Chlorhexidine and green tea extract reduce dentin erosion and abrasion in situ

Objectives

This in situ/ex vivo study aimed to analyse the impact of possible MMP-inhibitors (chlorhexidine and green tea extract) on dentin wear induced by erosion or erosion plus abrasion.

Methods

Twelve volunteers took part in this cross-over and double-blind study performed in 4 phases of each 5 days. Bovine dentin samples were worn in palatal appliances and subjected to extraoral erosion (4 times/day, Coca-Cola, 5 min) or erosion plus abrasion (2 times/day, fluoride-free toothpaste and electrical toothbrush, 15 s/sample). Immediately after each erosion, the appliances were reinserted in the mouth and the oral cavity was rinsed for 60 s with: 250 ppm F solution (SnF₂/AmF, pH 4.5, Meridol-Gaba, Switzerland), 0.12% chlorhexidine digluconate (0.06% chlorhexidine, pH 6.0, Periogard-Colgate, Brazil), 0.61% green tea extract solution (OM24^®, 100% Camellia Sinensis leaf extract, catechin concentration: 30 ± 3%, pH 7.0, Omnimedica, Switzerland) or deionized water (pH 6.0, control). Dentin loss was assessed by profilometry (μm). The data were analysed by two-way repeated measures ANOVA and Bonferroni post hoc test.

Results

There was a significant difference between the conditions (Ero × Ero + Abr, p < 0.001) and among the solutions (p < 0.001). All solutions (F: 1.42 ± 0.34; 1.73 ± 0.50, chlorhexidine: 1.15 ± 0.26; 1.59 ± 0.32, green tea: 1.06 ± 0.30; 1.54 ± 0.55) significantly reduced the dentin wear when compared to control (2.00 ± 0.55; 2.41 ± 0.83) for both conditions. There were not significant differences among green tea extract, chlorhexidine and F solutions.

Conclusions

Thus, the possible MMP-inhibitors tested in this study seem to be a promising preventive measure to reduce dentin erosion-abrasion, but their mechanism of action needs to be investigated in further studies.     

Effects of different amine fluoride concentrations on enamel remineralization

Objectives

The aim of this study was to investigate the effects of decreasing fluoride concentrations on repeated demineralizing challenges on human enamel.

Materials and methods

In 24 teeth, 3 mm × 3 mm windows were prepared on the buccal and lingual sides and treated in a cycling demineralization–remineralization model. Remineralization was achieved with 100, 10 and 0.1 ppm fluoride from anime fluoride. Coronal sections were cut through the artificial lesions, and three sections per tooth were investigated using polarized light microscopy and scanning electron microscopy with quantitative element analysis.

Results

The morphology of the lesions was studied, and the extensions of the superficial layer and the body of the lesion were measured. Using element analysis, the Ca, P and F content were determined. The body of the lesion appeared remineralized after application of 100 ppm fluoride, while remineralization of the lesion was less successful after application of 10 and 0.1 ppm fluoride. The thickness of the superficial layer increased with decreasing fluoride concentrations, and also the extension of the body of the lesion increased. Ca and P content increased with increasing fluoride concentrations.

Conclusions

The effectiveness of fluoride in enamel remineralization increased with increasing fluoride concentration.

Clinical relevance

A consistently higher level of fluoride in saliva should be a goal in caries prevention.     

Effect of fluoride varnish and gel on dental erosion in primary and permanent teeth

Objective

To assess the effect of a fluoride varnish and gel on the erosive wear of primary and permanent teeth.

Design

Sixty human primary (n = 30) and permanent (n = 30) enamel specimens were randomly assigned to one of the following groups: APF gel (1.23% F), NaF varnish (2.26% F), and control (no treatment). Fluoride gel was applied for 4 min and fluoride varnish for 24 h. Six daily demineralisation-remineralization cycles of 5 min of immersion in a cola drink (pH 2.3) and 30 min in artificial saliva were conducted during 7 days. All specimens were stored in artificial saliva between and after cycles. Surface Knoop microhardness (%SMHC) readings were performed at baseline, 48 h and 7 days. Data were tested using ANOVA and Tukey's tests (p < 0.05).

