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Table of Contents   
ORIGINAL ARTICLE  
Year : 2023  |  Volume : 26  |  Issue : 1  |  Page : 67-72
Morphological assessment of the surface profile, mesiodistal diameter, and contact tightness of Class II composite restorations using three matrix systems: An in vitro study


Department of Conservative Dentistry and Endodontics, Bangalore Institute of Dental Sciences, Bengaluru, Karnataka, India

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Date of Submission13-Jul-2022
Date of Decision16-Sep-2022
Date of Acceptance03-Oct-2022
Date of Web Publication08-Dec-2022
 

   Abstract 

Context: Sectional matrices and contact rings are valuable aids to establish proximal contact tightness in Class II composite restorations.
Aims: This study aims to evaluate the proximal contact area in Class II composite restorations using three matrix systems based on morphological analysis, mesiodistal (M-D) diameter and contact tightness.
Subjects and Methods: A standardized DO cavity was prepared in 30 plastic molar teeth. They were randomly divided into three groups (n = 10) and restored using Tetric N-Ceram composite material and three matrix systems – Saddle matrix, Palodent system, and Palodent Plus system. The quality of proximal contacts was assessed by measuring the maximum M-D diameter of the restored teeth using a digital caliper; the tightness of the proximal contact area using Unifloss and a standardized metal blade (30 μm). Qualitative assessment of contact morphology was done by visual means while quantitative assessment of contour was done using Medit scanner superimposing method and ExoCAD software.
Statistical Analysis Used: One-way ANOVA test was used to compare the mean M-D diameter (in mm) in the occlusal third, middle third, and the proximal contact area between the three groups. Chi-square test was used to compare the proximal contact area tightness using the passage of Unifloss. The buccolingual and occluso-gingival morphology was also compared among the three groups. The level of significance (P value) was set at P < 0.05.
Results: For the occlusal and middle third, significantly larger diameters were achieved with the Palodent Plus system than with the Saddle matrix. More flat contours were seen in the case of the Saddle matrix than in the case of the Palodent system while the Palodent Plus system exhibited a minimal depth of concavity as determined by three-dimensional imaging of the contact morphology.
Conclusions: Palodent Plus and Palodent matrix systems established superior contacts and contours than the Saddle matrix.

Keywords: Palodent plus matrix; Palodent system; proximal contact; Saddle matrix

How to cite this article:
Kumari S, Raghu R, Shetty A, Rajasekhara S, Padmini SD. Morphological assessment of the surface profile, mesiodistal diameter, and contact tightness of Class II composite restorations using three matrix systems: An in vitro study. J Conserv Dent 2023;26:67-72

How to cite this URL:
Kumari S, Raghu R, Shetty A, Rajasekhara S, Padmini SD. Morphological assessment of the surface profile, mesiodistal diameter, and contact tightness of Class II composite restorations using three matrix systems: An in vitro study. J Conserv Dent [serial online] 2023 [cited 2023 Feb 5];26:67-72. Available from: https://www.jcd.org.in/text.asp?2023/26/1/67/362918

   Introduction Top


Achieving proper contacts and contours is paramount during restorative procedures. An ideal contact protects and supports the teeth and periodontal tissues. An adequate proximal contact established during the restorative procedures ensures proper functioning of the stomatognathic system.[1],[2]

Two issues to consider when recreating the proximal surface are – contact tightness and surface contour. The contact strength depends on the size, location, and shape of the proximal contact areas. This in turn depends on the proximal contours of the two contacting teeth.[3],[4]

The proximal contact, also known as the contact area, refers to the area where the proximal surfaces of adjacent teeth touch each other. It is commonly found in the upper middle third of the crowns of most teeth, beneath the marginal ridges, and on both proximal ends of the tooth equator. When the contact is too loose or open, it can lead to food impaction, periodontal pocket formation, and development of proximal caries. On the other hand, excessively tight proximal contact makes it difficult to pass the dental floss through the contact area, leading to periodontal damage.[5],[6],[7],[8],[9] Optimal restoration of the contact region will aid in the development of the ideal embrasure form, protecting the health of the gingival col and allowing proper deflection of food during mastication.[3],[6]

