Distribution of initial caries lesions in relation to fixed orthodontic therapy. A systematic review and meta-analysis

BACKGROUND

Initial caries lesion (ICLs) adjacent to orthodontic brackets are the most common side effect of orthodontic treatment with fixed appliances. The reported prevalence is uncertain and varies considerably across studies, from 27% to 97%.

OBJECTIVES

This paper was designed to evaluate and synthesize the available evidence on the prevalence and incidence rates of ICLs in relation to orthodontic treatment. Selection criteria: The review (Prospero protocol CRD42023412952) included randomized and non-randomized clinical trials of interventions, cohort studies, and cross-sectional studies, published after 1990 on the prevalence or incidence of ICLs during or after orthodontic treatment with fixed appliances. Search methods: Pubmed, Scopus, and Embase databases were searched from 1990 until 01 May 2023. The risk of bias assessment was performed with RoB 2 and ROBINS-I tool and the Joanna Briggs Institute Critical Appraisal Checklist. Data collection and analysis: The proportion of individuals with ICLs, reported as the number/percentage of individuals/teeth with ICLs or mean number of ICLs per subject, were used to synthesize results.

RESULTS

The search yielded a total of 468 papers; 21 studies were included in the systematic review, 2 of which were not included in the meta-analysis. The prevalence rate [95%CI] of ICLs was 0.57% [0.48; 0.65] in 1448 patients, 0.22% [0.14; 0.33] in 11583 teeth, with a mean number of lesions equal to 2.24 [1.79; 2.70] in 484 patients evaluated. The incidence rate of new carious lesions developed during orthodontic treatment was 0.48% [0.33; 0.63] in 533 patients, 0.15% [0.08; 0.26] in 1890 teeth with a mean number of ICLs equal to 2.29 [1.12; 3.46] in 208 patients evaluated.

LIMITATIONS

Although the high number of included studies and the overall good quality, there was a significant heterogeneity in the collected data.

CONCLUSION

The prevalence and incidence rates of ICLs in subjects undergoing orthodontic treatment are quite high and raise some concerns in terms of risk assessment of orthodontic treatment. ICLs represent an alarming challenge for both patients and professionals. Effective caries prevention strategies during treatment need to be considered and implemented where appropriate.

Revealing bactericidal events on graphene oxide nano films deposited on metal implant surfaces

At the time when pathogens are developing robust resistance to antibiotics, the demand for implant surfaces with microbe-killing capabilities has significantly risen. To achieve this goal, profound understanding of the underlying mechanisms is crucial. Our study demonstrates that graphene oxide (GO) nano films deposited on stainless steel (SS316L) exhibit superior antibacterial features. The physicochemical properties of GO itself play a pivotal role in influencing biological events and their diversity may account for the contradictory results reported elsewhere. However, essential properties of GO coatings, such as oxygen content and the resulting electrical conductivity, have been overlooked so far. We hypothesize that the surface potential and electrical resistance of the oxygen content in the GO-nano films may induce bacteria-killing events on conductive metallic substrates. In our study, the GO applied contains 52 wt% of oxygen, and thus exhibits insulating properties. When deposited as a nano film on an electrically conducting steel substrate, GO flakes generate a Schottky barrier at the interface. This barrier, consequently, impedes the transfer of electrons to the underlying conductive substrate. As a result, this creates reactive oxygen species (ROS), leading to bacterial death. We confirmed the presence of GO coatings and their hydrolytic stability by using X-ray photoelectron spectroscopy (XPS), μRaman spectroscopy, scanning electron microscopy (SEM), and Kelvin probe force microscopy (KPFM) measurements. The biological evaluation was performed on the MG63 osteoblast-like cell line and two selected bacteria species: S. aureus and P. aeruginosa, demonstrating both the cytocompatibility and antibacterial behavior of GO-coated SS316L substrates. We propose a two-step bactericidal mechanism: electron transfer from the bacteria membrane to the substrate, followed by ROS generation. This mechanism finds support in changes observed in contact angle, surface potential, and work function, identified as decisive factors. By addressing overlooked factors and effectively bridging the gap between understanding and practicality, we present a transformative approach for implant surfaces, combating microbial resistance, and offering new application possibilitie.

Systematic review and network meta-analysis of restorative therapy and adhesive strategies in root caries lesions

AIM

This systematic review and network meta-analysis (NMA) aimed to establish a clinically relevant hierarchy of the different adhesive and/or restorative approaches to restore cavitated root caries lesions through the synthesis of available evidence.

