What is Osteogenesis Imperfecta?

Imagine if your bones were as fragile as thin glass, breaking from even the smallest bump or fall. That is what happens in people with osteogenesis imperfecta (OI), also known as brittle bone disease. OI is a genetic condition that affects how bones grow and repair themselves. People with OI are born with bones that can bend or break easily, sometimes even without an accident happening. Scientists have found that OI happens mainly due to genetic changes in two important genes—COL1A1 and COL1A2 [1]. These genes help the body make type I collagen, a protein that acts like the main framework inside bones and teeth, helping them stay strong and flexible. As shown in Figure 1, when type I collagen is affected, it can lead to both bone and tooth problems. Mutations in COL1A1 and COL1A2 can either reduce the amount of collagen made or lead to incorrectly shaped collagen fibers, both of which weaken bones and teeth [2].

OI can range from mild to very severe. Some people may only break a few bones in their lifetimes, while others might break hundreds. Scientists have grouped OI into types based on how severe it is. Those with moderate to severe types of OI, like Type III and IV, are more likely to experience problems with their teeth—a condition known as dentinogenesis imperfecta (DI). In fact, around half of all people with OI have DI, but it does not affect everyone the same way [3]. Baby teeth are often more affected than adult teeth and, in some cases, only the baby teeth show signs of DI [3]. This means that someone with OI might have very fragile baby teeth but later grow adult teeth that look and feel stronger. OI can also affect how the jaw grows, leading to bite problems like underbites (when the lower teeth stick out beyond the upper teeth) or open bites (when the top and bottom teeth do not touch when the mouth is closed. These problems can make chewing or speaking difficult. Some kids with OI may also have teeth that come in earlier or later than usual. These are some of the reasons why it is important for kids with OI to see a dentist early—even before their baby teeth come in.

What is Dentinogenesis Imperfecta?

DI is a condition that makes teeth weak and discolored due to problems with the dentin, the layer beneath the enamel. Dentin is the inner layer that makes up the structure and color of teeth, while enamel is the strong, protective coating that covers each tooth. DI happens when type I collagen, which helps form dentin, is not made correctly. Without strong collagen, the dentin structure becomes weaker and poorly organized, making the teeth more fragile. People with DI often have teeth that appear yellow-brown or bluish-gray. Scientists describe this as opalescent, meaning the teeth appear both shiny and cloudy at the same time [4].

Because of weak collagen, the dentin in DI teeth has fewer and more irregular tubules, which are tiny channels that help transport nutrients through the tooth [3]. As shown in Figure 2, these tubules are often abnormally shaped, fewer in number, and display unusual branching patterns. Under a microscope, DI dentin appears disorganized and patchy, unlike the neat and structured pattern seen in healthy teeth. These changes make the dentin less capable of protecting the tooth, which explains why it wears down and breaks more easily. Even everyday activities like chewing can cause the dentin to wear down faster than usual. Over time, this can lead to teeth becoming shorter and losing their natural shape. DI can often be identified just by looking at the teeth or through X-rays. DI teeth sometimes have unusual shapes, such as bulbous or rounded crowns and short roots [4]. X-rays may also show pulp canal obliteration, a condition where the nerve canals inside the tooth shrink or disappear entirely. When this happens, the tooth can lose its natural transparency and appear more discolored, making the yellow-brown or bluish-gray shades even more noticeable.

Why Do DI Teeth Look Different?

The unusual color of DI teeth comes from how light passes through them. Normally, enamel is thick and strong, helping reflect light and keep teeth looking bright. But in DI, the enamel is often thinner, and the dentin underneath is softer and more disorganized. Because the enamel is slightly see-through, the color of the dentin shows through, making the teeth appear yellow-brown or bluish-gray rather than white. This effect is even more noticeable in baby teeth, which naturally have less enamel—in fact, the enamel in permanent teeth is about twice as thick as in baby teeth [5]. Research shows that enamel thickness plays a major role in how much dentin color is seen, with thinner enamel making teeth appear more translucent and increasing the discoloration [6].

These structural changes affect how light is absorbed and reflected, making DI teeth appear darker and cloudier than normal teeth (Figure 3).

How Rare is DI?

DI is considered a rare condition, affecting about one in every 6,000–8,000 people [7]. It can happen in both boys and girls and usually appears in childhood, when baby teeth first start to come in. DI often runs in families because it is a genetic condition, meaning it can be passed down from parents to children—even if it looks a little different from one person to another.

Even though it is not very common, scientists have been studying DI for a long time. In fact, the first description of this condition was made back in 1882 [7]. Before it was known as DI, the condition was referred to as “hereditary opalescent dentin” because of the way the teeth looked—shiny, cloudy, and colorful, like an opal!

DI can also occur without OI. In this case, it is called DI type II, and it is mainly caused by mutations in a gene called DSPP (dentin sialophosphoprotein).

How Can We Help and Protect Teeth With DI?

People with DI need to take extra care of their teeth. Dentists often recommend wearing a mouth guard during sports, avoiding sticky or hard candy, and visiting the dentist regularly to check for signs of wear.

Above all, it is important to be kind to people with DI. Some kids with DI might feel embarrassed or hurt if others make fun of the color or shape of their teeth. It is important to remember that everyone’s smile is different, and we should always be thoughtful about what we say.

Conclusion: Why this Matters

Teeth and bones may seem very different from each other, but they both rely on the same protein—type I collagen—to stay strong. When this protein does not function properly, as in OI, it can lead to fragile bones and dental problems like DI. DI helps explain why some people’s teeth look different in color or shape and why they might wear down more easily. By understanding how these conditions work, doctors and dentists can spot signs early and provide care to protect teeth before problems get worse. Everyone’s smile is unique, and learning about conditions like DI helps us appreciate those differences.

Glossary

Genes: ↑ Instruction books stored in each cell that teach the cell and the body to function.

Type I Collagen: ↑ The most common type of collagen, a protein found mainly in bones, skin, and dentin that supports the body’s structure.

Mutations: ↑ Small changes or “typos” in a gene that mess up the instructions on how to make proteins.

Dentin: ↑ The inner layer of a tooth located beneath the enamel.

Enamel: ↑ The hard outer layer of a tooth that protects the dentin.

Opalescent: ↑ A term describing teeth that appear shiny and cloudy at the same time, often due to DI.

Tubules: ↑ Tiny channels in dentin that help transport nutrients through the tooth.

Pulp Canal Obliteration: ↑ A condition where the nerve canals inside the tooth shrink or disappear, often seen in DI teeth.

Conflict of Interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

AI Tool Statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

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