Biomechanical behaviour of bulk-fill resin composites in class II restorations

Marginal integrity and physicomechanical properties of a thermoviscous and regular bulk-fill resin composites

OBJECTIVES

To evaluate the marginal integrity (MI%) and to characterize specific properties of a thermoviscous bulk-fill resin composite, two regular bulk-fill resin composites, and a non-bulk-fill resin composite.

MATERIALS AND METHODS

VisCalor bulk (VBF), Filtek One Bulk Fill (OBF), and Aura Bulk Fill (ABF) were evaluated. Filtek Z250 XT (ZXT) was used as non-bulk-fill control. MI% was evaluated in standardized cylindrical cavities restored with the composites by using a 3D laser confocal microscope. The following properties were characterized: volumetric polymerization shrinkage (VS%), polymerization shrinkage stress (Pss), degree of conversion (DC%), microhardness (KHN), flexural strength (FS), and elastic modulus (EM). Data were analyzed by one-way and two-way ANOVA, and Tukey HSD post-hoc test (α = 0.05).

RESULTS

VBF presented the highest MI% and the lowest VS% and Pss (p < 0.05). DC% ranged from 59.4% (OBF) to 71.0% (ZXT). ZXT and VBF presented similar and highest KHN than OBF and ABF (p < 0.05). ABF presented the lowest FS (p < 0.05). EM ranged from 5.5 GPa to 7.7 GPa, with the values of ZXT and VBF being similar and statistically higher than those of OBF and ABF (p < 0.05).

CONCLUSIONS

Thermoviscous technology employed by VisCalor bulk was able to improve its mechanical behavior comparatively to regular bulk-fill resin composites and to contribute to a better marginal integrity in restorations built up in cylindrical cavities with similar geometry to a class I cavity as well. Although presenting overall better physicomechanical properties, Z250 XT presented the worst MI%.

CLINICAL RELEVANCE

The marginal integrity, which is pivotal for the success of resin composite restorations, could be improved using VisCalor bulk-fill. The worst MI% presented by Z250 XT reinforces that non-bulk-fill resin composites shall not be bulk-inserted in the cavity to be restored.

Clinical performance of different bulk-fill composite resin systems in class II cavities: A 2-year randomized clinical trial

OBJECTIVES

This study evaluated the clinical performance of bulk-fill resin composite systems with different viscosities in class II cavities.

MATERIALS AND METHODS

A total of 80 class II restorations were performed with a single operator in 50 patients using four different bulk-fill resin composite materials: Filtek™ Bulk Fill, Heated Filtek™ Bulk Fill, G-ænial™ BULK Injectable, and SonicFill3. A double-blinded randomized clinical trial was designed to evaluate the two-year clinical performance of the four bulk-fill composite resins using modified FDI criteria. Data were analyzed descriptively. Level of significance was set at 0.05. Differences between groups were tested using Wilcoxon-signed-rank and Mann-Whitney-U test as nonparametric tests.

RESULTS

Data were analyzed using Kruskal-Wallis, Mann-Whitney U, and Wilcoxon signed rank tests (p < 0.05). Eighty restorations were available for evaluation, with a survival function of 100%. No statistically significant differences were observed between the four groups regarding assessing esthetic, functional, and biological properties during different follow-up periods.

CONCLUSIONS

After 2 years of clinical follow-up, the bulk-fill composite systems with different viscosities seem to be esthetically, functionally, and biologically acceptable, with a promising clinical performance in class II cavities.

Marginal integrity in minimally invasive molar resin composite restorations: Impact of polymerization shrinkage

OBJECTIVES

This study utilized non-linear finite element (FE) models to explore polymerization shrinkage and its impact on marginal integrity in molars following both selective caries removal (SCR) and conventional treatment. Specifically, we performed 2D in silico simulations to study residual stresses post-resin polymerization shrinkage and their influence on the marginal integrity of various restoration types.

METHODS

Initially, FE models were developed based on a cohesive zone framework to simulate crack propagation along the bonded interfaces between restoration and tooth structure in SCR-treated molars with class I and class II restorations. The modeled resin composite restorations first underwent polymerization shrinkage and were then subjected to various occlusal loading conditions. Stress magnitudes and distributions were identified to evaluate the margin integrity and predict the mechanism and location of interfacial failure.