MATERIALS AND METHODS

A systematic search was conducted in Medline/Web of Science/Embase/ Cochrane Library/Scopus/grey literature. RCTs investigating ≥2 restorative strategies (restorative /adhesive materials) for root caries lesions in adult patients were included. Risk of bias within studies was assessed (Cochrane_RoB-2) and the primary outcome was survival rate of restorations at different follow-up times (6-/12-/24-months). Network meta-analyses were conducted using a random effects model stratified by follow-up times. I2-statistics assessed the ratio of true to total variance in the observed effects. All available combinations of adhesives (1-SE: one-step self-etch; 2-3ER: two-/three-step etch-and-rinse) and restorative materials (conventional composite (CC) as well as conventional and resin-modified glass ionomer cements (GIC, RMGIC)) were included. Risk of bias across studies and confidence in NMA (CINeMA) were assessed.

RESULTS

547 studies were identified and nine were eligible for the NMA. In total, 1263 root caries lesions have been restored in 473 patients in the included clinical trials. Patients involved were either healthy (n = 6 trials), living in nursing homes (n = 1 trial) or received head-and-neck radiotherapy (n = 2 trials). There was statistically weak evidence to favour either of material/material combination regarding the survival rate. A tendency for higher survival rate (24-months) was observed for 2-3ER/CC (OR24mths 2.65; 95%CI=1.45/4.84) as well as RMGIC (OR24mths 2.05; 95%CI=1.17/3.61) compared to GIC. These findings were though not statistically significant and confidence of the NMA was low.

CONCLUSION

An evidence-based choice of restorative strategy for managing cavitated root caries lesions is currently impossible. There is a clear need for more standardised, well-designed RCTs evaluating the retention rate of root caries restoration approaches.

Partial Pulpotomy in Young Permanent Teeth: A Systematic Review and Meta-Analysis

The aim of the present systematic review was to evaluate the clinical and radiographic success of partial pulpotomies in deep caries processes or post-eruptive defects in young, vital permanent teeth. Four electronic databases, PubMed, Scopus, Embase, and Google Scholar, were searched, followed by a manual search in the reference lists. Randomized controlled trials evaluating partial pulpotomy with a follow-up period of ≥12 months were included. A meta-analysis using a random effects model was performed. A total of 3127 articles were retrieved, and after duplicate removal, 2642 were screened by title and abstract; 1 additional article was found during the manual search, and 79 were identified. Finally, six papers were included in the review. Regardless of the partial pulpotomy modalities or material used, there were no significant differences between clinical and radiographic success rates (cumulative success rate 91.8-92.3%). Five studies were included in the meta-analysis that did not indicate any statistically significant differences in success rates when mineral trioxide aggregate was compared to other materials (95% confidence interval: 0.239 to 1.016; p = 0.055). The present research systematically evaluates the evidence and summarizes the available data on partial pulpotomy in young permanent teeth. Given its high clinical and radiographic success rate, partial pulpotomy should be considered when vital pulpal therapy needs to be performed in highly damaged young permanent teeth, as this procedure provides a biological benefit and allows more invasive endodontic treatments to be postponed.

Design, development and validation of a questionnaire to assess dentists' knowledge and experience in diagnosing, recording, and managing root caries

OBJECTIVES

The prevalence of root caries is increasing globally, especially in the elderly population, and even though the number of patients with root caries lesions is augmenting, there are still many discrepancies in how dentists manage this condition. The present study aimed to develop and validate a questionnaire to evaluate how dentists diagnose, record and manage root caries lesions, and to verify the validity and reliability of this questionnaire.

MATERIALS AND METHODS

An expert panel developed a self-administered questionnaire survey with three domains: (1) dentists' knowledge on diagnosis, recording, and managing root caries; (2) information about their current general clinical routines; (3) their demographics. The original English [E] version was translated into three different languages (French [F], German [G], Italian [I]), and subsequently back-translated into English by independent dentists. For the validation, 82 dentists (20-22 for each of the translated versions) accepted to answer the questionnaire at two different time-points (with 1-week interval). The data was quality checked. Construct validity, internal reliability, and intra-class correlation (ICC) were assessed.

RESULTS

Seventy-seven dentists completed the questionnaire twice [E: 17; F: 19; G: 19; I: 22]. The mean ICC (standard deviation) was 0.98(0.03) for E, 0.90(0.12) for F, 0.98 (0.04) for G, and 0.98 (0.01) for I. Overall, the test-retest reliability was excellent (mean ICC (SD): 0.96 (0.08)). Furthermore, the questionnaire demonstrated good internal reliability (inter-observer reliability; Fleiss kappa: overall:0.27(fair); E:0.30 (fair); F: 0.33(fair); G: 0.33(fair); I: 0.89 (almost perfect)).

CONCLUSION

The questionnaire was validated and is suitable to be used in the four languages to assess the knowledge of dentists on diagnosing, recording and managing root caries.

CLINICAL SIGNIFICANCE

The present questionnaire was validated and seems to be a good tool to evaluate how dentists diagnose, record, and manage root caries lesions both in its original (English) and its translated (French, German, and Italian) versions.

