Biomedical Engineering Reference
In-Depth Information
20.1 IntroduCtIon
This chapter intends to outline the contributions offered by numerical techniques, in particular by
finite element (FE)-based bone remodeling simulation for the investigation of biomechanical prob-
lems in the dental field. The chapter focuses on two specific fields: orthodontics and prosthodontics.
Orthodontic procedures are usually performed to treat malocclusions (improper bites) result-
ing from irregular teeth or to control as well as modify facial growth for purely aesthetic reasons
(Verna, Zaffe, and Siciliani 1999). Tooth movements resulting from orthodontic treatment are real-
ized through biological responses induced by mechanical stimulus (Henneman, Von den Hoff, and
Maltha 2008). In prosthodontics, prosthetics are used to restore the bite to aid in chewing and
maintain the position of teeth. A dental implant that resembles a tooth or group of teeth to replace
missing teeth is often used to support restoration (Shillingburg 1997). Functional loading induced
by the implant can result in changes in the surrounding bone tissue (Palmer et al. 2012).
In the last couple of decades, FEA has been used extensively in the dentistry field (Beaupre,
Orr, and Carter 1990a, 1990b; Li et al. 2011; Lin, Lin, and Chang 2010; Ojeda et al. 2011;
Kojima and Fukui 2005). A series of computational procedures are employed to calculate the
stress and strain resulting from external force, pressure, thermal change, and other factors. FE
analysis has evolved as an effective tool to study tooth movement as well as dental implants.
However, a more detailed understanding of the alveolar bone's response is necessary for the
further development of orthodontics and prosthodontics. As human bone, including the alveolar
bone, can rebuild itself in accordance with the mechanical environment, it is imperative that
not only biomechanical analysis but also mechanobiological factors are taken into account in
further research.
The ability of bone tissue to adapt to external mechanical loading is called bone remodeling
(Fyhrie and Carter 1986). Bone remodeling is a biological process during which old bone tissue
is removed (resorption) and new bone tissue is formed (Huiskes et al. 1987). The process involves
groups of osteoclasts and osteoblasts that function as organized units called basic multicellular units
(BMUs). Resorption lacunae created by osteoclasts are subsequently filled by osteoblasts as part of
the BMUs. Normally, there is a balance between resorption and formation; however, bone loss will
occur as a result of an imbalance in the remodeling process.
At present, when an artificial fixation is implanted or an orthodontic force is applied, bone
remodeling can be simulated in FE models to predict the bone response. According to the level of
research, these simulation studies can be classified into two main groups:
1.
Macroscale model
: These models focus on the prediction of apparent bone density and
elastic modulus distribution as a consequence of the bone remodeling process. In the
field of prosthodontics, preliminary studies emphasized the adaptive behavior of alveo-
lar bone under load via FE-based remodeling simulations (Mellal et al. 2004). These
simulations led to an important conclusion: peak strains and strain energy densities were
consistent with in vivo data, which indicates that both parameters can be employed as a
bone remodeling stimulus. Furthermore, based on the traditional model developed for long
bone, Li et al. (2007) proposed a new mathematical equation relating the rate of change
in bone density with a mechanical stimulus that can simulate both underload and overload
resorptions. This is a very useful modification, because the new remodeling algorithm can
describe bone loss under excessive loading. Meanwhile, a remodeling simulation by Chou
et al. predicted non-homogeneous density/elastic modulus distribution around various den-
tal implant systems (Chou, Jagodnik, and Muftu 2008). Additionally, Daniel Lin and his
coworkers reviewed existing numerical studies, analyzed published remodeling data, and
assessed different biomechanical remodeling stimuli (Field et al. 2009). Since then, they
have developed a series of numerical dental models correlated to clinical computerized
tomography (CT) data, and contributed significantly to the development of alveolar bone
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