Short-term efficacy of caries resin infiltration during treatment with orthodontic fixed appliances. A randomized controlled trial.

OBJECTIVES: Objective of this trial was to assess the masking results in initial caries lesions (ICL) that were resin infiltrated during fixed orthodontic treatment in comparison to contralateral teeth that were fluoridated only. TRIAL DESIGN: A randomized, controlled, split-mouth trial. METHODS: Adolescent patients (age range: 12-18 years) with fixed orthodontic appliances who had developed ICL [ICDAS 1 or 2 (International Caries Detection and Assessment System)] during orthodontic treatment were consecutively recruited and randomly assigned to either resin infiltration (Icon) with up to 3 etching procedures (Inf) or to a fluoride varnish (Tiefenfluorid) (FV). Both interventions were performed according to the manufacturer's recommendations. Outcome assessors were blinded to the applied intervention. Primary and secondary outcomes included the evaluation of the appearance of the ICL before (T0) and 1 week after (T1) treatment by digital photographs (ΔE), laser fluorescence readings (DD), and ICDAS scores. BLINDING: Due to the treatment nature neither the operators nor the patients could be blinded. However, outcome assessors and the statistician were blinded. RESULTS: Fifteen patients (9 female) with 60 ICL were included (mean age: 14.6 years). At baseline FV and Inf did not differ significantly in ΔE (median ΔE0,T (25th/75th percentiles):10.7(9.1/20.9): ΔE0,I:13.4(10.3/18.5); P = 0.469), DD (P = 0.867) and ICDAS (P = 0.521). One-week after treatment (T1) ΔE values (P < 0.001), DD values (P < 0.001), and ICDAS scores (P = 0.014) for Inf were significantly reduced, whereas ΔE values (P = 0.125) and ICDAS scores (P = 0.073) for FV remained unchanged. LIMITATION: Natural remineralizing in the standard interventional control group cannot be observed yet, since up to 6 months are needed to naturally remineralize ICL. CONCLUSIONS: Based on our short-term data, resin infiltration effectively masked ICL during treatment with fixed orthodontic appliances. Fluoridation was not able to immediately improve the visual appearance of ICL. Further longer-term assessment should focus not only on the aesthetic outcome, but also on the caries inhibitory effect of resin infiltration during treatment with fixed orthodontic appliances. TRIAL REGISTRATION: German Clinical Trials Register (DRKS-ID: DRKS00011797).

Correlation of quantitative light-induced fluorescence and qualitative visual rating in infiltrated post-orthodontic white spot lesions.

OBJECTIVES: The aim of this prospective, clinical single-centre study was to evaluate the masking efficacy of post-orthodontic resin infiltration after 12-month follow-up and correlate quantitative and qualitative outcome measures. METHODS: Patients with completed fixed orthodontic treatment and the presence of one or more vestibular active non-cavitated white spot lesion/s (WSL) [ICDAS 1 or 2 (International Caries Detection and Assessment System)] were provided with resin infiltration 3-12 months after bracket removal. All patients (n = 31) participating before (t0) intervention were invited again and examined after 12 months (t2). Enamel demineralization was scored using quantitative light-induced fluorescence [QLF (DeltaF[flourescence], DeltaQ[lesion volume], White Spot Area)] and qualitative visual rating [11-point Likert-scale from 0 (no lesions visible on any tooth) to 10 (all teeth affected on the entire vestibular surface)]. RESULTS: In 17 patients (7 female and 10 male) 112 WSL (ICDAS 1: n = 1; ICDAS 2: n = 111) in 112 teeth were (re)examined. Before treatment (t0) a significant, weak (DeltaF), and moderate (DeltaQ, White Spot Area) correlation was observed between the quantitative and the qualitative rating (P < 0.002) [median DeltaF: -7.31 (-10.4/-6.58)%; DeltaQ:-2.25 (-10.8/-0.41)% mm2; White Spot Area: 0.34 (0.05/1.16) mm2; visual rating:3.7 ± 1.2]. Resin infiltration led to significantly increased fluorescence and decreased visual scores (P < 0.001) 7 days (t1) and 12 months (t2) after treatment. No significant changes based on DeltaF [-6.55 (-7.29/-6.08)%] and on visual ratings [1.0 ± 1.0] were observed between t1 and t2 (P = 1.000). After 7 days (t1) the correlation between the quantitative and the qualitative ratings remained significant, weak to moderate (P < 0.002). After 12 months (t2) the correlation was (non-)significant and weak for DeltaF, DeltaQ, and White Spot Area (P ≤ 0.097). LIMITATIONS: Since the overall masking efficacy of resin infiltration has been shown previously, an untreated control group was omitted. CONCLUSIONS: When assessing the masking efficacy of infiltrated post-orthodontic WSL only a weak to moderate correlation was found between QLF values and visual ratings. Furthermore, over time this correlation decreased. Thus, it remains unclear if QLF is a viable method to assess and quantify infiltrated post-orthodontic WSL over time. TRIAL REGISTRATION: German Clinical Trials Register (DRKS-ID:DRKS00005067).

Improved Surface Layer Erosion of Pit and Fissure Caries Lesions in Preparation for Resin Infiltration.

