Clinical study with short implants – Relation among insertion torque, osseointegration and bone loss

Background

The use of short implants has gained popularity in the last years, since they have demonstrated high long-term survival and success rates. Also, they allow to reduce treatment time, morbidity and costs compared to bone regeneration procedures. Adequate primary stability and osseointegration are of extreme importance for long-term success of implant therapies.

Aim/Hypothesis

The aim of this study was to assess the relationship between insertion torque (primary stability), premature osseointegration failure and bone loss in patients with short morse taper implants after a 1-year follow-up.

Material and Methods

Healthy, non-smoking patients with a minimum of 6–8 mm of vertical bone and 6 mm of horizontal bone, evaluated by tomographic examination, were included. A total of 20 morse taper 4 and 5 mm in diameter and 5 and 6 mm in length dental implants were installed in 11 patients. During implant placement procedures, insertion torques were recorded using a torque wrench and implants were left submerged. After 6 months, second-stage surgeries were performed, signs of premature osseointegration failures evaluated (absence of mobility), provisional crowns delivered and x-rays taken. 1-year after loading, control x-rays were taken. Bone levels were measured in x-rays from the implant platform to marginal bone using ImageJ 1.52d analysis software (National Institutes of Health, Bethesda, USA). Loading and follow-up x-rays were compared to assess the amount of bone loss. Data collected was analyzed using different statistical tests in the SPSS software (IBM Statistics version 21).

Results

The mean follow-up time after implant placement was 18.75 ± 7 months. Three implants were excluded (15%), two due to mechanical failures and one due to biological failures. Mean values for mesial bone measurements at loading (0.95 ± 0.74) and at control x-rays (0.88 ± 0.83), and for distal bone levels at loading (1.12 ± 0.92) and at control x-rays (1.08 ± 0.91) were used to calculate the amount of bone loss in mesial (0.146) and distal sites (0.326), respectively. Correlation values between insertion torque, mesial (r = −0.240) and distal bone loss (r = 0.127) were calculated, as well as for insertion torque and osseointegration (r = 0.291).

Conclusion and Clinical Implications

Initial and follow-up values for bone loss showed no statistical differences, thus short implants showed stable bone levels after 1 year of installation. No relation between insertion torque and bone loss nor insertion torque and osseointegration was found, meaning that initial torque has no direct influence on the amount of bone loss and does not predict osseointegration failures. This study demonstrates the success of short implants in a short-term period.