Premolars Research Articles

Investigation of fracture resistance with different diameters of polyetherketoneketone posts and cores material: A pilot study

Objectives: The primary objective of this study is to investigate the resistance to fracture of Polyetherketoneketones PEKK, used as post and core by fabrication in different diameters in the canal, and comparing the test results for each group. Methods: Thirty extracted mandibular premolars were selected, endodontically treated and prepared to receive the post and cores milled from polyetherketoneketone disk. The specimens were randomly divided into five groups (n = 6) respectively: group 1 received pekk post with diameter = 0.70 mm, group 2 received pekk post with diameter = 0.90 mm, group 3 received pekk post with diameter = 1.10 mm, group 4 received pekk post with diameter = 1.50 mm, and group 5 received pekk post with diameter = 1.70 mm. All the posts were cemented using a self-adhesive resin cement. Fracture resistance was tested using a universal testing machine, failure patterns were then observed visually and radiographically. For the fracture resistance test, the Universal Testing machine employed the load cell of 10KN and the speed of the cross head of 1mm/min. Data was analyzed using Oneway analysis of variance (ANOVA) followed by Tukey post-hoc test in order to determine significant differences among groups and the materiality threshold was set at α = 0.05. Results: Statistical analysis revealed that the observed differences among the five groups were not significant. None of the PEKK posts caused any fracture in the root, and this observation was visually and radiographically confirmed across all groups. Conclusions: The dentist will be able to turn the diameter of the PEKK post and core as thin as 0.70mm till 1.70mm depending on the clinical requirement with no risk of root fracture, as specified by the guidelines of this research.

An in vitro comparison of the fracture resistance of MOD inlay restorations using different lithium disilicates

Objective: The objective of this study was to evaluate and compare the fracture resistance of MOD inlay preparations restored with two different lithium disilicate glass ceramics. Materials and Methods: Standardized MOD inlay cavities were prepared on 64 human permanent premolar teeth and divided into two groups to be restored with lithium disilicate glass-ceramic materials, i.e. Group I with IPS e.max Press HT and Group II with Shofu Vintage LD Press T. The fracture resistance was assessed using a universal testing machine and recorded in Newtons (N). Statistical analysis was done using SPSS software (Version 17.0, IBM, USA). P <0.05 was set as a statistically significant level. Unpaired Student’s t-test was used to compare the fracture resistance values of both groups. Results: The mean fracture resistance value obtained for Group I (IPS e.max Press HT) was 565.04 N while that obtained for Group II was 732.75 N. Statistically significant difference was found in this intergroup comparison (P = 0.002). Conclusion: The fracture resistance of MOD inlay preparations restored with Vintage LD Press T (Shofu) was significantly higher than those restored with IPS e.max Press HT (Ivoclar Vivadent).

Effect of Collagen Plug and Bone Graft on Bone Formation in Rabbit Extraction Model

1. Purpose : This study aimed to investigate the differences in bone regeneration capacity following extraction between a control group without biomaterial placement and experimental groups where biomaterials were inserted (including xenograft, synthetic bone-containing collagen plugs, and collagen plugs).2. Materials and Methods : Bilateral extraction of maxillary first premolars or second premolars was performed, dividing the rabbits into four groups [① Group 1 :no bone graft or collagen plug inserted, ② Group 2: collagen plug inserted after extraction, ③ Group 3: collagen plug containing synthetic bone inserted after extraction, ④ Group 4: xenograft material inserted after extraction]. After euthanized the rabbit, Four and eight weeks postoperatively, the extent of bone formation were evaluated histologically and radiographically.3 Results : The degree of new bone formation using histological analysis showed higher results in both the control groups at weeks 4 and 8, although not statistically significant. Across all groups, higher bone formation was observed at 8 weeks compared to 4 weeks. In radiological analysis using micro CT, Bone Mineral Density (BMD) and Bone Volume/Tissue Volume(BV/TV) were highest in Group 4. Trabecular bone thickness(Tb.Th) was highest in the control group, but not statistically significant.4. Conclusion : In all groups, the degree of new bone formation at 4 and 8 weeks did not show statistically significant differences histologically and radiologically.

