Surface roughness and wettability of enamel and dentine surfaces prepared with different dental burs

Scanning electron microscope analysis to evaluate the effect of pretreatment with ozone and sodium hypochlorite on pits and fissures of primary teeth

Introduction

The cornerstone of preventative therapy is made up of pit and fissure sealants and fluorides. Resin sealants have been shown to help reduce fissure decay in both primary and permanent teeth. Etching of primary molars is not effective due to prismless enamel, higher organic content, and diversity in fissure shape. Methods of pretreatment of pits and fissures have been hypothesized to promote microporosities in etched enamel and hence sealant adherence. Examining the etching pattern and surface roughness of the enamel surface can be used to gauge these.

Objective

This study aimed to evaluate the effect of pretreatment with ozone gas and 5.25% sodium hypochlorite solution on pits and fissures of primary teeth to check for the etching pattern and surface roughness.

Materials and Methods

Thirty noncarious primary molars were sectioned to retain the crowns, and randomly divided into three groups, sodium hypochlorite, ozone gas, and control. Each sample was pretreated with the agent, washed, followed by etching with 37% phosphoric acid. Samples were sectioned and subjected to scanning electron microscope analysis to evaluate the etching pattern and surface roughness.

Results

Comparison of the etching pattern in three groups showed a statistically insignificant difference (P=0.364). Surface roughness was highest in the hypochlorite group followed by ozone and control which showed a statistically significant difference (P = 0.001). The surface area between the three groups showed a statistically insignificant difference.

Conclusion

Sodium hypochlorite is a better pretreatment agent compared to ozone gas and acid etching alone. However, as all results were not statistically significant further research must be carried out to prove the effectiveness of these agents.

Physicochemical Properties of Dentine Subjected to Microabrasive Blasting and Its Influence on Bonding to Self-Adhesive Prosthetic Cement in Shear Bond Strength Test: An In Vitro Study

The aim of this in vitro study was to assess the influence of microabrasive blasting on the physicochemical properties of dentine and shear bond strength (SBS) of self-adhesive resin cement (Maxcem Elite, Kerr, Orange, CA, USA) bonded to the dentine surface. Ninety cylindrical specimens with exposed dentine of human teeth were prepared and divided into three randomized, parallel sample sets A, B, and C. Groups B and C were subjected to abrasive blasting using a micro-sandblasting device (Microetcher IIa, Danville Materials, Carlsbad, CA, USA) with two gradations of Al₂O₃ abrasives (Group B, abrasion with a gradation of 50 μm; group C, abrasion with a gradation of 27 μm). SEM imaging, profilometry, chemical composition analysis, contact angle measurements, surface free energy, and SBS tests were performed. The resulting data were statistically analyzed using the Statistica software (ver. 13.3, Tibco Software Inc., Palo Alto, CA, USA). Microabrasive blasting caused changes in surface topography, structural features, and the connection strength between the dentin surface and self-adhesive prosthetic cement. Air microabrasion through the multifactorial positive reorganization of the treated surface of dentine is recommended as a pretreatment method in fixed prosthodontics adhesive cementation protocols.

Limited Etching Time Increases Self-adhesive Resin Cement Adhesion to Enamel

AIM

To evaluate the influence of different enamel etching times on the bond strength of two self-adhesive resin cements (RCs) with and without thermocycling (TMC).

METHODS

One hundred twenty bovine teeth were used. Blocks of enamel (8×4×2mm) were obtained, polished, and randomly divided into two groups, according to the RC used: MaxCem Elite or RelyX U200. Groups were subdivided into four groups (n=16), according to the etching time: Control (0 seconds), 5 seconds, 10 seconds, and 20 seconds. Three RC cylinders (1-mm diameter) were built on each enamel block. The specimens were submitted to two storage conditions: 24 hours in distilled water or TMC (5000 cycles/5°C-55°C). Afterward, the specimens were submitted to the shear bond strength (SBS) test. The failure modes and adhesive interfaces were analyzed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Data were analyzed with three-way analysis of variance (ANOVA) and Tukey test (α=0.05).

RESULTS

Etching increased the SBS for both the RCs,especially forthe groups etched for 5 and 10 seconds. TMC affected negatively the SBS of the control groups (p<0.05). No resin tags were observed in control groups, and the formation of tags was time dependent.

