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For orthopaedics

What is proven between bite and pelvis – and what is not

Hardly any topic between dentistry and orthopaedics attracts more claims than this one. We have split the chain into its two links and examined each separately. What emerges is less than the advertising says – and more than the sceptics expect.

You know these patients

Recurrent neck and shoulder girdle complaints without a structural correlate. Misalignments that can be corrected and come back. Adolescents with postural abnormalities during growth. And incidentally, often only when asked: grinding, TMJ sounds, pressure in front of the ear.

The connection

The chain has two links. Both are proven.

  1. 01Link A · proven

    Link A — bite position and head posture

    A meta-analysis of six studies with 505 participants finds the association in both directions: Class II is associated with increased head extension and forward head posture, Class III with a straighter cervical spine and a more posterior head position. 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 identified and undisputed: the supra- and infrahyoid muscles, platysma and dorsal neck extensors connect the lower jaw and cervical spine; head extension exerts, via stretched soft tissue, a dorsocaudal force on the lower jaw .

    The opposite direction is even better documented: Head posture measurably changes 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 with.

  2. 02Link B · proven

    Link B — head posture and body posture

    Here the data are better than for link A, because they come not from dentistry but from spinal surgery: standing sagittal alignment is a continuous chain from head to foot, relative to the gravity line.

    What matters, however, is how this chain works. It is a compensation system, not a transmission system. If lumbar lordosis decreases, the pelvis counteracts – correlation r = −0.72 to −0.80. With ageing, the trunk tilts forward and is compensated by increased cervical lordosis, pelvic tilt and knee flexion. The purpose is explicitly stated in the literature: to maintain a horizontal gaze.

  3. 03Where the evidence ends

    And that is why little arrives at the bottom

    From two proven 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 designed 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 rounding changed. Thoracic kyphosis, lumbar lordosis, pelvic tilt and knee position when 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 keeping quiet about them.

Indication

When a referral is worthwhile

First, and without exception: red flags and unclear findings belong in specialist work-up, before any functional diagnostics. The CMD perspective complements, it does not replace.

Worthwhile

  • Rapidly recurring cervical spine and shoulder girdle complaints with jaw signs (clicking, bruxism, pressure in front of the ear)
  • Persistence beyond three months despite guideline-based first-line treatment
  • Treatment-resistant tension-type headaches with jaw involvement
  • Before major dental reconstruction with known postural problems – for a functional baseline

Not worthwhile

  • Structural scoliosis with the expectation of influencing it via the bite – there is no basis for this
  • Leg length discrepancy or pelvic obliquity as the sole question
  • Acute complaints before orthopaedic work-up is complete

Your patient remains yours.

After the assessment or after regulation is complete, we always refer back to you. We only provide further treatment at your explicit written request.

Measures we refer to and do not reinterpret: scoliosis from a Cobb angle ≥ 10° with vertebral rotation; clinically relevant leg length discrepancy from 10 mm; healthy left-right weight distribution when standing between 48.5 and 51.5 %.

Next steps

Three routes – your choice

  • 01

    I want to know more

    The full-text sources, our measurement protocols and the clinical explanatory model with its level of evidence disclosed.

    Request documents
  • 02

    I have a question about a case

    Call-back from the CMD specialist, not from reception.

    Ask a question
  • 03

    I would like to refer

    By phone, email or letter – whatever suits you. The findings report comes back to you.

    Referral

Other specialties

To the overview