Dental trauma on primary teeth at different root resorption stages-A dynamic finite element impact analysis of the effect on the permanent tooth germ

Effect of wire diameter and extent of wire composite splint on the mobility of luxated and anchor primary teeth: A typodont study

BACKGROUND/AIMS

The recommendations for splinting are well established for the injuries of permanent dentition; however, ambiguity still exists for the injuries in primary dentition. Hence, this study aimed to determine the most appropriate dimensions of stainless steel wire and its extent, for achieving the physiologic mobility in primary dentition.

MATERIAL AND METHODS

This study was designed as an in vitro experiment by using a typodont model of primary dentition. The baseline mobility of primary maxillary incisors was calibrated to the physiologic mobility of natural primary incisors by using a Teflon tape wrapped around the roots of resin teeth. Splinting was done using a stainless steel wire of 0.2 mm (Group I), 0.3 mm (Group II), and 0.4 mm (Group III). These groups were subdivided (a, b, and c) on the basis of the extent of the splint, and pre splint mobility (Pre-PV) and post-splint mobility (Post-PV) were tested by Periotest M. The splint effect was calculated by subtracting Post-PVs and Pre-PVs.

RESULTS

The normal values of mobility in healthy human volunteers ranged from 10.5 to 13. The overall splint effect was higher in Group III irrespective of the extent of the splint, whereas it was found to be the lowest in Group I (b and c). The splint effect increased with the extent of the splint in all the groups. Among all the groups, the splint effect on the anchor teeth was observed to increase with the extent of the splint and the diameter of the wire.

CONCLUSION

The mobility of the injured and anchor teeth splinted with 0.2-mm stainless steel wire was similar to the pre-splint and physiologic mobility. The most favorable extension was one tooth adjacent to the injured tooth on each side for both 0.2- and 0.3-mm wires.

Methods and applications of finite element analysis in dental trauma research: A scoping review

Finite Element Analysis (FEA) is vital for understanding dental traumatology (DT) biomechanics, aiding diagnosis, treatment planning, and outcome prediction. This review explores FEA applications in DT research, evaluates their quality and outcomes, and assesses methodological aspects. Accordingly, recommendations for future researchers are provided. The study adhered to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for scoping reviews and registered in Open Science framework. A comprehensive search using relevant text-words and MeSH terms was performed in established databases. The inclusion criteria encompassed all Finite element analysis (FEA)-based Dental traumatology (DT) studies without language or publication year restrictions. Risk of bias was assessed with the Risk of bias tool for the use of finite element analysis in dentistry (ROBFEAD) tool. Forty-six studies published from 2001 to 2023 were included in the qualitative synthesis. The studies were categorized into five domains and six subdomains based on objectives. Maxillary central incisors and surrounding structures were commonly modelled (n = 27). Most studies utilized Computed tomography (CT), Cone Beam CT, or micro CT. Traumatic injury forces ranged from 100 N to 2000 N, and occlusal forces ranged from 150 N to 350 N. All studies were rated as high risk of bias. Fory-six studies were categorized, with most focusing on stress distribution and fracture patterns in dento-alveolar structures under various conditions, while few assessed displacements. Methodological quality lacked robustness in model development and substructure properties. Future studies should address these limitations and enhance reporting practices.

Evaluation of the effect on the permanent tooth germ and the adjacent teeth by finite element impact analysis in the traumatized primary tooth

BACKGROUND

One of the primary concerns in the paediatric emergencies is traumatic dental injuries.

OBJECTIVE

This study aimed to create trauma in primary teeth and reveal its effects finite element analysis.

DESIGN

Three-dimensional models were created using cone-beam computed tomography images, representing a maxillary primary central incisor. An impact force moving at a speed of 10 m/s was simulated on the labial tooth surface in two directions: buccal and incisal.

RESULTS

The stress and deformation experienced in the adjacent tooth due to the primary tooth were higher than those generated in the permanent tooth. Forces applied in the incisal direction resulted in higher levels of stress and deformation in the permanent tooth germ. The difference between the stress and deformation values in primary teeth in the forces applied in the buccal and incisal directions is 21% and 75%, respectively; in the permanent tooth germ, this difference was 233% and 100%, respectively.