Results

For primary enamel, the mean %SMHC (±SD) after 48 h and 7 days was, respectively: gel (31.0 ± 14.4 and 36.9 ± 7.5), varnish (26.7 ± 9.5 and 38.3 ± 8.7), and control (35.8 ± 8.6 and 45.0 ± 8.6). For permanent enamel, such values were: gel (37.5 ± 7.7 and 27.8 ± 7.5), varnish (31.7 ± 9.6 and 27.4 ± 11.1) and control (48.6 ± 6.4 and 43.1 ± 6.4). In primary enamel, erosion inhibition by fluoride was not significant at 48 h (p = 0.203) and 7 days (p = 0.082). In permanent specimens, both products showed a significant effect (p < 0.001).

Conclusions

Both fluoride varnish and gel were able to inhibit erosive enamel loss but mainly in the permanent experimental groups. Primary and permanent enamel substrates reacted differently to both demineralization by a cola drink and remineralization by fluoridated compounds.     

Titanium surface topography after brushing with fluoride and fluoride-free toothpaste simulating 10 years of use

Objectives

To conduct a controlled study contrasting titanium surface topography after procedures that simulated 10 years of brushing using toothpastes with or without fluoride.

Methods

Commercially pure titanium (cp Ti) and Ti–6Al–4V disks (6 mm Ø × 4 mm) were mirror-polished and treated according to 6 groups (n = 6) as a function of immersion (I) or brushing (B) using deionised water (W), fluoride-free toothpaste (T) and fluoride toothpaste (FT). Surface topography was evaluated at baseline (pretreatment) and post-treatment, using atomic force microscope in order to obtain three-dimensional images and mean roughness. Specimens submitted to immersion were submerged in the vehicles without brushing. For brushed specimens, procedures were conducted using a linear brushing machine with a soft-bristled toothbrush. Immersion and brushing were performed for 244 h. IFT and BFT samples were analysed under scanning electron microscope with Energy-Dispersive X-ray Spectroscopy (EDS). Pre and post-treatment values were compared using the paired Student T-test (α = .05). Intergroup comparisons were conducted using one-way ANOVA with Tukey post-test (α = .05).

Results

cp Ti mean roughness (in nanometers) comparing pre and post-treatment were: IW, 2.29 ± 0.55/2.33 ± 0.17; IT, 2.24 ± 0.46/2.02 ± 0.38; IFT, 2.22 ± 0.53/1.95 ± 0.36; BW, 2.22 ± 0.42/3.76 ± 0.45; BT, 2.27 ± 0.55/16.05 ± 3.25; BFT, 2.27 ± 0.51/22.39 ± 5.07. Mean roughness (in nanometers) measured in Ti–6Al–4V disks (pre/post-treatment) were: IW, 1.79 ± 0.25/2.01 ± 0.25; IT, 1.61 ± 0.13/1.74 ± 0.19; IFT, 1.92 ± 0.39/2.29 ± 0.51; BW, 2.00 ± 0.71/2.05 ± 0.43; BT, 2.37 ± 0.86/11.17 ± 2.29; BFT, 1.83 ± 0.50/15.73 ± 1.78. No significant differences were seen after immersions (p > .05). Brushing increased the roughness of cp Ti and of Ti–6Al–4V (p < .01); cp Ti had topographic changes after BW, BT and BFT treatments whilst Ti–6Al–4V was significantly different only after BT and BTF. EDS has not detected fluoride or sodium ions on metal surfaces.

Conclusions

Exposure to toothpastes (immersion) does not affect titanium per se; their use during brushing affects titanium topography and roughness. The associated effects of toothpaste abrasives and fluorides seem to increase roughness on titanium brushed surfaces.     

Potential agents to control enamel caries-like lesions

Objectives

To assess whether pastes containing casein phosphopeptide–amorphous calcium phosphate (CPP–ACP) and calcium sodium phosphosilicate (CSP) control artificial caries lesion progression.

