Influence of Apical Root Resection on the Biomechanical Response of a Single-rooted Tooth: A 3-dimensional Finite Element Analysis

Endodontic Microsurgery Outcomes over 10 Years and Associated Prognostic Factors: A Retrospective Cohort Study

INTRODUCTION

This retrospective cohort study aimed to evaluate long-term healing outcomes (10-17.5 years) after contemporary endodontic microsurgery (EMS) and identify the associated prognostic factors.

METHODS

Clinical and radiographic data of an EMS cohort (2006-2013) from the electronic database of the dental hospital were reviewed retrospectively by 2 independent examiners to determine their survival and healing outcomes, and potential prognostic factors were analyzed by Cox proportional hazards regression and logistic regression (α = 0.05).

RESULTS

Through strict inclusion and exclusion criteria and 721 EMS-treated teeth in the cohort, 309 (42.9%) were included (male = 35.0%; female = 65.0%; age = 45.83 ± 15.53 years) with a mean final follow-up of 152.26 ± 26.37 months (range, 120-211 months; median = 148 months). Clinical and radiographic assessments found an 80.5% 10-year survival rate with 63.4% of success. Collectively, tooth type, tooth mobility, preoperative lesion size, clinical crown-to-root ratio, and crown restorations at follow-up were significantly associated with long-term success and survival over 10 years.

CONCLUSIONS

The preoperative status and condition of the tooth including its alveolar bone support and adequate full-crown restorations may be relevant prognostic determinants of success and survival after EMS over time.

3D finite element analysis of stress distribution on the shape of resected root-end or with/without bone graft of a maxillary premolar during endodontic microsurgery

Background/purpose

Apical root resection pattern affects the stress distribution behavior in the apical region of the resected tooth. The purpose of the study was to compare the biomechanical responses of resected teeth between endodontic microsurgery (horizontal resection) and targeted endodontic microsurgery (round resection).

Materials and methods

Five different models were developed. The basic model without resection (NR) was regarded as the control model, and the others involved: horizontal resection without bone grafting (HN), horizontal resection with bone grafting (HG), round resection without bone grafting (RN), and round resection with bone grafting (RG) models. A static load of 100 N was applied to the buccal and palatal cusps of all the teeth in a 30° oblique direction. The maximum von-Mises stress and tooth displacement values were analyzed and compared.

Results

Both the HN and RN models exhibited lower stress distribution values on bone compared with the NR (control) model. Regarding maximum stress distribution at the root apex, the stress value of the RN model was slightly higher compared to the HN model, whereas the RG model displayed a slightly lower stress value in comparison with the HG model. For maximum tooth displacement value, there were no significant differences between the HN and RN models, as well as the HG and RG models.

Conclusion

The round resection pattern had comparable stress distribution behaviors at the root apex and tooth displacement values with the horizontal resection pattern. Targeted endodontic microsurgery might provide better biomechanical response of the resected tooth after root-end resection.

Evaluation of stress distributions of calcium silicate-based root canal sealer in bulk or with main core material: A finite element analysis study

This research aimed to assess the stress distribution in lower premolars that were obturated with BioRoot RCS or AH Plus, with or without gutta percha (GP), and subjected to vertical and oblique forces. One 3D geometric model of a mandibular second premolar was created using SolidWorks software. Eight different scenarios representing different root canal filling techniques, single cone technique with GP and bulk technique with sealer only with occlusal load directions were simulated as follows: Model 1 (BioRoot RCS sealer and GP under vertical load [VL]), Model 2 (BioRoot RCS sealer and GP under oblique load [OL]), Model 3 (AH Plus sealer with GP under VL), Model 4 (AH Plus sealer with GP under OL), Model 5 (BioRoot RCS sealer in bulk under VL), Model 6 (BioRoot RCS in bulk under OL), Model 7 (AH Plus sealer in bulk under VL), and Model 8 (AH Plus sealer in bulk under OL). A static load of 200 N was applied at three occlusal contact points, with a 45° angle from lingual to buccal. The von Mises stresses in root dentin were higher in cases where AH Plus was used compared to BioRoot RCS. Furthermore, shifting the load to an oblique direction resulted in increased stress levels. Replacing GP with sealer material had no effect on the dentin maximum von Mises stress in BioRoot RCS cases. Presence of a core material resulted in lower stress in dentin for AH Plus cases, however, it did not affect the stress levels in dentin for cases filled with BioRoot RCS. Stress distribution in the dentin under oblique direction was higher regardless of sealer or technique used.