RESULTS AND DISCUSSION

The FE models computed polymerization shrinkage stresses of less than 1 MPa, exerting a minor influence on the composite/tooth interface. Occlusal loading, however, significantly impacted the load-bearing capacity of the composite/tooth (c/t) interface, potentially jeopardizing the restoration integrity. Especially under bi-axial occlusal loading, interfacial debonding occurred in the vertical cavity walls of the class I restorations, increasing the risk of failure. Notably, SCR-treated teeth exhibited better margin integrity than restored teeth after complete caries removal (NCR). These findings provide valuable insights into the mechanical behavior of SCR-treated teeth under different loading conditions and highlight the importance of considering the load scenarios that may lead to failure at the c/t interface. By investigating the factors influencing crack initiation and delamination, this novel research contributes to the optimization of restorative treatments and aids in the design of more resilient dental restorations.

In-vitro evaluation of fracture resistance of teeth restored with different high-viscosity glass ionomer restorative materials and bulk-fill composite resins

OBJECTIVES

This study aimed to evaluate the effect of restorations made with a glass-hybrid restorative system (GHRS), a high-viscosity glass ionomer restorative material (HVGIC), a high-viscosity bulk-fill composite resin (HVB), a flowable bulk-fill composite resin (FB), and a nanohybrid composite resin (NH), which are commonly preferred in clinical applications on the fracture resistance of teeth in-vitro.

MATERIALS AND METHODS

One hundred intact human premolar teeth were included in the study. The teeth were randomly divided into ten groups (n = 10). No treatment was applied to the teeth in Control group. Class II cavities were prepared on the mesial surfaces of the remaining ninety teeth in other groups. For restoration of the teeth, a GHRS, a HVGIC, a HVB, a FB, and a NH were used. Additionally, in four groups, teeth were restored using NH, GHRS, and HVGIC with open and closed-sandwich techniques. After 24 h, fracture resistance testing was performed. One-way ANOVA and Tukey HDS tests were used for statistical analysis of the data.

RESULTS

The fracture resistance values of Control group were statistically significantly higher than those of GHRS, HVGIC, FB, NH, HVGIC-CS, GHRS-OS, and HVGIC-OS groups(p < 0.05). There was no statistically significant difference observed between the fracture resistance values of Control, HVB, and GHRS-CS groups (p > 0.05).

CONCLUSION

It can be concluded that the use of HVB and the application of GHRS with a closed-sandwich technique may have a positive effect on the fracture resistance of teeth in the restoration of wide Class II cavities.

CLINICAL RELEVANCE

The use of high-viscosity bulk-fill composite resin and the application of glass-hybrid restorative system with the closed-sandwich technique in the restoration of teeth with wide Class II cavities could increase the fracture resistance of the teeth.

Comparison between Different Bulk-Fill and Incremental Composite Materials Used for Class II Restorations in Primary and Permanent Teeth: In Vitro Assessments

INTRODUCTION

Several advantages, including improved aesthetics and conservative cavity preparation, made resin-based composite (RBC) a popular restorative material. However, several limitations come with RBC restorations such as the necessity for proper isolation of the tooth and an incremental layering for the material due to the limitations of the depth of cure. Despite these advantages and limitations, the usage of these restorative materials is increasingly being expanded due to the advancement made since their introduction. To overcome some of the limitations, several types of RBC restorations were developed.

MATERIALS AND METHODS

Four different RBC materials used for class II restorations in primary and permanent teeth were compared: Z350 XT Filtek™ Universal Restorative (ZXT), Filtek™ Bulk Fill Flowable Restorative (FBF), Beautifil-Bulk Flowable (BBF) and Tetric™ N-Flow (TNF). Flexure strength, elastic modulus, surface roughness, microhardness and microleakage were assessed using standard methods or previously published protocols. The data and differences between the groups were analyzed using One-way analysis of variance (ANOVA), Tukey's multiple comparisons, Kruskal-Wallis and Wilcoxon rank-sum (Mann-Whitney) tests.

