Pediatric Dentistry - a Clinical Approach, 3ed.

CHAPTER 21. Occlusal Development, Malocclusions, and Preventive and Interceptive Orthodontics

Bengt Mohlin, Anna Westerlund, Maria Ransjö, and Jüri Kurol

Craniofacial development and growth

Dental occlusion is strongly influenced by the craniofacial development and growth which determine size and relative proportions of the jaws. The craniofacial region is one of the most complex parts of the body. The development and growth of structures in the craniofacial complex is under genetic control and influenced by epigenetic and environmental factors. Not surprisingly, dentofacial deformities, large disproportions between the jaws, and severe discrepancies in occlusion are caused by disturbances in the development and growth [1,2].

Development of the head and face starts early during embryogenesis with interactions between the three germ layers. Formation, migration, and differentiation of the cranial neural crest cells, a multipotent cell population, are critical events in development of the craniofacial region. Expression of specific genes and interactions between signaling pathways regulate the continued development of the neural crest cells. They give rise to most of the bones, connective tissues, and cartilage in the craniofacial region and are also involved in tooth development. Mutations of regulatory genes cause craniofacial anomalies, sometimes associated with disturbed tooth development (see Chapter 4). Nearly a third of all birth defects involve the craniofacial complex [1].

The human face is largely already recognizable after the seventh prenatal week, even if the facial structures are not proportional or completely developed. The fetus has a proportionally large head; at 2 months it is approximately 50% of the body length but the proportions change over time due to differences in growth rate. The relative size of the head compared to the body length is approximately 25% at birth, decreasing to approximately 12% in an adult (Figure 21.1). Also the neurocranium to the face proportions change during the prenatal and postnatal period due to differential growth. The fetus has a large cranium compared to the face and this is also noticeable in the newborn (Figure 21.2). Since growth rates are differential, the neurocranium has nearly completed its growth in 5‐year‐old children while the jaws have reached approximately 50% of adult size [2].

Illustration of the changes in human body proportions during development and growth. It features a human at 2 months, at 4 months, at birth, at 2 years, at 15 years, and at 30 years.

Figure 21.1 Changes in body proportions during development and growth.

(Redrawn from WJ Robbins et al. Growth. Yale University Press 1928, figure 63. Reproduced with permission of Yale University Press.)

Illustration of the changes in proportions of the human head. It features an infant skull (bottom left) and an adult skull (top right).

Figure 21.2 Changes in proportions of the head.

(Redrawn from GH Lowery, Growth and development of children, 6th ed. Chicago: Mosby, 1973. Reproduced with permission of Elsevier.)

The bones in the cranial base are formed by endochondral ossification, starting with initial cartilage models. Cartilage remnants (synchondroses) between the ossification centers are important growth sites in the cranial base. The cranial vault and facial bones (including maxilla and mandible) are formed by direct intramembranous ossification with fibrous sutures being the important sites for bone apposition and remodeling. The sutures and synchondroses between the different craniofacial bones fuse and terminate growth at different times. Premature closure of synchondroses or sutures may cause detrimental defects in growth and development depending on closure time and position [1].

By application of tensile forces it is possible to increase apposition of bone in a suture (before closure). Orthodontists can take advantage of this mechanism, e.g., when treating skeletal cross bites with a rapid maxillary expansion of the midpalatal suture.

General principles discussed in the growth and development of the craniofacial skeleton are displacement, due to growth and remodeling in sutures, and apposition and resorption processes at bone surfaces. Since the maxilla is attached to the anterior cranial base, whereas the mandible is suspended under the middle cranial fossa, growth of the cranial base is of major importance for the intermaxillary relations and, thus, for development of the occlusion. The maxilla is displaced downward and forward in relation to the anterior cranial base by growth and adaptation in the maxillary sutures. The sagittal relation between the jaws is maintained by marked growth of the mandible (Figure 21.2).

Within the framework of this complex facial development, the erupting teeth come into interdigitation. However, individual variability in growth of the cranial base and the jaws is wide and the coordination of development in the various components is not always perfect. This is partly compensated for by dentoalveolar mechanisms.

Occlusal development

Primary dentition

At birth the crowns of the primary teeth have to a great extent been formed, while root development has not yet started (see Chapter 4). Thus, the gum pads are low and the palatal vault is flat. When the jaws are closed there is normally contact only in the posterior region of the gum pads, and the mandible is retruded in relation to the maxilla. During the first year of life, however, the sagittal jaw relationship improves, allowing the incisors to erupt in a normal sagittal relation.

Occlusion in the posterior segments is first established around 16 months of age, when the primary first molars come into occlusal contact. Once a good intercuspidation in all three planes is achieved, the jaws are normally closed to the same position each time and normal development occurs. The established occlusion has a guiding role in the interrelation between the jaws and subsequently for the proper positioning of later erupting permanent teeth (canines and second molars). Further stabilization of the occlusion is achieved by the occlusion of the large mesiopalatal cusps of the maxillary second molars.

With the eruption of primary teeth the alveolar processes develop, and there is a considerable increase in facial height. The growth of the maxillary alveolar process also results in an increase in palatal height. The primary teeth erupt almost perpendicular to the jaw bases. The interincisal angle is approaching 180°, and the occlusal plane is flat. During development, the dentoalveolar segments generally move anteriorly in relation to basal structures of the jaws (Figures 21.2 and 21.3).

Line drawing of the lateral view of a human head. It displays the facial growth in a normal girl from 2 months (dash line) to 5 years and 2 months (solid line) of age.

Figure 21.3 Facial growth in a normal girl from 2 months to 5 years 2 months of age. Superimposition was made on the nasion–sella line registered at sella. Note the magnitude of mandibular growth from a marked retruded position.

The primary dentition is characterized by half‐circular dental arches. The most conspicuous feature is the space surplus in the front region of both jaws, needed later to accommodate the broader permanent front teeth. Especially marked diastemata are often found between the lateral incisors and the canines in the maxilla and the canines and first molars in the mandible. These diastemata are referred to as “primate spaces.” The primary second molars erupt without proximal contact with the primary first molars. However, in most children these molars drift into proximal contact between the third and fourth years of life.

As to the basal relationships of the jaws, young children differ from older children and adults by being more maxillary prognate and mandibular retrognate. At 2 years, the overjet is on average 4 mm, with a range of 2–6 mm. With attrition of the teeth and growth of the mandible, the overjet shows a steady decrease up to the age of 5 years, where an edge‐to‐edge incisor relationship is common.

The primary incisors generally erupt into a rather deep overbite if there is no obstacle to hinder them. The individual variation is, however, wide. On average, the overbite decreases up to the age of 5–6 years as an effect of attrition.

The molar relations in the primary dentition may be divided into two types:

·     the primary dental arches end in a mesial step, i.e., the distal surface of the second molar in the mandible is mesial to the corresponding surface in the maxilla (Figure 21.4, left)

·     the dental arches end in the same vertical plan (Figure 21.4, right).

Line drawing of the terminal plane of the primary dentition. It displays the permanent molars erupting directly into normal occlusion (left) and permanent molars erupting into a cusp‐to‐cusp relation (right).

Figure 21.4 With a mesial step in the terminal plane of the primary dentition, the permanent molars may erupt directly into normal occlusion (left). If the primary dental arches end in the same vertical plane, the permanent molars will erupt into a cusp‐to‐cusp relation (right).

