Search Results (13)

This study aimed to assess the fracture resistance and fracture patterns of endodontically treated permanent mandibular molars restored with either preheated or nonpreheated conventional composite resin or short fiber-reinforced composite resin (SFRC). One hundred and twenty mandibular molars with prepared mesio-occluso-distal (MOD) cavities were allocated to six groups: positive control (intact teeth, no restoration, n = 20), negative control (endodontically treated but unrestored, n = 20), and four experimental groups restored with conventional composite, preheated composite, SFRC, or preheated SFRC (n = 20 each). After thermocycling, fracture resistance was tested using a universal testing machine at 0.5 mm/min. Data were analyzed using Jamovi software (Version 2.4.8; The Jamovi Project, Sydney, Australia). Normality was assessed with the Kolmogorov–Smirnov test. Group differences were evaluated using the Kruskal–Wallis test followed by the Dwass–Steel–Critchlow–Fligner post hoc test. The association between fracture modes and fracture strength categories was examined using the chi-square test of independence. A p-value < 0.05 was considered statistically significant. The positive control showed significantly greater fracture strength than all restored groups (p < 0.05). All restored groups had significantly higher fracture resistance than the negative control (p < 0.05), with no significant differences among the restored groups (p > 0.05). A significant association was found between fracture mode and fracture strength (χ²(1) = 6.97, p = 0.008). The preheated SFRC group showed a higher rate of restorable fractures compared to others, suggesting improved clinical reparability with preheating. Full article

Finite element analysis has been widely applied in restorative dentistry, but there is limited evidence directly comparing the biomechanical behavior of amalgam and bulk-fill composite resins in standardized cavity designs. This study aimed to evaluate the stress distribution in enamel, dentin, and restorative materials under different cavity configurations and filling materials. A 3D model of a maxillary molar was reconstructed from dental tomography using Geomagic Design X 2020. Four cavity models were created with Solidworks 2013: Class I (occlusal, Group A), Class II disto-occlusal (Group B), Class II mesio-occlusal (Group C), and Class II mesio-occluso-distal (Group D) cavities. Each model was restored with either amalgam or bulk-fill composite and a 600 N occlusal force was applied. Maximum principal stresses were analyzed with ABAQUS software. The highest stress was observed in the bulk-fill composite restoration of the Class II MO cavity (231 Mpa), whereas the lowest stress occurred in amalgam restoration of Class I cavity. Overall, amalgam restorations showed lower stress concentrations than bulk-fill composites, especially in complex cavity designs. These results suggest that cavity configuration and restorative material selection influence stress distribution and may impact the long-term biomechanical stability of restored teeth. Full article

Background/Objectives: It is unclear whether enamel margins should be beveled in direct resin-based restorations. This study evaluated the influence of enamel beveling on the marginal quality of mesio-occluso-distal (mod) cavity boxes. Methods: Seventy-five caries-free human molars were divided into three groups. Mod-cavities with the entire margin in the enamel were prepared ± proximal bevel (n = 25). Twenty-five beveled mod-cavities served as control. Each group was restored with five material combinations: micro hybrid composite with etch-and-rinse (ER) or self-etch (SE) adhesive, compomer with ER or SE, and low-shrinkage composite with ER. A complex filling technique was used in the control. After artificial aging (1000 thermal cycles, 5/55 °C), the percentage of continuous margins (PCM) of the proximal boxes was analyzed by scanning electron microscopy using epoxy replicas (×300), and the marginal seal was assessed by light microscopy after dye penetration (×64). Statistical analysis was performed using Kruskal–Wallis and Mann–Whitney U tests (p < 0.05). Results: No significant differences in PCM were found between the restorative systems (p = 0.075). The composite with low shrinkage showed the highest mean PCM of all groups (78.1%). Significant differences in marginal seal were observed between the restoratives after bevel preparation (p < 0.05). Beveling significantly improved the PCM only for the hybrid composite (p < 0.05), whereby the effect on marginal seal was less pronounced. Conclusions: Clinicians should be aware that beveling mod-cavities does not necessarily improve the marginal quality of direct resin-based restorations bonded with well-established adhesives and may be more beneficial for traditional hybrid composites. Full article