CONCLUSIONS

Based on the findings of this study, it is crucial to thoroughly evaluate not only the affected primary tooth but also the adjacent teeth and the permanent tooth germ in traumatic dental injuries. This comprehensive examination allows for the anticipation and management of potential long-term problems.

3D finite element analysis of stress distribution as a result of oblique and horizontal forces after regenerative endodontic treatment part II: comparison of material thickness

AIM

This study aimed to evaluate the stress distribution caused by secondary trauma forces after regenerative endodontic treatment (RET) using different thicknesses of coronary barrier material with three-dimensional finite element analysis(FEA).

METHOD

A control model was created using the tomography image of the immature maxillary central tooth with computer software.Study models were created with the modulus of elasticity and Poisson's ratio of the materials used in RET.Enamel, dentin, cementum, periodontal ligament, cortical, and cancellous bone were modeled. Coronary barrier materials were applied in 3 mm and 5 mm thicknesses (Model 1: control model, model 2:3 mm/Calcium Enriched Mixture(CEM), model 3:3 mm/Mineral Trioxide Aggregate(MTA), model 4:3 mm/Biodentin, model 5:5 mm/CEM, model 6:5 mm/MTA, model 7:5 mm/Biodentin). For the trauma force simulation, 300 N force in the horizontal direction was applied to the buccal surface of the tooth in the first scenario. For the second scenario, maximum bite force simulation, a force of 240 N in the oblique direction was applied to the palatal surface of the tooth. FEA was performed with Algor Fempro. The resulting stresses were recorded as Von Mises, maximum, and minimum principal stresses.

RESULTS

Lower stress values were obtained in 5 mm models compared to 3 mm models. However, the difference between them was insignificant. Lower stress values were obtained in all RET models compared to the control model. The lowest stress values in dental tissues and bone tissue were obtained in the CEM models.

CONCLUSION

This is the first study in which the stress caused by different thicknesses of CEM on dental tissues was evaluated with FEA. RET strengthens immature teeth biomechanically. CEM and Biodentin are more successful materials in stress distribution than MTA. Considering the cost of treatment, 3 mm material thickness is ideal for RET since there is no significant difference between the stress values resulting from the use of 5 mm and 3 mm coronary barrier material.

The effect of pulp volume and impact direction on the stress and strain distribution during an impact

BACKGROUND/AIM

Dentoalveolar trauma has a high incidence in different age groups, including the extremes, children, and older people. Mouth aging leads to some changes, one of them being the pulp volume reduction. The aim of this study was to evaluate the influence of different pulp cavity volumes and the impact direction on the stress and strain distribution of a maxillary central incisor.

MATERIAL AND METHODS

Twenty cone beam computed tomography sets of images were selected and the pulp cavity volume was measured by ITK-SNAP software. The mean pulp cavity volume for age group of 10- to 12-year-olds was calculated to obtain the largest one. Subsequent reductions (25%, 50%, 75% and 100%) in the pulp volume values were made to simulate the aging process. The maxilla anterior segment was modeled in the Rhinoceros 5.0 software. The three-dimensional volumetric mesh was generated using the Patran software (MSC. Software), with isoparametrics, 4-noded tetrahedral elements, and exported to Marc/Mentat (MSC. Software) as element number 134. A non-linear dynamic impact analysis was performed in which a steel ball reached the central incisor at a speed of 5 m/s in the horizontal or vertical direction. The stresses were evaluated by modified von Mises stresses. The strains and the total displacement were also recorded.

RESULTS

The pulp volume mean value for the age group of 10- to 12-year-olds was 65.05 mm3 . Stress concentrations were slightly different for the different pulp volumes. Impact directions resulted in different stress distribution. Higher stress values were present with the horizontal impact (range between 25.18 MPa and 24.08 MPa for enamel and 38.89 MPa and 37.03 for dentin) when compared to vertical impact (range between 15.30 MPa and 14.58 for enamel and 24.77 to 22.03 MPa for dentin). Total displacement was different for the two impact directions and higher for the horizontal impact.

