The Bilateral Forward Chewing Exercise Theory (BFCET)

Abstract

The pressure applied to the jaw from chewing can significantly influence bone remodeling and potentially alter the skull's morphology, including in adults. This process involves intricate mechanisms such as mechanical loading, osteoblastic activity, and potentially epigenetic changes. Mechanical loading refers to the forces exerted on the jaw during chewing, which stimulate bone cells, initiating remodeling. Osteoblasts, the bone-forming cells, and osteoclasts, the bone-resorbing cells, work in tandem to remodel bone in response to these mechanical stresses. Increased mechanical loading from chewing can enhance osteoblastic activity, leading to bone formation and increased bone density in the jaw.

Epigenetic modifications, which involve changes in gene expression without altering the underlying DNA sequence, can also be influenced by environmental factors such as mechanical stress. Mechanotransduction, the process by which cells convert mechanical stimuli into biochemical signals, plays a crucial role in this context. Mechanical stress from chewing can influence the expression of genes involved in bone formation and remodeling, potentially leading to epigenetic modifications.

The most direct effects of chewing-related mechanical loading are observed in the jaw and facial bones. Increased osteoblastic activity can lead to changes in the size, shape, and density of these bones. Furthermore, the craniofacial skeleton is interconnected, suggesting that changes in one area can influence the development and structure of adjacent areas, potentially affecting overall skull morphology.

While bone remodeling is more pronounced during growth and development, it continues throughout adulthood, allowing adults to experience changes in bone structure in response to mechanical stress. The extent of these morphological changes in the adult skull due to chewing is likely to be more limited compared to changes during childhood and adolescence when bones are more malleable. However, significant mechanical loading over time can still lead to noticeable changes.

While the primary effects of chewing-induced mechanical stress are on the jaw and facial bones, there is potential for these forces to influence the overall morphology of the skull through increased osteoblastic activity and possible epigenetic changes. The extent of these changes in adults is less dramatic than in younger individuals due to the reduced plasticity of bones, but significant remodeling is still possible with consistent mechanical loading over time.

Introduction

The changes that can be expected from increased mechanical loading on the jaw through activities like chewing can be grouped into several categories: bone density, bone shape, alignment, and overall facial structure. This section provides a detailed look at each of these areas to understand how mechanical stress can induce modifications in craniofacial morphology.

Bone Density and Strength

Increased bone density is one of the most immediate effects of regular mechanical loading. Hard chewing stimulates osteoblastic activity, leading to denser and stronger bone in the jaw. This process not only enhances the bone's resilience but also contributes to a thicker and more robust jawbone, especially in areas subjected to the most significant stress.

Bone Shape and Morphology

Mechanical loading can also influence the shape and morphology of bones, particularly the mandible (lower jawbone). Consistent mechanical stress from activities like chewing can lead to a more defined and potentially broader mandible, resulting in a more pronounced jawline. Additionally, this stress can affect tooth alignment, promoting an even distribution of forces across the teeth and jaw, which can further enhance the structural integrity and appearance of the jaw.

Alignment and Structural Adjustments

The temporomandibular joint (TMJ), which connects the jawbone to the skull, can adapt to increased mechanical stress, potentially improving jaw function and reducing the risk of TMJ disorders. Regular mechanical loading can also promote facial symmetry by encouraging balanced growth and development of the jaw and surrounding structures. This balanced growth is crucial for maintaining harmony in facial features and ensuring optimal function of the jaw.

Overall Facial Structure

Increased bone density and changes in jaw morphology can lead to more pronounced and defined facial features, particularly in the lower face. While the primary effects of mechanical loading are seen in the jaw, secondary effects on the midface are also possible due to the interconnected nature of craniofacial structures. This can include slight adjustments in the maxilla (upper jaw) and cheekbones, contributing to a more cohesive and aesthetically pleasing facial profile.

Secondary Effects

Improved oral health is a notable secondary benefit of increased mechanical loading. Stronger bones and better alignment can reduce the risk of dental issues such as misalignment, cavities, and periodontal disease. Additionally, enhanced mastication efficiency resulting from stronger and more aligned jaw and teeth structures can aid in better digestion and overall health.

The Influence of Masticatory Muscles on Craniofacial Morphology

The idea that mechanical loading from chewing could expand the entire skull, or most of it, involves understanding how masticatory (chewing) muscles interact with the craniofacial skeleton and how mechanical forces influence bone remodeling. Here’s an analysis of why this might or might not happen:

Masticatory Muscles and Their Influence

The primary muscles involved in chewing are the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles. These muscles primarily act on the mandible (lower jaw) and the maxilla (upper jaw), exerting forces on these bones during mastication. These muscles attach to various parts of the skull, including the mandible, zygomatic arch, and temporal bone. The forces they exert during chewing can influence the shape and density of these bones.