Both situations are favorable for the later guidance of the permanent first molar into normal occlusion. It should, however, be noted that the occlusion undergoes dynamic changes with jaw growth, with dental attrition, mesial drift of the dental arches on the jaw bases, and increased sagittal mandibular growth (Figure 21.3). At the time of eruption of the permanent first molar, a mesial step between the dental arches (Figure 21.4 left) is the most favorable.

Permanent dentition

The mixed dentition lasts from the eruption of permanent mandibular first incisors and first molars (about 6.5 years of age) until shedding of the last primary tooth (about 12 years of age) (see Chapter 5). The first permanent molars erupt in contact with the primary second molars. Thus, the establishment of molar sagittal relation will depend of the type of “step” between the distal surfaces of the maxillary and mandibular primary molars (Figure 21.4). The permanent first molars frequently establish a cusp‐to‐cusp relation. This relation normally turns into an Angle Class I after shedding of the primary second molars because of the greater leeway space in the mandible. In lateral segments the combined widths of the primary molars and canines are larger than the erupting successors and this extra space is called leeway space.

Sufficient space for the permanent molars is created by the sagittal growth of the jaws. Most important is the growth in the distal direction by apposition of bone on tuber in the maxilla and by the resorption at the anterior border of the mandibular ramus. Dental development and tooth eruption are not always coordinated in time with the growth of the jaws. Thus, the molars may erupt into an ectopic position.

Front teeth

The discrepancies in size between the primary and the permanent front teeth, amounting to 7 mm in the maxilla and 5 mm in the mandible, are neutralized in three ways:

·     by utilizing space surplus (diastemata) normally present in the primary dentition

·     by the proclined eruption path of the permanent incisors (Figure 21.5), which may add about 5 mm to the arch perimeter

·     by a transversal increase in intercanine distance, which may add about 3 mm to the arch.

Illustration of permanent maxillary incisors erupting at a more labial inclination than their primary predecessors. Vertical lines display the different of width and length of the dental arch after eruption.

Figure 21.5 The permanent maxillary incisors erupt at a more labial inclination than their primary predecessors. Consequently, the dental arch becomes wider and longer.

Thus, the space for the permanent maxillary incisors is normally sufficient. However, in cases of insufficient diastemata between primary incisors, crowding may develop. In cases with anterior forced bite the proclination of the maxillary incisors is likely to be reduced. This may also contribute to development of crowding of the teeth. The mandibular incisors need less space (5 mm), but the diastemata are also smaller and the eruption path is steeper. Thus, a temporary crowding may exist until it is corrected by the increase in transversal width. However, lack of space at eruption of mandibular front teeth often occurs, and the amount of the spacing in the primary dentition is a good indicator for the prognosis of the later accommodation of the front teeth. Crowding is generally more pronounced in girls than in boys [3].

Lateral segment

When the primary molars and canines are shed, there is a net gain of space in the dental arches (leeway spaces 2.5 mm in the mandible, 1.5 mm in the maxilla) available for the eruption of the premolars and canines and also allowing a mesial migration of especially the mandibular molars to turn any cusp‐to‐cusp relations between first molars into a neutral relation. In the maxilla, the leeway space is needed to accommodate the canines, which are 2 mm larger than their predecessors (Figure 21.6). The increase in maxillary intercanine width in connection with eruption of the canines may also add some space. In the mandible, there is no corresponding gain in intercanine width related to canine eruption. The premolars will normally have sufficient space for eruption unless space is lost due to lack of space in the front, or because of early loss of primary molars due to caries or ectopic eruption of permanent first molars.

Illustration of primary canines and molars occupying more space. It displays “leeway space” which is greater in the mandible (2.5 mm) than in the maxilla (1.5 mm).

Figure 21.6 The primary canines and molars occupy more space than is necessary for the corresponding group of permanent teeth. The difference is called the “leeway space” and is greater in the mandible (2.5 mm) than in the maxilla (1.5 mm).

Even after completion of the permanent dentition (third molars excluded) the dynamic changes of the dental arches and occlusion continue. On average, the overjet decreases and the dental arches become shorter through mesial drift in the lateral segments, often resulting in a “physiologic” crowding in the lower anterior front of an average of 0.5–1 mm from 12 to 20 years of age. The mean overbite decreases slightly up to the age of 18 years. The transverse dimension of the dental arches, however, tends to remain relatively stable from the early permanent dentition. An increase of palatal height up to adulthood has been reported, thus demonstrating a slow continuous eruption of the teeth. Clinical consequences of that growth will result in an increasing infraposition of ankylosed teeth and implants [4].

Supervising occlusal development in the primary and mixed dentition

In pediatric dentistry the diagnosis and supervision of dental and occlusal development are very important. The responsible dentist should know what to look for in certain developmental stages and also when preventive, interceptive, or corrective measures are indicated and most effective. The eruption of teeth and the developmental status in the jaws may vary by several years within the same age group of individuals. Therefore, a description of dental stages (see Box 7.3) can be made instead of age for describing physiologic maturity. The dental age can be used to estimate the age of children with unknown dates of birth.

Malocclusions

Primary dentition

Etiology

The genetic factors determining the size and position of the jaws are present from conception. Therefore, many of the genetically determined skeletal deviations manifest themselves in the primary dentition. This is especially true for Angle Class II and III, but also for deviations in the transversal dimension, which later are seen as posterior cross bite and scissors bite.

Functional factors such as chewing habits and the chewing resistance of the diet can play a role in the development of malocclusions. This is based on observations of skull materials from people living with primitive feeding habits, and on animal experiments comparing the results of chewing a soft and a hard diet. The evidence is, however, still limited [5,6]. Breathing habits may play a role for facial growth and dental arch morphology. A study reported improvement of open bites and cross bites in young children tonsillectomized because of sleep apnea [7]. It should be remembered, however, that a large proportion of open bites spontaneously correct themselves [8,9].

Habits, mostly dummy and finger sucking, still rank high as etiologic factors for the development of malocclusions in the primary dentition [10] (Box 21.1Figures 21.7 and 21.8).

Photo of the posterior cross bite (patient’s left side). It displays the midline deviation and mandibular lateral shift, and frontal open bite in a dummy sucker.

Figure 21.7 Posterior cross bite (patient’s left side), midline deviation and mandibular lateral shift, and frontal open bite in a dummy sucker.

Photo of the results of finger sucking. It displays an asymmetrical left side open bite and overjet.

Figure 21.8 Results of finger sucking. Asymmetrical left side open bite and overjet.

Box 21.1 Sucking habits and their influence on the primary dentition

·     Dummy sucking is much more prevalent in Scandinavian children than finger sucking. Sucking habits vary a lot between different ethnic groups. In developing countries sucking habits in children are less common. The sucking habit is more prevalent in urban than in rural areas, and in girls than in boys according to Scandinavian studies [12].

·     Dummy sucking often leads to posterior cross bite and open bite, and less often to overjet (Figure 21.7). Finger sucking more often leads to overjet and proclination of the maxillary front, and more seldom to posterior cross bite (Figure 21.8).

·     The mechanism behind the development of cross bite caused by dummy sucking is the narrowing of the maxilla by frontal pressure, also believed to be caused by the lowering of the tongue, negative pressure in the mouth, and increased muscular pressure from cheeks and lips, in the canine region. The effect is especially great if the maxilla has in addition a genetically conditioned narrow pattern.

·     The benefit of dummy sucking compared to finger sucking is that children are weaned from dummy sucking at an earlier age than from finger sucking, usually by the age of 3–4 years, and very few proceed with the habit into the mixed dentition. A limited number of finger suckers (about 10%) continue with the habit into the mixed dentition period.

