Buccolingual Direction Research Articles

Comparative Evaluation of Canal Transport and Centralization Between ProTaper Next and XP-endo Shaper Systems Using CBCT Analysis: An In Vitro Study.

Aim: This study compared the apical transportation and centering ratio of ProTaper Next (PTN) and XP-endo Shaper (XPS) nickel titanium (NiTi) rotary files in curved root canals using cone beam computed tomography (CBCT). Methodology: The current in vitro study involved the mesiobuccal canals of mesial roots in 44 extracted mandibular first molars that exhibited apical curvature ranging from 10° to 30°. Two experimental groups were randomly formed from the teeth (n = 22) and subjected to instrumentation with PTN and XPS. CBCT scans were performed before and after instrumentation on the teeth, and the apical transport and centering ratio were calculated at 3, 4, and 5 mm from the apex. Group comparisons were conducted using an independent t-test with a significance level set at alpha = 0.05. Results: Comparisons within groups did not reveal any statistically significant differences in the magnitude of canal transportation in the buccolingual (BL) and mesiodistal (MD) directions at any level from the apex, neither in the XPS group nor in the PTN group (p > 0.05). Canal transportation in both BL and MD directions was significantly greater in PTN than in XPS (p < 0.05). The centering ratio in the MD and BL directions was the same at 3, 4, and 5 mm from the apex in the PTN (p > 0.05) and also in the XPS (p > 0.05) groups. The centering ratio was significantly higher in XPS than in PTN (p < 0.05) except at 5 mm from the apex in the MD direction and 4 and 5 mm from the apex in the BL direction (p > 0.05). Conclusions: Both buccolingually and mesiodistally, PTN led to greater apical transport than XPS and also showed a lower centering ratio.

Residual dentin thickness and biomechanical performance of post-and-core-restored mandibular premolars: A finite element analysis study.

Endodontically treated teeth often require post-and-core restorations for structural support because of extensive hard tissue loss. Assessment of the effect of the residual dentin thickness on the biomechanical performance of these restorations is lacking. The purpose of this study was to evaluate the residual dentin thickness in mandibular premolars after post-and-core restorations using cone beam computed tomography (CBCT) and to analyze the stress distribution with finite element analysis (FEA). The CBCT data from 236 mandibular premolars having undergone post-and-core restorations were examined. An imaging software program (NNT; NewTom) was used to measure the buccolingual and mesiodistal root diameters in cross-sections 5 to 11mm from the radiologic apex. The CBCT derived measurements were subsequently integrated into an FEA model. A 3-dimensional (3D) mandibular premolar model reflecting the residual dentin thickness was created with a computer-aided design software program (Hypermesh 9.0; Altair Engineering). A static force of 100N was applied directly to the buccal cusp tip at 45, 60, 75, and 90 degrees to the long axis of the tooth, and the stress distribution of dentin was analyzed by using an FEA software program (ANSYS APDL 18.0; Ansys Inc). CBCT analysis showed that the buccolingual root diameter was wider than the mesiodistal diameter and that the residual dentin thickness of the buccal aspect was approximately 0.3mm thinner compared with the lingual aspect along the root. The proportions of residual dentin thickness values in the buccolingual direction of the mandibular premolar teeth no less than 1mm exceeded 96.2% at 5 to 11mm from the apex. The proportions of residual dentin thickness values in the mesiodistal direction of the mandibular premolar teeth >1mm were 92.1% and 88.2% at 11mm from the apex after post space preparation and decreased further to 70.8% and 58.9% at 5mm from the apex. The von Mises stresses of the mandibular premolar model with residual dentin thickness were mainly localized to the cervical area (region C, cervix) and the post apex (region A, apex) in the buccolingual direction. Tensile and compressive stress were concentrated on regions C and A on the buccal and lingual sides, respectively. The actual residual dentin thickness model demonstrated higher maximum tensile stress compared with the 1-mm residual dentin thickness model under various loading conditions. During the process of post space preparation in mandibular premolars, sufficient dentin thickness should be retained in the apical region. The tensile stresses of mandibular premolars after clinical post-and-core restoration were mainly concentrated in the cervical area and the post apex, and the maximum tensile stress value was higher than the ideal 1-mm residual dentin thickness model.

