Root Furcation Research Articles

Effectiveness of nonsurgical re-instrumentation: Tooth-related factors.

To investigate tooth-related factors that influence pocket closure (PC) and the reduction of pocket probing depths (PPD) after nonsurgical re-instrumentation (NSRI) as part of step 3 therapy. A total of 480 patients (10,807 teeth) presenting with residual pockets 6.33±3.79 months after steps 1 and 2 of periodontal therapy were included and retrospectively analyzed before and 5.93±4.31 months after NSRI. Reduction of PPD and PC rates following NSRI were associated with tooth-related factors, namely tooth type, arch, number of roots, furcation involvement (FI), pulp vitality, mobility, type of restoration, presence of plaque, and bleeding on probing (BOP), using mixed-effects regression models. NSRI reduced periodontal pockets persisting after initial cause-related therapy by (mean±SD) 1.32±1.79mm in PPD, and PC rate was 40%. Moderate pockets (4-5mm) responded better to NSRI than deep pockets (≥6mm) in terms of PC (51% vs. 16%). Both PPD reduction and PC rates of deep residual pockets were significantly influenced by tooth type, arch, number of roots, and presence of BOP. Tooth type, arch, number of roots, and presence of BOP at re-evaluation (before NSRI) had a significant and clinically relevant influence on NSRI as part of step 3 therapy. Considering these factors, particularly for deep residual pockets, may allow more tailored re-intervention. The present study aimed to investigate the influence of tooth-related factors on the outcome of repeated nonsurgical therapy of periodontitis. Therefore, 480 patients (10,807 teeth) presenting with clinical symptoms of persistent periodontitis after initial therapy were administered repeated nonsurgical therapy and retrospectively analyzed. Therapy outcomes were associated with tooth-related factors, namely tooth type, tooth location (maxilla/mandible), number of roots, involvement of the root furcation area in multi-rooted teeth, pulp vitality, mobility, restoration, presence of plaque and bleeding upon periodontal probing, using mixed-effects models. The results revealed that repeated nonsurgical therapy was effective in reducing inflammation and clinical signs of disease, with moderate residual periodontal defects responding better than deep defects. Healing of deep defects after repeated nonsurgical therapy; however, was significantly influenced by the factors: tooth type, location, number of roots, and bleeding on probing. Considering these factors, particularly in deep residual defects which are commonly suggested to be treated surgically, may allow less invasiveness and thus a more tailored re-intervention.

Clinical insights into tooth extraction via torsion method: a biomechanical analysis of the tooth-periodontal ligament complex.

Traditionally, extracting single, flat- or curved-rooted teeth through twisting is unfeasible. However, our clinical practice suggests that such teeth can be extracted efficiently through moderate twisting in a minimally invasive manner. Given the lack of studies on biomechanics of the tooth-periodontal ligament (PDL) complex during torsion, which has further constrained its application, we assessed the feasibility of the torsion method for extracting single-rooted teeth and evaluated its minimally invasive potential. Using three-dimensional finite element analysis, we examined the stress distribution of the tooth and PDL during torsion. Then, we examined changes in the optimal torsion angle (OTA) and stress distribution across various anatomical scenarios. During torsion loading, stress concentration was primarily observed on the sing-rooted tooth surface near the alveolar crest, whereas molars at the root furcation. The OTA was found to increase under conditions such as narrowing of root width, decrease in the root apical curvature, change from type I to IV bone, alveolar bone loss, and shortening of root length. Moreover, the clinically validated model demonstrated that 74% of outcomes fell within the standard OTA range. In conclusion, the decrease in PDL area necessitated a larger angle for complete PDL tearing. Single-rooted teeth with root width-to-thickness ratios of ≥0.42 and apical curvatures of ≤30°are suitable for extraction using the torsion method. This study confirms the feasibility of the torsion method for minimally invasive tooth extraction and expands its indications, laying the theoretical foundation and essential insights for its clinical application.

