Halo Sectional
Matrix System
White Paper™

Dr. Rafael Beolchi

INTRODUCTION
The restoration of the proximal surface ofClass II cavities has always been an important
objective for the dental practitioner. There areseveral reasons why the reestablishment ofoptimum form and function is important: support,alignment, and stabilization of the dentition
are the fundamental ones. Also, the protection
and preservation of both tooth and interdental
gingival papilla, and consequently, the rest of theperiodontal complex. A good contact between
teeth helps to prevent food impaction and deter
the formation of proximal carious lesions.
Several features like the correct interproximal formor contour (embrasure shape), optimum proximal
contact surfaces, consistent marginal ridge
elevations, and central groove continuity withina dental arch are paramount. Absent or open
contacts and/or proximal contact surfaces may giveroom to poorly aligned dentition, which in turn may
cause food impaction, halitosis, caries formation,and periodontal disease—just some of the reasons
why the knowledge of accurate tooth anatomy isessential for a functional dental rehabilitation.
With the requirement of so many anatomic
details, the optimum form and function associatedwith the proximal surface tooth anatomy has
included numerous obstacles over the years,especially after the improvement of esthetic
materials to be used in the posterior region. If
by one side the development of new toothlike
composite resins and bonding technique allowed
for conservation of tooth structure, by the otherit brought new challenges and problems.
Tight, well-contoured proximal contact areas in theposterior region were more easily achieved withdental amalgam, especially due to its mechanicalproperties and handling characteristics. Today,
composite resin has replaced the metallic directmaterial as the posterior restorative material ofchoice, with reports of it being used in at least
58% of posterior restorations according to somestudies. The way in which posterior composite
restorations are now placed went through a rapidchange in the last few years, greatly because of
the change and improvements in composites’
composition and formulas, and the new materials
and technologies available. Nevertheless,persistent challenges are still encounteredby the practitioner, and new improvements inthis field will be discussed further ahead.

Halo™ Sectional Matrix System White Paper

MATRIX SYSTEMSIn order to facilitate the reconstruction of proximal
contact surfaces, several different matrix systems
have been proposed. The re-creation of proximal
anatomy is based on three pillars: the matrix orband, the wedges (generally made of wood orplastic), and the device responsible for holding thematrix in place (the matrix retainer). It is important
to note that a rapid separation is also desired,
which is usually accomplished by the wedge, thering (in systems where it is available as the matrix
retainer), or both. Over the last decade, all three:matrices, wedges, and ring (matrix retainers)
went through rapid changes and development.
Historically, the Tofflemire system is probably
the most popular matrix system. When usedwith amalgam, it produced good and predictable
anatomy and contact points. Today, it is still
employed for insertion of composite resin, being
widely used around the world. However, moredeveloped matrix systems have been introduced,
bearing great characteristics more suitable forthe demands posed by composites. One of themain reasons is because of the peculiarities of
the contact point that is obtained with the useof the Tofflemire matrix systems—usually too
close to the occlusal surface. It is common thatafter even the initial occlusal adjustments, thecontact point is lost due to this proximity. Anothercommon mishap is when there is a fracture ofthis anatomical portion of the restoration.
Ring matrix systems that include a separation
ring, sectional matrices, and custom-fitted
plastic wedges have become popular, with oneof the first matrix systems being introduced in
the 1990s. It was the first generation to utilize
this concept exclusively as the restoration ofposterior teeth using composite resin increased.

