InVitro Sorption ofAlbumin, Immunoglobulin G,andLysozyme to EnamelandCementumfromHumanTeeth

Sorption ofthree 125I-labeled humanproteins (albumin, immunoglobulin G,andlysozyme) toenamel and cementumwas investigated. Allthreeproteins sorped mostwhensuspended in0.0005 M solution of phosphate orcalcium chloride wheretheleast competition between solute ionsandlabel occurred. The addition ofhumanserum tolabeled proteins caused a decrease intheir sorption whichcouldbepartially reversed byincreasing theconcentration oflabel. Kinetic experiments demonstrated thatsorption was dependent on protein concentration andincubation timeandthatmostofthesorption occurred within the first minute ofthereaction. Inconclusion, thebinding ofthethreelabeled proteins was affected bythe charge ofthesolute ions andwas dependent onionconcentration andreaction time. Sorption correlated for themostpartwiththepKvalues oftheproteins andthuslysozyme, themostbasic protein, sorped more thanimmunoglobulin G,whichsorped more thanalbumin. Inall cases,cementumboundmore basic protein thandidenamel. Increased levels ofalbumin sorption toenameloccurred whentheprotein was suspended intheCaCl2solution rather thaninphosphate. Inaddition, based on Scatchard analysis, approximately twice asmany potential protein binding sites were foundforcementumversusenamel. Theattachment ofbacteria totooth surfaces isundoubtedlyimportant intheetiology andprogress ofdental disease (7, 10). Colonization ofsupragingival tooth surfaces bygrampositive bacteria isoften mediated bytheselective adsorption ofsalivary proteins toenamel (1). Modification ofthis supragingival surface canstrongly influence thepattern of bacterial colonization andtheresulting pattern ofdental disease (6). Although salivary interactions withenamel and withattached gram-positive bacteria areunderstood tobe critical tothecaries process (12, 22), little isknownabout thesorption ofproteins tocementum.Furthermore, the effect ofcemental acquisition ofserumproteins on the subsequent bacterial colonization ofcementumispoorly understood (2). Nevertheless, itseemsreasonable topostulate thatsorption ofserumproteins torootsurfaces may influence thenature (25), andperhaps also thequantity (9), ofsubgingival bacterial attachment tocementumandmay thusaffect theprogression ofperiodontal disease. Thestudy thatfollows constitutes partofa series ofexperiments designed toexplore thecharacteristics oftheinteractions of subgingival serumproteins withcementumandtodefine the conditions that promote orinterfere withthese interactions.