Evaluation of Injectate Distribution of the Middle Mental Nerve Block Within the Mandibular Canal in a Cadaveric Canine Model.

Awareness among veterinarians has increased regarding the need for comprehensive pain relief, but many companion animal veterinarians do not administer regional analgesia pre-emptively during dental procedures. The middle mental nerve (MMN) block desensitizes the ipsilateral mandibular incisor and canine teeth as well as soft tissues rostral to the delivery site. There is little published information on the efficacy of the MMN block in dogs. The objective of this study was to determine injectate distribution within the mandibular canal using a radiopaque contrast media/methylene blue solution. Half a milliliter of solution was injected within the opening of the middle mental foramen using a standard hypodermic syringe and a 25G x 25 mm needle. The course of the injectate was traced both via computed tomography (CT) and, in some cadavers, gross dissection. Post-treatment CT revealed that in 90% of the cases, the contrast diffused at least as far caudally as the mesial root of the third premolar tooth. The injectate was not identified within the canal of 5% of cadaveric mandibles examined. Although the solution used diffused caudally within the mandibular canal when injected using recommended clinical techniques, this may not completely represent the extent of clinical effects experienced in live patients. This technique also confirmed that the needle does not need to be advanced into the mandibular canal to achieve adequate diffusion to at least the mesial root of the third premolar tooth.

Analysis of Impacted Mandibular Second Premolar Finding Trough Panoramic Radiograph: A Case Report

Abstract: An impacted tooth is a tooth that cannot erupt to its normal functional position after the development of the root. The mandibular second premolar is the third most impacted that can potentially cause problems in the tooth and surrounding structures. Panoramic radiography can detect and evaluate the impacted tooth, surrounding tissues, and possible pathologies including cysts and tumors. This study aimed to discuss the findings of impacted mandibular second premolar on panoramic radiograph. We reported a 13-year-old male patient who came to RSIGMP-UMI complaining of protruding upper front teeth and occasional food impaction in the right lower anterior molar area. Panoramic radiograph showed a vertical angulation of tooth 45, with the crown directed towards the occlusal line between teeth 46 and 44, and the apex directed towards the mandibular ramus border approaching the mandibular canal, with an inclination 0° and type I. Panoramic radiographs are essential in dentistry, particularly in orthodontic treatment. In this case, the radiograph revealed an impacted mandibular second premolar. Extraction of this tooth is often necessary for optimal treatment outcomes. However, in this case, the patient's parents were still hesitant to proceed with tooth extraction. Keywords: impacted teeth; second premolar teeth; panoramic radiography

Mental Foramen as a Guide to Establish Sexual Dimorphism among Eastern Indian Population: An Observational Cross-sectional Study on Dry Bones

Abstract Context: The study deals with a role of mental foramen in determining the sexual dimorphism of mandibles as well as generating the sufficient data for the dental surgeons regarding location and measurements of the same. Aims: The aim of the study was to determine the location of mental foramen with respect to the different bony points of mandible and the presence of accessory foramen, if any and to establish sexual dimorphism among mandibles in relation to mental foramen and assessing the role of mento-submental angle for the same. Settings and Design: An observational cross-sectional study was conducted at Medical Colleges of West Bengal. Materials and Methods: Two hundred and eighty dry mandibles were used. Digital images were captured with digital camera after placing the bones in anatomical position for suitable views. Measurements were taken with the help of ImageJ software. Statistical analysis was performed using the SPSS software. Statistical Analysis Used: Measures of central tendency were determined. Significance was tested using the Chi-square test or unpaired Student’s t test, as applicable. Results: Most of the mental foramina were in line with the second premolar tooth or between the first and second premolars. Distance from the alveolar margin and the diameters of foramen were statistically significant among the genders. Mento-submental angle was significantly lower in males as compared to females being <115° and >115°, respectively. The prevalence of accessory mental foramen was very low in both genders. Conclusions: Sexual dimorphism can be well established from the morphometry of mental foramen of mandibles in the Eastern Indian population.