CONCLUSION

Pulp volume did not significantly affect the stress, strain, and total displacement during the impact but the impact direction did affect the evaluated parameters during impact.

mTORC1 signaling pathway regulates tooth repair

Tooth germ injury can lead to abnormal tooth development and even tooth loss, affecting various aspects of the stomatognathic system including form, function, and appearance. However, the research about tooth germ injury model on cellular and molecule mechanism of tooth germ repair is still very limited. Therefore, it is of great importance for the prevention and treatment of tooth germ injury to study the important mechanism of tooth germ repair by a tooth germ injury model. Here, we constructed a Tg(dlx2b:Dendra2-NTR) transgenic line that labeled tooth germ specifically. Taking advantage of the NTR/Mtz system, the dlx2b⁺ tooth germ cells were depleted by Mtz effectively. The process of tooth germ repair was evaluated by antibody staining, in situ hybridization, EdU staining and alizarin red staining. The severely injured tooth germ was repaired in several days after Mtz treatment was stopped. In the early stage of tooth germ repair, the expression of phosphorylated 4E-BP1 was increased, indicating that mTORC1 is activated. Inhibition of mTORC1 signaling in vitro or knockdown of mTORC1 signaling in vivo could inhibit the repair of injured tooth germ. Normally, mouse incisors were repaired after damage, but inhibition/promotion of mTORC1 signaling inhibited/promoted this repair progress. Overall, we are the first to construct a stable and repeatable repair model of severe tooth germ injury, and our results reveal that mTORC1 signaling plays a crucial role during tooth germ repair, providing a potential target for clinical treatment of tooth germ injury.

Dental trauma splints for the mixed dentition - A finite element analysis of splint material, splint extension, missing teeth, and PDL representation

BACKGROUND/AIMS

Dental traumatic injuries are common in children during the mixed dentition stage. These injuries usually require splinting for stabilization, which is complicated by the various stages of the permanent tooth development and primary tooth exfoliation. The aim of this study was to evaluate the effect on mobility of splint materials and extensions for an avulsed central incisor, stabilized with and without the adjacent incisor under intrusive and extrusive loading with different periodontal ligament (PDL) conditions.

MATERIALS AND METHODS

Seventeen 3D model variations were created from a CBCT scan of a 7-year-old patient without erupted permanent upper lateral incisors. A 1000 N palatal load on the right central incisor simulated the avulsion injury and created an increased alveolus and bone deformation, resulting in an increased PDL thickness of 0.45 mm. Wire-resin composite splints with 0.9 mm cross-section (WCS) or 1.0 mm diameter nylon-resin composite splints (NCS) were created. The models simulated conditions with and without the adjacent upper central incisor. Two PDL conditions were investigated, simulating detached PDL or PDL with polyether impression material-like properties. Mobility was calculated under simulated biting loads in horizontal and vertical (intrusive and extrusive) directions.

RESULTS

The NCS allowed greater tooth mobility of the avulsed incisor than the WCS, irrespective of splint extension, PDL condition, or load application. During horizontal loading, polyether-like properties for the PDL allowed around 0.2 mm mobility of the avulsed tooth with the WCS, similar to the intact tooth, whereas a simulated detached PDL allowed 25% more mobility with a WCS than with a NCS.

CONCLUSIONS

Based on the FEA analysis, a 1.0 mm NCS may be suitable for splinting avulsion injuries during the mixed dentition stage compared to the considerably more rigid WCS. The NCS models provided flexibility for PDL healing while maintaining stability, even when missing adjacent teeth increased span widths. Extensions beyond directly adjacent teeth did not alter the mobility with the NCS but should still be considered an extra protection in case of bond failure or exfoliation.

Dental Abnormalities in Immature Dogs with a History of Mandibular Fractures

This study was performed to report the dental abnormalities encountered in immature dogs with a history of mandibular fracture. Dogs were included in the study if mandibular fractures were diagnosed by means of oral examination and diagnostic imaging, they were treated with non-invasive or minimally invasive methods, and there was a follow-up examination of at least 90 days after the initial presentation with the last follow-up visit occurring at 6 months of age or older. Eleven dogs met the inclusion criteria. Dental abnormalities occurred exclusively in those dogs that had sustained fracture of the mandibular body or fracture at the transition of mandibular body and mandibular ramus. A high number of developing permanent teeth located in or near the mandibular fracture were affected (73.5%). The most common dental abnormalities were failure of eruption or partial eruption (29.0%), resorption (22.6%), abnormal shape (19.4%), and enamel hypoplasia (16.1%). The majority of deciduous teeth (64.3%) in or near the mandibular fracture exfoliated uneventfully. Ten out of 11 dogs needed a surgical procedure to treat dental abnormalities after mandibular fracture healing. The development of the tooth germs located in or near a mandibular fracture is frequently affected. Radiographic evaluation of the area of trauma is recommended until eruption and full development of the teeth are completed.

