Maximizing Minimally Invasiveness in the Treatment of Deep Intrabony Defects: When (Flap)Less is More
- Open Access
- 01.12.2026
- REVIEW
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Abstract
Introduction
Minimally invasive approaches have traditionally been associated with specific clinical procedures in general surgery. However, the concept extends beyond technical execution to a broader treatment philosophy emphasizing preservation, precision, and patient-centered care. Indeed, true minimal invasiveness entails avoiding irreversible interventions unless necessary, ensuring optimal timing, and maintaining biological integrity [1].
In periodontology, deep intrabony defects, highly susceptible to disease progression [2], have been a primary focus of minimally invasive periodontal therapy. Seminal studies [3‐5] demonstrated the efficacy of minimally invasive surgical techniques (MIST) in regenerating periodontal structures while reducing morbidity and chair time. More recent advancements highlight the potential of non-surgical approaches in achieving comparable regenerative outcomes. Building upon MIST principles, minimally invasive non-surgical techniques (MINST) emerged [6], facilitated by advancements in magnification, fiber-optic lighting, and microsurgical instruments. MINST represents a shift towards less traumatic, highly effective interventions, emphasizing enhanced healing dynamics and patient-centered outcomes.
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In 2017, Aimetti et al. [7] introduced the “Flapless” approach, aiming at a surgical intervention, but further refining the minimally invasive paradigm by eliminating incisions entirely. By gently retracting the interproximal papilla without full flap reflection, this approach aims to preserve gingival architecture and enhance clot stability, thus accelerating healing and improving patient-reported outcomes [8].
This narrative review critically evaluates the scientific foundations, clinical applications, limitations, and future directions of the flapless approach. It also explores procedural execution, regenerative potential with adjunctive therapies, and comparisons with alternative minimally invasive techniques.
Scientific Foundations for the Flapless Approach
Minimally Invasive Dentistry is the application of “a systematic respect for the original tissue”, it is based on tissue preservation, preferably by prevention and early intervention and then by minimizing tissue loss should intervention be required [9]. This principle recognizes more biological value to the original healthy tissue and is a concept that can be implied on all aspects of the dental profession [9].
Periodontitis is a chronic inflammatory disease of the tooth supporting tissues, with a prevalence of approximately 50% of the population in its moderate and severe form [10, 11]. Thus, applying the concepts of minimally invasive dentistry in the whole periodontal treatment approach could be of a great value in minimizing tooth loss and the need of periodontal surgery, as well as the patient perception [12]. And thus, potentially reducing cost, time and patient’s morbidity.
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When it comes to deep intrabony defects > 3 mm, different regenerative techniques and approaches have been proposed, evolved and modified over the years along with the evolvement of instruments, materials, and magnification systems (Fig. 1). One of the most significant evolvement goes back to 1985, when the papilla preservation technique (PPT) was proposed, minimizing the invasiveness of the surgery and aiming to reduce the risk of membrane exposure [13]. Ten years later, a new modification to this technique was proposed. The modified papilla preservation technique (MPPT) shifted the incision line to the vestibular side apical to the defect, allowing better healing, reducing soft tissue trauma and better tissue adaptation with the possibility to advance the flap more coronally after reflecting the papilla to the other side without challenging the visibility and accessibility to the intrabony defect [3], later another modification to the incision design was made to allow papillary preservation in posterior areas or in narrow interpoximal spaces; simplified papilla preservation technique (SPPT) [14]. The concept of MIS was proposed by Harrel in 1998, minimizing both incisions and flap reflection [15], and the technique of MPPT was adopted alongside the principles of Harrel to create what was called MIST [4].
Fig. 1
Evolution of the operative techniques used for the treatment of infrabony defects
Subsequently, other modifications were introduced in order to minimize soft tissue trauma and to have better aesthetic results involving only a single incision without the elevation of papilla [16]. These evolvements allowed to shift the concept of periodontal regeneration adopting even less invasive approaches, by single flap procedures (M-MIST and SFA) as the modified minimally invasive surgical technique [17, 18], or the entire papilla preservation technique [19]. Ensuring stable and continuous closure of the interproximal space remains a key determinant of clot protection and wound stability, irrespective of the surgical or non-surgical approach adopted. The adoption of minimally invasive concepts, together with advances in biomaterials, microsurgical instruments, and magnification systems, has progressively led to techniques that eliminate surgical incisions altogether, as in MINST and flapless. This evolution potentially enhances postoperative vascular recovery and promotes greater stability of the blood clot within the interproximal space—factors considered critical for wound stability and early healing [6, 20, 21].
