DentAI – How Much Does an Implant Really Improve Chewing?

Reading guide: Wherever this text offers a reading or interpretation, it is labelled Interpretation. The rest reports the paper's own findings.

Why this paper was written

When a patient comes for implants, the first reason is usually wanting to chew better. The common assumption, among patients and dentists alike, is that an implant-supported denture almost always improves chewing.

The problem is that patient satisfaction and actual chewing performance are two separate things, and the link between them is weak. A patient can be fully satisfied with a denture while the real efficiency of breaking down food has barely changed, and the reverse is also true. The paper stresses that this weak link has been shown repeatedly, both in conventional-denture wearers and in implant-denture wearers.

This systematic review looked only at objective measures. Objective here means standard tests that directly measure how finely food is broken down or mixed, not a satisfaction questionnaire. The question was simple: when we actually measure it, how much do implants improve chewing?

From hundreds of papers the authors found 18 that had these measures. Those 18 papers reported 14 studies in total, because some studies were published in more than one paper.

A note on the strength of the evidence: by the time of this review, few studies had been done on the topic, and a substantial share of them were not strongly designed. Patients were not randomly assigned between two treatments, or there was no comparison group at all. The findings should therefore be read as the best then available, not as the last word. Wherever the evidence is weaker, the text says so.

1. Implant-supported fixed partial dentures versus removable partial dentures

Only one randomized study exists in this comparison, in patients with Kennedy Class I and II mandibular partial edentulism. Patients were assigned to two groups: one received implant-supported fixed partial dentures, the other conventional removable partial dentures.

The result was that no difference was seen between the two groups. Chewing performance improved by the same amount in both, and the implant-supported fixed prosthesis showed no advantage over the removable partial denture.

That is unexpected, but the authors' explanation is coherent. In that study the buccolingual width of the occlusal platform of the fixed prosthesis was deliberately narrowed to reduce load on the implants. As a result the chewing surface of the removable partial denture was wider than that of the fixed prosthesis. Another study has shown that a wider occlusal platform in a removable partial denture is associated with better chewing capacity. The authors suggest that the larger chewing surface of the removable partial denture may have offset part of the retention and support advantage of the fixed prosthesis.

Two further points belong beside this result. First, the implants in that study were blade-vent implants, which differ fundamentally from the cylindrical implants in common use today, so any direct generalization to current systems should be cautious. Second, this is the only study that made this comparison, and a single study is not a firm base for a definitive conclusion.

2. Implant-supported fixed complete dentures versus complete dentures

Three studies made this comparison, but none were randomized and none had a control group. In all of them, chewing performance was measured in the same patient before and after treatment.

In the mandible, an implant-supported fixed complete denture produced a large improvement over the patient's previous denture, and that improvement lasted up to ten years. In the maxilla, two studies also showed a large improvement. A third, small maxillary study saw a large effect that did not reach statistical significance, most likely because of the very small number of patients rather than the absence of an effect.

Three qualifications change that picture:

First, the study population was pre-selected. These patients had sought a fixed prosthesis because they had problems with their denture. That is, a group that had not adapted to a removable prosthesis. The paper states explicitly that it is unclear whether a patient who has adapted well to a denture, or is satisfied with it, would benefit to the same degree.

Second, the comparison was with the patient's own previous denture, not with a newly made complete denture. None of these studies had a control group with a new complete denture.

Interpretation: When the reference is the patient's previous prosthesis, part of the improvement can simply be the effect of making a new prosthesis, not the effect of the implant. The authors themselves say that conclusive evidence requires randomized studies comparing a fixed prosthesis with a new complete denture.

Third, and clinically the most interesting: at ten-year follow-up, patients with a fixed prosthesis in both jaws did not differ significantly in chewing performance from patients who had one only in the mandible. The authors infer that the maxillary fixed prosthesis's contribution to chewing performance may be limited, but they stress that this hypothesis needs better studies.

3. Implant overdentures versus complete dentures

The strongest evidence in this paper is in this section, and the important point is that the whole answer depends on one variable: residual mandibular ridge height. Depending on how much ridge remains, the answer changes completely.

Patients with an average or good ridge

In patients whose ridge height was in the normal range, a new overdenture and a new complete denture gave similar results, and no advantage for the implant was seen. In the average-ridge subgroup, the conventional-denture group's improvement was even slightly greater, but that difference was not significant and should not be read as superiority of the conventional denture. The correct statement is that in this group neither treatment outperformed the other.