·     After the dummy sucking habit has ceased in the primary dentition there will be a high grade of self‐correction of the open bite created by the habit. However, the possibilities for self‐correction of the posterior cross bite will depend on how large the discrepancy in width of the maxilla and mandible is, and how locked the intercuspidation is.

Prevalence

Malocclusions may be divided into four main groups (Box 21.2):

·     deviations in the sagittal plane

·     deviations in the vertical plane

·     deviations in the transversal plane.

·     deviations in available space.

Box 21.2 Prevalence of malocclusions in the primary dentition (%)

 

Boys

Girls

Space conditions

   

Crowding in the maxilla

1.5

2.9

Crowding in the mandible

0.5

1.9

Spacing in the maxilla

51.0

43.3

Spacing in the mandible

41.9

39.9

Vertical malocclusions

   

Frontal open bite >0 mm

21.8

23.9

Frontal deep bite >3 mm

18.1

18.9

Frontal deep bite >5 mm

3.6

2.0

Sagittal malocclusions

   

Maxillary overjet

35.8

23.9

Maxillary overjet >6 mm

11.9

11.9

Distal molar relations

49.5

49.0

Negative overjet >0 mma

0

0

Mesial molar relations

1.0

0.5

Transversal malocclusions

   

Posterior cross bites

10.6

17.3

Scissors bitea

0

0.5

a Cases not recorded in these investigations.

Sagittal plane

Malocclusions in the sagittal plane (Box 21.2) are usually or traditionally measured as deviations in molar relationships and/or size of overjet/negative overjet. However, in the primary dentition we will often find that molar relationships do not give any exact expression for future relations of either jaws or dental arches. Thus, it is more valid to use the canine relations when judging the sagittal relationships in the primary dentition.

Distal molar relationship

Distal molar relations in combination with large overjet is prevalent [11]. In the primary dentition this will be a small problem, but very often this malocclusion will also appear in the permanent dentition. Only in extreme cases where the mandible is held in a distal position, as with a scissors bite or very deep bite, will treatment in the primary dentition be indicated (Figure 21.9).

Photo of a human dentition with bilateral scissors bite in combination with forced distal occlusion.

Figure 21.9 Bilateral scissors bite in combination with forced distal occlusion.

Mesial molar relationship

Mesial molar relations (Angle Class III) with or without negative overjet have a very low prevalence. Negative overjet may exist in neutral molar relation, and we may have mesial molar relation without negative overjet. The malocclusions are divided into three main groups. In reality, most cases present a mixture of skeletal and dentoalveolar deviations:

·     skeletal

·     dentoalveolar

·     functional (forced bite).

In skeletal Class III malocclusions, the size of the maxilla and mandible and/or their positions are disproportional. This may occur in three combinations (Figure 21.10):

·     the maxilla is small and/or distally placed

·     the mandible is large and/or mesially placed

·     a combination of these.

Photo of a human dentition with skeletal class III malocclusion without compensation. It displays the mandible being mesially placed.

Figure 21.10 Skeletal class III malocclusion without compensation. Note mesial relations between canines.

Whether there will be a normal overjet in the front, an edge‐to‐edge bite, or a negative overjet will depend on the dentoalveolar compensation, which is the degree of labial inclination of incisors in the maxilla and the lingual inclination of the incisors in the mandible.

In cases of dentoalveolar negative overjet there may be a normal relation between the dental arches (best judged on the canine relationship), and the negative overjet is then due to lingual inclination of incisors in the maxilla and labial inclination of incisors in the mandible (Figure 21.11). With forced negative overjet the patient can often bite edge to edge in the retruded contact position of the mandible, but slides forward into negative overjet (pseudo Class III) for full occlusion. The treatment needed for Class III occlusions and anterior cross bite will depend on the severity of the malocclusion and to what extent it causes dissatisfaction for the patient. The dentoalveolar anterior cross bites can usually be left untreated in the primary dentition unless they cause negative effects on space conditions.

Photo of a human dentition displaying a dentoalveolar anterior cross bite.

Figure 21.11 Dentoalveolar anterior cross bite.

Vertical plane

Malocclusions in the vertical plane (Box 21.2) do not constitute a large problem in the primary dentition. There is a high prevalence of frontal open bite, but it is nearly always dentoalveolar, and often the result of sucking habits. It will most often close when the sucking habit ceases [12,13]. There is also a high prevalence of moderate deep bite, but this has little practical significance unless combined with forced cross bites. Severe deep bite is often combined with overjet and distal occlusion or sometimes scissors bite in lateral segments (Figure 21.12) and will be corrected if these malocclusions are to be treated.

Photo of a human dentition displaying an unilateral scissors bite in the primary.

Figure 21.12 Unilateral scissors bite in the primary dentition.

Transversal plane

Malocclusions in the transversal plane (Box 21.2) are dominated by the unilateral forced posterior cross bites; the prevalence is between 10 and 23% [14]. The large range is due to differences in the populations studied, in prevalence of dummy sucking, and also in differences in diagnostic technique. The prevalence of bilateral cross bite and scissors bite is between 3 and 6% [13].

The unilateral forced cross bite is characterized by a narrow, but symmetrical maxilla (Figure 21.13a). In the retruded contact position, the molars will meet cusp‐to‐cusp. To find a stable occlusion, the mandible has to slide to one of the sides, creating a unilateral forced cross bite (Figure 21.13b). The cusps on the cross bite side are often deeply locked into each other, and with little chance of self‐correction (full cross bite) (Figure 21.14). In some patients the maxilla is wider, and the teeth on the cross bite side will meet cusp‐to‐cusp (half cross bite). If the maxilla is very narrow, a bilateral cross bite may be the result. These occlusions are normally not forced and occlude without midline deviation. A bilateral cross bite may be associated with an Angle Class III relation.

Diagram of forced posterior cross bite. It displays symmetrical jaws with narrow maxillary jaw. In retruded position, molars occlude cusp‐to‐cusp (top) and an occlusion with forcing of bite to the left (bottom).

Figure 21.13 Forced posterior cross bite. The jaws are symmetrical, but the maxillary jaw is narrow. In the retruded position, the molars occlude cusp‐to‐cusp (a). Full occlusion needs forcing of the bite to the left (b).

Photo of the "Classical” unilateral posterior cross bite. Narrow maxilla has lack of space with the mandibular midline forced to the cross bite side.

Figure 21.14 “Classical” unilateral posterior cross bite. Narrow maxilla with the mandibular midline forced to the cross bite side. Note lack of space in the maxilla.

Cross bites normally establish at eruption of the primary canines and primary second molars. Thus, they may be diagnosed at about 3 years of age. It is important to decide whether the cross bite should be treated in the primary dentition, whether it could be expected to self‐correct, or whether treatment can be postponed until the early mixed dentition (Box 21.3).

Box 21.3 Posterior cross bite decisions

·     Check for deviation between the retruded contact position and the intercuspal position

·     Check if there are obstacles towards increase in transversal width in the canine area

·     Check if an asymmetric occlusal and or craniofacial development can be expected

Clinically:

·     Check the retruded contact position for any midline deviation between this position and intercuspal position

·     Check if there are any primary contacts in RCP usually found between primary canines

·     Decide if grinding is appropriate or if transversal expansion should be preferred

·     Decide about the proper time for expansion

Space conditions

Space conditions (Box 21.2) have a somewhat different meaning in the primary dentition than in the permanent dentition. As the increased spacing of the front teeth in the primary dentition is a natural anatomical feature reflecting growth, small spaces or crowding will indicate that crowding may also appear in the permanent dentition. Crowding with rotated and displaced teeth occurs most often in the permanent mandibular front, but is seldom seen in the primary dentition.

