1.Can posterior disc displacement also present with posterior open bite?

Posterior disc displacement is rare, but a transient disc displacement can cause a posterior open bite.

2. How do we check and diagnose a co-cr discrepancy? Especially in patients with dual bite/increased overjet patients.

This is a clinical diagnosis. Some of the philosophies that teach this are the Dawson Institute, Pankey institue, Roth Williams/FACE philosophy (if you are an orthodontist) and OBI (bioesthetic dentistry).

3. What is an orthogonal orientation?

It is aligning the facial skeleton with the orthogonal planes: axial, coronal and sagittal. What I am trying to do is to simulate the situation that a patient would be in a cephalostat with ear rods to help me see the asymmetries due to pathology and those due to skull base asymmetries. In the axial view, I orient the external auditory canals to the coronal plane. In the coronal view, I orient the same structure to the axial view. In the sagittal view I align the hard palate to the axial plane (you can use Frankfort plane if you’d like, but I’ve found that it is more cumbersome and does not add much).

4. What was the link between the open bite and the resorption?

Two hypotheses: 1) When teeth are impacted for a long time, like in the case of primary failure of eruption or even normal impaction, they may develop resorption, 2) resorption that involves the tooth surface creates a cavity that bone can grow into creating a mechanical failure of eruption. Chicken or the egg? There is no way for us to know at this point what came first in this patient.

5. What is the final diagnosis?

As with many radiographic explorations, the final diagnosis often comes with clinical correlation. But there are several separate findings to note:

1. Facial asymmetry due to: Mandibular asymmetry (growth deficit in the ramus, not originating from the condyle – not condylar hypoplasia
or loss of condylar volume), Maxillary asymmetry (a combination of maxillary sinus hypoplasia or atelectasis, failure of eruption of the left posterior teeth and subsequent diminished development of the alveolar process and position of the maxilla on the skull base due to rotation of the sphenoid bone to the right), Skull base asymmetry (noted above), and possibly a small contribution from the cervical spine (which I mentioned as a teaching point in the presentation, but I don’t think it contributes much to this patient’s presentation).
2. A dual bite/CR-CO discrepancy, which is a clinical diagnosis, but there are several signs here, such as the regressive remodeling in the right condyle that is not posteriorly displaced, the inferior position of both condyles and the single contact on the right third molars with open bite on the rest of the teeth.
3. Left large open bite, which may be due to either primary failure of eruption of the maxillary teeth or a mechanical failure of eruption on both  maxillary and mandibular teeth due to ankylosis or the tongue habit.

6. Can an ankylosed tooth and tooth fractures be diagnosed on CBCT?

It depends. Traditional ankylosis (loss of PDL and bone abutting tooth) and fractures are difficult radiographic diagnoses to make because it necessitates the evaluation of a very fine structure. In order to adequately visualize these, a very high resolution (0.1mm voxel or less) small field of view is needed, and even with this it is difficult to see, especially if the fracture fragments are not displaced and even more so if the tooth is root canal treated because the artifact associated with the metal of the filling obscures the fracture. In the case of fractures, the radiographic sign for their presence is often the bone loss that is associated with it (in the case of a complete vertical fracture, it would appear as J-shaped bone loss that wraps around the apex). Ankylosis due to bony ingrowth into an external resorption cavity is very easy to see on CBCT.

7. The second patient can also be helped with orthopedic orthodontics utilizing variations of the ALF and / or Crozat appliances in combination with Osteopathic treatment.

The ALF (Advanced Lightwire Functional) appliance is one of the methods that has been suggested in correcting craniofacial bone malalignment in conjunction with osteopathic manipulation earlier in life. Other teachers of similar methods are the Facial Beauty Institute in Tennessee, Dr. Marie-Josephe Deshayes in France and Dr. Myroslava Drohomyretska in Ukraine. I am not promoting any one treatment method and have no financial or other interest when I name these methods, rather I aim to help dentists find the avenues that they seek. In your individual exploration, you should use your judgement and always question to seek the answers you desire.

