Continuing Education Activity

Malocclusion often develops when a child begins transitioning into mixed dentition. Malocclusion can cause speech problems, difficulty eating, changes in facial structure, and tongue and cheek biting. Since there is no known etiology behind malocclusion, an interprofessional team approach is crucial to allow for an earlier diagnosis. Diagnosis is standardized with the use of classification systems and radiographs. Orthodontists use several methods to treat malocclusion, including palatal expanders, spacers, braces, and clear aligners. This activity defines and distinguishes the different types of malocclusion seen in orthodontics and highlights the role of the interprofessional team in diagnosing and utilizing various techniques to treat malocclusion.

Objectives:

• Understand the pathophysiology of malocclusion.
• Describe the etiology behind malocclusion.
• Identify the different classes of malocclusion.
• Apply best practices when treating malocclusion.

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Introduction

Orthodontics seeks to achieve esthetic and functional improvement via mechanical therapy that moves teeth into a more ideal position. Determining the ideal dental position for each patient depends on several factors, including facial profile, facial balance, and aesthetic concerns.[1] In addition to facial problems, orthodontics looks to improve the relationship between the maxillary and mandibular teeth when they come together and function. The biological and functional coordination of how teeth come together is termed occlusion. Over the years, a consensus has emerged on which features are considered ideal or normal occlusions.[2] However, it is uncommon to find individuals who exhibit the characteristics of ideal occlusion without orthodontic treatment. Morphological differences in tooth shape and size, and sagittal positions of the maxilla and mandible create a plethora of occlusions that an individual can display. Only 8% of cases of malocclusion have a known cause. The remaining 92% have unknown etiology but likely result from environmental and genetic factors.[3]

Classification of Malocclusion

Acknowledged as the "father of modern orthodontics," Dr. Edward Hartley Angle established 3 classes of malocclusion according to the position of the mesiobuccal cusp of the upper first molar concerning the buccal groove of the lower first molar. Angle class I molar classification (also known as neutroclusion) is determined by the mesiobuccal cusp of the maxillary first molar occluding with the buccal groove of the mandibular first molar. A class II molar classification (mesoclusion) is determined by the mesiobuccal cusp of the maxillary first molar, occluding mesial to the buccal groove of the mandibular first molar. Lastly, a class III molar classification is determined by the mesiobuccal cusp of the maxillary first molar occluding distal to the buccal groove of the mandibular first molar (distoclusion).[4]

Class I malocclusion is further categorized into 3 types by Dewey. In Dewey type 1, the incisors are crowded, the canines are positioned labially, or both.[5] In Dewey type 2, the maxillary incisors protrude. In type 3, the anterior teeth occlude edge to edge, or there is a crossbite, or both.[5] The Anderson classification further categorizes class I malocclusion into types 4 and 5. In type 4, there is a posterior crossbite, which could be unilateral or bilateral. Type 5 occlusion is a class I molar relationship with mesioversion of the permanent first molar due to the extraction of a second deciduous molar or premolar.[6] 

Around 32% of individuals with malocclusion have a class II. A class II molar relationship occurs when the mandible is retrognathic relative to the maxilla. Class II interarch relationship is categorized into 2 divisions. A Class II division 1 is when the maxillary incisors are protruded with an excessive overjet and deep overbite. The maxillary arch is often V-shaped, narrow in the canine region, and broad between the molar regions. Patients with a class II molar relationship, division 1, have a shorter upper lip and often fail to close their anterior lip. A class II division 2 is when the maxillary central incisors are palatally inclined and may be overlapped by the maxillary lateral incisors. A deep overbite and a broad maxillary arch define a class II division 2. There is a normal upper lip seal and a deep mental groove. Unlike Division 1, Division 2 has a normal-sized mandible.[7]

A Class III molar relationship occurs when the mandible is positioned anterior to the maxilla. Mandibular teeth protrude over the maxillary teeth. Class III malocclusion is distinguished by the alignment of teeth into 3 types. In class 3 type 1, the arch is abnormally shaped. In class 3 type 2, the mandibular teeth are tilted lingually. In class 3 type 3, the maxillary teeth are tilted lingually.[8]

Ackerman and Profitt's classification system for malocclusion is used to classify and describe different types of misalignment of the teeth and jaws. It is based on Angle classification. In Ackerman and Profitt's classification system, malocclusion is divided into classes I, II, III, IV, V, and VI. These categories are based on the relationship between the maxillary and mandibular teeth and the jaw position.

