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Orthodontic relapse and the demand for improved esthetics often necessitate retreatment in adult patients. This case report highlights the successful management of an adult female patient with bimaxillary protrusion, previously treated with a non-extraction approach. Treatment included lingual passive self-ligating appliances, premolar extractions, and mini-screws to reinforce anchorage. The patient's facial profile and dental esthetics were significantly improved after 20 months of treatment, achieving a stable occlusion and reduced bimaxillary protrusion. This case demonstrates that lingual appliances can be an effective and esthetic treatment option for complex orthodontic retreatment in adult patients. Careful biomechanical planning and attention to specific challenges, including torque control and bowing effect, are essential for successful outcomes.

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Aim Rotation of the mandibular premolars during aligner treatment is a difficult movement to achieve accurately. The purpose of this study is to compare the effects of different attachment types and positions used in clear aligner treatments on the rotation movement and retention of clear aligners in the rotated first premolar teeth. The study also addressed the stress values in periodontal ligaments (PDLs) with finite element analysis. Materials and methods For purposes of this research, we created a mandibular tooth model and modeled the premolar tooth with a 30° rotation. Twelve separate groups were created by attaching horizontal rectangular, vertical rectangular, ellipsoid, and semi-ellipsoid attachments to the premolar tooth in buccal, lingual, and combined buccal and lingual ways. A model without attachments was created to be used as the control group. An activation movement of 0.25 mm was applied to the first premolar tooth in all 12 models. The study evaluated clear aligner displacement, von Misses stress on the PDL, and tooth displacements using the finite element stress analysis method. Results It was found that the group with horizontal rectangular attachments placed on both the buccal and lingual sides had the highest stress value in the PDL (0.1971 MPa) and the highest displacement in the tooth (0.1267 mm). Conversely, the group with semi-ellipsoid attachments placed both buccally and lingually had the least displacement movement in clear aligners (0.1441 mm). Conclusion The results indicate that groups with attachments provided better retention than groups without attachments. Models with horizontal, rectangular attachments showed significantly more tooth displacement compared to other models. Horizontal rectangular attachments placed buccally and lingually combined to provide tooth movement in rotated mandibular first premolars can be recommended for clinical use.

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This study aimed to assess the alterations in the temporomandibular joint among adult patients undergoing orthodontic treatment involving the extraction of four premolars. A cohort of 44 adults, with a mean age of 24.2 years, underwent orthodontic therapy that included quadruple premolar extractions. Cone-beam computed tomography scans were performed before and after the treatment to evaluate the temporomandibular joints. The three-dimensional assessment focused on the condylar position relative to the cranial base and the articular fossa, the axial condylar rotation, and the joint spaces. Notably, a significant posterior shift of the condyle was detected (P≤0.01), averaging a 0.41mm retraction. The posterior joint space narrowed by 0.32mm post-treatment. Additionally, a medial tilt of 0.62° in the condyle's long axis was observed in the frontal plane. No significant changes were recorded for the other condylar positions, rotations, or joint space dimensions. The findings suggest that orthodontic treatment with four premolar extractions may instigate condylar repositioning and rotation. These insights can inform refinements in treatment protocols.

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The objective of this study was to assess alterations in maxillary sinus mucosa thickness and the distances between the apexes of specific teeth and the maxillary sinus base in adult patients undergoing orthodontic treatment with the extraction of four first premolars. Twenty-one adults, averaging 24.85 years of age, received orthodontic therapy involving the extraction of all four first premolars. Cone-beam computed tomography scans were conducted before and after treatment to evaluate changes. Notably, post-treatment scans revealed a significant increase (P= 0.044) in the distance between the apex of the second premolar and the maxillary sinus floor, with an average augmentation of 1.0141 millimeters. However, no notable alterations were detected in the distances between the apexes of other teeth and the maxillary sinus or in maxillary sinus mucosa thickness. These findings suggest that orthodontic treatment with the extraction of four first premolars may elevate the distance between the maxillary sinus floor and the second premolar apex, which provides a reference for risk assessment and surgical design of first premolar extraction during orthodontic treatment.

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The mandibular first premolar, which is the anteriormost tooth in the mandibular arch, differs from other teeth in that it typically has two roots and two to four canals. The current case involves treating a mandibular first premolar with two canals through endodontic therapy. The 42-year-old male patient's left mandibular first premolar was diagnosed with irreversible pulpitis. The lateral view X-ray depicted two canals. In the dental procedure, endodontic treatment involves working under an operating microscope and using magnification to treat the affected tooth. After canal shaping the tooth was treated with the crown after it had been cleaned and then adjusted for the bite. As aforementioned, no signs of periapical disease were observed when the tooth was rediscovered a year later. However, this case study indicates that any shift in the anatomy of the canal in premolars should be well monitored and controlled to improve endodontic treatment outcomes of such teeth as the mandibular first premolars.