RESULTS

The study found that BBF (86.24 ± 7.41 MPa) and ZXT (64.45 ± 11.52 MPa) had higher flexural strength than FBF (50.89 ± 8.44 MPa) and TNF (50.67 ± 9.40 MPa), while both exhibited the highest values of surface roughness. Elastic modulus was the highest with BBF, which was not statistically significant from FBF or ZXT (p > 0.05). ZXT (109.7 ± 7.83 VH) exhibited the highest value of microhardness, which was statistically significant from the other three materials (p < 0.0001). Microleakage was assessed after thermocycling for 20,000 cycles to simulate two years in the mouth. FBF (70%) exhibited the most resistance to microleakage.

CONCLUSIONS

Different types of RBC restorations exhibit different characteristics. The clinician needs to choose the most appropriate restorative material based on different clinical scenarios.

Comparison of Shear Bond Strength and Microleakage between Activa™ Bioactive Restorative™ and Bulk-Fill Composites-An In Vitro Study

Bioactive materials have emerged as a promising alternative to conventional restorative materials as part of more conservative dentistry. The aim of this study was to evaluate and compare the shear bond strength (SBS) and microleakage of a new bioactive restorative material, two bulk-fill restorative composites, and a conventional composite at 24 h, 4 weeks, and 8 weeks. Three hundred and sixty molars and premolars were divided into four groups: ACTIVA™ BioACTIVE Restorative™, Filtek™ Bulk-Fill Restorative Composite, Tetric^® N-Ceram Bulk-Fill Composite, and G-aenial^® Composite. The normality of the data was determined with the Kolmogorov-Smirnov test, then the two-way ANOVA and Fisher's test were used for analyzing SBS data, and the Kruskal-Wallis and DSCF tests were conducted to analyze the microleakage. In the SBS test, there were no statistically significant differences between materials (p = 0.587), and the relation between material and time (p = 0.467), time points showed statistically significant differences (p = 0.016). As for the microleakage, statistically significant differences were found for all three time periods (p < 0.05), showing the conventional composite to have the lowest microleakage, followed by the bioactive material, and lastly the two bulk-fill composites. In conclusion, the new bioactive material has similar evaluated properties to bulk-fill composites (bond strength) and conventional composites (bond strength and microleakage) and can be used as an alternative restorative material.

Fracture resistance of defective amalgam restorations repaired with a resin-based composite material

BACKGROUND

Repair is used to increase the longevity of defective restorations, such as large amalgams. The aim of this study was to investigate the fracture resistance and fracture modes of mesio-occlusodistal (MOD) amalgam molar restorations with extensive cuspal fracture repaired or replaced using a bulk-fill resin-based composite material.

METHODS

Amalgam restorations were placed in 84 permanent extracted molars and randomly assigned (n = 14) to groups: (1) MOD amalgam, (2) composite repair of 1-cusp fracture and adjacent proximal box, (3) composite repair of 1-cusp fracture, (4) composite repair of 2-cusp fracture, (5) replacement of 1-cusp defect and existing MOD amalgam, (6) replacement of 2-cusp defect and MOD amalgam. Each molar was prepared to simulate the assigned fracture and either repaired or replaced. Specimens were aged and then loaded to fracture. Fracture resistance and fracture modes were recorded.

RESULTS

The authors found significant differences (P < .001) between group 4 (1,652.3 N) and groups 5 (3,095.0 N), 1 (2,669.8 N), 6 (2,658.6 N), and 2 (2,442.9 N) as well as between group 3 (2,133.5 N) and group 5 (3,095.0 N). The results of the Fisher exact test showed differences among groups (P < .001), with group 5 having the highest number of nonrestorable fractures as well as higher fracture resistance on average.

CONCLUSIONS

Composite material is a viable option for the repair and replacement of cuspal defects, especially in the case of a 1-cusp fracture and 1-cusp fracture involving the adjacent proximal box.

PRACTICAL IMPLICATIONS

Within the limitations of this study, the repair of cusp fractures in existing MOD amalgam-restored molars is an appropriate treatment option, although replacement of the defect and existing restoration with resin-based composite will withstand higher forces.

