Enamel Surface Roughness of Preferred Debonding and Polishing Protocols

Objective:: This study investigated the surface roughness of enamel after debonding and instrumentation with commonly used methods.

Methods:: Part I: a survey was sent to active members of the American Association of Orthodontists to determine popular bonding, debonding, and polishing protocols. Part II: brackets were bonded to the buccal surface of 30 extracted human premolar teeth. After debonding, residual adhesive was removed with 12-, 16-, and 20-fluted titanium carbide burs as based upon the survey results. The teeth were scanned with a surface profilometer for surface roughness. Part III: the teeth were further polished using a Reliance Renew polishing point or a prophy cup with pumice and rescanned for surface roughness.

Results:: Part I: the majority of respondents used a generic bracket-removing plier to remove fixed appliances (53%) and a high-speed handpiece for adhesive removal (85%). The most popular bur was a 12-fluted carbide bur without water spray. The majority of respondents used pumice paste and/or Reliance Renew points after adhesive removal. Part II: there was a significant difference in enamel surface roughness when 12-, 16-, and 20-fluted carbide burs were compared via surface profilometry. Part III: further polishing with a Reliance Renew point or a prophy cup and pumice did not provide a significantly smoother surface.

Conclusions:: The results show large variation in debonding and polishing techniques. Creating a smooth enamel surface is equally possible with 12- or 20-fluted carbide burs. Further polishing with pumice and prophy cup or Renew point does not provide an enamel smoother surface.     

Efficiency of powered systems for interproximal enamel reduction (IER) and enamel roughness before and after polishing—an in vitro study

Objective

This aims to evaluate the efficiency of three different powered interproximal enamel reduction (IER) systems and to assess enamel roughness before and after polishing using different polishing times.

Material and methods

Four metal strips of the G5 ProLign Set (swissdentacare, SDC, Grancia, Switzerland), four segmental discs of the ASR-Set 4594 and two sonic tips of the SonicLine Set (both Gebr. Basseler GmbH & Co. KG, Komet, Lemgo, Germany) were evaluated. Human extracted incisors served as the medium. Enamel reduction was determined in five intervals of 15 s each. Polishing was performed for 15 and 30 s using the manufacturers’ recommended polishing systems. Enamel roughness (Ra) was quantitatively assessed by confocal laser scanning microscopy (CLSM).

Results

Significant differences in terms of enamel reduction were found among the working ends of all tested systems. The time needed to remove 0.1, 0.2 and 0.3 mm of enamel was determined. Surface analysis showed significantly higher mean Ra values for nine out of ten working ends before polishing. This was still the case for five working ends after 15 s and for two after 30 s of polishing.

Conclusion

The graining and the system used have a significant influence on enamel reduction. The time needed for polishing depends on the last working end used; a polishing time of 30 s is not always appropriate.

Clinical relevance

Knowledge about the cutting efficiency of powered IER working ends might help the clinician to estimate better the amount of enamel reduction during the stripping process.

     

Effects of air-polishing devices with different abrasives on bovine primary and second teeth and deciduous human teeth

Objective

The present study investigates the effect of air polishing using different combinations of devices and abrasive powders on bovine secondary and primary dentition and on human deciduous teeth.

Materials and methods

Lower incisors of freshly slaughtered calves and cows were partially embedded in polyurethane and polished flat. Human deciduous incisors and second molars were subjected to the same procedure. These various tooth types (bovine secondary, bovine primary, human deciduous) were then randomly assigned to 22 groups containing 10 teeth each. The specimens in each group were treated by a specific combination of an air-polishing device (n=2; PROPHYflex 3®, Air-Flow® Handy 2+) and an abrasive (n=3; Air-Flow® Pulver Classic, ClinPro? Prophy Powder, PROPHYpearls®) applied from a distance of 5±0.5 mm at maximum setting for 60 s. Additional groups of specimens were polished with CCS® 40 or Cleanic® pastes applied with a rotating brush at low speed. A Perthometer PCV profilometer was used to analyze the degrees of surface roughness and enamel reduction in each group.

