Randomized clinical trial on the performance of direct and indirect composite restorations in patients with severe tooth wear

In clinical dentistry there is an increase in the prevalence of tooth wear
among younger subjects. It is recognized that tooth wear has two main
etiological causes: 1) erosion by chemical etching of the enamel and dentine by
acids from either extrinsic, e.g., soft drinks, or intrinsic, gastric, sources,
and 2) mechanical wear by grinding tooth contacts or food. In the Netherlands
erosive tooth wear has been shown to have increased over the past years among
youngsters (Truin et al., 2005). In a recent longitudinal study, the prevalence
of erosive tooth wear at 16 yr was ± 40%, with about 10% already showing
localized complete loss of enamel (El Aidi et al., 2010). In that study the
prevalence as a result of mechanical wear was not specifically studied. In a
systematic review on tooth wear, independent of the etiological factors, it was
found that the predicted percentage of adults presenting severe tooth wear
increases from 3% at the age of 20 years to 17% at the age of 70 years (Van *t
Spijker et al., 2009). Also in the deciduous dentition of children the
prevalence of severe wear into the dentin significantly increases with age,
however, a large range, between 0 and 82%, was found in literature (Kreulen et
al., accepted 2010). In these reviews, tooth wear was defined as wear exposing
the dentin of teeth, which is commonly depicted as the starting point of severe
tooth wear.

It seems reasonable to conclude that the prevalence of tooth wear increases,
the individual severity does as well. However, the natural course of severe
tooth wear has never been described. We do not know whether those 10% of the
youngsters showing already wear into dentin are at risk for severe tooth wear
in the future. Severe tooth wear often leads to functional problems, difficulty
with and pain during eating and speaking and esthetical problems, due to
shortening of front teeth.

Thus, patients with severe generalized pathological tooth wear present a
complex problem in dentistry and a challenge for the general dental
practitioner. Loss of tooth tissue due to caries leads to lesion progression
into the deep of the tooth and are usually restored with direct *fillings*, the
most common dental restorative procedure. As a contrast, in tooth wear the
outer surface of the tooth is lost, including the morphological and functional
features. The restoration of the morphological form and function of the worn
dentition is often highly complicated by the fact that these worn teeth are
much shorter and smaller, which has resulted in a loss of vertical dimension
of occlusion (VDO). Therefore, to restore form and function, an increase of
vertical dimension of occlusion is necessary (the distance between the jaws has
to be increased to provide space for the restorations).

To increase the vertical dimension of occlusion several materials and
techniques are used. Traditionally, the more invasive technique, crowns are
placed. Nowadays, also composite materials are frequently used, based on the
principle of 'minimally invasive'. Meaning that no additional tooth material
has to be removed and that the technique is reversible. These composite
materials, intended for direct use in the oral cavity, show to have improved
mechanical characteristics which can be used for extensive crown-like
restorations to build-up teeth (Kuijs et al., 2006; Hamburger et al., submitted
2010). Based on these studies, use of composite restorations is the first
treatment of choice when the loss of vertical dimension is less than 3 mm. In
case the tooth wear is more severe, also the more invasive techniques can be
used.

There is no established evidence based protocol for the treatment of patients
with severe tooth wear. Traditionally, when the loss of vertical dimension is
more than 3 mm, the approach is to use indirect, dental technician made, dental
crowns and/or uplays and where needed removable prosthetic appliances. The
disadvantage of this technique is the removal of sound tooth tissue in order to
obtain sufficient retention to the worn dentition.
Composite materials, intended for direct use in the oral cavity, show to have
improved mechanical characteristics which can be used for extensive crown-like
restorations to build-up teeth (Kuijs et al., 2006; Hamburger et al., submitted
2010). There is substantial clinical experience that *direct* as well as
*indirect* composite restorations are feasible alternatives in the treatment of
severe tooth wear. Moreover, another advantage of this technique are the
adhesive properties of the composite material, compared to the traditional,
more invasive, technique using metal-porcelain crowns. However, no clinical
evidence exists that there is a difference in clinical performance between the
restorations made with the two techniques.

If a person suffers from pathological wear (>=3mm loss of vertical dimension),
the restoration of the teeth includes a direct and indirect adhesive technique
to build up the worn dentition and to raise the bite. However, it is not known
which intervention is preferable in these patients. Therefore, we hypothesize
that both techniques present equal clinical performance; furthermore, no
temporary bite-raise appliance (splint) is necessary to test the increase of
vertical dimension of occlusion.

Aim of this study is to investigate the clinical performance of two restoration
techniques, making use of 'direct' and an 'indirect' composite restorations as
a minimal invasive intervention in patients with severe tooth wear. '
Moreover, the clinical necessity of a removal temporary bite-raise appliance
(splint) is investigated

Randomized controlled clinical trial, with two independent variables:
1) Placement technique (direct versus indirect)
2) Pre-testing of the new vertical dimension (with or without use of temporary
bite-raise appliance)

Patients will be randomized (block-randomization) divided over two treatment
protocols (indirect and direct) and over the use of a temporary appliance (with
or without).

The whole procedure is identical to that of a 'normal' dental treatment when
using direct and indirect composite restorations, with the exceptions of using
questionnaires regarding the Quality of Life, making dental impressions and
intra-oral light-photographs.

After finishing the treatment, patients will be recalled after 1, 3 and 5
years.
During those visits, dental impressions and intra-oral light-photographs will
be made to register the status of the restorations and a questionnaire
regarding the Quality of Life will be filled in.
Normal regular dental check-up will be performed by their own general dentist.

The most important benefit for the patients is the rehabilitation of their
dentition. Functionality (teeth are less sensitive, a better occlusal
stability, etc) and esthetics will be improved immediately after finishing the
treatment