Epithelial rests of Malassez in experimental animals at different ages

Epithelial rests of Malassez (ERMs) are fragments of Hertwig’s sheath in the periodontal ligament. There is extensive knowledge of their role in the etiology of pathological processes and current evidence links them to maintenance of periodontal homeostasis. The aim of this study was to assess the behavior of ERMs with relation to the changes in periodontal tissues during growth in an experimental model with Wistar rats. Mesiodistal sections were made of the first lower molars from Wistar rats aged 1 month (n=7), 3 months (n=7) and 5 months (n=6). Sections were stained with H&E to evaluate number of ERMs/ mm, size/area of ERMs (μm2), height of periodontal ligament (PL.h) (μm), area of cement in the furcation zone (C.Ar) (μm2) and bone area related to the ERM zone (BAr/TAr)(%). Posthoc Bonferroni and ANOVA were applied for statistical analysis of results. Number of ERMs/mm declined significantly with age (1m: 4.34±1.51, 3m: 1.48±0.89, 5m: 0.27± 0.50, p≤0.05), and there was great variability in size. There was significant increase in C.Ar (1m: 3418.96 ± 905.88, 3m: 19365.76 ± 5500.52, 5m: 32182.76 ± 7114.51, p≤ 0.05) and interradicular (BAr/TAr) (1m: 25.26 ± 2.37, 3m: 44.70 ± 3.95, 5m: 46.81 ± 7.80, p≤ 0.05: 1 vs 3, 1 vs 5). There was significant decline in PLh at 5 months (1m: 141.42 ± 29.25, 3m: 162.06 ± 28.21, 5m: 124.72 ± 18.67, p≤ 0.05: 1 vs. 3, 3 vs. 5). The decline in number of ERMs as animal age increases may be related to the significant increase in C.Ar and reduction in PL.h. It remains to ascertain its relationship with the increase observed in BAr/ TAr. Further studies are needed to learn more about the role of ERMs and their relationship with periodontal tissues when confronted with different normal and pathological stimuli.

The two extremes of physiological tooth resorption in primary tooth with or without the permanent successor tooth

ABSTRACT Introduction: Assessment of two radiographic images reveals two distinct, extreme situations of physiological tooth resorption, characteristic of primary teeth with or without permanent successor, due to partial anodontia. Discussion: In all primary teeth, rhizolysis begins after the completion of formation, thanks to the apoptosis of their cells. When apoptosis induced by cementoblasts has denuded the root of these cells, the process of rhizolysis inevitably begins: This will be accelerated by mediators arising from the pericoronal follicle. When there is no permanent successor due to partial anodontia, rhizolysis occurs extremely slowly, and months later, without the epithelial rests of Malassez that were dead due to apoptosis, alveolodental ankylosis becomes established, and the tooth will gradually be replaced by bone, still within a physiological context. Conclusion: Rhizolysis and physiological tooth resorption may occur rapidly or slowly, early or late, and this depends on the presence of the permanent tooth, or its absence due to partial anodontia.

Diagnosis of alveolodental ankylosis in unerupted canines: one of the answers to why the canine does not come

ABSTRACT Introduction: Teeth frequently fail to erupt and situations arise that prevent the canines from reaching the occlusal plane. Objective: Discourse about the three situations in which the canine does not reach the occlusal plane, and remains unerupted; and at the same time, point how to make a safe diagnosis of alveolodental ankylosis - one of the three causes -, based on tomography. Conclusions: Ankylosis occurs in impacted teeth by atrophy of the periodontal ligament, including the epithelial rests of Malassez. The tomographic signs of alveolodental ankylosis in unerupted canines are the interruption of hypodense periodontal space, discontinuity of the lamina dura and its continuity with the root surface, which gradually loses its regular shape.

Mandibular anterior crowding: normal or pathological?

ABSTRACT The teeth become very close to each other when they are crowded, but their structures remain individualized and, in this situation, the role of the epithelial rests of Malassez is fundamental to release the EGF. The concept of tensegrity is fundamental to understand the responses of tissues submitted to forces in body movements, including teeth and their stability in this process. The factors of tooth position stability in the arch - or dental tensegrity - should be considered when one plans and perform an orthodontic treatment. The direct causes of the mandibular anterior crowding are decisive to decide about the correct retainer indication: Should they be applied and indicated throughout life? Should they really be permanently used for lifetime? These aspects of the mandibular anterior crowding and their implication at the orthodontic practice will be discussed here to induct reflections and insights for new researches, as well as advances in knowledge and technology on this subject.

Epithelial rests of Malassez: from latent cells to active participation in orthodontic movement

ABSTRACT Introduction: The epithelial rests of Malassez (ERM) represent a group of cells in the periodontal ligament classically consisting of latent or quiescent structures associated with pathological processes. However, recent evidence shows that these structures cannot be considered only as cellular debris. The ERM is a major tissue structure, with functions in maintaining the homeostasis of periodontal tissue, including the maintenance of orthodontic movement. Objective: The present literature review aims at presenting the potential functions of ERM, with emphasis on orthodontic movement and the functional structure of the periodontium. Conclusion: ERM cells have a functional activity in modulation of orthodontic movement, trough their potential for differentiation, maintenance functions and the capacity of repairing periodontium.