Investigation of the furcation morphology of permanent mandibular first molars by using micro-computed tomography

BackgroundTo investigate the anatomic features of the root furcation of permanent mandibular first molars.MethodsA total of 50 extracted mandibular first molars (25 two-rooted and 25 three-rooted) were collected and scanned using micro-computed tomography. The digital models of teeth and root canal systems were reconstructed three-dimensionally. The tooth models were displayed in parallel projection mode from buccal and distal views. Screenshots were captured and subsequently analyzed using Image-Pro Plus 6.0 software after calibration. The furcation angle, root trunk length, maximum depth and level of distal root concaves of mesial roots, and length of enamel projections were measured, and the furcation types (classified into type V, type U and type W) were detected. Statistical analysis was performed using the Shapiro-Wilk’s test, one-way analysis of variance, Student’s t-test and Chi-square test.ResultsThe mean furcation angle between the distobuccal (DB) and distolingual (DL) roots (in distal view) was the greatest (59.2°), whereas the furcation angle between the mesial and DL roots (in buccal view) was the smallest (25.4°) among the four furcation angles (all p < 0.05). Regarding the furcation types, bucco-lingual root trunk length, maximum depth and site of the distal root concavities, and enamel projection length, no significant differences were detected between the three- and two-rooted molar groups (all p > 0.05). The frequency of type V was the highest (54.0%), followed by type U (26.0%), and type W had the lowest occurrence rate (20.0%). The mean length of distal root trunk in the three-rooted mandibular molars was significantly greater than that of the buccal/lingual one (3.7 mm vs. 3.0 mm, p < 0.01). The maximum depth of the distal concavities of the mesial roots was on average 0.66 ± 0.19 mm, and the site was located at an average of 2.8 ± 1.3 mm below furcation. The mean length of buccal enamel projections was significantly longer than that of lingual ones (3.1 mm vs. 0.7 mm, p < 0.01).ConclusionsThe furcation anatomy of the mandibular first molar is complex, and the presence of the DL root may further complicate its topography. A thorough understanding of these anatomic features is essential for successful periodontal treatment.

Micro–Computed Tomographic Analysis of Radicular Dentin Thickness in Mandibular Second Molars Across Diverse Anatomic Root Variations: Identifying Potential Danger Zones

IntroductionThis study aimed to investigate radicular dentin thicknesses in mandibular second molars (MSMs), considering variations in root configuration and the morphology of the pulp chamber floor (PCF). The types of radicular grooves and potential danger zones were also identified. MethodsA total of 149 MSMs were scanned with micro–computed tomographic imaging and classified into 4 groups according to root fusion and PCF morphology as follows: (1) 45 with fused roots and C-shaped PCFs, (2) 45 with fused roots and non–C-shaped PCFs, (3) 14 with a single canal, and (4) 45 with separated roots. The first 2 groups were subdivided into Ω-shaped, U-shaped, and V-shaped radicular groove subgroups. Measurements included minimum and mean dentin thickness from the start of the radicular groove or root bifurcation extending 5 mm apically, the ratio of outer to inner dentin thickness, and the distribution of dentin thickness. ResultsΩ-shaped and U-shaped subgroups showed significant thinner minimum inner wall thickness than V-shaped subgroups at 2–5 mm from the starting point of the radicular groove in both C-shaped and non–C-shaped pulp floor categories (P < .05). The mesial roots of separated rooted MSMs showed significant thinner dentin than a non–C-shaped floor regarding minimum and mean inner thickness and mean outer thickness (P < .05). Teeth with a single canal had significantly thicker walls compared with the other 3 groups. ConclusionsIn MSMs, caution must be exercised, especially in the presence of Ω-shaped and U-shaped grooves in C-shaped roots and around the root furcation of separated roots.

More molar distal movement than pretreatment cone-beam computed tomography posterior space available at the root level in mandibular dentition distalization with microimplants.

