Hello! Hope you're doing well and having no pain with the concerned tooth. If, by inserting pin and building core you mean post and core procedure, it is completely safe. Post and core is a modality to salvage badly broken tooth. The procedure starts with a good endodontic treatment followed by building the post and core. The post, which is the intra-radicular part provides retention for the core, while core makes up for the missing crown structure of the tooth. Evolution of dentistry has contributed to availability of a lot of techniques and materials for post and core. As for the crown, with evolution of newer ceramics like zirconia, an all ceramic crown well withstands the biting forces and serves well if done properly. I hope this answers your queries. Please take care!