Method for evaluating polymerization stress influence caused by contemporary composite filling materials shrinkage

FIELD: medicine; medical engineering.

SUBSTANCE: method involves calculating proportions of bound and free composite surfaces and C-factor values. Adjustment coefficients are additionally introduced for taking retention substrate properties in consideration and estimate is found from formula , where CSF is the configuration-substrate factor; Si is the hard dental tissues; Sj is the composite contact surface; Sk is the metal contact surface; Sm is the free surface area; A is the hard dental tissues retention capability (A=1); B is the composite material retention capability (B=2); C is the metal retention capability (C=3). CSF value growing relative to the C-factor, low adhesion level and increased polymerization stress influence caused by contemporary composite filling materials shrinkage is considered to be the case.

EFFECT: objectively described polymerization shrinkage process; reduced risk of traumatic complications.

1 dwg, 1 tbl

 

The invention relates to medicine, namely to the dentist, and can be used to assess the effects of polymerization shrinkage of composites for restoration of defects of hard tissues of teeth.

The lack of modern composite filling materials is polymerization shrinkage, which constitutes 2-4% [6]. Theoretical justification of the influence of polymerization stress was laid out in the concept of factor configuration (C-factor), which is defined as the ratio of bound and free surfaces of the composite and has the highest value in deep cavities [3, 4]. Initially, the concept of C-factor (CF) was developed for sealing one portion of the composite (Bulk technique). When researching options for the filling, made with the use of a larger number of increments (portions), it makes sense to evaluate each portion separately. After each utverzhdenii and gave shrinkage portion of a new initial situation (secondary cavity) for subsequent portions. This situation can be considered in two aspects:

a) change the shape of the cavity and, accordingly, the value factor,

b) subsequent portions occurs contact not only with the bottom and walls of the cavity, as well as with already polymerized surface of the composite.

Due to the layer, inhibited by oxygen, communication composite compositions which is more stable what is the relationship composite bond of hard tooth tissues. As a consequence, cannot be considered hard tissues of the tooth covered by the bond, and the surface of the cured composite as equal substance. The last layer of the composite is the most important because of its volumetric shrinkage may be responsible for weakening the adhesive bond with the hard tissues of the tooth. Research has concluded that the existing concept of C-factor does not fully reflect all clinical situations. In our opinion, the curing of portions of the composite in contact with the already utverzhdennym composite or some other substrate, creating the best conditions for adhesion, for example, with the surface of the metal matrix or tab leads to more severe damage to the connection zone composite-dentin. According to the existing concept With factor all surfaces of the composite in contact with any substrate, are considered as equivalent associated surface. It remains unclear the fact that during the curing portion of the composite in contact with a solid substrate, and pre-utverzhdennym filling material or a metal surface, there is significant damage to the adhesive zone composite-dentin. The usual calculation With factor cannot reflect negativnog the influence caused by the contact portions of the composite with the surface of the cured filling material or other substrate.

The objective of the invention is to develop a method to estimate the influence of curing stress taking into account the surface area and properties of the substrate.

The task to solve due to the fact that impose additional correction factors that take into account the retention properties of the substrate, and the evaluation is made according to the formula

where CSF - configuration-substrate" factor;

Sithe area of contact with the hard tissues of a tooth.

Sj- the area of contact with the composite;

Sk- area contact with the metal;

Sm- the area of the free surface of the composite,

And - retention capacity of the hard tissues of the tooth (A=1);

In - retention ability of the composite (b=2);

P - retention capacity of the metal (S=3).

and the increase in CSF relative to the C-factor indicates a low level of adhesion and increasing the influence of curing stresses caused by shrinkage modern composite filling materials.

In the formula, you can include correction factors for other substrates, such as ceramics, etc. as a result of calculation according to the modified formula more objectively reflect the results obtained in the study of desinic properties of advanced composites.

The effectiveness of this method is confirmed by the results of measurement of joint strength of the composite and solid substances tooth obtained in the study method microspine rupture [5].

In identically prepared groups with cavities 1 class, a horizontal technology applications of the composite, as with natural walls and artificial composite or metal walls, the decrease of the tensile strength (figure 1) [1, 2].

The drawing shows the performance of adhesion (MPa) for different substrates during application of the composite horizontal modified technique.