Evaluation of the masking efficacy of caries infiltration in post-orthodontic initial caries lesions: 1-year follow-up

OBJECTIVES

This study aimed to qualitatively and quantitatively assess the masking efficacy and color stability of resin infiltration on post-orthodontic ICL after 1 year.

MATERIALS AND METHODS

In 17 adolescents, 112 ICL (ICDAS-1: n = 1; ICDAS-2: n = 111) in 112 teeth were treated by resin infiltration (Icon, DMG) 3 to 12 months after bracket removal. The etching procedure was performed up to 3 times. Standardized digital images were taken before treatment (T0), 7 days (T7) and 12 months (T365) after treatment. Outcomes included the evaluation of the color differences between infiltrated and healthy enamel at T0, T7, and T365 by quantitative (colorimetric analysis (ΔE), ICDAS scores) and qualitative methods (5-point Likert scale (deteriorated (1), unchanged (2), improved, but not satisfying (3), improved and no further treatment required (4), completely masked (5)).) Differences between time points were analyzed by using Friedman test (ΔΕ) and chi-square tests (ICDAS).

RESULTS

The median color difference (25th/75th percentiles) between carious and healthy enamel at baseline (ΔΕ0) was 10.2(7.7/13.6). A significant decrease was observed 7 days after treatment (ΔΕ7 = 3.1(1.8/5.0); p < 0.001; ICDAS; p < 0.001). No significant changes based on ΔΕ (p = 1.000), and ICDAS grade (p = 0.305) were observed between T7 and T365 (ΔΕ12 = 3.4 (1.8/4.9)). Furthermore, at T365 four experienced dentists classified 55% and 39% of the lesions as "improved and no further treatment required" and "completely masked," respectively (Fleiss kappa: T365 = 0.851 (almost perfect)).

CONCLUSION

Resin infiltration efficaciously masked post-orthodontic ICL 7 days and 12 months after treatment. These results for most of the teeth could not only be observed by quantitative but also by qualitative analysis.

CLINICAL RELEVANCE

Resin infiltration efficaciously masks post-orthodontic initial carious lesions. The optical improvement can be observed directly after treatment and remains stable for at least 12 months.

Aesthetic caries infiltration - Long-term masking efficacy after 6 years

OBJECTIVES

This study aimed to evaluate the masking efficacy of caries infiltration technique of initial caries lesions (ICL) six years after debonding and single treatment.

METHODS

In 10 adolescents, 74 ICL (ICDAS 2) in 74 teeth were treated by resin infiltration (Icon, DMG) at a mean (SD) of 1.2 (1.2) months after bracket removal. The etching procedure was performed up to 3 times. Standardized digital images were taken before treatment (T₀), seven days (T₇) and 6 years (T₂₁₉₀) after treatment. Outcomes included the evaluation of the color differences between carious and healthy enamel at T₀, T₇ and T₂₁₉₀ by quantitative colorimetric analysis (ΔE), ICDAS scores, quantitative light-induced fluorescence (QLF; ΔF,ΔQ,WS Area) and qualitative visual evaluation (5-point Likert-scale [deteriorated (1), unchanged (2), improved, but not satisfying (3), improved and no further treatment required (4), completely masked (5)).

RESULTS

The median color difference ΔΕ₀ (25^th/75^th percentiles) at T₀ was 10.3 (8.56/13.0). At T₇ a significant decrease was observed (ΔΕ₇=3.7 (2.0/5.8); p<0.001; Friedmann-test; ICDAS p<0.001; Chi-square test). No significant changes based on ΔΕ (p=0.972; Friedmann-test) and ICDAS grading (p=0.511, chi-square test) were observed between T₇ and T₂₁₉₀ (ΔΕ₂₁₉₀=2.9 (1.8/4.2)). Furthermore, at T₂₁₉₀ four experienced dentists classified 50% and 37% of the lesions as "improved and no further treatment required" and "completely masked", respectively (Fleiss kappa: T₂₁₉₀: 0.782 (substantial agreement)).

CONCLUSION

Aesthetic caries infiltration can effectively mask post-orthodontic initial caries lesions for at least 6 years. These results for most of the teeth could not only be observed by quantitative but also by qualitative analysis.

CLINICAL SIGNIFICANCE

Resin infiltration efficaciously masks post-orthodontic initial carious lesions. The optical improvement can be observed directly after treatment and remains stable for at six years.

