Purpose: To assess the retentive force of telescopic crowns using polyetherketoneketone (PEKK) high-performance polymer in relation to conventional materials over a long period of time in an in vitro setting. Materials and Methods: Thirty-six sets of primary and secondary crowns were fabricated as per the double crown-retained prostheses approach. Six samples were included in each of the five test groups (1: zirconia/PEKK [Zr/PEKK]; 2: titanium/PEKK [Ti/PEKK]; 3: cobalt-chrome/PEKK [CoCr/PEKK]; 4: PEKK/PEKK; and 5: gold/PEKK [Au/PEKK]) and the single control group (gold/galvano-gold [Au/GA]). The insertion-removal test was performed for 20,000 cycles, and the surface condition was observed. Retentive forces were analyzed using two-way ANOVA (α<0.05).
Results:The retention forces in groups Zr/PEKK and Ti/PEKK significantly decreased over time (group 1: p = 0.035 and group 2: p = 0.001), whereas retentive force increased significantly in groups PEKK/PEKK, Au/PEKK, and control (group 4: p = 0.001, group 5: p = 0.008, and control: p = 0.042). Similar wear was observed on the primary crown in groups PEKK/PEKK, gold/PEKK, and control. Conclusions: Groups PEKK/PEKK and Au/PEKK showed a transition of retentive force similar to the control group. Groups PEKK/PEKK and Au/PEKK had similar wear on the surface compared to control. Therefore, PEKK has a promising clinical potential.
In 2014, the American Association of Oral and Maxillofacial Surgery (AAOMS) recommended surgical treatment for medication-related osteonecrosis of the jaw (MRONJ) patients classified as Stage 3. In 2016, the Japanese position paper recommended surgical treatment classified as Stage 2. Some systematic review reported effectiveness of surgical treatment for MRONJ. However there is no concerted consciousness on the treatment methods of MRONJ patients in the present. This study aimed to retrospectively elucidate clinical outcomes of the surgical treatment of MRONJ patients under the same criteria. This study included 86 patients in 40 osteoporosis patients (5 men and 35 women, average age: 78.8 years) and 46 cancer patients (18 men and 28 women, average age: 67.7 years). The outcome was classified into two categories: Healing or No healing in each stage. Among 86 patients, MRONJ was found in 91 jaws, of which 69 jaws (75.8%) were surgically operated. Total healing rate of surgical treatment was 85.5%, and total healing rate of conservative treatment was 4.5%. It was suggested that surgical treatment for MRONJ had a high clinical response rate in all stages.
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