Tooth fusion

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Tooth fusion [also known as syndontia or double teeth] occurs when two separate tooth germs fuse to form one tooth. [1] The fusion may be complete (involves crown and root) or partial (involves only the crown), depending on the stage of tooth development when the teeth started to fuse. Tooth fusion is difficult to distinguish from tooth gemination, thus, both conditions are often referred to together as “double teeth”. [1]

Contents

Double teeth can cause other dental problems such as crowding, ectopic eruption of adjacent teeth, gum issues, cavities, malocclusion, poor esthetics, and more. [1] Treatment depends on whether the tooth is a primary or permanent tooth, the degree of fusion, and its functional & esthetic impact. [2]

Diagnostic features

Clinical

Double formations, joined teeth, dental twinning or double teeth are more common in primary teeth with a prevalence of 0.5 - 0.7%, but can occur in permanent teeth. [1] Unlike tooth gemination, tooth fusion is more common in the mandibular incisors. [3] [4] [5] Like tooth gemination, tooth fusion is more common in the anterior teeth (incisors and canines). Double teeth affect both sexes equally and some studies report higher occurrence in Asian and Indigenous populations. [4] [2] If a double tooth is present, then there may be a higher chance of other dental anomalies (see Related Abnormalities section). [1] [5]

Double teeth are usually larger than normal teeth, may have an incisal notch present on the crown of the tooth, and may have a groove/fold in the enamel on the labial surface that can extend further down the root. In fused teeth, this groove may not symmetrically divide the tooth in half if one of the fused teeth is abnormally shaped or an extra tooth. [4] [6]

Mader’s “two-tooth” rule can help distinguish between tooth fusion and gemination. If the double tooth is counted as two teeth and the number of teeth in the mouth is normal, then the double tooth is likely a fused tooth. However, in some rare cases a tooth is fused to an extra tooth in which case counting the double tooth as two teeth will result in an increased number of teeth in the mouth. [1]

Radiographic

Fused teeth tend to have separate pulp chambers and root canals, unlike in tooth gemination which tends to have a single pulp chamber and root canal. However, the degree of separation will depend on where & when the fusion occurred so the pulp chamber and/or root canal may be completely fused into one. [1] [7]

Disease mechanism

Tooth fusion occurs when at least the dentin of developing tooth germs fuse. When only the cementum (root portion) of teeth is fused, this is known as concrescence. [4]

The exact cause of tooth fusion is unknown, but is the result of alterations in embryonic tooth development. Environmental (e.g. trauma, thalidomide exposure, hypervitaminosis A of the mother, viral infections), systemic, and genetic factors can cause formation of double teeth. [1] [8] [6] While the specific pathophysiology of double teeth is difficult to determine, many purport it is due to force that brings tooth germs close together during development with necrosis of the tissue separating them allowing for the enamel organ and dental papilla to unite. [1] [3] [9] [10] The extent of fusion depends on when during tooth development this union occurs.

Treatment and management

Whatever the cause of the double tooth (fusion or gemination), management depends on the morphology of the crown, root, & endodontic system, the type of dentition (primary or  permanent), and the orthodontic (e.g. crowding, malocclusion, ectopic eruption or impaction of adjacent teeth), periodontal, esthetic, & other functional concerns. [1]

If the double tooth will have little impact functionally or esthetically, then it can be monitored with an emphasis on oral hygiene and prevention (e.g. topical fluoride). [1] [2]

The groove present on the enamel of double teeth can increase  caries-risk and depending on how far the groove extends down the root even gum issues. [1] Thus, if possible this groove can be sealed to decrease caries-risk. [7] [11]

As double teeth are large and tend to be in the visible anterior teeth, one may consider altering their shape to improve esthetics. The tooth can be selectively grinded to achieve a more esthetic shape. A dental crown may even be placed to achieve this. If the two teeth have separate root systems, then they can be cut in half, however,  root canal treatment may be needed. Alternatively, instead of cutting the tooth in half and leaving both teeth, one of the double teeth can be removed after splitting the tooth structure. This too may require root canal treatment and/or reshaping of the tooth that is not removed. In the previous scenarios, if the double tooth is separated without doing root canal treatment, then root canal treatment may be needed in the future as connections may exist between the root systems of double teeth even if they appear separate on an x-ray. Finally, the double tooth could be removed and the space replaced by autotransplantation of another tooth or closing the space using braces. [1]

