Premature loss of primary teeth can cause functional disturbances and, because of the possibility of drifting of adjacent teeth, can result in space loss, difficulty in eruption of their successors, and, consequently, occlusal problems. Thus, premature loss of primary teeth needs careful attention during development of the dentition.
The consequences of premature extraction of primary teeth have been the subject of discussion for many years. In 1742, French physician Pierre Fauchard spoke of the inevitability and undesirability of removing primary teeth before their natural shedding.
The consequence of premature loss of primary teeth has been evaluated in several longitudinal and cross-sectional studies. In a review of previous studies, Owen3 revealed a large controversy in opinions on space management in the past. Some authors, such as Lundström,4 Linder-Aronson,5 and Seipel,6 believe that space
maintainers are usually a waste of time and even are harmful 19% of the time. On the other hand, many researchers believe that premature loss of primary teeth usually results in space closure and causes harmful effects in the permanent dentition.3,7–10 Owen3 concluded that the following general trends are evident:
• The incidence of space closure increases with time. For all experiments, at least 96% of premature losses result in some closure within 12 months.
• The highest and earliest incidence of closure happens after premature loss of the maxillary primary second molar.
• Some mandibular extraction spaces show no closure.
• The rate of space closure is higher in the maxilla than in the mandible.
• Rates of closure in the mandible are more varied.
• The greatest amount of space closure in a given unit of time occurs at the maxillary primary second molars and then the mandibular primary second molars.
• There is complete agreement that space closure in the maxilla is predominantly caused by mesial movement of the teeth posterior to the extraction space. In the mandible, space closure is predominantly caused by distal movement of the teeth anterior to the space.
• There is evidence that the tooth mesial to the affected molar can drift distally into the space. Therefore, loss of space or arch length can occur from both directions.4
• Reports of space opening are only associated with late extraction.
The rates of the space lost after primary tooth loss differ. Northway et al10 stated that the space loss was greatest in the first 6 months and occurred in smaller amounts after that, with the least occurring 1 year after tooth loss.
Johnsen7 evaluated primary first molar loss in 10 white children during the mixed dentition stage (8 had bilateral and 2 unilateral premature primary first molar loss).
At the initial visit, alginate impressions, photographs, and radiographs were taken.
In all patients, the primary canine was present at the initial impression, and the primary second molars were present at the final impression. For six of the patients extraction was within 1 month of the initial casts; for one it was within 3 months; and for the remaining three it was more than 6 months after the casts were prepared.
Final measurements of the distances between the permanent first molars and permanent incisors were taken on the initial and final casts and compared. Spaces at the extraction site were measured from teeth immediately adjacent to the extraction
site. Johnsen7 reported no significant mesial movement of the mandibular permanent molars after mandibular primary first molar loss but some space loss at the maxillary molars, especially if the permanent molars were erupting. Space loss in the mandible after premature loss of the primary first molar was the result of distal movement of the anterior teeth, especially in the presence of mandibular anterior crowding.
Northway et al10 digitized 107 dental casts from University of Montreal growth samples. Longitudinal data were collected annually from the age of 6 years, for an average observation period of 5.9 years. Trying to determine different aspects of early loss of primary teeth, Northway et al10 reported the following:
• Regarding dimensional loss due to caries or primary tooth loss (the first molar [D], the second molar [E], or both the first and second molars [D + E]), they found that in both sexes significantly greater amounts of space were lost in the mandible, with an average loss of 1.7 mm (ranging from 0.9 to 3.7 mm), than in the maxilla, with an average loss of 1.2 mm (ranging from 0.7 to 3.0 mm).
• The maxillary D loss group experienced a later increase in the amount of maxillary D + E loss.
• In both arches, the greatest loss of space occurred as a result of mesial molar movement; maxillary canine migration was significant only when the maxillary primary molars were lost as early as 9 years of age.
• In the mandible, maximum canine migration occurred after mandibular primary first molar loss.
• More space was lost in the first year following an extraction than in the successive years.
• In the maxilla, the rate of loss was age related (more space loss in younger children); in the mandible, the rate of loss was not age related.
• There was no significant difference in age for space opening during the emergence of the succedaneous teeth in the mandible; the opening occurred during second premolar eruption.
• Permanent molar mesial drift occurred in the maxilla after both E and D + E loss.
• Mesial movement of the mandibular permanent molar occurred only after E loss.
• Maxillary D loss affected maxillary canine relationships, while mandibular D + E loss affected mandibular canine relationships.