Biocompatibility of mineral trioxide aggregate and biodentine as root-end filling materials: an in vivo study

This study evaluated the biocompatibility of mineral trioxide aggregate (MTA) and Biodentine (BD) as root-end filling materials. Six mongrel dogs were divided into two equal groups according to the evaluation period; group A: one month and group B: three months. Three premolars of the same quadrant in each arch were used, summing up 36 teeth (6 teeth/dog). These teeth were randomly subdivided into three subgroups according to the root-end filling material used: MTA, BD and no root-end filling material (control). Endodontic access cavities were performed for induction of periapical pathosis. After the infection period, root canal instrumentation and obturation were accomplished. One day after root canal procedures, root-end surgery was performed. Surgical access was achieved and the root-end was resected approximately 3 mm above the apex. Root-end cavity was prepared ultrasonically and filled with the tested materials. All samples were evaluated by radiography and histopathology (Inflammation and new hard tissue formation). Data were collected and subjected to statistical analysis. In group A, MTA subgroup exhibited significant higher mean inflammatory score than BD subgroup (P < 0.05) while no significant difference was recorded between MTA and BD subgroups in group B (P > 0.05). Regarding mean mineralization score, there was no significant difference between all subgroups in both groups A and B (P > 0.05). Biodentine exhibited favorable biocompatibility in the initial stage of healing than MTA and comparable biomineralization. Clinical relevance: Biodentine could be considered as an acceptable alternative to MTA in peri-radicular surgeries.

Elasto-Static Analysis of Composite Restorations in a Molar Tooth: A Meshless Approach

Dental caries and dental restorations possess a long history and over the years, many materials and methods have been invented. In recent decades, modern techniques and materials have brought complexity to this issue, which has created the necessity to investigate more and more to achieve durability, consistency, proper mechanical properties, efficiency, beauty, good colour, and reduced costs and time. Combined with the recent advances in the medical field, mechanical engineering plays a significant role in this topic. This work aims at studying the elasto-static response of a human molar tooth as a case study, respecting the integral property of the tooth and different composite materials of the dental restoration. The structural integrity of the case study will be assessed through advanced numerical modelling resorting to meshless methods within the stress analysis on the molar tooth under different loading conditions. In this regard, bruxism is considered as being one of the most important cases that cause damage and fracture in a human tooth. The obtained meshless methods results are compared to the finite element method (FEM) solution. The advantages and disadvantages of the analysed materials are identified, which could be used by the producers of the studied materials to improve their quality. On the other hand, a computational framework, as the one presented here, would assist the clinical practice and treatment decision (in accordance with each patient's characteristics).

Finite element evaluation of dentin stress changes following different endodontic surgical approaches

The aim was to compare the effect of different endodontic surgical treatments on the stress distributions in dentin of a simulated first mandibular molar tooth using the finite element analysis method. Three surgical endodontic procedures (apical resection, root amputation, and hemisection) were simulated in a first mandibular molar. Biodentine or mineral-trioxide-aggregate was used to repair the surgery site in apical resection and root amputation models; the remaining root canal spaces were filled with gutta-percha. Access cavities were restored using resin composite. In hemisection model, root canal was filled with gutta-percha, and coronal restoration was finished with a monolithic zirconia crown. A sound tooth model was created as a control model. An oblique force of 300 N angled at 45° to the occlusal plane was simulated. Maximum von Mises stresses were evaluated in dentin near the surgery regions and the entire tooth. Apical resection/Biodentine and apical resection/mineral-trioxide-aggregate models generated maximum von Mises stresses of 39.001 MPa and 39.106 MPa, respectively. The recorded maximum von Mises stresses in root amputation models were 66.491 MPa for root amputation/Biodentine and 73.063 MPa for root amputation/mineral-trioxide-aggregate models. The highest maximum von Mises stress value among all models was observed in the hemisection model, measuring 138.87 MPa. Hemisection induced the highest von Mises stresses in dentin, followed by root amputation and apical resection. In apical resection, Biodentine and mineral-trioxide-aggregate did not show a significant difference in stress distribution. Biodentine in root amputation may lead to lower stresses compared to mineral-trioxide-aggregate.

Enucleation of jaw cyst combined with intentional replantation to retain cyst-involved teeth

BACKGROUND

Jaw cysts often deeply involve adjacent tooth roots, making it difficult to preserve them. The purpose of this retrospective study was to investigate the effectiveness of an intentional replantation (IR) strategy combined with cyst enucleation in preserving cyst-involved teeth during jaw cyst removal.

MATERIALS AND METHODS

Fifteen patients with jaw cysts and deeply involved teeth were treated with IR and cyst enucleation. All patients received root canal therapy prior to surgery, except for one patient who received it during surgery. The involved teeth were extracted, and the root surface was carefully cleaned before IR and cyst enucleation. Patients were followed up for 12-14 months, with indicators including clinical complaints, replanted tooth stability, and root resorption.

RESULTS

No cyst recurrence was observed, and all replanted teeth survived with good local gingival condition and no marked swelling or recession. Radiographic findings showed clear periodontal space surrounding the replanted teeth. One replanted tooth exhibited slight root resorption due to occlusal trauma, but the resorption ceased after occlusal adjustment.

