Mesio-occluso-distal Research Articles

Comparative Evaluation of Fracture Resistance of Endodontically Treated Teeth Restored with Different Core Build-up Materials: An In Vitro Study.

The aim is to evaluate the fracture resistance of endodontically treated teeth restored with posterior direct composite (PRC) resin, bulk-fill composite resin, dual-cure composite (DCC) resin, and short fiber-reinforced composite (SFC) resin material.Materials and methodsNinety sound maxillary premolar teeth were divided into 6 groups which comprised 15 teeth each. Group I was a negative control group where neither cavity preparation nor root canal treatment was done on the specimen. Group II was named positive control group as it was left unrestored after mesio-occluso-distal (MOD) preparation and root canal treatment. Groups III to VI were filled with PRC, bulk-fill composite, DCC, and SFC, respectively, and subjected to fracture testing in a universal testing machine.ResultsAfter statistical analysis, it was seen that group VI had increased mean fracture resistance as compared to other groups.ConclusionIt was concluded that short fiber-reinforced composite proved to have superior properties that other experimental groups and hence can be used as a core build-up material.Clinical significanceThe core build-up is requisite as the residual tooth structure after endodontic procedure decreases and core build-up supplements the resistance and retention of the tooth structure.How to cite this articleKaur B, Gupta S, Grover R, et al. Comparative Evaluation of Fracture Resistance of Endodontically Treated Teeth Restored with Different Core Build-up Materials: An In Vitro Study. Int J Clin Pediatr Dent 2021;14(1):51–58.

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

Background/purposeCuspal 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 methodsSixty 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.ResultsMean 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).ConclusionIn 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.

The Effects of Various Restorative Techniques on the Fracture Resistance of Pulpotomized Permanent Premolars.

Aim This study aimed to evaluate the effects of various restorative techniques on the fracture resistance of pulpotomized premolars with mesioocclusodistal (MOD) cavities treated with mineral trioxide aggregate (MTA) or calcium enriched mixture (CEM) cement. Materials and Methods One hundred and eight sound extracted maxillary premolars were randomly assigned to nine experimental groups (n = 12). The teeth in group 1 did not receive any preparation. Class II MOD cavities were prepared in the other experimental groups. In groups 2, 4, 6, and 8, tooth-colored MTA was used for pulpotomy. In groups 3, 5, 7, and 9, CEM cement was used for pulpotomy. Groups 2 and 3 were left unrestored. Groups 4 and 5 were restored with amalgam. Groups 6 and 7 were restored with a conventional composite resin, and groups 8 and 9 were restored with bulk-fill giomers. Fracture resistance was measured, the fracture pattern of each specimen was assessed, and the results were statistically analyzed. Results The fracture resistance of group 1 was significantly higher than those of the other groups (p < 0.05). The fracture resistance of group 2 (MTA + amalgam) was statistically lower than those of all experimental groups (p values < 0.05) except groups 3, 4, and 5 (p values > 0.05). No statistically significant differences were found between the groups restored with amalgam, conventional composite resin, and bulk-fill giomer (groups 4, 5, 6, 7, 8, and 9) (p values < 0.05). The highest rate of mode 1 fracture (restorable fracture) was observed in group 1 followed by groups 8 and 9. Conclusion No significant differences were found among the fracture resistances of the restored teeth using various restorative techniques. Bulk-fill giomers followed by conventional composite resin were better able to prevent unfavorable fractures compared to amalgam. Therefore, they seem to be more reliable for the restoration of pulpotomized teeth with MOD cavities.

Influence of Cavity Geometry on the Fracture Strength of Dental Restorations: Finite Element Study

The main purpose of this work was to analyze the stress distribution in premolars restored with indirect IPS Empress® CAD onlays or inlays. The three-dimensional geometry of a human first premolar was created using modeling software. The tooth fixation system was simulated through box geometry, comprising a cortical bone layer with 2 mm of thickness over a layer of trabecular bone with 15 mm of thickness. The tooth had the following approximated crown dimensions: 10.35 mm buccolingual length; 7.1 mm mesiodistal width; and 7.0 mm cervico-occlusal height. The mesio-occluso-distal (MOD) cavity preparations followed the suggestions available in the literature. The cement geometry was modified to include cohesive zone models (CZM) to perform the adhesive joint’s strength prediction. The loading body was created assuming contact between the food bolus and the tooth surface. Numerical solutions were obtained by performing static analysis and damage analysis using the finite element method. Von Mises stress values generated in the ceramic inlay restoration ranged from 1.39–181.47 MPa, which were on average 4.4% higher than those of the onlay ceramic restoration. The fracture strength of the onlay restoration was about 18% higher than that of the inlay restoration. The onlay design seems to contribute to higher homogenization of the adhesive resin cement strain and higher tooth structure protection.

