Driler
One must imagine Driler happy
- Joined
- Sep 13, 2023
- Posts
- 106
- Reputation
- 81
Intro
Hello everybody, welcome to the second episode of The Evaluation of Bonesmashing. Where we answer the first out of three relevant questions I outlined last time. “Does bone have enough adaptive ability to induce meaningful growth”. If bone cannot even adapt well enough to cause a meaningful structural change, one that would influence facial attractiveness then it would be impossible for this practice to work. To assess that we cannot do that by measly restating the Wolff’s law as science doesn’t work by just repeating after a 19th century German surgeon like some would like you to believe. We must do this in a proper way, by updating ourselves on the current scientific consensus behind the law and then proceed from there.
Development of the Wolff’s Law From the 19th to the 21th Century
This idea it stems from what is called Wolff’s law. Most peoples understanding of this idea is surface level, as just one sentence that was said 150 years ago. I will quickly go over it now and a more elaborate explanation is done in the yt video. Major contributor to our present day understanding was Harold Frost. He developed the ”mechanostat” hypothesis. Suggesting that changes in bone structure are brought about by a feedback system in which changes in local mechanical stress stimulates bone cells to adapt bone structure. Frost's theory is special in its separation between modeling and remodeling processes and its description of mechanical loading windows.
Modeling-Remodeling Distinction
Between 1964-1973 it was hypothesised that two operationally different systems affect bone mass and architecture. Scientific findings undisputedly indicated that in the same bone, modeling and remodeling can simultaneously respond in opposite ways to the same stimulus. Despite both utilizing the same kinds of osteoblasts and osteoclasts. So let me explain now why that is. Although bone tissue is unique in a sense that a major portion of it is unalive mineral and thus its somewhat inert, it cannot act as such within confines of the human body. Unlike other alive tissue in witch cell division and apoptosis can occur, giving these tissue the ability to grow and enact turnover. Bone being largely made of inert mineral prevents it from simply doing the same. Thus It requires specific mechanisms by witch it could perform such a processes. Bone must not only possess a method by witch it can structurally change but also to perform turnover of tissue or mineral in bones case. The role of modeling and remodeling is exactly that and thus, despite using the same biologic machinery, they respond differently to the same stimuli. "Modeling plays a role of tissue development and growth while remodeling acts as a mechanism of tissue turnover and maintenance." Concerning the latter.
Remodelling
Bone remodelling is constantly happening inside all of your bones. It entails the resorption of old or damaged bone, followed by the deposition of new bone material, typically in pattern matching prior resorption. So even in abstinence of significant structural alteration to the skeleton, remodelling is still active playing the role of bone maintenance and only changing structure in specific instances. There exists four major functions remodeling serves: general maintenance, Mx repair, mineral homeostasis (not interesting) and adaptation to underloads. First two typically leave no structural change after they take place whilst the latter pair often modifies bone structure.
Bone maintenance - In a scenario of normal loading where bones expected amount of stimuli match the actual, remodeling is somewhat tampered down and resorbs and forms equal amounts of bone.
Adaption to underloads - If stimuli was to suddenly go down we would consider bone to be in disuse and as your body isn't very fond of keeping stuff it doesn’t use around. Remodeling will be rallied up in a manner that emphasizes resorption. Thus the objective of such remodeling process would be to remove what is perceived as excess bone.
Fx repair - A more unique function of remodeling is the repair of Mx. Mechanical usage creates small microfractures inside bone. Remodeling serves as to resorb damaged bone and form new lamellae. Due to microfracture formation growing exponentially with a rise in load it can out-pass the ability of remodeling to repair damage. In such instances instead of lamellar bone formation woven one takes its place, as the anarchic nature of it allows for quicker formation.Bone maintenance - In a scenario of normal loading where bones expected amount of stimuli match the actual, remodeling is somewhat tampered down and resorbs and forms equal amounts of bone.
Adaption to underloads - If stimuli was to suddenly go down we would consider bone to be in disuse and as your body isn't very fond of keeping stuff it doesn’t use around. Remodeling will be rallied up in a manner that emphasizes resorption. Thus the objective of such remodeling process would be to remove what is perceived as excess bone.
“Henceforth global remodeling can either remove or conserve bone, but does not really increase bone mass as evident from these scenarios.”
