Orthodontics: Principles and Practice Basavaraj Subhashchandra Phulari
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IntroductionCHAPTER 1

Humans have attempted to straighten the teeth for thousands of years before orthodontics became a dental specialty in the late nineteenth century. Proper alignment of the teeth has long been recognized to be an essential factor for esthetics, function and overall preservation of dental health. Malposed/poorly aligned teeth may predispose to a number of unfavorable sequelae such as poor oral hygiene predisposing to periodontal diseases and dental caries, poor esthetics giving rise to psychosocial problems, increased risk of trauma, abnormalities of function and temporomandibular joint (TMJ) problems (Box 1.1).
Orthodontics is the branch of dentistry concerned with the growth of the face, development of occlusion and the prevention and correction of occlusal anomalies/abnormalities. The term “orthodontics” comes from Greek: “orthos” meaning right or correct and “odontos” meaning tooth (Flowchart 1.1). The term ‘orthodontics’ was first coined by Le Felon in 1839.
Knowing the definition is often an important initial step in understanding any subject. A number of definitions have been put forward over the years to explain what orthodontics is. Some of the widely followed definitions are given below:
In 1911, Noyes gave the first definition of orthodontics as “The study of the relation of the teeth to the development of the face and the correction of arrested and perverted development.”
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Flowchart 1.1: Derivation of the term orthodontics
In 1922, The British Society of Orthodontists proposed that “Orthodontics includes the study of growth and development of jaws and face particularly and the body generally, as influencing the position of the teeth; the study of action and reaction of internal and external influences on the development, and the prevention and correction of arrested and perverted development.”
Later, the American Board of Orthodontics (ABO) and the American Association of Orthodontists (AAO) stated that, “Orthodontics is that specific area of dental practice that has, as its responsibility, the study and supervision of the growth and development of the dentition and its related anatomical structures from birth to dental maturity, including all the preventive and corrective procedures of dental irregularities, requiring the repositioning of teeth by functional or mechanical means to establish normal occlusion and pleasing facial contours.”
The term ‘malocclusion’ was first coined by Guilford and it refers to any irregularities in occlusion beyond the accepted range of normal category. Malocclusions are caused by hereditary or environmental factors or more commonly, by both the factors acting together. One of the most common causes of malocclusion is the disproportion in size between the jaw and the teeth or between the maxillary and the mandibular jaws. A child who inherits mother's small jaw and father's large teeth, may have teeth that are too big for the jaw, causing crowding in the arch. Abnormal oral habits, such as thumb/digit sucking, lip biting and mouth breathing may also cause malocclusion by adversely affecting the normal occlusal development.
Malocclusion can be presented in a number of ways. Some of the common characteristics of malocclusion include:
  • Overcrowded teeth
  • Spacing between the teeth
  • Improper “bite” between maxillary and mandibular teeth
  • Disproportion in the size and the alignment between the maxillary and the mandibular jaws.
It must be appreciated that not all malocclusions need treatment. Treatment of malocclusions that are mildly unesthetic and not detrimental to the health of the teeth and their supporting structures may not be needed and is not justified.
Although orthodontic treatment improves facial appearance and is occasionally performed for cosmetic reasons, it should be aimed at restoration of overall dental health.
2Jackson has summarized the aims of orthodontic treatment that are popularly known as Jackson's Triad (Fig. 1.1). They are:
  1. Functional efficiency
  2. Structural balance
  3. Esthetic harmony.
Functional Efficiency
The teeth along with their surrounding structures, are required to perform certain significant functions such as mastication and phonation. Orthodontic treatment should increase the efficiency of the functions performed.
Structural Balance
Orthodontic treatment not only affects teeth but also the soft tissue envelop and the associated skeletal structures. The treatment should maintain a balance between these structures and the correction of one should not affect the health of the other.
Esthetic Harmony
The orthodontic treatment should enhance the overall esthetic appeal of the individual. This might just require the alignment of certain teeth or movement of the complete dental arch, including its basal bone. The aim is to get results which go well with the patient's personality and make him or her look more esthetically appealing.
The general field of orthodontics can be divided into the following three categories based on the nature and time of intervention:
  • Preventive orthodontics
  • Interceptive orthodontics
  • Corrective orthodontics.
Preventive Orthodontics
Preventive orthodontics is defined as “Action taken to preserve the integrity of what appears to be the normal occlusion at a specific time.” As the name implies, preventive orthodontics includes actions undertaken prior to the onset of a malocclusion, so as to prevent the anticipated development of a malocclusion.