Finite element analysis of Onlay restorations: Influence of Design and Onlay Material on Stress Distribution in Mandibular Molars

Background & Objective: Onalys are considered as conservative restorations for posterior teeth. The aim of this study was to evaluate the influence of the preparation design and the material of onlays on stress distribution in mandibular molars, using finite element analysis. Materials & Methods: A 3D model of a mandibular molar was obtained from a CBCT image. Using reverse engineering programs, modification was performed to isolate the dental structures and create their 3D objects. Then, mesio-occluso-distal (MOD) cavities were represented with two widths of the occlusal cavity: one third and two thirds of the intercuspal distance. Therefore, two designs of preparation were performed, conservative and extensive designs. Onlays from three restorative materials were represented; lithium disilicate ceramic, polymer-infiltrated ceramic network (PICN) and nanofill composite resin. Vertical and oblique loads of 600N were applied. Then, stress distribution was studied according to von Mises theory. Results: Color maps showed that stress highly concentrated in tooth structures in the conservative models than in the extensive models. Lithium disilicate ceramic onlays absorbed most of the stress with the least stress concentration in the adjacent structures. On the Contrary, composite resin onlays transmitted most of the stress to the neighboring structures. Furthermore, PICN onlays associated with more stress concentration in dental tissues than lithium disilicate ceramic onlays. The oblique load caused higher stresses in all models than vertical load. Conclusion: Within the limitations of this study, lithium disilicate ceramic onlay was seen to be a suitable choice to restore mandibular molars with large cavities. Moreover, resin composite onlay might be an unfavorable restoration in terms of stress redistribution in restored dental structures.

Fracture resistance of endodontically treated premolars restored with bulk-fill composite resins

Coronal restoration of endodontically treated teeth (ETT) with mesio-occluso-distal (MOD) cavities is of a great importance in long-term success of the treatment. This study evaluated the effect of fiber reinforcement on the fracture resistance (FR) of ETT restored with flowable or paste bulk (PB)-fill composite resin compared to conventional composite (CC) resin. In this in vitro experimental study, eighty maxillary premolars were divided into eight groups (n = 10). The first group was left intact (G1) and the other groups received MOD cavities along with endodontic treatment. G2: Remained unrestored while the other experimental groups were restored with three types of composite resin with or without fiber insertion. G3: CC resin, G4: PB fill, G5: Flowable bulk fill (FB). G6: Fiber + CC, G7: Fiber + PB, and G8: Fiber + FB. FR was tested at crosshead speed of 1 mm/min and recorded in Newton. Data were analyzed using one-way analysis of variance and Tukey's tests at significance level of P < 0.05. G1 and G2 revealed the highest and the lowest FR, respectively. The mean FR of the testing groups in Newton was as follows: G1 = 1204.8 A, G2 = 352.1 C, G3 = 579.6 BD, G4 = 596.7 BD, G5 = 624.9 BDE, G6 = 858.3 E, G7 = 529.6 CB, and G8 = 802.5DE. Different uppercase letters indicate the significant difference between the groups. The effect of fiber insertion on FR depended on the type of composite resin; the highest reinforcing effect was obtained in the CC resin + fiber, followed by bulk-fill flowable + fiber, and flowable bulk (FB)-fill composite resin. The strength of the former was significantly higher than the conventional and PB fill with and without fiber.

Fatigue Performance and Stress Distribution of Endodontically Treated Premolars Restored with Direct Bulk-fill Resin Composites.