Methods

Enamel slabs of bovine teeth were embedded in polyester resin and had their enamel surfaces serially polished, and tested for surface microhardness (SMH, 25 g, 5 s). Incipient caries-like lesions were pre-formed and specimens were evaluated by microhardness test (SMH_post-lesion) and randomly assigned to five treatment groups (n = 15): (1) regular dentifrice (RE, 1,100 ppm F); (2) dentifrice with calcium sodium phosphosilicate (CSP); (3) amorphous calcium phosphate stabilized by casein phosphopeptide (CPP–ACP); (4) CPP–ACP with 900 ppm F (CPP–ACP + F) and (5) control group—unexposed to any remineralizing agent. Treatments were applied five times, after the de-remineralization period in the cariogenic challenges. Post-treatments SMH measurements were conducted (SMH_{post-treatment}).

Results

ANOVA was applied for data evaluation and revealed a significant difference among the treatments (p = 0.0161). Tukey's test was conducted and the percentage of mineral loss was calculated. Specimens exposed to CSP (7.1%), RE (6.7%) and CPP–ACP + F (3.8%) showed lower mineral loss than those that in the control group (−11.0%). CPP–ACP group (3.2%) differed from the control, CSP and RE groups.

Conclusions

Depending on the agent used, a remineralizing effect may be expected, which reflects in caries lesions progression.     

Interplay between fluoride and abrasivity of dentifrices on dental erosion–abrasion

Objectives

Eroded teeth are more susceptible to toothbrushing wear than sound teeth. We tested the hypothesis that fluoride and abrasivity of dentifrices can interact, modulating the development of erosive–abrasive lesions.

Methods

Human enamel and root dentin specimens were submitted to cycles of demineralization, remineralization and toothbrushing using six dentifrices formulated with three different abrasivity levels: low (L), medium (M) and high (H); with (+F) and without (−F) fluoride. Surface loss was quantified by optical profilometry and compared among groups (α = 0.05).

Results

In dentin, it was ranked: L < M < H, for both +F and −F dentifrices. In enamel, +F dentifrices had similar results; however for −F formulations, M and H did not differ. Fluoride reduced surface loss in enamel, at all abrasive levels. In dentin, the same fluoride effect was observed but only for the low abrasive formulation.

Conclusions

Both fluoride and abrasivity were important modulators of enamel surface loss, while abrasivity had a higher impact than fluoride on dentin.     

Clinical evaluation of polypropylene glycol-based caries detecting dyes for primary and permanent carious dentin

Objective

The aim of this study was to compare the clinical efficacy of new caries detecting dye Caries Check Blue (CCB) with Caries Check (CC) and Caries Detector (CD) using a laser fluorescence device (DIAGNOdent).

Method

Primary and permanent teeth with dentin caries were stained with polypropylene glycol (MW = 300) based new caries detecting dyes CCB, CC, or propylene glycol (MW = 76) based CD. In the CCB and CC groups, stained dentin was completely removed. In the CD groups, pink-stained dentin was retained according to the manufacturers’ instructions. Cavities before and after caries removal were measured with the DIAGNOdent. Data were analyzed using ANOVA and Fisher’s PLSD multiple comparison test at α = 0.05. Regression analyses were performed between DIAGNOdent readings and scores obtained from the clinical parameters.

Results

The DIAGNOdent readings after caries removal were: primary-CCB (13.2 ± 10.4), primary-CC (14.3 ± 16.7), primary-CD (9.0 ± 5.2), permanent-CCB (22.7 ± 13.4), permanent-CC (10.6 ± 6.8) and permanent-CD (9.7 ± 9.0). Significant differences were identified between the permanent-CCB and all other groups. Correlation coefficients between DIAGNOdent readings and clinical parameters were low.