CONCLUSIONS

IR combined with cyst enucleation is an effective strategy for thoroughly cleaning jaw cysts and preserving teeth involved in the cyst.

The effect of periapical bone defects on stress distribution in teeth with periapical periodontitis: a finite element analysis

BACKGROUND

Apical periodontitis directly affects the stress state of the affected tooth owing to the destruction of the periapical bone. Understanding the mechanical of periapical bone defects/tooth is clinically meaningful. In this study, we evaluate the effect of periapical bone defects on the stress distribution in teeth with periapical periodontitis using finite element analysis.

METHODS

Finite element models of normal mandibular second premolars and those with periapical bone defects (spherical defects with diameters of 5, 10, 15, and 20 mm) were created using a digital model design software. The edges of the mandible were fixed and the masticatory cycle was simplified as oblique loading (a 400 N force loaded obliquely at 45° to the long axis of the tooth body) to simulate the tooth stress state in occlusion and analyze the von Mises stress distribution and tooth displacement distribution in each model.

RESULTS

Overall analysis of the models: Compared to that in the normal model, the maximum von Mises stresses in all the different periapical bone defect size models were slightly lower. In contrast, the maximum tooth displacement in the periapical bone defect model increased as the size of the periapical bone defect increased (2.11-120.1% of increase). Internal analysis of tooth: As the size of the periapical bone defect increased, the maximum von Mises stress in the coronal cervix of the tooth gradually increased (2.23-37.22% of increase). while the von Mises stress in the root apical region of the tooth showed a decreasing trend (41.48-99.70% of decrease). The maximum tooth displacement in all parts of the tooth showed an increasing trend as the size of the periapical bone defect increased.

CONCLUSIONS

The presence of periapical bone defects was found to significantly affect the biomechanical response of the tooth, the effects of which became more pronounced as the size of the bone defect increased.

The effect of root canal treatment and post-crown restorations on stress distribution in teeth with periapical periodontitis: a finite element analysis

AIM

To evaluate the effects of root canal treatment (RCT) and post-crown restoration on stress distribution in teeth with periapical bone defects using finite element analysis.

METHODOLOGY

Finite element models of mandibular second premolars and those with periapical bone defects (spherical defects with diameters of 5, 10, 15, and 20 mm) were created using digital model design software. The corresponding RCT and post-crown restoration models were constructed based on the different sizes of periapical bone defect models. The von Mises stress and tooth displacement distributions were comprehensively analyzed in each model.

RESULTS

Overall analysis of the models: RCT significantly increased the maximum von Mises stresses in teeth with periapical bone defects, while post-crown restoration greatly reduced the maximum von Mises stresses. RCT and post-crown restoration slightly reduced tooth displacement in the affected tooth. Internal analysis of tooth: RCT dramatically increased the maximum von Mises stress in all regions of the tooth, with the most pronounced increase in the coronal surface region. The post-crown restoration balances the internal stresses of the tooth and is most effective in periapical bone defect - 20-mm model. RCT and post-crown restoration slightly reduced the tooth displacement in all regions of the affected tooth.

CONCLUSIONS

Root canal treatment seemed not to improve the biomechanical state of teeth with periapical bone defects. In contrast, post-crown restoration might effectively balance the stress concentrations caused by periapical bone defects, particularly extensive ones.

Expert consensus on digital guided therapy for endodontic diseases

Digital guided therapy (DGT) has been advocated as a contemporary computer-aided technique for treating endodontic diseases in recent decades. The concept of DGT for endodontic diseases is categorized into static guided endodontics (SGE), necessitating a meticulously designed template, and dynamic guided endodontics (DGE), which utilizes an optical triangulation tracking system. Based on cone-beam computed tomography (CBCT) images superimposed with or without oral scan (OS) data, a virtual template is crafted through software and subsequently translated into a 3-dimensional (3D) printing for SGE, while the system guides the drilling path with a real-time navigation in DGE. DGT was reported to resolve a series of challenging endodontic cases, including teeth with pulp obliteration, teeth with anatomical abnormalities, teeth requiring retreatment, posterior teeth needing endodontic microsurgery, and tooth autotransplantation. Case reports and basic researches all demonstrate that DGT stand as a precise, time-saving, and minimally invasive approach in contrast to conventional freehand method. This expert consensus mainly introduces the case selection, general workflow, evaluation, and impact factor of DGT, which could provide an alternative working strategy in endodontic treatment.