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This retrospective study assessed maxillary premolar and molar teeth and identified roots with incomplete apical bone coverage using cone beam computed tomography in 161 dogs. The associated dorsal anatomic sites that the roots communicated with were the ventral nasal meatus, maxillary recess, infraorbital canal, and pterygopalatine fossa. The study found that all roots of the maxillary premolar and molar teeth have the potential for incomplete apical bone coverage, with 26.7% having incomplete apical bone coverage. No significant association with sex was found. A significant association with weight was found, and this lowered with increasing body weight. Facial index, as a determinate of skull shape, was found to be significant in only 35.7% of roots in univariate and 14.2% of roots in multivariate modeling. Knowledge of the anatomy of these roots plays an important role in safe and effective extraction techniques, in reducing iatrogenic trauma, and in understanding the potential local effects of periodontal and endodontic disease.

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A complete understanding of canal morphology is essential to achieve successful endodontic treatment. Although mandibular second premolars are reported to have usually only one root canal at the apex, in this case we reported a mandibular second premolar with three root canals and taurodont morphology. A patient was referred to the endodontic department at Mashhad Faculty of Dentistry with a chief complaint of pain in her mandibular right second premolar tooth. The diagnosis of pulpal necrosis and chronic apical periodontitis was established. The initial radiograph showed a taurodont premolar with two roots. However, with cone-beam computed tomography assistance, three root canals were confirmed. The root canal treatment process was successfully managed with a dental operating microscope. Using cone-beam computed tomography and a dental operating microscope greatly facilitated the determination of tooth morphology and successful following nonsurgical endodontic treatment.

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Introduction: This study aimed to compare the effectiveness of two endodontic cleaning techniques, passive ultrasonic irrigation (PUI) and the XP-endo Finisher R (XPR) system, in removing residual filling material during endodontic retreatment procedures. Materials and Methods: Forty mandibular premolars with oval canals were divided into four groups based on the sealer used (AH-Plus or Bio-C Sealer) and the cleaning technique employed (PUI or XPR). To ensure uniformity of canal volume among groups, initial micro-CT scans were conducted. The canals were instrumented, filled, and then re-instrumented before undergoing either PUI or XPR cleaning techniques. Residual filling material volumes were assessed through micro-CT scans, and statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney U tests. Results: Following instrumentation, there was no significant difference in residual filling material volumes between AH-Plus and Bio-C Sealer groups (1.35 mm3and 1.02 mm3, respectively; P>0.05). However, after supplementary cleaning techniques, XPR-cleaned specimens exhibited significantly less residual material compared to PUI-cleaned specimens (0.01 mm3 and 0.29 mm3 for Bio-C Sealer, and 0.07 mm3 and. 0.30 mm3 for AH-Plus, P<0.05). Conclusion: The XPR system was found to be more effective than PUI in removing residual filling material from Bio-C Sealer-filled root canals. This highlights its potential as a useful supplementary cleaning technique in endodontic retreatment procedures.

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Proclination of anteriors is significantly found in developing malocclusions and affecting both aesthetics and function. In patients with protrusions or crowding, extraction therapy is often necessary. Orthodontic treatment is initiated with the extraction of maxillary first premolars to address the protrusions or crowding and achieve a harmonious occlusion. There are two ways to retract anteriors during extraction space closure: friction or frictionless. The present case report explains the innovative treatment approach for the correction of anterior protrusion using multiple variability (MV) loops. Even with the good efficiency of the MV loop, meticulous wire bending is one of the disadvantages of the loop, and it requires clinician skills. Smaller loop fabrication will be the future scope of the appliance to increase patient compliance toward the treatment using MV loop as it will cause less hindrance in the vestibular region.

