Early implant loading in the atrophic posterior maxilla- 1-stage lateral versus crestal sinus lift and 8 mm-long hydroxyapatite coated implants: An 11-year randomised controlled trial

Background

Not all patients have adequate bone volumes to received dental implants. This condition is not uncommon especially in the posterior jaw and in particular below the maxillary sinuses. There are three main problems associated with bone augmentation procedures in general- the cost and duration of the treatment, the higher patient morbidity, and not necessarily ideal success rates.

Aim/Hypothesis

The aim of this randomised controlled trial was to compare the outcome of fixed prostheses supported by 10 to 16 mm long implants inserted in maxillary sinuses augmented according to a lateral approach technique with 50% particulated autogenous bone harvested from the oral cavity and 50% Bio-Oss versus 8 mm long implants placed in crestally augmented sinuses with autogenous bone according to the Cosci technique (9, 10). All implants were to be early loaded at 45 days after placement.

Material and Methods

Forty partially or fully edentulous patients having 3 to 6 mm of residual crestal height and at least 4 mm thickness below the maxillary sinuses were randomised according to a parallel group design to receive either one to three 10 to 16 mm long hydroxyapatite coated implants (20 patients) after lateral sinus lifting with 50% anorganic bovine (Bio-Oss) and 50% autogenous bone or 8 mm-long implants (20 patients) after crestal sinus lifting with autogenous bone. Implants were submerged and left to heal for 45 days before being loaded. Within one week after abutment connection, implants were loaded with screw-retained full acrylic provisional prostheses. Definitive metal-ceramic prostheses were provisionally cemented 45 days after abutment connection. Outcome measures were- prosthesis and implant failures, any complications, radiographic peri-implant marginal bone level changes. In addition, the stability of individual implants was assessed with Osstell and Periotest by blinded outcome assessors, but the Periotest was discontinued. All patients were followed up to 11 year after loading.

Results

One patient per group dropped out. One implant failed in the short implant group versus five implants in three patients of the longer implant group, the difference being not statistically significant. Three prostheses could not be delivered or were replaced in the long implant group versus one crown on short implants, the difference being not statistically significant. Six complications occurred in six patients of the short implant group versus ten complications in seven patients of the long implant group, the difference being not statistically significant different, however, the two major postoperative complications occurred in the longer implant group- one abscess and one sinusitis which determined the complete failure of the treatment in two patients (four implants lost). A total of 1.26 mm of peri-implant marginal bone was lost after 11 years at long implants and 0.64 mm at short implants, the difference between the two groups was statistically significant

Conclusion and Clinical Implications

In atrophic maxillary sinuses with a residual bone height of 3 to 6 mm, 8 mm short implants placed in simultaneously crestally lifted sinus might be a preferable choice than 1-stage lateral sinus lifting for placing longer implants since they appear be associated with less morbidity. Implants placed with an insertion torque superior to 35 Ncm joint together under the same prosthesis, can be early loaded at 6 weeks.