Difference Between Micrognathia and Retrognathia

The key difference between micrognathia and retrognathia is that micrognathia is the condition of having an abnormally small mandible, while retrognathia is the condition where the mandible is displaced posteriorly with respect to the maxilla although not necessarily small.

The mandible (lower jaw or jawbone) is the largest, strongest and lowest bone in the human facial skeleton. This forms the lower jaw and holds the lower teeth in the right place. It is the only movable bone in the skull. The mandible is connected to the temporal bone by the temporomandibular joint. The word mandible comes from the Latin word “mandibula”. Males usually have a squarer, stronger, and larger mandible than females. Micrognathia and retrognathia are two types of abnormal mandibles.

CONTENTS

1. Overview and Key Difference
2. What is Micrognathia 
3. What is Retrognathia
4. Similarities Between Micrognathia and Retrognathia
5. Side by Side Comparison – Micrognathia vs Retrognathia in Tabular Form
6. Summary

What is Micrognathia?

Micrognathia is a condition in which a child has a very small lower jaw. It is also called mandibular hypoplasia. This condition is common in infants. The child with micrognathia has a mandible that is much shorter (smaller) than the rest of their face. The children may be born with this disease. Otherwise, it can develop later in life. It certainly happens with children who are suffering from abnormal genetic conditions such as trisomy 13, progeria, and fetal alcohol syndrome, etc.

In some cases, this problem goes away as the jaw of a child grows with age. This means it usually self corrects during growth, most probably due to the increase in the size of jaws. In severe conditions, micrognathia can cause feeding or breathing problems. It can be also present both in adults and children. This makes the intubation process difficult either during anaesthesia or in emergency situations. Micrognathia can also lead to a condition called malocclusion of the teeth. This means the teeth of a child do not align correctly. This condition can be detected by the naked eye as well as other methods such as dental or skull X-Ray testing.

What is Retrognathia?

Retrognathia is a condition in which the lower jaw is set further back than the upper jaw. It is also called mandibular retrognathia. Often, the difference in placement of the lower and upper jaw is only noticeable. Some people are born with retrognathia, and others develop this condition later in their life.

The condition of retrognathia can be difficult to manage. It can affect your ability to sleep and eat physically. Sometimes, it affects self-esteem and self-confidence. This is because this condition is visually noticeable. Treatments usually are orthodontic appliances, braces, hardware, or surgery. In mild cases, treatment may not be needed. The common causes of retrognathia are Pierre-Robin syndrome, hemifacial microsomia, Nager syndrome, Treacher Collins syndrome, surgery to remove a tumour, and facial fractures. Retrognathia can be diagnosed through an inferior facial angle (IFA) or X-ray.

What are the Similarities Between Micrognathia and Retrognathia?

• These conditions are related to the mandible.
• Both can cause changes in facial appearance.
• They are a result of genetic conditions.
• Both can be observed in children.

What is the Difference Between Micrognathia and Retrognathia?

Micrognathia is a condition having an abnormally small mandible, while retrognathia is a condition where the mandible is displaced posteriorly with respect to the maxilla, although not necessarily small. So, this is the key difference between micrognathia and retrognathia. Moreover, in micrognathia, the mandible is small, but in retrognathia, the mandible is not necessarily small.

The below infographic lists the differences between micrognathia and retrognathia in tabular form.

Summary – Micrognathia vs Retrognathia

The mandible is located inferiorly in the facial skeleton. It is the largest and strongest bone of the face. It forms the lower jaw, and it acts as a receptacle to the lower teeth. Furthermore, it is also connected on either side with the temporal bone through the temporomandibular joint. Micrognathia is an abnormally small mandible. On the other hand, retrognathia is a mandible that is displaced posteriorly with respect to the maxilla. Thus, this is the main difference between micrognathia and retrognathia.

Reference:

1. “Micrognathia.” Children’s Hospital of Philadelphia, The Children’s Hospital of Philadelphia, 12 May 2014, Available here.
2. “Retrognathism.” An Overview | ScienceDirect Topics, Available here.

Image Courtesy:

1. “Pitt-rogers-danks syndrome” By Marie Sogaard et al – Sogaard M, Tümer Z, Hjalgrim H, Hahnemann J, Friis B, Ledaal P, Pedersen VF, Baekgaard P, Tommerup N, Cingöz S, Duno M, Brondum-Nielsen K. Subtelomeric study of 132 patients with mental retardation reveals 9 chromosomal anomalies and contributes to the delineation of submicroscopic deletions of 1pter, 2qter, 4pter, 5qter and 9qter. BMC Med Genet. 6, 21. 2005. doi:10.1186/1471-2350-6-21. PMID 15904506. (CC BY 2.0) via Commons Wikimedia
2. “Nager acrofacial dysostosis patient frontal view” By Abdollahi Fakhim, Shahin, Nikzad Shahidi, Mehrnoush Mousaviagdas – A Case Report: Nager Acrofacial Dysostosis. Iranian Journal of Otorhinolaryngology. 2012;24(66):45-50. PMID:24303385 (CC BY 3.0) via Commons Wikimedia