Bleaching effectiveness,hydrogen peroxide diffusion,and cytotoxicity of a chemically activated bleaching gel

Objectives

The objective of this study was to evaluate the bleaching effectiveness, hydrogen peroxide diffusion (H₂O₂), and cytotoxicity of a bleaching gel with 35 % H₂O₂ either associated with ferrous sulfate (FeSO₄) or not.

Materials and methods

Enamel/dentin discs adapted to artificial pulp chambers were placed in compartments containing a culture medium (Dulbecco's Modified Eagle's Medium (DMEM)) and distributed into the following groups: G1—no treatment (negative control), G2—10 % carbamide peroxide (one application for 4 h), G3—35 % H₂O₂ (three applications for 15 min), and G4—35 % H₂O₂ + 0.004 g FeSO₄ (three applications for 15 min). After treatments, the extracts (DMEM + bleaching components that diffused across enamel and dentin) were applied on human dental pulp cells (HDPCs) and odontoblast-like cells (MDPC-23). Cell viability (MTT assay, Kruskal–Wallis and Mann–Whitney, α?=?5 %), quantification of H₂O₂ diffusion, and color change of the enamel/dentin discs (Commission Internationale de I'Eclairage L*a*b* system) were assessed (analysis of variance and Tukey's tests, α?=?5 %).

Results

For both cells, a significant reduction in cell viability was observed for G3 and G4 compared with G1 and G2. No statistical difference was observed between G3 and G4. The rate of H₂O₂ diffusion was significantly higher in G3 compared with that in G2 and G4. The ΔE value for G4 was statistically higher than that of the other groups.

Conclusions

Chemical activation of H₂O₂ by FeSO₄ improves the bleaching effectiveness. However, this metal ion has no significant protective effect against pulp cell cytotoxicity.

Clinical relevance

Although the chemical activation of H₂O₂ by adding FeSO₄ to the bleaching agent improved the bleaching effectiveness, this metal ion has no significant protective effect against pulp cell cytotoxicity.     

Pretreatment of natural caries lesions affects penetration depth of infiltrants in vitro

Objectives

Limited evidence exists about the usefulness of ethanol or acetone application to desiccate caries lesions before resin infiltration. Therefore, this in vitro study aimed to compare the penetration depths (PD) of an infiltrant (DMG, Germany) into natural caries lesions using various pretreatments.

Material and methods

Extracted permanent human molars and premolars showing non-cavitated caries lesions were etched (90 s, 15 % HCl gel) and stored in pooled saliva (7 days). Lesions were etched again (30 s, 15 % HCl gel), washed (30 s), air-dried (30 s), and randomly allocated to one of the pretreatments: none (negative control), air-drying (incubator, 37 °C, 24 h; positive control), once ethanol (E1), twice ethanol (E2), once acetone (A1), and twice acetone (A2). Subsequently, the infiltrant was applied for 5 min and light-cured. Ground sections were prepared for analyses of lesion depths (LD) and PD using confocal microscopy.

Results

Median LD (Q25/Q75) of all lesions (n?=?91) and lesions ≥500 μm (n?=?57) were 629 (395/798) and 731 (638/876)?μm, respectively. When all lesions were analyzed, no significant differences between various pretreatments could be observed (p?>?0.05, Kruskal–Wallis). For lesions ≥500 μm, significantly deeper PP was observed in groups PC, E1, A1, and A2 compared with NC (p?<?0.05; Mann–Whitney), but not after adjustment for multiple comparison (p?>?0.05).

Conclusion

Application of either ethanol or acetone, followed by air-drying, is suitable to prepare caries lesions for resin infiltration in vitro.

Clinical relevance

This paper shows that proper drying is an important step prior to caries infiltration.     

Effectiveness of a desensitizing agent before in-office tooth bleaching in restored teeth

Objectives

The aim of this clinical trial was to evaluate the effectiveness and tooth sensitivity associated with bleaching in patients with composite restorations in anterior teeth after the application of a desensitizing agent.