To compare the mandibular posterior space available before treatment and the distance of molar distalization achieved after mandibular dentition distalization with microimplants. A total of 66 Class I or III adult patients (mean age = 24.46 ± 4.89 years) who underwent molar distalization using microimplants were retrospectively included. The posterior space available distal to the second molar before treatment and the distance of distalization achieved after treatment were measured using axial cone-beam computed tomography images (0, 2, 4, and 6 mm apical to the second molar root furcation). Changes in lingual cortical thickness and molar root length after treatment were examined. Paired t-test or Wilcoxon signed-rank test was performed to compare measurements before and after treatment. Spearman correlation analysis was performed to assess the relationship between thinning of the cortical plate and root resorption. Achieved distalization distance was significantly greater than pretreatment posterior space available by 0.8 mm at all root levels (P < .001). The difference was greater toward the root apex level and greater in the Class III group than the Class I group. Lingual cortical thickness was significantly decreased after treatment along with resorption of the second molar distal root (P < .001). In addition, a positive correlation was found between thinning of the cortical plate and distal root resorption of the molar (P < .001). Achieved distalization distance of the mandibular molar using microimplants was greater than the pretreatment posterior space available. Thinning of the lingual cortex and root resorption were observed after distalization.

Micro-CT and histological examination of accessory canals in 34 equine cheek teeth.

Accessory canals and apical deltas have been extensively studied in human dentistry. Their clinical role as a difficult to clean reservoir for bacteria during endodontic treatments has been well described. Many papers describe in detail the pulp anatomy of equine dentition but little attention has been given to their apical ramifications. The goal of this paper is to describe the presence and anatomy of these accessory canals and apical deltas in healthy equine cheek teeth and discuss their possible relevance in the light of equine endodontics. To accomplish this, 15 maxillary and 19 mandibular healthy cheek teeth were collected ranging from Triadan 06 s to 11 s with eruption ages from 4 to 9 years. Their root anatomy was documented in detail based on micro computed tomography images. A subset of 3 teeth also underwent histological examination. Accessory canals were found in all but two teeth examined. Up to 44 accessory canals per tooth have been found with locations ranging from the root furcation down to the apex of the root and with highly variable diameters. Apical deltas in different stages of development were found in 84% of the roots. The presence of accessory canals identified on microCT images could be confirmed using histological examination although some of them were obliterated by reparative dentin. Accessory canals can be found in most equine cheek teeth and add complexity to their endodontic anatomy. This could have important implications for their treatment in case of pulp pathology. In humans, failure to remove bacterial biofilm from such canals has been associated with failure of endodontic treatment. Research on diseased equine teeth is required to gain a better understanding of their clinical relevance in horses.

A Wnt10a-Notch signaling axis controls Hertwig’s epithelial root sheath cell behaviors during root furcation patterning

Human with bi-allelic WNT10A mutations and epithelial Wnt10a knockout mice present enlarged pulp chamber and apical displacement of the root furcation of multi-rooted teeth, known as taurodontism; thus, indicating the critical role of Wnt10a in tooth root morphogenesis. However, the endogenous mechanism by which epithelial Wnt10a regulates Hertwig’s epithelial root sheath (HERS) cellular behaviors and contributes to root furcation patterning remains unclear. In this study, we found that HERS in the presumptive root furcating region failed to elongate at an appropriate horizontal level in K14-Cre;Wnt10afl/fl mice from post-natal day 0.5 (PN0.5) to PN4.5. EdU assays and immunofluorescent staining of cyclin D1 revealed significantly decreased proliferation activity of inner enamel epithelial (IEE) cells of HERS in K14-Cre;Wnt10afl/fl mice at PN2.5 and PN3.5. Immunofluorescent staining of E-Cadherin and acetyl-α-Tubulin demonstrated that the IEE cells of HERS tended to divide perpendicularly to the horizontal plane, which impaired the horizontal extension of HERS in the presumptive root furcating region of K14-Cre;Wnt10afl/fl mice. RNA-seq and immunofluorescence showed that the expressions of Jag1 and Notch2 were downregulated in IEE cells of HERS in K14-Cre;Wnt10afl/fl mice. Furthermore, after activation of Notch signaling in K14-Cre;Wnt10afl/fl molars by Notch2 adenovirus and kidney capsule grafts, the root furcation defect was partially rescued. Taken together, our study demonstrates that an epithelial Wnt10a-Notch signaling axis is crucial for modulating HERS cell proper proliferation and horizontal-oriented division during tooth root furcation morphogenesis.