Comparison of fatigue lifetime of new generation CAD/CAM crown materials on zirconia and titanium abutments in implant-supported crowns: a 3D finite element analysis.

Due to the dynamic character of the stomatognathic system, fatigue life experiments simulating the cyclic loading experienced by implant-supported restorations are critical consideration. The aim of this study was to examine the effect of different crown and abutment materials on fatigue failure of single implant-supported crowns. Models were created for 10 different designs of implant-supported single crowns including two zirconia-reinforced lithium silicates (crystallized and precrystallized), monolithic lithium disilicate, polymer-infiltrated ceramic networks, and polyetheretherketone supported by zirconia and titanium abutments. A cyclic load of 179 N with a frequency of 1 Hz was applied on palatal cusp of a maxillary first premolar at a 30° angle in a buccolingual direction. In the models with titanium abutments, the polymer-infiltrated ceramic network model had a lower number of cycles to fatigue failure values in the implant (5.07), abutment (2.30), and screw (1.07) compared to others. In the models with zirconia abutments, the crystallized zirconia-reinforced lithium silicate model had a higher number of cycles to fatigue failure values in the abutment (8.52) compared to others. Depending on the fatigue criteria, polyetheretherketone implant crown could fail in less than five year while the other implant crowns exhibits an infinite life on all models. The type of abutment material had an effect on the number of cycles to fatigue failure values for implants, abutments, and screws, but had no effect on crown materials. The zirconia abutment proved longer fatigue lifetime, and should thus be considered for implant-supported single crowns.

Endodontic treatment of a two-rooted mandibular first premolar with four root canals: a case report

BackgroundMandibular first premolar has a complex and variable anatomy of the root canal system, which often leads to failure of endodontic treatment due to missing root canals. Identifying the complete structure of the root canal system to ensure that all root canals are perfectly cleared and filled becomes critical to the success of root canal therapy. This report introduced a unique case of endodontic treatment of a two-rooted mandibular first premolar in the buccolingual direction with a total of four canals.Case presentationAn adult male patient with a lower left first premolar was diagnosed with acute apical periodontitis and treated with open pulp drainage in a general hospital. One day later, due to the complexity of the root canal structure, the patient was referred to our clinic for subsequent treatment. The tooth #34 was diagnosed with abnormal central cusp, apical periodontitis, and incomplete fracture through clinical and x-ray examinations. Cone-beam Computed Tomography (CBCT) results showed that the tooth #34 processed two roots with a buccolingual bifurcation and a total of 4 root canals: 1 lingual canal, 2 mesiobuccal canals, and 1 distobuccal canal. Notably, the buccal root presented a C-shaped configuration, and the mesiobuccal canals were of 2-1 type. The tooth was treated with microendodontics and crown restoration. One year after the treatment, the follow-up results showed that the tooth #34 was functioning normally without any abnormalities.ConclusionThis report enhances our understanding of the anatomical variations in the root canal system of the mandibular first premolar and emphasizes the importance of CBCT in identifying anatomical variations within the root canal system. Clinicians must be aware of such changes in the mandibular first premolar during treatment to ensure a perfect treatment and better prognosis in clinical practice.

