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Routine custom trays are difficult to use to makeimpressions for patients with microstomia, scleroder-

mia, or perioral burns.1 Several types of split custom

trays have been introduced to accommodate these situ-

ations.2-6 The use of an orthodontic expansion screw

(2 guide pins and a screw) without the screw axis,

serves as a guide or key and keyway to fabricate a split

custom tray (Fig. 1). Preparation of a butt joint along

the 2 pieces of a maxillary tray can enhance its stabi-

lization during border correction and impression mak-

ing (Fig. 2). The expansion screw is placed vertically inthe handle of the custom tray to accommodate the lim-

ited space (Fig. 3). The length of the guide pins in the

expansion screw can be reduced for easier insertion and

removal if necessary.

Maxillary and mandibular trays require different

locations for the key and keyway. For the maxillary tray,

the holes must be located in the overlay piece and the

guide pins are placed in the other half for better access

(Fig. 3). For the mandibular tray, guide pins are placed

in the overlay piece and holes are located in the other

half (Fig. 4).

I express my app rec ia ti on t o M . B idgo l i , D D S, pos tgraduate st u -

den t i n p ros thodont i cs , who con t r i bu ted t o t he comple t ion o f t h i scase.

U se of orth odontic expansion screw in fabricating section custom trays

Al i M i r fazael ian, D D S, M Sca

Scho ol o f D ent i st r y, Tehran U niversi t y o f M edica l Sc ienc es, Tehran, I ran

aAssistant Professor, D epartm ent of Prostho don t ics .J Prosthe t D ent 200 0;83 :474-5 .

Fig. 1. Three-ax is expans ion sc rew af ter remo val o f sc rew.

Fig. 2. M ax i l l a r y tr ay ( under l y ing p iec e ) w i t h bu t t j o in t a longl ine o f separat ion. F i rst par t o f handl e w i th expan sion sc rewis em bedded in ac r y l i c r esin .

Fig. 3. Tw o p ieces o f max i l la ry sect iona l t ray a f ter separa t ion .

Fig. 4. M andi bu lar sec t ional t rays in pat ient s m ou th. Lengthof gu ide p ins reduced for eas ier inser t ion and removal .

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A PRI L 2 0 0 0 4 7 5

REFERENCES

1 . Laney WR. D i agnos i s and t rea tmen t i n p rosthodon t i cs. Ph i l ade lph ia : Lea

& Feb ige r ; 1983 . p . 53 -4 .

2 . M o g h a d a m B K . P r el i m i n a r y i m p r e s si o n i n p a t i e n t s w i t h m i c r o st o m i a . J

Pros the t Den t 1992 ;67 :23 -5 .

3 . A l - H a d i L A . A s im p l i f i e d t e c h n i q u e f o r p r o st h e ti c t r e at m e n t o f m i c r o st o -

m i a i n a p a t i e n t w i t h s c l e r o d e r m a : a c a se r e p o r t . Q u i n t e s se n c e I n t

1 9 9 4 ; 2 5 : 5 3 1 - 3 .

4 . Arcu r i M R, E i ke l L , Dee ts K. Max i l l a ry sec ti ona l im pression techn ique fo rm i c ros tomic pa t i en ts. Qu in tessence D en ta l Techno l 1 986 ;10 :627-9 .

5 . M cCord JF, Tyson KW, B la i r IS . A sec t i ona l com p le te den tu re fo r a pa t i en t

w i th m ic ro s tom ia . J Prosthe t Den t 1989 ;61 :645-7 .

6 . Luebke RJ. Sec t i ona l im pression t ray fo r pa t i en ts w i th cons t r i c ted o ra l

open in g . J Prosthe t Den t 198 4 ;52 :13 5-7 .

Reprint requests to:

D R A LI M IRFAZAELIAN

D EPA R T M EN T O F PR O S T H O D O N T I C S

SC HO O L O F D ENTI STRY

TEHRAN U N I V E RSI T Y O F M EDICAL SCIENCES

TEHRAN

IRAN

FA X : ( 9 8 2 1 ) 6 4 0 1 1 3 2

E-M A I L: m i r -a l i@nrcgeb .ac . i r

C o p y r i g h t 2 0 0 0 b y T h e E d i t o r i a l C o u n c i l o f The Jour na l o f P ros thet i c

D ent istry.

0 0 2 2 - 3 9 1 3 / 2 0 0 0 / $ 1 2 . 0 0 + 0 . 1 0 / 4 / 1 0 5 3 7 8

d o i : 1 0 . 1 0 6 7 / m p r . 2 0 0 0 . 1 0 5 3 7 8

In vitro, relative microleakage of five restorative systems

Grobler SR, Rossouw RJ, Van Wyk Kotze TJ. Int Dent J

1999;49:47-52.

Purpose. It has been reported that a good seal prevents microleakage, which prevents pulpal irri-

tation and recurrent dental caries. This in vitro study evaluated the relative microleakages of 5

restorative systems to cementum / dent ine.

Material and methods. Sixty-five human permanent canines were prepared class 5 cavities (10

to 15 for each group of tested materials) in the cut root apices of these teeth (below the cemen-

toenamel junction). Teeth were restored with 5 restorative systems (Dyract, Optibond MFA,

AeliteBond, All-Bond 2, and ScotchBond M P). Ro ot apices were sealed and the t eeth coated with

nail varnish, except for 1 mm surrounding t he restoration. Specimens were thermocycled (500)

in a 2%m ethylene b lue solution. Root sections, including the restorations, were dissolved in acid

and the concentration of the dye determined spectrophotometrically. Statistical analysis using a

Kruskal-Wallis multiple comparison was calculated for the 5 materials at a 5%level of significance.

Results. The sequence for the microleakage values were as follows: Dyract < OptiBond MFA