What is established between bite and pelvis – and what is not
Hardly any topic between dentistry and orthopaedics attracts more claims than this one. We have taken the chain apart into its two links and examined each one separately. What comes out is less than the advertising says – and more than the scepticism expects.
You know these patients
Recurring neck and shoulder girdle complaints without a structural correlate. Postural deviations that can be corrected and come back. Adolescents with postural abnormalities during growth. And in passing, often only when asked: grinding, jaw joint noises, pressure in front of the ear.
The chain has two links. Both are established.
Link A — bite position and head posture
A meta-analysis of six studies with 505 participants finds the association in both directions: Class II goes with increased head extension and forward posture, Class III with a straighter cervical spine and a head held further back. Order of magnitude 1.3 to 2.9 degrees (NL/VER +1.27°; OPT/CVT +2.94° for Class II; NL/VER −2.67° for Class III).
The anatomical pathway is named and undisputed: the supra- and infrahyoid muscles, platysma and dorsal neck extensors connect the lower jaw and the cervical spine; head extension exerts a dorsal-caudal force on the lower jaw via stretched soft tissues.
The opposite direction is even better documented: head posture measurably changes the occlusal contacts – differently when sitting than when lying down. For our own work this means that a bite registration without controlled head posture records a different occlusion from the one the person lives in.
Link B — head posture and body posture
Here the data are better than for link A, because they do not come from dentistry but from spinal surgery: standing sagittal alignment is a continuous chain from head to foot, related to the line of gravity.
What is decisive, however, is how this chain works. It is a compensating system, not a transmitting system. If lumbar lordosis decreases, the pelvis counter-steers – correlation r = −0.72 to −0.80. With ageing the trunk tips forward and is compensated by increased cervical lordosis, pelvic tilt and knee flexion. The literature names the purpose explicitly: to maintain a horizontal gaze.
And that is why little arrives at the bottom
From two established links it follows logically that the jaw system and body posture are related. It does not follow that body posture can be changed via the bite. Two small effects in series produce a smaller one – and if the middle link is expressly built to compensate for deviations, nothing measurable arrives at the end of the chain.
A prospective study tested exactly this: 24 CMD patients, Michigan splint, three months, 3D body scan before and after. Forward head posture and shoulder protraction changed. Thoracic kyphosis, lumbar lordosis, pelvic tilt and knee position in standing did not. In the authors' words: “The influence of occlusal splints on global posture is limited and only small effects on cervicocranial parameters were found.”
What we conclude from this for ourselves: we treat the top link of the chain and measure what happens there. We record posture and statics to see what arrives there – not to correct them via the bite. Anyone who promises you that has not read the studies or is concealing them.
When a referral is useful
First and without exception: red flags and unclear findings belong in a specialist work-up, before any functional diagnostics. The CMD perspective is complementary, not a substitute. We do not call any of your diagnoses into question.
Useful
- rapidly recurring cervical spine and shoulder girdle complaints with jaw signs (clicking, bruxism, pressure in front of the ear)
- persistence over three months despite guideline-based first-line treatment
- treatment-resistant tension headaches with jaw involvement
- before major dental restoration in patients with known postural problems – to establish a functional baseline
Not useful
- structural scoliosis with the expectation of influencing it via the bite – there is no basis for that
- leg length discrepancy or pelvic obliquity as the sole question
- acute complaints before the orthopaedic work-up is complete
Measures we refer to and do not reinterpret: scoliosis from a Cobb angle of ≥ 10° with vertebral rotation; clinically relevant leg length discrepancy from 10 mm; healthy left–right weight distribution in standing between 48.5 and 51.5 %.
Three routes – you choose
I want to know more
The sources in full text, our measurement protocols and the clinical explanatory model with the level of evidence disclosed.
I have a question about a case
A call back from the CMD specialist, not from reception.
I would like to refer
By phone, e-mail or letter – whichever suits you. The findings report comes back to you.