM revealed that, the dentine surfaces irradiated by laser showed a scaly and rugged appearance and open dentinal tubules without smear layer production. Conclusions: It was concluded that Er:YAG laser treatment reduced shear bond strength of resin composite to dentin in comparison with conventional treatment with high speed rotary and treatment with sono-abrasion. Different Er:YAG laser distance irradiations did not influence the shear bond strength of composite to dentin.

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.

Evaluation of Changes in Temperature of Zirconia Frameworks During Grinding Under Different Chair-Side Conditions: An In Vitro Study

Aim: To evaluate the changes in the temperature of zirconia during grinding under different clinical conditions. Materials and Methods: A total of 60 zirconia framework specimens were fabricated and divided into groups of 10 specimens each. Two different handpieces, namely, a high-speed handpiece (HSH) and a low-speed handpiece (LSH), were used for grinding with and without water cooling. Fine- and coarse-grit diamond burrs were used with the HSH, separately. The following six groups were created: (a) HSH fine-grit with water cooling, (b) HSH coarse grit with water cooling, (c) HSH fine grit without water cooling, (d) HSH coarse grit without water cooling, (e) LSH with water cooling, and (f) LSH without water cooling. Each zirconia framework was ground until 1 mm3 of the material was removed. Temperature values corresponding to the grinding techniques were compared and statistically analyzed. One-way analysis of variance was used to compare the group parameters, while the Tukey honest significant difference test was used to detect significant differences between the groups. The significance level was set at P &lt;.05. Results: The highest mean temperature was measured in the case of grinding with the LSH without water cooling (54.7 °C ± 11.6 °C), while the lowest mean temperature was observed in the case of grinding with the HSH using the coarse-grit diamond rotary instrument under water cooling (22.6 °C ± 0.6 °C). Conclusions: The grinding of zirconia must be performed with an HSH under water cooling. Further, when water cooling is used, neither the type of handpiece nor the grain type of the rotary instrument used as it has a significant effect on the temperature.

Morphological surface analysis and tensile bond strength of the immediate dentin sealing submitted to different temporary cement removal treatments

The aim of this study was to evaluate the morphological surface and the microtensile bond strength (μTBS) of the immediate dentin sealing (IDS) submitted to four different methods for removing temporary cement. Molar teeth received IDS with adhesive system (Adper Scotchbond Multipurpose, 3 M ESPE). Temporary restorations were made with eugenol-free temporary cement (RelyX Temp NE, 3 M ESPE). After the storage (7 days; 37 °C), the samples were submitted to four methods for removing temporary cement: periodontal curette (PC); sodium bicarbonate sandblasting (SB); aluminum oxide sandblasting (AO); and abrasion with diamond bur (DB). The control group (C) received no treatment. The morphological surface analysis (n = 2) and IDS thickness (n = 3) were analyzed using scanning electron microscopy (SEM). Resin composite blocks (Filtek Z250, 3 M ESPE) were produced and cut into sticks (~1 mm2) for μTBS (n = 9). Fracture patterns were analyzed on stereomicroscope and classified as adhesive, mixed, cohesive-dentin or cohesive-resin. Data were submitted to Shapiro-Wilk test and one-way ANOVA followed by Tukey's post hoc test (α = 0.05). PC and SB groups showed the lowest and the highest μTBS values, respectively (ρ < 0.05). The adhesive failure pattern was more frequently observed in all groups. All methods for removing temporary cement promoted morphological surface changes. SB had the best surface morphology and temporary cement removal. IDS thickness showed no significant difference for all groups. The SB method promoted the highest μTBS, removing the temporary cement without jeopardizing the IDS thickness.

Influence of zirconia surface treatments of a bilayer restorative assembly on the fatigue performance.