Material and methods

Bleaching was performed with 35 % hydrogen peroxide gel in 30 patients with composite restorations in anterior teeth, divided according to the prior application of a desensitizing agent (De), or a placebo (Pl), on maxillary superior teeth. Color was recorded at baseline, 1 week after each session and 6 months after treatment. The experience of tooth sensitivity (TS) was recorded on an NRS (0–4) during bleaching and 24 h after each session. Bleaching effectiveness was evaluated by one-way ANOVA and Tukey's tests (α?=?0.05). The percentage of TS was evaluated by Fisher's exact test. For each treatment, periods were compared using the Wilcoxon signed-rank test (α?=?0.05), and at each period, treatments were compared using Mann–Whitney U test.

Results

Both groups showed similar tooth color enhancement and color stability after 6 months (p?<?0.05). No significant difference in prevalence of sensitivity was detected between groups (p?<?0.001). Higher TS intensity (median [first/third quartiles]) was observed for Pl (1.5 [1/1.75]) compared with De (0.5 [0/1]) during treatment (p?<?0.05).

Conclusions

The use of a desensitizing gel (5 % potassium nitrate, 2 % sodium fluoride) before tooth bleaching in patients with composite restorations did not reduce the prevalence of tooth sensitivity, but reduced the intensity of TS during bleaching.

Clinical relevance

Although the use of a desensitizing agent before bleaching, in patients with composite resin restorations, did not reduce the prevalence of TS, a reduction of the TS intensity during the protocol was observed without jeopardizing the whitening outcome.     

The use of NaOCl in combination with CHX produces cytotoxic product

Objectives

The combination of sodium hypochlorite (NaOCl) and chlorhexidine (CHX) yields a “precipitate potentially toxic” (PPT). The aim of this study was to evaluate the tissue response to implanted polyethylene tubes filled with PPT-soaked fibrin sponge.

Methods

Forty rats received four polyethylene tubes each; each tube was filled with fibrin sponge soaked by 2.5 % NaOCl, 2.0 % CHX, PPT (2.5 % NaOCl plus 2.0 % CHX), or not soaked (control). The observation time points were 7, 15, 30, 60, and 90 days. At each time point, eight animals were killed, and the tubes and surrounding tissues were removed, fixed, and prepared for light microscopic analysis by performing glycol methacrylate embedding, serial cutting into 3-μm sections, and hematoxylin–eosin staining. Qualitative and quantitative evaluations of the reactions were performed. Results were statistically analyzed by Kruskal–Wallis test (p?<?0.05).

Results

All chemical solutions caused moderate reactions at 7 days. On day 30, PPT group was more cytotoxic than the control group and the CHX group (p?<?0.05). On days 15 and 60, PPT group was more cytotoxic than the control group (p?<?0.05). On day 90, there was no statistically significant difference between the different groups.

Conclusion

PPT is more cytotoxic than NaOCl and CHX alone, particularly in the short term.

Clinical significance

Protocols which suggest the use of CHX and NaOCl must be revised because this mixture produces cytotoxic product.     

The effects of low-fluoride toothpaste supplemented with calcium glycerophosphate on enamel demineralization

Objectives

The aim of the present study was to evaluate the effects of different concentrations of calcium glycerophosphate (CaGP) in toothpastes with low-fluoride (low-F) concentrations on enamel demineralization by using a bovine enamel and pH cycling model.

Materials and methods

Experimental toothpastes containing 0 or 500 μg F/g (NaF) and CaGP concentrations of 0, 0.1, 0.25, 0.5, 1, and 2 % were manufactured. A commercial toothpaste was used as a positive control (1,100 μg F/g). After polishing and hardness tests, enamel blocks were subjected to pH cycling for 5 days and toothpaste treatment twice daily. The treatment regimen involved soaking all blocks in the corresponding slurry for 1 min (2 ml/block). Surface and cross-sectional hardness and fluoride concentrations in enamel were analyzed. The hardness data were analyzed using a one-way ANOVA followed by a Bonferroni post hoc test. Fluoride concentrations were analyzed using a Kruskal–Wallis followed by a Student–Newman–Keuls post hoc test.