From this perspective, they should not be conflated with traditional non-surgical periodontal treatment, as its goal extends beyond infection control toward guiding healing in a more reconstructive direction [4]. It had been shown that a less invasive, less traumatizing flap leads to faster recovery of the gingival blood flow postoperatively, resulting in enhanced healing and better clot stability [22].Thus, the elimination of the incision and adopting a flapless approach, may theoretically result in a faster recovery of blood flow post operatively and a higher stability of the blood clot in the interpoximal area, resulting in biological healing condition that might move from a repair to a regeneration process [20].
Indications and Contraindications for the Flapless Approach
Residual pathological pockets with an intrabony pattern of bone resorption following initial therapy present an elevated risk of disease progression [23]. From the European Federation of Periodontology Treatment Guideline [24], Step III periodontal therapy implies the recommendation for surgical periodontal regeneration with papilla preservation techniques for treating unresolved deep intrabony defects [25]. However, accumulating evidence supports the efficacy of MINST as a non-inferior alternative [26].
The ability to accurately identify defects suitable for specific treatment modalities is crucial for achieving personalized and tailored therapy. To this regard, the flapless approach is particularly indicated for site-specific treatment of residual deep intrabony defects (≥ 3 mm) with probing depths (PPD) of ≥ 6 mm. Criteria for suitability include:
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marginal soft tissue integrity to allow for atraumatic instrumentation;
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localized interproximal defects without extensive buccal/lingual extension;
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favorable defect morphology, typically deep and narrow intrabony lesions.
To the last regard, it was suggested that narrower, deeper defects yield superior outcomes in MINST, whereas defects exceeding 45° show less favorable responses [27]. Moreover, from the first investigation conducted, it appeared that the results of the flapless procedure achieved better results in anterior sextants compared to posterior ones [7]. While the flapless approach has primarily been evaluated for residual intrabony defects, broader applications of MINST in managing residual pockets irrespective of defect type have also been reported [28]. Interestingly, while defect morphology is a well-established determinant of outcomes in surgical periodontal regeneration, its role appears less critical in non-surgical approaches such as flapless and MINST. This may be attributed to the preservation of marginal soft tissues in these techniques, maintaining the ‘soft tissue walls’ that contribute to clot stability and wound healing, thereby minimizing the influence of underlying bony architecture.
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Conversely, factors that may limit the potential of the flapless technique include:
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systemic conditions affecting periodontal healing (e.g., uncontrolled diabetes, radiation therapy, pregnancy/lactation);
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anatomical constraints such as furcation involvement;
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inadequate endodontic treatment;
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thin phenotype;
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fragile papillary tissue prone to ulceration.
It should be noted, however, that many of these systemic contraindications are general considerations applicable to all periodontal surgical procedures. In this context, the reduced biological invasiveness of the flapless approach may offer theoretical advantages in selected medically compromised patients. Nonetheless, no clinical studies have yet specifically evaluated the use of flapless techniques in such patient populations.
Technical Execution
The flapless procedure per definition is an independent Step III treatment modality of periodontal therapy. The correct diagnosis and meticulous pre-procedural conditions, including FMPS < 15% and absence of marginal inflammation, especially at the site of interest, are fundamental in order to achieve successful outcomes. As suggested by prior literature, the site-specific inflammatory and infectious burden should be minimized before regenerative periodontal treatment in order to decrease complications [33].
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The flapless procedure, as initially described [7, 8] involves the following steps, performed under amplification either by surgical loupes with a magnification of x 3.5 and fibre-optic lighting or microscope (Fig. 2).
Fig. 2
Step-by-step description of the flapless approach with adjunctive enamel matrix derivatives (EMD); (a) clinical view at baseline; (b) gentle lateral papilla displacement; (c) sub-gingival instrumentation and degranulation of the defect; (d) root surface conditioning with 24% EDTA (PrefGel, Institut Straumann, Basel Switzerland); (e) application of EMD on dried root surface; (f) repositioning and gentle compression of gingival margin
1.
