Improvement of Mandibular Kinetics and Quality of Life in Elderly with Mini-Implant Retained Overdentures: A Preliminary Study

Abstract

Successful health management in older adults requires adequate nutrition, which is often compromised by oral health issues like edentulism. Tooth loss can reduce masticatory function, especially when rehabilitation treatments fail. The present study aims to generate initial information on the potential effects of the placement of mandibular mini-implants in patients with complete maxillary and mandibular dentures on mandibular kinetics, electromyographic activity, and quality of life. Participants with complete dentures, adequate mandibular bone height, and good general health were recruited. All underwent cone beam computed tomography for diagnosis and planning to place two mandibular mini-implants. Mandibular movements were analyzed using electromagnetic articulography and electromyography before treatment and five months after implant placement. Oral health-related quality of life (OHRQoL) was assessed using the OHIP-7sp at baseline and six months post-treatment. Five subjects were included (mean age 69.7 ± 10.8 years). All mini-implants demonstrated a 100% initial success rate. At five months, significant improvements were observed in the vertical range of maximum opening, as well as in the area, trajectory, and range of frontal and sagittal movement envelopes (p < 0.05)—along with increased movement symmetry. OHRQoL also improved, with greater esthetic satisfaction, communication, and social engagement. Mandibular mini-implants improved mandibular movements and prosthetic stability, enhancing patients’ oral health-related quality of life without altering muscle activity.

1. Introduction

Edentulism significantly impacts masticatory function and oral health-related quality of life (OHRQoL) [1,2]. Although edentulism can now be treated more effectively, thanks to advances in dental prosthetics, patients using complete prostheses often struggle with chewing stability and efficiency. Progressive bone resorption following tooth extraction further complicates prosthetic rehabilitation, especially in highly atrophied mandibles [3].

In response to these challenges, total mandibular prostheses stabilized with mini-implants have become a viable alternative. Mini-implants feature a diameter of less than 3.5 mm and offer significant advantages in terms of less invasive surgery, adaptability to narrow bone sites, and are more economical than standard-diameter implants [4,5]. These implants provide improved prosthesis stability and have been shown to increase patient satisfaction [1,5].

Previous studies have shown that overdentures retained by conventional implants can improve either masticatory performance or mandibular movement patterns [6,7]. However, whether such outcomes can also be achieved in patients rehabilitated with mini-implants remains unclear. To date, the available evidence refers mainly to overdentures retained by conventional implants, while the specific impact of mini-implants on both masticatory performance and mandibular movement dynamics has not been investigated. Furthermore, no study has simultaneously assessed these two outcomes in this clinical context, which underscores the originality and relevance of the present investigation.

Mandibular dynamics are an essential component of mastication and are determined by a complex series of three-dimensional movements of interrelated rotations and translations. Mandibular movements are determined by the combined and simultaneous actions of the temporomandibular joint and associated musculature [8]. These movements can be divided into two main categories: border and functional [9]. Border movements occur when the mandible reaches the extreme limits of its range of motion and are limited by temporomandibular joint (TMJ) anatomy and dental occlusion. Conversely, functional movements are not restricted by external factors but are modulated by the individual’s neuromuscular responses [8].

Mastication is a complex motor-sensory process that involves rhythmic movements of the mandible to crush and mix food, facilitating the formation of a food bolus that can be swallowed [10]. This process is accomplished through chewing cycles in which the mandible moves from maximum intercuspation (MIP) toward a desired opening, then moves laterally to chew the bolus between opposing teeth and finally returns to MIP [8].

The biomechanics of border and functional movements are studied using advanced techniques such as electromagnetic articulography (3D-EMA) and surface electromyography (EMG). Three-dimensional-EMA, a method based on electromagnetic induction principles, makes it possible to record mandibular movements in three dimensions accurately and in real time. This noninvasive technique offers detailed spatial resolution and a high sampling frequency, facilitating the assessment of trajectories and ranges of motion during mastication [11,12]. EMG measures the electrical activity of masticatory muscles during chewing cycles, providing crucial information on muscle energy expenditure and muscle function [13,14].

