Given that lingual orthodontic appliances are bonded onto functional surfaces, the purpose of this study was to assess the nature of occlusal contacts directly after appliance removal (T1) and after a retention period of 3–20months (T2-T3). Adult patients were chosen as their adaptation potential is limited and they may show prosthetic restorations or tooth wear. The sample consisted of 35 consecutive patients treated by the same orthodontist, having undergone lingual orthodontic treatment with customized appliances. Subjects with edentulous spaces were excluded from the investigation, as were those whose orthodontic treatment had been terminated early either following poor cooperation or at the patient’s request. Occlusal contacts were evaluated with carbon paper (horseshoe type) and a T-scan III sensor, a computerized system for occlusal analysis that records intercuspation force and surface distribution.

Nineteen patients completed the study with a mean age of 32years (19–63), including five extraction and six surgical cases. T-scan III records showed high reproducibility. During the retention phase, the quality of contacts increased but no significant change in their location occurred. Asymmetric contacts became more balanced with time, except for some surprising cases.

Even when the set-up goal is reached, occlusal forces may be distributed unevenly, remaining asymmetric and potentially signaling a functional imbalance.