Prevention of root resorption in hypofunctional teeth by occlusal function recovery

Abstract

Objective: To clarify whether occlusal hypofunction is one of the key determinants for root resorption during tooth movement and root resorption is prevented by its recovery. Materials and Methods: The rats were randomly divided into one control and two experimental groups: hypofunctional and recovery groups. In the hypofunctional group, an anterior metal cap and bite plate were attached to the maxillary and mandibular incisors to simulate occlusal hypofunction. In the recovery group, the appliances were removed 7 weeks after their use, and the rats were allowed to bite for 4 weeks after removal. At the age of 16 weeks, the upper first molars were moved and after 0, 7, 14, and 21 days, the maxillae were resected. The resorption area was quantified morphohistologically and tartrate-resistant acid phosphatase (TRAP)-positive cells on the root surface were counted. We also examined the expressions of receptor activator of nuclear factor-kB ligand (RANKL), macrophage-colony stimulating factor (M-CSF), and interleukin (IL)-8 immunohistochemically.Results: The amount of root resorption and the number of TRAP-positive cells were significantly greater in the hypofunctional group than in the control and recovery groups. Moreover, immunoreactivity for RANKL, M-CSF, and IL-8 was detected in the periodontal ligament and on the root surface in the hypofunctional group. Conclusion: Occlusal hypofunction is one of the critical factors for root resorption; however, root resorption may be prevented by recovery of occlusal function. (Angle Orthod. 2016;86:214-220.)

Comparisons of orthodontic root resorption under heavy and jiggling reciprocating forces during experimental tooth movement in a rat model

“…Therefore, the present model represents a method for inducing efficient tooth movement and root resorption. Furthermore, Hayashi et al 9 established a method for achieving a jiggling movement in rats. We referred to this method and produced a force applications in opposing directions force by moving the roots of rat molars bucco-palatally once a week for 21 days in vivo .…”

“…The animals were anesthetized with pentobarbital sodium (40 mg/kg of body weight) for the application of orthodontic devices. Experimental tooth movement was induced using the method described by Hayashi et al 9 with a quad helix-type device (diameter: 0.012 inches [0.3048 mm], stainless steel wire; Tomy International, Inc., Tokyo, Japan) ligated to a maxillary first molar cleat with a 0.008-inches (0.2032 mm) stainless steel ligature wire (Tomy International, Inc.). The maxillary first molar was palatally or buccally moved by the appliance with a force of 10 g or 50 g ( Figure 1 ).…”

“…The following in vivo experiments were performed, as described by Nakano et al 10 Each sample was sliced continuously into 4-µm sections perpendicular to the long axis of the through center of pulp at distal palatal (DP) root of the maxillary first molar in the frontal cross-section, and prepared for hematoxylin and eosin (H&E) and immunohistochemical staining. 9 The periodontal tissue was observed in the buccal and palatal portions of the DP root of the left first upper molar. Detailed observations were made in the A area, a section of the root 300 µm in height and 225 µm in width in the direction from the top of the alveolar bone surface on the palatal side (box A); and in the B area, a section 300 µm in height and 225 µm in width that accounted for less than 150 µm of the root in the direction of the bifurcation on the buccal side (box B), on the pressure/tension side during tooth movement ( Figure 3 ).…”

Alteration of extracellular matrix proteins in atrophic periodontal ligament of hypofunctional rat molars

“…Atrophic changes of the PDL-surrounding hypofunctional teeth include narrowing of the periodontal space, collagen disorganization, and vascular constriction. Finally, it induces dental root and alveolar bone resorption [ 3 , 4 ]. Despite the extensive literature on hypofunctional teeth and their surrounding periodontal tissues, the effect on the PDL’s extracellular matrix (ECM) components remains elusive.…”

BBS7–SHH Signaling Activity Regulates Primary Cilia for Periodontal Homeostasis

“…Occlusal hypofunction impedes neuromuscular responses through effects on burst-generating neurons (Aung et al, 2020). Atrophic changes following occlusal hypofunction include reductions in PDL thickness (Kaneko et al, 2001), collagen fiber, and alveolar bone density (Shimizu et al, 2011;Kasahara et al, 2017), and also increase the susceptibility of root resorption (Hayashi et al, 2016) (Figure 1A). Moreover, the expression of vascular endothelial growth factor (VEGF) was also reduced in the occlusal hypofunctional PDL, which may affect periodontal remodeling and cell proliferation during wound healing (Miyagawa et al, 2009;Motokawa et al, 2015).…”