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Fig. 1.1: Aims of orthodontic treatment (Jackson's triad)
Preventive orthodontics encompasses all those procedures that attempt to ward off untoward environmental attacks or anything that would change the normal course of events. They include the care of deciduous dentition with restoration of carious lesions that might change the arch length; monitoring of eruption and shedding timetable of teeth; early recognition and elimination of oral habits that might interfere with the normal development of the teeth and jaws; removal of retained deciduous teeth and supernumeraries, which may impede eruption of permanent teeth and maintenance of space following premature loss of deciduous teeth to allow proper eruption of their successors.
Interceptive Orthodontics
Interceptive orthodontics implies that an abnormal situation (malocclusion) already exists when the action is taken. Certain interceptive procedures are undertaken during the early manifestation of malocclusion to lessen the severity of malocclusion and, sometimes, to eliminate the cause.
Interceptive orthodontics is defined by the American Association of Orthodontists as “That phase of the science and art of orthodontics employed to recognize and eliminate potential irregularities and malpositions in the developing dentofacial complex.”
Interceptive procedures include serial extraction, correction of developing anterior crossbite, control of abnormal oral habits, removal of supernumeraries and ankylosed teeth and elimination of bony or tissue barriers to erupting teeth.
Certain procedures undertaken may be common to both preventive and interceptive orthodontics. However, the timing of the services rendered is different. Preventive orthodontic procedures are carried out before the manifestation of a malocclusion, while the goal of interceptive orthodontics is to intercept a malocclusion that has already been developed or is developing, so as to restore a normal occlusion.
Corrective Orthodontics
Corrective orthodontics, like interceptive orthodontics, is also undertaken after the manifestation of a malocclusion. It employs certain technical procedures to reduce or correct the malocclusion and to eliminate the possible sequelae of malocclusion.
Corrective surgical procedures may require removable or fixed mechanotherapy, functional or orthopedic appliances, or in some cases, an orthognathic/surgical approach.
Today orthodontists have a wide array of appliances in their armamentarium to treat malocclusions. Success of orthodontic treatment depends on the appropriate 3selection of the appliances, the timing of the treatment, the type of tooth movement and/or skeletal changes desired, age of the patient and other factors. There are basically four types of orthodontic appliances, which can either be used individually or in combination to treat malocclusions.
  1. Removable orthodontic appliances
  2. Fixed orthodontic appliances
  3. Functional appliances
  4. Orthopedic appliances/Extra-oral force appliances
Removable Orthodontic Appliances
Removable orthodontic appliances are so called because they can be removed and fitted back into the mouth by the patient (Fig. 1.2).
Use of removable appliances requires careful case selection for the success of the treatment. They are ideally used when simple tipping movement of teeth is sufficient to correct a certain type of malocclusion. The range of malocclusions that can be treated with removable appliances alone is limited. They can also be used as passive appliances to maintain the teeth in their corrected positions after active phase of orthodontic therapy, e.g. retainers. Removable orthodontic appliances can be used in conjunction with fixed mechanotherapy.
Fixed Orthodontic Appliances
Fixed orthodontic appliances are so called because they are fixed to the teeth and cannot be removed by the patient. Fixed orthodontic therapy involves fixation of attachments (brackets) to the teeth and application of forces by arch wires or auxiliaries via these attachments (Fig. 1.3).
Fixed appliances are indicated when multiple tooth movements are required for correction of malocclusion, such as rotations and bodily movement of the teeth. Fixed mechanotherapy allows fine finishing and settling of occlusion. There are a number of fixed orthodontic techniques such as: Begg's, Edgewise, pre-adjusted Edgewise, straight wire and lingual techniques.
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Fig. 1.2: Removable orthodontic appliance
Functional Appliances
Functional appliances/myofunctional appliances are those appliances that utilize the forces of the circumoral musculature for their action to effect the desired changes (Fig. 1.4). They act principally by holding the mandible away from the normal resting position to effect growth modification of the mandible.
Orthopedic Appliances/Extraoral Force Appliances
Orthopedic appliances use extraoral forces of high magnitude (>400 g/side) to bring about skeletal changes. Intermittent application of such high forces in the growth period aids in correction of skeletal malocclusions by growth modification. Orthopedic appliances like functional appliances require good patient compliance for their success, e.g. headgears and chin cup (Fig. 1.5).
Appropriate timing of orthodontic treatment is essential to accomplish the desired treatment outcome and its long-term stability. Timing of orthodontic intervention is related to the stage of dentition.
