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Authors: Dr. Rathika Rai, Dr. Sonu Elsa John and Dr. K.R.Geetha

Fig.1 INTRODUCTION

Microstomia is defined as an abnormally small oral orifice.Adequate oral aperture is essential for facial expression, oral feeding and speech. Furthermore, it can be an obstacle for proper oral hygiene. Decreased oral aperture can occur , acutely caused by an infectious or odontogenic inflammatory process, but the real problem arises when it is structural or permanent, which can be due to various factors such as orofacial burns, carcinoma, .cleft lip, trauma, scleroderma, genetic disorders, surgery, head and neck radiation, reconstructive lip surgeries, connective tissue disease, fibrosis of masticatory muscles or facial burns. Hardening of the skin around the mouth causes the oral opening to become limited1.Moreover, fibrosis of the salivary glands results in dryness in the mouth.

The orbicularis oris muscle, the primary muscle of the lips, forms the sphincter around the mouth and the philtral columns The muscular layer is separated from the skin by a thin subcutaneous layer and from the mucosa below by a thin submucosal layer that contains the adnexa, sensory end organs, and lymph nodes. In acquired cases, perioral facial traumas may result in scarring and contraction caused by the involvementand infiltration of the complex perioral musculature during the healing process depending on the depth of injury2. However, in genetic disorder related cases, the etiology of the condition is variable and mostly remains uncertain.

Management of microstomia is a complex treatment modality and demands complex functional and aesthetic requirements of soft tissues of circumoral region. Treatment of the latter was based on mainly on surgical techniques, non-surgical approaches or combinationof both methods. It is important to highlight the reconstruction of the orbicular sphincter for adequate lipfunction beside lip symmetry, which is the main objective of microstomia reconstruction3.

Surgery may be considered as a treatment option when the mouth circumference length is less than 160 mm4 but inadequate rehabilitation of the surgical procedure may result in a scar.Management of patients with limited mouth opening becomes a challenge for any kind of restoration . Its compounded when requires a full mouth restoration in the form of complete denture . A wide mouth open¬ing is required for proper tray insertion and alignment which is not possible in patients with restricted mouth opening .The normal mouth opening of an individual is 35-45 mm on an average.

The placement of loaded trays is cumbersome due to the obstruction in the path of placement. Designing the bulk and height of the impression tray also becomes a tedious procedure to record the soft tissues accurately . Several modifications can be done to the conventional tray to record the soft tissues at ease .
 
Fig.2
 
Fig.3
CASE REPORT

A female patient aged 47 years , reported to the Department Of Prosthodontics, for a maxillary and mandibular complete denture . On extra oral examination , she was malnourished with dry skin . She was systemically healthy .On clinical examination , the temporomandibular joint was normal . The mouth opening was recorded as 30 x 30 mm .The subject had bleeding corners of the mouth which could be attributed to the dry skin .However intra oral examination revealed that the mucosa was not dry so possibility of any syndrome was also ruled out .A complete blood investigation was carried out to rule out any systematic disorders which could contribute to the limited mouth opening .The blood reports inferred normal values and hence long term edentulism was the suggestive etiology for the microstomia .
 
Fig.4
 
Fig.5


The treatment plan was to fabricate a complete denture with the existing mouth opening . Preliminary impression of the upper and lower arch was made by manually adapting the elastomeric impression material ( AqausilSoft Putty , Regular Set , Dentsply) , as the stock tray could not be placed in the mouth .. A preliminary impression of the maxilla and mandible was made for fabricating a special tray of both the arches . And the impression was poured using type II dental plaster(plaster of paris , dental grade). A wax spacer (Hindustan Modelling Wax, No .2 )was adapted on the upper and lower casts and a special tray was fabricated using autopolymerising acrylic resin (DPI RR- Cold Cure) .

