The advent of Sandwich dentures was a breakthrough in denture technology, solving a number of problems that are relevant to conventional removable products.

The presence of a large number of advantages makes the "Sandwich" an interesting solution, which is worth familiarizing yourself with in more detail.

History of creation

Sandwich prostheses were developed in Russia by a group of dental specialists at the Persona-Life clinic based on advanced modern technical solutions.

The name was obtained based on the features that combine several materials with different physical properties. This allows you to solve a wide range of problems that are typical for prostheses of the traditional covering design.

Such a prosthesis does not require the use of a fixing paste and provides the best fit to the mucosa.

Design features

"Sandwich" is a dental invention, devoid of the disadvantages of conventional overdentures. Thanks to the frame made of high-strength materials, it is mounted on remaining teeth and leaves hard sky free while providing firmness and a snug fit.

The latter is achieved through the use of a substrate made of soft hypoallergenic material, which is able to change properties in accordance with changes occurring in the oral cavity.

A distinctive feature of the prosthesis is the presence hard and strong fasteners providing engagement for the remaining teeth. This design is more reliable than traditional clasp and allows you to fasten the product well without the use of pastes.

In addition, the high density of fasteners allows for effective fixation of the whole structure during the day, and also greatly simplifies the care procedures. Unlike conventional ones, the Sandwich prosthesis is not so demanding on oral hygiene.

This type is optimal in terms of habituation and does not cause gag reflexes when used. This is achieved both due to the materials used and due to the lack of a covering part, since it is on the hard palate that most of the receptors that stimulate the gag reflex when they overlap are located.

Indications

Indications for use are as follows:

1. loss a large number teeth;
2. difficulties with the use of clasp prostheses (including gag reflex);
3. the possibility of using prostheses for bruxism, epilepsy and other diseases in which the wearing of traditional designs is contraindicated.

Contraindications

The only contraindication to use is only individual intolerance and allergic reactions to the materials from which the prosthesis is made.

Such cases have not yet been identified due to the neutrality of the plastic fractions used.

Advantages

The design has a number of advantages. These include:

1. No need in turning supporting teeth.
2. Security tight fixation in the patient's oral cavity, due to the characteristics of the device. At the same time, the prosthesis does not use additional fixing elements that are visible to prying eyes. There is also no need to use adhesives.
3. High speed manufacturing (on average, two visits to the dental clinic are enough to create).
4. No need to manufacture a new model due to changes occurring in the oral cavity. The prosthesis "Sandwich" is easy corrected, and its repair is very simple and efficient.

   In addition, the presence of soft connections with the mucosa allows you to adapt to the ongoing changes without losing a secure fit.

5. Long term service of at least 10 years.
6. High level comfort when wearing. Due to the fact that the prosthesis does not have a palate cover, it does not affect diction and does not change the taste perception when eating. In addition, the prosthesis does not require removal during sleep, and removal can only be performed for hygiene procedures.
7. High elasticity at the level of nylon prostheses.

Along with the above, the Sandwich denture has another significant advantage - under it no food leftovers. This is achieved due to the presence of additional soft covering elements covering the mucosa from the sides.

This effect is ensured by a tight fit and the use of elastic compounds at the points of contact with the mucosa, which create good adhesion and prevent contamination of the cavity under the prosthesis.

Flaws

Against the background of a large number of advantages, the number of disadvantages is much less. These include just a few factors:

1. the prosthesis cannot be used if there are diseases of the oral cavity;
2. it is necessary to have multiple own teeth or it must be possible to install implants, since support is required for fixation in the oral cavity.
3. has sufficient rigidity only at a high fixation level.

Installation

The manufacturing and installation technology is as simple as possible for the patient. Initially, the doctor examines the oral cavity, treats the remaining teeth, which should perform a supporting function, and makes an impression. Already to the second a visit to a specialist, the prosthesis is ready.

Of course, the installation in two visits provides absence complex operations associated with the treatment of existing teeth. Otherwise, first of all, a panoramic x-ray of the jaws is taken, after which the doctor assesses the condition of the teeth and carries out the necessary treatment.

Also, in the presence of diseases of the oral cavity, a specialist can prescribe a treatment course of drugs designed to strengthen the mucous membrane and prepare it for the installation of a prosthesis.

Despite the apparent simplicity, the installation of the prosthesis has a number of features that you should be aware of. In the absence of one or more teeth, the doctor considers the possibility of installing implants, which, after fixing the crown, will begin to perform load-bearing functions.

