Quality and Survival of Direct Light-Activated Composite Resin Restorations in Posterior Teeth: A 5- to 20-Year Retrospective Longitudinal Study

Flowable bulk-fill versus layering restorative material on Class II restorations: A randomized clinical trial

OBJECTIVE

This study evaluated the clinical performance of Class II restorations made with flowable bulk-fill base versus conventional layering ORMOCER-based restorative material in a split-mouth randomized clinical trial.

METHODS

Thirty patients received two class II restorations (n = 60) performed with different strategies. All preparations received the application of the universal self-etching adhesive system according to the manufacturer's recommendation, followed by the placement of a sectional matrix, wooden wedge, and separation ring. The first restoration was performed using 4 mm of flowable bulk-fill material covered by 2 mm of conventional viscosity restorative material (Bulk-fill technique). The second restoration was performed only with the conventional viscosity material, with a maximum of 2 mm thick increments, up to fill the cavity (Layering technique). After occlusal adjustment, the same polishing system was used for all restorations. Evaluations using the FDI criteria were conducted after 7 days, 12, and 24 months. Data were analyzed with the Fisher's Exact test (α=0.05).

RESULTS

From 30 participants, 24 attended the 24-month recall, and 48 restorations were evaluated. All restorations received acceptable overall scores for esthetic and biological properties after this period, while only 6.66 % of the restorations exhibited unacceptable overall scores for the functional properties in both groups. No significant differences between the tested restorative materials and techniques were found for each FDI criterion assessed. The success rate after 2 years was 93.33 % for both groups.

CONCLUSION

Both restorative materials exhibited good clinical performance for the parameters analyzed with no differences between them after 24-month follow-up.

CLINICAL RELEVANCE

Flowable bulk-fill ORMOCER-based material is a suitable alternative for direct Class II restorations, providing good clinical outcomes and simplifying the restorative procedure.

CLINICAL TRIAL REGISTRATION NUMBER

RBR-6mvp9w.

Long-term clinical comparison of a resin-based composite and resin modified glass ionomer in the treatment of cervical caries lesions

This 72-month study compared the clinical effectiveness of a resin-based composite (RBC) (Spectrum TPH3, Dentsply Sirona) with a resin-modified glass ionomer cement (RMGIC) (Riva Light Cure, SDI) in restoring cervical caries lesions (CCLs). Thirty-three patients, each with at least two CCLs, were enrolled. After caries removal, the dimensions of the cavities were recorded. In a split-mouth study design, a total of 110 restorations were randomly placed. Fifty-five restorations were placed with RBC using an etch-and-rinse adhesive system (Prime&Bond NT, Dentsply Sirona), while the remaining 55 were restored with RMGIC. The restorations were assessed at baseline, 6, 12, 18, 24, 36, 60, and 72 months according to modified USPHS criteria. Statistical analysis included Pearson Chi-square, Friedman tests, Kaplan Meier, and Logistic Regression analysis (p < 0.05). After 72 months, 47 restorations in 19 patients were evaluated (55% follow-up rate). Seventy-five percent of the RBC (n = 26) and 74% (n = 21) of the RMGIC restorations were fully retained. There were no significant differences between materials regarding retention and marginal adaptation (p > 0.05). Cavity dimensions, caries activity, and retention exhibited no correlation (p > 0.05). The increase in marginal staining in both groups over time was significant (p < 0.001). RMGIC restorations exhibited higher discoloration than RBC restorations (p = 0.014). At 72 months, three secondary caries lesions were detected in both restoration groups: two RMGIC and one RBC. There were no reports of sensitivity. After 72 months, both RBC and RMGIC restorations were clinically successful, with similar retention and marginal adaptation scores. However, it is noteworthy that RMGIC restorations tend to discoloration over time compared to RBC. The trial is registered in the database of "Clinical Trials". The registration number is NCT0372-2758, October 29, 2018.

Influence of Cavity Lining on the 3-Year Clinical Outcome of Posterior Composite Restorations: A Randomized Controlled Clinical Trial

The purpose of this randomized, split-mouth-designed controlled and single-blinded clinical study was to evaluate the 3-year clinical performance of Class I and Class II resin composite restorations placed with or without cavity lining with a flowable composite. Fifty patients with treatment needs in two premolars or molars were included. One of the teeth was restored using the nanohybrid composite (Grandio®SO, control group), in the test group a high viscosity flowable composite was additionally applied as a first layer. In both groups, the same self-etch adhesive system was applied. Clinical evaluation after 3 years was carried out using the modified USPHS/Ryge criteria. At the 3-year follow-up the recall rate was 92%. Four restorations failed in the test group (8.7%), three due to the loss of vitality and one after fracture. The control group exhibited a cumulative success rate of 100%, while the test group achieved a success rate of 91.3%. This led to significant differences in the annual failure rate (AFR) between the two groups, with rates of 0% and 2.9% (p < 0.05; Mann-Whitney U-test). After 3 years the cumulative survival rate including all restorations was 95.7%. Statistical analysis revealed significant differences for the parameters: tooth vitality, marginal discoloration, success rate, and AFR. The other parameters exhibited no significant differences. Consequently, the nanohybrid composite demonstrated excellent performance over a 3-year period, whereas the utilization of a flowable composite for the cavity lining did not appear to exert a beneficial influence on clinical outcomes.

Compatibility versus reaction diffusion: Factors that determine the heterogeneity of polymerized adhesive networks

OBJECTIVES

Heterogeneity and phase separation during network polymerization is a major issue contributing to the failure of dental adhesives. This study investigates how the ratio of hydrophobic crosslinkers to hydrophilic comonomer (C/H ratio), as well as cosolvent fraction (ethanol/water) influences the degree of heterogeneity and proclivity for phase separation in a series of model adhesive formulations.

METHODS

Twelve formulations were investigated, with 4 different C/H ratios (7:1, 2.2:1, 1:1, 0.5:1) and 3 different overall cosolvent fractions (0, 10 and 20 wt%). The heterogeneity and phase behavior were characterized using Fourier Transform Infrared Spectroscopy (FT-IR), dynamic mechanical analysis (DMA), small-angle x-ray scattering (SAXS) and atomic force microscopy (AFM).

RESULTS

In resins without cosolvent, all characterizations confirm reduced heterogeneity as C/H ratio decreases. However, when 10 or 20 wt% of cosolvent is included in the adhesive formulation, a higher degree of heterogeneity and even distinct phase separation with domains ranging from a few hundreds of nanometers to a few micrometers in size form. This is particularly noticeable at lower C/H ratios, which is surprising as HEMA is commonly considered a compatibilizer between hydrophobic crosslinkers and aqueous (co)solvents.

SIGNIFICANCE

Our experiments demonstrate that formulations with lower C/H ratio and thus a lower viscosity experience later onsets of diffusion limitations during polymerization, which favors thermodynamically driven phase separation. Therefore, to determine or predict the resulting phase structure of adhesive materials, it is necessary to consider the kinetics and diffusion constraints during the formation of the polymer network and not just the compatibility of resin constituents.

Longevity of composite restorations in posterior teeth placed by dental students: a 12-year retrospective study

OBJECTIVES

To evaluate the longevity of resin composite restorations placed in posterior teeth by dental students, using data from electronic records from 2008 to 2019.

MATERIALS AND METHODS

Demographic (gender and age) and clinical variables (dental group, position in dental arch, and the number of restored surfaces) were evaluated. The 5-year follow-up was assessed according to the day the restoration was placed. Kaplan-Meier curves were generated to calculate the annual failure rate. Data were analyzed by Chi-Square, Kruskal-Wallis, and Mann-Whitney tests (α = 0.05).

RESULTS

In total, 3.883 records relative to return periodicity were analyzed. The final sample consisted of 900 restorations from 479 patients. The majority were females, aged between 31 and 60. In total, 256 failures were reported (success rate = 78%), showing an annual failure rate of 2.05%. The main reasons for failures were restoration replacement (55.5%), endodontics (21.9%), prosthetics (14.5%) and extraction (8.2%). There was a higher risk of failure in restorations involving three or more surfaces (p = 0.000) and in patients over 60 years (p < 0.001). In females (p = 0.030), molars (p = 0.044), and maxillary teeth (p = 0.038) failed in a shorter time.

CONCLUSIONS

Resin composite restorations placed in permanent posterior teeth by dental students had high survival rates. The main reason for failure was the replacement of restorations. The age group and the number of restored surfaces significantly affected the success of the restorations.

CLINICAL RELEVANCE

The electronic health records over 12 years showed that 78% of the resin restorations in posterior teeth placed by dental students were successful for a minimum of five years.

