Restoring Function and Confidence: Navigating Prosthetic Challenges in a patient with Myasthenia Gravis

By Dr. Jaspreet Kaur Bopara, A/Prof. Dr. Lim Ghee Seong and Dr. Siti Fauzza Ahmad

Introduction

Removable dentures play a significant role in addressing the complex challenges related to tooth loss and are intended to substitute for absent teeth, addressing both functional and aesthetic concerns. They are recognized for effectively restoring masticatory function, which enhances the physical act of chewing and promotes a varied diet, thereby improving nutrition and overall health, particularly in patients with compromised immunity. Furthermore, these appliances have a significant psychosocial impact, leading to an enhanced quality of life (Jar et al., 2023) and a renewed sense of self-confidence and assurance (Amasyalı et al., 2017). The presence of systemic conditions can modify dental treatment due to their direct or indirect impact on oral tissues, bacteraemia, immune system compromise, drug interactions, sensory and motor impairments, and alterations in patients’ psychological status (Gade et al., 2021).

Myasthenia gravis (MG) is a rare autoimmune disorder marked by muscular weakness, resulting from the obstruction of neuromuscular transmission due to circulating autoantibodies that primarily target the nicotinic acetylcholine receptor (AChR) and associated proteins in the postsynaptic membrane of skeletal muscles. The severity of muscle weakness ranges from minor impairment affecting solely the ocular muscles to generalized muscle weakness. In 85% of cases, the initial presentation is defined by ocular muscular weakness, manifesting as ptosis and/or diplopia (Gilhus et al., 2015). The discovery of a reduction in acetylcholine receptors at the neuromuscular junctions in patients with MG has resulted in significant progress in the understanding of the nature of this disease, leading to a more accurate diagnosis and a more effective treatment strategy.

The present case report presents various challenges encountered in a patient with myasthenia gravis, emphasizing the application of current knowledge and specific precautions in dental treatment according to the recent clinical guidelines. The report delineates the standard procedural stages involved in denture fabrication and the dental management determined by the oral manifestations and complications presented by the patient.

Case Description

A 62-year-old Malay woman presented to the Prosthodontic Postgraduate Clinic with a complaint that her upper dentures are too loose and she is unable to bite and chew her foods properly. She also expresses dissatisfaction with the appearance of her current dentures which have insufficient tooth display as compared to her old pictures (Fig 1). Additionally, shecomplained of occasional pain with her present dentures due to gum impingement on the left side . Upon examination and investigation, it was determined that both the upper and lower arches are partially dentate as she lost many teeth due to caries and periodontal problems many years ago. The definitive treatment plan included a maxillary complete acrylic denture and mandibular partial cobalt – chrome denture, tailored to address the patient’s unique needs. The treatment outcomes were successful, providing improved oral function and aesthetics for the patient.

Since the patient is a lecturer, she feels self-conscious about the retention of her current dentures especially when lecturing for extended periods of time. She experiences occasional pain, especially during biting on the left side, where the metal of her dentures holds on to a loose tooth. She has been wearing her upper dentures for the past 3 years and had never worn lower dentures. Some of her teeth were extracted due to periodontal problems 10 years ago. She also stated that she noticed a small crack line on her current dentures.

Her medical history includes hypertension, diabetes mellitus, and myasthenia gravis. She is currently on Gliclazide, Metformin, and Vildagliptin twice daily, as well as Mestinon (Pyridostigmine bromide) 60 mg three times a day. She stated that she previously used Sacha Inchi oil as a supplement for overall health. She undergoes routine follow-ups every six months at Pusat Perubatan University Malaya (PPUM) . No drug allergies have been reported.

She leads a non-smoking lifestyle, abstains from alcohol, and has no particular dietary restrictions. She is married and resides with her husband and two children. Her oral hygiene regime includes brushing twice a day with fluoridated toothpaste and she ocassionally uses mouthwash. Additionally, she soaks her dentures in a cleansing tablet solution (Polident, GSK or Jaysuing, China) once a day.

She was well ambulated and attentive but had slurring of speech and an unsteady gait, likely due to diplopia. Clinical assessment showed a symmetrical facial structure, with a class III skeletal profile, competent lips, and a normal mouth opening of 25–35mm. Slight clicking was noted in both temporomandibular joints, but no tenderness or palpable submandibular lymph nodes were detected.

Intraoral examination revealed a partially dentate maxilla and mandible with moderate oral hygiene. The maxillary residual ridge (Fig 3) displayed moderate resorption, an irregular contour, and firm overlying mucosa. Inflammation was noted on the maxillary anterior alveolar ridge, attributed to chronic trauma from underextended denture flanges. It was noted that tooth 27, 36 and 48 was periodontally compromised due to grade III mobility and bleeding on probing with furcation involvement. Her plaque score was 82 % and bleeding score was 8 %. The highest Basic Periodontal Examination (B. P. E) score that was charted was 4* at the lower left quadrant. Tooth 36 had signs of erosion on the distal occlusal surface while tooth 48 exhibited buccal caries with an ICDAS score of 04. The lower anterior segment showed crowding and attrition, with tooth 41 missing.