The penetration of a low-viscosity resin (infiltrant) into caries lesions depends on the erosion of the relatively impermeable surface layer (SL) that covers the lesion body. The present study aimed to evaluate the effect of different abrasive pretreatments on erosion of the SL and on penetration of an infiltrant into occlusal caries lesions, simultaneously. Sixty extracted human molars showing International Caries Detection and Assessment System (ICDAS-2) lesions were randomly allocated to 5 groups. A small area of each lesion was covered with resin before etching. Twelve lesions each were etched with either 15% HCl-gel (H120) or 37% H3PO4-gel (P120) for 120 s. Furthermore, the standard 15% HCl-gel or either one of two experimental etchants (HCl-gel or H3PO4-gel, each including abrasives) were applied for either 120 s or 30 s using a brush (surface pressure 150 g) (H30B, P120BA, H30BA). After rinsing and drying, all lesions were infiltrated for 180 s (Icon; DMG). From each tooth sections were prepared and visualized using confocal microscopy. SL of unetched areas and the lesion depth were 33 (23/51) µm and 537 (274/876) µm, respectively, both not differing significantly between groups. H120, H30B, and H30BA showed significantly higher SL reduction compared with P120 or P120BA, but only for H30BA SL was eroded almost completely (p < 0.05; Mann-Whitney test). Compared to other groups, occlusal lesions were significantly more infiltrated in H30BA (p < 0.05; Mann-Whitney test). HCl-gel including abrasives that was rubbed onto the enamel surface with a brush seems to be most effective to erode SLs of caries lesion situated in fissures and enable an almost complete subsequent resin infiltration.

Effects of the association of high fluoride- and calcium-containing caries-preventive agents with regular or high fluoride toothpaste on enamel: an in vitro study.

OBJECTIVES: The aim of this in vitro study was to compare the caries-preventive effect of various high fluoride- and calcium-containing caries-preventive agents (> 22.000 ppm F- [ppm]) in adjunct to use of regular (1450 ppm) or high (5000 ppm) fluoride toothpaste on sound as well as demineralized enamel. MATERIALS AND METHODS: Bovine enamel specimens (n = 276; 5 mm × 3.5 mm × 3 mm) having one sound surface [ST] and one artificial caries lesion [DT] were randomly allocated to 12 groups. Interventions before pH-cycling were no intervention ([SC1/SC5]), application of varnishes/solutions containing NaF (22,600 ppm; Duraphat [NaF1/NaF5]); NaF + tricalcium phosphate (22,600 ppm; Clinpro White Varnish [TCP1/TCP5]); NaF + CPP-ACP (22,600 ppm; MI Varnish [CPP1/CPP5]); silver diammine fluoride (35,400 ppm; Cariestop 30%[SDF1/SDF5]); and NaF + calcium fluoride (45,200 ppm; Biophat[CaF1/CaF5]). During pH-cycling (28 days, 6 × 120 min demineralization/day) half of the specimens in each group were brushed (10 s; 2 × /day) with either 1,450 (NaF; named, e.g., TCP1) or 5,000 ppm (NaF; e.g., TCP5) dentifrice slurry. Differences in integrated mineral loss (∆∆Z) and lesion depth (∆LD) were calculated between values after initial demineralization and after pH-cycling using transversal microradiography. RESULTS: After pH-cycling, SC1/SC5 showed significantly increased ∆ZDT/LDDT values, indicating further demineralization (p < 0.05; paired t-test). Decreased ∆ZDT values, indicating non-significant remineralization, could only be observed in CaF1/CaF5 (p > 0.05; paired t-test). Additional use of all varnishes/solutions significantly decreased ∆∆ZDT/∆∆ZST and ∆LDDT/∆LDST compared to SC1/SC5 (p < 0.05;ANCOVA). Between 1450 and 5000 ppm dentifrices, a significant difference in ∆∆ZDT/∆∆ZST and ∆LDDT/∆LDST could only be observed for SC1/SC5 (p < 0.05; ANCOVA). CONCLUSION: Under the conditions chosen, all fluoride varnishes/solutions significantly reduced demineralization. Furthermore, a significant dose-response characteristic for fluoride varnishes could be revealed. However, no additional benefit could be observed, when varnishes were combined with high fluoride instead of regular fluoride dentifrices. CLINICAL RELEVANCE: For children and adolescents with high caries risks varnishes containing more than 22,600 ppm should be further investigated, as they offered higher caries-preventive effects in vitro. Furthermore, there seems to be no difference in the demineralization-inhibitory capacity of fluoride varnishes when used in combination with either standard or highly fluoridated dentifrices.

Increasing dental zirconia micro-retentive aspect through ultra-short pulsed laser microstructuring: study on flexural strength and crystal phase characterization.

