Mandibular Overdentures Retained by Mini Implants: a Clinical Trial Comparing Different Surgical and Loading Protocols (SMIS)

Mandibular Overdentures Retained by Mini Implants: a Clinical Trial Comparing Different Surgical and Loading Protocols

One-piece TiZr Mini Implants With Miniaturized Carbon-based Coating Prosthetic Connection for Mandibular Overdentures: a Factorial, Randomized Clinical Trial Testing the Outcomes of Immediate/Delayed Loading and Flapped/Flapless Surgery

This study aims to test the combined effects of different loading protocols and surgical approaches on clinical and patient-reported outcome measures (PROMs) following the use of four mini implants for mandibular overdenture retention. The main study hypotheses are: There are significant improvements in PROMs following implant intervention compared to baseline measures; Immediately loaded mini implants have similar failure rates compared to mini implants receiving a delayed 6-week protocol. Flapless surgery has similar post-insertion outcomes compared to flapped surgery.

This study aims to test the combined effects of different loading protocols and surgical approaches on clinical and patient-reported outcome measures (PROMs) following the use of four mini implants for mandibular overdenture retention. Main study hypotheses: There are significant improvements in PROMs following implant intervention compared to baseline measures; Immediately loaded mini implants have similar failure rates compared to mini implants receiving a delayed 6-week protocol; Flapless surgery has similar post-insertion outcomes compared to flapped surgery. Statement of clinical relevance: Mini implants are an alternative to standard implants for overdentures. They are suitable for insertion in narrow ridges, are less invasive, simpler, less costly, and faster to perform, and are especially advantageous for older and frail patients who would benefit from more conservative and less burdensome treatments. Although previous studies reported favorable outcomes regarding patient oral comfort and function, there is a need for implant/attachment systems with higher predictability on implant survival and retention performance in the long-term. This study aims to provide clinical evidence on the newly developed 2.4mm one-piece TiZr mini implant with a miniaturized carbon-based coating attachment. Methods: This is a randomized clinical trial using a factorial design, to test the effectiveness of a mandibular overdenture retained by four mini implants. Participants will be randomized using a 2×2 factorial design: immediate/delayed loading (factor 1) and flapless/flapped surgery (factor 2). New conventional complete dentures will be provided as the baseline treatment. Next, eligible participants will be those who completed a 6-month period of denture usage, and are in need of implants to improve the function of the mandibular denture. Imaging exam should present a minimum of 5.4 mm of ridge width in the interforaminal region (recommended for flapless surgery). Included subjects to take part in the RCT will be randomized to the treatment groups according to the combined study factors - loading protocols: immediate (IL) or delayed (DL); and surgical approaches: flapless (FLS) or flapped (FPS) surgery. Hence, the combined factors will results in four groups: IL/FLS (Group I) IL/FPS (Group II) DL/FLS (Group III) DL/FPS (Group IV) Considering the patient's perspective this study design assumed a "worst" protocol (delayed and flapped - Group IV) and a "best" protocol (flapless and immediate - Group I) and two other intermediary conditions (flapped/immediate and flapless/delayed). All participants will receive four Straumann® Mini Implant System (one-piece Tissue Level implants) with an Optiloc® prosthetic connection and PEEK matrix inserts. Surgery will follow the workflow for the surgical procedure for the Straumann® Mini Implant System concerning preoperative planning, implant bed preparation and implant insertion. For the prosthetic procedures, we will perform a chairside incorporation of the retentive inserts to convert the existing well-fitting and well-functioning lower denture into an overdenture with the Optiloc® Retentive System/Straumann® Mini Implants. Outcomes will include short-term outcomes (Patient perceived burdens in surgery, postoperative swelling and pain, consumption of analgesics and surgical time) and long-term - 1-year (implant survival and success, peri-implant marginal bone level changes, PROMs, retention force, prosthodontic events) outcomes. Sample size calculation resulted in a total of 74 participants, 18 in each of the four groups. Data analysis will include descriptive and bivariate analyses, Kaplan-Meier curves and regression models using Generalized Estimating Equations (GEE) for longitudinal data.

A factorial experiment of two factors is planned, each with two possible values or "levels", and whose experimental units take on all possible combinations of these levels across all such factors (2×2 factorial design), allowing the study to determine the effect of each factor on the response variable, as well as the effects of interactions between factors on the response variable. The tested factors will be: loading protocol (immediate or delayed), and surgical approach (flapped or flapless), resulting in a factorial experiment with four treatment combinations in total. Hence, the design is denoted a 2² factorial, which identifies the number of factors (n=2) and how many levels each factor has (n=2) there are in the design (2²=4).