Results

The mineral loss with the toothpaste containing 500 μg F/g and 0.25 % CaGP was lower than that in the other groups (p?<?0.05). Fluoride concentrations in the enamel treated with 0.1, 0.25, and 0.5 % CaGP toothpastes were similar to those in the enamel treated with the 500 μg F/g toothpaste (p?>?0.05). A greater concentration of CaGP reduced the fluoride levels in enamel (p?<?0.05).

Conclusions

The results from the present in vitro study show that a low-F (500 μg F/g) toothpaste is capable of maintaining the efficacy of 1,100 μg F/g toothpaste when supplemented with 0.25 % of CaGP.

Clinical relevance

The developed toothpaste prevents caries as a standard one and is safe for individuals of any age group.     

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.     

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.     

Six months of high-dose xylitol in high-risk caries subjects—a 2-year randomised, clinical trial

Objectives

The hypothesis was that the daily use of a high dose of a xylitol chewing gum for 6 months would reduce the increment of decayed permanent first molar surfaces (ΔD₆S) in high-risk schoolchildren after 2 years.

Methods

In this randomised, clinical trial, 204 schoolchildren with a high caries risk were assigned to two experimental groups, xylitol and non-xylitol. Caries status, salivary mutans streptococci, and lactobacilli were re-evaluated 2 years later in 74 xylitol-treated and 83 non-xylitol-treated schoolchildren. Differences in mean ?D₆S between groups registered at baseline and at follow-up were evaluated using the nonparametric Mann–Whitney U test.

Results

Outcome was the development of detectable carious lesions initial (D₁–D₂) and manifest (D₃) in the permanent first molars. In the xylitol group, the difference in proportion of children with decayed first permanent molars at baseline and follow-up was 1.43 % for manifest lesion and 2.86 % for initial lesions; while in the non-xylitol group was 10.26 % (p?<?0.01) and 16.66 % (p?<?0.01), respectively. A statistically significant difference regarding means was also observed in the non-xylitol group: the ?D₆S for manifest lesion was 0.18 (p?=?0.03) and 0.67 (p?=?0.02) for initial lesion.

Conclusion

The use of a chewing gum containing a high dose of xylitol for a period of 6 months has been shown to produce a long-term effect on caries development in high caries-risk children.

Clinical relevance

A school-based preventive programme based on 6 months’ administration of a high dose of xylitol via chewing gum proved to be efficacious in controlling caries increment in high-risk children.     

Perioperative use of an anti-inflammatory drug on tooth sensitivity caused by in-office bleaching: a randomized, triple-blind clinical trial

Objectives

The aim of this study was to determine the effect of etoricoxib 60 mg on tooth sensitivity (TS) caused by in-office bleaching.

Materials and methods

A triple-blind, parallel design, randomized clinical trial was conducted on 30 healthy, young adults who received either a placebo or etoricoxib. The drugs were administered 1 h before the bleaching process and after 24 h. Treatment was performed with 35 % hydrogen peroxide gel. The TS was recorded on three scales: VAS, 0–4, and 0–100. Shade evaluations were performed before and 30 days after bleaching with a visual shade guide and a spectrophotometer. The percentage of patients who reported TS at least once during treatment and the TS intensity were evaluated by Fisher’s exact and Mann–Whitney U tests, respectively. Tooth color changes were evaluated by repeated measures ANOVA.

Results

There were no significant differences in the percentage of patients with TS, intensity of TS, and color between the groups.

Conclusions and clinical significance

The anti-inflammatory medication etoricoxib 60 mg was unable to reduce the presence and intensity of TS. NCT01300780 (protocol No. 17838/2010).     

Postoperative tooth sensitivity with a new self-adhesive resin cement—a randomized clinical trial

Objectives

This study evaluated and compared sensitivity of teeth after cementation of full-coverage crowns with a new self-adhesive resin cement (SARC). A resin-modified glass ionomer cement (RMGIC) served as control.

