Diamond Bur Research Articles

Influence of polishing in the roughness of a composite resin after contact with beer and ron: in vitro study

Objective: Evaluate the surface roughness, weight and color of a composite resin, submitted to two finish and polish systems, after contact with beer and rum. Materials and methods: 63 Brilliant TM NG (COLTENE, USA) composite resin discs of 10 mm in diameter and 2 mm thick, after 24 hours of permanence in distilled water, randomly divided into three groups (n: 21) for polishing using Sof-flex (3M-USA) discs and fine-grained diamond burs (KG-Sorensen, Brazil) and third group without any procedure, for each sample the initial measurement was made in weight, roughness and color. The samples were subdivided into three subgroups and submerged in rum, beer or artificial saliva for 7 days; performing a new evaluation of weight, color and roughness. The data obtained were collected in Excel tables and statistically analyzed through Kruskal Wallis, Wilcoxon, Anova and Tukey tests. Results: The Tukey test, considering polishing systems and immersion substances, verified that polishing with diamond burs and contact with beer and rum produced changes in surface roughness (p = 0.00) with no influence on weight and color Results: The rum showed greater variation in surface roughness of composite resin, polishing with Sof-lex (3M-USA) discs caused less variation in values of roughness and color. No changes in weight.

Influence of Class V preparation on in vivo temperature rise in anesthetized human pulp during exposure to a Polywave® LED light curing unit

ObjectiveThis in vivo study evaluated pulp temperature (PT) rise in human premolars having deep Class V preparations during exposure to a light curing unit (LCU) using selected exposure modes (EMs). MethodsAfter local Ethics Committee approval, intact first premolars (n=8) requiring extraction for orthodontic reasons, from 8 volunteers, received infiltrative and intraligamental anesthesia and were isolated using rubber dam. A minute pulp exposure was attained and sterile probe from a wireless, NIST-traceable, temperature acquisition system was inserted into the coronal pulp chamber to continuously monitor PT (°C). A deep buccal Class V preparation was prepared using a high speed diamond bur under air-water spray cooling. The surface was exposed to a Polywave® LED LCU (Bluephase 20i, Ivoclar Vivadent) using selected EMs, allowing 7-min span between each exposure: 10-s in low (10-s/L), 10-s (10-s/H), 30-s (30-s/H), or 60-s (60-s/H) in high mode; and 5-s-Turbo (5-s/T). Peak PT values and PT increases over physiologic baseline levels (ΔT) were subjected to 1-way, repeated measures ANOVAs, and Bonferroni’s post-hoc tests (α=0.05). Linear regression analysis was performed to establish the relationship between applied radiant exposure and ΔT. ResultsAll EMs produced higher peak PT than the baseline temperature (p<0.001). Only 60-s/H mode generated an average ΔT of 5.5°C (p<0.001). A significant, positive relationship was noted between applied radiant exposure and ΔT (r2=0.8962; p<0.001). SignificanceIn vivo exposure of deep Class V preparation to Polywave® LED LCU increases PT to values considered safe for the pulp, for most EMs. Only the longest evaluated EM caused higher PT increase than the critical ΔT, thought to be associated with pulpal necrosis.

Effect of different surface treatments on the ceramic veneer surface: morphological analysis

Objective: The aim of this study was to evaluate the effect of different surface clinical treatments on the roughness (Ra) of a lithium disilicate ceramic veneer. Material and Methods: Forty-eight lithium disilicate discs with ceramic veneer and glaze layer were manufactured and distributed into six groups (n=8) according to the surface treatment performed: G1, glaze layer (control group); G2, diamond bur 4138F; G3, diamond bur 4138F + 4138FF; G4, diamond bur 4138F + new glaze layer; G5, diamond bur 4138F + ceramic polishing kit; G6, diamond bur 4138F + rubber cup with diamond paste + felt with diamond paste. Surface Ra measurement (µm) was performed using a profilometer before and after surface treatments, and one specimen from each group was subjected to Scanning Electron Microscopy (SEM) after treatment. Two-way ANOVA and Tukey's test (5%) were used for data analysis. Results: Group 2 (3,00 ± 0,61)b showed higher values of Ra, followed by Group 3 (1,93 ± 0,45)c, Group 6 (1,56 ± 0,22)ac, Group 5 (1,14 ± 0,68)a and Group 4 (0,90 ± 0,26)a. G4, G5 and G6 were not different between each other and control group (1,11 ± 0,21)a. SEM imaging revealed surface smoothness in G1, G4 and G5, and presence of irregularities in G2, G3 and G6. Conclusion: it is possible to conclude that different surface clinical treatments influences the roughness of a lithium disilicate ceramic veneer. Keywords: Ceramics; Dental porcelain; Dental polishing.