The assessment of longitudinal outcomes will be performed by an assessor blinded to the surgical/loading protocols

The Burdens in Oral Surgery Questionnaire (BiOS-Q) will be used to assess patient-perceived burdens. It includes 16 items concerning all aspects of procedures occurring during a surgery. Responses for each item are assessed using a visual analogue scale (VAS) ranging from 0 = no expression of the attribute (e.g. not unpleasant at all) to 100 = maximum expression (e.g. very unpleasant).

Each implant will be assessed according to the health scale of the International Congress of Oral Implantologists (ICOI-Pisa health scale). After clinical assessment, each implant will be classified as 'success', 'satisfactory survival', 'compromised survival' or 'failure'.

A 100-cm graduated visual analog scale will be used to evaluate participants' assessments of pain and discomfort regarding the surgical process. Each participant will indicate their level of pain and discomfort with each parameter by marking a point along the scale.

A 100-cm graduated visual analog scale will be used to evaluate participants' assessments of pain and discomfort regarding the surgical process. Each participant will indicate their level of pain and discomfort with each parameter by marking a point along the scale.

A 100-cm graduated visual analog scale will be used to evaluate participants' assessments of pain and discomfort regarding the surgical process. Each participant will indicate their level of pain and discomfort with each parameter by marking a point along the scale.

The number of analgesics consumed by the participant during the post-operative and healing period will be recorded in the patient's file.

The McGill Denture Satisfaction Instrument - DSI (Awad & Feine, 1998; de Grandmont et al., 1994) will be used to assess patients' satisfaction relating to their prostheses. This is a treatment-specific patient-based outcome assessing satisfaction relating to several aspects of the mandibular prosthesis, including general satisfaction, comfort, stability, aesthetics, chewing ability (ease of chewing), chewing efficiency (ability to crush food in small particles), ease of cleaning, ability to speak and oral condition (condition of their mouth, which can refer to oral health status and was measured by "In general, are you satisfied with your oral condition?''. The subjects will answer on a 100 mm visual analogue scale (VAS) anchored by the words 'not at all satisfied' and 'extremely satisfied'.

The McGill Denture Satisfaction Instrument - DSI (Awad & Feine, 1998; de Grandmont et al., 1994) will be used to assess patients' satisfaction relating to their prostheses. This is a treatment-specific patient-based outcome assessing satisfaction relating to several aspects of the mandibular prosthesis, including general satisfaction, comfort, stability, aesthetics, chewing ability (ease of chewing), chewing efficiency (ability to crush food in small particles), ease of cleaning, ability to speak and oral condition (condition of their mouth, which can refer to oral health status and was measured by "In general, are you satisfied with your oral condition?''. The subjects will answer on a 100 mm visual analogue scale (VAS) anchored by the words 'not at all satisfied' and 'extremely satisfied'.

The McGill Denture Satisfaction Instrument - DSI (Awad & Feine, 1998; de Grandmont et al., 1994) will be used to assess patients' satisfaction relating to their prostheses. This is a treatment-specific patient-based outcome assessing satisfaction relating to several aspects of the mandibular prosthesis, including general satisfaction, comfort, stability, aesthetics, chewing ability (ease of chewing), chewing efficiency (ability to crush food in small particles), ease of cleaning, ability to speak and oral condition (condition of their mouth, which can refer to oral health status and was measured by "In general, are you satisfied with your oral condition?''. The subjects will answer on a 100 mm visual analogue scale (VAS) anchored by the words 'not at all satisfied' and 'extremely satisfied'.

The McGill Denture Satisfaction Instrument - DSI (Awad & Feine, 1998; de Grandmont et al., 1994) will be used to assess patients' satisfaction relating to their prostheses. This is a treatment-specific patient-based outcome assessing satisfaction relating to several aspects of the mandibular prosthesis, including general satisfaction, comfort, stability, aesthetics, chewing ability (ease of chewing), chewing efficiency (ability to crush food in small particles), ease of cleaning, ability to speak and oral condition (condition of their mouth, which can refer to oral health status and was measured by "In general, are you satisfied with your oral condition?''. The subjects will answer on a 100 mm visual analogue scale (VAS) anchored by the words 'not at all satisfied' and 'extremely satisfied'.

The cross-culturally adapted Brazilian version of the Oral Health Impact Profile for edentulous subjects (OHIP-EDENT) will be used. It contains 19 items divided in four different subscale domains: (I) masticatory discomfort and disability (four items), (II) psychological discomfort and disability (five items), (III) social disability (five items), and (IV) oral pain and discomfort (five items). The items are answerable by a 3-point Likert scale and responses will be summed to result an overall score. Higher scores represent worse OHRQoL.