A Lipoma of Large Proportion in the Oral Cavity: A Case Report

Background Lipoma is a benign neoplasm that can affect the whole body and rarely occurs in the oral cavity. It is slow-growing and asymptomatic, and conservative surgical treatment with total removal of the lesion is the treatment of choice. It originates from epithelial cells of mature adipose tissue. Case Presentation The aim of this study was to report a clinical case of a large lipoma in a 21-year-old male patient with melanoderma who presented a nodule in the region of the buccal vestibule extending from the region of the second molar to the ipsilateral canine, with an approximate size of 40 mm in its largest diameter in the anteroposterior direction and approximately 20 mm in diameter in the buccolingual direction. The initial diagnostic hypothesis was based on an ultrasound of the face, which detected a solid, circumscribed, echogenic nodule compatible with a lipoma of the face. Surgical treatment with excisional biopsy was chosen. The histopathological examination revealed fragments with the presence of discrete acanthosis and clear hyperkeratosis in the epithelium, along with the proliferation of mature adipocytes constituting a neoplastic parenchyma surrounded by a stroma. Conclusion The findings have confirmed the diagnosis of oral lipoma. The patient has evolved with a good prognosis and remained under follow-up without recurrence or sequelae. The present report has corroborated what has been observed in similar cases described in the literature regarding recurrence and excellent prognosis.

Stress distribution of customized abutment material and angles in dental implant systems: A finite element analysis

Aim: Dental implants and abutments are often made from titanium for its biocompatibility and excellent material properties. However, in patients with thin gingival biotypes, titanium abutment margins may be visible and aesthetically unpleasing. This study aims to use finite element analysis to evaluate stress distribution in implant components, restoration materials, and biological tissues for implants placed at different angles using various customized abutment materials. Methodology: 3D models of a three-member implant-supported fixed prosthesis were created using SolidWorks, with implants placed at positions 44 (4I) and 46 (6I). These models were imported into EXOCAD to design prosthetic restorations on custom abutments at three angles: straight (KD0), 10 degrees (KD10), and 20 degrees (KD20). Abutments were made from alumina (AL), titanium (TI), and zirconia (ZI). A 150N load was applied to the occlusal table at a 30° angle in the buccolingual direction. Stress distribution was measured as von Mises Stress values (vMS). Results: For implants, the lowest vMS value was observed in the KD0-AL group (4I: 9.984 MPa, 6I: 22.91 MPa), while the highest vMS value was found in the KD20-TI group (4I: 25.30 MPa, 6I: 42.03 MPa). Custom abutment and custom abutment screws (in general) showed higher vMS values in AL material and lower vMS values in TI material. In contrast, for cortical bone and restoration material, higher vMS values were observed in the TI material and lower vMS values in the AL material. Conclusion: Dental implants require effective stress distribution from occlusal loads to ensure long-term success. Excessive stress on the abutment and abutment screw can compromise the prosthetic outcome. Therefore, titanium (TI) abutments are preferred in the posterior region for their durability, despite being less aesthetically pleasing. Additionally, a higher implant angle reduces strength, negatively impacting the implant's performance.

Usefulness of the Magnetodynamic Mallet in Tooth Extraction: A Case Series

Background: Tooth extraction techniques have been refined over the years in order to be less traumatic and to better preserve alveolar bone. A recently introduced extraction method involves the use of the Magnetic Mallet®, which allows clinicians to be more precise and perform extractions faster. Moreover, the instrument enables the procedure to be less traumatic for patients. The aim of the present study was to clinically evaluate whether extractions performed using the Magnetic Mallet® can lead to less buccolingual bone resorption. Methods: Between February 2023 and June 2023, nine patients with an average age of 62 years underwent 29 extractions using the Magnetic Mallet®. Sectorial CBCTs were performed in order to measure buccolingual bone thickness at time 0 (T0, before extraction) and 3 months after extraction (T3M). All the extractions were performed by two different expert operators exclusively using the Magnetic Mallet®. For statistical analysis, a two-sample t-test was performed to determine the difference between the measurements taken at T0 and those taken at T3M in the 29 dental elements and the difference in bone loss between the surgeries conducted by the two clinicians. Results: A total of 22 teeth were extracted in the upper jaw and 7 in the lower jaw. The average degree of mobility was 1. The average degree of force impressed by the instrument to extract the teeth was 2, while the average frequency of blows administered was 7. The average time taken for the extractions was 3½ min. After 3 months, the mean buccolingual bone resorption was 1.54 mm (SD: ±). The difference in buccolingual bone thickness between T0 and T3 was significant at an alpha significance level of 0.01. No difference in bone resorption was found between the surgeries conducted by the two clinicians. Conclusions: The use of the Magnetic Mallet® results in bone loss in the buccolingual direction comparable with existing data in the literature on healing the post-extraction socket. This tool seems to be predictable in producing the same results between different operators.