OBJECTIVES: Although ultra-short pulsed laser (USPL) microstructuring has previously improved zirconia bond-strength, it is yet unclear how different laser-machined surface microstructures and patterns may influence the material's mechanical properties. Therefore, the aim of this study was to assess the flexural strength of zirconia after different USPL settings creating three different geometrical patterns with structures in micrometer scale. METHODS: One hundred sixty zirconia bars (3Y-TZP, 21 × 4 × 2.1 mm) were prepared and randomly divided into five groups (n = 32): no surface treatment (negative control-NC); sandblasting with Al2O3 (SB); and three laser groups irradiated with USPL (Nd:YVO4/1064 nm/2-34 J/cm2/12 ps): crossed-lines (LC), random-hatching (LR), and parallel-waves (LW). Bars were subjected to a four-point flexural test (1 mm/min) and crystal phase content changes were identified by X-ray diffraction. Surface roughness and topography were analyzed through 3D-laser-profilometry and SEM. Data were analyzed with parametric tests for roughness and Weibull for flexural strength (α = 5%). RESULTS: LR (Mean[95%CI]: 852.0 MPa, [809.2-894.7]) was the only group that did not show a significantly different flexural strength than NC (819.8 MPa, [796.6-842.9]), (p > 0.05). All laser groups exhibited higher Weibull moduli than NC and SB, indicating higher reliability and homogeneity of the strength data. An increase of monoclinic phase peak was only observed for SB. CONCLUSION: In conclusion, USPL created predictable, homogeneous, highly reproducible, and accurate surface microstructures on zirconia ceramic. The laser-settings of random-hatching (12 ps pulses) increased 3Y-TZP average surface roughness similarly to SB, while not causing deleterious crystal phase transformation or loss of flexural strength of the material. Furthermore, it has increased the Weibull modulus and consequently material's reliability. CLINICAL SIGNIFICANCE: Picosecond laser microstructuring (LR conditions) of 3Y-TZP ceramic does not decrease its flexural strength, while increasing materials realiability and creating highly reproducible and accurate microstructures. These features may be of interest both for improving clinical survival of zirconia restorations as well as enhancing longevity of zirconia implants.

Demineralization Inhibitory Effects of Highly Concentrated Fluoride Dentifrice and Fluoride Gels/Solutions on Sound Dentin and Artificial Dentin Caries Lesions in vitro.

OBJECTIVES: The aim of this in vitro study was to compare the demineralization inhibitory effect of gels/solutions used in combination with either standard or highly fluoridated dentifrices on sound dentin as well as on artificial dentin caries-like lesions. METHODS: Bovine dentin specimens (n = 240) with two different surfaces each (sound [ST] and artificial caries lesion [DT]) were prepared and randomly allocated to twelve groups. Weekly interventions during pH-cycling (28 days, 6 × 120 min demineralization/day) were: the application of gels/solutions containing amine fluoride/sodium fluoride (12,500 ppm F [ppm]; pH = 4.4; AmF); NaF (12,500 ppm; pH = 6.6; NaF1); NaF (12,500 ppm; pH = 6.3; NaF2); silver diamine fluoride (14,200 ppm; pH = 8.7; SDF); acidulated phosphate fluoride (12,500 ppm; pH = 3.8; APF), and no intervention (standard control; S). Furthermore, half of the specimens in each group were brushed (10 s; twice per day) with dentifrice slurries containing either 1,450 ppm (e.g., AmF1450) or 5,000 ppm (e.g., AmF5000). Differences in integrated mineral loss (ΔΔZ) and lesion depth (ΔLD) were calculated between values before and after pH-cycling using transversal microradiography. RESULTS: After pH-cycling Ss showed significantly increased ΔZDT and LDDT values, indicating further demineralization. In contrast, except for one, all groups including fluoride gels/solutions showed significantly decreased ΔZDT values. Additional use of most fluoride gels/solutions significantly enhanced mineral gain, mainly in the surface area; however, acidic gels/solutions seemed to have negative effects on lesion depths. SIGNIFICANCE: Under the present pH-cycling conditions the highly fluoridated dentifrice significantly reduced caries progression and additional application of nearly all of the fluoride gels/solutions resulted in remineralization. However, there was no difference in the remineralizing capacity of fluoride gels/solutions when used in combination with either standard or highly fluoridated dentifrices.

Do bleaching gels affect the stability of the masking and caries-arresting effects of caries infiltration-in vitro.

OBJECTIVES: The aim of this study was to evaluate the influence of different bleaching gels on the masking and caries-arresting effects of infiltrated and non-infiltrated stained artificial enamel caries lesions. MATERIALS AND METHODS: Bovine enamel specimens (n = 240) with each two sound areas (SI and SC) and each two lesions (DI and DC) were infiltrated (DI and SI), stained (1:1 red wine-coffee mixture,70 days), and randomly distributed in six groups to be bleached with the following materials: 6%HP (HP-6), 16%CP (CP-16), 35%HP (HP-35), 40%HP (HP-40), and no bleaching (NBl,NBl-NBr). Subsequently, specimens were pH-cycled (28 days, 6 × 60 min demineralization/day) and all groups except NBl-NBr were brushed with toothpaste slurry (1.100 ppm, 2×/day, 10 s). Differences in colorimetric values (ΔL, ΔE) and integrated mineral loss (ΔΔZ) between baseline, infiltration, staining, bleaching, and pH cycling were calculated using photographic and transversal microradiographic images. RESULTS: At baseline, significant visible color differences between DI and SC were observed (ΔEbaseline = 12.2; p < 0.001; ANCOVA). After infiltration, these differences decreased significantly (ΔEinfiltration = 3.8; p < 0.001). Staining decreased and bleaching increased ΔL values significantly (p ≤ 0.001). No significant difference in ΔΔE was observed between before staining and after bleaching (ΔEbleaching = 4.3; p = 0.308) and between the bleaching agents (p = 1.000; ANCOVA). pH-cycling did not affect colorimetric values (ΔEpH-cycling = 4.0; p = 1.000). For DI, no significant change in ΔZ during in vitro period was observed (p ≥ 0.063; paired t test). CONCLUSIONS: Under the conditions chosen, the tested materials could satisfactorily bleach infiltrated and non-infiltrated stained enamel. Furthermore, bleaching did not affect the caries-arresting effect of the infiltration. CLINICAL RELEVANCE: The present study indicates that bleaching is a viable way to satisfactorily recover the appearance of discolored sound enamel and infiltrated lesions.

