Supramolecular Composite Hydrogel Loaded with CaF2 Nanoparticles Promotes the Recovery of Periodontitis Bone Resorption

Treatments to reduce periodontal inflammation and rescue periodontitis bone resorption have been of interest to researchers. Bone tissue engineering materials have been gradually used in the treatment of bone defects, but periodontal bone tissue regeneration still faces challenges. Considering the biocompatibility factor, constructing bionic scaffolds with natural extracellular matrix properties is an ideal therapeutic pathway. Based on the pathological mechanism of periodontitis, in this study, short peptide and nanometer inorganic particles were comingled to construct NapKFF-nano CaF2 supramolecular composite hydrogels with different ratios. Material characterization experiments confirmed that the composite hydrogel had suitable mechanical properties and a three-dimensional structure that can function in the resorption region of the alveolar bone and provide spaces for cell proliferation and adhesion. The release of low concentrations of fluoride and calcium ions has been shown to have positive biological effects in both in vivo and in vitro experiments. Vitro experiments confirmed that the composite hydrogel had good biocompatibility and promoted osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Microbiological experiments confirmed that the composite hydrogel inhibited the activity of periodontal pathogenic bacteria. In animal studies, composite hydrogel applied to periodontitis rats in vivo can effectively repair alveolar bone resorption. This composite hydrogel has a simple preparation method and is inexpensive to produce, yet it has antibacterial and osteogenesis-promoting incremental effects, which makes it well suited for the treatment of periodontitis bone resorption, providing a new strategy for periodontal bone tissue engineering.

Total mesialization of the mandibular dentition using a mini-implant-supported device : A finite element analysis

PURPOSE

Total mandibular arch mesialization using mini-implants is challenging due to anatomic limitations. The aim of this study was to introduce a mini-implant-supported device for total mesialization of the mandibular dentition and to analyze the biomechanical properties of the device.

METHODS

Finite element models were constructed to explore the effect of friction and force direction on the force transmission efficiency of the device. In addition, the three-dimensional displacement of each tooth was evaluated with two force application points (2 or 8 mm hooks) under three force conditions (symmetric: 150 g of force on both sides, or asymmetric: 100 and 200 g of force on each side).

RESULTS

The force transmission efficiency was 66.7% under a friction coefficient of 0.15 and parallel pushing and pulling forces. The force transmission efficiency was 65.90 and 66.63% when the pushing force was 15° away from the pulling force on the sagittal and horizontal planes, respectively. The mandibular dentition moved mesially with a greater tendency for incisor labial crown tipping, mesial molar rotation and buccal second molar crown tipping when using the 8 mm hook compared to that when using the 2 mm hook. Rigid archwires resulted in more consistent tooth mesialization than stainless steel archwires. Asymmetric forces resulted in asymmetric dental arch mesialization.

CONCLUSION

The forces transmitted by the presented mini-implant-supported device varied depending on the friction level and force direction. The device should be able to achieve symmetric or asymmetric total mesialization of the mandibular dentition.

Open-Full-Jaw: An open-access dataset and pipeline for finite element models of human jaw

BACKGROUND

State-of-the-art finite element studies on human jaws are mostly limited to the geometry of a single patient. In general, developing accurate patient-specific computational models of the human jaw acquired from cone-beam computed tomography (CBCT) scans is labor-intensive and non-trivial, which involves time-consuming human-in-the-loop procedures, such as segmentation, geometry reconstruction, and re-meshing tasks. Therefore, with the current practice, researchers need to spend considerable time and effort to produce finite element models (FEMs) to get to the point where they can use the models to answer clinically-interesting questions. Besides, any manual task involved in the process makes it difficult for the researchers to reproduce identical models generated in the literature. Hence, a quantitative comparison is not attainable due to the lack of surface/volumetric meshes and FEMs.

METHODS

We share an open-access repository composed of 17 patient-specific computational models of human jaws and the utilized pipeline for generating them for reproducibility of our work. The used pipeline minimizes the required time for processing and any potential biases in the model generation process caused by human intervention. It gets the segmented geometries with irregular and dense surface meshes and provides reduced, adaptive, watertight, and conformal surface/volumetric meshes, which can directly be used in finite element (FE) analysis.

RESULTS

We have quantified the variability of our 17 models and assessed the accuracy of the developed models from three different aspects; (1) the maximum deviations from the input meshes using the Hausdorff distance as an error measurement, (2) the quality of the developed volumetric meshes, and (3) the stability of the FE models under two different scenarios of tipping and biting.

CONCLUSIONS

The obtained results indicate that the developed computational models are precise, and they consist of quality meshes suitable for various FE scenarios. We believe the provided dataset of models including a high geometrical variation obtained from 17 different models will pave the way for population studies focusing on the biomechanical behavior of human jaws.

