Introduction and Definition

Class II caries (also called proximal or interproximal caries on posterior teeth) refer to carious lesions occurring on the mesial and/or distal surfaces of premolars and molars. In orthodontic literature and clinical practice, the term “Class II caries” has taken on a specific connotation: white-spot lesions (WSLs), incipient decay, or frank cavitation that develop on the mesial and distal surfaces of teeth during or shortly after fixed appliance therapy, especially in patients with Class II malocclusion who often present with deeper overbite, crowding, and plaque stagnation zones beneath archwires and around brackets.

These lesions are one of the most significant iatrogenic side-effects of comprehensive fixed orthodontic treatment. Studies consistently report prevalence rates of new Class II WSLs ranging from 30–73% of patients and up to 96% of teeth during active treatment, with the maxillary lateral incisors, maxillary canines, and mandibular premolars being particularly vulnerable (Richter 2011, Heymann 2013, Julien 2013, Tufekci 2011).

Etiology and Risk Factors Specific to Orthodontic Patients

The development of Class II caries follows the classic ecological plaque hypothesis, but fixed appliances dramatically alter the oral microenvironment:

1. Increased plaque retention sites
– Brackets, bands, archwires, elastomeric rings, and transpalatal arches create hundreds of new stagnation areas.
– Subgingival margins of banded molars and bondable attachments near the gingival margin are especially problematic.

2. Altered self-cleansing
– Lips, cheeks, and tongue can no longer sweep proximal surfaces effectively.
– Deep overbites and Class II elastics often force the lower lip inward, trapping plaque against mandibular premolar distal surfaces.

3. Rapid shift in biofilm composition
– Within days of bonding, Streptococcus mutans and Lactobacillus counts increase 10–100-fold (Rosenbloom 2011).
– Lower resting pH and reduced salivary access accelerate demineralization.

4. Patient-level risk factors repeatedly identified in prospective studies
– Poor oral hygiene (OHI score >2)
– High baseline DMFT
– Frequent sugar intake (>4 exposures/day)
– Irregular orthodontic visits (>8 weeks)
– Duration of treatment >30 months
– Adolescent males (worse compliance)
– Pre-existing WSLs (Enaia 2011, Boersma 2005)

Clinical Presentation and Diagnosis

Early Class II lesions are usually not detectable on bitewing radiographs because they are masked by the bracket or band. This is a critical point that cannot be overemphasized.

Stages (modified from Gorelick 1977 and Øgaard 1989):
– Score 0: No visible WSL
– Score 1: Visible only when air-dried (incipient, reversible)
– Score 2: Visible without drying, matte surface, <2 mm width
– Score 3: Visible cavitation or >2 mm width
– Score 4: Cavitation with dentin involvement

Best diagnostic sequence in practice:
1. Thorough prophylaxis and air drying
2. Visual examination under good light with 3-in-1 air
3. Transillumination with fiber-optic light (especially mandibular premolars)
4. Bitewing radiographs only after debonding or if cavitation suspected
5. Optional adjuncts: QLF (Quantitative Light-induced Fluorescence), DIAGNOdent, or Canary System (limited evidence for routine use in orthodontics)

Prevention Strategies – Evidence-Based Hierarchy

Contemporary systematic reviews (Benson 2021 Cochrane, Derks 2022 EJO meta-analysis) rank interventions from highest to lowest effect size:

1. High-dose fluoride varnish (22 600 ppm F, 5% NaF) applied every 3 months at routine visits
– Reduces WSL incidence by 70% (95% CI 0.18–0.44) – strongest evidence (Stecksén-Blicks 2007, Perrini 2019).

2. Fluoride-releasing bonding composites or glass-ionomer cements for bracket adhesion
– RMGIC (resin-modified glass ionomer) reduces WSLs around brackets by ~45% compared to conventional composite (Rogers 2010, Marcusson 2021).

3. Daily use of fluoride toothpaste 1450–5000 ppm + additional 0.2% NaF rinse
– 5000 ppm toothpaste (prescription) shows superior results in high-risk patients (Sonesson 2019).

4. CPP-ACP (casein phosphopeptide–amorphous calcium phosphate) pastes (MI Paste Plus, Recaldent)
– Moderate evidence (level 1b) when used twice daily in addition to fluoride (Robertson 2011, Beerens 2018).

5. Chlorhexidine varnish
– Weak or no effect on WSL incidence in most orthodontic trials (Øgaard 2006, Kronenberg 2009).

6. Sealants on proximal surfaces before banding/bracketing
– Highly effective in molars (68–85% reduction) if moisture control is perfect (Hu 2020, Jia 2023). Unfortunately, difficult to apply on mesial surfaces of second molars.