Long-term costs of post-restorations: 7-year practice-based results from Germany.

OBJECTIVES: We evaluated the initial and follow-up treatment costs of different post-restorations in a practice-based German healthcare setting. METHODS: A total of 139 incisors, canines, or premolars received post-restorations placed by eight general dental practitioners in Germany, and were followed over a mean ± SD 7.1 ± 4.5 years. Preformed metal (MP, n = 68), glass-fiber (GF, n = 28), or cast post-and-core buildups (MC, n = 23) had been used to retain crowns or bridge anchors. Preformed metal and glass-fiber had also been used to retain directly built up post-retained composite restorations (PC, n = 20). Material and treatment costs for the initial post-restorations as well as restorative, endodontic, or surgical re-treatments were estimated from a public-payer-perspective in Germany. Associations between total and annualized total costs and covariates were assessed using generalized linear modeling. The study was registered in the German Clinical Trials Register (DRKS-ID: DRKS00012938). RESULTS: MC showed highest initial treatment costs (557.23 Euro), but the least re-treatments (6/23, 26%), while PC showed lowest initial costs (203.52 Euro) but the most re-treatments (11/20, 55%). Costs for MP/GF post-crowns were initially similarly costly (496.47/496.87 Euro), and both also showed similar re-treatments (35%/36%). The overall annual failure rate was 5.2% (MC: 3.5%, MP: 4.6%, GF: 5.3%, PC: 10.3%). Including costs for the resulting re-treatments, mean total costs were 591.66 Euro (MC), 548.31 Euro (MP), 526.37 Euro (GF), and 361.81 Euro (PC). Annualized total costs were 171.36 Euro (MC), 141.75 Euro (MP), 146.12 Euro (GF), and 135.65 Euro (PC). Total and annualized total costs were highest for MC, with PC being the significantly less costly option (p < 0.001). CONCLUSIONS: Within German healthcare, both initial and follow-up costs for post-restorations were considerable. Saving costs initially may, at least partially, be offset by more complications long-term. CLINICAL RELEVANCE: Dentists need to be aware that the placement of posts is not only initially costly but also comes with significant long-term costs for treating occurring complications. This should be communicated with patients and considered during treatment planning.

Analysis of relative bacterial activity and lactate dehydrogenase gene expression of caries-associated bacteria in a site-specific natural biofilm: an ex vivo study.

OBJECTIVES: Detecting bacterial activity is considered a promising approach to monitor shifts from symbiosis to dysbiosis in oral microbiome. The present study aimed at investigating both the relative bacterial activity and the lactate dehydrogenase (ldh) gene expression of caries-associated bacteria in a site-specific natural biofilm. MATERIAL AND METHODS: Sixty subjects (age, mean ± SE: 30.1 ± 1.4) were allocated to two groups: caries-free subjects (CF) or caries-active subjects (CA). CF presented one sound surface (CFS, n = 30). CA presented two donor sites: a cavitated caries lesion (CAC, n = 30) and a sound reference surface (CAS, n = 30). Real-time quantitative PCR (q-PCR) on species or genus level and total bacteria was performed targeting the 16S gene, the 16S rRNA, the ldh gene, and the ldh mRNA (increasing 16S ribosomal RNA copy numbers can function as an indicator of increased energy metabolism). As the 16S rRNA abundance represents the number of ribosomes, while the 16S gene abundance represents the number of genomes, the quotient of the relative abundances functions as a measure for the relative bacterial activity (%). RESULTS: Both lactobacilli and S. mutans showed the highest relative bacterial activity in CAC ((mean ± SE) 218 ± 60% and 61 ± 16%, respectively) and the lowest values for both sound reference surfaces (69 ± 48%; 8 ± 3%). Significant differences were found between CAC and CAS as well as between CAC and CFS for both lactobacilli and S. mutans (p < 0.05). The ldh gene expression of lactobacilli and S. mutans only showed moderate values in CAC (1.90E+03 ± 2.11E+03; 2.08E+04 ± 4.44E+04 transcripts/µl) and CFS (2.04E+03 ± 2.74E+03; 8.16E+03 ± 6.64E+03 transcripts/µl); consequently no significant differences were detected. CONCLUSION AND CLINICAL RELEVANCE: Caries-associated bacteria (lactobacilli and S. mutans) showed the highest relative bacterial activity in plaque of cavitated lesions, the lowest in sound surfaces, allowing the detection of a significant activity shift in health and disease for caries-active patients. However, no significant differences in ldh gene expression could be determined.