Development and validation of risk of bias tool for the use of finite element analysis in dentistry (ROBFEAD)

There has been a systematic review of studies that used FEA in dental sciences, but no adequate risk of bias (RoB) analysis technique has been developed. Therefore, the development and validation process of RoB in studies using the finite element analysis in dentistry (ROBFEAD) tool is described. In the first phase of development, the scope of the tool and possible modifications were covered, and validation was done in the second phase. The developed tool comprised 6 domains and a total of 22 guiding questions in these domains. This article proposes the development and validation of ROBFEAD, a tool for measuring RoB in finite element research in dentistry.

Orthodontic Internal Resorption Assessment in Periodontal Breakdown-A Finite Elements Analysis (Part II)

This finite elements analysis (FEA) assessed the accuracy of maximum shear stress criteria (Tresca) in the study of orthodontic internal surface resorption and the absorption-dissipation ability of dental tissues. The present study was conducted over eighty-one models totaling 324 simulations with various bone loss levels (0-8 mm), where 0.6 N and 1.2 N were applied in the intrusion, extrusion, rotation, tipping, and translation movements. Tresca criteria displayed localized high-stress areas prone to resorption for all situations, better visible in the dentine component. The internal resorptive risks are less than external ones, seeming to increase with the progression of the periodontal breakdown, especially after 4 mm. The internal and external surface high-stress areas are strictly correlated. The qualitative stress display for both forces was almost similar. The rotation and tipping displayed the highest resorptive risks for the pulp chamber, decreasing with bone loss. The resorptive risks seem to increase along with the progression of periodontal breakdown if the same applied force is kept. The dentine resemblance to ductile based on its high absorption-dissipation ability seems correct. Tresca seems to supply a better predictability of the prone-to-resorption areas than the other failure criteria.

Effect of apical root resection, orthodontic extrusion, and surgical crown lengthening on load capability

OBJECTIVES

This study aims to investigate the load-to-fracture of procedures changing crown-to-root ratio (RCRR) aimed to restore severely damaged upper central incisors to avoid tooth extraction compared to implant placement. There is no evidence on load capability after apical root resection (AR), orthodontic extrusion (OE), and surgical crown lengthening (SCL) in respect to RCRR, respectively.

MATERIAL AND METHODS

Human maxillary central incisors were endodontically treated, decoronated, and divided into 4 groups (n = 48). The following specimen preparation was performed: (I) adhesive core-and-post build-up (control), (II) as (I) and 2 mm apical root resection (AR), (III) before adhesive core-and-post build-up teeth were shortened 2 mm coronally (OE) (IV) as (I), but specimens were embedded 4 mm instead of 2 mm below the CEJ (SCL), group (V) implant-borne restoration with individual all-ceramic abutments (n = 12; ∅4.1/l = 12 mm) (IBR). All specimens received all-ceramic crowns, thermo-mechanical (TML), and subsequent linear loading (LL) until failure. RCRR were calculated and log-rank, Kruskal-Wallis, Mann-Whitney U, ANOVA, and chi-square tests applied (p = 0.05).

RESULTS

Fracture loads after subsequent LL differed significantly (p = 0.001) between groups, while implants showed the highest values. Fmax median (min/max) were as follows: (I) 252 (204/542), (II) 293 (243/443), (III) 253 (183/371), (IV) 195 (140/274), and (V) 446 (370/539). Pair-wise comparison showed significant differences (p = 0.001) between group I/IV and group V, I, and IV (p = 0.045), II and IV (p = 0.001), and III compared to IV (p = 0.033), respectively. RCRR below 1 significantly increased load capability compared to RCRR = 1.

CONCLUSIONS

OE appears to preferably ensure biomechanical stability of teeth that are endodontically treated and receive core-and-post and crown placement compared to SCL. AR has no adverse biomechanical impact. RCRR < 1 is biomechanically beneficial.

CLINICAL RELEVANCE

For endodontically treated and restored teeth, orthodontic extrusion should be preferred compared to surgical crown lengthening prior single-crown restoration. As orthodontic extrusion, apical root resection has no adverse effect on load capability. Single-crown implant-borne restorations are most load capable.

Assessment of the Orthodontic External Resorption in Periodontal Breakdown-A Finite Elements Analysis (Part I)

This Finite Elements Analysis (FEA) assessed the accuracy of Tresca failure criteria (maximum shear stress) for the study of external root resorption. Additionally, the tooth absorption-dissipation ability was assessed. Overall, 81 models of the second mandibular premolar, out of a total of 324 simulations, were involved. Five orthodontic movements (intrusion, extrusion, rotation, translation, and tipping) were simulated under 0.6 N and 1.2 N in a horizontal progressive periodontal breakdown simulation of 0-8 mm. In all simulations, Tresca criteria accurately displayed the localized areas of maximum stress prone to external resorption risks, seeming to be adequate for the study of the resorptive process. The localized areas were better displayed in the radicular dentine-cementum component than in the entire tooth structure. The rotation and translation seem prone to a higher risk of external root resorption after 4 mm of loss. The resorptive risks seem to increase along with the progression of periodontal breakdown if the same amount of applied force is guarded. The localized resorption-prone areas follow the progression of bone loss. The two light forces displayed similar extensions of maximum stress areas. The stress displayed in the coronal dentine decreases along with the progression of bone loss. The absorption-dissipation ability of the tooth is about 87.99-97.99% of the stress.

