Do Implant Coatings Affect Healing of Placed Implants? An Umbrella Review.

PURPOSE: To analyze the available evidence and assess the effect of different implant coatings on healing outcomes. MATERIALS AND METHODS: Using the PICOS strategy, a structured question was formed. A protocol was agreed upon and registered with PROSPERO (no. CRD42022321926). The MEDLINE, Embase, Cochrane Database of Systematic Reviews, Scopus, Web of Science, Pubmed, and ScienceDirect databases were searched using a structured strategy. Study selection was independently carried out in duplicate, first by title and abstract, then by full-text assessment. Quality and risk of bias were independently assessed in duplicate using AMSTAR 2 and ROBIS. Data extraction was independently undertaken in duplicate using a predefined extraction form. RESULTS: The search yielded 11 systematic reviews for inclusion. The most commonly assessed coatings were based on calcium phosphate-including hydroxyapatite (HA), brushite, and bioabsorbable nano-HA-followed by bisphosphonate, then bioactive glass coatings. Included reviews most frequently assessed marginal bone loss (MBL), bone-to-implant contact (BIC), and survival/success rates. There was considerable heterogeneity and small sample sizes. The quality assessment suggested low confidence in the reviews and high risk of bias. CONCLUSIONS: The included reviews provide weak evidence that implant coatings improve osseointegration and reduce MBL following implant placement. There was weak evidence for progressive complications for calcium phosphate coatings. Further research and long-term multicenter controlled clinical trials with improved standardization and control of bias are required to better understand the effects of coating implants.

Kinetics of Hypobromous Acid Disproportionation.

The kinetics of aqueous hypobromous acid disproportionation are measured at 25.0 degrees C from p[H(+)] 0.2 to 10.2. The reactions are second order in HOBr with a maximum rate at pH 3-8. The rate of disproportionation decreases significantly above pH 8 as OBr(-) forms. Another suppression observed below pH 3 is attributed to the reversibility of initial steps in the decomposition. The rate expression is given by -d[Br(I)]/dt = n{(c/(c + [H(+)])k(1a) + k(B)[B])[HOBr](2) + k(1b)[OBr(-)](2)}, where k(1a) = 2 x 10(-)(3) M(-)(1) s(-)(1), k(B)[B] is a general-base-assisted pathway, k(1b) = 6 x 10(-)(7) M(-)(1) s(-)(1), n is a stoichiometric factor that ranges from 2 to 5, and c is a ratio of rate constants that is equal to 0.03 M. Decomposition is catalyzed by HPO(4)(2)(-) (k(B) = 0.05 M(-)(2) s(-)(1)) and by CO(3)(2)(-) (k(B) = 0.33 M(-)(2) s(-)(1)). Above pH 8, the first observable product is BrO(2)(-) (initially n = 2). Below pH 4, n = 5 due to Br(2) and BrO(3)(-) formation. From pH 4 to 7, n varies from 5 to 3. A detailed mechanism is presented.

Equilibrium and Kinetics of Bromine Hydrolysis.

Equilibrium constants for bromine hydrolysis, K(1) = [HOBr][H(+)][Br(-)]/[Br(2)(aq)], are determined as a function of ionic strength (&mgr;) at 25.0 degrees C and as a function of temperature at &mgr; approximately 0 M. At &mgr; approximately 0 M and 25.0 degrees C, K(1) = (3.5 +/- 0.1) x 10(-)(9) M(2) and DeltaH degrees = 62 +/- 1 kJ mol(-)(1). At &mgr; = 0.50 M and 25.0 degrees C, K(1) = (6.1 +/- 0.1) x 10(-)(9) M(2) and the rate constant (k(-)(1)) for the reverse reaction of HOBr + H(+) + Br(-) equals (1.6 +/- 0.2) x 10(10) M(-)(2) s(-)(1). This reaction is general-acid-assisted with a Brønsted alpha value of 0.2. The corresponding Br(2)(aq) hydrolysis rate constant, k(1), equals 97 s(-)(1), and the reaction is general-base-assisted (beta = 0.8).