Effects of Dentifrices Differing in Fluoride Content on Remineralization Characteristics of Dentin in vitro.

OBJECTIVES: The aim of this study was to compare the caries preventive effect of highly fluoridated dentifrices and gels on sound dentin as well as on artificial dentin caries-like lesions. METHODS: Bovine dentin specimens (n = 240), with 2 different surfaces each (1 sound surface [sound treatment (ST)] and one caries lesion [demineralized treatment (DT)]), were prepared and randomly allocated to one highly (6 × 120 min demineralization/day [H]) and one lowly cariogenic (6 × 60 min demineralization/day [L]) pH-cycling model. Treatments during pH-cycling (28 days) were: brushing 2×/day with: 0 ppm F [H0/L0], 1,450 ppm F [H1,450/L1,450], 2,800 ppm F [H2,800/L2,800], 5,000 ppm F [H5,000/L5,000], 5,000 ppm F plus TCP [H5,000+TCP/L5,000+TCP], and 12,500 ppm F [H12,500/L12,500] containing dentifrices/gels. Dentifrice/gel slurries were prepared with deionized water (1:2 wt/wt). Differences in integrated mineral loss (∆∆Z) and ∆ lesion depth were calculated between values before and after pH-cycling using transversal microradiography. RESULTS: The correlation between ΔΔZDT and F- was strong for the highly (rH = 0.691; p < 0.001) and moderate (rL = 0.500; p < 0.001) for the lowly cariogenic model, indicating a fluoride dose-response for both. Significant differences for ΔΔZDT and ΔΔZST could be found between H0, H1,450, H5,000, and H12,500 as well as L0, L5,000, and L125,000 (p ≤ 0.046; analysis of covariance [ANCOVA]). Except for 0 ppm F-, no significant difference in ΔΔZST and ΔΔZDT could be found between the highly and lowly cariogenic model (p ≥ 0.056; ANCOVA). CONCLUSION: For both pH-cycling conditions a dose-response for fluoride could be revealed. For elderly people with exposed root surfaces, the use of gels containing 12,500 ppm F instead of regularly (1,450 ppm F) or highly (5,000 ppm F) fluoridated dentifrices should be further investigated, as it offered higher caries-preventive effects in vitro.

How to Intervene in the Root Caries Process? Systematic Review and Meta-Analyses.

The aim of this review as part of the preparation for a workshop organized by the European Federation of Conservative Dentistry (EFCD) in conjunction with the European Organisation for Caries Research (ORCA) was to systematically analyze available evidence of non-, micro- as well as invasive interventions for root caries lesions (RCLs). For each treatment strategy, a separate systematic review was either performed (micro-invasive and choice of restorative material) or updated (non-invasive and excavation technique) each of them following PRISMA guidelines, and if possible meta-analyses were performed. Besides the general advice to improve tooth brushing with fluoride toothpaste main findings for non-invasive interventions in RCLs, the use of dentifrices containing 5,000 ppm F- as well as professionally applied chlorhexidine varnish or silver diamine fluoride seemed to be more efficacious to arrest root caries compared to conventional fluoride toothpaste or placebo respectively. However, this conclusion is based only on a few randomized clinical trials. For micro-invasive treatments, only 2 studies focusing on sealants were available without clear conclusions. A recent review on the comparison of atraumatic restorative treatment compared with conventional treatment concluded that there is insufficient data to clearly rule out if any difference with regard to restoration longevity between both techniques exists. When restoring coventionally, composites performed better than resin-modified and glass ionomer cements. However, all materials showed rather high annual failure rates in the majority of the studies and evidence is based on a low number of prospective studies with a rather high risk of bias.

Evaluation of Restorative Materials Containing Preventive Additives in a Secondary Caries Model in vitro.

The incorporation of antibacterial agents into dental restorative materials is a promising strategy for secondary caries prevention. Previously, Carolacton affected Streptococcus mutans biofilm formation on composite materials in vitro. The present study evaluated secondary caries formation adjacent to Carolacton-containing composites and conventional restorative materials using an artificial biofilm model. Standardized cavities were prepared in bovine dentin-enamel samples (n = 175) and restored with various dental materials (Tetric EvoCeram [T], GrandioSo composite without [G] and with Carolacton [GC], Grandio Flow without [F] and with Carolacton [FC], GrandioSo containing sodium fluoride [GNaF], and Ketac Fil [K]). After artificial aging, S. mutans was grown on the samples for 7 days. The investigation of gap sizes and secondary caries formation was performed using confocal laser scanning microscopy and transversal microradiography. Median gap size in enamel was 9.4 µm (interquartile range 7.9-12.7). Compared to all other groups significant differences in gap sizes could be observed for Ketac Fil (p < 0.001; Mann-Whitney test). Only GrandioSo composite containing 30% sodium fluoride and Ketac Fil showed significantly smaller lesion areas in enamel (p < 0.001; Mann-Whitney test) than all other groups which was confirmed by the mineral loss data (p < 0.001; Mann-Whitney test). Based on the present in vitro results, it seems that Carolacton-containing composite in the current formulation within the shown simplified monoculture biofilm model is not able to prevent caries formation compared to fluoride-releasing restorative materials.