Finite Elements Analysis of Tooth-A Comparative Analysis of Multiple Failure Criteria

Herein Finite elements analysis (FEA) study assesses the adequacy and accuracy of five failure criteria (Von Mises (VM), Tresca, maximum principal (S1), minimum principal (S3), and Hydrostatic pressure) for the study of tooth as a structure (made of enamel, dentin, and cement), along with its stress absorption-dissipation ability. Eighty-one 3D models of the second lower premolar (with intact and 1-8 mm reduced periodontium) were subjected to five orthodontic forces (intrusion, extrusion, tipping, rotation, and translation) of 0.5 N (approx. 50 gf) (in a total of 405 FEA simulations). Only the Tresca and VM criteria showed biomechanically correct stress display during the 0-8 mm periodontal breakdown simulation, while the other three showed various unusual biomechanical stress display. All five failure criteria displayed comparable quantitative stress results (with Tresca and VM producing the highest of all), showing the rotational and translational movements to produce the highest amount of stress, while intrusion and extrusion, the lowest. The tooth structure absorbed and dissipated most of the stress produced by the orthodontic loads (from a total of 0.5 N/50 gf only 0.125 N/12.5 gf reached PDL and 0.01 N/1 gf the pulp and NVB). The Tresca criterion seems to be more accurate than Von Mises for the study of tooth as structure.

Comparison of the biomechanical differences in the occlusal movement of wild-type and BMP9 knockout mice with apical periodontitis

Apical periodontitis is a common clinical disease caused by bacteria; bacterial metabolites can cause an imbalance in bone homeostasis, bone mass reduction, and tooth loss. Bone resorption in apical periodontitis causes a concentration of stress in the tooth and periodontal tissues during occlusion, which aggravates the disease. Emerging evidence indicates that bone morphogenetic protein 9 (BMP9), also known as growth differentiation factor 2(Gdf2), may play an important role in tooth and dentoalveolar development. Herein, we investigated the role of BMP9 in the development of apical periodontitis and its effects on the biomechanics of dentoalveolar bone. Apical periodontitis models were established in five BMP9 knockout (KO) mice and five C57BL/6 WT (wild-type) mice. At baseline and 14, 28, and 42 days after modeling, in vivo micro-computed tomography analysis and three-dimensional (3D) reconstruction were performed to evaluate the apical lesion in each mouse, and confirm that the animal models were successfully established. Finite element analysis (FEA) was performed to study the stress and strain at the alveolar fossa of each mouse under the same vertical and lateral stress. FEA revealed that the stress and strain at the alveolar fossa of each mouse gradually concentrated on the tooth cervix. The stress and strain at the tooth cervix gradually increased with time but were decreased at day 42. Under the same lingual loading, the maximum differences of the stress and strain at the tooth root in KO mice were greater than those in WT mice. Thus, these findings demonstrate that BMP9 could affect the biomechanical response of the alveolar fossa at the tooth root in mice with apical periodontitis. Moreover, the effects of BMP9 on the biomechanical response of the alveolar bone may be site-dependent. Overall, this work contributes to an improved understanding of the pathogenesis of apical periodontitis and may inform the development of new treatment strategies for apical periodontitis.

Multifactorial Analysis of Endodontic Microsurgery Using Finite Element Models

Background: The present study aimed to classify the relative contributions of four biomechanical factors—the root-end filling material, the apical preparation, the root resection length, and the bone height—on the root stresses of the resected premolar. Methods: A design of experiments approach based on a defined subset of factor combinations was conducted to calculate the influence of each factor and their interactions. Sixteen finite element models were created and analyzed using the von Mises stress criterion. The robustness of the design of experiments was evaluated with nine supplementary models. Results: The current study showed that the factors preparation and bone height had a high influence on root stresses. However, it also revealed that nearly half of the biomechanical impact was missed without considering interactions between factors, particularly between resection and preparation. Conclusions: Design of experiments appears to be a valuable strategy to classify the contributions of biomechanical factors related to endodontics. Imagining all possible interactions and their clinical impact is difficult and can require relying on one’s own experience. This study proposed a statistical method to quantify the mechanical risk when planning apicoectomy. A perspective could be to integrate the equation defined herein in future software to support decision-making.