• Class I: The maxillary teeth are slightly forward of the mandibular teeth, and the jaw is aligned properly.
• Class II: The maxillary teeth are significantly forward of the mandibular teeth, and the jaw is underdeveloped.
• Class III: The mandibular teeth are significantly forward of the maxillary teeth, and the jaw is overdeveloped.
• Class IV: The maxillary teeth are significantly behind the mandibular teeth.
• Class V: The maxillary teeth are significantly forward of the mandibular teeth, and the jaw is overdeveloped.
• Class VI: The mandibular teeth are significantly behind the maxillary teeth.[9]

Several skeletal causes of malocclusion may require surgery. These include jaw discrepancies, facial asymmetry, cleft lip and palate, and craniofacial abnormalities. Additionally, although much less common, facial or jaw injuries can cause malocclusion. It is important to note that surgical treatment of malocclusion is typically only recommended in severe cases, and other treatment options, such as braces, may be tried first. A thorough evaluation by an orthodontist or oral and maxillofacial surgeon is needed to determine the most appropriate treatment approach.[10]

Etiology

The etiology of malocclusion is often multifactorial, mainly influenced by genetic and environmental factors. Inherited factors are also believed to be involved, but their exact role is yet to be fully understood. While most cases of malocclusion have unknown etiology, the correlation between genetics and malocclusion has been studied extensively. Data suggests that a specific malocclusion, Class III mandibular prognathism, is passed down through generations via specific growth factors and genetic markers. Dating back to the 1300s, the heritability pattern of mandibular prognathism is evident in the European royal Habsburg family. Nicknamed the “Habsburg Jaw,” interbreeding among family members allowed the genes encoding mandibular prognathism to be expressed across multiple generations.[11]

Inherited characteristics can also influence malocclusion. More specifically, a disproportionate relationship between tooth and jaw size can cause crowding or spacing. A disproportion in the size or shape of the maxilla and mandible can also cause malocclusion. The size and shape of teeth and jaws can be inherited together or independently. Studies have shown that the more independently these characteristics are inherited, the more likely there is to be a malocclusion disproportion. Compared with earlier generations, malocclusion has become more prevalent as outbreeding between distinct human populations has increased. This can be attributed to the fact that these populations inherit discordant characteristics of teeth and jaws.[12]

Environmental factors can also play a role in the development of malocclusion. This is often seen in children who habitually suck on their thumbs. When pressure is placed against the roof of the mouth, the lower incisors and maxillary molars are pushed lingually, and the upper incisors are pushed labially. Furthermore, the jaw is positioned downward, allowing posterior teeth to erupt and resulting in the separation of the incisors.[13]

Epidemiology

Malocclusion is often developed when a child begins transitioning into mixed dentition. Overall, there is no significant difference between males and females. However, female dental eruption and maturation tend to occur faster than in males. Therefore, it is common for females to receive orthodontic treatment before males.[14] Studies have shown that the black population has malocclusions more frequently. However, there is no genetic evidence supporting this.[15]

