|Year : 2020 | Volume
| Issue : 12 | Page : 1643-1647
Assessment of Marginal Opening for Different Cementation Techniques for Heat-Pressed Ceramic Veneers
WM S A L Qahtani
Department of Prosthodontics, College of Dentistry, King Khalid University, Abha, Saudia Arabia
|Date of Submission||25-Aug-2019|
|Date of Acceptance||21-Jan-2020|
|Date of Web Publication||23-Dec-2020|
Dr. WM S A L Qahtani
Department of Prosthodontics, College of Dentistry, King Khalid University, Abha
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aims: The aim of this study is to evaluate the gap distance of two cementation techniques for laminate veneers fabricated on maxillary anterior teeth using heat-pressed ceramic, finger pressure, and ultrasonic cementation techniques. Material and Methods: A total number of 42 extracted natural central incisors were prepared to receive ceramic laminate veneers, laminate veneers were constructed in the laboratory using heat-pressed ceramic according to manufacturer's instructions (IPS e.max). Ceramic veneers were divided into two groups and cemented using two different cementation techniques (Ultrasonic, finger pressure). Marginal gap distance was measured in microns at the margins using a stereomicroscope and special computer software (quantitative assessment). Results: The ultrasonic cementation technique recorded 63.3 ± 27.8 μm, which was significantly lower than the finger pressure technique (91.5 ± 21.4 μm). Conclusions: The ultrasonic cementation technique improved the gap distance at the tooth/ceramic interface when compared to the finger pressure technique using the light cure cement.
Keywords: Cementation, ultrasonic, veneers
|How to cite this article:|
L Qahtani WS. Assessment of Marginal Opening for Different Cementation Techniques for Heat-Pressed Ceramic Veneers. Niger J Clin Pract 2020;23:1643-7
| Introduction|| |
The laminate veneer is a conservative alternative to full coverage for improving the appearance of an anterior tooth treating severe discolorations, a diastema, and enamel defects. Laminate veneers have evolved over the last several decades to become one of esthetic dentistry's most popular restorations. For any cemented restoration, the weak link is at the restoration cement-tooth interface.
Moreover, the cervical enamel/luting composite interface has repeatedly been reported to be more vulnerable to microleakage than the incisal enamel/luting composite interface in vitro.
The ultrasonic cementation technique improved the gap distance at the tooth/ceramic interface compared to the finger pressure cementation technique. Ultrasonic cementation helps to achieve even thickness at cement tooth interface depending on the principle of oscillation. Heat-pressed ceramics are becoming increasingly popular in dentistry. The benefits of heat-pressed ceramics, as opposed to the more traditional method of sintering, are decreased porosity, increased flexural strength, and excellent marginal fit. It is a point of interest to investigate the effect of different cementation techniques on the marginal integrity of heat-pressed ceramic veneers.
Zaimoglu et al. in 1992 investigated the microleakage beneath porcelain laminate veneers. The restorations were located according to the preparations made below or above the cementoenamel junction of extracted maxillary incisors. They found that greater microleakage was recorded at the dentine composite resin interfaces than at the enamel/composite resin interfaces.
| Materials and Methods|| |
Forty-two freshly extracted maxillary central incisors were collected, scaled, and cleaned with pumice. The teeth were chosen to be equal in the mesiodistal width and incisocervical length of the coronal portion as much as possible measured by using a digital measuring caliber.
