What Are the Developmental Disturbances According to the Number of Teeth?
The developmental disturbances of our teeth would be associated with varying clinical presentations. These disturbances pertaining to the number would be associated primarily with either a change in the number of teeth present in the primary or permanent dentition. These conditions or developmental anomalies may usually range from the absence of all teeth (anodontia) to having more teeth than the average number of teeth (hyperdontia).
What Is Dental Agenesis?
Some dentists may also use the term "dental agenesis," which is attributed to the failure to develop all or some part of the enamel organ during the embryogenesis phase (failure to develop during embryonic growth). Mild cases of dental agenesis are usually noticed later in life until the second decade of life (10 to 20 years for young adults and adolescents). Some forms of dental agenesis are, however, devastating or debilitating in terms of poor esthetics and functionality to the suffering individual resulting in a poor or meek quality of life.
What Are the Different Types of Developmental Disturbances According To the Number of Teeth?
1. Anodontia: The condition where there may be a complete failure of the dentition to develop.
2. Hypodontia: This condition is characterized by the absence ranging from only one tooth to a maximum of six teeth.
3. Oligodontia: This is the condition specifically referring to the absence of more than six teeth in the human dentition.
4. Hyperdontia: This is a developmental anomaly that manifests with an increased number of teeth than the teeth present in the normal dentition. In other words, it is characterized by the presence of one or more additional teeth in the oral cavity.
What Causes Dental Agenesis?
Agenesis of teeth may often be attributed to certain syndromes that markedly manifest with the absence of a single tooth or to the probable failure of all the teeth in an arch or both arches (maxillary and mandibular arches) to develop. Research indicates that mutations within certain signaling pathways during embryogenesis (the beta-catenin pathway) may trigger gene mutations in seven different genes, which include AXIN2 (axis inhibition protein 2), EDA (anhidrotic ectodermal dysplasia gene), WNT10A (Wingless-related integration site 10A), WNT10B (Wingless-related integration site 10B), PAX9 (paired box gene 9), LRP6 (low-density lipoprotein receptor-related protein 6), and MSX1 (Msh Homeobox 1) in non-syndromic conditions associated with dental agenesis.
Milder cases of dental agenesis that manifest only with selected teeth in an individual can still be typically restored by the dentist through non-invasive measures.
In terms of agenesis, the different classifications or definitions for anodontia, hypodontia, oligodontia, and hyperdontia are as follows:
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Anodontia is the complete agenesis (absence) of the dentition.
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Hypodontia is the agenesis of lesser than six teeth failing to develop.
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Oligodontia is the dental agenesis of six or more teeth failing to develop.
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Hyperdontia is defined by the dental literature as rather a supernumerary tooth or tooth structure that appears in addition to the normal or the regular number of teeth present in the maxillary and mandibular dental arches.
What Is the Differential Diagnosis of Developmental Disturbances According to the Number of Teeth?
Although these different developmental anomalies (anodontia, hypodontia, and oligodontia) may be rooted in the same causative or etiologic factors, the appearance or manifestation of each condition mainly depends on the severity or extent of the underlying cause. The suggested etiology for the failure of teeth has multiple hypotheses in the dental literature. They would be majorly caused because of fifteen specific genes in non-syndromic cases. The term syndromic hypodontia is used when dental agenesis is associated with a syndrome, as seen in the condition called ectodermal dysplasia. Similarly, orofacial clefting is a pathologic condition that is associated with either the displacement or rampant failure of the development of one or more teeth in the arch and should be considered a differential diagnosis.
In severe cases, when multiple teeth remain unerupted in a child or young adolescent, either in the primary or the permanent dentition phase, they would be linked to varying syndromes. In a few syndromes like cleidocranial dysplasia, an excess number of teeth may also be present. This condition is also a rare congenital skeletal form of dysplasia that follows an autosomal dominant inheritance pattern that should be considered as a differential diagnosis by the dentist.
Other syndromes associated with multiple or redundant teeth are trichorhinophalangeal syndrome and Gardner syndrome.
How Is the Dental Agenesis Condition Managed?
Hyperdontia or an extra number of teeth can generally be managed by surgical extraction, especially if the supernumerary tooth presents the patient with just periodontal, restorative, or other concerns like difficulty chewing or biting food (masticatory concerns). In the case of hypodontia, where a specific set of teeth are missing, there would be several restorative options to be considered. These treatment options range from substitution for a single missing tooth to fixed prosthodontic appliances or bridges, and in patients older than 18 years, dental implants can be considered. With multiple missing teeth, however, the treatment modalities can become definitely more complicated and invasive by the dental surgeon.
Extensive hypodontia or hyperdontia is both extreme conditions associated with common oral manifestations. Hence as elaborated above, these patients should be further evaluated for underlying syndromic or systemic conditions to confirm before proceeding ahead with the treatment strategy. The clinician would preliminarily also require appropriate radiographic imaging, preferably panoramic (orthopantomogram) or three-dimensional imaging like CBCT (cone-beam computed tomography systems), to assess the extent of hypodontia or hyperdontia accurately. After this imaging, the dentist would determine the appropriate course of treatment for these patients.
Conclusion:
Developmental disturbances in the number of teeth like in dental agenesis or even excess number of teeth as in hyperdontia are oral conditions that require multiple appointments as well as complex prosthetic and functional rehabilitation by the dental surgeon to restore the patient's functional esthetics and masticatory efficiency.