CONCLUSION

The 10 seconds etching time was more effective in increasing the enamel-resin bond strength. TMC negatively affected bond strength in specimens without acid etching.

[Clinical pathway and preparation method of high-precision tooth shoulder platform]

A clear shoulder platform that can be easily identified by doctors and technicians or machines (mouth scan and warehouse scan) is important to obtaining a good long-term and stable fixed prosthesis treatment effect. At present, the pre-paration of the shoulder platform is usually based on free hands, and the practical operation is mainly guided by experience. Moreover, no comprehensive and objective preoperative design, intraoperative verification, and final test are available. Thus, the accuracy of shoulder platform preparation needs to be improved. In this study, the clinical pathway of "three determination, three selection, and three steps" with high accuracy of preparation and the precise shoulder preparation method of "bur-tip guidance" are proposed in detail.

Machinability of high-speed enamel cutting with carbide bur

The cutting of tooth enamel using a high-speed air-turbine handpiece and carbide bur is a key procedure in oral surgeries, such as the minimally invasive extraction. However, presently little is known about the cutting mechanics and material removal mechanism related to tooth enamel machinability. In this study, the machinability of high-speed enamel cutting with carbide bur is studied by a computer-aided numerical control system. The dynamic cutting forces of enamel of the occlusal, buccal/lingual, and proximal surfaces were measured by the force measuring system. The force ratio, cutting torque, rotating speed, specific cutting energy, and bur wear were analyzed. The microstructure of enamel and carbide burs was observed by the scanning electron microscope, and the relationship between enamel microstructures and machinability was further analyzed. The results show that during the high-speed enamel cutting with carbide bur, the chip thickness is on the nano-scale, and the plastic deformation of the machined surface is obvious. With increased material removal rate, the cutting force, torque, specific cutting energy, and bur wear increases accordingly, whereas the rotating speed decelerates (p < 0.05). The different angles between the cutting direction and the axial direction of the enamel rods give rise to the large differences in the cutting mechanics and mechanism of the proximal, buccal/lingual, and occlusal surfaces of the teeth. When the cutting direction is parallel, vertical, and oblique 45° to the axial direction of the enamel rods, the force required for material fracture and crack propagation increases, and the cutting force increases as a consequence. Parallel and oblique 45° cutting are the main modes of tooth segmentation in the minimally invasive extraction. In comparison with the parallel cutting mode, the cutting force, torque, and cutting ratio of the oblique 45° cutting mode can be significantly increased, and the tool wear is obviously accelerated. This is the lowest priority in segmentation surgery, hence the problems of overload and temperature rise need to be considered. The cutting mechanics and cutting mechanism obtained in this study will provide scientific process guidance for dental cutting operations with the air-turbine handpiece driving bur.

Minimal invasive microscopic tooth preparation in esthetic restoration: a specialist consensus

By removing a part of the structure, the tooth preparation provides restorative space, bonding surface, and finish line for various restorations on abutment. Preparation technique plays critical role in achieving the optimal result of tooth preparation. With successful application of microscope in endodontics for >30 years, there is a full expectation of microscopic dentistry. However, as relatively little progress has been made in the application of microscopic dentistry in prosthodontics, the following assumptions have been proposed: Is it suitable to choose the tooth preparation technique under the naked eye in the microscopic vision? Is there a more accurate preparation technology intended for the microscope? To obtain long-term stable therapeutic effects, is it much easier to achieve maximum tooth preservation and retinal protection and maintain periodontal tissue and oral function health under microscopic vision? Whether the microscopic prosthodontics is a gimmick or a breakthrough in obtaining an ideal tooth preparation should be resolved in microscopic tooth preparation. This article attempts to illustrate the concept, core elements, and indications of microscopic minimally invasive tooth preparation, physiological basis of dental pulp, periodontium and functions involved in tool preparation, position ergonomics and visual basis for dentists, comparison of tooth preparation by naked eyes and a microscope, and comparison of different designs of microscopic minimally invasive tooth preparation techniques. Furthermore, a clinical protocol for microscopic minimally invasive tooth preparation based on target restorative space guide plate has been put forward and new insights on the quantity and shape of microscopic minimally invasive tooth preparation has been provided.