Results

PROPHYpearls® created significantly (p<0.05; t-test) more surface roughness and enamel reduction than both Air-Flow® and ClinPro?. There was no significant difference between the latter two abrasives. Any surface changes created by blasting or polishing were significantly (p<0.05; t-test) smaller on the bovine secondary teeth than on bovine primary or human deciduous teeth, with no significant difference between the latter two. The degrees of surface roughness induced by air polishing surpassed the effect of CCS® 40 paste but resembled the effect of Cleanic® paste.

Conclusion

Both Air-Flow® Handy 2+ and PROPHYflex 3® are appropriate devices to remove plaque and discoloration from the surface of deciduous teeth. PROPHYpearls® powder is excessively aggressive.     

Qualitative and quantitative evaluation of human dental enamel after bracket debonding: a noncontact three-dimensional optical profilometry analysis

Objectives

The aim of this study was to undertake a qualitative and quantitative evaluation of changes on enamel surfaces after debonding of brackets followed by finishing procedures, using a high-resolution three-dimensional optical profiler and to investigate the accuracy of the technique.

Materials and methods

The labial surfaces of 36 extracted upper central incisors were examined. Before bonding, the enamel surfaces were subjected to profilometry, recording four amplitude parameters. Brackets were then bonded using two types of light-cured orthodontic adhesive: composite resin and resin-modified glass ionomer cement. Finishing was performed by three different methods: pumice on a rubber cup, fine and ultrafine aluminum oxide discs, and microfine diamond cups followed by silicon carbide brushes. The samples were subsequently re-analyzed by profilometry.

Results

Wilcoxon signed-rank test, Kruskal–Wallis test (p?U test with Bonferroni correction (p?Conclusions The 3D optical profilometry technique was able to provide accurate qualitative and quantitative assessment of changes on the enamel surface after debonding.

Clinical relevance

Morphological changes in the topography of dental surfaces, especially if related to enamel loss and roughness, are of considerable clinical importance. The quantitative evaluation method used herein enables a more comprehensive understanding of the effects of orthodontic bonding on teeth.     

Influence of various polishing methods on pulp temperature

Objective

After orthodontic debonding, adhesive removal can lead to rises in pulp temperature, causing histological changes or pulp necrosis. The objective of this study was to measure increases in pulp temperature during adhesive removal using different instruments and various cooling procedures.

Materials and methods

A thermoelement was introduced into the pulp chamber of 10?human incisors. The teeth were immersed in a 36°C water bath up to the cementoenamel junction. Two carbide burs, one polishing disk and two rubber points were used for polishing. All measurements were taken over a 10?s period by a single investigator, under slight pressure and with constant motion. Three cooling procedures were examined: no cooling, air cooling and water cooling. Pulp temperatures were measured before polishing and after 10?s of polishing.

Results

Without cooling, the two rubber points revealed clinically relevant temperature increases of 6.1°C and 12.4°C. Cooling with air and with water reduced pulp temperature in conjunction with all polishing methods. Air cooling was most efficient, except in combination with the polishing disk.

Conclusion

Under these study conditions, carbide burs and polishing disks can be used safely and without risk to the pulp, even without cooling. On the other hand, rubber points cause a marked increase in pulp temperature when used without cooling.     

The effect of surface conditioning on the bond strength of resin composite to amalgam

Objectives

This study evaluated the effect of different surface conditioning methods on the tensile bond strength (TBS) and integrity of the amalgam-resin composite interface, using commercially available restoration repair systems.

Methods

One hundred and sixty Gamma 2 amalgam specimens were stored in artificial saliva for 2 weeks and then randomly assigned to one of the following conditioning groups (n = 20/group): Group 1: air abrasion, alloy primer and ‘Panavia 21’, Group 2: air abrasion and ‘Amalgambond Plus’, Group 3: air abrasion and ‘All-Bond 3’, Group 4: diamond bur, alloy primer and ‘Panavia 21’, Group 5: diamond bur and ‘Amalgambond Plus’, Group 6: diamond bur and ‘All-Bond 3’, Group 7: silica coating technique, and Group 8: non-conditioned amalgam surfaces (control group). Subsequently, resin composite material was added to the substrate surfaces and the amalgam-resin composite specimens were subjected to TBS testing. Representative samples from the test groups were subjected to scanning electron microscopy and surface profilometry. The data was analysed statistically with one-way ANOVA and post hoc Tukey's tests (α = 0.05).