There are situations when instead of a complete bearing tooth (one or all) there are only roots. In this case, the doctor performs them training, depulping (if necessary) and installs the fixture on which the crown is mounted.

Thus passes recovery a tooth that can already play the role of a carrier during the installation of the prosthesis.

In some cases, such a procedure has to be performed on most bearing teeth, which complicates the preparatory work for installation and requires additional dental operations.

Life time

The “Sandwich” prosthesis has high mechanical strength, and the high-quality Italian-made materials underlying it do not change their properties for a long time.

This combination of characteristics allows specialists to establish a warranty period for this type of structure in 10 years from the moment of manufacture.

In practice, the service life can significantly exceed the declared one, since the design of the prosthesis does not have a large number of elements that can break during use.

I must say that the service life also directly depends on the quality of the preparatory work and the treatment of teeth, which play the role of carriers. If these measures are carried out with a high level of quality, the overall service life increases significantly.

Care

The difference is absence needs for regular care. Due to the elastic design and reliable fixation, the prosthesis does not need to be removed at night, and if necessary, it enough to rinse under running water.

Hygiene procedures also include the use of tablets with protective ingredients for construction.

Price

The cost of the denture itself is on average 45 thousand rubles. However, this price is not final due to the fact that its installation can be carried out exclusively on healthy teeth.

This means that the cost of the installation will include the price for the treatment of abutment teeth, the creation of a panoramic image of the oral cavity and other preparatory operations. The amount may increase by approx. up to 60 thousand if there is no need for implants.

Reviews

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2 Comments

• Alevtina

  July 28, 2016 at 13:05

  I am a pensioner, I lived a hard life, in my youth I did not properly take care of my teeth. Plus, not the best genetics did their job. I was retired with a few teeth. Thanks to my children for not leaving me with this problem. Dental prosthesis "Sandwich" has become a real find for me. Already at the second appointment, my prosthesis was ready, and the doctor expertly installed it. The design is perfectly fixed, I quickly got used to it. And most importantly, now caring for my “new” teeth does not require much time and effort. I recommend to everyone!

Direct restorations using the posterior sandwich technique are an aesthetically effective and cost-effective method of restoring hard tissue defects. But in the vast majority of cases, composite materials are used.

L. A. Lobovkina

Candidate of Medical Sciences, Doctor of the Highest Category, Head of the Treatment and Prevention Department of Branch No. 6 of the FGKU “GVKG im. Burdenko" Ministry of Defense of the Russian Federation

A. M. Romanov

Candidate of Medical Sciences, Chief Physician of the Implamed Clinic (Moscow)

Composites pros and cons

Currently, in most cases, composite materials are used for direct restoration of teeth. In cases of large restorations, the adhesion of the composite to the tooth enamel helps to reinforce the structure of the tooth, unlike metal restorations, which do not have these advantages. However, along with the advantages, they have a number of disadvantages: polymerization shrinkage and deformation of large-volume fillings over time, insufficient biocompatibility with hard tooth tissues, lack of a cariesstatic effect, and high cost. In addition, taking into account the peculiarities of the anatomical structure of dentin and its insufficient mineralization, composites are not recommended for use in children and adolescents (under 14 years of age).

SIC - will it replace?

Given the above, more attention should be paid to glass ionomer cements (GIC), which have a physical and chemical affinity for hard tooth tissues. Due to its diffusion-based adhesion to both healthy and partially demineralized dentine, glass ionomer cement is an ideal material for sealing a cavity, preventing the access of nutrients to bacteria and reducing any colonies remaining in the cavity to a latent state. It has also been proven that fluorine and other apatite-forming ions can penetrate carious dentin to a considerable depth, thus remineralizing it.

Given the peculiarities of the anatomical structure of dentin and its insufficient mineralization, composites are not recommended for use in children and adolescents (under 14 years of age).

How to restore a large cavity?

In the practice of a dentist, significant difficulties often arise when restoring teeth with large carious cavities that spread under the gums, as well as when restoring hard tissues due to defects in the neck or root of the tooth. Since composites are hydrophobic materials (i.e. afraid of the presence of moisture), it is impossible to achieve good adhesion to the hard tissues of the tooth in the above cases.

Therefore, in some cases it is more expedient to use the sandwich technique, which consists in the use of GRC in combination with composite materials. In addition, in patients with a "problem" oral cavity (having a low level of hygiene, a high rate of KPU and a high incidence of "recurrent" caries), they can be used independently.

Disadvantages of JIC

It is worth noting that, along with the positive characteristics, GICs have a significant drawback - high opacity, which does not allow obtaining highly aesthetic restorations using only these materials.

