Introduction
The general term for non-carious loss of dental tissue (non-carious
cervical lesion (NCCL)) is tooth wear which describes the loss of hard
dental tissue due to various etiological factors, including chemical and
mechanical processes(1). According to Loomans et al., tooth wear, when
abnormal for the age of the patient, causes pain and discomfort,
functional issues, or decline in aesthetic appearance, and if
progressing, may result in complex undesirable complications. Tooth wear
can be classified as erosion, abrasion, attrition, and abfraction (2).
The clinical observations have shown that the wear mechanisms do not act
alone but interact with each other and usually with synergic effect on
each other to cause the destruction of dental surfaces(3). The increased
occurrence of erosive wear has been reported in young populations due to
dietary habits, a growing tendency to consume soft and energy drinks,
and the impact of stress. Regardless of the causative factors, tooth
wear may affect oral health, personal comfort, loss of vertical
dimension of occlusion (VDO), tooth sensitivity, hyperactive muscles,
temporomandibular joint problems and pulpal involvement(4). However,
aesthetic complaints exist, particularly in young adult patients. The
incisal edges may also show signs of wear, shortening due to the loss of
enamel support, and subsequent fracture, depending on the progression. A
high prevalence of tooth wear has been reported in the young population,
which can be reflective of the future dental problems in this
generation. Also, in elderly population complete loss of dentition is
now second to severe tooth wears as dental problem. For successful
treatment of the above cases, paying close attention to the anterior
guidance ,posterior contacts and TMJ is essential(5).
The significance of anterior
guidance
Following centric relation (CR), anterior guidance is the most
significant factor that must be determined when restoring an occlusion.
Aside from its key role in aesthetics, anterior guidance is a crucial
factor in protecting the posterior teeth. This protective role of
anterior guidance is so important that if the posterior teeth are not
protected from lateral and protrusive stresses by the separating effect
of the anterior teeth, they will be subjected to high and non-vertical
stress over time which can lead to worn dentition. Patient comfort is
determined by how accurately the anterior guidance is coordinated with
the functional pattern of other parts of masticatory system (6).
Posterior-anterior
contacts
The following formula should be kept in mind when analyzing the anterior
guidance: “Lines in the front and dots in the back. ” The dots
in the back merely show the contact points on posterior teeth which
means maximum Intercuspation (MI) contacts are coincide with CR. The
lines in the front demonstrate the role of anterior teeth in separating
the posterior teeth during all eccentric movements. Thus, the stable
contacts of anterior teeth in CR and sliding contacts in lateral
movements are fundamental issues in extensive restorations (7). This is
why this scheme is called “mutually protected system”.
Treatment options
The biggest problem with restoring worn dentition is there is no space
for restorative material to provide optimum resistance and retention
form. A variety of treatment options have been proposed, including
elective endodontic treatment, surgical crown lengthening for
restoration of worn teeth with insufficient restorative space, and
prosthetic treatments(8). However, these conventional methods are very
costly, time-consuming, and invasive. They destroy a considerable amount
of tooth structure and are accounted as an irreversible path for both
the patient and dentist. Another problem with these invasive treatment
plans is they are heavily dependent on laboratory precision, in fact if
dentist has no access to a skillful laboratory whole treatment can lead
to a failure. With advances in adhesion and dental bonding agents,
minimally invasive restorations have been introduced to preserve the
residual tooth structure. More invasive approaches as the treatment
options can be postponed until more advanced ages.
An alternative treatment option is occlusal veneers which are considered
a conservative approach to increase the VDO in cases with severely worn
teeth. The durability of these restorations and their ease of
construction make them an appropriate conservative treatment option(9).
But they are costly and still needs a skillful ceramist.
An ultra-conservative and simple treatment is proposed using a
combination of composite resin and the Dahl principle to resolve the
anterior teeth wear. The Dahl approach involves the creation of
inter-occlusal space through axial movement of the teeth via an
appliance or the restorations placed in the supra-occlusion and
subsequently re-creating the occlusal contacts of the full arch over a
time span. The primary Dahl appliance is based on a metal
cobalt-chromium appliance cemented on the palatal surfaces of the upper
anterior teeth(10). However, the quality and long-term esthetical
properties of directly bonded restorations are more dependent on the
operator, they have been used recently to create the proper space with
low to moderate durability compared to indirect restorations (11).
Concerning the directly bonded restorations, as stated by Craig, while
using the composites for the restoration of worn teeth is superior to
using ceramics due to their lower modulus of elasticity and seemingly
satisfactory clinical performance, they require maintenance owing to
their limited mechanical and physical properties(12).