Class V Restorations

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Recent Publication

An article by Dr. Walford covering Class V preparations can be found in the December 2011 issue of Oral Health Journal.

Oral Health Journal, December 2011

This article covers preparation axioms and instrumentation for Incisal Attrition, Class V, and Cusp tip restorations It can be found at http://www.oralhealthgroup.com/news/preparations-in-composite-resin-part-i-principles-and-instrumentation-for-class-v-cusp-tips-and/1000738881/?type=Print%20Archivesexternal link

Class Vs on mandibular bicuspids in Gradia X, shade A3.5

The significance of the composite class V in the quest for excellence

The class V restoration is a watershed in the transition to more advanced composite restorations.Once the practitioner can place a difficult posterior Class V without violating any principles, amalgam or ionomer materials can be discarded. These materials are less attractive and generally rougher than well finished composite.Once simple Class Vs are routinely successful, the practitioner can advance confidently to large and complex composite restorations where tissue bleeding might otherwise be an insuperable obstacle.

For example,
  • multiple surface restorations with subgingival decay or fracture
  • multiple surface restorations with almost no coronal structure
  • patients with poor gingival health, fragile capillaries,(as in the elderly,) uncontrolled or circumstantial hypertension, high anxiety, or blood thinning medications. These conditions all promote ready gingival bleeding, which destroy successful composite placement when not completely managed.

A powerful and reliable method of tissue management eliminates hemorrhage as a clinical challenge. Successful tissue management in Class V restorations has spin-off advantages: it advances us into better crown and bridge work, through better tissue management and isolation during preparations and impressions.

As well, it builds restorative skills in resin placement on other facial surface, such as:
  • freehanding missing cusps from the gumline without a matrix
  • building composite pontics over wire or cast adhesive frameworks
  • repairing fractured porcelain on crowns or bridges
  • layering missing cusps in MODB or larger restorations
  • placing attractive direct veneers on anterior teeth

Perfect saliva control

Another critical step in Class V excellence is achieving perfect isolation. In study club we emphasize active saliva and water evacuation in conjunction with passive absorbent media. When saliva is well controlled, a quadrant of Class Vs can be placed with hardly a swallow on the patient's part over a long appointment. Isolation of this caliber not only makes the patient comfortable, secure, and unlikely to gag, but also provides a stable platform in which the necessary focus and calm for precision cutting and stress-free placement can take place, without iatrogenic slips. Nothing faults an appointment more than a tense, twitching, convulsively swallowing patient due to poor isolation practices. In the lower arch, the hygoformic saliva ejector is the device of choice. See Hygoformic Saliva Ejector

Perfect gingival control

While rubber dam is often best practice in treating occlusal and supragingival surfaces,it is usually an impediment at the cervical. The 212 or other retraction clamps have limited applicability to posterior Class Vs, and often skew proper visualization and access.

Our method is to pre-operatively place a fine, tightly-braided retraction cord impregnated with epinephrine and aluminum sulfate in the sulcus. There are few cords that are appropriate for this application. Because most cords are formulated for crown and bridge use, they are designed to expand the sulcus after placement.In Class V treatment, however, expansion is counterproductive: cord expansion encroaches into the operative site. Few cords meet the specification of retraction without becoming bulkier. Twisted 3-strand cord, or self-expanding braids unwind and interfere with instrumenting the gingival line.

Ferrous salts are the most common astringent product, but they are contraindicated for composite placement. Stain may develop postoperatively in the gingival margin of the composite. If you see brown/black stain on the margins of recently-placed Class Vs, it is probably for this reason.

What does the cord contribute to the process?
  • Constricts blood flow pre-operatively
  • Reduces sulcular fluid flow
  • Visually delineates the gingival margin by increasing contrast ( an ideal cord is dark-colored)
  • Retracts gingiva apically by up to a millimeter, and ,in so doing,follows the architecture of the gingival cuff. This allows placement of the gingival margin following the intrinsic curvature of the gingival collar. Predictable tissue rebound will cover the gingival margin of the restoration, thereby preserving natural aesthetics. Mechanical retraction risks tearing of the attachment apparatus or distortion the gingival line. If retraction is skewed, a skewed aesthetic result can be expected. Worse, subsequent recession from the iatrogenic insult may expose the restored margin to recurrent decay.
  • Reduces or eliminates hemorrhage during preparation; improves preparation visibility and reduces preparation time and operator stress
  • Maintains a hemorrhage-free and sulcular fluid-free field during placement, ensuring uncontaminated bonding
  • Displaces plaque, if present, beyond the intended margins, thereby reducing contamination at placement.
  • Prevents flowable resin from descending into the sulcus during placement, i.e., acts as a resin coffer-dam

What if breakthrough bleeding occurs?

If breakthrough hemorrhage occurs, we use a method we call "Hemostatic Etching" See Hemostatic Etching To quickly summarize the method, at the very end of the etching process (after 10 seconds), our etchant, liquid 37% phosphoric acid, is titrated with a pledglet containing a saturated solution of aluminum chloride. As aluminum chloride is an acid salt, it admixes well. Aluminum chloride exhibits high surface tension, revealed when placed on a hard surface as it "beads-up" like water on a freshly waxed automobile. The liquid phosphoric acid reduces this surface tension and increases penetration into the field.

