Objective:To observe the clinical effect of tooth extrusion with progressive methods for anterior teeth with crown-root fracture.

Objective: To avoid the affection of the injury to the healthy orth-teeth and the beauty because of the absorption of the alveolar bone after the teeth extraction,by remaining teeth with crown and root fracture under gingiva within 3 mm.

Objective To observe clinical efficacy of crown lengthening surgery for the treatment of crown-root-fractured teeth,subgingival fractured edge.

Clinical efficacious investigation of partial pulpotomy in treatment of crown fracture with pulp exposure in immature permanent incisors;

Three years clinical observation of effect of young permanent incisal teeth with crown fracture restored by IPS Empress porcelain laminate veneers;

The restorations of immature permanent teeth with crown fractures by carbon fiber posts and resin cores;

Subcellular structures of the root cap cells of hairy roots in astragalus membranaceus induced by infection of Agrobacterium rhizogenes;

This artical summarized the research progress on hydrotropism of plant root system internationally from three aspects such as,how to induce hydrotropism by roots,root cap is the site of apperceiving humidity gradient,and the research on hydrotropism at the molecular level.

The number of border cell reached the max when root length was 15 mm and when root length was 1 mm the PME activity of root cap achieved the max.