Results

The mean TBS of amalgam-resin composite ranged between 1.34 and 5.13 MPa and varied with the degree of amalgam surface roughness and the type of conditioning technique employed. Significantly highest TBS values (5.13 ± 0.96 MPa) were obtained in Group 1 (p = 0.013).

Conclusion

Under the tested conditions, significantly greater tensile bond strength of resin composite to amalgam was achieved when the substrate surface was conditioned by air abrasion followed by the application of the Panavia 21 adhesive system.

Clinical significance

Effecting a repair of an amalgam restoration with resin composite via the use of air abrasion and application of Panavia 21 would seem to enhance the integrity of the amalgam-resin composite interface. Clinical trials involving the implementation of this technique are indicated to determine the usefulness of this technique.     

不同邻面抛光方法对牙釉质表面粗糙度及表面形貌的影响

目的：评价4种邻面抛光方法对邻面釉质表面粗糙度及显微形貌的影响,为邻面抛光方法的选择提供依据。方法：选择21颗离体牙前磨牙,沿颊舌面中线纵剖后获得邻面釉质试件42枚,再用自凝塑料包埋,暴露邻面釉质,用浮石粉抛光,并超声清洗。将42个试样均分为6组,分别作如下处理：A组空白对照,不做处理;B组：阴性对照,采用标准金刚砂车针切磨触点及其周围釉质,切磨后不抛光;其余4组为实验组,经标准金刚砂车针切磨后分别采用以下方法抛光：C组：极细粒度金刚砂车针抛光;D组：裂钻抛光;E组：矽粒子抛光;F组：彩虹抛光条抛光。之后用粗糙度仪测定釉面粗糙度,并进行扫描电镜观察。结果：标准金刚砂车针切磨后粗糙度大幅度增加（P〈0.05）,釉质表面发生明显条形凹陷性缺损;经4种方法抛光后,釉质表面粗糙度均有显著下降（P〈0.05）,显微形貌均较阴性组光滑,其中矽粒子抛光组可达到较空白对照组更为光滑的表面。结论：实验涉及的4种不同邻面抛光方法均有助于降低釉质切磨区域的表面粗糙度,但抛光效果存在差异;采用矽粒子抛光可完全抵消牙体预备时旋转器械对邻牙邻面的切磨作用,获得最为光滑的釉质表面。     

Brushing force of manual and sonic toothbrushes affects dental hard tissue abrasion

Objectives

This study aimed to determine the brushing forces applied during in vivo toothbrushing with manual and sonic toothbrushes and to analyse the effect of these brushing forces on abrasion of sound and eroded enamel and dentin in vitro.

Materials and methods

Brushing forces of a manual and two sonic toothbrushes (low and high frequency mode) were measured in 27 adults before and after instruction of the respective brushing technique and statistically analysed by repeated measures analysis of variance (ANOVA). In the in vitro experiment, sound and eroded enamel and dentin specimens (each subgroup n?=?12) were brushed in an automatic brushing machine with the respective brushing forces using a fluoridated toothpaste slurry. Abrasion was determined by profilometry and statistically analysed by one-way ANOVA.

Results

Average brushing force of the manual toothbrush (1.6?±?0.3 N) was significantly higher than for the sonic toothbrushes (0.9?±?0.2 N), which were not significantly different from each other. Brushing force prior and after instruction of the brushing technique was not significantly different. The manual toothbrush caused highest abrasion of sound and eroded dentin, but lowest on sound enamel. No significant differences were detected on eroded enamel.

Conclusion

Brushing forces of manual and sonic toothbrushes are different and affect their abrasive capacity.

Clinical significance

Patients with severe tooth wear and exposed and/or eroded dentin surfaces should use sonic toothbrushes to reduce abrasion, while patients without tooth wear or with erosive lesions confining only to enamel do not benefit from sonic toothbrushes with regard to abrasion.     

Fracture toughness and hardness of a Y-TZP dental ceramic after mechanical surface treatments

Objectives

The aim of the investigation was to evaluate the effects of surface mechanical treatments of all-Y-TZP restorations. In order to do that, surface roughness (Rs), fractal dimension (Df), fracture toughness (Ft), Vickers hardness (Hv), crack length (Cl), and opening (Co) were determined.

