title: Within-subject comparison of two rigid bar designs connecting two interforaminal implants: patients' satisfaction and prosthetic results.
abstract: BACKGROUND
  There is evidence for the superiority of two-implant overdentures over complete dentures in the mandible. Various anchorage devices were used to provide stability to overdentures. The aim of the present study was to compare two designs of a rigid bar connecting two mandibular implants.
  
  
  METHODS
  Completely edentulous patients received a new denture in the maxilla and an implant-supported overdenture in the mandible. They were randomly allocated to two groups (A or B) with regard to the bar design. A standard U-shaped bar (Dolder bar) was used connecting the two implants in a straight line. For comparison, precision attachments were soldered distal to the bar copings. Group A started the study with the standard bar (S-bar), while group B started with the attachment-bar (A-bar). After 3 months, they had to answer a questionnaire (visual analogue scale [VAS]); then the bar design was changed in both groups. After a period of another 3 months, the patients had to answer the same questions; then they had the choice to keep their preferred bar. Now the study period was extended to another year of observation, and the patients answered again the same questionnaire. In vivo force measurements were carried out with both bar types at the end of the test periods. The prosthetic maintenance service carried out during the 6-month period was recorded for both bar types in both groups. Statistical analysis as performed with the SPSS statistical package (SPSS Inc., Chicago, IL, USA).
  
  
  RESULTS
  Satisfaction was high in both groups. Group B, who had entered the study with the attachment bar, gave slightly better ratings to this type for four items, while in group A, no differences were found. At the end of the 6-month comparison period, all but one patient wished to continue to wear the attachment bar. Prosthetic service was equal in groups A and B, but the total number of interventions is significantly higher in the attachment bar. Force patterns of maximum biting were similar in both bar designs, but exhibited significantly higher axial forces in the attachment bar.
  
  
  CONCLUSIONS
  Both bar designs provide good retention and functional comfort. High stability appears to be an important factor for the patients' satisfaction and oral comfort. Rigid retention results in a higher force impact and appears to evoke the need for the retightening of occlusal screws, resulting in more maintenance service.
authors.affiliation: Department of Prosthodontics, School of Dental Medicine, University of Bern, Bern 3010, Switzerland. regina.mericske@zmk.unibe.ch
authors.forename: Regina
authors.initials: R
authors.lastname: Mericske-Stern
authors.forename: Dieter
authors.initials: D
authors.lastname: Probst
authors.forename: Fritz
authors.initials: F
authors.lastname: Fahrländer
authors.forename: Marc
authors.initials: M
authors.lastname: Schellenberg
mesh_terms: D000368:Aged; D001732:Bite Force; D018592:Cross-Over Studies; D015921:Dental Implants; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention / Q000295:instrumentation*; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003828:Denture, Overlay; D005260:Female; D017048:Health Care Costs; D006801:Humans; D007575:Jaw, Edentulous / Q000534:rehabilitation; D008297:Male; D008334:Mandible; D008875:Middle Aged; D017060:Patient Satisfaction; D011795:Surveys and Questionnaires
chemical_list: D015921:Dental Implants