The teeth were stored in normal saline solution at room temperature. A specially designed circular mold of 2.5 cm diameter and 3 cm height was constructed. The mold was formed of two parts: an inner split ring and an outer assembling ring. Standardized preparations were done on the labial surface of all teeth. The reduction was performed by using a diamond depth cutter wheels. Standardized preparations were done with the depth of 0.5 mm at incisal half using laminate veneer set (LVS) #1* and 0.3 mm depth at the cervical half using LVS#2*. Special two-grit diamond stones (LVS #3 and #4*) were used to remove the excess enamel till the depth of the original grooves to uniformly reduce the labial surface. This unique LVS two-grit diamond is specifically designed for bulk reduction with coarse grit to facilitate added retention and better refraction of the light being transmitted back out through the laminate. The marginal area was prepared with fine grit that created definitive, smooth finish line to enhance the seal at the periphery. (* Komet, Gebr Brasseler GmbH and KG, Trophagener Weg 25.32657 Legmo, Postfach 160.32631 Legmo, Germany. LVS set for porcelain laminate veneers. Set 4151.) A specially designed perforated circular tray of 2.5 cm diameter and 3 cm height was constructed for impression making. After the application of separating agent, the wax pattern was done using cervical wax at the marginal areas until the finish line. Then body wax was used for the buildup of the laminate veneer wax pattern. A special silicon ring former was used and was slipped into the plastic ring base. Special investment was mixed following the manufacturer's instructions using machined vacuum mixer. The ring was then placed in a preheated burnout furnace at a temperature of 850°C for 60 min for wax elimination following the manufacturer's instructions. A special porcelain furnace was used for the ceramic pressing. (Ivoclar Vivadent, Inc. IPS e.max is a registered trademark of Ivoclar Vivadent, Inc. 627329 Rev. 0 2/2009).
The test samples were divided into equal groups of 21 specimens each according to the type of cementation technique employed. Group 1: The constructed laminate veneers were cemented by ultrasonic vibration insertion technique [Figure 1]. Group 2: The constructed laminate veneers were cemented by finger pressure insertion technique. Rely X Veneer cement (3M Center Building 275-2SE-03 St. Paul, MN 55144-1000 U.S.A. 1-800-634-2249) was used according to manufacturer's instructions. The ultrasonic unit SONICflex 2003x Airscaler was set at power 2 and was turned on each time for 5 s to minimize the heating of the cementation tip (SONICflex cem #12). The total ultrasonic seating time was 30 s applied on several points with different angulations over the surface.
The veneers were put with gentle finger pressure (gentle sliding circular motion is done until seating of the veneer is obtained) [Figure 2].
After cementation, the teeth were stored in distilled water for 24 h, then subjected to thermocycling between two water baths at (5°C—55°C) for 100 cycles (1 min in between each cycle).
The specimens were examined with a stereomicroscope (SZ-PT-Olympus, Japan) using image analysis software (Image J, I.29Z, NIH.USA), a computerized program to monitor the interfacial gap distance in microns at the enamel/ceramic interface at six different areas for each margin (cervical, incisal, and two proximal) for each sample, by examining the extent of die penetration with ×25 magnification [Figure 3].
|Figure 3: Bar graph of the mean gap distance using the ultrasonic and finger pressure cementation technique with the Relyx Veneer cement|
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Descriptive statistics were presented as means ± standard deviations (frequency distributions).
Analytical tests used included independent sample t-test for comparing two groups.
| Results|| |
The significance level of P < 0.05 was used throughout all statistical tests within this study.
The ultrasonic cementation technique recorded (63.3 ± 27.8 μm) which was significantly lower than the finger pressure technique (91.5 ± 21.4 μm). The average of regions was taken [Table 1].
|Table 1: Mean gap distance and standard deviations of veneers cemented using the ultrasonic and finger pressure cementation techniques with the Rely X Veneer cement|
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| Discussion|| |
Today, porcelain veneers are no longer in the experimental stage; they have gained respect as a durable and reliable restorative treatment method. Patients and dentists are enthusiastic about their superb esthetic properties and conservative tooth preparation. Bonding of ceramics to natural tooth substrate is reported to be stronger at the enamel layer as reported by Atsu et al. The long-term clinical performance of laminate veneers depends on a number of factors with marginal adaptation being one of the significance. It is critical to establish an acceptable marginal adaptation in laminate veneers because of the inherent limitations of composite resin luting agents, such as relatively high polymerization shrinkage.
The marginal gap between the restoration and tooth substance can influence the longevity of the restorations and leakage.
