Diamond Bur Research Articles

In vitro assessment of natural extract as irrigant on root dentin microhardness

To determine the effect of a natural extract of of 2.5% concentration on the of root canal when used as an irrigating solution. This was an in comparative study where and twenty intact single-rooted teeth were selected and with a diamond bur to get an apical-coronal length of 10 mm and were randomly separated into three groups as per the used; Group 1 (control): Irrigation with Normal saline, Group 2: Irrigation with Smear Clear solution, Group 3: Irrigation with 2.5% extract solution. were prepared using Pro Taper Universal Rotary Files with intermittent irrigation with the respective irrigating solution. The teeth were then embedded in acrylic resin and subjected to Vicker's Hardness test, and the data obtained were analyzed using one way ANOVA. When Group 2(51.80±9.80 VHN and 52.66±5.28 VHN) was compared with Group 3(44.98±4.34 VHN and VHN) the values showed a statistically significant difference (p< 0.05).When Group 3 (44.98±4.34 VHN and VHN) was compared with Group 1(65.37±8.80 VHN and 67.74±9.56 VHN), the values did show a statistically significant difference (p> 0.05). Within the limitations of this study, teeth irrigated with normal saline showed the least reduction in followed by irrigation with leaf extract solution and Smear Clear.

Influence of different ceramic materials and surface treatments on the adhesion of Prevotella intermedia

Ceramics are used in oral rehabilitation; however, these materials are prone to formation of biofilms that may cause periodontal diseases. This study aimed to evaluate the influence of distinct surface treatments on ceramic surface roughness and biofilm formation of oral bacteria (Prevotella intermedia). Eighty-four specimens of the following four ceramic systems were produced: LC - leucite-based glass ceramic, LD - lithium disilicate-based glass ceramic, LSZ - glass ceramic based on zirconia-reinforced lithium silicate, and ZR - monolithic zirconia. These were submitted to three different surface treatment protocols: C - control, G - glazing, and GDB - grinding with diamond bur (n = 7). The surface characteristics were assessed using a confocal laser microscope (Ra) and a scanning electron microscope (SEM). Thereafter, the groups were contaminated with a bacterial strain of P. intermedia ATCC 25611. The biofilms formed were quantified by counting the colony forming units (CFUs) and analyzed with scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM). Data were analyzed by using a 2-way ANOVA and the Tukey test (ɑ = 0.05). Results showed that greater roughness was associated with GDB (p < 0.05). The same was also true for the ceramic material ZR (p < 0.05). There was a statistical significant difference in the CFU counts between the materials (p < 0.05) that revealed a greater amount of bacterial adhesion in the LC and ZR groups (p > 0.05). Thus, it was suggested that the surface roughness of the ceramic materials favored bacterial adhesion; and thus, finishing of ceramic surfaces with GDB should be avoided.

Flexural strength and crystalline stability of a monolithic translucent zirconia subjected to grinding, polishing and thermal challenges

The objective of this study is to investigate the magnitude of structural degradation of a monolithic translucent zirconia caused by clinically relevant grinding and polishing procedures, when associated or not with low temperature degradation (LTD), induced by accelerated hydrothermal aging using autoclave or thermocycling. Ninety disks (Ø12 × 1 mm) were prepared from dental zirconia for monolithic restorations (Vipi Block Zirconn Translucent, Vipi). The specimens were divided into 3 groups (n = 30) according to surface treatment: As Sintered (untreated), Grind (diamond bur), Grind + Polish (diamond bur + polish); and then subdivided according to aging method (n = 10): Baseline (no aging), Autoclave (134 °C, 2.2 kgf/cm2 pressure for 5 h), and Thermocycling (200,000 cycles, 5 °C and 55 °C, for 15 s each). Roughness, biaxial flexural strength and percentage of monoclinic phase were evaluated. Regarding surface treatment, the Grind group presented higher roughness and greater flexural strength compared to As Sintered group, while Grind + Polish showed intermediate roughness and flexural strength similar to Grind group. Aging had little effect on roughness, but yielded a significant reduction in flexural strength. Tetragonal to monoclinic phase transformation was observed in all groups, caused by both mechanical stresses (grinding and polishing) and LTD, which was similarly induced by the traditional autoclave method, as well as the thermocycling method. The use of diamond burs to grind zirconia surface may result in deleterious effects on the surface quality of monolithic zirconia restorations, yet has a potential toughening effect by phase transformation. However, when zirconia is exposed to LTD, regardless of the surface treatment, degradation of the surface quality and strength are observed.

