1. Definition and rationale of minimally invasive surgical technique (MIST) in periodontal regeneration.
2. Case selection and indications, including defect morphology and interdental space requirements.
3. Preoperative assessment and instruments, including magnification and microsurgical equipment.
4. Surgical principles and flap design, including papilla preservation and access incisions.
5. Operative steps, such as debridement, root surface management, regenerative material placement, and wound closure.
6. Modified minimally invasive surgical technique (M-MIST) and its distinguishing features.
7. Use with regenerative materials, including enamel matrix derivative and bone grafts where described in the supplied texts.
8. Clinical outcomes, advantages, limitations, and complications.
9. Postoperative care and evaluation of healing.

1. Definition and rationale of minimally invasive surgical technique (MIST) in periodontal regeneration.
2. Case selection and indications, including defect morphology and interdental space requirements.
3. Preoperative assessment and instruments, including magnification and microsurgical equipment.
4. Surgical principles and flap design, including papilla preservation and access incisions.
5. Operative steps, such as debridement, root surface management, regenerative material placement, and wound closure.
6. Modified minimally invasive surgical technique (M-MIST) and its distinguishing features.
7. Use with regenerative materials, including enamel matrix derivative and bone grafts where described in the supplied texts.
8. Clinical outcomes, advantages, limitations, and complications.
9. Postoperative care and evaluation of healing.

Minimally Invasive Surgical Technique (MIST)

Introduction

• Periodontal regeneration remains one of the primary therapeutic approaches toward management of periodontal defects. Selection of an appropriate therapeutic approach is based on accurate assessment of the periodontal defect, past clinical experience, familiarity with regenerative and resective techniques, and patient selection for regenerative options. Successful regenerative surgery requires delicate and timely tissue management to minimize tissue shrinkage. Important surgical considerations are good passive flap closure for encasement of graft materials and a flap design allowing tension-free suture placement.
  Source: Newman and Carranza’s Clinical Periodontology and Implantology, 14th ed., Chapter 63, “Therapeutic Considerations.”
• The concepts of using conservative and minimally invasive flap approaches have been introduced as minimally invasive surgery (MIS). By using these surgical principles, modifications have developed into the minimally invasive surgical technique (MIST), the modified minimally invasive surgical technique (M-MIST), and the single-flap approach (SFA). The flap design for these techniques minimizes the number of incisions and, as a result, surgical trauma, especially when performed using magnification and microsurgical techniques.
  Source: Newman and Carranza’s Clinical Periodontology and Implantology, 14th ed., Chapter 63, “Therapeutic Considerations.”
• Harrel and Rees proposed the minimally invasive surgery approach with the aim of producing minimal wounds, minimal flap reflection, and gentle handling of the soft and hard tissues. A papilla preservation flap may be used in the context of a minimally invasive, high-power magnification-assisted surgical technique to provide greater wound stability and further limit patient morbidity. This approach is particularly suited for treatment in conjunction with biologically active agents such as enamel matrix derivatives (EMDs), growth factors, and/or grafting materials.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique.”

