Ultrasonic vs Radiographic Measurement of Gingival Biotype. A Novel Method

Labial Gingival and Osseous Thickness of Upper and Lower Incisors in Thick and Thin Biotypes

This clinical study consists on taking 2 different records of the upper and lower incisors area : 1) a perpendicular x-ray and 2) an ultrasonic measurement of gingival thickness on the labial plate. Both measurements are used in order to measure gingival and bone thickness.

The aim was to verify the reliability of the tissue measurements of an ultrasonic technique compared with the radiographic technique and to verify whether the biotype has correlation between the maxillary and mandibular biotype in the same patient.

The examination of the patients included:

• One color photograph of the upper and lower incisors complex with the periodontal probe introduced on the gingival sulcus
• Gingival thickness of the most protruded upper and lower incisors was measured with the biometric scanner PIROP. A lip expander was placed and clorhexidine gel was applied on top of the ultrasonic head for better wave conduction. Measurements were taken 10 times at the same point and a mean measurement was obtained.
• A tangential radiograph was taken on each patient perpendicular to the axis of the crown of the central upper and lower incisors with a periapical film holding system, and a metal strip (5mm x 1mm x 0,1mm) placed labial to the keratinized gingiva following the inclination of the incisor. A lip expander was used to keep the lips from touching the metal strip. Air was blown over the attached gingiva before placing the metal strip. The metal strip was placed along the long axis of the most protruded lower incisor crown.

All patients were evaluated and categorized in one of three possible categories: A1 (7 patients, 23,3%), A2 (12 patients, 40%), and B (11 patients, 36,7%). The patients were assigned into each category by two examiners, according to the visual and clinical aspect of the keratinized gingiva in the lower incisors. Group A1 and A2 both had thin keratinized gingiva and differed in width (group A1 comprised values ≤2mm, and group A2 had width values >2mm of keratinized gingiva). Group B comprised thick and wide keratinized gingiva. Width of gingiva was measured with a periodontal probe. Thickness of gingiva was assessed by probe transparency, where the examiner determined whether the periodontal probe was visible through the marginal soft tissue.

Radiographic measurements

Radiographs were scanned at a 1:1 scale. Scanned images were saved in JPEG format. Millimetric measurements were made using the Adobe Photoshop program to a 0.1mm precision. Four measurements were taken on each radiograph:

1. Gingival thickness on the upper incisor
2. Bone thickness on the upper incisor
3. Gingival thickness on the lower incisor
4. Bone thickness on the lower incisor

Gingival thickness was measured on the radiographs to compare it with the measurements taken with the biometric scanner. This was a founded and a reliable method to validate the use of the scanner. A master file was created and the data were statistically analyzed using a statistical software package.

Size of the sample was obtained with the correlation of lower gingiva and thickness of lower gingiva. The result was 26 calculated with the correlation coefficient 0,587. A 20% tax of follow-up loss was estimated.

Intraexaminer reliability was determined using intraclass correlation coefficient (ICC) with a positive confidence interval at 95% (IC 95%). An ICC was used to compare the valid method for group classification between visual and probe transparency methods.

The data were subjected to 95% confidence interval for the mean of all variables. The strength of correlation was determined by a P value <0.05, which was considered statistically significant.

Inclusion Criteria:

• aged 18 years or older,
• presence of all lower incisors
• good periodontal health without bone loss or gingival inflammation
• no dental compensations of skeletal malocclusion
• crowding of less than 4mm
• no history of dental or traumatic lesions in lower incisors

Exclusion Criteria:

• gingival inflammation
• daily smokers
• patients taking drugs that causes gingival inflammation