Effect of Different Methods for the Overhang Amalgam Restorations Removal on Periodontal Health Status

Overhanging tooth restorations due to environmental change of the balance between beneficial bacteria and periodontopathogens lead to periodontal breakdown. This study aim was to evaluate the periodontal status after using different techniques for amalgam overhang removal. The proximal restorations were examined clinically and then radiographically by taking bitewing radiograph. From a total of 1200 patients examined in College of Dentistry, Hawler Medical University and (Khanzad) Specialized Centre for Dentistry for presence of proximal amalgam restoration, for this interventional and prospective study, 45 patients with amalgam overhang were divided into three groups each 15 patients according to size and position of amalgam overhang each had one type of the following treatment (Refilling, Diamond Bur, EVA system) and 15 patients without amalgam overhang (control group) selected completed the trial. Clinical periodontal parameters were measured in teeth with amalgam overhang at baseline, 2 week, 1 and 3 months after removal of amalgam overhang. The results showed that the periodontal parameters showed a gradual decrease in all groups throughout the follow-up visits (except calculus index) and became a statistically significant in the 3 months follow-up following treatment (P &lt; 0.001), with more reduction found in refilling group followed by EVA system then diamond bur group. In conclusion that it is better to replace the restoration rather than to use the other methods of treatment according to periodontal health which recorded by periodontal parameters.

Adhesive bond strength between orthodontic resin and acrylic surfaces

The use of orthodontic treatments in patients with temporary prostheses has been increasing, the purpose of this in vitro research is to measure the adhesive bond strength between orthodontic resin and acrylic surfaces by applying different procedures. Objective. To compare the adhesive bonding strength between orthodontic resin and acrylic surfaces under different application protocols. Methodology. Transversal, experimental, prospective study. In vitro with acrylic provisions, was carried out in the laboratory of the Faculty of Dentistry of the Universidad Veracruzana region of Veracruz. In the period of February-June of the year 2019. The sample was conformed by two control groups of specimens and four experimental ones, each group conformed by 20 specimens, in total 120 provisional ones were made in acrylic Nic Tone of quick self-cure. The tests performed by the ULTRATESTER machine were expressed in MPa. Later, the data obtained were processed in Excel tables (version) for statistical processing in SPSS version 24. Contribution. When comparing the pre-cutting protocol of acrylic surfaces with fine diamond bur and the protocol without pre-cutting, no statistically significant differences were found, therefore, this step could be omitted in clinical practice.

Chemical and Mechanical Roughening Treatments of a Supra-Nano Composite Resin Surface: SEM and Topographic Analysis

Background: Repairing a restoration is a more advantageous and less invasive alternative to its total makeover. The aim of this study was to analyze the effects of chemical and mechanical surface treatments aimed at increasing the roughness of a supra-nano composite resin. Methods: 27 cylindrical blocks of microhybrid composite were made. The samples were randomly divided into nine groups (n = 3). The samples’ surface was treated differently per each group: acid etching (35% H3PO4, 30 s and 60 s), diamond bur milling, sandblasting and the combination of mechanical treatment and acid etching. The samples’ surface was observed by a scanning electron microscope (SEM) and a confocal microscope for observational study, and surface roughness (Ra) was recorded for quantitative analysis. Results: The images of the samples sandblasted with Al2O3 showed the greatest irregularity and the highest number of microcavities. The surfaces roughened by diamond bur showed evident parallel streaks and sporadic superficial microcavities. No significant roughness differences were recorded between other groups. The difference in roughness between the control group, diamond bur milled group and sandblasted group was statistically significant. (p &lt; 0.01). Comparison between the diamond bur milled group and the sandblasted group was also significant (p &lt; 0.01). Conclusion: According to our results, sandblasting is the best treatment to increase the surface roughness of a supra-nano composite.

The Influence of Autoclaving on Diamond Burs Fabricated via Different Methods.