Randomized in situ evaluation of surface polishing protocols on the caries-protective effect of resin Infiltrant

The aim of this placebo-controlled randomized in situ study was to evaluate the effect of different surface polishing protocols on enamel roughness, bacterial adhesion and caries-protective effect of a resin infiltrant. Seventy-five bovine enamel samples having artificial caries lesions were treated with a resinous infiltrant and afterwards randomly dividided into five polishing protocols: aluminum oxide flexible disks (Al₂O₃-Disks), silicon carbide tips (SIC-Tips), silicon carbide brush (SIC-Brush), silicon carbide polyester strips (SIC-Strips) or no polishing [negative control (NC)]. Average surface roughness (Ra) was assessed by profilometry. Samples were mounted in palatal appliances under a mesh for biofilm accumulation. Fifteen volunteers wore the intraoral appliances (14-days) and cariogenic challenge was triggered by sucrose solutions. Biofilm formed was collected for microbiological analysis of caries-related bacteria (Streptococcus mutans, Lactobacillus acidophilus) and demineralization was assessed by cross-sectional microhardness. Mean Knoop hardness numbers (Kg/mm²) were plotted over lesion depth (µm) and area under the lesion curve was subtracted from sound enamel to determine demineralization (ΔS, Kg/mm²xµm). Data were analyzed by ANOVA and post-hoc comparisons (α = 0.05). NC resulted in significantly higher Ra means than Al₂O₃-Disks and SIC-Strips. Bacterial counts were not significantly different between the groups (p > 0.05). Regards ΔS means, however none of the groups were significantly different to NC (6983.3 kg/mm²xµm /CI 4246.1-9720.5, p > 0.05). Conclusions: Polishing protocols (Al₂O₃-Disks, SIC-Strips) significantly decreseased roughness of infiltrated-enamel, however none of the polishing protocols could signicantly decrease bacterial counts nor resulted in significant less demineralization.

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).

Long-term caries prevention of dental sealants and fluoride varnish in children with autism spectrum disorders: a retrospective cohort study

The aim was to compare two strategies for caries prevention in children with Autism Spectrum Disorders (ASDs). Participants were retrospectively retrieved and divided in two groups. Group one had first permanent molars treated with fluoride varnishes, FA group (n = 92, 9.43 ± 2.44 years) whilst the second, with dental sealant plus fluoride varnishes, FA + S group (n = 140, 7.77 ± 2.57 years). Logistic and multivariate analysis were run to evaluate the caries incidence, the retention rate of sealants, and background factors associated with caries risk over a period of at least 11 years. Survival rates from dental caries were statistically significantly higher in the FA + S group compared to the FA group (LogRank test p < 0.01). Dental sealant plus fluoride varnish played as a protective factor towards the development of caries (HR = 0.25 95%CI = 0.00/0.55 and HR = 0.34 95%CI = 0.00/0.66 in the upper right and left first molars; HR = 0.32 95%CI = 0.00/0.66 and HR = 0.26 95%CI = 0.00/0.58 in the lower right and left first molars). Dental sealants retention rate was high, ranging between 58.02% and 64.29%. No baseline variable was statistically significantly associated to the risk of caries development. Combined dental sealant and fluoride varnish application was more effective in reducing caries risk in first permanent molars of ASDs children than fluoride varnish alone. This preventive strategy should be therefore routinely applied in high caries risk patients as ASDs children.

The Effect of Toothpastes Containing Natural Extracts on Bacterial Species of a Microcosm Biofilm and on Enamel Caries Development

This study investigated the effects of herbal toothpaste on bacterial counts and enamel demineralization. Thirty-six bovine enamel samples were exposed to a microcosm biofilm using human saliva and McBain saliva (0.2% sucrose) for 5 days at 37 °C and first incubated anaerobically, then aerobically–capnophilically. The following experimental toothpaste slurries (2 × 2 min/day) were applied: (1) Vochysia tucanorum (10 mg/g); (2) Myrcia bella (5 mg/g); (3) Matricaria chamomilla (80 mg/g); (4) Myrrha and propolis toothpaste (commercial); (5) fluoride (F) and triclosan (1450 ppm F), 0.3% triclosan and sorbitol (Colgate^®, positive control); (6) placebo (negative control). The pH of the medium was measured, bacteria were analyzed using quantitative polymerase chain reaction, and enamel demineralization was quantified using transverse microradiography. The total bacterial count was reduced by toothpaste containing Myrcia bella, Matricaria chamomilla, fluoride, and triclosan (commercial) compared to the placebo. As far as assessable, Myrcia bella, Matricaria chamomilla, and Myrrha and propolis (commercial) inhibited the outgrowth of S. mutans, while Lactobacillus spp. were reduced/eliminated by all toothpastes except Vochysia tucanorum. Mineral loss and lesion depth were significantly reduced by all toothpastes (total: 1423.6 ± 115.2 vol% × μm; 57.3 ± 9.8 μm) compared to the placebo (2420.0 ± 626.0 vol% × μm; 108.9 ± 21.17 μm). Herbal toothpastes were able to reduce enamel demineralization.