Materials and methods

Y-TZP bar-shaped specimens (n?=?30) were subdivided into three groups: as received by milling center (M), after coarse polishing (CP), and after fine polishing (FP). The specimens were examined under both confocal laser and electron scanning microscopes. One-way ANOVA and post hoc tests were used to analyze the data (α?=?0.05).

Results

The FP group showed a significantly lesser amount of Rs (P?<?0.05). The Df analysis confirmed the significantly lesser amount of surface complexity within the FP group (P?<?0.05). The Hv values were not significantly different among the groups. The Ft was significantly lesser within the FP group (P?<?0.05). At the same time, both Cl and Co were significantly higher within the FP group (P?<?0.05). Likewise, the FP treatment showed a significant decrease in roughness and surface complexity associated to a decrease of fracture toughness with a significant microcrack increase.

Conclusions

The present study suggests that the fine polishing procedure in all-YTZP restorations produces surface embrittlement.

Clinical relevance

Because of the surface embrittlement, mechanical surface polishing of all-zirconia restorations should be avoided.     

Long-term bonding to eroded dentin requires superficial bur preparation

Objectives

This study aims to evaluate the influence of different surface preparation techniques on long-term bonding effectiveness to eroded dentin.

Materials and methods

Dentin specimens were eroded by pH cycling or were left untreated as control, respectively. Five different “preparation” techniques were applied: (1) cleaning with pumice, (2) air abrasion, (3) silicon polisher, (4) proxo-shape, and (5) diamond bur. The three-step etch-and-rinse adhesive OptiBond FL (O-FL; Kerr) and the mild two-step self-etch adhesive Clearfil SE Bond (C-SE; Kuraray) were evaluated. Micro-tensile bond strength was measured after water storage for 24?h and 1?year. Fracture analysis was performed by stereomicroscopy and SEM. Interfaces were characterized by TEM. Differences were statistically analyzed with a linear mixed effects model (α?=?0.05).

Results

Erosion reduced bond strength in all groups, but this effect was less prominent when eroded dentin was prepared by diamond bur. Storage lowered bond strength in almost all groups significantly, but this ageing effect was more prominent for the eroded surfaces than for non-eroded controls. Whereas after 1-year control specimens revealed superior bond strength with the three-step etch-and-rinse adhesive (O-FL), the mild two-step self-etch adhesive (C-SE) revealed a better 1-year bond strength to eroded dentin. The interface at eroded dentin appeared very prone to degradation as was shown by the increased amount of adhesive failures and by the silver infiltration detected by TEM.

Conclusions and clinical relevance

Although a minimally invasive approach should clinically always be strived for, superficial preparation (or minimal roughening) with a diamond bur is recommendable for long-term bonding to eroded dentin.     

Qualifying the lapped enamel surface: A profilometric,electron microscopic and microhardness study using human,bovine and ovine enamel

Objective

When enamel specimens are prepared for erosion and abrasion studies, the assumption is often made that specimens prepared in the same way will have the same baseline surface characteristics. This study aimed to test the null hypothesis that there are no significant differences in baseline surface characteristics of human, ovine and bovine enamel specimens prepared using the same method.

Design

Twenty enamel slabs were prepared from bovine, human and ovine incisor crowns and polished with 3 μm aluminium oxide paste. Roughness average (Ra), bearing parameters (MR1, MR2, Rpk, Rk, Rvk), surface microhardness and scanning electron microscopy (SEM) were used to compare the different tissues. One way Analysis of Variance (ANOVA) was used to quantitatively compare surface characteristics between tissue types.

Results

Human, bovine and ovine enamel roughness and microhardness were significantly different to one another at baseline (P < 0.001); ovine enamel was the roughest and softest, and bovine enamel was the smoothest and hardest. SEM allowed a visual comparison to be made between tissue types, confirming the quantitative data.

Conclusions

Enamel from human, bovine and ovine specimens showed significantly different surface characteristics after lapping and polishing. The null hypothesis is rejected, recognising that the same preparation techniques will not necessarily result in consistent baseline roughness or surface characteristics between tissue types. Surface studies should lap and polish samples with a standardised approach, whilst ensuring that baseline data are recorded for comparison.     

