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ABSTRACTPurposeThis study aimed to evaluate the effect of the components of tobacco smoke from heated tobacco products (HTPs), referred to as Tobacco Smoke Components (TSCs), on tooth movement and the number of osteoclasts in rat models.Materials and MethodsWistar rats were divided into the following groups: control, distilled water-administered, cigarette TSCs-administered, and HTP TSCs-administered. Tooth movement was experimentally induced within each group using the Waldo method. Measurements were performed for tooth movement and the number of osteoclasts.ResultsBoth cigarette and HTP TSCs decreased the number of osteoclasts and delayed the rate of tooth movement. The TSCs of cigarettes were particularly shown to have a stronger effect than the HTPs.ConclusionHTP TSCs significantly affected the rate of tooth movement; thus, orthodontists should be aware of the patient’s smoking status, as well as smoking method (paper or heated), and encourage smoking cessation during treatment.

In dentistry, orthodontic root resorption is a long-lasting issue with no effective treatment strategy, and its mechanisms, especially those related to senescent cells, remain largely unknown. Here, we used an orthodontic intrusion tooth movement model with an L-loop in rats to demonstrate that mechanical stress-induced senescent cells aggravate apical root resorption, which was prevented by administering senolytics (a dasatinib and quercetin cocktail). Our results indicated that cementoblasts and periodontal ligament cells underwent cellular senescence (p21+or p16+) and strongly expressed receptor activator of nuclear factor-kappa B (RANKL) from day three, subsequently inducing tartrate-resistant acid phosphatase (TRAP)-positive odontoclasts and provoking apical root resorption. More p21+senescent cells expressed RANKL than p16+senescent cells. We observed only minor changes in the number of RANKL+non-senescent cells, whereas RANKL+senescent cells markedly increased from day seven. Intriguingly, we also found cathepsin K+p21+p16+cells in the root resorption fossa, suggesting senescent odontoclasts. Oral administration of dasatinib and quercetin markedly reduced these senescent cells and TRAP+cells, eventually alleviating root resorption. Altogether, these results unveil those aberrant stimuli in orthodontic intrusive tooth movement induced RANKL+early senescent cells, which have a pivotal role in odontoclastogenesis and subsequent root resorption. These findings offer a new therapeutic target to prevent root resorption during orthodontic tooth movement.