The present study aims to evaluate whether the placement of mandibular mini-implants in patients with complete maxillary and mandibular dentures improves mandibular kinetics, electromyographic activity, and quality of life. As a preliminary investigation, the findings are intended to provide initial insights that can inform the design of future clinical studies and the optimization of dental prostheses for edentulous patients. It is hypothesized that, in this exploratory context, the placement of mandibular mini-implants may be associated with preliminary improvements in mandibular function, electromyographic activity, and oral health-related quality of life.

2. Materials and Methods

This prospective preliminary clinical study was approved by the Scientific Ethics Committee No. 121_22 of the University de La Frontera, Temuco, Chile. Given the preliminary and exploratory nature of this clinical study, a convenience sampling method was used, based on the availability of participants during the recruitment period.

Elderly patients treated at the Teaching and Clinical Dental Center (Clínica Odontológica Docente Asistencial, CODA) of the Universidad de La Frontera, Temuco, Chile, were invited to participate in this study. Participation was voluntary and required written informed consent.

Table 1. Inclusion and exclusion criteria.

Criteria	Inclusion	Exclusion
Clinical	- Wearing complete maxillary and mandibular acrylic dentures. - Adequate occlusal stability (balanced occlusion). - General health status classified as ASA I or II.	- Use of removable partial dentures. - Presence of active pathological oral lesions - Systemic medical conditions contraindicating implant placement. - High-dose antiresorptive therapy - Severe uncontrolled systemic diseases - Known allergy to carrots
Anatomical	- Residual mandibular bone height of 13 mm or more.
Behavioral	- Commitment to scheduled clinical appointments. - Ability to read and understand the questionnaires used in evaluation. - Willingness to cooperate throughout the entire follow-up period.	- Neuromotor conditions impairing response to assessment tools or ability to follow clinical instructions.

summarizes the main inclusion and exclusion criteria categorized as clinical, anatomical, and behavioral.

Occlusal stability was clinically evaluated by verifying a balanced occlusion, ensuring that the dentures exhibited simultaneous and even contact on both sides during static and dynamic occlusion, as well as the absence of sliding or displacement of the teeth in centric relation. Furthermore, it was confirmed that the occlusion was reproducible and consistent, meaning that the occlusal position did not vary with each mandibular closure. This criterion was determined by a specialist dentist during the patient’s initial evaluation.

The residual mandibular bone height was assessed using cone beam computed tomography (CBCT), in accordance with accepted radiographic standards for pre-implant planning.

Exclusion criteria included the presence of active pathological oral lesions such as infections, mucositis, or undiagnosed ulcers, and any systemic medical condition that could contraindicate implant placement. In particular, patients undergoing high-dose antiresorptive therapy—such as intravenous bisphosphonates for cancer metastases—were excluded due to the elevated risk of osteonecrosis. Similarly, individuals with severe uncontrolled systemic diseases, including advanced rheumatoid arthritis, were considered unsuitable candidates because of their potential to compromise healing and implant success. These exclusions were established to eliminate local and systemic factors that could introduce variability in post-surgical outcomes.

Patients with a known allergy to carrots were excluded due to the use of carrots as the standardized test food in the masticatory assessment. This exclusion criterion was implemented to prevent any potential allergic reactions during the functional evaluation.

These criteria were selected to ensure a baseline level of oral and systemic health that would allow reliable evaluation of implant-supported overdenture function, particularly in an elderly population. Patients over 65 years of age often present with comorbidities and oral conditions that may compromise surgical outcomes or prosthetic performance.

After signing the informed consent form, a cone beam computed tomography (CBCT) scan of the mandibular canine area was requested. Measurements of bone height and thickness were taken for the subsequent planning of implant placement surgery.

In this study, the primary outcomes were mandibular kinetics and quality of life. The secondary outcome was the success of the mini-implants. The covariates studied included participant age, baseline bone parameters, duration of edentulism, and prior implant failure. Baseline bone parameters were obtained from cone beam computed tomography (CBCT) scans and included bone density, cortical thickness, marginal bone contour, and bone width, evaluated by a radiologist.

2.1. Evaluation of Mandibular Movements

Border and functional mandibular movements were evaluated in the Oral Physiology Laboratory at the Universidad de La Frontera (Temuco, Chile) using a 3D electromagnetic articulograph (EMA; AG501, Carstens Medizinelektronik, Bovenden, Germany) and a surface electromyograph (EMGs VIII, ArtOficio, Santiago, Chile). All evaluations were performed in triplicate by the same operator (J.A.-A.).