Evaluation of thin-threaded implants primary stability in type IV bone right after maxillary sinus floor elevation: A human cadaver study.

The bone-implant interface plays a crucial role in obtaining sufficient primary stability for dental implants in weak bone supports. The aim of this human cadaver study was to evaluate the primary stability of new thin-threaded implants when placed in type IV bone right after maxillary sinus floor elevation. The study followed the CACTUS (ChAracteristics of Cadaver Training and sUrgical Studies) guidelines. Twenty-four edentulous maxillary posterior zones with type IV bone and a residual bone height of 4mm were selected using computed tomography scans. First, an osteotome sinus floor elevation was performed (C.M.C Tech, IBS IMPLANT, Daejeon, South Korea). Implants with thin threads (MagiCore, IBS IMPLANT, Daejeon, South Korea) were placed simultaneously. Samples were divided into two groups: Group 1 (G1): 11mm-long implants with an elevation of 8mm; Group 2 (G2): 7mm-long implants with an elevation of 4mm. Primary stability was assessed using resonance frequency analysis (RFA). The average primary stability values in the mesiodistal (MD) direction were 45.67±3.09 Implant Stability Quotient (ISQ) for G1 and 38.76±16.94 ISQ for G2, and in the buccolingual direction were 43.33±13.23 ISQ for G1 and 38.47±16.14 ISQ for G2. The primary stability of the thin-threaded implants was compatible with clinical osseointegration in sinus sites with limited bone contact area in both experimental situations. Clinical studies are needed to confirm these encouraging results.

Three-dimensional analysis of force distribution on maxillary dentition while distalization of first and second molars simultaneously with clear aligners

Objective: To explore the force distribution on the maxillary dentition when the first and second molars distalized simultaneously with different step sizes using clear aligners in vitro in order to provide a theoretical basis for the rational design of molar distalization. Methods: Clear aligners were designed to simultaneously distalize the maxillary first and second molars bilaterally, with rectangular attachments placed on the buccal surfaces of the first and second premolars, as well as the second molars. Based on different step sizes, the aligners were divided into three groups: Group A (0.15 mm per step), Group B (0.20 mm per step), and Group C (0.25 mm per step). Ten aligners were fabricated for each group using 0.76 mm thick polyethylene terephthalate glycol (PET-G) sheets. A three-dimensional force measurement system was used to measure the forces exerted on each tooth by the aligners, the first and second molars served as the target teeth and the remaining teeth as anchorage teeth. The three-dimensional force data were compared among the three groups. Results: In the mesiodistal direction, the forces on the central and lateral incisors were relatively small among all three groups, with no statistically significant differences (P>0.05). However, significant differences were observed in the forces on the canines, first premolars, second premolars, first molars, and second molars (P<0.05). The distal forces on the second molars in Groups B and C were (6.13±1.45) N and (6.83±1.58) N, respectively, significantly higher than that in Group A [(3.51±1.01) N] (P<0.05). The distal force on the first molars in Group C [(6.62±0.89) N] was significantly higher than that in Groups A and B (P<0.05). The mesial reactive forces on the first and second premolars in Groups B and C were significantly higher than those in Group A (P<0.05). The mesial reactive force on the canines in Group C [(-2.98±1.33) N] was significantly higher than that in Group A [(-1.69±0.68) N] (P<0.05), while there were no significant differences between Groups B and C in the forces on the canines, first premolars, and second premolars (P>0.05). In the buccolingual direction, there were no statistically significant differences in the forces on the central and lateral incisors among three groups (P>0.05), but significant differences were observed in the forces on the canines, second premolars, and second molars (P<0.05). The buccolingual forces on the canines, second premolars, and second molars in Group B were (-0.56±0.54), (-2.07±0.95), (1.13±0.55) N, respectively, significantly higher than those in Group A (P<0.05), but there were no significant differences compared to Group C (P>0.05). Compared to the mesiodistal and buccolingual forces, the vertical forces on the target and anchorage teeth were relatively small in all three groups. Conclusions: When using 0.76 mm thick PET-G sheets to fabricate clear aligners for simultaneous molar distalization, a step size of 0.20 mm per step is recommended. To prevent buccal tipping of the molars during distalization, it is advisable to design lingual displacement for the molars and buccal displacement for the adjacent anchorage teeth to counteract the unfavorable forces, with attachments placed on the primary anchorage teeth.