Bond strength of bulk-fill resin composites

 Aim: Evaluating the resin-dentin bond strength of Class II conventional and bulk-fill composite restorations, using different cavity sizes before and after aging. Methods: Seventy-five human molars were distributed into groups according to the buccolingual width of the cavities, conservative (n=25) and extended (n=50). They were divided according to the restorative material: conventional (Z100/control group) or bulk-fill resin composites (Filtek Bulk Fill/FBF; Tetric N Ceram Bulk Fill/TNCBF; Filtek Bulk Fill Flow/FBFF; Surefill SDR flow/SDR). The restored teeth were sectioned on sticks (n=50 per restorative materials + width cavities group), half were stored in Water/Ethanol 75% for 30 days and the other half were submitted to the immediate microtensile bond strength (μTBS) test. Data were analyzed applying the Three-Way Analysis of Variance (ANOVA), Bonferroni test, test t, and Weibull analyses (p<0.05). Results: SDR and FBF presented lower μTBS values for extended preparation when compared to the conservative preparation, before aging. After aging, only for the FBFF, a decrease in the μTBS values was observed. Comparing the μTBS values, before and after aging, the SDR demonstrated lower μTBS values after aging when the conservative cavity was used. A decrease in the μTBS values was observed for the Z100, the FBF and, the FBFF, after aging, when the extended cavity was used. Conclusion: The effect of cavity preparation and aging on the resin-dentin of Class II is material dependent. Most of the bulk-fill resin composites evaluated presented a similar performance to the conventional resin composites for all the conditions of this study.

Effects of wall compliance and light-curing protocol on wall deflection of simulated cavities in bulk-fill composite restoration

Background/purpose

Cuspal deflections in composite restoration have been investigated with considering wall compliance of human tooth cavity and light-curing protocol. The purpose of this study was to investigate effects of mold wall compliance and radiant emittance of LED light on the wall deflection of simulated aluminum mold cavities restored with a bulk-fill composite.

Materials and methods

Sixty aluminum molds simulating a class II mesio-occluso-distal (MOD) cavity (6 W × 8 L × 4 D mm; W, width; L, length; D, Depth) were prepared and allocated to three groups with varying mold wall thicknesses of 1, 2, and 3 mm. The molds were bulk-filled with a bulk-fill composite and photo-cured. Four light-curing protocols were used: three duty ratios/exposure times: 100%/20 s, 50%/40 s, or an increasing mode (0 → 100%)/40 s with a pulse width modulated (PWM) LED curing light and one 20 s exposure time with a commercial LED light.

Results

Mean mold wall deflection at 2000 s decreased with increasing mold wall thickness (1, 2, and 3 mm) (p < 0.05). Wall deflections with 1- and 2-mm-thick molds exhibited no statistically significant differences among light-curing protocols (p > 0.05). However, in the 3-mm-thick mold, wall deflections with low radiant emittance were significantly lower than those with high radiant emittance (p < 0.05).

Conclusion

In composite restoration of class II MOD cavities, lowering the radiant emittance of LED light can reduce the mold wall deflection only in low compliance cavities.

Implementation in restorative treatments in public health: a 10-year analysis of resin composite procurement in Brazil

This study aims to assess the resin composite purchases in a public health system and understand the variables associated with its cost and with the decision-making process over a period of 10 years. Secondary data collection was performed using the Brazilian Healthcare Prices Database (BDHP) from 2010 to 2019. All conventional and bulk-fill composites were selected. Date of purchase, institution type and location, procurement modality, number of purchased items, manufacture, and unit prices were collected. A multiple linear regression model assessed the influence of price in the procurement variables, while a multinomial logistic regression compared purchase probabilities between the materials. In total, 18,138 observations were collected with 2,129,294 purchased units and a total cost of USD 43,504,260.00. Conventional composites appeared in 98.5% of the procurement process. Nanofilled conventional composites were the most purchased materials, with an increased probability of purchase over time, despite its higher prices. An increase in prices was predicted for bulk-fill materials when compared to conventional ones. The odds of purchasing this category increased by 3.14x for every price increase over the years. Sociodemographic and type of institution influences the prices and the probability of procurement in the healthcare system. Nanofilled and bulk-fill resin are increasingly included in clinical practice. These findings highlight possible modifications to the standard-of-care in restorative treatments and how the translation of knowledge may occur from the development of new materials to the clinical application considering the economic impact of these modifications.

