Narrow palate, narrow upper jaw: symptoms and options in adults

The palate is made of two halves joined by a bone suture running from front to back along its middle. Cleveland Clinic explains that expansion appliances slowly move these two halves apart and that the gap between them fills with new bone. In childhood this suture is open, so expansion is relatively easy; after adolescence the suture gradually fuses, and in adults the same appliance mostly tips the teeth sideways rather than moving the bone. This is what makes a narrow upper jaw in adults a separate subject.

More than one factor plays a part in the upper jaw staying narrow. Cleveland Clinic says that in children who breathe through their mouth the face can be narrow, the lower jaw can sit further back and the upper and lower teeth may not fit together. When the nasal airway is blocked, the tongue rests on the floor of the mouth and so gives the upper jaw no support from the inside; this is one possible explanation for why mouth breathing and a narrow palate are often seen together. Inherited facial structure, childhood habits such as thumb-sucking, and cleft lip and palate are also among the causes listed. In adults there is often more than one cause; what matters is not the cause but measuring the current situation correctly.

The most obvious sign is a crossbite in the back teeth. Cochrane's orthodontic review defines this as the upper back teeth closing inside the lower ones, and says it is seen in about 4 per cent of children and adolescents in Europe and about 17 per cent of those in America. The review notes that crossbite has been linked with tooth wear, abnormal development of the jaws, joint problems and an unbalanced appearance of the face. When the bite is off on one side, the lower jaw can shift to that side as it closes; over time this shift can turn into a habit of chewing on one side.

You can do a simple check at home. In front of a mirror, pull your lips to the sides with your fingers and close your back teeth together. Normally the outer surfaces of the upper premolars and molars slightly cover the lower ones from the outside. If on one or both sides you see the lower teeth sticking out and the upper ones sitting inside, you may have a crossbite. If you feel your jaw shifting to one side as you slowly close your mouth, note this too. This check does not make a diagnosis, but it makes clear what to tell your dentist.

The key distinction is whether the problem lies in the teeth or in the bone. Sometimes the bony base of the jaw is wide enough but the upper back teeth are tilted inwards; this is a dental crossbite and can be corrected with orthodontic braces or aligners. Sometimes the bony base itself is narrow; the upper teeth have already tilted outwards to try to compensate, and pushing them further out does not solve the problem. Cleveland Clinic sums this up in one plain sentence: braces can move teeth, but they cannot move the jawbone. This distinction is made with an examination, models and, when needed, a 3D CBCT scan.

Age alone does not decide it. A systematic review of studies that assessed the degree of fusion of the palatal suture with CBCT says the relationship between the suture's maturation and chronological age is weak, and that very different stages are seen at the same age, especially in young adults. In other words, of two 20-year-olds, one may still have a partly open suture while the other's has fused. This is why the choice of expansion approach in an adult rests on imaging, not on age.

A narrow upper jaw also has a visible aesthetic effect: dark triangles on both sides of the teeth, between the cheeks and the teeth, when you smile. In a study in which a group of 30 assessors were shown the same faces with different smile widths, a broad smile with filled sides was found more attractive than a narrow smile; this finding was the same for female and male faces. The authors recommended that wide dark corners be added to the problem list in orthodontic treatment planning. This is a perception study; a narrow jaw is not the only cause of dark corners, as the alignment of the teeth and the movement of the lips also play a part.

In an upper jaw with no teeth, the picture arises by a completely different route. After teeth are lost the jawbone shrinks, and this shrinkage progresses in different directions in the two jaws. In a study examining 123 dry edentulous jawbones, 24 upper and 99 lower, the upper jaw was found to shrink inwards and upwards and the lower jaw outwards and downwards, so that the edentulous upper jaw ended up level with the lower jaw or inside it. This is why the upper jaw looks 'narrow' in someone who has been without teeth or has worn dentures for years; here the problem is not congenital but comes from shrinkage after tooth loss. When full-mouth fixed teeth are being planned, this difference is taken into account as information that affects the angle of the implants and the arch on which the teeth will be set.