The body regulates remodelling via organised cell units called BMUs or basic multicellular unit. These are an assembly of osteoclasts and osteoblasts that form a temporary anatomic structure that functions through the ARF process. An activation stimulus can make one begin, starting with osteoclastic resorption of old bone with the subsequent formation of new lamellae by osteoblast. Such a sequence of a single BMU takes 4 to 6 months turning over about 0.05 mm3 and ending with BMUs self-destruction but also leaving secondary osteons or haversian systems in compacta. As the BMU advances through bone, being lead by osteoclasts, it resorbs bone leaving empty space behind. This space, devoid of bone, can either be fully replaced by osteoblasts or only partially filled, leading to a net zero or loss effect of that particular BMU after its completion. Examining the net effect of all BMUs on a certain bone site allows us to inquire into the remodeling activity of that bone site.
(Less important until modeling)
Bone Balance
BMU based remodeling presents the following features: a) bone turnover, b) net gains and losses and c) space temporarily absent of bone due to evolving resorption spaces. Those features depend on the following characteristics of the exact remodelling process: a) on how many new BMU arise annually, b) on how much bone each BMU has resorbed and formed upon its completion and c) on how long the typical BMU takes to become completed. Considering we know approximate values of annual BMU arisal and their lifespan. I will now show you some values Frost derived from this examining the absolute and net effect a sum of BMU have on a certain bone site
The Activation Function - μ
Since there exists 2x10 BMU at any moment. We can define our first characteristic of a specific remodeling process as the activation function or the number of BMU completed in a certain time period in a certain bone site. Expressed in no./mm2/yr
Turnover – Vb
Bone turnover is defined only as the amount of bone resorbed and replaced by new. Pretty much the amount of bone that's been processed. Bone turnover rate is determined by the intensity of BMU activity and is partly independent of what the net balance between resorption and formation is instead it relies on the absolute activity of both. We can define Vb as turnover of a average BMU involved in the examined remodeling process.
Calculation for Bone Turnover - Vt
Multiplying that by the activation function. We get the bone turnover for a certain bone site in a certain time period. Witch is expressed in mm3/mm2/yr as Vt
Net Balance - ΔB.BMU
Then we can look if formation lacks behind resorption witch will determine the net effect per completed BMU, we will call that ΔB.BMU. So if bone formation doesn’t match resorption, ΔB.BMU is negative.
Calculation for Bone Balance - B
We can also multiply ΔB.BMU with the activation function witch yields bone balance during a certain time period on a certain bone site. If it is positive means new bone is being built and negative equates to bone loss. It is expressed in mm3/mm2/yr.
BMU based remodeling presents the following features: a) bone turnover, b) net gains and losses and c) space temporarily absent of bone due to evolving resorption spaces. Those features depend on the following characteristics of the exact remodelling process: a) on how many new BMU arise annually, b) on how much bone each BMU has resorbed and formed upon its completion and c) on how long the typical BMU takes to become completed. Considering we know approximate values of annual BMU arisal and their lifespan. I will now show you some values Frost derived from this examining the absolute and net effect a sum of BMU have on a certain bone site
The Activation Function - μ
Since there exists 2x10 BMU at any moment. We can define our first characteristic of a specific remodeling process as the activation function or the number of BMU completed in a certain time period in a certain bone site. Expressed in no./mm2/yr
Turnover – Vb
Bone turnover is defined only as the amount of bone resorbed and replaced by new. Pretty much the amount of bone that's been processed. Bone turnover rate is determined by the intensity of BMU activity and is partly independent of what the net balance between resorption and formation is instead it relies on the absolute activity of both. We can define Vb as turnover of a average BMU involved in the examined remodeling process.
Calculation for Bone Turnover - Vt
Multiplying that by the activation function. We get the bone turnover for a certain bone site in a certain time period. Witch is expressed in mm3/mm2/yr as Vt
Net Balance - ΔB.BMU
Then we can look if formation lacks behind resorption witch will determine the net effect per completed BMU, we will call that ΔB.BMU. So if bone formation doesn’t match resorption, ΔB.BMU is negative.
Calculation for Bone Balance - B
We can also multiply ΔB.BMU with the activation function witch yields bone balance during a certain time period on a certain bone site. If it is positive means new bone is being built and negative equates to bone loss. It is expressed in mm3/mm2/yr.
Modelling
Bone modeling is the less researched out of two. It changes the architecture of a bone as to adapt it to a certain stress and leaves either a net positive change or no overall change in terms of global bone mass. We can make a slightly vague and abstract distinction between modeling, bone growth and modeling drifts in terms of the outcome although they do rely on the same physiologic mechanisms.
