These patterns of tension and compression, are further proposed to result in patterns of bone resorption and deposition that lift the tooth into the mouth. This new theory proposes firstly that areas of tension and compression are generated in the soft tissues surrounding unerupted teeth by the distribution of bite forces through the jaws. This idea may have been superseded by a further recent theory. Inherent in most of the theories outlined above is the idea that a force is generated in the periodontal ligament beneath unerupted teeth, and that this force physically drives teeth out through the bone. There is good evidence from experimental animals that a traction force is unlikely to be involved in tooth eruption: Animals treated with lathyrogens that interfere with collagen cross-link formation showed similar eruption rates to control animals, provided occlusal forces were removed. Theorists hypothesize that the periodontal ligament promotes eruption through the shrinking and cross-linking of their collagen fibers and the contraction of their fibroblasts. The most widely held current theory is that while several forces might be involved in eruption, the periodontal ligament provides the main impetus for the process. Later, the "ligament" Sicher observed was determined to be merely an artifact created in the process of preparing the slide. This theory postulated that a ligament below a tooth, which Sicher observed under a microscope on a histologic slide, was responsible for eruption. The cushioned hammock theory, first proposed by Harry Sicher, was taught widely from the 1930s to the 1950s. In addition, some believed teeth were pushed upward by vascular pressure or by an anatomic feature called the cushioned hammock. Continued Bone Formation Theory advocated that a tooth is pushed upward by the growth of the bone around the tooth. According to Growth Displacement Theory, the tooth is pushed upward into the mouth by the growth of the tooth's root in opposite direction. There have been many theories over time that have been eventually disproven. 2.1 Signs and symptoms of tooth eruptionĪlthough researchers agree that tooth eruption is a complex process, there is little agreement on the identity of the mechanism that controls eruption.
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