In this regard, companies producing dental materials are looking for ways to improve the GRC, including increasing their aesthetics.

The Rationality of the Sandwich Technique

In some cases, it is more expedient to use the sandwich technique, which consists in the use of GRC in combination with composite materials.

The use of such translucent reactive glass provides the material with better aesthetics than its counterparts by reducing opacity and increasing transparency. Therefore, with very similar physical and manipulation characteristics of modern condensable glass ionomers, the choice of material for restoration should be carried out taking into account its aesthetics.

In addition, another advantage of "Ionophil Molyar" is the convenience of its introduction and ease of adaptation to the bottom and walls of the cavity. It also has a low cost. So, for one restoration (depending on the size of the cavity to be filled) the material costs an average of 20-40 rubles, which makes this cement quite affordable even for budgetary medical institutions.

It has also been proven that fluorine and other apatite-forming ions can penetrate carious dentin to a considerable depth, thus remineralizing it.

Sandwich technique on the posterior tooth [Clinical Case Study]

Patient T., 24 years old, came to the dental clinic with complaints of short-term pain from temperature stimuli in the region of the 4.7 tooth (Fig. 1). An objective examination of tooth 4.7 revealed a restoration that did not meet clinical requirements. Given the patient's low level of caries resistance of hard tissues of the teeth, as well as a large cavity, the sandwich technique was chosen for treatment.

Rice. 1. Tooth 4.7: initial clinical situation.

Conduction anesthesia UbistesiniForte 1.5 ml was performed, the tooth surfaces were cleaned from the pellicle with Clint paste (VOCO), the color of the future restoration was determined. A rubber dam was placed, the failed restoration was removed and a cavity was formed. After drug treatment of the cavity with a 2% solution of chlorhexidine, a base pad was applied from the SIC "Ionophil Molyar" (Fig. 2).

Rice. 2. A gasket from the SRC "Ionophil Molyar" was applied.

Next, the cavity was adhesively prepared and restored with the Grandio nanohybrid composite (VOCO), which has reduced polymerization shrinkage, improved physical and mechanical characteristics, and the highest color stability. Then the rubber dam was removed and the restoration was finished (Fig. 3).

Rice. 3. Tooth 4.7: final view after restoration.

Double-curing glass ionomer cement "Ionolux" (VOCO, Germany), which appeared relatively recently on the dental market, has already managed to win the love of many dentists. Ionolux combines glass ionomer and composite parts, which determine its excellent properties.

So, due to the composite component, its aesthetic qualities have improved, it has become possible to immediately finish processing immediately after polymerization, the formation of a chemical bond with composites and very low solubility in water have been noted.

Unlike analogues, when working with "Ionolux" there is no need for adhesive preparation of hard tissues of the tooth (for example, there is no stage of priming of hard tissues), since it is a self-adhesive cement. It is well known that the more curing mechanisms a GIC has, the less it releases fluoride ions into the surrounding tissues. However, in terms of the release of fluorine ions, "Ionolux" is not inferior to classical GRC.

First Molar Sandwich Technique Example [Clinical Case Study]

Patient L., 23 years old, came to the dental clinic with complaints of spontaneous night pains, aggravated by the action of temperature stimuli in the area of ​​the 3.6 tooth. An objective examination of tooth 3.6 revealed a carious cavity filled with food debris and softened dentin. When probing - a sharp pain at one point. Initially, endodontic treatment was performed (Fig. 4).

Rice. 4. Tooth 3.6 after endodontic treatment.

Considering the presence of a large cavity in the patient, the sandwich technique was chosen for treatment (Fig. 5). Next, the adhesive preparation of the cavity and its restoration with the Grandio nanohybrid composite were carried out. After removing the rubber dam, macro- and micro-contouring of the restoration was performed.

Rice. 5. A gasket from the SRC "Ionolux" was applied.

For this purpose, low and ultra-low abrasion diamond burs (SSWhite ) were used, as well as Dimanto universal polishing heads (VOCO ) with air-water spray without polishing paste (Fig. 6). The final view of the restoration of tooth 3.6 is shown in Figure 7.

Rice. 6. Tooth 3.6: polishing step with the Dimanto polishing head.

Rice. 7. Tooth 3.6: final view after restoration.

Using JIC [Conclusions]

Along with the positive characteristics of the GRC, they have a significant drawback - the high opacity of the material, which affects the final result of the restoration.

