Aesthetic dental challenges for the paediatric patient

Composite shade selection

Consider wiping teeth with gauze/polishing teeth prior to restoring. When assessing the composite shade, apply a button of composite to the tooth, without etching or bonding, and spot cure for 5 seconds. The composite button can be removed easily with a flat plastic prior to starting the restoration. In emergency visits, where time is limited, A2 composite on the VITA shade guide is normally a good match for most paediatric trauma cases. In any case, shade correction can be addressed at subsequent visits.

Crown selection and adjustment

When selecting the crown size, it is useful to compare the mesiodistal width of the crown form with the mesiodistal width of the tooth. However, if the tooth has been fractured and complete loss of incisal edge has occurred, the contralateral incisor can be used to gauge the mesiodistal width and the appropriate crown form selected. A hole should be pierced in the mesial or distal incisal angle with a sharp explorer. This will create a core vent for the escape of air bubbles that can become entrapped in the crown. Take care not to damage the proximal seam of the strip crown and ensure this is intact before placement. Ideally curved-ended scissors (eg Beebee Crown Scissors), are used to roughly trim the margins to match those of the fractured tooth. Remember to take into consideration the rise of the gingival margin in the interproximal zone.

Moisture control

Moisture control is of key importance for placement of composite restorations. Use of a dry dam in anterior aesthetic work for paediatric patients is useful as ear ties can be used to stretch the dam and hold it in place. This negates the need for using local anaesthetic, rubber dam clamps and rubber dam frames to isolate the tooth/teeth to be restored. The following isolation techniques can be used. The choice is dependent on the level of patient co-operation and amount of tooth structure remaining. In certain cases, it may be necessary to give local anaesthetic and place an anterior rubber dam clamp to isolate a tooth when there is minimal tooth structure remaining.

Tooth preparation and final crown adjustments

A 2-mm bevel should be placed on the enamel edge to increase surface area for bonding and to blend the transition from composite to enamel. Place the strip crown over the prepared tooth and refine the margins using curved-ended scissors to ensure it seats so that the incisal edge of the crown is level with the adjacent tooth. The margins should sit just below the edge of the fracture line. However, in severe fractures, consider complete coronal coverage with the crown form to improve composite retention. Conduct a primary assessment of the occlusion to avoid lengthy adjustments at the end. Ask the patient to close teeth gently together when the crown is in place to assess for any occlusal interference. Selectively etch the tooth with 37% phosphoric acid, ensuring you protect neighbouring teeth using celluloid strips or PTFE tape, and do not over etch.⁹ Apply primer and bond in accordance with the manufacturer's instructions and light cure. Fill the strip crown with the chosen shade of composite. For improved aesthetics, the strip crown could be lined with a thin layer of enamel shade composite and the centre of the crown filled with a dentine composite shade. Ensure the composite is well packed and there are no air blows.

Seating the crown

Seat with gentle pressure and allow excess to extrude from the strip crown. Use a sharp explorer to remove the excess and apply more pressure to ensure the crown is fully seated and no further excess composite extrudes on pressure. Light cure each aspect for 20 seconds (labially, mesially, palatally and distally). Remove the strip crown gently with a blunt-ended instrument, such as a flat plastic, by wedging it between the strip crown and tooth and gently moving around the tooth, applying gentle upwards pressure. Carry out finishing and polishing and check occlusion after rubber dam removal.

