Expedited polychromatic Class IV restoration

When designing or improving an entire smile, be it directly or indirectly, the clinician or technician is a creator, tasked with producing an artistic masterpiece. However, in the case of an incisal fracture, the clinician is less a creator and more a master forger, needing to mimic all optical aspects of the surrounding and adjacent dentition. This can be challenging in terms of shade selection, because the most color variability is typically found at the incisal third of the incisor. This holds especially true of younger patients, who often have prominent translucencies and opacities in this region.

Several tactics can help manage the layering of the composite masses in these scenarios. The use of a palatal stent is a predictable way to do this.1–4 In this technique, a wax-up or mock-up of the fractured area is fabricated on a model and a putty PVS stent or index is fabricated. From that, a thin layer of a strong, semitranslucent composite—typically a nano- or microhybrid—is placed on the stent, replicating the palatal surface. Subsequent layers of composite of varying opacity and translucency are then layered to the facial, creating a seamless restoration (Figs. 1a–1c). Because it is created from a wax-up, occlusal factors should be well controlled.

Figs 1a-c
Palatal stent used to guide layering of Class IV restoration.

A disadvantage with this technique is that a mock-up is needed, either intraorally or with a wax-up on a model. This can be time-consuming and may require a second appointment, which may be difficult or impractical, especially with a pediatric or emergency patient. Additionally, in cases of small fractures, placement of composite masses may be more difficult to manage than with larger fractures.

An alternative approach, the “blank canvas technique,” can provide an expedited polychromatic restoration for small fractures, emergency cases or pediatric patients. It uses a chromatic microhybrid base, followed by tints or opaquers if needed, and covered by a thin layer of an achromatic microfilled composite. The objective is to mask the fracture and provide a lifelike restoration that matches the translucencies and opacities of the surrounding dentition.

Materials
Chromatic microhybrid canvas
A chromatic microhybrid is used as the base or canvas of the restoration. Approximately 80–85% of the restoration will be composed of microhybrid composite.

The advantage of the chromatic microhybrid is twofold. First, its high flexural strength will help resist against occlusal loading.5,6 Secondly, the high opacity of the microhybrid will help mask any fractures.7,8

The issue with microhybrids is that they do not hold a polish well, and may look dull over time.

Tints and opaquers
In lieu of using composite bodies to replicate the varying translucencies and opacities, flowable opaquers and tints will be used for this function.

The polychromatic appearance of the incisal edge is a function of light being either reflected or transmitted through the buccal and lingual surfaces of the enamel. This is an optical effect and not an anatomic feature; the translucent or opalescent phenomena is observed when light is reflected within the crystalline structure of the enamel. When light is transmitted in this same area, an opacity can be seen at the incisal edge.9 This is referred to as a counteropalescent effect or, more commonly, an “incisal halo.”10

A strong opalescence will typically have a strong counteropalescence. To illustrate, Fig. 2 demonstrates an incisal halo that can be observed on the incisal edge of the fracture on tooth #9. A more traditional opalescence/ counteropalescence pattern can be seen on #8.

The appearance of translucency can be replicated with gray, violet or blue tints. To enhance the incisal halo, a white or shade opaquer can be used. Note that flowable opaquers can also be used to reproduce calcifications or maverick effects and help mask fracture lines.11

Microfilled composite
The final and most facial portion of the restoration will be a microfilled composite, which is easy to polish and maintain its polish over time.12 Fig. 3 shows a nine-year follow of a layered composite veneer on Tooth #9. The patient had not seen a dentist since the veneer was completed. Exposed to the same oral conditions, the dull appearance of the microhybrid on the distoincisal portion can be contrasted with the high luster noted on the microfilled composite.

Fig 2
Incisal halo noted on fractured portion of #9. Typical clinical presentation of incisal halo noted on #8 restoration.
Fig 3
Difference between the high-luster microfill, left, versus a microhybrid, after nine years.

Microfilled composites are radiolucent, especially when compared with microhybrids,13 which may present a diagnostic issue on radiographs, especially in interproximal areas. Because they are inherently weak, microfills should not be placed on any areas that will be under occlusal loading.6 Only a small amount will be used, keeping the occlusal loading on the much stronger microhybrid composite.

Case example with tints
A patient was unhappy with a two-week-old restoration on the incisofacial surface of tooth #8 because she thought the central incisors did not match. Upon inspection, it was noted that although the single-shade composite did match the base shade of the tooth, additional color (hue) was needed to mimic the adjacent tooth (Fig. 4).

The teeth were isolated with a heavy latex-free rubber dam (Isodam, 4D Rubber). The existing composite was removed; a chromatic microfilled composite was placed and a white tint (Creating Color, Cosmedent) was applied with a #8 K-file in a horizontal motion to replicate the horizontal pattern (Fig. 5). An achromatic microfilled composite was then added. Fig. 6 demonstrates the immediate postop result, and Fig. 7 reveals the four-year follow-up, demonstrating the retained polish of the microfilled composite.