Effectiveness of palatal anchorage device (PAD) for maxillary anterior retraction with clear aligners using finite element study.

The palatal anchorage device (PAD) is commonly used in fixed appliance for anchorage, but the biomechanics of PAD in patients treated with clear aligners(CAs)remains poorly understood, especially in its elastic mode and force magnitude. This study aimed to assess the biomechanical effects of using PAD for retraction during clear aligner treatment (CAT) with the extraction of two maxillary first premolars. Four finite element models were created: (1) Incisors retraction (IR) with active contraction of the clear aligner only; (2) IR with PAD using different forces (50,75,100g) or not; (3) PAD without IR (forces of 50,75,100g), and (4) Different elastic directions (D1, D2, D3) from aligner to PAD without IR. IR caused lingual tipping and extrusion of the central incisors, as well as mesial and buccal tipping of the first molar. PAD during IR provided strong anchorage for the first molar, with elastics slightly increasing the lingual tipping and extrusion of the central incisors. Elastics applied to the U-shaped arch led to central incisor intrusion and reduced lingual retraction. The highest stress was observed on the mesial attachment of the canine. PAD effectively reinforced posterior anchorage in CAT, while anterior positioning facilitated anterior teeth intrusion. The biomechanical importance of the canine's mesial attachments in maxillary teeth treatment planning was highlighted.

Sealing Ability of Bioceramic Sealer after Ultrasonic Activation of Different Root Canal Irrigating Solutions

Aim To evaluate and compare the sealing ability of bio ceramic root canal sealer after ultrasonic activation of root canal irrigation solutions 3% NaOCl , 40% Citric acid & Neem leaf extract .  Materials and Methods In this study, 42 mandibular premolar teeth with single roots and canals were divided into three groups for irrigation: 3% NaOCl, 40% citric acid, and Neem leaf extract. After access preparation and glide path creation with a #10 K-file (0.02 taper), the canals were instrumented using a crown-down technique to an ISO size of 30, with saline as the irrigant. Ultrasonically activated irrigation was used, followed by saline in all groups. The canals were obturated with Dentsply Gutta- percha and Bio C sealer, 1mm short of the working length, and sealed with temporary restorations. Teeth were incubated at 37°C for 3 days, and horizontal sections at 3mm from the apex were taken. Confocal laser scanning microscopy measured sealer penetration, and statistical analysis was conducted to compare results between groups.  Results The results suggest that 40% citric acid is the most effective irrigant for enhancing sealer penetration into dentinal tubules at the apical third, both in terms of percentage and depth of penetration, compared to 3% NaOCl and neem leaf extract. This indicates that citric acid may improve the sealing ability of root canal treatments more effectively than the other tested irrigants.  Conclusion The results suggest that 40% citric acid is the most effective irrigant for enhancing sealer penetration into dentinal tubules at the apical third, both in terms of percentage and depth of penetration, compared to 3% NaOCl and neem leaf extract. This indicates that citric acid may improve the sealing ability of root canal treatments more effectively than the other tested irrigants.

Evaluation of dental students' learning curve in intraligamentary anesthesia using different syringe systems: A prospective crossover study.