Conclusions

When dentin stained with Caries Check Blue or Caries Check was completely removed, the DIAGNOdent readings were higher than those recorded when palely-stained pink dentin was retained with the Caries Detector, with significant difference observed for the permanent-CCB group. Caries Check Blue may be used clinically to avoid excessive removal of caries-affected or sound dentin in permanent teeth but not in primary teeth.     

Effects of fluoride concentration and temperature of milk on caries lesion rehardening

Objectives

The aim of the present in vitro study was to investigate the effects of fluoride concentration and temperature of milk on caries lesion rehardening under pH cycling conditions.

Methods

Incipient caries-like lesions were formed in human enamel specimens, characterized using Vickers surface microhardness (VHN) and assigned to seven treatment groups (n = 18 per group): fluoride was tested at five levels (0, 2.5, 5, 10, 20 mg/l, all 22 °C) and milk temperature at three levels (4, 22, 60 °C), but only for 10 mg/l F. Lesions were pH cycled for 15d (4×/daily 10 min milk treatments, 1×/daily 4 h acid challenge, remineralization in human/artificial saliva mixture). VHN of specimens were measured again and changes from lesion baseline were calculated. Subsequently, enamel fluoride uptake (EFU) was determined using the micro drill technique.

Results

Lesions responded to fluoride in a dose–response manner with higher fluoride concentrations resulting in more lesion rehardening (20 > 10 ≥ 5 ≥ 2.5 > 0 mg/l F). Furthermore, fluoridated milk at 60 °C was found to be more efficacious than at 4 °C (60 ≥ 22 > 4 °C). EFU results were similar (20 > 10 > 5 > 2.5 ≥ 0 mg/l F; 60 > 22 ≥ 4 °C).

Conclusions

Both fluoride concentration and milk temperature are likely to contribute to the anti-caries potential of fluoridated milk.     

Remineralization of enamel subsurface lesions by chewing gum with added calcium

Objectives

Chewing sugar-free gum has been shown to promote enamel remineralization. Manufacturers are now adding calcium to the gum in an approach to further promote enamel remineralization. The aim of this study was to compare the remineralization efficacy of four sugar-free chewing gums, two containing added calcium, utilizing a double-blind, randomized, crossover in situ model.

Methods

The sugar-free gums were: Trident Xtra Care, Orbit Professional, Orbit and Extra. Ten subjects wore removable palatal appliances with four human-enamel half-slab insets containing subsurface demineralized lesions. For four times a day for 14 consecutive days subjects chewed one of the chewing gums for 20 min. After each treatment the enamel slabs were removed, paired with their respective demineralized control slabs, embedded, sectioned and mineral level determined by microradiography. After 1-week rest the subjects chewed another of the four gums and this was repeated until each subject had used the four gum products.

Results

Chewing with Trident Xtra Care resulted in significantly higher remineralization (20.67 ± 1.05%) than chewing with Orbit Professional (12.43 ± 0.64%), Orbit (9.27 ± 0.59%) or Extra (9.32 ± 0.35%). The form of added calcium in Trident Xtra Care was CPP–ACP and that in Orbit Professional calcium carbonate with added citric acid/citrate for increased calcium solubility.

Conclusions

Although saliva analysis confirmed release of the citrate and calcium from the Orbit Professional gum the released calcium did not result in increased enamel remineralization over the normal sugar-free gums. These results highlight the importance of calcium ion bioavailability in the remineralization of enamel subsurface lesions in situ.     

An in situ study investigating dentine tubule occlusion of dentifrices following acid challenge

Objectives

To investigate the dentine occlusion and acid resistance of dentifrices developed to treat dentine hypersensitivity.

Methods

This was a single centre, single blind, randomised, split mouth, four treatments, two period crossover, in situ study in healthy subjects. Subjects wore buccal intra-oral appliances each fitted with four dentine samples over four consecutive days with one study product applied per appliance; 8% strontium acetate in silica base, 1040 ppm sodium fluoride (Sensodyne^® Rapid Relief), 8% arginine, calcium carbonate, 1450 ppm sodium monofluorophosphate (Colgate Sensitive Pro-Relief^®), 1450 ppm sodium fluoride (control paste) and water. On days 3 and 4, two agitated grapefruit juice challenges (ex vivo) occurred for 1 min. At the end of each treatment day 1 dentine sample was removed from each appliance for scanning electron microscopy (SEM). The extent of tubule occlusion was measured using an examiner-based visual scoring index (three trained examiners).

