The expression of MMP-1, -8, and -13 mRNA in the periodontal ligament of rats during tooth movement with cortical punching

Combined effect of photobiomodulation with a matrix metalloproteinase inhibitor on the rate of relapse in rats

OBJECTIVE

To investigate combined effect of photobiomodulation with a matrix metalloproteinase (MMP) inhibitor on the relapse rate in relation to MMP expression in rats.

MATERIALS AND METHODS

Fifty-two rats were divided into four groups according to the treatment modality: control group, irradiation group, doxycycline group, and irradiation with doxycycline group. During a relapse period of 5 days after orthodontic movement, maxillary central incisors were treated by low-level laser therapy (LLLT) as a photobiomodulation and/or doxycycline as a synthetic MMP inhibitor. Relapse rate was evaluated in association with MMP expression at the gene and protein levels.

RESULTS

Relapse rates were increased by LLLT (1.57-fold) and decreased by doxycycline (0.83-fold) compared with the control, showing positive correlation with the levels of expression for all MMPs in the periodontal ligament (PDL). LLLT concomitant with doxycycline administration resulted in no significant differences of relapse rate and MMP expression from the control.

CONCLUSIONS

The combined effect of photobiomodulation with an MMP inhibitor around the relapsing teeth proved to be antagonistic to PDL remodeling activity during relapse. This study suggests a basis for developing a novel biologic procedure targeting the MMP-dependent PDL remodeling to control the relapse rate.

Targeting polymer therapeutics to bone

An aging population in the developing world has led to an increase in musculoskeletal diseases such as osteoporosis and bone metastases. Left untreated many bone diseases cause debilitating pain and in the case of cancer, death. Many potential drugs are effective in treating diseases but result in side effects preventing their efficacy in the clinic. Bone, however, provides a unique environment of inorganic solids, which can be exploited in order to effectively target drugs to diseased tissue. By integration of bone targeting moieties to drug-carrying water-soluble polymers, the payload to diseased area can be increased while side effects decreased. The realization of clinically relevant bone targeted polymer therapeutics depends on (1) understanding bone targeting moiety interactions, (2) development of controlled drug delivery systems, as well as (3) understanding drug interactions. The latter makes it possible to develop bone targeted synergistic drug delivery systems.

Effects of low-intensity laser therapy on periodontal tissue remodeling during relapse and retention of orthodontically moved teeth

This study was designed to investigate the effects of low-intensity laser therapy (LILT) on periodontal ligament (PDL) remodeling during relapse and retention after the completion of orthodontic movement. The maxillary central incisors (n = 104) of the 52 rats were randomly divided into five groups according to the treatment modality: baseline control group without any intervention (n = 8); relapse group without retainer after tooth movement (n = 24); retention group with fixed retainer after tooth movement (n = 24); lased relapse group without retainer after tooth movement and LILT (n = 24); lased retention group with retainer after tooth movement and LILT (n = 24). LILT was daily performed using a gallium-aluminum-arsenide diode laser in a biostimulation mode: wavelength of 780 nm, continuous waves at 70 mW output power, a preset low intensity of 1.75 W/cm(2) in contact mode, resulting in energy dose of 5 J/cm(2) per irradiation for 3 s. The animals were euthanized on days 1, 3, and 7 after removal of the orthodontic appliance. Real-time RT-PCR was performed for quantitative analysis of matrix metalloproteinases mRNA expression. Immunoreactivities of collagen and tissue inhibitor of metalloproteinase were observed on the compression and tension sides. LILT significantly facilitated the expression of five tested MMP mRNAs in both relapse and retention groups. TIMP-1 immunoreactivity was inhibited by LILT in both groups, whereas Col-I immunoreactivity was increased by LILT only in the retention group. These results indicate that LILT would act differently on the stability after orthodontic treatment according to additional retainer wearing or not. LILT when combined with a retainer on the moved teeth may shorten the retention period by accelerating periodontal remodeling in the new tooth position, whereas, LILT on the moved teeth left without any retainer would rather increase the rate of relapse after treatment.