This study evaluated the influence of different surface treatments of zirconia used to enhance bonding with veneering porcelain, and thermocycling on the resistance to porcelain cracking and delamination during fatigue test. Bilayer ceramic discs were made from zirconia blocks (IPS e.max Zircad MO, Ivoclar Vivadent - 0.7 mm thickness) and randomized into 8 groups (n= 15) according to two factors: 'zirconia surface treatment' (Control; Grinding - diamond bur; Air-abrasion - aluminum oxide particles; and Liner - application of a ceramic liner [IPS e.max Zirliner, Ivoclar Vivadent]); and 'thermocycling' (presence - 12,000 thermal cycles; 5-55ºC; or absence). The discs were veneered with porcelain (IPS e.max Ceram, Ivoclar Vivadent - 0.7 mm; totaling 1.4 mm thickness) according to ISO 6872:2015 for biaxial flexure strength testing. Fatigue tests (step-stress approach; 20 to 100 MPa; step of 10 MPa; 10,000 cycles per step; 10 Hz frequency) were run, followed by the data analysis (Kaplan-Meier and Mantel-Cox post-hoc tests). Analysis of roughness, topography, crystallographic phase arranges and fractography were also executed. The surface treatment and thermocycling did not influence the porcelain crack nor delamination resistance. When only comparing the surface treatments for crack resistance outcome, the liner application depicted the worst fatigue performance in comparison to grinding and air-abrasion, while all groups were similar for delamination. Neither the surface treatment of the zirconia nor the thermocycling influences the porcelain crack resistance or the resistance to delamination of the bilayer porcelain-veneered zirconia specimens.

Tensile bond strength of acrylic and composite denture teeth to milled CAD/CAM resins

Objective: was to evaluate effect of different surface treatment on tensile bond strength of two different types of artificial teeth to CAD/CAM denture base. Materials and Methods: 160 specimens were fabricated and divided into two main groups according to the denture base material. Group (A) for conventional denture base (HCAR denture base) and Group (B) for CAD/CAM denture base. According to the artificial teeth each group of denture base was subdivided into two subgroups, subgroup (I) for conventional acrylic denture teeth and subgroup (II) for composite resin denture teeth. According to the surface treatment each subgroup of artificial teeth were subdivided into four subgroups as following: Subgroup 1: no surface treatment (control group). Subgroup 2: sandblasting with 250 micron alumina particles. Subgroup 3: roughening with diamond bur. Subgroup 4: specimens were treated by dichloromethane. Results: The results showed that Pre-polymerized CADCAM acrylic resin denture bases specimens exhibited non-significant lower bond strength than HCAR denture base specimens (p>0.05), acrylic resin denture teeth demonstrated higher bond strength to denture bases than composite resin denture teeth (p≤0.05). Conclusion: the Pre-polymerized CADCAM acrylic resin denture bases specimens exhibited non-significant lower bond strength than HCAR denture base specimens, and acrylic resin denture teeth demonstrated higher bond strength to denture bases than composite resin denture teeth, the bond strength of the denture teeth treated with both dichloromethane and sandblasting was improved while the bond strength of the denture teeth treated by roughening with diamond bur was decreased.

The influence of different surface treatment protocols and bonding agents on the repair microtensile bond strength of six-month’ aged composite: An in vitro study

Objective: to compare the effect of three surface treatment protocols and two intermediate agents on repairing aged composite, regarding microtensile bond strength (µTBS) and mode of fracture, at two time intervals. Material and methods: Six-month aged microhybrid composite blocks, were randomly distributed into three groups, subjected to; Fine, Super Fine grit diamond burs or Erbium- Yag Laser surface treatment. Each block had both One Coat bond SL (Bond) and Brilliant Flow flowable composite (Flow) intermediate agents, alongside. Blocks were incrementally repaired using nanohybrid composite, cut into beams, then randomly subjected either immediately (IM) to µTBS test or after thermocycling (TC) for 5000 cycle. Mode of failure was determined using stereomicroscope. Data were analyzed through three-way ANOVA followed by pairwise comparison with Bonferroni correction. Kruskal Wallis test compared groups for failure mode analysis (?=0.05)Results: Super Fine grit showed the highest mean µTBS compared to control for both intermediate agents, IM and after TC at P&lt;0.05. No difference between Fine grit and Laser application for all groups (P&gt;0.05). IM, Bond showed the highest µTBS compared to TC, Flow for all tested groups. Beams roughened with Fine and Super Fine burs showed significantly lower adhesive failures than those roughened with Laser. Flow suffers significantly higher adhesive failure than those with Bond. For TC tested groups; beams with Super Fine bur and Bond showed significantly lower adhesive failure at P=0.029.Conclusions: Super Fine grit and Bond provide the highest µTBS and the least adhesive failure; moreover TC resulted in significant decrease in µTBS.