This prospective crossover preclinical trial aimed to evaluate the learning curve of dental students in successfully administering intraligamentary anesthesia (ILA) using three different syringe systems. Dental students performed ILA using three devices in two separate sessions, each targeting mandibular and/or maxillary premolars. The devices included two manual systems (pistol-type and lever-based) and one computer-controlled local anesthetic delivery system (CCLAD). The primary research parameter was the success rate of anesthesia, defined as the percentage of successful ILA administrations confirmed by a negative response to a cold test. Secondary parameters included pain experienced during needle penetration and injection, students' self-reported levels of mental tension and handling of the syringes, and any potential side effects. A total of 110 students performed ILA on 599 teeth during the study period. When comparing the CCLAD system to the manual syringes, the CCLAD system exhibited a significantly higher overall success rate in the first session (92.5% vs. 77.4%; p<0.001), potentially due to its precise control of anesthetic flow and pressure, which likely facilitated more effective anesthetic delivery. However, when examining the individual manual techniques, no significant difference was found between the pistol-type manual and the CCLAD system (p=0.66). All techniques' success rate increased from the first to the second session (80.4% vs. 86.9%; p=0.0357). Additionally, penetration pain demonstrated a significant decrease across all techniques (p<0.01). Notably, students' anxiety levels decreased, and self-assurance increased significantly over the sessions. Undesired reversible side effects were documented in 10.9% of cases. These findings suggest that repeated practice of ILA, particularly with different syringe systems, enhances anesthetic success and psychological readiness for patient interaction. Additional training sessions may further improve proficiency.

Multi-Scale Characterization of Conventional and Immediate Dental Implant Systems

We hypothesized that the different post-implantation healing stages between the conventional and immediate implantations produce different amounts and tissue composition of the peri-implant bone. Thus, the objective of the current study was to examine whether the stability of dental implant systems is associated with characteristics of the interfacial bone area at different post-implanation healing periods. Mandibular molars were extracted from each beagle dog. After 10 weeks post-extraction, a screw-type titanium dental implant was placed in the molar location following a conventional dental implant (Con) procedure. Simultaneously, mandibular premolars were extracted and the same type of dental implant was placed in the distal site of the extracted premolar root following an immediate dental implant (Imm) procedure. The implant stability quotient (ISQ) values were not significantly different between Con and Imm groups at 0-, 3-, and 6-weeks post-implantation. However, 3D micro-computed tomography and 2D histological images confirmed that the Imm system had more gaps between the bone and implant than the Con system. On the other hand, the nanoindentation modulus value at the bone–implant interface was significantly higher for the Imm group than the Con group at both 3 weeks and 6 weeks post-implantation. The current results from multi-scale characterization suggest that the higher interfacial bone quality of the Imm system, despite its earlier post-implantation stage, plays a crucial role in maintaining stability comparable to that of the Con system.

ETIOPATHOGENIC ASPECTS OF ODONTOGENIC MAXILLARY SINUSITIS OF PERIAPICAL ORIGIN

Anatomically, the roots of the upper premolar and molar teeth are near the maxillary sinuses. Thus, periapical inflammation of the elements close to the sinuses enables the formation of odontogenic sinusitis. This study aimed to analyze the available literature on the etiopathogenic aspects of odontogenic maxillary sinusitis of periapical origin. A literature review was conducted in the following databases: SciELO, MEDLINE/Pubmed, and LILACS, using the keywords "Maxillary Sinusitis", "Dentistry", "Tooth" and "Infection". Articles written in English, Spanish, and Portuguese were included; those that fit the focus of the paper and those that were most relevant in terms of outlining the desired information. Papers reporting odontogenic sinusitis arising from an operative process were excluded. Odontogenic maxillary sinusitis (OMS) occurs due to sinus infection caused by inflammation of one or more dental elements near this cavity. Despite presenting specific features, sinusitis of odontogenic and non-odontogenic origin are quite similar, making the differential diagnosis difficult. Cone-Beam Computed Tomography (CBCT) is considered the reference standard for diagnosis, and the best treatment is to eliminate the causal factor. It was also found that apical periodontitis is the main non-iatrogenic cause and premolars and molars are the most affected teeth due to their anatomical location near the maxillary sinuses. The anatomical location of the maxillary sinus and the roots of the molars and premolars will allow, through the proximity between them, the OMS. In cases where periodontitis has proven to be the most frequent non-iatrogenic cause of this condition, also due to a great symptomatological similarity with non-odontogenic sinusitis, complementary examinations such as CBCT are necessary. Moreover, the treatment can be performed in a case-specific manner, through accurate diagnosis and etiopathogenesis.