Materials and methods

Eighty-eight full-coverage crowns were cemented to vital teeth with either the self-adhesive cement iCem (Heraeus Kulzer; n?=?44) or the RMGIC GC Fuji PLUS (GC, n?=?44). Before preparations, patients were questioned for sensitivity (patient sensitivity, PS). In addition, air was blown for 2 s onto the buccal cementoenamel junction (air sensitivity, AS), and ice spray was applied in the cementoenamel junction area (ice sensitivity, IS). Patient responses were recorded with a visual analog scale. After cementation of the crowns, patients were recalled for follow-up (f/u) visits at 1 day, 1 week, and 3 weeks. PS, AS, and IS were recorded during each visit. Data were analyzed with Mann–Whitney U tests.

Results

The two groups revealed comparable sensitivity scores at baseline. SARC showed significantly lower PS sensitivity scores at 1 day (p?=?0.02) and significantly lower AS scores at 1-week follow-up (p?=?0.01). IS generally produced the highest sensitivity scores with SARC revealing significantly lower scores at all follow-up visits.

Conclusion

Cementation of crowns with the SARC tested in this study resulted in overall lower postoperative sensitivity than with the RMGIC.

Clinical relevance

Among other clinical advantages, some self-adhesive resin cements seem to lower postoperative sensitivity of crowned teeth.     

Effectiveness and mode of action of whitening dentifrices on enamel extrinsic stains

Objectives

This study was conducted in order to investigate the mode of action and the whitening effect of whitening dentifrices.

Material and methods

Two hundred fifty-six bovine enamel specimens (10?×?10 mm²) were prepared, partially stained, and assigned into eight groups (n?=?32): six whitening dentifrices, one nonwhitening and deionized water (negative control), and further divided in two subgroups (n?=?16), according to the test model: chemical (dentifrice slurry treatment only) or chemo-mechanical (slurry?+?toothbrushing). Specimens were treated with dentifrice slurries 2×/day for 1 min and toothbrushed or not, according to each model. In between dentifrice treatments, specimens were artificially stained for 5 h. This protocol was repeated for 5 days and enamel color changes (?E) were measured after each day (days 1–5). The abrasive level of the dentifrices was determined following the ISO11609 guidelines.

Results

In the chemo-mechanical model, the whitening action of all dentifrices was observed after day 1, being higher than the negative control group (p?<?0.05). In days 2–5, nonsignificant changes in color were observed for all groups (p?>?0.05). Differences on ?E among dentifrices were observed, and they seemed to correlate well with their abrasive level (r ²?=?0.80). In the chemical model, no significant differences were observed among groups (p?>?0.05), with ?E remaining constant throughout the study. Higher ?E values were observed in the chemo-mechanical model compared to the chemical (p?<?0.05).

Conclusions

All tested dentifrices were effective in whitening stained enamel and their mode of action showed to be mainly mechanical (toothbrushing abrasion).

Clinical relevance

The abrasive level of dentifrices seems to determine its whitening effectiveness.     

Levels of potential oral cancer salivary mRNA biomarkers in oral cancer patients in remission and oral lichen planus patients

Objectives

To gather preliminary data concerning the feasibility of using seven salivary mRNAs—IL-8; IL-1β; dual specificity phosphatase 1 (DUSP1); H3 histone family 3A (H3F3A); ornithin decarboxylase antizyme 1 (OAZ1); S100 calcium-binding protein P (S100P); and spermidine/spermine N1-acetyltransferase 1 (SAT1)—for detecting development of oral squamous cell carcinoma (OSCC) in oral lichen planus (OLP) patients and OSCC patients whose disease was in remission.

Materials and methods

Saliva samples were collected from five study groups (25 subjects/group): newly diagnosed OSCC, OSCC-in-remission, disease-active OLP, disease-inactive OLP, and normal controls. The salivary mRNA levels were determined by a pre-amplification RT-qPCR approach with nested gene-specific primers. Mean fold changes between each pair of study groups were analyzed by the Mann–Whitney U test.

