In this study, a powder blend representing 6061 Al-alloy was first mixed with Al 2 O 3 ceramic particles and then foamed by using the powder compact melting method. 6061-Al 2 O 3 foams and control specimens 6061 foams (without ceramic reinforcement) were produced. The effects of both different ratios of Al 2 O 3 particle addition and different kinds of heat treatment on hardenability, structure and mechanical behavior of the final foams were investigated. Foams that were fully heat treated had the highest hardness values, and they performed best with an increase in collapse strength up to 100% over the untreated samples. Improved cell structure and decreased drainage were obtained when the Al 2 O 3 addition was not more than 5 vol%. The compression test results were interpreted in terms of the foam's microstructure, and correlations were made relating to the unloading modulus and compression strength of the foams to the relative density.
Purpose
This study evaluated the efficacy of treating periodontitis using subgingival nano-hydroxyapatite powder with an air abrasion device (NHAPA) combined with scaling and root planing (SRP).
Methods
A total of 28 patients with stage III periodontitis (grade B) were included in this study, although 1 was lost during follow-up and 3 used antibiotics. The patients were divided into a test group and a control group. All patients first received whole-mouth SRP using hand instruments, and a split-mouth approach was used for the second treatment. In the test group, the teeth were treated with NHAPA for 15 seconds at 70% power per pocket. Subgingival plaque samples were obtained from the 2 deepest pockets at the test and control sites before treatment (baseline) and 3 months after treatment. The full-mouth plaque index (PI), gingival index (GI), papillary bleeding index (PBI), bleeding on probing (BOP), probing depth (PD) and clinical attachment level (CAL) were recorded at baseline and at 1- and 3-month post-treatment. Real-time polymerase chain reaction was used to determine the colonisation of
Treponema denticola
(
Td
),
Porphyromonas gingivalis
(
Pg
), and
Aggregatibacter actinomycetemcomitans
in the subgingival plaque.
Results
From baseline to the first month, the test group showed significantly larger changes in BOP and CAL (43.705%±27.495% and 1.160±0.747 mm, respectively) than the control group (36.311%±27.599% and 0.947±0.635 mm, respectively). Periodontal parameters had improved in both groups at 3 months. The reductions of PI, GI, BOP, PD, and CAL in the test group at 3 months were greater and statistically significant. The total bacterial count and
Td
and
Pg
species had decreased significantly by the third month in both groups (
P
<0.05).
Conclusions
Applying NHAPA in addition to SRP improves clinical periodontal parameters more than SRP alone. Subgingival NHAPA may encourage clot adhesion to tooth surfaces by increasing surface wettability.
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