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Journal of Clinical and Diagnostic Research. 2018 Jan, Vol-12(1): ZH01-ZH03 11
DOI: 10.7860/JCDR/2018/30607.11057 Clinician’s Corner
Dentistry Section
A Novel Complete Denture
Impression Technique with
Thermoplastic Stock Trays
TECHNIQUE
Stainless steel stock trays used for primary impressions are
basically designed as vehicles to carry and support relevant
impression materials. Plastic modelling compound and irreversible
hydrocolloids are the materials of choice for primary impressions in
complete dentures. The obtained primary casts are then used for
the fabrication of custom trays for master impressions. Regular
clinical practice involves patient appointments for both primary
and master impressions. Massad earlier proposed the use of
low temperature edentulous stock tray with putty as stoppers
and used elastomeric impression materials for peripheral tracing
and master impression [1,2]. Herein, we propose an original
technique of a thermoplastic stock tray (KLARITY WhiteTM,
Meditronix) with built in tissue stoppers and spacer design that
can be adapted to the patient’s edentulous arch, to be further
used for peripheral tracing and master impression, thus reducing
the above mentioned additional appointments [3]. The present
article will throw light on the procedure of customising the
tray with peripheral tracing, master impression and the clinical
challenges faced.
1. Construct dental stone casts from a standard size maxillary or
mandibular stock tray as shown in [Table/Fig-1].
2. Place 4×4 mm tissue stoppers (Modelling wax, DPI) on the
dental cast with a spacer (2 mm Modelling wax, DPI) design of
choice (Boucher’s design), 4 mm short of sulcus.
3. Typical property of a thermoplastic polymer is its ability to
be moulded with temperature. Manually mold the softened
thermoplastic sheet (KLARITY WhiteTM, Meditronix) to even
thickness on the prepared cast using Bunsen Burner at a
temperature of 85°C and temperature at 45°C in warm water
bath as shown in [Table/Fig-2,3] as a prefabricated tray [3].
Further adapt the material for fabricating handle on the tray
using Bunsen flame and warm water bath.
SIVARANJANI GALI1, PRIYANKA AIYER2, ANOOP SHARMA3
Keywords: Dental impressions, Impression trays, Peripheral tracing
ABSTRACT
Primary impressions in complete dentures are generally made with stainless steel stock trays. Conventional clinical procedures
therefore, require additional patient appointments for primary and master impressions. We propose a unique single appointment
technique of a thermoplastic stock tray for peripheral tracing and master impression for complete denture patients.
[Table/Fig-1]: Dental stone casts prepared from available stainless steel stock
trays.
[Table/Fig-2]: Tissue stoppers and spacers adapted on the stone casts.
[Table/Fig-3]: Thermoplastic mandibular and maxillary trays with built in tissue
stoppers and spacers (Boucher’s design).
4. Adapt the prefabricated thermoplastics tray at a temperature
of 45°C (warm water bath) to the patient’s edentulous arches
and cool the tray in water bath at room temperature as shown
in [Table/Fig-4].
5. Trim the trays 2 mm short of the sulcus in the patient mouth to
accommodate for peripheral tracing modelling compound.
6. Follow the conventional procedure of peripheral tracing and
master impression with elastomeric or zinc oxide eugenol
impression paste as shown in [Table/Fig-5,6,7].
Sivaranjani Gali et al., Impression Technique using Thermoplastic Trays www.jcdr.net
Journal of Clinical and Diagnostic Research. 2018 Jan, Vol-12(1): ZH01-ZH03
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thermoplastic materials are used in dentistry such as modelling
compounds, thermoplastic waxes including baseplate and pattern
waxes, and reversible hydrocolloids. Thermoplastic material, as
prefabricated stock trays can be readily adapted as custom trays
in the patient’s mouth compared to the conventional procedures of
stock and custom trays. The uniqueness of the proposed impression
technique unlike earlier techniques, is the idea to incorporate the
philosophy of selective pressure technique in the prefabricated
thermoplastic stock tray. This will enable the clinician to select the
prefabricated trays with tray designs based on the examination
and diagnosis of the patient’s mucosal and ridge condition at the
first appointment [5]. Therefore, there are advantages of reduced
appointment time and material cost compared to the conventional
procedures.
