Occlusal disharmony-induced stress causes osteopenia of the lumbar vertebrae and long bones in mice

Abstract

Excessive exposure to glucocorticoids causes osteoporosis in children and adults. Occlusal disharmony is known to induce an increase in serum corticosteroid levels in murine models, but the influence of occlusal disharmony-induced stress on the bone mass during the growth period has not yet been clarified. The purpose of this study was to investigate whether occlusal disharmony-induced stress decreases bone mass. Five-week-old C57BL/6J male mice were used. A 0.5-mm increase in the vertical height of occlusion was used to induce occlusal disharmony for a period of 7 days. Serum corticosterone levels were significantly higher on post-induction day 7, with radiological evidence of osteopenia of the third lumbar vertebra and long bones of the hind limbs. Osteopenia was associated with a reduction of the mechanical properties of the tibia and femur, with significant suppression of bone formation parameters and an increase in bone resorption parameters, as evaluated by bone histomorphometric analysis of the tibial/femur metaphysis. Our findings at the level of bones were supported by our assessment of serum markers of systemic metabolism. Therefore, occlusal disharmony-induced stress may lead to osteopenia and reduce the mechanical strength of bone through an increase in serum glucocorticoid levels in mice.Occlusal disharmony frequently occurs during growth due to mixed dentition, as the primary dentition is changing to permanent dentition. Several lines of evidence indicate that occlusal disharmony increases serum corticosteroid levels in young animals. As the serum corticosteroid level is considered to be a marker of 'stress' in rodents, it is plausible that occlusal disharmony would cause stress 1-4 . The high frequency of bruxism (teeth grinding) during the period of growth further suggests the possible existence of occlusal disharmony-induced stress in childhood [5][6][7] . By contrast, it is well known that excessive exposure to glucocorticoids causes osteopenia 8 . As an example, the use of steroid medications in children for the treatment of immune-related diseases, such as asthma and skin allergies, commonly results in bone-related side effects, including fractures and slowed bone growth 9 . Given the significant effects of stress-induced hormone on bone metabolism 10 , evaluation of the effect of occlusal disharmony-induced stress on skeletal tissue is warranted.Our aim in this study was to use a mouse model of occlusal disharmony to evaluate the effects of occlusal disharmony-induced stress on bone mass and bone mineral density, as well as on the mechanical properties of the long bones and lumbar vertebrae, which are expected to be differentially affected by mechanical loading [11][12][13] . ResultsIncrease in serum corticosterone level with occlusal disharmony. Serum corticosterone levels were measured at baseline and after the induction of occlusal disharmony (Fig. 1). Serum corticosterone levels were significantly higher in the disharmony than in the control group on post-induction days 1, 3 and 7 (Fig. ...

Effects of occlusal disharmony on cardiac fibrosis, myocyte apoptosis and myocyte oxidative DNA damage in mice

“…BW of the Control and Pro groups was similar and showed no significant change during the experimental period. Conversely, BW of the BO and BO + Pro groups gradually decreased and reached a minimum at 4 days after the BO treatment in accordance with previous findings [9,42] (Fig 1B, S1 Fig of S1…”

“…Comparison of the levels of serum corticosterone level, a key biomarker for stress [6,9], in the control and BO mice at 14 days after the BO treatment revealed a significantly increase of approximately 3.6-fold at 14 days after BO treatment (n = 5 each) (Fig 2B, S3A Fig of S1 Data). These data suggest that the mice are stressed at 14 days after the BO treatment.…”

“…(±)-Propranolol hydrochloride (#P0884; Sigma, St. Louis MO, USA) was directly dissolved in drinking water (1g/L; freshly prepared every day) [17]. Because the BO mice cannot easily eat the standard pellet food (CE-2: 334.9 kcal/100g; CLEA Japan) but can take paste food, the standard pellet food was changed to paste food three days before the BO treatment in all groups, as in previous studies [9,15]. Body weight (BW), food intake, and water intake were monitored throughout the 2-week experimental period (Control: n = 6; BO: n = 8; Pro: n = 6; BO + Pro: n = 10) ( Fig 1B and S1 and S2 Figs of S1 Data).…”

“…These findings suggest that occlusal disharmony might cause stress with activation of sympathetic nerve activity and decreased parasympathetic activity, as well as impaired learning and memory. More recently, occlusal disharmony induced by a tooth height increase (0.5 mm) with composite resin in mice was found to be associated with osteoporosis of the lumbar vertebrate and long bones of the hind limb [9]. All of these results suggest that improvement of occlusal disharmony may yield sustained gains in health and well-being.…”

“…Therefore, the aim of this study was to examine the effects of occlusal disharmony on stress markers, heart rate (HR) control via the autonomic nervous system, systolic cardiac function, histology and signal transduction in the heart, using bite-opening (BO) mice, which have previously been used in research on occlusal disharmony [8,9,15].…”