Effect of mass variation on vibration properties of the tooth in drilling operation

Dental cavity represent one of the widespread illness of the tooth. Method for treating of the tooth is to drill the cavity and to fill the hole with suitable material. Measurements show that during drilling the tooth vibrates with increasing mass that causes unpleasant feeling for patient. The aim of the paper is to give the theoretical explanation for this phenomena and to give suggestion for vibration elimination. During drilling, mass of the tooth is decreasing and the so called ‘reactive force’ occurs. Drilling and reactive force cause tooth vibration. The system is modeled as a nonlinear time variable system. An analytical procedure for solving of the equation of vibration is developed. The solution is assumed in the form of the generalized trigonometric function with time variable amplitude and phase. It is obtained that not only the amplitude but also the frequency of tooth vibration in drilling are increased. In addition to reactive force the drilling velocity, diameter of the drill tool and spindle speed affect the vibration level. The appropriate values of these parameters would eliminate or decrease the patient bad feeling.

Biomechanical analysis of the maxillary molar intrusion: A finite element study

INTRODUCTION

The purpose of this study was to analyze and clarify tooth movement when intruding the maxillary molars using intrusive forces between the maxillary first and second molars.

METHODS

A finite element method was used to simulate the long-term orthodontic movement of the maxillary dentition by accumulating the initial displacement of teeth produced by elastic deformation of the periodontal ligament. Intrusive forces of 2 N were applied buccally to the archwire between the maxillary first and second molars. Two different sized transpalatal arches (TPAs) (0.036 in and 0.06 in) and a gradually increased constriction bend and torque toward the posterior teeth were applied to prevent buccal tipping of the posterior teeth when intruding the maxillary posterior teeth.

RESULTS

The whole maxillary dentition rotated clockwise as the intrusive force passed posteriorly to the center of resistance. Buccal crown tipping of the maxillary posterior teeth and lingual tipping of the maxillary incisors occurred. Their tipping decreased with a constriction bend and lingual crown torque and when a TPA was applied.

CONCLUSIONS

Supplemental procedures such as a constriction bend and lingual crown torque and a TPA could effectively prevent the buccal crown tipping of the maxillary posterior teeth when intruding on them.

Effect of Class II elastics on different mandibular arch preparation stabilized with aligners and stainless-stseel wires: a FEM study

Finite Element Models that simulate the effects of Class II elastics on the mandibular arch in six different scenarios, using various immobilization methods of the posterior dentition, were studied. Per-element distribution of linear elastic stress-strain and total displacement were computed. Maximum strain on the PDL, and maximum stress on alveolar bone increased with posterior tip-back, and with the use of archwires vs. aligners. The configuration of the dentition affects the performance of aligners. They perform best on an un-leveled mandibular arch. Applying Class II elastics results in vertical side effects that can be modulated by various mandibular stabilization methods. This is likely to be clinically relevant for high-angle patients, and may explain the differing effects on the facial profile observed using various treatment modalities. 1- Increasing mandibular molar tip-back generally resulted in less eruption tendencies, with mandibular anchorage preparation resulting in the least amount of calculated vertical displacement. 2- Unexpectedly, with Class II forces the use of aligner technology on an un-leveled curve of Spee resulted in improved vertical control when compared to aligner use on a leveled dentition. 3- Generally, using an archwire results in better transmission of stresses to adjacent teeth than the use of aligners. 4- Simulating interarch elastics requires implementing a medial component/orientation of the forces to better emulate clinical situations. 5- A hypothetical configuration: 15o tip-back of the mandibular second molar and aligner stabilization displayed the least amount of vertical movement and the most forward horizontal movement of the 2nd molar.

Biomechanical analysis for total distalization of the maxillary dentition: A finite element study

INTRODUCTION

This study aimed to identify the tooth movement patterns relative to various force angulations (FAs) when distalizing the total maxillary dentition.

METHODS

Long-term orthodontic movement of the maxillary dentition was simulated by accumulating the initial displacement of teeth produced by elastic deflection of the periodontal ligament using a finite element analysis. Distalization forces of 3 N were applied to the archwire between the maxillary canine and first premolar at 5 different FAs (-30°, -15°, 0°, 15°, and 30°) to the occlusal plane.

RESULTS

Maxillary incisors and molars showed lingual and distal tipping at all FAs, respectively. At a force angulation of 30°, almost bodily distalization of the total maxillary dentition occurred, but incisors showed considerable lingual tipping because of the effect of clearance gap (0.003-in, 0.022 × 0.025-in bracket slot, 0.019 × 0.025-in archwire) and elastic deflection of the archwire. Medial displacement of the maxillary anterior teeth occurred because of lingual tipping during distalization. The occlusal plane rotated clockwise at all FAs because of extrusion of the maxillary incisors and intrusion of the maxillary second molars, and the amounts decreased as FA increased.

CONCLUSIONS

Tooth movement patterns during distalization of the total maxillary dentition were recognized. With an understanding of the mechanics, a proper treatment plan can be established.