Three-dimensional evaluation of mandibular midline distraction: A systematic review

Area of Science:

• Orthodontics and Dentofacial Orthopedics
• Biomedical Engineering
• Craniofacial Surgery

Background:

• Systematic review registration: PROSPERO CRD42014010010.
• Limited high-quality evidence exists for mandibular midline distraction (MMD).

Purpose of the Study:

• To review literature on mandibular midline distraction (MMD) using 3D imaging.
• To analyze effects of different distractor types on mandibular condyle, TMJ, skeletal, dental, soft tissue, and biomechanical parameters.

Main Methods:

• Comprehensive literature search conducted up to March 27, 2017, across multiple databases (Embase, Medline, Web-of-science, Scopus, Cochrane, Google Scholar).
• Followed PRISMA guidelines for systematic reviews.
• Included 15 studies (2 prospective, 2 retrospective, 1 case-report, 10 computational analyses) after assessing 31 full-text papers; evidence quality was low (Level 4-5).

Main Results:

• Limited studies with small sample sizes and low evidence quality were identified.
• Bone-borne distraction is favored for skeletal outcomes.
• Tooth-borne distraction causes significant dental tipping; hybrid distractors with parasymphyseal step osteotomy show superior stability under masticatory loads.

Conclusions:

• Bone-borne distractors are preferable for skeletal effects; tooth-borne distractors cause dental tipping.
• Hybrid distractors offer optimal stability; chewing effects are minimal during latency.
• No permanent temporomandibular joint (TMJ) symptoms were reported, but soft tissue effects remain under-researched.