To investigate the fatigue performance and stress distribution of endodontically treated maxillary premolars with occlusal (O), mesio-occlusal (MO), or mesio-occluso-distal (MOD) cavities filled directly with bulk-fill composite. Besides the intact teeth (control group), sixty sound maxillary first premolars, standardized by size and morphology, were subjected to root canal treatment and randomly allocated to three groups throughout cavity preparations (O/MO/MOD). All cavities were restored with a bulk-fill composite (Tetric N-Ceram Bulk fill) and universal adhesive (Tetric N-Bond Universal) using etch-and-rinse mode. Half of the specimens of each group underwent 20,000 thermocycles (5°C-55°C). All specimens were subjected to a 50-N load perpendicular to their buccal bevels on the palatal cusps for 1,200,000 cycles. The survival curve and fracture mode were analyzed by log-rank and Fisher's exact tests, respectively. Finite element analysis (FEA) was conducted to simulate the working condition of premolars with O/MO/MOD cavities. The von Mises stress and the first principal stress were calculated for three FEA models. Premolars with O cavity restorations exhibited better stress distributions than did those with MO and MOD cavity restorations. Compared to the intact premolars, no significant difference was detected in the fatigue performance of O/MO/MOD restorations, regardless of whether they underwent thermocycling. Only one specimen presented unrestorable fracture, while the rest of the fractured premolars were restorable. The cavity design of endodontic premolars restored with a bulk-fill composite has no influence on the stress distribution or fatigue survival, with a biomechanical performance similar to that of an intact tooth.

Effect of Direct and Indirect Materials on Stress Distribution in Class II MOD Restorations: A 3D-Finite Element Analysis Study.

The aim of this study is to investigate the stress distributions of different restoration options for class II mesio-occluso-distal (MOD) cavities. A class II MOD cavity with proximal box gingival floor 1 mm below cementoenamel junction was designed in a mandibular first molar tooth model. 3D finite-element analysis (FEA) and 3D-CAD modelling were used to examine the occlusal stresses distributed to the remaining buccal enamel (RBE), remaining lingual enamel (RLE), adhesive surfaces, and restorative materials by direct and indirect materials resulting from a 600 N of static occlusal load stimulating foodstuff. von Mises (VM) and maximum principal (Pmax) stresses were evaluated for two CAD/CAM materials and three direct materials. CAD/CAM materials exerted less stress than the direct restorative materials. Significant von Mises and Pmax stress value differences were seen among all restoration models on RBE. Reducing RLE and including it into the cavity would be a more effective option for this model in this scenario. As VM and Pmax stresses of PIHC CAD/CAM material for RBE and dentin were significantly lower than other tested materials, it may be the choice of material for indirect MOD restorations.

Frequency and Localization of Overhanging Restorations

Objectives: The aim of this retrospective study was to determine the frequency and localization of the overhanging restorations by observing patients’ routinely taken panoramic radiographs. Materials and Methods: The panoramic radiographs of 4,960 patients who applied to a dental clinic in University between 2015 and 2016 and had one or more previous restorations were retrospectively examined. The study group included 243 patients (133 females and 110 males) with a mean age of 39.7 ± 12.5 years. Superposed interdental areas were not evaluated. Frequency distributions and percentages were calculated for the categorical data as to the surface of the maxillary-mandibular premolar and molar teeth, also the presence or absence of root canal treatment. Chi-square tests were used to compare data relating to the localization and frequency of overhanging restorations. Results: In the radiological evaluation of 243 patients, a total of 280 overhanging restorations were detected. Root canal treatment was present in 45.4% of the teeth with an overhanging restoration. The frequency of overhanging restorations in the maxilla was significantly higher (60.4%) than that of the mandible (39.6%), (p&amp;lt;0.05). The frequency of overhanging restorations in molar teeth (82.9%) was significantly higher than that of premolar teeth (p&amp;lt;0.05). Of all the overhanging restorations, 90.4% were in Class II cavities and 9.6% were in mesio-occluso-distal (MOD) cavities. More than half (57.3%) of the overhanging margins in the Class II restorations were distal; 42.7% were mesial surfaces (p&amp;lt;0.05). The most frequent restorations with overhanging were found in the maxillary molars (49.6%) and the least frequent were in the premolar teeth of the mandible (6.4%). Conclusions: The restorations with overhanging margins determined most often at the disto-occlusal margins of the maxillary molars. The frequency of overhanging restorations was higher in areas that are difficult to reach during treatment.