Enhanced immunomodulation and periodontal regeneration efficacy of subgingivally delivered progranulin-loaded hydrogel as an adjunct to non-surgical treatment for Class II furcation involvement in dogs.

To evaluate the effect of subgingival delivery of progranulin (PGRN)/gelatin methacryloyl (GelMA) complex as an adjunct to scaling and root planing (SRP) on an experimental periodontitis dog model with Class II furcation involvement (FI). A Class II FI model was established, and the defects were divided into four treatment groups: (a) no treatment (control); (b) SRP; (c) SRP + GelMA; (d) SRP + PGRN/GelMA. Eight weeks after treatment, periodontal parameters were recorded, gingival crevicular fluid and gingival tissue were collected for ELISA and RT-qPCR, respectively, and mandibular tissue blocks were collected for micro computed tomography (micro-CT) scanning and hematoxylin and eosin (H&E) staining. The SRP + PGRN/GelMA group showed significant improvement in all periodontal parameters compared with those in the other groups. The expression of markers related to M1 macrophage and Th17 cell significantly decreased, and the expression of markers related to M2 macrophage and Treg cell significantly increased in the SRP + PGRN/GelMA group compared with those in the other groups. The volume, quality and area of new bone and the length of new cementum in the root furcation defects of the PGRN/GelMA group were significantly increased compared to those in the other groups. Subgingival delivery of the PGRN/GelMA complex could be a promising non-surgical adjunctive therapy for anti-inflammation, immunomodulation and periodontal regeneration.

Treatment choice for first permanent molars affected with molar-incisor hypomineralization, in patients 7–8 years of age: a questionnaire study among Swedish general dentists, orthodontists, and pediatric dentists

PurposeThe aim of this study was to investigate attitudes and preferred therapy choice for first permanent molars (FPM) with Molar-Incisor Hypomineralization (MIH).MethodsAn online questionnaire was sent out to general dentists (n = 559) working in the Public Dental Service in Region Västra Götaland, orthodontists (n = 293), and pediatric dentists (n = 156) (members from each interest association), in Sweden. The questionnaire contained three parts: general questions regarding the respondents, patient cases, and general questions regarding extraction of FPMs with MIH. Statistics were carried out using Chi-squared tests, with a significance level of 5%.ResultsA response rate of 36% was obtained. Orthodontists and pediatric dentists were more prone to extract FPMs with both moderate and severe MIH, compared to general dentists. When restoring FPMs with moderate MIH, resin composite was preferred. Compared to the general dentists, the pediatric dentists were more prone to choose glass-ionomer cement in the FPMs with severe MIH. The most common treatment choice for FPMs with mild MIH was fluoride varnish. “When root furcation is under development of the second permanent molar on radiographs” was chosen as the optimal time for extracting FPMs with severe MIH, and the general dentists based their treatment decisions on recommendations from a pediatric dentist.ConclusionExtraction of FPMs with moderate and severe MIH is considered a therapy of choice among general dentists and specialists, and the preferred time of extraction is before the eruption of the second permanent molar.

Is the assessment of the mandibular molar danger zone affected by field of view and voxel size in cone beam computed tomography examinations?

