1. Introduction

Parkinson’s disease (PD) is a progressive illness of the central nervous system, which is characterized by movement and motor activity disorder, accompanied by psychological and social disturbances [1]. Nearly one million Americans are living with PD and approximately 60,000 are diagnosed with PD each year. The cause of PD is unknown, and although there is presently no cure, there are available treatments such as medication and surgery to manage its symptoms [2]. PD is a neurological condition involving loss of dopamine-producing neurons in the substantia nigra of the basal ganglia [3]. PD and Parkinsonian signs that occur in old age are expected to increase dramatically in the next decades [4]. Therefore, there is an urgent need to establish more effective treatments. Four motor symptoms are considered cardinal in PD: tremor, slowness of movement (bradykinesia), rigidity, and postural instability [5]. Moreover, a person with PD has two to six times the risk of developing dementia compared to the general population [5] [6]. Previously, I reported cases in which severe dementia improved dramatically after denture placement [7]. Considering the above possible association between PD and dementia, therefore, there may be a close relationship between dental health and brain function. However, no report has been published on a connection between dental treatment and PD. Here, I report on two cases in which PD symptoms improved after dental treatment.

2. Case Reports

2.1. Case 1

Subject, Methods, and Result

The subject was a man in his 60s, who was diagnosed with PD more than 10 years ago. He could not stand by himself due to rigidity (Figure 1), and he experienced tremor in his fingers, and masked face (hypomimia). He spoke very little. He had tried seven kinds of medication, which were effective at the onset of the disease, but gradually became ineffective. At his first visit, he hardly received medical treatment. Then, by consulting his oral cavity, more than five dental caries and two teeth which need root canal treatment are found. I performed two root canal treatments on this patient, and the infected dentin in the oral cavity was removed as much as possible and filled with glass ionomer cement. All the dental materials used were selected using the Bi-Digital O-Ring Test [8] [9]. Immediately after the treatments, he was able to walk by himself, albeit with some bradykinesia, postural instability, and masked face. As a result of the root canal fillings and subsequent prosthetic treatments, his symptoms of PD almost disappeared one month later, and his daily life became normal without any other treatment (Figure 2). No side-effects were seen with this treatment. For more than two years past, he is still in good condition without any medical treatment.

In order to watch the actual experiment described in this case, please visit the YouTube movie:

Dental treatment for Parkinson’s disease, part 1 https://www.youtube.com/watch?v=vbDwGoI1o7c

(last checked: 15 Feb 2020).

2.2. Case 2

Subject, Methods, and Result

The subject was a woman in her 40s. She was diagnosed with PD independently at three hospitals six years ago, and her symptoms had gradually worsened. The main symptom was rigidity, accompanied by speech problems and knee joint pain. The last three years, she had been taking Levodopa (L-Dopa). This medication was very effective against rigidity, but did not improve the speech disorder and knee pain. The effect of a single drug administration lasted about half a day. When the drug was no longer effective, the rigidity recurred. At her first visit, she was receiving medication at the medical department. At that time, her oral condition was no subjective symptoms, though presented an apical lesion in the lower left first molar. I extracted the lower left first molar under infiltration anesthesia. Twenty minutes after the tooth extraction, she was able to run, and her knee pain during knee flexion and speech problems also improved. Later, she also succeeded in reducing the medication. No side effects were seen with this treatment. After that, although a slight rigidity recurred, speech disorder and knee pain disappeared, as well as quantity of taking medicine (drug amount) reduced for more than three months. It shows that by performing dental prosthesis procedures at the defect region, her PD condition improved.

In order to watch the actual experiment described in this case, please visit the YouTube movie:

Dental treatment for Parkinson’s disease

https://www.youtube.com/watch?v=fthGQbm2g9s

(last checked: 15 Feb 2020).

3. Discussion

PD is a chronic and progressive neurological disease, meaning that symptoms continue and worsen over time. Thus far, it has been impossible to reverse the progression of the illness through medication or surgery. There are few reports of the effects of dental treatment on PD so far. However, the dental technique presented here did not only alleviate the symptoms, but also to reverse the progression of the illness without any side-effects. In case 1, even medication worked well in the initial stage, the effect was not lasting because of medicine resistance. However dental treatment was effective when any medical approaches were no longer dealing with the subject’s symptoms. Since so far, despite no medical treatment, he has been in good condition for more than two years. In case 2, medication worked well for the subject at the first consultation, but the effect was not long-lasting. Then after taking the dental treatment, the subject’s condition improved. After that, although a slight rigidity recurred, speech disorder and knee pain disappeared, as well as quantity of taking medicine (drug amount) reduced for more than three months. The underlying reason why this treatment was so dramatically successful remains unclear. More investigation is needed with multidisciplined cooperation. I hypothesize that harmful signals by apical lesions, periodontal infections, and infected dentin may be transmitted from the oral area to the midbrain via the trigeminal nerve, which is the largest of the 12 cranial nerves (Figure 3). The trigeminal nerve reaches the midbrain (mesencephalic nucleus of trigeminal nerve, Figure 4) and may affect the substantia nigra in the midbrain. The substantia nigra is a basal ganglia structure located in the midbrain that plays an important role movement [10]. PD is characterized by loss of dopaminergic neurons in the substantia nigra pars compacta [11]. I have previously reported the relationship between dental health and other pathological conditions [7] [12] [13] [14] [15]. A systemic disease, in which dentistry is involved in the cause, may be considered intractable. This illness may be such a case.

4. Conclusion

I herein report on two cases of PD improved through dental treatment. Harmful stimulation by apical lesions, infected dentin, and periodontal disease was transmitted to the midbrain via the trigeminal nerve, which may affect the substantia nigra, reducing the amount of dopamine in the midbrain. Removal of harmful stimuli from the oral area may allow the substantia nigra to regain its proper function and produce sufficient dopamine. Since no treatment is considered to reverse the progression of PD, it is significant to find new treatments. To clarify more details of this action, further research is needed in the future with the cooperation of dentistry, medicine, and other medical fields.

Acknowledgements

The subjects agreed for his case to be reported.