Objectives and principles of MIST

1. Minimal wound formation
   • The objective is to produce minimal wounds and minimal flap reflection.
   • Incisions are strictly intrasulcular to preserve all the height and width of the gingiva.
   • Mesiodistal extension of the incision is kept to a minimum consistent with access to the defect.
     Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique.”
2. Preservation of interdental papilla
   • The defect-associated interdental papilla is accessed by either the simplified papilla preservation flap (SPPF) or modified papilla preservation technique (MPPT).
   • Papilla preservation is intended to optimize wound stability and permit primary closure of the interdental wound.
   • The preservation of soft tissue height is particularly important in the esthetic area.
     Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique”; Newman and Carranza’s Clinical Periodontology and Implantology, 14th ed., Chapter 63.
3. Minimal flap reflection
   • A very small full-thickness flap is elevated with the objective of exposing only 1 to 2 mm of the defect-associated residual bone crest.
   • The full-thickness flap is elevated only enough to expose the buccal and lingual bone crest delineating the defect in the interdental area.
   • When possible, only the defect-associated papilla is accessed and vertical releasing incisions are avoided.
     Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique.”
4. Gentle handling of soft and hard tissues
   • Defects are debrided with the combined use of mini-curettes and power-driven instruments, and roots are carefully planed.
   • During instrumentation, flaps are slightly reflected and carefully protected with periosteal elevators and frequent saline irrigations.
   • Delicate and timely tissue management is required to minimize tissue shrinkage.
     Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique”; Newman and Carranza’s Clinical Periodontology and Implantology, 14th ed., Chapter 63.
5. Stable clot and primary closure
   • Primary closure of the papilla in the absence of tension is a major objective.
   • The buccal and lingual flaps are repositioned at their original level, without coronal displacement, to avoid additional tension in the healing area.
   • Stable flap adaptation, preservation of blood supply, and passive suturing support blood-clot stability and minimize bacterial contamination.
     Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique.”

Case selection and preoperative considerations

A. Patient-associated characteristics

• Before a regenerative approach, low levels of plaque and residual infection, high levels of compliance, and absence of adverse conditions such as smoking, stress, uncontrolled diabetes, or other systemic diseases must be well established.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Decision-making algorithm highlighting the clinical conditions to be checked before periodontal regeneration.”
• The tooth selected for treatment should be strategically important to maintain by using regenerative periodontal therapy. Tooth importance in prosthetic rehabilitation, endodontic status, and osseous defect characteristics influence therapeutic success.
  Source: Newman and Carranza’s Clinical Periodontology and Implantology, 14th ed., Chapter 63, “Tooth and Defect Related Considerations.”

B. Endodontic status, local contamination, and mobility

• Endodontic diagnosis and eventual treatment should be performed well in advance of the regenerative approach.
• Vital teeth should preferably be kept vital, with the exception of a tooth whose apex is involved with the periodontal lesion.
• Non-vital teeth must be properly treated with root canal therapy. Existing root canal therapies should be carefully evaluated, and improper treatments should be corrected.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45.
• Local contamination of the defect-associated pocket should be as low as possible. The presence of bleeding on probing should be controlled with additional gentle root planing and the use of local antimicrobials a few weeks before regeneration.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45.
• Teeth with class II or class III mobility should be splinted before or immediately after the surgical procedure. Tooth hypermobility should be re-evaluated during the early healing phase, and any detected increase in mobility should be managed.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45.

C. Defect characteristics

• Characteristics of the defect, including overall osseous pocket depth, width, and walls, influence clinical outcome following regenerative surgery.
• Improved regenerative results are more likely in osseous defects that are narrow, circumferential, and have a three-wall or two-wall configuration.
• A wide osseous lesion with one wall or no wall is less amenable to regenerative procedures.
  Source: Newman and Carranza’s Clinical Periodontology and Implantology, 14th ed., Chapter 63, “Tooth and Defect Related Considerations.”
• The shortest mesiodistal extension and minimal flap reflection are used when the intrabony defect is a pure three-wall defect or has shallow two-wall and/or one-wall subcomponents located entirely in the interdental area.
• A larger coronoapical elevation of the full-thickness flap is required when the coronal portion of the intrabony defect has a deep two-wall component.
• In a deep one-wall defect, the full-thickness flap is elevated to the same extent on both buccal and lingual aspects.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique.”