Lack of space as such should not be treated in the primary dentition but should be a reminder to monitor the eruption of the permanent incisors carefully. With no or little spacing, the permanent central incisors will most often resorb both primary central and lateral incisors during eruption, thus shifting the lack of space further distally in the dental arch.

Mixed and permanent dentition

Etiology

Box 21.4 contains examples of problems identified during supervision and guidance of the developing dentition [15]. Malocclusions in the primary dentition may, unless they are treated, persist in the permanent dentition. However, malocclusions may self‐correct in some children, while in other children with a normal primary dentition, a malocclusion may develop in the mixed and permanent dentition, respectively [13]. The main groups of malocclusions and their prevalence in the permanent dentition are listed in Box 21.5.

Box 21.4 Common problems in the early mixed dentition, 6–9 years

·     Habits causing malocclusions

·     Tooth eruption disturbances

·     Functional malocclusions

·     Obstacles to normal development of space for the teeth

·     Agenesis of permanent teeth

·     Large overjet increasing the risk for traumatic injuries

Box 21.5 Prevalence of malocclusions in the permanent dentition (%)

 

Boys

Girls

Space conditions

   

Crowding in the maxilla

20.6

26.3

Crowding in the mandible

33.0

31.7

Spacing in the maxilla

8.1

4.3

Spacing in the mandible

5.1

2.5

Vertical malocclusions

   

Frontal open bite >0 mm

2.3

1.8

Frontal deep bite >5 mm

22.7

14.5

Sagittal malocclusions

   

Maxillary overjet >6 mm

15.9

12.5

Distal molar occlusion

23.2

25.8

Mandibular overjet >0 mm

0.7

0.2

Mesial molar occlusion

4.1

4.5

Transversal malocclusion

   

Posterior cross bite

9.4

14.1

Scissors bite

7.1

7.9

A malocclusion may develop as a result of genetic and/or environmental factors. The environmental factors may include oral habits, reduced activity in jaw muscles, hypertrophic tonsils and adenoids, dental trauma, early loss of primary teeth, and severe chronic disease in childhood. However, dentoalveolar compensatory mechanisms may reduce the effects of aberrant jaw relations. A stable interdigitation between upper and lower teeth may preserve a normal relation between mandibular and maxillary teeth even in subjects with less favorable growth.

Sagittal plane

Distal molar occlusion and increased overjet are common malocclusions in the mixed and permanent dentition (Boxes 21.4 and 21.5). An increased maxillary overjet may be the result of protrusion of the maxillary alveolar process, retrusion of the mandibular alveolar process, increased labial inclination of the maxillary incisors, lingual inclination of the mandibular incisors, and protrusion of the maxilla and retrusion of the mandible (Figure 21.15). Oral habits, especially finger sucking, may have an adverse effect on incisor inclination. Incompetent lip closure with the lower lip resting behind the maxillary incisors may also be associated to large overjet and further increase of the overjet. Distal molar occlusion may arise because of mesial migration of permanent maxillary molars due to early loss of primary second molars, inappropriate adjustment of the permanent first molars in the mixed dentition.

Photo of the lower portion of a face. It displays an incompetent lip closure with the two central incisors slightly peeking through.

Photo of a human dentition displaying maxillary overjet, incisor proclination, and distal occlusion.

Photo of a protrusion of the maxilla and retrusion of the mandible as observed from below.

Figure 21.15 (a) Incompetent lip closure, (b) maxillary overjet, incisor proclination, distal occlusion, and (c) deep bite is a common combination.

Mandibular prognathism is often genetically determined. Retrusion of the maxilla, occurring in some syndromes, may cause mandibular pseudoprognathism. Mesial molar occlusion often occurs as a result of skeletal mandibular prognathism.

Vertical plan

Frontal open bite of dentoalveolar origin may be due to incomplete eruption of incisors or reduced vertical development of the anterior alveolar processes, usually due to a sucking habit (Figure 21.16). Frontal open bite is common in the primary and the mixed dentition. In those ages, it is very often a transient phenomenon. A major contributing factor is an anterior tongue position at rest in order to allow the child to breathe normally. In this period, there is a discrepancy between tongue volume and available space in the oral cavity. The adenoids are often large. By reduction of adenoids and increased oral space due to growth a large proportion of these frontal open bites close spontaneously and the prevalence is low in the permanent dentition (Box 21.5). Skeletal open bite may be due to a posterior rotation of the mandible during growth.

Photo of a human dentition displaying dentoalveolar frontal open bite.

Figure 21.16 Dentoalveolar frontal open bite.

Dentoalveolar deep bite may develop in cases with increased overjet and the prevalence is increased in the permanent dentition. Excessive eruption of the incisors may occur when normal contact between maxillary and mandibular incisors is absent, for instance in Angle Class II:2 malocclusions with steep incisor inclination. Skeletal deep bite may develop if the mandible has an anterior rotation during growth. This is often associated with strong masticatory muscles.

Transversal plane

Dentoalveolar cross bite or scissors bite of a single tooth is often the result of crowding. Total forced unilateral posterior cross bite with mandibular midline deviation is often a consequence of a narrow maxilla (Figure 21.17). Skeletal unilateral cross bites or scissors bite may be associated with asymmetry in the cranial base, the maxilla or the mandible. Bilateral cross bite and scissors bite are rare types of malocclusion. They are most often of a skeletal origin and in many cases they are combined with deviations in the sagittal and vertical dimensions. Bilateral cross bite may, for instance, be associated with Angle Class III malocclusion.

Photos of a unilateral cross bite in the early mixed dentition (top) and of a narrow maxilla in retruded position (bottom).

Figure 21.17 (a) Unilateral cross bite in the early mixed dentition. (b) Note the narrow maxilla in retruded position which needs active transversal expansion.

Space conditions

Crowding and spacing in the dentition depend on available space in the dental arches and the mesiodistal diameter of the teeth. Both size of jaws and size of teeth are strongly genetically influenced. Also, the minimal interproximal and occlusal dental wear in modern humans may partly explain the marked increase in occlusal anomalies. Observations from ancient skull materials, populations with primitive dietary habits, and from animal experiments using soft or hard diet, indicate an association between oral function and morphology. A high functional activity in jaw muscles changes mandibular morphology and contributes to more available space for the teeth. The prevalence of impacted wisdom teeth has been found to be much lower in skulls from earlier periods compared to modern populations [6,9]. Early loss of primary teeth is also a cause of dentoalveolar crowding in the permanent dentition, depending on the region involved, the stage of occlusal development, the general space conditions in the dental arches, and the interdental locking, which may prevent tooth migration. Loss of second primary molars and primary canines seems to have the most negative consequences. Another effect of early loss of primary teeth may be delayed eruption of permanent successors. Supernumerary teeth and agenesis also have an impact on space conditions.

Mesiodens

Moderate spacing of maxillary incisors is not uncommon in the early mixed dentition. A more pronounced medial diastema may indicate the presence of an extra tooth mesial to the central incisor roots: a mesiodens (Figure 21.18). If active closure is planned, and also to allow for closure in connection with the eruption of lateral incisors and canines, removal may be necessary. Otherwise, half of the mesiodens will erupt in a palatal position and can easily be removed. Most of those which do not erupt may be left in place and could, if necessary, be supervised radiographically. There is no need to routinely remove mesiodens [16].