Machinability of enamel under grinding process using diamond dental burrs

Enamel grinding is a critical dental surgery process. However, tooth damage during the process remains a significant problem. Grinding forces, burr wear, and surface quality were characterised in relation to grinding speed, enamel orientation, grinding depth, and burr grit grain size. Results indicated that enamel rod orientation, grinding depth, and grinding speed critically affected enamel grinding. Occlusal surface grinding resulted in significantly higher normal forces, surface roughness, and marginally greater tangential forces than axial surface grinding. Damage to enamel machined surfaces indicated the significant impact of diamond grit size and rod orientation. Burr wear was primarily diamond grit peeling off and breakage. Surface roughness of axial and occlusal sections was largely influenced by grinding speed and diamond grit size. Improving the surface quality of machined enamel surfaces could be realised using fine burrs, reducing the grinding speed and grinding depth, and adjusting the feed direction vertical to the rod orientation. Enamel surface quality and roughness could be improved by reducing brittle failure and circular runout during the grinding process, respectively.

Effect of etching with potassium hydrogen difluoride and ammonium hydrogen difluoride on bonding of a tri-n-butylborane initiated resin to zirconia

The purpose of the current study was to evaluate the effect of etching with potassium hydrogen difluoride (KHF₂) and ammonium hydrogen difluoride (NH₄HF₂) on the bond strength of a self-polymerizing methyl methacrylate resin (MMA-TBB) bonded to zirconia. Zirconia disks were prepared using the following surface treatment: no treatment, alumina blasting, and etching with KHF₂ or NH₄HF₂. The specimens were bonded with the MMA-TBB. The shear bond (Ø=5 mm) strength was measured. The surface free energies of the specimens were determined by measuring contact angles. The KHF₂ and NH₄HF₂ groups exhibited higher shear bond strength and surface free energy than did the alumina blasting and no treatment groups. Compared with alumina blasting, etching with KHF₂ and NH₄HF₂ exhibited superior bonding ability of mechanical retention to zirconia.

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

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

What is the changing frequency of diamond burs?

PURPOSE

The purpose of this study was to determine the changing frequency of a diamond bur after multiple usages on 3 different surfaces.

MATERIALS AND METHODS

Human 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).

RESULTS

All 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).

CONCLUSION

Diamond 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.

Effect of dentin surface roughness on the shear bond strength of resin bonded restorations

PURPOSE

This study aimed to investigate whether dentin surface preparation with diamond rotary instruments of different grit sizes affects the shear bond strength of resin-bonded restorations.

MATERIALS AND METHODS

The buccal enamel of 60 maxillary central incisors was removed with a low speed diamond saw and wet ground with silicon carbide papers. The polished surfaces of the teeth were prepared with four groups of rotary diamond burs with super-coarse (SC), coarse (C), medium (M), and fine (F) grit sizes. Following surface preparation, 60 restorations were casted with nickel-chromium alloy and bonded with Panavia cement. To assess the shear bond strength, the samples were mounted on a universal testing machine and an axial load was applied along the cement-restoration interface at the crosshead speed of 0.5 mm/min. The acquired data was analyzed with one way ANOVA and Tukey post hoc test (α=.05).

RESULTS

The mean ± SD shear bond strengths (in MPa) of the study groups were 17.75 ± 1.41 for SC, 13.82 ± 1.13 for C, 10.40 ± 1.45 for M, and 7.13 ± 1.18 for F. Statistical analysis revealed the significant difference among the study groups such that the value for group SC was significantly higher than that for group F (P<.001).

CONCLUSION

Dentin surface roughness created by diamond burs of different grit sizes considerably influences the shear bond strength of resin bonded restorations.

