title: Investigation of mucosa-induced residual ridge resorption under implant-retained overdentures and complete dentures in the mandible.
abstract: OBJECTIVE
  This study aimed to investigate and compare the residual ridge resorption (RRR) induced by an implant-retained overdenture (IRO) and associative biomechanics and by a conventional complete denture (CD) without implants.
  
  
  METHODS
  Cone beam computed tomography was used to quantify RRR in a three-dimensional (3D) manner before and after 1 year of treatment with either IROs or CDs. Twenty patients were treated with IROs, and nine patients were treated with CDs in the mandible. Their maximum bite forces were recorded. The same sets of high-resolution scan images were used to create patient-specific 3D finite element analysis models. The hydrostatic stresses, contact surface deformation, and strain energy absorption in soft tissue mucosa were correlated with the changes in RRR for patients with and without implants.
  
  
  RESULTS
  With the IROs, contact surface deformation on the mucosa was two times greater than with CDs (0.32 ± 0.23 mm vs 0.16 ± 0.06 mm) and was in agreement with the amount of RRR measured, which was also two times higher for the IRO than the CD (-3.8% ± 4.5% vs -1.9% ± 0.4%). Taking into account the differences in bite forces with and without implants, which again were twice as high with IROs, the hydrostatic stress within the mucosa was found to correlate well to the RRR map measured over the 1-year interval of treatment.
  
  
  CONCLUSIONS
  IROs resulted in at least twice the RRR as CDs. This could be caused by the higher hydrostatic stress and less effective energy absorption capabilities of the mucosa underneath the IRO. While implants associated with the IRO provide stronger bite force, they could potentially concentrate hydrostatic stress and cause greater RRR compared to a conventional CD.
authors.forename: Rohana
authors.initials: R
authors.lastname: Ahmad
authors.forename: Junning
authors.initials: J
authors.lastname: Chen
authors.forename: Mohamed I
authors.initials: MI
authors.lastname: Abu-Hassan
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.forename: Michael V
authors.initials: MV
authors.lastname: Swain
mesh_terms: D000328:Adult; D000368:Aged; D001732:Bite Force; D001862:Bone Resorption; D054893:Cone-Beam Computed Tomography; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported / Q000009:adverse effects*; D003824:Denture, Complete; D003828:Denture, Overlay; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D006874:Hydrostatic Pressure; D021621:Imaging, Three-Dimensional; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging / Q000601:surgery*; D008875:Middle Aged; D009061:Mouth Mucosa; D010539:Permeability; D015203:Reproducibility of Results
chemical_list: D015921:Dental Implants