Seven pre-calibrated EMA sensors were used to analyze mandibular border movements: one active sensor, three reference sensors, and three attached to the bite plane accessory. In addition, the articulography was fitted with a grounded connector placed on the patient’s wrist. The active sensor was placed at the interincisive line, and the reference sensors were positioned in a polylactic acid (PLA) shell filament (Figure 1a (CB)(CL)). These sensors served as a baseline system to standardize the recording of the mandibular sensor while ignoring the participant’s head movement [11]. The bite plane accessory is an accessory of the articulography, which locates the coordinate origins in the occlusal plane. The bite plane sensors were placed in the central and lateral areas of the attachment grooves (Figure 1b).

In addition to the EMA sensors, four self-adhesive electrodes (Signa gel, Parker Laboratories, nc, Fairfield, NJ, USA) were affixed to evaluate the functional mandibular movements of mastication (Figure 1a (ET)(EM)). These electrodes were placed parallel to the direction of the fibers of the masseter muscles and anterior portion of the temporalis muscle. In addition, a reference sensor was attached to the elbow.

2.1.1. Evaluation of Mandibular Border Movements: Before Mini-Implants Installation and Five Months After

Initially, a reference recording was made, for which the subject held his head vertically with the Frankfort plane parallel to the floor. This record defined the frontal, sagittal, and horizontal anatomical planes. With the participants seated upright, three repetitions of the border movements described above were recorded to obtain the frontal, horizontal, and sagittal planes of Posselt’s envelopes of motion (

Table 2. Mandibular border movements.

Envelope	Right	Left
Front	Mandibular displacement with tooth contact from MIP to maximum right laterality. From the position of maximum right laterality, movement of the right lateral opening until MO is reached.	Mandibular displacement with tooth contact from MIP to maximum left laterality. From the position of maximum left laterality, movement of the left lateral opening until MO is reached.
Horizontal	Mandibular displacement with dental contact from CR to maximum right laterality followed by protrusive displacement to the left until MPC is reached.	Mandibular displacement with dental contact from CR to maximum left laterality followed by protrusive displacement to the left until MPC is reached.
Envelope	Anterior	Posterior
Sagittal	Mandibular displacement with MIP to MPC tooth contact followed by anterior opening until MO is reached.	Mandibular displacement with PMI to CR tooth contact followed by posterior opening until MO is reached.

MIP, maximum intercuspation; MO, maximum opening; CR, centric relation; MPC, maximum protrusion with contact.

) [15].

2.1.2. Evaluation of Functional Mandibular Movements During Mastication (EMG Synchronized with 3D EMA): Before Mini-Implants Installation and Five Months After

To assess mandibular kinematics using EMA and EMG activity of the masseter muscles and anterior portion of the temporalis muscle, raw carrots cut into 1 cm³ (3.5 g) cubes were used [11]. Once the AG501 3D EMA sensors and EMG electrodes were in place (Figure 1a), each participant was asked to hold the food between the tongue and palate until they were instructed to begin chewing. The participant was instructed to start chewing as normally as possible for one minute. The participants chewed carrots on three different occasions, with a two-minute pause between each, and drank water to eliminate possible residues.

The data from each recording were processed using Matlab^® routines (Matlab R2019a; MathWorks), yielding the following data: area (mm²) of each masticatory cycle in the frontal, sagittal, and horizontal planes; frequency: number of chewing cycles in one minute; speed: mandibular movement during opening and closing.

2.2. Mini-Implants

2.2.1. Surgical Procedure

In each patient, two 2.0 × 13 mm MINI Overdenture Fixtures (MEGAGEN, Chile) were installed in the mandibular canine region, following prior planning and CBCT imaging analysis. Implant placement and overdenture construction were performed by the same operator. The surgical sites were prepared according to the drilling protocol recommended by the manufacturer of the mini-implants used (MINI Overdenture Fixture, MEGAGEN). The implants were placed using a single-stage approach, with a minimally invasive flap elevated only in the mandibular canine region. The surgical site for mini-implant placement was planned in this region due to its favorable biomechanical and morphological characteristics. Planning was performed within a safety zone using CBCT imaging to ensure optimal positioning and avoid anatomical risks. Bone height measurements were taken from the marginal cortical to the mandibular incisive canal and to the basal cortical, along with an analysis of bone width. Additional measurements were performed when necessary to guarantee a safe surgical approach. The angulation and depth of each implant were determined individually for each patient based on the CBCT measurements. Upper canines served as orientative reference points to maintain the correct prosthetic axis and occlusal relationship throughout the rehabilitation, and the implants were subsequently inserted manually using a torque wrench.