Tooth sensitivity management

It has been suggested that desensitizing toothpastes could be used pre-operatively to reduce sensitivity prior to the treatment appointment.¹⁵ Casein phosphopeptide amorphous calcium phosphate (CPP-ACP) has been recommended to aid remineralization early after eruption when enamel has not fully matured.¹⁶ The casein phosphate stabilizes the calcium phosphate and improves the bioavailability of calcium and phosphate in saliva. This has been shown to significantly improve sensitivity in MIH-affected teeth after 4 months.¹⁷ Tooth Mousse (GC Corporation, Tokyo, Japan) and MI Paste Plus (GC Corporation, Tokyo, Japan) are common dental products containing CPP-ACP. Research has shown that a combination of CPP-ACP and fluoride enhances remineralization.^18,19 Enamelon Treatment Gel (Premier Dental, USA) is available and contains both fluoride (970ppm F) and ACP. Novamin (NovaMin Technology, GlaxoSmithKline, UK) is a toothpaste with an active bioglass particulate repair agent that mineralizes dentine porosities and reduces sensitivity.²⁰ This can be used in Essix retainers overnight. Sensitivity can be managed during treatment by use of a rubber dam and high volume suction to protect other sensitive teeth during treatment.¹⁴ Local infiltration with articaine 4% local anaesthetic,²¹ the use of intraligamental, intra-osseous and palatal anaesthesia as an adjunct to standard local anaesthesia techniques¹⁵ and the use of inhalation sedation for additional pain management²² could also be considered.

Treatment

Superficial enamel hypomineralization and intrinsic yellow/brown staining is amenable to tooth whitening with 10% carbamide peroxide to brighten the surrounding enamel.

Microabrasion

Microabrasion is a useful technique to blend very superficial developmental mineralization defects limited to the enamel layer and internalized superficial stains. Microabrasion uses an acid and an abrasive compound to remove only a superficial enamel layer, and is considered a minimally invasive and safe technique.²⁹ This creates a dense prism-free surface that alters the optimal properties of enamel and is described as the ‘abrosion effect’.³⁰ It may also aid in minimizing the challenges of masking the defect later with a direct/indirect composite restoration or a ceramic veneer if required, following completion of skeletal growth.

Indications for microabrasion include:²⁹

Microabrasion should not be used in those with sensitive teeth, poor co-operation or in those with deep hypoplastic lesions of enamel, such as amelogenesis imperfecta or in cases of dentinogenesis imperfecta.³¹ The main consideration for enamel microabrasion is the depth and location of the hypomineralization and/or staining.³² The depth can be estimated by transillumination using an LED source on the labial or palatal surface.³³ The more light blocked by the enamel opacities/staining, the darker the colour of this area and the deeper the hypomineralization/staining is. This diagnosis should be made in wet conditions as there is a greater difference in refractive index between air and enamel than water and enamel. Microabrasion should be used cautiously in those with a defective lip seal as the anterior teeth will dehydrate more easily and this will accentuate the opacity.³⁰

This technique has several advantages. It is safe, conservative, leaves enamel surfaces lustrous, reduces bacterial colonization of the enamel surface and has lasting, stable aesthetic results.^30,33

Clinical technique for microabrasion³⁴ (Figure 2)

Pre-operative photos and sensibility testing should be taken prior to treatment.

The teeth requiring microabrasion should be isolated using a rubber dam to protect the gingiva.

A slurry is made in a dappen pot using an equal mix of 37% phosphoric acid and pumice and is applied to the teeth using a rubber cup in a slow speed handpiece at 1000ppm for 30–40 seconds. (Alternatively, a wooden stick can be used to rub on the slurry for 1–2 minutes to reduce acid splatter.)

Rinse off the slurry and repeat the application up to three times, if required.

Apply fluoride after microabrasion: 0.2% sodium fluoride liquid or 2800ppm sodium fluoride toothpaste. Toothpaste should be white and not coloured.

Advise patient not to consume coloured food/drink for at least 48 hours following their treatment.

Arrange for a 1-month post-treatment review with photographs.

Alternatively, 6.6% hydrochloric acid with silicon carbide particles (eg Opalustre, Ultradent, UK) may be used up to 10 times for 60 seconds.^29,34 Another option is to apply an equal mix of 18% hydrochloric acid and pumice using a rubber cup or wooden spatula for 5 seconds, up to a maximum of 10 times. For this latter technique, it is recommended to apply Vaseline to the gingiva and a mixture of sodium bicarbonate and water on the rubber dam behind the teeth in case of spillage.³⁵

Treatment of white spot lesions

Carious lesions scoring an ICDAS 0 or 1 have only slight subsurface enamel hypomineralization (limited to external half of enamel in most cases). Remineralization of these opacities may be obtained by fluoride or casein phosphopeptide treatment (CPP-ACP Tooth Mousse).