In terms of surface contours, it is recommended that the interproximal contact be ideally contoured to avoid damage to the surrounding periodontal tissues and supporting bone. Therefore, recreating proper proximal contacts during restorative treatment is critical for preserving the health and longevity of the dentition.[3],[7],[8],[10]

Conventionally, amalgam restorations used circumferential straight metal matrix bands. While they were suitable for Class II amalgam restorations, they caused many problems when employed for Class II composite restorations. These matrix bands provide occluso-gingivally thin contacts, and the height of the contour of the restoration is shifted higher up close to the occluso-proximal line angle. As a result, when the marginal ridge area is smoothened, the contact area is quickly lost. A straight matrix band forms a narrower marginal ridge in the restoration that is more prone to fracture.[11]

Currently, composite resins have replaced amalgam for most direct posterior restorations but their handling characteristics are entirely different from that of amalgam. Obtaining tight proximal contact with composites has long been a challenge for dentists. In Class II amalgam restorations, the plastic nature of the material helps in condensation to achieve a tight proximal contact, but resin-based Composites have the inherent disadvantage of polymerization shrinkage. In addition, the increase viscosity causes it to slump during placement, preventing positive proximal pressure on the matrix band.[12],[13],[14]

To overcome the drawbacks of the Tofflemire matrix, recently sectional matrix systems have been introduced such as the Saddle matrix, Palodent system, and Palodent Plus system. The Saddle matrix is a sectional matrix made of stainless steel (50 μm thickness) and has its maximum curvature at the cervical region. A spring clip ensures the retention of the matrix. It is simple and easy to use and is reported to provide optimum contact and contour.[11],[13],[14]

Palodent matrix is a first-generation sectional matrix system developed for posterior composites. It uses an extremely thin (0.01 mm) contoured sectional matrix and contact rings to provide optimum separation between the contacting teeth. This approach separates the adjacent teeth minimally to optimize the proximal contacts, especially when the composite resin is used.[10],[15],[16]

A new sectional matrix, the Palodent Plus system, has been recently developed. The matrix band is made of dead soft material with a nylon fiber coating to avoid the composite from sticking and it exhibits an excellent occluso-gingival contour. The system includes two Niti rings (one for premolars and the other for molars), which are more stable and provide better retention and separation force. The plastic tines have a V-shaped notch that allows them to be placed over the wedge. This system also consists of an anatomically contoured wedge that avoids encroaching on the interdental papilla while adapting the band properly at the gingival seat region.[11],[13],[17]

Various methods are available to evaluate interproximal contacts. These may include qualitative methods (visual observation, the use of dental floss or metal strip) or quantitative methods (three-dimensional [3D] morphologic reconstruction).[3]

The purpose of this study was to evaluate the proximal contact area in Class II composite restorations using three matrix systems based on visual analysis of mesiodistal (M-D) diameter and contact tightness as well as by 3D reconstruction. The null hypothesis is that there will be no difference in the contacts and contours established by all three matrix systems.


   Subjects and Methods Top


Thirty Frasaco (Franz Sachs and Co. Gmbh, Tettnang, Germany) posterior teeth were used in this study. Standardized disto-occlusal cavity preparations were done with number 245 carbide bur in a high-speed handpiece and restored using Tetric-N Ceram (Ivoclar, Vivadent) composite material and three matrix systems – Saddle matrix, Palodent, and Palodent Plus system. All restorative procedures were performed by a single operator.

The study was divided into three groups.

  • Group I – Ten Class II (DO) cavities restored with Tetric N-Ceram (Ivoclar, Vivadent) using Saddle matrix (TORVM, Russia)
  • Group II – Ten Class II (DO) cavities restored with Tetric N-Ceram (Ivoclar, Vivadent) using the Palodent system (Dentsply, Caulk, USA)
  • Group III – Ten Class II (DO) cavities restored with Tetric N-Ceram (Ivoclar, Vivadent) using Palodent Plus system (Dentsply, Sirona USA)
  • The material was adapted and carved using a Teflon-coated instrument and cured for 20 s from occlusal and proximal directions. The final finishing and polishing of the restorations were done with fine diamond burs.