Step-stress vs. staircase fatigue tests to evaluate the effect of intaglio adjustment on the fatigue behavior of simplified lithium disilicate glass-ceramic restorations

The aim of the study was to compare the outcomes for the fatigue mechanical behavior of bonded simplified lithium disilicate restorations, with and without an internal adjustment by grinding with diamond bur in running two fatigue tests: Staircase and Step-stress testing approaches. Ceramic discs (IPS e.max CAD) were prepared (Ø = 10 mm; thickness = 1.0 mm), submitted to an in-lab simulation of CAD/CAM milling (#60 SiC paper) and allocated into 2 groups according to the internal adjustment by grinding of the cementation surface: no adjustment (CTRL); or grinding with a coarse diamond bur (GR). Adhesive cementation (Multilink N) was performed onto epoxy resin discs (Ø = 10 mm; thickness = 2 mm) after ceramic/epoxy surface treatments. The cemented assemblies of each group were randomly assigned into 2 subgroups considering two fatigue tests (n = 15): Staircase – SC (250,000 cycles; 20 Hz), or Step-stress – SS (10,000 cycles per step; 20 Hz). Roughness, topographic and fractographic analyses were additionally performed. Statistical analyses were carried out using the Dixon and Mood method for Staircase data, and Kaplan–Meier and Mantel-Cox (log-rank) tests for Step-stress data. Ceramic restorations having its intaglio surface ground (GR group: SC test = 306.67 N; SS test = 646.67 N) presented lower fatigue failure load (FFL) values than the CTRL group (SC test = 879.28 N; SS test = 1090.00 N), regardless of the fatigue testing approach. The percentage of mean FFL decrease comparing the CTRL to GR group was higher for SC (65.1%) than the SS (40.7%) approach. However, a different total number of cycles was applied for each method. Both fatigue tests were able to detect the negative effect of internal adjustments of lithium disilicate glass-ceramic simplified restorations on their mechanical behavior. Therefore, both methods can be applied for similar evaluations (fatigue testing for ceramic restorations).

Debonding of Orthodontic Ceramic brackets: A comprehensive review of the literature – Part 1

The purpose of this 2 part literature review is to evaluate various debonding techniques for orthodontic ceramic bracket removal and their clinical applications.In part 1, and studies on mechanical and ultrasonic debonding techniques have been reviewed. Mechanical debonding (use of diamond burs, special pliers) is most widely applicable in clinical practice. Use of recommended pliers by manufacturers is key to minimize bracket failure modes as these pliers are designed specifically for the brackets. Ultrasonic debonding is advantageous in minimizing bracket failure but requires greater time to debond ceramic brackets than mechanical debonding and it may be uncomfortable to the patient due to longer duration of use. Studies on electrothermal and Laser debonding have been reviewed in part 2 of the literature review.

Factors Affecting the Wear Behavior of Monolithic Zirconia and the Antagonists: Literature Review

Background:The use of zirconia-based ceramics to produce monolithic restorations has increased due to improvements in the optical properties of the materials. Traditionally, zirconiabased ceramics were veneered with porcelain or glass-ceramic and were not directly exposed to the oral environment. Therefore, there are several doubts regarding the wear of the monolithic zirconia restoration and their antagonists. Additionally, different surface treatments are recommended to promote a smooth surface, including glaze and several polishing protocols. To support the correct clinical application, it is important to understand the advantages and limitations of each surface treatment.Objective:The aim of this short literature review is to investigate the factors that may affect the wear of monolithic zirconia restorations in service and their antagonists.Methods:Pubmed/Medline database was accessed to review the literature from a 10-year period using the keywords: zirconia, monolithic, prosthesis, wear. Both clinical and in vitro studies were included in the review.Results:Studies investigated the effect of several surface treatments, including grinding with diamond- burs, polishing and glazing, on the surface roughness, phase transformation and wear capacity of monolithic zirconia. The wear behavior of monolithic zirconia was frequently compared to the wear behavior of other ceramics, such as feldspathic porcelain, lithium disilicate-based glassceramic and leucite-reinforced glass-ceramic. Human tooth, ceramics and resin composites were used as antagonist in the investigations. Only short-term clinical studies are available (up to 2 years).Conclusion:Literature findings suggest that zirconia monolithic restorations are wear resistant and unlikely to cause excessive wear to the antagonist, especially when compared to feldspathic porcelain and glass-ceramics. Monolithic zirconia should be polished rather than glazed. Yet, none of the polishing systems studied was able to completely restore the initial surface conditions of zirconia after being adjusted with burs. More clinical evidence of the antagonist tooth wear potential of monolithic zirconia is needed.