Thus, the restoration of defects in the region of the posterior group of teeth with the help of a composite is a very popular method of caries treatment. However, one should not forget that in a number of clinical situations, the sandwich technique is more preferable. In addition, the sandwich technique used in these clinical cases provides not only a therapeutic effect, but also reduces the cost of restoration due to less use of a more expensive composite material, which is especially important in an economic crisis.

Sandwich Technique A Cheaper And Faster Way To Restoration Posterior Teeth In The Conditions Of The Economic Crisis updated: December 30, 2016 by: Alexey Vasilevsky

"Sandwich technique" is often used in modern
restorative dentistry and is
using cements in combination with
composite materials for restoration
decayed tooth and
replacement of tooth dentin. Layering
the above materials resembles a sandwich
(English - sandwich).

The "sandwich technique" method is used:
■ In patients with poor hygiene.
■ In patients with increased caries susceptibility.
■ When restoring significant carious cavities.
■ When restoring cavities in pulpless teeth in combination with
composite material.
■ When filling defects with non-carious lesions of hard tissues in
combined with composites.
■ When filling defects in the cervical region and in the region of the root of the tooth in
combinations with composite material.
■ With a "combined" tunnel (approximal chewing cavity of class I-II, with
preserved marginal ridge).
■ When restoring a class II cavity prepared according to the
"vertical tunnel".
■ When filling, when it is impossible to achieve absolute dryness
carious cavity.

Closed "sandwich"
GIC or compomer fills the cavity up to the dentin-enamel border,
top is covered with composite material. Closed
"sandwich technique" is used in cavities of I, II, III, IV, V classes according to
Black.

Open "sandwich"
The method consists in using glass ionomer cement in
areas in contact with the gums, without overlap in this area
composite material. Open "sandwich technique" can
be used for filling cavities II, III, V classes according to
Black.

With the "sandwich technique":
In the cavities of class I according to Black, the GIC should
close the bottom of the carious cavity and
reach the enamel-dentine border.

In the cavities of class II according to Black, it is necessary to form
gingival wall of proximal cavities
so that the JIC does not reach the contact point.
The composite material must be completely
overlap GIC on the chewing surface and
partially/completely on the proximal.

■ In Class V cavities according to Black in the presence of carious
cavity located under the gum, the SIC should
line the bottom of the carious cavity and restore
defect up to the gingival margin (gingival margin 2 mm).
■ In combined cavities - CRC or compomer

borders.
■ In the vertical tunnel technique - material
fills the tunnel and cavity up to enamel-dentine
borders.

Material requirements
GRC and compomers used in the "sandwich technique" must
have:
- compressive strength to withstand occlusal
load;
- tensile strength (resistance of composite
shrinkage);
- sufficient working time, but fast hardening;
- low sensitivity to moisture;
- radiopacity;
- chemical and mechanical adhesion to the composite;
- elasticity;
- good aesthetics (sufficient number of colors).

Methodology for using hybrid JRC
Vitremer (ZM ESPE) in the "sandwich technique":

1. The tooth is cleaned with a paste. The color of the tooth and future is determined
restoration. The cavity is prepared with a maximum
preservation of enamel and dentin. Dentin color is determined
according to the available color. To isolate from moisture
cofferdam, cotton rollers are used. If it is needed,
matrix is ​​set.
2. Dentin is dried with an indirect jet of air or excess
moisture is removed with a foam ball or applicator.
Dentin should remain moist (shiny).
3. Rubbing the primer for 30 seconds, drying,
light polymerization - 20 s.
4. Material preparation. Shake the powder bottle
before mixing. Depending on the size of the cavity
use an equal number of spoons of powder and drops
liquids. The orange capsule is filled with material.
5. GIC is introduced into the prepared cavity.

6. To condense the material in the cavity, use a wrung out
cotton ball moistened with distilled water. Not
recommended for compacting material
alcohol, mixing liquid, primer.
7. Traditional GRC chemical curing adopted
use as follows in "sandwich technique":
- 1 visit: filling of the entire cavity of the JIC;
- 2nd visit: removal of the top layer of GIC (thickness 2-3 mm) and
covering with composite material.
8. When used in the Vitremer "sandwich technique" and the restoration
cavities can be completed in 1 visit.

9. After self-curing (4-6 min) or light curing
material, it is necessary to remove excess cement from the tooth enamel.
10. The cavity is washed and dried, on enamel and GIC for 15 s
etching gel is applied, washed off for 20-25 s.
11. An adhesive system (e.g. Adper Single Bond) is applied to
dried surfaces of GRC and enamel. After applying the second
the bond layer is dried for 5 s and polymerized with light 10
With.
12. Introduction of composite material.
13. Stages of final processing of the restoration (polishing,
grinding).