Fiber-reinforced composites (FRCs) are recognized for enhancing the fracture resistance of structurally compromised teeth. However, the optimal orientation and placement of fibers in direct resin composite restorations remain under debate. This study aimed to evaluate the fracture resistance of maxillary premolars with mesio-occluso-distal (MOD) cavities restored using polyethylene fibers with different placement techniques, compared to conventional incremental composite restoration. Methods: Sixty intact maxillary premolars were randomly assigned to six groups (n = 10). Group 1: intact teeth (positive control); Group 2: MOD cavity without restoration (negative control); Group 3: MOD cavity restored with nanohybrid composite using the incremental technique; Group 4: polyethylene fiber placed on the pulpal floor; Group 5: fiber placed circumferentially along cavity walls (wall-papering technique); Group 6: fiber placed buccolingually in an occlusal groove (occlusal splinting). Fracture resistance was assessed using a universal testing machine. Failure mode was also analyzed. Results: Group 6 (occlusal splinting) exhibited the highest fracture resistance (1137.72 ± 316.20 N), significantly exceeding Group 3 (546.93 ± 59.89 N) and other fiber-reinforced groups (p < 0.05). Failure mode analysis revealed no significant differences between the fiber-reinforced groups and the intact teeth. Group 6 also had the highest percentage of restorable fractures (90%). Conclusions: Incorporating polyethylene fibers, especially through occlusal splinting, significantly improves fracture resistance in MOD-restored maxillary premolars. This technique may offer a promising alternative to conventional composite restorations in structurally weakened posterior teeth. Full article

This study aimed to evaluate the effect of direct restorations using unidirectional glass fiber orientations and a short-fiber-reinforced composite (SFRC) on the fracture resistance of endodontically treated premolars with mesio-occluso-distal cavities. Ninety double-rooted premolars were selected. Fifteen teeth were left intact/as a control group. The endodontic treatment and cavity preparations of seventy-five teeth were performed and divided into five experimental groups: Resin composite (RC), modified transfixed technique + RC, circumferential technique + RC, cavity floor technique + RC, and SFRC + RC. All teeth were fractured under oblique static loading at a 30° angle using a universal testing machine. The fracture patterns were observed and classified. Data were analyzed with one-way analysis of variance, Pearson chi-square, and Tukey HSD post hoc tests (p = 0.05). The highest fracture strength values were obtained in intact teeth (599.336 N), followed by modified transfixed + RC treated teeth (496.58 N), SFRC + RC treated teeth (469.62 N), RC (443.51 N), circumferential + RC treated teeth (442.835 N), and cavity floor + RC treated teeth (404.623 N) (p < 0.05). There was no significant difference between the RC and the circumferential technique + RC (p > 0.05). Unrepairable fractures were observed at low rates (20%) in the modified transfixed + RC and SFRC + RC teeth, and at higher rates in RC (73.3%), cavity floor + RC (60%), and circumferential + RC (80%) teeth. The application of an SFRC or the modified transfixed technique yielded an improved fracture strength and the fracture pattern of ETPs being restored with a universal injectable composite. Full article

Introduction: The aim of this in vitro study was to compare the quality of marginal sealing at the cervical margins of indirect and direct composite resin restorations in mesio-occluso-distal (MOD) cavities. Material and method: MOD preparations were performed on 30 extracted teeth. The mesial cervical margin of each tooth was relocated using a flow composite resin (Enamel Plus HRi Flow, Micerium, Avegno, GE, Italy), then the samples were divided into three groups. In group A, the cavities were directly restored using a nanohybrid composite resin (Miris 2 Coltène Whaledent, Altstaetten, Switzerland) and a universal adhesive (ScotchBond Universal, 3M ESPE, St. Paul, MN, USA) by the etch-and-rinse strategy, for group B, the restoration procedure was similar but the self-etch strategy was used, and the samples in group C were filled using the inlay technique. Each sample was stored for 48 h in a 2% methylene blue solution, then it was cut in a mesio-distal direction using a Struers Secotom 50 device (Cleveland, OH, USA). The marginal sealing and adhesive interface were assessed for each sample at the cervical margin by optical microscopy (OM) and scanning electron microscopy (SEM). One-way ANOVA and Bonferroni post-hoc tests were used with a significance level of 0.05. Results: Significant differences were recorded within groups A and C, between mesial and distal margins (p = 0.02 in group A and p = 0.043 in group C). Conclusions: The marginal sealing is more effective in MOD inlay restoration compared to direct restorations. Relocation of the cervical margin with flow composite resin and the use of different adhesive strategies do not improve the marginal sealing. Full article

