The meticulous handling of details prior to veneer bonding directly influences the final outcome of veneer restoration, encompassing factors such as color, bonding retention, accurate and stable positioning, among others. Each detail must be meticulously addressed. Therefore, a four-handed operation is essential, where both the dentist and the assistant need to be thoroughly familiar with the preparatory work for veneer bonding.
Upon receiving the finally prepared by China HINNO Dental completed veneer, the first step is to inspect the seating of each restoration and the margin adaptation on the model.
Each tooth’s seating should be checked individually, followed by the examination of the contact relationship between each veneer and the adjacent teeth to ensure uniform pressure. Once the inspection is confirmed as satisfactory, an appointment with the patient can be scheduled. In fact, these inspections are rigorously conducted by HINNO Dental Lab before shipment to ensure no issues.
Remove the patient’s temporary restoration and thoroughly clean the tooth surface of any residual temporary cement using a scaler or a low-speed sanding disc, as any residue may interfere with the seating of the restoration.
As with inspecting the restoration on the model, the same process should be carried out on the teeth. First, check the margin adaptation of each tooth, and then the contact areas. Good seating on the model does not necessarily equate to good seating in the mouth.
Precautions:
If there are gaps at the margin of a restoration, do not attempt to compensate with bonding resin; instead, it must be redone.
Similarly, if the contact point between two teeth is too loose or has gaps, it must also be redone without compromise.
If the contact point between two teeth exhibits excessive pressure, do not rush to adjust the proximal contact; this is a task for after bonding and does not require redoing.
If the contact point obstructs the seating of the porcelain veneer, it needs to be redone. This phenomenon is relatively uncommon.
If the restoration seats well in the mouth, the next consideration is color. There are various porcelain veneer bonding kits, almost all of which have a trial bonding function to preview the color effect after bonding and confirm with the patient before proceeding with the final bonding.
Install the rubber dam for the patient after the trial bonding, not before, as the tooth color may change due to dehydration after installing the rubber dam. After installing the rubber dam, thoroughly clean the prepared tooth surface using a polishing cup and non-fluoride polishing paste.
Porcelain Surface Treatment
As with inlays, a device is needed to handle the restoration. Typically, a filling instrument with sticky wax is attached to the labial side of the porcelain veneer. Handle with care to prevent the restoration from falling off.
Due to its strong corrosiveness and toxicity, hydrofluoric acid is prohibited from clinical use. However, it is indispensable for porcelain veneer treatment. When using it, keep it away from the patient, and the practitioner should wear gloves, a mask, and protective glasses to avoid danger. Never use it inside the patient’s mouth.
It is recommended to etch the restoration’s inner surface with 10% hydrofluoric acid for 90 seconds to create micropores for micromechanical retention with the adhesive. Then, rinse thoroughly with plenty of water, but rinsing alone is insufficient as some invisible contaminants may remain.
Place the rinsed restoration in 95% ethanol or acetone and ultrasound clean it for 4-5 minutes in the usual ultrasonic cleaner for instruments to completely remove residuals and remineralized salts on the porcelain veneer surface.
Silanization is an indispensable step that allows chemical bonding between the restoration and the bonding resin. Silanization of porcelain is a delicate and sensitive process that must be performed according to scientific guidelines.
Apply a layer of silane coupling agent to the inner surface of the porcelain restoration, then blow-dry to evaporate the solvent. Repeat this process three times. To enhance silane activation, dry the restoration in a 100°C oven for one minute or with an electric blow dryer for two minutes, ensuring complete removal of moisture and other contaminants.
After drying, apply a thin layer of resin adhesive to the inner surface of the restoration without light exposure. Then, apply the bonding resin without bubbles, as bubbles can create light-absorbing areas affecting the future color effect. Place the restoration under a light shield.
Preparation of Tooth Surface
Isolate adjacent teeth and etch the tooth surface with 35% orthophosphoric acid for 30 seconds, then rinse with water and dry. The best drying method is to drop a drop of ethanol on the tooth surface and blow-dry thoroughly.
Apply a thin layer of bonding agent to the tooth surface, also without light exposure. From this point on, keep the operating area away from strong light to prevent premature resin curing. Remove the restoration from under the light shield and seat it slowly. Excess bonding resin will extrude from the edges until the restoration is fully passively seated.
Use a rigid instrument, such as a probe, to remove the extruded bonding resin in a direction parallel to the restoration surface. A soft brush is not recommended as it may push the bonding resin into the gingival sulcus or proximal contacts, making it difficult to remove. Use a light-curing lamp with an intensity higher than 850 mW/cm² to intermittently cure the lingual side for 90 seconds and then the labial side for 60 seconds. It is advisable to place an oxygen barrier on the margins to ensure complete curing of the exposed bonding resin, forming a good marginal seal.
After curing, use a No. 12 blade to gently remove excess resin to avoid damaging soft tissues. Then, use a rotating instrument to polish the restoration’s edges.
If bonding multiple veneer restorations, bond them one by one, repeating the above steps each time. Do not bond multiple restorations simultaneously to save time.
Occlusal Adjustment
If the procedure is properly followed, porcelain veneers are very secure after bonding. However, if the porcelain veneer restoration exhibits early contact, the risk of fracture is extremely high or inevitable. Therefore, occlusal adjustment after bonding is essential (except for open-window veneers).
Use differently colored occlusion paper to check for any early contact points in the patient’s centric occlusion, protrusive occlusion, and lateral occlusion, striving to restore the patient’s original occlusion relationship.
Reviewing the content above, bonding includes the following steps:
- Restoration inspection
- Trial bonding
- Porcelain surface treatment
- Tooth surface treatment
- Bonding
- Removal of excess adhesive
- Occlusal adjustment
- Polishing
Four points deserve special emphasis: - Always bond porcelain veneers under the isolation of a rubber dam.
- When bonding multiple porcelain veneers, bond them one by one.
- Thoroughly remove excess bonding resin.
- Occlusal examination after bonding is indispensable.
