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Splint Adjacent Implant Crowns or Keep Them Separate?

When two or more implants sit side by side, one of the first questions in designing the prosthesis is whether the crowns should be joined together (splinted) or whether each implant should get its own crown. Splinting makes the load be shared between the implants. Separate crowns, on the other hand, make cleaning simpler, and also make it easier to build the emergence profile, adjust the contacts and achieve a passive fit. Below we look at which one the clinical evidence shows to be superior.

∆ 1. Peri-implant bone loss

In a review published in 2018, no difference in bone loss was seen between splinted and separate crowns, and this held especially in the posterior region. The 2025 AO/AAP review showed slightly less bone loss with separate crowns. But according to the same paper this difference was about one tenth of a millimetre, and the authors themselves considered it probably clinically insignificant. The discussion of the same paper also notes that when more than two implants are splinted together, recent studies have reported more bone loss at the middle implant. So in terms of bone, neither approach has a real advantage, and what makes the difference is whether the area can be cleaned.

∆ 2. Implant survival

The 2018 review reported higher survival for splinted implants. A closer look, however, shows that this advantage was seen mainly in external-connection (external hex) implants, and that there was no significant difference in internal-connection implants. In addition, the study table of the same review shows that a considerable share of the studies were done on short implants, and that follow-up ranged from one year to more than twenty years. The authors themselves also say they could not examine the effect of splinting separately by implant length and diameter. For this reason the finding should be generalised with caution to today's implants, which have internal connections and ordinary lengths. Nor can one conclude from this paper that short implants must always be splinted.

∆ 3. Mechanical complications

The real advantage of splinting shows up in mechanical complications. In the 2018 review, when the results of all studies were pooled statistically, no significant difference in prosthetic complications was seen between splinted and separate crowns. Nevertheless, when its studies are examined one by one, screw loosening and loss of retention are reported more often with separate crowns. A 2024 review (full text was not available; based on the abstract) showed this point more clearly. In this review, which examined only adjacent posterior implants with internal connections, biological complications did not differ between the two groups, but mechanical complications were clearly more frequent with separate crowns. The 2025 review likewise recommends that, in situations such as a large interarch distance, heavy occlusal force and a tall clinical crown, splinting be preferred to reduce mechanical complications.

∆ 4. Occlusion and bruxism

An implant has no periodontal ligament, so it does not absorb and distribute occlusal force the way a natural tooth does, and it also lacks the mechanoreceptors needed to regulate chewing force. A 2025 review on occlusal overload showed that excess force and habits such as bruxism are associated with bone loss and peri-implantitis. Moreover, if this force coincides with plaque-induced inflammation, its effect is amplified. The evidence in this review is heterogeneous, and part of it comes from laboratory and modelling studies. Even so, all the findings point in the same direction and show that the decision to splint does not replace implant-protective occlusion.

The same review reports that canine guidance produces less stress and bone loss than group function. In canine guidance, during lateral jaw movement only the canines are in contact and the posterior teeth disclude, so posterior implants receive no lateral load. In group function, the canine is in contact together with the premolars and sometimes the first molar on the working side, and the lateral load is shared among these teeth, so a posterior implant also carries part of that load. That said, this review does not specify in which region the implants were, and its evidence for this comparison is limited.

∆ 5. Pterygoid and tuberosity implants

With pterygoid and tuberosity implants the situation is different. A 2024 review of these implants showed that when they are not connected to other implants and carry a single crown or an overdenture, their survival is lower. The number of tuberosity implants with single crowns in this review was small, but according to the same paper their one-year survival was reported at about 77 percent, which is clearly low. For this reason the authors suggest that connecting these implants to more anterior implants with a fixed prosthesis may be beneficial.

∆ 6. Food impaction, black triangles and hygiene

In my clinical experience, when a little bone loss occurs around adjacent implants, the papilla between two separate crowns becomes shorter. As a result, the open space between the crowns, the so-called black triangle, becomes larger. This increases food impaction and the patient's sense of food impaction, and it is one of the most common complaints after separate crowns are delivered. With splinted crowns this space stays open less, but in return access to the area between the implants becomes harder. So we are facing a trade-off. Separate crowns make cleaning easier but raise the chance of food impaction. Splinted crowns reduce food impaction but make cleaning harder.

For this reason, when I join crowns together, I design the connector so that dental floss can pass through the space between the gingiva and the crowns. I also always teach the patient how to thread the floss under the connector and clean around each implant. I also recommend a water flosser. The 2025 review likewise recommends a floss threader and a small-diameter interdental brush for restorations with limited hygiene access.

∆ Summary: a simple decision path

If two adjacent implants have internal connections and ordinary lengths, the crown height is ordinary and the patient has no bruxism, separate crowns are the logical choice, because they are easier to clean and nothing is lost in terms of bone.
If the crown height or interarch distance is large, the occlusal force is heavy, or there is a history of screw loosening, splinting should be seriously considered.
For external-connection implants, the survival evidence favours splinting.
If more than two implants are splinted, hygiene access, especially around the middle implant, must be built into the prosthesis design.
Pterygoid and tuberosity implants are better splinted to other implants.
If bone loss and opening of the space between the crowns are likely, food impaction with separate crowns has to be weighed against the difficulty of cleaning splinted crowns. If splinting is chosen, the connector must leave room for floss to pass, and hygiene instruction and use of a water flosser are part of the treatment.
In every case, occlusal control and attention to bruxism are a core part of the treatment.

In practice, the main question is not whether splinting or separate crowns is better. The main question is where the greater risk comes from in each patient: from force or from plaque. If the risk from force is greater, splinting helps, provided the patient can keep the area under it clean. If the main risk is hygiene, separate crowns are the safer choice.