This paper investigates the influence of cavity configuration and post-endodontic restoration on the fracture resistance, failure mode and stress distribution of premolars by using a method of fracture failure test and finite elements analysis (FEA) coupled to Weibull analysis (WA). One hundred premolars were divided into one control group (G_contr) (n = 10) and three experimental groups, according to the post-endodontic restoration (n = 30), G₁, restored using composite, G₂, restored using single fiber post and G₃, restored using multifilament fiberglass posts (m-FGP) without post-space preparation. Each experimental group was divided into three subgroups according to the type of coronal cavity configuration (n = 10): G_1O, G_2O, and G_3O with occlusal (O) cavity configuration; G_1MO, G_2MO, and G_3MO with mesio-occlusal (MO); and G_1MOD, G_2MOD, and G_3MOD with mesio-occluso-distal (MOD). After thermomechanical aging, all the specimens were tested under compression load, and failure mode was determined. FEA and WA supplemented destructive tests. Data were statistically analyzed. Irrespective of residual tooth substance, G₁ and G₂ exhibited lower fracture resistance than G_contr (p < 0.05), whereas G₃ showed no difference compared to G_contr (p > 0.05). Regarding the type of restoration, no difference was highlighted between G_1O and G_2O, G_1MO and G_2MO, or G_1MOD and G_2MOD (p > 0.05), whereas G_3O, G_3MO, and G_3MOD exhibit higher fracture resistance (p < 0.05) than G_1O and G_2O, G_1MO and G_2MO, and G_1MOD and G_2MOD, respectively. Regarding cavity configuration: in G₁ and G_2, G_1O and G_2O exhibited higher fracture resistance than G_1MOD and G_2MOD, respectively (p < 0.05). In G₃, there was no difference among G_3O, G_3MO and G_3MOD (p > 0.05). No difference was found among the different groups and subgroups regarding the failure mode. After aging, premolars restored with multifilament fiberglass posts demonstrated fracture resistance values comparable to those of an intact tooth, irrespective of the different type of cavity configuration. Full article

Background and objectives: Even with the demand for high esthetics, the strength of the material for esthetic applications continues to be important. In this study, monolith zirconia (MZi) crowns fabricated using CAD/CAM were tested for fracture resistance (FR) in teeth with class II cavity designs with varying proximal depths, restored through a deep marginal elevation technique (DME). Materials and Methods: Forty premolars were randomly divided into four groups of ten teeth. In Group A, tooth preparation was conducted and MZi crowns were fabricated. In Group B, mesio-occluso-distal (MOD) cavities were prepared and restored with microhybrid composites before tooth preparation and the fabrication of MZi crowns. In Groups C and D, MOD cavities were prepared, differentiated by the depth of the gingival seat, 2 mm and 4 mm below the cemento-enamel junction (CEJ). Microhybrid composite resin was used for DME on the CEJ and for the restoration of the MOD cavities; beforehand, tooth preparations were conducted and MZi crowns were and cemented using resin cement. The maximum load to fracture (in newtons (N)) and FR (in megapascals (MPa)) were measured using the universal testing machine. Results: The average scores indicate a gradual decrease in the load required to fracture the samples from Groups A to D, with mean values of 3415.61 N, 2494.11 N, 2108.25 N and 1891.95 N, respectively. ANOVA revealed highly significant differences between the groups. Multiple group comparisons using the Tukey HSD post hoc test revealed that Group D had greater DME depths and showed significant differences compared with Group B. Conclusions: FR in teeth decreased when more tooth structure was involved, even with MZi crowns. However, DME up to 2 mm below the CEJ did not negatively influence the FR. Strengthening the DME-treated teeth with MZi crowns could be a reasonable clinical option, as the force required to fracture the samples far exceeded the maximum recorded biting force for posterior teeth. Full article

Background: Mesio–occluso–distal (MOD) cavity preparations are often fragile due to the amount of tooth and carious structure removed. MOD cavities can often fracture if left unsupported. Aim: The study investigated the maximum fracture load of mesi–occluso–distal cavities restored using direct composite resin restorations with various reinforcement techniques. Method: Seventy-two freshly extracted, intact human posterior teeth were disinfected, checked, and prepared according to predetermined standards for mesio–occluso–distal cavity design (MOD). The teeth were assigned randomly into six groups. The first group was the control group restored conventionally with a nanohybrid composite resin (Group I). The other five groups were restored with a nanohybrid composite resin reinforced with different techniques: the ACTIVA BioACTIVE-Restorative and -Liner as a dentin substitute and layered with a nanohybrid composite (Group II); the everX Posterior composite resin layered with a nanohybrid composite (Group III); polyethylene fibers called “Ribbond” placed on both axial walls and the floor of the cavity, and layered with a nanohybrid composite (Group IV); polyethylene fibers placed on both axial walls and the floor of the cavity, and layered with the ACTIVA BioACTIVE-Restorative and -Liner as a dentin substitute and nanohybrid composite (Group V); and polyethylene fibers placed on both axial walls and the floor of the cavity and layered with the everX posterior composite resin and nanohybrid composite (Group VI). All teeth were subjected to thermocycling to simulate the oral environment. The maximum load was measured using a universal testing machine. Results: The highest maximum load was exhibited by Group III with the everX posterior composite resin, followed by Group IV, Group VI, Group I, Group II, and Group V. A statistically significant difference was demonstrated between groups (p = 0.0023). When adjusting for multiple comparisons, there were statistical differences specific to comparisons between Group III versus I, Group III versus II, Group IV versus II, and Group V versus III. Conclusions: Within the limitations of the current study, it can be concluded that a higher maximum load resistance can be achieved (statistically significant) when reinforcing nanohybrid composite resin MOD restorations with everX Posterior. Full article