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In recent years, dental implants have become a trend in the treatment of human patients with missing teeth, which may also be an acceptable method for companion animal dentistry. However, there is a gap challenge in determining appropriate implant sizes for different dog breeds and human. In this study, we utilized skull computed tomography data to create three-dimensional models of the mandibles of dogs in different sizes. Subsequently, implants of various sizes were designed and subjected to biomechanical finite element analysis to determine the optimal implant size. Regression models were developed, exploring the relationship between the average weight of dogs and the size of premolar implants. Our results illustrated that the regression equations for mean body weight (x, kg) and second premolar (PM2), third premolar (PM3), and fourth premolar (PM4) implant length (y, mm) in dogs were: y = 0.2785x + 7.8209, y = 0.2544x + 8.9285, and y = 0.2668x + 10.652, respectively; the premolar implant diameter (mm) y = 0.0454x + 3.3506, which may provide a reference for determine suitable clinical implant sizes for dogs.

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Odontogenesis, the process of tooth formation, is complex and susceptible to disruptions that can result in dental anomalies such as tooth impaction. The mandibular second premolar, though less commonly impacted than wisdom teeth, presents a unique challenge in pediatric dentistry due to its intricate etiology and the need for timely intervention. This case report aims to highlight the significance of early diagnosis and conservative management strategies in treating mandibular second premolar impaction. The case involves a pediatric patient with impacted mandibular second premolars. Initial treatment included the use of a lower removable appliance with an expansion screw to alleviate crowding, followed by a fixed space maintainer and a Haas rapid palatal expander. These interventions created the necessary space for the premolars to erupt. Self-ligating brackets were later applied, reducing friction and improving periodontal health. The patient underwent two CBCT examinations to monitor progress, which confirmed the successful eruption and alignment of the impacted premolars without the need for surgical exposure. This case underscores the effectiveness of early diagnosis and minimally invasive treatment in managing mandibular second premolar impaction. The tailored approach facilitated the natural eruption of the teeth, highlighting the importance of individualized treatment plans. Future research should focus on optimizing these conservative strategies to enhance patient outcomes in similar cases.

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OBJECTIVES: This study aimed to investigate the influence of access cavity designs on the mechanical properties of a single-rooted mandibular first premolar tooth under various static loads using a finite element analysis. MATERIALS AND METHODS: 3-dimensional FEA designs were modeled according to the access cavity designs: an intact tooth (control), traditional access cavity (TEC-I), traditional access cavity with Class-II mesio-occlusal cavity design (TEC-II), conservative access cavity (CEC), ninja access cavity (NEC), caries-driven access cavity (Cd-EC), buccal access cavity (BEC) and bucco-occlusal access cavity (BOEC). After the simulated access cavity preparations, root canal treatment was simulated and three different static loads which mimicked oblique and vertical mastication forces were applied to the models. The stress distribution and maximum Von Misses stress values were recorded. The maximum stress values were obtained on both enamel and dentin under multi-point vertical loads. RESULTS: The maximum stress values were obtained on both enamel and dentin under multi-point vertical loads. Under all load types, the minimum stress distribution was observed in the control group, followed by CEC, NEC and BEC designs. The highest stress concentration was detected in Cd-EC and TEC-II designs. Under single-point vertical loading, the stress was mostly concentrated in the lingual PCD area, while under multi-point vertical loading, the entire root surface was stress-loaded except for the lingual apical third of the root. CONCLUSION: Preserving tooth tissue by simulating CEC, NEC and BEC access cavities increased the load capacity of a single-rooted mandibular first premolar following simulated endodontic treatment.

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BACKGROUND: Osteogenesis imperfecta (OI) is an inherited disorder characterized by bone fragility and skeletal alterations. The administration of bisphosphonates (BPs) to patients with OI reduces pain, thereby improving their quality of life. The main mechanism of action of BPs is the inhibition of osteoclast action. In the oral cavity of children with OI during growth and development, physiological processes that require the function of osteoclasts occur. The aim of this investigation was to study the dental development of premolars and the root resorption of primary molars in children with OI medicated with BPs according to age and sex. METHODS: An observational and analytical study was designed. The study sample consisted of 26 6- to 12-year-old children with a confirmed diagnosis of OI treated with BPs with available panoramic radiographs. The control group consisted of 395 children with available panoramic radiographs. Both groups were divided into subgroups according to sex and age. The third quadrant was studied, focusing on the first left temporary molar (7.4), the second left temporary molar (7.5), the first left permanent premolar (3.4) and the second left permanent premolar (3.5). The Demirjian method was used to study the dental development of 3.4 and 3.5, and the Haavikko method was used to study the root resorption of 7.4 and 7.5. The Mann‒Whitney U test was used for comparisons, and p < 0.05 indicated statistical significance. RESULTS: The mean chronological age of the 421 patients was 9.21 years (95% CI 9.05-9.37). The sample was reasonably balanced by sex, with 52.5% (221 patients) boys versus 47.5% (200 patients) girls. Delayed exfoliation and tooth development were described in children with OI (p = 0.05). According to sex, the root resorption of primary molars and tooth development were significantly lower in boys in both groups and in girls in the OI group, but the differences between the age groups were not significant. CONCLUSIONS: Children with OI treated with BPs exhibit delayed dental development of the premolars and delayed root resorption of the primary molars. Boys exhibited delays in both variables, but the differences by age subgroup were not significant. These clinical findings support the importance of clinically and radiographically monitoring the dental development and root resorption of primary teeth in children with OI treated with BPs to avoid alterations of the eruptive process.

