| Abstract|| |
Making impressions in microstomia patients is often cumbersome. A modification of standard impression procedure is often necessary while treating such patients. This article describes the fabrication of a custom sectional impression tray with interlocking type of a handle for definitive impression procedures in a microstomia patient.
Keywords: Microstomia, sectional trays, definitive impression procedures
|How to cite this article:|
Fernandes AS, Mascarenhas K, Aras MA. Custom sectional impression trays with interlocking type handle for microstomia patients. Indian J Dent Res 2009;20:370-3
Cases of limited mouth opening are often discussed in prosthodontics. ,,,,,,,,,,, Microstomia may be the sequelae of orofacial burns, carcinoma, cleft lip, trauma, scleroderma, Plummer Vinson's syndrome, genetic disorders, surgery, or natural ageing processes. ,,,,,, The reduced mouth opening hinders conventional dental treatment; hence alternative treatment procedures have to be chosen to overcome the clinical difficulties while managing such a patient.
|How to cite this URL:|
Fernandes AS, Mascarenhas K, Aras MA. Custom sectional impression trays with interlocking type handle for microstomia patients. Indian J Dent Res [serial online] 2009 [cited 2019 Sep 15];20:370-3. Available from: http://www.ijdr.in/text.asp?2009/20/3/370/57371
Several stock and custom tray designs have been described in literature. Sectional impression trays have been fabricated using recesses,  orthodontic screws,  Lego blocks  (Lego systems Inc., Enfield, CT), dowel plug holes and a screw joint for rigid connection,  locking levers,  and interlocking tray segments.  Flexible impression tray  with silicone putty has been also used in making impression in a microstomia patient.
This article describes the fabrication of custom sectional tray with interlocking type handle for definitive impression procedures.
| Technique|| |
Fabrication of a tray handle (anterior lock)
The handle functions as an anterior lock and has two parts, the male and the female unit [Figure 1]. The male unit has an external and an internal flange having an interconnecting isthmus, which is 2 mm short of the inferior portion of internal flange. The internal flange is short of the inferior portion of external flange by 2 mm. A horizontal plate connects the superior ends of both the flanges [Figure 1]. The female unit has an internal recess of which the terminal ends approximate the width of isthmus. The terminal ends appear as a slot in the medial wall. This slot is short of the inferior portion by 4 mm. Fabricate wax patterns (Modelling wax; DDP Pvt. Ltd., Ratnagiri, India) of the above-mentioned designs and then invest, de-wax, and acrylize in autopolymerizing resin (DPI Pvt. Ltd., Mumbai, India) [Figure 2]a and b. These patterns can also be cast in base metal alloy [Figure 3]a and b. This will save clinical time in fabricating the handle in future as it can be sterilized and reused.
The posterior lock (for maxillary tray)
The press button (Press button; Needle industries India Pvt. Ltd., Nilgiris, Tamil Nadu) functions as a posterior lock and has a male and female part [Figure 4]a and b. These buttons are commercially available.
Fabrication of maxillary tray [Figure 5] in two sections:
- Apply separating media (Cold Mold Seal, DPI Pvt. Ltd., Ratnagiri, India) to the cast and adapt a wax spacer on to it (Modelling wax; DDP Pvt. Ltd., Ratnagiri, India). Section the spacer along the midline.
- Fabricate the first half of the tray up to the midline in autopolymerizing resin (DPI Pvt. Ltd.).
- Place the female unit of the handle in the anterior aspect of this half of the tray and female button in the posterior aspect.
- Once set, apply petroleum jelly along the midline over the first half of the tray, and fabricate the second tray segment with the male unit of the handle interlocked in the female unit.
- Extend the second segment 2 mm medially over the first segment along the midline to enable proper orientation of both the segments.
- In the posterior aspect of the second segment, extend the acrylic plate of 1 × 0.9 cm medially over the first segment in which the male button is placed so that it interlocks the female button in the first segment.