Human Fetal Osteoblast Response on Poly(Methyl Methacrylate)/Polystyrene Demixed Thin Film Blends: Surface Chemistry Vs Topography Effects

Recent advances in materials sciences have allowed for the development and fabrication of biomaterials that are capable of providing requisite cues to instigate cells to respond in a predictable fashion. We have developed a series of poly(methyl methacrylate)/polystyrene (PMMA/PS) polymer demixed thin films with nanotopographies ranging from nanoislands to nanopits to study the response of human fetal osteoblast cells (hFOBs). When PMMA was in excess in the blend composition, a nanoisland topography dominated, whereas a nanopit topography dominated when PS was in excess. PMMA was found to segregate to the top of the nanoisland morphology with PS preferring the substrate interface. To further ascertain the effects of surface chemistry vs topography, we plasma treated the polymer demixed films using an atmospheric pressure dielectric barrier discharge reactor to alter the surface chemistry. Our results have shown that hFOBs did not have an increased short-term cellular response on pristine polymer demixed surfaces. However, increasing the hydrophilicty/wettability of the surfaces by oxygen functionalization causes an increase in the cellular response. These results indicate that topography alone is not sufficient to induce a positive cellular response, but the underlying surface chemistry is also important in regulating cell function.

Effect of surface treatment on enamel surface roughness

Purpose:

To compare the effects of different methods of surface treatment on enamel roughness.

Materials and Methods:

Ninety human maxillary first premolars were randomly divided into three groups (n=30) according to type of enamel surface treatment: I, acid etching; II, Er:YAG laser; III, Nd:YAG laser. The surface roughness of enamel was measured with a noncontact optical profilometer. For each enamel sample, two readings were taken across the sample—before enamel surface treatment (T1) and after enamel surface treatment (T2). The roughness parameter analyzed was the average roughness (Ra). Statistical analysis was performed using a Paired sample t test and the post-hoc Mann- Whitney U test, with the significance level set at 0.05.

Results:

The highest Ra (average roughness) values were observed for Group II, with a significant difference with Groups I and III (P<0.001). Ra values for the acid etching group (Group I) were significantly lower than other groups (P<0.001).

Conclusion:

Surface treatment of enamel with Er:YAG laser and Nd:YAG laser results in significantly higher Ra than acid-etching. Both Er:YAG laser or Nd:YAG laser can be recommended as viable treatment alternatives to acid etching.

Influence of surface treatment of contaminated zirconia on surface free energy and resin cement bonding

Influences of contamination and cleaning methods on the bonding of resin cement to zirconia ceramics were examined. Airborne particle-abraded zirconia (IPS e.max ZirCAD) specimens were contaminated with saliva and cleaned with tap water (SC) or by application of 37% phosphoric acid (PA), Ivoclean (IC), or additional airborne particle abrasion (AB). Specimens without contamination served as controls. After application of Monobond Plus to the surface of the specimens, resin cement was mixed and inserted into a mold. Surface free energies of the specimens were determined by measuring contact angles. Surface treatment and storage conditions significantly influenced bond strength, while there was no significant interaction between the two factors. Surface free energies of the SC and IC groups were significantly lower than those of the other groups. Additional AB of saliva-contaminated zirconia increased the strength of bonding with the resin cement as well as increased surface free energy.

Effect of rotary cutting instruments on the resin-tooth interfacial ultra structure: An in vivo study

Objectives: To evaluate the effect of cutting teeth with different types of burs at various speeds on surface topography of tooth surface and interfacial gap formation at resin-tooth interface. Material and Methods: The human molars were divided into seven groups: Diamond bur in airrotor (DA) & micromotor (DM), crosscut carbide bur in airrotor (CCA) & micromotor (CCM), plain carbide bur in airrotor (CA) & micromotor (CM) and #600-grit silicon carbide paper (SiC). In five samples from each group Class II box-only cavities were restored. The occlusal surface of four teeth per group was flattened. Two out of four teeth were acid etched. Teeth were subjected for scanning electron microscopy (SEM). Results: Interfacial gap was observed in all groups with no significant difference. SEM observations revealed CA, CCA & DA were coarser than CM, CCM, DM and SiC. SEM of etched tooth surfaces revealed complete removal of amorphous smear layer in CA & CM, partial removal in CCA, CCM, DA & DM and no removal in SiC. Conclusions: Selecting an appropriate bur and its speed may not play an important role in bonding in terms of interfacial gap formation. Variable changes were observed in surface topography with different burs before and after acid etching.

Key words:Surface topography, resin-tooth interface, interfacial gap, bonding.

Influence of oscillating and rotary cutting instruments with electric and turbine handpieces on tooth preparation surfaces

STATEMENT OF THE PROBLEM

Rotary and nonrotary cutting instruments are used to produce specific characteristics on the axial and marginal surfaces of teeth being prepared for fixed restorations. Oscillating instruments have been suggested for tooth preparation, but no comparative surface roughness data are available.

