What to do when they tell you there is not enough bone

The older version of this page listed four types of dental implant the way a menu lists dishes. That framing misses what people are actually asking when they search for it. Almost nobody wants a taxonomy. They want to know what happens now that a dentist has looked at their scan and said there is not enough bone.

That sentence sounds like a verdict. It is closer to a fork in the road. The important point is not that one route has "won" the evidence. It is that the evidence is uneven: some comparisons have randomized trials behind them, while others rely mostly on observational series.

The four routes

Among implant-supported approaches for a jaw with insufficient bone, there are four broad strategies, sometimes combined. They are not the only ways to restore a jaw, and removable prostheses remain an option outside the scope of this article.

You can use a shorter implant that fits the bone already there. You can build the bone up first, with a graft or a sinus lift, and place a standard implant afterwards. You can angle the implants to reach areas where bone is denser, which is the principle behind the All-on-4 approach covered in our guide to choosing between All-on-4, All-on-6 and All-on-8. Or, in a severely atrophic upper jaw, you can use zygomatic implants whose anchorage engages the zygomatic bone rather than depending on enough alveolar bone for a conventional implant.

A CT or CBCT scan, a clinical examination and the prosthetic plan help determine which of those routes are actually available in your case, as we covered in who qualifies for dental implants. What follows is what the published evidence says about each, and where the evidence is thinner than the confidence around it.

What randomized trials say about sinus lifting

Sinus floor elevation is a common answer to insufficient bone in the posterior upper jaw. The randomized evidence does not show that it is automatically superior to a graftless alternative when a short implant is anatomically feasible.

A Cochrane review updated in 2014 included 18 randomised controlled trials and 650 participants overall. But only four trials, involving 102 participants, directly compared longer implants placed with sinus augmentation against shorter implants placed without augmentation. At one year, those four trials found no evidence of a difference in implant or prosthesis failure. They did find more complications at sinus-lift sites, with a Peto odds ratio of 4.77 and a 95 percent confidence interval from 1.79 to 12.71. The result was statistically significant, but heterogeneous.

The earlier 2010 version of the same Cochrane review had already concluded that it was still unclear when sinus lift procedures were needed.

Read that carefully, because it is easy to over-read. It does not mean sinus lifting is unnecessary, and it does not apply to every kind of bone graft. These trials addressed specific situations in the atrophic posterior maxilla. The 2014 reviewers rated 11 of the 18 included trials at high risk of bias, five at low risk and two as unclear. What the review supports is a narrower point: when a shorter implant is a realistic alternative, the need for sinus augmentation should be justified for that patient rather than treated as automatic.

Short implants, tested at five years

The Cochrane review also left a genuine long-term uncertainty. The trials comparing short implants with sinus augmentation had not yet followed patients long enough to say much about later outcomes.

A 2023 systematic review pooled five randomized trials with at least five years of follow-up, covering 203 patients and 393 implants. For implant survival, the pooled risk ratio was 0.97, with a 95 percent confidence interval from 0.94 to 1.00 and a p value of 0.07. That means the review did not detect a statistically significant difference. It does not prove that the treatments are statistically equivalent. The authors reported five-year survival of 95.78 percent for short implants and 99.5 percent for standard implants with sinus elevation. Biological complications were lower with short implants, with a risk ratio of 0.46, and the pooled marginal bone-loss result also favoured the short-implant group.

The evidence is still small, and it is not fully independent of the earlier Cochrane evidence. At least some of the five-year reports are longer follow-ups of trial programmes already represented in the 2014 review. So this is better read as longer follow-up of an overlapping randomized evidence base, not as a completely separate confirmation.

Zygomatic implants, and the number nobody can give you

For a severely resorbed upper jaw, when conventional implants cannot obtain adequate anchorage, zygomatic implants use the zygomatic bone for support. They are a complex surgical treatment and the evidence base is very different from the randomized evidence behind the short-implant versus sinus-lift question.

Survival is consistently high in the systematic reviews, but those reviews are dominated by observational series. A 2023 meta-analysis of 18 studies covering 1,349 zygomatic implants in 623 patients found 96.2 percent survival at a mean follow-up of 75.4 months. An earlier 2016 review of 68 studies covering 4,556 implants reported a cumulative survival rate of 95.21 percent at twelve years. The 2016 review found that most failures occurred in the first six months. The 2023 review estimated failure at roughly 2 percent in the first year and about half a percent per year afterwards.

Complications are where the picture stops being tidy, and the honest answer to "how often does sinusitis happen" is that there is no single defensible number for every zygomatic-implant technique and follow-up period.

Major reviews have produced pooled or descriptive estimates ranging from 2.4 percent to 14.2 percent. A 2021 meta-analysis reported 4.7 percent. Those numbers are not measurements of the same thing under the same conditions. Surgical approach, follow-up duration, diagnostic criteria and whether a study systematically looked for sinus disease all vary. The 2016 review reporting 2.4 percent says explicitly that complications were probably underestimated because many included studies did not report whether they occurred, and it notes that sinusitis can develop years after surgery.