Mesio-distal (M-D) diameter

The quality of proximal contacts was assessed by measuring the maximum M-D diameter of the restored teeth using a digital vernier caliper (Stainless hardened-China). The restored tooth was fixed to the external jaw of vernier caliper to measure the M-D diameter at the same height for all restored teeth, namely at the transition between the middle and occlusal third [Figure 1]a and [Figure 1]b. Each sample was measured five times by a blinded evaluator. Finally, the scores were averaged for each set of measurements.
Figure 1: The quality of proximal contacts was assessed by measuring the maximum mesiodistal diameter. ((a) Occlusal-third, (b) Middle-third) using a digital caliper and the tightness of the proximal contact area using a standardized metal blade (30 μm) (c)

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Proximal contact tightness

Tightness of the proximal contact area was assessed qualitatively using unifloss and metal matrix strip (30μm thickness). Both were inserted into the interdental space and resistance to insertion was assessed by applying FDI criteria [Figure 1]c. The metal strip was held by two-needle holders at a distance of 2 cm and inserted into the interdental space.

Qualitative assessment of contour

Two independent observers visually assessed the surface profiles of the contact morphology. Preoperative contour was assessed before the cavity preparation. Qualitative assessment of contact morphology after restoration was visually inspected with regard to their buccolingual and occluso-cervical aspects. The profile contours on the buccal-lingual aspect were defined as concave, convex, and flat. On the occlusal-cervical aspects, the surface profiles were defined as anatomic (with convex contour) or nonanatomic (flat profile).

Quantitative assessment of contour

The degree of concavity was quantitatively evaluated by measuring the area and depth of the concavity using 3D image reconstruction. A stone jig with the impression of the distal surface of the artificial tooth was used as a positioner for the horizontal placement of the restored teeth. Quantitative assessment of contour was done using the Medit scanner superimposing method and ExoCAD software. A Hypertext Markup Language-based program was developed to quantify the concavity of the proximal contours. The greatest distance from the concave surface to be orthogonal to the plane was defined as the depth of the concavity.

One-way ANOVA test was used to compare the mean M-D diameter (in mm) in occlusal and middle third as well as proximal contact area (in mm) between the three groups.

Chi-square test was used to compare the proximal contact area using the passage of Unifloss and buccolingual and occluso-cervical morphology between the three groups. The level of significance was set at P < 0.05.


   Results Top


M-D diameters of the restorations were obtained with each matrix system. For the occlusal and middle third, significantly larger diameters were achieved with the Palodent Plus system. The teeth restored using the Saddle matrix and Palodent system showed significantly smaller diameters [Table 1].
Table 1: Comparison of mean mesial distal diameter (mm) between three groups using one-way ANOVA test

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The Palodent Plus system values were significantly better than the two other matrix systems with respect to proximal contact tightness [Table 2] and [Table 3].
Table 2: Comparison of mean Proximal Contact area (in mm) using Metal Strip between 3 groups using One-way ANOVA Test

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Table 3: Comparison of Proximal Contact area by passage of Unifloss between 3 groups using Chi Square Test

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The visual inspection of the contact morphology revealed more flat contours both on buccolingual and M-D aspects in the case of Saddle matrix than in case of Palodent and Palodent Plus systems [Table 4]. Palodent Plus and Palodent system exhibited a minimal depth of concavity when compared to Saddle matrix, as determined by 3D imaging of the contact morphology [Figure 2]a, [Figure 2]b, [Figure 2]c.
Table 4: Comparison of Bucco-lingual and Occluso-Cervical Morphology between 3 groups using Chi Square Test

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Figure 2: The depth of the concavity in the present study, (a) saddle matrix (3 mm), (b) palodent matrix (2.90), and (c) Palodent Plus (2 mm)

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   Discussion Top


Tight proximal contact and adequate marginal adaptation are critical for maintaining the integrity of the dental arch and periodontal health.[12] At present, resin composites are the primary choice for posterior restorations due to their excellent aesthetics and improved mechanical properties. But achieving correct proximal contacts and contours with composite resins still remains a challenge. A material with superior handling properties and a matrix system that provides stability and improved contour is required for an effective Class II composite restoration.[5],[18],[19] The present study employed Tetric N-Ceram which is a nanocomposite with excellent properties.

It has been reported that a major factor in recreating near-ideal contacts and contours while placing Class II composite restorations is the matrix system that is employed.[20] Over the past few decades, novel matrix systems designed specifically for posterior composite restorations have been introduced.[13] The present study compared the three efficacy of currently popular matrices (Saddle matrix, Palodent, and Palodent Plus systems) in restoring proper proximal contacts and contours for Class II composite restorations.