Comparative evaluation of remaining dentin thickness and root canal transportation in curved canals with newer nickel-titanium single and multiple rotary file systems: A cone-beam computed tomography study.

The purpose of this study was to evaluate and compare the remaining dentin thickness and root canal transportation of WaveOne GOLD, XP-endo Shaper, and GenEndo file systems to assess their performance in curved canals using cone-beam computed tomography (CBCT) imaging. Seventy-five extracted maxillary first molars were selected with a curvature ranging between 15° and 30°. The samples were allocated into three groups (n = 25) and shaped using WaveOne GOLD, XP-endo Shaper, and GenEndo files. CBCT images were captured before and after instrumentation. The remaining dentin thickness and root canal transportation were measured at 3, 5, and 7 mm from the apex in both mesiodistal and buccolingual directions. The data were statistically analyzed using one-way ANOVA followed by Tukey's post hoc test. GenEndo file system demonstrated greater preservation of remaining dentin thickness and resulted in less root canal transportation compared to the WaveOne GOLD and XP-endo Shaper systems across all three levels. GenEndo file system which comprises multiple files has removed less amount of dentin and canal transportation when compared to single file systems, i.e., WaveOne GOLD and XP-endo Shaper file systems.

Comparison of 1- and 3-piece directly 3-dimensional printed indirect bonding trays: An in vitro study

This study aimed to compare the transfer accuracy of indirect bonding trays of different thicknesses and numbers of pieces. Digital indirect bonding was performed on 56 printed resin models, divided into 4 groups with 14 models in each: 1-mm 1-piece tray (OPT), 2-mm OPT, 1-mm 3-piece tray (TPT), and 2-mm TPT. The trays were designed using Appliance Designer (3Shape A/S, Copenhagen, Denmark). Angular (torque, tip, or angulation) and linear (mesiodistal, buccolingual, occlusogingival, or vertical) differences were compared by using open-source GOM Inspect software (GOM GmbH, Braunschweig, Germany). In the buccolingual direction, the 1-mm TPT (0.180 ± 0.041 mm) was significantly more accurate than the 1-mm OPT (0.240 ± 0.032 mm). In the vertical direction, significant differences were seen between the 1-mm and 2-mm OPTs (1-mm OPT: 0.220 ± 0.043 mm; 2-mm OPT: 0.428 ± 0.143 mm; P= 0.003) and between the 1-mm and 2-mm TPTs (1-mm TPT: 0.210 ± 0.072 mm; 2-mm TPT: 0.340 ± 0.062 mm; P= 0.004) in the total region. In the tip angle, significant differences were seen between the 1-mm and 2-mm OPTs and between the 1-mm OPT and TPT. In the torque angle, a significant difference was seen between the 1-mm TPT (2.815°±0.350°)and 2-mmTPT (2.368° ± 0.245°; P= 0.017). Both the thickness and the splitting of the trays impacted the bracket bonding accuracy. The 1-mm trays were more accurate than the 2-mm trays. Despite a few statistically significant differences between the 1-mm OPT and TPT, the 1-mm OPT was recommended for clinical use, considering the designing and placing of the trays.

