Correlation Between Colour and Hypersensitivity of First Permanent Molars With Molar Incisor Hypomineralisation (MIH)

Aim of the study is the correlation between the colour of the enamel defect and hypersensitivity in young first permanent molars. Children diagnosed with MIH from the onset of eruption of the first permanent molar, matched by age with children with sound first permanent molars are investigated. Children screened by the school dental services of Basel-Stadt as well children attending the department of children and adolescents (KJZM) of the University Centre for Dental Medicine in Basel (UZB), diagnosed with MIH on one or more first permanent molars receive a letter of information- invitation to be seen in the department of children and adolescents (KJZM).

The control group consists of fit and healthy children 5-8 years old, who attend the department of children and adolescents (KJZM-UZB) for their regular dental check-ups.

A written informed consent will be obtained from the parents/legal guardians. Colour definition The exact colour determination of the teeth will be carried out as follows: The teeth are photographed with a canon SLR camera. (Canon EOS 80D; Canon inc. Japan), a ringflash (Macro Ring Lite MR-14EXII; Canon) and a macro lens (EF-S 60mm 1:2:8 USM; Canon) will be used. All camera settings (1/250, aperture F20, iso-sensitivity 100 and a fixed white balance AWBW (white priority), flash intensity +/-0) and the tooth-lens distances (25 cm) are standardized by one operator (VM, SR). A colour reference card (grey card) is photographed together with the tooth of interest in order to identify and equalize the colour deviations. The resulting photo will be uploaded to the Photoshop Adobe 6 and the values of the RGB code (0-255 for each of the three colours) will be determined. The tolerance range is set to +/- 10. If the 3 colours are within the tolerance, the photo can be used to determine the colour of the tooth to be examined. The darkest part of the tooth is then determined. The degree of darkness is indicated by a number between zero and one hundred, where L=100 is white and L=0 is black (Wiedrichs et al. 2023).

The sensitivity of the teeth will be assessed by using the Schiff Cold air Sensitivity Scale (Schiff et al 1994). Teeth will be dried by an air blast defined at 5 bar. Prior to the examination patient will be introduced to the procedure by "tell-show-do" method. Based on the patient's reaction, the sensitivity to the air shock is divided into:

0 no reaction to the stimulus

• reaction, but continuing with the stimulus possible
• reaction, moving, demanding termination
• painful, immediate abandonment of procedure In addition to the sensitivity, assessed by the main investigator (VM or SR), the Wong-Baker Faces Pain Rating Scale (Wong-Baker FACES Foundation 2022) will be applied. The scale consists of six faces representing different expressions of pain, ranging from a laughing face with no pain (score 0) to a crying face with severe pain (score 10). Each face has a numerical score from 0 to 10 indicating pain intensity. Children will be asked to select the face that best describes their current pain experience.

Each appointment lasts a maximum of 30 minutes. In addition to the Schiff-Cold-Air-Scale-Test, hypersensitivity is also determined using the Face-Pain-Scale.

MIH Study Group

Inclusion criteria

• Children between 5 to 8 years with MIH molars with or without hypersensitivity according to the MIH-TN Index (Bekes et al 2016)
• Children with first molars in occlusion
• Children fit and healthy

Exclusion criteria

• MIH first permanent molars that have already received any kind of dental treatment
• Children diagnosed with HSPM (hypomineralised second primary molars)
• Children older than 8 years - Children younger than 5 years
• Children with any cranio-facial and/or other developmental dental defects
• Children diagnosed with parafunctions (attrition/ erosion)
• Children and/or parents who did not consent to the study
• Children with MIH teeth that show clinically visible enamel loss during the eruption
• Children without the first molars in occlusion

Non- MIH Control Group

Inclusion criteria

• Children between 5 to 8 years with no clinically affected molars
• Children fit and healthy

Exclusion criteria

• Children who have already received any kind of dental treatment on their permanent or primary teeth
• Children diagnosed with MIH or any other disease of the teeth
• Children older than 8 years
• Children younger than 5 years
• Children with any cranio-facial and/or other developmental dental defects
• Children diagnosed with parafunctions (attrition/ erosion)
• Children and/or parents who did not consent to the study