Influence of sonic activation of epoxy-resin and calcium silicate sealer on postoperative pain: a patient-blinded, parallel group, randomized clinical trial

BackgroundThis clinical study aims to compare postoperative pain after single-visit root canal treatment of teeth with asymptomatic apical periodontitis using epoxy-resin-based AH Plus and calcium silicate-based Endosequence BC sealers with or without sonic activation.MethodsThis study included 72 individuals with one first or second mandibular premolar tooth with asymptomatic apical periodontitis. They were randomly divided into four groups according to the root canal sealer (AH Plus or Endosequence BC) and activation protocol (sonic activation or non-activation) (n = 18). The participants were ask to rate their postoperative pain intensity on a NRS scale as none, minimal, moderate, or severe after 24 h, 48 h, 72 h, and 7 days following treatment. Patients were also asked to record the number of prescribed analgesic medication tablets (400 mg of ibuprofen) taken. Statistical analysis were performed using the Mann-Whitney U test, the Friedman test, the Spearman’s correlation test, the Chi-square test. Significance level was established at 0.05.ResultsThere was no statistically significant difference in postoperative pain scores or analgesic intake between AH Plus and Endosequence BC sealers regardless of the activation protocol (p > 0.05). There was no statistically significant difference in postoperative pain scores between the sonic activation and non-activation groups (p > 0.05). A weak positive correlation was detected between Endoactivator sonic activation and sealer extrusion (r = 0.36).ConclusionsAH Plus and EndoSequence BC root canal sealers showed similar results in terms of prevalance and intensity of postoperative pain. Sonic activation and non-activation groups had similar postoperative pain scores.Clinical trial registrationThe study was retrospectively registered with ClinicalTrials.gov (NCT06403293). Date of Registration: 07/05/24.

Root canal cleanliness and debris extrusion following retreatment of thermoplastic injection technique and bioceramic-based root canal sealer.

To evaluate the amount of apically extruded debris and to determine the remaining filling material on the root canal walls by microcomputed tomography (micro-CT), following the root canal retreatment of root canals filled with different obturation techniques (single cone technique, thermoplasticised injection technique) and the different root canal sealers [bioceramic-based, epoxy resin-based root canal sealer]. 60 single rooted human premolar teeth were prepared with the ProTaper Gold system (Dentsply Maillefer) up to the F4 file and the samples were divided into 4 groups according to obturation procedures: Single cone technique + AH Plus sealer(epoxy resin-based root canal sealer, Dentsply International Inc., York, PA, USA); Single cone technique + Sure-Seal Root(bioceramic-based root canal sealer, Sure Dent Corporation, Gyeonggi-do, South Korea); thermoplastic injection technique[Calamus Dual Obturation System(Dentsply-Tulsa Dental, Tulsa, OK, USA)] + AH Plus(Dentsply International Inc.); Sure-Seal Root(Sure Dent Corporation) + Calamus Dual Obturation System (Dentsply-Tulsa Dental). The teeth were inserted into preweighed Eppendorf tubes and retreatment was performed. The tubes were kept in an incubator at 37°C for 14days to obtain the dry debris weight. Following the removal of the root canal fillings, the samples were scanned with a micro-CT device to analyse the volume of filling residues. Retreatment of samples obturated with epoxy-resin or bioceramic based root sealers combined with Calamus system resulted in higher amount of apical extrusion compared to their combination with single cone technique (p = 0.026 for Single cone technique + AH Plus sealer vs Calamus + AH Plus sealer and p = 0.005 for Single cone technique + Sure-Seal root sealer vs Calamus + Sure-Seal root sealer). The most debris was observed in the Calamus + Sure-Seal root sealer group, the least debris was observed in the Single cone technique + AH Plus sealer group. The percentage of residues was the highest in the Single cone technique + Sure-Seal root sealer and the lowest in the Calamus + AH Plus sealer group, but there were no significant differences between groups (p = 0.463). No correlation was observed among the groups in terms of extruded debris and remnants inside the root canal. When combined with bioceramic based sealer, thermoplasticised injection technique did not affect the cleanliness of root canal walls; however, it increased its apical extrusion potential during retreatment. The obturation method does not play a role in the removability of bioceramic based root canal sealer, however the use of bioceramic-based root canal sealers with cold obturation techniques may be beneficial in preventing apical extrusion.

