Effect of Molar Replacement on Glycemic Control in Adults With Uncontrolled Type 2 Diabetes

Diabetes is one of the leading causes of death and disability worldwide. The current prevalence of the most common form of diabetes, type 2 diabetes (T2D), is estimated at 9.2% among individuals aged 20-79 years in Europe. First-line management of T2D relies on therapeutic lifestyle modifications (diet and physical activity), with pharmacological treatment added in case of failure. Despite the wide range of available pharmacological options, up to 50% of individuals living with T2D who adhere to treatment do not achieve their glycemic targets. There is therefore a need to identify alternative strategies to reduce blood glucose levels.

Individuals living with T2D generally have poorer oral health than the general population, with a reduced number of teeth and more frequent and severe periodontitis. This results in lower masticatory efficiency compared with the general population, as masticatory efficiency mainly depends on the number of teeth in occlusion, particularly the presence of premolars and molars. The persistence of at least one pair of first molars plays a major role in determining the ability to grind and mix food. Masticatory efficiency influences dietary choices.

It is currently unknown whether improving masticatory efficiency in individuals with uncontrolled diabetes, through the replacement of missing teeth, modifies dietary habits and improves diabetes control. The hypothesis of this study is that, in individuals with uncontrolled T2D, restoring masticatory efficiency by replacing missing molars with fixed implant-supported prostheses will lead to improved dietary quality and better glycemic control.

This is a multicenter, open-label, two-arm parallel-group, superiority randomized controlled trial. Participants will be randomized in a 1:1 ratio to receive either:

Intervention: replacement of one pair of molars with implant-supported prostheses in addition to standard care for the management of type 2 diabetes (T2D);

Control: standard care for the management of T2D only.

The primary objective is to evaluate the impact of replacing one pair of molars with implant-supported prostheses in individuals living with uncontrolled T2D and reduced masticatory efficiency, at 9 months post-randomization, on glycemic control.

The primary endpoint is the difference in HbA1c between randomization and 9 months post-randomization.

Regarding individual benefits, all patients included in the study will benefit from a comprehensive oral health assessment allowing screening for dental caries, dental infections, periodontal disease, oral mucosal pathologies (including pre-cancerous and cancerous lesions and oral candidiasis), xerostomia, malocclusion, and temporomandibular joint disorders. These conditions are more frequent in patients with T2D. All included patients will subsequently receive dental care aimed at eliminating infectious foci and treating any carious lesions and periodontal diseases that may be present. The assessment and dental care will improve patients' oral health and contribute to a better oral health-related quality of life. They may also potentially improve diabetes control, as infectious foci and periodontal diseases are responsible for local and systemic inflammation that complicates glycemic control.

For patients included in the intervention group, restoration of a functional molar pair in occlusion is expected to significantly increase masticatory efficiency and further improve oral health-related quality of life. The intervention may also lead to changes in dietary habits toward a healthier and more balanced diet. Such dietary changes could be beneficial for diabetes control. As reduced masticatory efficiency is associated with a higher risk of coronary heart disease, the intervention may also reduce the risk of cardiovascular disease. The implants and implant-supported prostheses used to restore a molar pair are provided as part of the research.

Inclusion criteria

• Adults aged between 18 and 75 years
• Type 2 diabetes diagnosed for more than 6 months, according to the diagnostic criteria of the International Diabetes Federation
• Insufficiently controlled type 2 diabetes (HbA1c between 7.5% and 10.5%)
• Type 2 diabetes under stable treatment for at least 3 months (no initiation or discontinuation of antidiabetic treatments, and no change in basal insulin dose greater than ±50% compared with the initial dose)
• Presence of all teeth up to the second premolars, i.e. presence of maxillary and mandibular incisors, canines and premolars. The absence of premolars extracted for orthodontic reasons or due to agenesis is not taken into account. Teeth replaced by fixed tooth- or implant-supported prostheses are considered present.
• Absence of functional molar pairs not compensated by a partial prosthesis, or presence of only one functional molar pair. The absence of a pair may be due to the absence of both molars or only one molar (molar without an antagonist). Third molars are not taken into account.

Exclusion criteria

• Recent diabetes (< 6 months), intensified insulin therapy (≥ 3 injections/day) or insulin pump use
• Type 1 diabetes
• Type 2 diabetes with HbA1c > 10.5%
• Comorbidities contraindicating part of the oral rehabilitation (particularly implant placement) or impacting masticatory efficiency, such as end-stage renal disease or stroke within the past 6 months
• Smoking >10 cigarettes/day
• Presence of severe crestal defects, insufficient prosthetic space, malocclusions and/or parafunctions contraindicating part of the oral rehabilitation
• Severe periodontitis (Stage III or IV, Grade C)
• Cancerous or precancerous lesions of the oral mucosa
• Allergy to anesthetics or antibiotics required for dental surgery
• Pregnant or breastfeeding woman
• Participation in another interventional study involving human participants or being within the exclusion period following a previous study involving human participants, where applicable
• No affiliation to a social security scheme
• Patient benefiting from State Medical Aid (AME)
• Individual deprived of liberty or under legal protection measures
• Refusal or inability to provide written informed consent