To evaluate the influence of repetitive autoclaving on diamond burs fabricated via different methods. A total of 96 diamond burs were divided into 12 groups according to fabrication method (single-element electroplating, multi-element electroplating, or brazing) and number of times autoclaved (0, 5, 10, or 15). The surface characteristics and components of the diamond burs were examined using scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS). The cutting efficiency of the diamond burs was tested with a constant-pressure cutting appliance. Compared to the nonautoclaved group, the cutting efficiency of the multi-element and single-element electroplated diamond burs decreased significantly after autoclaving 5, 10, and 15 times (P < .05). The cutting efficiency of the brazed diamond burs started to decrease significantly after 10 cycles (P < .05). Cracks appeared on the surfaces of multi-element electroplated diamond burs after 10 and 15 cycles, but were absent in the single-element electroplated and brazed diamond burs. A reduction of nickel was detected in the multi-element electroplated and brazed diamond burs, but not in the single-element electroplated diamond burs. Repetitive autoclaving could reduce the cutting efficiency of diamond burs. The extent of the reduction was related to fabrication method and number of autoclaving times, suggesting that used diamond burs should be separately autoclaved to avoid shortening the life spans of unused ones.

Piezotome Versus Surgical Bur: Which is More Effective in Reducing the Postoperative Pain and Edema Following Open Sinus Lift Surgery?

The aim of this study was to compare the piezotome versus surgical bur on postoperative edema and pain following open sinus lift surgery. This was a double-blinded split mouth randomized clinical trial. The subjects who were candidates for bilateral open sinus lifting in the posterior maxilla were included in this experiment. Each maxillary side was assigned randomly to one group, piezosurgery or surgical diamond bur for sinus lifting. Postoperative pain and edema were evaluated on the second and seventh days after the surgery, using the VAS scale. Data were analyzed by SPSS software. In this study, 20 subjects including 10 females (50%) and 10 males (50%) with a mean age of 50.87 ± 9.04years participated. The mean duration of surgery in piezosurgery (240.13 ± 49.5s) was significantly higher than the surgical bur technique (135.07 ± 43.53s) (P < 0.001). Pain and edema were significantly decreased on the seventh day postoperatively compared to the second day in both group (P < 0.05). Pain and edema were similar between the two study groups on the second and seventh days after surgery. The results of this study depicted that the piezosurgery clinical outcomes were similar to surgical bur following open sinus lift surgery.

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.

Use of dynamic navigation for a minimal invasive finding of root canals: a technical note

Aim: the aim of this technical note was to evaluate the potential application of dynamic navigation for a minimally invasive finding of the root canal. Methodology: extracted human teeth were fixed into a prefabricated phantom model in place of the correspondent teeth and pre-operatively scanned with the marker plate containing the fiducial markers with a cone beam computed tomography, imported on the ImplaNav software (ImplaNav, BresMedical, Sydney, Australia) and obtaining a 3D reconstruction. Open access cavity was performed with a diamond bur in using real-time navigation. This procedure was aimed to directly identify the pulp horns and the root canal entrances with a unique hole for each canal. Results: all access cavities were prepared according to a minimally invasive endodontics approach with the dynamically guided ImplaNav software. No perforations occurred and all the canals were successfully located. Conclusions: our results demonstrated a possible application of this technology in minimal finding of root canals. This protocol may have potentialities in teaching dental students to start their approach in endodontic field.

Surface Roughness and Microbial Adhesion After Finishing of Alkasite Restorative Material

This study is aimed to evaluate and compare the surface roughness and microbial adhesion to alkasite restorative material (Cention N), resin-modified glass ionomer (RMGI), and composite resin. And to examine the correlation between bacterial adhesion and surface roughness by different finishing systems.&lt;br/&gt;Specimens were fabricated in disk shapes and divided into four groups by finishing methods (control, carbide bur, fine grit diamond bur, and white stone bur). Surface roughness was tested by atomic force microscope and surface observation was performed by scanning electron microscope. Colony forming units were measured after incubating Streptococcus mutans biofilm on specimens using CDC biofilm reactor.&lt;br/&gt;Cention N surface roughness was less than 0.2 μm after finishing procedure. Control specimens of resin and Cention N specimens were significantly (&lt;i&gt;p&lt;/i&gt; = 0.01) rougher. Pearson correlation coefficient (PCC = 0.13) indicated a weak correlation between surface roughness and &lt;i&gt;S. mutans&lt;/i&gt; adhesion to the specimens.&lt;br/&gt;Compared with resin specimens, RMGI and Cention N showed lower microbial adhesion. Surface roughness and bacterial adhesion were not significantly different, regardless of the finishing systems.

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.