Effectiveness of Activated Sodium Hypochlorite Irrigation by Shock Wave-Enhanced Emission Photoacoustic Streaming, Sonic and Ultrasonic Devices in Removing Enterococcus faecalis Biofilm From Root Canal System.

Aim: To compare shock wave-enhanced emission photoacoustic streaming (SWEEPS) with sonic- and ultrasonically activated irrigation systems in removing Enterococcus faecalis biofilm from the root canal system. Methodology: Fifty human single-canalled mandibular premolars were included in the study. After access cavity preparation, the root canals were prepared to a standardized size and taper. Then, the entire root surface was covered with two layers of resin, and the root apices were sealed before sterilization. All root canals were inoculated with E. faecalis biofilm, and the samples were incubated aerobically for 2 weeks at 37 °C. Biofilm formation was confirmed by scanning electron microscopy. All samples were randomly divided into five groups (n = 10 each) based on their irrigation activation method as A (no treatment or negative control), B (no irrigation or positive control), C (sonically activated irrigation (SAI)), D (ultrasonically activated irrigation (UAI)), and E (needle irrigation activated by an Er: YAG laser device using a SWEEPS quartz tip (SWEEPS)). Then, dentine chips were retrieved, vortexed, and diluted for colony-forming unit counts. Data were analysed using analysis of variance and post-hoc Tukey tests (α = 5%). Results: All methods could significantly reduce E. faecalis biofilm compared with control so that the UAI, SWEEPS, and SAI groups indicated a 23.54%, 14.89%, and 7.81% biofilm reduction, respectively. UAI demonstrated a significantly more effective reduction of E. faecalis biofilm than SAI (p = 0.004). Conclusions: All irrigation activation methods significantly reduced E. faecalis biofilm, with ultrasonic use being the most effective.

Fechamento de diastemas com faceta direta de resina composta: relato de caso

The search for an aesthetic standard is increasingly frequent and restoring a harmonious smile represents a real challenge for restorative dentistry. Composite resins are aesthetic and adhesive materials that have received special attention for ensuring predictable and lasting results with minimal tooth sacrifice. The technique of making direct veneers is simple, but requires discretion and attention from its indication to the final stages of its execution. The procedure has high success rates and predictable results with desirable longevity for anterior teeth. The objective of this study was to present a clinical case of diastema closure with direct composite resin veneers on anterior teeth and maxillary first premolars, with the aid of diagnostic wax-up for better accuracy of work on anterior teeth. It is concluded that the application of the direct restorative technique allowed a fast, low, cost and less invasive treatment. Providing a satisfactory result, raising self-esteem and allowing a restoration of the patient's facial aesthetics.

Efficacy of Bone Anchored Pendulum Appliance Over Conventional Pendulum Appliance during Molar Distalization in the Orthodontic Management of Class II Malocclusion : A Systematic Review