An atraumatic insertion of local anesthesia at the site of interest.
2.
A gentle lateral papilla displacement carried out by using an atraumatic gingival retractor or microsurgical mirror in order to allow for optimal root visualization and gain access to the intrabony defect.
3.
Precise debridement of the exposed root surface with the combined use of magnetostrictive ultrasonic device and minicurets and with extended thin shank narrowing to a probe-sized tip. Instrumentation performed until no residual calculus can be detected by a gentle and careful root detection with a periodontal explorer and by visual investigation, facilitated by gentle papilla displacement.
4.
The careful removal of granulation tissue within the intrabony component by the use of minicurettes with caution to avoid supracrestal soft tissue trauma. This step allows to further increase the intra-surgical visibility due to reduced bleeding and space provision.
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In case the EMD is applied, the root surface is conditioned for 2 min with 24% EDTA and thoroughly rinsed with sterile saline solution, allowing to remove smear layer, residual plaque and blood on the exposed root surface.
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After drying the root surface by means of sterile thread gauzes and gentle use of air syringe, EMD is immediately applied on the dried root surface.
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Eventually, a gentle compression of the gingival margin is applied by means of sterile wetting gauzes and blunt instruments, such as papilla retractor, until a complete pocket marginal closure is attained.
During the first postoperative day, patients are advised to avoid using interdental brush and flossing in the treated area. From the following days, patients follow their home oral hygiene procedures as usual. Recall visits are then scheduled at 2 weeks, and then every 3 months for the first year, when supra-gingival soft or hard deposits are removed, and oral hygiene instruction reinforced.
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Adjunctive Therapies to Enhance Outcomes
The use of EMD is recommended in association with periodontal regenerative therapy [24] and is considered–alongside the use of barrier membranes–the gold standard for the surgical treatment of deep intra-bony defects [34]. EMD was firstly used in periodontal reconstructive therapies in 1997 [35], and has become one of the most heavily researched dental products [36]. EMD is a composite of enamel matrix proteins, 90% of which is composed of porcine-derived amelogenin [37, 38]. EMD stimulates fibroblast proliferation, migration, and collagen production, critical for PDL regeneration [37, 39]. It also promotes the differentiation of mesenchymal cells into cementoblasts, aiding in new cementum formation [38]. EMD also indirectly supports bone regeneration by stimulating the proliferation and differentiation of osteoblasts [40], and by also promoting primary osteoblast growth [41]. It also fosters angiogenesis [42], as well as possessing an anti-inflammatory effect [43], as well as anti-apoptotic effects enhancing cell survival [44]. In periodontal regeneration, histological studies on humans demonstrated that EMD has an increased potential to support formation of new cementum, bone, a new periodontal ligament, and a new connective tissue attachment when used as an adjunct to nonsurgical periodontal treatment [45].
Biologically active agents such as growth factors and biomimetic scaffolds were also integrated to different flapless protocols in order to enhance clinical and histologic results. Topical application of Hyaluronic Acid (HA) was found to have an additional clinical benefits when used as an adjunctive to non-surgical periodontal therapy [46]. Furthermore, the application of HA in residual pockets during supportive periodontal care increased the probability of pocket closure and thus the need for periodontal surgery [47]. Moreover, when used as an adjunctive to MINST for treating intrabony defects ≥ 3 mm, it was found to significantly reduce gingival recessions [48]. There is also a low-quality evidence supporting the additional benefit of autologous platelet concentrates during the surgical treatment of infrabony defects [49], as well as recombinant human platelet-derived growth factor and fibroblast growth factor [50‐53]. However, evidence supporting their use specifically in combination with MINST or flapless protocols remains limited.
This area represents a relevant opportunity for future research, particularly given the theoretical advantages of combining biologic agents with techniques that preserve soft tissue integrity and maximize wound stability. Under this perspective, the adjunctive use of such healing modulators may not only enhance regenerative outcomes in intrabony defects but could also contribute to improved management of suprabony or combined defects, favoring tissue repair within a sealed wound environment.