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 ∆Z_DT/LD_DT values, indicating further demineralization (p < 0.05; paired t-test). Decreased ∆Z_DT 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 ∆∆Z_DT/∆∆Z_ST and ∆LD_DT/∆LD_ST compared to SC₁/SC₅ (p < 0.05;ANCOVA). Between 1450 and 5000 ppm dentifrices, a significant difference in ∆∆Z_DT/∆∆Z_ST and ∆LD_DT/∆LD_ST 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.

The Effect of Solutions Containing Extracts of Vochysia tucanorum Mart., Myrcia bellaCambess., Matricaria chamomilla L. and Malva sylvestris L. on Cariogenic Bacterial Species and Enamel Caries Development

This study evaluated the effect of experimental solutions containing plant extracts on bacterial species and enamel caries prevention. Microcosm biofilm was produced from human saliva mixed with McBain saliva (0.2% sucrose) on bovine enamel for 5 days (3 days under anaerobiosis and 2 days under aerobiosis) at 37°C. From the 2nd day, the following treatments were applied (1 × 60 s/day): Vochysia tucanorum (10 mg/mL); Myrcia bella (5 mg/mL); Matricaria chamomilla (80 mg/mL); Malva sylvestris, fluoride, and xylitol (Malvatricin Plus®); 0.12% chlorhexidine (CHX, PerioGard®); and PBS (negative control). The medium pH was measured. Quantitative polymerase chain reaction was performed for the detection of Streptococcus mutans and Lactobacillus spp. Enamel demineralization was measured by spectral-domain optical coherence tomography. The data were compared by means of the Kruskal-Wallis/Dunn, two-way ANOVA/Bonferroni, and ANOVA/Tukey tests (p < 0.05). The pH decreased after sucrose exposure; only CHX reestablished pH >5.5 by the last day. CHX also eliminated Lactobacillusspp., but the other treatments did not differ significantly from PBS. Malvatricin Plus® and CHX eliminated S. mutans, but the other treatments did not differ from PBS. Similar results were seen concerning the reduction of lesion depth and reflectivity. The experimental natural-extract solutions were ineffective against cariogenic bacteria and in preventing the development of enamel caries.

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.

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.

Hand-held bioprinting for de novo vascular formation applicable to dental pulp regeneration

Aim of the study: Deep carious lesions may cause irreversible pulpitis and the current endodontic treatment typically removes the whole dental pulp tissue, which finally reduces lifespan of the teeth. Nowadays, the most frequent treatment is based on removing the infected tissue and filling the root canal with inert synthetic materials. Tissue engineering approaches are important alternatives to the current treatment, because they can potentially maintain the biological function of the tooth instead of sacrificing it.Materials and Methods: In this study, we propose a tissue engineering approach based on a hand-held in situ bioprinting strategy. Our approach enabled bioprinting of cell-loaded collagen-based bioinks with suitable rheological, structural and biological properties, which allowed for vasculogenesis in the root canal.Results: The rheological properties of the bioprintable bioink were measured by oscillatory amplitude sweep testing and were corroborated by macroscopic evaluation after in vitro culture, in which printed bioinks maintained their original form without contraction. Moreover, we showed evidence for successful vasculogenesis in bioprintable bioinks with comparable quality and quantity to control fibrin and collagen non-bioprintable hydrogels.Conclusions: We conclude that hand-held bioprinting holds potential for in situ treatment of dental diseases with successful evidence for vascular tube formation, as an asset for maintenance of the biological function of the tooth.

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.

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.

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.

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.

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.

A New Laser-Processing Strategy for Improving Enamel Erosion Resistance

In the present study, a new automatic laser-processing strategy allowing standardized irradiation of natural tooth areas was investigated. The objective was to find a combination of laser parameters that could cause over a 600°C temperature increase at the enamel surface while not damaging enamel, avoiding temperature change above 5.5°C in the pulp and increasing enamel erosion resistance. Seventy-seven bovine enamel samples were randomly divided into 6 laser groups and 1 negative control (C/no treatment/ n = 11). A scanning strategy (7 × 3 mm) was used for the CO₂ laser treatment (λ = 10.6 µm, 0.1-18 J/cm²) with different pulse durations-namely, 20 µs (G20), 30 µs (G30), 55 µs (G55), and 490 µs (G490), as well as 2 modified pulse distances (G33d, G40d). Measurements of temperature change were performed at the surface (thermal camera/50 Hz), at the underside (thermocouples), and at the pulp chamber using a thermobath and human molars ( n = 10). In addition, histology and X-ray diffraction (XRD/ n = 10) were performed. Erosion was tested using an erosive cycling over 6 d, including immersion in citric acid (2 min/0.05 M/pH = 2.3) 6 times daily. Surface loss was measured using a profilometer and statistical analysis with a 2-way repeated-measures analysis of variance (α = 0.05). Only G20 fulfilled the temperature requirements at the surface (619 ± 21.8°C), at the underside (5.3 ± 1.4°C), and at the pulp (2.0 ± 1.0°C), and it caused no mineral phase change and significant reduction of enamel surface loss (-13.2 ± 4.0 µm) compared to C (-37.0 ± 10.1 µm, P < 0.05). A laser-scanning strategy (20 µs/2 kHz/1.25 J/cm², 3.4 mm/s) has been established that fulfilled the criteria for biological safety and significantly increased enamel erosion resistance (64%) in vitro.