A three-dimensional finite element analysis of permanent maxillary central incisors in different stages of root development and trauma settings

BACKGROUND AND OBJECTIVES

Differences in dental maturation may affect the prognosis and clinical management of traumatized teeth. However, evaluation of the outcomes of dental trauma to the tooth and support structures in an in vivo model involves major methodological and ethical implications. Thus, the aim of the present study was to perform a three-dimensional finite element analysis of permanent maxillary central incisors in different stages of root development under different trauma settings.

METHODS

The study factors included two trauma conditions (B, buccal; I, incisal) on upper permanent central incisors showing three different stages of root development (CR, complete rhizogenesis; IRA; incomplete rhizogenesis in the apical third of the root; and IRM, incomplete rhizogenesis in the middle third of the root) to yield six models. The complete rhizogenesis model was obtained with a cone-beam computed tomography examination of an extracted tooth. The two incomplete rhizogenesis models were modeled on the basis of similar examinations of patients. Trauma was simulated by applying a 300 N static surface to surface load on the incisal edge or perpendicular to the buccal surface of the tooth. The displacement and equivalent von Mises (σvM) stress values were obtained for alveolar bone, periodontal ligament, apical papilla, and dentin for the quantitative analysis. A σvM color-coded scale was used for qualitative analysis.

RESULTS

The force direction had a greater influence on the stress than the root-formation stage. Buccal forces resulted in higher stress concentration in the bone and periodontal ligament, especially in B-CR. Lower stress was found on the periodontal ligament as the root formation progressed (decrease of 8% from B-IRA to B-CR and 11% from B-IRM to B-CR). The incomplete rhizogenesis models showed higher σvM stress peak values in dentin in comparison with complete rhizogenesis (increase of 52% from B-CR to B-IRA and 56% from B-CR to B-IRM).

CONCLUSIONS

Buccal forces yielded greater stress values regardless of the stage of rhizogenesis. Teeth with fully formed roots showed a higher stress concentration in the alveolar bone and periodontal ligament in comparison with immature teeth, with the latter presenting high stresses in the tooth crown.

Splint stiffness and extension effects on a simulated avulsed permanent incisor-A patient-specific finite element analysis

BACKGROUND/AIM

Splinting is an important procedure after avulsion. However, the role of splint stiffness and extension is not fully understood. The aim of this study was to evaluate the effect of splint stiffness and extensions on the mobility and stress on an injured tooth under physiological biting load.

MATERIALS AND METHODS

Three-dimensional (3D) finite element models were created from a cone beam computer tomogram of a patient with normal occlusion. An avulsion injury of the right central incisor was created with a 1000 N load application on the palatal of the injured tooth, causing increased socket width. Splints made from four materials were tested: 0.9 mm diameter wire-composite splint (WCS1), 0.4 mm diameter wire-composite splint (WCS2), 1.0 mm diameter nylon-composite splint (NCS), and a 2 mm high by 0.2 mm thick plastic strip composite splint (PSS). Three splint extensions (involving 6, 5, and 3 teeth) were evaluated. Mobility of the avulsed tooth and the maximum principal stress distributions in the adjacent teeth were calculated.

RESULTS

The injured incisor tooth mobility was not affected by the splint extensions. The NCS and PSS stabilized the avulsed incisor but allowed, respectively, 10 and 20 times more mobility under horizontal loading than the WCS1, which inhibited most mobility, while the WCS2 allowed double the mobility compared with WCS1. The NCS and PSS allowed more tooth mobility, mainly in the extrusion direction. Splints were 2-3 times more effective in limiting mobility under intrusive loads than extrusive loads. High levels of stress were found at the base of the composite attachments in the adjacent incisors.

CONCLUSION

Splinting an avulsed tooth to one or two teeth bilaterally using a nylon splint or a plastic strip is appropriate for tooth stabilization and should be recommended over the 0.4mm wire-composite splint, while the 0.9 mm orthodontic wire is too rigid and not recommended.

