The effects of low level laser therapy and led- meditated photobiomodulation on the pulp canal volume of human premolars undergoing orthodontic tooth movement

Abstract

Introduction:

The purpose of this present study was to investigate the effects of low level laser therapy and LED-meditated photobiomodulation on pulp volume using Micro-CT.

Methods:

To investigate the effects of low level laser therapy (LLLT) and LED photobiomodulation (LED PBM) on pulp volume, Micro-CT scans of maxillary premolars that were collected previously as part of 3 different randomized clinical trials was used.

All three trials included 20 patients each that were selected from the orthodontic waiting list at the Sydney Dental Hospital, requiring bilateral maxillary first premolar extractions. In each patient the maxillary premolars on one side were randomly assigned as the experimental side and received either LLLT or LED PBM, and the other side premolars served as control. In Trials 1 and 2, premolars on both sides were tipped buccally to induce orthodontic root resorption using 150 g of force for 28 days, after which they were extracted and scanned using Sky Scan1171 desktop Micro-Ct system.

In Trial 1: The experimental premolars received LLLT (808nm AIGaAs diode laser), and the control premolars received sham-laser on days 0,1,2,3,7,14 and 21. Laser setting were 0,18W power, 1.6J per point and duration of 9s continuous mode and 4.5s for pulse mode.

In Trial 2: The experimental premolars received LED using OrhoPulse device, 850nm wavelength, 60mW/cm power continuous from approximately fifty-four LEDs spaced 5mm apart in two banks of 3X9 elements embedded within a flexible silicone matrix. The Led array is specified to produce a power density of 60 mW/cm.

Trial 3 had a slightly different methodology, in that the aim of Trial 3 was to assess the effects of LLLT on repair of orthodontic root resorption crater volume. Therefore in this study after the active force was applied for 28 days, the active appliances were removed and the teeth were retained for 6 weeks. LLLT commenced with weekly laser applications on the experimental side and the other side received sham laser to blind operator and the patients. After 6 weeks, the maxillary first premolars were extracted and scanned with Micro-CT. The setting for the LLT commenced with weekly laser application on the experimental side and the other side received sham laser to blind the operator and patients. After 6 weeks, the maxillary firs premolars were extracted and scanned with Micro-CT. The setting for the LLLT used in Trial 3 were: Continuous beam 660-nm, 75-mW aluminum-gallium-indium phosphorous laser with 1/ex2 spot size of 0,260 cm2, power density of 0,245 W/cm2 and fluence pf 3.6J/cm2. Avizo 3D software 2019 was used to digitally measure the volume of the pulp tissue. 120 premolars from the three studies were segmented into 3 types of tissue as crown, canal and pulp using tresholded intensity values related to material attenuation. To minimize variability between samples, only the volume from the cementoenamel junction (CEJ) to the apical tip of the tooth was considered for evaluation. The scale for all of the datasets was 17.66 micron. The ‘Material Analysis’ function of the Avizo software was used to analyse the segmented components. This provided a quantification of the volume of each material to be compered as a ratio between pulp and the entire tooth. All measurements were performed by the same operator.

The samples will be analysed in 2 manuscripts as follows:

1. Effects of low laser therapy and photobiomodulation on pulp volume of maxillary first premolars. 2. Effects of 808nm AIGaAs diode laser versus 660-nm, 75-mW aluminum-gallium-indium phosphorus laser on pulp volume of maxillary first premolars.