The philosophy of selective impression technique is fundamentally
based on loading the denture bearing areas that can withstand
pressure and relieving areas that cannot withstand the functional
load [6]. The concept of selectively applying pressure is based on
the variance in histology of the denture bearing mucosa. It is the
underlying anatomic structures supporting and limiting the prosthesis
that determine the success of complete dentures [7]. There are an
array of customised tray designs proposed to follow the principle
of selective pressure technique. The present technique follows
Boucher’s concept of spacer design, of placing 1 mm baseplate
wax all over the maxilla except the posterior palatal seal area and
Sharry’s concept of placing four tissue stops 4 mm in width in the
molar and cuspid region extending from palatal aspect of the ridge
upto the vestibule [8].
Prefabricated trays of thermoplastic material with built in tissue
stoppers (Sharry design) of 4×4 mm (Baseplate wax, DPI) at the
cuspid and molar region and spacers (Boucher’s design) were
fabricated in our laboratory [8]. It is important to adequately
soften the thermoplastic material at the recommended
temperature of 85°C and adapt the material closely onto the cast
with even thickness for the fabrication of tray with the spacer
and stopper design. The spacers appear as debossed areas
and the tissue stoppers appear as embossed areas in the stock
tray. It is also essential, to shape the moulded tray meticulously
to the patient’s denture bearing and limiting structures, without
injuring the tissues at the suggested temperature of 45°C during
the procedure. The tray was adapted to the patient’s posterior
palatal seal area and border extensions of the tray were trimmed
accordingly. Thermal properties of the tray material (KLARITY
White TM, Meditronix) such as high melting point above 140°C
and low softening point (below 100°C, ~85°C) enabled the use
of low fusing modelling compound (~55°C) for peripheral tracing
without the risk of deformation [4]. Technically, we assumed the
adaptation of the thermoplastic tray in patient’s mouth may be
difficult due to the presence of saliva. However, use of Bunsen
flame followed by tempering eased the tray adaptation in the
patient mouth.
LIMITATION
Limitations of the present technique concerns to the retention
of thermoplastic properties following chemical sterilisation of
trays for re-use, and skill of the operator in controlling the tray
thickness during the manipulation.
CONCLUSION
A single appointment impression technique of thermoplastic
stock trays with tissue stoppers and custom tray designs can be
effectively adapted to patient’s edentulous arches and further used
for peripheral tracing and master impression.
[Table/Fig-5]: Tracing performed on the thermoplastic tray (maxillary).
[Table/Fig-6]: Peripheral tracings on the maxillary and mandibular thermoplastic
tray.
[Table/Fig-7]: Secondary impressions made from maxillary and mandibular ther-
moplastic trays.
[Table/Fig-4]: Thermoplastic tray being adapted in the patients’ maxillary and
mandibular arches.
DISCUSSION
The thermoplastic material used in the technique is a styrene based
epsilon caprolactone polymer with cross-linking agents and fillers,
used mostly to support artificial limb prosthesis [4]. A number of
www.jcdr.net Sivaranjani Gali et al., Impression Technique using Thermoplastic Trays
Journal of Clinical and Diagnostic Research. 2018 Jan, Vol-12(1): ZH01-ZH03 33
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PARTICULARS OF CONTRIBUTORS:
1. Associate Professor, Department of Prosthodontics, Faculty of Dental Sciences, Ramaiah University of Applied Sciences, Bengaluru, Karnataka, India.
2. Postgraduate Student, Department of Prosthodontics, Faculty of Dental Sciences, Ramaiah University of Applied Sciences, Bengaluru, Karnataka, India.
3. Postgraduate Student, Department of Prosthodontics, Faculty of Dental Sciences, Ramaiah University of Applied Sciences, Bengaluru, Karnataka, India.
NAME, ADDRESS, E-MAIL ID OF THE CORRESPONDING AUTHOR:
Dr. Sivaranjani Gali,
Associate Professor, Department of Prosthodontics, Faculty of Dental Sciences, M S Ramaiah University of Applied Sciences,
Bangalore-560054, Karnataka, India.
E-mail: nature79gali@gmail.com
FINANCIAL OR OTHER COMPETING INTERESTS: None.
Date of Submission: Jun 12, 2017
Date of Peer Review: Sep 02, 2017
Date of Acceptance: Nov 13, 2017
Date of Publishing: Jan 01, 2018