Repair Bond Strength and Leakage of Non-Aged and Aged Bulk-fill Composite.

This study evaluated repair protocols of a non-aged and aged bulk-fill composite in terms of bond strength and leakage. Ninety-six bulk-fill resin specimens were constructed; half were submitted to thermocycling. Specimens were divided into six groups (n = 16) according to the repair treatments: CG: no repair (control group); Ad: adhesive; DbAd: abrasion with diamond bur + adhesive; SbAd: sandblasting + adhesive; DbSiAd: abrasion with diamond bur + silane + adhesive; and SbSiAd: sandblasting + silane + adhesive. Resin blocks were bonded to the treated surfaces to simulate repair, and the specimens were submitted to microtensile bond strength testing. The failure area was evaluated under a stereomicroscope (40X magnification), and leakage after specimen immersion in silver nitrate solution for 24 h was evaluated under a microscope (200X magnification). Three-way ANOVA (surface treatment, chemical agent, aging) and Tukey's test were performed. Ad and DbAd groups showed the lowest bond strengths, while Ad was the only group negatively influenced by aging. The other groups were statistically similar to the CG in both conditions. All groups exhibited leakage, but groups without silane presented a greater percentage of leakage, mainly when diamond burs were used. Thermocycling did not influence leakage, nor did surface treatment in groups with silane. For composite repair, the use of silane is recommended, mainly when diamond burs are used as a mechanical surface treatment.

Tribological behaviour of dental diamond burs after different exploitation times

ABSTRACT The purpose of this investigation was to compare the wear of diamond-coated dental burs applied on specimens made of four different materials used in dental prosthetics. Cutting was performed using a dental air turbine handpiece. Identical coarse-grit diamond burs were mounted on the handpiece and subjected to a 1.5 N load. Dental burs were divided into four groups according to the type of material on which the cutting was performed (leucite glass ceramic, zirconium oxide, CoCrMo alloy and polymethylmethacrylate). The wear of the dental burs was determined as the amount of their weight loss during different time intervals. After each time interval, all the burs were cleaned, weighed, and analysed by an SEM. The greatest bur weight loss was measured in the group of dental burs used to perform cutting on the ZrO2 specimen, while the smallest weight loss was measured in the group used on the polymethylmethacrylate specimen.

Shear Bond Strength of Different Adhesive Systems in Amalgam Repair

The purpose was to evaluate the effect of different adhesive systems on shear-bond-strength between amalgam and resin composite. 48 amalgam specimens were condensed into plastic tubes (4 mm diameter × 5 mm height). The specimens were kept in incubator for 24 h at 37°C, aged by thermal cycling 1000 times between 5–55°C. The specimens’ surfaces were finished with coarse diamond burs and randomly divided into 4 groups (n = 12) with respect to different surface conditioning methods: etchant+universal adhesive (All-Bond Universal, Bisco), universal adhesive, alloy primer (Z-Prime, Bisco)+universal adhesive, self-adhesive resin cement (BisCem, Bisco). The old amalgam specimens were placed into plastic tubes (4 mm diameter × 8 mm height) and all adhesive systems were used according to manufacturer’s instructions. Resin composite (Charisma Classic, Haraeus Kulzer) was placed and polymerized 20 s. The samples were incubated in distilled water at 37°C for 24 h prior to the shear-bond-strength test. The shear-bond-strength test was accomplished using a universal testing device. Statistical analyzes were made with One-way ANOVA and Tukey HSD tests. There was no significant difference between self-adhesive resin cement and alloy primer applied groups but showed better bond strength values than self-etch and etch&rinse adhesive applied groups. The application of self-adhesive resin cement and alloy primer+universal adhesive in amalgam repair exhibited successful outcomes.