8. How can we learn more about unlocking the maxilla?

You can look into the Cranial Academy’s introductory course in cranial osteopathy. This is a course that is specifically tailored for more traditionally-trained medical and dental professionals to learn how to apply this knowledge in their clinical practice and patients’ diagnosis. Also, see the question above.

9. How can I learn about cervical spine asymmetry?

Find courses by Mariano Rocabado (he travels to Europe and the US for teaching often, but has courses based in Chile). He is a physical therapist that has played a big role in helping dentists understand the role and contribution of the cervical spine to the TMJs and occlusion. Other avenues to explore to attain this understanding is teaming up with an upper cervical chiropractor, such as one trained in the Blair technique (they have a manual you can purchase, but it is a little confusing). A good book to have to understand the complex biomechanics are Kapandji’s The Physiology of the Joints. If you are looking for radiology books: Swichuk’s Imaging of the Cervical Spine in Children (excellent if you are an orthodontist because it has a lot of plain film imaging and describes the normal development of the C-spine) and Ross’ Specialty Imaging Craniovertebral junction (more complex, more pathology, less alignment, more radiologist level) are good.

10. Is it the atlas or the axis that is responsible for the lateral open bite?

A: The C0/C1 or C1/C2 subluxation can be responsible for occlusal canting. I’m not sure about the relationship to a posterior open bite (yet), but if such a thing happens, it would be due to distraction of the condyle as a result of the relationship with the skull base being altered. This is a good question for Mariano Rocabado.

11. I know that vaulted palate is associated with deviated septum, which is also associated with midface asymmetries. Do you pay attention to low tongue posture and deep palatal vault?

As a radiologist viewing this patient in only this time point, I cannot comment on the tongue posture with confidence as I don’t know what the patient did with his or her tongue at the time of scan acquisition. I do look at the transverse dimension of the maxilla, nasal cavity, spur formation and palatal vault morphology when assessing for the risk factors for sleep-disordered breathing, but without the clinical correlation, these are just findings that tell us about the remodeling the face in response to function and development and not absolute indicators of abnormality on their own.

12. Do you observe calcified pineal glands?

I do mention them when I see them, but the jury is still out on their clinical relevance. Traditional radiology sees them as physiologic calcification of no consequence. There are some interesting ideas out there with regards to sleep disruption and sense of direction in homing pigeons.😉

13. What about the cervical resorption. Any idea for an etiology?

There is a full text article available on Pubmed on the subject: Rotondi O, Waldon P, Kim SG. The Disease Process, Diagnosis and Treatment of Invasive Cervical Resorption: A Review. Dent J (Basel). 2020 Jul 1;8(3):64. doi: 10.3390/dj8030064. PMID: 32630223; PMCID: PMC7557762.

14. As you mention an example about the cant which can be due to cervical subluxation. so how can we diagnose it in the clinical setup or do we have to have CBCT for a cant ?

Osteopathic physicians and chiropractors have been diagnosing these conditions clinically and with plain film radiography for generations, but some have recently made the shift to CBCT, and not many have made the correlation to the occlusion. I recommend teaming up with one of these clinicians, and perhaps taking one of the courses I mentioned above to more fully understand the process. Remember that the patient alignment in the CBCT is most likely not going to be in natural head posture unless you really make that effort. The priority for you as a dentist is to diagnose the craniofacial complex, so if bringing the patient into natural head posture compromises the scan quality (motion artifact or not including important parts of the anatomy such as the TMJs and anterior face), then don’t bother. Patient positioning in a chin rest or any of the other head stabilizing techniques will change natural head posture, so don’t read too much into the cervical spine alignment on CBCT without having a good base of knowledge on cervical spine alignment. If you see abnormality in the cervical spine, note it, but don’t make it priority unless you know what you are doing and working as a team with an osteopath, chiropractor or physical therapist.