Upon assessing her existing dentures, several problems were noted. The maxillary denture had poor aesthetics and lacked sufficient retention and stability. The patient maintained fair denture hygiene and said she never used denture adhesive due to its sticky texture. Upon smiling, her upper teeth were not visible (Fig 4).

The findings from pulp sensibility test indicated that all teeth investigated are vital except for tooth 27. Dental Panoramic Tomogram (DPT) radiograph (Fig 5) of the patient reveals moderate resorption of the alveolar bone in both arches. Tooth 27, 36 and 48 exhibit widening of the periodontal ligament (PDL) space, discontinuity of the lamina dura at the apices, and vertical and horizontal bone loss up to apical third of the root with furcation involvement. Tooth 41 is missing. Additionally, radiopaque areas in the regions of tooth 18 and 28 are indicative of impacted teeth. Intraoral periapical (IOPA) radiograph (Fig 6) was taken to confirm these findings.

Given these findings, the diagnosis included partially dentate maxilla (Kennedy classification II) and mandible (Kennedy classification II mod I), moderate caries on tooth 48 with ICDAS score 04, non-carious tooth surface loss (localized erosion) with tooth 36 and chronic generalized periodontitis stage 4 grade C, stable, with risk factor diabetes mellitus.The primary treatment goals were to improve patient’s self-confidence and quality of life by restoration of oral function and to improve soft tissue health. The treatment plan was structured into three phases: preparatory, prosthetic, and maintenance.

In the preparatory phase, oral hygiene maintenance was reinforced and a thorough description and discussion of various treatment options were given. Maxillary primary impression was taken using thermoplastic impression compound (Hoffman, Berlin, Germany) followed by alginate (Krompan, Lascod, Illinois, USA) for taking the final primary impressions of the maxillary and mandibular arches. Following this, type III gypsum (Elite Rock, Zhermack, Badia Polesine, Italy) was poured to form study models (Fig 7).

The patient was referred for a thorough periodontal evaluation and ultimately, she requested and consented to undergo extraction for tooth 27, 36 and 48 due to its unfavourable prognosis. This was preceded by the temporary relining of the maxillary acrylic partial denture (Fig 8). For the definitive prosthetic solution, she opted for an acrylic removable complete denture for the maxillary arch and a partial cobalt-chromium denture for the mandibular arch.

Following a three-month period of wound healing post-extraction, border moulding was conducted for both arches utilizing greenstick impression compound (Kerr, California, USA) with special tray. Final impressions were taken using regular body polyvinylsiloxane (PVS) impression material (GC Exaflex regular, GC America, Alsip, USA) for maxillary arch and mandibular arch (Fig 9). The impressions were casted using type III dental stone (Elite Rock, Zhermack, Badia Polesine, Italy) to fabricate master cast models (Fig 10).

From the mandibular working cast, a refractory model was produced after effectively blocking all the undercuts and spacer was created. Subsequently, the framework wax-up was conducted on the refractory model, and the Co-Cr framework was fabricated using the conventional casting method. The Co-Cr framework (Fig 11) was tried intraorally, ensuring a precise fit before registering the jaw relation in a centric position.

Modelling wax was utilized to fabricate the occlusal bite rims on light-cured acrylic base plates for the partially dentate maxilla and mandible. On the following visit, maxillomandibular relationship was established at centric relation. Subsequent to recording the jaw relation, the master casts were mounted on a semi-adjustable articulator (Protar evo 5, Kavo, Illinois, USA) (Fig 12).

The placement of teeth was done using acrylic teeth (Naperce, Yamahachi Dental MFG, Aichi, Japan) within a bilateral balanced occlusion scheme (Fig 13). Clinical trials involving waxed trial dentures were conducted. Occlusion in centric relation was verified, followed by evaluations of aesthetics and phonetics. Heat cured polymethyl methacrylate (PMMA) denture base resin (Huge Dental, Zhengzou, China) was used for packing and processing according to the manufacturer’s instructions.

On the day of denture delivery, post-insertion evaluations confirmed satisfactory retention, stability and adequate extension. Articulating paper (CL, Germany’s Articulating paper) was used to adjust occlusion in both centric and eccentric movements and no heavy localised occlusal contacts were found (Fig 14). The patient’s oral hygiene and any signs or symptoms were reviewed two weeks after the final prosthesis delivery.

Upon review, plaque build-up was noted in the lower anterior teeth (Fig 15). Oral hygiene guidelines were reiterated, and she was advised to brush her teeth three times a day using a soft-bristled toothbrush, rinse with mouthwash, maintain proper hydration, chew sugar-free gum or candy to promote saliva flow, and clean her dentures regularly.

No pain or discomfort was reported by the patient. Retention and stability of the dentures were evaluated following Kapur’s technique (1967). Retention was assessed by placing the thumb and index fingers on the labial and lingual surfaces of the central incisors and applying a vertical pulling force along the path of insertion. Stability was tested by positioning the fingers on the buccal surfaces of the premolars and shifting the denture in horizontal, anteroposterior, and mediolateral directions. The results indicated very good retention and stability. After the initial review, the patient was scheduled for follow-up appointments every six months, transitioning to yearly assessments once her oral hygiene improves.

