Anterior Open Bite Malocclusion: From Clinical Treatment Strategies towards the Dissection of the Genetic Bases of the Disease Using Human and Collaborative Cross Mice Cohorts

Abstract

Anterior open bite malocclusion is a complex dental condition characterized by a lack of contact or overlap between the upper and lower front teeth. It can lead to difficulties with speech, chewing, and biting. Its etiology is multifactorial, involving a combination of genetic, environmental, and developmental factors. Genetic studies have identified specific genes and signaling pathways involved in jaw growth, tooth eruption, and dental occlusion that may contribute to open bite development. Understanding the genetic and epigenetic factors contributing to skeletal open bite is crucial for developing effective prevention and treatment strategies. A thorough manual search was undertaken along with searches on PubMed, Scopus, Science Direct, and Web of Science for relevant studies published before June 2022. RCTs (clinical trials) and subsequent observational studies comprised the included studies. Orthodontic treatment is the primary approach for managing open bites, often involving braces, clear aligners, or other orthodontic appliances. In addition to orthodontic interventions, adjuvant therapies such as speech therapy and/or physiotherapy may be necessary. In some cases, surgical interventions may be necessary to correct underlying skeletal issues. Advancements in technology, such as 3D printing and computer-assisted design and manufacturing, have improved treatment precision and efficiency. Genetic research using animal models, such as the Collaborative Cross mouse population, offers insights into the genetic components of open bite and potential therapeutic targets. Identifying the underlying genetic factors and understanding their mechanisms can lead to the development of more precise treatments and preventive strategies for open bite. Here, we propose to perform human research using mouse models to generate debatable results. We anticipate that a genome-wide association study (GWAS) search for significant genes and their modifiers, an epigenetics-wide association study (EWAS), RNA-seq analysis, the integration of GWAS and expression-quantitative trait loci (eQTL), and micro-, small-, and long noncoding RNA analysis in tissues associated with open bite in humans and mice will uncover novel genes and genetic factors influencing this phenotype.

Keywords: Collaborative Cross mice; etiology; malocclusion; open bite; treatment.

Figure 1

Overbite denotes the vertical alignment or the space between the upper central incisor of the maxilla and the corresponding central incisor of the mandible. (A) A normal or physiological overbite typically measures about 2–3 mm. (B) An open bite refers to a reduced overbite, usually measuring less than 0 mm. (C) Open bite combined with a Class I dental relationship. (D) Open bite in association with a Class II dental relationship. (E) Open bite in connection with a Class III dental relationship.

Figure 2

Various categories of open bites exist, and a visual representation in the form of a diagram can help elucidate these distinctions.

Figure 3

A schematic depiction of the vertical dimension illustrates a physiological overbite (A) and a skeletal open bite (B). (A) In a physiological vertical dimension, there is a balanced relationship between the upper facial height (UFH 50%) and lower facial height (LFH 50%). (B) A skeletal open bite is characterized by an elevated lower facial height (LFH 54%) in comparison to the upper facial height (UFH 46%).

Figure 4

A schematic illustration of the vertical dimension showcases a physiological overbite (A) and a dentoalveolar open bite (B). (A) In a physiological vertical dimension, there exists a harmonious relationship between the upper facial height (UFH 50%) and lower facial height (LFH 50%). (B) A dentoalveolar open bite occurs due to the infraocclusion or protrusion of the front teeth, maintaining a balanced relation between the upper facial height (UFH 50%) and lower facial height (LFH 50%).

Figure 5

A schematic portrayal of the vertical dimension demonstrates a physiological overbite (A) and the coexistence of a skeletal and dentoalveolar open bite (B). (A) In a physiological vertical dimension, there is an equilibrium between the upper facial height (UFH 50%) and lower facial height (LFH 50%). (B) A combined skeletal and dentoalveolar open bite results from the posterior rotation of the mandible and the infraocclusion of the front teeth, leading to an elevated lower facial height (LFH 54%) in contrast to the upper facial height (UFH 46%).

Figure 6

A diagram depicting various treatment approaches for open bite, which can be categorized based on factors such as age, growth stage, causative factors, functional considerations, and aesthetic concerns.

Figure 7

An anterior portion of the dental arches without contact is meant by a malocclusion in this context (A); (B) the posterior teeth in occlusion.

