Effect of different endodontic access preparations on the biomechanical behavior of lithium disilicate and resin nanoceramic onlay restorations: An in vitro and 3D finite element analysis study

Effect of Cavity Designs on Instrumentation, Obturation, and Fracture Resistance of Mandibular First Premolars With Vertucci V Canal

INTRODUCTION

This study aimed to assess the effect of cavity designs on instrumentation, obturation and fracture resistance for mandibular first premolars with Vertucci V canal.

METHODS

Mandibular first premolars with Vertucci V canal were scanned with microcomputed tomography. A total of 20 teeth with moderately curved canal were prepared with conservative endodontic cavity (CEC/M) or traditional endodontic cavity (TEC/M), and 30 with severely curved canal were prepared with CEC (CEC/S), modified CEC (MCEC/S) or TEC (TEC/S). CECs and MCEC were prepared using dynamic navigation systems. TECs were prepared freehand. Canals were prepared with WaveOne Gold, irrigated and then obturated with single-cone technique using iRoot SP sealer and WaveOne Gold gutta-percha cones. After restoration, all teeth were submitted to fracture resistance test. Removal of pericervical dentin, volume of dentin removal, area of untouched canal wall, accumulated hard tissue debris, centering ability, voids in canal filling, and load at fracture were evaluated.

RESULTS

MCEC and CEC groups preserved more pericervical dentin above the alveolar bone level and more fracture resistance than TEC groups. At 3 mm from apical foramen, lower centering ability in mesiodistal direction was found in buccal canal of CEC/S group. More voids were found in the lingual canal for CEC/S compared with TEC/S (P < .05).

CONCLUSIONS

CEC and MCEC prepared with dynamic navigation system could preserve more dentin above the alveolar bone and fracture resistance than TEC prepared freehand. For teeth with severely curved V canal, MCEC showed similar ability in instrumentation and obturation as TEC.

Stress distribution in the closure of anterior maxillary diastemas using different restorative approaches: a finite element analysis

OBJECTIVE

This finite element analysis study aims to evaluate the effects of restoring 1 mm and 2 mm diastemas in maxillary anterior incisors with different CAD-CAM materials on stress distribution and to compare full crown and laminate veneer restorations.

MATERIALS AND METHODS

Maxillary anterior tooth models simulating laminate veneer and full crown restorations were created. The experimental groups were categorized into four based on diastema width (1 mm and 2 mm) and CAD-CAM materials. Loads of 50 N, 150 N, and 250 N were applied vertically at 0° and obliquely at 30° and 60° angles to the central incisor's incisal midpoint. Von Mises stress values were analyzed numerically and visually with color-coded comparisons for all models.

RESULTS

When laminate veneer restorations were used to close diastemas, the highest stress values under a 250 N vertical load and 2 mm diastema were observed in the lateral incisor. IPS E.max exhibited a stress value of 166.88 MPa for the superstructure, while Lava Ultimate recorded 35.49 MPa in the lateral incisor. Within the dentin, the highest stress was 45.92 MPa for IPS E.max and 65.74 MPa for Lava Ultimate in the lateral incisor. When full crown restorations were employed, the highest stress values under a 250 N vertical load were again recorded in the lateral incisor. IPS E.max showed a stress value of 198.03 MPa for the superstructure, while Lava Ultimate demonstrated 40.80 MPa. The highest stress values within the dentin were 65.20 MPa for IPS E.max and 65.74 MPa for Lava Ultimate in the lateral incisor.

CONCLUSIONS

This finite element analysis highlights that the type of restoration and diastema width significantly affect stress distribution in anterior teeth. IPS E.max material exhibited higher stress values, leading to more significant stress accumulation than other materials in laminate veneer and full crown restorations. Additionally, Lava Ultimate showed the highest stress values within the dentin. These findings underscore the importance of selecting appropriate CAD-CAM materials and restoration types to optimize stress distribution in diastema closures, providing critical insights for restoration planning.

Three-dimensional finite element analysis of the impact of access cavity preparation on first molar fracture resistance: A scoping review

Access cavity preparation represents the initial step in root canal treatment. Minimally invasive approaches have gained increasing attention and involve advancements in the traditional access cavity preparation. Simultaneously, the development of three-dimensional finite element analysis (3D-FEA) has provided a theoretical foundation for evaluating the merits and drawbacks of various access cavity preparations. Studies using static loading 3D-FEA have suggested that conservative access cavity preparation reduces the concentration of stress in the cervical region, thereby strengthening fracture resistance. However, the lack of support from clinical data raises concerns about the validity of this suggestion. Conversely, studies involving cyclic loading 3D-FEA and dynamic loading 3D-FEA have challenged the prevailing perspectives by taking into account additional factors such as filling materials, thus providing a more comprehensive understanding of the impact of access cavity preparation on fracture resistance. Existing research lacks a comprehensive comparison of the different 3D-FEA methods, and this review fills this gap by providing a systematic assessment of different 3D-FEA methods and their applications in access cavity preparation.

Biomechanical behavior and Weibull survival of CAD-CAM endocrowns with different marginal designs: A 3D finite element analysis

OBJECTIVES

To evaluate and compare the effect of tooth preparation designs and different CADCAM. materials on stress distribution and Weibull survival probability of endocrowns. applied to root canal-treated lower first permanent molar using the 3D finite element. analysis method.