Histological and Thermometric Examination of Soft Tissue De-Epithelialization Using Digitally Controlled Er:YAG Laser Handpiece: An Ex Vivo Study.

The purpose of this study was histological and thermometric examination of soft tissue de-epithelialization using digitally controlled laser handpiece (DCLH) - X-Runner. Commonly used techniques for de-epithelialization include scalpel, abrasion with diamond bur, or a combination of the two. Despite being simple, inexpensive and effective, these techniques are invasive and may produce unwanted side effects. It is important to look for alternative techniques using novel tools, which are minimally invasive and effective. 114 porcine samples sized 6 × 6 mm were collected from the attached gingiva (AG) of the alveolar process of the mandible using 15C scalpel blade. The samples were irradiated by means of Er:YAG laser (LightWalker, Fotona, Slovenia), using X-Runner and HO2 handpieces at different parameters; 80, 100, and 140 mJ/20 Hz in time of 6 or 16 sec, respectively. The temperature was measured with a K-type thermocouple. For the histopathological analysis of efficiency of epithelium removal and thermal injury, 3 random samples were de-epithelialized with an HO2 handpiece, and 9 random samples with an X-Runner handpiece with different parameters. For the samples irradiated with DCLH, we have used three different settings, which resulted in removing 1 to 3 layers of the soft tissue. The efficiency of epithelium removal and the rise of temperature were analyzed. DCLH has induced significantly lower temperature increase compared with HO2 at each energy to frequency ratio. The histological examination revealed total epithelium removal when HO2 handpiece was used at 100 and 140 mJ/20 Hz and when DCLH was used for two- and threefold lasing at 80, 100, and 140 mJ/20 Hz. Er:YAG laser with DCLH handpiece may be an efficient tool in epithelium removal without excessive thermal damage.

The effect of Er:YAG laser and bulk filled composite type on marginal adaptation of class II cavities: an SEM analysis study

Purpose: To evaluate the effect of cavity preparation method (Er:YAG laser or diamond bur) and bulk-filled composite material type on marginal adaptation mesial occlusal (MO) class II cavities. Materials and Methods: Two-surface box cavities (4-mm proximal depth and 5-mm occlusal width) were prepared on 60 human mandibular molar teeth. Cavities were prepared using Er:YAG laser or diamond burs in an air-turbine hand-piece. All cavities were applied Single Bond Universal dentin bonding agent. The cavities were further subdivided into three subgroups according to the restorative material used; two bulk-filled composites [Filtek Bulk Fill Posterior (3M ESPE) and SonicFill 2 (Kerr)] and one traditional composite material Filtek Ultimate Universal Restorative (3M ESPE). Restorations were evaluated using scanning electron microscopy at ×200 magnification for their adaptation to the approximal margins of the tooth. Results were analyzed using the two-way ANOVA and Tukey Post Hoc Test (p < 0.05). Results: A total of 900 SEM figures were obtained from all groups. Filtek Bulk Fill Posterior, SonicFill 2, and Filtek Ultimate Universal Restorative exhibited statistically similar gapped margins. However, the lowest scores of gapped margins were observed with SonicFill 2 (4.22%). Conclusions: Completely gap-free margins were not obtained with any of the tested materials. Bulk-fill composite materials showed similar marginal adapatation compared with standard composite. Marginal adaptation of Er:YAG laser prepared cavities was more irregular and had more gaps, but was statistically similar to diamond bur-prepared cavities.

Shear bond strength of ceramic brackets bonded to surface-treated feldspathic porcelain after thermocycling.