1. Modeling operates with no or just a slight increase in global bone mass, think of it as sculpting or fitting form to function.
2. Bone growth is self-evidently the same process just with a large increase in global bone mass.
3. Whereas modeling drifts are unique growth patterns that form bone on one cortex while resorbing it on the opposite side. Thus by altering the bone’s curvature or orientation a long bone would grow transversely.
Unlike remodeling, neither one of these requires prior resorption albeit resorption is still a vital part of the modeling process. For the sake of simplicity, I will use these three terms synonymously to each other.
Longitudinally & Appositional
First is longitudinal growth of long bones through the process of endochondral ossification at the phys-is. Whilst the radial growth of bone, radial meaning converging into something, occurs by a process called appositional bone growth. Radial growth is a result of intramembranous ossification occurring on the periosteum. Although the growth of each facial bone varies, appositional bone growth is a main contributor in craniofacial development.
Purpose
So as I just said modeling is mechanically controlled. In the next episode we will examine exactly how the overreaching of typical peak strains inside bone above a range centred around 6% of the fracture strain evokes modeling drifts to begin changing bone structure in ways that lower the strains towards the bottom of that range or MESm. As well as that modelling drifts tend to stay OFF in instances where peak strains stay below the MESm.
2. Bone growth is self-evidently the same process just with a large increase in global bone mass.
3. Whereas modeling drifts are unique growth patterns that form bone on one cortex while resorbing it on the opposite side. Thus by altering the bone’s curvature or orientation a long bone would grow transversely.
Unlike remodeling, neither one of these requires prior resorption albeit resorption is still a vital part of the modeling process. For the sake of simplicity, I will use these three terms synonymously to each other.
Longitudinally & Appositional
First is longitudinal growth of long bones through the process of endochondral ossification at the phys-is. Whilst the radial growth of bone, radial meaning converging into something, occurs by a process called appositional bone growth. Radial growth is a result of intramembranous ossification occurring on the periosteum. Although the growth of each facial bone varies, appositional bone growth is a main contributor in craniofacial development.
So as I just said modeling is mechanically controlled. In the next episode we will examine exactly how the overreaching of typical peak strains inside bone above a range centred around 6% of the fracture strain evokes modeling drifts to begin changing bone structure in ways that lower the strains towards the bottom of that range or MESm. As well as that modelling drifts tend to stay OFF in instances where peak strains stay below the MESm.
“Global modeling can add bone but apparently does not reduce bone mass thus it can adapt bone to overloads but probably not to underloads. Henceforth modeling will mean architectural changes by modeling drifts and “remodeling” will mean bone turnover by BMUs.”
Change in shape but not size
A characteristic bone tissue has is that it can adapt to overloads without a increase in size. Thus a change in shape doesn’t necessitate growth. Location and pattern of bone formation doesn’t necessary follow the same features of the resorption process that proceeded before. This implies that material is being removed from one site and formation takes place at another site of the same bone. This may stand in favor of bonesmashings validity but I'm not sure yet and I will cover this idea in a dedicated manner soon. Nevertheless we may still examine what is the maximum growth rate and assess if it fulfils the potential of causing a meaningful impact on aesthetics.
A characteristic bone tissue has is that it can adapt to overloads without a increase in size. Thus a change in shape doesn’t necessitate growth. Location and pattern of bone formation doesn’t necessary follow the same features of the resorption process that proceeded before. This implies that material is being removed from one site and formation takes place at another site of the same bone. This may stand in favor of bonesmashings validity but I'm not sure yet and I will cover this idea in a dedicated manner soon. Nevertheless we may still examine what is the maximum growth rate and assess if it fulfils the potential of causing a meaningful impact on aesthetics.
The Maxima
Outro
If you recall the question I presented at the start. We have now answered the first since we know that it is possible to induce meaningful growth but what force is needed to create adequate stressor and does bonesmashing induce such. That will be answered after we define a way of analyzing stressors in the next episode by figuring out how bones detect mechanical stimuli, witch will predominantly be called strain onwards, and the subsequent translation of strain into a biochemical signal that can be understood by osteoclast and osteoblast. In upcoming episodes I will present concrete proof that this works and talk about how hormonal balance effects this process. Along with some practices, supplements and even pharmaceutical interventions that can help achieve the desired outcome faster and more efficiently. All of this will result in a scientifically supported method of bonesmashing that can change your facial structure extremely effectively.
