Parkinson’s disease (PD) is a complex multisystem neurodegenerative disorder with onset in the fifth or sixth decade of life.^[1] PD related physiological changes can impair bodily functions and balance as well as induce changes in the stomatognathic system.^[2] There appear to be multiple ways in which PD impairs orofacial functions. There is a decrease in both jaw movement velocity and mobility. The chewing process and the production and positioning of the food bolus are complicated by the stiffness, decreased movement, and tremor.^[3] It can affect voluntary and automatic movement leading to pharyngeal motor abnormalities that are a prominent cause of dysphagia, resulting in weight loss and a decreased standard of life.

Multiple oral health concerns, such as xerostomia, burning mouth syndrome, and poor oral hygiene, are encountered by individuals with PD. Poor oral hygiene exacerbates caries, plaque and food debris accumulation leading to poor periodontal health, tooth loss and negative impact on masticatory efficiency.^[1] Severe tooth loss has been shown to be significantly prevalent among people with PD in literature.^[4] Apart from the reduced efficacy to carry out daily oral hygiene practice, the majority of PD patients follow a drug regimen, which may worsen their oral health since it alters the quantity and quality of saliva secreted, aggravating oral problems and/or hastening their progression.^[4]

Studies have shown that in moderate and advanced PD, mastication, and orofacial function are compromised, and as the disease progresses, the severity of the dental and orofacial issues increases.^[3] Another study concluded that higher number of masticatory cycles was required to chew and ingest food in the PD group than the non-PD group suggesting disruption in the orofacial myofunctional characteristics.^[5] These disruptions contribute to weight loss, and increased risk of malnutrition affecting their quality of life (QoL).^[6] For these people to regain their masticatory efficiency and improve QoL, oral rehabilitation with fixed or removable prosthesis (RP) is essential. However, the inability to control the orofacial-pharyngeal muscles, both voluntarily and involuntarily, makes oral rehabilitation more difficult by aggravating issues including, chin and mouth tremors, and difficulty with mastication.^[1]

Past reviews have presented impact of PD on general oral health. There is only one review that evaluated the impact of oral rehabilitation in PD patients but it studied only the influence on QoL of PD patients and not on other significant parameters. Furthermore, only complete denture was used for rehabilitation in the articles included in this review.^[7]

However, to the best of the author’s knowledge, no review has been done to assess the effectiveness or impact of rehabilitation with prosthesis either fixed or removable on various oral functions and QoL or satisfaction of PD patients. Hence, this systematic review was planned with intention of analyzing the effectiveness of prosthodontic rehabilitation in patients with PD.

The PROSPERO database has the study protocol registered under Registration ID CRD42024570296. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) standards were followed in the reporting of the review.^[8] Figure 1 shows the flowchart created using the PRISMA guidelines.

The study was conducted a systematic review utilizing the population, intervention, comparison, and outcomes (PICO) framework to answer the question “What is the effectiveness of prosthodontic rehabilitation in patients with PD?” PICO framework was used for studies, where intervention was done in PD patient and comparison was done with patients with or without Parkinson but without intervention.

P: Patients with PD.

I: Rehabilitation with either fixed or RP.

C: Patients without prosthodontic rehabilitation with or without PD.

O: Effectiveness of prosthodontic rehabilitation on various oral aspects and QoL.

The literature search was conducted in the PubMed and CINAHL database to identify pertinent articles using the following search items (“Parkinson disease” OR “Parkinson’s disease” OR “Parkinsonism”) AND (“Dental prosthesis” OR “Removable prosthesis” OR “Denture” OR “dentures” OR “Complete denture” OR “Denture, complete” OR “Removable partial denture” OR “Denture partial removable” OR “Dental implants” OR “Oral rehabilitation” OR “Overdenture” OR “denture, overlay” OR “fixed prosthesis” OR “Crown” OR “Fixed partial denture”). The search strategy used for various databases is depicted in Table 1. The search was done for the articles from the year of inception to 2024 in English language. In addition, an examination of gray literature was conducted using Google Scholar to find pertinent papers that could not be found using the given search parameters. Further search criteria (inclusion and exclusion criteria’s) were applied to the articles and after reading the entire text of the articles, those that met the requirements were chosen for review. To identify any further relevant article, the bibliography of the chosen articles was manually searched as well.

Using the search parameters, a total of 92 abstracts appeared in PubMed. Based on inclusion and exclusion criteria, eight articles were selected for full-text reading. Out of eight articles, two were rejected as one studied the effect of PD on RP hygiene and not the effectiveness of prosthesis and the other included PD patients with and without dentures and studied the oral health but not the consequence of denture wear. From the CINAHL database, after removing the duplicates, only one article was found to be suitable for inclusion in the review. Five articles were selected from Google Scholar for full-text reading. One was excluded as the full text was not available and another was rejected as chewing ability and oral Health-related QoL (OHRQoL) was studied in frail elders with and without prosthesis but not specifically the PD patients. One more article was rejected as it studied the masticatory function and oral sensorimotor ability in PD patients and included denture wearers and nondenture wearers but did not study the impact of dentures on these functions. Thus, 9 articles were included in this systematic review.^[12-20]

Risk of bias assessment done using various tools depicted seven out of nine selected articles of high quality and two or fair quality [Tables 8-10].