Effect of Low Level Laser Therapy on Postoperative Pain After Single Visit Endodontic Treatment: A Placebo-Controlled Randomized Clinical Trial

Objective: To evaluate the effect of low-level laser therapy (LLLT) on postoperative pain after root canal treatment. Methods: This study was designed as a randomized, single-blinded, placebo-controlled trial of 2 groups. Forty-two patients were included in the study according to the inclusion and exclusion criteria. The treatment procedures were performed by one operator. After local anesthesia and rubber dam isolation, access cavity preparation was performed by diamond burs with high-speed handpieces under the water cooling. Instrumentation of procedures was performed by Reciproc R50 files. Irrigation protocol was completed, canals were dried, filled with gutta-percha cones and AH Plus sealer. After chemo- mechanical instrumentation and root canal filling procedures, LLLT were applied for 60 seconds per tooth using Nd-YAG laser ( λ=1064 nm, 100 mJ, 10 Hz, 1-W) The same procedures as in the laser group were performed, been completed but the laser was not activated in this group. These patients were assigned as a placebo group. Postoperative pain was measured and documented via the Visual Analogue Scale. Results: The independent sample t-test was performed after normality and homogeneity tests. No statistically significant differences were detected between the groups in terms of demographic data (age and tooth number) (P &amp;gt; .05). No statistically significant difference was found between the groups at the 4th, 8th, 48th, and 72nd hours (p&amp;gt;.05). However, there was a statistically significant difference between groups at the 12th (p=.030) and 24th hours (p=.041). Conclusion: LLLT can decrease postoperative pain after root canal treatment of single-rooted teeth.

Effect of Tribochemical Coating on Composite Repair Strength.

Tribochemical treatment of existing composite surfaces is highly effective for composite repair. When repairing an old composite restoration, the clinician should try to use the same composite originally used for the restoration. If the information about the original restoration is not known, a composite with strong mechanical properties should be used for the repair restoration. This study evaluated the effect of tribochemical coating on composite-to-composite repair interfacial fracture toughness (iFT). Sixty beam-shaped specimens (21×4×3 ± 0.2 mm) were prepared with a nanofill composite (Filtek Supreme Ultra [FSU]) and a nanohybrid composite (Clearfil Majesty ES-2 [CME]) and aged for 50,000 thermocycles (5°C-55°C, 20-second dwell time) and then sectioned in half. The resulting 120 hemispecimens (60 for each composite) were randomly assigned to different repair methods (n=10): universal adhesive (Clearfil Universal Bond Quick [CUB]), sand-blasting followed by CUB, or tribochemical coating (CoJet, CoJet sand, Espe-Sil, and Visio-Bond). The repair surface was prepared with a diamond bur (Midwest #471271), rinsed, and dried. Each aged composite brand (FSU, CME) was repaired with either the same composite or the opposite composite. All adhesives and composites were light cured with a high-irradiance LED curing light (Elipar DeepCure-S). After postrepair storage in 100% humidity and at 37°C for 24 hours, iFT was measured as KIc (MPa m½). Data were analyzed for statistical significance using two-way analysis of variance (ANOVA) and the Tukey honest significant difference post hoc test (α=0.05). Regardless of the substrate composite, ANOVA showed significant differences for surface treatment (p<0.0001) and repair composite (p<0.0001). Mean iFT values (SD) ranged from 0.91 (0.10) MPa·m½ to 2.68 (0.12) MPa·m½. Repairs made with FSU after CoJet resulted in significantly higher iFT (FSU: 2.68 MPa·m½; CME: 2.21 MPa·m½) when compared to the other experimental groups. The repair iFT was higher with CoJet treatment and when the nanofill composite FSU was used as the repair composite.