The aim of this research was to evaluate the mechanical impact of utilizing different fiber-reinforced composite (FRC) systems to reinforce inlay-retained bridges in dissected lower molars with different levels of periodontal support. A total of 24 lower first molars and 24 lower second premolars were included in this study. The distal canal of all molars received endodontic treatment. After root canal treatment, the teeth were dissected, and only the distal halves were kept. Standardized class II occluso-distal (OD) (premolars) and mesio-occlusal (MO) (dissected molars) cavities were prepared in all teeth, and premolar–molar units were created. The units were randomly distributed among four groups (n = six/group). With the aid of a transparent silicone index, direct inlay-retained composite bridges were fabricated. In Groups 1 and 2, both discontinuous (everX Flow) and continuous (everStick C&B) fibers were used for reinforcement, while in Groups 3 and 4, only discontinuous fibers (everX Flow) were used. The restored units were embedded in methacrylate resin, simulating either physiological periodontal conditions or furcation involvement. Subsequently, all units underwent fatigue survival testing in a cyclic loading machine until fracture, or a total of 40,000 cycles. Kaplan–Meyer survival analyses were conducted, followed by pairwise log-rank post hoc comparisons. Fracture patterns were evaluated visually and with scanning electron microscopy. In terms of survival, Group 2 performed significantly better than Groups 3 and 4 (p < 0.05), while there was no significant difference between the other groups. In the case of impaired periodontal support, a combination of both continuous and discontinuous short FRC systems increased the fatigue resistance of direct inlay-retained composite bridges compared to bridges that only contained short fibers. Such a difference was not found in the case of sound periodontal support between the two different bridges. Full article

Hybrid bioactive composite resins combine the benefits of glass ionomer cements with composite resins. Its self-adhesiveness is achieved through functional polyacrylic acids and carboxylic groups, hybridizing the smear layer and establishing ionic interactions between calcium and dentin. These materials are defined as having good aesthetics, moisture tolerance, durability, simplicity in technique and handling and are able to maintain a low microfiltration rate while releasing calcium, phosphate and fluorine. The aim of the present study was to evaluate microleakage in restorations using Surefill One™ bioactive resin. The null hypothesis is that this type of resin does not obtain a lower microleakage rate when compared to other materials. An in vitro study was carried out using thirty-six premolars and molars extracted for orthodontic reasons. Identical preparations were thus performed in all of them (Class V with 4 mm mesio-distal, 3 mm occluso-gingival and 3 mm in depth) and divided into different experimental groups: one positive control, one negative control and two tests with bioactive composite resin and conventional composite resin (Surefill One™ and Spectra™ ST HV, respectively). Through quantitative techniques using nuclear medicine, it was possible to evaluate microleakage through the use of a radioactive isotope, technetium. Radioactivity emitted by the specimens was detected by a gamma camera. The different groups were compared using the Kruskal–Wallis test and the Games–Howell test for multiple comparisons. The results of the experimental study point to statistically significant differences between the test groups (p = 0.002) with increased microleakage in the bioactive composite resin group. Based on the present microleakage study, it was possible to conclude that the bioactive composite resin (Surefill One™) does not reduce the microleakage rate when compared to a conventional nanohybrid composite resin (Spectra™ ST HV). However, Surefill One™ can be used in temporary restorations, primary teeth and in cases of tissue remineralization, thus avoiding more invasive procedures. Full article

Excessive cavity preparation and root canal treatment leads to a weakened tooth structure with a lower resistance to fracture. Fiber reinforcement is frequently used to reinforce such teeth, and multiple fiber types and possible applications exist. Various methods for utilizing long fibers to internally splint the remaining cavity walls in the case of large mesio-occluso-distal (MOD) cavities have been proposed; however, no summary of their performance has been written up to now. Our study aims to review the available literature to evaluate and compare the mechanical performance of the different materials and methods utilized for horizontal splinting in large MOD cavities. Three independent authors performed a thorough literature search using PubMed, ScienceDirect, and Google Scholar up until January 2022. The authors selected in vitro studies that used long fibers placed horizontally in posterior teeth with large MOD cavities to reinforce these teeth. From 1683 potentially relevant articles, 11 publications met our inclusion criteria. Seven out of eleven studies showed that horizontal splinting with long fibers improved the fracture resistance of the restored teeth. Three articles showed no significant difference between the fracture resistance of the restored groups. Only one article reported a lower fracture resistance to the horizontally splinted group, compared to conventional direct composite restoration. Within the limitations of this review, evidence suggests that long fiber reinforcement could be used to improve the fracture resistance of heavily restored teeth. Full article

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. Full article