Results

In total, 28 subjects ((12 males and 16 females with a mean age of 34.7 years (SD 8.41 years)) completed the study. On day 2, both test dentifrices demonstrated significantly better dentine tubule occlusion than water (p < 0.0001) and control paste (8% strontium p = 0.0003 and 8% arginine p = 0.0019). After 3 and 4 days of twice daily brushing with acid challenges on days 3 and 4 the strontium-based dentifrice demonstrated significantly better dentine occlusion than all other treatments (p < 0.0001).

Conclusions

Strontium acetate and arginine-based dentifrice result in statistically significant dentine tubular occlusion compared to controls, but the arginine-based dentifrice is more susceptible to acid challenge.

Clinical significance

Erosive beverages are an important aetiology in DH by exposing dentine tubules. Their consumption has increased significantly over the past decade in the UK. This 4-day in situ study investigated the properties of commercially available dentifrices designed to occlude dentine tubules and their resistance to an agitated acid challenge.     

Dentist-time expenditure for two different adhesive all-ceramic systems

Objectives

The purpose of this clinical investigation was to compare a chair-side adhesive all-ceramic system to a laboratory processed adhesive all-ceramic system with respect to quality and time expenditure for the dentist.

Methods

The same dentist treated 10 patients, who were each to receive two large posterior single tooth restorations of similar location and extent. One restoration was made in the laboratory by using the IPS Empress™ system [LAB], the other one was done chair-side by utilizing the Cerec™ system [CHAIR]. The time expenditure was measured for [LAB] and [CHAIR] and compared by the Wilcoxon signed rank test. The restorations were also evaluated according to the USPHS criteria.

Results

The mean time expenditure for the dentist with low-level assistance was 111:03 min [S.D. ± 24:09 min] for [LAB] and 115:31 min [S.D. ± 15:54 min] for [CHAIR]. Time expenditure with medium level assistance for the operator was 100:53 min [S.D. ± 23:59] for [LAB] and 105:50 [S.D. ± 15:28] for [CHAIR]. Assuming a high level of assistance, the mean time values were 53:11 min [S.D. ± 14:29] for [LAB] and 54:29 min [S.D. ± 09:21] for [CHAIR]. The baseline investigation according to the modified USPHS criteria did not reveal any differences between [CHAIR] and [LAB].

Conclusion

There were no statistical significant differences with respect to time expenditure or quality between [LAB] and [CHAIR] in this study.     

Association between periodontitis and systemic bone mineral density in Japanese community-dwelling postmenopausal women

Objective

The purpose of this cross-sectional study was to evaluate the association between loss of attachment (LA) which is clinical index of periodontitis and bone mineral density (BMD) of the lumbar vertebrae and femur measured with dual energy X-ray absorptiometry (DXA) in Japanese community-dwelling postmenopausal women.

Subjects and methods

Subjects were 347 women aged 55–74. The oral cavity was divided into 6 areas according to the WHO's method for the determination of the clinical attachment level score (CALscore); the LA was measured at 6 sites using a WHO probe in 17, 16, 11, 26, 27, 37, 36, 31, 46, and 47, and the values were recorded in mm. Then, we assessed BMD of the lumbar vertebrae (L2–L4) and femur (femoral neck, proximal part) by DXA. Based on these data, analysis of covariance was used to estimate relation between periodontitis and systemic BMD status excluding effect of age. Multiple linear regression analysis was used to estimate relation between periodontitis and BMD adjusted for 17 variables.