The aim of this study was to evaluate the effect of six different surface conditioning methods on the shear bond strength of ceramic brackets bonded to feldspathic porcelain. A total of 60 feldspathic porcelain disks were fabricated and divided into six subgroups including 10 specimens in each. Specimens were first treated one of the following surface conditioning methods, namely, 37% phosphoric acid (G-H3PO4), 9.4% hydrofluoric acid (G-HF), grinding with diamond burs (G-Grinding), Nd:YAG laser (G-Nd:YAG), Airborne-particle abrasion (G-Abrasion). Specimens were also coated with silane without surface treatment for comparison (G-Untreated). A total of 60 ceramic brackets were bonded to porcelain surfaces with a composite resin and then subjected to thermocycling 2500× between 5°C and 55°C. The shear bond strength test was carried out using a universal testing device at a crosshead speed of 0.5 mm/min. Failure types were classified according to the adhesive remnant index. Analysis of variance and Tukey tests were used for statistical analysis (α = 0.05). Microstructure of untreated and surface-treated specimens was investigated by scanning electron microscopy. Using G-Abrasion specimens resulted in the highest shear bond strength value of 8.58 MPa for feldspathic porcelain. However, the other specimens showed lower values: G-Grinding (6.51 MPa), G-Nd:YAG laser (3.37 MPa), G-HF (2.71 MPa), G-H3PO4 (1.17 MPa), and G-Untreated (0.93 MPa). Airborne-particle abrasion and grinding can be used as surface treatment techniques on the porcelain surface for a durable bond strength. Hydrofluoric acid and phosphoric acid etching methods were not convenient as surface treatment methods for the feldspathic porcelain.

Analysis of enamel surface roughness after different adhesive removal techniques for orthodontic bracket debonding

The objectives of this study were to explore traditional resin removal procedures in the debonding process and evaluate the Er:YAG laser as a plausible option. Sixty premolar teeth were bonded with brackets. Then, brackets were removed and five adhesive clean-up methods were tested against control teeth: (a) Er:YAG laser at 200 mJ and 20 Hz; (b) Er:YAG laser at 305 mJ and 10 Hz; (c) 20-fluted flame-shaped tungsten carbide bur at high-speed; (d) #8-fluted round tungsten carbide bur at low-speed; and (e) #5 round end tapered fine diamond bur at high speed. Quantitative measurements including average (Avg) profile height, total indicator run-out (TIR), arithmetic average roughness (Ra), and time were made using profilometry. Qualitative evaluation of tooth surfaces was done using SEM. The two laser settings produced a statistically higher TIR, Ra, and time compared to the controls (P < 0.001). There was no statistical difference between the three bur techniques in regards to surface texture or time. Qualitatively, the 20-fluted carbide bur left the smoothest surface. The Er:YAG laser at the tested settings would not be appropriate for adhesive removal. The interaction of the Er:YAG wavelength under these conditions was not comparable to the 20-fluted flame-shaped tungsten carbide bur at high speed for orthodontic adhesive removal leaving a smoother enamel surface.

Impact of 35% Hydrogen Peroxide on Color and Translucency Changes in Enamel and Dentin.

This study evaluated the effects of tooth bleaching with high-concentration of hydrogen peroxide on alterations of translucency parameter (TP) and color of dentin and enamel. The crown of five human molars was sectioned into four slices parallel to buccal surface. The dentin of external slices containing buccal/ lingual enamel was fully removed with diamond bur; while these slices were used to assess alterations on enamel. Alterations on dentin were assessed into the center of internal slices. The color of specimens was measured over white and black backgrounds using a spectrophotometer (CieL*a*b) at baseline, allowing to calculate the TP by difference between the color measured over each background. Specimens were submitted to three 15-min applications of 35% hydrogen peroxide followed by their storage in water for one-week. Afterwards, the color measurements were repeated at both backgrounds. Color (∆L, ∆a, ∆b and ∆E) and translucency (∆TP) changes were calculated and data individually analyzed by T-test (α = 0.05). Influence of hard tissue and assessment time on each color parameter was also analyzed by 2-way repeated measure ANOVA (α = 0.05). Tooth bleaching resulted in increased lightness for the enamel, whereas no alteration on this parameter occurred for dentin. No difference between the tooth hard tissues was observed regards the other color parameters and ∆E. A slightly reduction on TP was observed only for the enamel. In conclusion, 35% hydrogen peroxide caused similar color and translucency changes on dentin and enamel.

