Traditional titanium implants do not completely meet the clinical requirements because they are bioinert. The surface of titanium implants, modified by strontium ions, can enhance osseointegration and reduce peri-implantitis. In this paper, the biological properties of titanium implant surfaces modified by strontium ions were reviewed. Strontium ions can be coated on the implant surface by hydrothermal treatment, electrochemical deposition, phosphate chemical conversion, flame-spraying, supramolecular self-assembly, magnetron sputtering, laser deposition and alkali etching. Implant surfaces modified by strontium ions can not only promote osteogenesis and early osseointegration but also inhibit bacterial growth and reduce postoperative infections. Even better osseointegration and antibacterial effects can be achieved when strontium ions are incorporated with other elements, such as silver, zinc, gallium, and calcium. However, most of the studies on the use of strontium ion-modified titanium implants are animal experiments and in vitro experiments, and the observation time is short compared with the actual service life of the implants. Thus, the conclusions obtained may be different from the actual clinical application, and the long-term effects need to be studied. In addition, the osteogenic effects of various modification methods also need to be compared. Future research can focus on the following points: ① to find efficient modification methods that can be widely used in the clinic; ②to study how to control the concentration of strontium ions near the implant to exert their biological function and reduce their toxic side effects; and ③ to conduct long-term follow-up clinical trials to observe their osteogenic and antibacterial effects.

Objective: To explore the early failure of narrow-diameter implants (NDIs) and to provide a reference for clinical implant restoration. Methods: From April 2017 to April 2020, data from a total of 725 patients (with 1 001 NDIs) who accepted implant restoration due to dentition defects were collected from the department of dental implantology in a stomatological hospital; 353 males and 372 females were included. The early failure rate of 1 001 NDIs was retrospectively analyzed. Univariate generalized estimated equation (GEE) and multivariate GEE were used to explore risk factors, including age, sex, implant location, materials, surface modification, length, bone augmentation and healing procedure, associated with early failure of NDIs. Results: There were 34 cases of early failure among 725 patients, including 38 NDIs. The early failure rate of NDIs was 4.69% at the patient level and 3.80% at the implant level. There was no significant difference in the early failure rate of NDIs among different age groups, sexes, implant materials, surface modifications, lengths, and healing procedures (P>0.05). Univariate analysis showed that there was a significant difference between the early failure rate of NDIs in the anterior maxilla group (2.16%) and the anterior mandible group (8.64%) at the implant level (P<0.001). However, there was no significant difference in the early failure rate between the anterior maxilla group and the posterior group (3.35%) (P>0.05). In addition, in the anterior region, the early failure rate of NDIs in the group with simultaneous bone augmentation was significantly lower than that of the group without bone augmentation (P<0.05). However, multivariate GEE analysis showed that the early failure rate of NDIs was only significantly positively correlated with implants in the mandibular anterior region (P<0.01). Conclusion The overall early survival rate of Straumann 3.3 mm NDIs is greater than 95%. The early failure of NDIs in the anterior mandible region is much higher than that in the anterior maxilla region and posterior region.

Objective : To explore the etiology, clinical manifestations, diagnosis and treatment of multiple idiopathic root resorption to provide a reference for clinical diagnosis and treatment. Methods: The clinical data of a case of multiple idiopathic root resorption were analyzed retrospectively, and the related literature was reviewed. Results: The patient had no history of orthodontic correction, occlusal trauma, trauma history or other causes of root resorption. Clinical examination revealed full-mouth gingival congestion, redness, a loose texture, and variable degrees of destruction of the alveolar bone. Imaging examination showed that teeth 13, 16, 26, 36, 46 had idiopathic root resorption. The diagnoses were multiple idiopathic root resorption and periodontitis. The pathology tests showed that a large number of osteoclasts were present in the soft tissue surrounding the teeth. Whole-exome sequencing showed that there was a strong correlation between gene mutations (WNT7a and HSPG2) and the present phenotype. Root resorption of teeth without periodontitis was stopped after periodontal treatment during the 19-month follow-up. Tooth 13 was removed, and extraction socket preservation was performed. The etiology of idiopathic root resorption may be related to gene mutations, but it is not clear. At present, there is no effective treatment. Conclusion Multiple idiopathic root resorption has an unknown etiology, but it may be related to WNT7A and HSPG2 gene mutations. The rate of root resorption can be slowed by controlling periodontal inflammation.