Fig 4
Initial presentation of unaesthetic single-shade restoration.
Fig 5
#8 K-file used to create horizontal hyperchromatic effects.
Fig 6
Immediate postop photo..
Fig 7
Four-year recall of restoration.

Blank canvas demonstration

PREPARATION

Masking the fracture involves a two-step approach.

The first preparation is a chamfer, 1–1.5 mm long and 0.5 mm deep, along the periphery of the fracture, typically made using a round diamond bur. This preparation is to help mask evidence of the fracture. The chamfer will be covered with a microhybrid.

The second preparation will be a long bevel—often referred to as an infinity bevel or a starburst bevel14—which will help allow the microfilled composite to blend into the body of the tooth. The long bevel is prepared with a flame diamond and placed in an irregular pattern.

Fig. 8 demonstrates the initial situation with an MILF fracture on Tooth #9. Rough and sharp areas were smoothed, and a round diamond bur was used to create the shallow chamfer for the transition zone (Fig. 9). A flame diamond was used to create the infinity bevel (Fig. 10).

Fig 8
Initial preop photo demonstrating Class IV fracture.
Fig 9
Round diamond bur used to create chamfer of transition zone.
Fig 10
Flame diamond used to create infinity bevel.

COMPOSITE LAYERING
A chromatic microhybrid (Renamel Microhybrid, Cosmedent)—Shade A1 in this example—was used to recreate most of the restoration. The microhybrid will compose the entirety of the palatal aspect, and must cover the entirety of the chamfer of the transition zone on the facial aspect. It is not advisable to have the microhybrid go past the chamfer margin, because it may leave no room for the microfilled composite and that aspect of the restoration may look dull over time, creating an optical disharmony.

Note that if the chamfer is not covered completely, a fracture may still be visible. If needed, a flowable opaquer could be added to further mask the fracture line. This creates the “blank canvas.” Excess or occlusion can be adjusted at this point. This is done dry, then an unfilled resin (Complete Unfilled Resin, Cosmedent) is added onto the restoration. Fig. 11 demonstrates the placed and adjusted microhybrid.

Because the adjacent central incisor had a large amount of incisal translucency, as well as a prominent incisal halo, a thin, sharp probe (Matt’s Probe) was used to place gray tint (Creative Color, Cosmedent) on the incisal third, taking care to avoid the incisal edge (Fig. 12).

Fig 11
Chromatic microhybrid placed over chamfer of transition zone, creating a “blank canvas.”
Fig 12
Flowable gray tint placed to simulate translucency.

The inherent opacity of the microhybrid could often serve as the incisal halo at the edge of the tooth, though if desired, the incisal halo can be further enhanced using a flowable opaquer. In this case, a 50/50 combination of white and A1 opaquer, mixed in a resin keeper, was applied to the incisal edge using the probe (Fig. 13). Fig. 14 shows the effect of cured tints and opaquers over the microhybrid composite, revealing a polychromatic effect.

Fig 13
Flowable opaquer used on incisal edge to replicate the incisal halo.
Fig 14
Tints and opaquer cured. Note creation of polychromatic appearance.

To enhance the incisal effects of the tints and opaquers and provide a lasting polish, a small amount of achromatic microfilled composite (Light Incisal, Cosmedent) was placed as a final layer. The composite should cover the infinity bevel created by the flame diamond and should be only on the facial aspect of the restoration, not placed on any occluding areas. Fig. 15 illustrates the placed, shaped microfilled composite. (A chromatic composite could also be used if incisal effects are not pronounced.) Using a combination of discs and polishers, the restoration was finished to mimic the adjacent tooth (Fig. 16).

Fig 15
Achromatic microfill used to overlay facial aspect.
Fig 16
Final outcome.

Figs. 17–21 illustrate some other clinical examples of teeth restored with the technique.

Fig 17
Fig 18
Fig 19
Fig 20
Fig 21

Conclusion
The blank canvas technique presents an expedited method to resolve polychromatic Class IV fractures in cases such as trauma (both adult and pediatric) as well as for small fractures, where it may be difficult to manipulate composite masses or if a palatal stent might be untenable.

Table 1 lists advantages and disadvantages of the technique.

Table 1

Note that nanofilled or nanohybrid composites can also be used for this technique if a smaller inventory is desired, though there may be a slight aesthetic and functional compromise.

References
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2. Manauta J, Salat A, Putignano A, Devoto W, Paolone G, Hardan LS. Stratification in anterior teeth using one dentine shade and a predefined thickness of enamel: a new concept in composite layering–Part II. Odontostomatol Trop. 2014 Sep;37(147):5–13.
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10. Sensi LG, de Oliviera Arajuho F, Marson FC, Monteiro S. Reproducing Opalescent and Counter-Opalescent Effects with Direct Resin Composites. Quintessence of Dental Technology. 2007;28, 1–10.
11. Peyton JH, Gilbert BJ. Tips for preventing a visible fracture line in a Class IV composite. J Cosmetic Dent. 2019;35(1):22–25.
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