Lesions scoring ICDAS 2, have a greater depth of subsurface demineralization without surface cavitation. Remineralization treatments may not guarantee full depth re-precipitation of lost minerals, resulting in a residual white opacity that may stain because of the inclusion of external pigments over time. The treatment of choice is resin infiltration with Icon.¹⁰

Fluorosis

Fluorosis is hypomineralization of the enamel as a result of excess fluoride being incorporated during its formation.⁴³ It is caused by systemic absorption of fluoride during dental development. There is, therefore, a delayed diagnosis as teeth must be assessed clinically. Fluorosis is characterized by symmetrical involvement of homologous teeth. The extent of fluorosis and the teeth involved can help to estimate the time of excessive fluoride ingestion. Clinically, there are thin, horizontal, white lines, which may be accompanied by irregular chalky zones creating a parchment-type appearance.¹⁰ Discolouration can occur due to infiltration of exogenous pigments. In more severe cases, there are alterations to the fluorotic enamel from physical and chemical substances in the mouth resulting in pits and fissures.¹⁰ Fluorosis classifications include Dean's Index and Horowitz's Tooth Surface Index of Fluorosis (TSIF). The TSIF classification includes extent of enamel involvement and the clinical picture (Table 4). Histologically, fluorosis (TSIF ≤4) have a hypermineralized surface layer without pitting, and a hypomineralized subsurface layer similar to white spot lesions, which usually extends less than one-third into enamel.¹⁰

Chronological hypomineralization (Figure 3)

Chronological hypomineralization of a permanent tooth results from periodontal trauma or peri-apical infections affecting primary teeth. Age at the time of the trauma can present with varying sequelae. Trauma and consequent disturbance during the maturation phase of amelogenesis results in hypomineralization, and trauma during the secretion phase can lead to hypoplasia.¹⁰ Clinical presentation of the hypomineralizations can vary. Generally, they are well-defined white lesions affecting the incisal third of crowns. They can exhibit brown discolouration when haemorrhage has occurred into the hypomineralized area.¹¹ They are asymmetrical insofar as they can affect the opposing teeth and not usually contralateral teeth. Histologically, they are similar to white spot lesions and fluorosis in that they have a subsurface layer of hypomineralization with a superficial layer of mineralized enamel. However, there is great variation in the depth of this hypomineralized layer and in the angle formed with the enamel surface layer.¹⁰

Treatment

The issue lies in accessing the area of hypomineralization that lies beneath a deeper layer of healthy enamel than in cases of white spots and fluorosis. Resin infiltration alone would require excessive pre-erosion treatment with hydrochloric acid to expose the hypomineralized inner layer. The option is then to remove all or part of the lesion. Removing the entire lesion is destructive and risks dentine exposure. If removing only the healthy overlying enamel to access the ceiling of the lesion, will the adhesive bond to the hypomineralized enamel be satisfactory? Studies have shown it is difficult to achieve direct adhesion to hypomineralized enamel.⁴⁹ In light of these challenges, a new protocol for deep infiltration has been developed.⁴¹

What cases are suitable for the deep infiltration technique?

This technique is designed for cases where the hypomineralization originates from the enamel–dentine layer, as in MIH, or for opacities with deeper hypomineralization arising from the surface (eg severe fluorosis, some cases of chronological hypomineralization). The use of a blue light-curing unit labially/palatally can help to assess the depth of the hypomineralization. It has been suggested that for areas where the blue light shines through as dark blue/black, the hypomineralization is considered deep and the deep infiltration approach should be used.⁵⁰

Aetiology

Tooth discolouration can impact on a person's self-image, confidence and physical attractiveness.⁶² The cause of discolouration after root canal treatment is most commonly due to breakdown products of haemoglobin or other haematin molecules from the dental pulp, often following trauma.⁶³ Iatrogenic causes of discolouration include dental materials such as gutta percha or cements in the coronal part of the access cavity, and coronal pulpal remnants left in access cavity (Table 6).²⁴ With the availability of magnification for root canal treatments and wide availability of long shank/gooseneck burs or heated instruments for removal of coronal gutta percha, iatrogenic causes of staining should be avoided.

