OVERVIEW

What is double teeth malformation?

Double teeth malformation refers to an abnormal tooth development morphology where two developing tooth germs fuse or combine into one due to mechanical pressure factors during development; or when a single tooth germ splits into two, resulting in an abnormal crown morphology resembling two teeth. This form is referred to as double teeth morphology.

Clinically, double teeth malformation is generally classified into fused teeth, concrescent teeth, and geminated teeth based on morphology and origin.

Is double teeth malformation common?

Overall, it is relatively uncommon in clinical practice. Among them:

• Fused teeth: Most commonly seen in deciduous mandibular incisors.
• Geminated teeth: Can occur in both deciduous and permanent dentition.
• Concrescent teeth: Occasionally found in the second and third molar regions of the maxilla.

Are double teeth malformation and "double-row teeth" the same condition?

No, they are not the same. The phenomenon of "double-row teeth" commonly seen in children's mouths is not a malformation but is caused by retained deciduous teeth. Retained deciduous teeth refer to deciduous teeth that fail to fall out on schedule despite the eruption of successor permanent teeth, or deciduous teeth that remain in the permanent dentition.

Factors such as abnormal eruption direction of successor permanent teeth, congenital absence of permanent teeth, and genetics can contribute to this condition. Clinically, it often manifests as deciduous teeth not shedding while successor permanent teeth erupt from the lingual, palatal, labial, or buccal sides, creating the "double-row teeth" appearance.

How many types of double teeth malformation are there?

As a special organ of the human body, teeth are not solid or single-structured. They can be divided into dental tissues (enamel, dentin, cementum, and pulp) and periodontal tissues. Double teeth malformation is mostly caused by abnormal tooth germ development during tooth formation. Based on tooth germ and other causes, it can be classified into the following three types:

• Fused teeth: Formed by the fusion of enamel or dentin from two normal tooth germs. The fusion of two tooth germs can be influenced by external forces during development and genetic factors.
• Geminated teeth: An abnormal tooth morphology formed when the enamel organ of a single tooth germ invaginates during development, leading to incomplete separation. On X-rays, the crown may appear completely or incompletely separated, but the root portion shares a single root or root canal.
• Concrescent teeth: Refers to two or more teeth with essentially completed morphological development that, under significant external forces such as dental crowding or traumatic displacement, have their roots brought close together. The cementum covering the roots then proliferates and binds them together.

SYMPTOMS

What are the manifestations of double teeth malformation?

• Fused teeth:

• If fusion occurs early, it means the complete fusion of two different tooth germs, clinically presenting as crown and root fusion;

• If fusion occurs later, incomplete fusion of the two tooth germs may result in teeth with fused crowns but separated roots, or separated crowns but fused roots. Generally, there may be one or two root canals, depending on the fusion during development.

What conditions should double teeth malformation be differentiated from?

Double teeth malformation should be distinguished from retained deciduous teeth, with the primary differentiation being among fused teeth, concrescence, and gemination.

CAUSES

What are the causes of double teeth anomalies?

• Fused teeth: The cause of fusion is generally believed to be pressure. If this pressure occurs before the calcification of two teeth, the crowns fuse together. If the pressure occurs after the crown development is complete, it results in a single root with two separate crowns. Some literature also suggests a genetic predisposition.

• Geminated teeth: Geminated primary teeth are often accompanied by congenital absence of their successor permanent teeth.

• Concrescence of teeth: The cause of concrescence is generally attributed to trauma or dental crowding, leading to the resorption of interdental bone, which brings adjacent teeth closer together. Subsequently, hyperplastic cementum can fuse the two teeth.

DIAGNOSIS

How is double tooth deformity diagnosed?

It is diagnosed through clinical oral examination of the unique tooth morphology and a history of trauma.

What tests do patients with double tooth deformity need to undergo? Why are these tests necessary?

• General oral examination: including visual inspection, probing, percussion, and palpation. This is a routine oral examination to assess the general condition of teeth, dentition, and oral hygiene.
• X-ray examination: X-rays reveal the morphology of tooth roots and root canals, aiding in further diagnosis.

TREATMENT

Which department should I visit for double teeth deformity?

Dentistry.

Does double teeth deformity require hospitalization?

No.

How is double teeth deformity treated?

• Fused teeth:

  • If the morphology is relatively normal or without major abnormalities, the patient has good dental maintenance awareness, and it does not affect the dentition, no treatment may be necessary;

  • If the morphology is abnormal, or there are grooves, ridges at the fusion site, or varying degrees of localized separation at the incisal edge, which can easily retain food and eventually lead to caries while also affecting aesthetics, early pit and fissure sealing or light-cured resin restoration is recommended. The treatment effect at this stage is good, similar to regular tooth filling, without affecting function or aesthetics;

  • If it is a fused deciduous tooth in the anterior region, its abnormal morphology and function may cause abnormal eruption of the successor permanent tooth. In this case, regular X-ray monitoring is advised for the child. Once the successor permanent tooth is due to erupt but the fused tooth remains retained, extraction should be considered to provide sufficient space and time for the eruption of the successor permanent tooth while ensuring its health.

• Concrescence: Concrescent teeth have more grooves and ridges in morphology, making them more prone to food debris accumulation and eventual caries if brushing is inadequate or there are blind spots. Therefore, based on the fusion characteristics of the crown and root, separation is required to preserve the functional tooth, remove the non-functional half, perform vital pulp therapy or root canal treatment if the pulp is exposed, followed by subsequent crown restoration or orthodontic treatment to close the gap.

• Gemination: The treatment is similar to concrescence. When normal function is affected, removal of the non-functional half and restoration are recommended, with good repair outcomes.

DIET & LIFESTYLE

What should patients with double tooth deformity pay attention to in their diet?

Double tooth deformity mainly involves abnormal tooth morphology, which can easily lead to food retention and difficulty in cleaning. Therefore, if manual dexterity is poor and teeth cannot be cleaned effectively, it is recommended to consume less sugary and sticky foods and minimize the intake of carbonated beverages.

What should patients with double tooth deformity pay attention to in daily life?

Maintain oral hygiene, rinse the mouth after meals, brush teeth correctly and effectively morning and night, and undergo regular dental check-ups.

PREVENTION

Can double teeth malformation be prevented?

Based on the causes of double teeth malformation, it primarily results from abnormalities during tooth germ development and cannot be prevented. However, fused teeth may occur due to external forces, so avoiding external pressure is advisable. If double teeth malformation is detected, early examination and appropriate treatment at a dental clinic are recommended.