Dental crowding

When teeth fail to fit the size of their arch, it can be defined as a condition known as crowding. This lack of coordination between tooth size and the dimensions of their arch may cause various forms of malocclusion such as rotation, displacement, or eruption problems. In other words, when there is insufficient space in the mouth for the proper placement of each tooth in its respective area, crowding may arise. Tooth crowding is one of the most frequent orthodontic anomalies. Sometimes, crowded teeth cause problems for patients. Tooth brushing is difficult to practice in conditions like crowded teeth because areas such as the interdental are difficult to access by the toothbrush which leads to plaque accumulation and calculus formation. Plaque and calculus will cause caries and gingivitis or even further destruction of periodontal tissue which causes tooth mobility.


Archeological studies show that Hunter-gatherers had almost no malocclusion and dental crowding, and the condition first became common among the world’s earliest settlers some 12,000 years ago in Southwest Asia. The connection between chewing, diet, and related dental wear patterns is well-known in the scientific literature. Today, malocclusion and dental crowding affect around one in five people in modern-world populations. The condition has been described as the “malady of civilization.” The study of ancient Egyptian skeletons from Amarna, Egypt reveals extensive tooth wear but very little dental crowding, unlike modern Americans. In the early 20th century. Investigations have shown that a reduction in jaw size in response to softer and processed foods during and following the Industrial Revolution (1,700 CE to present) was an important factor in increased rates of poor dental occlusion. The study of ancient Egyptian skeletons from Amarna, Egypt revealed extensive tooth wear but very little dental crowding, unlike modern Americans. David Greene studied the teeth of skeletons excavated in Sudan just south of Egypt along the Nile and documented a long-term trend in a dental-size reduction for the 10,000-year period. Anthropologists think that increases in dental crowding and malocclusion occurred with the transition from a primitive to a modern diet and lifestyle. Corrucini termed malocclusion a “disease of civilization.” Two French dentists, Bunon and Bourdet were among the pioneers who explained that the extraction of more than one uneven tooth can enhance the rest of the teeth. Paisson was the first to recommend the procedure to relieve the crowding and align the teeth. in 1929 Kjellegren used serial extractions to alleviate crowding.

Classification of crowding

Dental crowding is defined by the amount of space that would be required for the teeth to be in the correct alignment. It is obtained in two ways. 1) by measuring the amount of space required and reducing this from calculating the space available via the width of the teeth. Or 2) by measuring the degree of overlap of the teeth.

The following criterion is used:

0-4mm = Mild crowding
4-8mm = Moderate crowding
>8mm = Severe crowding

Late Crowding

It is not uncommon for crowding of the mandibular incisor teeth to appear as early as age 17 or up to age 25. This tendency presents itself no matter how initially aligned the teeth were, leading to mild crowding of the lower incisors, or making already existing mild crowding worse. To explain this phenomenon, three main theories have been put forward.

Treatment of crowding

The treatment of crowding depends on the severity, age of the patient, soft tissue posture, and arch width. In a mixed dentition stage where the premolars are erupting, space maintenance is of primal importance to prevent crowding. Serial extractions of the deciduous and later permanent teeth are carried out to resolve the crowding in a growing patient with mixed dentition.


The following methods are employed in Orthodontics for gaining space for correcting crowding situations. 1. Expansion of the dental arch 2. Visualization of the posterior teeth 3. Interproximal reduction of teeth 4. Extraction of teeth

Expansion of the dental arch

If the crowding is resultant in the narrowing of the dental arch as is more evident in the maxillary arch, A procedure called the expansion of the maxillary or mandibular arch is carried out and this gain space for mild to moderate crowding to settle. Mild anterior expansion can be achieved with archwire with advancement stops made before the molar tubes. for mild to moderate anterior expansion, expansion screw appliances that are removable can be used, particularly when anterior cross bites are noted.