Results

Salivary levels of OAZ1, S100P, and DUSP1 mRNAs were significantly higher in newly diagnosed OSCC patients, compared to: (1) normal controls (p?=?0.003; p?=?0.003; and p?<?0.001, respectively); (2) OSCC-in-remission (p?<?0.001; p?=?0.001; and p?<?0.001, respectively); (3) disease-active OLP (p?<?0.001; p?=?0.016; and p?<?0.001, respectively); and (4) disease-inactive OLP (p?=?0.043; p?<?0.001; and p?<?0.001, respectively). No significant differences were found in the levels of salivary IL-8, IL-1β, H3F3A, and SAT1 mRNAs between newly diagnosed OSCC patients and the normal controls (p?=?0.093, 0.327, 0.764, and 0.560, respectively).

Conclusion

Salivary OAZ1, S100P, and DUSP1 mRNAs are candidate biomarkers for detecting OSCC development in OSCC patients in remission and in OLP patients.

Clinical relevance

The results of this study serve as the basis for a further large-scale study which may lead to a non-invasive screening method for early detection of OSCC.     

Does dental and oral health influence the development and course of bisphosphonate-related osteonecrosis of the jaws (BRONJ)?

Purpose

The main causes for the occurrence of bisphosphonate-related osteonecrosis of the jaws (BRONJ) are the application of aminobisphosphonates and the extraction of teeth. However, the question which factors in dental and oral health are relevant has not been answered completely.

Materials and methods

In a retrospective study, 50 patients who were treated with BRONJ between 2000 and 2009 were analyzed. As underlying diseases, they suffered from breast cancer (n?=?24), multiple myeloma (n?=?16), prostate cancer (n?=?5), osteoporosis (n?=?4), and kidney cancer (n?=?1). The data were collected from the patient charts of the treating dentists, oral and maxillofacial surgeons, general practitioners, and oncologists. The time of occurrence of BRONJ after treatment onset with bisphosphonates (BP) was examined with Kaplan–Meier estimator and logrank test (level of significance 0.05).

Results

At the time of BP treatment, onset the decayed, missing, and filled teeth (DMFT) index was 20.5?±?4.2. Patients with a DMFT value less than 20 showed a significantly longer BRONJ-free time interval after BP treatment onset with 39.7?±?1.1 months compared to patients with a DMFT value higher than 20, in whom BRONJ appeared after 14.4?±?2.8 months (p?<?0.001). However, the DMFT value had no influence on the success rate of BRONJ treatment. As a pre-existing oral disease, 60 % of the patients (n?=?30) had marginal periodontitis; 38 % (n?=?19), apical periodontitis; and 22 % (n?=?11), a pressure lesion from their dentures. In patients with marginal periodontitis, BRONJ occurred after 26.3 months (range 20.9–31.3) and in patients without marginal periodontitis, after 27.4 months (range 14.6–40.1) (p?=?0.58). Only 20 % of the patients with marginal periodontitis received adequate treatment. Without parodontal treatment, BRONJ occurred 15 months earlier compared to patients with parodontal treatment (p?=?0.12). The state of the periodontium did not influence the healing rate of BRONJ (p?>?0.999).

Conclusion

The present study highlights the great benefit of good dental and oral health in the prevention of BRONJ; but it also shows that after the appearance of BRONJ, these factors do no longer seem to play a relevant role in the disease course.     

Effect of seating forces on cement–ceramic adhesion in microtensile bond tests

Objectives

The aim of this study was to evaluate the effect of different seating forces during cementation in cement–ceramic microtensile bond strength (μTBS).