Effect of Grinding and Multi-Stimuli Aging on the Fatigue Strength of a Y-TZP Ceramic.

This study aimed to investigate the effect of grinding and multi-stimuli aging on the fatigue strength, surface topography and the phase transformation of Y-TZP ceramic. Discs were manufactured according to ISO-6872:2008 for biaxial flexure testing (diameter: 15 mm; thickness: 1.2 mm) and randomly assigned considering two factors "grinding" and "aging": C- control (as-sintered); CA- control + aging; G- ground; GA- ground + aging. Grinding was carried out with coarse diamond burs under water-cooling. Aging protocols consisted of: autoclave (134°C, 2 bars pressure, 20 hours), followed by storage for 365 days (samples were kept untouched at room temperature), and by mechanical cycling (106 cycles by 20 Hz under a load of 50% from the biaxial flexure monotonic tests). Flexural fatigue strengths (20,000 cycles; 6 Hz) were determined under sinusoidal cyclic loading using staircase approach. Additionally, surface topography analysis by FE-SEM and phase transformation analysis by X-ray Diffractometry were performed. Dixon and Mood methodology was used to analyze the fatigue strength data. Grinding promotes alterations of topographical pattern, while aging apparently did not alter it. Grinding triggered t-m phase transformation without impacting the fatigue strength of the Y-TZP ceramic; and aging promoted an intense t-m transformation that resulted in a toughening mechanism leading to higher fatigue strength for as-sintered condition, and a tendency of increase for ground condition (C < CA; G = GA). It concludes that grinding and aging procedures did not affect deleteriously the fatigue strength of the evaluated Y-TZP ceramic, although, it promotes surface topography alterations, except to aging, and t-m phase transformation.

A randomised controlled study on the use of finishing and polishing systems on different resin composites using 3D contact optical profilometry and scanning electron microscopy

ObjectivesThe aim of this study was to evaluate theeffects of different finishing and polishing techniques on the surface roughness of microhybrid and nanofilled resin composites. MethodsThe resin composites included were Filtek Z250 (a universal microhybrid resin composite) and Filtek Supreme XTE (a universal nanofill resin composite). Ninety cylindrical-shaped specimens were prepared for each composite resin material. The polishing methods used included tungsten carbide bur (TC); diamond bur (Db); Sof-Lex discs (S); Enhance PoGo discs (PG); TC + S; Db + S; TC + PG; Db + PG. Polymerisation against a Mylar strip without finishing and polishing acted as the control group. Surface roughness was measured using a 3D contact optical profilometer and surface morphology was examined by scanning electron microscope examination. ResultsThe results showed that the Mylar-formed surfaces were smoothest for both composites. Finishing with the 20 μm diamond finishing bur caused significantly greater surface irregularity (P < 0.0001) and damage than finishing with the tungsten carbide finishing bur. The Enhance PoGo polishing system produced smoother surfaces than the Sof-Lex disc polishing system; this difference was statistically highly significant (P < 0.0001). ConclusionFor both composites, the Mylar-formed surfaces were smoothest. Where indicated clinically, finishing is better conducted using a tungsten carbide bur- rather than a diamond finishing bur. The Enhance PoGo system was found to produce a smoother surface finish than the Sof-Lex system. Clinical significanceIf finishing and polishing is required the use a tungsten carbide finishing bur followed by Enhance PoGo polishing may be found to result in the smoothest surface finish.