Background: Pendulum appliance used commonly used to achieve molar distalization in the management of borderline class II malocclusion is associated with mesial tipping of the maxillary premolars and proclination of maxillary incisors post-distalization, resulting in round tripping and increased treatment time. Bone Anchored Pendulum Appliance (BAPA) is one of the modifications of the pendulum that could effectively prevent anchorage loss. Aim: To evaluate the effectiveness of Bone Anchored Pendulum Appliance(BAPA) over the Conventional Pendulum Appliance(CPA) for the distalization of maxillary molar in the management of Class II malocclusion. Materials and Methods: A web search was done in Google Scholar, MEDLINE, Web of Science, LILAC and COCHRANE Library databases using PRISMA guidelines. The search included RCTs and Non RCTs (Both Prospective and Retrospective studies) comparing distalization achieved by BAPA with CPA in Class II malocclusion. The Risk of bias was assessed using the ROBINS - I tool. Results: Of the initial 745 articles, 5 studies met the inclusion criteria and were included to the systematic review. The BAPA showed between 4.8 -6.4 mm of molar distalization and between 9 °-11.3° of distal tipping of molars while the distalization achieved with CPA was between 2mm -6.4mm with 6.67° -14.50° of distal tipping. While CPA groups showed mesial tipping of premolars, distal tipping of premolars was observed with the BAPA appliances. Conclusions: BAPA were found to significantly reduce anterior anchorage loss, distalise the premolars and molars. There is moderate evidence that BAPA provides greater distalization with reduced incidence of unwanted tooth movements.

ProDesign Logic Files Effect on Apical Foramen Wear and Shape Transformation After Foraminal Enlargement.

This study aimed to evaluate the effect of ProDesign Logic files 45.01 and 50.01 on apical foramen wear and shape transformation after foraminal enlargement at tooth length (TL) and 1 mm beyond. Sixty freshly extracted single-rooted lower human premolars teeth were distributed randomly into five groups (n = 12): Group 1 (40.05 WL) (control): No foraminal enlargement, Group 2 (45.01 TL): Specimens underwent foraminal enlargement with 45.01 Prodesign Logic file at TL; Group 3 (45.01 TL + 1): Specimens underwent foraminal enlargement with 45.01 Prodesign Logic file at 1 mm beyond TL; Group 4 (50.01 TL): Specimens underwent foraminal enlargement with 50.01 Prodesign Logic file at TL; Group 5 (50.01 TL + 1): Specimens underwent foraminal enlargement with 50.01 Prodesign Logic file at 1 mm beyond TL. Scanning electron microscopy was used to evaluate apical foramen variations and shape alterations. Data were analyzed by Student's t-test, Kruskal-Wallis, and Mann-Whitney test. Significant differences (p < 0.01) were observed among all tested groups compared to the control group in terms of the average worn area of the apical foramen. Foraminal enlargement led to significant shape transformation, resulting in round-shaped foramina. ProDesign Logic 45.01 and 50.01 files at TL causes notable wear and round-shaped foramina.

Post-Space Disinfectants With Sodium Hypochlorite and Methylene Blue Loaded in Silver and Quartz Nanoparticles Activated by Photodynamic Therapy. A SEM Analysis.

Post-space disinfectants methylene blue loaded with silver (Ag) and Quartz nanoparticles (NPs) and MB alone activated by photodynamic therapy (PDT) on the survival of Enterococcus faecalis, smear layer (SL) removal efficacy, and extrusion bond strength (EBS) of fiber posts to canal dentin. Hundred mandibular premolars underwent root canal treatment using the rotary ProTaper system. The canals were obturated and post-space was prepared up to a length of 8 mm, maintaining a 5 mm seal. To assess antibacterial efficacy E. faecalis were inoculated in the canal (n = 20). The samples were then randomly allocated into four groups according to the canal disinfectant used to sterilize the canals. Group 1: 2.5% NaOCl+17% EDTA, Group 2: MB-PDT, Group 3: MB@QP-PDT, and Group 4: MB@AgNP-PDT (n = 25). SEM analysis was conducted on five samples from each disinfectant group to assess the removal of the SL. Survival rates were calculated (n = 5 from each group). Glass fiber post (GFP) was cemented to the root dentin of the remaining samples followed by artificial aging. Sectioning of the specimens was performed in all three-thirds of the canals. PBS was assessed followed by failure evaluation. ANOVA and Tukey post hoc test were used to compare the E. faecalis survival rate and PBS of fiber post among different investigated groups. Group 4 (MB@AgNP-PDT) treated canals exhibited the minimum survival rate (0.30 ± 0.04 CFU/mL) of E. faecalis and maximum PBS. However, the highest survival rate and minimum bond strength of GFP were observed in Group 1 (NaOCl+17% EDTA) and Group 2 (MB-PDT) treated teeth respectively. The highest SL removal was recorded in the coronal section of the samples of Group-4 disinfected with MB@AgNP-PDT. The lowest removal of SL was recorded in Group 2 samples sterilized with MB-PDT at apical one-third. Silver nanoparticles when utilized as nano-carriers to enhance the efficiency of MB activated by PDT, have been shown to exhibit the highest antimicrobial potency, improved capacity for SL removal and improved PBS.

