Objective: Despite the increased popularity of endocrowns, there is no clear consensus considering their effectiveness to restore severely-destructed endodontically treated premolars. This study aimed to assess the biomechanical behavior of endodontically treated maxillary first premolars restored with a novel endocrown system compared to the conventional one. Materials and methods: Twenty sound human maxillary first premolars were collected. After endodontic treatment, they were divided into 2 groups (n=10) according to the system used for endocrown fabrication. Group C (Control): conventional monolithic IPS e.max CAD endocrowns. Group P: novel bi-layered endocrowns (Pekkton ivory coping veneered with cemented IPS e.max CAD). All specimens were subjected to 10000 thermal cycles followed by 240000 dynamic load cycles. Surviving specimens were subjected to fracture resistance test followed by qualitative analysis using Stereomicroscopy and Scanning Electron Microscopy. Results: A significantly higher load was observed for Group P (1831.37 ± 240.69 N) than Group C (1433.47 ± 174.39 N) (p ⟨ 0.001). A statistically significant difference was observed considering the failure mode (p = 0.036), with more favorable fractures detected with Group P. Conclusions: The tested novel endocrown system improved the biomechanical behavior of the tooth/ restoration complex in the restored endodontically treated maxillary first premolars. Clinical significance: The tested novel endocrown system with a PEKK coping veneered with cemented IPS e.max CAD can be considered a promising option for restoration of severely-destructed endodontically treated premolar teeth. It can be considered as a conservative alternative option to the conventional treatment modalities.

Objective To date, there is no clear consensus in the literature which endocrown design with which material is the most effective treatment option to restore endodontically treated maxillary premolars with extensive loss of tooth structure. The aim of this study was to evaluate the stress distribution pattern and failure probability of maxillary first premolars restored with a novel endocrown system compared to the conventional one by means of Finite Element and Weibull analyses. Materials and methods Two finite element (FE) models representing two endocrown systems used for restoration of severely-destructed endodontically treated maxillary first premolar tooth were generated: model C for the conventional monolithic IPS e.max CAD endocrown and model P for the novel bi-layered endocrown (PEKKTON ivory coping veneered with cemented IPS e.max CAD). A static occlusal compressive load was axially and centrally-applied. Modified von Mises and maximum principal stress values on the remaining tooth structure, cement lines and restorative materials were evaluated separately. Weibull function was incorporated with FE analysis to calculate the long term failure probability. Results Regarding stresses occurred in the remaining tooth structure (enamel and dentin), model P transmitted less stresses than model C. The individual enamel of model C showed about 5% and 40% risk of failure at normal and maximum occlusal load values, respectively, while for model P, it had no failure risk at both values. For dentin, model C showed about 13% failure risk at the normal masticatory force, while model P showed only 2%. At clenching value, model C dentin showed about 44% failure risk, while only 9% was resulted for model P. Conclusions Compared to the conventional endocrown system, the positive impact of the studied novel endocrown system on the stress distribution pattern and also on the survival/failure probability of the restored severely-destructed endodontically treated maxillary first premolar teeth was reflected (more tooth-friendly), not only at normal masticatory forces but also at the maximum functional loads. Clinical significance The novel endocrown system using a PEKK coping veneered with cemented IPS e.max CAD can be considered a favorable option for restoration of severely-destructed endodontically treated premolar teeth, with more protection for residual tooth structure. Despite the conventional endocrown system may benefit the durability of tooth bonding, it should not be selected for restoration of clenching cases because of the too high overall failure risk.

