A novel tooth-coloured crown system to treat dental caries in children – Development and validation

Background and objectives: Traditional dental caries treatment in children involves surgical removal of the infected dental tissues and subsequent restorations using a filling material. The Hall Technique is known as a ‘no drill, no pain’ restorative procedure using metal preformed crowns. Although clinically effective, this technique has a major aesthetic limitation, the crown is silver rather than tooth-coloured. The objectives of the current study were to develop a novel tooth-coloured crown system for treatment of dental caries in children, and to evaluate the proof of concept, using benchtop testing to examine cementation strength, surface hardness and wear resistance, an ex vivo model for heat penetration, and an in simulo trial for acceptability to clinicians and marginal adaptation. Methods: A variation of novel thermoplastic resin preformed systems (PFC) were developed. For mechanical testing, metal PFCs were used as controls. The novel thermoplastic resin crown materials were tested for heat transfer into the dental pulp, cementation bond strength, surface hardness and wear resistance. To validate the new crown systems, six clinicians evaluated five different crown designs and the clinical protocol and gave feedback via a post-trial questionnaire; responses were statistically analysed. The marginal seal of the different PFCs were analysed under an optical microscope and micro-CT scanner. Results: The tooth-coloured thermoplastic crown materials did not show clinically significant heat transfer to the pulp space and bonded better with resin than a glass ionomer (GIC) cement. Initially, metal PFCs had significantly better surface hardness and wear properties; however, after modifying the thermoplastic resins, they showed comparable wear properties up to 12 months. The response of clinicians to the new treatment method was overall positive or neutral (average score on 5-step Likert scale of 3.57±0.24). Clinicians significantly favoured the aesthetics of the tooth-coloured crowns over metal PFCs (3.67±0.28, p=0.002). All six participants commented that the new treatment would be “more acceptable to the child and the parent”. Recommendations were made to improve the clinical utility of the novel tooth-coloured crowns. Conclusion: The novel thermoplastic PFCs were found to have acceptable marginal seal, cementation bond strength and the heat generated from thermoplastic crown materials did not affect the pulp. The novel tooth-coloured crowns were significantly better aesthetically than the metal PFCs and were acceptable in a clinical simulation trial. The dental practitioners reported that they were more likely to use these as an alternative to the metal PFC. There is a need for a further in simulo trial, incorporating the improved functional characteristics of the prototype crowns, prior to conducting a clinical trial.