Effect of composite thickness over the fiber post on fracture resistance of endodontically treated teeth

Aim: This study aimed to assess the effect of composite thickness over the fiber post on fracture resistance of endodontically treated teeth. Methods: This in vitro, experimental study was performed on 50 sound human premolars, which were randomly divided into 5 groups (n=10). Teeth in Group 1 remained intact while other specimens underwent root canal treatment with a Mesio-occluso-distal (MOD) cavity preparation, restored with fiber posts with a distance of 1.5 mm to the occlusal surface in groups 2 and 4 and 0.5 mm in groups 3 and 5. 24 hours of incubation was applied for groups 1-3 and 1 year of incubation for groups 4 and 5. Thereafter fracture strength measured using a Universal Testing Machine at a crosshead speed of 1 mm/minute. Data were analyzed using Shapiro-Wilk, Two-Way ANOVA and Tukey HSD. Results: The results showed a significant difference in terms of fracture resistance (P 0.05). Also, Tukey HSD revealed no statistically significant differences between Group 1 and 4 at one year. However, Group 1 (1255.25±280.61N) exhibited significantly higher fracture resistance than that of Group 5 (855.72±300.20N) at one year (P=0.027). The difference between other groups was not significant at any time point (P>0.05). Conclusions: By covering the fiber post with 1.5 mm thickness of composite resin and cuspal reduction of 2 mm, the fracture resistance of endodontically treated teeth can be increased to the level of sound teeth.

Evaluation of Marginal Adaptation and Wear Resistance of Nanohybrid and Alkasite Restorative Resins

Introduction: Polymerisation shrinkage stresses developed during curing of adhesive resin cements may cause debonding at the margins of cavity leading to microgap formation with secondary caries and consequently restorative failure. Thus, a restoration should have good marginal integrity and wear resistance to obtain high success with clinical longevity. Aim: To compare the influence of thermo-mechanical stresses on marginal quality and wear of class II Mesio-Occluso-Distal (MOD) restorations filled with Solare Sculpt or Cention N. Materials and Methods: An in vitro study was conducted at GITAM Dental College and Hospital, Visakhapatnam on 80 human extracted mandibular molars by preparing mesio-occlusal-distal class two cavities that restored either with Solare Sculpt or Cention N resin composites. Baseline evaluations were recorded for marginal gaps (in μm) through Scanning Electron Microscope (SEM), and the weights of the samples were recorded by an electronic balancing instrument to measure the amount of wear (in grams). Following thermo-mechanical cyclic loading, all the restored teeth were evaluated again to record the same parameters. The statistical analysis was done using Statistical Package for the Social Sciences (SPSS) programme for windows version 22.0 (IBM, NY) software. An independent t-test for intergroup comparison and a dependent t-test for intragroup comparisons were done to analyse the tested parameters with the significance level established at (p≤0.05). Results: In intergroup comparison, no difference in marginal adaptation was observed before thermo-mechanical loading between two materials with a p-value of 0.3625, but after therm-omechanical loading Cention N exhibited significantly superior marginal adaptation with a p-value of 0.0374. Both the materials have shown a significant difference in the marginal adaptation after thermo-mechanical loading in the intragroup comparison with Cention N (0.0002) and Solare sculpt (0.0001) p-values. The wear rate was not different statistically between the materials with a p-value of 0.7144 before thermo-mechanical loading and 0.2285 after thermo-mechanical loading. Conclusion: Marginal adaptation of Cention N was superior to Solare Sculpt, whereas both the materials exhibited a similar wear rate.

Fracture behavior of root-amputated teeth at different amount of periodontal support \u2013 a preliminary in vitro study

BackgroundThe purpose of this study was to evaluate the effect of the amount of periodontal support on the fracture resistance of root-amputated maxillary molar teeth restored with either direct class. I. restorations or class II. mesio-occluso-distal (MOD) indirect overlay restorations with cuspal coverage.MethodsSixty sound maxillary first molars were collected and randomly divided into four groups. In Groups 1 and 2, MOD cavities were prepared and all cusps were reduced by 2 mm, whereas in Group 3 and 4, only a conservative Class I. cavity was prepared. Subsequently, root canal treatment was performed and the mesio-buccal roots were amputated. Groups 1 and 2 were restored with indirect composite overlay, while Groups 3 and 4 received direct composite fillings. After restoration, teeth were embedded as follows: Groups 1 and 3: normal bone level, Groups 2 and 4: furcation involvement. The specimens were submitted to static fracture resistance testing. Fracture thresholds and fracture patterns were measured and evaluated.ResultsGroup 1 had the highest fracture resistance (2311,6 N) among the restored groups and showed statistically significant difference compared to Group 2 (p = 0.038) and Group 4 (p = 0.011). There was no statistically significant difference in terms of fracture resistance between the rest of the groups. In terms of the fracture patterns, Group 3 was characterized by the highest percentage (60%) of mostly favorable fractures, while the rest of the groups showed predominantly unfavorable ones.ConclusionsThe amount of periodontal support seems to influence the fracture resistance of root-amputated and restored maxillary molars.