Influence of internal angle and shape of the lining on residual stress of Class II molar restorations

Polymerization shrinkage is a major side effect of resin composite materials that affects the success and longevity of caries restorations. This study was to analyze the effect of the internal angle and shape of the lining on the shrinkage residual stress of dental restorations in Class II mesio-occlusal-distal (MOD) cavities through finite element analysis (FEA). A 3D reconstructed model of a human mandibular first molar was created from micro-CT images, and then the tooth was prepared as a Class II MOD cavity. 3D models of four regular internal corner shapes of Class II MOD cavities with different internal angles of lining and one 90° filleted corner model were created. The thermal expansion technique was applied to approximate the shrinkage impact of composite resin polymerization in the FE software ABAQUS. Von Mises stress was taken as a metric. The results showed that the level of residual stresses in the Class II MOD cavities was greatly dependent on the internal angle of the lining. The maximum von Mises stress in tooth tissue decreased as the internal angle of the lining increased. The internal shapes of the lining had no obvious effect on the stress, and the filleted corner model had less stress. This lining strategy is appropriate for Class II MOD cavities with serious loss of tooth tissue.

In-vitro-cytotoxicity of self-adhesive dental restorative materials

OBJECTIVES

Although the introduction of self-adhesive composites in restorative dentistry is very promising, the innovation of new materials also presents challenges and unknowns. Therefore, the aim of this study was to investigate the cytotoxicity of four different self-adhesive composites (SAC) in vitro and to compare them with resin-modified glass ionomer cements (RM-GIC), a more established group of materials.

METHODS

Samples of the following materials were prepared according to ISO 7405/10993-12 and eluted in cell culture medium for 24 h at 37 °C: Vertise Flow, Fusio Liquid Dentin, Constic, Surefil One, Photac Fil and Fuji II LC. Primary human pulp cells were obtained from extracted wisdom teeth and cultured for 24 h with the extracts in serial dilutions. Cell viability was evaluated by MTT assay, membrane disruption was quantified by LDH assay and apoptosis was assessed by flow cytometry after annexin/PI staining.

RESULTS

Two SAC (Constic and Vertise Flow) and one RM-GIC (Photac Fil) significantly reduced cell viability by more than 30% compared to the untreated control (p < 0.001). Disruptive cell morphological changes were observed and the cells showed signs of late apoptosis and necrosis in flow cytometry. Membrane disruption was not observed with any of the investigated materials.

CONCLUSION

Toxic effects occurred independently of the substance group and need to be considered in the development of materials with regard to clinical implications.

CLINICAL SIGNIFICANCE

SAC have many beneficial qualities, however, the cytotoxic effects of certain products should be considered when applied in close proximity to the dental pulp, as is often required.

Factors influencing the longevity of posterior composite restorations: A dental university clinic study

Objectives

This retrospective study aimed to assess the performance of posterior composite resin restorations (PCRRs) and evaluate the influence of patient-specific factors on restoration outcomes.

Methods

A total of 189 PCRRs were examined in 54 patients, with evaluations based on Modified USPHS criteria. Patient-specific factors were analyzed. Statistical analyses, including chi-square tests, independent samples t-tests, and ANOVA tests, were conducted.

Results

Patients aged over 50 exhibited higher DMFT averages and a higher rate of unsuccessful restorations. Despite higher DMFT scores in females, gender doesn't significantly impact restoration outcomes. Secondary caries correlated with.plaque scores, significantly affecting restoration survival. Marginal adaptation, retention deficiencies, and secondary caries were primary causes of failure. Multi-surface restorations faced higher failure risk due to elevated plaque scores. Class-V restorations showed a higher failure rate, challenging the number of surfaces and longevity correlation.

Conclusions

This study identified key factors influencing posterior composite resin restorations-(PCRRs) in patients over 50, including higher DMFT averages and more unsuccessful restorations. No significant difference was found between brushing; frequency and DMFT rates, possibly due to the absence of non-brushers. Secondary caries; correlated with elevated plaque scores, impacting restoration survival. Primary causes of; failure included marginal adaptation issues, retention deficiencies, and secondary caries, with multi-surface restorations facing a higher risk. However, tooth vitality, beverage and acidic food consumption, and oral hygiene habits did not significantly affect PCRR outcomes.

Clinical significance

Patient-specific factors significantly impact PCRRs' long-term performance. Dentists must tailor strategies, emphasizing regular monitoring and preventive measures for extended survival.

Comparison of Various Commonly Used Luting Cements on the Success of Composite Inlays Assessed by the Levels of the Microleakage-An In vitro Study

Introduction

Indirect composite restoration is one of the commonly followed procedures in the posterior teeth. The success of this is dependent on many factors, one being the luting cement. Hence, the current study explores the microleakage of the two luting cements at 2 different times.

Materials and Methods

Eighty extracted human teeth were taken, and class II cavities were made that were to receive the composite inlays. They were grouped as supragingival and subgingival, which for further divided as were further subdivided to be observed for marginal leakage at cervical and occlusal margins, at the end of a day and 1 month. Each group had ten specimens. The luting cements that were evaluated were Variolink N and RelyX Unicem. After the composite inlay restoration was done for all the specimens, the sections were put on slides, and a stereomicroscope was used to measure the amount of dye penetration. Leakage was evaluated and compared using Mann-Whitney U test.

Results

At the end of 1 day, there was no significant alteration in the microleakage in the occlusal or cervical regions for either region supragingivally or subgingivally between the two luting cements. Significant difference between the two cements at the cervical borders at the end of a month was seen for both the margins. When compared supragingivally and subgingivally at the end of 1 day or at the end of 1 month, there was not a significant difference for any of the cements.

Conclusion

Within the constraints of the current investigation, it can be said that there was similar microleakage for both Variolink N and RelyX Unicem at the conclusion of a day's storage time. After a 1-month storage period, RelyX Unicem showed more cervical microleakage than Variolink N.

Clinical evaluation of lithium disilicate versus indirect resin composite partial posterior restorations - A 7.8-year retrospective study

OBJECTIVE

To evaluate retrospectively the longevity of lithium disilicate ceramic (LidiSi) vs. laboratory-processed resin-based composite (RBC) inlay/onlay/overlay restorations and risk factors associated with restoration deficiencies and failures.

METHODS

Patients (n = 91) receiving LidiSi (73.1%) and RBC (36.9%) inlays/onlays/overlays between 2007 and 2017 were selected. The restorations were evaluated using the modified U.S. Public Health Service criteria. The survival of the restorations was analyzed using the Kaplan-Meier method and log rank test. Factors affecting the occurrence of deficiencies were examined by logistic regression analysis. This was performed with the use of the Generalized Estimating Equation model including Repeated measurements (GEER), with the consideration that the same patient had several teeth in the sample. Risk estimation was conducted for each evaluated criterion (p < 0.05).

RESULTS

The survival of LidiSi and RBC restorations were 96.8% and 84.9%, respectively after a mean observation period of 7.8 ± 3.3 years. The annual failure rate was 0.2% for LidiSi and 1.0% for RBC. The probability of survival was above 98% for both restorations in the first 6 years, however, it dropped to 60% for RBC by the end of the 15th year. For both materials the reasons for failure included secondary caries, restoration fracture, and endodontic complication. In addition, LidiSi also failed due to tooth fracture, while RBC due to marginal gap formation and loss of retention. Among the evaluated risk factors, material of restoration (OR=6.8, CI95%:3.1-14.9), oral hygiene (OR=8.0, CI95%: 2.9-22.1], and bruxism (OR=1.9, CI95%: 1.1-3.3) showed a significant impact on the evaluated criteria.

SIGNIFICANCE

LidiSi and RBC restorations showed similarly excellent 6-year survival, however, in the long term significantly more failures should be expected for RBCs.

An In Vitro Study regarding the Wear of Composite Materials Following the Use of Dental Bleaching Protocols

Composite materials used in dental restorations are considered resistant, long-lasting and aesthetic. As the wear of restorations is an important element in long-term use, the aim of this study was to evaluate the surface condition of nanohybrid and microfilled composite resins, after being subjected to the erosive action of dental bleaching protocols. This paper reflects a comparative study between one nanofilled composite and three microfilled composites used in restorations. For each composite, three sets of samples (under the form of composite discs) were created: a control group, an "office bleach" group with discs bleached with 40% hydrogen peroxide gel, and a "home bleach" group with discs bleached with 16% carbamide peroxide gel. Wear was numerically determined as the trace and the coefficients of friction obtained using a tribometer, the ball-on-disk test method, and two balls: alumina and sapphire. For all composite groups, there were statistically significant differences between the wear corresponding to the control and bleaching groups, for both testing balls. Regarding the composite type, the largest traces were recorded for GC Gradia direct anterior, for all groups, using the alumina ball. In contrast, for the sapphire ball, 3M ESPE Filtek Z550 was characterized by the largest traces. With respect to the friction coefficients, the "office bleach" group recorded the largest values, no matter the composite or the ball type used. The 3M ESPE Valux Plus composite recorded the largest friction coefficients for the alumina ball, and 3M ESPE Filtek Z550 for the sapphire ball. Overall, the "office bleach" group was characterized by higher composite wear, compared to the "home bleach" protocol or control group. Nanofilled composite resins showed superior wear resistance to microfilled resins after undergoing a bleaching protocol.

Periapical Status of Non-Root-Filled Teeth With Amalgam, Composite, or Crown Restorations: A Cross-Sectional Study

OBJECTIVES

This study aimed to evaluate the periapical status (PAS) of restored non-root-filled (RNRF) teeth amongst a group of patients attending dental teaching clinics at Jordan University of Science & Technology. It also aimed to assess the association of type and quality of coronal restorations and periapical disease.

