The purpose of the present meta-analysis was to test the null hypothesis of no difference in the implant failure rate, postoperative infection, and marginal bone loss for patients being rehabilitated with immediately loaded non-submerged dental implants or delayed loaded submerged implants, against the alternative hypothesis of a difference. An electronic search without time or language restrictions was undertaken in March 2014. Eligibility criteria included clinical human studies, either randomized or not. The search strategy resulted in 28 publications. The inverse variance method was used for a random- or fixed-effects model, depending on the heterogeneity. The estimates of an intervention were expressed as the risk ratio (RR) and mean difference (MD) in millimetres. Twenty-three studies were judged to be at high risk of bias, one at moderate risk of bias, and four studies were considered at low risk of bias. The difference between procedures (submerged vs. non-submerged implants) significantly affected the implant failure rate ( P = 0.02), with a RR of 1.78 (95% confidence interval (CI) 1.12–2.83). There was no apparent significant effect of non-submerged dental implants on the occurrence of postoperative infection ( P = 0.29; RR 2.13, CI 0.52–8.65) or on marginal bone loss ( P = 0.77; MD −0.03, 95% CI −0.23 to 0.17).
Historically, the original Brånemark protocol for placing dental implants prescribed a two-stage surgery with a submerged healing period of at least 3 months in the mandible and 6 months in the maxilla, allowing the implant to osseointegrate without being exposed to external forces. After bone healing, a second surgery is performed to connect a healing abutment. One of the main reasons for implant insertion in the two-stage procedure was to minimize the risk of infection, since the peri-implant tissue is allowed to heal separate from the oral microbial environment. Extended treatment times, the requirement for two surgical interventions, and the need for interim prostheses during healing are disadvantages of conventional implant treatment.
Over time, the concepts of implant placement in fresh extraction sockets, immediate loading, and non-submerged implants were introduced, focusing on shorter and less invasive procedures. To reduce the treatment time and offer the patient early function and aesthetics, it is necessary to use a one-stage surgical procedure and to load the implants as soon as possible. In the one-stage surgical approach (non-submerged implant), the coronal part of the implant is positioned above the gingiva level in the case of single-part implants, or transmucosal healing abutments are placed in the case of two-part implants. In the one-stage surgical approach, the implant can be loaded immediately or not. The encouraging early experiences of immediate loading in the mandible and the development of new implant designs and surfaces have inspired researchers to further explore applications of immediate loading.
Inserting implants in one stage has several advantages. Only one surgical intervention is required, which is convenient for the patient, especially for the medically compromised patient. In addition, there is a considerable cost-benefit advantage. The prosthetic phase can start earlier because there is no wound-healing period related to a second surgical procedure. Furthermore, the implants are accessible for clinical monitoring during the osseointegration period. It allows for a healed peri-implant mucosa at the time of prosthetic rehabilitation. Although immediate loading of implants shortens the treatment duration and also provides patients with an acceptable aesthetic appearance, there is concern that immediate loading may increase the risk of implant failure.
The aim of this meta-analysis was to compare the survival rate, postoperative complications, and marginal bone loss of non-submerged immediately loaded dental implants with those of submerged delayed loaded implants. The present study presents a more detailed and in-depth analysis of the influence of the submerged and non-submerged approaches on implant failure rates previously assessed in a published systematic review.