title: Restoration gaps needed to exceed a threshold size to impede sealed lesion arrest in vitro.
abstract: OBJECTIVE
  After selective excavation, bacteria are sealed beneath restorations. Leaking restorations could maintain carbohydrate-supply, leading to lesion progression and pulp damage. It is unclear if fluid (and thereby carbohydrate) exchange occurs through any interfacial gaps, or if such exchange only occurs in case gaps exceed a certain threshold size. We investigated how different restoration gap sizes impact on survival of sealed bacterial in vitro.
  
  
  METHODS
  Bacterially contaminated artificial residual lesions were induced on the pulpo-axial walls of standardized dentin micro-cavities using acetic-acid demineralization and a continuous-culture Lactobacillus rhamnosus biofilm-model. Adhesive restorations with different gap sizes (0/100/200/400 μm) were placed (n=24/group). Restorations were submitted to cyclic loading (42 g/0.2 Hz) under highly cariogenic conditions in a mastication-simulating artificial mouth. After 25 days, the number of sealed viable bacteria was determined as colony-forming units.
  
  
  RESULTS
  After 25 days, CFU were significantly reduced in all groups (-99.99%, p<0.001/Mann-Whitney). Significantly more viable bacteria remained in restorations with gaps ≥ 200 μm (p<0.001).
  
  
  CONCLUSIONS
  Restoration gaps needed to exceed a threshold size to impede lesion arrest in vitro. There is great need to better understand why such threshold exists and which factors (mastication forces, restoration material, lesion location) could moderate the observed association.
  
  
  CONCLUSIONS
  A certain gap sizes was necessary to allow sufficient fluid exchange for bacterial survival in vitro. It is not possible to deduct clinical recommendations at present.
authors.affiliation: Department of Operative and Preventive Dentistry, Charité - Universitätsmedizin Berlin, Germany. Electronic address: falk.schwendicke@charite.de.
authors.forename: Falk
authors.initials: F
authors.lastname: Schwendicke
authors.affiliation: Department of Operative and Preventive Dentistry, Charité - Universitätsmedizin Berlin, Germany.
authors.forename: Charlotta
authors.initials: C
authors.lastname: Diederich
authors.affiliation: Department of Operative and Preventive Dentistry, Charité - Universitätsmedizin Berlin, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Paris
mesh_terms: D000134:Acid Etching, Dental; D000818:Animals; D018407:Bacterial Physiological Phenomena; D018441:Biofilms / Q000254:growth & development; D002326:Cariogenic Agents; D002417:Cattle; D015169:Colony Count, Microbial; D003188:Composite Resins; D003731:Dental Caries / Q000382:microbiology*; D003737:Dental Cavity Preparation; D003738:Dental Cements; D003743:Dental Enamel / Q000033:anatomy & histology / Q000382:microbiology; D003763:Dental Leakage / Q000382:microbiology*; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry; D003793:Dental Restoration, Permanent; D017220:Dentin-Bonding Agents; D018450:Disease Progression; D052201:Lacticaseibacillus rhamnosus / Q000502:physiology; D017001:Tooth Demineralization / Q000382:microbiology
chemical_list: D002326:Cariogenic Agents; D003188:Composite Resins; D003738:Dental Cements; D003764:Dental Materials; D017220:Dentin-Bonding Agents
keywords: Biofilm; Demineralization; Dental caries; Restoration leakage; Selective excavation