METHODS

This was a cross-sectional study. To be included, participants needed to have at least 1 non-root-filled tooth restored with either direct or indirect restoration. A sample of 491 participants was examined. Clinical examination and digital periapical radiographs were used to record material used and assess the quality of the restorations. Chi-square test and logistic regression analysis were used to analyse the association between PAS and gender, age, restoration material/type, and quality.

RESULTS

Overall, 26.3% of the participants were diagnosed with apical periodontitis (AP) on 1 or more of the examined teeth. No significant differences in the prevalence of AP were observed when comparing amalgam to composite or indirect restorations (P = .386). Furthermore, no association was reported between AP and gender or age, while a significant association was observed with the restoration's quality (P < .001).

CONCLUSIONS

The high prevalence of AP in the examined sample is of clinical concern and suggests that more attention should be directed towards dental health awareness in Jordan. Teeth restored with inadequate restorations were twice as likely to have AP.

Marginal Adaptation of In Vitro Class II Restorations Made Out of Bulk or Conventional Composite Using Single- or Multi-Layered Techniques

Objective: Testing the influence of various restorative materials (conventional or bulkfill composites) and filling techniques (single- or multi-layered techniques) on the in vitro marginal adaptation of large class II direct composites with supra and sub-gingival margins subjected to thermomechanical loading (TML). Methods: A total of 40 prepared teeth were attributed randomly to five experimental groups. In Group 1, restorations were made of multi-layered high-viscosity conventional composite (Tetric EvoCeram); in Groups 2 and 3, restorations were made of a high viscosity bulkfill composite (Tetric EvoCeram Bulk Fill) applied in one (Group 2) or three layers (Group 3); in Groups 4 and 5, restorations were made of a flowable bulkfill composite (SDR flow) applied in one (Group 4) or two layers (Group 5), covered with a layer of high-viscosity conventional composite (Ceram-X Universal). A single adhesive (OptiBond FL) was used in all groups. All specimens were submitted to a staged TML comprising three phases (2 × 500,000 and 1,000,000 cycles) at 50 N with 3350 thermal cycles (5 to 55 °C) every 500,000 cycles. The tooth-restoration interfaces on proximal surfaces were evaluated quantitatively by scanning electron microscopy, before and after each TML phase, hence at three timepoints (T0, T1, T2 and T3). The following segments were considered for evaluation: proximal, vertical enamel margins (assessed individually on both restoration sides), cervical enamel (restoration side above CEJ) and cervical dentin margin (restoration side below the CEJ). Results: TML induced a significant reduction in continuous adaptation at both enamel and dentin margins in all groups, with percentages of continuous margins ranging from 75.2 to 91.8% at T0, and decreasing to values ranging from 21.3 to 73.9% at T3. Both composite systems and layering protocols had a significant influence on marginal adaptation of the restorations, with statistical associations depending on the restoration group and the timepoint considered. Defective margins in enamel were all of a cohesive nature with micro-fractures, while in dentin, interfacial gaps were the main defect observed. Conclusions/Clinical significance: The present results highlighted significant degradation of marginal adaption after long-term in vitro fatigue test using materials even with high-viscosity conventional resin composites, applied with a proper layering approach in medium-large sub-gingival cavities. While no significant differences were observed at the dentin cervical margins, there was a tendency for better adaptation at the enamel margin when using a higher modulus material with a multi-layered technique.

Full analysis of the effects of modeler liquids on the properties of direct resin-based composites: a meta-analysis review of in vitro studies

OBJECTIVES

This study systematically revised the literature to answer the following question: do modeler liquids (MLs) affect the properties of direct resin-based composites (RBCs)?

MATERIALS AND METHODS

The review followed the PRISMA statement, and the search was conducted in PubMed, Scopus, Web of Science, Embase, and Lilacs databases. Studies were included if they investigated the properties of RBCs prepared using the restorative dental modeling insertion technique (RDMIT). The risk of bias was performed with the RoBDEMAT tool. Statistical analyses were conducted using Review Manager, and heterogeneity was assessed with the Cochran Q test and I² statistics.

RESULTS

From 309 studies identified, 25 met the eligibility criteria, and 23 were meta-analyzed. In total, 27 MLs and 23 RBCs were evaluated. Modeled and non-modeled RBCs showed similar results in terms of cohesive strength, flexural strength, load-to-fracture, modulus of elasticity, work of fracture, degree of conversion, solubility, weight change, microhardness, and color change. Sorption and roughness benefited from the use of MLs, whereas translucency and whitening index were more adequate in the non-modeled RBCs. Aging affected similarly the modeled and non-modeled RBCs. Most studies showed a moderate risk of bias.

CONCLUSIONS

Modeled and non-modeled RBCs performed similarly in most of the properties, and the use of non-solvated lubricants offered beneficial effects in some cases.

CLINICAL RELEVANCE

When a balance has to be made between the RDMIT and the conventional technique, our review supports the safe application of modeler liquids for the handling of composite increments during the sculpting fabrication of direct resin-based restorations.

Teeth Restored with Bulk–Fill Composites and Conventional Resin Composites; Investigation of Stress Distribution and Fracture Lifespan on Enamel, Dentin, and Restorative Materials via Three-Dimensional Finite Element Analysis

Objectives: the aim of this study was to examine the stress distribution of enamel, dentin, and restorative materials in sound first molar teeth with restored cavities with conventional resin composites and bulk–fill composites, as well as to determine their fracture lifetimes by using the three-dimensional finite element stress analysis method. Materials and Methods: an extracted sound number 26 tooth was scanned with a dental tomography device and recorded. Images were obtained as dicom files, and these files were transferred to the Mimics 12.00 program. In this program, different masks were created for each tooth tissue, and the density thresholds were adjusted manually to create a three-dimensional image of the tooth, and these were converted to a STL file. The obtained STL files were transferred to the Geomagic Design X program, and some necessary adjustments, such as smoothing, were made, and STP files were created. Cavity preparation and adhesive material layers were created by transferring STP files to the Solidworks program. Finally, a FE model was created in the ABAQUS program, and stress distributions were analyzed. Results: when the bulk–fill composite and conventional resin composite materials were used in the restoration of the cavity, the structures that were exposed to the most stress as a result of occlusal forces on the tooth were enamel, dentin, restorative material, and adhesive material. When the bulk–fill composite material was used in restoration, while the restorative material had the longest fracture life as a result of stresses, the enamel tissue had the shortest fracture life. When the conventional resin composite material was used as the restorative material, it had the longest fracture life, followed by dentin and enamel. Conclusion: when the bulk–fill composite material was used instead of the conventional resin composite material in the cavity, the stress values on enamel, dentin, and adhesive material increased as a result of occlusal forces, while the amount of stress on the restorative material decreased. In the fracture analysis, when the bulk–fill composite material was used instead of the conventional resin composite material, a decrease in the number of cycles required for the fracture of enamel, dentin, and restorative materials was observed as a result of the forces generated in the oral cavity.

A 23-Year Observational Follow-Up Clinical Evaluation of Direct Posterior Composite Restorations

The purpose of this observational follow-up clinical study was to observe the quality of posterior composite restorations more than 23 years after application. A total of 22 patients, 13 male and 9 female (mean age 66.1 years, range 50–84), with a total of 42 restorations attended the first and second follow-up examinations. The restorations were examined by one operator using modified FDI criteria. Statistical analysis was performed with the Wilcoxon Mann–Whitney U test and Wilcoxon exact matched-pairs test with a significance level of p = 0.05. Bonferroni–Holm with an adjusted significance level of alpha = 0.05 was applied. With the exception of approximal anatomical form, significantly worse scores were seen for six out of seven criteria at the second follow-up evaluation. There was no significant difference in the first and second follow-up evaluations in the grades of the restorations with regard to having been placed in the maxilla or mandible, as well as for one-surface or multiple-surface restorations. The approximal anatomical form showed significantly worse grades at the second follow-up when having been placed in molars. In conclusion, the study results show that significant differences regarding FDI criteria in posterior composite restorations occur after more than 23 years of service. Further studies with extended follow-up time and at regular and short time intervals are recommended.

Color Stability of Resin Cements after Water Aging

The color stability of resin cements plays a key role in the achievement of esthetically-pleasant restorations. Resin luting materials can be mainly divided into two main classes: adhesive (relying on previous application of adhesive systems) or self-adhesive (also known as one-step cements). The different chemical compositions determine their physio-mechanical characteristics which, in turns, influence their color stability. To evaluate the color variations of different dual-cured resin cements after water aging, 80 disc-shaped specimens (15 mm in diameter and 1.2 mm thick) were obtained from the following resin cements (n = 10): (1) Maxcem Elite Universal, MCU (Kerr); (2) RelyX Universal, RXU (3M); (3) Calibra Ceram, CAL (Dentsply); (4) Multilink, MUL (Ivoclar-Vivadent); (5) Panavia V5, PAN (Kuraray); (6) Calibra Universal, CUN (Dentsply); (7) SpeedCEM Plus, SCP (Ivoclar); and (8) Panavia SA, PSA (Kuraray). After light-polymerization, the specimens were measured with a spectrophotometer and CIELab* values were recorded. The specimens were then placed in a digitally controlled thermostatic water bath at 60° for 30 days and afterwards the color measurements were repeated. Color differences were calculated for each specimen before and after water-aging procedures with ΔEab formula and the data were statistically analyzed (p < 0.05). The type of cement statistically influenced the ΔEab (p < 0.05), with MCU showing the lowest color variations (4.3 ± 0.7) whereas RXU and PSA the highest (16.9 ± 1.6 and 16.8 ± 1.2, respectively). No differences were observed between CAL, CUN and SCP (p = 0.05). Color stability is related to the chemical composition of the resinous luting materials, thus material dependent.

