CBCT Evaluation of Adult Maxillary Expansion: A Comparative Analysis of Mini-implant Assisted Slow Palatal Expansion (MASPE) and Mini- screw Assisted Rapid Palatal Expansion (MARPE)

Background: Tooth-borne maxillary expansion is a common orthodontic treatment used predominantly in childhood and adolescence to address narrow dental arches before the fusion of mid-palatal and circummaxillary sutures. the introduction of pure bone-borne maxillary expanders offers a potential solution to mitigate adverse effects associated with Mini- screw Assisted Rapid Palatal Expansion (MARPE).

Aim: This consecutive retrospective study compared Mini-implant Assisted Slow Palatal Expansion (MASPE) with rapid palatal expansion (MARPE) using a bone-borne skeletal expander in adults with a narrow maxilla. CBCT scans analyzed transverse changes and potential pterygoid process deformation before (T1) and after expansion (T2).

Materials and Methods: The Force Controlled PolyCyclic (FCPC) SLOW palatal expansion group (FCPC-MASPE-G) comprised 35 adults aged 18–54 years and received a skeletal expander limiting expansive force only allowing 500 cN at the activation wrench (force control). Discontinuous, polycyclic activations according to the FCPC-protocol were applied. The MARPE-group (n = 6) underwent continuous RAPID activation without FCPC until the desired width was reached. CBCT scans were taken pre and post-expansion. Inclusion criteria for both groups were successful outcomes without surgical assistance.

Results: The maxilla opened transversally in both groups, mildly V-shaped, with a pyramidal shape in the coronal plane, impacting the zygomatic bone. Width measurements at T2 indicated superior mechanical response in FCPC- MASPE-G. Response of zygomaticomaxillary sutures was similar in both groups (p < 0.001 to 0.025). Pterygoid process deformations were notably less in FCPC-MASPE-G (0.87–1.35 mm, p < 0.001) compared to MARPE-G (2.70–3.04 mm,

p < 0.001 to 0.009). Dental measurements were similar (p < 0.001 to 0.023), but the ratio “Mid-palatal suture Opening Related to Expander opening” (M.O.R.E.-factor) was better with 84% in FCPC-MASPE-G than with 50% in MARPE-G.

Discussion: This study demonstrates that the conventional tooth-borne expanders may be inadequate for adult patients, innovative techniques such as MARPE and slow expansion protocols offer promising alternatives. With careful consideration of expansion protocols and advancements in imaging technology, orthodontic treatment can be tailored to optimize outcomes while minimizing risks for adult patients requiring maxillary expansion.

Conclusion: Slow expansion with FCPC protocol effectively widens the maxilla in adults, with significant impact on bones and sutures and less pterygoid process deformation compared to rapid expansion. Cranial complications were absent in both groups.