Comparative evaluation of different adhesive strategies of a universal adhesive in class II bulk-fill restorations: A 48-month randomized controlled trial

OBJECTIVES

To compare the clinical performance of the universal adhesive used in etch-and-rinse (ER) and self-etch (SE) adhesive strategies for 48-month in class II bulk-fill restorations.

METHODS

A total of 84 class II bulk-fill resin composite (Tetric EvoCeram Bulk Fill) restorations were placed in 35 participants by one operator using the universal adhesive's (Adhese Universal VivaPen) etch-and-rinse or self-etch mode randomly. The restorations were evaluated by two calibrated examiners at baseline and after 6-, 12-, 24-, 36- and 48-month using modified USPHS criteria. The comparison of the two adhesive strategies for each evaluation criteria was performed with the chi-square test. The baseline scores were compared with those at the recalls using the Friedman and Cochran's Q-test (p < .05).

RESULTS

At 48-month, 74 restorations were evaluated in 30 participants (recall rate: 85.7%). Marginal discoloration was statistically more frequent in SE approach (p < .05), whereas no significant difference was observed between the two strategies in terms of marginal adaptation (p > .05). There were statistically significant differences between the baseline and 48-month recall in the SE group in terms of marginal adaptation and discoloration (p < .05). In ER group, significant differences were found between baseline and 48-month only for marginal adaptation (p < .05). None of the restorations showed post-operative sensitivity. Secondary caries was observed in one restoration from SE group.

CONCLUSIONS

The tested bulk-fill restorative exhibited better clinical performance only in terms of marginal discoloration when the universal adhesive was used with ER strategy.

CLINICAL RELEVANCE

Though ER approach of the tested universal adhesive appears to be advantageous in terms of marginal discoloration, both adhesive strategies had similar impact on the clinical success of bulk-fill resin restorations.

Bonding States of In Vitro Class 2 Direct Resin Composite Restoration Applied by Various Incremental Techniques

Incremental techniques are always required for clinical cases of deep and/or large cavities restored with resin composite materials. The purpose of this study was to examine the bonding states of class 2 direct resin composite restoration applied by various incremental techniques after cyclic loading to simulate the intra-oral environment to define the appropriate technique. Three types of resin composites, namely, bulk-fill (B), flowable (F), and conventional resin composite (C), were applied to standardized class 2 cavities by incremental techniques with single- or bi-resin restoratives. After cyclic loading, the micro-tensile bond strength (μ-TBS) of the dentin cavity floor was measured. The Weibull modulus and Weibull stress values at 10%/90% probability of failure were analyzed. Single-resin incremental restorations with B or F and bi-resin incremental restorations with F + B and F + C demonstrated superior μ-TBS (quantitative ability), bonding reliability, and durability (qualitative ability) compared with the single-resin restoration with C (as control). Furthermore, F + B and F + C restoration yielded an excellent performance compared with the single-resin restorations with B, F, and C. In particular, the F + C restoration, which indicates not only the maximum mean µ-TBS, but also the highest values of the Weibull parameters, may be the optimal restoration method, including the esthetic benefits.

Effect of different coronal restorations on the fracture resistance of teeth with simulated regenerative endodontic treatment: An in vitro study

This study investigated the effect of different coronal restorations on the fracture resistance (FR) of immature teeth with simulated regenerative endodontic treatment. A total of 120 lower premolars were divided into eight groups. Except for negative control, the root canals were instrumented with rotary files and Peeso reamers. Fifteen instrumented teeth were acted as positive control (unrestorated). In the remaining 90 teeth, regenerative endodontic treatment procedures were performed. Ninety teeth were randomly divided into 6 groups according to coronal restoration type; Filtek Z550, Filtek Bulk fill Restorative (FBR), SDR+Filtek Z550, EverX+Filtek Z550, Ribbond+FBR and Ribbond+SDR+Filtek Z550. After thermal ageing, the restorated teeth were subjected to vertical loading force. FR values was obtained as follows: Negative control > Ribbond+FBR = Ribbond+SDR+Filtek Z550 > Filtek Z550 = FBR =SDR+Filtek Z550 = EverX+Filtek Z550 > Positive control, (P < 0.05). The use of Ribbond in combination with composite resin enhanced the FR of teeth.