Correlation between relative bacterial activity and lactate dehydrogenase gene expression of co-cultures in vitro.

OBJECTIVES: The present study aims at correlating the relative bacterial activity with the H+ concentration and the ldh expression of caries-associated bacteria in co-cultures. MATERIALS AND METHODS: Well plates were prepared with BHI medium and cultures of Lactobacillus paracasei and Fusobacterium nucleatum. Bacterial growth at 37 °C was measured using a microplate-photometer before and after adding sucrose to the samples. Samples of co-cultures (n = 12) and single-species cultures (n = 3) were taken and pH was assessed. Real-time quantitative PCRs were applied targeting the 16S-gene, the 16S-rRNA, the ldh-gene, and the ldh-mRNA. RESULTS: For L. paracasei with sucrose, an increase in relative bacterial activity (62.8% ± 23.5% [mean, SE]) was observed, while F. nucleatum showed a clear decrease in relative bacterial activity (- 35.0% ± 9.6%). Simultaneously, the H+ concentration increased (1.15E-05 mol*l-1 ± 4.61E-07 mol*l-1). Consequently, a significant positive correlation was found between L. paracasei's relative bacterial activity and H+ concentration (Spearman rank correlation, r = 0.638; p = 0.002), while F. nucleatum exhibited a negative correlation (r = - 0.741; p ≤ 0.001). Furthermore L. paracasei with sucrose showed a moderate, but significant positive correlation between relative bacterial activity and ldh-expression (r = 0.307; p = 0.024). CONCLUSIONS AND CLINICAL RELEVANCE: The relative bacterial activity after sucrose pulse showed a significant correlation not only to the acid production (H+ concentration) but also to ldh expression of L. paracasei. However, further research is required to confirm these findings in a mature biofilm in vivo.

Effect of NaF, AmF, KF gels and NaF toothpaste combined with a saliva substitute on dentin lesions in vitro.

OBJECTIVE: The aim of the present in vitro study was to evaluate the remineralizing effects of NaF, AmF, KF gels and NaF toothpaste in combination with a potentially demineralizing saliva substitute (Glandosane; pH = 5.1) being widely used in Germany. METHODS: In each of 120 dentin specimens, three artificial lesions were created. One lesion was covered for analysis of pre-demineralization (ΔZB). Treatments during pH cycling (3 × 1 h demineralization/day [pH = 5.0] and 3 × 3 h Glandosane/day; 12 h 100%humidity) were as follows: no treatment (NT), application (5 min,2×/day) of 12.500 ppm F- [pH = 6.04] (NaF-gel1), 12.500 ppm F- [pH = 7.34] (NaF-gel2), 12.500 ppm F- [pH = 5.82] (AmF-gel), 1450 ppm F- [pH = 7.35] (KF-gel), and 5000 ppm F- [pH = 8.14]; (NaF-TP) for 7 days (E1). Subsequently, from each specimen, one lesion was covered, while the remaining lesion was cycled for another 7 days (E2). Differences in integrated mineral loss (ΔΔZE1/ΔΔZE2) were calculated between values before and after pH cycling. RESULTS: Mean (95%CI) ΔZB was 3851 (3762;3939) vol% × µm. Except for NaF-gel2 and NaF-TP, specimens of all other groups further demineralized. Only NaF-gel2 induced a significant gain in mineral content (p ≤ 0.004; paired t test). Significant differences in the change of mineral loss were found between NT and all fluoride groups for both ΔΔZE1 and for ΔΔZE2 (p < 0.05, Bonferroni post hoc test). However, only NaF-gel2 and NaF-TP induced remineralization. CONCLUSION: Under the in vitro conditions chosen, all fluoride agents could significantly hamper the adverse effects of a demineralizing saliva substitute. CLINICAL SIGNIFICANCE: In combination with a demineralizing saliva substitute, slight mineral gain was only observed for neutral NaF-gel2 and 5000 ppm F- toothpaste.

Failure loads of all-ceramic cantilever fixed dental prostheses on post-restored abutment teeth: influence of the post presence and post position.

The influence of a fiber post-restored abutment tooth on the load capability of a three-unit zirconia framework cantilever fixed dental prosthesis (cFDP) was evaluated after simulated clinical function. Human lower sound premolars (n = 64) were distributed, in equal numbers, to four experimental groups: two vital abutment teeth (group I; control); mesial abutment tooth post-restored (group II); distal abutment tooth post-restored (group III); and mesial and distal abutment teeth post-restored (group IV). All specimens received an adhesively luted three-unit cFDP of veneered zirconia. Simulated clinical function was performed by two subsequent sequences of thermal-cycling (2 × 3,000 cycles) and mechanical loading (1.2 × 106 load cycles from 0 to 50 N) (TCML). Four specimens failed during TCML (one in each of groups I and IV and two in group II). The maximum load capability ranged from 365 to 538 N and was not significantly different between groups. Specimens with post-restored abutments failed mainly because of abutment tooth fracture of the distal abutment. The presence or position of post-restored abutment teeth has no significant impact on load capability of all-ceramic three-unit cFDPs. The risk of tooth fracture of the distal abutment teeth of a cFDP was significantly increased when one abutment tooth, irrespective of its position, was post-and-core restored.

