1,721,043 research outputs found
Nanoindentation and Raman spectroscopy measurements on dual-cure luting cement for dental conservative restoration
Full text linkThe employment of innovative all-ceramic materi-als and adhesive cement, as well as the development of new bonding procedures, allow clinicians to use minimally invasive approaches in conservative restorations. In particular, dual-cure cement allows for obtaining higher aesthetic and functional results. However, the reduced light transmission through ceramic materials could prevent the proper curing and affect the adhesion of these materials to the tooth surface. In this context, the development of an accurate measurement methodology to assess the extent of polymerization of dental resin-based luting cement and to correlate the conversion degree with the mechanical properties is of particular importance from the clinical and scientific point of view. A measurement approach that exploits Raman Spectroscopy and nano-hardness measurements is hereby proposed. In particular, in this study, two different light-curing protocols are employed on a dual-cure luting cement, usually used for the full-crown restoration of single-rooted teeth. The effect of different times and tack-curing steps on the polymerization shrinkage of resin-based luting cement is investigated. The pre-liminary results allow concluding that both curing protocols lead to a good polymerization, without significant differences in the degree of conversion along the cement-tooth interfacial surface, as proved by the almost constant ratio of the Raman vibration characteristic peaks. However, the nanoindentation modulus was lower in the case of the tack-cured protocol
A Three-step Etch-and-Rinse vs a Universal Adhesive in Nanohybrid Composite Anterior Restorations: A Retrospective Clinical Evaluation
Full text linkPurpose: To retrospectively evaluate the clinical behavior of direct anterior composite restorations performed with a universal adhesive or with a three-step etch-and-rinse (E&R) adhesive. Material and methods: Patients were randomly treated with a three-step E&R adhesive (Optibond FL, Kerr) or a universal adhesive (Clearfil Universal Bond Quick, Kuraray Noritake) applied in E&R mode. All restorations were performed with a nanohybrid composite (ClearFil Majesty ES-2, Kuraray Noritake) by the same experienced operator. Two calibrated examiners evaluated the restorations using a dental mirror and explorer, in accordance with modified United States Public Health Service (USPHS) procedures. Clinical events were registered and classified as either failure (F), survival (SR), or success (S). Results: 168 restorations were evaluated in 90 patients with an average follow-up period of 37.9 (± 22.9) months. A total of 132 restorations were performed on vital teeth, and 36 were performed on endodontically treated teeth (ETT). A total of 128 Class-IV and 40 Class-III restorations were performed. In 89 restorations, a three-step E&R adhesive was applied (14 Class-III and 75 Class-IV), while in 79, a universal adhesive was used (26 Class-III and 53 Class-IV, p = 0.0091). A Cox regression analysis was performed (p < 0.05) to analyze which factors were involved in the failure of the restorations, considering failure (F) as restorations that needed re-intervention at the follow-up period of 37.9 (± 22.9) months. No statistically significant differences were observed when considering parameters directly involved with the adhesives tested. Endodontically treated teeth were more prone to fractures (p = 0.0006) compared to vital teeth. Restorations made with universal adhesives failed by fracturing significantly more frequently (p = 0.0234), while restorations made on endodontically treated teeth had a significantly worse outcome (p = 0.0001). Restorations made on canines also failed significantly more frequently (HR = 3.8, 95% CI = 1.4-10.1, p = 0.0062). Conclusions: Based on the obtained results, both the universal adhesive and the three-step E&R adhesive proved to be good treatment choices for direct anterior restorations after 37.9 (± 22.9) months of follow-up. Tooth vitality seems fundamental for the prognosis of a direct anterior composite restoration over time
Impedance measurements for demineralized tooth lesions assessment
Full text linkThis work deals with the design and development of a non invasive though rather effective solution to detect carious lesions. The main aim of the study is to develop a simple automatic approach for the assessment of the tooth demineralization, which represents the earlier stage of the dynamic carious process, by means of impedance spectroscopy. In particular, impedance measurements were carried out on 50 extracted human teeth. Teeth were demineralized in-vitro according to a validated protocol; then, a morphological analysis of the tooth surface was performed by scanning electron microscopy to confirm enamel demineralization. The proposed approach tries to take advantage of the change of impedance phase due to the demineralization process. Data analysis confirmed that the best frequency for discriminating between demineralized and non-demineralized teeth is about 15 Hz, and this parameter can be used for building up an automatic classifier based on Multilayer Perceptron (MLP) topology. Impedance data were processed by using a modified single neuron, which allows classifying demineralized and sound teeth with an error rate of about 7%, estimating therefore the presence of carious lesions in progress. The presented work can be considered as a feasibility study with a final goal to conceive a simple and low-cost measurement system to identify caries at an early stag
Influence of Thickener and Mineral Supplementation of Bleaching Gels on Enamel Demineralization