O. E. Khidirbegishvili,

G. B. Makhviladze

Georgia, Tbilisi

In the early 1970s, Alan Wilson developed a new glass ionomer cement (GIC) based on the well-known silicate cement. The early GICs were difficult to work with and were very sensitive to water absorption and dehydration. The material gained true recognition only in 1984, when it began to be supplied to the market in capsules (Ketac Aplicap system, ESPE). It took some time before this material was combined with a stronger composite. With the use of the so-called "sandwich method", such negative qualities of the composite as compression, leakage and secondary caries were eliminated. This method was first described by W. McLean in 1977.

However, the traditional sandwich method had many disadvantages. The total duration of such restoration significantly exceeded the time spent on amalgam restoration. The full cure time of GIC (24 hours) is one of the main reasons why clinicians have abandoned this method. Another significant disadvantage was the etching of incompletely cured GIC. Intensive drying led to the destruction of the cement. In addition, the binders were water-repellent (hydrophobic), which did not allow a strong bond to be obtained. Most often, problems arose at the contact points, and concerned the occlusal wear of the composite and the dissolution of the GIC at the junction with the composite. The latter was due to long-term etching, washing, and especially drying of the GRC before applying the composite. Therefore, the sandwich method had to be modified.

After the preparation of the cavity, the dentin was first cleaned and the enamel was etched, and then the GIC was applied. The cement etching procedure could be omitted, and the bonding agent could be immediately applied to the GRC and the etched enamel. Then, without waiting for the cement to harden, the composite was placed immediately after the application of the binder. The advantage of this modified sandwich method is that it saves time and that the not fully cured cement can compensate for polymerization shrinkage of the composite. However, the greatest advantage is that the still soft GIC does not undergo washing and drying, which provides the best conditions for its curing and the disappearance of the cement at the composite-GIC interface.

The Modified Sandwich Method is a clear advancement in terms of improved restoration quality and time savings. However, this method also has significant drawbacks. First of all, this is due to the fact that the GIC layer is under the composite and has no connection with the environment, (closed sandwich). As is known, GIC has an anti-caries and mineralizing effect, due to a rather extensive flow of fluorine ions that occurs for a long time. However, the GIC, which is under the composite, will not fully show its preventive properties associated with the release of fluorine, since this requires the replenishment of fluoride ions when using fluorine-containing drugs. In addition, the absorption of water by the GIC leads to swelling, which compensates for the compression of the material. The fulfillment of these important conditions, in fact, was hindered by the layer of the composite, which completely covered the GIC.

Later, a method was proposed open sandwich- GIC overlaps any wall of the carious cavity, contacting after the composite is applied to it, with the environment of the oral cavity. The open sandwich method is more reliable. But, unfortunately, this method also has disadvantages. In case of poor oral hygiene (i.e. low pH), some of the GIC may disappear within a few years due to its dissolution. This is especially facilitated by the proximity of the gingival papilla and difficult access to the proximal surfaces for complete hygienic cleaning.

These cements contain 12% to 18% water. In clinical settings, water may be absorbed from dentin or saliva. The absorption of water leads to swelling, which can compensate for the shrinkage of the material. When cured, when GRC cannot absorb water, they shrink by 3-4%. The thermal expansion coefficient of CIC is approximately the same as that of enamel and dentine, hence these cements have a good thermal insulation value. In terms of bending strength and wear resistance, GRC is inferior to composites. Despite the fact that GICs have high biocompatibility, they still have certain disadvantages, such as the degree of acidity (pH), emission of small amounts of aluminum, filling maturation time (24 hours), surface roughness, discoloration, etc.

One of the most important advantages of GRC is that they release fluoride compounds for a long time. In addition to fluorides, other minerals are released, such as silicates and calcium ions, which also participate in the mineralization process. After maturation, glass ionomer cements can re-absorb fluorides and then slowly release them. This can happen, for example, when using fluoride-containing toothpastes or lozenges. In this way, the GRCs act as a reservoir of fluorides. It is this factor that can explain their bacteriostatic and mineralizing effect, as a result of which there is no recurrence of caries. It should be noted that GIC can enter into a chemical bond with the hard tissues of the tooth due to the formation of ionic and covalent bonds between the carboxylate groups of polyacrylic acid with hydroxyapatite. The connection of dentin with collagen has not yet been proven. Noteworthy are such positive properties of JIC as good marginal fit and minimal shrinkage.