Effect of wall thickness on shape accuracy of hollow zirconia artificial teeth fabricated by a 3D printer.

This study aimed to analyze how the wall thickness of 3D-printed hollow zirconia teeth affects shape accuracy. Datasets with measurement points were created for different artificial teeth resembling the mandibular right first molar (Geomagic Design X, 3D Systems). Reference distances were 9.8 mm for mesio-distal direction (M-D), 10.9 mm for bucco-lingual direction (B-L), 7.0 mm for MB-BB and DB-BB, and 4.5 mm for ML-LB and DL-LB. The outer geometry was identical for all artificial teeth with wall thicknesses of 0.30, 0.50, 0.75, and 1.00 mm. Twenty zirconia teeth were fabricated using a 3D printer (CeraFab 7500 Dental, Lithoz) for each group and sintered before support removal. After performing analog distance measurements using a micrometer screw, the digital distance measurements and angular deviations between measurement points on 3D scans were analyzed. Possible effects were investigated using nonparametric ANOVA, followed by Tukey's honest significant difference (HSD) test for multiple comparisons. The shape accuracy was acceptable for artificial teeth with wall thicknesses of ≥0.5 mm. The largest distance deviation was observed for a wall thickness of 0.3 mm. In particular, DB-BB showed a median deviation of >56.2 µm, which is significantly larger than that for other test groups, ranging from 7.4-9.5 µm (P < 0.05). In most cases, angular deviations were the largest for teeth with 0.3-mm wall thickness (11.6°) and remained below 5.0° for the other test groups. Acceptable accuracy was obtained for artificial teeth with wall thicknesses of at least 0.5 mm.

The morphology of alveolar bone of the mandibular second and third molars in skeletal Class III patients.

To investigate the alveolar bone morphology of the mandibular second and third molars in skeletal Class III patients from a buccolingual direction. Sixty skeletal Class III patients were recruited. The alveolar bone width, buccal cortical bone thickness and lingual cortical bone thickness were measured in five planes from mesial to distal and at five depths from gingival to root. The effects of the gender of the patients, the second molar lingual inclination and the third molar on alveolar bone width and cortical bone thickness were evaluated. To explore the effect of third molar extraction on alveolar bone morphology, the measurements before and after third molar extraction were compared. The impacted third molar had significantly greater alveolar bone width and thicker buccal cortical bone at the cervical third of the molar, while the erupted third molar had greater alveolar bone width at the apical third. Three weeks after third molar extraction, these advantages would weaken owing to the reconstruction of the alveolar bone. Patients with lingually inclined molar were observed to own thicker lingual cortical bone. Males tended to have greater alveolar bone width, but no significant differences were shown in this study. The growth of the third molar and the second molar lingual inclination affect the alveolar bone morphology of the mandibular second and third molars significantly, but gender has trivial effects on the morphology. The alveolar bone morphology of the mandibular second and third molars would change 3 weeks after third molar extraction.

Quality analysis of four filling techniques in ovoid root canals prepared with M® instruments

Aims: This study aimed to assess the quality of various filling techniques in ovoid root canals prepared using M® instruments. Materials and Methods: Sixty ovoid root canals underwent endodontic treatment with M® instruments and were subsequently divided randomly into four experimental groups, each employing a different obturation technique: TU - single cone; TL - active lateral condensation; TH - Tagger hybrid; TS - Schilder technique. Digital radiographs were taken in both mesiodistal and buccolingual directions to examine the filled teeth. The percentage of filling material and empty spaces was quantified using Photoshop® software. Data were subjected to statistical analysis using the one-way ANOVA test and T test (? = 0.05). Results: In the TL and TS groups, there was a significantly lower average percentage of unfilled spaces compared to the TU and TH groups (P&lt;0.0001). When analyzing the radiographic directions, the mesiodistal view exhibited the highest mean percentage of unfilled spaces, with differences in filling quality observed only in the TU and TL groups. Conclusions: Active lateral condensation and Schilder techniques demonstrated superior performance in achieving effective filling of ovoid root canals.