Radiograph of two mesiodens as the cause of large median diastema.

Figure 21.18 Radiograph showing two mesiodens as the cause of large median diastema.

Agenesis of teeth

Agenesis of a maxillary lateral is usually detected radiographically when the tooth is not erupting and occurs in 2–3% of children. Space closure is usually the first choice [17]. In patients with a pronounced excess of space the treatment is often directed towards space maintenance and later replacement with an implant. Both space closure and replacement by implants are usually well accepted by treated individuals.

Agenesis of a mandibular premolar is usually detected from bitewing radiographs, preferably early, at the age of 8–9 years. The prevalence is 4–5%. The primary molar, which is approximately 11 mm wide, may be left in the dental arch or extracted depending on space conditions and occlusion (Figure 21.19).

Radiograph of a persisting 85 and agenesis of 45 in an 18-year-old boy.

Figure 21.19 Boy at 18 years of age with persisting 85 and agenesis of 45. The tooth is in good condition and may continue functioning for many years.

Spontaneous space closure, orthodontic space closure and, on rare occasions, autotransplantation and prosthetic rehabilitation including oral implants are possibilities to discuss with the orthodontist.

Median diastema

This may be seen in the presence of mesiodens, congenital absence of lateral incisors, or a fibrous frenulum. With time the diastema will close with mesially directed forces from erupting lateral incisors and later maxillary canines. Frenectomy is not commonly used nowadays.

Eruption disturbances and deviation in tooth position

In the primary and mixed dentition periods, obstacles to normal occlusal development should be identified and removed. Otherwise treatment of crowding ought to be postponed to the permanent dentition when the individual is mature enough to decide on treatment.

Ectopic first molars

The ectopic first molar resorbs the distal part of the primary molar and may be locked during eruption. The mesially tipped permanent molars may be moved distally with a spring on a removable appliance or with a sectional wire. The use of orthodontic appliances or separating elastics is preferred instead of earlier recommended brass wire. The resorption of the primary molar will then stop.

Impacted canines

If after clinical examination and judgment the supervising dentist suspects an ectopic eruption, an extended radiographic investigation is indicated and contact with an orthodontist is necessary. With early detection it is possible in almost 80% of cases to change the ectopic path of eruption by early extraction of the primary canines [18]. The treatment should be planned together with an orthodontist (Figure 21.20and Box 21.6).

Three radiographs of early extraction of the primary canine and the changing of the path of eruption of palatal ectopic maxillary canines.

Figure 21.20 Early extraction (a, b) of the primary canine may spontaneously change the path of eruption (c) of palatal ectopic maxillary canines.

Source: Persson & Thilander 1995 [2]. Reproduced with permission of Gothia Fortbildning.

Box 21.6 Maxillary ectopic canines [10,18]

Facts

·     Prevalence about 2%

·     85% are palatal

·     More girls: two out of three

·     Seven out of 10 are unilateral

·     Age at eruption: girls 10.5 years, boys 11.5 years

·     Palpable bulge in the buccal sulcus about 1.5 years before eruption

·     With mesial migration of the canine, the risk for severe root resorptions increases

Suggested policy

·     Digital palpation should start at about 9–10 years of age depending on individual maturity

·     Early extraction of primary canines before 13 years of age may result in spontaneous correction of palatally ectopic canine cases [18]

Ankylosis of primary molars

With a successor present in a normal position, supervision only is necessary. Normal shedding will occur, however, about 6 months later than normal (Chapter 5). If ankylosis occurs early, before the age of 6–7 years, the vertical eruption of neighboring teeth and vertical development of the alveolar process will leave the ankylosed primary molar in a position near or sometimes below the gingival margin. If the permanent first molar shows a pronounced tendency to tip in over the infraoccluded primary molar, this tipping should be treated early. With agenesis of the successor, the treatment should be planned together with an orthodontist according to space conditions and occlusion [19] (Chapter 4). Early removal of the primary molar is often beneficial, otherwise there may be a considerable reduction of the height of the alveolar process making later replacements far more difficult. Early removal of the primary molar also allows the permanent molar to move forward, thus completely or partially closing the gap.

The pedodontic treatment approach to orthodontic problems

The pediatric dentist’s treatment approach to orthodontic problems is to:

·     prevent the development of malocclusions

·     intercept malocclusions that have started to develop

·     correct malocclusions associated with increased risk for tooth damage, ectopic eruption, or dysfunction

·     refer extensive malocclusions to specialists in orthodontics when treatment is indicated [9,15,20].

Prevention

As the major part of the etiologic factors are of genetic origin, such malocclusions cannot be prevented to any large extent, and we have to focus on the environmental causative factors and eliminate them with preventive measures.

Early loss of teeth

The loss of necessary space for the accommodation of the permanent teeth is still an important cause of malocclusions within Angle Class I. Every effort to maintain the mesiodistal dimension of the arches is important, first of all to reduce the need for early extraction of teeth, especially the “key teeth”—the primary second molars and canines. The significance of the primary teeth as “space maintainers” for the permanent teeth is evident, especially after early loss of the primary second molars because of caries or ectopic eruption of permanent first molars. Thus, caries prevention and appropriate caries restoration are of the greatest importance for occlusal development. In an individual where the primary molars are lost early it is likely that a lack of space will lead to later extraction therapy of permanent teeth.

Sucking habits

Sucking is believed to give rise to several malocclusions (Box 21.4) [12]. It may be beneficial to break pacifier or finger sucking habits to prevent the development of a functional cross bite. Cross bites will often persist and will need active treatment. The treatment itself (removable plates, Quad Helix) will usually stop the habit. Before active treatment the child should be motivated and give consent for the habit breaking and have understood and accepted the procedure. A good question to ask the child is: “Do you want to stop the sucking habit?” A negative response usually means postponed treatment. Another situation when breaking the habit is motivated is when it contributes to an increase of overjet and thus an increased risk for traumatic tooth injuries. Anterior open bite is usually corrected spontaneously if the habit is broken. Finger sucking is a more long‐lasting and “deep‐seated” habit than the use of a pacifier. About 10% of children continue with the habit into their mixed dentition. Helping these children to stop the habit could be psychologically well motivated.

Failure in tooth eruption

Monitoring the shedding of the primary teeth and the eruption of the permanent teeth is very important as many malocclusions manifest themselves during these processes (see Chapter 5). Primary retention is seldom observed in the primary dentition, but there is a high prevalence of secondary retention, caused by temporary ankylosis, in primary molars (up to 12%). Normally, such teeth will loosen and be shed with the permanent successor in a normal position. If the ankylosis persists for a long period, the infraposition will increase, leaving a greatly reduced height of the alveolar process. On rare occasions the neighboring teeth may tilt into the space (Figure 21.21). Presence of the permanent successor should always be checked radiographically. If the tooth is missing in a young individual and there is expected to be a considerable vertical reduction of the alveolar process, this can motivate an early removal of the ankylosed tooth.

Radiograph of an ankylosis of primary molars. It displays of infraposition of 75 (secondary retention) and tipping of 36.

Figure 21.21 Ankylosis of primary molars resulting in infraposition of 75 (secondary retention) and tipping of 36.

Primary teeth may also persist in the jaw without being ankylosed and without being in infraposition (Figure 21.19). This happens regularly to teeth with agenesis of their permanent successors. In such cases the fate of the persisting tooth should be discussed with an orthodontist. In cases where the occlusion otherwise is excellent and the persisting tooth is in good condition (negligible caries, no infraposition, no significant resorption of roots, etc.), the primary tooth may be maintained, and may function for many years. If the occlusion and the condition of the persisting tooth are less favorable, the tooth should be extracted and the space closed by natural mesial drift, by orthodontic means or, more seldom, by autotransplantation, implants or prosthodontic reconstructions. The prognosis for space closure is most favorable in the maxilla and in cases with crowding.