ObjectiveTo verify if assessment of the danger zone (DZ) in the mesial root of mandibular molars is affected by field of view (FOV) and voxel sizes in cone beam computed tomography (CBCT) scans. Study DesignForty mandibular molars were scanned by micro-computed tomography, creating the reference standard. The teeth were then submitted for CBCT scans with FOVs of 10 × 5.5 cm and 5 × 5.5 cm and voxel sizes of 0.4, 0.2, 0.15, and 0.075 mm3. The smallest dentin thickness in the DZ from the mesiobuccal and mesiolingual canals was measured at 2, 4, and 6 mm apical to the root furcation. Descriptive statistics, paired t-tests, and intraclass correlation coefficients were used for statistical analysis with significance established at P<0.05. ResultsAll CBCT measurements overestimated the DZ dentin thickness (P<0.001) compared to the reference standard. The greatest overestimation occurred in the 5 × 5.5 cm FOV with 0.4 mm3 voxels (P = 0.007). Dentin thickness measured with the 5 × 5.5 cm FOV and 0.075 mm3 voxels was significantly smaller and produced the best ICC value with the reference standard (0.936). ConclusionsCBCT overestimates the dentin thickness of the DZ regardless of FOV and voxel sizes. The 5 × 5.5 cm FOV showed the best performance with the 0.075 mm3 voxel size, but it performed poorly with 0.4 mm3 voxels.

Restoration-oriented anatomical analysis of alveolar bone at mandibular first molars and implications for immediate implant placement surgery: a CBCT study.

This cone-beam computed tomography (CBCT) study aimed to analyze the anatomical characteristics of alveolar bone at mandibular first molar (MFM) and their implications for immediate implant placement surgery. 100 patients with 140 MFMs were reviewed retrospectively. We first performed a 3D reconstruction of the patient's CBCT data to determine a reference plane with ideal implant placement and orientation. The following parameters of MFM region were analyzed: mesial-distal socket size (MD-SS), buccal-lingual socket size (BL-SS), root furcation fornix to inferior alveolar nerve (IAN) distance (RF-I), interradicular bone thickness (IRB), mesial/distal root apex to the IAN distance (MRA-I/DRA-I), thickness of the buccal/lingual bone of the mesial root (MR-B/MR-L), thickness of the buccal/lingual bone of the distal root (DR-B/DR-L). The MD-SS of MFM was 8.74 ± 0.76 mm, and the BL-SS was 8.26 ± 0.72 mm. The MR-B, DR-B was 1.01 ± 0.40 mm and 1.14 ± 0.50 mm, and the difference was statistically significant (P = .001). The values of the MR-L, DR-L were 2.71 ± 0.78 mm and 3.09 ± 0.73 mm, and the difference was also statistically significant (P < .001). The mean distance of RF-I was 15.68 ± 2.13 mm, and the MRA-I was 7.06 ± 2.22 mm, which was greater than that of DRA-I (6.48 ± 2.30 mm, P < .001). The IRB at 2 mm, 4 mm apical from the furcation fornix, and at apex level was 2.81 ± 0.50 mm, 3.30 ± 0.62 mm, and 4.44 ± 1.02 mm, respectively. There is relatively sufficient bone mass in interradicular bone in height, but an adequate width is lacking for the bone between the mesial and distal root after the extraction of the MFM for immediate implantation. The thickness of the MFM buccal bone is relative thin, especially for the mesial root.

Topographic study of antral teeth on computed tomography in a beninese population

The topographical relationships between the root tips and the floor of the maxillary sinus favour the occurrence of odontogenic maxillary sinus pathologies. Knowledge of these relationships may help to prevent such pathologies. The aim of this study was to investigate the anatomical relationships between the maxillary sinuses and the apices of the maxillary roots in a Beninese population using computed tomography (CT) images of the maxilla.: This was a descriptive study of CT scans of facial masses performed between January 2020 and January 2023 in subjects aged at least 18 years without tumour or traumatic sinus pathology. The CT images were in Dicom format. Horos, Excel and SPSS software were used for data collection, entry and analysis.: Of the 346 CT scans collected, 255 were included in the analysis. The mean age of the subjects was 42.65±16.57 years and the sex ratio was 2. More than half of the cases involved 3rd molars within the sinus. In 99% of cases, the sinus alveolar recess was located in the root furcation zone. The mean volume of the right sinus was 13.78±4.59 ml and that of the left sinus was 13.65±4.75 ml. Anterior sinus extensions were located in the premolar region (75%) and posterior sinus extensions were located in the tuberosity region (88 to 90%). In 3 out of 4 subjects the sinus floor had an irregular shape.: These various insights into the relationships between the maxillary root apices and the sinus floor will be of considerable help to dental surgeons in the prevention of odontogenic maxillary sinus pathology.