Impact of Periodontal Attachment Loss on the Outcome of Endodontic Microsurgery: A Systematic Review and Meta-Analysis

Background and Objectives: Endodontic microsurgery (EMS) aims to eradicate the sources of infection once the apical root resection removes most of the infected anatomical structures and repairs potential procedural errors in the apical region. An endodontic-periodontal lesion yields a pathological communication between the pulp and the periodontium. The purpose of this systematic review and meta-analysis is to evaluate the impact of periodontal attachment loss on the outcome of teeth submitted to EMS. Materials and Methods: PRISMA guidelines were followed. An electronic search was performed in EBSCOhost, Embase and PubMed databases with the following search key: (“endodontic microsurgery” AND “outcome”). No filters were used concerning the year of publication or language. Only randomized clinical trials, prospective and retrospective clinical studies in humans, with a minimum one-year follow-up, defined clinical and radiographic outcome criteria and estimable success rate for endodontic-periodontal lesion were included. Statistical analysis was performed using OpenMeta[Analyst] software. Results: Of a total of 113 articles, 34 were selected for full-text reading after duplicates deletion and title and abstract analysis. Thirteen and six studies were included in the systematic review and meta-analysis, respectively. A total of 2775 pooled teeth were submitted to EMS, of which 492 teeth and 4 roots had periodontal involvement. According to the qualitative analysis, success rates of the endodontic-periodontal group ranged from 67.6% to 88.2%. Meta-analysis revealed that the absence of periodontal attachment loss was predictive of a higher likelihood of success with an odds ratio of 3.14. Conclusions: Periodontal attachment loss presents a risk factor for EMS outcome. Although endodontic-periodontal lesions were associated with lower success rates considering a 1 to 10 years follow-up period, long-term successful prognosis following EMS has been reported, therefore presenting a fully valid and viable therapeutic option for the management of this type of lesions.

Relationship Between Crown to Root Ratio and Alveolar Bone Support in Patients With Unilateral Cleft Lip and Alveolus

OBJECTIVES

To evaluate the tooth lengths, crown to root ratios (CRRs), and alveolar bone support (ABS) around cleft-adjacent maxillary central incisors (U1s) in patients with unilateral cleft lip and alveolus (UCLA) and to investigate the relationships between CRR and ABS.

DESIGN

This is a retrospective study.

SETTING

Cleft Lip and Palate Care Center of Shanghai Ninth People's Hospital, Shanghai, China.

PATIENTS

Fifty-eight Chinese patients with UCLA.

MAIN OUTCOME MEASURE

Cone beam computed tomography data from 58 nonsyndromic patients with UCLA (36 males, 22 females; mean age = 12.65 ± 3.64 years) were evaluated. Crown length and root length, alveolar bone thickness (ABT), and the distances between the cementoenamel junction and alveolar bone crest on 4 surfaces of cleft-adjacent U1 were measured and compared with those of noncleft side in the same patients. Crown to root ratio and frequency of dehiscence were calculated and comparisons were also made between cleft and noncleft sides. Regression analysis was performed to explore the association between CRR and ABS.

RESULTS

The CRR of cleft-adjacent U1 and alveolar bone crest heights (ACHs) on the 4 surfaces were significantly greater than those of noncleft side (P < .01). A 3 mm labial, all lingual, and apico-distal ABTs decreased on the cleft side (P < .01). A positive correlation was found between lingual ACH and CRR (R = 0.316, P < .05), between the 3 mm (R = 0.417, P < .05) and 6 mm labial (R = 0.448, P < .05) ABT and CRR. A negative correlation was found between the 3 mm and 6 mm labial ABTs and the root length.

CONCLUSIONS

It can be suggested that the CRR is related to ACH and ABT. The lingual ACH, the 3 mm, and 6 mm labial ABTs tend to increase with the increasing CRR.

Prognostic Factors of Long-Term Outcomes in Endodontic Microsurgery: A Retrospective Cohort Study over Five Years

The aim of this study was to analyze the long-term outcomes of endodontic microsurgeries in a cohort and identify their association with prognostic factors. A cohort of endodontic microsurgeries followed up periodically with complete clinical and radiographic records for at least 5 years were reviewed retrospectively. Their survival and healing status and profile characteristics were analyzed by Pearson chi-square test and logistic regression (α = 0.05) to identify prognostic factors that influenced outcomes. Of 652 cases in the cohort, 225 (34.5%) were included. The mean follow-up period was 90.4 months (range, 60–168 months). The long-term success rate was 80.5%, and the 5-year survival rate was 83.5%. Logistic regression showed higher success in anteriors compared to molars (OR = 5.405, (95% CI, 1.663–17.571; p = 0.005)) and in teeth with crown restorations (OR = 10.232, (95% CI, 3.374–31.024; p < 0.001)). Conversely, lower success was found in teeth with periodontal disease (OR = 0.170, (95% CI, 0.032–0.900; p = 0.037)) and maxillary sinus involvement (OR = 0.187, (95% CI, 0.035–0.994; p = 0.049)). Endodontic microsurgery has a highly favorable long-term outcome. Tooth position, crown restoration, periodontal disease, and maxillary sinus involvement were identified as main prognostic factors.

