INTRODUCTION: This three-part article summarizes ideas already described elsewhere by the author. Part 1. New way of diagnosing the dentition. For diagnostic purposes origin and appearance of the three tissue types - ectoderm, mesoderm (ectomesenchyme) and peripheral nerves - are depicted on orthopantomograms. Same tissue types are marked on the root surface (peri-root sheet). Part 2. Factors provoking root resorption. Resorption can be explained from the composition of the peri-root sheet. Deviations (inborn or acquired) in each of the three tissue layers can provoke inflammation, resulting in resorption. Orthodontic forces resulting in resorption can occur in normal peri-root sheets, but also in peri-root sheets with inborn deviations, important to diagnose. Part 3. How to prevent root resorption - Clinical guidelines. General diseases and different dental morphologies are signs predisposing for root resorption (ectoderm and mesoderm), so are local or general virus attacks (neuroectoderm). Resorption often occurs in dentitions never treated orthodontically.

MATERIAL AND METHOD: The author performed a review of the literature in order to present a new diagnostic approach incorporating histological and embryological concepts.

RESULTS: The review revealed different etiologies and sites involved in root resorption. Patients presenting variations of the peri-root sheet are most exposed to root resorption.

DISCUSSION: At this stage, it is difficult to diagnose these variations. The author offers diagnostic recommendations to be followed prior to orthodontic treatment. Even when no orthodontic treatment is given, root resorption can occur unexpectedly. In these cases, resorption prevention is currently impossible.