Single Lower Molar: Immediate vs. Delayed Loading. One Year Results of a Randomized Controlled, Prospective Split-Mouth Clinical Study

Abstract

Statement of the Problem: There are not many studies available that are prospectively assessing, in a split mouth design, immediate loading of implants vs. the conventional approach. The aim of this study is to compare the outcome of immediate versus delayed implant loading, when replacing single lower molars bilaterally. Materials and Methods: This study was designed as a randomized, controlled, prospective, split-mouth clinical trial. Twenty patients, bilaterally missing first mandibular molars, were randomly assigned to be treated with an implant-supported prosthesis. A total of 40 implants (NobelReplace Tapered Groovy NobelBiocare) were bilaterally installed, replacing the inferior first molars. All the implants were inserted in native healthy bone with an insertion torque of 35/45 N.cm. One molar was restored with a non-occluding temporary crown within 24 h after implant placement, while the other side was restored after 3 months, according to a two-stage procedure. Final restorations with zirconia or metal-ceramic crowns were provided 6 months after implant placement. All implants were installed in healed sites. Follow-up checks were conducted at 3, 6 and 12 months after prosthetic loading. Methods of Data Analysis: The following outcome criteria were used: Implant success: The removal of implants was dictated by instability, progressive marginal bone loss, infection, or implant fracture. The stability of individual implants was measured at the time of definitive crown delivery (4–5 months after implant placement) by applying 35 Ncm of removal torque..Marginal bone loss: Periimplant marginal bone levels were evaluated on intraoral radiographs taken with the parallel technique at the time of implant placement and at 6 months and 1 year after definitive loading. Periimplant mucosal response: Probing pocket depth (PPD) and bleeding on probing (BOP) were measured with a periodontal probe at 6 months and 1 year after definitive crown delivery. Complications: Prosthetic complications, such as provisional or definitive crown fracture and abutment mobility or fracture, were evaluated. Statistical analyses were conducted using the JMP statistical software program (ver. 7.0; SAS Institute, Cary, NC, USA). Statistical significance was tested at the 0.05 probability level, and all values are presented as mean standard deviation. Results: Twenty patients were considered eligible and treated. No patient dropped out of the study within 1 year after definitive loading. No deviation from the protocol occurred. Assessments of procedure success are shown below. Implant success: All implants appeared stable at the time of definitive crown delivery. After 1 year of follow-up, the cumulative survival rate was 100% for delayed and immediately loaded implants. Marginal bone loss: Mean marginal bone loss was 0.83 0.1 mm in immediately loaded implants and 0.86 0.2 mm in two-stage delayed loading implants; no significant difference was found between groups at 6 and 12 months (p 0.05), Periimplant mucosal response: No significant difference (p 0.05) in PPD or BOP value was found between the two implant insertion methods Prosthetic complications: Two provisional acrylic crowns fractured 2 months after immediate loading. Two zirconiaceramic crowns had partial ceramic fractures. Conclusions: Within the limitations of this study the present findings seem to confirm that immediate loading of single lower molar implants restored with a nonoccluding temporary crown is a viable option comparable to the conventional two-stage delayed loading approach.