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\begin{document}

\title{Conservative and Cost-effective Rehabilitation of a Deep Bite Patient
with Worn Dentition: A Case Report of the Dahl Technique Approach}



\author[1]{Mahla  Rezaei}%
\author[1]{Hossein  Chalakinia}%
\author[1]{Maedeh  Doost Mohammadi}%
\author[1]{Farzaneh Khosravi}%
\affil[1]{Mashhad University of Medical Sciences}%


\vspace{-1em}



  
  \date{May 19, 2024}


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\sloppy


\textbf{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).

\subsection*{The significance of anterior
guidance}

{\label{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).

\subsection*{Posterior-anterior
contacts}

{\label{posterior-anterior-contacts}}

The following formula should be kept in mind when analyzing the anterior
guidance: ``\emph{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''.

\subsection*{Treatment options}

{\label{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).

\section*{Case report}

{\label{case-report}}

\textbf{Consent Statement}

Informed consent was obtained from the patient. All the guidelines of
the Declaration of Helsinki were followed and the patient's information
was kept confidential

\subsection*{The patient's condition and
requests}

{\label{the-patients-condition-and-requests}}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

The patient was a 36-year-old woman without any systemic disease with
the chief complaint of unaesthetic teeth and an unpleasant feeling of
tooth grinding during sleep (figure 1).

After examination, a list of patient problems was obtained. The patient
had no endodontic or periodontal problems. Regarding the angle
classification, the patient had a CL 2 DIV II jaw relationship along
with occlusal plane can't, reduced overjet, severe deep bite, and
anterior crowding (figure 2).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

\textbf{Figure 2.} The Intraoral frontal view of the patient.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

Attrition was seen at the incisal edge of anterior teeth and occlusal
surface of posterior teeth (figure 3).

Likewise, abfraction was evident in the cervical region of posterior
teeth, indicating that the patient had an occlusion problem. The
fracture of the left upper second premolar was also observable (figure
4).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image4/image4}

\end{center}
\end{figure}

The aesthetic characteristics of the patient were assessed from three
macro-, mini-, and micro-aesthetic views, and the following problems
were reported for the patients:

\begin{itemize}
\tightlist
\item
  \textbf{From a macro-aesthetic view:} asymmetrical eyes (the
  inter-pupillary line was not parallel with the horizon plan).
\item
  \textbf{From a mini-aesthetic view:} the incisal plane was not
  parallel with the horizon; the smile arch did not coincide with the
  lower lip; the presence of occlusal plane canting; more gingiva was
  shown at the right side; midline deviation; asymmetrical smile; the
  RED proportion was not respected.
\item
  \textbf{From a micro-aesthetic view:} discoloration of teeth;
  anatomical proportions were not respected; asymmetry in gingival
  height and zenith; the problems with crowding and the longitudinal
  axis of teeth.
\end{itemize}

\subsection*{The treatment plan
selection}

{\label{the-treatment-plan-selection}}

The examinations suggested that the lack of stable contacts in palatal
segments of the upper anterior teeth caused the dental cingulum loss in
the upper jaw dentition. This alteration led to overgrowth of upper and
lower teeth and ultimately aggravated the deep bite. During the
examination of the casts, the CR contact of the lower anterior teeth on
palatal tissues was observed.

The aesthetic treatment plan will be preceded by creating a stable
posterior and anterior occlusion. The first stage of treatment consisted
of establishing stable contacts by cingulum restoration for upper
anterior teeth while creating smooth edges for the lower anterior teeth
to ensure stable contacts of lower anterior teeth on palatal surfaces of
the upper anterior teeth. Thus, after the clinical examination of the
patient and analysis of the study casts, the Dahl technique was decided
to be used for restoring and establishing occlusal contacts in correct
positions to modify the occlusion and open the bite (figure 5).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image5/image5}