Regarding the maximum M-D diameter of the restored molar, the Palodent Plus system achieved maximum M-D diameter followed by the Palodent system and Saddle matrix system [Table 1].

Various methods may be employed to assess proximal contact tightness. They include: Passing dental floss between the contact areas, use of tooth pressure meter or using standardized metal blades of varying thickness (shim stock strips).[2],[21]

The proximal contact was examined in the current study using Unifloss and a metal strip. A preliminary evaluation of the contact strength was done using dental floss which was followed by the insertion of a metal strip (30 μm) to provide more accurate information regarding the contact tightness.[2],[22] The width of the blade that passed through the contact area from an occlusal direction was evaluated. Accordingly, it was observed that the contact was weak with Saddle matrix as the metal strip was easily passing through the contact area. However, in the case of Palodent and Palodent Plus matrices, the metal blade was able to pass only when slight pressure was applied indicating that the contact may be considered good [Table 2] and [Table 3].

The proximal contour is one of the key factors that influence the long-term success of the restoration. It depends on the type and design of the matrix system that is used.[20] To further describe the contact characteristics established by the three matrix systems used in this study, the achieved contour was assessed both qualitatively and quantitatively.

Qualitative assessment of contour by visual means revealed that regarding the buccolingual morphology, convex profiles were obtained to the maximum extent with Palodent Plus system (80%) followed by Palodent (70%) and Saddle matrix (20%). In the occluso-cervical direction, anatomically correct contours were once again superior with Palodent Plus (80%) followed by Palodent (60%), while Saddle matrix was inferior (20%) [Table 4].

The use of 3D image reconstruction to quantitatively recreate the proximal contour is a practically beneficial method to study the morphology of the contact area.[3] Based on this, clinicians can select the most appropriate matrix system for Class II composite restorations. In the present study, 3D morphologic analysis showed that Palodent Plus and Palodent matrix systems demonstrated a minimum difference in contour when compared to the Saddle matrix. Depth of concavity was minimal for Palodent Plus (2 mm) and followed by Palodent matrix (2.90mm). Both had had good contact tightness, and less buccal and lingual overhangs [Figure 2]b and [Figure 2]c. This is in accordance with a study comparing Tofflemire matrix, Supermat matrix (circumferential matrix), and Palodent system which concluded that sectional matrices with separating rings demonstrated the tightest contact between the restoration and adjacent tooth. It was also observed that the Palodent matrix recreated the contact point more cervically than the circumferential matrices. However, none of the tested matrices could recreate the original proximal contact features of a normal tooth.[23] A recent clinical study evaluating proximal contacts in Class II composite restorations using Palodent Plus matrix system has also revealed that this matrix is capable of providing adequate contact tightness and contours.[20] The current result is consistent with prior findings that a micro-thin matrix and a spring action ring can improve contact tightness.

On the other hand, the contacts formed with the Saddle matrix were loose, with a greater depth of concave morphology (3 mm) [Figure 2]a, with both buccal and lingual overhangs, indicating that the concavity was caused by the composite materials being overextended to the buccal and lingual sides rather than a deficiency in the central zone. It has been shown in earlier studies that precontoured sectional matrices like the Saddle matrix which do not incorporate separating forces are incapable of recreating optimal contact areas.[15],[24]

Based on the results of the present study, the Palodent Plus matrix with its superior features produced the best contacts and contours for Class II composite restorations followed by the Palodent matrix. Saddle matrix is incapable of achieving adequate contact tightness and proximal contours for posterior composite restorations.

The observations of this study cannot be directly applied to clinical practice as it was performed on typodont teeth and there was no provision for micro-movement due to the absence of periodontal ligament.[23] Further in vivo studies are therefore needed to validate the findings of our study.


   Conclusions Top


The achievement of optimal contacts and contours for Class II composite restorations largely depends on the type of matrix system used. Palodent Plus and Palodent sectional matrix systems showed nearly similar performance in terms of proximal contact tightness, proximal contour, and overhangs of the restorations while the Saddle matrix demonstrated poor results.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Correspondence Address:
Dr. Suchitra Kumari
12/1, 2nd Cross, Lakkasandra, Bengaluru - 560 027, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcd.jcd_403_22

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