Discussion

The patient and her family expressed satisfaction with the fabrication of the new denture, as her new smile resembles her previous photographs (Fig 16). The new prosthesis has demonstrated effective retention and has enhanced her masticatory, phonetic, and aesthetic functions. The treatment was deemed successful, leading to a significant enhancement in her self-confidence and quality of life.

One of the challenges faced in this case is the medically compromised condition of the patient. She was diagnosed with a chronic autoimmune antibody-mediated neuromuscular disorder known as Myasthenia gravis (MG) a few months before the dental treatment. The patient presented with droopy eyelids, double vision, difficulty in making facial expressions due to muscle weakness, problems chewing & difficulty in swallowing, & slurred speech which makes the denture fabrication process more challenging. In addition, the patient desired to restore her smile to its previous appearance, resembling the one depicted in her old photographs.

To improve patient comfort and facilitate dental treatment, early morning sessions were scheduled to leverage the generally elevated muscular strength observed in the morning and to mitigate daily muscle atrophy. Moreover, to enhance the efficacy of local anaesthesia, mepivacaine was administered during the tooth extraction, as ester-type local anaesthetics,

such as procaine (Novocaine), are hydrolyzed by plasma cholinesterases and exhibit diminished effectiveness in individuals with MG (Yarom et al., 2005). The patient’s lower anterior teeth had wider interproximal gaps due to periodontal problems, which modifies the denture’s design. The lingual interrupted plate design is also advantageous because retaining loops can be included to allow for the replacement of one or more incisor teeth in the future and it is more aesthetic. In addition, the patient’s maxillary torus, despite its small size, may impact the denture’s stability. A thin layer of foil was placed over the torus on the master cast to serve as a spacer, reducing friction between the denture and the torus.

Moreover, patient has a thick ropey and increased saliva secretion and has the need to spit out frequently due to sensation of nausea. This may occur as an adverse reaction to the drug, named Mestinon (pyridostigmine), which has muscarinic action of the acetylcholinesterase inhibitor leading to increased salivation (Yarom et al., 2005). The presence of an optimal salivary flow with adequate consistency holds importance particularly in edentulous patients. The presence of thick ropey saliva can influence maxillary denture retention by providing negative hydrostatic pressure in the area anterior to the posterior palatal seal, causing downward dislodgement of the denture (Sachdeva et al., 2014). Thick and viscous saliva is associated with poor retention because of thick and discontinuous film between denture & mucosa (Jacob et al., 2013). Consequently, edentulous MG patients with complete dentures may encounter masticatory challenges, marked by diminished chewing efficacy. Poorly fitted dentures may further aggravate muscular weakness, therefore, it was ensured that the dentures were not overextended nor possessed thick flanges that could exacerbate muscle weakness and disrupt salivary flow.

Conclusion

In conclusion, a comprehensive dental assessment, along with specific considerations, was diligently performed. The patient’s concerns and expectations regarding aesthetics and chewing functionality were successfully resolved. Overall, the goal of improving the patient’s quality of life through dental care was effectively achieved.

References

• Amasyalı, M., & Sabuncuoğlu, F. A. (2017). Level of social appearance anxiety in individuals with and without alignment of teeth. Turkish journal of orthodontics, 30(1), 1.
• Gade, J., Mahule, A., Aparna Trivedi, D. V. G., & Shaikh, A. (2021). Prosthodontic Management of Patients with Systemic Disorders. European Journal of Molecular & Clinical Medicine, 8(03), 2021.
• Gilhus, N. E., & Verschuuren, J. J. (2015). Myasthenia gravis: subgroup classification and therapeutic strategies. The Lancet Neurology, 14(10), 1023-1036.
• Jar, H. A., Alabbas, B. M., & Khormi, A. A. (2023). The effect of dentures on oral health and the quality of life. Int J Community Med Public Health, 10(12), 5067-5071.
• Jacob, S. A., & Gopalakrishnan, A. (2013). Saliva in prosthodontic therapy-all you need to know. J Dent Sci, 1(1), 13-25.
• Kapur, K. K. (1967). A clinical evaluation of denture adhesives. The Journal of prosthetic dentistry, 18(6), 550-558.
• Sachdeva, Shabina & Noor, Rana & Mallick, Rizwana & Perwez, Eram. (2014). Role of saliva in complete dentures: an overview. 2. 51-54.
• Yarom, N., Barnea, E., Nissan, J., & Gorsky, M. (2005). Dental management of patients with myasthenia gravis: a literature review. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, 100(2), 158-163.

Acknowledgement:

I would like to give a special thanks to my lecturers and supervisors, who have dedicated their time and effort to mentoring me and ensuring the successful completion of this case. Their expertise and encouragement have been truly inspiring.

I would also like to express my sincere appreciation to the staff in the dental prosthetic laboratory for their invaluable assistance in guiding me through the denture fabrication process. Their patience and expertise have greatly contributed to my learning experience.

Thank you all for your support and dedication.