Prevention of root surface caries using a dental adhesive

Clinical Investigation of the Inhibitory Effects of Tooth-Coating Materials on Initial Active Root Caries: A Pilot Randomized Controlled Trial

Background and Objectives: Caredyne ZIF-C is a novel, capsule-mixed zinc-containing prototype glass ionomer cement (GIC). Zinc ions are reported to inhibit root dentin demineralization, dentin collagen degradation, bacterial growth, acid production, and in vitro bacterial biofilm formation. However, the effectiveness of GICs against initial root caries lesions is unclear. Therefore, this study aimed to evaluate the efficacy of GICs, especially the new zinc-containing Caredyne ZIF-C GIC, as tooth-coating materials in patients with initial active root caries. Materials and Methods: A total of 58 lesions in 47 older adults (age > 65 years) were randomly allocated to one of the following three groups: Caredyne ZIF-C, Fuji VII (a conventional GIC), and sodium fluoride (NaF). All the lesions were treated with the assigned materials without removing the infected dentin, and the rates of dental plaque attachment and coating material fall-out were evaluated after 3, 6, and 12 months. The failure rate was defined as the number of teeth that needed restoration due to caries progression. Results: The plaque attachment rates tended to be lower in the material-coated root surfaces than in the healthy exposed root surfaces after 3, 6, and 12 months, although the differences among the three groups were not significant. Moreover, the coating material fall-out rate tended to be lower in the Caredyne ZIF-C group than in the Fuji VII group. There was no significant difference in the failure rate among the three groups at the 12 months mark. Conclusions: Though this pilot study offers a new direction for suppressing the progression of initial active root caries by controlling plaque attachment using GICs including Caredyne ZIF-C, clinical studies with a larger sample size are needed.

Systematic review and meta-analysis on physical barriers to prevent root dentin demineralization

The present review systematically analyzed in vitro and in situ studies investigating physical diffusion barriers (sealants, desensitizer or adhesives) to prevent the development or the progression of root (dentin) demineralization. Three electronic databases (PubMed-Medline, CENTRAL, Ovid-EMBASE) were screened for studies from 1946 to 2022. Cross-referencing was used to identify further articles. Article selection and data abstraction were done in duplicate. Languages were not restricted. The type of outcome was not restricted, and their mean differences (MD) were calculated using fixed- or random-effects models. Risk of Bias was graded using Risk of Bias 2.0 tool. From 171 eligible studies, 34 were selected for full-text analysis evaluating 69 different materials, and 17 studies-still evaluating 36 different materials-were included (3 in situ and 14 in vitro). Ten studies evaluated desensitizers; 8 adhesives; and 1 infiltration. Meta-analyses were possible for all 17 studies. Meta-analyses revealed that lesion depth after no treatment was significantly higher than after the application of single-step adhesives (MD[_95%CI] = - 49.82[- 69.34; - 30.30]) and multi-step adhesives (MD[_95%CI]=-60.09 [-92.65, -27.54]). No significant differences in the lesion depth increase between single- and multi-step adhesives could be observed (MD[_95%CI]=30.13 [-21.14, 81.39]). Furthermore, compared to no treatment the increase of the lesion depth was significantly hampered using desensitizers (MD[_95%CI] = - 38.02[- 51.74; - 24.31]). Furthermore, the included studies presented unclear or high risk. A physical diffusion barrier can significantly hamper the increase of lesion depth under cariogenic conditions. Furthermore, multi-step adhesives seem not to be more effective than single-step adhesives. However, this conclusion is based on only few in vitro and in situ studies.

Evaluation of decalcifying effect of maleic acid and EDTA on root canal dentin using energy dispersive spectrometer

OBJECTIVE

The aim of this study was to evaluate mineral contents of root canal dentin after treatment with 7% maleic acid (MA) or 17% EDTA.

STUDY DESIGN

Thirty pieces of teeth were divided into 3 groups: 1) 17% EDTA; 2) 7% MA; and 3) saline. All specimens were treated for 0, 1, 5, 10, 15 minutes. Levels of calcium, phosphorus, magnesium, sodium, sulfur, and oxygen were measured using energy dispersive spectrometer. Data were analyzed using 1-way analysis of variance. Tukey honest significant difference and Bonferroni test were used for comparison between the groups and time periods.

RESULTS

MA reduced maximum amount of calcium and phosphorus at all time intervals, but was significant only up to 5 minutes (P < .001). Oxygen, sulfur, and magnesium were decreased more with saline and least with MA (P < .001). Sodium was decreased more with MA and least with EDTA (P < .001).

CONCLUSIONS

MA decalcifies the root dentin, with most calcium and phosphorus extracted during the first 5 minutes, compared with EDTA.