Throughout the procedures, no bone grafts were required, as the bone structures provided sufficient support and stability for successful implant placement. Once implants were located, the flap was closed with suture (silk 4.0, Ethicon, Johnson & Johnson MedTech, Somerville, NJ, USA). Oral antibiotic treatment was prescribed with Amoxicillin (875 mg; Optamox, Pharma-Investi, Santiago, Chile) every 12 h for 7 days post-surgery, along with analgesics (Lysine clonixinate 125 mg, Nefersil, Pharma-Investi, Chile) for 4 days. All patients were instructed to refrain from wearing their prostheses for one week after surgery.

2.2.2. Prosthodontics

The patients’ existing prostheses were converted into overdentures. Prior to the conversion, all prostheses met established prosthodontic standards, ensuring proper fit, function, and esthetics, which facilitated a predictable and effective adaptation to implant-supported overdenture use. A ball attachment system was employed to provide adequate retention and stability of the overdenture.

The contact points of the prosthesis with the mini-implant retainers were alleviated as soon as the mini-implants were installed, and they were kept that way for three months using tissue conditioner (Ufi Gel P, VOCO). All subjects had checkups at 1, 4, 8, and 12 weeks after surgery. After three months, the success rate of the mini-implants was evaluated according to the currently accepted clinical evaluation criteria, the “ICOI Pisa Implant Health Quality Scale” [16,17]. Once the success of the mini-implants was verified, retention copings were placed inside the complete mandibular prosthesis to connect it to the mini-implants using permanent hard relining for dental prostheses (Ufi Gel Hard; VOCO). All subjects were monitored at the first, fourth, eighth, and twelfth week after the prosthesis was connected onto the mini-implants. Patients were educated in oral hygiene techniques to optimize the care and maintenance of the overdenture.

2.3. Quality of Life Assessment

An operator (J.A.A.) applied the ultra-short version of the Oral Health Impact Profile (OHIP-7SP) questionnaire at baseline and 6 months after the installation of mini-implants for total prosthesis stabilization [18]. This tool quantifies OHRQoL in elderly denture wearers.

2.4. Statistical Analysis

The data were recorded in a Microsoft Excel spreadsheet. A descriptive statistical analysis was performed, including the calculation of the mean and standard deviation for continuous variables. For comparisons of paired measurements (before and after) within the same subjects, the Wilcoxon signed-rank test was applied. All data processing and analysis were conducted using IBM SPSS Statistics for Windows, version 23.0, and a p-value < 0.05 was considered indicative of statistical significance.

3. Results

A total of 21 patients were recruited, of whom 7 met the study’s eligibility criteria (Figure 2). Six subjects (five women and one man) ultimately participated in the study, with a mean age of 69.7 ± 10.8 years (

Table 3. Characteristics and Alveolar Bone Parameters.

Patient	Age	Bone Density	Marginal Contour	Cortical	Bone Width 4.3 (mm)	Bone Width 3.3 (mm)
Subject 1	60	Normal	Flat	Thick	5.0/6.2	6.2/7.4
Subject 2	61	Normal	Flat	Thick	5.0/5.9	5.3/6.2
Subject 3	81	Normal	Angled	Thick	2.7/3.3	1.8/4.5
Subject 4	61	Normal	Angled	Normal/vestibulat Thick lingual	1.1/1.8	0.9/3.2
Subject 5	71	Normal	Angled	Thick	6.8/8.2	7.0/8.4
Subject 6	84	Normal	Rounded	Normal/vestibulat Thick lingual	5.6/7.2	6.0/7.7

). One subject withdrew from the study before its conclusion.