Primary teeth may also persist even if their successors are present. That may occur to the primary second molars in both jaws if the position of premolars does not allow resorption of all roots at the same time. In the maxilla especially, the palatal root may be left unresorbed and keep the tooth longer in place even if the buccal roots are completely resorbed (Figure 21.22). Ectopic eruption is a substantial problem during eruption of permanent teeth (Figure 21.23). The “classic” ectopic eruption is that of the first molars, especially in the maxilla, where the mesial part of the crown is locked beneath the distal curvature of the primary second molar. However, investigations show that in 60% of cases the ectopic teeth are released (“jump cases”). In the other 40% of cases (“hold cases”) distal movement of the ectopic molar to allow it to erupt normally is indicated. Even severely resorbed primary second molars usually persist and function as space maintainers.

Radiograph of a persisting 65 due to a slight ectopic position of 25. It displays the resorbing of buccal roots and the intact palatal root.

Figure 21.22 Persisting 65 due to a slight ectopic position of 25. The buccal roots are resorbed, while the palatal root is still intact.

Photo of a human dentition displaying an ectopic eruption of 26.

Radiograph of a human dentition displaying an ectopic eruption of 26.

Figure 21.23 (a, b) Ectopic eruption of 26.

The maxillary canines may also show ectopic eruption (or be impacted). Ectopically erupting canines in a labial position and with none or small mesial displacement will probably not mean an increased risk for resorption of permanent incisors. The tooth can be allowed to erupt in a buccally displaced position and can, if treatment is requested for esthetic reasons, be corrected during the permanent dentition period. Buccal displacement of a canine is probably often caused by lack of space for the tooth. The palatally positioned canines may be more complicated to bring into normal position, depending on the degree of deviation in their position. Extraction of a persisting primary canine and increase of available space by, for instance, distal movement of the lateral segments may normalize the eruption of a palatal canine. While they are in ectopic positions, the canines may cause resorption of the lateral and even the central incisors (Figures 21.24 and 21.25). Early detection of such cases is an important responsibility of the pediatric dentist.

Three radiographs displaying ectopic eruption of 13,23 with almost completely destroyed the roots of 12,22 and also resorbed the roots of 11,21.

Figure 21.24 Ectopic eruption of 13,23 has almost completely destroyed the roots of 12,22 and also resorbed the roots of 11,21. Extraction of 12,22 was needed.

Photo of a human dentition after extraction of 12,22 and orthodontic treatment and grinding of canine cusps.

Figure 21.25 Same case as in Figure 21.24 after extraction of 12,22 and orthodontic treatment and grinding of canine cusps.

Palpation of the buccal area of the canines with normal eruption will reveal a bulge/swelling about 1.5 years before eruption (in boys at 11.5 years and in girls at 10.5 years of age). About 7 out of 10 impaction cases are unilateral and are easily distinguished as a clear difference between the two sides. With bilateral impaction or ectopic eruption the clinician must use his or her clinical experience and feelings to decide whether the tooth should be palpable according to the individual’s somatic and dental development. The prevalence of ectopic maxillary canines is approximately 2%; 85% of the ectopic eruptions are palatal; and girls are more affected than boys [10,18,21]. In almost 50% of cases with ectopic eruptions incisor resorption will occur, often severely into the pulp. Therefore, early supervision, starting not later than 10 years of age, with palpation of the buccal canine area is most important to avoid severe complications and more prolonged orthodontic treatment with fixed appliances.

Trauma

Prevention of trauma is also prevention of malocclusion because trauma to teeth may cause exarticulation or loss of teeth due to primary or secondary pulp necrosis, ankylosis, etc. Permanent teeth may also be severely damaged in crown development because of trauma to primary teeth, and also root dilacerations may occur. Studies have shown a highly significant correlation between large overjet and incompetent lip posture and traumatic tooth injuries. There is also an association between the size of the overjet and prevalence and severity of tooth injuries. So far, no study specifically looking at the effect of overjet on traumatic tooth injuries has been presented. Nevertheless, the strong correlation between overjet and tooth injuries justifies correction of a large overjet in the late primary or early mixed dentition. An early treatment is motivated by the fact that many injuries occur before the age of 10 years [9,20]. The most commonly used removable appliance to correct a Class II malocclusion with large overjet is an activator. There are several different activators available with different designs. However, all activators have in common that they are functional appliances, where the idea is that modified function results in modified growth and morphology. This appliance has, however, mostly dentoalveolar effects.

Interceptive orthodontics

Interceptive treatment aims to break a negative developmental path. An example is a reduction in the width of the upper dental arch caused by a sucking habit. The discrepancy in width between the arches may force the individual to occlude in a lateral position in comparison to retruded contact position (RCP) in order to establish reasonably good interdigitation. As described above, the child often learns to keep the mandible laterally displaced at rest. This may cause an asymmetric occlusal development. The lateral cross bite can also be an obstacle to the expected gain in width of the maxillary dental arch up to and including eruption of the canines. The result may be an increased lack of space for the teeth. Likewise, an anterior forced cross bite can interfere with the expected proclination of the maxillary incisors on eruption. Again, if left untreated this may contribute to increased crowding.

Deep bite

It should be evaluated whether the deep bite is the result of overeruption of maxillary incisors or due to a skeletal pattern; the profile, shape of the mandible, and lower face height indicating a skeletal deep bite. Fixed appliances are usually required in these cases.

Early treatment may be indicated in patients with vertically unstable incisor relation, i.e., pronounced Class II:2 cases where overeruption of incisors is likely to occur. Treatment may start with a removable plate with frontal expansion to procline the incisors and thereafter an activator.

Protruding maxillary incisors, Class II

Early retraction treatment is recommended for trauma prophylactic reasons, especially if the upper lip is short and is not protecting the incisors. Activators or removable plates can be used.

Anterior forced cross bite and Class III

The main aim of treatment is to remove obstacles for the lengthening of the maxillary dental arch that occurs when the permanent incisors erupt. Treatment can be performed when the child is motivated and cooperative, normally at 5 years of age. The maxillary dental arch will then be in correct position before eruption of the permanent incisors, which otherwise may erupt into anterior cross bite. Treatment alternative will be a frontal expansion plate.

In cases of skeletal Class III it was a common procedure in the past to use chin caps to try to restrict the growth of the mandible. The opinion now is that it is questionable whether this effect can be obtained. Furthermore, the strong and long‐lasting pressure against the chin may also have adverse effects on the temporomandibular joints. If the basal malocclusion is caused by maxillary retrognathia, anterior protraction of the maxilla by means of a reversed headgear, e.g., Delaire mask, is a better solution. The mask may be used in the primary dentition, but since good cooperation is needed, the treatment may better be postponed until the early mixed dentition. One of the major reasons to treat is to create a dental compensation in order to reduce the influence of a deviant growth pattern. The evidence for good long‐lasting effects of such treatment is still insufficient. However, the effect of the reversed headgear may be positive in patients with cleft lip and palate.