Enhancing Fracture Resistance in Coronal Structure of Endodontically Treated Teeth by Placing Horizontal Posts in Buccolingual Direction: Case Report

Enhancing Fracture Resistance in Coronal Structure of Endodontically Treated Teeth by Placing Horizontal Posts in Buccolingual Direction: Case Report

Comparative evaluation of the remineralizing potential of Salvadora persica and probiotic yogurt on incipient enamel lesions: An ex-vivo study.

Salvadora persica (miswak) is known to exert antibacterial, antifungal, antioxidant, and anticariogenic effects by elevating the pH of plaque after the consumption of sucrose. The study aimed to compare the effectiveness of S. persica and probiotic yogurt in the remineralization of tooth enamel on artificially produced enamel lesions. A total of 40 intact human premolars were collected and each tooth was sectioned longitudinally into 2 identical halves in a buccolingual direction. The buccal halves were selected for inclusion in this study, and standardized windows (5 mm× 3 mm) were isolated on the buccal surface of the enamel. The samples were incubated in a demineralizing solution at 37°C for 96 h. Subsequently, they were randomly selected for treatment with one of the experimental remineralizing solutions (S. persica or probiotic yogurt). After treatment, the samples were examined using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and polarized light microscopy at baseline, after demineralization and after remineralization. The remineralizing effect of S. persica was found to be greater than that of probiotic yogurt. With regard to mineral content, S. persica exhibited the highest calcium and phosphorus levels among all groups. No significant differences were observed between the samples treated with S. persica and normal enamel. Salvadora persica extract has been demonstrated to effectively reduce the demineralization of enamel in experimental conditions. Furthermore, it has the potential to restore the mineral content to its original level.

Effect of Chlorhexidine Treatment on Microleakage of Glass Ionomer, Giomer and Methacrylate-Based Composite Restorations in Class V Cavities

Purpose: The aim of this in vitro study was to evaluate the effect of material selection and chlorhexidine digluconate (CHX) pretreatment on microleakage in Class V cavities restored with 3 different restorative materials. Materials and Methods: Thirty freshly extracted sound human molars were cleaned and stored in distilled water. Sixty standard Class V cavities were prepared on gingival 1/3 of buccal and lingual surfaces of each tooth. Teeth were randomly assigned into 3 groups corresponding to the selected restorative material (Fuji II LC Capsule/FC, GC; Beautifil Flow Plus/BF, Shofu; and GrandioSo Flow/GF, VOCO). Lingual cavities were pre-treated with CHX (Cavity Cleanser, Bisco). The cavities were restored according to manufacturer's instructions using the materials' own adhesive systems. Teeth were stored in distilled water (24°C) for 6 months for aging. Specimens were immersed in 2% methylene blue solution for 1 h and sectioned longitudinally in buccolingual direction. Occlusal/gingival margins were examined for dye penetration and scored under x8 and x20 magnification using stereomicroscope (Leica MZ7.5, Leica Microsystems). Statistical analysis was performed using chi-square test with a significance level of p0.05). There was no statistically significant difference between the amount of microleakage of GF, FC and BF restorations in CHX-treated and untreated cavities (p&gt;0.05). Conclusion: Application of CHX as cavity cleaner could not prevent dye penetration in Class V cavities restored with giomer, glass ionomer, and resin composites. Key Words: Chlorhexidine gluconate, composite resin, glass ionomer, microleakage.