An evaluation of the Effect of Surface Treatment On Amalgam Repair

The purpose of this in vitro study was to evaluate the effect of different surface treatments on shear bond strength of repaired amalgam using two types of amalgam. 120 acrylic blocks (2.7cm diameter by 2.0cm high) were constructed from cold cure resin, each one contained cylindrical hole (7mm diameter by 2mm high) on its circular face that filled with amalgam. The samples were divided into immediate repair group and delayed repair group, which was stored and incubated at 37C0 for one month. After aging the amalgam surface of delayed repair was finished with carbide bur and polished with abrasive rubber cup then divided into three groups according to the surface treatment that include group with out surface treatment, group roughened with diamond bur and the last group was abraded with aluminum oxide (50m) particles size, both immediate and delayed repair were further subdivided according to the type of amalgam used into three subgroups. The repair procedure was done by using a Teflon split mold which containing an opening (3mm diameter by 5mm high) then all the samples were storage and incubated at 37C0 for one week prior to testing.Testing was done by applying shear force at the interface between the initial and repair amalgam with special designed chisel shape rod by using Zwick testing machine at across head speed of 5mm/min.Analysis of the results showed that the shear bond strength in immediate repair were significant higher than of delayed repair and the group roughened with diamond bur is higher than group treated with aluminum oxide and untreated group.The shear bond strength of delayed repair of amalgam is less than that of immediate repair, the surface produced by roughening the samples with a diamond bur will give best strength than the surface treated by aluminum oxide and untreated surface (smooth surface) and the same types of amalgam restorations used in amalgam repair gave better result than different type of amalgam.

Comparison of Gap Volume after Retrofilling Using 4 Different Filling Materials: Evaluation by Micro–computed Tomography

IntroductionThe purpose of this study was to evaluate the gap volume between dentin and root-end filling materials. MethodsFour root-end filling materials were compared in the present study: ProRoot MTA (PRM; Dentsply Tulsa Dental, Tulsa, OK), MTA Angelus (MAG; Angelus, Londrina, Brazil), EndoCem MTA (ECM; Maruchi, Wonju, Korea), and RetroMTA (RTM; BioMTA, Seoul, Korea). Forty-eight single-rooted, extracted human teeth were instrumented with nickel-titanium instruments and oburated with gutta-percha. The apical 3 mm of the root tip was resected, and root-end preparation was performed with a diamond bur. The root-end cavity was filled with the experimental filling materials for the 4 designated groups (n = 10). Then, the samples were scanned with micro–computed tomographic (micro-CT) imaging. Three-dimensional images of the samples were reconstructed, and the volume of the gap between the tooth surface (dentinal wall) and the root-end filling materials was measured. The percentage volume of the gap between the tooth structure and the root-end filling material (VG%) was calculated. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests at a significance level of 95%. ResultsThe median VG% values for the PRM, MAG, ECM, and RTM groups were 0.00472, 0.00134, 0.00014, and 0.00071, respectively. The ProRoot MTA group showed the greatest gap volume percentage among the experimental groups with a significant statistical difference (P < .05). ConclusionsFrom the micro-CT analysis, ProRoot MTA had a greater gap volume percentage than other root-end filling materials.

What is the changing frequency of diamond burs?

PURPOSEThe purpose of this study was to determine the changing frequency of a diamond bur after multiple usages on 3 different surfaces.MATERIALS AND METHODSHuman premolar teeth (N = 26), disc shaped direct metal laser sintered CoCr (N = 3) and zirconia specimens (N = 3) were used in this study. Groups named basically as Group T for teeth, Group M for CoCr, and Group Z for zirconia. Round tapered black-band diamond bur was used. The specimens were randomly divided into three groups and placed with a special assembly onto the surveyor. 1, 5, and 10 preparation protocols were performed to the first, second, and third sub-groups, respectively. The subgroups were named according to preparation numbers (1, 5, 10). The mentioned bur of each group was then used at another horizontal preparation on a new tooth sample. The same procedure was used for CoCr and zirconia disc specimens. All of the bur surfaces were evaluated using roughness analysis. Then, horizontal tooth preparation surfaces were examined under both stereomicroscope and SEM. The depth maps of tooth surfaces were also obtained from digital stereomicroscopic images. The results were statistically analyzed using One-Way ANOVA, and the Tukey HSD post-hoc tests (α=.05).RESULTSAll of the groups were significantly different from the control group (P<.001). There was no significant difference between groups Z5 and Z10 (P=.928). Significant differences were found among groups T5, M5, and Z5 (P<.001).CONCLUSIONDiamond burs wear after multiple use and they should be changed after 5 teeth preparations at most. A diamond bur should not be used for teeth preparation after try-in procedures of metal or zirconia substructures.

Influence of material and surface treatment on composite repair shear bond strength.