Results

Significant differences were observed in the mean value between the mean CALscore = 0 and CALscore ≥ 1 groups in the Z value in lumbar vertebrate (106.9 ± 18.7 vs. 102.3 ± 1.0, p < 0.05, t-test). Multiple regression analysis was conducted using the mean LA as dependent variable. Lumbar vertebral BMD (regression coefficient: B = −1.039 ± 0.379, p = 0.007), femoral neck BMD (B = −1.332 ± 0.627, p = 0.034), and proximal femoral BMD (B = −1.329 ± 0.536, p = 0.014) all exhibited a significant negative correlation with the mean LA.

Conclusion

A significant negative correlation was observed between periodontal disease and truncal bone BMD in this study.     

Effect of cariogenic biofilm challenge on the surface hardness of direct restorative materials in situ

Objectives

The presence of cariogenic biofilm could result in surface degradation of composite and ionomeric restorative materials. Thus, this study evaluated in situ the alterations in the surface microhardness of these materials under biofilm accumulation and cariogenic challenge.

Methods

In a split-mouth, double-blind, cross-over study, 10 volunteers wore palatal intra-oral devices containing bovine enamel slabs restored with composite resin (CR – Z250) or resin-modified glass ionomer (RMGI – Vitremer). Two phases of 14 days were carried out, one for each restorative material. In one side of the device, biofilm was allowed to accumulate under a plastic mesh, whereas in the opposing side, regular brushing was carried out 3 times/day with a dentifrice containing 1100 μg F/g as NaF. A 20% sucrose solution was applied extra-orally 10×/day on each restored dental slab. Knoop microhardness was used to calculate the percentage of surface hardness loss (%SHL).

Results

All materials showed a decrease in surface hardness after the in situ period. The restorative materials presented the following average for %SHL: RMGI without biofilm accumulation = 8.9 and with biofilm accumulation = 25.6, CR without biofilm accumulation = 14.7 and with biofilm accumulation = 17.0.

Conclusion

Biofilm accumulation and the presence of cariogenic challenge promoted faster degradation of ionomeric materials, but this was not observed for composite resin.

Clinical significance

The oral environment affects the surface hardness of aesthetic restorative materials. Biofilm accumulation and cariogenic challenge promote surface degradation for ionomeric materials, but not for composite resin.     

Assessment of laminate technique using glass ionomer and resin composite for restoration of root filled teeth

Objective

To evaluate the open laminate technique using glass ionomer cements (GIC) in association with a low shrink composite for restoring root filled premolars.

Methods

Extensive MOD cavities plus endodontic access and root filling were performed in intact extracted maxillary premolars. Three restoration types were evaluated: (1) resin composite alone; (2) resin-modified GIC (RM-GIC) open laminate plus resin composite; (3) conventional GIC open laminate plus resin composite (n = 8 for all groups and tests). Three tests were conducted to assess restorations: (A) inward cusp deflection during light curing, using DCDTs; (B) fracture strength using a ramped oblique load at 45° to the long axis in a servohydraulic testing machine in comparison with intact and unrestored teeth; (C) proximal marginal leakage using methylene blue dye and the effect of thermocycling. Data were analysed using 1-way ANOVA for cuspal deflection and fracture strength and Fisher's exact test for leakage.

Results

Laminate restorations resulted in significantly less cuspal deflection compared with resin composite (4.2 ± 1.2 μm for RM-GIC and 5.1 ± 2.3 μm for conventional GIC vs. 12.2 ± 2.6 μm for composite, P < 0.001). Fracture strength was not significantly different among all groups. Failure with all restorations was predominantly adhesive at the tooth-restoration interface. The two laminate groups showed significantly better marginal seal than composite alone, but sealing ability of conventional GIC deteriorated after thermocycling.

Conclusions

Laminate restoration of root filled teeth had beneficial effects in terms of reducing cuspal deflection and marginal seal, with acceptable fracture strength.     

Randomized controlled split-mouth clinical trial of direct laminate veneers with two micro-hybrid resin composites

Objectives

This randomized, split-mouth clinical study evaluated the survival rate of direct laminate veneers made of two resin-composite materials.