Validation of a method of quantifying 3D leakage in dental restorations

Statement of problemA reliable and validated protocol for nondestructive analysis of the entire restorative interface that could be applicable in studies assessing the adaptation of direct and indirect restorations is lacking. PurposeThe purpose of this in vitro study was to validate a 3D protocol for microleakage assessment in class II mesio-occluso-distal (MOD) cavities restored with composite resin. Material and methodsSixteen human third molars received standardized class II MOD preparations with cervical margins located 1 mm apical to the cemento-enamel junction. The specimens were restored with Filtek Bulk Fill Posterior (FBP) or Filtek Bulk Fill Flowable (FBF) and submitted to 10 000 thermocycles (5 °C and 55 °C with a 30-second dwell time at each temperature and 5-second transfer time). The specimens were scanned with microcomputed tomography (μCT) before and after immersion in 50% ammoniacal silver nitrate solution for 12 hours. Scanned data were processed, and the 3D amount of infiltrated silver nitrate was analyzed through the entire adhesive interface. In addition, the linear distance of silver nitrate infiltration was assessed using 3 axial images obtained from each specimen proximal box (2D analysis). Data were tested for homogeneity by using the Shapiro-Wilk test and evaluated by using 1-way ANOVA, followed by the post hoc Tukey HSD test (α=.05). ResultsFBP showed significantly lower leakage than FBF for both 2D and 3D analyses. A low correlation was observed between the assessment methods. ConclusionsThree-dimensional analysis of microleakage using μCT is a predictable and more reliable method for nondestructive and comprehensive analysis of the entire specimen.

Fracture behaviour of MOD restorations reinforced by various fibre-reinforced techniques – An in vitro study

PurposeThe aim was to evaluate the fracture resistance of various direct restorative techniques utilizing different fibre-reinforced materials for restoring deep class II. MOD cavities in molar teeth. Material and methodsTwo hundred forty intact mandibular third molars were randomly divided into twelve groups (n = 20). Except for the control group (G12), deep mesio-occluso-distal (MOD) cavities were prepared all other groups. After adhesive treatment and rebuilding the missing interproximal walls with composite, the specimen were restored with different fibres and a final occlusal layer of composite as follows: composite only (G1), short fibre-reinforced composite (SFRC) (G2), glass fibre net (GFN) on the base of the cavity bucco-lingually (BL) and SFRC (G3), SFRC and GFN on top of it BL (G4), SFRC and occlusal splinting with GFN (G5), GFN circumferentially and SFRC (G6), polyethylene fibres (PF) on the base of the cavity BL and composite (G7), composite and PF on top of it BL (G8), composite and occlusal splinting with PF (G9), PF circumferentially and composite (G10), transcoronal splinting with PF (G11). Fracture-resistance for the restored teeth were tested using universal-testing machine. Fracture thresholds and fracture patterns were measured and evaluated. ResultsThe transcoronal splinting (G11) yielded the highest fracture resistance among the restored groups. Groups 1, 3 and 4 showed significantly lower fracture resistance values compared to intact teeth. ConclusionIncorporating polyethylene or a combination of short and bidirectional glass fibres in certain positions in direct restorations seems to be able to restore the fracture resistance of sound molar teeth.

Can Fiber Application Affect the Fracture Strength of Endodontically Treated Teeth Restored with a Low Viscosity Bulk-Fill Composite?