Posterior cross bites

Treatment need and cost–benefit of treatment of posterior cross bites in the primary dentition have been discussed in several reports because some cross bites will self‐correct, some treated cross bites will relapse. Moreover, some cross bites are combined with other malocclusions and thus their treatment may be postponed until a complete treatment later (Box 21.7). The economic aspects of early treatment have also been discussed [22]. Two major reasons for correction of posterior cross bites have been stated. The first is that the cross bite (functional and nonfunctional) may be an obstacle to the expected gain in transversal width until eruption of the upper canines. This may contribute to a space deficiency at a later stage for the maxillary teeth. The second reason is a risk for asymmetrical occlusal development.

Box 21.7 Arguments for early treatment of forced unilateral posterior cross bites

·     May prevent unilateral chewing and marginally decrease the risk for temporomandibular disorders

·     May decrease the risk to establish an atypical neuromuscular movement pattern

·     Will prevent the cross bite from being transferred to the permanent dentition where the steep cusps of the permanent first molars may lock the cross bite even more

·     May hinder asymmetrical facial development in the frontal plane

·     Will increase the width in the maxillary front, and thus also improve the space condition before eruption of the wider permanent incisors

·     May prevent traumatic biting of the cheeks and tongue

The cross bite removable plate with palatal screw or Coffin coil may be used. Another useful appliance requiring less strict cooperation is the Quad Helix lingual arch which is often used today (Figure 21.26). The plate has to be worn at all times, except during meals and tooth brushing. The expansion may be about 5 mm, and if 0.5 mm (half a turn) is activated each week, the cross bite will be corrected in about 10 weeks. After the active expansion, the plate is used for retention for a couple of months. There are different designs of Quad Helix appliances. In one type, the lingual arch is directly soldered to the bands. Another type has square palatal tubes, making activations outside the mouth possible. The orthodontic bands are cemented to the teeth, and thus the appliance does not require patient cooperation. Often, all the expansion may be done by the first activation. Thus, the Quad Helix requires fewer visits, and is therefore claimed to have a better cost–benefit than plates [22]. The treatment time with a Quad Helix is around 6 months followed by a retention period of equal length. In a study comparing removable plate, Quad Helix appliance, composite onlays and no treatment the Quad Helix appliance was superior to the expansion plate in success rate and treatment time. Moreover, treatment with the expansion plate was unsuccessful in one third of the subjects. Cross‐bite correction with composite onlay in the mixed dentition was ineffective, and spontaneous correction in the mixed dentition did not occur [23].

Photo of a maxillary front as observed from below. A removable appliance for frontal expansion has been placed.

Figure 21.26 Removable appliance for frontal expansion of the maxillary front.

Crowding

It is important to distinguish the forced cross bites which are interfering with optimal occlusal development from correction of primary crowding, usually of a genetic origin. Treatment of crowding with resulting displacement of teeth is usually motivated if the individual is clearly dissatisfied with the appearance. Such treatment decisions should normally be postponed to the permanent dentition period, allowing the individual to be mature enough to be able to decide [24]. A young individual cannot be expected to be able to make a decision until occlusal development is, at least, almost completed. Attempts to influence space by approximal grinding or even worse by so‐called serial extraction have no scientific support and should be avoided. In general, treatment in the mixed dentition should be restricted to removal of obstacles for normal occlusal development and to correct malocclusions that may increase the risk for tooth damage. Early extractions such as serial extractions have probably more negative than positive effects and may also be a traumatic experience for the child. There also seems to be a risk for negative influence on the development of the alveolar process.

In summary, orthodontic treatment in the primary and mixed dentition periods should focus on ensuring optimal occlusal development and to reduce risks for tooth damage, i.e., root resorptions and traumatic injuries. A complete treatment plan including expected growth, occlusal development, and space conditions should always precede treatment. There is otherwise a great risk of focusing on details in deviation from ideal occlusion. It is also important to remember that malocclusion primarily means a biologic variation which very often is completely acceptable. Orthodontic diagnosis should not be confused with pathology. Orthodontic treatment should only be considered when obvious negative consequences of malocclusions can be identified and if the individual is clearly aware of the possible benefit of treatment. For a few individuals with a pronounced dissatisfaction with visible tooth malpositions, early treatment may be motivated. Normally, corrective orthodontic treatment to improve esthetics should be postponed to the permanent dentition period.

Permanent dentition

Corrective orthodontic treatment

By this age most tooth eruption disturbances and malocclusions should already have been diagnosed. Decisions may have been made earlier to supervise the development, assess the severity and consequences for the individual, and postpone the start of treatment, especially if the need for intervention is less pronounced and the benefit of treatment is limited. As previously stressed, orthodontic treatment should only be considered if malocclusion causes pronounced problems for the individual. The presence of malocclusion is not per se an indication for treatment. It is important to identify and evaluate satisfaction of the patient. The patient is also entitled to a correct description of functional and health problems that may be related to the malocclusions. Generally, no major health risks have been associated with untreated malocclusions so far. The following areas ought to be evaluated and discussed with the patient. Preventive, interceptive treatment and treatment to prevent tooth damage have been discussed previously.

General decisions for orthodontic treatment

Dissatisfaction with appearance

This is no doubt the major reason for demand for orthodontic treatment [9,20,24,25]. So far, there has not been found any profound psychological influence of malocclusions or orthodontic treatment. Teenagers, however, tend to relate self‐esteem and influence on their relations with other teenagers to presence of malocclusion. Motivation to undergo treatment seems to be a social norm and relates to the beauty culture in teenagers’ reference groups and society in general. Recent studies indicate a positive influence on quality of life by orthodontic treatment. Orthodontically treated subjects tend to express a higher level of satisfaction with appearance compared to those with untreated malocclusions. Follow‐up into adult age indicates a higher tolerance to variations in tooth positions compared to younger individuals. On the other hand, untreated adults tend to rank their general appearance lower than individuals without malocclusions. Visible crowding mainly influences satisfaction with appearance [24,25]. An evaluation of the psychosocial benefit of an orthodontic treatment must always be individualized.

Caries and periodontitis

Subjects with malocclusions do not have more caries than those with ideal occlusion [9,20]. There is insufficient evidence to establish an association between malocclusion and periodontitis. Studies of oral hygiene in relation to malocclusions have revealed that there is a slightly higher tendency for plaque accumulation in subjects with displacement of teeth or large overjet. This is only true, however, for those with an average level of oral hygiene. The influence of the dominant hand has, for instance, been found to have a greater influence than malocclusions.

Speech

Malocclusions such as frontal open bite, large overjet, mandibular overjet, or frontal spacing could be suspected to influence consonant articulation in a negative way. Available studies indicate that deviation of speech in relation to malocclusions usually is of a mild or, at most, moderate severity [9,20]. In subjects with severe neuromuscular disturbances these can cause both speech deficiencies and severely altered craniofacial and occlusal development. In children with cleft lip and palate there is often a nasality in the speech due to incomplete closure of the soft palate.

Chewing function

The effect of chewing is dependent on the size of the mastication surface. The food is more effectively broken into smaller particles in subjects with larger contact area between upper and lower teeth. The scientific basis to establish negative health effects related to limited chewing ability is still insufficient. It should not be forgotten, however, that a good ability to chew and to bite off the food can have a great psychological value.