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.

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 (ΔΔZ) and lesion depth (ΔLD) 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 ΔΔZ of the dentifrice with 0 ppm F, sound surfaces showed significantly higher ΔΔZ and ΔLD 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.

Effects of dentifrices differing in fluoride compounds on artificial enamel caries lesions in vitro

The aim of this study was to compare the caries-preventive effect of a stabilized stannous fluoride/sodium fluoride dentifrice containing sodium hexametaphosphate with those of a regular, solely sodium fluoride-containing and amine fluoride-containing dentifrice on pre-demineralized bovine enamel specimens using a pH-cycling model. Bovine enamel specimens with two artificial lesions each were prepared. Baseline mineral loss of both lesions was analyzed using transversal microradiography (TMR). Eighty-five specimens with a mean (SD) baseline mineral loss of 3393 (683) vol% × µm were selected and randomly allocated to five groups (n = 13/15). Treatments during pH-cycling (28 days and 2 × 20 min demineralization/day) were: brushing twice daily with slurries of AmF (1400 ppm F^-), NaF (1450 ppm F^-), SnF₂/NaF (1100 ppm F^-/350 ppm F^-), and fluoride-free (FF) dentifrices or they were immersed in distilled water and remained unbrushed (NB). Subsequently, from each specimen one lesion was covered with acid-resistant varnish, while the remaining lesion was demineralized for another 14 days. Differences in integrated mineral loss (∆∆Z) were calculated between values before and after pH-cycling (∆∆Z _E1) as well as before pH-cycling and after second demineralization (∆∆Z _E2) using TMR. Treatments AmF and NaF induced a significantly higher mineral gain (∆∆Z _E1/∆∆Z _E2) compared to treatments FF and NB (p < 0.05; ANOVA test). Except for treatments AmF and NaF no significant differences in mineral loss between before and after pH-cycling could be observed (p < 0.05; t test) [∆∆Z _E1: AmF:1563 (767); NaF:1222 (1246); SnF₂/NaF:258 (1259); FF:-52 (1223); NB:-151 (834)]. Both dentifrices with either AmF or NaF promoted remineralization, whereas SnF₂/NaF dentifrice did not promote remineralization in a biofilm-free pH-cycling model.

Combined Tin-Containing Fluoride Solution and CO2 Laser Treatment Reduces Enamel Erosion in vitro

The aim of this in vitro study was to evaluate the effect of combined CO2 laser and tin-containing fluoride treatment on the formation and progression of enamel erosive lesions. Ninety-six human enamel samples were obtained, stored in thymol solution and, after surface polishing, randomly divided into 6 different surface treatment groups (n = 16 in each group) as follows: no treatment, control (C); one CO2 laser irradiation (L1); two CO2 laser irradiations (L2); daily application of fluoride solution (F); combined daily fluoride solution + one CO2 laser irradiation (L1F), and combined daily fluoride solution + two CO2 laser irradiations (L2F). Laser irradiation was performed at 0.3 J/cm2 (5 µs/226 Hz/10.6 µm) on day 1 (L1) and day 6 (L2). The fluoride solution contained AmF/NaF (500 ppm F), and SnCl2 (800 ppm Sn) at pH 4.5. After surface treatment the samples were submitted to an erosive cycling over 10 days, including immersion in citric acid (2 min/0.05 M/pH = 2.3) 6 times daily and storage in remineralization solution (≥1 h) between erosive attacks. At the end of each cycling day, the enamel surface loss (micrometers) was measured using a 3D laser profilometer. Data were statistically analyzed by means of a 2-level mixed effects model and linear contrasts (α = 0.05). Group F (-3.3 ± 2.0 µm) showed significantly lower enamel surface loss than groups C (-27.22 ± 4.1 µm), L1 (-18.3 ± 4.4 µm) and L2 (-16.3 ± 5.3 µm) but higher than L1F (-1.0 ± 4.4 µm) and L2F (1.4 ± 3.2 µm, p < 0.05). Under the conditions of this in vitro study, the tin-containing fluoride solution caused 88% reduction of enamel surface loss, while its combination with CO2 laser irradiation at 0.3 J/cm2 hampered erosive loss almost completely.