PURPOSE

To compare the surface roughness of simulated tooth preparations produced by oscillating instruments versus rotary cutting instruments with turbine and electric handpieces.

MATERIAL AND METHODS

Different grit rotary cutting instruments were used to prepare Macor specimens (n=36) with 2 handpieces. The surface roughness obtained with rotary cutting instruments was compared with that produced by oscillating cutting instruments. The instruments used were as follows: coarse, then fine-grit rotary cutting instruments with a turbine (group CFT) or an electric handpiece (group CFE); coarse, then medium-grit rotary cutting instruments with a turbine (group CMT) or an electric handpiece (group CME); coarse-grit rotary cutting instruments with a turbine handpiece and oscillating instruments at a low-power (group CSL) or high-power setting (group CSH). A custom testing apparatus was used to test all instruments. The average roughness was measured for each specimen with a 3-dimensional optical surface profiler and compared with 1-way ANOVA and the Tukey honestly significant difference post hoc test for multiple comparisons (α=.05).

RESULTS

Oscillating cutting instruments produced surface roughness values similar to those produced by similar grit rotary cutting instruments with a turbine handpiece. The electric handpiece produced smoother surfaces than the turbine regardless of rotary cutting instrument grit.

CONCLUSION

Rotary cutting instruments with electric handpieces produced the smoothest surface, whereas the same instruments used with a turbine and oscillating instruments achieved similar surface roughness.

Effect of lactic Acid etching on bonding effectiveness of orthodontic bracket after water storage

Objective. To determine the effect of lactic acid at various concentrations on the shear bond strength of orthodontic brackets bonded with the resin adhesive system before and after water storage. Materials and Methods. Hundred extracted human premolars were divided into 5 treatment groups and etched for 30 seconds with one of the following agents: lactic acid solution with (A) 10%, (B) 20%, (C) 30%, and (D) 50%; group E, 37% phosphoric acid (control). Metal brackets were bonded using a Transbond XT. Bonding effectiveness was assessed by shear bond strength after 24 hours and 6 months of water storage at 37°C. The data were analyzed with 2-way analysis of variance and Tukey's Honestly Significant Difference (HSD) test (α = .001). Results. Lactic acid concentration and water storage resulted in significant differences for brackets bond strength (P < .001). 20% lactic acid had significantly higher mean bond strength values (SD) for all conditions: 24 hours [12.2 (.7) MPa] and 6 months [10.1 (.6) MPa] of water storage. 37% phosphoric acid had intermediate bond strength values for all conditions: 24 hours [8.2 (.6) MPa] and 6 months [6.2 (.6) MPa] of water storage. Also, there were differences in bond strength between storage time, with a reduction in values from 24 hours and 6 months for all experimental groups (P < .001). Conclusion. Lactic acid could be used in place of phosphoric acid as an enamel etchant for bonding of orthodontic brackets.

Effect of different burs on the topography of smear layer formation on the dentinal surface: a scanning electron microscope study

Whenever a hand or a rotary instrument is used to eliminate tooth tissue, the mineralized matrix shatters rather then being uniformly sheared, producing considerably quantities of cutting debris. Much of the debris made up of very small particles of mineralized collagen matrix over the surface of dentin is known as smear layer. The clinical outcome of dental restorations is dependent upon the surface preparations, smear layer formation and hybrid layer which which provides a stable adhesion. Different surface morphology is produced by use of different burs. The thickness of the smear layer is affected by various factors as type of the bur, use of water spray and speed of rotation. Bonding is enhanced when smear layer is completely removed or modifed. The purpose of this in vitro study is to evaluate the effect of different burs on the topography of the smear layer formation and thickness on dentinal surface.

