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Thermotransduction and heat stress in dental structures during orthodontic debonding

Effectiveness of various cooling strategies

Temperaturweiterleitung und Hitzebelastung dentaler Strukturen im Rahmen des orthodontischen Debondings

Effektivität unterschiedlicher Kühlverfahren

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Journal of Orofacial Orthopedics / Fortschritte der Kieferorthopädie Aims and scope Submit manuscript

Abstract

Objectives

Recent studies have indicated possible thermal damage to pulpal tissue during orthodontic debonding. This study aimed to analyze the thermal loads acting upon dental structures and their transfer to the pulp during orthodontic debonding. Specific goals were to analyze temperature changes in local dental tissues, thermotransduction to the pulp cavity, and the effectiveness of common cooling strategies and of simulated intrapulpal circulation.

Materials and methods

Metal brackets were bonded to five extracted human molars and subsequently removed. While a carbide bur was applied to debond the residual composite from the tooth surface, various cooling strategies (no/air/water cooling) were employed with or without simulated intrapulpal circulation, accompanied by temperature measurements with a thermographic infrared camera on the enamel surface and with measuring probes in the pulp cavity. Appropriate evaluation software was used to calculate the enamel-to-pulp temperature gradients and for statistical analysis.

Results

Significant differences in temperature rise and heat development over time, both on the enamel surfaces and in the pulp cavities were found. The mean temperature rises associated with no/air/water cooling were 90.7/46.6/9.2 °C on the enamel surface versus 9/8/4.6 °C inside the pulp. However, thermotransduction from enamel to pulp remained below 10 % of the surface measurements in all groups. Simulated intrapulpal microcirculation was found to significantly reduce intrapulpal temperature levels.

Conclusion

During debonding of residual bracket adhesives, provided that a carbide bur is properly used, our data indicate a low risk of reaching critical intrapulpal temperatures even in the absence of dedicated cooling and no risk if the instrumentation is accompanied by air or water cooling.

Zusammenfassung

Zielsetzung

Aktuelle Studien weisen auf eine Gefahr einer thermischen Schädigung pulpalen Gewebes während des kieferorthopädischen Debondings hin. Ziel der vorliegenden Studie war es, die Temperaturbelastung dentaler Strukturen und deren Transduktion zur Pulpa hin zu analysieren. Hierbei sollten insbesondere die tatsächliche lokale Temperaturveränderung der beteiligten Gewebe, die stattfindende Temperaturübermittlung zum Pulpenkavum, die Effektivität gebräuchlicher Kühlverfahren und der mögliche Einfluss einer simulierten pulpalen Zirkulation untersucht werden.

Material und Methoden

An 5 extrahierten humanen Molaren wurden Metallbrackets in Schmelz-Ätz-Technik befestigt und anschließend entfernt. Das Debonding des auf dem Zahn verbliebenen Komposits wurde mit einem Hartmetallfinierer in Kombination mit verschiedenen Kühlmethoden (Wasserkühlung, Luftkühlung, keine Kühlung) sowie ohne und mit Installation einer experimentell simulierten Pulpazirkulation Durchgeführt. Temperaturmessungen auf der Schmelzoberfläche erfolgten mittels einer Infrarotkamera, im Pulpenkavum mit Messsonden. Die Kalkulation der Temperaturgradienten sowie die statistische Analyse wurden mit der Software Prism durchgeführt.

Ergebnisse

Die Anwendung unterschiedlicher Kühlverfahren ergab signifikante Unterschiede bezüglich des Temperaturanstiegs und des zeitlichen Verlaufs für die Schmelzoberfläche und das Pulpenkavum. Für den Zahnschmelz wurde eine Temperatursteigerung von durchschnittlich 90,7 °C (ohne Kühlung), 46,6 °C (Luftkühlung) und 9,2 °C (Wasserkühlung) gemessen werden. Sie betrug im Pulpenkavum hingegen ohne Kühlung 9 °C, mit Luftkühlung 8,2 °C und mit Wasserkühlung 4,6 °C. Die Temperaturübertragung vom Zahnschmelz zur Pulpa war unter Verwendung der getesteten Kühlmodalitäten signifikant unterschiedlich und lag in allen Gruppen unter 10 % der extern gemessenen Temperatur. Die Simulation einer Mikrozirkulation reduzierte insbesondere die intrapulpalen Messwerte in signifikantem Maße.

Schlussfolgerungen

Die vorliegenden Daten stellen die thermalen Effekte und deren Weiterleitung von extrakoronal in die Zahnpulpa dreier häufig verwendeter Debondingverfahren gegenüber und vermitteln Einblick in den zeitlichen Verlauf sowie die tatsächliche Belastung dentaler Strukturen. Auf Grundlage der erhobenen Daten kann bei regelrechtem Entfernen des Klebers mit Hartmetallfinierern sowie unter Verwendung einer Luft- oder Wasserkühlung von keinem und bei Unterlassung einer zusätzlichen Kühlung von einem geringen Risiko des Erreichens kritischer pulpaler Temperaturen ausgegangen werden.

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Acknowledgments

We wish to thank Ms. Beate Schiermeyer for technical support in performing the experiments. The study was supported by University of Bonn Medical School.

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Author notes

    Authors and Affiliations

    1. Department of Orthodontics, University of Bonn, Bonn, Germany

      Philipp Kley, Katharina Küpper, Andreas Jäger & Michael Wolf

    2. Department of Operative Dentistry and Periodontology, University of Bonn, Bonn, Germany

      Matthias Frentzen & Susann Kecsmar

    3. Department of Operative Dentistry and Periodontology, University of Marburg, Marburg, Germany

      Andreas Braun

    4. Private Orthodontic Office, Kieferorthopädie am Friesenplatz, Cologne, Germany

      Katharina Küpper

    5. Department of Orthodontics, University of Jena, Jena, Germany

      Michael Wolf

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    1. Philipp Kley
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    Correspondence to Michael Wolf.

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    Conflict of interest

    P. Kley, M. Frentzen, K. Küpper, A. Braun, S. Kecsmar, A. Jäger, and Michael Wolf state that there are no conflicts of interest.

    The accompanying manuscript does not include studies on humans or animals.

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    PD Dr. med. dent. Michael Wolf.

    P. Kley and M. Wolf contributed equally to the manuscript.

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    Kley, P., Frentzen, M., Küpper, K. et al. Thermotransduction and heat stress in dental structures during orthodontic debonding. J Orofac Orthop 77, 185–193 (2016). https://doi.org/10.1007/s00056-016-0023-7

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