Deciduous Dentition
Orthodontic treatment during this stage mainly includes the following:
  • Parental education
  • Care of deciduous dentition
  • Space maintenance
  • Elimination of abnormal oral habits.
Early Mixed Dentition
Orthodontic treatment during this stage includes the monitoring of shedding timetable, serial extraction, space maintenance and control of abnormal oral habit. Although most corrective orthodontic procedures are performed in older children and adolescents, it may be advantageous in some cases to begin the treatment early before all the permanent teeth have erupted and facial growth is complete.
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Fig. 1.3: Fixed orthodontic appliance
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Fig. 1.4: Activator, a myofunctional orthodontic appliance
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Fig. 1.5: Orthopedic appliance
Advantages of early orthodontic treatment include:
  • Correction of bite problems by guiding jaw growth and controlling the width of the upper and lower dental arches.
  • Reduction or elimination of abnormal swallowing or speech problems.
  • Growth modification using functional and orthopedic appliances is best done in this period where significant growth is taking place.
  • Shortening and simplification of later orthodontic treatment.
  • Prevention of later tooth extractions.
  • Improvements in appearance and self-esteem.
  • Parental education.
Late Mixed Dentition/Early Permanent Dentition
Most corrective orthodontic treatments are carried out in late mixed dentition or early permanent dentition stage.
Late Treatment
  • Many types of orthodontic treatments are feasible after adolescence. However, growth modification procedures to correct skeletal malocclusion may not be feasible due to cessation of growth.
  • Surgical treatment involving orthognathic surgeries are best carried out in late teens/early adulthood after the cessation of growth.
From the era of finger pressure application to invisalign treatment, the field of orthodontics has witnessed profound development in the form of newer appliance designs and techniques, which have only increased the scope of orthodontics.
Monitoring and Assessment of Developing Dentition
  • Shedding and eruption schedule is closely monitored to ensure the normal course of events.
  • Space maintainers are given in case of premature loss of primary teeth to facilitate the eruption of successor teeth.
  • Habit breaking appliances are given to eliminate deleterious oral habits, such as thumb/digit-sucking and lip-biting, which can adversely affect the development of dentofacial structures.
  • Planned extraction of certain deciduous and/or permanent teeth (serial extraction) done in selected cases can prevent future development of crowding by providing adequate space for the remaining teeth to erupt.
Correcting Malocclusions of Dental Origin
Malocclusions of dental origin include abnormalities of intra-arch alignment and inter-arch relationship of teeth. They can be managed by removable or fixed orthodontic appliances.
Correcting Malocclusions of Skeletal Origin
Skeletal malocclusions include conditions where the upper and lower jaws are abnormally related to each other.
  • Growth modification: Skeletal malocclusions can be treated successfully by modifying the growth of jaws during active growth period using functional or orthopedic appliances.
  • Surgical correction: Severe skeletal malocclusion in adults can be corrected by orthognathic/surgical approach.
Adult Orthodontics
Better understanding of bone cell reactions to orthodontic forces and improvements in appliance design has made orthodontic treatment feasible in adult age as well. Orthodontic treatment in adults may involve the following:
  • Adjunctive orthodontic procedures: They refer to limited orthodontic treatment carried out to facilitate other dental procedures. Adjunctive orthodontic 5procedures include uprighting of tilted abutment teeth prior to bridge work, space gaining for placement of implants, etc.
  • Comprehensive orthodontic treatment: It is usually carried out in young adults and involves full-fledged orthodontic treatment with or without extraction of teeth.
  • Mouthguard/Sportsguard: Mouthguards are often used during contact sports, such as boxing to prevent trauma to the teeth.
  • Night guards: Night guards can be given in bruxism to prevent further loss of tooth structures by clenching of teeth.
Management of Dentofacial Anomalies
Dentofacial anomalies such as cleft lip and cleft palate are usually associated with impaired facial appearance, speech, hearing, mastication, deglutition, and dental occlusion. Thus, management of such patients often requires a multidisciplinary approach with a long-term treatment plan and individualized rehabilitation program designed to address the treatment needs. Malocclusion is usually present and orthodontic therapy with or without corrective jaw surgery is frequently indicated.
  • Improved confidence
  • Well-aligned teeth that are easier to keep clean and healthy.
  • Ideally positioned teeth, which lessen the chance of gingivitis and advanced gum disease.
  • Closed spaces to avoid the need for a bridge or denture.
  • Better chewing and food digestion.
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