Costs of Implant-supported Over-Dentures (IOD) can be halved using a digital workflow

INTRODUCTION/RATIONALE
Edentulism (being toothless) can lead to significant functional impairment, as
well as unfavorable aesthetic and psychological changes in patients. Reported
drawbacks include restrictions in diet and limited ability to eat certain
foods, speech impairment, loss of support for facial musculature which leads to
an ageing effect. Edentulism is even classified as a physical handicap by the
WHO.

The conventional method for treating edentulism is to provide Complete Dentures
(CD). However, CDs do restore chewing function only to a limited degree. Due to
unfavorable forces, an irreversible and progressive decrease of basal bone
volume is induced, leading to loss of retention and stability. Subsequently,
due to soreness, further impaired functioning will occur, also in psychological
sense.

As the amount of bone loss is four times higher in the lower jaw than in the
upper jaw, retention problems will first occur in the lower jaw. Therefore,
most edentulous patients are provided with dental implants already within the
first years of edentulism. With respect to their upper-CD, patients function
satisfactorily during the first 10 years. However in time, due to progressive
resorption, also retention problems of the upper-CD will occur.
Fortunately, to overcome the above mentioned drawbacks of CD*s, the success of
Implant-retained Over-Dentures (IOD*s) in terms of stability, function, speech,
and patient satisfaction has been shown in many studies; both for the lower jaw
as the upper jaw. An extra advantage of the presence of functioning implants is
that also the clinically significant progressive bone loss is prevented.

Of the Dutch population 11.6% above 16 years (1.6 million) is fully edentulous;
so 1.6 million persons wear a CD in both the upper and lower jaw. Another 4,9%
(700.000) is edentulous in one jaw. According the report of Zorginstituut
Nederland, every year about 40.000 patients are treated with Conventionally
produced IODs (C-IODs) with a total yearly cost for fabrication of ¤105
million.

Our goal is to manufacture a 3D-IOD which is designed digitally, and
subsequently 3D-printed. Such 3D-IOD, can be made cheaper, faster and more
patient friendly. To prove such a statement, patients should at least be even
satisfied about their 3D-IOD as their C-IOD (non-inferiority). In the same
time, cost and time spent on treatment sessions should be significantly lower.
In literature no publications can be found which compare C-IODs with 3D-IODs,
simply because of the fact that a digitally designed and 3D-printed IOD is a
novel technique.


Besides costs, the most striking benefits are the reduction of the number of
treatment sessions and the active participation of the patient in designing his
3D-IOD. Also, technical advantages are introduced. Traditionally, C-IODs are
press-cured using 2-component PMMA, which has a major drawback; toxic residual
monomer needs to be flushed out meticulously. Furthermore, shrinkage will occur
after press-heating, thus frustrating its fit. Such complications are bypassed
using 3D-printing techniques

This effectiveness study entails a randomized controlled trial; 36 patients
will be provided both with Conventionally Implant supported Over Dentures
(C-IOD's) as with 3D-printed Implant supported Over Dentures (3D-IOD's) in
both the lower jaw as well in the upper jaw.

Follow-up period is 24 months; 18 patients will start the first year with a
C-IOD, followed by wearing a 3D-IOD the next year (group A). The other 18
patients wear their IOD*s in reverse order (Group B). The C-IOD and 3D-IOD data
will be compared on a number of outcome variables: before treatment, after 12
months and after 24 months of follow- up.

Before start of the treatment, and after 12 months, patients in both group A
and B will receive a questionnaire (OHIP-20) to determine changes in the Oral
Health Related Quality of Life (OHRQoL) after the first IOD-installation. After
one year, patients of group A and group B switches from one IOD-modality to the
other. At 24 months again the OHIP-20 questionnaire needs to be filled in.

According to the protocol, which is generally used in implant treatment,
immediately after IOD-installation and during the supportive care appointments
after 6, 12, 18 and 24 months, the clinical variables PPD (Pocket Probing
Depth), CAL (Clinical Attachment Level) will be recorded. Additionally, at the
start of the study, after one year and after two years, standardized
radiographs will be made.

Based on above mentioned data, implant survival, marginal bone level, changes
in soft tissue (PPD, CAL) position will be assessed. In addition patient*s
overall satisfaction will be scored.

The only burden is the extra time spent on

1) the registration of the digital data during the making-of the conventional
IOD (2 hours)
2) the session in which one IOD-type will be changed for the other (1 hour)
3) time to fill in the OHIP-20 questionnaire and the overall satisfaction VAS
score (three times 0,5 hour).

The clinical parameters are measured during regular controls and would be
executed anyway, as these are a part of the regular control.