Apoptosis in pulp elimination during physiological root resorption in human primary teeth

Abstract

Pulp samples of 50 healthy human teeth with indication for extraction were examined to evaluate the role of apoptosis in pulp elimination during physiological root resorption. Two groups were formed: a test group (n=30) composed of pulp samples of primary teeth with physiological root resorption and a control group (n=20) composed of pulp samples of permanent maxillary third molars. Morphological evidence of apoptosis as well as in situ detection of cellular DNA fragmentation by TUNEL assay and detection of internucleosomal pattern of fragmentation of the genomic DNA by electrophoresis were observed. The apoptotic index of the primary tooth group was significantly higher than that of the permanent tooth group (51.01 ± 0.52 versus 25.32 ± 0.68) (p<0.001). TUNEL reaction showed intense and diffuse labeling in the pulp samples of primary teeth, which were discrete in the controls. Intense DNA internucleosomal fragmentation, a specific pattern for apoptosis, was observed in primary tooth pulps DNA by electrophoresis, in the permanent tooth pulps this pattern fragmentation of the genomic DNA for apoptosis were not present. These results seem to indicate a role of apoptosis in pulp elimination during the physiological root resorption of human primary teeth.

Caspase‐3/caspase‐8, bax and bcl2 in pulps of human primary teeth with physiological root resorption

“…Pulps of 40 healthy human primary teeth were collected. Twenty samples were used for RNA extraction and the others for immunohistochemical reaction, according to a statistical evaluation carried out in a previous study 2 . Previously to the teeth extraction, indicated by orthodontic reasons, a clinical and radiographic examination certified that they were free of fracture or any pathology that could have contaminated their pulps.…”

“…During this process, all root structures are eliminated, including the pulp 1 . Apoptosis is the mechanism responsible for the death of pulp cells during the physiological root resorption in human primary teeth; however, its pathway has not been well characterised yet 2 …”

Dental findings in 14q terminal deletion syndrome

“…JAG2, a component of the Notch signaling pathway, lies near this junction. Impaired apoptosis, which has been suggested to play a role in pulp elimination during root resorption (Rodrigues et al, 2009), may contribute toward primary tooth over-retention because of haploinsufficiency of proapoptotic genes in the deleted region. We propose that heterozygous deletion of JAG2, perhaps in combination with more distal genes, may contribute toward the craniofacial phenotype of 14q terminal deletion syndrome.…”

Apoptotic factors in physiological and pathological processes of teeth and periodontal tissues – literature review

“…The mechanism of pulp atrophy is not known. Studies have shown that apoptosis progresses more intensively in the pulp of primary teeth than in permanent teeth, hence, apoptosis probably takes part in pulp atrophy during root resorption [17].…”