7. Professional mechanical cleaning + motivation at every visit
– Still the foundation; no substitute for plaque removal.

Emerging and Controversial Preventive Tools

– Silver diamine fluoride (38% SDF) applied at bonding and every 6 months
– Very promising pilot data show almost complete arrest of existing lesions and prevention of new ones (Maté 2024, Featherstone 2023). Concerns remain about black staining near brackets (aesthetic trade-off).

– Arginine-containing toothpastes (Colgate Elmex Pro-Argin 8%)
– Some evidence of reduced demineralization in situ models; limited orthodontic-specific RCTs.

– Xylitol gum or lozenges
– Modest effect; compliance poor.

Management of Established Class II Caries During Treatment

Scenario 1 – Incipient WSLs (Score 1–2)
– Intensify prevention: 5000 ppm toothpaste, MI Paste Plus 2×/day, 0.2% NaF rinse nightly
– Microabrasion with 6.6% HCl + pumice after debonding (if needed)
– Resin infiltration (Icon®) – gold standard for post-orthodontic WSLs
– 84–96% improvement in appearance and arrest of progression (Knosel 2019, Gu 2023 systematic review).

Scenario 2 – Cavitation discovered mid-treatment
– Difficult situation. Options:
a) Temporary restoration with glass-ionomer (high fluoride release) and continue treatment
b) Remove bracket/band, restore with composite, rebond (adds 1–2 visits)
c) Early deband of affected tooth and permanent restoration
– Mandibular second molars with distal cavitation are frequently extracted or left for post-treatment restorative care.

Post-Debonding Management and Long-Term Prognosis

Most WSLs regress partially within the first 6–24 months after appliance removal due to surface abrasion and remineralization (Øgaard 1988, Al Maaitah 2011). However:

– 10–15% of lesions remain aesthetically unacceptable
– Lesions >2 mm or with cavitation almost never regress completely without intervention
– Resin infiltration performed within 3 months of debond yields best aesthetic outcome

Special Considerations in Class II Malocclusion Patients

Patients treated for Class II division 1 or 2 often have:
– Deep bite → plaque trap on mandibular premolar distal surfaces
– Use of Class II correctors (Forsus, Herbst, Carriere) → additional plaque traps
– Prolonged treatment duration → higher risk

Orthodontists should:
– Delay bonding of lower second molars if hygiene is borderline
– Prefer bondable tubes instead of bands on first molars when possible
– Schedule 8–10 week intervals maximum
– Use open-coil or steel ligatures instead of elastomeric rings when feasible

Expert Consensus and Guidelines

– American Association of Orthodontists (AAO) White Spot Lesion Advisory (2022):
“5% NaF varnish at every adjustment visit is currently the single most effective preventive measure.”

– European Orthodontic Society (EOS) 2023 position paper:
Recommends RMGIC or compomer for bonding in high-caries-risk patients and mandatory prescription of 5000 ppm fluoride toothpaste.

– World Federation of Orthodontists (WFO) informed consent template now specifically lists “permanent white or brown marks on teeth (30–50% risk)” and “possible need for fillings after braces.”

Conclusion

Class II caries remain the most common adverse effect of fixed orthodontic treatment. While complete elimination is unrealistic, a contemporary evidence-based protocol can reduce incidence from >70% to <15% of patients:

1. Identify high-risk patients at start (questionnaire + baseline WSL photos)
2. Bond with fluoride-releasing material when indicated
3. Apply 5% NaF varnish every 3 months without fail
4. Prescribe 5000 ppm toothpaste + nightly fluoride rinse for moderate/high-risk cases
5. Use resin infiltration early post-debond for any aesthetic lesions
6. Maintain rigorous hygiene motivation and short appointment intervals

Orthodontists who adopt this systematic approach not only minimize iatrogenic damage but also fulfill their ethical and medico-legal duty of care in an era of increasingly litigious patients.

References (selected)

– Beerens MW et al. (2018) J Dent Res
– Benson PE et al. (2021) Cochrane Database Syst Rev
– Enaia M et al. (2011) Am J Orthod Dentofacial Orthop
– Gu Y et al. (2023) Eur J Orthod (systematic review on Icon)
– Heymann GC et al. (2013) Angle Orthod
– Hu H et al. (2020) Am J Orthod Dentofacial Orthop (proximal sealants)
– Julien KC et al. (2013) Am J Orthod Dentofacial Orthop
– Knosel M et al. (2019) Clin Oral Investig
– Øgaard B et al. (1988, 1989, 2006) multiple seminal papers
– Perrini F et al. (2019) Angle Orthod (fluoride varnish meta-analysis)
– Sonesson M et al. (2019) Eur J Orthod (5000 ppm)
– Stecksén-Blicks C et al. (2007) Caries Res (Duraphat landmark study)

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