Dental implants are now widely used and have demonstrated good survival rate. However standard implant placement requires sufficient bone height for their use. Short implants (≤6 mm) are a potential option that may avoid the use of bone regeneration procedures.
The aim of this review was to compare whether implant supported crowns on short or standard implants have similar clinical outcomes in the posterior alveolar bone
Methods
Searches were conducted in the Medline/PubMed, Embase and Cochrane Library databases by 2 independent reviewers. Randomised controlled trials (RCTs) comparing short implants (≤6 mm) and standard implants (>6 mm) supporting single crowns in the posterior region of the maxilla or mandible of partially edentulous patients in the same study, with a minimum of 10 implants per group and at least 1-year follow-up period after loading.
Two reviewers independently extracted data and assessed quality using the Cochrane risk of bias tool. survival rates and complications were assessed by the risk ratio (RR), and MBL was assessed by the mean difference (MD) with corresponding 95% confidence intervals (CI).
Results
- 5 RCTs involving a total of 372 implants (184 short; 188 standard) placed in 281 patients were included.
- The survival rate of the short implants (≤6 mm) was similar longer implants (>6 mm) at 1 year but poorer at 5 years.
| No. of studies | Risk ratio (95%CI) | |
| 1 year | 5 | 0.99 (0.97 – 1.02) |
| 5 years | 4 | 0.94 (0.90 – 0.99) |
- There was no significant difference in marginal bone loss (MBL).
Conclusions
The authors concluded: –
The present study suggested that, although short implants have a higher crown-to-implant (C/I) ratio, they do not affect MBL. However, long-term follow-up comparisons indicated that short implants (≤6 mm) have a poorer survival rate than standard implants (6 mm) (P=.01). Non-splinted crowns supported by short implants should be used with caution in the posterior alveolar bone.
Comments
The authors have searched 3 major databases, preregistered the review protocol on PROSPERO and aimed to follow the PRISMA guideline for reporting systematic reviews. The question being considered has been previously addressed in a number of systematic reviews that we have considered here at the Dental Elf. The most recent of these being by Chen et al (Dental Elf – 4th Dec 2019). The Chen studys definition of short implants ranged from 4-8mm unlike the current review which had a cut off of 6mm for short implants. Interestingly only one of the studies is common to both reviews. While no differences were seen at one year shorter implant performed less well at 5 years. As 10-year or more implant survival data is available for standard length implants longer term data on short implants including patient-centerred outcomes is needed.
Links
Primary Paper
Xu X, Hu B, Xu Y, Liu Q, Ding H, Xu L. Short versus standard implants for single-crown restorations in the posterior region: A systematic review and meta-analysis [published online ahead of print, 2020 Jan 24]. J Prosthet Dent. 2020;S0022-3913(19)30670-5. doi:10.1016/j.prosdent.2019.09.030
Other references
Dental Elf – 4th Dec 2019
Dental implants: Long or short with bone augmentation in the posterior jaw?
Dental Elf – 5th Apr 2019
