The goal of this clinical trial is to learn if the Bioflx crown (a tooth-colored material) is as effective as the standard stainless steel crown for treating severely decayed baby back teeth in children aged 4 to 10 years old. The study also aims to evaluate parent and child satisfaction with these restorative options.

The main questions it aims to answer are:

1. Is the Bioflx crown as effective as the stainless steel crown in terms of durability, staying in place, and protecting the tooth from new decay?
2. Does the Bioflx crown maintain better gum health and cause less wear on the opposing teeth compared to the stainless steel crown?

Researchers will compare the Bioflx crown to the stainless steel crown to see which material works better to restore tooth function and health.

Participants will:

1. Receive one Bioflx crown and one stainless steel crown on similar teeth on opposite sides of the mouth.
2. Visit the clinic for two separate appointments, spaced 1 to 2 weeks apart, to have the crowns placed.
3. Return for checkups at 3 months and 6 months so researchers can examine the health of the teeth and gums.
4. Answer questions about how happy they are with the appearance and feel of the crowns.

The standard treatment for fixing severely decayed baby back teeth is the stainless steel crown, which is a durable metal cap. While these metal crowns work very well, many parents and children prefer a more natural, tooth-colored look. This study tests a newer option called the Bioflx crown, which is made of a flexible, tooth-colored material.

The Treatment Process The crowns are placed during two separate visits, usually 1 to 2 weeks apart. It gives the child time to get used to the first crown and ensures their bite is comfortable before the second one is placed. It makes the appointments shorter and easier for the child to handle. The side of the mouth that gets the metal crown and the side that gets the tooth-colored crown is randomized.

How Success is Measured

After the crowns are placed, researchers will check them again at 3 months and 6 months. They will use professional standards to evaluate the effectiveness of the crowns, focusing on:

1. Durability: Do the crowns stay glued to the teeth and resist wearing down from chewing?
2. Prevention: Does the new material prevent new cavities from forming at the edges of the crown?
3. Gum Health: Do the gums around the tooth stay healthy, or do they become red and swollen?
4. Satisfaction: How do the child and parent feel about the color, size, and shape of the tooth-colored crown compared to the metal one?

Inclusion Criteria:

• Children with at least two carious primary molars located on both the right and left sides of the dental arch and indicated for crown placement

• Children and their parents have ability to communicate in Vietnamese

• Primary molars indicated for full-coverage crown restoration, including teeth with:

  • Multi-surface caries
  • Extensive caries or enamel-dentin defects
  • Interproximal caries
  • High risk of failure with other restorative materials
  • Teeth following pulpotomy or pulpectomy

Exclusion Criteria:

• Uncooperative children
• Presence of psychiatric or neurological disorders affecting communication ability
• Malocclusion (crossbite or scissors bite)
• Having abnormal parafunctional habits
• Teeth with root resorption exceeding one half of the root length