All participants exhibited normal bone density in the interforaminal region. Marginal bone contour was predominantly angled towards the vestibular side (50% of cases), flat in 33%, and rounded in 17% of cases. Cortical thickness was mostly classified as thick; two participants showed normal vestibular cortical thickness combined with thick lingual cortical thickness. The mean bone width in the right mandibular canine region (4.3) was 4.5 mm (range: 1.1–6.8 mm) at the superior third and 5.6 mm (range: 1.8–8.2 mm) at the middle third of the mandibular body. In the left mandibular canine region (3.3), the mean bone width was 4.6 mm (range: 0.9–7.0 mm) at the superior third and 6.3 mm (range: 3.2–8.4 mm) at the middle third. These measurements were obtained from cone beam computed tomography (CBCT) scans evaluated by a radiologist.

All participants had more than five years of total edentulism and no prior experience with dental implants.

3.1. Mini-Implants

At the first-week follow-up, two of the six patients reported difficulties removing the prosthesis. As a result, a clinical training session was held on prosthetic removal and insertion techniques. Two subjects also required adjustment and new relining for retentive cup adjustment. All patients demonstrated proper oral hygiene techniques. At 12 weeks postoperatively, healing progressed without complications in all subjects. All subjects were classified in group I on the health scale for dental implants [16,17], indicating an initial success rate of 100% for the mini-implants three months after insertion (Figure 3).

3.2. Evaluation of Mandibular Movements

3.2.1. Evaluation of Mandibular Border Movements

Table 4. Mandibular border movements (MBM) before mini-implant placement and five months after.

			MBM Before	MBM After	p-Value
Maximum Opening	Trajectory [mm]		50.87 ± 12.02	48.48 ± 6.24	0.616
	Vertical range [mm]		36.72 ± 5.49	40.09 ± 4.04	0.05 *
Non-Contacting Side	Trajectory [mm]	Right eccentric	21.71 ± 11.30	18.93 ± 7.38	0.472
		Right concentric	22.42 ± 13.99	21.01 ± 10.17	0.711
		Left eccentric	17.17 ± 8.01	17.80 ± 5.6	0.879
		Left concentric	23.14 ± 10.96	22.97 ± 6.09	0.913
	Ranges [mm]	Right	8.65 ± 3.2	9.37 ± 3.05	0.879
		Left	9.62 ± 4.60	11.31 ± 3.07	0.215
Frontal Envelope	Area [mm2]	Frontal	219.39 ± 76.17	325.54 ± 113.93	0.004 *
	Trajectories [mm]	Right side	14.49 ± 9.21	21.78 ± 9.74	0.022 *
		Right opening	40.11 ± 11.56	48.80 ± 8.06	0.003 *
		Left side	17.28 ± 9.54	19.93 ± 8.52	0.396
		Left opening	39.34 ± 11.02	47.49 ± 7.03	0.007 *
	Ranges [mm]	Right opening	5.79 ± 2.23	8.11 ± 1.78	0.005 *
		Left opening	6.02 ± 2.84	7.36 ± 1.79	0.145
Horizontal Envelope	Area [mm2]	Horizontal	58.27 ± 62.92	92.38 ± 54.47	0.064
	Trajectories [mm]	Right	32.96 ± 11.95	35.18 ± 11.88	0.744
		Left	34.36 ± 11.74	35.36 ± 11.76	0.777
	Ranges [mm]	Right	6.90 ± 2.61	7.84 ± 2.55	0.170
		Left	7.95 ± 2.56	8.30 ± 2.72	0.679
Sagittal Envelope	Area [mm2]	Sagittal	264.44 ± 140.40	294.81 ± 162.31	0.306
	Trajectories [mm]	Protrusion	62.25 ± 15.01	70.46 ± 13.84	0.14
		Retrusion	43.87 ± 9.32	53.33 ± 9.93	0.002 *
	Ranges [mm]	Protrusion	8.75 ± 3.46	11.00 ± 3.01	0.025 *
		Retrusion	15.05 ± 5.37	16.47 ± 3.59	0.122

Descriptive statistics are presented as mean ± SD; p-values were calculated using the Wilcoxon signed-rank test. * p < 0.05.

presents the results of the evaluation of mandibular border movements before the installation of mini-implants and five months after treatment. A significant increase in the vertical range of the maximum opening was noted after treatment (p < 0.05). On the other hand, a significant increase in area was observed in the frontal envelope, as well as in right laterality and the right and left opening trajectories. In contrast, left laterality did not show significant changes. Despite an increasing trend, the area in the horizontal envelope was not statistically significant. Finally, a substantial increase in the retrusion trajectory was identified in the sagittal envelope, with an improvement in the protrusion range (p < 0.05). However, the total area of the envelope did not experience significant changes. These findings highlight specific improvements in certain mandibular movements following mini-implant treatment.