Finite element analysis of different carbon fiber reinforced polyetheretherketone dental implants in implant-supported fixed denture

ObjectivesThe purpose of this study is to determine the feasibility of polyetheretherketone-based dental implants, and analyze the stress and strain around different kinds of dental implants by finite element analysis. MethodsThe radiographic data was disposed to models in Mimics 19.0. 3D models of implants, crowns and jawbones were established and combined in SolidWorks 2018. Appling axial and oblique loads of 100 N, cloud pictures were exported in Ansys Workbench 18.0 to calculate and analyze the stress and strain in and around different implants. ResultsOblique load tended to deliver more stress to bone tissue than axial load. The uniformity of stress distribution was the best for 30% short carbon fiber reinforced polyetheretherketone implants at axial and buccolingual directions. Stress shielding phenomenon occurred at the neck of 60% continuous carbon fiber reinforced polyetheretherketone and titanium implants. Stress concentration appeared in PEEK implants and the load of bone tissue would aggravate. Conclusions30% short carbon fiber reinforced polyetheretherketone implants demonstrate a more uniform stress distribution in bone-implant contact and surrounding bone than titanium. Stress shielding and stress concentration may be avoided in bone-implant interface and bone tissue. Bone disuse-atrophy may be inhibited in PEEK-based implants.

In vitro study examines posterior torque impact on 3D mechanics of anterior teeth in clear aligner treatment

IntroductionThis study utilizes investigate the impact of posterior torques on the three-dimensional force exerted on the lower anterior teeth during the retraction in orthodontic clear aligners treatment.MethodsFour groups of mandibular dental arch light-cured resin models will be created, including: mandibular posterior teeth with standard torque, mandibular posterior teeth with labial torque, and mandibular posterior teeth with lingual torque. Each group will consist of 12 sets of clear aligners. The aligners will be worn, and measurements will be taken using the six-axis measurement platform to evaluate the three-dimensional force exerted on the lower anterior teeth under various initial torques applied to the mandibular posterior teeth. SPSS 26.0 used for ANOVA analysis, α = 0.05 significance level.ResultsComparing mandibular posterior teeth with standard torque to those with labial torque, no statistically significant changes were observed in buccolingual force. In the mesiodistal direction, mandibular incisors exhibited a significant decrease in distal force, while canines showed a significant increase. Both findings had a significance level of P < 0.05; Lingual torque on mandibular posterior teeth, compared to standard torque, led to a significant increase in lingual force for incisors and a significant increase in labial force for canines in the buccolingual direction (P < 0.05). Additionally, mandibular incisors exhibited a significant decrease in distal force in the mesiodistal direction (P < 0.05).ConclusionVarying initial torques on mandibular posterior teeth significantly impact force on lower anterior teeth. Labial torque reduces lingual force on incisors and increases distal force on canines. Lingual torque increases lingual force on incisors and labial force on canines.

Microleakage of two resin composites by using different light curing systems

This study was conducted to evaluate marginal microleakage of two resineomposite (Glacier resin composite and Filtek P 60 resin composite) either cured witheonventional light cure unit ( Astralis 5) or light emitting diodes (LED) light cure unit»Radii). Forty class V cavities were prepared in 20 extracted second premolars, onebuccaly and one palataly in each tooth. Each cavity was located lmm coronal toeementoenamel junction and lmm apical to it. The teeth were randomly divided into 4groups, each group of five teeth (I0 cavities): Group I was filled with Glacier resincomposite and cured with LED curing unit. Group ll filled with Glacier and curedin ith Astralis 5 curing unit. Group lll filled with Filtek P60 resin composite and curedv- ith LED curing unit. Group IV filled with Filtek P 60 and cured with Astralis curingxnit. The teeth were stored in distilled water for seven days. Then the apices of theteeth were sealed with sticky wax and the teeth were covered with two layers of nailvamish except lmm around the restoration. The teeth were immersed in 0.5% basicfaehsin dye for 24 hours at 37°C in the incubator and then were longitudinallyxctioned in a buccolingual direction and the extent of dye penetration was recorded.The statistical analysis of the result revealed that the use of LED light cure unit,results in highly significant reduction in the microleakage occlusally and gingivally