Factors Influencing Mesial or Distal Drift
Primary teeth act as space maintainers for the permanent teeth. Proper timing of the exchange of primary with permanent teeth is an important factor in the proper disposition of the permanent teeth in the dental arch. The effects of an early loss of a primary tooth may be as follows: shortening of arch length, tipping of the adjacent permanent teeth and supraeruption of the opposite tooth. In this article, there is a brief discussion on the factors influencing mesial or distal drift.
Factors Influencing Mesial or Distal Drift
The factors which influence the extent and rate of mesial or distal drift are discussed below:
Degree of crowding:
- It is directly related to the rate and extent of drift.
- In an uncrowded arch there may be little or no movement of teeth but in a crowded arch adjacent teeth quickly move into the spaces provided by the extraction of teeth.
- Loss of 2nd primary molar allows mesial drift of the 1st permanent molars, especially if it is unerupted: however, a center line shift occurs only in very crowded arches.
- In contrast, extraction of a primary canine, allows permanent incisors to drift distally, but mesial drift of teeth is minimal.
- Extraction of a primary 1st molar allows some mesial and distal drift to occur.
Relative amount of mesial and distal drift of teeth is expected following extraction of a primary tooth.
Age of patient:
- The earlier a primary tooth is extracted, the greater the opportunity for drilling of teeth, but over eruption of opposing teeth may limit movement.
- If a primary molar is extracted before eruption of the permanent 1st molar, mesial drift of the latter is inevitable even in arches that are not crowded.
- Therefore, the extraction of a primary tooth can have profound effects on the developing permanent dentition.
- A tooth should never be extracted before first assessing its likely effects and then plan treatment to prevent or eliminate those effects.
- Since an important factor that determines drifting of teeth is the degree of crowding in the arch, it is essential to assess this before appropriate treatment can be planned.
The gingival conditions should also be considered from the point of view of developing malocclusion.
Generalized prepubertal periodontitis:
In the primary teeth prepubertal gingivitis may show root resorption with clefting and inflammation of the gingival, rapid destruction of the alveolar bone and a premature loss of the primary teeth that may affect the eruption and drifting of permanent teeth and lead to a malocclusion.
- Children with hypophosphatasia may show premature exfoliation of their primary teeth (due to failure of anchorage of periodontal fibers) which may affect alignment of the permanent teeth which are known to be normal on eruption.
- Loss of attachment with breakdown of alveolar bone, exposure of root, tooth mobility and premature tooth loss may occur in dentin dysplasia, juvenile periodontitis, papillon leferve syndrome, leukemoia, neutropenia, scurvy, diabetes, hypophosphatasia, mercury toxicity and radiation.
- Counting of teeth will reveal the presence of supernumerary teeth. Approximately, 0.3% of kids have extra teeth in the primary dentition.
Functional relationships and TMJ:
- There is a possible or potential functional element in every malocclusion.
- The patients usual occlusal position may be due to occlusal interferences in the undeviated path of closure.
- Any interference may prompt a reflex shifting of mandible during closure to an occlusal position dictated by cusps and forcing an imbalance of musculature.
- Such malocclusions may be termed as functional malocclusions.
- They are important because of their potential for affecting future growth and imbalance in craniofacial skeleton as well as distorting the form of the alveolar arches.
- The situation where the erupting permanent tooth causes resorption of primary tooth due to improper direction of eruption can be termed as ectopic eruption.
- This condition is more commonly seen during the eruption of the upper first permanent molar wherein the deciduous second molar roots are resorbed.
- The other region where this may be observed is the mandibular anterior teeth.
The above article discusses about the factors influencing mesial or distal drift.