METHODS

A root canal-treated lower first permanent molar was prepared for endocrowns with a. butt joint or with a ferrule design by placing, circumferentially, a 1-mm wide shoulder. finish line. The prepared molar was scanned for the two designs and modeled on a 3D. Finite element model. Monolithic zirconia (IPS e.max ZirCAD MT, FCZ), lithium. disilicate (IPS e.max CAD, EX), and nano-ceramic resin composite (Lava Ultimate, LU). CAD-CAM materials were used for each preparation to design the virtual endocrown. A. total of six models were built according to the different tooth preparation designs and. endocrown materials. An occlusal load of 600 N and a transverse load of 20 N in. magnitude that simulates the average occlusal load was directed toward the occlusal. surfaces. von Mises and maximum principle values were evaluated Weibull risk-ofrupture. analysis was used to analyze the survival probability of the restorations and. tooth in the different models.

RESULTS

The highest von Mises were found in the butt joint design for FCZ, EX, and LU (45.3. MPa, 35.2 MPa, and 24.2 MPa, respectively) compared to the ferrule design for the. same materials (42.6 MPa, 31.2 MPa, and 23.6 MPa, respectively). For von Mises. stress distribution in the remaining part of tooth structure (dentin), the highest stresses. were found in LUFerrule which was closely similar to LUButt joint (135.4 MPa and. 134.7 MPa, respectively), followed by EXFerrule and FCZFerrule (132.2 MPa and. 131.7 MPa, respectively), while the lowest stresses were found in EXButt joint and. FCZButt joint (129.0 MPa and 128.4 MPa, respectively). Shear stresses within the. resin cement were the highest in FCZ and EX compared to LU. EX was found to be the. most reliable material with the highest survival probability, while FCZ showed the. lowest survival probability according to the Weibull risk-of-fracture results.

SIGNIFICANCE

Materials with high elastic modulus transfer more stresses to the endocrown and less. to the remaining tooth structure. Endocrown tooth preparation with ferrule design has. better stress distribution and magnitude compared to the butt joint design.

Onlays/partial crowns versus full crowns in restoring posterior teeth: a systematic review and meta-analysis

BACKGROUND

Tooth-colored onlays and partial crowns for posterior teeth have been used increasingly in clinics. However, whether onlays/partial crowns could perform as well as full crowns in the posterior region was still not evaluated thoroughly.

METHODS

A literature search was conducted without language restrictions in Pubmed, Embase, Cochrane Central Register of Controlled Trial and Web of science until September 2021. RCTs, prospective and retrospective observational studies with a mean follow-up of 1 year were selected. Cochrane Collaboration's tool was adopted for quality assessment of the RCT. The quality of observational studies was evaluated following Newcastle-Ottawa scale. The random-effects and fixed-effects model were employed for meta-analysis.

RESULTS

Four thousand two hundred fifty-seven articles were initially searched. Finally, one RCT was identified for quality assessment and five observational studies for qualitative synthesis and meta-analysis. The RCT was of unclear risk of bias while five observational studies were evaluated as low risk. The meta-analysis indicated no statistically significant difference in the survival between onlays/partial crowns and full crowns after 1 year (OR = 0.55, 95% CI: 0.02-18.08; I² = 57.0%; P = 0.127) and 3 years (OR = 0.65, 95% CI: 0.20-2.17; I² = 0.0%; P = 0.747). For the success, onlays/partial crowns performed as well as crowns (OR = 0.58, 95% CI: 0.20-1.72; I² = 0.0%; P = 0.881) at 3 years. No significant difference of crown fracture existed between the two methods (RD = 0.00, 95% CI: - 0.03-0.03; I² = 0.0%; P = 0.972).

CONCLUSIONS

Tooth-colored onlays/partial crowns performed as excellently as full crowns in posterior region in a short-term period. The conclusions should be further consolidated by RCTs with long-term follow-up.

The practicability of different preparation of mandibular molar restored by modified endocrown with intracanal extension: Computational analysis using finite element models

BACKGROUND AND OBJECTIVE

Post-core-crown (PCC) and endocrown are two common restorative methods for severely damaged molars, but exhibit disadvantages. This study aimed to explore the practicability of modified endocrown with a 2 mm intracanal extension (MED) to restore defective teeth using finite element analysis (FEA).

METHODS

Five groups of numerical models of mandibular molars restored by three MEDs, a PCC, and a routine endocrown after root canal treatment were devised by FEA software. We constructed 4 mm, 3 mm, and 2 mm thickness of MED restorations to restore mandibular molars that were prepared to 1 mm, 2 mm, and 3 mm from the cemento-enamel junction (CEJ). Furthermore, PCC and routine endocrown were used to compare the stress distribution with MED. Lithium disilicate glass-ceramics (EMAX) and resin nanoceramics (LU) were considered restorative materials, and a vertical load of 600 N and an oblique load of 200 N were applied to the restorations.

RESULTS

In three MEDs by LU, 2 mm thickness of restoration generated the highest stress on prepared teeth, while the thickness of EMAX did not significantly influence the stress value. MED by LU generated higher stress around the CEJ, and reduced the stress on the middle and lower root compared to MEDs by EMAX, PCC by EMAX, and PCC by LU. MED by EMAX caused lower stress around the CEJ, and generated higher stress in the chamber walls after extended root canals compared with MED by LU, endocrowns by LU, and endocrowns by EMAX. There was an evident stress concentration at the last but one layer, which was a thin area of the tooth root in all restorative models.

CONCLUSIONS

The use of modified endocrown may be considered an effective restorative method to restore defective mandibular molar, but suitable restorative material must be selected based on the tooth preparation method and deficiencies in the tooth structure.