Ingestion and egestion of polystyrene microplastic fragments by the Pacific oyster, Crassostrea gigas.

Marine microplastics (MPs) pose a risk to human health through accumulation in maricultural organisms, particularly bivalves. Various studies have reported the presence of MP particles in Pacific oysters (Crasostrea gigas). In this study, we investigated the size-specific ingestion and egestion of polystyrene (PS) MPs by Pacific oysters. The cultivation density of C. gigas was maintained at 1 L of filtered seawater per oyster (n = 5) during the MP ingestion and egestion experiments. On exposure to 300 n/L of PS MP fragments for 7 d, 60.4% of the PS was ingested within 6 h (7.25 × 102 ± 1.36 × 102 n/indv.), and the ingestion was saturated at 12 h (1.2 × 103 ± 2.2 × 102 n/indv.) in C. gigas. The maximum MP ingestion capacity (Igmax) of a single Pacific oyster was 73.0 ± 16.3 n/g wet weight. Further, 62.9% of the PS MP particles were egested for 7 d from the saturated single C. gigas. Ingestion and egestion varied according to the PS MP size. In the case of <50 µm PS MP, ingestion rate was low but MP amount and net-ingestion efficiency was significantly higher than other PS MP sizes. In addition, egestion, egestion rate, and net-egestion efficiency for <50 µm PS MPs were significantly higher than other PS MP sizes. Therefore, smaller MPs (<50 µm) normally exhibit the highest ingestion and egestion rates; therefore, the 50-300 µm size fraction exhibited the highest residual possibility (particles >1000 µm were excluded). Additionally, considering the net-egestion efficiency, the most economical and efficient depuration period was 24 h. This study clarifies the size-specific MP accumulation in oysters, and the egestion results suggest that the potential risk of MPs to human health through the intake of maricultural products could be reduced by depuration.

Resonance Frequency Analysis of Tapered Implants Placed at Maxillary Posterior Sites After Lateral Sinus Augmentation: A 1.5-year Follow-Up Prospective Study.

OBJECTIVES: To use resonance frequency analysis to evaluate tapered implants placed at maxillary posterior sites after lateral sinus augmentation. MATERIALS AND METHODS: Patients who had missing teeth in the maxillary posterior area and required lateral sinus augmentation before implant placement were enrolled in this study. After a 6-month healing period, a tapered implant (Osstem TSIV) was placed. Implant success rate, survival rate, and marginal bone loss of the implants were measured. For resonance frequency analysis, implant stability quotient (ISQ) values were measured at each visit during a 1.5-year follow-up period. RESULTS: Twenty-four patients completed the study procedure. The residual bone height was 2.57 ± 1.10 mm (mean ± SD). Healing of the grafted area was uneventful in all cases, and 55 tapered implants were installed. The implant success rate was 95.56%, and the survival rate was 100% throughout the observation period. The marginal bone loss was limited to 0.22 ± 0.44 mm. ISQ increased gradually from 68.40 ± 11.14 to 82.24 ± 4.75 during the 1.5-year follow-up period. CONCLUSION: The tapered implants showed good initial and final stability after placement in the soft bone of the maxillary posterior area after lateral sinus augmentation.

Dimensional alterations following vertical ridge augmentation using collagen membrane and three types of bone grafting materials: A retrospective observational study.

BACKGROUND: Various biomaterials have been introduced for vertical ridge augmentation to replace autogenous block bone grafting. PURPOSE: This retrospective study radiographically evaluated dimensional alterations of the vertically augmented alveolar ridge using collagen membrane and 3 types of materials: autogenous bone block, allogenous bone block, and particulated bone substitute. MATERIALS AND METHODS: The electronic medical records of 32 patients who received vertical ridge augmentation using 3 types of materials were searched: 9 for autogenous bone block, 12 for allogenous bone block, and 11 for particulated bone substitutes. The vertical bone gain, progression of bone resorption, and peri-implant marginal bone loss after prosthetic loading were measured on follow-up radiographs. RESULTS: The alveolar ridge was vertically augmented by 5.13 ± 1.61, 4.54 ± 2.48, and 3.90 ± 0.85 mm (mean ± standard deviation) after grafting with autogenous bone block, allogenous bone block, and particulated bone substitute, respectively. The radiographic vertical height of the augmented ridge that received autogenous bone block reduced continuously during the first year but was stable thereafter. Sites that received allogenous bone block or particulated bone substitute exhibited dimensional shrinkage for up to 1.5 years postsurgery. However, the peri-implant marginal bone loss did not exceed 1 mm throughout the observational periods in all groups. CONCLUSIONS: The clinical findings of this study suggest that the alveolar ridge can be vertically augmented using either allogenous bone block or particulated bone substitute. However, they require a longer healing period to ensure dimensional stability compared to the autogenous bone block.