Varying numbers of implants have been reported in the literature as being used to supported fixed full-arch prostheses for completely edentulous arches. Many factors are reported to influence the decision regarding the number if implants chosen. This systematic review was designed to evaluate surgical and prosthetic outcomes associated with five or more implants, and compare these with using less than five implants, when providing full-arch fixed prostheses for completely edentulous arches. Primary outcomes investigated were implant and prosthesis survival. Secondary outcomes included distribution of implants, implant inclination, loading protocol and mode of prosthesis retention.
- There is no statistically significant difference in implant survival rates associated with the use of fewer than five implants when compared to five or more implants when supporting a fixed dental prosthesis. This statement is based on outcomes reported in 93 studies (9 RCTs, 42 Prospective and 42 Retrospective) with a median follow-up of 8 years (range: 1–15 years).
- There is no statistically significant difference in outcomes (implant and prosthesis survival) for full-arch FDPs in the maxilla supported by fewer than five implants (median follow-up of 5.5 years) when compared to five or more implants (median follow-up of 8 years). This statement is based on the analysis of data from 50 groups of patients, extracted from the 28 studies that reported numbers of implants for the maxilla (1 RCT, 13 Prospective and 14 retrospective), and from the 19 papers that reported for both groups (3 RCT, 7 Prospective and 9 Retrospective), among which 26 reported on fewer than five implants, and 24 reported on five or more implants. In all, 47 publications reported outcomes for the maxilla (4 RCTs, 20 Prospective and 23 Retrospective). Of the 26 studies documenting outcomes for fewer than five implants, the majority reported on the use of four implants incorporating distally tilted posterior implants and an immediate loading protocol (23 reports with a median followup of 5.5 years). A majority of the 24 studies documenting outcomes for five or more implants reported use of six implants positioned in a parallel configuration and utilizing an immediate loading protocol (20 reports with a median follow-up of 8 years).
- There is no statistically significant difference ( p < 0.05) in outcomes (implant and prosthesis survival) for full-arch FDPs in the mandible supported by less than five implants (median followup of 5.5 years) when compared to five or more implants (median follow-up of 5.5 years). This statement is based on the analysis of data from 72 groups, among which 58 reported on fewer than five implants and 14 reported on five or more. Data were extracted from 65 publications that reported on the mandible (8 RCT, 29 Prospective and 28 Retrospective). Of the 14 studies documenting use of five or more implants to support a complete arch prosthesis in the mandible, a majority used five implants (10 reports with a median follow-up of 4 years) in a parallel configuration (12 reports) and with an immediate loading protocol (8 reports). Of the 58 studies documenting use of fewer than five implants, a majority used four implants (41 studies with a median follow-up of 5.5 years and a range of 1–10 years). A parallel configuration was reported in 27 papers and use of posterior distally inclined implants reported in 31. An immediate loading protocol was reported as being used in 48 of the 58 articles.
- The final prosthetic plan should be considered when developing a surgical plan for implant treatment of edentulous arches. Factors to be considered include:
a. Prosthesis material
b. One-piece or segmented prostheses
c. Aesthetic factors (e.g., lip support, smile line)
d. Condition of the opposing dentition
e. Available space for the prosthesis
f. Anatomy of the edentulous ridge (maxilla, mandible, bone volume and quality, anatomic limitations)
g. Planned implant distribution (AP distribution) and cantilever length
h. Space available for hygiene and maintenance
i. Patient preference and compliance
- When patients present with teeth in place, all treatment options should be considered as part of the informed consent process and appropriate consideration should be given to preservation of teeth. When the decision is made to rehabilitate the patient with a fullarch prosthesis, and tooth extraction is required, planning consideration must be given to the space required for the prosthesis in all dimensions.
- A minimum number of four appropriately distributed implants are recommended to support a one-piece full-arch fixed prosthesis. However, the impact of future implant loss/complications on prosthesis support should be considered when choosing implant number. Additional implants can provide options for fixed fullarch segmented prostheses.
- When selecting the placement and loading protocol, the following conditions should be considered:
a. Systemic conditions
b. Implant stability (insertion torque/ISQ)
c. The need for bone grafting at the time of placement
d. Implant size and shape
e. Experience and skill of the clinician These modifiers should be considered for each site where an implant is planned.
- As part of a comprehensive plan, and when clinician skill and oral environment are favourable, the invasiveness of surgery can be reduced through utilization of improved implant materials, surfaces and designs (short, narrow, tapered), prosthetic connections and placement options (tilted implants).
- Bone augmentation is recommended when there is a need to increase implant distribution or number in response to the prosthetic plan. These procedures are more invasive and challenging, increasing the level of clinician skill and experience required.