Is Inflammation a Friend or Foe for Orthodontic Treatment?: Inflammation in Orthodontically Induced Inflammatory Root Resorption and Accelerating Tooth Movement

Abstract

The aim of this paper is to provide a review on the role of inflammation in orthodontically induced inflammatory root resorption (OIIRR) and accelerating orthodontic tooth movement (AOTM) in orthodontic treatment. Orthodontic tooth movement (OTM) is stimulated by remodeling of the periodontal ligament (PDL) and alveolar bone. These remodeling activities and tooth displacement are involved in the occurrence of an inflammatory process in the periodontium, in response to orthodontic forces. Inflammatory mediators such as prostaglandins (PGs), interleukins (Ils; IL-1, -6, -17), the tumor necrosis factor (TNF)-α superfamily, and receptor activator of nuclear factor (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) are increased in the PDL during OTM. OIIRR is one of the accidental symptoms, and inflammatory mediators have been detected in resorbed roots, PDL, and alveolar bone exposed to heavy orthodontic force. Therefore, these inflammatory mediators are involved with the occurrence of OIIRR during orthodontic tooth movement. On the contrary, regional accelerating phenomenon (RAP) occurs after fractures and surgery such as osteotomies or bone grafting, and bone healing is accelerated by increasing osteoclasts and osteoblasts. Recently, tooth movement after surgical procedures such as corticotomy, corticision, piezocision, and micro-osteoperforation might be accelerated by RAP, which increases the bone metabolism. Therefore, inflammation may be involved in accelerated OTM (AOTM). The knowledge of inflammation during orthodontic treatment could be used in preventing OIIRR and AOTM.

Keywords: CRISPR/Cas9 gene editing; fabry disease; induced pluripotent stem cells; inflammatory.

Figure 1

The schema of periodontal responses within the PDL on the pressure side.

Figure 2

The progress panoramic radiograph of severe root resorption. (A): Pretreatment, (B): 1 year after start active treatment, (C): 2 years after start active treatment, (D): Post-treatment (2.5 years after start active treatment).

Figure 3

The dental radiograph of severe root resorption of Figure 2D (A): Right side, (B): Left side).

Figure 4

Risk factors of OIIRR.

Figure 5

Histopathological staining (Hematoxylin-Eosin (H.E) staining), tartrate-resistant acid phosphatase (TRAP), and Receptor activator of nuclear factor kappa-B ligand (RANKL) immunohistochemical staining during rat experimental tooth movement after 7 days (performed by Yamaguchi M). In the 10 g group after 7 days, RANKL positive cells were observed in the bone resorption pit of the alveolar bone surface. In the 50 g group after 7 days, RANKL positive cells were observed in the root resorption pit. Bars: 50 μm. A, alveolar bone; P, periodontal ligament; C, cementum; D, dentin.

Figure 6

The schema of mechanism of OIIRR. Abbreviations; OIIRR = orthodontically induced inflammatory root resorption, hPDL cells = Human periodontal ligament cells, PGE2 = prostaglandin E2, IL-1 = interleukin 1, IL-6 = interleukin 6, IL-17 = interleukin 17, RANKL = Receptor activator of nuclear factor ligand, RANK = Receptor activator of nuclear factor, TNF-alpha = tumor necrosis factor-alpha.

Figure 7

The schema of AOTM in rat experimental tooth movement model by MOPs [132]. Abbreviations: AOTM = accelerating orthodontic tooth movement, MOPs = micro-osteoperforations.

Figure 8

Effect of MOPs on tooth movement (ref. 132). * Significantly different from corresponding the tooth movement (TM) group and the TM+MOPs group (p < 0.05). Values are shown as the mean ± SD of 5 rats.

Figure 9

Pretreatment facial and intraoral photographs. (Patient is 29 years 2 months old).

Figure 10

Pretreatment radiographs (a), lateral cephalogram; (b), panoramic radiograph).

Figure 11

Progress intraoral photographs of corticision and piezocision (A), Maxilla; (B), Mandibular). The corticision procedure was performed between the lower canine to canine areas. Subsequently, the patient underwent the piezocision procedure.

Figure 12

Progress intraoral photographs after 2 months of start of active treatment.

Figure 13

Progress intraoral photographs after 11 months of start of active treatment.

Figure 14

Post-treatment facial and intraoral photographs (after 16 months of start of active treatment; 31 years 2 months old).

Figure 15

Post treatment radiographs (a), lateral cephalogram; (b), panoramic radiograph).

Figure 16

Superimposition of the cephalometric tracings at pretreatment and posttreatment. (A), The sella-nasion plane at sella; (B), Cephalometric superimpositions. Palatal plane at ANS and Mandibular plane at Me.