title: The effect of implant macro-thread design on implant stability in the early post-operative period: a randomized, controlled pilot study.
abstract: BACKGROUND
  Available literature suggests there is a transient drop in implant stability from approximately week 0 to week 3-4 as a result of peri-implant bone remodeling as it transitions from a primary, mechanical stability to a secondary, biological stability. Research investigating the influence of macro-thread design on this process is scant.
  
  
  OBJECTIVE
  The specific aim of this study was to evaluate the role of macro-thread design on implant stability in the early post-operative healing period using resonance frequency analysis (RFA).
  
  
  METHODS
  Seven patients, each missing at least two posterior teeth in the same arch, were included in the study. Three patients qualified for four implants resulting in a total of 10 matched pairs. All sites were healed (>6 months), non-grafted sites with sufficient bone to place implants. Each site in a matched pair was randomly assigned to receive either a control (Megagen EZ Plus Internal; EZ) or test (Megagen AnyRidge; AR) implant. The test implant incorporates a novel thread design with a wide thread depth and increased thread pitch. RFA was used to determine implant stability quotient (ISQ) values for each implant at the time of placement and weekly for the first 8 weeks.
  
  
  RESULTS
  Implants consistently achieved a relatively high insertion torque (30-45 N/cm) and high initial ISQ value (79.8 ± 1.49). Baseline ISQ values for test (AR; 79.55 ± 1.61) and control (EZ; 80.05 ± 1.37) implants were similar. A general pattern of stability from baseline through all eight follow-up evaluations was observed for the test implants. A pattern of decreasing ISQ values was observed for the control implants across the early follow-up evaluations up to week four, where the value plateaued. There was a statistically significant main effect due to implant type (P < 0.01) and a statistically significant interaction between implant type and time (P < 0.01), indicating that the test and control implants performed differently at certain time points.
  
  
  CONCLUSIONS
  Within the limitations of this study, macro-thread design appears to play a role in implant stability in the early post-operative healing period as assessed by RFA. These findings may have important implications related to immediate or early loading protocols.
authors.affiliation: Section of Periodontics, UCLA School of Dentistry, Los Angeles, CA, USA.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: McCullough
authors.affiliation: Postgraduate Periodontics Residency Program, Section of Periodontics, UCLA School of Dentistry, Los Angeles, CA, USA.
authors.forename: Perry R
authors.initials: PR
authors.lastname: Klokkevold
mesh_terms: D000368:Aged; D000069343:Bone-Implant Interface; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D010865:Pilot Projects; D011184:Postoperative Period; D011446:Prospective Studies; D013997:Time Factors
keywords: biomechanics; bone-implant interactions; clinical research