Stress distribution of Class V composite resin restorations: A three-dimensional finite element study

Clinical Evaluation of Bioactive Restorative Material versus Resin Modified Glass Ionomer in Cervical Restorations: A Randomized Controlled Clinical Trial

Abstract: Objective: In the context of great attention given to fluoride containing restorative material and development of easily applied and reliable material for different clinical situations. This current study aimed to compare Bioactive resin-based composite (ACTIVA) to Resin modified glass ionomer (RMGI) in cervical restorations. Materials and methods:  Fuji II LC® capsules (conventional resin modified glass ionmer), or ACTIVA™ BioACTIVE-RESTORATIVE™ (enhanced resin-modified glass-ionmer) with using Etch-Rite™ and Prime&Bond universal (universal adhesive system) were applied randomly in thirty anterior teeth and six premolars with class V cavities; all materials were applied according to manufacturers’ instructions. Restorations were evaluated at baseline (one week), after six months, and after 12 months by two blinded assessors using modified USPHS criteria. Results:  The results in this study were ordinal data, so Mann-Whitney test was used to compare between tested materials. Freidman test was used to test the effect of time within tested materials. Kruskal Wallis test used to compare the interaction between variables for all tested parameters. The results were statistically significant when p≤0.05. There was no significant difference between interaction of both restorations and time in marginal discoloration (p=0.051), recurrent caries (p=1.00) and retention analysis (p=1.00), but there was a significant change in marginal adaptation (p=0.001), surface roughness (p=0.017), color change (p= 0.004) and surface luster (p=0.017) with 100 % survival rate in this study. Conclusions: Both conventional resin-modified glass ionmer and enhanced resin-modified glass ionomer are acceptable as intermediate restoration. Bioactive restorations proved to retain its esthetic characteristics over the conventional one. Bioactive restorations with an adhesive system can be used as long-term restoration in small-defined cavities, not in stress-bearing areas.   Clinical relevance: Within the limitations of this study, ACTIVA BIO-ACTIVE Restorative showed similar results to FUJI II LC in class V cavity restorations.  

Finite element analysis of V-shaped tooth defects filled with universal nanohybrid composite using incremental technique

The aim of the present paper is to study the stresses and strains in fillings of V-shaped tooth defects made of universal photo-cured nanohybrid composite (UPC) using incremental technique. Numerical modeling with FEA and microleakage test are performed. Inhomogeneous distribution of the equivalent Von Mises stresses after polymerization of the two UPC layers is found, as the maximal value after polymerization of the first layer is 1.5 times lower compared to that of second one. In the first layer, maximum stresses are concentrated on dentin surface in cervical region of the obturation border and in occlusal region of the obturation volume. In the second layer, maximum stresses are generated in cervical area of the obturation volume and on dentin surface occlusally along the obturation border. The displacement after polymerization of each layer is inhomogeneous, as its values are more than 2 times smaller compared to that in fillings of glass-ionomer cement and flowable composite. In the first layer, the displacement is maximal on surface in the cervical region, while in the second layer it is maximal on surface occlusal of the obturation. The adequacy of the model used is confirmed by the microleakage test results. It is proven that UPC is better choice for filling of V-shaped defects due to the lower microleakage.

Effects of Root Maturation and Thickness Variation in Coronal Mineral Trioxide Aggregate Plugs Under Traumatic Load on Stress Distribution in Regenerative Endodontic Procedures: A 3-dimensional Finite Element Analysis Study

INTRODUCTION

Regenerative endodontic procedures (REPs) are the best biological-based treatment choice for managing necrotic immature permanent teeth. This study aimed to evaluate the stress distribution of immature maxillary permanent incisors and periodontal tissues under a traumatic load after root maturation achieved by REP with thickness variation in coronal mineral trioxide aggregate (MTA) plugs.

METHODS

Five different mathematical 3-dimensional finite element analysis models of an immature permanent maxillary incisor were created. These involved immediate postoperative models after REP with varying coronal MTA plug thickness (model 1: 3-mm MTA and model 2: 5-mm MTA), postoperative models after REP with varying coronal MTA plug thickness with 15% volumetric root maturation (model 3: 3-mm MTA and model 4: 5-mm MTA), and a control model (model 5: a mature, healthy maxillary incisor). After the modeling procedures, a traumatic horizontal force load of 400 N was applied, and 3-dimensional finite element analysis was performed. The minimum principal, maximum principal, and von Mises stress criteria were calculated for evaluation.

RESULTS

Regardless of the coronal MTA plug thickness, tensile stress in cervical root surfaces decreased with root maturation after REP. Using the 5-mm MTA plug reduced all types of stress in the middle third of the root. In bone tissue, the difference in MTA thickness did not affect stress values. However, stress decreased in most of the bony surfaces with root maturation after REP.

CONCLUSIONS

Using the 5-mm coronal MTA plug may help in providing biomechanical advantages regarding stress transmission. Also, because root maturation after REP provided a more favorable stress distribution as mentioned, regenerative treatments can be recommended for immature permanent maxillary incisors for a good prognosis.

Are Increased Masticatory Forces Risk for Primary 2nd Molars without Successors? A 3D FEA Study

OBJECTIVE

Persistent primary teeth with healthy crown-root structures and acceptable functional and esthetic properties may be preserved over a long-term period if needed. However, they may experience root resorption, ankylosis or infraocclusion especially in the second or third decades of life. Despite a lack of sufficient detailed data, increases in occlusal forces by age are known to cause destructive stresses on root surfaces and periodontal tissue. The aim of this study was to evaluate the effect of increasing occlusal forces on mandibular persistent primary molars by using 3D finite element analysis.

STUDY DESIGN

The impact of increased masticatory forces on compressive and tensile stresses in tooth and surrounding tissue was simulated in two different models (simulating child and adult mouths) by using 3D finite element analysis.

RESULTS

In both models, the stress values increased by age and compressive stresses were seen on internal root surfaces, while the tensile stresses focused on the furcation area and external root surfaces.

CONCLUSION

It was concluded that practices such as reducing occlusal surface width may be used to diminish the occlusal forces for long-term tooth survival in persistent primary molars.