GIC consists of two components - powder and liquid. The powder consists of calcium-aluminum-silicate glass with inclusions of droplets saturated with calcium fluoride. The liquid consists of distilled water or one of the varieties of polycarboxylic acid, which contains about 5% tartaric acid. After mixing powder and liquid in the first stage, a carboxylate gel is formed, which is sensitive to moisture and drying. In the case of the initial ingress of moisture, the binding time increases, the strength and hardness of the GIC decreases. Therefore, protection by means of varnishes or matrices is necessary. If the GIC is allowed to dry out at this stage, it becomes matte-opaque, cracks, and does not fully bond. However, after a few hours, when aluminum ions penetrate the matrix, forming a water-soluble calcium-aluminum-carboxylate gel, further penetration of water contributes to the final stabilization of the cement. All these factors must be taken into account by the clinician when working with SIC.

Attempts have been made to increase the strength and wear resistance of the material by adding metals such as silver and amalgam. However, this had the opposite effect. The only advantage of such GRCs is their high susceptibility to X-rays. Other developments include plastic-reinforced GRCs (plastic-modified GRCs) and "compomers". The exact name of the latter group is "polyacid-modified plastics". The name indicates that, in fact, these are composite materials to which they tried to give the properties of GRC. However, these new materials did not justify our hopes. None of these materials could bond directly to the tooth structure, meaning that a bonding system was needed. In addition, compomers only cure when exposed to light. The reaction mechanism is similar to that for composites: there is practically no acid-base reaction. Based on this, compomers are stronger than GIC, but weaker than composites. It is questionable whether this level of fluoride release is sufficient to protect dental tissues, since the amount of fluoride emission and absorption is determined by the acid-base reaction. It should be noted that light-cured GICs are more convenient to use, but have unpleasant side effects. These materials, due to water absorption, expand significantly (up to 5%), and the polymerization shrinkage is 7%. In addition, light-curing GICs have an insufficient depth of cure for layers with a thickness of more than 2 mm.

Recently, plastic-modified GICs have appeared. These materials are chemically cured and do not require exposure to light. The advantage of this combination is that the glass ionomer component (acid-base), in contrast to the light-cured version, acquires the property to cure properly. The positive qualities of such cements include high strength, low solubility and very high bonding strength. This material is especially suitable for fixing prostheses with very weak retention. The disadvantage of this cement is the presence of HEMA material in its composition. Hence, there is a very high probability of swelling as a result of water absorption. Based on the foregoing, it can be concluded that far from all innovations are achievements and that GRC reinforced with plastic are acquiring more and more properties of composites, and composites - more and more properties of GRC.

In the course of 20 years of use, glass ionomer has gained wide recognition as a filling material. Despite the fact that during this time we have not been able to completely eliminate its shortcomings and obtain a perfect filling material, JIC can rightly be attributed to one of the first "biomimetic" filling materials in the history of dentistry. It owes this, first of all, to such phenomenal properties as the release of fluorides, remineralization, bacteriostatic effect and a complete chemical connection with the tissues of the tooth. None of the modern filling materials can "boast" of these qualities. However, new ways must be found to overcome the significant shortcomings of this material and to use its unique capabilities more rationally. Therefore, I want to offer my developments of sandwich technology, which differ from those previously proposed.

First of all, it seems to me that the opinion of the authors, who consider the sandwich technique as one of the options for basic linings, seems wrong. The sandwich technique usually refers to the combination of two permanent filling materials. It is well known that for linings, special gasketing GICs are used, and for sandwich technology, restorative GICs are used for the restoration of tooth crowns.

Should in this case be called a base lining a permanent filling material that fills the cavity to the enamel-dentin border, and its amount is greater than or equal to the amount of the composite? It is important to note that the sandwich technique is not used to protect tooth tissues from the toxic effects of the composite (separating function), but, on the contrary, as a means of bonding the composite with tooth tissues. The sandwich technique can be considered as an alternative to the adhesive technique for non-carious lesions of the hard tissues of the tooth, when the enamel and dentin are pathologically changed, and the adhesive systems, designed for the normal structure of the tooth tissues, do not provide a sufficiently strong adhesion of the filling, and, therefore, the GIC layer under a composite filling cannot be considered a gasket. Therefore, in this case, the definition will be more correct - a glass ionomer filling covered with a composite.