Effect of modeling liquids on resin composite roughness and color parameters after staining and toothbrushing

This study evaluated surface roughness, color stability, whitening index, and opacity of different types of modeling liquids for resin composite coating after exposure to staining and toothbrushing. Disc-shaped resin composite (Vittra APS, FGM) specimens were fabricated and divided into four groups (n = 10 each): control group, Composite Wetting resin (Ultradent Products), Adper Scotchbond Multipurpose adhesive (3M ESPE), and Adper Universal adhesive (3M ESPE). Surface roughness (Ra) was measured using a rugosimeter, while color stability (∆E00), whitening index (WI), and opacity (%) were measured using a spectrophotometer. Assessments were made at four time points: after polishing (baseline, T1), after immersion in red wine for 24 h (T2), and after 5,000 (T3) and 10,000 (T4) cycles of toothbrushing. Scanning electron microscopy images were captured to analyze the scratches created. The data were statistically analyzed by two-way repeated-measures analysis of variance and Tukey's honestly significant difference tests (α = .05). Modeling with the Wetting resin resulted in higher surface roughness (p < 0.05) and low color stability, which were attributable to porosities. Higher color change values were observed in the control group after staining. Both adhesives showed the lowest mean ΔE00 values (p < 0.005). WI decreased after staining, except with the use of the Universal adhesive (p < 0.005). The lowest opacity values were observed at baseline for all groups (p < 0.005). The Universal and Scotchbond adhesives had lower surface roughness, better color stability, higher WI, and the lowest opacity values after staining with red wine and toothbrushing.

A comparative life cycle assessment of dental restorative materials

OBJECTIVES

Different types of direct-placement dental materials are used for the restoration of structure, function and aesthetics of teeth. The aim of this research investigation is to determine, through a comparative cradle-to-gate life cycle assessment, the environmental impacts of three direct-placement dental restorative materials (DRMs) and their associated packaging.

METHODS

Three direct-placement dental materials; dental amalgam, resin-based composite (RBC) and glass polyalkenoate cements (GIC) are assessed using primary data from a manufacturer (SDI Limited, Australia). The functional unit consisted of 'one dental restoration' of each restorative system under investigation: 1.14 g of dental amalgam; 0.25 g of RBC (plus the adhesive = 0.10 g); and 0.54 g of GIC. The system boundary per restoration included the raw materials and their associated packaging materials for each DRM together with the processing steps for both the materials and packaging. The environmental impacts were assessed using an Egalitarian approach under the ReCiPe method using Umberto software and the Ecoinvent database. Nine different impact categories were used to compare the environmental performance of these materials.

RESULTS

Dental amalgam had the highest impact across most of the categories, but RBC had the highest Global Warming Potential. The highest sources of the environmental impacts for each restorative material were: Amalgam, derived from material use; RBC, derived from energy use in processing material and packaging material; GIC, derived from material and energy use for packaging.

SIGNIFICANCE

Less intensive energy sources or more sustainable packaging materials can potentially reduce the impacts associated with RBC and GIC thus making them suitable alternatives to dental amalgam.

Application of Tribology Concept in Dental Composites Field: A Scoping Review

Tribology is the discipline concerning the application of friction, lubrication, and wear concepts of interacting surfaces in relative motion. A growing interest has developed in tribology application in medical biomaterials, such as resin composites used in restorative dentistry. Yet, the keywords "tribology" and "biotribology" are little applied in the pertinent publications. The aim of this scoping review was to offer an overview of tribology application in dental composites research and to identify knowledge gaps and address future research. A literature search was conducted on Pubmed and Scopus databases and the studies investigating the tribological behavior of resin composites were included for qualitative synthesis. The majority of studies on dental tribology were published in the research areas of mechanical engineering/nanotechnology and differed in several methodological aspects. The preponderant engineering approach and the lack of standardized testing make the laboratory findings poorly informative for clinicians. Future research should focus on the tribological behavior of dental materials composites by means of an integrated approach, i.e., engineering and clinical, for improving development and advancement in this field of research.

Cytotoxic Evaluation of the New Composite Resin through an Artificial Pulp Chamber

The aim of this study was to analyse the cytocompatibility of Surefil One (SuO) with respect to the release of monomers from the material. The following reference materials were chosen: SDR Flow Plus (SDR, Dentsply Sirona, Konstanz, Germany), One Q Bond (Q, Dentalica, Milan, Italy), and Ketac (K, 3M-ESPE, USA). Fifteen dentin discs (2 mm thickness and diameter) were obtained from 15 third molars and were used in this study. After dentin disc permeability measurement, murine fibroblasts were grown, and the pulp surface of the dentinal disc was placed in direct contact with the cells immersed in DMEM. The experimental materials were positioned on the occlusal side of each dentinal disc until a uniform thickness of 2 mm was obtained. Then, the discs were inserted into an artificial pulp chamber for 24 hours to assess the cytocompatibility. Afterwards, the moles of monomers leached from the specimens in DMEM were determined using HPLC. Statistical analysis was performed using ANOVA (p < 0.05). Under the experimental conditions, the toxic effect induced by all tested materials was slight or absent. Diurethane dimethacrylate and acrylic acid were not found in the culture media. It is concluded that all materials have good cytocompatibility consistent with the nondeterminability of the monomers released after polymerization.

The Effect of Simulated Chewing on the Surface Roughness of Direct and Indirect Resin-Composites Opposed by Zirconia: An In Vitro Study

Purpose

To assess the surface roughness of two different light-cured resin-composites when opposed by monolithic zirconia after simulated mastication.

Materials and Methods

Materials included a direct restorative nanohybrid (n = 10) and an indirect microhybrid (n = 10) resin-composite (Tetric EvoCeram and Sinfony, respectively). The antagonist material was 3 mol% yttria-stabilized tetragonal zirconia polycrystalline ceramic. Each material was subjected to in vitro chewing against zirconia using a chewing simulator for 250,000 cycles. A 3D profilometer was used to assess the surface roughness parameters of each resin-composite before and after the simulated chewing. Independent t-test and paired sample t-test were performed to compare roughness values for both materials and to compare baseline and after chewing simulation values (p = 0.05).

Results

Sinfony showed significantly greater roughness values compared to Tetric EvoCeram (p ≤ 0.025) before and after simulated chewing, except for Sa and Sv parameters after simulated chewing where the difference between the two materials was insignificant (p = 0.06 and 0.89, respectively). Surface roughness increased for both materials after simulated chewing compared to baseline values, but the difference was insignificant (p ≥ 0.065). However, Sa (p = 0.04) and Sv (p = 0.012) for Tetric EvoCeram were significantly higher after compared to before chewing simulation.

Conclusion

Tetric EvoCeram had a smoother surface than Sinfony before and after simulated chewing. Surface roughness for both materials was higher after simulated chewing compared to baseline values which represent surface damage that was significant for Tetric EvoCeram while Sinfony showed better resistance.

Adhesive Ability of Different Oral Pathogens to Various Dental Materials: An In Vitro Study

Introduction. In dental treatments, the reason for secondary caries and the failure of root canal treatment is the microbial infection, which concerns most dentists. The challenge of how to reduce the number of bacteria at the filling materials and the number of residual bacteria in the root canal has become a research hotspot. In this study, the bacterial adhesion properties of several common dental materials were compared to provide a theoretical basis for the selection of antibacterial properties of dental materials. Methodology. Three commonly used dental restorative materials and five sealers in root canal treatment were selected. Each material block was immersed in the corresponding supragingival (Streptococcus mutans and Actinomyces viscosus) or subgingival (Porphyromonas gingivalis and Enterococcus faecalis) bacterial solution and cultured under anaerobic conditions at 37°C for 2, 4, 6, 8, 12, 16, 20, and 24 h. The adhesion of bacteria was observed, and the number of different bacteria adhering to various material model disks was calculated at different time intervals under a scanning electron microscope. The adherent CFU load of the materials was determined by colony counting. Results. Streptococcus mutans and Actinomyces viscosus exhibited the strongest adhesion ability to the resin material blocks. Porphyromonas gingivalis and Enterococcus faecalis exhibited the highest adhesion ability to the AH-Plus sealer block. Conclusions. In dental treatments, dental materials should be selected based on the chemical, physical, and biological properties of materials. In addition, it is necessary to develop new antibacterial dental materials.