Figure 4 presents mandibular border movements (MBM) before (complete prostheses) and five months after (overdentures) the installation of mini-implants. Posselt’s envelope formed in the frontal, sagittal, and horizontal planes before the installation of the mini-implants is characterized as uneven and asymmetrical, as are the chewing cycles. In contrast, five months after installing two mini-implants, Posselt’s envelope in the frontal, horizontal, and sagittal planes was more even, symmetrical, and stable. In addition, the chewing cycles were characterized as drop-shaped, symmetrical, and even.

3.2.2. Evaluation of Functional Mandibular Movements

Table 5. Functional mandibular movements before mini-implant placement and five months after.

		FMM Before	FMM After	p-Value
Areas	Frontal	20.13 ± 10.58	24.76 ± 13.57	0.796
	Sagittal	10.96 ± 7.60	10.10 ± 5.22	0.879
	Horizontal	6.40 ± 5.68	4.40 ± 2.10	0.326
Speed	Ascent	29.44 ± 10.47	34.82 ± 7.18	0.196
	Descent	34.96 ± 9.05	41.04 ± 6.31	0.163
Number of cycles		61 ± 12.7	78.4 ± 17.8	0.225

Descriptive statistics are presented as mean ± SD; p-values were calculated using the Wilcoxon signed-rank test.

shows that five months after mini-implant placement, there were no statistically significant changes in functional mandibular movements. However, trends toward improvement were noted, including increased chewing cycles and slight changes in movement areas and velocities, suggesting enhanced functional stability and chewing quality closer to natural dentition [20].

Table 6. Normalized areas of Posselt’s during functional mandibular movements before mini-implant placement and five months after.

	Normalized Area Before	Normalized Area After	p-Value
Frontal	5.83% ± 4.07	9.37% ± 4.66	0.026 *
Sagittal	5.83% ± 2.22	7.17% ± 3.66	0.361
Horizontal	6.72% ± 3.25%	16.94% ± 9.5	0.002 *

Descriptive statistics are presented as mean ± SD; p-values were calculated using the Wilcoxon signed-rank test. * p < 0.05.

shows that the normalized areas of Posselt’s envelope increased significantly in the frontal and horizontal planes five months after mini-implant placement, while the sagittal plane showed a non-significant increase.

Table 7. Electromyography (EMG) analysis of the activity of the masseter and temporalis muscles during functional mandibular movements before the placement of mini-implants and five months after.

Record [uV]. Level of Muscle Activation
Muscle	Before	After	p-Value
Right Temporal	24.50 ± 11.09	24.28 ± 7.04	0.140
Left Temporal	17.95 ± 4.82	25.26 ± 10.48	0.88
Right Masseter	23.09 ± 7.34	24.44 ± 10.25	0.623
Left Masseter	17.39 ± 5.45	16.02 ± 5.69	0.277

Descriptive statistics are presented as mean ± SD; p-values were calculated using the Wilcoxon signed-rank test.

presents the electromyographic (EMG) activity of the temporalis and masseter muscles, revealing no statistically significant changes in muscle activation after the intervention. Although slight variations were observed, these were not significant. Overall, the placement of mini-implants did not significantly affect muscle activity during functional mandibular movements.

3.3. Quality of Life Assessment

Subjects reported an increase in oral health-related quality of life in most parameters; however, no statistically significant difference was observed in the overall OHIP-7Sp score. The average score before the installation of the mini-implants was 8.3 points, decreasing to 7 points after five months, which indicates improvement without reaching statistical significance (p = 0.854). Importantly, a statistically significant improvement was detected in the specific item “dental problems have made you feel totally unhappy” (p = 0.015), with responses shifting from being reported frequently to almost never. In addition, patients expressed satisfaction with esthetics and reported better communication and socialization. However, two subjects reported experiencing unexpected prosthesis dislodgment during use.