Figure 8

Posterior open bite is the loss of contact between the posterior teeth. Subfigure (A) shows the posterior open bite from first premolar to the second molar, and (B) the same patient shows contact in anterior area, while open in the posterior area.

Figure 9

False (A) or dental (B) open bite. (A–C) During tooth development and tooth eruption. (D–F) After tooth development and complete tooth eruption.

Figure 10

An anterior open bite results from digit sucking. After preventing finger sucking by using a special device, spontaneous closure of the anterior open bite occurred (A–C).

Figure 11

An anterior open bite (A), the upper jaw shape results from thumb sucking during growth (B).

Figure 12

Patient with a temporomandibular joint fracture in the growth phase, the result was ankylosis and growth disorders in the ramus mandible, an open bite developed (A–D).

Figure 13

Patient with an anterior open bite. Due to the narrowed tongue space in the upper jaw and, thus, narrowed airways, there was a developmental disorder of the alveolar bone and the teeth. (A–D) Situation before treatment, (D) shows the narrowed airway. (E–H) The extra-oral and intraoral images after treatment, there was spontaneous bite closure after maxillary expansion. The physiological tongue position led to an expansion of the airways.

Figure 14

Skeletal open bite in a 10-year-old female patient, treated with growth-influencing measures. (A–C) Profile photo shows a long face with a skeletal open bite, which is confirmed intraorally and skeletal or cephalometrically. (D,E) Overdevelopment of the maxilla and alveolar bone resulted in posterior rotation of the mandible and thus posterior displacement of the mandible, resulting in the lower face lengthening. (F–H) treatment results of influencing the growth of the upper jaw in the vertical dimension, a harmonization of function and form, and, thus, a change in aesthetics. (I) Representation of the growth inhibition of the maxilla in the vertical direction, the autorotation of the mandible, and the alteration in position of the mandible.

Figure 15

Skeletal open bite of a 25-year-old patient treated by orthognathic surgery. (A–C) The photograph shows a long face with a skeletal open bite, which is confirmed intraorally and is skeletal or cephalometric. (D,E) To correct the vertical relation, impaction of the maxilla was performed, and the excess bone of the maxilla was reduced. (F) A result of the maxillary action, the mandible autorotates with a change in sagittal and vertical position. (G,H) Simulation of the surgical impaction of the maxilla and the reaction of the mandible as described with cranial and simultaneous ventral autorotation. The greater the impact, the greater the autorotation of the mandible. (I–K) Situation after the treatment. (L) Superposition of the cephalograms pretreatment (black) and posttreatment (red).

Figure 16

Skeletal and dental open bite in a 23-year-old man treated by orthognathic surgery. (A–C) Situation before the treatment, extended lower face due to the skeletal structure. The open bite has additionally strengthened the infra occlusion of the front teeth. (D) During the pre-surgical preparation, part of the open bite was corrected by extruding the front teeth. (E,F) Simulation of the surgical procedure. After impaction of the maxilla, the mandible autorotated with a change in position in the vertical and sagittal planes (E); for the final correction of the skeletal disgnathia, a dorsal displacement of the mandible (F) was carried out. (G,H) Description of maxillary impaction. (I,J) Representation of the surgical adjustment of the mandible for the correction of the position of the mandible. (K–M) Situation after the treatment.

Figure 17

The Skeletal and dental open bite in a 25-year-old patient, treatment is dentoalveolar. It is crucial that the patient does not have any functional or aesthetic disorders extra-orally. (A–C) Situation before the treatment. (D) Presentation of the biomechanics used for ventoalveolar closure of the open bite; extrusion of the front and intrusion of the molars. (E–G) Situation after the treatment.

Figure 18

Dentoalveolar open bite in a 27-year-old patient, the treatment is dentoalveolar. The patient has no extra-oral functional or aesthetic disorders. There were intraoral dental functional and aesthetic disorders. (A–E) Before treatment, the infraocclusion of the front teeth in the upper jaw is clearly visible (E). (F–J) After treatment, to close the open bite, the maxillary front was extruded (J).

Figure 19

Process for creating system genetic datasets using cellular, molecular, and clinical trait data in order to investigate relationships between malocclusion and open bite phenotypes. Using QTL mapping in the CC mouse model and humans, regulatory genomic areas associated in phenotypic variance monitoring characteristics may be discovered by integrating SNP genotype data and RNA expression. The combination of existing data with future candidate gene association studies in people has the potential to find susceptibility genes linked to the development of open bite malocclusion in humans.