The effect of exposed glass fibers and particles of bioactive glass on the surface wettability of composite implants

Measurement of the wettability of a material is a predictive index of cytocompatibility. This study was designed to evaluate the effect of exposed E-glass fibers and bioactive glass (BAG) particles on the surface wettability behavior of composite implants. Two different groups were investigated: (a) fiber reinforced composites (FRCs) with different fiber orientations and (b) polymer composites with different wt. % of BAG particles. Photopolymerized and heat postpolymerized composite substrates were made for both groups. The surface wettability, topography, and roughness were analyzed. Equilibrium contact angles were measured using the sessile drop method. Three liquids were used as a probe for surface free energy (SFE) calculations. SFE values were calculated from contact angles obtained on smooth surfaces. The surface with transverse distribution of fibers showed higher (P < 0.001) polar (γ^P) and total SFE (γ^TOT) components (16.9 and 51.04 mJ/m², resp.) than the surface with in-plane distribution of fibers (13.77 and 48.27 mJ/m², resp.). The increase in BAG particle wt. % increased the polar (γ^P) value, while the dispersive (γ^D) value decreased. Postpolymerization by heat treatment improved the SFE components on all the surfaces investigated (P < 0.001). Composites containing E-glass fibers and BAG particles are hydrophilic materials that show good wettability characteristics.

Surface characterization of Ti and Y-TZP following non-thermal plasma exposure

Novel non-thermal plasma (NTP) technology has the potential to address the bonding issues of Y-TZP and Ti surfaces. This study aims to chemically characterize and evaluate the surface energy (SE) of Y-TZP and Ti surfaces after NTP application. Y-TZP and Ti discs were treated with a hand-held NTP device followed by SE evaluation. Spectra of Y-TZP 3d and Ti 2p regions, survey scans, and quantification of the elements were performed via X-ray photoelectron Spectroscopy (XPS) prior and after NTP. Separate Y-TZP and Ti discs were NTP treated for contact angle readings using (10-methacryloyloxydecyl dihydrogenphosphate) MDP primer. Significant augmentation of SE values was observed in all NTP treated groups. XPS detected a large increase in the O element fraction on both Y-TZP and Ti surfaces. Reduction of contact angle reading was obtained when the MDP primer was placed on NTP treated Y-TZP. Ti surface showed high SE before and after NTP application on Ti surfaces. NTP decreased C and increased O on both surfaces independently of application protocol. Wettability of MDP primer on Y-TZP was significantly increased after NTP. The high polarity obtained on Y-TZP and Ti surfaces after NTP applications appear promising to enhance bonds.

Influence of natural bovine enamel roughness on bond strength after etching

OBJECTIVE

To determine and compare the longitudinal and transverse roughness parameters of the enamel surface of bovine teeth and evaluate the influence of these parameters on bond strength.

MATERIALS AND METHODS

Ninety bovine incisors were used. The surface roughness of enamel was measured with a profilometer. For each tooth, five readings were taken in the longitudinal plane and five were taken in the transverse plane of the long axis of the tooth in an area equal to the size of the bracket base. The metal brackets were bonded with Transbond XT, and bond strength was evaluated in a universal test machine.

RESULTS

There was a statistical correlation (P < .01) between the longitudinal and transverse roughness measurements. There was no correlation between roughness measurements (longitudinal and transverse) and bond strength (P > .05), nor was there a correlation between total roughness (longitudinal Ra and transverse Ra) and bond strength. The Student's t-test showed that there was a statistically significant difference (P < .05) between longitudinal and transverse roughness.

CONCLUSION

The transverse roughness is greater than the longitudinal roughness, there is a strong correlation between longitudinal and transverse roughness, and there is no correlation between enamel roughness and bond strength.

Effectiveness of high speed instrument and air abrasion on different dental substrates

The aim of this study was to compare the effectiveness of high speed (HS) and air abrasion (AA) instruments on groups of teeth (deciduous, permanent, bovine), in terms of preparation time, topography and presence of smear layer. Each group consisted of 5 teeth that had their buccal/lingual surfaces prepared by using either HS or AA. All procedures were standardized and timed. The teeth were then sectioned and prepared for evaluation of both the topography and the presence of smear layer by scanning electron microscopy. As regards preparation time, HS yielded preparations 1.5 times quicker than AA did on the three types of dental substrates (Wilcoxon test, p < 0.05). In both techniques (Kruskal-Wallis Test, p < 0.05) the preparation time was influenced by the dental substrate, particularly in deciduous teeth (Mann-Whitney test with Bonferoni's correction, p < 0.017), which required a longer preparation time. In the descriptive analysis of the topography, no difference was found between the substrates. Nonetheless, the different instruments used determined distinctive topographies. Both techniques produced a smear layer (chi2 McNemar, p > 0.05) in all substrates, but with different formations. In conclusion, the HS instrument was found to be more rapid than the AA. No difference was found between the three dental substrates as regards both the topography and the presence of smear layer. The differences found in the present study were only in relation to the effects of each instrument used.