In vitro evaluation of shear bond strength of orthodontic metal brackets to aged composite using a self-adhesive composite: Effect of surface conditioning and different bonding agents

Bracket bonding to composite surfaces is increasing. This study sought to assess the effect of different adhesives (acid etchant+Transbond XT™, acid etchant+Vertise Flow™, Vertise Flow™) with different surface treatments (no preparation, bur, sandblasting, Er:YAG laser) on shear bond strength (SBS) of metal brackets to aged composite. In this in vitro, experimental study, Filtek™ Z250 composite discs were fabricated (10×4mm). After thermocycling (10,000 cycles between 5-55°C), the samples were randomly divided into three groups (n=48) based on the type of adhesive namely acid etchant+Transbond XT™, Vertise Flow™, and acid etchant+Vertise Flow™. Samples in each group were randomly divided into four subgroups (n=12) based on the surface treatment including no-treatment, diamond bur, sandblasting and Er:YAG laser. Samples in each group were randomly divided into three subgroups (n=12) based on the type of adhesive namely acid etchant+Transbond XT™, Vertise Flow™, and acid etchant+Vertise Flow™. After bracket bonding to composite discs, the samples underwent thermocycling (5000 cycles between 5-55°C), and their SBS was measured in a universal testing machine. The samples were then inspected under a stereomicroscope at x10 magnification to determine their mode of failure and adhesive remnant index (ARI). No significant difference was noted in SBS between adhesives in no-preparation and laser groups (P>0.05). In all adhesive groups, sandblast had highest SBS, but it was not significantly different in Vertise Flow™ groups, with and without etching. The SBS provided by acid etchant+Transbond XT™ was significantly higher than that of the other two adhesives (P<0.05). The SBS of sandblasted samples was significantly higher compared with other surface treatments in all adhesive subgroups (P<0.05). Bracket bonding to aged composite using Vertise Flow™ with or without surface treatment can serve as an alternative to the conventional orthodontic adhesives.

Load bearing capacity and Weibull characteristics of inlay-retained resin-bonded fixed dental prosthesis made of all-ceramic, fiber-reinforced composite and metal-ceramic after cyclic loading

PurposeThe objectives of this study were to evaluate the load bearing capacity of RBFDPs made of different materials after cyclic loading, and classify the failure types after loading. Materials and methodsSound human mandibular first premolars and first molar pairs (N = 60 per tooth type, n = 10 per group) were randomly divided into six experimental groups to receive one of the following inlay-retained RBFDP types: RC: Resin composite only, DFRC: Direct E-glass fiber-reinforced composite (FRC), IFRC: Indirect E-glass FRC, LS: Lithium disilicate glass-ceramic, ZR: Yttria-stabilized tetragonal zirconia, MC: Metal-ceramic. Box preparations were made in abutment teeth using diamond burs followed by standardized ultrasonic burs. The teeth were conditioned employing an etch-and-rinse adhesive system and the indirect RBFDPs were cemented adhesively. The specimens were subjected to cyclic loading for x1.200.000 in distilled water alternating between 5 and 55 °C (Zurich Chewing Simulator). They were then loaded to failure from the occlusal surface in the Universal Testing Machine (cross-head speed: 1 mm/min). Failure types were classified as repairable or irreparable depending on the location and size. Data were analyzed using Welch and Tamhane's T2 post-hoc tests (α = 0.05). Weibull modulus for each group was calculated based on parametric distribution analysis of censored data for maximum fracture load. ResultsMean load bearing capacity (N) of Groups LS (1274 ± 270), ZR (1567 ± 363) and MC (1544 ± 787) were significantly higher than those of other groups (p < 0.05). RC, DFRC, IFRC (601 ± 130 - 819 ± 270) and MC did not show significant difference (p > 0.05). Weibull modulus (m) was the highest in Group LS (m = 5.3) followed by Group RC (m = 5.1). Other groups presented Weibull moduli ranging between 1.4 and 3.3. Only in Group ZR, 2 early debonding occurred during cyclic loading. While in this group predominantly irreparable failures (debonding with without tooth fracture) were observed (8 out of 10), all other groups presented mainly single or a combination of repairable failures (chipping in the veneering material). DFRC, IDRC and MC did not show any debonding from the abutment teeth. ConclusionConsidering load bearing capacity, repairable failure types and Weibull moduli, lithium disilicate seem to be more durable than those of other material options for posterior inlay-retained RBFDPs. Due to early debondings and catastrophic irreparable failure types, zirconia RBFDPs should be indicated with caution in the posterior region.