The clinical uses of mineral trioxide aggregate (MTA) and other bioactive cements include, but are not limited to, pulp capping, pulpotomy, perforation repair and apical plugs during apexification. The drawbacks of MTA include its relatively long setting time, difficult handling, high cost and discolouration potential.⁶⁴ Valles et al showed that Biodentine was more colour stable than ProRoot White MTA, Portland cement with bismuth oxide and Angelus White MTA under a combination of light and anaerobic conditions, similar to the clinical setting.⁶⁵

Discolouration using MTA (ProRoot, tooth-coloured ProRoot, Angelus, white Angelus) may result from blood contamination during placement, interaction of bismuth oxide with sodium hypochlorite irrigation or placement of MTA in a light, oxygen-free environment.⁶⁶ To avoid MTA-related discolouration, placement of a double layer of dentine bonding agent in the access cavity prior to cement placement in the root canal⁶⁷ or careful avoidance of blood contamination during MTA placement has been recommended. Alternatively, Biodentine could be considered because it has been shown to discolour less than MTA. Tooth discolouration resulting from bioactive endodontic cements is amenable to treatment by internal tooth whitening.⁶⁸

Treatment (Figure 6)

The conservative treatment of choice in children for non-vital discoloured anterior teeth is the inside/outside open bleaching technique with 10% carbamide peroxide.

Mechanism of action of 10% carbamide peroxide

Carbamide peroxide consists of equal amounts of hydrogen peroxide and urea. Carbamide peroxide releases (ie is equivalent to) approximately 3.5% hydrogen peroxide and a 3:1 relationship in terms of tooth whitening strength. The hydrogen peroxide breaks down into active free radicals that enter the dentinal tubules and decompose the molecules responsible for staining, thereby lightening the discolouration.

The inside/outside closed bleaching technique²⁴

This technique seals 10% carbamide peroxide into the access cavity using a temporary restorative material. The patient carries out single tooth whitening externally.

Benefits of open and closed inside/outside bleaching techniques

Risks of internal bleaching techniques

Both techniques require good patient compliance and this should be explained to the patient and parent/guardian as part of informed consent. The patient must understand that, in the open technique, they need to return for closure of the access cavity to prevent bacterial ingress into the root canal. In both techniques, it is important to stress that neighbouring composite restorations will not bleach with the tooth and these may require replacement after the desired tooth shade from tooth whitening is achieved. Internal bleaching carries the risk of invasive cervical root resorption. This has been defined as a type of external root resorption characterized by invasion of root dentine by fibrovascular tissue derived from the periodontal ligament.⁷⁰ Heithersay investigated 257 teeth for the causative factors of invasive cervical resorption. He concluded that trauma, orthodontics, intra-coronal tooth whitening, and surgery were strongly associated.⁷¹ The literature states that the use of 30% hydrogen peroxide, application of heat and a lack of a cervical barrier prior to commencing tooth whitening are risk factors for invasive cervical resorption following intra-coronal bleaching.^72,73 10% carbamide peroxide releases only 3.5% hydrogen peroxide and the authors could find no cases of invasive cervical resorption reported from its use in the literature. Tooth whitening can cause gingival irritation. However, 10% carbamide peroxide's original purpose was as an oral antiseptic and therefore, gingival contact is not a concern. The urea present has beneficial cariostatic and antibacterial effects that improve gingival scores in patients who are likely to have poor gingival health from lack of motivation due to sensitivity.²⁴

Restorative options

Tooth whitening could be considered a first-line option because it is conservative of tooth structure and will, at the very least, lighten the base tooth colour, making masking discolouration with restorative materials easier. If the patient is under 18 and the discolouration is still of concern, composite veneers using the strip crown technique described earlier could be considered as an interim solution until the patient's gingival tissues have matured and skeletal growth is complete At that stage, a porcelain veneer may be considered as a definitive restoration, bearing in mind that it could be destructive of hard dental tissue.