Materials and methods

Forty-five blocks (5?×?5?×?4 mm³) of a glass-infiltrated alumina-based ceramic (In-Ceram Alumina) were fabricated according to the manufacturer’s instructions and duplicated in resin composite. Ceramic surfaces were polished, cleaned for 10 min in an ultrasonic bath, silica coated using a laboratory type of air abrasion device, and silanized. Each treated ceramic block was then randomly assigned to five groups (n?=?9) and cemented to a composite block under five seating forces (10 g, 50 g, 100 g, 500 g, and 750 g) using a dual-cured resin cement (Panavia F). The ceramic–cement–composite assemblies were cut under coolant water to obtain bar specimens (1 mm?×?0.8 mm²). The μTBS tests were performed in a universal testing machine (1 mm/min). The mean bond strengths values were statistically analyzed using one-way ANOVA (α?≤?0.05).

Results

Different seating forces resulted in no significant difference in the μTBS results ranging between 13.1?±?4.7 and 18.8?±?2.1 MPa (p?=?0.13) and no significant differences among cement thickness.

Conclusions

Excessive seating forces during cementation seem not to affect the μTBS results.

Clinical relevance

Excessive forces during the seating of single all-ceramic restorations cementation seem to display the same tensile bond strength to the resin cement.     

Dentofacial characteristics of patients with rheumatoid arthritis

Objectives

The aims of this study are to evaluate the dentofacial morphology of patients with rheumatoid arthritis (RA) and to compare the morphological data with those of healthy age- and sex-matched control subjects.

Methods

Twenty-seven RA patients (mean age, 45.77?±?8.64 years) and 25 healthy subjects (mean age, 44.80?±?8.24 years) participated in this prospective study. Clinical and functional evaluations of the RA patients were assessed. The erythrocyte sedimentation rate, C-reactive protein level, rheumatoid factor level, and anti-citrullinated peptide antibodies (ACPA) titers of RA patients were determined, and DAS28 scores were calculated. Linear and angular measurements were performed on cephalometric tracings and condylar erosion was evaluated on lateral panoramic radiographs. Statistical comparison of the two groups was performed with an independent samples t test. Pearson correlation analysis was used to assess the relationship between the clinical and laboratory parameters.

Results

Based on DAS28 scores, no patient with RA was in the remission period, 3 patients had low, 23 had medium, and 1 had high disease activity. Sixteen (59.26 %) patients with RA had positive ACPA titers. Lateral cephalometric radiographs revealed statistically significant difference between the two groups for the measurement of U1–NA (millimeter; p?=?0.047), U1–NA (degrees; p?=?0.031), L1–NB (degrees; p?=?0.030), IMPA (L1–MP; p?=?0.001), interincisal angle (U1–L1; degrees; p?=?0.022) and midface length (Co–A; millimeter; p?=?0.033). A significant positive linear correlation was found between disease duration time and DAS28 scores (r?=?0.066, p?=?0.040).

Conclusions

Dentoalveolar effects of RA on dentofacial morphology are more significant than the skeletal effects. Future studies with larger sample sizes are required to evaluate the exact effects of RA on dentofacial morphology.

Clinical relevance

Clinicians should consider the fact that RA-associated dentoalveolar changes can be observed and may affect the orthodontic treatment process.     

Self-etching aspects of a three-step etch-and-rinse adhesive

Purpose

The purpose of this study is to assess the marginal adaptation of cavities restored with a three-step etch-and-rinse adhesive, OptiBond FL (OFL) under different application protocols.

Materials and methods

Twenty-four class V cavities were prepared with half of the margins located in enamel and half in dentin. Cavities were restored with OFL and a microhybrid resin composite (Clearfil AP-X). Three groups (n?=?8) that differed in the etching technique were tested with thermomechanical loading, and specimens were subjected to quantitative marginal analysis before and after loading. Micromorphology of etching patters on enamel and dentin were observed with SEM. Data was evaluated with Kruskal–Wallis and Bonferroni post hoc test.

Results

Significantly lower percent CM (46.9?±?19.5) were found after loading on enamel in group 3 compared to group 1 (96.5?±?5.1) and group 2 (93.1?±?8.1). However, no significant differences (p?=?0.30) were observed on dentin margins.

Conclusions

Etching enamel with phosphoric acid but avoiding etching dentin before the application of OFL, optimal marginal adaptation could be obtained, evidencing a self-etching primer effect.

