The dental implant industry constantly offers new options to increase the success these devices. Besides innovations on their surfaces, there is also a large list of implant shapes and lengths. In many clinical situations, it is impossible to place dental implants since there is not enough residual vertical bone height. The so called “standard implants” cannot be placed because they would interfere or damage anatomical structures and created problems to the patients.
That is to say, not every patient has adequate bone volumes to receive dental implants. This condition commonly appears in the posterior areas of upper and lower jaws. Tooth loss in the posterior jaws favors the resorption process of bone, causing greater proximity to the inferior alveolar nerve (lower jaw) and maxillary sinus (in the upper jaw), limiting the use of longer implants called “standard”. The most common procedure to solve these problems is bone augmentation. This provides the amount of bone needed to compensate the lost structures and host the total length of the standard implant without damaging anatomical structures.
Generally speaking, there are two options commonly used to increase the ridge height in the posterior maxilla such as sinus floor elevation procedure in the maxilla (internal or external) and vertical bone augmentation in the mandible. However, the drawbacks of these procedures could be the cost and duration of the treatment, the morbidity and the possibility of complications associated to these surgeries. It is important to understand that short implants are very different from “mini implants.”
The last ones are only used in severely resorbed jaws in terms of thickness and not height. Their mechanics and healing is very different from the classic dental implant.
To prevent all these interventions, the implant market offers the so called “short implants”. These devices have the same surface and designs of standard implants but their main feature is the reduced length. There is no consensus about the definition of short implants. Some consider them less than 10 mm while others consider short implants those less than 8 mm.
Short implants are used since they are considered to be simpler and more effective tools to treat resorbed jaws. Currently, implants up to 4mm in length are available and appear in scientific papers (Calvo-Guirado et al 2014, Slotte et al. 2012).
Despite these benefits, short implants with length less than 8 mm (extra-short implants) should be used with caution because they may have greater risks of failure if compared to standard dental implants (Lemos et al. 2016).
The possible complications derive from an unfavorable ratio between crown length and implant length. If the implant crown is more than double length of the short implants, complications may occur. The biting forces may be too much to bear for the short implants. In case of long crown and short implant, it is recommended to attach 2 crowns and 2 short implants together to improve the resistance to biting forces
In summary, the results of scientific reviews suggest that no statistical difference between the survival rates of short implants (5–8 mm) and standard implants (>8 mm); Short implants showed the same survival rate as standard implants. Complications such as implant marginal bone loss, prosthesis failures and complication rates are similar to standard implants. Short implants can be considered a predictable treatment for posterior jaws, especially in cases that require complex and unpredictable surgical procedures to provide bone for standard implants (Fan et al. 2016).
-Lorenzo Mordini DDS, MS