Bio-active restorative materials with antibacterial effects: new dimension of innovation in restorative dentistry

Restorative materials in the new era should be "bio-active", and antibacterial effects are highlighted as one of the important properties. In order to achieve resin-based restoratives with antibacterial effects, an antibacterial monomer MDPB has been developed. The primer incorporating MDPB demonstrated cavity-disinfecting effects, and the world's first antibacterial adhesive system employing the MDPB-containing primer was successfully commercialized. MDPB is potentially applicable to various restoratives since immobilization of the antibacterial component by polymerization of MDPB enables no deterioration in mechanical properties of cured resins and exhibition of inhibitory effects against bacterial growth on their surfaces. For glass-ionomer cements used for atraumatic restorative treatment, the approach to provide antibacterial activity has been attempted by addition of chlorhexidine. Incorporation of 1% chlorhexidine diacetate was found to be optimal to give appropriate antibacterial and physical properties, being effective to reduce the bacteria in affected and infected dentin in vivo.

Effects of a self-etching resin coating system to prevent demineralization of root surfaces

OBJECTIVES

The purpose of this study was to evaluate the ability of an experimental self-etching resin coating system to protect against demineralization of the root surface in vitro, comparing its effectiveness with two commercial one-step self-etching adhesives.

METHODS

The experimental resin coating system (EC), consisting of a self-etching primer and an acrylate-based resin, or the two commercial self-etching adhesives, Adper Prompt-L Pop (AD) and Clearfil Tri-S Bond (S3), was applied to the cementum of a human extracted tooth root. The specimens were immersed in acetate buffer at pH 5.5 for 4 weeks, and the degree of demineralization underneath the materials was evaluated by microscopic observation and contact microradiography. Each material's sealing and interfacial ultrastructure on the cementum was morphologically examined by scanning electron microscopy, and their bonding ability to cementum was determined by microtensile bond strength (MTBS) tests.

RESULTS

Application of AD and S3 showed limited effects to protect against demineralization, but no demineralization was observed for EC. EC showed greater coating thickness than the other two materials, with formation of integral hybridized layers with cementum. Although the MTBS values for EC were significantly lower than those for AD and S3, cohesive failure in resins was the prevalent fracture mode for EC, showing no possible disadvantages in bonding ability.

SIGNIFICANCE

The experimental resin coating system effectively prevented acid demineralization on root surfaces due to its ability to produce an appropriately thick coating and an integral hybridized layer.

Calcium Loss From Root Canal Dentin Following EDTA, EGTA, EDTAC, and Tetracycline-HCl Treatment With or Without Subsequent NaOCl Irrigation

The aim of this study was to determine the extent of calcium removal on root canal dentin after 17% EDTA, 17% EGTA, 15% EDTAC, and 1% tetracycline-HCl treatment; with or without subsequent use of 2.5% NaOCl. Extracted single-rooted human teeth were bisected longitudinally and the root halves (n=100) were isolated with nail varnish, leaving the root canal exposed. The samples were immersed in the test solutions for 1 and 5 minutes, after which the amount of calcium ion (Ca(2+)) release into the solutions was determined by flame photometry. Regardless of treatment time, all single (treatment solution only) and combined (treatment solution with subsequent NaOCl application) irrigation regimens removed significantly more Ca(2+) than control treatment (distilled water). Compared with other groups, treatment with 17% EDTA and 17% EDTA + 2.5% NaOCl resulted in the maximum amount of Ca(2+) removal from root canal dentin (p<0.05). All combined-treatment groups except 17% EGTA + 2.5% NaOCl removed significantly more Ca(2+) than their single-treatment versions (p<0.05). Within each test group, extending the treatment time to 5 minutes resulted in significantly more Ca(2+) removal (p<0.05).

Treating root-surface caries

This article summarizes the effectiveness of restorative materials used to restore root surfaces, the mechanisms by which these materials reduce caries, and placement techniques for restoring root-surface lesions. Patients may be classified into low, medium, and high caries risk groups for root caries, and specific dental restorative material recommendations are made for each category. Effective plaque control, xylitol-containing chewing gums, antimicrobial agents, fluoride-releasing restorative materials, topically applied fluoride, and fluoride-containing toothpastes provide maximum protection for the high caries risk patient.

Cytotoxicity tests of in situ polymerized resins: methodological comparisons and introduction of a tissue culture insert as a testing device

The in vitro cytotoxic potential of six commonly used methacrylate polymers was evaluated using human oral fibroblast cultures with different cell-material contact systems. A tissue culture insert was introduced to test resin-released components. Both acute and delayed cytotoxic effects of resin were quantified by cellular enzymatic and DNA synthetic activities of fibroblasts over a 6-day exposure period. Resin toxicity was material-dependent. Statistical analysis showed that the experimental conditions significantly contributed to the overall toxicity and the cytotoxicity pattern for a given material. DNA synthesis activity of human oral fibroblasts assayed by 3H-thymidine incorporation was more sensitive to resins than cellular enzyme activity, as determined by tetrazolium bromide reduction. However, extended exposure increased the cytotoxicity of all resins, as measured by tetrazolium bromide reduction, which seemed to be a better indicator of the development of resin toxicity than 3H-thymidine incorporation. Removal of the oxygen inhibition layer on resin specimens partially enhanced cell viability, indicating that this surface layer together with other unknown factors contributed to resin toxicity.

