Preventive orthodontics: Is it a logical and predictive procedure?

So as a result, Ben Franklin was almost on the mark when it came to preventive orthodontics (34.1/1.9 = 17.9/16 = 1.1).

This procedure usually involves wearing a preformed appliance called Nite-Guide (Bergersen, 1995) only while sleeping to guide the erupting permanent teeth into an ideal occlusion. Usually two appliances are involved (Figs. 1a and 1b), and the second and last appliance serves as the retainer until about age 12. Once the permanent teeth erupt straight, the adult collagenous fibers form to stabilize them, which can prevent future relapse.

Because crowding of the lower arch is the most common of the various elements of a malocclusion and, because its orthodontic correction typically occurs at about age 12, the fibers are well-established by this time and usually result in about 75 percent relapse post-retention (Little et al, 1981; Little et al, 1988).

It is logical therefore, to concentrate on the developmental results that are most applicable to the lower arch. A graph (Fig. 2) of crowding changes in non-crowded (Moorrees, 1959) and crowded (Bolton Sample / Bergersen, 1966) non-treated sample cases show that the major developmental increases in incisal crowding occurs during the eruption of these teeth.

Once they are fully erupted, they retain the crowding during further growth of the jaws to age 17. Both groups start out in the deciduous dentition quite similarly; however, by age 8, after the full eruption of the permanent lower incisors has occurred, the resultant crowding is considerably different.

If a preventive technique were to be initiated at the start of the incisal eruption period, a result might occur that would more resemble the non-crowded sample of Moorrees.

Can this increase in crowding be predicted? Referring to Fig. 3, it is easily seen that different degrees of crowding occur depending on whether a child has deciduous mandibular interproximal spacing, closed contacts or actual incisal crowding at 4.7 years of age.

This observation of the mandibular arch is probably the best predictor of potential crowding of all the possible variations according to statistics. Fig. 4 indicates the risk for crowding by age 8 from the observation of deciduous incisal spacing at 5.7 years. Obviously, incisal spacing of 3 mm or less will result in a future crowding risk of 83 percent or higher, which would be a strong indication for preventive intervention.

Another significant principle is to count the number of broken contacts of the lower adult incisal area before or during their eruption. Potential broken contacts can be predicted before the adult incisors break tissue (Fig. 5), and they do not self-correct as further eruption takes place (Schwarz, 1932).

These broken contacts can predict both the risk of crowding, stated as percentages, as well as the amount of expected crowding (Fig 6).

It should be observed that there is little change in the lower incisal dentition once the incisors are fully erupted (Fig. 2). This indicates that a preventive or interceptive procedure should ideally be initiated as the first adult incisor breaks tissue at around 6½ years of age. Once the teeth are fully erupted, adult collagenous fibers begin their development in order to stabilize these teeth.

Any attempt to correct crowding after the full eruption of these teeth has to deal with the resistance that these fibers produce. An important study (Sanin et al, 1973) indicated that lower incisors that erupt straight at age 8 remain straight 82 percent of the time by age 14, and those that erupted crowded at age 8 remained crowded or increased their crowding by 14 years of age 89 percent of the time.

This research study is very compelling for early intervention in order to obtain straight teeth prior to the collagenous fiber development for their optimum retention. In conclusion, preventive orthodontics is a logical procedure and with a careful analysis of the deciduous dentition prior to age 6, can provide important predictive information to aid in the diagnosis of an early developing malocclusion.

Note: This article was published in today: Greater New York Dental Meeting, Official Meeting News, Dec. 2, 2013. A complete list of references is available from the publisher.