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Giant pandas have a high incidence of tooth wear, loss, and fracture since their diet is specifically bamboo. Dental implantation is a common treatment for tooth loss in humans while rarely reported in wild animals. To explore the applicability of dental implantation in giant pandas, this study measured mandible parameters of the giant panda, from an adult skeletal specimen. The mandible bone block model was developed using computer-aided design 3D mechanical drawing software. Implants of different radius and thread types of the third premolar tooth (PM3) were assembled and imported into an analysis software system for finite element analysis. As a result, the reverse buttress implant with a radius of 7.5 mm and 8.3 mm, and a length of 15 mm was found to be the most suitable implant for use in the giant panda PM3. This study provides a reference for appropriate clinical giant panda dental implantation, although, the feasibility of giant panda dental implantation needs to be studied further.

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Purpose: The aim of this study was to evaluate the prevalence and the morphology of c-shaped root canal(s) in mandibular premolars using cone beam computed tomography (CBCT) images. Materials and methods: CBCT images of 1095 mandibular premolars were examined at coronal, middle, and apical levels of the root canals. The type, the level, and the position (buccal or lingual) of the c-shaped anatomy were recorded. Absolute counts and percentages of different groups and subgroups of C-shape morphologies were calculated. The Chi-square test was used to compare the prevalence of C-shaped morphology between mandibular first and second premolars. The Z-test for proportions in independent groups was used to analyze the differences in mandibular C-shaped premolar proportions between location (left and right side) and tooth (first or second premolars) (p=0.05). Results: C-shaped root canal morphology was present in 44 teeth. The percentage of c-shaped morphologies was 6.9% and 1.6% in mandibular first and second premolars, respectively. Comparison of the first and the second premolars showed that C1 type (p=0.008) and C4b type (p=0.013) configurations are more common in the first premolars at the coronal level. In contrast, the C2 type configuration showed significantly higher prevalence in the second premolars (p=0.009). Additionally, the C4c type configuration was significantly frequent on the right premolars at the coronal level (p=0.038). Conclusion: C-shape canal morphology is a rare but complex anatomic feature in mandibular premolars. Therefore, clinicians should be aware of this complex root canal anatomy for the success of endodontic treatment in mandibular premolar teeth.

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Statement of the Problem: As a developmental disorder characterized by an abnormal bend and angle in the longitudinal axis of the tooth root, dilaceration can cause complications in routine dental procedures such as endodontics, orthodontics, and surgical treatments. Purpose: The purpose of this study was to investigate the prevalence of dilaceration in maxillary and mandibular premolar teeth in a population of Shiraz city based on cone-beam computed tomography (CBCT). Materials and Method: This is a retrospective cross-sectional study on 927 premolar teeth and 132 CBCT radiographs of patients obtained from four private radiology clinics in Shiraz (Iran). In this study, the presence, location, direction, and severity of dilaceration in premolar roots as well as its relationship with gender were investigated. Chi-square and Fisher tests were used to analyze the data. Results: The results showed that 17% of the studied 927 teeth had dilaceration. The prevalence of dilaceration was significantly higher in women than in men (20.3% vs. 13.6%, p= 0.005). The dilaceration rates were significantly higher in the mandibular first and second premolar teeth (31.6% and 26%, p= 0.002) than in the other teeth. In addition, the highest prevalence was in the distal direction with mild severity in the apical third of the root (p< 0.001). Conclusion: According to the results of this study, the prevalence of dilaceration was relatively high in mandibular premolar teeth especially in women.