Clinically, this method confers nearly absolute success without resorting to more heavy-handed methods, such as electrosurgury or laser cautery, and without the loss of time entailed with these resective methods, nor with the potential damage to the attachment or architecture of the gingival collar.

When Hemostatic Etching fails,which it occasionally may in Class V restorations, it indicates that the tissue is deeply inflamed and/or there is a fragility in the patient's clotting system. It is best to re-think the situation at such a time, temporize with a zinc oxide material such as IRM, and adopt a tissue-recovery program involving better hygiene and chlorhexedine rinsing. A definitive final restoration can be placed several weeks later when tissue healing and re-epithelialization has taken place. In the author's experience this is a very rare occurrence: Hemostatic Etching has proven extremely effective over a period of decades of use without post-operative sequelae.

Preparation design for composite as compared to gold foil or amalgam

Our prototypical class V preparation borrows from classic gold foil principles: *occlusal margin perpendicular to the long axis of the tooth, rising to the proximal line angles in a "smiley" outline form.
  • The gingival margin is placed one-half millimeter subgingivally, in the "caries-protective zone", by the simple expedient of placing the gingival margin to the cord-retracted level of the gingival tissue.
  • Axial depth is cut to a consistent plane,to provide aesthetic control, balance contraction effects, and develop definitive finish lines near the line angles.

However, in contrast to gold foil or amalgam,
  • External line angles are radiused, not sharp.
  • Internal line angles are the radiused, from the use of the 330 bur
  • Explicit internal retention features are absent; all walls are divergent.

Oclusal Margin in enamel

The occlusal margin is lightly beveled, with a Conservative Composite Bevel(CCB) See Conservative Composite Bevel. This minimally divergent bevel (6 degrees), exposes rod ends for optimal etching and bonding, and sacrifices no more tooth structure than absolutely necessary.

Conventional wisdom, in contrast, advocates a 45 degree bevel on the occlusal margin of a Class V. In my opinion, this extension is grossly unnecessary and condemns the patient to a lifetime of overly-prominent facial restorations. The CCB, in contrast, produces a virtually invisible, stable, stain resistant occlusal margin that is decay-proof if mated to a resin with suitable shade and opacity, incremented properly, and finished judiciously,

See the examples below,prepared with CCB occlusal margins, and restored using a a number of different resins. The photos illustrate the esthetic potential and consistently controlled results obtainable. This method produces restorations that are 100% retained over time and completely stable clinically.

Instrumentation Sequence

  1. The initial preparation preparation is cut with a sharp 330 FG bur, following the retracted tissue line and preparing the occlusal line into sound enamel. The bur is 90 degrees to the surface of the tooth. This will produce an outline form that is slightly undercut by the divergence of the bur throughout the preparation.
  2. Once cut to depth and outline, a 12-fluted 7406 finishing bur is used to refine all margins, including the gingival and proximal margins. This will produce a slight divergence to all cavosurface margins.

Why the 7406 or 7404 burs?

These large diameter burs smooth out irregularities generated by the small radius of the 330 bur. In some cases a 7404 FG carbide, the next step smaller in the series, is more suitable for gingival and proximal refinement. These large-diameter, unaggressive finishing burs clean up the margin and simultaneously establish a minimally-beveled enamel cavosurface, where the preparation is in enamel, that is rod-end bonded not rod-side bonded. Such a margin is also easy to adapt resin to during placement, and finishes readily and polishes with clarity. The less-aggressive cut of a finishing bur is effective for this step, rather than an operative bur of equivalent diameter, such as a 703. The rake angle and greater depth of the blades of a 703, for example, easily leads to overcutting in both depth and outline form enlargement.

Prep-less Preparations?

Our recommended Class V preparation is similar whether the etiology is abfraction, abrasion, or caries-induced lesions. This author rejects the "prepless" cervical restoration, as inferior in lifespan, and aesthetics, due to
  • uncontrolled prep depth = uncontrolled aesthetics
  • uncontrolled margin exit angle = indefinite finish lines
  • uncontrolled depth = uncontrolled contraction effects
  • uncut tooth structure = sclerotic and uncut enamel that resist etching and produces lower adhesion values, early leakage, and premature loss
  • uncut gingival margins = uncontrolled margin placement with respect to the gingival tissues = caries recurrence
  • uncut occlusal margin = uncontrolled and unartistic occlusal margin inclination
  • un-instrumented proximo-occlusal and proximo-gingival radii = uncontrolled radii placement or depth = thin, unstable and unpredictable margin placement and tendency to produce both undercontour and root damage in finishing
  • no gingival retraction = likely contamination with crevicular fluid,dental plaque or pellicle at the margins during placement.

In summary, the prepless restoration is inferior with respect to almost every important clinical variable.

Restoration Quality

The patient expects a restoration for their hard-earned treatment dollar, not a procedure. A procedure is not a restoration. We shortchange the patient and the profession when we abdicate controlling the variables that impart beauty, longevity and clinical intelligence to the Class V restoration.

Specifics on preferred resins, matrixes, placement methods, curing, instruments, finishing and polishing methodology are omitted in this brief overview. More detail can be found at ClassV