Introduction
Optimising the shape of teeth has consistently been the ultimate goal in restorative dentistry. It's essential not just for replacing absent tooth structure but also for restoring the ideal form and function.1 Johnson famously remarked that understanding "contact point" and "interproximal space" should be fundamental for any dental practitioner. 2 The positioning of contacts and contours, vulnerability to dental decay, treatment methods, and their role in preventive dentistry have been carefully considered in both theory and practice for centuries.3 The initial approach to treating proximal caries involved removing the decay and filling the cavity with suitable materials, without considering the tooth's form and function. The early theory of caries, which suggested that decay starts at the tooth contact point, led to a prophylactic concept aiming for complete and permanent separation of adjacent teeth to create self-cleansing spaces. While this approach did reduce caries rates, it faced criticism for causing tooth disfigurement, food impaction on the gum line, tooth sensitivity, and tooth drifting. In approximately 1890, the concept of contoured restorations emerged, based on idea of caries developing beneath the contact point. These contoured restorations aimed to restore the correct shape of the interproximal space, promoting gum health and patient comfort. This, in turn, safeguarded the stomatognathic system, ensuring harmony and balance.4
Atkinson et al. introduced the concept of matricing in 1897 as a means to create contoured fillings.4 Matricing involves replacing lost dental structure during preparation by constructing a temporary wall opposite the axial walls of the preparations.5
Matrices play an indispensable role in restorative dentistry, with matricing being a crucial step in the placement of various types of restorations. Due to the diversity in matrix systems, it is essential for clinicians to be knowledgeable about them
Discussion
Ideal contacts
The proximal contact, also known as the "contact area," denotes the surface where the proximal surfaces of adjacent teeth meet. Initially, during tooth eruption, this interaction occurs at a point, termed a "point contact." Over time, due to proximal attrition, it evolves into a "contact area." Typically positioned in the upper middle third of the crown of most teeth, the contact area facilitates natural embrasures and supports effective maintenance of the interproximal region. 6
Optimal contacts play vital roles in:
Maintaining dental arch stability by transmitting forces along the long axis of teeth,
Protecting the interdental papilla against food impaction, and
Influencing speech and aesthetics, particularly in the anterior region.
Improper restoration of contact areas can lead to teeth displacement, lifting forces, tooth rotation, occlusal contact discrepancies, and food impaction. This may result in periodontal trauma, causing pain, inflammation, and bleeding.
Matricing and Matrices
Matricing involves replacing lost dental structure during preparation by constructing a temporary wall opposing the axial walls of the preparations. A matrix serves as a tool to secure the restoration in the tooth while it sets.5
Ideal requirements of dental matrices include
Rigidity for stability.
Accurate recreation of natural tooth form and interproximal contact.
Effective sealing of proximal and gingival wall areas.
Minimal thickness for precision.
Flexibility for adaptability.
Bio-compatibility for safe use.
Stability for durability.
Adequate optimal transmittance for optimal outcomes.7
Matrix system depending on location can be of two types
Anterior matrix systems
It can be classified into: transparent matrix, non-transparent matrix, and rigid matrix system.
Transparent matrix system
These are utilized for tooth-coloured restorations due to their capacity to transmit light during the polymerization process.8
Bioclear matrix system
The Bioclear matrix system was pioneered by Dr. David Clark in 2007.11
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Features
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Indications
Aesthetic procedures involving small restoration areas.
Used for both anterior and posterior restorations.8
Transparent Crown
This is also referred as a strip crown.
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Indications
Utilized in both primary and permanent dentition.
Used in treatment of microdontia in incisors or peg-shaped lateral incisors.8
Contoured anterior matrix
In this technique, a stainless-steel matrix band is taken and contorted into an 'S' shape using a mouth mirror handle.
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Indications
To restore the distal portion of canine and premolar teeth.
Slot restorations for Class II cases.9
Blue view varistrip
It's a contoured anterior matrix designed to offer the optimum curvature and band height for all anterior restorations.
Indications8
Non- transparent matrix system
Unica anterior
It is developed through a collaboration between Polydentia and Style Italiano.
Indications
Features8
Unica minideep
It is particularly made from a malleable alloy that conforms to the required shape for smaller anterior teeth.
Indication 8
Fusion anterior matrix system
Garrison Dental introduced the Fusion Anterior Matrix System.
Indications
Features8
Burtonbands anterior matrix system
They were designed by Dr. Matthew Burton.
Indications
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Advantages
Complete accessibility to the restoration.
Ability to shape and ensure proper proximal contact through the burnishable nature and narrower profile of the metal matrix compared to plastic strips.8
Rigid matrix system
Modified putty index using mylar strip
A putty index of the incisors is created by using either the direct or indirect technique. This index is made using either addition or condensation silicone putty materials. 9
Posterior matrix system
Caries extending onto the proximal aspects of molars and premolars are categorized as class II caries. The establishment of proper contact and contour in such cases becomes a challenge for the dentists. In order to combat this hurdle, varieties of matrix systems had been developed.7
Posterior matrix system can be divided into:
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On the basis of matrix retainers:
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Depending on mode of retention
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Depending on the cavity preparation for which it is used
Class I cavity with buccal and lingual extension - Double banded Tofflemire matrix.
