Jump to content

ILM – Laser-assisted preventive and curative dental treatment

In cooperation with numerous industrial partners and with the support of public funds, researchers at the ILM are focusing on the optimisation of sealer materials and remineralisation substances as well as on effective and permanent preventive caries treatment.

Application of the demineralisation model to dental erosion on the untreated surface of the dental enamel. Top: Light microscope image of the eroded surface of the dental enamel. Bottom: Microscope image (LSM 510) of the longitudinal section through the demineralised and eroded tooth zone. © ILM

The preventive and curative measures used by dentists to conserve teeth are either based on fluoride therapy in which fluoride ions are topically or systemically added to the hard dental substance or on polymerising plastics (sealers) that seal the enamel surface. If initial damage to the dental enamel surface caused by either acids (initial caries) or by excessive consumption of acid-containing food (erosion) such as fruit or juices remains undetected, the only way to save the damaged teeth is through restorative measures.

For the last few years, the ILM has been working with a number of industrial partners in publicly funded projects investigating the optimisation of sealer materials and remineralisation substances and the effective and permanent prevention of caries. The starting point of the projects was the development of demineralisation models where the dental enamel surface could be specifically damaged in a way that represented the real situation. Four different de- and remineralisation models were established, representing the entire range of tooth decay, from light initial up to strong surface-damaging caries.

The next step was the evaluation of different analysis methods that provided quantitative information relating to the dental enamel damage (demineralisation volume, demineralisation degree) and the curative effect, i.e. the remineralising effect of remineralisation substances. Some of the methods optimised for the assessment of changes in tooth morphology and sealer materials were high-resolution energy dispersive X-ray radiation (EDX), confocal laser scanning microscopy and spectroscopic methods (FTIR) and material testing methods (hardness determination, tribology, thermocycling).

Using equipment, which was specifically adapted to hard tooth material, it is possible to assess the effectiveness of new laser-assisted therapies as well as conventional therapies used for the prevention of caries. These developments also enable the production of innovative materials (nanomaterials, amorphous calcium phosphates) for the sealing and reconstruction of hard tooth material.

The photo shows an electron microscope image with a swamp-like grey structure.<br />
Electron microscope image (Hitachi S-5200) of nanomaterial optimised for the repair of initial caries. © ILM
Optimised laser scanning microscope (LSM510) used for the evaluation of demineralisation and erosion depths. The red arrows point towards the demineralisation zone. The application of the demineralisation model on erosion caries on untreated dental enamel surface. Top: Light microscope image of the eroded enamel surface. Bottom: Microscope image (LSM 510) of the longitudinal section of the demineralised and eroded zone. © ILM

Reconstruction of initially damaged and eroded hard tooth substance

Light microscope image presenting the protective effect achieved by synchronous laser irradiation and protective flour varnish application. Top: intact enamel surface with demineralisation damage. Bottom: Untreated reference sample with loss of surface integrity and major demineralisation damage. © ILM

The goal of this research project is the full remineralisation of the heavily demineralised hard tooth substance resulting from the effect of acids (bacterial metabolism, food). The long-term goal is the restructuring of eroded and pitted tooth surfaces. The natural remineralisation process of the enamel by way of calcium and phosphate ions in saliva and professional fluoridation measures only have a limited repair effect in cases of intensive acid attack. Remineralisation is limited to the enamel layer close to the surface; the lower, more heavily damaged hard tooth substance is not remineralised. Using the laser-assisted remineralisation method developed at the ILM it is also possible to remineralise deeper demineralisation zones.

ILM researchers developed a fluoride-free thermally activatable nanomaterial that is applied using an Er:YAG laser, thus achieving a great depth effect. The chosen acid-stable material matrix has a surface-stabilising effect and maintains the ionic exchange of the hard tooth substance with the oral environment through its diffusible characteristics. In addition, bacteria are prevented from settling in the treated tooth enamel through the formation of narrow diffusion paths (s<4μm). The integrated nanoparticles and the amorphous calcium phosphates bind to the damaged tooth enamel, thereby achieving a remineralisation of 35%, which is the highest percentage averaged across the entire demineralisation zone. Repeated application (n=4) can achieve a build-up of layers on the surface of the tooth enamel, bringing the long-term goal, i.e. the restructuring of eroded hard tooth substance, considerably closer.

Laser-assisted tooth treatment for the prevention of caries

It is envisaged that the laser-induced morphological changes of the enamel close to the surface will lead to a reduced acid solubility of the enamel crystal and hence achieve the permanent prevention of caries. Initial investigations have shown that the use of subablative Er:YAG laser irradiation achieves a preventive effect of up to 70%. However, thermally induced tensions might lead to microfissures on the tooth surface.

In a BMBF-funded research project (Caries prevention with femtosecond laser technology, FKZ: 01EZ0415) the preventive effect of other laser sources, in particular short-pulse lasers (titanium-sapphire laser, Q-switch Nd:YAG laser), was investigated on newly extracted teeth. The teeth were irradiated with 10 different wavelengths, from the ultraviolet range to the near infrared range (#=340nm-1200nm). The triple Nd:YAG laser wavelength (#=355nm) was additionally applied synchronously with an Er:YAG laser irradiation (laser burst operation) that was optimised in terms of thermally induced tensions.

These investigations have for the first time led to a permanent and practical prevention of caries, which achieves a remineralisation of up to 80% without causing damage to the tooth surface or pulp. Total, albeit temporary, acid resistance of the tooth surface can be achieved with preventive fluoride varnish (Fluor-Protektor-Lack, Ivoclar-Vivadent GmbH).


Website address: https://www.gesundheitsindustrie-bw.de/en/article/press-release/ilm-laser-assisted-preventive-and-curative-dental-treatment