Ultrastructure of cementum and periodontal ligament after continuous intrusion in humans: a transmission electron microscopy study

Abstract

An ultrastructural study of the cementum and periodontal ligament (PDL) changes after continuous intrusion with two different and controlled forces in humans was carried out. Twelve first upper premolars, at stage 10 of Nolla, orthodontically indicated for extraction from six patients (mean age 15.3) were used. They were divided into three experimental groups, distributed intra-individually as follows: control (not moved), continuously intruded for 4 weeks with 50 or 100 cN force, utilizing a precise biomechanical model with nickel titanium super-elastic wires (NiTi-SE), which were developed and calibrated individually. The teeth were extracted, fixed, decalcified, and conventionally processed for examination in a Jeol 100 CX II transmission electron microscope. Evident signs of degeneration of cell structures, vascular components, and extracellular matrix (EM) of cementum and PDL were observed in all the intruded teeth, with more severe changes towards an apical direction and in proportion to the magnitude of force applied. Resorptive areas and an irregular root surface of the intruded teeth were noticed, according to the same pattern described above. Concomitant, areas of repair were also revealed in the cementum and PDL although the magnitude of forces remained the same throughout the experimental period. Thus, a reduction of continuous force magnitude should be considered to preserve the integrity of tissues.

Periodontal Ligament Hydrostatic Pressure with Areas of Root Resorption after Application of a Continuous Torque Moment

“…The hydrostatic pressure in the PDL obviously depends on the magnitude of the force being applied. This contradicts the findings of Owman-Moll et al 20,21 and Maltha et al 22 but is in agreement with the findings of Faltin et al, 3,6 Casa et al, 4 and Chan and Darendeliler, 5 who observed that the extent of root resorption depended on the magnitude of the applied force system.…”

Comparison of anterior and posterior mini-implant-assisted maxillary incisor intrusion: Root resorption and treatment efficiency

“…[10][11][12] Hence, a precise and unequivocal diagnostic method of imaging is needed to both prevent and monitor resorption, which is possible only by three-dimensional volumetric evaluation. Currently, cone-beam computed tomography (CBCT), as employed in rapid maxillary expansion and molar intrusion, is the leading tool for in vivo dental imaging in the field of root resorption research.…”

Three-dimensional morphology of root and alveolar trabecular bone during tooth movement using micro-computed tomography

“…The relationship between root resorption and orthodontic force magnitude is very important to consider and allows orthodontists to manage treatment risk; although several studies have investigated this relationship, [9][10][11][12][13][14][15] no clear consensus has been reached because of study differences, such as methods and samples. We propose that it is necessary to study the relationship between root resorption and orthodontic force using a new method.…”