Evaluating the Restoration of External Root Resorption Under Biomechanical Stress: A Finite Element Analysis.

Root resorption is a complex problem in endodontic treatment that considerably affects the structural integrity of teeth. This study aims to assess the biomechanical efficacy of various restorative materials and approaches in treating external root resorption, emphasizing their capacity to improve stress resistance and guarantee long-term success. This research employed finite element analysis (FEA) to assess stress distribution in mandibular premolars with external root resorption. Eight models, demonstrating apical and mid-level resorption, were repaired using mineral trioxide aggregate (MTA), Biodentine, or a mixture of these materials with gutta-percha. In order to evaluate each technique's biomechanical performance, the models were exposed to both vertical and oblique stresses. The findings demonstrated that complete canal obturation with Biodentine or MTA greatly lowered stress levels, with Biodentine exhibiting a marginal advantage. The hybrid approach utilizing gutta-percha produced elevated stress concentrations, especially under oblique loading conditions. MTA and Biodentine are effective in enhancing resistance to biomechanical forces in teeth with external resorption. However, the combination of gutta-percha with these materials reduces resistance, especially under oblique forces. These findings highlight the importance of material selection in restoring resorbed teeth and improving clinical outcomes.

Anchorage loss of the posterior teeth under different extraction patterns in maxillary and mandibular arches using clear aligner: a finite element study

BackgroundExtracting the premolars is an effective strategy for patients with bimaxillary dentoalveolar protrusion. Clear aligners (CAs) close the extraction spaces through shortening the length of aligners. The contraction force generated by the terminal of aligners makes the posterior teeth tip mesially, which is known as the roller coaster effect. This phenomenon is even worse in the 2nd premolar extraction cases. Posterior anchorage preparation is commonly used to protect the angulation of molars, taking the form of presetting distal tipping value. However, the distal tipping design aggravates the anchorage loss of anterior teeth simultaneously. This study aimed to explore the different anchorage loss of the posterior teeth when the 1st or 2nd premolars were extracted using CAs, respectively in maxillary and mandibular arches, further providing guidance for anchorage preparation design in clinical practice.MethodsTwo bimaxillary finite element models with different extraction patterns were established to simulate the anterior en-masse retraction process of the CAs. In Model 1, the maxillary and mandibular 1st premolars were extracted, while in Model 2, the 2nd premolars were extracted. Finite element analysis methods were utilized to analyze the tipping angle of the anterior and posterior teeth.ResultsCompared between two models, the anterior teeth exhibited a greater lingual inclination tendency and the posterior teeth exhibited a slighter mesial tipping tendency in Model 1 regarding individual tooth. The closer to the extraction spaces, the greater the tip, and the distal tipping tendency of the 1st premolars was more evident than the mesial tipping tendency of the 1st molars in Model 2. Compared between the maxillary and mandibular arches, the mesial tipping tendency of individual posterior tooth was more evident in the maxilla. In addition, the highest hydrostatic stress of the periodontal ligaments was concentrated on the cervical and apical parts directly adjacent to the extraction spaces, and it exhibited relatively uniform distribution in Model 1.ConclusionsThe individual posterior tooth showed the same mesial tipping direction but to different degree when the 1st or the 2nd premolars were extracted during clear aligner treatment. Presetting anchorage preparation design for the posterior teeth is essential to alleviate the roller coaster effect, especially in the 2nd premolar extraction cases. Furthermore, larger anchorage preparation value should be proposed for the maxillary posterior teeth.