New techniques and ceramic materials have been introduced in an attempt to improve the marginal fit of the restorations. Examples of new manufacturing techniques introduced in dentistry are the commonly used pressable ceramics, which showed less vertical and horizontal marginal discrepancies than computer-aided design (CAD)/computer-aided manufacturing (CAM) technology. This also was augmented by Hashem et al. in 2018.
The polymerization shrinkage of resin-based composites under confined conditions generates stress at the tooth/restoration interface, which may lead to gap formation
The use of ultrasonic in dentistry extends over three decades. It had several applications in the field of dentistry. Previous investigators,, recommended the use of the ultrasonic packing technique to increase the procuring flow of the material, thus increasing adaptation to the cavity walls and margins and decreasing its surface and bulk porosity. The ultrasonic technique can be used with highly filled and consecutively viscous luting cement for luting of bonded restorations to improve the marginal gap and reduce polymerization shrinkage. These study results were in accordance with Escobar et al.'s in 2019 where they found that active ultrasonic application improved the bond strength and the nanoleakage. In case of using luting composites, this method has the disadvantage that such instruments must be operated without water to prevent contamination of the composite, but, at the same time, it will quickly overheat if cooling water is not passed over the stack and may produce damage for the restoration; therefore it should be operated for only a short period (10 s) and for short frequency range. The direction of oscillation is important for the flow properties of cement as stated by Walmesly and Lumely who found that the film thickness at different locations is influenced by the probe (i.e., vibratory tip) orientation of the ultrasonic device. They stated that the horizontal vibrator did not produce vertical strokes to depress the castings; however, the perpendicular vibration produced strokes that depress the castings producing a thinner film thickness for all power settings than did the horizontal vibrations (where the vibratory tip was parallel to the occlusal surface). They added that vertical vibration provided the most efficient transfer of vibration through any inlay (restoration) to the underlying luting agent, consequently leading to a change in the viscosity of the cement and allowing the restoration to seat easily. The results of the ultrasonic cementation technique recorded the least gap distance at the tooth/ceramic interface when compared to the finger pressure technique. This observation confirms previous reports regarding the effect of ultrasonic vibration on the cementation of tooth-colored inlays in accordance with Peutzfeldt. This finding could be attributed to the increase in the flow of the luting cement with an observed decrease in viscosity (thixotropy) due to the acoustic energy applied, thus, decreasing the number and size of the voids in the luting cement hence increasing the adaptation of the material. Moreover, any object, in the path of an ultrasonic beam, is subjected to a radiation force, which tends to push the luting cement in the direction of the propagation waves. This may cause a redistribution of the filler particles of the cement leading to optimum particle size distribution. These findings were also in agreement with those of Laird and Walmsley who stated that applying ultrasonic vibration for just a few seconds decrease the microporosity due to the disruption of air bubbles by the cavitational activity and acoustic microstreaming effect of ultrasonic waves, thus improving adaptation. These findings were also attributed to the increase in the flow of the viscous composite resin due to ultra-sonication leading to increased adaptability of the material, decreased air entrapment, and decreased formation of air pockets and microporosities especially at the tooth/restoration interface. This was in agreement with Benedicenti et al. The increase in the flow of the material due to ultra-sonication was attributed to the thixotropy of the resinous matrix according to Noack and Mohsen and Gilbert. This physical characteristic plays a major role in the ultimate success of the restoration and governs the ease of manipulation, placement technique and finally the capacity of the material to adhere to the tooth structure. On the contrary, Caceres et al. 2017 found that the use of ultrasonic devices did not decrease the gap formation with cementing the fiber posts.
Further studies are recommended to study the microleakage levels comparing the two-cementation techniques.
| Conclusion|| |
Within the limitations of this study, the ultrasonic cementation technique improved the gap distance at the tooth/ceramic interface when compared to the finger pressure technique using the light cure cement.
Financial support and sponsorship
Many thanks to the King Khalid University for their unlimited support and encouragements.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
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