Conduta de graduandos em Odontologia em relação ao uso de pontas diamantadas nas práticas clínicas e seu estado de conservação

O objetivo do estudo foi conhecer a conduta dos graduandos de Odontologia em relação ao uso de pontas diamantadas e suas condições de conservação. Foram aplicados questionários aos 98 acadêmicos regularmente matriculados nas disciplinas clínicas do curso (7° ao 10° períodos), a fim de avaliar as características sobre uso, armazenamento, esterilização e condições das pontas diamantadas utilizadas na prática clínica. Pontas diamantadas foram recolhidas para análise em microscópio eletrônico de varredura (MEV), onde foram observados aspectos relativos ao seu estado de conservação. Foram realizados cálculos de frequência para análise estatística. Observou-se que 44,9% dos estudantes utilizavam empacotamento individual para proceder a esterilização; 27,6% usavam o instrumento por um período de 1 a 2 anos até o seu descarte e 87,8% usavam o mesmo instrumento de 1 a 2 vezes por semana; 66,3% afirmaram que não utilizavam nas clínicas os mesmos instrumentos empregados em atividades laboratoriais; 73,5% empregavam água, sabão e escova para lavagem e 45,9% utilizavam luva de procedimento, gorro, máscara e jaleco; 51% empregavam seringa de ar para secagem; 39,8% não faziam desinfecção; 100% utilizavam autoclave; 87,8% relataram boas condições de uso; 59,2% já trocaram seus instrumentos e 81,6% concordam em utilizar o próprio instrumento em sua cavidade bucal. Nas imagens do MEV pode-se observar perdas estruturais de diamantes, processo de oxidação do aglutinante e até perda severa de parte ativa dessas pontas diamantadas. Os graduandos apresentaram conduta adequada frente ao armazenamento, utilização e esterilização de suas pontas diamantadas. Entretanto, após análise em MEV as pontas não apresentavam bom estado de conservação.

Simulated clinical adjustment and intra-oral polishing of two translucent, monolithic zirconia dental ceramics: An in vitro investigation of surface roughness

ObjectiveTo assess the surface roughness and residual flaws in two translucent zirconia substrates following simulated clinical adjustment and intra-oral finishing/polishing. Materials and methodsSpecimens were prepared from two translucent (5Y-ZP/8Y-ZP) and one conventional (3Y-TZP) zirconia substrates (n = 84 p/g). Arithmetic mean roughness parameter (Ra) was determined for all experimental groups at four stages (n = 21 p/g): (1) as-sintered, (2) surface grinding using a zirconia cutting diamond bur, (3) polishing using 1-step, 2-step or 4-step intra-oral polishing kits, and (4) laboratory polishing/glazing. Scanning electron microscopy (SEM) was used to evaluate residual surface flaws. Data were statistically analysed using a two-way ANOVA test, multiple and pairwise comparisons were performed using a Bonferroni post hoc test. ResultsRa was significantly higher for as-sintered and ground 5Y-ZP/8Y-ZP compared to 3Y-TZP (p ≤ 0.001). Material type and polishing protocol had statistically significant effect on Ra (p < 0.001). The 4-step polishing resulted in the lowest Ra in 3Y-TZP/5Y-ZP (p ≤ 0.001). No significant differences were observed between different polishing protocols in 8Y-ZP (p≥0.655). Glazing significantly reduced Ra in all materials compared to other polishing protocols (p ≤ 0.001) except for the 4-step protocol in 3Y-TZP (p = 0.195). SEM revealed pronounced surface flaws in ground 5Y-ZP/8Y-ZP. Grinding of 3Y-TZP induced ductile material removal and thereby, minimal cohesive material loss. The 4-step polishing protocol resulted in the fewest and shallowest surface flaws in all groups. Glazing of 3Y-TZP resulted in the most homogenous surface contrary to 5Y-ZP/8Y-ZP. ConclusionsThe finest surface finish was achieved using the 4-step polishing protocol in all studied materials. This protocol might be inadequate however for polishing of ground 5Y-ZP/8Y-ZP as a result of the pronounced surface damage induced by the grinding process. The glazing of 5Y-ZP/8Y-ZP might not be as predictable as for 3Y-TZP. Clinical significanceThe higher susceptibility to surface damage, as a result of increasing dopant concentration, may render polishing of ground, translucent zirconia more complicated compared to the conventional 3Y-TZP counterparts.