Patients with a resorbed ridge

Here the picture reverses completely. In patients with ridge height below about 21 mm, an implant overdenture produced a large improvement, whereas the same patients given a new complete denture not only did not improve but chewed a little worse. Another randomized study in patients with a far more resorbed ridge (about 14 mm) confirmed the same advantage in the first year.

A point that is usually not quoted

One study compared several groups side by side and found that an implant overdenture on a resorbed jaw outperformed a complete denture on that same resorbed jaw, but was still weaker than a complete denture on a tall, healthy ridge.

So the order of chewing performance came out as:

1. Complete denture on a tall ridge
2. Implant overdenture on a resorbed jaw
3. Complete denture on a resorbed ridge

Above all of these, unsurprisingly, sat the natural dentition.

Interpretation: This pattern shows that implants do not necessarily bring a patient with a severely resorbed ridge up to the level of a patient with a healthy ridge; they close part of the functional gap. That belongs in how patient expectations are managed.

The time issue

In the same study of patients with a severely resorbed ridge, the overdenture advantage that was fully clear in year one was no longer significant in year four.

The explanation the authors propose is that a patient with a resorbed jaw needs a much longer adaptation period to get used to a new complete denture. Note that this is a possible explanation from the authors, not something the study measured directly.

Interpretation: If that explanation is right, part of the implant advantage is "arriving faster" rather than "reaching a higher ceiling." For a patient whose age or circumstances do not allow a long adaptation period, that time difference alone can be decisive.

4. Implant type and attachment system

Three studies examined this, and all three reached the same result: none of these choices produced a significant difference in chewing performance.

• When two different implant types (IMZ and transmandibular) were compared, patients' chewing performance did not differ.
• When three different protocols were compared — short implants, implants placed after augmentation, and transmandibular — chewing performance was again the same in all three groups.
• When three attachment systems were compared — ball-socket and bar-clip and magnets — all three produced a substantial improvement, but none outperformed the others.

The authors' own conclusion is that the amount of implant support and the level of attachment retention have a limited effect on chewing performance. In other words, more support or more retention does not necessarily translate into better chewing.

Interpretation: Attachment choice should therefore rest on ease of maintenance, cost, interocclusal space, and tissue conditions, not on the argument that one type chews better.

One limitation should also be kept in view. In all of these studies the patient's maxilla had a conventional complete denture. It has never been tested what happens to chewing performance if retention and stability are improved in both jaws at the same time.

5. Jaw-reconstruction patients

In patients after partial mandibulectomy and reconstruction with a fibula free-flap, both a conventional prosthesis and an implant-supported prosthesis improved chewing performance on the defect side, but the improvement with the implant prosthesis was far greater.

This advantage was seen only on the defect side. On the intact side of the mouth, the two prostheses performed essentially the same.

The authors also add a clinical recommendation: in these patients implant treatment should be deferred until one year after surgery. Their argument is the high rate of recurrence and metastasis (about one-third of cases), reported in another source, not in this chewing-performance study.

For maxillectomy patients, no study was found that compared chewing performance with a conventional versus an implant prosthesis, and the authors treat that as a clear gap.

Clinical summary

The paper's own conclusion is that the objective benefits of implant-supported or retained dentures in chewing performance, relative to conventional dentures, are limited to mandibular overdentures in fully edentulous patients with a resorbed mandible and/or patients who have difficulty adapting to complete dentures.

More simply, there are two groups of patients for whom an implant overdenture makes a real, measurable difference: a fully edentulous patient whose mandible is severely resorbed, and a patient who, whatever you do, cannot get along with a conventional denture.

For the other groups reviewed, from Kennedy Class I and II partial edentulism to the edentulous patient with a good ridge, there was no strong evidence of an objective chewing advantage.

Interpretation: That does not make implants worthless. Comfort, confidence, eliminating clasps, bone preservation, and overall patient satisfaction are all fully legitimate reasons to choose implants. None of them is "chews better," and those two kinds of reason should not be mixed in the consultation.

The paper's own clinical recommendation is exactly that: the dentist should be aware of the limits of implants' functional benefits and explain them clearly to the patient so that treatment decisions are informed.

Overall caveat

The search for this review ran through June 2007. Implant design, occlusal protocols, and materials have changed since then.

Interpretation: The paper's overall logic — that ridge height is the determining variable, and that adding more retention does not necessarily raise chewing efficiency — is likely still standing. Specific comparisons, though, should be read as historical.

Primary source:
Fueki K, Kimoto K, Ogawa T, Garrett NR. Effect of implant-supported or retained dentures on masticatory performance: a systematic review. J Prosthet Dent. 2007;98(6):470-477.