Objective The aim of this study is to evaluate the effects of different fiber insertion techniques and thermomechanical aging on the fracture resistance of endodontically treated mandibular premolar teeth restored using bulk-fill composites. Materials and Methods Eighty human mandibular premolar teeth were randomly divided into eight groups: Group IN, Group BF, Group PRF1, Group PRF2, Group IN-TMA, Group BF-TMA, Group PRF1-TMA ,and Group PRF2-TMA. Group IN (intact) and Group IN-TMA (intact but subjected to thermomechanical aging) served as control groups. In the other six groups, endodontic treatment was performed and standardized mesio-occluso-distal (MOD) cavities were prepared. In BF, PRF1, and PRF2, the cavities were restored with bulk-fill composite only, bulk-fill/Ribbond, and bulk-fill/additional Ribbond, respectively. In BF-TMA, PRF1-TMA, and PRF2-TMA, the teeth were subjected to thermomechanical aging after the restorations. All of the teeth were fractured on the universal testing machine. Fracture surfaces were analyzed with a stereomicroscope. Results Control groups showed significantly higher fracture strengths than tested groups (P<0.05). No statistically significant difference was observed among the tested groups (P>0.05). Most of the favorable fractures were seen in PRF1, PRF2, and PRF2-TMA. Most of the unfavorable fractures were seen in BF-TMA. Conclusions Although fiber insertion with different techniques did not increase the fracture strength of teeth restored with bulk-fill composites, it increased the favorable fracture modes. Thermomechanical aging did not change the fracture strength of the groups.

Evaluation of fracture resistance of endodontically treated premolars restored by alkasite cement compared to various core build-up materials

Aim: This study aimed to compare the fracture resistance of endodontically treated premolars restored by alkasite cement (Cention N), composite resin, and glass ionomer cement (GIC). Materials and Methods: Fifty freshly extracted mandibular and maxillary premolars with typical morphology were selected and mounted on acrylic cylinders. Five groups were made with ten teeth in each group as follows: Group A: intact teeth with no restoration (control); Group B: unfilled teeth with prepared mesio-occluso-distal (MOD) cavity; Group C: teeth with MOD cavity restored with nanohybrid composite; Group D: teeth with MOD cavity restored with type IX GIC; and Group E: teeth with MOD cavity restored with Cention N. Root canal treatment was done for groups B, C, D, and E after MOD cavity and before placement of the coronal filling. The specimens were mounted on a universal testing machine, and load was applied until the specimen fractured. The values were tabulated and subjected to statistical analysis. Results: The mean value of fracture resistance was highest in Group A (2015 N) followed by Group C (1504 N) and Group E (1319 N). Groups D and B showed the lowest reading. However, there was no statistical difference between Groups C and E. Conclusions: Within the limitations of the study, it can be concluded that composite is the material of choice for restorations in endodontically treated tooth. Alkasite cement can be used as an alternative to composite resin due to ease of manipulation.

Effect of the restorative technique on load-bearing capacity, cusp deflection, and stress distribution of endodontically-treated premolars with MOD restoration.

ObjectivesTo evaluate the influence of the restorative technique on the mechanical response of endodontically-treated upper premolars with mesio-occluso-distal (MOD) cavity.Materials and MethodsForty-eight premolars received MOD preparation (4 groups, n = 12) with different restorative techniques: glass ionomer cement + composite resin (the GIC group), a metallic post + composite resin (the MP group), a fiberglass post + composite resin (the FGP group), or no endodontic treatment + restoration with composite resin (the CR group). Cusp strain and load-bearing capacity were evaluated. One-way analysis of variance and the Tukey test were used with α = 5%. Finite element analysis (FEA) was used to calculate displacement and tensile stress for the teeth and restorations.ResultsMP showed the highest cusp (p = 0.027) deflection (24.28 ± 5.09 µm/µm), followed by FGP (20.61 ± 5.05 µm/µm), CR (17.72 ± 6.32 µm/µm), and GIC (17.62 ± 7.00 µm/µm). For load-bearing, CR (38.89 ± 3.24 N) showed the highest, followed by GIC (37.51 ± 6.69 N), FGP (29.80 ± 10.03 N), and MP (18.41 ± 4.15 N) (p = 0.001) value. FEA showed similar behavior in the restorations in all groups, while MP showed the highest stress concentration in the tooth and post.ConclusionsThere is no mechanical advantage in using intraradicular posts for endodontically-treated premolars requiring MOD restoration. Filling the pulp chamber with GIC and restoring the tooth with only CR showed the most promising results for cusp deflection, failure load, and stress distribution.

Comparative Assessment of Cuspal Deflection in Premolars Restored with Bulk-Fill and Conventional Composite Resins.