Objective Rehabilitation of endodontically treated premolars with extensive coronal destruction through endocrown approach remains a controversial topic in reconstructive dentistry. There is no clear consensus in the literature which endocrown design with which material is the most effective restoration option for severely-destructed endodontically treated premolars. The aim of this study was to assess the biomechanical behavior of endodontically treated maxillary first premolars restored with a novel endocrown system compared to the conventional one varying the applied load type through finite element and in vitro analyses. Materials and methods For finite element analysis, two models representing two endocrown systems used for restoration of severely-destructed endodontically treated maxillary first premolar tooth were generated: Model C for the conventional monolithic IPS e.max CAD endocrown and Model P for the novel bi-layered endocrown (PEKKTON ivory coping veneered with cemented IPS e.max CAD). Modified von Mises stress values on the remaining tooth structure, cement lines and restorative materials were evaluated separately under axial and oblique loading of 450N. For in vitro analysis, forty sound human bifurcated maxillary first premolars were collected, endodontically-treated, and divided into 2 main groups (n = 20) according to the system used for endocrown fabrication; Group C: the conventional monolithic endocrowns and Group P: the novel bi-layered endocrowns. All specimens were subjected to an artificial thermomechanical aging protocol. Each main group was subdivided into two subgroups (n = 10) according to the loading type (axial and oblique) applied during the fracture resistance test. Qualitative analysis using Stereomicroscopy and Scanning Electron Microscopy was performed. Data were statistically analyzed at p-value ≤ 0.05. Results Regarding stress distribution pattern of remaining tooth structure (enamel and dentin), both endocrown systems and cement lines under both axial and oblique load application, Model P resulted in lower stresses than Model C. The oblique stress values of all analyzed structures were higher than corresponding values resulted axially. Considering failure load, a significantly higher load was recorded for Group P when axial or oblique loading was applied (p = 0.00). A significantly higher failure load was recorded with axial loading for both main groups. With regard to failure mode, a statistically significant difference was observed between main groups (p = 0.033), with more favorable failures detected for Group P axially. Conclusions Compared to the conventional endocrown system, the studied novel system improved the biomechanical behavior within tooth/restoration complex of the restored severely-destructed endodontically treated maxillary first premolar teeth, whatever the applied load type. Clinical significance The novel endocrown system using a PEKK coping veneered with cemented IPS e.max CAD can be considered a favorable promising option for restoration of severely-destructed endodontically treated premolar teeth, with more protection for residual tooth structure. It can be considered as a conservative alternative option to the conventional treatment modalities not only for normal clinical conditions, but also for parafunctional cases.

Statement of the problem: The optical properties of the zirconia based ceramic restoration may be affected by its fabrication protocol and the veneer thickness.Objectives: This study was aimed to investigate the effect of repeated rings and veneer thickness on the nal color and translucency of zirconia based ceramic restorations.Materials and methods: 80 disc-shaped zirconia cores (diameter: 10×1 mm) were constructed then divided based on the veneer thickness into 2 main groups (A) and (B) (n=40) with 0.5 mm and 1.00 mm veneer thicknesses, respectively. According to the number of ring cycles (1, 3, 5, and 7), each main group was further subdivided into four subgroups (n=10). A spectrophotometer was utilized to measure the color and translucency after consecutive rings then used to measure them after articial thermomechanical aging. Data analysis was performed by One-way ANOVA analysis, Paired t-test and Tukey post hoc test.Results: All measured L*, a* and b* and ΔΕ values showed statistical signicant differences after repeated ring cycles. Increasing the veneer thickness for all tested subgroups resulted in statistically signicant increasing in mean values of L*, a* and b*. Increasing the number of ring cycles signicantly increased the TP, while increasing the zirconia veneer thickness signicantly decreased them. Following fatigue aging, statistically signicant differences were noticed for all color coordinates with all tested subgroups with increased TP.Conclusions: Both ring cycles and veneer thickness had an impact on optical properties of zirconia-based ceramic restorations. Color parameters and translucency were inuenced by articial fatigue aging