Methods

A total of 23 patients (mean age: 52.4 years old) received 96 direct composite laminate veneers using two micro-hybrid composites in combination with two adhesive resins (Ena-Bond-Enamel HFO: n = 48, Clearfil SE Bond-Miris2: n = 48). Enamel was selectively etched with 38% H₃PO₄ for 30 s, rinsed 30 s and the corresponding adhesive resin was applied accordingly. Existing resin composite restorations in good conditions (small or big) were not removed but conditioned using silica coating (CoJet) and silanized (ESPE-Sil). Restorations were evaluated at baseline and thereafter every 6 months. Additional qualitative analysis was performed using modified USPHS criteria.

Results

Mean observation period was 41.3 months. Altogether, 12 absolute failures were observed [survival rate: 87.5%] (Kaplan–Meier). The survival rates with the two resin composites did not show significant differences [Enamel HFO: 81.2%, Miris2: 93.8%] (p > 0.05). The presence of existing composite restorations on the prepared teeth did not affect the survival rate significantly (intact teeth: 100%, small restorations: 90.6%, big restorations: 82.7%) (p > 0.05). Surface roughness and marginal discolouration were the main qualitative deteriorations observed until the final recall. Secondary caries and endodontic complications did not occur in any of the teeth.

Conclusion

Early findings of this clinical study with the two micro-hybrid composite laminate veneers showed similar survival rate and their clinical performance was not significantly influenced when bonded onto intact teeth or onto teeth with existing restorations with the protocol applied.     

Clinical performance of a new laser fluorescence device for detection of occlusal caries lesions in permanent molars

Objectives

To determine the clinical performance of a laser fluorescence device (DIAGNOdent pen, KaVo) to discriminate between different occlusal caries depths (D₀–D_1–4; D_0–2–D_3,4) in permanent molars.

Methods

In this prospective, randomized two-centre-study 120 sound/uncavitated carious sites in 120 patients were measured after visual and radiographic caries assessment. In cases of operative intervention (n = 86), the lesion depths after caries removal were recorded (reference). In cases of preventive intervention (n = 34), the sites were reassessed visually/radiographically after 12 months to verify the status assessed before (reference). The discrimination performance was determined statistically (Mann–Whitney test, Spearman’s rho coefficient, and areas under the receiver operating characteristic curves (AUCs)). Sensitivities (SE) and specificities (SP) were plotted as a function of the measured values and cut-off values for the mentioned thresholds suggested.

Results

Sound sites (n = 13) had significantly minor fluorescence values than carious sites (n = 107) (P < 0.0001) as had sites with no/enamel caries (n = 63) compared to dentinal caries (n = 57). The AUCs for the same discriminations were 0.92 and 0.78 (P < 0.001). For the D₀–D_1–4 threshold, a cut-off at a value of 12 (SE: 0.88, SP: 0.85) and for the D_0–2–D_3,4 threshold at 25 (SE: 0.67, SP: 0.79) can be suggested. A moderate positive correlation between the measurements and the caries depths was calculated (rho = +0.57, P = 0.01).

Conclusion

Within this study, the device’s discrimination performance for different caries depths was moderate to very good and it may be recommended as adjunct tool in the diagnosis of occlusal caries.     

Chipping behaviour of all-ceramic crowns with zirconia framework and CAD/CAM manufactured veneer

Objectives

The aim of this in vitro study was to assess the ultimate load to failure of zirconia based crowns veneered with CAD/CAM manufactured ceramic.

Methods

32 identical, anatoform zirconia (Sirona inCoris ZI, mono L F1) frameworks (thickness 0.6 mm) were constructed (Sirona inLab 3.80). Afterwards, 16 crowns were completed using a CAD/CAM manufactured lithium disilicate ceramic veneer (IPS e.max CAD, Ivoclar Vivadent). The remaining 16 frames were veneered using conventional manual layering technique. For the CAD/CAM manufactured veneers, the connection between framework and veneer was accomplished via a glass fusion ceramics. Before fracture tests, half of the specimens underwent thermocycling and chewing simulation (1.2 million chewing cycles, force magnitude F_max = 108 N). To further investigate the new technique, finite element computations were carried out on the basis of the original geometry.