No full textObjective: This study evaluated the effect of the type of thickener and mineral supplementation of bleaching gels on enamel demineralization. Materials and Methods: Enamel specimens were divided into five groups according to the type of thickener: CA-Carbopol, AE-Aerosil 200, PO-Poloxamer 407, GG-Guar gum, and HEC-Hydroxyethyl cellulose. Each group was subdivided into three subgroups according to the level of mineral supplementation: none, saturation concentration, and maximum addition. The microhardness (KHN), surface roughness (Ra), color change (ΔE00), and mineral content (DD) were measured before and after the treatment, and the changes were calculated. The data was analyzed with two-way ANOVA and Tukey's test. Results: ANOVA showed significant differences among the groups (p GG>CA>PO>AE. %Ra—CA>HEC>PO>GG>AE. DE00—AE>GG>PO>HEC. Ý—HEC>PO>GG>CA>AE. The supplementation reduced the means of %KHN, %Ra, and Ý, without affecting the DE00. The effect of the supplementation level was not statistically significant. Conclusion: It was concluded that the type of thickener and the use of mineral supplementation significantly influenced the deleterious effects on the enamel
Effect of lithium disilicate veneers of different thickness on the degree of conversion and microhardness of a light-curing and a dual-curing cement
Full text linkPurpose: Various materials and systems for bonding lithium disilicate to the tooth substrate are available to clinicians, who can adapt the materials to each clinical situation to maximize the performance of indirect esthetic restorations. This study aimed to evaluate the degree of conversion (DC) and the microhardness (MH) of a dual-curing and a light-curing cement under lithium disilicate discs of different thicknesses. Materials and Methods: A total of 48 lithium disilicate (IPS e.max CAD, Ivoclar Vivadent) samples were prepared and divided into three groups (n = 16) according to the thickness (group A was 0.6 mm; group B was 1.0 mm; group C was 1.5 mm). Each group was further divided into two subgroups (n = 8) according to the resin cement employed, NX3 (Kerr) or Choice 2 (Bisco). A standardized quantity of cement was placed on the sample, and DC was evaluated with an attenuated total reflectance Fourier transformed infrared spectrophotometer (Nicolet IS10, Thermo Scientific). Twenty-four hours after DC was established, Vickers test was performed on the cement with a microindentometer (Leica Microsystems). Results were statistically analyzed with analysis of variance test and significance set at P < .05. Results: Statistical analysis showed cement type had a significant influence (P = .005) on DC. MH results were influenced by thicknesses only between 0.6 and 1.5 mm when light-cured cement was employed. Conclusion: The light-curing and the dualcuring cements reached comparable DCs between 0.6 and 1.5 mm. However, the light-curing resin showed a higher DC and MH
Evaluation of Composite Adaptation to Pulpal Chamber Floor Using Optical Coherence Tomography
Full text linkIntroduction A coronal seal is fundamental for a positive outcome to endodontic therapy. In this in vitro study, we evaluated the adaptation of composite resins in postendodontic restorations using optical coherence tomographic (OCT) imaging. Our null hypothesis was that there would be no difference in marginal adaptation to the pulp chamber floor between resin composites of different viscosities. Methods Thirty intact upper molars extracted for periodontal reasons were selected, endodontically treated, and filled with gutta-percha. The excess gutta-percha was entirely removed from the pulp chamber floor, and teeth were randomly divided into 3 groups (n = 10) according to the material used for the restoration: group 1: 0.5-mm horizontal layer of flowable composite followed by nanohybrid composite, group 2: bulk layering of bulk fill flowable composite; and group 3: oblique layering of nanohybrid composite. The degree of adaptation to the cavity floor was assessed using OCT imaging, and images were analyzed with the software program ImageJ (National Institutes of Health, Bethesda, MD) to assess the marginal gap between the composite and the pulp chamber floor. Collected data were statistically analyzed using analysis of variance testing, and statistical significance was set at P <.05. Results Flowable composites showed significantly better adaptation than traditional packable nanohybrid composites (P <.05). All significant differences were found between groups 1 and 2. Conclusions Within the limitations of this OCT imaging-based in vitro study, it was concluded that the flowable composite (flow + nanofilled; flow bulk fill composite) adapted better to the pulp chamber floor than the packable nanohybrid composite resin. Further studies are necessary to confirm these results
Indagine conoscitiva sull’approccio alle lesioni bianche dello smalto post-ortodontiche
No full textOBJECTIVESWhite enamel lesions (WSLs) are an increasingly present clinical occurrence, not infrequently observed at the end of orthodontic treatment. Their presence observed during the removal of orthodontic devices raises perplexities of an aesthetic nature and puts clinicians in front of the doubt on how to intervene from a therapeutic point of view since it seems no standardized protocols still exist. Consequently, aim of this work was to evaluate the knowledge, therapeutic and informative approach of the dental team on WSLs after orthodontic treatment.MATERIALS AND METHODSAn electronic survey (Qualtrics) of 21 multiple choice questions was sent via email and social networks (Facebook, WhatsApp) to various professionals usually involved in the management of WSLs, including general dentists, pedodontists, orthodontists and hygienists. Participation was voluntary, anonymous and unpaid. The survey was divided into four macro-sections: 1) demography; 2) vocational training; 3) knowledge of WSLs; 4) methods of treatment (therapeutic and informative).RESULTSOf the 248 who completed the interview, 81% were female and aged between 22-50 years, with a prevalence between 22-35 years. Of these, 38% were hygienists, 26% students, 20% dentists practicing orthodontics, 8% dentists specializing in orthodontics, 6% pedodontists and 2% general dentists not practicing orthodontics. Most of the clinicians interviewed (73%) stated that a diagnosis of WSLs was made at the end of the orthodontic treatment. Inadequate home oral hygiene, incorrect diet, quality and quantity of saliva, susceptibility and age have been considered the risk factors that can most influence their onset. 