Comparative Assessment of Cephalometric Parameters on Lateral Cephalograms in the Retruded Contact Position and in the Intercuspal Position With Centric Relation (ICP‑CR) in Prosthodontic Patients: A Cross‑Sectional Diagnostic Study

BACKGROUND. The accuracy of cephalometric diagnostics in prosthodontic dentistry is directly determined by the reproducibility of the mandibular position during lateral cephalogram acquisition. In clinical practice, two reference positions are employed — the intercuspal position combined with centric relation (ICP‑CR) and the retruded contact position (RCP), which is fixed using occlusal registration templates. However, a comparative assessment of the comparability of cephalometric parameters obtained in these positions remains insufficiently investigated, which underpins the relevance of the present study.

AIM. To conduct a comparative evaluation of skeletal, dental, and soft‑tissue cephalometric parameters derived from lateral cephalograms obtained in the retruded contact position and in the ICP‑CR position, as well as to determine clinically significant differences between these positions, accounting for patient sex, age, and occlusion type.

METHODS. The study included cephalometric measurement data from lateral cephalograms of 50 patients, acquired in two positions: the retruded contact position (RCP) and ICP‑CR. Sagittal (ANB, WITS), vertical (SN/MP, FH/MP), dental (U1/APg, L1/APg), and soft‑tissue (SnN'Pg', Jarabak ratio) parameters were analyzed. For each parameter, mean values, standard deviations, mean differences (Δ = ICP‑CR − RCP), and mean absolute differences |Δ| were calculated. Paired t‑tests were performed, effect sizes were computed using Cohen's d, Pearson correlation coefficients were calculated, and subgroup analyses were conducted by sex, age, and occlusion type.

RESULTS. The most stable parameter was SN/MP (mean Δ = +0.6°; SD Δ ≈ 2.1°; d < 0.2). A statistically significant systematic difference was found in the SnN'Pg' parameter (Δ = −1.4°; SD Δ ≈ 3.2°; t ≈ 2.59; p ≈ 0.014; d ≈ 0.44). According to WITS, there was a tendency towards significance (Δ ≈ +0.5 mm; p ≈ 0.06–0.09). The greatest individual variability was observed for FH/MP (individual Δ up to ±7°) and L1/APg (SD Δ ≈ 3.8 mm). In the subgroup of patients with Class II occlusion, the most pronounced differences were observed for ANB (+0.9°), WITS (+1.5 mm), and SnN'Pg' (−2.1°; p < 0.05). In patients under 18 years of age, |Δ| for WITS and L1/APg was greater than in adults (p ≈ 0.04–0.07).

CONCLUSION. The retruded contact position and ICP‑CR demonstrate acceptable group‑level reproducibility for the majority of skeletal cephalometric parameters. However, systematic differences in the soft‑tissue profile (SnN'Pg') and substantial individual variability in FH/MP and dental parameters indicate the clinical significance of the choice of registration position, particularly in patients with Class II occlusion and hyperdivergent growth pattern. ICP‑CR is recommended as the primary position for diagnostic evaluation, with repeat registrations indicated when discrepancies exceed 2–3°. A limitation of the present study is that the statistical analysis was performed using aggregated data, which constrains the application of more detailed analytical methods.