The tray was trimmed 2 mm short of sulcus and the tray was sectioned in the center using a thin cutting disk , and a second impression was made using medium bodied elastomeric impression material( AquasilMonophase , Dentsply )and a cast was poured using dental stone (Gem Stone ). As selective pressure impression technique was to be followed , a spacer 2 mm thick was adapted and an auto polymerizing special tray was fabricated .
 
Fig.6
 
Fig.7
 
Fig.8
 
Fig.9


A line was marked in the center of the tray to create two equal halvesand were sectioned using a thin cutting disk .The maxillary halves were held together by press buttons which were adapted anteriorly and posteriorly for stability , the lower tray was similarly sectioned in the center and the two halves were stabilized posteriorly using a wooden ice cream stick and in the center with the help of die pins . Both the upper and lower trays were checked in the patient’s mouth to ensure that there is no airway obstruction after placement of the two halves .

Once the fit of the upper and lower trays were verified , border molding was done in increments using green stick compound (DPI Pinnacle Tracing Sticks ) . Both the sections were placed together in the maxilla and stabilized using the press buttons and the posterior palatal seal was recorded .The sections were then removed and loaded with light bodied elastomeric impression material (DentsplyAqausil Ultra LV Light Body ) . Isolation of the arch was ensured and both the halves were placed in the mouth and stabilized using the press buttons .After the final set of the material ,the upper tray was removed in two halves was reassembled using the press buttons.

For the lower arch , border molding was done using green stick compound(DPI Pinnacle Tracing Sticks ) owing to the reduced viscosity of the material when compared to heavy bodied putty in two halves , and later the tray was loaded with light bodied elastomeric impression material and the two halves were placed together and stabilized using thewooden ice cream stick . The tongue movements were compromised due to the superior placement of the stick.Border movements were recorded by asking the patient to pucker and swallow . After the final set of the material , the tray was removed in two halves and reassembled outside using die pins , and the cast was poured using dental stone .

Following this upper and lower denture base were fabricated .In the lower denture base , die pins were placed horizontally in the41 and 31region and occlusal rims were fabricated .Maxillomandiular relationship was recorded and sealed using the nick and notch method. The upper and lower casts were articulated and teeth arrangement was done(Acry Rock, Ruthenium ). During the try in appointment, the denture base was verified for fit and minor adjustments were done .

The upper denture was processed by the conventional pressure molding technique and the number of press buttons for retention were reduced to one as two press buttons were obstructing the patient’s airway . In the lower denture the die pin was shifted to the premolar region due to reduced vertical dimension and in anticipation of the acrylic fracture due to the reduced vertical dimension .Hence ,for aesthetic reasons the lower denture was processed using conventional pressure molding technique with a split in the premolar region . After finishing and polishing , dentures were inserted . Dentures were evaluated for aesthetics , speech and mastication .

The method of inserting and removing the denture was instructed to the patient ,post operative instructions were given . Adequate oral hygiene instructions were dictated . Subsequent recall visits were scheduled and was noted to have fully healed corners of the mouth and increase in the mouth opening .

DISCUSSION

Prosthodontic management of microstomiawhether acquired or congenital is the challenge to the finesse of the operator .Several methods have been proposed on management of microstomia and the review of literature reveals the same . McCord et aldescribeda maxillary complete denture consisting of two pieces joined by a stainless steel rod with a diameter of 1mm fitted behind the central incisors5.

Robert JLuebke described a sectional impression procedure for edentulous patient by using 2 plastic sectional impression trays assembled with Lego building blocks and autopolymerizing resin6. Naylor and Manor et al described a technique for construction of flexible prosthesis with oral augmentation exercises to increase mouth opening7 .

Whale et al introduced a collapsible mandibular swing lock complete denture with a cast chromium frame work with a lingual hinge and a conventional labial hinge8 . Suzukiyintroduced a design where the denture was fabricated in two parts to prevent denture deflection during chewing . Rigid connection was given using Co-Cr-Ti alloy9.

Al – Hadiet al described the fabrication of three piece sectional maxillary denture and a one piece mandibular complete denture10 . Watanabe et al described a prosthesis which presented a cast iron – platinum magnetic attachment system applied to a sectional collapsed denture11 .