Objectives:It has been reported that bulk-fill composites simplify tooth restoration with no adverse effect on the success rate. This study sought to assess the cuspal deflection of premolars with mesio-occluso-distal (MOD) cavities restored with bulk-fill and conventional posterior composite resins.Materials and Methods:This in-vitro experimental study was conducted on 64 human maxillary premolars. MOD cavities were prepared on teeth and restored with Filtek P60 conventional composite and Filtek Bulk Fill flowable, X-tra fill, and X-tra base bulk-fill composites in four groups (n=16). Distance between the cusp tips was measured before, five minutes, 24 hours, 48 hours, and one week after restoration. The data were analyzed using repeated-measures analysis of variance (ANOVA) and Tukey’s test (α=0.05).Results:The mean±standard deviation (SD) of cuspal deflection at five minutes after the restoration was 13.5±5.3, 12.2±3.5, 11.3±4.4, and 10.4±3.7 μm for Filtek P60, Filtek Bulk Fill, X-tra fill, and X-tra base, respectively. ANOVA showed that bulk-fill composites did not cause a significant reduction in cuspal deflection compared to P60 (P>0.05). Cuspal deflection in all groups significantly decreased with time (P<0.05).Conclusion:Bulk-fill composites have no superiority over P60 in the reduction of cuspal deflection. The cuspal deflection was variable at different time points in all groups and decreased over time.

Influence of Cavity Pretreatments on the Fracture Resistance of Premolars with Self-adhesive Cemented Composite Inlay

The aim of this study is to investigate whether different cavity pretreatment approaches affect the strength of premolars restored with self-adhesive (SA) resin cemented-composite resin inlays after mechanical and water aging. A total of 120 intact maxillary premolars were divided into 10 groups (n = 12). Mesio-occluso-distal (MOD) cavities were prepared in the teeth of nine groups, except group I in which the teeth remained intact. In group II, cavities were unrestored. Following fabrication of composite resin inlays for groups III-X, in group III, the inlays were cemented using the etch-and-rinse (E and R) adhesive/conventional resin cement. In other groups, cementation was performed using a SA cement with or without cavity pretreatments as follows: group IV: SA cement alone, group V: acid etching of enamel and dentin, group VI: acid etching of enamel, group VII: universal adhesive in the selective enamel-etching mode, group VIII: universal adhesive in the E and R mode, group IX: ethylenediaminetetraacetic acid (EDTA) conditioning, and group X: 20% polyacrylic acid conditioning. After aging processes, static fracture resistance was tested. Data were analyzed using one-way ANOVA and Dunn tests (α = 0.05). Fracture resistance of the 10 groups yielded a significant difference (p < 0.001). The median fracture resistances in Newton were the following: Gr I = 1025A, Gr II = 311BC, Gr III = 785A, Gr IV = 500B, Gr V = 435B, Gr VI = 775A, Gr VII = 805A, Gr VIII = 411BC, Gr IX = 397BC, and Gr X = 312C. Unlike the conventional method, SA cementation could not restore the strength of inlay-cemented premolars. Selective enamel acid etching with or without universal adhesive significantly increased the fracture resistance. Selective enamel acid etching is recommended for increasing the fracture resistance of the SA cemented composite inlay to the level of intact teeth.

Impact of various pressures on fracture resistance and microleakage of amalgam and composite restorations.

Pressure changes can influence dental restorations especially among divers. The aim of the current study was to evaluate the fracture resistance and microleakage of mesio-occluso-distal (MOD) amalgam and composite restorations undergoing pressure changes via diving and aviation simulation. For the fracture resistance test, 60 sound maxillary premolar teeth were randomly allocated to two groups. Each group was then divided into three subgroups (n = 10) for simulating scuba-diving (pressure cycle to 203 kPa, 2 bar), flight (50.6 kPa, 0.5 bar), and control (atmospheric pressure). The teeth underwent pressure cycles for one month and then the fracture resistance test was conducted on them using the Instron testing machine. Microleakage scores were afterwards recorded by using a 2% methylene blue dye for 24 hours. Composite restorations showed significantly higher fracture resistance values compared to the amalgam group (P < 0.05). The control group had significantly higher fracture resistance values compared to the dive group, whereas there was no significant difference between the control group and the flight group (P = 0.083). No significant difference in the level of microleakage was observed between restoration materials or pressure cycles (P > 0.05). Composite restorations showed better fracture resistance compared to the amalgam group. However, diving pressure cycles demonstrated adverse effects on the fracture resistance values of both restorative materials.