Results

Nearly all (87.5%) conventionally veneered crowns failed already during chewing simulation, whereas crowns with CAD/CAM manufactured veneers were non-sensitive to artificial ageing. Crowns veneered with lithium disilicate ceramic displayed ultimate loads to failure of about 1600 N.

Conclusion

The CAD/CAM production of veneers for restorations with zirconia framework is a promising way to reduce failures originating from material fatigue.     

Interfacial fracture toughness of different resin cements bonded to a lithium disilicate glass ceramic

Objectives

To evaluate the effect of HF acid etching and silane treatment on the interfacial fracture toughness of a self-adhesive and two conventional resin-based cements bonded to a lithium disilicate glass ceramic.

Methods

Lithium disilicate glass ceramic discs were prepared with two different surface preparations consisting of gritblasted with aluminium oxide, and gritblasted and etched with hydrofluoric acid. Ceramic surfaces with a chevron shaped circular hole were treated by an optimized silane treatment followed by an unfilled resin and then three different resin cements (Variolink II, Panavia F2, and Multilink Sprint). Specimens were kept in distilled water at 37 °C for 24 h and then subjected to thermocycling. The interfacial fracture toughness was measured and mode of failures was also examined. Data were analysed using analysis of variance followed by T-test analysis.

Results

No statistically significant difference in the mean fracture toughness values between the gritblasted and gritblasted and etched surfaces for Variolink II resin cement was found (P > 0.05). For the gritblasted ceramic surfaces, no significant difference in the mean fracture toughness values between Panavia F2 and Variolink II was observed (P > 0.05). For the gritblasted and etched ceramic surfaces, a significantly higher fracture toughness for Panavia F2 than the other cements was found (P < 0.05).

Conclusions

The interfacial fracture toughness for the lithium disilicate glass ceramic system was affected by the surface treatment and the type of luting agent. Dual-cured resin cements demonstrated a better bonding efficacy to the lithium disilicate glass ceramic compared to the self-adhesive resin cement.

Clinical significance

The lithium disilicate glass ceramic surfaces should be gritblasted and etched to get the best bond when used with Panavia F2 and Multilink Sprint resin cements, whereas for the Variolink II only gritblasting is required. The best bond overall is achieved with Panavia F2.     

In vitro efficacy of experimental tin- and fluoride-containing mouth rinses as anti-erosive agents in enamel

Objectives

The aim of this in vitro study was to investigate the efficacy of various experimental tin- and fluoride-containing mouth rinses with stepwise reduced concentrations of the active agents on erosion progression in enamel.

Methods

Human enamel specimens were subjected to a cyclic demineralisation and remineralisation procedure for 10 days with 6 demineralisation periods per day, 5 min each. Erosive demineralisation was performed with 0.05 M citric acid (pH 2.3). Except in the control groups, the specimens were treated for 2 min with experimental mouth rinses after the first and sixth demineralisations. The tin concentrations ranged between 800 and 2800 ppm, and fluoride concentrations of 500 and 250 ppm were used. All preparations were adjusted to pH 4.5. As positive control, a commercially available, tin-containing mouth rinse was used (pH 4.2, 409 ppm Sn²⁺, 250 ppm F⁻). Tissue loss was determined profilometrically.

Results and conclusion

As expected, the highest tissue loss was found in the negative control group. All experimental mouth rinses were able to reduce tissue loss significantly (p ≤ 0.001). The best reduction was achieved by the 2800 ppm Sn²⁺, 500 ppm F⁻ solution (80%). The lowest reduction was achieved by the 800 ppm Sn²⁺, 250 ppm F⁻ solution (54%). Amongst the 500 ppm F⁻ solutions, in the Sn²⁺ concentration range of 2800–800 ppm, only small differences in efficacy were observed, meaning that the tin concentration can probably be reduced without losing efficacy. This factor is particularly important if one regards the possible clinical applicability of such mouth rinses.