Investigation of the Effects of Adhesive Materials of Different Types and Thicknesses on Dental Tissue Stress via FEM Analysis

The aim of this study was to investigate the types and thicknesses of adhesive materials used in restorative treatment in dentistry in class I occlusal and class II disto-occlusal cavities and to examine the effects of stress distribution on enamel, dentin, restoration material, and adhesive material using the finite element stress analysis method. A 3-dimensional geometry of the tooth was obtained by scanning the extracted 26 numbered upper molar tooth with dental tomography. The 3D geometry obtained by using the Geomagic Design X 2020.0 software was divided into surfaces, and necessary arrangements were made. With the Solidworks 2013 software, 2 different cavity modeling, class I occlusal and class II disto-occlusal, with a cavity angle of 95 degrees on the 3D model, as well as 10, 30, and 50 micrometers thick, four types of adhesive materials and the modeling of the bulk-fill composite material on it were made. With finite element stress analysis, the stress distribution was analyzed using the Abaqus software. The materials used in the study are included in the simulation as isotropic linear elastic. Periodontal ligament and jawbone were not included in the analysis. A total of 600 N pressure was applied on the models. In our study, it was observed that the amount of stress on the tooth structures changed when the thickness, elastic modulus, and Poisson ratios of the adhesive material were changed. In addition, when all models are examined, it is seen that when the thickness is increased, more stress is placed on the adhesive material compared to the restoration, while when 50-micrometer-thick adhesive material is used, more stress is placed on the restoration compared to the adhesive material.

The effect of filling technique on the cuspal strain, polymerization shrinkage stress, enamel crack formation and depth of cure of restored molars

OBJECTIVE

Evaluate the effect of different restorative filling techniques on the residual shrinkage stress (ShrS), cuspal strain (CS), depth of cure (DC), and enamel crack formation (Ec) in molars with MOD restorations.

METHODS

Post-gel shrinkage, elastic modulus, compressive and diametral tensile strength of the Filtek One Bulk Fill composite were calculated. Sixty molars with MOD preparations were restored using four filling techniques: Bulk; Horizontal; Oblique; Natural enamel and dentin substitution (NEDS) technique. CS was measured using a strain gauge (n = 10). The DC (n = 5) was measured using Knoop hardness. Shrinkage stress/strain was analyzed using 3D finite element analysis. The Ec analysis was carried out by transillumination. Two-way ANOVA with repeated measures and Tukey's HSD test (α = 0.05) was performed for the CS data. Two-Way ANOVA and Tukey's HSD test was performed for the DC data (α = 0.05).

RESULTS

CS was higher at the lingual cusp for the horizontal and NEDS technique. No statistical difference was found between the buccal and lingual CS values for the Bulk (p = 0.367) or Oblique techniques (p = 0.192). CS values were lower for the Bulk. More enamel cracks were found for the Bulk. DC was lower at 4 mm regardless the filling technique. The Horizontal showed the highest ShrS values. The Bulk generated the lower ShrS values.

SIGNIFICANCE

A Bulk technique caused the lowest shrinkage stress/strain. An Oblique technique yielded the best balance between stress, strain and crack formation. NEDS technique is a good alternative to decrease the number of increments while maintaining the stress levels nearby the Oblique technique.

[Light-curing effectiveness using led lamps: a review]

Introduction

LED lamps have a new light-curing technology which can be monowave or polywave, which allows it to reach more initiators such as camphorquinone, Lucirin TPO and Propanodione, which have a wide variety of advantages and disadvantages. These lamps have evolved over time, as have different ergonomics, longevity, systems and quality standards.

Objective

The objective of this literature review is to improve the clinician on the proper use of different LED lamps and how they influence the efficiency of resin photopolymerization.

Material and methods

Extensive research has been carried out in the existing literature on this topic. From the beginning of this information until April 18, 2022, the bibliographic search carried out includes 86 articles published in the Medline database through PubMed, LILACS, Science Direct and SciELO, and there is no language restriction.

Results

The photopolymerization effects of Polywave and Monowave LED lamps present significant differences between the compressive strength of the light-cured resin, with single-wave and polyvalent LED lamps where the types of light and lamp directly influence the compressive strength of the resin. composite resins.

Conclusion

The type of light and lamp directly affects the efficiency of the photopolymerization of the composite resin, so it is concluded that LED lamps with single wave technology (Monowave) produce a greater depth of photopolymerization than those with multiple wave technology (Polywave).

Survival of direct resin composite onlays and indirect tooth-coloured adhesive onlays in posterior teeth: a systematic review

Objective To compare the survival of direct resin-composite used as onlays and indirect tooth-coloured adhesive onlays in posterior teeth, along with modes of failure, deterioration and variables affecting survival.Materials and methods PubMed, Embase, The Cochrane Library, Web of Science and Scopus were searched systematically up to 16 October 2020. In total, 3,768 studies were screened, with their results for survival, failure mode, deterioration and variables affecting survival.Results In total, 30 studies were selected. Survival rates in included studies greater than three years in length were 73.1-100%, with a median survival of 92.5% and median follow-up length of 5.1 years. The most prevalent failure mode was fracture, followed by pulpal episodes, debonding and caries. The most prevalent deterioration criteria were loss of marginal integrity and discolouration.Conclusions Survival of direct resin composite onlays and indirect tooth-coloured adhesive onlays in posterior teeth is acceptable (73.1-100%) in the medium-term. There is a need for more studies on direct cusp covering resin composite restorations, zirconia onlays and studies comparing material types. Fracture was the most prevalent failure mode. Restoration margins were the most prevalent area of deterioration.Clinical significance Direct and indirect tooth-coloured adhesive onlays can be a reliable and more conservative way to restore posterior teeth across a range of material options.

Triacrylamide-Based Adhesives Stabilize Bonds in Physiologic Conditions

In this study, an acrylamide-based adhesive was combined with a thiourethane-based composite to improve bond stability and reduce polymerization stress, respectively, of simulated composite restorations. The stability testing was conducted under physiologic conditions, combining mechanical and bacterial challenges. Urethane dimethacrylate was combined with a newly synthesized triacrylamide (TMAAEA) or HEMA (2-hydroxyethyl-methacrylate; control) to produce a 2-step total-etch adhesive system. Methacrylate-based composites (70 wt% silanized filler) were formulated, containing thiourethane oligomers at 0 (control) or 20 wt%. Standardized preparations in human third molars were restored; then, epoxy replicas were obtained from the occlusal surfaces before and after 7-d storage in water or with Streptococcus mutans biofilm, which was tested after storage in an incubator (static) or the bioreactor (mechanical challenge). Images were obtained from the replicas (scanning electron microscopy) and cross sections of the samples (confocal laser scanning microscopy) and then analyzed to obtain measurements of gap, bacterial infiltration, and demineralization. Microtensile bond strength of specimens stored in water or biofilm was assessed in 1-mm2 stick specimens. Data were analyzed with analysis of variance and Tukey's test (α = 0.05). HEMA-based materials had greater initial gap measurements, indicating more efficient bonding for the acrylamide materials. When tested in water, the triacrylamide-based adhesive had smaller gaps in the incubator or bioreactor. In the presence of biofilm, there was less difference among materials, but the acrylamide/thiourethane combination led to statistically lower gap formation in the bioreactor. HEMA and TMAAEA-based adhesives produced statistically similar microtensile bond strengths after being stored in water for 7 d, but after the same period with biofilm-challenged specimens, the TMAAEA-based adhesives were the only ones to retain the initial bond strength values. The use of a stable multiacrylamide-based adhesive led to the preservation of the resin-dentin bonded interface after a physiologically relevant challenge. Future studies will include a multispecies biofilm model.

Effects of Charcoal Toothpaste on the Surface Roughness, Color Stability, and Marginal Staining of Resin Composites

OBJECTIVE

This study was designed to evaluate the effects of charcoal toothpaste on the surface roughness, color stability, and marginal staining of resin composite restorations.

METHODS

A total of 100 bovine incisors was collected. The crowns were sectioned and randomly divided into 10 groups (n=10) according to two study factors: toothpaste groups and nanoparticle resin composite groups. Five toothpastes-Bianco Pro Clinical (Bianco Oral Care, Uberlândia, MG, Brazil) - Control group; Bianco Carbon (Bianco Oral Care); NAT, Natural Suavetex Carvão Ativado (Suavetex, Uberlândia, MG, Brazil); Nano Action Black Be Emotion (Polishop, Jundiaí, SP, Brazil); and BIW, Black is White (Curaprox, Curaden AG, Kriens, Switzerland)-and two resin composites-Z350XT, Filtek Z350XT (3M Oral Care) and Vittra, Vittra APS (FGM, Joinville, SC, Brazil)-were used. Circular cavities with a diameter of 4 mm and a depth of 1 mm were prepared on the buccal face of the tooth crowns and restored with resin composites. The specimens were subjected to three months of simulated toothbrushing. The surface roughness (right angle [Ra], in micrometers [μm]) of the resin composites was measured before and after toothbrushing in five areas per specimen. The resin composite color and luminosity changes (ΔE and ΔL, respectively) were measured using reflectance spectroscopy (Vita EasyShade). Macro photographs were taken before and after toothbrushing to qualitatively analyze the marginal staining (MSt) of the resin composite restorations. Scanning electron microscopy (SEM) was performed before and after the simulated toothbrushing. Ra data were analyzed using two-way analysis of variance with repeated measures and the Tukey HSD test; MSt was analyzed using Kruskal-Wallis and Dunn tests (α=0.05), and the resin composite color change was analyzed using the clinically unacceptable level of ΔE > 3.3.