The first list covers signs that suggest the problem may lie more in the alignment of the teeth; for these, see your orthodontist. The second list covers signs that suggest the bony base is narrow or that another problem is also present; for these, the assessment should be more thorough.

The sequence starts by separating out any accompanying health problems, then moves on to whether the problem lies in the teeth or the bone, and finally to the treatment approach.

1. 1

   Questions about sleep and the nose

   You will be asked about snoring, breathing stopping during sleep, daytime tiredness and constant mouth breathing. If these are present, an assessment by a GP or an ear, nose and throat specialist is arranged for sleep apnoea and nasal blockage.

2. 2

   Examining the bite and any shift

   The dentist looks at whether the crossbite is on one side or both, whether the lower jaw shifts to one side as the mouth closes, at tooth wear and at the jaw joint.

3. 3

   Dental or skeletal

   The width of the bony base and the tilt of the upper teeth are measured with models, an intraoral scan and, when needed, a 3D CBCT scan. There is a CBCT study showing that bone defects on the outer surface of the back teeth are seen more often in adults with a crossbite; this makes it even more important to see the bone before pushing the teeth outwards.

4. 4

   Assessing the palatal suture

   In adults, how far the suture has fused cannot be predicted from age; the stage seen on the CBCT scan guides whether miniscrew-assisted expansion or surgical assistance will be needed.

5. 5

   Choosing the expansion approach

   For dental problems, orthodontic braces or aligners; for a narrow bony base, expansion anchored to the bone with screws (MARPE) or surgically assisted expansion (SARPE); if the jaws are also mismatched front to back or vertically, orthodontics and jaw surgery are planned together.

6. 6

   Expansion and waiting

   Cleveland Clinic says that in adolescents and adults reaching the result takes longer than in children and can take up to a year, and that once the desired width has been achieved the appliance can be left in place for another 4 to 6 months for the bone to consolidate. The alignment of the teeth is then completed with orthodontics.

7. 7

   The plan in an upper jaw with no teeth

   If all the teeth have been lost, expansion does not come into it. The width and height of the bone and the position of the sinuses are measured on the CBCT scan; the angle of the implants and the arch on which the fixed teeth will be set are decided accordingly. At implant72, the implants and fixed teeth are completed in 3 days / 72 hours and the teeth fitted on day 3 are the final teeth; that is why a tooth arrangement that takes the narrowed arch of the upper jaw into account is planned from the start, on the CBCT scan.

The options vary according to where the problem lies and how big it is. Each has its own cost and limits.

The following are common decision errors in treating a narrow upper jaw in adults, and the risks of the treatment itself. We set them out so that you can ask your dentist the right questions.

Timings vary with the person and the method. The flow below is the usual course described by the sources; the plan of your orthodontist and surgeon takes priority.

1. The first days

   Cleveland Clinic says a new expansion appliance can cause mild pain, headache, more saliva and a lisp in the first days. With SARPE, swelling and pain after the operation are added to this.

2. Active expansion

   The appliance's screw is turned at set intervals. A gap opening between the front teeth can be a sign that the bone really is separating; Cleveland Clinic notes that this gap is closed later with orthodontics.

3. The waiting period

   Once the desired width has been reached, the appliance stays in place for a few more months so that the bone can fill in and consolidate in the opened area.

4. Orthodontics and retention

   Aligning the teeth to the new arch is completed with orthodontics. Because some relapse is expected, how and for how long retainers will be used after treatment is discussed.

You will not find figures here. These are the headings that determine the scope of treatment for a narrow upper jaw:

Whether the problem lies in the teeth or the bone

There is a big difference in scope between a dental problem solved with orthodontics alone and a skeletal narrowing that needs bone expansion.

Expansion method

MARPE adds screws and a special appliance; SARPE adds an operation, anaesthesia and surgical follow-up.

Length of orthodontics

Aligning the teeth and retention after expansion can take months to years.

Accompanying problems

If there is a blocked nose, sleep apnoea or a front-to-back jaw mismatch, assessment and treatment by other specialists are added.

Bone condition in an upper jaw with no teeth

If the bone volume is adequate, implants are planned directly; if it is not, options such as bone augmentation or zygomatic implants change the scope.