Effect of length of apical root resection on the biomechanical response of a maxillary central incisor in various occlusal relationships

AIM

To investigate the stress distribution and tooth displacement of a maxillary central incisor with various apical root resection lengths and occlusal relationships using finite element (FE) analysis.

METHODOLOGY

A maxillary central incisor was scanned by micro-CT. First, the FE intact incisor model with dentine, enamel, pulp and root surrounded by alveolar bone and periodontal ligament was designed based on the micro-CT image data. Then, six FE models with varying lengths of apical root resection were established to simulate the clinical treatment and reveal the clinically applicable limit of apical root resection during endodontic microsurgery. For each model under different loading conditions, the maximum von Mises stress (σ max) at the root apex, root cervix, alveolar bone and periodontal ligament and the maximum tooth displacement (ΔR max) were calculated and compared.

RESULTS

In a normal occlusion, more than 6 mm of root resection resulted in a marked increase in the ΔR max values (>10%) and σ max values of alveolar bone (>50%); the stress levels at the root apex increased dramatically when the apical root was resected more than 7 mm. With increased overjet, apical root resection did not change the stress level markedly until it reached 8 mm, but the ΔR max increased markedly (>10%) if the root was resected more than 5 mm. With deep overbites, the σ max increased significantly (>50%) when the root was resected more than 4 mm whilst the ΔR max decreased. With increased overjet and deep overbite, more than 6 mm of resection resulted in a substantial σ max increase (>50%) of alveolar bone and the ΔR max increased markedly (>10%) when the root was resected 8 mm. Additionally, the σ max and the ΔR max values were greater with increased overjet and lower with deep overbites.

CONCLUSIONS

Using FE analysis, apical root resection of more than 6 mm resulted in a marked increase of stress distribution and tooth displacement in normal and increased overjet with deep overbite occlusal relationships. In increased overjets or deep overbites, more than 5 mm or 4 mm, respectively, stress distribution and tooth displacement increased markedly.

Effect of Root Resection Length and Graft Type Used After Apical Resection: A Finite Element Study

PURPOSE

Apical resection is a surgical technique that involves removing a tooth's root tip and sealing the apical extent of the root canal system. However, evidence-based information on the biomechanical effects of apically resected tooth determinants is lacking. The aim of the present study was to examine the biomechanical effects of using different graft materials and the effect of different resection quantities on the tooth radix.

MATERIALS AND METHODS

Thirty finite element models of mandibular central incisors with 1-cm defects in their apical regions were constructed using SolidWorks software (SolidWorks, Waltham, MA). Resections of 0, 1, 2, 3, 4, and 5 mm were created at the root tips, and tissue regeneration was simulated in the empty cavity models using the material properties of healed bone, an allograft, a xenograft, and hydroxyapatite to the grafts used to fill the apical sites. A 100-N force was applied to the various groups of teeth in the oblique (45°) direction, and the maximal von Mises stress and displacement values were determined using Ansys, version 16, software (ANSYS, Inc, Canonsburg, PA).

RESULTS

The highest of these values was observed in the 5-mm resected and empty model. Increasing the resection amount caused the stress and displacement to increase. The lowest stress and deformation values were seen in the hydroxyapatite group, followed by the xenograft group and the allograft group.

CONCLUSIONS

The results of the present study have shown that grafting into the apical defect provides biomechanical support for resection of the root structure.

The Effect of Resection Angle on Stress Distribution after Root-End Surgery

Introduction:

This study aimed to investigate the influence of the resection angle on the stress distribution of retrograde endodontic treated maxillary incisors under oblique-load application.

Methods and Materials:

A maxillary central incisor which was endodontically treated and restored with a fiber glass post was obtained in a 3-dimensional numerical model and distributed into three groups according to type of resection: control; restored with fiber post without retrograde obturation, R45 and R90 with 45º and 90º resection from tooth axial axis, respectively and restored with Fuji II LC (GC America). The numerical models received a 45^º occlusal load of 200 N/cm² on the middle of lingual surface. All materials and structures were considered linear elastic, homogeneous and isotropic. Numerical models were plotted and meshed with isoparametric elements, and the results were analyzed using maximum principal stress (MPS).

Results:

MPS showed greater stress values in the bone tissue for control group than the other groups. Groups with apicectomy showed acceptable stress distribution on the fiber post, cement layer and root dentin, presenting more improved values than control group.

Conclusion:

Apicectomy at 90^º promotes more homogeneity on stress distribution on the fiber post, cement layer and root dentin, which suggests less probability of failure. However, due to its facility and stress distribution also being better than control group, apicectomy at 45^° could be a good choice for clinicians.