Pathophysiology

Loss of permanent teeth and hypodontia can shift an otherwise ideal occlusion. Hypodontia may be caused by trauma or a lack of tooth development. For instance, the loss of a maxillary tooth can allow the eruption of the opposing mandibular tooth into the opposing edentulous space. The adjacent teeth may also tip or shift to the empty space.[16] Impacted teeth characteristically remain under the gingival tissue and do not erupt into their ideal position. Impacted teeth can be a significant cause of malocclusion, leading to the shifting of adjacent teeth. When impacted teeth do not erupt into the dental arch, additional space exists for adjacent teeth to shift into, which can hinder their eruption later. Impacted third molars are often encountered during adolescence or early adulthood and may interfere with occlusion if not extracted or exposed.[17]

History and Physical

The following qualities define an ideal occlusion: class I molar and canine classification, 1- to 2-mm overjet, 1- to 2-mm overbite, slight to no crowding, and protective guidance movements. Furthermore, the incisal edges and buccal cusps of the teeth in the mandibular arch should align to form a smooth curve. Likewise, the smooth curve in the maxilla encompasses the central fossae of posterior teeth and the cingulum of the canines and incisors. Other ideal qualities include alignment of the maxillary and mandibular midlines with each other and the face. Angle class I is present in around 60% of the affected population and is the most common molar relationship. Depending on the case, symptoms of malocclusion can vary from mild to severe. Notable signs of malocclusion include misaligned teeth, speech problems, decreased masticatory function and efficiency, alteration from nasal to mouth breathing, and changes in facial structure.[18]

Evaluation

The patient's primary dental provider often evaluates malocclusion. The primary dental provider may be a general dentist, pediatric dentist, or orthodontist. Referrals to the orthodontist are made for patients with malocclusions that may adversely affect their dental health and quality of life. A simple oral evaluation is the most common way to diagnose malocclusion; however, radiographs help to evaluate further. Extraoral radiographs, such as panoramic and cone-beam computed tomography, are common imaging modalities used to examine patients.[19] 

Each imaging method allows the clinician to determine the position of the teeth and evaluate whether they are emerging at the right time and in the right place within their respective jaws. A CBCT image is beneficial in several ways, especially as it provides a 3-dimensional view of the entire face. This allows for a more accurate diagnosis of the malocclusion and permits analysis of a patient's airway and temporomandibular joint.[20] One such radiograph unique to orthodontics is the cephalometric projection. The cephalometric projections capture a lateral image of the face, allowing relationships between the skull and the jaws to be determined. These projections can also help orthodontists predict a patient's dental age and growth potential, and highlight sagittal discrepancies, all of which can aid treatment planning.[21]

Treatment / Management

There are several methods to treat malocclusion. Palatal expanders are traditionally used before braces treatment to treat a narrow palate, crowding, or crossbite. Rapid palatal expansion (RPE) works by placing a force on the 2 maxillary bones to split the mid-palatal suture. Palatal expanders are most useful during adolescence, as the maxillary bones become fused during puberty. The expander contains a screw turned daily or as directed by the patient's orthodontist. Every turn places pressure on the maxillary bone, allowing only 1 mm or less of expansion.[22]

Spacers can be used before or during orthodontic treatment to increase interproximal space. Spacers are normally utilized between molars if there is not enough space for metal bands to be placed around them. Spacers can be made of different materials depending on how long they need to remain in the mouth. Rubber spacers are traditionally used for 1 to 2 weeks and normally fall out once the space is adequate. Metal spacers are commonly used for more than 6 weeks but can also be used for short-term space management.[23]

The traditional way to treat malocclusion is with braces. There are several types of braces made with different materials. Two of the more notable types are metal and ceramic braces. Traditional metal braces consist of brackets placed on the teeth that need correction and an archwire that holds the brackets together. When tightened, the archwire applies pressure to the brackets, helping align and straighten the teeth. Ceramic braces are the same as metal braces except that they come in an enamel-like color, so that the braces are less noticeable. Brackets can also be made out of stainless steel and gold.[24] For patients concerned with esthetics, lingual braces can be placed. Lingual braces are essentially the same as traditional braces, except the brackets are placed on the lingual surfaces of teeth as opposed to the buccal surfaces.[25]

Over the past few years, clear aligners have become increasingly popular, especially in adult patients. Clear aligners utilize CAD/CAM technology to digitally scan the dental arches to create clear, removable trays. Clear aligner treatment uses multiple sets of aligners, each for a different stage of treatment. Patients wear each stage tray for 1-2 weeks, depending on the orthodontist's treatment plan.

