title: The effect of 2 versus 4 implants on implant stability in mandibular overdentures: A randomized controlled trial.
abstract: BACKGROUND
  Dental research is rich with articles that investigated the influence of host-site variables, some implant-related variables (implant length, diameter, taper, design, location, and surface topography), different loading protocols or surgical procedures, and measurement methodology on dental implant stability. However, the number of implants and its effect on implant stability remain unclear.
  
  
  OBJECTIVE
  The purpose of this randomized clinical trial was to investigate the influence of implant number on implant stability by comparing 2 versus 4 implants in mandibular implant overdentures.
  
  
  METHODS
  The trial included 20 participants with edentulous mandibular ridges. Participants were randomly assigned to 2 equal groups, a 4-implant (experimental) group consisting of 4 implants installed in lateral-canine and premolar regions; and a 2-implant (control) group, consisting of 2 implants in lateral-canine regions. Implant stability was measured using resonance frequency analysis at implant placement and then at 1, 3, 6, 9, and 12 months. The Student t test was used to compare the implant stability quotient (ISQ) values of the anterior implants in the 4-implant and 2-implant groups. One-way ANOVA followed by the post hoc Bonferroni test was used to compare ISQ values among the different follow-up periods within each group (α=.05).
  
  
  RESULTS
  Mean ISQ values for anterior implants in the 4-implant group were slightly higher than those recorded for the 2-implant group at all follow-up periods. However, these differences were not statistically significant (P>.05). Within-group comparison revealed an initial decrease in implant stability for all implants. This decrease was statistically significant for the 2-implant group (P<.001) and for posterior implants in the 4-implant group (P<.001). This was then followed by a gradual increase in ISQ values for all implants in both groups.
  
  
  CONCLUSIONS
  Increasing the number of implants from 2 to 4 in mandibular implant overdentures did not have a significant influence on implant stability.
authors.affiliation: Assistant Professor, Quality Assurance Committee, Prosthodontic Department, Faculty of Oral and Dental Medicine, Sana'a University, Yemen.
authors.forename: Wafa'a R
authors.initials: WR
authors.lastname: Al-Magaleh
authors.affiliation: Associate Professor, Oral and Maxillofacial Prosthodontic Department, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia; and Associate Professor, Removable Prosthodontic Department, Faculty of Oral and Dental Medicine, Cairo University, Egypt. Electronic address: amalswelem@hotmail.com.
authors.forename: Amal A
authors.initials: AA
authors.lastname: Swelem
authors.affiliation: Professor, Prosthodontic Department, and Evidence Based Dentistry Centre, Faculty of Oral and Dental Medicine, Cairo University, Egypt.
authors.forename: Iman A W
authors.initials: IAW
authors.lastname: Radi
mesh_terms: D015921:Dental Implants; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D019094:Dental Prosthesis, Implant-Supported; D003828:Denture, Overlay; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible; D008875:Middle Aged
chemical_list: D015921:Dental Implants