Micro-CT evaluation of apical delta morphologies in human teeth

The apical delta is an intricate system within the root canal and incompletely debridement may affect the long-term prognosis of root canal therapy. The aim of the present study is to investigate the morphologic features of apical deltas in human teeth with micro-computed tomography (micro-CT) using a centreline-fitting algorithm. One hundred and thirty-six apical deltas were detected in 1400 teeth. Molars had more apical deltas (15.8%) than anterior teeth (6.3%). In maxillary molars, the mesiobuccal root had a significantly higher prevalence of apical delta than the palatal root or the distobuccal root. The median vertical distance of the apical delta was 1.87 mm with 13% more than 3 mm. The median diameter and length of the apical delta branches were 132.3 and 934.5 μm. Apical delta branches were not straight with cross-sectional shapes being non-circular. These morphological features of apical delta may complicate debridement of the infected root canal system.

Influence of Dentoalveolar Ankylosis on the Biomechanical Response of a Single-rooted Tooth and Surrounding Alveolar Bone: A 3-dimensional Finite Element Analysis

INTRODUCTION

Dentoalveolar ankylosis necessarily accompanies the loss of periodontal ligament (PDL), which might alter the biomechanical response of the tooth. The purpose of this study was to investigate the influence of dentoalveolar ankylosis on a single-rooted tooth and the surrounding alveolar bone structures in the biomechanical standpoint.

METHODS

A basic model of an intact maxillary central incisor and the surrounding bone structures was chosen for the numeric analysis. From this basic model, 6 different models were further developed by combining 3 types of endodontic status (an intact model, a nonsurgically treated model, and a surgically treated model) and 2 types of periodontal attachment condition (models with or without PDL). For each condition, maximum von Mises stress (σ max) in dentin and bone and maximum tooth displacement (ΔR max) were calculated.

RESULTS

In models with dentoalveolar ankylosis, stress was concentrated on the cervical dentin around the cementoenamel junction and the alveolar bone crest, whereas the stress was more evenly distributed along the entire length of the root in models with normal PDL. The models with dentoalveolar ankylosis showed higher stress values in dentin (44.72%-80.56% of σ max increase) and bone (24.23%-80.68% of σ max increase) and lower tooth displacement (59.22%-63.97% of ΔR max decrease) compared with the models with normal PDL.

CONCLUSIONS

Dentoalveolar ankylosis exerts significant changes on the biomechanical response of a single-rooted tooth and the surrounding bone structures. The dentoalveolar complex with ankylosis showed characteristic stress concentrations, increased stress values, and decreased tooth displacement compared with that with normal PDL.

Changes of Root Length and Root-to-Crown Ratio after Apical Surgery: An Analysis by Using Cone-beam Computed Tomography

INTRODUCTION

Apical surgery is an important treatment option for teeth with post-treatment periodontitis. Although apical surgery involves root-end resection, no morphometric data are yet available about root-end resection and its impact on the root-to-crown ratio (RCR). The present study assessed the length of apicectomy and calculated the loss of root length and changes of RCR after apical surgery.

METHODS

In a prospective clinical study, cone-beam computed tomography scans were taken preoperatively and postoperatively. From these images, the crown and root lengths of 61 roots (54 teeth in 47 patients) were measured before and after apical surgery. Data were collected relative to the cementoenamel junction (CEJ) as well as to the crestal bone level (CBL). One observer took all measurements twice (to calculate the intraobserver variability), and the means were used for further analysis. The following parameters were assessed for all treated teeth as well as for specific tooth groups: length of root-end resection and percentage change of root length, preoperative and postoperative RCRs, and percentage change of RCR after apical surgery.

RESULTS

The mean length of root-end resection was 3.58 ± 1.43 mm (relative to the CBL). This amounted to a loss of 33.2% of clinical and 26% of anatomic root length. There was an overall significant difference between the tooth groups (P < .05). There was also a statistically significant difference comparing mandibular and maxillary teeth (P < .05), but not for incisors/canines versus premolars/molars (P = .125). The mean preoperative and postoperative RCRs (relative to CEJ) were 1.83 and 1.35, respectively (P < .001). With regard to the CBL reference, the mean preoperative and postoperative RCRs were 1.08 and 0.71 (CBL), respectively (P < .001). The calculated changes of RCR after apical surgery were 24.8% relative to CEJ and 33.3% relative to CBL (P < .001). Across the different tooth groups, the mean RCR was not significantly different (P = .244 for CEJ and 0.114 for CBL).

CONCLUSIONS

This CBCT-based study demonstrated that the RCR is significantly changed after root-end resection in apical surgery irrespective of the clinical (CBL) or anatomic (CEJ) reference levels. The lowest, and thus clinically most critical, postoperative RCR was observed in maxillary incisors. Future clinical studies need to show the impact of resection length and RCR changes on the outcome of apical surgery.