33% of the clinicians interviewed believed that the identification/management of these lesions is the task of hygienists. 57% of those interviewed tend to inform patients/parents/guardians about the possibility of developing WSLs during orthodontic treatments, against 16% who are not in the habit of informing patients about these important side effects of the therapy. The most widely used therapeutic approach for the treatment of WSLs involves regular reminders of professional oral hygiene, treatment with toothpaste or fluoride varnishes and instructions on an adequate diet. Only 4% of those interviewed used resin infiltration or microabrasion to reduce the aesthetic problem associated with WSLs, considered by many therapy professionals to be unpredictable or of which they report lack of adequate knowledge.CONCLUSIONSWSLs are an ever-present topic. The results of the study showed that there is no one-way line for the management of this clinical eventuality, requiring greater collaboration between all healthcare professionals involved in the treatment of the orthodontic patient. Due to an incomplete familiarity with some therapeutic approaches (such as resin infiltration and microabrasion), these are not considered for the treatment of WSLs, possibly limiting operative practices.CLINICAL SIGNIFICANCEGreater attention must be paid to the interception of WSLs by all professionals involved in the management of the orthodontic patient. This provides for more adequate communication between the various operators and pushes for the establishment of a common operating protocol
Influence of benzalkonium chloride on dentin μTbs and MMPs activity
No full textPurpose/aim: Benzalkonium chloride (BAC) is a nitrogenous cationic surface-acting agent containing a quaternary ammonium group claimed to inhibit dentin matrix metalloproteinases (MMPs) in addition to its disinfectant ability. The aim of the studywas to investigate the adhesive bond strength and the dentin enzymatic activity of a multi-mode universal adhesive system (All-Bond Universal; Bisco Inc., ABU) and an experimental adhesive with BAC blended within its formulation (SBAC, Bisco Inc.,) employed in etch-and rinse (E&R) or self-etch (SE) mode.
Materials and methods: A standardized smear layer was created using a 180-grit silicon-carbide paper on 32 middle/ deep human dentin surfaces. Specimens were assigned to the following groups (n = 8) according to the adhesive procedure: G1: SBAC employed in E&R mode after dentin etching with 35% phosphoric acid for 15 s. G2: SBAC employed in SE mode on untreated dentin. G3: ABU employed in E&R mode after dentin etching with 35% phosphoric acid for 15 s. G4: application of ABU in SE mode on untreated dentin. All adhesives were applied according to manufacturer’s instructions and cured for 20 s. Composite buildups were created on the bonded surfaces, then specimens were cut for microtensile bond strength test (TBS) and stressed to failure at a crosshead speed of 1mm/min after 24-h storage in artificial saliva at 37 ◦C. TBS data were analyzed using two-way ANOVA and Tukey’s multiple comparison tests. Additionally, enzymatic activity was evaluated using a zymographic assay on protein extracts obtained from adhesive-treated dentin powder of each tested group.
Results: Results of TBS showed no significant differences after 24h storage in artificial saliva within the four groups. Furthermore, zymographic analysis revealed increased expression of dentin endogenous MMP-2 and -9 after application of All Bond Universal in SE mode, while in the E&R mode the expression of the MMP-2 decreased and MMP-9 was inhibited. SBAC employed in SE mode increased the expression of MMP-2, while inactivating the MMP-9. The application of SBAC in the E&R mode also inactivated MMP-9, while MMP-2 activity was significantly decreased. Conclusions: Further studies and longer aging are needed to clarify the influence of BAC blended within the adhesive formulation in improving bond longevity and dentin MMPs inhibition
Effects of Surface Pretreatments on Bond Strength and Morphology of Aprismatic Enamel
No full textTo evaluate the effect of different pretreatment protocols and adhesives on the shear bond strength and surface morphology of aprismatic enamel
The role of polymerization in adhesive dentistry
No full textAdhesive systems are resin-based materials that reach their final mechanical properties through a polymerization process. Previous literature correlated the failure of the adhesive interface to low polymer setting. Adhesives systems are elaborate mixtures of different molecules of both hydrophilic and hydrophobic nature, included in the formulation to adequately infiltrate the complex dental substrate or added to prolong the stability of the adhesive layer over time. Each adhesive component may influence the polymerization reaction of the material. Photopolymerization is a complex reaction that has several clinical implications, and besides the material composition, it is influenced by multiple factors, including the substrate characteristics, the operator technique, and the light cure unit properties. This review is focused on the analysis of factors that have a potential role in the setting of adhesive materials and thus the ultimate characteristics of the adhesive layer and the stability of the resin-dentin interface
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