Ultra-morphological characteristics of dentin surfaces after different preparations and treatments.

Using transmission electron microscopy (TEM), this study investigated the characteristics of smear layers after preparation of dentin surfaces using different methods. In addition, this study analyzed, using scanning electron microscopy (SEM), the interactions of smear layers with the various acidic agents used subsequently to treat the dentin surface. Mid-coronal dentin surfaces were prepared according to one of five instrumentation methods: fracture; grinding with carbide bur; grinding with regular-grit diamond bur; grinding with superfine-grit diamond bur; or grinding with 600-grit silicon carbide (SiC) abrasive paper. Then, each prepared dentin surface was further divided into control (no further treatment) or treatment with one of the following agents: phosphoric acid solution (PAS); phosphoric acid gel (PAG); Clearfil SE Bond 2 Primer (SE2); or Scotchbond Universal Adhesive (SBU). Longitudinal ultra-thin sections were made for TEM observations. Dentin discs, representing each surface preparation and treatment method described above, were created, and the morphology was examined by SEM. The TEM results revealed differences in thickness and denseness of the smear layer, according to the different methods of instrumentation used to prepare the dentin surface. The two forms of phosphoric acid completely removed the smear layer in all groups. Agglomerated silica particles were observed on the top of the collagen layer after etching with PAG. For all dentin surfaces, except for that prepared with SiC, SE2 demonstrated better etching efficacy on different smear layers, whereas SBU provided only superficial interaction.

Repair of defective resin composite restorations in primary teeth: current trends in Brazilian undergraduate Dental programs

Este estudo investigou o ensino do reparo de restauração direta de resina composta em dentes decíduos nos cursos de graduação em Odontologia no Brasil. Um questionário referente a este tópico foi desenvolvido e enviado por e-mail para 205 cursos de Odontologia entre maio e setembro de 2019. Os dados obtidos foram analisados descritivamente. A taxa de resposta foi de 43,4% e dos cursos respondentes, 82% incluíram esse tópico em seu currículo. As duas razões mais comumente relatadas para o ensino do reparo de restaurações de resina composta foram preservação da estrutura dentária (95,9%) e redução do risco de complicações pulpares (71,2%). No que diz respeito ao protocolo para reparo, poucos instituições (24,7%) ensinaram o desgaste mecânico da porção da resina a ser reparada com pontas diamantadas. Por outro lado, o condicionamento com ácido fosfórico da superfície preparada foi recomendado por 87,7% das instituições e 76,7% indicaram aplicação de adesivo na superfície preparada. O material mais comumente ensinado para reparo foi resina composta convencional. O ensino do reparo de restaurações de resina composta com falhas foi estabelecido dentro do currículo dos cursos de graduação em Odontologia no Brasil. No entanto, não há consenso sobre o protocolo clínico para reparo.

Effect of surface treatments on repair strength, roughness and morphology in aged metal-free crowns

Aim: The roughness and micromorphology of various surface treatments in aged metal-free crowns and the bond strength of these crowns repaired with composite resin (CR) was evaluated in vitro. Methods: A CR core build-up was confectioned in 60 premolars and prepared for metal-free crowns. Prepared teeth were molded with the addition of silicone, and the laboratory ceromer/fiber-reinforced crowns (SR Adoro/Fibrex Lab) were fabricated. Subsequently, the crowns were cemented and artificially aged in a mechanical fatigue device (1.2 X 106 cycles), then divided into 4 groups (n = 15) according to the surface treatment: 1) phosphoric acid etching (PA); 2) PA + silane application; 3) roughening with a diamond bur + PA; and 4) sandblasting with Al2O3 + PA. After the treatments, the crowns (n = 2) were qualitatively analyzed by scanning electron microscope (SEM) and surface roughness (n = 5) was analyzed before and after the surface treatment (Ra parameter). The remaining crowns (n = 8) received standard repair with an adhesive system (Tetric N-Bond) and a nanohybrid CR (Tetric N-Ceram), and the microshear bond strength (SBS) test was performed (0.5 mm/min). Roughness and SBS data were analyzed by one- and two-way ANOVA, respectively, as well as Tukey’s post-test (α = 0.05). Results: Sandblasting with Al2O3 + PA resulted in the highest final roughness and SBS values. The lowest results were observed in the PA group, whereas the silane and diamond bur groups showed intermediate values. Conclusion: It may be concluded that indirect ceromer crowns sandblasted with aluminum oxide prior to PA etching promote increased roughness surface and bond strength values.