\end{center}
\end{figure}

In order to increase the bite in the original Dahl technique, a partial
metal appliance is placed on the palatal surfaces of the upper anterior
teeth to create an inter-occlusal space of 1.8-4.7 mm. Thus, a
combination of interior intrusion (40\%) and posterior eruption (60\%)
will be achieved. In this technique, the average time of achieving an
ideal occlusion is six months for most people, and the chief reason for
treatment failure is the non-cooperation of the patients in using the
appliance which is why we altered the anterior guidance to act as fixed
anterior bite plan and to have stable anterior contacts(13).
Alternatively, this technique allows for cingulum restoration, providing
sufficient space for the posterior teeth eruption and anterior guidance
correction by creating composite stops on the anterior teeth without the
need to use an appliance. This, in turn, will increase the possibility
of the patient's cooperation and improve the treatment effectiveness.
The objective of this treatment was to provide the lost space due to
tooth wear in anterior, remove the posterior teeth from contact, and
provide space for vertical movement (eruption) of teeth.

Both mandibular and maxillary anterior teeth were restored in this
patient, and the composite stops were created on the anterior dentition
of both jaws. After this restoration, the patient's bite was opened, and
by creating enough space in the posterior between the teeth of both
jaws, the restoration of worn posterior teeth also became possible
(figure 6).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image6/image6}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image7/image7}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image8/image8}

\end{center}
\end{figure}

A follow-up was conducted on the patient to evaluate and compare the
level of occlusal contacts. The observations were recorded by
photography before, immediately after, at four and ten weeks after
performing composite corrections (figure 7-9). Tooth contacts were found
to be re-established at the end of week 10 (figure 10 \& 11). Then soft
tissue crown lengthening (CL) was carried out by the electro-surgery
device to correct the gingival levels of the left central, lateral and
canine teeth of the patient. After shaping and preparing the anterior
teeth of both jaws, the impressions for the construction of ceramic
laminates was taken by a one-stage technique using polyvinyl siloxane
(PVS). After delivering the lithium di-silicate laminates, a night guard
was fabricated for the upper jaw, and its necessity and method of use
were explained to the patient. The final result was very pleasant for
the patient (figure 12).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image9/image9}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image10/image10}

\end{center}
\end{figure}















\section*{}

{\label{section-7}}

\section*{Discussion}

{\label{discussion}}

The present case report is concentrated on the treatment plan for a
patient with pathologic deep bite, progressive wear, and anterior deep
bite. The pathological deep bite has signs and symptoms (including
traumatic palatal soft tissues, unstable occlusion, tooth wear, and
aesthetic issues) that their treatment process may demand decisions like
orthodontic treatment or reshaping or compromised restorations(14). One
of the challenges in the treatment of deep bite patients is the limited
available space for placement of the required restorations. These
conditions become increasingly complicated when the occlusal wear occurs
in a deep bite occlusion.

The compensatory dentoalveolar growth, which occurs continuously and
following wear issues, fills the space required for the reconstruction
of the worn teeth. Under these circumstances, the following treatment
options can be used to provide the space needed for retention,
stability, and aesthetics:

1. Orthodontic intrusion and proclination of the supra-erupted teeth

2. Teeth reduction in the same or opposite arch, occlusal plane
correction, and occlusal reconstruction with and without surgical crown
lengthening.

3. Temporally increasing the VDO in posterior teeth (using Dahl
appliance, direct or indirect restorations with full or partial
coverage, and orthodontic extrusion of posterior teeth)

4. Elective endodontic procedure to provide adequate space and grip from
inside of the dental structure using the post-retained restorations or
Richmond crown(15, 16).

Each of these treatment options has its particular indications and
considerations. On the other hand, the wear of buccal surfaces of the
anterior teeth in the lower jaw (which also occurred in the present
case) is another problem that demands reconstructing anterior guidance.

VDO can be increased using the fixed prosthesis or removable appliance.
Concerning the method applied to increase the VDO, those studies that
used the fixed prosthesis reported fewer complications compared to those
that used the removability feature. The Dahl technique utilizes a local
appliance or restoration in the supra-occlusion position on the anterior
teeth, allowing the posterior teeth to extrude and anterior teeth
intrude to achieve full arch contacts over a time period. However, the
success of this appliance is fully dependent on the patient's
cooperation. Several complications have been reported, including TMJ
dysfunction, possible tenderness during treatment, sensitivity,
unpredictable tooth movement, and tilt or drift of other teeth(17).
Another method for increasing the VDO includes orthodontic extrusion,
usually the posterior extrusion of teeth combined with
anterior-posterior repositioning of anterior teeth with limited
intrusion. Nevertheless, the intrusion is much more complicated in
adults, and orthodontic treatment requires a time duration of 6-12
months, which is significant for equalizing the mesiodistal spacing that
occurs during the teeth forward movement(18). A better therapeutic
option to gain space in this patient is fixed dahl technique, which is
basically a anterior bite block in order to create space in anterior
section allowing us to properly restore patients anterior guidance and
esthetics while posterior teeth untouched and in contact.

