Peri-implantitis is an inflammatory disease caused by biofilm, and when it progresses, it leads to implant loss. To prevent peri-implantitis, it is important to perform maintenance including plaque control. Therefore, we conducted a search for literature comparing the prognosis of patients who did and did not receive maintenance after implant treatment. The search yielded three retrospective cohort studies. In all three studies, the risk of developing peri-implantitis was higher in patients who did not receive maintenance compared to those who received maintenance for more than 5 years. Therefore, regular maintenance visits, mainly for oral hygiene, after implant treatment are important to prevent peri-implantitis and are strongly recommended.

Currently, many manufacturers are developing intraoral scanners, but there are still many unclear points about their implant position reproducibility. Therefore, this study compared the implant position reproducibility between the optical impression method using various intraoral scanners and the conventional silicone impression method, using a jaw model of a case with a missing 21 (FDI) of the maxilla.

A master model was produced with an implant body (Xive Implant, Dentsply Sirona) implanted in the 12 corresponding part of the maxillary gypsum model about 1 mm below the bone margin. First, a scan body was attached to the master model, and basic data of the master model was acquired using a high-precision scanner (D1000, 3Shape) (MM). Next, an optical impression of the master model was taken by various intraoral scanners (Primescan, Dentsply Sirona ; Trios3, 3Shape ; Trios4, 3Shape ; iTero element 5D, Zimmer Biomet Dental), and master model data were acquired five times each (Primescan : PRS, Trios3 : TR3, Trios4 : TR4, iTero element 5D : IT5). Next, a working model was produced by a master model using the open tray method. A scan body was attached to a working model, and data were acquired using a high-precision scanner (IMP, n＝5). The acquired data for MM was imported into 3D analysis software, then the data of IMP, PRS, TR3, TR4, and IT5 were superimposed, respectively. The difference in position data was visualized by color mapping. In this study, it was assumed that the error range of the superstructure was within 50 nm, and the precision ratio with respect to the surface area of the scan body was calculated. Statistical processing was then performed and the results were compared. From the color mapping analysis, the scan bodies of PRS and IT5 showed many errors within ±20 μm, while the IMP showed a surface error of －50 μm or more above the scan body. As a result of statistical processing, no statistically significant difference was found between PRS, TR3, TR4 and IT5, but a significant difference was found between PRS, TR3, TR4, IT5 and IMP.

From the above, as a result of comparing the implant position reproducibility of various intraoral scanners using 3D analysis software, the optical impression method using the intraoral scanner has higher implant position reproducibility than the silicone impression method.

Purpose : Titanium and its alloys used for dental implants are known to corrode in fluoride-containing solutions. Electro chemical measurements are effective for determining the corrosion resistance of metallic materials. The purpose of this study was to clarify the corrosion behavior of commercially pure titanium and its alloys in a fluoride-containing solution using electrochemical measurement.

Method : Commercially pure titanium (TI), Ti-6Al-4V (TAV), and Ti-7Nb-6Al (TNB) were prepared by polishing with abrasive papers. The solutions used were saline (SAL) and fluoride-containing saline solution (NAF). Electrochemical measurements were calculated using a potentiostat. The open circuit potential (OCP), polarization resistance (Rp), and passive current density (I₃₀₀ and I₅₀₀) derived from the anodic polarization curve in a solution at 37℃ were evaluated.

Results : When immersed in SAL, all alloys showed stable OCP curves up to 60 min, and superior corrosion resistance was indicated from the Rp value and I₃₀₀ to I₅₀₀ values. When immersed in NAF, the OCP curve showed a gradual decrease in potential for the first 30 min then a sudden drop. In addition, the Rp value of specimens placed in NAF was significantly lower than those placed in SAL. The I₃₀₀ and I₅₀₀ values in NAF were greater than those in SAL, and TAV and TNB had greater values than TI, with TAV having the highest value.

Conclusion : All titanium alloys had superior corrosion resistance in SAL. In NAF, the passive film was destroyed in all titanium alloys, and TAV and TNB showed lower corrosion resistance to fluoride than TI.

Bone-anchored implant superstructures are recognized as predictable treatment modalities for edentulous patients with a high survival rate of the implants. However, prosthodontic complications, such as fracture and artificial teeth wear, sometimes occur under long-term use, resulting in the need to reproduce the prostheses. This article introduces a new digital workflow using an intraoral scanner and novel scan gauges to reduce the number of appointments for the patient.

A 55-year-old man with a chief complaint related to masticatory difficulty was referred due to fracture and tooth wear of prostheses. In 2010, four implants had been placed in both the upper and lower edentulous jaws and treated with bone-anchored bridges made from acrylic resin. During 10 years of use, the prostheses had become severely damaged. The damaged prostheses were tentatively fixed and used as provisional restorations for adjustment of the occlusion and mucosal aspects. To reproduce the prostheses, an intraoral scanner and novel scan gauges were used to transfer the positions of the implants, morphology of the mucosa, occlusion, and shape of the provisional restoration at the first appointment. The reproduced definitive prostheses made from a zirconia framework cemented on a titanium base were provided at the second appointment.

It is suggested that this reproduction method can not only reduce the number of appointments and distress of the conventional impression-taking for both patient and dentist, but also provide precise prostheses.

To date, many bone substitutes have been developed and used overseas, but there was no bone substitute approved under Japanese regulations for dental implants. Recently, a bone substitute containing absorbable carbonate apatite as the main component was approved for application to dental implants for the first time in Japan, and has been clinically applied. However, there are no reports of ridge augmentation using this bone filling material. We report the histological observation of cases of sinus lift and ridge augmentation with carbonated apatite bone substitute.