Objectives:The aim of this study is to investigate the influence of the composite material and surface treatment to the bond strength when repairing an aged composite surface with new composite.Materials and Methods:One hundred and sixty resin blocks of methacrylate composite and silorane composite prepared and aged in artificial saliva for 6 months. Specimens treated either with a diamond bur (DB) or air abrasion (AA), conditioned with orthophosphoric acid (OA) or sodium hypochloride (SH) and repaired with methacrylate or silorane composite using the corresponding adhesive system. Repaired composites underwent thermocycling fatigue (×5000), and bond strength was measured at shear.Results:Methacrylate achieved the highest bond strengths as repair material, in all combinations (26.54-55.56 MPa). Silorane only reached 8.12 MPa when repairing silorane treated with DB and OA. For all other treatment combinations repairing with silorane led to pretest failures. The most susceptible to repair composites/surface treatment combination is when repairing methacrylate treated with AA and SH and methacrylate composite (55.56 MPa).Conclusions:Silorane composites are not suitable to be used when repairing an old composite restoration. The repair material is the most critical factor, while aged surface treatment has only a minor influence to the shear bond strength.

Corneal dystrophies

The article reviews modern clinical, morphological, and genetic aspects of corneal dystrophies based on the most recent international classification updated in 2015. Corneal dystrophies is a group of slow progressing, non-inflammatory corneal pathologies, most of which are characterized by variability of the associated traits. The existence of such pathologies makes important their differential diagnosis from acute inflammatory processes of various etiology, which require urgent therapy. Conservative treatment suitable for dystrophies is usually associated with disorders of the anterior corneal surface and employ symptomatic tactic (lubricants, epithelizing agents, soft contact lenses). No effective etiopathogenetically targeted treatment is currently known. In cases with significant visual acuity decrease, it is possible to perform phototherapeutic keratectomy, abrasive polishing of Bowman's membrane with diamond bur and various types of keratoplasty depending on the depth of involvement.

Effects of different ceramic primers and surface treatments on the shear bond strength of restorative composite resin to zirconium.

Data are limited about the effect of ceramic primers on the bond of zirconia to restorative resin composite. The aim of this study was to assess the effect of different surface treatments and two ceramic primers on shear bond strength (SBS) of zirconia to restorative resin composite. 100 samples of zirconium ceramic blocks were randomly divided into 5 groups (n = 20) and received the following surface treatments: a)Control groupb)AL2O3 abrasionc)Nd:YAG laserd)Er:YAG lasere)Bur preparation.Next, each group was divided into two subgroups of 20. In ten out of 20 specimens in each group, monobond plus and Tetric ceram composite resin were applied on the surface. ZPrime Plus and Elite composite were applied on the surfaces of the remaining 10 specimens in each group. Samples were then subjected to shear bond strength test in a universal testing machine until fracture. The mean SBS were calculated and statistically analyzed by two-way ANOVA and T-Test. P < 0.05 was considered statistically significant. In ZPrime plus subgroups, diamond bur yielded the highest bond strength. Laser groups showed no significant difference with the control group. In monobond plus subgroups, SBS of air abrasion and diamond bur subgroups was highest and Nd:YAG laser showed the lowest SBS. The lowest bond strength belonged to the Nd:YAG laser subgroup of monobond plus group. Type of surface preparation significantly affected the bond strength.

Shear Bond Strength of Ceramic Orthodontic Brackets to CAD/CAM Provisional Materials: Influence of Surface Treatments and a Novel Adhesive System

Objective: To evaluate the effect of surface treatments and flash-free adhesive on the shear bond strength of ceramic orthodontic brackets to CAD/CAM provisional materials. Materials and Methods: Specimens (n=160) from each provisional material (CAD-Temp and C-Temp) were categorized into four groups according to the surface treatment methods: C (no surface treatment), HP (37% H3PO4), DB (mechanical roughening by diamond bur) and SB (mechanical roughening by sandblasting). Half of the specimens in each group were bonded to one of the maxillary central incisor ceramic brackets according to the used adhesive system: (APC PLUS or APC Flash-free). All specimens were 5000-times thermocycled before the shear bond strength testing (SBS). Data were analyzed using three-way ANOVA, Tukey’s multiple comparison tests. The adhesive remnant index (ARI) was also evaluated. The level of significance was set at 5% for all statistical tests.Results: C-Temp significantly recorded higher SBS than CAD-Temp (p<. 001). DB and SB groups utilizing flash-free adhesive significantly recorded higher SBS (P<. 05) compared to other groups in the tested materials. Higher ARI scores were recorded in CAD-Temp and flash-free adhesive.Conclusions: Bonding of orthodontic brackets to provisional restorations is a challenge for orthodontists in adult comprehensive cases that could be improved by an appropriate material, surface treatments, and adhesive system. Mechanical surface treatments and flash-free adhesive would enhance SBS of ceramic orthodontic brackets to CAD/CAM provisional materials. The higher ARI scores reported with CAD-Temp and flash-free adhesive reduces chair time for excess removal.