Space gained by this technique in 40\% anterior intrusion and 60\%
extrusion of posterior teeth in 10 week time period. By literature
during a year original VDO is regained by muscles. It is by far the most
conservative while effective treatment plants for this case.

Conservative ceramic coverage is the most durable aesthetic option among
the mentioned restorative methods. However, design selection, proper
preparation, skillful ceramist and choosing the ceramic material play a
significant role in the long-term success of this treatment. Numerous
factors, including the amount of remaining tooth structure, restoration
material type, finish line design, restoration thickness, and cement
types, can affect the mechanical behavior of occlusal veneers. There are
various ceramic materials that can potentially be used in low thickness
for high-stress situations. High-glass ceramics have lower compressive
strength, whereas the low-glass types such as lithium disilicate (LDS),
zirconia-reinforced lithium silicate (ZLS), and hybrid ceramics offer
appropriate aesthetics and much higher strength. Bonding of glass
ceramics is one of their significant properties for partial coverage
restoration applications(19).

While composite resin, LDS, ZLS, and hybrid ceramics can be employed for
posterior occlusal coverage, disagreement exists in the literature
regarding the superiority of composite resin or ceramic restoration(20).
In the present case, composite occlusal veneers were utilized to
increase the VDO, which seems to be a conservative treatment. Given the
higher aesthetic characteristics of ceramic laminates, disilicate
lithium laminates were eventually constructed for the anterior teeth of
both jaws. However, both approaches had a reliable performance for both
functional and aesthetic purposes. Long-term clinical trials are needed
to find the best material, thickness, and treatment plan.

\section*{Conclusion}

{\label{conclusion}}

Dealing with wear problems the Dahl technique, if used correctly, can
provide clinicians with an alternative solution to treat occlusal and
wear issues, particularly in mild and moderate localized cases of tooth
wear. This method can save the patients from the risk of tooth wear in
all teeth. The clinical ease and the fact that composite restorations
can be customized and modified intraoral over a week or two provide
better controllability of the treatment outcome. This can be regarded as
the ultimate preventive dentistry. So this treatment plan while being
conservative and providing satisfactory esthetic, it helps to rebuild
anterior guidance. The patient was excited about the final treatment
outcome. In addition to the aesthetical aspect, this treatment plan was
simple, conservative, cost-effective, and durable and could prevent
further anterior and posterior progressive teeth wear.

\section*{Conflict of interest}

{\label{conflict-of-interest}}

No Conflict of interest is declared.

\section*{Figure legends}

{\label{figure-legends}}

Figure 1. Frontal smile view of the patient.

Figure 2. The Intraoral frontal view of the patient.

Figure 3. Mandibular occlusal view.

Figure 4. Maxillary occlusal view.

Figure 5. diagnostic cast

Figure 6. Occlusal adjustment. Creation of composite stops on anterior
teeth: Resulting on enough space for posterior teeth eruption, restoring
cingulum and anterior adjustment.

Figure 7. Immediately after tooth contact adjustment with composite.

Figure 8. Four weeks after tooth contact adjustment with composite.

Figure 9. Ten weeks after tooth contact adjustment with composite.

Figure 10. Reestablishment of occlusal contacts after 10 weeks.

Figure 11. Occlusion after cementation. A, Dots in the back. B, Lines in
the front.

Figure 12. Final result.

\section*{Abbreviations}

{\label{abbreviations}}

NCCL: non-carious cervical lesion

VDO: vertical dimension of occlusion

CR: centric relation

MI: means maximum Intercuspation

TMJ: temporomandibular joint

CL: crown lengthening

PVS: polyvinyl siloxane

\section*{References}

{\label{references}}

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