The relation between incisal guidance angle and the growth a
The incisal guidance angle (IGA) is related to the temporomandibular joint (TMJ), and changes to the IGA are often involved in the prosthetic and orthodontic treatment of anterior teeth.

The aim of this study was to investigate age-related morphological differences in the TMJ in subjects with different IGAs. The study was published in the BMC Oral Health.

Cone-beam computed tomography (CBCT) images of 274 patients were included (group 1, IGA < 45°; group 2, 45° ≤ IGA ≤ 60°; group 3, IGA > 60°). Each group was then divided into 4 age groups. TMJ morphology was assessed by linear measurements, angular measurements, and subjective evaluations. The IGA and occlusal plane angles were also measured.

- The anterior inclination of the condyle (AIC) increased with age in the three IGA groups but decreased from 17 years onward in group 2.

- In the age groups analysis, the AIC in group 1 was smaller than that in group 3 but larger than that in group 2.

- Articular eminence inclination (AEI) decreased with age in group 1 but increased with age in group 3.

- The AEI in group 2 was larger than that in group 1 at 17–25 years, and it was larger in group 3 than in group 1 at 26–33 years. The IGA had a weak correlation with AEI.

In particular, the articular fossa of patients with shallower incisal guidance changed to a flatter shape with age, whereas the condylar anterior slope and articular eminence of patients with steeper incisal guidance changed towards a steeper alignment. There was a correlation between IGA and TMJ shape.