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Ten-year outcomes of M-MIST
therapy for intrabony defects with
and without regeneration materials

    Ten-year outcomes of M-MIST
    therapy for intrabony defects with
    and without regeneration materials

    Pierpaolo Cortellini, Simone Cortellini, Daniele Bonaccini, Maurizio S. Tonetti



    Clinical outcomes of periodontal regeneration are obtained
    by applying different surgical techniques and regenerative
    Surgical techniques have become efficient because of the
    adaptation of modified incisions to preserve the interdental
    tissue. These techniques are designed to maintain the integrity
    of the papilla to allow better wound closure, protection of the
    coagulum, and first-intention healing.
    Enamel matrix derivative (EMD) and resorbable membranes
    are the “gold-standard” materials for deep intrabony defects in
    combination with deproteinised bovine bone mineral (DBBM)
    for non-supporting defects.
    To reduce the flap dimensions, healing time, and patient
    discomfort, and to improve wound stability, minimally invasive
    surgical approaches have been introduced, such as the
    modified minimally invasive surgical technique (M-MIST) and
    the single-flap approach (SFA). Although minimally invasive
    surgical approaches – with and without biomaterials – for
    treating intrabony defects have been compared, the long-term
    stability of the outcomes had not been explored before.



    The aim of this study was to compare the clinical stability of
    treatment with the M-MIST technique, alone and in combination
    with two different regenerative approaches in intrabony defects,
    and to evaluate the costs of reintervention required over a 10-
    year period.

    Materials & methods

    • A 10-year follow-up of a randomised controlled trial comparing three
    different modalities in deep intrabony defects: M-MIST alone, M-MIST
    + EMD, M-MIST + EMD + DBBM.
    • Forty-five participants presenting one deep intrabony defect, located
    in the inter-proximal area and not extending into the furcation area.
    • Patients were randomly assigned to one of the three treatment
    groups: (i) M-MIST alone (n=15), the suture was tightened
    to have blood-clot stability; (ii) M-MIST + EMD (n=15),
    ethylenediaminetetraacetic acid (EDTA) was applied for two minutes
    before applying EMD; (iii) M-MIST + EMD + DBBM (n=15), EDTA and
    EMD were applied before DBBM was placed.
    • Clinical measurements –plaque scores, bleeding on probing,
    pocket probing depth (PPD), and clinical attachment level (CAL)–
    were evaluated one week before surgery and at the follow-up
    • Radiographic examinations –distance between the cementoenamel
    junction and the bottom of the defect [CEJ-BC] and distance between
    the cementoenamel junction and the tooth apex [CEJ-A]– were
    performed with an electronic ruler one week before surgery and at the
    follow-up examinations.
    • Long-term supportive periodontal care (SPC): patients were enrolled
    every three months and, in case of disease recurrence, non-surgical
    root debridement, access-flap surgery, or regenerative surgery were

    Figure 1: Complication-free survival

    Figure 1: Complication-free survival

    Mantel-Haenszel complication-free survival curves for the three groups
    (modified minimally invasive surgical technique [M-MIST] in red,
    M-MIST + enamel matrix derivative [EMD] in green, and M-MIST + EMD +DBBM
    in blue). The diagram shows the interval until the first recurrence of
    periodontitis event observed at the experimental teeth. No significant
    differences were observed between groups.

    Mean cumulative cost of recurrence (in euros) over the 10 year
    observation period. The diagram shows all periodontitis recurrence
    events observed and the actual cost of management of the recurrence
    and includes the cost of surgical treatment. The dashed lines represent
    the 95% CI. M-MIST is in red, M-MIST EMD is in green, and M-MIST
    EMD DBBM is in blue.


    Experimental population:
    • Three subjects were lost to follow-up for reasons unrelated to
    treatment: one in each group –two after four years and one after six
    • The sample was considered homogeneous as no differences
    between groups were observed regarding the full-mouth plaque and
    bleeding scores at different time points.
    • All subjects were compliant regarding SPC.
    Clinical and radiographic outcomes:
    • No significant intergroup differences were observed at baseline,
    one year, and 10 years regarding CAL, PPD, and radiographic
    bone-level changes.
    • Intragroup differences were significant between baseline and one
    year, but no significant changes were observed between one year
    and 10 years.
    • Study had 13.3% power to detect a 0.2mm intergroup difference in
    CAL between the one- and the 10-year follow-up (ANCOVA).

    Complication-free survival:
    • Ten events requiring additional periodontal therapy were observed:
    three in the M-MIST group, five in the M-MIST + EMD + DBBM
    group, and two in the M-MIST + EMD group. The respective
    survival until the occurrence of the first event requiring additional
    periodontal therapy beyond regular SPC was four years, four years,
    and two years.
    • No significant differences in complication-free survival between the
    three groups were observed, which was 7.46 years (95% CI: 7.05-
    7.87) for the whole population.
    Mean cumulative cost of recurrence:
    • Without including the surgical cost, the group with the highest cost
    of managing disease recurrence was the M-MIST + EMD + DBBM
    • The cost of the global treatment, including surgical cost and the
    cost of recurrence management, was also higher for the M-MIST +
    EMD + DBBM group.


    No information was
    given on whether
    the periapical
    radiographs were
    standardised or not.
    • Statistical power may
    benefit from bigger
    sample groups.

    Conclusions & impact:

    • Teeth presenting intrabony defects associated with deep pockets can be successfully treated with
    an M-MIST approach, with or without regenerative material.
    • Avoiding regenerative material provides the same short- and long-term benefits at lower cost,
    compared to a regenerative approach with biomaterial.
    • If the patient is compliant with the SPC programme, treated teeth can be maintained over 10 years.
    • Avoiding regenerative materials in the M-MIST technique for treating intrabony defects can provide
    satisfactory survival at a lower cost.