Clinical diagnosis and treatment of furcation involvement

Furcation involvement (FI) is the lesion and destruction of periodontium that spread to the root furcation of multi-root teeth, where periodontal pockets, loss of periodontal attachment and resorption of alveolar bone are formed. Furcation involvement is a common concomitant lesion of periodontitis. The severity of furcation involvement can directly affect the prognosis of periodontitis. However, the specificity of the anatomical structure of the root furcation greatly increases the difficulty of treatment. Therefore, early detection and treatment of furcation involvement is crucial for the prevention and control of periodontitis. This paper briefly describes the pathogenesis of furcation involvement and discusses the diagnosis, classification and treatment of this disease, which is helpful to improve the clinical diagnosis and treatment of furcation involvement.

Current Understanding of the Regulatory Mechanism of Tooth Root Development and Future Perspectives.

The purpose of this review article is to understand tooth root development and its regulation through evolution and epigenetics as well as future implications involving root regeneration and tissue engineering. we performed a comprehensive PubMed search to review all published studies related to the molecular regulation of tooth root development and regeneration until August 2022. Articles selected include original research studies and reviews. Epigenetic regulation strongly influences dental tooth root patterning and development. One study highlights how genes such as Ezh2 and Arid1a are crucial components in the development of tooth root furcation patterning. Another study shows that loss of Arid1a ultimately leads to shortened root morphology. Furthermore, researchers are utilizing information about root development and stem cells to find alternative treatments in replacing missing teeth through a stem cell-mediated bioengineered tooth root (bio-root). Dentistry values preserving natural tooth morphology. Presently, implants are the best treatment for replacing missing teeth, but alternative future treatments might include tissue engineering/bio-root regeneration to restore our dentition.

Morphological analysis of anterior permanent dentition in a Chinese population using cone-beam computed tomography

PurposeMorphological analysis of permanent anterior dentition is essential for achieving an ideal treatment outcome and avoiding unnecessary failure. This study aimed to analyze the morphologies of anterior teeth in the Chinese population in depth.MethodsIn this retrospective study, 4309 anterior teeth from 401 Chinese patients were investigated using cone-beam computed tomography (CBCT) from 2019–2021. We summarized the morphological characteristics of the anterior teeth in terms of the root length, cementoenamel junction curvature (CEJ-C), root furcation and canal variations.ResultsWe found that the root lengths of the maxillary anterior incisors were similar (13.3 mm), while the root lengths of the mandibular central (12.2 mm) and lateral incisors (13.4 mm) varied significantly (p < .0001). Both the maxillary (16.6 mm) and mandibular canines (15.5 mm) were found to have greater root lengths than the corresponding incisors (p < .0001). The CEJ-C was significantly greater around incisors (2.5 mm) than around the canines (2.0 mm) in the maxilla (p < .0001), while the curvature remained similar in mandibular anterior teeth (1.8 mm). Root furcation was observed in mandibular canines and lateral incisors. Moreover, all types of Vertucci’s classification in anterior dentitions were observed, while two other new types were found. Among them, the maxilla was only observed to exhibit types I, II, III, and ST II, while the mandible was found to exhibit almost all types. However, Type I still accounts for the majority of dentitions.ConclusionsMorphological analysis of permanent anterior dentition revealed diversity in the tooth length, CEJ-C, furcation proportion, and canal variations. In general, mandibular anterior teeth showed a more complex structure than maxillary teeth.

