The crown-root ratio (C/R) theory of natural teeth has been widely recognized in the field of stomatology,and has important clinical significance in predicting and assessing the prognosis of natural teeth as well as for abutment selection during denture restoration. In the past few decades, scholars have advocated for the implantation of implants as long in length as possible to improve the success rate according to the theory of crown-root ratio of natural teeth. However, with the application of short implants, our philosophy of implantation has changed, and the relationship between the crown-implant (C/I) ratio and complications has become one of the current research hotspots. In this paper, the concept of the crown-implant ratio, the research progress of the C/I ratio, the implant survival rate and clinical complications of implant restoration were reviewed and summarized, and the following suggestions were put forward: although most studies have shown no significant correlation between the C/I ratio and implant survival or marginal bone loss, this relationship may increase the risk of mechanical complications. A C/I < 3 and a crown length < 15 mm are recommended in implant restoration; when ultra-short implants are applied, the implant system can increase the bone-to-implant contact area, and splint prostheses such as crown or bridge are recommended.

Objective : To explore the clinical effect of the alveolar crest approach in the treatment of odontogenic maxillary sinusitis and the repair of edentulous implants in this area. Methods: This was a retrospective case series of 20 patients with odontogenic sinusitis. The pathogenesis in each case was investigated. After elimination of the dental origin, each patient was treated with flushing, drainage and anti-inflammatories through the alveolar crest approach. Postoperative CBCT reexamination was performed to evaluate the therapeutic effect. Maxillary sinus elevation surgery with simultaneous or delayed implantation was performed after maxillary sinusitis healing was confirmed. The patients were followed postoperatively. Results : Twenty patients with odontogenic sinusitis were treated by the alveolar crest approach, and 17 were cured, for a cure rate of 85%. Among them, 17 of the maxillary sinusitis patients were followed for 1 year, with good results. Conclusion The alveolar crest approach is feasible for the treatment of odontogenic maxillary sinusitis and can serve as a minimally invasive method for the repair of edentulism in this area and implantation.

Objective : To investigate the effect of a laser-etched pure titanium surface on proliferation of the human osteosarcoma cell line MG63 and to provide a basis for study of implant surface modification. Methods: The pure titanium plate was cut into titanium pieces by a numerical control machine tool and divided into smooth surface and laser etching groups. The titanium surface of the laser etching group was etched with an Nd:YAG continuous wave laser using predetermined parameters, and the surfaces were observed by scanning electron microscopy (SEM). The surface micromorphology of each titanium sheet was evaluated. The relative element content of the titanium surface was measured by energy dispersive X-ray spectroscopy (EDS). The Ra value of each surface was determined using the Veeco roughness tester. MG63 cells were inoculated on 2 sets of titanium tablets. At 1, 3, and 6 h postinoculation, cell adhesion to the two groups of titanium sheets was observed under the microscope. At 24 h after inoculation, cellular F-actin was directly stained using immunofluorescence, and the morphology of the cytoskeleton was observed by laser confocal microscopy. Cell proliferation was examined at 1, 3, and 5 d using a MTS kit, and the data were analyzed with SAS 9.4. Results : The surface of the smooth surface group was smooth and flat, the element composition was pure titanium, and the roughness Ra was 179.23 nm. The surface of the laser-etched group formed a regular and uniform pore structure. The composition was mainly Ti, O, C, etc, and the surface roughness Ra was 14.11 μm. A large number of cells were uniformly distributed on the two titanium sheets in the observations at 1, 3, and 6 h. At 24 h postinoculation, MG63 cells were completely stretched on the two sets of titanium sheets and had extended a large number of pseudopods and microfilaments to cross-link with peripheral cells; moreover, the cell division phase was observed. The cell proliferation of the two groups at 1, 3, and 5 d showed a significant increase with time, indicating that no cytotoxicity occurred on the surfaces of the two groups. However, the cell proliferation in the laser-etched group was superior to that in the mechanical smooth surface group. Conclusion The surface morphology of titanium can be controlled by laser etching, which is conductive to increase the microstructure of implants without cytotoxicity and promoting osteoblast proliferation in the early stage.