Aim: This study aimed to evaluate the effect of hydroxyethyl cellulose adhesive strip in soft tissue preservation over immediately-placed dental implants in the mandibular molar area. Materials and Methods: Sixteen patients with non-restorable mandibular molars were equally randomized into two groups (n = 8). Following atraumatic extraction and immediate implant placement, group I received only figure-eight sutures, while group II received hydroxyethyl cellulose (HEC) adhesive strips covering the socket before suturing. Clinical evaluations included Landry soft tissue healing index and implant stability. Radiographic evaluation using CBCT was used to assess relative bone density and marginal bone loss. Results: All implants exhibited a 100% survival rate with no complications during the observation period. Both groups showed significant improvement in soft tissue healing over time (p < 0.001) with no intergroup differences. Implant stability, bone density, and marginal bone loss revealed comparable outcomes between groups (p >0.05). Conclusion: HEC adhesive strips demonstrated no significant superiority over conventional suturing in preserving soft tissue health or increasing bone density around immediately-placed implants in mandibular molar area.

Background This study aimed to assess the fracture behavior of endodontically treated maxillary first premolars restored with different lithium silicate-based endocrown restorations. Methods Thirty intact human maxillary first premolars were root canal treated. They were divided into three groups (n = 10) based on the CAD/CAM lithium silicate-based material used for endocrown fabrication: Group LD: Lithium disilicate-based ceramic (IPS e.max CAD), Group ZLS: Zirconia-reinforced lithium silicate-based ceramic (Celtra Duo), and Group ALD: Advanced lithium disilicate-based ceramic (Cerec Tessera). After adhesive cementation, all specimens underwent a thermomechanical aging process. Surviving specimens underwent fracture resistance testing, followed by analysis with stereomicroscopy and Scanning Electron Microscopy (SEM). Data were statistically analyzed at P-value ≤ 0.05. Results The mean failure load value was significantly higher for Group ALD (1853.89 ± 178.40 N) compared to Group LD (1425.57 ± 156.31 N) and Group ZLS (1364.12 ± 196.34 N). A statistically significant difference in failure mode was detected among tested groups, with more favorable fracture patterns observed within Groups ZLS and ALD. Conclusions All studied lithium silicate-based endocrown restorations expressed fracture load values that significantly surpassed the maximum human masticatory force reported for maxillary premolar region supporting their clinical use. Cerec Tessera endocrowns exhibited the best biomechanical behavior among tested restorative materials. Clinical trial number Not applicable.

Background This study aimed to evaluate the effect of incorporating different concentrations of nanochitosan (NCH) into Fuji Plus resin-modified glass ionomer luting cement (RMGIC; GC Corporation, Tokyo, Japan) on shear bond strength, film thickness, solubility, water sorption, and antibacterial activity. Methods The liquid component of fuji Plus RMGIC was modified by incorporating NCH at 0% (control), 5%, 10%, and 20% (v/v). A total of ten specimens were prepared per group for each test. Shear bond strength (SBS) was assessed using human mid-coronal dentine after thermocycling. Film thickness was measured in accordance with ISO 4049 and ANSI/ADA guidelines. Water sorption and solubility were assessed after 28 days in artificial saliva. Antibacterial activity against Streptococcus mutans was determined via the agar disc diffusion method. Data were analyzed using one-way ANOVA followed by Tukey’s post hoc test (α = 0.05). Results NCH incorporation significantly influenced the tested properties of RMGIC. Bond strength remained unaffected at 5% and 10% but significantly decreased at 20% (p ≤ 0.05). Film thickness increased only at 20% (p ≤ 0.05). Water sorption showed a concentration-dependent increase, while solubility significantly decreased with increasing NCH content (p < 0.0001). Antibacterial activity against Streptococcus mutans improved significantly with higher NCH concentrations, as evidenced by larger inhibition zones in all modified groups compared to the control (p < 0.0001). Conclusions Incorporation of NCH into RMGIC enhanced its antibacterial activity and reduced solubility without compromising bond strength or film thickness up to 10%. However, a 20% addition adversely affected the mechanical and handling properties.