Evaluation of Effectiveness of Mineral Trioxide Aggregate for Root Furcation Repair Using Diode Laser as Adjunct - An In Vitro Study

Background Most of the materials used for furcation perforation repair often leads to microleakage. Therefore novel techniques to prevent this are needed. This study aimed to determine the ability of Mineral trioxide aggregate MTA and Ethoxy benzoic acid Super EBA along with laser for sealing the root furcation.Methods About 108 human-extracted mandibular molar teeth were decoronated at directly above and beneath the furcal area. After access opening the canal orifices were closed with sticky wax. A furcal defect of 1 mm width was prepared. The specimens were allocated into six groups for furcation repair n18. Group 1 MTA Group 2 Super EBA Group 3 Laser MTA Group 4 Laser Super EBA Group 5 positive control Unrepaired furcal defect and Group 6 negative control Intact furcation. In Groups 3 and 4 furcal defects were irradiated with diode 980 nm laser before placing the materials. All specimens were submerged in 2 methylene blue solution for two days were cleaned with sterile water and sectioned mesiodistally. Microleakage was assessed using stereomicroscope. Data was analysed using SPSS version 22. One-way ANOVA and Post hoc Tukey tests were used P le0.05.Results Except for the MTALaser all groups demonstrated decreased microleakage which was statistically significant. The positive control group showed highest microleakage and the negative control group showed none.Conclusion MTA as adjunct to laser activation is effective in preventing microleakage in furcation defects.nbsp

X-ray evaluation of the design features of stump pin tabs

Carrying out an objective assessment of the quality of performance of the technique of prosthetics with stump pin tabs of the upper and lower molars. A retrospective assessment of the quality of dental preparation and modeling of root pin inlays was carried out by analyzing CBCT studies using the RadiAnt program. Measurements were carried out and 80 CBCT studies of patients who had tabs in their molars performed in various clinics of the city of Moscow were studied. Restoration of defects in the hard tissues of teeth with cast root pin tabs has specific features related to the anatomy of the roots and the distribution of the chewing load. An analysis of the practical implementation of the prosthetics technique and the compliance of the quality of the tabs with the requirements of clinical recommendations showed that they are performed only in 47.5% of cases with respect to modeling the length of the pin part of the tabs (relative to the length of the tooth root), in 40.0% of studies - on the quality of root canal filling; in 36.3% - on the residual thickness of the walls of the tooth root. The requirements for the ratio of the foliar and pin parts of the tabs were not met in any of the cases. In the case of tab modeling, the requirements for maintaining a safe zone in the area of root furcation and tooth tissue thickness of at least 1.0 mm were met only in 36.25 (32.50±3.75)% of cases. Improving the quality of prosthetics using tabs lies not only in the plane of a more responsible approach to determining indications for this type of prosthetics, performing techniques and algorithms, using modern tools, but also in the field of working out the methodology for manufacturing tabs in multi-root teeth taking into account the anatomy of the roots of chewing teeth, the distribution of chewing pressure and the number of pin parts of tabs.

Association of Mandibular Posterior Anatomic Limit with Skeletal Patterns and Root Morphology Using Three-Dimensional Cone Beam Computed Tomography Comprehensive Analysis.

This study aimed to clarify the relationship between the mandibular posterior anatomic limit (MPAL) and skeletal anteroposterior and vertical skeletal patterns, with consideration of factors that may be related. In total, 230 people were included: 49 Japanese, 122 Egyptian, and 59 Korean people. The MPAL was measured at 0, 2, 4, and 6 mm from the root furcation along the sagittal and cuspal lines at the distance from the distal root of the mandibular right second molar to the mandibular cortex of the lingual bone. Eight different MPALs were evaluated using multiple regression analysis with explanatory variables for anteroposterior and vertical skeletal patterns and qualitative variables for age, sex, population, the presence of third molars, number of roots, presence of C-shaped roots, and Angle malocclusion classification. The MPAL was significantly larger as the mandibular plane angle decreased. The MPAL near the root apex was significantly larger as the A-nasion-point B angle increased, and the MPAL near the root apex measured at the cuspal line was significantly larger for C-type roots. The present study showed that a C-shaped root affected the MPAL in addition to the anteroposterior and vertical skeletal patterns.