CAD/CAM diamond tool wear.

This study evaluated the wear of computer-aided design/computer-assisted manufacture (CAD/CAM) burs and the morphologic changes after a number of millings. Diamond burs (cylinder and step-bur) were divided into four milling groups: zero millings (G0); 15 millings (G1); 25 millings (G2); and 35 millings (G3). Seventy-five premolar crowns were milled using the Cerec Compact Milling unit and VitaBlock Mark II. Surface roughness, three-dimensional profile, and SEM were used for wear and surface damage evaluation. Two-way ANOVA and Tukey test (α = .05) showed that G3 produced statistically different values compared to G0 and G2, but not G1. The cylinder burs showed higher roughness values than step-burs for all groups. SEM showed similar diamond particle damage for cylinder burs and step-burs, and signs of surface damage, cracks, and particle losses for G3. Both cylinder burs and step-burs were able to sustain a larger number of milling procedures than indicated by the manufacturer.

Effect of occlusal contact of the loading rod tip on the fracture strength of ceramic crowns

Aim: The aim of this study was to verify the effect of the occlusal contact of the rod tip on the fracture strength of crowns made with different ceramic systems. Materials and Methods: Conical preparation was performed on bovine teeth with diamond burs in mechanical lathe, and crowns were made for all-ceramic, metal-ceramic, In Ceram, and IPS Empress 2 ceramic systems according to manufacturers' instructions in prosthetic laboratory. The crowns were fixed with resin-modified glass ionomer cement or dual-curing composite resin under a static load of 4 kg for 1 min. To simulate the clinical contact between loading and ceramic crowns, the rod tip was made in accordance with the occlusal form of the ceramic crown. After storage in distilled water at 37°C for 24 h, the samples were submitted to 60,000 mechanical cycles at a load of 35 N/2 Hz immersed in distilled water. The fracture strength test was performed in an Instron with a cross-speed of 0.5 mm/min. Results: Data submitted to one-way ANOVA for randomized experiments followed by Tukey's test (α = 0.05) showed greater value for IPS Empress 2 (208.12 kgf) with significant difference in relation to all-ceramic (149.32 kgf) and In Ceram (142.25 kgf), whereas metal-ceramic showed intermediary value (182.83 kgf). Conclusion: The loading of the rod tip in occlusal contact with the crown did not promote premature failures during the mechanical fatigue test, and two-ceramic systems showed different values of fracture strength after mechanical fatigue test, with better performance for crowns manufactured with IPS Empress 2.

Comparative Evaluation of Dentinal Caries in Restored Cavity Prepared By Galvanic and Sintered Burs.

Background:The occurrence of secondary caries is the most common reason for the restorations failures.Aim:The aim of the study was to evaluate and compare the anticaries effect of copper ions on the teeth restored with glass ionomer cement (GIC) and composite restorations in the cavity prepared by galvanic and sintered burs.Materials and Methods:A total of 40 premolars were divided into two halves buccolingually. Class V cavity was prepared with sintered diamond burs and galvanic diamond bur. Cavities were restored with either GIC or composite resin. The monospecies artificial microbial caries model was selected for induction of secondary caries. The lesions were measured at junction of restoration by confocal laser scanning microscope.Results:The results were statistically significant (P < 0.001) and suggested that the width of lesion was lowest in cavity prepared by sintered bur and restored with composite resin.Conclusion:The use of different burs in combination with various restorative materials influence the occurrence and width of caries lesion.