Evaluation of the surface free energy on root canal dentine walls treated with chelating agents and NaOCl

AIM

To evaluate ex vivo the effects of combined and single use of EDTA, RC-Prep and NaOCl on the surface free energy of canal wall dentine using the captive bubble technique.

METHODOLOGY

Eighteen extracted human pre-molar teeth were sectioned at the crown and the apical third, the remaining mid-root portion were bisected longitudinally. Thereafter, the root halves were embedded in resin blocks that exposed the dentine surface of the canal wall. The specimens were randomly assigned to six experimental groups (n = 6) after polishing. The root dentine surfaces of the first two groups were treated with 17% EDTA or RC-Prep followed by 2.5% NaOCl irrigation. Groups 3, 4 and 5 were treated with either 17% EDTA, RC-Prep or 2.5% NaOCl alone. Control specimens were irrigated with saline solution. The surface free energies of experimental groups were calculated by measuring air and octane contact angles on the canal wall dentine. Statistical analysis was performed using the Mann-Whitney U and Bonferroni post-tests at P = 0.05.

RESULTS

Compared with the control group; combined and single use of EDTA, RC-Prep and NaOCl irrigation significantly decreased the surface free energy of canal wall dentine surfaces (P < 0.05). Among all groups tested, the use of NaOCl as a final flush following RC-Prep treatment yielded increased wettability. Nevertheless, this value remained lower than that of the control group.

CONCLUSION

Use of chelating agents alone or in combination with NaOCl decreased the wettability of root canal wall dentine.

Effect of surface treatments on the spreading velocity of simplified adhesive systems

Objectives:

To determine the roughness of glass surfaces submitted to different treatments and to correlate it with the spreading velocity of two adhesive systems.

Materials and Methods:

Glass slides were used as substrates to evaluate the spreading velocity of Single Bond and Prime & Bond NT adhesive systems. Six different surface treatments were compared: 1) no treatment; 2) silanization (SL); 3) sandblasting (SB); 4) SB + SL; 5) 10% hydrofluoric acid treatment (HF); 6) HF + SL. Before and after treatments, surface roughness was measured by a profilometer (Ra, μm). Drop volumes (10 μl) of the adhesive systems were deposited onto substrates with a micropipette to observe materials spreading during 30s. Data were expressed in mm/s as spreading velocity. Statistical significances among groups were analyzed using one-way and two-way-ANOVA designs and the SNK test.

Results:

Significant differences in spreading velocity were found between materials (p < 0.001) and among treatments (p < 0.001). Silanization decreased the spreading velocity for both adhesives in comparison to groups where it was not performed (p < 0.05). Differences in roughness were found only for SB surfaces that were rougher than the others (p < 0.05). Silanization decreased the roughness of SB surfaces (p < 0.05). Linear regression did not indicate any correlation between spreading velocity and roughness (R = 0.173).

Conclusions:

Although surface treatments yielded different roughness, they did not provide differences in the spreading velocity of the simplified bonding systems studied. Silanization decreased bonding systems' spreading velocities.

Human foetal osteoblastic cell response to polymer-demixed nanotopographic interfaces

Nanoscale cell-substratum interactions are of significant interest in various biomedical applications. We investigated human foetal osteoblastic cell response to randomly distributed nanoisland topography with varying heights (11, 38 and 85 nm) produced by a polystyrene (PS)/polybromostyrene polymer-demixing technique. Cells displayed island-conforming lamellipodia spreading, and filopodia projections appeared to play a role in sensing the nanotopography. Cells cultured on 11 nm high islands displayed significantly enhanced cell spreading and larger cell dimensions than cells on larger nanoislands or flat PS control, on which cells often displayed a stellate shape. Development of signal transmitting structures such as focal adhesive vinculin protein and cytoskeletal actin stress fibres was more pronounced, as was their colocalization, in cells cultured on smaller nanoisland surfaces. Cell adhesion and proliferation were greater with decreasing island height. Alkaline phosphatase (AP) activity, an early stage marker of bone cell differentiation, also exhibited nanotopography dependence, i.e. higher AP activity on 11 nm islands compared with that on larger islands or flat PS. Therefore, randomly distributed island topography with varying nanoscale heights not only affect adhesion-related cell behaviour but also bone cell phenotype. Our results suggest that modulation of nanoscale topography may be exploited to control cell function at cell-biomaterial interfaces.