Surface characteristics of dental resin nanoceramic in in vitro finishing with dental handpiece and rotary burs

Surface roughness and texture are critical characteristics of dental restorative materials in determining the clinical performance of dental prostheses. This study aimed to quantitatively assess the effects of dental rotary finishing process, necessarily involved in clinical practice, on surface roughness and texture of dental resin nanoceramic (RNC). In vitro dental finishing was conducted on a computer-assisted apparatus with a dental handpiece and diamond burs. Four clinically applied finishing parameters (diamond grit size, depth of cut, feed rate and rotational speed) were selected. The finished surface topographies were measured based on optimized sampling conditions. The 3D amplitude parameters of Sq and Sz, functional parameters of Sbi and Sci, and spatial texture parameters of Sal and Str were obtained using a 3D no-contact chromatic confocal profilometer, and then were calculated and statistically analyzed using ANOVA for surface characterization. The results show that diamond grit size had significant effects on the all surface parameters of Sq, Sz, Sbi (P < 0.01), and Sal, Str, Sci (P < 0.05), while bur rotational speed was irrelevant to the parameters (P > 0.05). The functional parameters of Sbi and Sci relied mainly on diamond grit size and feed rate (P < 0.05). Standard bur and medium bur easily caused deep valleys on the RNC surface, while finer burs or slower feed rates could improve bearing property but diminish core liquid remained property. Small girt size, slower feed rate and decreased rotational speed could generate more regular and finer surface texture. Implications concerning the relationship between surface roughness and finishing process parameters were provided to facilitate the process selection and quality control of RNC prostheses.

Silane Effect of Universal Adhesive on the Composite-Composite Repair Bond Strength after Different Surface Pretreatments.

This study investigated the impact of a separate silanization step on the repair bond strength of composite substrates using a universal adhesive after various mechanical surface treatments. Composite specimens were aged and exposed to the following mechanical roughening treatments: diamond bur abrasion, aluminum oxide sandblasting, or silica coating. The specimens were then either left untreated or conditioned with universal adhesive (Scotchbond Universal), or a silane coupling agent was applied before the use of the universal adhesive or a conventional adhesive (Optibond FL). The conditioned surfaces and fresh substrate (positive control group) were covered with repair composite, and microtensile bond strength testing was performed. The significantly highest bond strength was obtained in the positive control group. Repair bond strength of the universal adhesive applied after a separate silanization step was similar to that without prior silanization, independent of the mechanical surface treatment. Moreover, after silica coating, no significant differences in the repair bond strength were detected among the different adhesive treatments. In conclusion, a separate silanization step before surface conditioning with the universal adhesive does not enhance the repair bond strength. On silica-coated composite substrates, repair bond strength values of the universal adhesive were similar to those of the conventional adhesive.

Grinding the intaglio surface of yttria partially- and fully-stabilized zirconia polycrystals restorations: Effect on their fatigue behavior

This study evaluated the effects of diamond bur grinding the intaglio surface of second (yttria partially-stabilized zirconia polycrystals, PSZ) and third-generation zirconia (fully-stabilized zirconia polycrystals, FSZ) adhesively cemented to dentin analogue substrate on the fatigue failure load, cycle number until failure, surface micromorphology and phase transformation. Disc-shaped specimens were produced from second (Katana ML-HT, Kuraray) and third-generation zirconia (Katana STML, Kuraray) and randomly allocated (n = 15) into two groups according to the intaglio surface treatment: Control – Ctrl (without grinding); Grinding – Gr (grinding at the center of the intaglio surface). The ceramic discs were adhesively cemented (Multilink Automix System) onto dentin analogue discs. Fatigue tests were executed by the step-stress method. The obtained data were analyzed by Kaplan Meier and Mantel-Cox tests. In addition, surface topography, roughness, phase transformation and fractography analyses were performed. SEM analysis showed that grinding increased the surface roughness and introduced defects in zirconia from both generations. Grinding increased the fatigue failure load, number of cycles to failure and survival rates of the second-generation zirconia statistically (control: 1373.33 N < grinding: 1600 N), while these same outcomes were reduced by grinding for the third-generation zirconia significantly (control: 766.67 N > grinding: 620 N). Thus, clinical adjustments with diamond burs damage the fatigue behavior of adhesively cemented third-generation zirconia.