The cross-culturally adapted Brazilian version of the Oral Health Impact Profile for edentulous subjects (OHIP-EDENT) will be used. It contains 19 items divided in four different subscale domains: (I) masticatory discomfort and disability (four items), (II) psychological discomfort and disability (five items), (III) social disability (five items), and (IV) oral pain and discomfort (five items). The items are answerable by a 3-point Likert scale and responses will be summed to result an overall score. Higher scores represent worse OHRQoL.

The cross-culturally adapted Brazilian version of the Oral Health Impact Profile for edentulous subjects (OHIP-EDENT) will be used. It contains 19 items divided in four different subscale domains: (I) masticatory discomfort and disability (four items), (II) psychological discomfort and disability (five items), (III) social disability (five items), and (IV) oral pain and discomfort (five items). The items are answerable by a 3-point Likert scale and responses will be summed to result an overall score. Higher scores represent worse OHRQoL.

The cross-culturally adapted Brazilian version of the Oral Health Impact Profile for edentulous subjects (OHIP-EDENT) will be used. It contains 19 items divided in four different subscale domains: (I) masticatory discomfort and disability (four items), (II) psychological discomfort and disability (five items), (III) social disability (five items), and (IV) oral pain and discomfort (five items). The items are answerable by a 3-point Likert scale and responses will be summed to result an overall score. Higher scores represent worse OHRQoL.

The incidence of prosthodontic repair/adjustment events will be recorded during the clinical assessments.

The time interval concerning the clinical visit for implant placement and delivery of the overdenture or denture adaptation will me measured and registered.

Procedure (Assessed during the clinical visit of implant placement and overdenture delivery or denture adaptation.)

To perform the masticatory performance test two gums in a dragée form will be used, one blue and one pink, which need to be stuck together manually by wetting them with water and applying moderate force. The participants will be instructed to chew 2 samples of the gum on theirs preferred chewing side for 20 and 50 chewing cycles, respectively, leaving an interval of 1 minute between each chewing sequence.

To perform the masticatory performance test two gums in a dragée form will be used, one blue and one pink, which need to be stuck together manually by wetting them with water and applying moderate force. The participants will be instructed to chew 2 samples of the gum on theirs preferred chewing side for 20 and 50 chewing cycles, respectively, leaving an interval of 1 minute between each chewing sequence.

To perform the masticatory performance test two gums in a dragée form will be used, one blue and one pink, which need to be stuck together manually by wetting them with water and applying moderate force. The participants will be instructed to chew 2 samples of the gum on theirs preferred chewing side for 20 and 50 chewing cycles, respectively, leaving an interval of 1 minute between each chewing sequence.

To perform the masticatory performance test two gums in a dragée form will be used, one blue and one pink, which need to be stuck together manually by wetting them with water and applying moderate force. The participants will be instructed to chew 2 samples of the gum on theirs preferred chewing side for 20 and 50 chewing cycles, respectively, leaving an interval of 1 minute between each chewing sequence.

Maximum voluntary bite force will be measured with a digital gauge (IDDK - Kratos, Cotia, São Paulo, Brazil) in the region of the first molar with three assessments per side.

Maximum voluntary bite force will be measured with a digital gauge (IDDK - Kratos, Cotia, São Paulo, Brazil) in the region of the first molar with three assessments per side.

Maximum voluntary bite force will be measured with a digital gauge (IDDK - Kratos, Cotia, São Paulo, Brazil) in the region of the first molar with three assessments per side.

Maximum voluntary bite force will be measured with a digital gauge (IDDK - Kratos, Cotia, São Paulo, Brazil) in the region of the first molar with three assessments per side.

Periapical radiographs will be obtained and the peri-implant bone level will be measured and compared longitudinally.

Periapical radiographs will be obtained and the peri-implant bone level will be measured and compared longitudinally.

Periapical radiographs will be obtained and the peri-implant bone level will be measured and compared longitudinally.

Inclusion Criteria: No contraindications for implant surgery (mainly related to uncontrolled systemic diseases); Enough bone height in the interforaminal area for an implant length of at least 10 mm; Ability to understand and answer the questionnaires used in the study and agree to participate by providing a written informed consent. Exclusion Criteria: Noncompliant participants; Disagreement to be randomly allocated to the treatment study groups; Signs of untreated temporomandibular disorders or uncontrolled systemic or oral conditions that require additional treatments.

Clinical data will be implemented electronically using a dedicated electronic data capturing (EDC) system (REDCap DMS, https://www.project-redcap.org/), hosted by the server infrastructure of the Federal University of Goias. Data will be entered in REDCap using either the web-based application or the REDCap mobile app for iOS/Android. Baseline and longitudinal health-related data, and patient identifying codes used for the analysis will be entered in a REDCap database. The Report Builder will be used to create customized reports that are queried in real time.

Data will be available after publication of the results in high-impact journals, and until two years hereafter

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