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The maxillary second premolar has long been regarded as a tooth with a straight root canal anatomy, typically featuring a single root with two canals. However, emerging evidence suggests this tooth may harbor a more intricate internal morphology, challenging conventional perceptions, and treatment approaches. One such variation is three root canals within the upper second premolar, which has been gaining increasing attention in endodontic literature. Root canal treatment of maxillary second premolars with three canals demands meticulous debridement, shaping, and disinfection. A combination of magnification, illumination, and appropriate instrumentation aids in locating, negotiating, and cleaning the accessory canals effectively. Thorough cleaning of accessory canals can be achieved through effective irrigation solutions such as sodium hypochlorite, ethylenediaminetetraacetic (EDTA), and chlorhexidine, which help dissolve organic tissues and remove debris. Techniques like ultrasonic and sonic activation, as well as negative pressure irrigation systems, enhance the penetration and effectiveness of these irrigants. Additionally, the use of modern nickel-titanium rotary files, ultrasonic irrigation, and supplementary chelating agents enhances the management of complex canal configurations.

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SUMMARY: The mandibular first premolar is commonly a single-rooted tooth with occasional presentation of radicular variations. This tooth usually has one root with only one canal (97.9 %). Presence of three canals is very rare. Anomalies may appear during odontogenesis which can lead to anatomical variations in teeth. Similarly, these variations may be associated with characteristics that can be attributed to specific population groups. Due to their low frequency, these additional canals can easily be missed. For this reason, a meticulous knowledge of tooth morphology and their possible anatomical variations are necessary, and the presence of extra roots and canals should be always considered before initiation of root canal treatment. Additionally, different radiographs and appropriated access cavity preparation is needed to ensure a success endodontic treatment. This article reports a diagnosis and endodontic treatment of a mandibular first premolar with three canals.

El primer premolar mandibular suele ser un diente unirradicular con presentación ocasional de variaciones radiculares. Este diente suele tener una raíz con un solo conducto (97,9 %). La presencia de tres canales es muy rara. Durante la odontogénesis pueden aparecer anomalías que pueden provocar variaciones anatómicas en los dientes. De manera similar, estas variaciones pueden estar asociadas con características que pueden atribuirse a grupos de población específicos. Debido a su baja frecuencia, estos canales adicionales pueden pasar desapercibidos fácilmente. Por esta razón, es necesario un conocimiento meticuloso de la morfología dental y sus posibles variaciones anatómicas, y siempre se debe considerar la presencia de raíces y conductos adicionales antes de iniciar el tratamiento de conducto. Además, se necesitan diferentes radiografías y una preparación adecuada de la cavidad de acceso para garantizar un tratamiento de endodoncia exitoso. Este artículo reporta un diagnóstico y tratamiento endodóntico de un primer premolar mandibular con tres canales.

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INTRODUCTION: The efficacy of root canal treatment is greatly impacted by a thorough understanding of root canal anatomy. This systematic review and meta-analysis aim to thoroughly investigate the root morphology and canal configuration (RMCC) of permanent premolars (PMs). METHODOLOGY: A comprehensive analysis was conducted following the PRISMA guidelines. Literature exploration was carried out across four electronic databases (PubMed, Embase, Cochrane, and Web of Science). The risk of bias assessment was conducted for the included studies utilizing the Anatomical Quality Assessment (AQUA) tool. Data analysis was performed utilizing SPSS and RevMAN5.3.3. The meta-analysis was applied with a 95% confidence interval to calculate odds ratios (OR). RESULTS: Among the 82 selected studies, 59 studies exhibited potential bias in domain one (objective(s) and subject characteristics), followed by domain three (methodology characterization). The majority of maxillary PM1s had either single root (46.7%) or double roots (51.9%), while three-rooted variants were uncommon (1.4%). Conversely, most other PMs exhibited a single root. In terms of canal configuration, maxillary PM1s predominantly featured double distinct canals (87.2%), with the majority of maxillary PM2s displaying either a single canal (51.4%) or double canals (48.3%). Mandibular PMs were primarily characterized by single canals, accounting for 78.3% of mandibular PM1s and 90.3% of mandibular PM2s. Subgroup analyses revealed higher incidences of single-rooted and single-canalled PMs among Asians compared to Caucasians. Additionally, women exhibited a higher incidence of single-rooted PMs, while men showed a greater frequency of double-rooted PMs. CONCLUSIONS: The comprehensive analysis indicated that maxillary PM1s predominantly possess double roots and double canals, whereas maxillary PM2s and mandibular PMs were primarily characterized by single-rooted with a single canal. Notably, single root and single canal were more prevalent among women and Asian samples.

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This paper illustrated successful endodontic non-surgical (re)treatments of molars and premolar with different taurodontic classifications and accompanied anomalies like C-shape and extra root canals in otherwise healthy patients. Magnification with illumination besides active irrigation with NaOCl were the most helpful items in managing these cases.