Frequency of Root Surface Microgrooves Associated with Periodontal Destruction.

Small linear microgrooves have been observed on root surfaces associated with osseous defects when videoscope-assisted minimally invasive surgery (V-MIS) is performed. The aim of this study was to evaluate the frequency of occurrence of these microgrooves associated with osseous defects. Videos of dry skulls from an anatomy department collection and videos made during consecutive V-MIS procedures on patients were evaluated to determine the presence or absence of microgrooves associated with osseous defects. In the dry skulls, 69 areas of apparent periodontal osseous defects were evaluated. In the V-MIS videos, 63 osseous defects were evaluated. In the dry skulls, 34 sites were positive for microgrooves on the root surfaces (49%), while in the V-MIS procedures 50 sites were positive for microgrooves (79%). Microgrooves of unknown origin were detected in a high percentage of osseous defects. Microgrooves may represent risk factors for site-specific progression of periodontal destruction.

Specific inactivation of Twist1 in the mandibular arch neural crest cells affects the development of the ramus and reveals interactions with hand2.

BACKGROUND: The basic helix-loop-helix (bHLH) transcription factor Twist1 fulfills an essential function in neural crest cell formation, migration, and survival and is associated with the craniosynostic Saethre-Chotzen syndrome in humans. However, its functions during mandibular development, when it may interact with other bHLH transcription factors like Hand2, are unknown because mice homozygous for the Twist1 null mutation die in early embryogenesis. To determine the role of Twist1 during mandibular development, we used the Hand2-Cre transgene to conditionally inactivate the gene in the neural crest cells populating the mandibular pharyngeal arch. RESULTS: The mutant mice exhibited a spectrum of craniofacial anomalies, including mandibular hypoplasia, altered middle ear development, and cleft palate. It appears that Twist1 is essential for the survival of the neural crest cells involved in the development of the mandibular ramal elements. Twist1 plays a role in molar development and cusp formation by participating in the reciprocal signaling needed for the formation of the enamel knot. This gene is also needed to control the ossification of the mandible, a redundant role shared with Hand2. CONCLUSION: Twist1, along with Hand2, is essential for the proximodistal patterning and development of the mandible and ossification.