Comparing the reliability and accuracy of clinical measurements using plaster model and the digital model system based on crowding severity.

BACKGROUND: This study aims to clarify whether 3Shape™ digital model system could be applied in orthodontic diagnostic analysis with certainty, especially under different crowding condition. Reliability, accuracy and efficiency of 3Shape™ digital model system were assessed by comparing them with traditional plaster cast. METHODS: 29 plaster casts with permanent dentition were transformed into digital models by 3Shape™ D800 scanner. All 29 models were categorized into mild-crowding (arch length discrepancy <3 mm), moderate-crowding (arch length discrepancy >3 mm and <8 mm), and severe-crowding group (arch length discrepancy >8 mm). Fourteen linear measurements were made manually using a digital caliper on plaster casts and virtually using the 3Shape™ Ortho Analyzer software by two examiners. Intra-class Correlation Coefficient (ICC) was used to evaluate intra-examiner reliability, inter-examiner reliability and reliability between two model systems. Paired t test was used to evaluate accuracy between two model systems. Kruskal-Wallis test followed by Mann-Whitney U test was used to evaluate the measurement differences between 3 groups in two model systems. RESULTS: Both intra-examiner and inter-examiner reliability were generally excellent for all measurements made on 3Shape™ digital model and plaster cast (ICC: 0.752-0.993). Reliability between different model systems was also excellent (ICC: 0.897-0.998). Half of the accuracy test showed statistically significant differences (p < 0.05) when digital models were compared with plaster casts. Furthermore, while assessing measurement differences between 3 groups in two model systems, the mandibular required space showed significant difference (p = 0.012) between mild crowding group (0.27 + 0.01 mm) and severe crowding group (0.20 + 0.09 mm). However, the differences were less than 0.5 mm and would not affect clinical decision. CONCLUSION: Using 3Shape™ digital model system instead of plaster casts for orthodontic diagnostic measurements is clinically acceptable.

A multicenter study of oral lichen planus in Thai patients.

AIM: Oral lichen planus is an oral mucosal disease that affects middle-aged patients. The characteristics of oral lichen planus in Thai patients from a multicenter were studied. METHODS: Data of 533 patients from the oral medicine clinics at Chulalongkorn and Mahidol (central Thailand), Chiang Mai (northern Thailand), and Khon Kaen (northeastern Thailand) universities during 2002-2007 were analyzed. The diagnosis of patients with oral lichen planus was clinically and/or histopathologically confirmed. RESULTS: There was a greater number of female patients than males (4:1). There were significant differences in age, sex, and some systemic diseases among the oral lichen planus patients from the three centers. Burning sensation was the most common symptom (72.9%), followed by pain (26.5%), roughness (6.4%), and then no other symptoms (7.9%). The most common site of lesions was found at the buccal mucosa (87.1%). Atrophic oral lichen planus was common in Thai patients. There were significant differences in the types of oral lichen planus, including reticular, atrophic, and ulcerative oral lichen planus among these patients from the three centers (P = 0.000). Nine cases (1.7%) showed dysplasia, but one case (0.2%) developed squamous cell carcinoma. CONCLUSION: Patients with oral lichen planus from the central, northern, and northeastern parts of Thailand presented with distinct characteristics. The malignant transformation of oral lichen planus was low in Thai patients.