Fracture strength of extended class I composite restorations with different restorative techniques

To evaluate the fracture strength of extended Class I restorations with different restorative techniques using nanofilled and nanohybrid composites. Sixty extracted human third molars were prepared with extended Class I cavities and divided into six groups: groups FS-F (Filtek bulk-fill Flow + Filtek Supreme Ultra, 3 M) and GR-F (X-tra base + GrandioSO, VOCO), restored with a flowable bulk-fill composite as a base covered by a nanofilled or nanohybrid composite; groups FB (Filtek One Bulk-Fill, 3 M) and AF (Admira Fusion X-tra, VOCO), restored with a bulk-fill resin composite; and groups FS (Filtek Supreme Ultra, 3 M) and GR (GrandioSO, VOCO), restored incrementally with a nanofilled or nanohybrid composite. Sound extracted teeth (n = 10) were used as a control group (CTL). The specimens were axially loaded until failure. Data were analyzed using one-way ANOVA and Games Howell test (α = 0.05). Groups CTL and GR-F demonstrated significantly higher mean fracture strength when compared to FS, AF, and GR (p < 0.05). Group AF obtained more repairable fractures than the other groups. Restorations made with a nanofilled bulk-fill composite or with conventional resin composites associated with a flowable bulk-fill base were able to reestablish the fracture strength to that of sound teeth.

Six-year clinical evaluation of bulk-fill and nanofill resin composite restorations

OBJECTIVES

This study aims to compare the performance of a bulk-fill and a nanofill resin composite in class II restorations after 6 years.

MATERIALS AND METHODS

Fifty patients having at least two class II carious lesions were recruited for the study. One lesion in each patient was randomly assigned to be restored using either the Tetric EvoCeram Bulk Fill (TB) or Filtek Ultimate (FU) resin composites with their respective adhesives. One hundred four restorations were placed by two calibrated operators. Restorations were evaluated at baseline and annually over the course of 6 years by two examiners using modified USPHS criteria. Data were statistically analyzed using the Chi-square and Cochran Q tests (p < 0.05).

RESULTS

Sixty-six restorations in 33 patients were evaluated after 6 years. Only one restoration was lost from FU group at 5 years. At the end of 6 years, marginal discoloration was observed in three (9.1%) TB and eight (36.4%) FU restorations creating a significant difference between the groups (p < 0.05). The FU group showed a significant increase in marginal discoloration at 6 years from the baseline (p < 0.05). Marginal adaptation was rated as Bravo for 9.1% and 24.2% of TB and FU restorations, respectively (p > 0.05). Significant degradation was observed within each group in terms of marginal adaptation (p < 0.05). There were no statistically significant differences between the groups for the other criteria tested (p > 0.05).

CONCLUSIONS

Bulk-fill restorations performed better for marginal discoloration. The remaining clinical performance criteria of bulk-fill and nanofill resin composite restorations were similar after 6 years.

CLINICAL RELEVANCE

Bulk-fill resin might be a better alternative to incrementally placed restorative in terms of marginal discoloration under clinical conditions.

Effects of cuspal compliance and radiant emittance of LED light on the cuspal deflection of replicated tooth cavity

The aim was to investigate effects of compliance and radiant emittance on cuspal deflection. A mesio-occluso-distal cavity was replicated using a flowable composite and steel rods with different diameters. To investigate the effect of cuspal compliance on deflection, the replicated tooth and extracted human tooth cavities were bulk-filled with a micro-hybrid composite. The replicated cavities with 2.0-mm-diameter steel rods were restored with bulk-filling of the micro-hybrid or a nano bulk-fill composite and photo-cured with four protocols. The cuspal deflection was the highest in the replicated tooth without steel rod, followed by with 1.0-, 1.5-, and 2.0-mm steel rods, and significantly lower in the human tooth. Cuspal deflections showed no significant differences among light-curing protocols, and that in the micro-hybrid composite were higher than the nano bulk-fill composite. To reduce cuspal deflection of a high compliance cavity, selecting the proper composite based on physical properties is more important than light-curing protocol.

