Bones appear as a really strong organ since they provide structure and support for the body. They are made of very hard tissues that give the impression to be very static, however bones are a very dynamic tissue. Indeed new bone tissue that replace the old one is constantly created in a process called bone remodeling.
Bone is remodeled thanks to the activity of osteoblasts and osteoclasts, that balance bone resorption and formation. The main purpose of remodeling is to meet its mechanical demands, suggesting that mechanical forces are among the most potent factors that influence this process . In fact, mechanical loads create microdamages into the bone tissues that trigger the healing process of remodeling . Figure 1 shows how the force simply impressed by a swelling can modify the bone shape over a long period of time.
Julius Wolff, 19th-century German anatomist and surgeon, is credited for first recognizing the paramount influence of mechanical forces on bone morphology and architecture. It has been found that extremely high-frequency microstrain activities (such as muscle contraction during resting state postural activity) are instrumental in maintaining bone mass, and further, how the absence of these activities results in bone resorption [3,4,5]. So, bone remodeling is mainly triggered by low magnitude forces that are protracted over a long period of time. For example, skull binding is a practice that clearly shows this phenomena: forces are applied to the skull over a long period of time with the results of Figure 2.
There are other several examples in customs and traditions among tribes around the world that perfectly show bone remodeling in all its essence. Foot binding is the custom of applying painfully tight binding to the feet of young girls to modify the shape of the foot. This practice is present in the Chinese culture and the outcome is shown in Figure 3.
Neck rings are a common practice of Kayan people, living in Myanmar (Burma). It consists of wearing neck coils from a very young age: their amount is then gradually increased over the years, pushing the clavicle and ribs down that remodel, giving the impression of a longer neck, as Figure 4 shows.
These concept can be applied to all the bones, but, in particular, bones in the facial complex have a faster rate of remodeling compared with other bones in the body. This comes from the presence of many sutures that are the major sites of bone growth. Extremely high frequency microstrains are the main trigger of bone remodeling, so tongue posture is the most important factor for maxilla (and craniofacial) development. When tongue posture is affected, maxilla drops down and back. This reduces the eye support, flattens the cheekbones, narrows the nasal airway, lengthens the mid facial third, and lowers the palate, which narrows and create malocclusion . The work of John Mew is what actually shows changes that can occur in the facial structure (and thus occlusion) by simply modifying the tongue posture to the correct one on the roof of mouth. He treated successfully several severe cases that were prospected requiring jaw surgery, as for the individual shown in Figure 5. The treatment consisted of appliances that modify oral posture that then affect maxilla development, reshaping it.
It is during the young stages of life, that bones considerably grow and shape according to forces stimuli: maxilla remodels through the tongue action, cranial vault reshapes with the expanding brain [7,8], and so on. Even the use of shoes have an influence on feet development and proprioception, since they affect force distribution . Furthermore, bones always remodel throughout the entire life of individuals, even in the elder phases: e.g. physical exercise (that implies presence of forces) is a good way for preventing and fighting osteoporosis, where bone weakness increases the risk of broken bones . Indeed, Figure 6 shows the difference of facial bones that reshape with aging, as a process present in the entire lifespan. Figure 7 instead shows how craniofacial changes can be obtained even in later stages of life, by correcting tongue posture.
So, bones reshape according to forces. In particular, the tongue is a muscle that has big impact on maxilla and craniofacial development (including occlusion). From head/neck to the feet, the body is a unique system. This means a wrong craniofacial development has huge repercussions on the entire body and this process continues during the entire life, eventually leading to symptoms, disorders and syndromes at some point in the later stages of life. Prevention is very important and particular attention has to be paid from the very first moment of life of a new born: avoidance of pacifiers and bottle-feeding, together with a proper food diet during the weaning phase, are proper actions that prevent the insurgence of bad habits maintained for the entire life of the individual, affecting his entire health.
 Chen, Jan-Hung, et al. “Boning up on Wolff’s Law: mechanical regulation of the cells that make and maintain bone.” Journal of biomechanics 43.1 (2010): 108-118.
 Burr, David B., et al. “Bone remodeling in response to in vivo fatigue microdamage.” Journal of biomechanics 18.3 (1985): 189-200.
 Fritton, Susannah P., Kenneth J. McLeod, and Clinton T. Rubin. “Quantifying the strain history of bone: spatial uniformity and self-similarity of low-magnitude strains.” Journal of biomechanics 33.3 (2000): 317-325.
 Allori, Alexander C., et al. “Biological basis of bone formation, remodeling, and repair—part III: biomechanical forces.” Tissue Engineering Part B: Reviews 14.3 (2008): 285-293.
 Weinbaum, S., S. C. Cowin, and Yu Zeng. “A model for the excitation of osteocytes by mechanical loading-induced bone fluid shear stresses.” Journal of biomechanics 27.3 (1994): 339-360.
 Mew, M. “Craniofacial dystrophy. A possible syndrome?.” British dental journal 216.10 (2014): 555-558.
 Baer, Melvyn J. “Patterns of growth of the skull as revealed by vital staining.” Human biology 26.2 (1954): 80.
 Opperman, Lynne A. “Cranial sutures as intramembranous bone growth sites.” Developmental dynamics 219.4 (2000): 472-485.
 D’AoÛt, Kristiaan, et al. “The effects of habitual footwear use: foot shape and function in native barefoot walkers.” Footwear Science 1.2 (2009): 81-94.
 Bonaiuti, Donatella, et al. “Exercise for preventing and treating osteoporosis in postmenopausal women.” The Cochrane Library (2002).
 The Skull Can Change Shape
 The Paracas Skulls
 Elongated skulls (coneheads) from all over the world.
 Foot binding and the standards of beauty
 Neck X-ray of a woman from the Kayan Tribe in Burma
 An elderly Padaung woman with neck rings, Kayah State, Myanmar.
 Orthodontic Evidences, by Orthotropics
 Our Face Bones Change Shape as We Age
4 thoughts on “Bone Remodeling”
Salve interessanti le tue valutazioni! Però mi sembra assurdo ampliare trasversalmente la mascella con la forza della lingua in età adulta. Dovesse succedere ciò, allargando la mascella verrebbe alterata L occlusione dato che la lingua esercita la sua forza solo sul mascellare e non sulla mandibola, cosa pensa?
in età adulta il rimodellamento osseo è un processo molto più lento che non in fase di crescita. Modificando la mascella si modifica l’occlusione, ma solitamente è poi la mandibola che segue l’arcata mascellare, adattandosi. Se ne trova conferma dal fatto che è inutile fare espansione dell’arcata mandibolare se non vi è sufficiente spazio nell’arcata mascellare in quanto questo porterebbe a una recidiva.
Ciao Luca, complimenti per il blog molto informativo. Io soffro di malocclusione di seconda classe che sto correggendo con l’apparecchio, almeno per quanto riguarda i denti perché è anche ossea e sono ormai adulto. Soffro di molti dei problemi che hai menzionato tra i sintomi. Un intervento maxillo facciale potrebbe essere la soluzione?
anchio vorrei sapere di piu’…..