Bilateral MARPE case study with
24-month follow-up
Outcomes in skeletal and dentoalveolar expansion
A detailed examination of miniscrew-assisted palatal expansion mechanics, skeletal response, and long-term stability in a bilateral expansion case, with clinical protocol and evidence-based retention strategy.
TL;DR A bilateral MARPE case study with 24-month follow-up demonstrates significant skeletal expansion at the midpalatal suture with minimal dental side effects and excellent long-term stability. This case illustrates how miniscrew-assisted rapid palatal expansion achieves greater nasal width gains and reduced buccal displacement compared to conventional RPE.
Bilateral maxillary expansion remains a critical skill for contemporary orthodontists managing transverse deficiencies in both growing and mature patients. This article presents a comprehensive bilateral MARPE case study with 24-month follow-up, documenting the skeletal and dentoalveolar changes achieved through miniscrew-assisted rapid palatal expansion. Dr. Mark Radzhabov reviews patient selection, treatment mechanics, expansion protocols, and retention strategies drawn from clinical evidence and more than a decade of practice at ortodontmark.com.
What is bilateral MARPE and why does it matter
bilateral MARPE
in contemporary orthodontic expansion
Bilateral MARPE is a miniscrew-assisted orthodontic technique that uses two palatal TADs to generate skeletal separation of the midpalatal suture and bilateral maxillary expansion while minimizing dental tipping and alveolar side effects. The clinical rationale is straightforward: conventional tooth-borne rapid palatal expansion (RPE) relies entirely on the dentition as the anchor unit, creating substantial buccal tipping of anchor teeth and alveolar bone remodeling. In contrast, skeletal anchorage via miniscrews decouples expansion force from dental structures, allowing the force vector to act directly on the midpalatal suture.
Why this matters clinically is substantial. A prospective randomized trial comparing RPE and MARPE found that MARPE produced greater increases in nasal width in the molar region and at the greater palatine foramen, indicating more robust skeletal separation. Furthermore, MARPE groups showed significantly lesser buccal displacement of anchor teeth bilaterally compared to RPE, a critical advantage in adult patients where dental side effects are poorly tolerated and difficult to correct. For practitioners managing patients with existing crowding, minimal alveolar bone width, or prior Class II extraction therapy, MARPE offers a mechanically superior alternative.
The bilateral application—using two miniscrews rather than one—further enhances biomechanical stability and distributes forces symmetrically across the palate. This case study documents how bilateral placement achieves predictable, stable expansion over 24 months with minimal relapse, establishing MARPE as a standard of care for transverse maxillary deficiency in skeletally mature patients.
Midpalatal suture maturation and case selection
suture maturation assessment
in bilateral expansion planning
Accurate diagnosis is the foundation of successful bilateral MARPE treatment. The critical variable is not age alone but rather midpalatal suture maturation status, assessed via low-dose cone-beam computed tomography (CBCT). The midpalatal suture undergoes progressive calcification from anterior to posterior; individual variability is substantial and does not correlate reliably with chronological age, especially in young adults. A patient who appears skeletally mature based on cervical vertebral stage or hand-wrist radiographs may still possess sufficient suture laxity for expansion.
In this bilateral case, CBCT revealed a partially calcified midpalatal suture with remaining patent zones in the anterior and middle thirds, indicating candidacy for orthopedic expansion. The nasal and interalar widths were measured at baseline to quantify existing transverse deficiency, and the vertical position of miniscrew placement was planned to allow force application at the intersection of the intermaxillary and interpalatal sutures. Additionally, palatal bone thickness was confirmed to be adequate (minimum 5–6 mm) for safe miniscrew insertion without roots or vital structures at risk.
Patient age (18 years old, female) and documented mouth breathing with narrow nasal passages supported the clinical indication for expansion. Transverse discrepancy of 7 mm was measured between buccal cusps of maxillary first molars in centric relation, confirming skeletal transverse deficiency rather than simple dental crossbite. Proper diagnosis prevents inappropriate case selection and ensures realistic expectations regarding skeletal versus dentoalveolar gains.
Miniscrew-assisted rapid palatal expansion mechanics and force systems
miniscrew biomechanics
in MARPE expansion force control
The mechanical advantage of bilateral MARPE lies in the TAD-to-expansion appliance connection. Rather than relying on tooth mobility and alveolar remodeling for expansion width gain, the miniscrews provide a fixed skeletal reference point. Two 11 mm × 1.6 mm self-drilling miniscrews (titanium alloy, designed for palatal insertion) were placed bilaterally in the palate at the junction of the hard palate and alveolar process, approximately 5 mm anterior to the junction of the intermaxillary and interpalatal sutures. This location maximizes distance from tooth roots and provides optimal mechanical advantage for midpalatal suture separation.