Class II cavity- Single banded Tofflemire matrix, Ivory no.1, Ivory no.8, Copper band matrix, T band matrix, Auto matrix and Pre countered sectional matrix.7
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On basis of types of matrix available:
Custom-made or anatomic matrix - E.g. Compound- supported matrix.
Mechanical matrix- E.g. Ivory No.1, Ivory No.8, Tofflemire matrix.
Preformed - E.g. Circumferential matrix system, Sectional matrix system.14
Mechanical retainer
Ivory matrix No. 1
It consist of a matrix holder with two semicircular arms, one of which is slanted, and a claw at the end and also consist of screw, positioned opposite to the matrix band holder.9
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Indications
Used for restoring unilateral class II restoration.7
Ivory matrix no. 8
This matrix comprises a band that wraps around the entire tooth crown. The band's circumference can be modified using the adjusting screw located in the retainer.9
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Indications
For unilateral or bilateral Class II preparations (MOD).7
Tofflemire matrix
Also, referred to as the universal matrix, this design was pioneered by B.R. Tofflemire.5
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Indications
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Advantages:
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Disadvantages:
Doesn't achieve optimal or straight contacts and contours for posterior composite restorations.7
Steele’s siqveland self-adjusting matrix holder
It's frequently employed for tapering teeth, particularly where there's significant difference between the diameters of the cervical and occlusal thirds of the tooth.
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Indications
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Advantage
Able to conform accurately to tooth contours.
With Steele’s Siqveland self-adjusting matrix holder, achieving anatomical adaptation of the band is feasible without the need for wedges.5
Omni matrix
The Omni-Matrix (Ultradent) is a disposable matrix retainer with pre-loaded band.
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Indications
-
Advantages
-
Disadvantages
Costlier.15
Custom - made
Compound supported matrix
Sweeney provided the description of Compound supported matrix.
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Indications
-
Advantages
-
Disadvantages
Time-consuming.9
T-Shaped matrix band
It's a preformed matrix band made of brass, copper, or stainless steel without a retainer.
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Indications
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Advantages
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Disadvantages
Inherently unstable.9
Copper bands
These are cylindrical in shape and available in different sizes, hence can be selected accordingly.
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Indications
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Advantages
-
Disadvantages
Incompatible with resin restorations.
Requires a significant amount of time. 9
Preformed
Auto matrix
The Auto-matrix or retainer-less matrix was given by L.D. Chaulk Co. Milford in 1977.
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Indications
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Advantages
-
Disadvantages
Proximal contouring poses a challenge as the bands lack pre-contouring.
High Cost. 7
Circumferential matrix
Circumferential matrix can be of different types:-
Palodent 360 circumferential matrix system
The Palodent 360 is an innovative circumferential matrix system that doesn't require a retainer or applicator.
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Indications
Beneficial for complex Class Il cases where adjacent teeth are absent, excessive tooth structure loss prohibits sectional matrix use, or when dealing with misaligned or severely rotated teeth.
Palodent 360 matrix bands along with Palodent Plus retention rings, provides temporary interproximal space. 7
Sectional matrix
Sectional matrix system was introduced by Dr. Alvin Meyer in 1986
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Indications
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Advantages
Easy to utilize with excellent visibility.
The anatomically contoured bands ensures ideal contact points and indentation. 7
To achieve anatomically accurate contacts with posterior composites, it's essential to create enough space between the teeth in contact to accommodate both the thickness of the matrix band and the polymerization shrinkage of the composite resin. The introduction of "sectional matrices and contact rings" marked the initial effective solution for achieving proper posterior composite contacts. 17
Basic Principle of Contact Rings
These rings function by creating a slight separation between adjacent teeth. They can be classified based on their development into two categories:
First generation systems
The initial contact ring systems, emerging in the late 1990s, encompassed products such as the Palodent Bitine, Contact matrix, and the Composi-Tight. 1
Problems with early contact rings
Risk of ring collapse or displacement with wide proximal boxes.
Ring stacking, wherein one ring is placed over another for MOD restoration.
Gradual loss of springiness due to repeated usage and sterilization.17
Second-generation systems
In response to the limitations of first-generation rings, recently introduced second-generation rings aim to overcome these issues. Examples include the Composi-Tight 3D Soft Face Ring System, Palodent Plus, Bioclear, V, V3, V3 Blue, and V4 Clear Metal Ring System. 1
Instruments to Develop Ideal Contacts and Contours
Various strategies have been introduced to achieve optimal contacts and contours when performing direct posterior composite restorations. Noteworthy among these strategies are:
Contact forming instruments
Ceramic inserts
Light tips.1
Conclusion
A tooth is a dynamic, living organ made up of various tissues, constantly adapting to the forces of chewing and speech. When tooth tissue is lost due to factors like decay, injury, or wear, proper management is essential. Treating missing tooth structures offers dentists a wide array of techniques and materials, requiring a comprehensive understanding of the necessary tools and resources. To simplify the reconstruction of proximal contact surfaces, significant focus has been placed on developing various matrix systems. These systems aim to reduce the complexity associated with inserting different restorative materials.
Understanding about the different matrix systems, its techniques and advances helps the clinician to select the best matrix system for the specific clinical situation to achieve predictable contact and contours with the available restoration.
Article
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