MECHANICAL SEPARATORS
Tooth displacement is achieved with a maximum
interdental separation of about 0.55 kg/mm,
and it is important to compensate for thethickness of the matrix when this one is removed.
According to Owens et al. (2016), “The practiceof flossing has traditionally been the method forthe evaluation of proximal contact achievement,with designations of tight, weak, or open.” Even
though it is an empirical form of classification, thedistinctive “click” felt when the dental floss goes
through the proximal restored area is usually agood sign, and something that many dentists
seek, as it usually implies a good contact point.
It is good to remember that in the days of thedental amalgam, both the expansion sufferedby the material and the packing required by theinsertion technique greatly helped the dentist toachieve a good contact point/surface between
the posterior teeth. With the passivity of insertion
when using composite materials, the pressuredelivered by the separation ring (or spring clamp)
systems and the wedges became responsible forthe separation force. This combination (ring andwedges) should guarantee the movement of the
tooth and compression of the periodontal ligament
space, allowing for an improved separation.
The idea behind rings (or clamps) is to provide
the separation necessary to achieve properinterproximal anatomy. From the myriad ofdesigns available, some do not adapt well tothe interproximal-occlusal anatomy, failing toprovide a good contact between matrix andtooth. This in turn results in flash on the marginsof the restoration that must be dealt with in thefinishing step. Others allow for a tighter contact,

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Halo™ Sectional Matrix System White Paper
but sometimes they misshape the matrix band,collapsing it in cases where a wider Class II
cavity is present or a cusp is missing. There isalso the problem of some rings being too bulky
to be used in challenging areas, such as what
happens to the second upper molar region.

tissues. It has a V-shape, and it helps to achieve a
better adaptation to the interproximal region. Theproblem is that some of the wedges may be toosoft, therefore helping to adapt the matrix to thetooth, but failing to provide a good separation.

A novel concept on this field, the Halo™ Sectional
Matrix System Ring proposes a solution witha unique beak design with built-in anatomical
contours that mimic the natural anatomy andhelps to decrease the finishing time. (Figure 1)
The Ni-Ti metallic ring is fabricated with glassfilled nylon tines that are strong and rigid, which
presents a 3D anatomy. This unique design
provides a better separation, and at the same time,
adapts the sectional matrix more tightly around thetooth without collapsing it on the margins wherewider Class II restorations are present. (Figure 2)
As for the other component responsible forseparation, the wedges, these can be fabricatedin many materials. The most popular design is still
the wooden wedges. Available in many sizes they
are a popular material, but can be harmful for thegingival papilla. On one side they provide a good
separation force, on the other this happens withthe expense of compressing, sometimes harming,
this portion of the periodontal apparatus.
Another fundamental role of the interdentalwedge is to help adapt the matrix band, providing
a good contour and a perfect fit to the toothstructure. Since the interproximal region isblocked from direct view after the completionof the restoration, this is important to avoid any
hidden overhangs, and the subsequent risk ofrecurrent decay due to bacterial colonization.
For this purpose, a new shape has been proposedin the last decade which is gentler to the soft

Figure 1

Figure 2
The new Halo Sectional Matrix System comeswith an innovation: the wedges have a hollow
design but are also firm (Figure 3). This new
material provides an active wedging for enhanced
separation, but makes the wedge gentle to thegingival papilla and easy to place. It also allows thewedges to be stacked when multiple wedges areneeded, providing a perfect adaptation between
the matrix band and the tooth, making sure no
overhangs will be present on the final restoration.
MATRICES
One of the main purposes of the matrix (band) is tocontain the restorative material so it can be shaped
into the proper lost proximal anatomy. Matrices
can be either circumferential or sectional. They
are the fundamental part for achieving the proper
anatomy of the tooth, as it is the type of matrix
system and not the composite resin material thatis primarily responsible for the tooth anatomy.