Localized Effects on Jaw and Facial Bones

Chewing directly impacts the mandible and maxilla, leading to potential changes in bone density, shape, and strength in these areas. Increased mechanical loading can stimulate osteoblastic activity, promoting bone growth and remodeling. The zygomatic arch (cheekbone) and parts of the temporal bone can also experience increased mechanical stress due to muscle attachment and force transmission, potentially leading to localized remodeling and changes in these areas.

Limited Influence on Entire Skull

The primary stress from chewing is concentrated in the areas where the masticatory muscles attach and exert force. While these forces can influence the jaw and parts of the face, they do not uniformly distribute across the entire skull. The skull comprises various bones connected by sutures. These sutures allow for some flexibility and growth during development but are less responsive to mechanical stress in adulthood. The mechanical forces from chewing are unlikely to affect the entire skull uniformly due to the structural nature of these bones and sutures.

Epigenetic and Systemic Factors

Mechanical stress can lead to epigenetic modifications that influence gene expression in bone cells. These changes can promote localized bone remodeling but are less likely to cause widespread changes across the entire skull. Overall nutrition, hormonal factors, and systemic bone health play a significant role in bone remodeling. While localized mechanical stress from chewing can enhance bone density and shape in specific areas, systemic factors are more influential in maintaining overall skull morphology.

The Bilateral Forward Chewing Exercise

Purpose: This exercise is specifically designed for individuals with an underdeveloped lower jaw or those experiencing overbites. It is not recommended for individuals with well-developed jaws due to the potential risks associated with the temporomandibular joint (TMJ).

Materials Required:

• Two equal pieces of hard gum, preferably Stronger Gum, known for its D3, K2, and xylitol properties and toughness.

Procedure:

1. Preparation:

2. Jaw Positioning:

Expected Outcomes:

• Lengthening of the Ramus: This exercise aims to stimulate bone remodeling in the ramus of the mandible, potentially leading to an increase in its length.
• Resetting of the Lower Jaw's Position: Regular forward positioning and mechanical loading can aid in repositioning the lower jaw, contributing to the correction of overbites.
• Increased Chin Point Projection: The forward jaw position and mechanical loading can enhance chin projection due to the LFCMH by promoting activity in the chin area.

Precautions:

• Begin gradually, increasing the duration and frequency over time to prevent overloading the TMJ. Slowly increase duration and/or the toughness of the gum to increase the TMJ's resistance to loading.
• If any discomfort or pain in the TMJ or jaw muscles occurs, discontinue the exercise and seek advice from a healthcare professional.
• Maintain proper overall posture and oral posture (tongue on the roof of the mouth) during the exercise to support optimal results.

Conclusion

The Bilateral Forward Chewing Exercise Theory (BFCET) proposes that targeted mechanical loading through specific chewing exercises can induce beneficial changes in craniofacial morphology, particularly for individuals with underdeveloped lower jaws or overbites. This theory is grounded in well-established principles of bone remodeling, mechanotransduction, and the influence of masticatory muscles on craniofacial development.

Key Points:

Research supports that mechanical stress from activities like chewing can stimulate osteoblastic activity, leading to bone formation and increased bone density. The forces exerted by masticatory muscles during chewing can influence the shape and density of the mandible and maxilla, promoting positive changes in jaw structure. Mechanical stress can induce epigenetic modifications, influencing gene expression related to bone remodeling and potentially enhancing the effects of the exercise. While the primary effects are localized to the jaw and facial bones, systemic factors such as nutrition and overall bone health play a significant role in the remodeling process.

References:

1. Development of functional interactions between skeletal and muscular systems
   BK Hall (Ed.), Bone, 9, Academic Press, Boca Raton (1994), pp. 165-191
   
   
2. Spreading the silence: epigenetic transcriptional regulation during Drosophila development
   Dev Genet, 15 (1994)
   
   
3. A mechanism for heterogeneous endothelial responses to flow in vivo and in vitro
   Peter F. Davies, Trevor Mundel, Kenneth A. Barbee
   
   
4. Mechanical stimulation by intermittent hydrostatic compression promotes bone-specific gene expression in vitro
   J Biomech, 28 (1995)
   
   
5. Recent advances in understanding mechanically induced bone remodeling and their relevance to orthodontic theory and practice
   Am J Orthod Dentofac Orthop, 103 (1993)
   
   
6. Mechanical induction of (beta)1-integrin-mediated calcium signaling in a hepatocyte cell line Exp Cell Res, 218 (1995)
   
   
7. Toro-Ibacache V, Ugarte F, Morales C, Eyquem A, Aguilera6 J, Astudillo W. Dental malocclusions are not just about small and weak bones: assessing the morphology of the mandible with cross-section analysis and geometric morphometrics. Clinical oral investigations 2019;23:3479-90.