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10 prosthetic section DENTAL TECHNOLOGY, JANUARY-MARCH 2025

CASE REPORT – METHOD AND TOOLS USED FOR

REGISTRATION AND CORRECT TRANSFER OF

PROSTHETIC COORDINATES FROM THE CLINIC TO THE LAB

CLAUDIO NANNINI, FRANCESCO ROMAGNOLI

INTRODUCTION
Every time we rehabilitate a full arch in which all posterior teeth on both
sides have been lost, we observe an altered anterior relationship due to pro-
trusive slippage of the mandible resulting from the absence of a posterior
stop. This leads to altered intermaxillary ratios in the sagittal plane, as well
as a loss of DVO, along with incorrect overbite and overjet values.
In such cases, we cannot rely on the technician to mount the initial study
models in the articulator using the Maximum Intercuspation (MI) position
and then simply raise the incisal rod to the DVO deemed correct during the
clinical examination. Doing so would result in the so-called "scissor effect,"
where we end up with the same DVO, but in a study model position that
does not correspond to the true spatial relationship of the two maxillae in
the oral cavity.
Therefore, the registration of the new position—both the new DVO and FIG 1: Initial image of the case, presented in the article
the updated antero-posterior intermaxillary relationship—must be per-
formed directly in the patient’s mouth.
This recorded position is identified as the “Reference Position.” To record
it correctly, it is absolutely crucial that the patient is in a state of muscular
relaxation. If the patient is muscularly contracted, they will be unable to
produce a position that is repeatable and unforced, which is precisely what
we are aiming for at this stage.
Thus, in such cases, it becomes essential to first resolve this issue before
approaching prosthetic rehabilitation. The clinician may therefore opt to use
plates or splints during the initial phase to achieve a state of joint and mus-
cular relaxation. This will allow for an accurate and reliable registration.
This new position will serve as the starting point of the rehabilitation
project, beginning with a case study using a diagnostic wax-up. This will
enable us to reestablish correct esthetic and phonetic relationships, along
with a stable posterior occlusion and proper anterior guidance. Following FIG 2
this esthetic-functional evaluation—performed using a mock-up—and with
the help of established transfer techniques between the clinic and laborato-
ry, we gain both certainty and predictability in the final outcome
(Figure 1).
This article aims to demonstrate, through the presentation of a clinical
case, how a straightforward yet precise and meticulous method can lead to
optimal, reproducible results—making them accessible to all clinicians and
no longer dependent solely on the operator's experience.

CASE PRESENTATION
The case presented in this article concerns a 75-year-old patient who report-
ed a variety of issues.
His initial complaint was progressive wear of the anterior teeth, which
over time had led to increased sensitivity to thermal changes and a decline
in the esthetics of his smile (Figure 2).
He also noted that the loss of his posterior teeth had caused a marked FIG 3
reduction in his chewing efficiency, leading to digestive difficulties.
As a result, his request was twofold: to enhance the esthetic appearance
FIG 2-3: Initial situation - intraoral and extraoral
of his smile and to regain proper masticatory function.
His focus, however, is solely on the upper arch, as he recently underwent
prosthetic treatment on the lower arch—which he reports as comfortable Dentally, he explained that he lost the posterior teeth in both
and has no desire to replace at this time (Figure 3). arches and his lower incisors several years ago due to periodon-
This case will therefore illustrate how to manage a clinical situation tal disease, and subsequently restored the lower arch with a
involving the rehabilitation of only one arch, while still requiring at least a removable prosthesis.
revision of the opposing arch. We will explore in the treatment plan how to approach and
During the general medical history, no significant systemic pathologies manage rehabilitation of the upper arch alone, alongside a func-
were detected through palpation, and the patient reported that he does not tional revision of the antagonist arch.
smoke and does not take any long-term medications. Extraoral clinical examination reveals a triangular facial shape