Long-term effects of various cleaning methods on polypropylene/ethylene copolymer retainer material

Objectives:To evaluate long-term light transmittance, surface roughness, and flexural modulus of polypropylene/ethylene copolymer retainer material after exposure to different cleaning methods.Materials and Methods:Standardized polypropylene/ethylene copolymer retainer specimens (n = 70, 50.8 mm × 12.7 mm × 1.0 mm) were subjected to seven chemical cleaning solutions: Invisalign cleaning crystals, Retainer Brite, Polident, Listerine mouthwash, 2.5% acetic acid, 0.6% NaClO, and 3% H₂O₂ for 6 months. The specimens were exposed to the different solutions twice a week for 15 minutes or according to manufacturer''s instructions, then stored in artificial saliva at 37°C. Another group of specimens (n = 10) were brushed with a standardized toothbrushing machine for 2 minutes twice a week. At baseline and 6 months, light transmittance, surface roughness, and flexural modulus of the specimens were quantified using spectrophotometry, profilometry and three-point bend testing, respectively. Qualitative analysis was performed using a scanning electron microscope (SEM). Statistical analyses were performed at a significance level of .05.Results:The results showed that light transmittance decreased significantly from baseline for all cleaning methods at 6 months. For an individual method, no significant differences were observed between specimens at baseline and 6 months in surface roughness and flexural modulus. No discernible differences in surface features were observed on SEM images.Conclusions:The results indicate that different cleaning methods affect the long-term light transmittance of the studied polypropylene/ethylene copolymer retainer material. However, for an individual cleaning method, no significant differences were shown for surface roughness or flexural modulus values at 6-months compared to baseline.     

Long‐Term Follow‐Up of CeraOne™ Single‐Implant Restorations: An 18‐Year Follow‐Up Study Based on a Prospective Patient Cohort

Background: Knowledge on long‐term clinical performance of more than 5 years on the single‐implant CeraOne? (Nobel Biocare AB, Gothenburg, Sweden) concept is limited. Purpose: The aim of this study is to report the long‐term clinical performance of the first CeraOne single‐implant restorations, installed 17 to 19 years ago. Materials and Methods: The group comprised 57 patients provided with 65 CeraOne single‐tooth restorations. Sixty‐two all‐ceramic and three metal‐ceramic crowns were cemented between 1989 and 1991. Patients were followed up clinically and with intraoral radiographs at placement, after 1, 5, and between 17 and 19 years after placement. Results: Data were available for altogether 48 patients, followed up on an average time of 18 years. Excluding deceased patients (n = 2) and failed implant patients (n = 2), only five patients were lost to follow‐up (8.8%). Two implants failed, resulting in an 18‐year implant cumulative success rate (CSR) of 96.8%, and altogether eight original single‐crown restorations were replaced (CSR 83.8%). The most common reason for crown replacement was infra‐position of the implant crown (n = 3). Many of the remaining original crowns showed various signs of implant crown infraposition at the termination of the study. In general, the soft tissue at the restorations was assessed to be healthy and comparable with the gingiva at the adjacent natural teeth. Bone levels were on an average stable with only few patients exhibiting bone loss of more than 2 mm during 18 years in function. Conclusion: This long‐term follow‐up study of single‐implant restorations shows encouraging results with few implant failures and minimal bone loss over an 18‐year period. Original single‐crown restorations were replaced more frequently, because of, for example, implant crown infraposition and veneer fractures. The CeraOne concept proved to be a highly predictable and safe prosthodontic treatment.