Qualitative and quantitative evaluation of enamel after various stripping methods

INTRODUCTION

In this study, we investigated ultramorphology, surface roughness, and microhardness of permanent and deciduous tooth enamel after various stripping methods.

METHODS

One hundred twenty deciduous and permanent teeth (n = 60 each) were used. Qualitative (scanning electron microscopy) and quantitative (surface roughness and microhardness tests) experiments were carried out in the following experimental groups: group 1, stripping disk; group 2, diamond-coated metal strip; group 3, stripping disk and Sof-Lex discs (3M-ESPE, Seefeld, Germany); group 4, diamond-coated metal strip and Sof-Lex discs; group 5 (chemical stripping), 37% orthophosphoric acid in conjunction with diamond-coated metal strip; group 6 (control), no stripping. Surface roughness values (Ra) for permanent and deciduous enamel were evaluated with Welch analysis of variance (ANOVA) and Tamhane tests, and Kruskal-Wallis and Mann-Whitney tests, respectively. Microhardness values were evaluated statistically with Kruskal-Wallis, 1-way ANOVA, and Duncan tests.

RESULTS

Deciduous and permanent teeth showed similar results in terms of surface roughness and surface morphology. Groups 3 and 4 had the smoothest deciduous and permanent enamel surfaces, whereas chemical stripping (group 5) produced the roughest surfaces in both enamel types. Stripping did not lead to a significant change in the microhardness of permanent enamel.

CONCLUSIONS

All stripping methods significantly roughened the enamel surfaces. Polishing the stripped surface with Sof-Lex discs decreased the roughness.

Effect of dentinal surface preparation on bond strength of self-etching adhesive systems

The aim of this study was to evaluate the effects of dentin surface treatments on the tensile bond strength (TBS) of the self-etching primer Clearfil SE Bond (CSE) and the one-step self-etching One-Up Bond F (OUB). The exposed flat dentin surfaces of twenty-four sound third molars were prepared with diamond bur at high-speed, carbide bur at low-speed or wet ground with #600 grit SiC paper. The adhesive systems were applied to the dentin surfaces and light-cured according to the manufacturers' instructions. A 6-mm high composite crown was incrementally built-up and each increment was light-cured for 40 seconds. After being stored in water (37°C/24 h), the samples were serially sectioned parallel to the long axis, forming beams (n = 20) with a cross-sectional area of approximately 0.8 mm². The specimens were tested in a Universal Testing Machine at 0.5 mm/min. The cross-sectional area was measured and the results (MPa) were analyzed by two-way ANOVA and Tukey Test (p < 0.05). Overall, the groups treated with CSE exhibited the highest TBS for all surface treatments. Dentin surfaces prepared with carbide bur at low speed reduced TBS in the CSE group; however, OUB was not affected by surface treatments. The effect of surface abrasive methods on TBS was material-dependent.

Bond strength of simplified-step adhesives to enamel prepared with two different diamond burs

BACKGROUND

Self-etching primers are reported to produce considerable etching on flat enamel surfaces. However, little is known about the influence of different enamel surface textures. In this study the influence of grinding enamel on bond strength of two all-in-one and one two-step adhesives was investigated.

METHODS

Resin composite was bonded to the ground enamel of extracted human third molars that was reduced 0.5 mm from the buccal or lingual surfaces using either regular- or superfine-grit diamond burs with each of the three adhesives. After 24 hours in 37 degrees C water, the specimens were sectioned into slabs of 0.7 mm thickness, trimmed to an hourglass configuration, and subjected to microtensile bond strength (MTBS) testing.

RESULTS

For all adhesive systems, MTBS to enamel ground with a regular-grit diamond bur was not significantly different from that with a superfine-grit diamond bur. The etching patterns of these adhesives were partly varied according to the aggressiveness of the adhesives.

CONCLUSION

The use of two different burs does not affect the tensile bond strength of the adhesives to enamel.