The main purpose of using GIC in sandwich technique is its preventive effect, mineralizing and bacteriostatic effect, reliable chemical bond with dentin, especially in restorations experiencing increased occlusal stress. The main purpose of using a composite in sandwich technology is to prevent such disadvantages of GIC as low strength, wear resistance and discoloration. The sandwich technique will be necessary until clinicians have the perfect filling material in their arsenal. Today, we are forced to combine JIC and composite, which successfully complement each other.

The main achievement of sandwich technology is the method open And closed sandwich. At the beginning of the article, the shortcomings of both of these methods were noted. To somehow compensate for these shortcomings, I want to propose a method half-open sandwich(Fig. 1). The essence of the method lies in the fact that the JIC communicates with the oral cavity using a small hole made in the center of the composite. Through this hole, both the release of fluorine ions and its subsequent accumulation occur when using fluorine-containing pastes and lozenges, which makes it possible to rationally use the preventive properties of the GIC. The main occlusal load is assumed by the composite, and the erasure of the GIC in this case is minimal. It must be taken into account that the chewing surface of the tooth is the most accessible and cleanable from a hygienic point of view, which to some extent prevents the dissolution of the GIC.

However, there are situations in the clinic when a different approach is needed. For example, if as a result of the preparation of carious lesions located on the chewing and vestibular surfaces of the molar, the prepared cavities communicate with each other, in this situation the chewing surface is covered with a composite to the enamel-dentin junction, and the rest of the cavity is filled with CIC, which communicates with the environment of the oral cavity. In this case, we can talk about combined sandwich method.

Fig.1. Various options for sandwich technology

The use of sandwich technology is possible:

1. With extensive loss of dental tissues with a preserved enamel margin.
2. With large cavities extending to the root cementum.
3. When replacing amalgam fillings with insufficient retaining cavity configuration.
4. When filling non-carious defects and cavities with pronounced mineralization.

This technique is especially necessary when the vault of the pulp chamber (dentinal bridge) is a thin and elastic septum, sometimes with signs of demineralization. In the pulp, as a rule, there are manifestations of focal inflammation, and the consequences of polymerization shrinkage of the filling material in such a situation are especially detrimental to it.

In this situation, it is difficult to guarantee the stabilization of the process, because The use of calcium hydroxide as a gasket is questionable. It has been scientifically proven that calcium hydroxide is a strong base and its use can lead to pulp necrosis, and there are no other medical pads that could cause reliable mineralization of tooth tissues. Therefore, if the clinician seeks to avoid depulpation of the tooth, the sandwich method should be performed. I want to propose a technique that is somewhat different from the above and it is advisable to call it late sandwich. At the first stages of this method, if possible, we remove decayed tissues and cover the entire cavity of the GIC for six months. With a favorable course of the process, the tooth tissues undergo mineralization due to the release of CIC fluoride compounds. Diffusion of fluoride in tooth tissues causes not only their mineralization, but also reduces the permeability of dentin, stops or slows down residual caries, and also worsens the living conditions of microorganisms.

Unlike the method closed sandwich, the absence of a composite layer promotes the absorption of water by the GRC, which leads to swelling, which compensates for the compression of the material. This is very important, since polymerization shrinkage of the material can adversely affect the condition of the dental pulp. It should also be noted that some JICs, such as 3M TM ESPE TM Ketac MoLar are capable of not only releasing fluorine ions, but also absorbing them from toothpastes, chewing gums, etc. with their subsequent release during the period of saliva pH decrease.

After this period, with a favorable course of the process, we partially remove the GRC layer and cover the remaining cavity with a more durable composite. In this case, the method late sandwich can be considered both preventive and diagnostic, allowing to determine the possibility of preserving the dental pulp.

The industry, based on the latest scientific achievements, will constantly offer more and more new dental materials, and only a few years after their application it will become clear how satisfactory they are. Traditional glass ionomer cements have not yet had their last word. Perhaps in the near future universal glass ionomer cements or composites will appear, as a result of which there will be no need to use a sandwich technique.

The material is taken from the author's monograph "Modern cariesology".

Restoration of teeth with aesthetic disorders - loss of color, changes in shape, destruction or poor-quality restorations - is one of the most popular routine procedures in practical dentistry. The ideal choice in such cases today is indirect restoration of teeth with ceramic veneers. However, ceramic false veneers may vary in color depending on the color of the prepared abutment teeth. Minimal preparation combined with opaque covering of the abutments allows the natural shade of heavily stained teeth to be recreated to create the natural color depth of porcelain veneers.