Stress evaluation of different implant lengths on atrophic edentulous mandibles with fixed full-arch implant-supported prosthesis: a finite element analysis

Finite element analysis was used to compare the effect of different implant lengths on atrophic mandible with full-arch fixed prostheses. Four models were constructed with different implant lengths: 4, 6, 8 and 10 mm. A 100-N occlusal load was applied. The stress at the bone level, implant, and prosthetic components were obtained. Similar behavior was observed for all groups, except for 4 mm, which showed more discrepant values ​​for all prosthetic components. Although longer implants presented better biomechanical behavior, the 4 mm implant seems to be a viable alternative for severely atrophic mandibles, however, further studies need to be carried out.

Influence of ceramic veneer thickness and antagonist on impact stresses during dental trauma with and without a mouthguard assessed with finite element analysis

BACKGROUND/AIM

Little is known about the effect of dental trauma and mouthguards (MG) on teeth with ceramic laminate veneers (CLV). The aim was to evaluate the influence of CLV thickness and the presence of a MG with and without antagonist tooth contact on impact stresses during dental trauma.

MATERIALS AND METHODS

Twelve 2D-finite element models of a head with maxillary structures and upper incisors, six with and six without antagonist tooth, were created in three CLV conditions: sound incisor (no CLV), 0.3 mm CLV, and 1.0 mm CLV. These were evaluated with and without a 4.0-mm ethylene-vinyl acetate MG, with and without an antagonist tooth. An impact analysis was performed in which the head frontally hits a rigid surface at a speed of 1 m/s (3.6 km/h). The results were analyzed using Critical modified von Mises (MPa). The mean of the 10% highest modified von Mises stresses in each structure was collected.

RESULTS

MG presence substantially reduced impact stresses in the CLV and tooth structures. The contact of the antagonist tooth promoted better stress distribution and reduced the stress levels in the traumatized tooth. Critical stress areas were found in the palatal enamel, incisal enamel, labial cervical area, and enamel under the CLV for all models without MG. In the models with MG, the stresses reduced significantly. Critical modified von Mises stress showed that sound or prepared enamel experienced more critical impact stresses than 0.3 or 1.0-mm thick CLV.

CONCLUSIONS

The use of 4.0 mm EVA mouthguard reduced the impact stress levels in models with 0.3-mm CLV and 1.0-mm CLV, similar to a sound tooth. The contact of an antagonist tooth and the MG better distributed the stresses and reduced the impact stress in the traumatized tooth.

3D finite element model based on CT images of tooth

Aim: This study aimed the description of a protocol to acquire a 3D finite element (FE) model of a human maxillary central incisor tooth restored with ceramic crowns with enhanced geometric detail through an easy-to-use and low-cost concept and validate it through finite element analysis (FEA). Methods: A human maxillary central incisor was digitalized using a Cone Beam Computer Tomography (CBCT) scanner. The resulted tooth CBCT DICOM files were imported into a free medical imaging software (Invesalius) for 3D surface/geometric reconstruction in stereolithographic file format (STL). The STL file was exported to a computer-aided-design (CAD) software (SolidWorks), converted into a 3D solid model and edited to simulate different materials for full crown restorations. The obtained model was exported into a FEA software to evaluate the influence of different core materials (zirconia - Zr, lithium disilicate - Ds or palladium/silver - Ps) on the mechanical behavior of the restorations under a 100 N applied to the palatal surface at 135 degrees to the long axis of the tooth, followed by a load of 25.5 N perpendicular to the incisal edge of the crown. The quantitative and qualitative analysis of maximum principal stress (ceramic veneer) and maximum principal strain (core) were obtained. Results: The Zr model presented lower stress and strain concentration in the ceramic veneer and core than Ds and Ps models. For all models, the stresses were concentrated in the external surface of the veneering ceramic and strains in the internal surface of core, both near to the loading area. Conclusion: The described procedure is a quick, inexpensive and feasible protocol to obtain a highly detailed 3D FE model, and thus could be considered for future 3D FE analysis. The results of numerical simulation confirm that stiffer core materials result in a reduced stress concentration in ceramic veneer.