2022 Volume 35 Issue 2 Pages 74-82
The RTB classification was proposed as a simplified classification of implants. R stands for rehabilitation, which is the purpose of implant treatment. R1 is for restoration of chewing function, R2 for esthetic function, and R3 for denture function. T stands for time, the number of years since implant treatment, where T1＜10 years, 10≤T2＜20 years, and T3≥20 years. B stands for bone, indicating bone resorption around the implant, and was evaluated in three groups : B1 : no resorption, B2＜3 mm, and B3≥3 mm. To determine the validity of the RTB classification, 1,463 implants and 294 patients were studied at two institutions over a 30-year period from 1990 to 2019. Bone resorption was determined from dental X-rays. Of the 1,463 implants, 110 implants were dropped or removed. This was 7.52％ of the total number of implants, and the simple survival rate was 92.48％. The results showed that items R and B of the RTB classification were predominantly associated with the removal ratio. B3 (bone resorption ≥3 mm) had a significantly higher removal ratio than B1 (no bone resorption) and B2 (bone resorption＜3 mm) (p＜0.01). These results suggest that examination items B1 to B3, which indicate the degree of bone resorption in the RTB classification, are effective indicators for determining the prognosis of implants. In addition to the RTB classification of R, T, and B, the presence or absence of bone construction during implant surgery, probing pocket depth (PPD), and bleeding on probing (BOP) during maintenance were also investigated as additional items. The classification was as follows : stage Ⅰ : PPD＜6 mm & BOP (－), Ⅱ : PPD＜6 mm & BOP (＋), Ⅲ : PPD≥6 mm & BOP (－), Ⅳ : PPD≥6 mm & BOP (＋).
The results showed that the bone construction group was significantly more likely to be classified as B2 or B3 than the group without bone construction (p＜0.01). Stage Ⅲ and Ⅳ had a significantly higher removal ratio than stage Ⅰ and Ⅱ (p＜0.01), and the percentage of B3 was also significantly higher (p＜0.01). The RTB classification is characterized by its simplicity and can be determined only by 1) medical interview, 2) intraoral examination, and 3) dental X-ray examination, enabling even dentists who do not perform implant treatment or who have just graduated from dental school to classify the implants.