Rapid Maxillary Expansion Devices

Rapid Maxillary Expansion (RME) is an orthodontic technique used to widen your upper jaw when it is too narrow. It involves the use of an expander appliance that is fixed to the teeth using bondable caps or using bands on premolars and molars. Rapid maxillary expanders also use mini-screws to the hard palate for anchorage. An expander appliance consists of a metal framework with an enclosed screw mechanism in the middle. This screw can be activated by a key. to widen the appliance either the patient, parent, or clinician can activate the screw. A twice-daily activation schedule is most commonly proposed in the literature. These maxillary expansion devices open up the sutures of the maxilla and allow bone deposition. The rapid expansion device is called HYRAX expander. Niti Expander is another example of a maxillary expansion device.

In Skeletally matured patients the RPE is less efficient and needs surgical intervention.

Distallization of molars

Molar distalization is a procedure of increasing the length of the dental arch by the backward movement of the buccal segment teeth, especially the molars. Maxillary molar distalization has been successfully used for more than 100 years. This technique is usually utilized to gain space to relieve crowding and to reduce the increased overjet Main advantage of this technique is that the space gained is in conservative methods and the need for extractions is avoided. Norman Kingsley described a device called headgear, which can result in maxillary molar distalization. This was the beginning of the universal use of headgear. The recommended amount of force is about 100 grams, which allows a tooth movement of 1 mm per month. Intraoral Appliances such as Pend-X and Pendulum appliances, Lip Bumper, Forsus, Herbst, Twin block, modified Nance holding arch, Japanese NiTi coils, systems using magnets for molar distalizing, Distal Jet, MARS and MARA appliances, Ghoshgarian TPA, Carriere appliance with class II elastics, and Sliding Jig with mini-screws combined with closed coil are the commonly used distallization devices. Some of these appliances can be anchored to the Bone using mini-screws to gain anchorage and avoid tipping off the teeth.

Interproximal reduction of teeth

Interproximal reduction of teeth or IPR is another method of gaining space in mild to moderate crowding cases. It is also known as slenderingDisking or stripping. IPR is an irreversible procedure and can be an alternative to dental extraction. Indications for the procedure include mild to moderate crowding (4 – 8mm), black triangles in anterior teeth, enhancing retention and stability after orthodontic treatment, and correction of the Curve of Spee. IPR is contraindicated for patients with a high risk for caries, poor oral hygiene, active periodontal diseases, multiple restorations, greater than 8mm of crowding per arch, hypersensitivity to cold, and large pulp chambers. About 50% of proximal enamel can be stripped without causing any dental or periodontal problems. According to Sheridan, 2.5mm of space from the IPR of five anterior contacts and 6.4mm of space from the IPR of eight posterior contacts can be obtained. It was recommended that no more than 0.5mm – 0.75mm should be removed from each proximal side of the anterior teeth. Abrasive metal strips, diamond-coated stripping disks, and air-rotor stripping are the main interproximal enamel reduction techniques.

Extraction of teeth

Extraction of teeth, particularly the 2 of 4 premolar teeth or incisors in the lower arch is a popular method of gaining space to correct orthodontic malocclusions such as crowding and protrusion. These extractions can be done to prevent future crowding which is called serial extractions or along with orthodontic mechanotherapy. In 1929, Kjellgren of Sweden used the term “serial extraction” for the first time. In the 1940s the technique was popularised in the United States by Hayes Nance as “planned and progressive extraction”. Nance is known as the Father of serial extraction in the United States. In 1970 Hotz in Switzerland called it active “supervision of teeth by extraction”. In 1940, Nance presented and illustrated his technique of “progressive extraction” and has been called the “Father of Serial Extraction philosophy”.

Extreme mandibular arch length discrepancy and bimaxillary protrusion are two conditions that almost always require premolar extractions. The advantages of treating malocclusions with extraction are that it improves the long-term stability of the teeth, better Cosmetic appearance, and The health of the teeth and gingival tissue. Without extractions, the teeth may have to be proclaimed which may not be a stable alternative and it can result in not so good appearance of the face. Extractions in orthodontics were reintroduced scientifically in the 1930s and with the advent of Begg’s technique reached its peak in the 1960s. Different extraction protocols have been followed for successful orthodontic treatment. The teeth to be extracted for crowding cases depend on the severity of the crowding and proclamation of the teeth.

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