A 2023 review separated the original surgical technique from an anatomy-guided approach and reported 9.53 percent sinusitis with the original technique and 4.39 percent with the anatomy-guided approach. That difference is worth knowing, but it is not a head-to-head treatment effect. Only one comparative study was available, so the authors did not perform a meta-analysis and said that differences in patient numbers, follow-up and reporting made a statistical comparison impossible.

Evidence published after 2023 has not made the complication rate collapse into one stable number. A 2025 meta-analysis focused on an externalized technique estimated sinusitis at 3.03 percent, with a 95 percent confidence interval from 1.05 to 5.98 percent and substantial heterogeneity. A 2026 umbrella review of systematic reviews still concluded that zygomatic-implant complications may be underestimated because of heterogeneity in the underlying literature.

Survival is not success

There is a distinction buried in these papers that changes how you read every figure above.

In the 2023 long-term review, survival meant that the zygomatic implant was still present at follow-up. "Success" was predominantly defined more strictly, as survival without biological or neurological complications. The authors also state that there are no recognized uniform criteria for zygomatic-implant success. Their pooled survival estimate was 96.2 percent. Their pooled success estimate was 95.7 percent, with a much wider 95 percent confidence interval from 87.8 to 98.6 percent.

So when a clinic quotes you a 96 percent survival rate, that can be a true and useful number about implants remaining in place. It is not a statement that 96 percent of patients had no sinus disease, no peri-implant soft-tissue problem and no prosthetic complication. Ask which outcome they are quoting.

Who writes this evidence

This section exists because you should be able to weigh where these numbers come from, and almost nothing written for patients explains the overlap.

The 2023 International Team for Implantology consensus report is easy to read as an independent confirmation of the reviews beneath it. It is not. The workshop commissioned three systematic reviews and one narrative review as the basis for its consensus statements. The Kämmerer surgical-technique review and the Brennand Roper long-term review quoted above were two of those commissioned reviews. When the consensus repeats figures such as 96.2 percent long-term survival or 14.2 percent sinusitis, it is largely carrying those review results forward, not reproducing them in a new patient population.

There is also substantial author overlap. Several authors of the surgical-technique review participated in the ITI consensus, and some are affiliated with centres that specialise in zygomatic-implant treatment. The long-term review was initiated and steered by the ITI Scientific Committee and also includes authors from specialist clinical centres. The ITI workshop itself was financially supported by the ITI. At the same time, the papers disclose these affiliations and declare no competing interests; the long-term review additionally discloses an unrelated BioHorizons grant to its first author.

That does not mean there is no independently produced evidence. The 2016 Chrcanovic review was written by authors with university affiliations, and the 2021 Gutiérrez Muñoz meta-analysis lists university affiliations, reports no external funding and declares no conflict of interest. The more defensible concern is narrower: a prominent part of the 2023 evidence package comes from an overlapping author network and should not be counted as several independent replications. Judge the evidence by study design, patient overlap, risk of bias and outcome definitions, not by the number of papers repeating the same estimate.

What the old list got wrong

The version of this page that stood here for seven years listed subperiosteal implants, ramus frames and transosteal implants beside mainstream endosseous options as though they occupied the same place in current treatment planning. That is misleading.

Traditional cast subperiosteal implants lost favour as endosseous osseointegrated implants became standard, in part because historical designs were associated with exposure, infection, mobility and other complications. But subperiosteal treatment has not simply disappeared. Custom CAD/CAM and additively manufactured subperiosteal implants are being studied again. A 2024 systematic review found 13 clinical studies and 227 patients, with a weighted mean follow-up of only 21.4 months. Survival in function was high in that short window, but partial exposure occurred in 25.6 percent of implants, and the authors specifically called for medium- and long-term evidence.

Ramus-frame and transosteal designs are also better described as niche or historical rather than mainstream contemporary choices. The practical correction is simple: this page should not present them as routine alternatives alongside short, tilted, augmented or zygomatic implant strategies, but it should not pretend that every non-endosseous design has vanished either.

The reason this matters is not historical tidiness. The old page told readers that if their jaw was not thick enough, the dentist would probably use a subperiosteal implant. That advice would send a patient into a conversation asking for the wrong thing.

What to ask before you accept a plan

Everything above is background for one conversation, and it is a conversation you can start by email before you book anything.

Implants in Costa Rica start at $950 at verified clinics against $3,000 to $7,000 in the United States, and the full price guide covers every treatment. Grafting, sinus lifting and zygomatic placement can each change the total treatment cost, which is a further reason to understand which route your case actually needs.

Published trials do contain some information about treatment time, procedural burden and costs, especially when short implants are compared with augmentation. What they do not provide is a robust cost comparison across all of the routes discussed here, and they do not tell us how outcomes change when surgery happens in one country and routine follow-up happens in another. Those remain real gaps. Our clinic selection guide covers how to verify who you are dealing with, and the dental implants page covers what a complete quote contains.