Surgical access

A. Selection of papilla-preservation approach

1. Simplified papilla preservation flap (SPPF)
   • The SPPF is performed when the width of the interdental space is 2 mm or narrower.
   • It is selected when interdental width is 2 mm or less as measured at the level of the supracrestal portion of the papilla.
   • The first incision is made across the defect-associated papilla, beginning at the gingival margin at the buccal line angle of the involved tooth and extending to the mid-interdental portion of the papilla under the contact point of the adjacent tooth.
   • The oblique incision is made with the blade parallel to the long axis of the teeth to avoid excessive thinning of the remaining interdental tissues.
     Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Simplified papilla preservation flap” and “Minimally invasive surgical technique.”
2. Modified papilla preservation technique (MPPT)
   • The MPPT is applied at interdental sites wider than 2 mm, or 3 mm or wider.
   • The MPPT provides access to defects associated with wider interdental spaces.
   • The interdental incision is extended to the buccal and lingual aspects of the two teeth adjacent to the defect.
     Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique” and Fig. 45-46.
3. Crestal incision
   • Crestal incision is used at a tooth neighboring an edentulous ridge.
     Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, Fig. 45-46.

B. Extension of flap

• When the residual buccal or lingual bony wall is very deep and difficult or impossible to reach by the minimal incision of the defect-associated interdental space, the flap is extended mesially or distally and one extra interdental space is included.
• The same approach is used if the bony defect extends to the buccal or palatal side of the involved tooth, if it involves two interdental spaces of the same tooth, or two approximal teeth.
• If a second interdental papilla is involved, it is accessed with SPPF or MPPT according to the indication.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique.”

C. Vertical releasing and periosteal incisions

• Vertical releasing incisions are performed if flap reflection produces tension at the extremities of the flap.
• These incisions are kept very short, within the attached gingiva, and never involve the mucogingival junction.
• The overall aim is to avoid vertical incisions whenever possible or to reduce their number and extent to a minimum where a clear indication exists.
• Periosteal incisions are never performed in the MIST approach.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique.”

Operative procedure of MIST

1. Flap elevation

• After the interdental incision, a small full-thickness flap is elevated.
• The purpose is exposure of only the residual bone crest required for debridement and root instrumentation, generally 1 to 2 mm of the defect-associated residual bone crest.
• The mesiodistal extension is limited to improve wound stability.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique,” Fig. 45-25.

2. Defect debridement and root surface instrumentation

• Defects are debrided using mini-curettes and power-driven instruments.
• Root surfaces are carefully planed.
• Flaps are carefully protected with periosteal elevators and frequent saline irrigations during instrumentation.
• In clinical illustration of MIST, a three-wall intrabony defect was exposed and carefully debrided before application of enamel matrix derivatives.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique,” Fig. 45-25.

3. Application of regenerative material

• At the end of instrumentation, the biologically active agent is applied and the flaps are repositioned.
• The approach is particularly suited for biologically active agents, including EMDs or growth factors, and/or grafting materials.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique.”
• For M-MIST, EMDs or no regenerative material are the elective choices.
• For MIST, EMDs may be used alone in containing defects or in combination with a filler in non-containing defects.
• If a large flap is elevated, stabilization may be achieved with barriers, fillers, barrier-plus-filler combinations, or EMDs/growth factors with fillers.
• EMDs alone are preferred in defects with prevalent three-wall morphology or well-supported two-wall defects.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Surgical step 3: Regenerative strategy.”

4. Suturing

• In most instances, a single modified internal mattress suture is placed at the defect-associated interdental area to obtain primary closure of the papilla without tension.
• Where a second interdental space has been accessed, the same technique is used for primary closure in that area.
• Vertical releasing incisions are closed with simple passing sutures.
• Buccal and lingual flaps are repositioned at their original level without coronal displacement.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique.”
• A single internal modified mattress suture is used when M-MIST or MIST is performed with EMDs alone.
• When a large flap with a periosteal incision is associated with a barrier, graft, or combination, two internal mattress sutures are applied in the defect-associated interdental area to obtain primary closure without tension.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Surgical step 4: Suturing strategy.”