4. Discussion

Although there has been significant advancement in preventive treatments for complete edentulism, it still affects a large part of the world’s population [21]. Implant-supported overdentures are an optimal option for fully edentulous patients who cannot opt for an implant-supported prosthesis due to bone quality, anatomical limitations, cost of treatment, or systemic medical conditions [22]. Overdentures retained by conventional implants show good long-term results but also present some limitations, such as cost, difficulty in placing the implant in reduced buccolingual dimensions of the bone, and the presence of chronic systemic diseases [23]. Mini-implant-retained overdentures are an alternative to rehabilitate edentulous patients who express dissatisfaction with conventional prostheses and who have limitations that prevent the placement of conventional implants [24,25]. This study evaluates the clinical success, mandibular movements, electromyographic activity, and oral health-related quality of life associated with the placement of mandibular mini-implants in patients with total prostheses.

In the present study, the placement of two mandibular mini-implants in the canine region demonstrated a significant improvement in patient satisfaction, retention, and stability of the prosthesis, showing outcomes similar to previous studies [25,26,27]. However, in certain instances, a potential lever effect was noted during mastication in the posterior regions, potentially compromising the treatment’s efficacy. This finding highlights the importance of carefully evaluating the distribution of occlusal forces and available bone tissue to consider the number of implants needed in each case.

It is important to note that the quality-of-life assessment conducted at 6 months does not exactly coincide in time with the evaluation of mandibular movements, which was performed at 5 months. It is worth emphasizing that, according to the literature, the highest quality of life scores is usually reached after the first 30 days of denture use and tend to remain stable throughout the first year of adaptation [28]. However, the additional interval between the two assessments may have facilitated greater prosthetic adaptation, consolidation of functional benefits, and other rehabilitation-related processes that could have contributed to the perceived improvement in quality of life. Consequently, the improvement observed in quality of life at 6 months cannot be entirely attributed to the functional improvement evaluated at 5 months; the extra month may also have made a significant contribution.

In this study, the mini-implants used were 13 mm long, which limited the number of subjects that could be rehabilitated, but contributed to a 100% success rate. Previous studies have indicated that longer mini-implants, up to 14 mm, have significantly lower failure rates than those shorter than 7–10 mm [23]. Therefore, bone availability permitting, longer mini-implants are recommended to ensure a higher success rate and treatment longevity.

A key advantage of mini-implants is their reduced surgical complexity, which allows their placement in areas with reduced bone thickness and, in many cases, without the need for surgical flaps [24,25]. This minimally invasive surgical approach reduces postoperative morbidity and increases patient treatment acceptance [23]. In this study, none of the patients reported postoperative complications or discomfort, confirming the benefits of this technique. In addition, mini-implants showed a lower incidence of prosthetic complications, such as fractures of the overdenture or occlusal adjustments, compared to conventional implants. This is due, in part, to the design of the mini-implant components, which enable more resin material to surround them and reduce the risk of fracture [12].

The improvement in prosthetic stability was also reflected in the analysis of the border movements. Significant improvements were observed in parameters such as the vertical range of maximum opening, frontal envelope parameters, retrusion trajectory, and protrusion range. These findings suggest that increased mandibular prosthetic functionality, primarily in the frontal plane, was facilitated by the prosthetic stabilization provided by the mini-implants, reaching values comparable to those of patients with functional dentition [29,30]. Previous studies have shown significant improvement in the mandibular opening range after one year of follow-up, equal to the results obtained in this study [31]. This is mainly due to the greater prosthetic retention provided by the mini-implants, which makes it possible for the prosthesis to follow the movements of the edentulous mandible more effectively during mouth opening. This increases the range of motion and reduces the risk of prosthesis dislodgement, improving its functionality and stability.

Prosthetic stability was also evidenced by chewing cycles during functional mandibular movements. Previous studies and our results show that patients rehabilitated with mini-implants present drop-shaped chewing cycles similar to those of a dentate patient compared to uneven cycles before the rehabilitation [31,32]. Consistent with prior studies, this supports the theory that the neuromuscular system gradually adapts to the new therapy and that the enhanced stability of the mini-implant-retained prosthesis is decisive in increasing the chewing cycle pattern [31,32].