Clinical Efficacy of the Flapless Approach
To date, the flapless approach has been exclusively assessed as a Step III treatment. In the first RCT evaluating the flapless approach for residual deep intrabony defects with or without adjunctive EMD, significant clinical improvements were observed at 6 and 12 months, with EMD-treated sites achieving greater clinical gains, a higher rate of complete pocket closure and increased radiographic bone fill (Fig. 3) [8]. Specifically, the flapless + EMD group showed a mean PPD reduction of 3.9 mm, CAL gain of 3.9 mm, and no increase in recession, slightly improving upon earlier findings from the same research group [7].
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Fig. 3
Representative cases for the flapless with adjunctive enamel matrix derivatives (EMD) (a–d). Clinical views at baseline (a); radiographic views at baseline (b); clinical views at 12 months (c); radiographic images at 12 months (d). Case treated by Dr.ssa G. Mariani
These findings align with prior studies on MINST [6, 21]. Anoixiadou et al. [54] eported comparable, or slightly superior, clinical outcomes following MINST, with a mean PPD reduction of 4.0 mm and CAL gain of 3.5 mm. However, differences in treatment protocols likely explain these variations, as their study applied MINST after a single session of supragingival and subgingival instrumentation, avoiding prior full-mouth disinfection. The well-established observation that the first instrumentation cycle offers the greatest therapeutic benefit may explain these results [55]. Jentsch et al. [28], evaluating MINST in residual pockets of various defect types, reported more modest improvements, with PPD reducing from 5.9 mm to 4.6 mm without adjunctive biomaterials. These findings suggest that intrabony defects, in particular, benefit more from defect-targeted re-instrumentation using minimally invasive strategies [25]. Earlier studies using MINST during initial therapy generally reported CAL gains around 2.5–2.8 mm, with slightly increased recession [6, 21].
In contrast, the adjunctive use of EMD in the flapless approach significantly improved treatment endpoints. Composite outcome success (COM) was achieved in 82.6% of cases in the flapless + EMD group, exceeding rates reported in MINST studies with adjunctive EMD, such as those by Anoixiadou et al. [54] (61.1%). Radiographic assessments further supported these findings, showing significantly greater bone defect fill in the flapless + EMD group (3.0 mm) compared to controls (1.8 mm). These radiographic outcomes surpassed those reported in previous MINST studies, although variations may be partly explained by baseline defect depth, as deeper defects exhibit greater regenerative potential. Additionally, an increase in defect angle at 12 months, particularly in EMD-treated sites, suggested enhanced bone maturation at the defect base [21]. Overall, adjunctive EMD appears to significantly enhance the regenerative outcomes of the flapless approach, aligning with recent systematic reviews reporting superior outcomes when EMD is combined with non-surgical therapy [56].
Compared to MIST, the flapless approach offers theoretical and clinical advantages by entirely preserving supracrestal soft tissues while allowing effective root debridement. In a randomized clinical trial [8], the outcomes of the flapless + EMD approach were clinically and radiographically comparable to MIST. Particularly when dealing with intrabony defects related to anterior teeth, this technique offers an additional advantage by reducing the risk of gingival recession. Indeed, negligible gingival recession was observed, making the flapless approach particularly suitable for esthetically sensitive areas.
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Finally, the flapless technique may align better with modern, patient-centered objectives in periodontal care. By eliminating incisions, it minimizes surgical morbidity and supports faster recovery, allowing patients to return to daily activities more quickly. These factors may also promote greater adherence to supportive periodontal therapy, as reduced procedural discomfort and postoperative limitations potentially enhance patient compliance.
Histological Healing
The goal of initial periodontal therapy is the resolution of inflammation and the establishment of periodontal stability, even in the presence of residual pockets [24]. Clinically, nonsurgical periodontal therapy by mechanical subgingival instrumentation is an efficacious mean to achieve infection control in periodontitis patients [57], and is the recommended treatment to be performed during step II periodontal therapy according to the latest clinical guidelines [24]. Nonsurgical periodontal therapy was found to be effective to achieve the above mentioned endpoints, not only in terms of reducing inflammation and probing pocket reduction, but also in clinical attachment level gain CAL, as a CAL gain of 0.5–1 mm is expected following subgingival instrumentation [58].