Screening of CO(2) laser (10.6 μm) parameters for prevention of enamel erosion

OBJECTIVE

The aim of this study was to screen CO(2) laser (10.6 μm) parameters to increase enamel resistance to a continuous-flow erosive challenge.

BACKGROUND DATA

A new clinical CO(2) laser providing pulses of hundreds of microseconds, a range known to increase tooth acid-resistance, has been introduced in the market.

METHODS

Different laser parameters were tested in 12 groups (n=20) with varying fluences from 0.1 to 0.9 J/cm(2), pulse durations from 80 to 400 μs and repetition rates from 180 to 700 Hz. Non-lased samples (n=30) served as controls. All samples were eroded by exposure to hydrochloric acid (pH 2.6) under continuous acid flow (60 μL/min). Calcium and phosphate release into acid was monitored colorimetrically at 30 sec intervals up to 5 min and at 1 min intervals up to a total erosion time of 15 min. Scanning electron microscopic (SEM) analysis was performed in lased samples (n=3). Data were statistically analysed by one-way ANOVA (p<0.05) and Dunnett's post-hoc tests.

RESULTS

Calcium and phosphate release were significantly reduced by a maximum of 20% over time in samples irradiated with 0.4 J/cm(2) (200μs) at 450 Hz. Short-time reduction of calcium loss (≤1.5 min) could be also achieved by irradiation with 0.7 J/cm(2) (300μs) at 200 and 300 Hz. Both parameters revealed surface modification.

CONCLUSIONS

A set of CO(2) laser parameters was found that could significantly reduce enamel mineral loss (20%) under in vitro erosive conditions. However, as all parameters also caused surface cracking, they are not recommended for clinical use.

Verification of nerve integrity after surgical intervention using quantitative sensory testing

PURPOSE

The aim of this study was to apply a standardized Quantitative Sensory Testing (QST) approach in patients to investigate whether oral surgery can lead to sensory changes, even if the patients do not report any sensory disturbances. Furthermore, this study determines the degree and duration of possible neuronal hyperexcitability due to local inflammatory trauma after oral surgery.

PATIENTS AND METHODS

Orofacial sensory functions were investigated by psychophysical means in 60 patients (30 male, 30 female) in innervation areas of infraorbital nerves, mental nerves and lingual nerves after different interventions in oral surgery. The patients were tested 1 week, 4 weeks, 7 weeks, and 10 weeks postoperatively. As controls for bilateral sensory changes after unilateral surgery, tests were additionally performed in 20 volunteers who did not have any dental restorations.

RESULTS

No differences were found between the control group and the control side of the patients. Although not 1 of the patients reported paresthesia or other sensory changes postoperatively, QST detected significant differences between the control and the test side in the mental and lingual regions. Test sides were significantly less sensitive for thermal parameters (cold, warm, and heat). No differences were found in the infraorbital region. Patients showed significantly decreased pain pressure thresholds on the operated side. QST monitored recovery over time in all patients.

CONCLUSIONS

The results show that oral surgery can lead to sensory deficits in the mental and lingual region, even if the patients do not notice any sensory disturbances. The applied QST battery is a useful tool to investigate trigeminal nerve function in the early postoperative period. In light of the increasing forensic implication, this tool can serve to objectify clinical findings.

Analysis of trigeminal nerve disorders after oral and maxillofacial intervention

Background

Quantitative sensory testing (QST) is applied to evaluate somatosensory nerve fiber function in the spinal system. This study uses QST in patients with sensory dysfunctions after oral and maxillofacial surgery.

Methods

Orofacial sensory functions were investigated by psychophysical means in 60 volunteers (30 patients with sensory disturbances and 30 control subjects) in innervation areas of the infraorbital, mental and lingual nerves. The patients were tested 1 week, 4 weeks, 7 weeks and 10 weeks following oral and maxillofacial surgery.

Results

QST monitored somatosensory deficits and recovery of trigeminal nerve functions in all patients. Significant differences (p < 0.05) between control group and patients were shown for cold, warm and mechanical detection thresholds and for cold, heat and mechanical pain thresholds. Additionally, QST monitored recovery of nerve functions in all patients.

Conclusion

QST can be applied for non-invasive assessment of sensory nerve function (Aβ-, Aδ- and C-fiber) in the orofacial region and is useful in the diagnosis of trigeminal nerve disorders in patients.