Fabrication of mandibular tray [Figure 5]
The handle fabrication and the procedure for its attachment are similar to that of the maxillary tray except that there is no posterior lock.
| Clinical Procedure|| |
In order to make a definitive impression, carry out the following step-by-step procedure. For convenience, the tray segment having the male unit of the handle is called as the male segment and the segment having female unit is called as the female segment.
- Evaluate the tray for its extensions intraorally.
- Carry out sectional border molding of both the segments with low fusing impression compound (DPI Pvt. Ltd.).
- Remove the wax spacer from the female segment and place relief holes.
- Apply petroleum jelly along the midline on the male segment.
- Load the female segment with zinc oxide eugenol impression paste (DPI impression paste; DPI Pvt. Ltd.), re-assemble it with the male segment intraorally, and make the impression. While reassembling first interlock the handle and then snap the posterior lock in place.
- After the impression material is set, dissemble the tray [Figure 6] and [Figure 7] and remove it.
- Trim any excess impression material along the midline and flush it against the edge of female segment.
- Remove wax spacer and place relief holes in the male segment.
- Apply petroleum jelly on the cut surface along the midline of the female segment and place it back into mouth.
- Carry the loaded male segment to the mouth, reassemble it, and make the impression.
- Once the impression material is set, remove the tray from the mouth and reassemble it [Figure 8] and [Figure 9]. Pour it in dental stone (Dutt Stone; Dutt Industries, Mumbai, India).
| Discussion|| |
One of the requirements of the sectional tray is the ease of reassembling and disassembling the tray in the mouth; this necessitates the locking mechanism not to be complicated.  Advantage of this design is that it is easy to reassemble and dissemble in spite of having two locks in the maxillary tray unlike the tray design described by Winkler. 
It is observed that in the absence of a posterior lock the tray would separate in the posterior palatal seal region making impression difficult. The sectional stock tray described by Chikahiro  and the custom sectional tray described by Mirfazaelian  lacks such a posterior lock, so probably it would have been advantageous if considerations are given for the use of a posterior lock in the maxillary sectional tray, as in the current design.
The placement of posterior lock similar to that of anterior lock would result in the interference with the tongue movements while making impressions. In addition, the angulations of both the locks should be the same to have parallel path of placement causing it more difficult to fabricate and to reassemble. Hence, a press button type posterior lock for the maxillary tray has been advocated. A posterior lock is not necessary in the mandibular tray because of its smaller surface area. The anterior lock itself is sufficient to stabilize the two segments.
The male unit of the handle being 'I' shaped (cross section) has a definite vertical and a lateral stop. It has a defined path of which is well guided. Once the units are interlocked, the entire segment becomes stable in all directions along with the help of a posterior lock in the maxillary tray.
Robert Luebke used Lego blocks  in fabrication of mandibular stock sectional tray and stated that it is difficult to use the same in the maxillary tray. Philip Baker used locking levers  as a locking unit in mandibular sectional tray but its use in maxillary tray was not evaluated. The use of locking levers in maxillary tray is difficult as it has to be placed at the posterior aspect of the tray and this may obstruct tongue function while making the impression. Therefore, the use of Lego blocks and locking lever in the maxillary tray is questionable.
The custom sectional tray with interlocking type handle gives better stability, ease of reassembling and disassembling, and easy placement and guided orientation of the two tray segments. However, the fabrication of the handle is time consuming, as it requires to be done with precision, but this factor can be eliminated as the handle can be fabricated once in metal and then reused.
| Conclusion|| |
Making good impressions is an important step in prosthodontic management of microstomia patients. This can be accomplished by using various sectional trays. Stability of a re-assembled sectional tray is necessary and it can be achieved by using an anterior and a posterior lock. These features are present in the current design that helps to overcome difficulties while making impressions in such patients.
| References|| |
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Aquaviva S Fernandes
Department of Prosthodontics, Goa Dental College and Hospital, Goa
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]