Caries-Preventive Effect of NaF, NaF plus TCP, NaF plus CPP-ACP, and SDF Varnishes on Sound Dentin and Artificial Dentin Caries in vitro.

The aim of this study was to compare the caries-preventive effect of different fluoride varnishes on sound dentin as well as on artificial dentin caries-like lesions. Bovine dentin specimens (n = 220) with one sound surface (ST) and one artificial caries lesion (DT) were prepared and randomly allocated to 11 groups. The interventions before pH cycling were as follows: application of a varnish containing NaF (22,600 ppm F-; Duraphat [NaF0/NaF1]), NaF plus tricalcium phosphate (22,600 ppm F-; Clinpro White Varnish Mint [TCP0/TCP1]), NaF plus casein phosphopeptide-stabilized amorphous calcium phosphate complexes (CPP-ACP; 22,600 ppm F-; MI Varnish [CPP0/CPP1]), or silver diamine fluoride (SDF; 35,400 ppm F-; Cariestop 30% [SDF0/SDF1]) and no intervention (NNB/N0/N1). During pH cycling (14 days, 6 × 120 min demineralization/day) half of the specimens in each group were brushed (10 s; 2 times/day) with either fluoride-free ("0"; e.g., TCP0) or 1,100 ppm F- ("1"; e.g., TCP1) dentifrice slurry. In another subgroup, the specimens were pH cycled but not brushed (NNB). Differences in integrated mineral loss (ΔΔZ), lesion depth (ΔLD), and colorimetric values (ΔΔE) were calculated between the values after initial demineralization and those after pH cycling, using transversal microradiography and photographic images. After pH cycling, no discoloration could be observed. Furthermore, NNB, N0, and N1 showed significantly increased ΔZDT/LDDT and ΔZST/LDST values, indicating further demineralization. In contrast, CPP0, CPP1, SDF0, and SDF1 showed significantly decreased ΔZDT/LDDT values, indicating remineralization (p ≤ 0.004; paired t test). CPP0, CPP1, SDF0, and SDF1 showed significantly higher changes in ΔΔZDT/ΔLDDT and ΔΔZST/ΔLDST than NNB, N0, and N1 (p < 0.001; Bonferroni post hoc test). In conclusion, under the conditions chosen, all fluoride varnishes prevented further demineralization. However, only NaF plus CPP-ACP and SDF could remineralize artificial dentin caries-like lesions under net-demineralizing conditions, thereby indicating that NaF plus CPP-ACP and SDF may be helpful to high-caries-risk patients.

Effects of Self-Assembling Peptide P11-4, Fluorides, and Caries Infiltration on Artificial Enamel Caries Lesions in vitro.

The application of a self-assembling peptide on noncavitated caries lesions is supposed to be a feasible approach to facilitate remineralization and mask their unfavorable appearance. However, demineralizing conditions are common in the oral environment, so the aim of this pH-cycling study was to compare recommended and novel treatment methods regarding their ability to hamper demineralization and as a consequence mask artificial enamel caries lesions. Artificial caries lesions were prepared in bovine enamel and randomly allocated to 11 groups (n = 22). Treatments before pH-cycling were as follows: the application of a self-assembling peptide (Curodont™ Repair [C]), a low-viscosity resin (Icon® [I]), 2 fluoride solutions (10,000 ppm F-: Elmex fluid [E] and 43,350 ppm F-: Tiefenfluorid® [T]), and no intervention (N). During pH-cycling (28 days, 6 × 60 min demineralization/day) half of the specimens in each group were brushed (10 s; 2 ×/day) with either fluoride-free (named e.g., C0) or NaF (1,100 ppm F-; e.g., C1) dentifrice slurry. In another subgroup specimens were pH-cycled but not brushed (NNB). Differences in integrated mineral loss (ΔΔZ), lesion depth (ΔLD), and colorimetric values (ΔΔE) were calculated between values after pre-demineralization, surface treatment, and pH-cycling. Specimens of C0, C1, NNB, N0, N1, T0, and E0 showed significantly increased ΔZ and LD values after pH-cycling (p ≤ 0.003; paired t test). C0, C1, NNB, and N0 showed significantly higher changes in ΔΔZ than E1, I0, I1, and T1 (p < 0.001; ANOVA). Significantly reduced colorimetric values could only be observed for I1, I0, E1, and E0 after treatment and after pH-cycling (p ≤ 0.027; paired t test). In conclusion, under the conditions chosen only the application of a low-viscosity resin could mask caries lesions significantly, whereas self-assembling peptides could neither inhibit lesion progression nor mask the lesions considerably.

Re- and Demineralization Characteristics of Enamel Depending on Baseline Mineral Loss and Lesion Depth in situ.