Tooth fusion
Milk.teeth.fusion.jpg
The fusion of two deciduous teeth.
Specialty Dentistry

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<span class="mw-page-title-main">Crown (dental restoration)</span> Dental prosthetic that recreates the visible portion of a tooth

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Hypodontia is defined as the developmental absence of one or more teeth excluding the third molars. It is one of the most common dental anomalies, and can have a negative impact on function, and also appearance. It rarely occurs in primary teeth and the most commonly affected are the adult second premolars and the upper lateral incisors. It usually occurs as part of a syndrome that involves other abnormalities and requires multidisciplinary treatment.

<span class="mw-page-title-main">Human tooth development</span> Process by which teeth form

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<span class="mw-page-title-main">Malocclusion</span> Misalignment between upper and lower teeth as the jaws close

In orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. The English-language term dates from 1864; Edward Angle (1855–1930), the "father of modern orthodontics", popularised it. The word derives from mal- 'incorrect' and occlusion 'the manner in which opposing teeth meet'.

<span class="mw-page-title-main">Maxillary central incisor</span> Tooth

The maxillary central incisor is a human tooth in the front upper jaw, or maxilla, and is usually the most visible of all teeth in the mouth. It is located mesial to the maxillary lateral incisor. As with all incisors, their function is for shearing or cutting food during mastication (chewing). There is typically a single cusp on each tooth, called an incisal ridge or incisal edge. Formation of these teeth begins at 14 weeks in utero for the deciduous (baby) set and 3–4 months of age for the permanent set.

Dilaceration is a developmental disturbance in shape of teeth. It refers to an angulation, or a sharp bend or curve, in the root or crown of a formed tooth. This disturbance is more likely to affect the maxillary incisors and occurs in permanent dentition. Although this may seem more of an aesthetics issue, an impacted maxillary incisor will cause issues related to occlusion, phonetics, mastication, and psychology on young patients.

<span class="mw-page-title-main">Concrescence</span> Medical condition

Concrescence is an uncommon developmental condition of teeth where the cementum overlying the roots of at least two teeth fuse together without the involvement of dentin. Usually, two teeth are involved with the upper second and third molars being most commonly fused together. The prevalence ranges 0.04–0.8% in permanent teeth, with the incidence being highest in the posterior maxilla.

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Dens evaginatus is a rare odontogenic developmental anomaly that is found in teeth where the outer surface appears to form an extra bump or cusp.

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Dental anatomy is a field of anatomy dedicated to the study of human tooth structures. The development, appearance, and classification of teeth fall within its purview. Tooth formation begins before birth, and the teeth's eventual morphology is dictated during this time. Dental anatomy is also a taxonomical science: it is concerned with the naming of teeth and the structures of which they are made, this information serving a practical purpose in dental treatment.

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<span class="mw-page-title-main">Enamel hypoplasia</span> Lack of tooth enamel

Enamel hypoplasia is a defect of the teeth in which the enamel is deficient in quantity, caused by defective enamel matrix formation during enamel development, as a result of inherited and acquired systemic condition(s). It can be identified as missing tooth structure and may manifest as pits or grooves in the crown of the affected teeth, and in extreme cases, some portions of the crown of the tooth may have no enamel, exposing the dentin. It may be generalized across the dentition or localized to a few teeth. Defects are categorized by shape or location. Common categories are pit-form, plane-form, linear-form, and localised enamel hypoplasia. Hypoplastic lesions are found in areas of the teeth where the enamel was being actively formed during a systemic or local disturbance. Since the formation of enamel extends over a long period of time, defects may be confined to one well-defined area of the affected teeth. Knowledge of chronological development of deciduous and permanent teeth makes it possible to determine the approximate time at which the developmental disturbance occurred. Enamel hypoplasia varies substantially among populations and can be used to infer health and behavioural impacts from the past. Defects have also been found in a variety of non-human animals.