In vitro evaluation of surface roughness, adhesion of periodontal ligament fibroblasts, and Streptococcus gordonii following root instrumentation with Gracey curettes and subsequent polishing with diamond-coated curettes

Objectives

The objective of the study was to evaluate the efficacy of an additional usage of a diamond-coated curette on surface roughness, adhesion of periodontal ligament (PDL) fibroblasts, and of Streptococcus gordonii in vitro.

Materials and methods

Test specimens were prepared from extracted teeth and exposed to instrumentation with conventional Gracey curettes with or without additional use of diamond-coated curettes. Surface roughness (Ra and Rz) was measured before and following treatment. In addition, the adhesion of PDL fibroblasts for 72 h and adhesion of S. gordonii ATCC 10558 for 2 h have been determined.

Results

Instrumentation with conventional Gracey curettes reduced surface roughness (median Ra before: 0.36 μm/after: 0.25 μm; p?<?0.001; median Rz before: 2.34 μm/after: 1.61 μm; p?<?0.001). The subsequent instrumentation with the diamond-coated curettes resulted in a median Ra of 0.31 μm/Rz of 2.06 μm (no significance in comparison to controls). The number of attached PDL fibroblasts did not change following scaling with Gracey curettes. The additional instrumentation with the diamond-coated curettes resulted in a two-fold increase in the number of attached PDL fibroblasts but not in the numbers of adhered bacteria.

Conclusions

Treatment of root surfaces with conventional Gracey curettes followed by subsequent polishing with diamond-coated curettes may result in a root surface which provides favorable conditions for the attachment of PDL fibroblasts without enhancing microbial adhesion.

Clinical relevance

The improved attachment of PDL fibroblasts and the limited microbial adhesion on root surfaces treated with scaling with conventional Gracey curettes followed by subsequent polishing with diamond-coated curettes may favor periodontal wound healing.     

The effect of alumina and aluminium nitride coating by reactive magnetron sputtering on the resin bond strength to zirconia core

PURPOSE

Although several surface treatments have been recently investigated both under in vitro and in vivo conditions, controversy still exists regarding the selection of the most appropriate zirconia surface pre-treatment. The purpose of this study was to evaluate the effect of alumina (Al) and aluminium nitride (AlN) coating on the shear bond strength of adhesive resin cement to zirconia core.

MATERIALS AND METHODS

Fifty zirconia core discs were divided into 5 groups; air particle abrasion with 50 µm aluminum oxide particles (Al₂O₃), polishing + Al coating, polishing + AlN coating, air particle abrasion with 50 µm Al₂O₃ + Al coating and air particle abrasion with 50 µm Al₂O₃ + AlN coating. Composite resin discs were cemented to each of specimens. Shear bond strength (MPa) was measured using a universal testing machine. The effects of the surface preparations on each specimen were examined with scanning electron microscope (SEM). Data were statistically analyzed by one-way ANOVA (α=.05).

RESULTS

The highest bond strengths were obtained by air abrasion with 50 µm Al₂O₃, the lowest bond strengths were obtained in polishing + Al coating group (P<.05).

CONCLUSION

Al and AlN coatings using the reactive magnetron sputtering technique were found to be ineffective to increase the bond strength of adhesive resin cement to zirconia core.     

Effect of artificial toothbrushing and water storage on the surface roughness and micromechanical properties of tooth-colored CAD-CAM materials

Statement of problem

Because of the different composition of resin-ceramic computer-aided design and computer-aided manufacturing (CAD-CAM) materials, their polishability and their micromechanical properties vary. Moreover, depending on the composition of the materials, their surface roughness and micromechanical properties are likely to change with time.

Efficacy of TiF4 and NaF varnish and solution: a randomized in situ study on enamel erosive–abrasive wear

Objectives

This in situ/ex vivo study analysed the anti-erosive/abrasive effect of TiF₄ and NaF varnish and solution on enamel wear.

Materials and methods

Twelve subjects took part in this study which was performed in three periods (phases) with the duration of 5 days each. Each two human enamel specimens per subject were pretreated with experimental NaF varnish or solution (phase A), experimental-TiF₄ varnish or solution (phase B) and placebo varnish or untreated control (phase C). The specimens were worn in palatal appliances; one enamel specimen, from each treatment, was subjected to erosion (ERO; cola soft drink, 4?×?90 s/day), and the other specimen was subjected to erosion plus abrasion (ERO + ABR; tooth brushing, 2?×?10 s/day). The tooth wear was quantified by a contact profilometer (micrometre) and analysed using two-way repeated measures ANOVA and Bonferroni’s test (n?=?12 subjects, p?<?0.05).