Regarding electromyographic activity, no significant differences were found in temporalis and masseter muscle activation after mini-implant placement, suggesting that the intervention did not alter muscle demands during functional movements. This finding is consistent with previous studies indicating that mini-implant placement stabilizes the prosthesis without affecting masticatory muscle dynamics [33].

In the present study, patients’ existing mandibular complete dentures were converted into overdentures, meaning participants were already well adapted to their prostheses before implant placement. Such pre-existing adaptation likely contributed to the preservation of established and efficient motor patterns in the masticatory muscles, even after the improvement in prosthetic stability [34]. From a neuromuscular standpoint, surface electromyography detects and monitors the biopotentials generated when a neurological or electrochemical stimulus triggers muscle fibers [35]. Therefore, in well-adapted patients, enhancing prosthesis stability without altering occlusal vertical dimension, occlusal scheme, or prosthesis design may not trigger significant modifications in muscular activation patterns.

By contrast, studies reporting significant EMG changes after mini-implant overdenture therapy frequently involve fabrication of new prostheses during treatment [34,36]. In such scenarios, neuromuscular adjustments are driven not only by the increased stability from implants but also by the need to adapt to altered occlusal relationships, new vertical dimension, and changed denture base contours [34,37,38]. Consequently, the absence of EMG changes in the present cohort likely reflects the stability of pre-existing neuromuscular coordination, as no new prosthesis was introduced and functional demands on the masticatory muscles remained essentially unchanged despite the mechanical improvement in retention.

Moreover, it should be noted that neuromuscular adaptation following prosthetic rehabilitation is not immediate; complete stabilization of muscle activity may require between 2 and 12 months [36]. Given that the follow-up period in the present study was relatively short, it is plausible that this limited observation time contributed to the absence of statistically significant differences in EMG activity before and after mandibular mini-implant placement.

Using mini-implants improved not only prosthetic functionality but also the patients’ quality of life. Previous studies have shown that mini-implant-retained overdentures significantly increase retention, stability, comfort, and esthetics, positively impacting patients’ social life and overall satisfaction [3,23,28]. In addition, these benefits have outweighed those of standard implant-supported overdentures [39]. Our findings support these observations, showing that mini-implants are a useful option, particularly for individuals unable to use traditional implants. This is due to the increased retention and stability of the prosthesis, which improve masticatory efficiency, overall comfort, and confidence in social life [26,40].

Limitations of the Study

The primary limitation of this study is the small sample size, which significantly restricts the generalizability of the findings and limits the statistical power. Additionally, the short-term follow-up period prevents a comprehensive evaluation of the long-term stability of functional improvements and the durability of mini-implants. These limitations underscore the need for caution when interpreting the results and highlight the importance of conducting future research with larger, more diverse populations and extended follow-up periods.

Despite these constraints, the preliminary findings remain encouraging. Mini-dental implants have shown clinical feasibility, high survival rates, acceptable levels of marginal bone loss, and positive patient-reported outcomes, suggesting potential value as a prosthetic solution in select patient populations.

5. Conclusions

The findings of this preliminary study suggest that mandibular mini-implants represent a promising and effective alternative for prosthetic stabilization, as a trend toward improved mandibular function and, consequently, overall quality of life was observed in patients. Their advantages, such as reduced postoperative morbidity and the relative simplicity of the surgical procedure, make them particularly suitable for individuals with financial constraints or medical conditions that limit the feasibility of conventional implant placement. However, it is important to emphasize that the exploratory nature of this study and the small sample size limit the generalizability of the results. Therefore, these preliminary findings serve primarily as a basis for informing and justifying future research. Further studies with larger and more diverse populations, and with longer follow-up periods, are needed to validate these results through more rigorous and robust statistical analyses. Such research will be essential to confirm the clinical efficacy, durability, and functional benefits of mandibular mini-implants, as well as to better understand their long-term impact on patient satisfaction and oral health-related quality of life. Ultimately, these efforts will contribute to establishing more robust, evidence-based guidelines for the use of mini-implants in prosthetic rehabilitation.