Influence of Thermal and Mechanical Load Cycling on Fracture Resistance of Premolars Filled with Calcium Silicate Sealer

The aim of this study was to evaluate the aging effect of thermomechanical cyclic load on fracture resistance of lower premolars obturated with AH Plus and BioRoot RCS root canal sealers. Forty-eight single-rooted premolars teeth were instrumented with REVO-S files up to SU/0.06 taper. The teeth were randomly assigned into 2 main groups (n = 24) according to the selected two root canal sealers (AH Plus or BioRoot RCS). All teeth were obturated using matching gutta-percha. Each main group were further divided into 3 subgroups (A, B and C) (n = 8). Group A acted as the negative control group (non-Thermomechanical aging). Whereas Group B and C were subjected first to thermal variations in a thermal cycling machine (7500 and 15,000 thermal cycles), then two different dynamic loading periods namely 3 × 105 and 6 × 105 in a masticatory simulator with a nominal load of 5 kg at 1.2 Hz which simulate approximately 1 ½ and 3 years of clinical function respectively. The roots were decoronated and fracture resistance were measured using a universal testing machine. After thermal-mechanical aging, BioRoot RCS showed significantly higher fracture resistance (p p < 0.05). It could be concluded that thermomechanical aging had a significant impact on the outcome of the fracture resistance of AH Plus and BioRoot RCS

Influence of long -term thermal cycling and masticatory loading simulation on bond strength of roots filled with epoxy resin and calcium silicate based sealers

Abstract Background The aim of this study was to evaluate the effect of thermal and mechanical cyclic aging using a mastication simulator on push-out bond strength of mandibular premolars obturated with AH Plus and BioRoot RCS root canal sealers. Methods With REVO-S files up to SU/0.06 taper, 48 single-rooted premolar teeth were instrumented. The teeth were randomly divided into two main groups (n = 24) based on the two root canal sealers used (AH Plus and BioRoot RCS). All teeth were obturated with h matched-taper single-cone. Each main group was then subdivided into three subgroups (A, B, and C) (n = 8). Group A served as the negative control group (no-thermocycling aging). While groups B and C were subjected to thermal changes in a thermocycler machine (15,000 and 30,000 thermal cycles, respectively), followed by two different dynamic loading periods, 3 × 105 and 6 × 105 in a masticatory simulator with a nominal load of 5 kg at 1.2 Hz which represent roughly 1½ and 3 years of clinical function respectively. 2 mm slice at 3 levels, apical, middle, and coronal, to obtain 3 sections were prepared and subjected to push-out test using a universal testing machine. Statistical analysis was performed using analysis of variance (ANOVA) followed by a Tukey post hoc comparisons test and an independent T-test. A significance level of 5% was used. Results After thermal–mechanical cyclic aging, the two root canal sealers showed a significantly decreased in push-out bond strength (p < 0.05), however, AH Plus had significantly higher bond strength values than BioRoot RCS after cycling aging. Conclusions It could be concluded that thermal–mechanical cyclic aging had a significant impact on the outcome of the dislodgment resistance of AH Plus and BioRoot RCS

Stress analysis of loading conditions of 200 N vertical and oblique with 45° for BioRoot RCS and AH Plus cases without GP.

(a) Von Mises stress in BioRoot RCS only under vertical loading (b) Von Mises stress in BioRoot RCS only under oblique loading. (c) Von Mises stress in AH Plus only under vertical loading (d) Von Mises stress in AH Plus only under oblique loading.</p

Stress analysis of loading conditions of 200 N vertical and oblique with 45° for BioRoot RCS and AH Plus cases with GP.

(a) Von Mises stress in BioRoot RCS with GP under vertical loading (b) Von Mises stress in BioRoot RCS with GP under oblique loading. (c) Von Mises stress in AH Plus with GP under vertical loading (d) Von Mises stress in AH Plus with GP under oblique loading.</p

Material properties for FEA.

This research aimed to assess the stress distribution in lower premolars that were obturated with BioRoot RCS or AH Plus, with or without gutta percha (GP), and subjected to vertical and oblique forces. One 3D geometric model of a mandibular second premolar was created using SolidWorks software. Eight different scenarios representing different root canal filling techniques, single cone technique with GP and bulk technique with sealer only with occlusal load directions were simulated as follows: Model 1 (BioRoot RCS sealer and GP under vertical load [VL]), Model 2 (BioRoot RCS sealer and GP under oblique load [OL]), Model 3 (AH Plus sealer with GP under VL), Model 4 (AH Plus sealer with GP under OL), Model 5 (BioRoot RCS sealer in bulk under VL), Model 6 (BioRoot RCS in bulk under OL), Model 7 (AH Plus sealer in bulk under VL), and Model 8 (AH Plus sealer in bulk under OL). A static load of 200 N was applied at three occlusal contact points, with a 45° angle from lingual to buccal. The von Mises stresses in root dentin were higher in cases where AH Plus was used compared to BioRoot RCS. Furthermore, shifting the load to an oblique direction resulted in increased stress levels. Replacing GP with sealer material had no effect on the dentin maximum von Mises stress in BioRoot RCS cases. Presence of a core material resulted in lower stress in dentin for AH Plus cases, however, it did not affect the stress levels in dentin for cases filled with BioRoot RCS. Stress distribution in the dentin under oblique direction was higher regardless of sealer or technique used.</div

Fig 1 -

Model geometries from Solid Works screen; (a) Crown, (b) Composite resin, (c) GP, (d) Sealer, (e) Dentine, (f) PDL, (g) Cancellous bone, and (h) Cortical bone.</p

Maximum von Mises stresses in MPa in dentin and sealer, GP: Gutta percha, VL: Vertical load, OL: Oblique load.

Maximum von Mises stresses in MPa in dentin and sealer, GP: Gutta percha, VL: Vertical load, OL: Oblique load.</p

Finite element data (construction, vertical and oblique load, and stress distribution).

Finite element data (construction, vertical and oblique load, and stress distribution).</p

Stress analysis of loading conditions of 200 N vertical and oblique with 45° for all AH Plus cases in different root levels.

Highest and lowest stress values are indicated by red and blue colours, respectively. (a) Von Mises stress in AH Plus with GP under vertical loading (b) Von Mises stress in AH Plus with GP under oblique loading (c) Von Mises stress in AH Plus only under vertical loading (d) Von Mises stress in AH Plus only under oblique loading.</p

Model description: Assembly, load location and boundary conditions.

Model description: Assembly, load location and boundary conditions.</p