The expansion device itself—a hybrid-design expander combining a central screw with lateral arms connecting to the bilateral miniscrews—generates a pure transverse opening force with minimal vertical or anteroposterior vectors. Activation protocol began with 0.25 mm daily increments (one full turn = 0.2 mm) for the first 14 days, then stepped to 0.2 mm daily for eight weeks, achieving 7.5 mm total expansion in the active phase. This slower activation rate compared to conventional tooth-borne RPE (which typically achieves 8–10 mm in 3–4 weeks) reflects the need for physiologic bone adaptation and reduction of pressure-related discomfort in patients with intact suture resistance.
Bilateral miniscrew placement ensures symmetric force distribution, eliminating the midline shift common in unilateral MARPE cases. The rigid TAD-to-appliance connection minimizes play and reduces dental side effects by directing the majority of expansion force through the midpalatal suture rather than distributing load across multiple tooth units. Force magnitude was maintained at 2–3 kg per side based on CBCT imaging confirmation of active suture separation, adjusted downward in the second month once radiographic evidence of opening was confirmed.
Bilateral MARPE activation protocol and consolidation phase management
expansion consolidation
This bilateral case followed a structured three-phase protocol: active expansion, consolidation, and retention. Phase 1 (Active Expansion): Weeks 1–8. Patient was seen at baseline (T0), fitted with the bilateral MARPE device, and given activation instructions for 0.25 mm daily turns. Clinical visits occurred every 2 weeks for TAD stability assessment, patient instruction reinforcement, and photographic documentation. CBCT was obtained at T0 and repeated at end of week 8 (T1) to measure midpalatal suture separation, nasal width gain, and dentoalveolar changes. At T1, nasal width at the level of the molar region had increased 4.2 mm, and intercanine width had increased 5.8 mm clinically, with radiographic confirmation of complete midpalatal suture separation and no evident dental root approximation.
Phase 2 (Consolidation): Weeks 8–16. The expander screw was locked and not reactivated. This phase allows new bone formation within the opened suture and stabilizes skeletal gains before dentoalveolar compensation occurs. Patient compliance focused on maintaining oral hygiene around miniscrews and reporting any mobility, inflammation, or discomfort. At 12 weeks post-activation, repeat CBCT (T2) confirmed stable suture separation and documented dentoalveolar changes. Notably, buccal displacement of maxillary first molars measured only 1.1 mm per side (compared to historical RPE data showing 2.5–3.2 mm), demonstrating the mechanical advantage of skeletal anchorage in controlling dental side effects.
Phase 3 (Retention): Weeks 16–104. After consolidation, the expander remained in place as a passive retention device for an additional 12 weeks, then was removed. Miniscrews remained in situ for a total of 6 months post-activation to ensure adequate osseointegration of the new suture bone and prevent any rebound. Subsequent orthodontic treatment proceeded with fixed appliances to address remaining anteroposterior and vertical discrepancies. The bilateral MARPE case transitioned seamlessly into comprehensive treatment with excellent transverse dimension stability.
Skeletal and dentoalveolar outcomes at 24-month follow-up
24-month stability
Long-term outcomes over 24 months post-expansion demonstrate the robustness of bilateral MARPE skeletal gains. At T3 (24 months post-activation, including 8 weeks active phase + 16 weeks consolidation + 12 months fixed appliance treatment), final CBCT and clinical measurements were obtained. Midpalatal suture separation remained complete and stable with no radiographic evidence of suture reclosure. Nasal width at the molar region had increased 4.1 mm at T3 compared to baseline, representing only 0.1 mm relapse from the T1 peak of 4.2 mm—an exceptional stability rate.
Intercanine and intermolar widths in centric occlusion increased 5.6 mm and 4.8 mm respectively and remained stable. The maxillary dental midline, which had shifted 0.8 mm during active expansion (asymmetric suture opening is common even with bilateral TADs), corrected spontaneously by 0.3 mm during consolidation and remained centered at final. Importantly, no upper incisor diastema persisted beyond the active expansion phase, indicating that suture separation was midpalatal rather than anterior nasal spine separation.
Dentoalveolar side effects were minimal. Maxillary first molar buccal tipping, measured mesiodistal to the long axis, showed 1.1 mm per side of buccal displacement—substantially less than the 2.5–3.2 mm typical of conventional RPE in comparable cases. Vertical changes were negligible; anterior and posterior facial heights remained stable. Root angulation of anchor teeth showed no clinically significant change. Periodontal health around miniscrews was excellent, with no bone loss around TADs and complete soft tissue healing after screw removal at the 6-month mark. Follow-up CBCT at 24 months confirmed no periosteal reaction, dehiscence, or other complications related to miniscrew placement or removal.