Temporomandibular disorders

Most studies indicate that there is a weak correlation between temporomandibular disorders (TMD) and malocclusions [9,20]. It has been estimated that occlusal variables may explain 10–20% of TMD. Most studies have found no or only minor influence of malocclusions on TMD. Some studies present significant correlations, but the type of malocclusion studied differs between studies. Longitudinally, it has been demonstrated that there are considerable variations in presence and severity of TMD in an individual over time [26,27]. Thus, few conclusions can be drawn [28]. Functional variables such as cuspid protection or nonworking side interferences appear only to have a small influence on TMD. Psychological factors and muscular endurance, on the other hand, seem to have greater influence than malocclusions. In adults, correlations have been found between Class II and III malocclusions, open bite, and functional cross bites. Class II, III, and open bite malocclusions are often characterized by a steep mandibular plane angle. A steep angle has been associated with less strong masticatory muscles, which may make such subjects more vulnerable to overload of the muscles. In line with that, less TMD has been observed in subjects with a deep bite. Follow‐up from teenage to about 30 years of age has revealed a pronounced reduction of signs and symptoms of TMD [26,27]. In summary, malocclusions do not seem to have a major influence on development of TMD.

The selection of orthodontic patients

There is, unfortunately, a tradition to select subjects for orthodontic treatment on the basis of presence of malocclusions and on how much the occlusion deviates from the constructed norm for the ideal occlusion. Dentists often appear to be the ones who initiate treatment [25]. Indices to prioritize for orthodontic treatment are constructed mainly in two ways. One includes a description of malocclusions and a ranking of malocclusion, i.e., the larger an overjet, the greater the treatment need. There seems to be an assumption of a relation between psychosocial dissatisfaction and oral health on one hand and the type and severity of malocclusions on the other. The other type is based on esthetic evaluation by a panel of observers ranking photos of various clinical situations. There appears to be no scientific evidence for the validity of any available index [20,29]. Instead, a treatment decision ought to be based on a thorough evaluation of the dissatisfaction of the patient. The patient should also be given good information of possible negative consequences for leaving the malocclusion untreated. The information should also include risks and discomfort of treatment and, not least, how extensive the treatment will be and how stable the treatment result is expected to be. Most of these discussions can be taken by the general dentist.

Acknowledgment

Thanks are given to Dr Pamela Uribe for her skillful help with the illustrations.

References

1.     1. Trainor PA. Molecular blueprint for craniofacial morphogenesis and development. In: Huang GTJ, Thesleff I, eds. Stem cells in craniofacial development and regeneration, 1st edn. 2014;3–29.

2.     2. Persson M, Thilander B. Craniofacial growth and development. In: Thilander B, Rönning O, eds. Introduction to orthodontics, 2nd edn. Solna: Förlagshuset Gothia, 1995;10–40.

3.     3. Moorrees CFA. The dentition of the growing child: A longitudinal study of dental development between 3 and 18 years of age. Cambridge, MA: Harvard University Press, 1959.

4.     4. Thilander B. Dentoalveolar development in subjects with normal occlusion. A longitudinal study between the ages of 5 and 31 years. Eur J Orthod 2009;31:109–20.

5.     5. Kiliaridis S. Masticatory muscle function and craniofacial morphology. Swed Dent J Suppl 36, 1986.

6.     6. Mohlin B, Sagne S, Thilander B. The frequency of malocclusion and the craniofacial morphology in a medieval population in Southern Sweden. OSSA 1979;5:57–84.

7.     7. Hultcrantz E, Larson M, Hellquist R, Ahlquist‐Rastad J, Svanholm H, Jakobsson OP. The influence of tonsillar obstruction and tonsillectomy on facial growth and dental arch morphology. Int J Pediatr Otorhinolaryngol 1991;22:125–34.

8.     8. Mason R. Tongue thrust. In: Oral motor 32–48.

9.     9. Mohlin B, Kurol J. To what extent do deviations from an ideal occlusion constitute a health risk? Swed Dent J 2003;27:1–10.

10. 10. Kurol J, Ericson S, Andreasen JO. The impacted maxillary canine. In: Andreasen JO, Kølsen Petersen J, Laskin D, eds. Textbook and color atlas of tooth impactions. Diagnosis, treatment and prevention. Copenhagen: Munksgaard, 1997;126–65.

11. 11. Ravn JJ. Longitudinal study of occlusion in the primary dentition in 3‐ to 7‐year‐old children. Scand J Dent Res 1980;88:165–70.

12. 12. Larsson E. The prevalence and aetiology of prolonged dummy and finger‐sucking habits. Eur J Orthod 1985;7:172–6.

13. 13. Dimberg L, Lennartsson B, Söderfeldt B, Bondemark L. Malocclusions in children at 3 and 7 years of age: a longitudinal study. Eur J Orthod 2013;35:131–7.

14. 14. Kurol J, Berglund L. Longitudinal study and cost‐benefit analysis of the effect of early treatment of posterior cross‐bites in the primary dentition. Eur J Orthod 1992;14:173–9.

15. 15. Kurol J, Thilander B, Zachrisson B, Linder‐Aronson S. Treatment of dentoalveolar and skeletal anomalies. In: Thilander B, Rönning O, eds. Introduction to orthodontics, 2nd edn. Solna: Förlagshuset Gothia, 1995; 112–68.

16. 16. Kurol J. Impacted and ankylosed teeth: why, when, and how to intervene. Am J Orthod Dentofacial Orthop 2006;129(4) Suppl 1: 86–90.

17. 17. Robertsson S, Mohlin B. The congenitally missing upper lateral incisor. A retrospective study of space closure versus restorative treatment. Eur J Orthod 2000;22:697–710.

18. 18 Ericson S, Kurol J. Early treatment of palatally erupting maxillary canines by extraction of primary canines. Eur J Orthod 1988;10:283–95.

19. 19. Kurol J, Thilander B. Infraocclusion of primary molars and the effect on occlusal development. A longitudinal study. Eur J Orthod 1984;6:277–93.

20. 20. Malocclusions and orthodontic treatment in a health perspective. A systematic literature review. The Swedish Council on Technology Assessment in Health Care, 2005.

21. 21. Ericson S, Kurol J. Resorption of incisors after ectopic eruption of maxillary canines. A CT study. Angle Orthod 2000;70:415–23.

22. 22. Hermanson H, Kurol J, Rönnerman A. Treatment of unilateral crossbites with quad‐helix and removable plates. A retrospective study. Eur J Orthod 1985;7:97–102.

23. 23. Petrén S, Bondemark L. Correction of unilateral posterior crossbite in the mixed dentition: a randomized controlled trial. Am J Orthod Dentofacial Orthop 2008;133:790.e7–790.e13.

24. 24. Shaw WC. Factors influencing the desire for orthodontic treatment. Eur J Orthod 1981;3:151–62.

25. 25. Trulsson U, Strandmark M, Mohlin B, Berggren U. A qualitative study of teenagers’ decisions to undergo orthodontic treatment with fixed appliance. J Orthod 2002;29:197–204.

26. 26. Egermark I, Magnusson T, Carlsson GE. A 20‐year follow‐up of signs and symptoms of temporomandibular disorders and malocclusions in subjects with and without orthodontic treatment in childhood. Angle Orthod 2003;73:109–15.

27. 27. Mohlin B, Derweduwen K, Pilley R, Kingdon A, Shaw WC, Kenealy P. Malocclusion and temporomandibular disorder: a comparison of adolescents with moderate to severe dysfunction with those without signs and symptoms of temporomandibular disorder and their further development to 30 years of age. Angle Orthod 2004;74:319–27.

28. 28. Thilander B, Bjerklin K. Posterior crossbite and temporomandibular disorders (TMDs): need for orthodontic treatment? Birgit Thilander. Eur J Orthod 2012;34:1–7.

29. 29. Mohlin B, Kurol J. A critical view of treatment priority indices in orthodontics. Swed Dent J 2003;27:11–21.