<span class="mw-page-title-main">Dental trauma</span> Medical condition

Dental trauma refers to trauma (injury) to the teeth and/or periodontium, and nearby soft tissues such as the lips, tongue, etc. The study of dental trauma is called dental traumatology.

<span class="mw-page-title-main">Running room</span> Dentistry terminology

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Tooth ankylosis refers to a fusion between a tooth and underlying bony support tissues. In some species, this is a normal process that occurs during the formation or maintenance of the dentition. By contrast, in humans tooth ankylosis is pathological, whereby a fusion between alveolar bone and the cementum of a tooth occurs.

Anterior teeth are some of the most scrutinized teeth, as the size, shape and color of the anterior upper teeth plays an important role in dental aesthetics and smile aesthetics. A few aesthetic anterior problems, such as dental caries, tooth fracture, enamel defects and diastemas, can be solved with composite restorations. Composite restorations can also improve dental aesthetics by changing the shape, color, length and alignment of teeth.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 Mamdani, Sajida; Pathak, Divya; Harrison, Mike; Bhujel, Nabina (2023-03-10). "Macrodontia and double teeth: a review and case series". British Dental Journal. 234 (5): 315–321. doi:10.1038/s41415-023-5571-9. ISSN   0007-0610.
  2. 1 2 3 White SC, Pharoah MJ (2014). "Chapter 21". Oral Radiology: Principles and interpretation (8th ed.). Elsevier.
  3. 1 2 Scheid RC, Weiss G (2017). Scheid, R. C., & Weiss, G. (2017). Woelfel's dental anatomy (Enhanced ninth edition.). Jones & Bartlett Learning. Chapter 11. Woelfel’s dental anatomy (Enhanced ninth edition.). Jones & Bartlett Learning. Chapter 11.
  4. 1 2 3 4 Neville BW, Damm DD, Allen CM, Chi AC (2016). "Chapter 2". Oral and maxillofacial pathology (4th ed.). Elsevier.
  5. 1 2 Hattab, Fn. (2014). "Double talon cusps on supernumerary tooth fused to maxillary central incisor: review of literature and report of case" (PDF). Journal of Clinical and Experimental Dentistry: e400–7. doi:10.4317/jced.51428.
  6. 1 2 Nandini, D.B (2014). "Diagnostic Dilemma of a Double Tooth: A Rare Case Report and Review". Journal of Clinical and Diagnostic Research. doi:10.7860/jcdr/2014/6556.3928. ISSN   2249-782X. PMC   3939503 .
  7. 1 2 Bernardi, Sara; Bianchi, Serena; Bernardi, Guglielmo; Tchorz, Jörg Philipp; Attin, Thomas; Hellwig, Elmar; Karygianni, Lamprini (2020-08-17). "Clinical management of fusion in primary mandibular incisors: a systematic literature review". Acta Odontologica Scandinavica. 78 (6): 417–424. doi:10.1080/00016357.2020.1734233. ISSN   0001-6357. PMID   32125202.
  8. ↑ Tuna EB, Yildirim M, Seymen F, Gencay K, Ozgen M (July 2009). "Fused teeth: a review of the treatment options. J Dent Child (Chic)". J Dent Child (Chic). 76 (2). American Academy of Pediatric Dentistry: 109–16. PMID   19619423.
  9. ↑ Hülsmann, M.; Bahr, R.; Grohmann, U. (December 1997). "Hemisection and vital treatment of a fused tooth – literature review and case report". Dental Traumatology. 13 (6): 253–258. doi:10.1111/j.1600-9657.1997.tb00051.x. ISSN   1600-4469.
  10. ↑ Knezević, A.; Travan, S.; Tarle, Z.; Sutalo, J.; Janković, B.; Ciglar, I. (December 2002). "Double tooth". Collegium Antropologicum. 26 (2): 667–672. ISSN   0350-6134. PMID   12528297.
  11. ↑ Tewari, N; Pandey, Rk (2011). "Bilateral fusion in primary mandibular teeth: A report of two cases". Journal of Indian Society of Pedodontics and Preventive Dentistry. 29 (1): 50. doi: 10.4103/0970-4388.79936 . ISSN   0970-4388.
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