Figure 33

Halo™ Sectional Matrix System White Paper
That is exactly one of the main problems of
the Tofflemire-type matrices when used withcomposites: it delivers an anatomy too parallelor too trapezoidal in relation to the tooth. As
mentioned above, the contact point obtained
is too close to the occlusal surface, and withocclusal adjustments, it might be removed. Inaddition to the lack of a well-contoured profile
from occlusal to cervical, they are likely tocreate problems for the gingival papilla regionin terms of food impaction. Also situations
like these are more prone to fracture overtime because of the masticatory loading.
A class of matrices worth mentioning is theautomatrices, sometimes used because of theirease of placement. However, these matrices usuallypresent the same anatomical setbacks similar to
those of the circumferential, discussed above.
Novel designs in matrix shapes and thickness(together with new rings and wedges) allowed fora better and predictable anatomy, both in occlusal
and proximal, the so-called sectional matrices.
One of the reasons why the sectional matrix
provides an improved interproximal anatomy
with proper marginal adaptation is becausesuch systems can be customized according to
the variety of the shapes and surfaces of theproximal surfaces of different teeth. However,
it is necessary that a ring (and/or the wedge)
acts as a displacement force, otherwise, there’salways the risk of getting a suboptimal contact
surface contour. In case of excessive separation
force, the matrix might get wrinkled.
There are two types of curvatures in the metallic
bands for the Halo Sectional Matrix System: oneis the “wrap-around” curvature, going from lingual
to buccal, and the other curvature goes fromgingival to occlusal (Figure 4). The buccal-lingual

curvature is unique to each size of band and it is
not incrementally sized, giving the right anatomy
for the right tooth. When used with its uniquely
designed ring, the matrix is adapted rather
than “smashed” against the tooth. In that way,
it is possible to achieve both a good separationand the proper anatomy at the same time.
The Halo band’s curvature also has a naturalanatomical shape based on measurementsfrom actual teeth, and the curve at the marginal
ridge creates ideal occlusal embrasure, reducing
finishing time and occlusal adjustments. (Figure 4)
There are no doubts that composite resins
have achieved prominence as a posterior ClassII restorative material. Improvements in bothmechanical and optical properties led to greater
survival rates, sometimes similar to those typicallyand historically found with amalgam restorations.
Still, difficulties persist regarding the insertionof these materials. Poor anatomy with open
and/or deficitary proximal contacts may cause
food impaction, a well-known factor for therecurrence of secondary caries as well as apotential cause for periodontal problems.
As stated by Owens et al. (2016),“An ideally reconstructed proximal
surface, taking into consideration bothanatomical and occlusal factors, aidsin the prevention of food impaction
and subsequent periodontal disease.
The stimulation of oral tissues and/orstabilization of the dentition within an archand the opposing occlusion are achieved
through correctly applied principles ofcurrent, evidence-based methodologies.”

Figure 44

Halo™ Sectional Matrix System White Paper

CONCLUSION
One of the primary challenges for dentists when
restoring posterior teeth using composite resin is
the establishment of anatomically correct
proximal contacts.

As new matrix systems appeared, what wasconsidered a very difficult task began to
become more predictable—that is, achievinga properly contoured Class II restoration withcomposite materials.

It is well-known that sectional matrices andseparation rings for insertion of Class II composite
resin restorations resulted in stronger contact
surfaces compared to the utilization of traditional
circumferential (Tofflemire) bands and woodwedges. The usage of the latter in conjunction withcurrent materials (such as composite resin) may
lead to clinical failure and decreased longevity ofthese restorations.

Today, a new matrix system has moved further
ahead, refining the anatomy provided by thematrix, the adaptability of the ring, and theseparation force of the wedges. The innovations
brought by the Halo Sectional Matrix Systemallow clinicians to achieve a more precise proximal
contact surface with anatomically correct contours
faster and more easily, a fundamental step for
optimum form and function of the dentition as
well as for stimulation and protection of theperiodontal complex.

A properly contoured proximal region with a sealed
interface (no overhangs or porosities) and an
anatomically correct occlusal and ridge anatomy iswhat should be achieved in every posterior
Class II restoration.

REFERENCE
Owens BM, Phebus JG. An evidence-based review of dental matrix systems. Gen Dent. 2016 SepOct;64(5):64-70. PMID: 27599285.

DR. RAFAEL BEOLCHI
Dr. Rafael Beolchi graduated from the University of São Paulo, Brazil in 2000. He
has maintained a private practice since 2001, working mainly in esthetic dentistry
and oral rehabilitation. In 2009, he received a master’s degree in Biomaterials. Helectures around the world, mainly on the advanced handling of dental materials
with an easy step-by-step approach. He now lives in Portugal where he ispursuing his second master’s degree.

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