RESULTS

Simulated brushing increased Ra irrespective of the resin composite or toothpaste used. No significant differences were found in Ra between the control group and all groups on which the charcoal toothpastes were tested. A clinically unacceptable level of resin composite color change (ΔE>3.3) was found after the use of most charcoal toothpastes. Use of Bianco Carbon resulted in marginal staining similar to that of the control group and was lower than that of the other charcoal toothpastes. Vittra brushed with black toothpaste showed the highest marginal staining.

CONCLUSION

Use of charcoal toothpaste resulted in Ra values of resin composites similar to those found with conventional toothpastes. Charcoal toothpaste generally resulted in clinical resin composite color changes (ΔE). All charcoal toothpastes, except Bianco Carbon, caused marginal staining of the resin composite restorations.

Mechanical Behavior of Alkasite Posterior Restorations in Comparison to Polymeric Materials: A 3D-FEA Study

The present investigation evaluated the effect of the combination of different dental filling materials in Class I cavities under occlusal loading using three-dimensional finite elements analysis (FEA). Six computer-generated and restored models of a lower molar were created in the CAD software and compared according to the biomechanical response during chewing load condition. Two adhesively bonded bulk restorative materials [bulk-fill resin composite (BF) or Alkasite (Alk)] were evaluated with or without the presence of a base material below (flowable resin composite or glass ionomer cement). A food bolus was placed on the occlusal surface mimicking the compressive occlusal load (600 N) during the static linear analysis. The maximum principal stress (tensile) was calculated as stress criteria in enamel, dentin and restoration. All models showed high stresses along the enamel/restoration margin with a similar stress trend for models restored with the same upper-layer material. Stress values up to 12.04 MPa (Alk) or up to 11.12 MPa (BF) were recorded at the enamel margins. The use of flexible polymeric or ionic base material in combination with bulk-fill resin composite or Alk did not reduce the stress magnitude in dentine and enamel. Class I cavities adhesively restored with bulk-fill resin composite showed lighter stress concentration as well as Alk. Therefore, adhesively bonded Alk restoration showed a promising mechanical behavior when used with different base materials or as a bulk restoration for posterior Class I cavity.

Finite element analysis and nanomechanical properties of composite and ceramic dental onlays

The aim is to evaluate the mechanical properties of the composite and ceramic based indirect restorative materials used in dental treatments with scanning nanoindentation test (NT). Finite element analysis (FEA) was applied to investigate the stress distribution. Four hybrid composite materials; Indirect resin composite (IRC), Resin nanoceramic (RNC), Polymer infiltrated ceramic (PIC) and Zirconia-reinforced lithium-di-silicate (ZRC) were divided into two subgroups for NT (n = 20) and fracture test (n = 40). Statistical analyses were performed with independent t-test, ANOVA and post-hoc Tukey tests (p ≤ 0.05). The highest hardness, elasticity and fracture toughness were observed in ZRC (p = 0.001). Frequency of vertical root fractures in RNC and IRC were statistically lower than ZRC (p = 0.032). Reinforced CAD-CAM ceramics revealed higher mechanical properties compared with IRC materials. The FEA model for fracture mechanism of RNC demonstrated lowest stress values and uniform stress distribution amongst all groups, while ZRC and PIC presented the highest fracture toughness.

Composite repair: On the fatigue strength of universal adhesives

OBJECTIVES

To determine whether the composition of universal adhesives and the use of silane coupling agents could affect the fatigue strength of composite repair.

METHODS

Composite samples were aged in water at 37 °C for 90 days and bonded to fresh composite to produce twin-bonded bar-shaped composite specimens (2 × 2 × 12 mm). Five universal adhesives, a multistep composite repair system and a hydrophobic solvent-free resin associated to a separate silane coupling agent application were used for bonding. Composite samples were tested under 4-pointflexure initially at quasi-static loading (n = 12) followed by cyclic loading (n = 25). The stress-life fatigue behavior was evaluated following the staircase method at 4 Hz. The unfractured side of cyclic loaded beams were evaluated under SEM to determine crack initiation sites. Fatigue data was analyzed by ANOVA and Tukey test and Wilcoxon Rank Sum Test (α = 0.05).

RESULTS

Bonding protocols were unable to restore the cohesive strength of the nanofilled composite (p < 0.05). Fatigue testing was more discriminative to reveal discrepancies in composite repair than conventional quasi-static loading. While the composition of universal adhesives affected composite repair potential, the highest endurance limits occurred for the separate silane coupling agent application. Crack propagation sites were mostly located on the aged composite surface.

SIGNIFICANCE

Although a trend for simplification invariably overruns current adhesive dentistry, composite repair using solely universal adhesives may result in inferior repair potential. The additonal use of silane coupling agents remains as an important procedure in composite repairs.

One-year clinical evaluation of bulk-fill composite resin restorations plasticized by preheating and ultrasonics: A randomized clinical trial

Introduction:

Aim:

Methodology:

Results:

Conclusion:

Fatigue analysis of restored teeth longitudinally cracked under cyclic loading

OBJECTIVE

To investigate the fatigue behavior of restored teeth, in particular the mechanisms of longitudinal dentinal cracking under cyclic mechanical loading, using finite element analysis (FEA) and the stress-life (S-N) approach.

METHODS

Ten root-filled premolars restored with resin composites were subjected to step-stress cyclic loading to produce longitudinal cracks. Fracture loads and number of cycles completed at each load level were recorded. FEA was used to predict the stress amplitude of each component under the global cyclic load. Both intact and debonded conditions were considered for the dentin-composite interface in the FEA. The predicted stress concentrations were compared with the fracture patterns to help elucidate the failure mechanisms. The S-N approach was further used to predict the lifetimes of the different components in the restored teeth. Cumulative fatigue damage was represented by the sum of the fractions of life spent under the different stress amplitudes.

RESULTS

Longitudinal cracks were seen in ~50% of the samples with a mean fracture load of 770 ± 45 N and a mean number of cycles to failure of 32,297 ± 12,624. The longitudinal dentinal cracks seemed to start near the line angle of the cavity, and propagated longitudinally towards the root. The sum of fractions of life spent for the dentin-composite interface exceeded 1 after ~7000 cycles when that for dentin was much lower than 1, indicating that interfacial debonding would occur prior to dentin fracture. This was supported by micro-CT images showing widened interfacial space in the cracked samples. In the debonded tooth, FEA showed dentinal stress concentrations at the gingival wall of the cavity, which coincided with the longitudinal cracks found in the cyclic loading test. The sum of fractions of life spent for dentin was close to 1 at ~30,000 cycles, similar to the experimental value.

SIGNIFICANCE

Debonding of the dentin-composite interface may occur prior to longitudinal cracking of dentin in root-filled teeth under cyclic loading. The approximate time of occurrence for these events could be estimated using fatigue analysis with stresses provided by FEA. This methodology can therefore be used to evaluate the longevity of restoration designs for root-filled teeth.

Comparison of physical and biological properties of a flowable fiber reinforced and bulk filling composites

OBJECTIVE

To evaluate in vitro the mechanical, biological, and polymerization behavior of a flowable bulk-fill composite with fibers as a dispersed phase.

METHODS

EverX Flow™ (GC Corporation) (EXF), one conventional bulk-fill composite (Filtek™ Bulk Fill Posterior Restorative, 3 M (FBF)), and one flowable bulk composite without fibers (SDR® flow+, Dentsply (SDR)) were tested. Samples were characterized in terms of flexural strength (ISO 4049), fracture toughness (ISO 20795-1), and Vickers hardness. Polymerization stress and volumetric shrinkage were evaluated. The in vitro biological assessment was achieved on cultured primary Human Gingival Fibroblast cells (HGF). The cell metabolic activity was evaluated using Alamar Blue assay at 1, 3, and 5 days of contact to the 3 tested composite extracts (ISO 10993) and cell morphology was evaluated by confocal microscopy. Data were submitted to One-Way analysis of variance (ANOVA) and independent t-test (α = 0.05).

RESULTS

FBF showed statistically higher Vickers hardness and flexural modulus than EXF and SDR. However, EXF showed statistically higher K_IC than FBF and SDR. EXF had the statistically highest shrinkage stress values and FBF the lowest. Archimedes volumetric shrinkage showed significantly lower values for FBF as compared to the other two composites. Slight cytotoxic effect was observed for the three composites at day one. An enhancement of metabolic activity at day 5 was observed in cells treated with EXF extracts.

SIGNIFICANCE

EXF had a significantly higher fracture toughness validating its potential use as a restorative material in stress bearing areas. EXF showed higher shrinkage stress values, and less cytotoxic effect. Fiber reinforced flowable composite is mainly indicated for deep and large cavities, signifying the importance for assessing its shrinkage stress and biological behavior.