Modified minimally invasive surgical technique (M-MIST)

• M-MIST is an enhancement of MIST designed especially to improve flap stability and provide self-ability to maintain space for regeneration.
• The surgical approach consists of a tiny interdental access through which only a buccal triangular flap is elevated.
• The papilla is left in place, connected to the root of the crest-associated tooth by its supracrestal fibers.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Modified minimally invasive surgical technique.”
• Through the tiny buccal triangular flap, or buccal “window,” the soft tissue filling the defect, namely granulation tissues, is sharply dissected from the papillary supracrestal connective tissue and bony walls with a microblade and removed with a mini-curette.
• The root surface is carefully debrided with hand and mechanical instruments.
• The supracrestal fibers of the defect-associated papilla and palatal tissues are left untouched.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Modified minimally invasive surgical technique.”
• Minimal wound and minimal flap elevation preserve most vessels supplying interdental tissues and provide advantages for healing of the interdental wound.
• The “hanging” papilla provides self-support to the interdental soft tissues and enhances space provision.
• Flap stability is increased because most tissues surrounding the bony defect are not incised or elevated, thereby enhancing blood-clot stability.
• Minimal flap trauma, integrity of blood supply, and absolute passivity in suturing facilitate primary closure and prevent bacterial contamination.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Modified minimally invasive surgical technique.”
• M-MIST is indicated when a defect involving one or two sides of a root can be cleaned through a tiny buccal window. In certain cases, M-MIST may be applied to both interdental spaces neighboring the defect-associated tooth, enabling instrumentation of a defect involving up to three sides of a root.
• It is not applicable to very deep defects involving the lingual side of a tooth where the diseased root surface cannot be instrumented easily from the small buccal window.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Surgical step 2: Flap design” and “Modified minimally invasive surgical technique.”

Magnification and microsurgical instrumentation

• Surgical procedures may be performed using an operating microscope or magnifying loupes at magnification of ×4 to ×16.
• Microsurgical instruments are used whenever needed as a complement to the normal set of periodontal instruments.
• The surgical procedure is preferably performed with magnification such as loupes or an operating microscope, and microsurgical instruments and materials should complement the normal periodontal set.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique” and “Surgical step 4.”

Results, advantages, and limitations

• In preliminary case series involving 53 deep intrabony defects, one-year results showed CAL gain of 4.8 ± 1.9 mm, with 88.7 ± 20.7% clinical resolution of the defect and greatly reduced patient morbidity.
• In treatment of multiple intrabony defects, the 44 treated defects gained on average 4.4 ± 1.4 mm of clinical attachment; 73% showed CAL improvements of at least 4 mm; residual PPDs were 2.5 ± 0.6 mm; and mean gingival recession increase was 0.2 ± 0.6 mm from baseline to one year.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45, “Minimally invasive surgical technique.”
• Conservative or minimally invasive procedures tend to show lower recession values than other access-flap surgical techniques. GTR studies suggest that MIS may be better suited for regeneration in the esthetic zone.
• Several minimally invasive approaches have shown statistical improvements when used with EMD, whereas no difference has been demonstrated when used with rhPDGF.
• Large-scale randomized controlled trials are needed to evaluate safety, efficacy, pain, postoperative complications, esthetics, patient satisfaction, and patient-reported outcomes.
  Source: Newman and Carranza’s Clinical Periodontology and Implantology, 14th ed., Chapter 63, “Therapeutic Considerations.”

Conclusion

• MIST is a conservative regenerative surgical approach characterized by minimal wounds, minimal flap reflection, papilla preservation, gentle soft- and hard-tissue handling, careful defect debridement, biologically active regenerative material application when indicated, stable flap adaptation, and tension-free primary closure.
• Selection among SPPF, MPPT, MIST, M-MIST, and extended flap design depends upon interdental space width, defect morphology, number of root surfaces involved, accessibility for instrumentation, and the regenerative strategy selected.
• The fundamental objectives are preservation of blood supply, clot stability, wound stability, prevention of bacterial contamination, reduction of patient morbidity, preservation of soft tissue heights, and periodontal regeneration in appropriately selected intrabony defects.
  Source: Clinical Periodontology and Implant Dentistry, 6th ed., Chapter 45; Newman and Carranza’s Clinical Periodontology and Implantology, 14th ed., Chapter 63.