Patients suffering from PD could experience difficulties during swallowing or speaking. These can occur at any moment, but as PD worsens, they often get worse. The muscles in the face, mouth, and throat used for speaking and swallowing are also impacted by PD in a similar way to how it affects movement in other body regions. This results in oral dysfunction. PD patients may experience difficulties in maintaining oral hygiene resulting in compromised dental health. Malnutrition can be spurred on by poor dental health, which can also impair appetite and digestion, compromising overall health and well-being. Impaired motor functions in PD affects the masticatory muscles which further affects the masticatory efficiency, oral perception, and oral motor ability and thus QoL of PD patients.

Assessment of chewing movement in patients with PD have shown that PD causes motor dysfunction causing alteration in chewing speed resulting in decline of the nutritional status.^[21] Maximal biting force and other chewing functions, including chewing speed, have been observed to decline with PD. Patients with PD experience decreased jaw mobility, as well as jaw tremor and stiffness in the masticatory and face muscles. They have rigidity and slowness in their orofacial muscles, as well as involuntary facial movements and reduced tongue movements that lead to orofacial pain, temporomandibular joint symptoms as well as difficulties with chewing, speech, and jaw mobility.^[22] PD patients exhibit postural deviations that might cause physical imbalance by shifting the head’s posture, which in turn shifts the mandibular position.^[23] Muscular compensation and a reduction in masticatory efficiency may result from this modification to the masticatory pattern.^[24]

Stereognosis is a complex sensory phenomenon and a vital function depicting oral perception of various objects without visual or auditory information. Any alteration in oral stereognosis have negative implications on mastication and swallowing.^[25] Studies have shown that oral stereognostic ability is impaired in edentulous patients than in dentate patients and the oral stereognostic level of totally edentulous patients (without denture) is higher than complete denture wearer.^[26] According to the results of a systematic analysis of the impact of CD on OSA in edentulous patients, rehabilitation using a full denture improves stereognostic ability in terms of accurately identifying test pieces and the amount of time needed to do so. In addition, a clear correlation between stereognostic ability and denture adaptation was observed.^[27] In relation to the type of prosthesis, study done to investigate OSA of dentate patients, CD wearers, and maxillary implant supported dentures did not found any statistically significant difference between conventional denture wearers and implant supported dentures wearers.^[28]

The OHRQoL is a subjective phenomenon and is crucial to clinical practice in determining the patient’s needs. OHRQoL could be affected by PD.^[3,29] In addition, PD patients with oral symptoms have lower OHRQoL than PD patients without oral symptoms.^[30] OHRQoL can be measured with several instruments. Compared to patients without PD, patients with PD have lower OHRQoL.^[31] PD patients may exhibit orofacial pain^[32] and this can significantly influence vital human needs such as eating and chewing, which can have a negative impact on the QoL.^[33] Studies included in this review suggest that prosthetic rehabilitation can have a positive impact on the QOL of PD patients. Although improved scores has been observed using RP, however, implant-supported fixed or RP offer more reliable rehabilitation option in PD patients. According to a systematic review on oral health and implant therapy in PD patients, PD patients have issues using mobile prostheses due to a lack of motor control, and muscle rigidity that make retention of the RP difficult. Implant therapy although have a lower survival rate in PD patients, however, considering the convenience it offers, implant therapy must be considered a treatment of choice for increasing the QoL of PD patients.^[34] Moreover, there is also evidence that despite motor impairments relating to movement and daily living activities and poor dental health, PD patients have a pleasant perspective of life assessed using Parkinson’s disease questionnaire-39.^[35]

EMG activity of the masticatory muscles decreases after tooth loss. In patients with PD, tooth loss is more evidently seen due to poor oral health. Evidence suggests that PD interferes with the EMG activity of the masticatory cycles by reducing muscular efficiency.^[2] The result of the study included in this review suggests that EMG activity is more in dentate individuals than partially dentate or completely edentulous patients with or without PD. This decrease in masticatory muscle electrical activity could be attributed to muscle atrophy, which is increased in PD patients due to motor symptoms that impair the masticatory function.^[18] People who have PD use more muscle fibers during masticatory movements than people who do not have the disease. This result in an increase in energy expenditure and indicate that PD patients had impaired functioning.^[16] According to a prior study comparing patients’ elevator muscle activity before and after receiving complete dentures, using complete dentures increases the occlusal vertical dimension, which in turn causes EMG alterations.^[36] Another research suggests that there is alteration in the EMG characteristics of the jaw muscles in patients receiving dental prosthesis rehabilitation. EMG activity assessment between nondenture wearers and those rehabilitated with fixed implant-supported (FIS) prosthesis and RP exhibited notable differences with the RP group exhibiting more variations than the ND participants suggesting that rehabilitation through FIS would better retain the physiology of the jaw muscles than RP.^[37]

Based on the limited research, it seems that oral rehabilitation of completely or partially edentulous PD patients result in improved oral functions. Strengths of this systematic review include the thorough electronic search in two databases, one supplementary database as well as manual search with comprehensive evaluation and quality assessment of the selected articles of different study designs. The limitation is this review is the scarcity of data, and language restriction. Search in more databases with inclusion of non-English publications could be done in further reviews.

This comprehensive evaluation suggests that prosthetic rehabilitation may be beneficial for persons with PD. Nevertheless, there is a paucity of long-term studies assessing the benefits of prosthetic rehabilitation whether with a fixed or RP in enhancing patients’ QoL and oral function. Various case reports or oral rehabilitation in these patients have been reported in the literature, however, long-term follow-up to study the influence on oral functional capacity is lacking. Hence, any evidence based conclusive finding cannot be withdrawn.