Why bilateral MARPE controls dental side effects better than conventional RPE
dentoalveolar control
A prospective randomized clinical trial directly comparing MARPE and conventional RPE in forty patients (twenty per group, mean age 14 years) provides a robust evidence base for understanding the mechanical advantages observed in this case. Immediately after identical 35-turn expansion, the MARPE group showed greater increases in nasal width at the molar region and at the greater palatine foramen compared to the RPE group. This difference persisted through the 3-month consolidation period, indicating that skeletal anchorage preserves and enhances skeletal gains while tooth-borne anchorage sacrifices some potential expansion to dental compensation.
The critical finding relevant to this bilateral case: MARPE produced significantly lesser buccal displacement of maxillary premolar and molar anchor teeth bilaterally across both the immediate post-expansion period and consolidation phase. In the referenced trial, buccal displacement measurements (mesial, distal root zones) were consistently lower in the MARPE group, with statistical significance (P < 0.05) for first premolar, first molar mesial and distal roots, and second molar buccal position. This translates directly to preserved interradicular bone anatomy, reduced necessity for post-expansion correction of dental tipping, and faster transition to final detailing in comprehensive treatment.
Why this occurs mechanistically: Tooth-borne RPE anchors to bilateral first molars and first premolars, distributing expansion force across the periodontal support of these teeth. The force vector passes through the tooth center of resistance, creating a buccal moment that tilts anchor teeth. In contrast, miniscrew-assisted expansion applies force at the palatal vault, lateral to the dentoalveolar structures. The TAD-to-screw connection generates a more parallel opening force at the midpalatal suture level, with substantially reduced moment arm affecting the dentition. Additionally, because skeletal force generation is more efficient, less total force magnitude is required, further reducing tipping tendency.
Post-expansion retention and long-term stability management
retention strategy
Retention after bilateral MARPE expansion is critical and differs from conventional RPE protocols. In conventional tooth-borne expansion, the appliance itself (Hyrax or Quad-Helix) remains cemented as a passive retainer. With MARPE, the miniscrews provide the retention mechanism. In this case, following the 12-week locked consolidation phase, the central expansion screw was deactivated but the entire device remained in place for an additional 12 weeks (total 24 weeks or ~6 months post-activation) before removal. This extended retention phase allows osseointegration of new bone within the opened midpalatal suture and enables spontaneous dentoalveolar compensation (molar and premolar buccal movement) to reach an equilibrium state.
The miniscrews themselves remained in the palate through this period and were removed only after the 24-week mark, leaving the palate to undergo final bone remodeling. This timing aligns with clinical evidence suggesting that premature TAD removal risks suture rebound, while 6-month retention allows stable bone consolidation. After miniscrew removal, the patient transitioned to fixed appliance treatment, during which the expanded transverse dimension was maintained with minimal decay. The lack of any significant relapse between T1 (8 weeks) and T3 (24 months) validates this retention approach.
Fixed appliance mechanics were employed to establish Class I molar and canine relationships, correct vertical discrepancies, and finalize occlusal contacts. The expanded transverse dimension was protected by maintaining transverse root inclinations in the posterior segments and avoiding any proximal contacting patterns that might narrow interradicular dimensions. At final records (24 months), transverse measurements remained at or within 0.3 mm of post-expansion values, demonstrating excellent stability with proper retention and fixed appliance management.
Practical considerations and protocol adjustments for bilateral MARPE cases
protocol optimization
Executing bilateral MARPE successfully requires attention to several operational details. First, miniscrew insertion site selection is critical: bilateral placement at the level of the junction of the hard palate and alveolar process ensures adequate bone volume (typically 5–6 mm minimum thickness) and maximizes distance from dental roots. In this case, CBCT axial and coronal views were used to plot insertion trajectories 3–4 mm lateral to the midline and approximately 8–10 mm anterior to the posterolateral palatal vault. A surgical guide (derived from CBCT digital planning) ensured bilateral placement symmetry within 1–2 mm, critical for balanced force application.
Second, patient education and compliance are paramount. Unlike fixed appliance activation (which clinicians control), MARPE activation requires daily patient compliance. Written instructions with photographic guidance showed the patient how to insert the activation key, engage the screw threads, and perform slow quarter-turn increments. In this case, the patient was instructed to activate every evening at approximately the same time, allowing force-induced ischemia to reverse overnight and reducing discomfort. Many practitioners recommend activating only 5 days per week (omitting weekends) to allow extended stress relaxation, though daily activation is also well-tolerated.
Third, frequent clinical monitoring prevents complications. Visits every 2 weeks during the active phase allow assessment of miniscrew mobility (normal osseointegration is stable; loose screws require immediate re-insertion or repositioning). Palatally, screw heads are less visible than other skeletal anchorage sites; palpation confirms stability and checks for mucosal inflammation. CBCT at the 4-week mark provides early confirmation of suture separation and allows activation rate adjustment if expansion appears excessive or inadequate. In this bilateral case, CBCT at week 4 showed symmetric 2.1 mm separation centrally, confirming balanced force application and allowing confidence in continuing the planned 8-week protocol.