Laboratory evaluation and clinical application of a new one-bottle adhesive

PURPOSE

The purposes of this project were to compare the enamel and dentin bond strengths of a new nanofilled one-coat adhesive system with its predecessor, an unfilled two-coat adhesive system; to analyze the dentin interfacial ultramorphology, using scanning and transmission electron microscopy (SEM and TEM); and to illustrate the clinical technique associated with the use of the new nanofilled one-coat adhesive system.

MATERIAL AND METHODS

Twenty flat dentin surfaces and 20 flat enamel surfaces were polished on the labial surface of bovine incisors mounted in acrylic resin. The specimens were equally and randomly assigned to four bonding groups: (1) dentin with Prime & Bond 2.1; (2) dentin with Prime & Bond NT; (3) enamel with Prime & Bond 2.1; and (4) enamel with Prime & Bond NT. A composite post was then adapted to the treated area and light-cured. After thermocycling, shear bond strengths were determined by testing the shear strength of the specimens. The data were analyzed using one-way analysis of variance (ANOVA) and Student's t-test. For SEM and TEM, six dentin disks were obtained from middle dentin of human third molars and assigned equally to each adhesive. The adhesives were applied to dentin according to manufacturer's directions. The hybrid layer and resin penetration into dentin tubules were analyzed at an ultramorphologic level, and the observations were compared.

RESULTS

Shear bond strengths were as follows: group 1: 17.8 +/- 4.1 MPa; group 2: 20.5 +/- 3.5 MPa; group 3: 24.7 +/- 6.7 MPa; and group 4; 27.0 +/- 5.4 MPa. Electron microscopy showed that both adhesives penetrated the dentin tubules and formed a fully infiltrated hybrid layer. The nanofiller included in the new one-application adhesive penetrated the dentin tubules and infiltrated the microspaces between the collagen fibers within the hybrid layer.

CLINICAL SIGNIFICANCE

The new one-application nanofilled adhesive tested in this study resulted in bond strengths and dentin hybridization comparable to those obtained with the corresponding two-application system. The clinical sequences presented illustrate the ease of use of the newest simplified adhesives.

Restorative therapy for erosive lesions

More needs to be learned about the etiology of erosion lesions before they can be accurately diagnosed, confidently treated and, more importantly, prevented. The treatment is dependent on the location and the degree of erosion. The decision to treat an erosion lesion should be based on careful consideration of the etiology and progression of the condition. Reasons for restoring noncarious enamel/dentin lesions are discussed and various therapeutic measures are provided. Preventive and restorative therapeutic measures for noncarious abrasive/ erosive lesions are proposed such as: a change of dietary or behavior patterns; application of desensitization products; intensive fluoride therapy with or without iontophoresis; brushing with desensitizing dentifrices; adhesive penetration with dentin bonding agents; glass ionomers and compomers; resin composites; composite or porcelain veneers; crown and bridge work; occlusal adjustments and nightguard fabrication if the abfraction factor coincides. The clinical durability of restorative therapy and important clinical factors related to the restoration of multifactorial defects are discussed.

Impregnation by dentine bonding agents into instrumented root-face dentine

OBJECTIVES

To examine the penetration of unfilled resin into instrumented root-face dentine, facilitated by five commercially available dentine bonding agents.

METHODS

Upper third molar teeth were decoronated, and a given dentine bonding agent and resin composite applied to the instrumented root face, according to the manufacturer's instructions. A control specimen was similarly prepared but not dentine primer was applied prior to resin composite. The teeth were sectioned longitudinally and the sectioned surface demineralized and deproteinated. Specimens were examined by scanning electron microscopy (SEM) for resin tag length and density in different areas of the root face.

RESULTS

Specimens treated with dentine bonding agent systems exhibited minimum resin penetration of peripheral root-face dentine and much longer penetration of resin tags in dentine above the pulp chamber. A possible 'hybrid' layer of resin-impregnated dentine was observed in all specimens where a dentine bonding agent system had been used but was not observed in control specimens. Resin tags were also more sparsely observed in control specimens.

CONCLUSION

Resin tag penetration is superior in both density and length of penetration in dentine overlying and adjacent to the pulp chamber, with shorter and sparser penetration exhibited in peripheral root-face dentine. The possible clinical implications of these observations are discussed.