Clinical relevance

A reliable adhesive interface was attained with the application of the three-step etch-and-rinse OFL adhesive with a selective enamel etching, representing an advantage on restoring deep cavities.     

Effects of long-term water storage on the microtensile bond strength of five experimental self-etching adhesives based on surfactants rather than HEMA

Objectives

The purpose of this study is to evaluate the hypothesis that replacing 2-hydroxyethyl methacrylate (HEMA) for surfactant dimethacrylates (SD) does not affect the immediate and long-term microtensile bond strength (μTBS) of experimental two-step self-etch HEMA-free adhesive systems applied on dentin.

Materials and methods

Five experimental HEMA-free two-step self-etching systems containing different SD (ethoxylated bisphenol A diglycidyl dimethacrylate (Bis-EMA 10, B10), Bis-EMA 30 (B30), poly-ethyleneglycol (400) dimethacrylate (PEG 400, P400), PEG 1000 (P1000), and PEG 400 urethane dimethacrylate (UDMA) (UP400)) and a HEMA-containing system (control) (HA) were formulated. Specimens were subjected to the μTBS test after 24 h and 6 and 12 months of storage. Data (in megapascals) were analyzed by Kruskal–Wallis and Dunn tests (α?=?0.05).

Results

Medians of the μTBS data after 24 h of storage are: HA?=?57.2^A, B10?=?26.2^BC, B30?=?24.0^C, P400?=?32.6^BC, P1000?=?37.3^B, and UP400?=?57.9^A; after 6 months are: HA?=?47.9^A, B10?=?18.5^B, B30?=?7.8^C, P400?=?16.1^B, P1000?=?14.6^BC, and UP400?=?51.6^A; and after 12 months are: HA?=?31.2^A, B10?=?15.2^B, B30?=?9.0^B, P400?=?9.1^B, P1000?=?13.3^B, and UP400?=?35.7^A. Between the HEMA-free groups, the adhesive system formulated with PEG 400 UDMA produced similar μTBS to the HEMA-containing group. Also, the storage of specimens decreased the μTBS (p?<?0.05).

Conclusion

Replacing HEMA for PEG 400 UDMA in an adhesive system formulation generated a satisfactory μTBS to dentin.

Clinical relevance

Surfactant dimethacrylates have a potential use in the development of HEMA-free self-etching adhesive systems, which are more chemically stable.     

Demineralization adjacent to orthodontic brackets after application of conventional and self-etching primer systems

Objectives

The goal of this work was to compare the demineralization of enamel associated with two different self-etching primers and traditional acid etching.

Materials and methods

A total of 15 volunteers (23–32 years, 8 male and 7 female) were provided with a removable archwire/resin appliance to be worn 20 h/day for 28 days. The device was attached to the mandibular posterior teeth and included samples of human enamel (from extracted third molars) located in both posterior vestibules. Both sides featured the same distribution of samples, including one untreated control sample (group A) and three samples with brackets (Victory? APC II) bonded to their surface after conditioning with a self-etching non-fluoride primer (iBond? Gluma® Inside; group B), a self-etching fluoride-releasing primer (Transbond? Plus; group C), or traditional acid-etching with 35?% phosphoric acid and Transbond? XT (group D). Mineral loss was assessed extraorally under standardized conditions using quantitative light-induced fluorescence (QLF) with a specialized camera system (Inspektor Pro). Results were expressed as relative fluorescence loss (ΔF in %). A baseline measurement (T0) was taken before the appliance was first inserted but with the brackets already bonded. Fluorescence loss was analyzed after 3 (T1), 7 (T2), 14 (T3), and 28 days (T4) and compared to the baseline loss (T0) for each of the four study groups (A to D). Kruskal–Wallis and Mann–Whitney U tests were used to compare the results for statistical significance.