However, this attachment gain following periodontal instrumentation is found to be an expression of repair by means of epithelial reattachment forming what is called “long junctional epithelium’’, rather than a complete regeneration of periodontal tissues. This was explained by the possibility that gingival epithelial cells migrate to occupy the empty space above the detoxified root surface faster than gingival connective tissue, or bone cells [59]. Earlier histologic studies on animals reported healing predominantly by the formation of long junctional epithelium with no new connective tissue attachment [60, 61]. Similar results were also confirmed on humans in advanced infrabony defects, where nonsurgical periodontal therapy, even with the use of EMD, could not achieve periodontal regeneration but only a gain of clinical attachment by long junctional epithelium [36].
However, the abovementioned studies had only investigated traditional nonsurgical therapy modalities, and up to this date, there is still a lack of direct histologic studies on both animal or human models studying the effect of flapless approach adopting the principles of minimally invasive periodontology. Some insight comes from early animal studies, which laid the foundation for understanding regenerative capacity in non-surgical contexts. For instance, Wikesjö demonstrated in non-human primates that guided tissue regeneration could result in histologically confirmed regeneration, but these findings were based on open-flap models [62]. In a similar vein, Bosshardt provided detailed histologic observations of periodontal healing following EMD application in beagle dogs, confirming cementum and bone formation [63]. However, these findings again emerged from surgically accessed defects.
In humans, only a few landmark studies have included histologic evaluation after non-surgical instrumentation. One of the rare examples is the work of Caton et al. [64], who observed limited new attachment formation after thorough non-surgical scaling and root planing, but mostly repair by long junctional epithelium. Similarly, Bowers et al. [65] found that without regenerative materials or surgical access, histological regeneration is minimal, reinforcing the view that mechanical debridement alone rarely induces true regeneration. While no direct human histological studies exist for MINST in a flapless setting, few animal studies have evaluated the regenerative potential of MINST with adjunctive use of biomaterials like EMD. In dogs, Sculean et al. [66] showed that EMD applied without flap elevation could promote new attachment formation, albeit to a limited extent compared to open-flap procedures.
Challenges and Limitations
Non-surgical periodontal therapy remains the cornerstone of periodontitis management. Yet, despite the evolution toward MINST, it still poses multiple challenges. These procedures, while reducing patient morbidity and promoting tissue preservation, are inherently skill-dependent and subject to a steep learning curve. Site-related factors such as defect depth, configuration, and the quality of overlying soft tissues significantly influence treatment outcomes. Moreover, surgeon-dependent variables—including dexterity, experience, and familiarity with minimally invasive instrumentation—play a decisive role in achieving optimal clinical and esthetic result [33, 67].
Persistent inflammation at residual pockets has been consistently associated with inferior regenerative outcomes and a higher risk of post-operative complication [68‐70]. Managing these residual inflammatory sites prior to regenerative procedures remains a clinical dilemma. Various strategies, including adjunctive local antimicrobial application, have been explored to enhance site readiness. For example, subgingival delivery of doxycycline has been shown to reduce local inflammation and improve soft tissue quality before surgery, as shown in the BOOST (BiO-Optimizing Site Targeted) protocol [70]. Optimizing local tissue conditions is not only critical for wound stability, but also for maintaining the integrity of the coagulum, especially when biomaterials such as EMD or growth factors are used [71].
One inherent limitation of the flapless approach lies in restricted access and visibility within deep periodontal pockets. This can compromise the effectiveness of subgingival debridement and increase the risk of incomplete calculus and biofilm removal—factors directly correlated with regenerative failure. Endoscopic-assisted subgingival debridement (EASD) was introduced to overcome this barrier. Initially proposed by Stambaugh et al. [72], EASD enables real-time visualization of root surfaces and has shown promising results in improving the efficacy of debridement [73‐75]. Recent randomized trials suggest that EASD may serve as a non-inferior alternative to papilla preservation flap surgery for isolated deep residual defects, positioning it as a candidate for re-instrumentation rather than a first-line alternative to surgical intervention in Step 3 therapy [76]. Nonetheless, EASD is not without drawbacks. Prolonged instrumentation time, high operator demands, and the cost of equipment and consumables have hindered its widespread adoption [27‐7].