Not enough bone is a starting point

The phrase sounds like the end of the conversation and it is closer to the beginning of a better one. Bone can sometimes be augmented, implants can sometimes be shortened or angled, and in severe maxillary atrophy the zygomatic bone may provide an alternative source of anchorage.

What the evidence does not support is treating one route as the automatic answer for every patient with "not enough bone." Ask which routes your scan leaves open, ask why the recommended one was chosen over the others, and ask whether the outcome being quoted is survival, success or freedom from a specific complication. A clinic that can answer those questions clearly is giving you information you can actually use.

Sources

• Esposito, M., Felice, P., and Worthington, H. V. (2014). Interventions for replacing missing teeth: augmentation procedures of the maxillary sinus. Cochrane Database of Systematic Reviews, (5), CD008397. doi.org/10.1002/14651858.CD008397.pub2
• Esposito, M., Grusovin, M. G., Rees, J., Karasoulos, D., Felice, P., Alissa, R., Worthington, H., and Coulthard, P. (2010). Effectiveness of sinus lift procedures for dental implant rehabilitation: a Cochrane systematic review. European Journal of Oral Implantology, 3(1), 7-26. PMID 20467595.
• Mester, A., Onisor, F., Di Stasio, D., Piciu, A., Cosma, A. M., and Bran, S. (2023). Short Implants versus Standard Implants and Sinus Floor Elevation in Atrophic Posterior Maxilla: A Systematic Review and Meta-Analysis of Randomized Clinical Trials with ≥5 Years' Follow-Up. Journal of Personalized Medicine, 13(2), 169. PMID 36836403. doi.org/10.3390/jpm13020169
• Brennand Roper, M., Vissink, A., Dudding, T., Pollard, A., Gareb, B., Malevez, C., Balshi, T., Brecht, L., Kumar, V., Wu, Y., and Jung, R. (2023). Long-term treatment outcomes with zygomatic implants: a systematic review and meta-analysis. International Journal of Implant Dentistry, 9(1), 21. PMID 37405545. doi.org/10.1186/s40729-023-00479-x
• Chrcanovic, B. R., Albrektsson, T., and Wennerberg, A. (2016). Survival and Complications of Zygomatic Implants: An Updated Systematic Review. Journal of Oral and Maxillofacial Surgery, 74(10), 1949-1964. PMID 27422530. doi.org/10.1016/j.joms.2016.06.166
• Gutiérrez Muñoz, D., Obrador Aldover, C., Zubizarreta-Macho, Á., González Menéndez, H., Lorrio Castro, J., Peñarrocha-Oltra, D., Montiel-Company, J. M., and Hernández Montero, S. (2021). Survival Rate and Prosthetic and Sinus Complications of Zygomatic Dental Implants for the Rehabilitation of the Atrophic Edentulous Maxilla: A Systematic Review and Meta-Analysis. Biology, 10(7), 601. PMID 34209770. doi.org/10.3390/biology10070601
• Kämmerer, P. W., Fan, S., Aparicio, C., Bedrossian, E., Davó, R., Morton, D., Raghoebar, G. M., Zarrine, S., and Al-Nawas, B. (2023). Evaluation of surgical techniques in survival rate and complications of zygomatic implants for the rehabilitation of the atrophic edentulous maxilla: a systematic review. International Journal of Implant Dentistry, 9(1), 11. PMID 37198345. doi.org/10.1186/s40729-023-00478-y
• Al-Nawas, B., Aghaloo, T., Aparicio, C., et al. (2023). ITI consensus report on zygomatic implants: indications, evaluation of surgical techniques and long-term treatment outcomes. International Journal of Implant Dentistry, 9(1), 28. PMID 37698775. doi.org/10.1186/s40729-023-00489-9
• Rebelo, H. L., Sales, P. H. H., Silva, P. G. B., Leão, J. C., and Carvalho, A. A. T. (2025). Effectiveness of zygomatic implants using the externalized technique in the rehabilitation of atrophic maxillae. A systematic review with meta-analysis. Medicina Oral, Patología Oral y Cirugía Bucal, 30(6), e774-e786. PMID 41086283. doi.org/10.4317/medoral.27117
• D'Ambrosio, F., Acerra, A., de Laurentiis, E., Babino, A., Santurro, A., and Giordano, F. (2026). Clinical Risk and Medico-Legal Implications in Zygomatic Implant Rehabilitation: An Umbrella Review of Systematic Reviews. Diagnostics, 16(6), 901. PMID 41897635. doi.org/10.3390/diagnostics16060901
• Anitua, E., Eguia, A., Staudigl, C., and Alkhraisat, M. H. (2024). Clinical performance of additively manufactured subperiosteal implants: a systematic review. International Journal of Implant Dentistry, 10(1), 4. PMID 38315326. doi.org/10.1186/s40729-024-00521-6

This article is for general information and is not medical advice. Which route suits your case requires an in-person evaluation and appropriate imaging by a licensed dentist or oral and maxillofacial specialist. The figures quoted here describe groups of patients, not individual outcomes. Prices shown are verified starting prices and vary by case complexity.