Clear aligner treatment is ideal for patients who cannot have many in-person appointments or are concerned with aesthetics. Unfortunately, there are drawbacks to clear aligner treatment, including patient compliance and case severity. Patients are instructed to wear clear aligners for at least 22 hours daily to ensure optimal tooth straightening. Additionally, if malocclusion is too severe, clear aligners are not recommended; traditional braces are usually suggested.[26] While various methods have been proven effective in treating malocclusion, newer technologies are still being tested to improve treatment effectiveness and efficiency. Perhaps in the near future, the use of low-level laser therapy for orthodontic movement, for example, may become a common practice in orthodontic offices.[27]

Differential Diagnosis

Potential causes of malocclusion may be considered in the differential diagnosis. Malocclusion can be inherited or caused by the genes one inherits from their parents. Additionally, certain habits, such as thumb sucking or prolonged pacifier use, can cause malocclusion. Skeletal abnormalities, such as abnormalities in the shape or size of the jaw or face, can cause malocclusion. Lastly, missing teeth, inadequate space, and trauma can cause malocclusion. To determine the cause of malocclusion, a thorough evaluation by an orthodontist is typically necessary. This may include taking a medical history, performing a physical examination, and ordering imaging tests such as panoramic radiographs. Based on the results of this evaluation, a diagnosis and treatment plan can be developed.[28]

Prognosis

Each case of malocclusion treatment is variable, depending on the severity, patient compliance, the amount of space available in both jaws, and the patient's overall oral health.[29]

Complications

Complications of untreated malocclusion include tooth decay and increased caries, as crowding can trap food and make it harder for the patient to clean interproximally. Additionally, gingivitis may develop due to plaque buildup. Malocclusion can also cause tooth loss, impacted teeth, jaw problems, and damage to adjacent and opposing teeth.[30]

Deterrence and Patient Education

Malocclusion can be diagnosed through visual and radiographic examinations of the teeth and face. If a malocclusion occurs, the patient is often referred to an orthodontist. Routine dental appointments can enable an early diagnosis of malocclusion, enabling early treatment. Malocclusion is often hereditary, so it is hard to prevent it. However, parents can prevent environmental factors that can cause malocclusion early on. Such measures include limiting thumb sucking and stopping bottle and pacifier usage early on.[31]

Enhancing Healthcare Team Outcomes

The management and treatment of malocclusion require an interprofessional team of dental healthcare professionals, including, but not limited to, general dentists, dental hygienists, orthodontists, and oral surgeons. An interprofessional team approach to treating malocclusion enables earlier diagnosis during routine oral hygiene appointments with a general dentist and a dental hygienist. If a malocclusion is too severe to be treated by a general dentist, a referral can be made for the patient to seek treatment by an orthodontist. In cases of malocclusion requiring surgical treatment, an oral surgeon can work with the orthodontist to correct the misaligned jaw utilizing orthognathic surgery.[32] 

Dental hygienists and general dentists play a critical role in monitoring patients' oral health and, when applicable, disease status. Many patients who receive traditional braces have a tougher time practicing proper oral hygiene. One of the most commonly neglected sites is the interproximal posterior areas of dentition. Gingivitis may develop if plaque builds up over time in the patient's supragingival and subgingival pockets. Depending on the severity of the disease, oral hygiene instruction and prophylaxis, or scaling and root planing, may need to be performed by the dentist or a dental hygienist.[33]

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Disclosure: Rea Ghodasra declares no relevant financial relationships with ineligible companies.

Disclosure: Melina Brizuela declares no relevant financial relationships with ineligible companies.