Yeniseyet al stated that,the cast hinge design reduced the overall costs and simplified the laboratory technique. This technique has proven to be simple, inexpensive and applicable to selected microstomic patients 12. Curaet al described an other technique used to fabricate mandibular and maxillary sectional trays and a folding maxillary complete denture for a patient with limited oral opening caused by systemic sclerosis. For the foldable denture, the anterior teeth had to be arranged on a second base and the hinge fitted at a location higher than the denture base13.

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 13. The advantage of the split denture in the maxilla is the presence of the anterior and posterior lock while recording the impression that does not break the seal at the posterior palatal seal region . Since the posterior lock should not interfere with the tongue movements , and also since the path of placement of the anterior and posterior lock should be uniform for convenient impression recording, a press button type of anterior and posterior lock was used. While processing the denture , the posterior press button was removed as the patients airway was being obstructed. Nevertheless the retention of the denture was satisfactory .

A press button was not essential in the lower denture due to the smaller surface area and reduced vertical dimension , in this case , and anterior lock was used with the help of readily available die pins . The die pin was placed in one half of the mandibular tray and the sleeve was placed in the second half of the tray . And to stabilize the tray during secondary impression an ice cream stick was used to counter act the forces exerted by the tongue .However during processing of the lower denture , the die pin was shifted to the premolar region as the denture split was visible when the patient smiles .

Precision attachment could have also been a treatment modality for the patient , however , owing to the reduced vertical dimension , the option was ruled out. Flexible denture were not advocated as the circumoral aperture of the patient was compromised 14. Hence a method had to be devised to accommodate for the reduced vertical dimension and the reduced circumoral aperture of the patient . A split upper and lower denture was the treatment of choice as the vertical and horizontal aperture was compromised .thetreatment results were satisfactory for the patient in spite of the upper and lower split dentures .

SUMMARY AND CONCLUSION

Treatment of limited mouth opening is a challenge , however , with proper handling and application of the readily available dental material leads to success of the prosthesis . Hence proper knowledge of the oral anatomy and characteristics of the dental materials help us provide a successful prosthesis to the patient thereby re - establishing the function and aesthetic needs .

REFERENCES
 
  1. Baker PS, Brandt RL, Boyajian G. Impression procedure for patients with severely limited mouth opening. The Journal of Prosthetic Dentistry. 2000;84(2):241-4.
  2. 2. Wust , kylie joie Journal of burn care & research . 27(1):86-92, January /February 2006 .
  3. Prithviraj D, Ramaswamy S, Romesh S. Prosthetic rehabili¬tation of patients with microstomia. Indian Journal of Dental Research. 2009;20(4):483.
  4. SmithaRavindran,* Vibha Shetty,†VeenaSaraf,‡ SapnaNarang . An improvised sectional custom tray technique for patients with microstomia . Journal of Oral Health Research, Volume 3, Issue 3, July 2012
  5. McCord JF, Tyson KW, Blair IS. A sectional complete denture for a patient with microstomia. J Prosthet Dent 1989;61:645-7.
  6. Luebke RJ. Sectional impression tray for patients with constricted oral opening. J Prosthet Dent 1984;52:135-7.
  7. Naylor WP, Manor RC. Fabrication of a flexible prosthesis for theedentulous scleroderma patient with microstomia. J Prosthet Dent 1983;50:536-8
  8. Wahle JJ, Gardner LK, Fiebiger M. The mandibular swing-lock complete denture for patients with microstomia. J Prosthet Dent 1992;68:523-7.
  9. Suzuki Y, Abe M, Hosoi T, Kurtz KS. Sectional collapsed denture for a partially edentulous patient with microstomia: A clinical report. J Prosthet dent 2000;84:256-9.
  10. Al-Hadi LA, Abbas H. Treatment of an edentulous patient with surgically induced microstomia: A clinical report. J Prosthet Dent 2002:87:423-6.

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