The clinical success of minimally invasive porcelain veneer preparations depends on the high precision of the impression material, the impression technique and the skill of the dental technician. Materials based on polyvinylsiloxanes (PVA) have demonstrated the ability to reproduce the smallest details in the impression of complex restorations. The impression technique also plays an important role in aesthetic restoration. For the manufacture of ceramic veneers, a one-stage two-layer impression technique is used using polyvinylsiloxane materials in combination with “double thread” gum retraction.

This clinical case describes an example of aesthetic restoration of anterior teeth using ceramic veneers with a preliminary one-stage two-layer impression.

Clinical case

A 22-year-old patient with satisfactory oral hygiene presented with a discolored central incisor 21 and a color defect in the composite restoration on the adjacent central incisor 11 (Fig. 1). The patient needed to restore aesthetics in the anterior region and close the small diastema between the anterior incisors. To restore the shape and color of the teeth, as well as to create a highly aesthetic appearance, the patient was offered the manufacture of ceramic veneers. For the analysis of occlusal relationships with the help of alginate material, impressions of the jaws were taken and diagnostic models were made from type IV synthetic gypsum. To correctly restore the contour of the central incisors, a wax setting was performed.

Based on the wax-up diagnostic model, a silicone matrix was fabricated to serve as a guide during the preparation of the central incisors. A minimal preparation of tooth 11 was carried out to a depth of 0.3 mm, the preparation area was completely within the boundaries of the enamel. Tooth 21 was prepared to a depth of 0.5 mm over the entire vestibular surface. The difference in tooth preparation depth was made to compensate for the gray tint of one of the teeth. After the preparation, the teeth were acid etched with a 37% phosphoric acid gel for 15 seconds, then washed and dried. An adhesive system for the total etching technique - TECO (DMG, Germany) was applied to tooth 21, exposed for 20 seconds. A1 opaque composite was then used in the gingival third of the crown to mask the gray tint. The prepared teeth were then polished with rubber heads and prepared for impression taking.

For isolation of soft tissues, the technique of double imposition of retraction threads was used. A wide retraction cord was placed in the sulcus and left for 5 minutes before taking the impression (Fig. 2). After the initial preparation, the teeth were rinsed with a water jet and dried. In accordance with the size of the patient's dental arch, an impression tray was selected. Minimally invasive preparations require an accurate impression using an appropriate technique, otherwise critical areas will not be clearly displayed. Thus, the choice in favor of a hydrophilic, in particular polyvinylsiloxane, material is necessary for an accurate representation of the preparation area. In addition, it makes sense to give preference to the sandwich technique due to the high accuracy and quality of the impression obtained with its help. To obtain an adequate consistency of impression materials, the use of automatic mixing systems is highly recommended. It has been shown that automatic mixing of polyvinylsiloxane materials avoids voids, eliminates the risk of contamination of material components and improves its physical properties compared to using materials for manual mixing. A cartridge with Honigum-MixStar Putty (DMG) impression material was installed in the automatic mixing machine (MixStar-eMotion, DMG) and the previously programmed setting was used in accordance with the manufacturer's recommendation.

The impression tray was carefully filled with a homogeneous mixture of Honigum-MixStar Putty (Fig. 3). Please note that the end sections of the spoon are completely filled first. Then, the corrective material Honi-gum-Light was applied from the gun over the Honigum-MixStar Putty base material (Fig. 4). It should be applied not only to the preparation area, but also along the entire length of the dental arch. This will allow you to correctly restore occlusal balance on the model.

At this time, the retraction cord was removed and the Honigum-Light material was simultaneously applied to the prepared teeth (Fig. 5). The filled spoon was placed in the mouth. After complete hardening of the material, the impression was removed from the mouth and studied (Fig. 6). All details of the minimal preparation were reproduced (Fig. 7). A close examination showed an accurate and detailed reproduction of the preparation margin. In addition, the accuracy of the PVA material was confirmed in the cross section (Fig. 8). Note the penetration of the Honigum-Light into the sulcus. Temporary crowns were made using Luxatemp (DMG) and the patient was released until the next visit.

On the basis of the obtained impressions, models were cast from type IV gypsum (Fig. 9). For teeth 11 and 21, porcelain veneers were fabricated with a thickness of 0.3 mm and 0.5 mm, respectively (Fig. 10). At the next visit, provisional restorations were removed and ceramic veneers were tried on. Due to the high transparency of ceramic veneers, glycerine-based try-in pastes were used. The veneers were cemented with clear cement for 11 and A3 opaque for 21 to mask discoloration. After the final approval of the designs with the patient, the veneers are fixed on the teeth. Restoration with adhesive luting with Vitique composite cement (DMG) provided an adequate esthetic result (Fig. 11).