Results

All fluoride varnishes and solutions reduced the enamel wear (around 25 %) significantly compared to the control and placebo varnish. There were no significant differences among the fluoride formulations and between the conditions ERO and ERO + ABR.

Conclusions

Therefore, it can be concluded that TiF₄ has the same protective potential as NaF formulations to reduce human enamel wear under this experimental in situ model.

Clinical significance

In vitro studies have indicated a better anti-erosive/abrasive effect of TiF₄ compared to NaF varnish. The present in situ study does not support the previous findings. Therefore, any of the tested professional fluoride varnishes in principle could be able to partially reduce enamel wear.     

Repair bond strength of microhybrid, nanohybrid and nanofilled resin composites: effect of substrate resin type, surface conditioning and ageing

Objectives

This study evaluated the microtensile bond strength (MTBS) of non-aged and aged resin-based composites (RBC) (nanohybrid and nanofilled) after two surface conditioning methods, repaired using the composite of the same kind or a microhybrid composite.

Materials and methods

Nanohybrid (Tetric EvoCeram—TE) and nanofilled (Filtek Supreme—FS) RBC blocks (5?×?5?×?6 mm) (N?=?128) were fabricated and randomly divided into two groups: (a) no ageing (control group) and (b) ageing (5.000 thermocycling, 5–55 °C). RBC surfaces were polished by up to 1,200-grit silicone carbide papers and conditioned with either (a) air abrasion with 30-μm SiO₂ particles (CoJet Sand) for 4 s + silane coupling agent (ESPE-Sil) + adhesive resin (VisioBond) (n?=?16) or (b) adhesive application only (Multilink A+B for TE; Adper ScotchBond 1XT for FS) (n?=?16). In half of the groups, repair resin of the same kind with the RBC and, in the other half, a different kind of composite (microhybrid, Quadrant Anterior Shine—AS) with its corresponding adhesive (Quadrant UniBond) was used. The specimens were submitted to MTBS test (0.5 mm/min). Data were analysed using three-way ANOVA and Tukey's tests. Degree of conversion (DC) of non-aged and aged resin composites (TE, FS) (n?=?3 per group) was measured by micro-Raman analyses.

Results

RBC type (p?=?0.001) and ageing affected the MTBS results significantly (p?=?0.001). Surface conditioning type did not show significant difference (p?=?0.726), but less number of pre-test failures was experienced with the CoJet system compared to adhesive resin application only. Repair strength on aged TE showed significantly less (p?<?0.05) MTBS than for FS. FS repaired with the same kind of RBC and adhesive resin presented the highest cohesive failures (43 %). DC was higher for TE (71 %) than for FS (58 %) before ageing.

Conclusion

On the aged RBCs, less favourable repair strength could be expected especially for nanohybrid composite. For repair actions, RBC surface conditioning could be accomplished with either adhesive resin application only or with CoJet system, providing that the latter resulted in less pre-test failures.

Clinical relevance

Clinicians could condition the resin surface prior to repair or relayering with either CoJet system or adhesive resin application only, depending on the availability of the system.     

Effect of polishing procedures and hydrothermal aging on wear characteristics and phase transformation of zirconium dioxide

Statement of problem

Yttria-stabilized zirconia used for the fabrication of crowns and fixed prostheses may require intraoral adjustments after placement and cementation. Grinding and polishing methods may result in changes in the surface characteristics of zirconia.

Laboratory evaluation of toothbrush/toothpaste abrasion resistance after smooth enamel surface sealing

Objectives

The use of dental sealants has been extended to smooth enamel surfaces. The present study was conducted to test the in vitro performance of four sealants with different characteristics (highly and lowly filled, self-etching features).