Despite growing clinical interest and patient acceptance of MINST and flapless regenerative procedures, limitations in the available evidence remain. One key gap is the scarcity of histological data evaluating true periodontal regeneration following MINST. Ethical constraints and the invasive nature of biopsy sampling limit the feasibility of histological confirmation in human studies, making most conclusions reliant on clinical surrogate endpoints such as CAL gain and radiographic bone fill [7, 8, 21, 54].
Additionally, there is insufficient high-quality, long-term data comparing various regenerative materials used in non-surgical settings. The heterogeneity of study designs, variation in defect characteristics, and differences in operator expertise further complicate the interpretation and generalization of outcomes. The role of host-related variables (e.g., systemic inflammation, immune profile, neuro-endocrine status) in determining regenerative outcomes in MINST-treated sites also remains underexplored [77‐79]. Moreover, one of the future goals would be to expand the indications of this technique, applying also to suprabony defect, furcation defect and peri-implantitis defects.
Conclusions
The flapless approach can be a viable therapeutic option for the minimally invasive treatment of residual pockets associated with deep intrabony defects, with EMD providing a boosting effect. This technique may be regarded as a complete soft tissue preservation flap for periodontal regeneration, which provides minimal soft tissue trauma and better wound stability, while reducing the chair time and patients’ discomfort. It has been demonstrated to be at least as effective as MIST, particularly in the esthetic anterior regions, however, further long-term and multi-center studies are warranted to provide additional clinical evidence.
Key References
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Aimetti M, Stasikelyte M, Mariani GM, Cricenti L, Baima G, Romano F. The flapless approach with and without enamel matrix derivatives for the treatment of intrabony defects: A randomized controlled clinical trial. J Clin Periodontol. 2024;51:1112–21.
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○ A pivotal randomized controlled trial demonstrating the clinical efficacy of the flapless technique with and without enamel matrix derivative (EMD). This is the first study to report one-year outcomes using the flapless approach, showing significant CAL gain, high rates of pocket closure, and enhanced bone fill, especially in the EMD group.
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Ribeiro FV, Mehta JJ, Monteiro MF, Moore J, Casati MZ, Nibali L. Minimal invasiveness in nonsurgical periodontal therapy. Periodontol 2000. 2023;91:7–19.
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○ A comprehensive review on the principles and clinical implications of minimally invasive non-surgical therapy (MINST), highlighting its evolution, indications, and outcomes across different clinical scenarios.
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Nibali L, Mehta J, Al-Shemeri D, Anoixiadou S, Parashis A, Vouros I. Association between defect morphology and healing of intrabony defects treated with minimally invasive non-surgical therapy: A pilot exploratory analysis of two cohorts. J Periodontal Res. 2023;58:708–14.
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○ An important clinical study suggesting that baseline defect morphology significantly influences outcomes following MINST, reinforcing the need for defect-specific treatment planning.
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Chatzopoulos GS, Anastasopoulos M, Zarenti S, Doufexi A-E, Tsalikis L. Flapless application of enamel matrix derivative in non-surgical periodontal treatment: A systematic review. Int J Dent Hyg. 2022;20:422–33.
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○ This systematic review critically evaluates the existing literature on the non-surgical use of EMD, including flapless applications. It identifies promising clinical trends but highlights the need for further high-quality studies, supporting the rationale for the present investigation.
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Aimetti M, Baima G, Lorenzetti V, Aliyeva N, Bottone M, Mariani GM, et al. A BiO-Optimizing Site Targeted (BOOST) Approach to Periodontal Regeneration Through Local Doxycycline Prior to Surgery: A Randomized Clinical Trial. J Periodontal Res. 2025.
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○ A recent RCT exploring how local anti-inflammatory conditioning before regenerative surgery improves early molecular and clinical outcomes. The study contributes mechanistic insight into preoperative modulation strategies relevant for minimally invasive protocols.
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Declarations
Consent for publication
This study is a narrative review and did not involve the enrollment of human or animal subjects. Therefore, no specific informed consent was required. However, written informed consent was obtained from patients for the use of original clinical photographs included in the manuscript.
Competing interests
The authors declare no competing interests.
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