Table 1 shows the results of the count values of CF on conventional and modified the formula for groups that examined the effect of changes in the properties of the substrate on the walls of adhesion in the bottom. In group A1 composite was introduced into the cavity 1 class 16 portions of the horizontal technology applications. In group A2 were used horizontal modified technique.

Table 1
Comparing values With factor (CF) and CS factor (CSF)
no portion of the compositeGroup
A1 (31,9)A2 (50,5) M1 (13,5)M2 (21,6)M3 (34,2)
CFCSFCFCSFCFCSFCFCSFCFCSF
11,251,25110,921,511,251,2511,5
2, 31,252,251,6721,362,321,252,251,67to 2.67
41,252,25342,073,611,252,2535
5, 9, 131,252,2511,50,922,131,252,2512
6, 7, 10, 11, 14, 151,252,251,67to 2.671,363,091,252,251,673,33
8, 12, 161,252,25352,07br4.611,252,25 36
Note: In parentheses are the tensile strengths (MPa).

Combined models were prepared as follows: in group Ml composite made 16 horizontal portions of the modified technique immediately after applying a thick-walled metal clip, group M2 with additional portions formed in the wall of the cavity 1 class of the cured composite. The recovery cavity spent 16 portions of the horizontal technique. Group M3 differed only horizontally by the modified method of filling a simulated cavity. Thus, groups M2 and M3 correspond to the groups A1 and A2. The introduction of the composite in contact with the metal caused a three-fold deterioration of the clutch in the field of composite-dentin (C=3), contact with utverzhdennym composite - double reduction clutch (In=2). The retention ability of dentin (A) was taken as 1.

In the whole group there is a decrease in tensile strength in identically prepared samples, while the CF values calculated by the usual formula, does not change for each subsequent portions and match for different substrates (table 1, group A1, M2, A2, M3). The CSF values in these groups are not the same and vary for different portions. In group M1, where the rate of adhesion are the lowest in oven, contact the last portion of the composite metal surface is accompanied by the biggest increase in CSF (2.2 times greater than the value CF) with the same engineering applications.

When considering changes in CSF from one portion of the composite to the following can be concluded that the maximum values of the factor "configuration of the substrate reaches horizontal technique, starting with 2 servings, and when modified with 5 portions, that is, since the formation of the 2 layers of the composite, when there is contact with surfaces already cured material. The modified formula more objectively reflects the processes of polymerization shrinkage and helps to develop methods applications, reducing the number of complications.

Sources of information

1. W. // Clinical dentistry./ No. 2 - 2003. - P.24-26.

2. W.// Panorama of prosthodontics/ No. 2. - 2003. - P.12-14.

3. Davidson C.L. The competition between the composite-dentin bond strength and the polymerization contraction stress /C.L. Davidson, A.J. de Gee, A. Reil-zer //J. Dent. Res. - 1984. - V. 63. - P.1396-1399.

4. Feilzer A.J. Setting stress in composite resin in relation to configuration of the restoration /A.J. Feilzer, A.J. De Gee, C.L. Davidson //J. Dent. Res. - 1987, No. 66.-R-1639.

5. Sano, H., Shono T., Sonoda, H., Takatsu T., Ciucchi C., Carvalho R., Pashley D.H. Relationship between surface area for adhesion and tensile bond strength - evaluation of micro-tensile bond test. Dent Mater. 1994; 10: 236-240.

6. Soltesz, U. Polymerisationsschrumpfung einiger neuerer Composite-Füllungs-werkstoffe /U. Soltesz //Zahnärztl Mitt. - 1998.- No. 88. - P.1404-1409.

the manual evaluation of the influence of curing voltage, associated with shrinkage modern composite filling materials, including calculation of the ratio of the area of free and associated surfaces of the composite and values With the factor, characterized in that it further introduce correction factors that take into account the retention properties of the substrate, and the evaluation is made according to the formula

where CSF - configuration-substrate factor;

Sithe area of contact with the hard tissues of a tooth.

Sj- the area of contact with the composite;

Sk- area contact with the metal;

Sm- the area of the free surface of the composite;

And - retention capacity of the hard tissues of the tooth (A=1);

In - retention ability of the composite (b=2);

P - retention capacity of the metal (S=3)

and the increase in CSF relative to the C-factor indicates a low level of adhesion and increasing the influence of curing stresses caused by shrinkage modern composite filling materials.



 

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