Page 19 - GP Fall 2020

monolithic samples. 30,32-34 More interesting- dent, Inc.) specimens for this group were Group LPZ: In this group, Lava Plus Zir-
ly, polished zirconia that was glazed by us- fabricated with low translucency (LT) lith- conia disks were monolithic yttrium-stabi-
ing a glaze spray showed less enamel wear ium disilicate that is provided in the form of lized zirconium oxide (Y-TZP; Lava Plus;
than air particle abraded zirconia that was pressable ingots by processing in the den- 3M ESPE), which were fabricated in the
glazed using a layering technique with glaze tal laboratory using the lost-wax technique. requested diameter (11 mm x 3mm) by the
ceramic. Staining and glazing the zirconia Specimens were prepared by contouring the manufacturer under the supervision of the
34
substructure caused more antagonistic tooth soft wax (ABF-wax; Metalor Dental, Inc.) author and then finished the same as pre-
wear than polishing. 33 into 11 mm diameter and 3 mm thickness vious groups and glazed according to the
disks according to the manufacturer’s in- manufacturer’s specifications.
However, development of low fusing por- struction. All wax specimens were attached
celain restorations with lower crystalline to wax sprues (Lincoln Dental Supply, Inc.). Ceramic discs from all groups were adjusted
fillers to glass matrix ratio, along with glaz- Investing was carried out with IPS Press in a way that simulates clinical situations.
ing and polishing of the restorations could VEST investment material (Ivoclar Viva- Disks were held in a metal block with dou-
improve their abrasiveness and affect the dent, Inc.). The reaction layers formed on ble-sided mounting square stickers (Scotch
antagonist surfaces differently. 20 the disks during the press procedure were Magic 810, 3M Co.) in a mini-lathe (Uni-
removed in an ultrasonic bath using IPS e. mat 3, Emco). A high-speed handpiece with
Studies on human beings who chewed on max Press Invex Liquid (Ivoclar Vivadent, a fine diamond bur (4380U0, Brasseler) was
different food items revealed that the ver- Inc.). Sprues were removed with fine dia- held parallel to the disk surfaces and mount-
tical force impulses evoked in the molar re- mond disks (No. 2751; Dedeco Internation- ed to the lathe feed table. A single stroke in
gion are of 20–30 N, and that the horizontal al, Inc.) in a laboratory using a micro-motor a single direction was applied to the glazed
chewing forces are measured to be approx- unit at a speed of up to 20,000 rpm (Ulti- surfaces of discs under the cooling effect of
imately 35% of the vertical ones. The slid- mate XL; NSK Nakanishi, Inc.) in order water. The lathe feed table was then turned

ing movement has been shown to be 0.8mm to prevent overheating and chipping of the 360º for the adjustment of the other halves
with a sliding speed of 40 mm/s and a com- disks. of disks. A new bur was used for each set of
plete chewing cycle frequency of 1.6 Hz. 14 six disks.
To assure surface smoothness and parallel-
A two-body wear contact of bi-directional ism prior to wear tests, all specimens were For repolishing, a slow-speed handpiece
back-and-forth sliding movements in which finished with applied force of 15 lbs. at the with a lithium disilicate polishing bur
a stylus runs against a flat surface, with no speed of 350 rpm for 2 minutes with dif- (W17DM, Brasseler), was held parallel to
lifting of the stylus, has been shown to build ferent grits of silicone carbide grinding pa- the disk surfaces and mounted to the lathe
up more homogenous forces, and avoids the per (120, 240, 320, 600 grit; Buehler) and feed table. Four strokes in a single direction
uncontrolled force impulses seen in con- Ecomet 250 (Buehler) under running water. were applied to repolish the adjusted disk
figurations that involve lifting of the speci- The specimens were then cleaned for one surfaces. A new bur was used each time.
mens. 35-39 However, the review of previous minute with a steam jet (11706; Triton SLA)
data shows a large variation in relation to and glazed according to the manufacturers’ Group E: Extracted intact human mandib-
wear test method qualification, applied specifications. ular third molars were collected from the
force, lateral movement, number and fre- oral surgery department at Tufts Universi-
quency of cycles, number of specimens, and Group EC: In IPS e.max CAD (Ivoclar ty School of Dental Medicine. The largest
selected materials and techniques. 35-49 Vivadent, Inc.) group, the LT lithium dis- teeth with flatter lingual surfaces were se-
ilicate that is provided in the form of CAD/ lected and cleaned with an ultrasonic scaler
The purpose of this in vitro study was to CAM blocks were designed and milled to (Cavitron GEN-119, Dentsply) to remove
investigate the wear of advanced ceramic rods measuring 11 mm in diameter and 17 saliva and debris, and placed in 0.05% thy-
systems against human enamel antagonists mm in length with an E4D processor (D4D). mol and distilled water at room temperature
in a newly designed wear stimulating device The rod was then cut into 11 mm x 3 mm for a period of two weeks. Enamel disks
(TA-317C Multiple Sample Vertical Friction diameter disks in their crystalline interme- were prepared (11 mm x 3 mm) from the
Wear Device) developed by the author. The diate block stage, by using the Isomet 1000 lingual surfaces of the teeth by using a slow
null hypothesis was that there are no differ- Precision Saw (Buehler). Specimens were speed hand-piece and trephine bur (No.
ences in the resulting wear of specimen or finished and glazed in a similar manner to 04-9485-01, ACE Surgical Supply, Inc.) to
antagonist materials when IPS e.max Press, those of Group EP. serve as the control group. The outermost
IPS e.max CAD, Noritake Super Porcelain surfaces of these enamel disks were then
EX-3, LAVA Plus Zirconia, or enamel disks Group SP: In this group, feldspathic por- ground with 2500 grade wet/dry silicon car-
are worn against enamel styluses (cusps). celain disks were fabricated with Noritake bide paper (Buehler) and polished (with 6
Super Porcelain EX-3 (Noritake Dental mu followed by 1 mu diamond suspension)
Materials And Methods Supply Co.) by placing the porcelain mix to obtain flat surface enamel specimens.
The study included 5 groups (n=12): IPS into a stainless steel mold (11mm x 3mm).
e.max Press (EP), IPS e.max CAD (EC), After the initial setting was achieved, disks Enamel stylus specimens were prepared by
Noritake Super Porcelain EX-3 (SP), LAVA were carefully removed from the mold and cutting the mesio-palatal cusp of the maxil-
Plus Zirconia (LPZ), and enamel (E). fired in a furnace (Programat P300/G2; Ivo- lary third molars under water with the Isom-
clar Vivadent, Inc.) and finished the same as et 1000 Precession saw (Buehler).
Specimen preparation previous groups and glazed according to the
Group EP: IPS e.max Press (Ivoclar Viva- All specimens were then embedded indi-
manufacturer’s specifications.
www.nysagd.org l Fall 2020 l GP 19