Impact of different axial wall designs on the fracture strength and stress distribution of ceramic restorations in mandibular first molar

BackgroundThe purpose of this study was to investigate the fracture strength and stress distribution of four ceramic restorations.MethodsForty human mandibular first molars were collected and randomized into four groups after establishing the distal defect: full crown group with 4 mm axial wall height (AWH) (FC4); short AWH crown group with 2 mm AWH (SC2); occlusal veneer group with 0 mm AWH (OV0); occlusal distal veneer group with only the distal surface prepared, and 4 mm AWH (OD4). The teeth were prepared according to the groups and the ceramic restorations were completed using celtra duo ceramic blocks. The ceramic thickness of the occlusal surface is about 1.5 mm and the edge is about 1 mm. The failure load values and fracture modes of each group were detected by mechanical test in vitro. According to the groups to establish three-dimensional finite element analysis (FEA) models, a 600 N loading force was applied vertically using a hemispherical indenter with a diameter of 6 mm. and compare the stress distribution under the condition of different restorations.ResultsIn vitro mechanical tests showed that the failure load values were SC2 (3232.80 ± 708.12 N) > OD4 (2886.90 ± 338.72 N) > VO0 (2133.20 ± 376.15 N) > FC4(1635.40 ± 413.05 N). The failure load values of the short AWH crown and occlusal distal veneer were significantly higher than that of occlusal veneer and full crown (P<0.05). The fracture modes of the full crown and occlusal veneer groups were mainly ceramic fractures and some were restorable tooth fractures. The short AWH crown and occlusal distal veneer groups presented with three fracture modes, the proportion of non-restorable tooth fracture was higher. The results of FEA show that under the spherical loading condition, the stress of ceramic was concentrated in the contact area of the loading head, the maximum von Mises stress values were FC4 (356.2 MPa) > VO0 (214.3 MPa) > OD4 (197.9 MPa) > SC2 (163.1 MPa). The stress of enamel was concentrated in the area where the remaining enamel was thinner, the maximum von Mises stress values was OD4 (246.2 MPa) ≈ FC4 (212.4 MPa) > VO0 (61.8 MPa) ≈ SC2 (45.81 MPa). The stress of dentin is concentrated in the root furcation and the upper third region of the root. However, stress concentration was observed at the tooth cervix in the full crown.ConclusionUnder certain conditions, the occlusal distal veneer shows better performance than the full crown.

Biomechanical Characteristics of Maxillary Molar Distalization Using Different Attachments with Clear Aligners: A 3-Dimensional Finite Element Analysis

This study aimed to compare the biomechanical characteristics of maxillary teeth in molar distalization with different orthodontic attachments. A 3-dimensional finite model of maxillary molar distalization with clear aligners was generated by computed tomography and contained different components. Four models—non-attachment (model A), horizontal rectangular attachment (model B), vertical rectangular attachment (model C), and combined attachment (model D)—were set up. The modalities of molar distalization were simulated using a finite element analysis. The results showed that the minimum displacement (rotation center) of the second molar in models A and B was located at the root furcation. In model C, the minimum displacement was located in the middle third of the palatal root. In model D, the minimum displacement was located at the apical third of the root. The anchorage teeth in all the four groups tended to have mesial tipping movement. Models B and D had more uniform stress distribution of the periodontal ligament than models A and C. Models with attachment had a larger tooth displacement pattern than that without attachment. Collectively, if molar distalization is planned before treatment, the appropriate application of attachments can help achieve the desired tooth movements more efficiently.