Influence of minimally invasive endodontic access cavities and bonding status of resin composites on the mechanical property of endodontically-treated teeth: A finite element study

OBJECTIVE

To study the mechanical behavior of endodontically-treated teeth with minimally invasive endodontic access cavities and resin composite restorations under different bonding conditions using finite element analysis (FEA).

METHODS

Four Class-II endodontic access cavities including the mesio-occlusal minimally-invasive (MO-MIE), mesio-occlusal conventional (MO-CONV), disto-occlusal minimally-invasive (DO-MIE), and disto-occlusal conventional (DO-CONV) cavities were prepared in 3D-printed maxillary first molars. Each tooth was subjected to root canal preparation and scanned using micro-CT to provide a 3D structural model which was virtually restored with resin composite. An intact 3D-printed molar was used as control. FEA was conducted under a 250-N vertical load. Three different interfacial bonding conditions between dentin/enamel and resin composite were considered, i.e. fully bonded, partially debonded, and fully debonded. The maximum principal stress of dentin and the normal tensile stress at the interfaces were recorded. The risk factor of failure for each component was then calculated.

RESULTS

In the fully-bonded tooth, the dentin-composite interface showed significantly higher stress and a higher risk factor than dentin, indicating that debonding at the dentin-composite interface would occur prior to dentin fracture. With the dentin-composite interface debonded, the enamel-composite interface exhibited higher stress and a higher risk factor than dentin, indicating that debonding at the enamel-composite interface would occur next, also prior to dentin fracture. With the resin composite fully debonded from the tooth, stress in dentin increased significantly. Irrespective of the bonding status, the CONV groups exhibited higher median stresses in dentin than the MIE groups.

SIGNIFICANCE

Within the limitation of this study, it was shown that debonding of the resin composite restoration increased the stress in dentin and hence the risk of dentin fracture in endodontically-restored teeth. Minimally-invasive access cavities could better safeguard the fracture resistance of interproximally-restored teeth compared to conventional ones.

Placement of Posterior Composite Restorations: A Cross-Sectional Study of Dental Practitioners in Al-Kharj, Saudi Arabia

Dental practitioner-related factors can affect the quality of composite restorations. This study aimed to investigate the clinical techniques used by dental practitioners (DPs) while placing direct posterior composite restorations. Methods: A questionnaire survey that sought information related to the placement of posterior composite restorations was delivered to 161 DPs working in the Al-Kharj area, Saudi Arabia. The collected data were statistically analyzed using Pearson’s Chi-square test and Fisher’s exact test considering the DP’s working sector and the answered questions. Results: A total of 123 DPs completed the survey (76.4% response rate). There was a statistically significant difference between DPs working in the private sector and those working in the governmental sector in 7 out of 17 questionnaire items namely: preparing a minimum depth of 2 mm, (p = 0.001); mechanical means of retention, (p = 0.003); operative field isolation, (p = 0.004); adhesive strategy, (p < 0.001); light-curing unit used, (p = 0.013); the use of radiometer, (p = 0.023), and dental matrix selection, (p < 0.001). Conclusion: The clinical techniques applied by DPs working in the private sector in Al-Kharj, Saudi Arabia when placing posterior composite restorations, including the specifications of cavity preparation, operative field isolation, and selection of the dental matrix system, may be substandard compared to those applied by DPs working in the governmental sector.

[Morphology accuracy evaluation of direct composite occlusal veneer using two types of modified stamp-technique]

OBJECTIVE

To evaluate the morphology accuracy of direct occlusal veneer using two types of modified stamp-technique, comparing the Results of two types of stamp and different composite resin.

METHODS

Model scanner was used to get the original data from the standard resin teeth in plastic model. Two types of stamps were made: solid silicon stamp and transparent silicon stamp. In the study, 54 resin tooth were randomly divided into 9 groups: Groups 1-8 were restored by direct composite resin, using general and bulk-filled composite resin in occlusal veneer (1 mm or 2 mm) with two types of stamp-technique (the solid silicon, and the transparent silicon), and the control group was restored by indirect way using CAD/CAM composite resin restoration by biocopy technique to mimic the original shape of the teeth. After the resin teeth were prepared for occlusal veneer, the direct and indirect composite resins were restored. After the restoration was finished, the data were obtained again by the same model scanner in the plastic model. 3D comparisons were made using the original and restoration data, the average difference and the root mean square of difference (RMS) were recoded from the software. The RMS of all the groups were analyzed using one way ANOVA (α=0.05).

RESULTS

The RMS of occlusal surface in solid silicon stamp group was (0.136±0.031) mm, in transparent silicon group was (0.130±0.024) mm, and in control group was (0.130±0.009) mm. There were no significant difference. While the RMS of buccal/lingual surface in solid silicon stamp group was the smallest [(0.135±0.020) mm, P < 0.05], and in transparent silicon group it was (0.147±0.021) mm, and control group (0.153±0.014) mm. The general composite resin using the two types of stamp had the largest occlusal RMS in 2 mm occlusal veneer, which were significantly larger than control group (P < 0.05).

CONCLUSION

The direct occlusal veneer using two types of modified "stamp-technique" had relatively good morphology accuracy. Direct occlusal veneer using bulk-filled composite resin made with two types of stamp technique had even more accurate morphology than using general composite resin. The solid silicon stamp had a better morphology accuracy in buccal/lingual surface than the transparent silicon stamp.

Thirty-six-month clinical evaluation of posterior high-viscosity bulk-fill resin composite restorations in a high caries incidence population: interim results of a randomized clinical trial

OBJECTIVES

This study compared the clinical performance of two bulk-fill (BF) and one conventional resin composite in a population with a high caries incidence.

MATERIALS AND METHODS

A total of 138 class I and II restorations were performed and randomly divided into three groups (n = 46) with equal allocation: Filtek BF (FBF; 3M ESPE), Tetric EvoCeram BF (TBF; Ivoclar Vivadent), and control Filtek Z250 (Z250; 3M ESPE). The evaluations were performed using the USPHS and FDI criteria at baseline and after 12 and 36 months by a previously calibrated evaluator. The Friedman and Wilcoxon tests for paired data were used for statistical analysis (α = 0.05).

RESULTS

The DMFT index at baseline was 9.44, with 87% from the decayed component. After 36 months, 108 restorations (n = 36) were evaluated. Two failures were observed for TBF at marginal adaptation and recurrence of caries, resulting in a survival rate of 94.44% and an annual failure rate (AFR) of 1.26%. No equivalence was observed between the criteria for surface roughness, marginal adaptation, and discoloration.

CONCLUSIONS

The 36-month clinical performance of high-viscosity BF resin composites was comparable to conventional incremental-filled resin composites. The FDI criteria better presented the restorations' clinical success. However, in the case of failure, both criteria provided the same result.

CLINICAL RELEVANCE

High-viscosity bulk-fill resin composites showed excellent performance after 36 months in a high caries incidence population. It can be considered a simplified alternative restoration method that reduces operating time and minimizes possible operator errors.

Back to the multi-step adhesive system: A next-generation two-step system with hydrophobic bonding agent improves bonding effectiveness

This study evaluated the bonding effectiveness of a newly developed two-step hydrophobic bonding material. Three groups using different bonding systems were compared: BZF group, using the new bonding system (BZF-29; GC, Tokyo, Japan); GPB group, using a one-step bonding system (G-Premio Bond; GC); and SE2 group, using a two-step bonding system (CLEARFIL SE Bond 2; Kuraray Noritake Dental, Tokyo, Japan). Microtensile bond strength (µTBS) was measured after storage in water for 24 h, 3 months and 6 months (n=25/group). Fracture surfaces were observed under scanning electron microscopy. The BZF group showed significantly higher µTBS than the other groups (p<0.001). Dominant failure patterns were cohesive failure for the BZF group (48-84%), mixed failure for the SE2 group (48-60%) and interface failure between adhesive and resin composite for the GPB group (48-52%). The hydrophobicity of the BZF-29 bonding system improves the long-term bonding effectiveness between adhesive and resin composite.

Effect of Shrinking and No Shrinking Dentine and Enamel Replacing Materials in Posterior Restoration: A 3D-FEA Study

The aim of the present study was to investigate the effect of shrinking and no shrinking dental filling materials combination in posterior restorations under the combined effects of polymerization shrinkage and occlusal load by means of 3D Finite Elements Analysis. Six computer-generated and restored class I or class II cavities models of a lower molar were designed in the CAD software and evaluated according to the cavity and restorative procedure. Different shrinking and no shrinking adhesive materials combination with diverse Young’s modulus were considered. A food bolus was modeled on the occlusal surface replicating the chewing load using static linear analyses Polymerization shrinkage was simulated for the shrinking different restorative materials. The maximum principal stress was selected as analysis criteria. All models exhibited higher stresses along the dentine restoration interfaces with different magnitude and a similar stress trend along enamel restoration interface. Stress values up to 22 MPa and 19 MPa were recorded in the enamel and restoration, respectively. The use of elastic not shrinking material layer in combination with bulk fill composite reduced the stress magnitude in dentine and enamel to replace dental tissues. Class I and class II posterior cavities adhesively restored with shrinking filling material’s combination showed the most unfavorable stress concentrations and the multilayer technique is a promising restorative alternative in posterior adhesive restorations when deep dentin and enamel volumes are missing.