Materials and methods

Eighty human teeth (lower incisors and premolars) were randomly divided into following sealant test groups: ProSeal^TM, LightBond^TM, OrthoSolo^TM, and Seal&Protect^®. Twenty untreated teeth served as a control group. Tooth brushing was conducted for a period of time simulating 12, 18, and 24 months. During the toothbrush abrasion protocol, the specimens were subjected to thermal and acidic challenge. Sealant thickness was determined with μCT imaging, and qualitative and quantitative surface effects were investigated using stereo microscopy and raster electron microscopy, respectively. Data were subjected to t test or Kruskal–Wallis/Mann–Whitney tests (alpha, 5 %).

Results

The wear behavior and film integrity of highly filled sealants were superior to lowly filled sealants. Even after 1 year of tooth brushing, significant surface deterioration with deleterious loss of enamel and discoloration was observed in all tested materials (χ²?=?15.349; P?=?0.004). The size of the observed defects increased over time.

Conclusion

These results suggest that the application of sealants on smooth enamel surfaces should be limited to special indications, and their usefulness has to be revisited.

Clinical relevance

Based on the results of this in vitro study, the general overall application of enamel sealants needs to be questioned.     

Adhesion of different brands of glass ionomer cements to a ceramometal alloy

Aims

The aim of the study was to assess, compare and evaluate the adhesive strength and compressive strength of different brands of glass ionomer cements to a ceramometal alloy.

Materials

(A) Glass ionomer cements: GC Fuji II - GC Corporation, Tokyo; Chem Flex — Dentsply DeTrey, Germany; Glass ionomer FX — Shofu-11, Japan; MR dental — MR Dental Suppliers Pvt. Ltd., England; (B) ceramometal alloy — Ugirex III; (C) cold cure acrylic resin; (E) temperature cum humidity control chamber; and (F) Instron universal testing machine.

Methods

Four different types of glass ionomer cements were used in the study. From each type of the glass ionomer cements, 15 specimens were made to evaluate the compressive strength and adhesive strength, respectively. Fifteen specimens were further divided into 3 subgroups each having 5 specimens. For compressive strength, specimens were tested at 2, 4 and 12 hours by using Instron universal testing machine. To evaluate the adhesive strength, specimens were surface treated with diamond bur, silicone carbide bur and sandblasting, and tested under Instron universal testing machine.

Results and conclusions

It was concluded from the study that the compressive strength as well as the adhesive bond strength of MR dental glass ionomer cement with a ceramometal alloy was found to be maximum compare to other glass ionomer cements. Sandblasting surface treatment of ceramometal alloy was found to be comparatively more effective for adhesive bond strength between alloy and glass ionomer cement.     

Boundary lubrication by brushed salivary conditioning films and their degree of glycosylation

Objectives

Toothbrushing, though aimed at biofilm removal, also affects the lubricative function of adsorbed salivary conditioning films (SCFs). Different modes of brushing (manual, powered, rotary–oscillatory or sonically driven) influence the SCF in different ways. Our objectives were to compare boundary lubrication of SCFs after different modes of brushing and to explain their lubrication on the basis of their roughness, dehydrated layer thickness, and degree of glycosylation. A pilot study was performed to relate in vitro lubrication with mouthfeel in human volunteers.

Materials and methods

Coefficient of friction (COF) on 16-h-old SCFs after manual, rotary–oscillatory, and sonically driven brushing was measured using colloidal probe atomic force microscopy (AFM). AFM was also used to assess the roughness of SCFs prior to and after brushing. Dehydrated layer thicknesses and glycosylation of the SCFs were determined using X-ray photoelectron spectroscopy. Mouthfeel after manual and both modes of powered brushing were evaluated employing a split-mouth design.

Results

Compared with unbrushed and manually or sonically driven brushed SCFs, powered rotary–oscillatory brushing leads to deglycosylation of the SCF, loss of thickness, and a rougher film. Concurrently, the COF of a powered rotary–oscillatory brushed SCF increased. Volunteers reported a slightly preferred mouthfeel after sonic brushing as compared to powered rotating–oscillating brushing.

Conclusion

Deglycosylation and roughness increase the COF on SCFs.

Clinical relevance

Powered rotary–oscillatory brushing can deglycosylate a SCF, leading to a rougher film surface as compared with manual and sonic brushing, decreasing the lubricative function of the SCF. This is consistent with clinical mouthfeel evaluation after different modes of brushing.