OBJECTIVES: The aim of this double-blinded, randomized, cross-over in situ study was to evaluate the re- and demineralization characteristics of sound enamel as well as lowly and highly demineralized caries-like enamel lesions after the application of different fluoride compounds. METHODS: In each of three experimental legs of 4 weeks, 21 participants wore intraoral mandibular appliances containing 4 bovine enamel specimens (2 lowly and 2 highly demineralized). Each specimen included one sound enamel and either one lowly demineralized (7 days, pH 4.95) or one highly demineralized (21 days, pH 4.95) lesion, and was positioned 1 mm below the acrylic under a plastic mesh. The three randomly allocated treatments (application only) included the following dentifrices: (1) 1,100 ppm F as NaF, (2) 1,100 ppm F as SnF2 and (3) 0 ppm F (fluoride-free) as negative control. Differences in integrated mineral loss (x0394;x0394;Z) and lesion depth (x0394;LD) were calculated between values before and after the in situ period using transversal microradiography. RESULTS: Of the 21 participants, 6 did not complete the study and 2 were excluded due to protocol violation. Irrespectively of the treatment, higher baseline mineral loss and lesion depth led to a less pronounced change in mineral loss and lesion depth. Except for x0394;x0394;Z of the dentifrice with 0 ppm F, sound surfaces showed significantly higher x0394;x0394;Z and x0394;LD values compared with lowly and highly demineralized lesions (p < 0.05, t test). CONCLUSION: Re- and demineralization characteristics of enamel depended directly on baseline mineral loss and lesion depth. Treatment groups should therefore be well balanced with respect to baseline mineral loss and lesion depth.

Analysis of Bacterial Activity in Sound and Cariogenic Biofilm: A Pilot in vivo Study.

Dental caries is a multifactorial disease with many associated microbial taxa, but only a few are notably contributing to acidogenicity. The ribosome number and the corresponding 16S ribosomal RNA (rRNA) concentration are considered a molecular indicator for general metabolic activity of bacteria, as they are elevated with increased anabolic and catabolic activities. We hypothesize that the activity of aciduric/acidogenic bacterial taxa, reflected by a rise in ribosomal counts, could resolve differences between plaque biofilm from sound surfaces and caries lesions. The included subjects were allocated to two groups: caries-free (CF) or caries-active (CA). CF subjects presented one donor site, namely one sound surface (CFS, n = 10), whereas CA subjects presented two donor sites: a cavitated lesion with an ICDAS score of 5-6 (CAC, n = 13), and a sound reference surface (CAS, n = 13). Four aciduric/acidogenic bacterial taxa (Streptococcus mutans, lactobacilli, Bifidobacterium dentium, and Scardovia wiggsiae) and one asaccharolytic taxon (fusobacteria) as a contrast were selected. 16S rRNA and 16S rRNA genes were quantified by quantitative PCR. Based on these parameters, bacterial and ribosomal counts, as well as relative activities were calculated as the quotient of relative ribosomal abundance and relative genome abundance. Caries-associated bacteria showed the highest relative activity in caries lesions (e.g. lactobacilli CAC: 177.5 ± 46.0%) and lower activities on sound surfaces (e.g. lactobacilli CAS: 96.3 ± 31.5%), whereas asaccharolytic fusobacteria were most active on sound surfaces and less active in caries lesions (CFS: 275.7 ± 171.1%; CAS: 205.8 ± 114.3%; CAC: 51.1 ± 19.0%). Thus, the present study suggests different activity patterns for biofilms from CF and CA individuals.

Surface Characterization and Short-term Adhesion to Zirconia after Ultra-short Pulsed Laser Irradiation.

PURPOSE: To evaluate the suitability of an ultra-short pulsed laser (USPL) to treat zirconia ceramic surfaces and increase their adhesion to dual-curing resin cement. MATERIALS AND METHODS: Twenty 10 × 10 × 5 mm³ blocks were prepared from a zirconia ceramic (Y-TZP). The specimens were polished and randomly assigned to four groups (n = 5) which received the following surface treatments: sandblasting (SB) with Al2O3 particles and silica coating (SC) with SiO2 particles as positive controls; two groups received USPL irradiation, one with 10 scan repetitions (L10) and the other with 20 (L20). Laser irradiation was performed at 1030 nm, 2.3 J/cm², 6 ps pulse duration. The ceramic blocks were duplicated in composite resin and cemented with a dual-curing resin cement. Half of the blocks were then stored in water (37°C) for 24 h and the other half for 1 month. At each time, 40 to 60 sticks per group were subjected to microtensile bond strength testing. Data were analyzed statistically using the Kruskal-Wallis test (α = 0.05). RESULTS: Laser-treated zirconia presented statistically significantly higher roughness than did SB and SC. After 24 h, the highest bond strength means (MPa) were achieved by L10 (42.3 ± 10.8) and L20 (37.9 ± 14.4), and both of them were statistically significantly higher than SB (22.0 ± 5.3) and SC (20.8 ± 7.1) (p < 0.05). After 1 month of storage, L10- and L20-treated zirconia still showed significantly higher bond strengths than did SB- and SC-treated zirconia (p < 0.05). CONCLUSION: USPL irradiation significantly increases bond strength of zirconia ceramic to dual-curing resin cement and might be an alternative for improving adhesion to this material.