Pulp survival after composite resin restoration of caries lesions in adults

Minimal intervention is generally achieved by using direct composite resin (CR) restorations. However, deep caries lesions may lead to pulpal complications. This study evaluated the risk of endodontic complications after CR restoration in relation to depth of caries lesions. Data on 507 teeth from 316 adults treated with CR were analyzed. Caries depth was expressed as a percentage of the distance between the outer edge of the dental enamel and the pulp base on preoperative radiographs. The interval between CR restoration and follow-up root canal treatment was obtained from electronic treatment records for a period of 24 months. A Cox proportional hazards model was used to investigate the association between risk of endodontic complications and caries depth. Sixteen teeth (3.2%) required root canal treatment within 24 months. No root canal treatment was required after CR treatment for caries affecting <50% of the outer edge of enamel and pulp. As compared with CR treatment of caries lesions with a size of <80%, there was a significantly higher risk of root canal treatment for caries lesions with a size of 80% to 89% (hazard ratio, [95% CI]: 34.68 [4.23-284.11]) and ≥90% (92.01 [10.36-817.41], respectively).

Effect of Layering Techniques on Polymerization Shrinkage Stress of High- and Low-viscosity Bulk-fill Resins

CLINICAL RELEVANCE

The use of layering techniques is still advisable with many bulk-fill resins and should be the default unless a particular resin is known to not need it.

SUMMARY

Objective: The purpose of this study was to investigate how layering techniques affect polymerization shrinkage stresses of high-and low-viscosity bulk-fill resins.Method: Six high-viscosity and six low-viscosity bulk-fill resins were evaluated. Aluminum blocks with a mesial-occlusal-distal (MOD) cavity were machined and randomly divided into groups for different filling techniques (bulk-fill vs horizontal layering vs oblique layering) and further subdivided according to type of resin (high- vs low-viscosity). The cuspal deflection resulting from the polymerization of bulk-fill resin bonded to a MOD cavity within an aluminum block was measured with a digimatic micrometer. Scanning electron microscopy analyses of tested resins were also conducted.Results: In the high-viscosity bulk-fill resins, cuspal deflection of the MOD cavity ranged from 11.2 to 18.2 μm with the bulk-filling technique, from 10.7 to 15.5 μm with the horizontal layering technique, and from 10.9 to 15.2 μm with the oblique layering technique. In the low-viscosity bulk-fill resins, cuspal deflection of the material ranged from 9.2 to 19.8 μm with the bulk-filling technique, from 8.2 to 15.7 μm with the horizontal layering technique, and from 8.4 to 16.4 μm with the oblique layering technique.Conclusion: Cuspal deflections for some high-and low-viscosity bulk-fill resins were significantly reduced by using layering techniques, but the resultant improvement of layering techniques was not applicable to all the bulk-fill resins used in this study.

The use of different adhesive filling material and mass combinations to restore class II cavities under loading and shrinkage effects: a 3D-FEA

3D tooth models were virtually restored: flowable composite resin + bulk-fill composite (A), glass ionomer cement + bulk-fill composite (B) or adhesive + bulk-fill composite (C). Polymerization shrinkage and masticatory loads were simulated. All models exhibited the highest stress concentration at the enamel-restoration interfaces. A and C showed similar pattern with lower magnitude in A in comparison to C. B showed lower stress in dentine and C the highest cusps displacement. The use of glass ionomer cement or flowable composite resin in combination with a bulk-fill composite improved the biomechanical behavior of deep class II MO cavities.

Treatment options for large posterior restorations: a systematic review and network meta-analysis

BACKGROUND

The best treatment option for large caries in permanent posterior teeth is still a matter of uncertainty in dental literature. The authors conducted a network meta-analysis to address the challenges related to rehabilitation of these teeth.

TYPES OF STUDIES REVIEWED

The authors selected prospective and retrospective studies that compared at least 2 different treatment alternatives for permanent teeth with a minimum of 5 years of follow-up. The authors searched databases from MEDLINE, Scopus, Cochrane Library, and Web of Science in October 2019 without language or year of publication restrictions.

RESULTS

From 11,263 studies identified, 43 studies fulfilled the eligibility criteria and were included in the final review. Only 13 studies were randomized controlled trials and were classified as low risk of bias. Gold (annual failure rate of 0.29%) and metal ceramic (annual failure rate of 0.52%) crowns performed better for indirect restorations and direct resin composite performed better for direct restorations (annual failure rate of 2.19%). The most substantial comparisons were between feldspathic and glass ceramics, followed by direct resin composite and amalgam; there were no statistically significant differences between these interventions. Results of the pairwise meta-analysis showed mainly glass ionomer as significantly more prone to failure than amalgam and direct composite resin.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

Reference standard direct and indirect materials except for glass ionomer can be used for restorations of large posterior caries.

[Factors influencing clinical application of bulk-fill composite resin]

Bulk-fill composite resin are simple to operate, and they reduce polymerization shrinkage and microleakage compare to traditional resin-based composites. However, their clinical application could be affected by numerous factors, such as the material itself, light curing, placement techniques, storage condition, and preheating. This review aimed to summarize the definitions, classifications, indications, clinical properties, and influencing factors of the clinical application of bulk-fill resin-based composites and discuss the ways to improve their clinical effectiveness.

Comparison of diode laser - Oral tissue interaction to different wavelengths. In vitro study of porcine periodontal pockets and oral mucosa

Background

The aim of this in vitro study was to evaluate the effect of diode lasers at different wavelengths and power settings in handmade incisions in periodontal pockets and in oral mucosa of porcine tissue considering thermal damage, necrosis and the affected area of the soft tissue.

Material and Methods

Combining the following laser wavelengths, 445nm, 532nm (KTP), 810nm, 980nm, 1064nm and 1470nm, and a power range from 0.5W to 2.0W in a continuous wave mode (CW), we made handmade incisions in porcine periodontal pockets and oral mucosa. After histological processing, we measured the area of ​​lost tissue, the area of ​​thermal damage and the area of ​​necrosis. Then, we performed ANOVA to evaluate the difference between groups and two-way ANOVA to identify the influence of the laser-type variables and the power on the results.

Results

We applied an ANOVA test to evaluate the results, where statistical analysis showed clear differences between the 1470nm and 810nm laser groups that refer to thermal damage and necrosis in the periodontal pocket surface. Regarding the oral mucosa surface, the 1064nm laser showed differences in the analysis of lost tissue. According to the applied power, all the variables we studied (lost tissue area, area of thermal damage and necrosis) showed higher values when using a power of 2.0W instead of 0.5W.

Conclusions

According to our results, the 810nm diode laser for oral soft-tissue biopsy using power ranges between 0.5W and 2W would be the best choice to avoid thermal damage in peri-incisional margins.

Key words:Laser surgery, soft tissue, diode laser, KTP laser, thermal damage, necrosis.

Effects of a 3D-printed orthosis compared to a low-temperature thermoplastic plate orthosis on wrist flexor spasticity in chronic hemiparetic stroke patients: a randomized controlled trial

Objective:

The aim of this study was to compare the effects of two kinds of wrist-hand orthosis on wrist flexor spasticity in chronic stroke patients.

Design:

This is a randomized controlled trial.

Setting:

The study was conducted in a rehabilitation center.

Participants:

A total of 40 chronic hemiparetic stroke patients with wrist flexor spasticity were involved in the study.

Interventions:

Patients were randomly assigned to either an experimental group (conventional rehabilitation therapy + 3D-printed orthosis, 20 patients) or a control group (conventional rehabilitation therapy + low-temperature thermoplastic plate orthosis, 20 patients). The time of wearing orthosis was about 4–8 hours per day for six weeks.

Main measures:

Primary outcome measure: Modified Ashworth Scale was assessed three times (at baseline, three weeks, and six weeks). Secondary outcome measures: passive range of motion, Fugl-Meyer Assessment score, visual analogue scale score, and the swelling score were assessed twice (at baseline and six weeks). The subjective feeling score was assessed at six weeks.

Results:

No significant difference was found between the two groups in the change of Modified Ashworth Scale scores at three weeks (15% versus 25%, P = 0.496). At six weeks, the Modified Ashworth Scale scores (65% versus 30%, P = 0.02), passive range of wrist extension ( P < 0.001), ulnar deviation ( P = 0.028), Fugl-Meyer Assessment scores ( P < 0.001), and swelling scores ( P < 0.001) showed significant changes between the experimental group and the control group. No significant difference was found between the two groups in the change of visual analogue scale scores ( P = 0.637) and the subjective feeling scores ( P = 0.243).

Conclusion:

3D-printed orthosis showed greater changes than low-temperature thermoplastic plate orthosis in reducing spasticity and swelling, improving motor function of the wrist and passive range of wrist extension for stroke patients.