Tan Weidong et al. Studied the restoration of Crown Defects in adolescents with light cured composite resin. The subjects of the study were 38 adolescent patients and 47 defective crowns, including 25 males and 13 females, aged 9-14 years, 39 maxillary central incisors and 8 lateral incisors. All patients were treated with root canal therapy. The post canal was prepared in the root canal. After the decayed necrotic tissue and thin-walled weak tip were removed, the glass fiber post was bonded to the root canal with double curing resin adhesive, and the light was irradiated for 3min. The remaining crown and fiber post after acid etching shall be coated with composite photosensitive resin by layered filling, and the cut ends shall be treated according to different ages. After the outermost resin is stacked, a layer of glycerin shall be coated, and then multiple and multi-directional illumination shall be conducted. The results showed that 46 incomplete crowns were successfully repaired, with an effective rate of 97.87%, and one failed, with a failure rate of 2.13%. The failure was due to the discoloration of the teeth caused by secondary caries.
Wang Yanfang also studied 23 adolescents with crown defects repaired with light cured composite resin, including 15 males and 8 females, aged 8-13 years. All 23 restored teeth were maxillary anterior teeth, without damage to the root and alveolar bone. The crown fracture was located above the gingiva, and the isolated parts were fresh and intact. 23 patients were treated with charisma and Karisma composite resin to repair the incomplete crowns, and the composite resin was completely cured by light. The results showed that there was no significant difference between the color of the crown and that of the adjacent teeth after the light cured composite resin restoration. The stability, shape and X-ray root tip film of the broken crown after reconnection were observed and followed up. The follow-up time ranged from 6 months to 2 years. At the 8th month, one restored crown fell off due to trauma and was well preserved after reconnection. At the 14th month, the broken end fell off in one case due to excessive force bite of the anterior teeth, and was well preserved after reconnection. The X-ray films of the rest broken crown reconnected teeth showed that the root was in good condition, the root tip was free of inflammatory shadow, and the stability, color and appearance were complete without damage. The retention rate of the broken crown was 91.3%.
Song Qiuying et al. Studied the restoration of molar crown defects with light cured composite resin. The subjects of the study were 84 patients with molar crown defects, including 51 males, 61 molars, 33 females, 35 molars, aged 24-72 years. All molar crown defects were 1 / 2-3 / 4, no gingivitis, periodontitis, no tooth loosening, etc. After 96 molars were treated with root canal therapy or plasticization, they were fixed with root canal screw. After fixation, they were fully rinsed and dried by conventional acid etching, and filled and cured with light curing composite resin. The results showed that all patients were followed up for 1-5 years, and the excellent and good rate was 100% within 3 years. After 5 years of follow-up, the excellent and good rate was 94.19%, and the failure rate was 5.81%. Among them, it is preferred that there is no uncomfortable feeling after filling, the filling body is complete, no looseness, no crack, the edges are close, and the chewing and tearing are good; Good: after filling, the crown is complete in shape, with cracks at the edges. The filling material has slight wear but no looseness. It has general chewing and biting function; The failure is that the filling body is loose, falls off or cracks with the tooth tissue, the root canal screw is loose, the filling material falls off, does not have the general chewing and biting function, and has obvious gingival inflammation.