Clinical Effectiveness of Bulk-Fill and Conventional Resin Composite Restorations: Systematic Review and Meta-Analysis

The objective of this systematic review and meta-analysis was to determine the clinical effectiveness of bulk-fill and conventional resin in composite restorations. A bibliographic search was carried out until May 2020, in the biomedical databases Pubmed/MEDLINE, EMBASE, Scopus, CENTRAL and Web of Science. The study selection criteria were: randomized clinical trials, in English, with no time limit, with a follow-up greater than or equal to 6 months and that reported the clinical effects (absence of fractures, absence of discoloration or marginal staining, adequate adaptation marginal, absence of post-operative sensitivity, absence of secondary caries, adequate color stability and translucency, proper surface texture, proper anatomical form, adequate tooth integrity without wear, adequate restoration integrity, proper occlusion, absence of inflammation and adequate point of contact) of restorations made with conventional and bulk resins. The risk of bias of the study was analyzed using the Cochrane Manual of Systematic Reviews of Interventions. Sixteen articles were eligible and included in the study. The results indicated that there is no difference between restorations with conventional and bulk resins for the type of restoration, type of tooth restored and restoration technique used. However, further properly designed clinical studies are required in order to reach a better conclusion.

Direct resin composite restoration of endodontically-treated permanent molars in adolescents: bite force and patient-specific finite element analysis

Objective To evaluate the influence of three levels of dental structure loss on stress distribution and bite load in root canal-treated young molar teeth that were filled with bulk-fill resin composite, using finite element analysis (FEA) to predict clinical failure. Methodology Three first mandibular molars with extensive caries lesions were selected in teenager patients. The habitual occlusion bite force was measured using gnathodynamometer before and after endodontic/restoration procedures. The recorded bite forces were used as input for patient-specific FEA models, generated from cone-beam computed tomographic (CT) scans of the teeth before and after treatment. Loads were simulated using the contact loading of the antagonist molars selected based on the CT scans and clinical evaluation. Pre and post treatment bite forces (N) in the 3 patients were 30.1/136.6, 34.3/133.4, and 47.9/124.1. Results Bite force increased 260% (from 36.7±11.6 to 131.9±17.8 N) after endodontic and direct restoration. Before endodontic intervention, the stress concentration was located in coronal tooth structure; after rehabilitation, the stresses were located in root dentin, regardless of the level of tooth structure loss. The bite force used on molar teeth after pulp removal during endodontic treatment resulted in high stress concentrations in weakened tooth areas and at the furcation. Conclusion Extensive caries negatively affected the bite force. After pulp removal and endodontic treatment, stress and strain concentrations were higher in the weakened dental structure. Root canal treatment associated with direct resin composite restorative procedure could restore the stress-strain conditions in permanent young molar teeth.

The effect of individualization of fiberglass posts using bulk-fill resin-based composites on cementation: an in vitro study

Objectives

This study evaluated the bond strength of various fiberglass post cementation techniques using different resin-based composites.

Materials and Methods

The roots from a total of 100 bovine incisors were randomly assigned to 5 treatment groups: G1, post + Scotchbond Multi-Purpose (SBMP) + RelyX ARC luting agent; G2, relined post (Filtek Z250) + SBMP + RelyX ARC; G3, individualized post (Filtek Z250) + SBMP; G4, individualized post (Filtek Bulk-Fill) + SBMP; G5, individualized post (Filtek Bulk-Fill Flow) + SBMP. The samples were subjected to the push-out (n = 10) and pull-out (n = 10) bond strength tests. Data from the push-out bond strength test were analyzed using 2-way analysis of variance (ANOVA) with the Bonferroni post hoc test, and data from the pull-out bond strength test were analyzed using 1-way ANOVA.

Results

The data for push-out bond strength presented higher values for G2 and G5, mainly in the cervical and middle thirds, and the data from the apical third showed a lower mean push-out bond strength in all groups. No significant difference was noted for pull-out bond strength among all groups. The most frequent failure modes observed were adhesive failure between dentine and resin and mixed failure.

Conclusions

Fiberglass post cementation using restorative and flowable bulk-fill composites with the individualization technique may be a promising alternative to existing methods of post cementation.