Results

The lowest percentages of fluorescence loss both at baseline and during the follow-up assessments was found in group C. While all three experimental groups (B, C, D) presented total decreases in fluorescence loss after 28 days, indicating remineralization, the decrease in group C was the largest. The Kruskal–Wallis test yielded no significant differences between the three groups other than a significantly lower percentage of fluorescence loss in group C than in group D during the last assessment (T4). The untreated samples of control enamel (group A) revealed increasing percentages of fluorescence loss over the entire study period.

Conclusion

Use of the self-etching primers (groups B and C) was not associated with patterns of enamel demineralization different from those noted after traditional etching with phosphoric acid (group D). The only significant difference we observed was between the self-etching fluoride-releasing primer (group C) and traditional etching (group D) at the final assessment (T4). Thus, the fluoride-releasing system Transbond? Plus was advantageous.     

Effect of Er,Cr:YSGG laser irradiation on bovine enamel surface during in-office tooth bleaching ex vivo

The aim of this in vitro study was to evaluate the effect of using Er,Cr:YSGG laser during in-office tooth bleaching on bovine enamel surface to evaluate the safety of this therapy on tooth tissues. Thirty-six enamel specimens were prepared from bovine incisors and divided into three groups: Group 1 specimens (control) received no bleaching treatment; Group 2 received a conventional in-office bleaching treatment (40 % H₂O₂); Group 3 received laser-assisted bleaching procedure (40 % H₂O₂) utilizing an Er,Cr:YSGG laser. The specimens were stored for 10 days after the bleaching treatment in artificial saliva. Vickers hardness was determined using a microhardness tester, and measurements for surface roughness were done using a VSI microscope. Three specimens for each experimental group were examined under SEM and mineral composition of the specimens was evaluated using EDS. Data were statistically analyzed using one-way ANOVA, Tukey’s post hoc, Wilcoxon signed rank and Kruskal–Wallis tests (a = 0.05). The Vickers hardness of the enamel was reduced after in-office bleaching procedures (p < 0.05), and changes in surface morphology of the enamel were observed. However, the surface roughness of the enamel was not influenced (p > 0.05), and no changes in mineral composition of the enamel were detected after in-office bleaching procedures (p > 0.05). The laser-assisted bleaching treatment with Er,Cr:YSGG laser did not influence the enamel surface compared to the conventional bleaching technique. The safety of the use of Er,Cr:YSGG laser during in-office tooth bleaching regarding the surface properties of the enamel was confirmed under in vitro conditions.     

A randomized clinical trial on the use of medical Portland cement,MTA and calcium hydroxide in indirect pulp treatment

Objectives

Studies on indirect pulp treatment (IPT) show varying success rates of 73 to 97 %. The necessity of re-opening the cavity and the question of the optimal capping material is still under debate. The aim of this prospective in vivo study was to compare the clinical and microbiological outcomes of mineral trioxide aggregate (MTA), medical Portland cement, and calcium hydroxide on the dentin–pulp complex of permanent and primary teeth treated with two-step IPT.

Materials and methods

In 86 regular patients (51 % men; 49 % women; age 17.2 years ±13.8), one deep carious lesion each was treated with incomplete caries removal, randomly selected capping with either calcium hydroxide (n?=?31), medical Portland cement (29) or white MTA (26), and re-entry (6.3 months ±1.0). Clinical (color, humidity, and consistency of dentin) and microbiological (Lactobacilli/Mutans Strep. counts) parameters were recorded at the first and second treatment.

Results

The IPT had a high success rate of 90.3 % regardless of the material used (p?=?0.72). The arrested lesions showed consistently darker, dry, and therefore, sclerotic dentine (p?<?0.05) as well as a decrease in bacterial counts at re-entry (Lactobacilli p?=?0.01/Mutans Strep. p?=?0.07).

Conclusions

The findings of this study support the use of the IPT as a treatment for deep carious lesions preferably with non-resorbing materials such as MTA or medical Portland cement.

Clinical relevance

The findings of this study could promote the improvement of the IPT as a one-step treatment of deep carious lesions when the remaining demineralized dentin would be sealed with durable restorations.