The bones of the face play a crucial role in protecting the sensory organs and allowing for functions like chewing and facial expressions. When considering facial bone strength, the mandible, or jawbone, stands out as the strongest and most durable.
Why is the Mandible the Strongest Facial Bone?
There are several reasons why the mandible is regarded as the strongest facial bone:
- It is the largest, thickest facial bone.
- It is the only movable facial bone, attached to the skull by the temporomandibular joints.
- It is made up of dense, compact bone designed to withstand high levels of strain.
- The shape and structure of the mandible optimizes strength.
- Large muscles like the masseter anchor onto the mandible, allowing it to exert force.
The size and thickness of the mandible contribute to its substantial strength. It is much thicker than other facial bones like the nasal bones or zygomatic arches. The body and rami (vertical portions) of the mandible contain dense, compact bone on the outer layer. This provides reinforced strength against fracture or breaks.
The mandible is also the only moveable facial bone. It is attached to the temporal bone of the skull by the temporomandibular joints. This allows movement for functions like chewing or speaking. The joint surfaces are covered in fibrocartilage to support mobility and reduce wear from repetitive motion. The thick condylar processes of the mandible anchor these joints.
As a movable bone subjected to significant strain, the mandible requires enhanced strength. Its Y-shape and curvature create an architectural structure able to withstand forces from multiple directions. The body of the mandible also has an external oblique line that adds further structural support.
Large, powerful muscles like the masseter and medial pterygoid attach onto the mandible. When these muscles contract during chewing or clenching, they exert great force. The mandible must be able to withstand these repeated muscular forces without fracturing.
For these reasons, the mandible has evolved as the strongest and most durable facial bone capable of withstanding powerful biting and chewing strains on a regular basis.
How Strong is the Mandible?
Research has quantified the impressive strength capacity of the human mandible. In terms of tolerable bite force, studies have demonstrated that the jaw can withstand an average of 70 pounds (around 300 newtons) of force. This allows us to bite through and chew most foods without damaging the mandible.
The compressive strength of mandibular bone has been measured at around 170 megapascals (MPa). To put this in perspective, the compressive strength of reinforced concrete is about 40 MPa. This highlights just how incredibly rigid and resistant to compression the mandible really is.
The mandible does have limits, however. Excessively wide opening of the jaws or traumatic injury from blows or accidents can still result in mandibular fractures. Non-impact fractures of the mandible can occur with biting forces exceeding 300 pounds.
While quite strong, the mandible still requires the additional support of the skull and connected muscles to maintain its full strength. When detached from the skull, isolated mandible specimens have fallen in the range of 70-90 MPa of compressive strength in testing.
Composition and Structure
The composition and microarchitecture of mandibular bone allows it to be both light yet extremely rigid. Compact bone forms a thick outer cortical layer while spongy trabecular bone fills the inner cavity. This provides an optimized combination of strength, resilience and light weight that is perfectly designed for the functional demands of the lower jaw.
The mandible contains substantial amounts of minerals like calcium and phosphate that help increase bone hardness. The organic matrix of bone is also infused with collagen fibers arranged in cross-linked networks that prevent cracking and fracture. Jamming of these collagen bundles dissipates energy and arrests crack propagation.
The orientation of trabecular struts inside the mandible maximizes strength. Struts are thickly packed along lines of tension and cross each other in triangular grids. This geometric arrangement minimizes shear stress and creates strength in multiple dimensions.
Remodeling of mandibular bone also allows it to adapt to changing loads and reinforce areas subjected to repeated forces. Chewing puts cyclical loads on the mandible that stimulate targeted bone remodeling to maintain optimal strength.
Mandibular Strength Throughout Life
The strength of the mandible varies across different stages of life. Mandibular bone mass and density increases during childhood and adolescence. The peak strength of the mandible is reached between the late teens and early 20s when growth stops. Bone strength remains high throughout early and middle adulthood.
After the age of 40, mandibular strength gradually declines with age. Studies show the mandible loses about 2% of bone mass each decade. Loss of mineral content, changes in collagen matrix proteins and reduced remodeling efficiency contribute to age-related decreases in mandibular strength.
This can increase the risk of fractures in the elderly from trauma. It also makes the mandible more vulnerable to pathologic fractures in cases of severe bone loss from osteoporosis or periodontal disease.
Proper nutrition, weight-bearing exercise, calcium and vitamin D intake can help preserve mandibular bone strength as a person gets older. Quitting smoking and avoiding excessive alcohol are other ways to maintain mandibular health with age.
The mandible exhibits an impressive ability to recover from fractures and other damage. Its excellent vascular supply and dense network of collagen fibers facilitate remarkably swift healing.
Most uncomplicated mandibular fractures heal within 4 to 8 weeks. The rigid immobilization provided by titanium plates and screws induces direct bone healing between fracture fragments. This allows for faster recovery compared to other mobile bones that heal slower by callus formation.
Remodeling continues long after a mandibular fracture heals to restore optimal shape and strength. Complete remodeling of the mandible after a fracture can take many months. However, the bone regains about 70% of original strength within a few months of the injury.
How Does Mandibular Strength Compare to Other Bones?
The mandible is the strongest and densest facial bone. But how does it compare in strength to other bones of the body?
Bones like the femur in the thigh and tibia of the lower leg support the weight of the body and have greater overall bone mass and strength. The femur is the single strongest bone, able to withstand compressive forces over 1300 MPa.
In terms of density, the mandible contains very thick cortical bone. But some bones have higher volumetric density, like the petrous portion of the temporal bone. This contains the densest cortical bone in the body, providing strength and protection to delicate inner ear structures.
While maybe not the absolute strongest bone in the body, the mandible outperforms all other facial bones. The maxilla and nasal bones fracture more easily in response to trauma. Even thickness of cortical bone is less in most areas of the skull compared to the robust mandible.
Role in Facial Structure and Function
The mandible’s strength and mobility allow it to provide crucial structural and functional roles:
- Chewing – The mandible holds and positions teeth to masticate food. Its motor actions like biting and grinding are powered by strong masseter muscles.
- Speech – Complex mandibular movements modulate airflow and create sound.
- Appearance – Mandibular shape and position determines facial width and lower third proportions.
- Protection – The mandible forms a protective floor for other facial structures.
- Airway Support – The mandible anchors tongue position to maintain airflow.
All these vital functions depend on the mandible having tremendous strength and resilience. Even everyday activities like chewing apply significant cyclical loads that require a durable mandible.
Clinical Conditions Affecting Strength
Some medical and dental conditions can detrimentally impact the strength of the mandible:
- Osteoporosis – Generalized or localized bone loss weakens the mandible and predisposes to fracture.
- Periodontal Disease – Chronic bacterial infection causes resorption of mandibular bone around teeth.
- Medications – Drugs like bisphosphonates used in cancer or osteoporosis treatment can lead to osteonecrosis of the jaw.
- Radiation Therapy – Head and neck radiation kills bone cells and impairs remodeling.
- Nutritional Deficiencies – Lack of vitamins C, D, or minerals like calcium undermine mandibular bone health.
These conditions highlight the importance of maintaining proper nutrition, dental hygiene and regular health screening. Preventing or promptly treating pathologies that affect the mandible is key to preserving its natural strength and function with age.
The mandible is unquestionably the most robust, resilient facial bone. Its thickness, architectural design and dense composition equip it to perform essential functions like chewing and speaking while withstanding significant loading forces. Proper prevention and management of conditions that could weaken mandibular bone is key to facial health and function.