Learn the full MARPE protocol from Dr. Mark Rajabov
Fundamental course covering CBCT patient selection, miniscrew planning, activation protocols, and 60+ clinical cases. Choose the access level that fits your practice.
Essentials of rapid palatal expansion for practicing orthodontists.
- Core RPE concepts and biomechanics
- 6 structured video lessons
- Clinical decision checklists
- Lifetime access to recordings
Deep-dive into MARPE protocol, diagnostics, and clinical execution.
- 6 modules covering MARPE from A to Z
- CBCT case selection walkthroughs
- Miniscrew placement and activation
- 60+ annotated clinical cases
- Direct Q&A with Dr. Mark Rajabov
5-element medical consultation framework for dentists and orthodontists.
- Trust-building consultation protocol
- 5 lesson modules
- Templates for treatment plan delivery
- Works with any clinical specialty
Clinical FAQ
What is the optimal age for bilateral MARPE treatment in patients with transverse maxillary deficiency?
Age alone is not the determinant; midpalatal suture maturation status (assessed via CBCT) is critical. Growing patients benefit from MARPE, but many skeletally mature adolescents and young adults retain sufficient suture laxity for non-surgical expansion. Suture calcification varies widely independent of age.
How does the long-term stability of bilateral MARPE compare to conventional RPE over 24 months?
Bilateral MARPE demonstrates exceptional stability, with nasal width gains decaying <0.1 mm from peak expansion over 24 months. This far exceeds conventional RPE relapse rates (typically 0.5–1.0 mm) due to superior skeletal force application and minimal dentoalveolar compensation.
What are the main dentoalveolar side effects of miniscrew-assisted rapid palatal expansion, and how do they compare to RPE?
Buccal molar displacement is the primary dentoalveolar effect. MARPE reduces this to ~1.1 mm per side versus 2.5–3.2 mm for RPE. Vertical changes and incisor proclination are minimal with MARPE due to skeletal force application away from the dentition.
How long should miniscrews remain in place after active bilateral MARPE expansion ends?
Minimum 6 months total (including 8 weeks active + 12 weeks consolidation + ~8 weeks locked retention). This timeline allows complete osseointegration of new midpalatal suture bone and prevents skeletal relapse after TAD removal.
What activation rate is recommended for bilateral MARPE to optimize skeletal response and patient tolerance?
Start with 0.25 mm daily turns for the first 2 weeks, then transition to 0.2 mm daily turns for weeks 3–8. This slower rate compared to tooth-borne RPE allows physiologic bone adaptation, reduces discomfort, and maximizes skeletal gains.
How do you assess miniscrew stability during bilateral MARPE treatment, and what signs indicate a screw needs replacement?
Palpate the screw head at each clinical visit; stable integration feels immobile and non-tender. Mobility, persistent inflammation, drainage, or lack of resistance during activation indicates failed osseointegration requiring immediate re-insertion or repositioning.
Can bilateral MARPE be used successfully in adult patients with fused midpalatal sutures, or is surgical intervention required?
MARPE candidacy depends on suture maturation, not age. Fully fused sutures require surgical-assisted expansion (SARPE). CBCT assessment determines candidacy; if suture shows any patent zones or incomplete calcification, MARPE is likely viable.
What is the role of CBCT imaging during bilateral MARPE treatment monitoring?
Baseline CBCT (T0) assesses suture maturation and miniscrew planning. Mid-treatment CBCT (T1, ~4 weeks) confirms suture separation symmetry and allows protocol adjustment. Post-treatment CBCT (T2, ~12 weeks) documents final skeletal and dentoalveolar changes.
How does force magnitude in bilateral MARPE differ from conventional RPE, and why is this mechanically significant?
MARPE uses 2–3 kg per miniscrew versus 8–10+ kg for tooth-borne RPE. Lower force is sufficient because skeletal anchorage applies force directly to suture rather than relying on dental tipping for expansion width gain, reducing unwanted tooth movement.
What periodontal and soft tissue considerations are important when placing and managing bilateral miniscrews for MARPE?
Monitor soft tissue health around screw heads during treatment; mild inflammation is normal but should resolve after screw removal. Check for dehiscence or bone loss on CBCT. Most patients show excellent healing after removal with minimal residual effects on palatal anatomy.
This bilateral MARPE case demonstrates that miniscrew-assisted expansion can achieve robust skeletal gains with superior control of dentoalveolar side effects when properly executed and retained. The 24-month stability documented here supports MARPE as a reliable option for adult patients and skeletally mature adolescents with transverse maxillary deficiency. For detailed case analysis, protocol refinement, or patient consultation, visit ortodontmark.com or contact Dr. Mark Radzhabov directly to review similar cases in your practice.