Laser phototherapy in the treatment of periodontal disease. A review

Many studies in the literature address the effect of low-power lasers in the management of pathologies related to periodontal tissues. Due to the lack of standardized information and the absence of a consensus, this review presents the current status of laser phototherapy (LPT) in periodontics and discusses its benefits and limits in the treatment of periodontal disease. The literature was searched for reviews and original research articles relating to LPT and periodontal disease. The articles were selected using either electronic search engines or manual tracing of the references cited in key papers. The literature search retrieved references on wound and bone healing, analgesia, hypersensitivity, inflammatory process and antimicrobial photodynamic therapy. Each topic is individually addressed in this review. The current literature suggests that LPT is effective in modulating different periodontal disease aspects in vitro, in animals, and in simple clinical models. Further development of this therapy is now dependent on new clinical trials with more complex study designs.

Influence of the additional Er:YAG laser conditioning step on the microleakage of class V restorations

The purpose of this study was to evaluate the influence of an additional Er:YAG laser conditioning step after laser cavity preparations, on the microleakage of class V composite restorations. Forty-eight bovine incisors were randomly divided into four groups: G1(control) cavities prepared with bur, G2- cavities prepared with laser (400 mJ/2 Hz), G3- cavities prepared and subsequently conditioned with Er:YAG laser (60 mJ/2 Hz); G4-idem for G3, but the laser conditioning was carried out without water-spray. All the cavities were restored using Clearfill SE Bond and Z-250 composite resin. The samples were thermal cycled for 700 cycles and then immersed in 50% silver nitrate solution. The sectioned restorations were exposed to a photoflood lamp to reveal silver nitrate penetration. The Kruskal-Walis one-way analyses of variance test and post hoc Wilcoxon pair-wise comparison were used to compare microleakage degrees. At the gingival margin G2 showed a lower microleakage mean than the control bur-prepared cavities (p = 0.0003). At occlusal margins there were no statistically significant differences between the groups (p = 0.28). It may be concluded that Er:YAG laser class V cavity preparations do not need to be followed by an additional laser conditioning step to result in levels of microleakage similar to or lower than those obtained after bur preparations.

Adhesives bonded to erbium:yttrium-aluminum-garnet laser-irradiated dentin: transmission electron microscopy, scanning electron microscopy and tensile bond strength analyses

The aim of this in vitro study was to investigate the effect of erbium:yttrium-aluminum-garnet (Er:YAG) laser irradiation on dentinal collagen by transmission electron microscopy and to analyze the resin-dentin interface by scanning electron microscopy. A tensile bond strength test was also applied. Specimens from 69 sound human third molars were randomly divided into three groups: control (no laser), and two irradiated groups, laser 250 (250 mJ/2 Hz) and laser 400 (400 mJ/4 Hz). Then, specimens were restored with two adhesive systems, an etch-and-rinse or a self-etch system. Although ultrastructural examination showed a modified surface in the irradiated dentin, there was no statistical difference in bond strength values between the laser groups and controls (P < 0.05). In conclusion, the use of Er:YAG laser for ablating human dentin did not alter the main adhesion parameters when compared with those obtained by conventional methods, thus reinforcing its use in restorative dentistry.

Bond strength of self-etching primer to bur cut, Er,Cr:YSGG, and Er:YAG lased dental surfaces

OBJECTIVE

The purpose of this study was to evaluate the tensile bond strength of a self-etching primer system to enamel and dentin surfaces treated with Er:YAG and Er,Cr:YSGG lasers.

BACKGROUND DATA

The recently introduced self-etching primer systems have been shown to adhere better to dental surfaces with thin or no smear layers. Moreover, there have been no previous reports on the bond strength of these adhesives to Er,Cr:YSGG laser-irradiated enamel and dentin, which have been shown to be free of a smear layer.

METHODS

Thirty samples of enamel and thirty of dentin were divided into three groups. The first group of each substrate served as a control with a standardized bur cut, and the other two groups were conditioned with Er:YAG (350 mJ, 10 Hz, 20 J/cm(2) for enamel; 300 mJ, 6 Hz, 17 J/cm(2) for dentin) and Er,Cr:YSGG laser (125 mJ, 20 Hz, 16 J/cm(2) for both substrates). After the bonding procedure, samples were restored with composite resin, and the tensile bond strength test was performed.

RESULTS

The ANOVA two-way analysis and the Tukey test at 5% significance level showed that for enamel and dentin, the bond strength values were statistically higher in Er:YAG-laser treated than in Er,Cr:YSGG-laser treated surfaces (p = 0.0001). However, bond strength means for both laser-irradiated groups were statistically lower than for the bur cut group (Er:YAG: p = 0.0281 and Er,Cr:YSGG: p < 0.0001). SEM observation of laser-irradiated surfaces revealed a roughened aspect and absence of smear layer.

CONCLUSIONS

The self-etching system adhesion was influenced by the type of erbium laser used, and the bond strength was higher in the Er:YAG-laser irradiated than in the Er,Cr:YSGG-laser irradiated surfaces.