sisyuubyou de tumetai mizu ga ha ni simimasu.

In this sentence, しみます means something like:

• stings
• feels sharp/painful
• is sensitive
• hits a nerve

So 冷たい水が歯にしみます means cold water hurts my teeth or my teeth are sensitive to cold water.

This is a very common use of しみる with things like:

• 冷たいものが歯にしみる = Cold things hurt my teeth.
• 傷にしみる = It stings a wound.
• 目にしみる = It stings the eyes.

So yes, しみる can mean to soak into / permeate, but in health/body contexts it often means to sting or affect painfully.

Here, で marks the cause or reason.

• 歯周病で = because of periodontal disease / due to gum disease

So the sentence structure is roughly:

• 歯周病で = because of gum disease
• 冷たい水が = cold water
• 歯にしみます = stings my teeth

A natural English translation would be:

• Because of gum disease, cold water hurts my teeth.

This で is often used for causes, especially in medical or situational contexts:

• 風邪で学校を休みました。 = I missed school because of a cold.
• 事故で電車が遅れました。 = The train was delayed because of an accident.

が marks 冷たい水 as the thing that causes the sensation.

So in:

• 冷たい水が歯にしみます

the cold water is what stings.

You can think of it like:

• As for what stings my teeth, it’s cold water.

In English, we might say Cold water hurts my teeth, but Japanese often marks the thing producing the sensation with が.

Other similar patterns:

• この薬がよく効きます。 = This medicine works well.
• 煙が目にしみる。 = Smoke stings the eyes.

に marks the target/location affected by the sensation.

• 歯にしみます = it stings in the teeth / it affects the teeth painfully

So the pattern is:

• X が Y にしみる
• X = thing causing the sting
• Y = place/body part affected

Examples:

• 塩が傷にしみる。 = Salt stings a wound.
• 煙が目にしみる。 = Smoke stings the eyes.

Here:

• 冷たい水が歯にしみます = Cold water stings my teeth.

Japanese often leaves out things that are obvious from context, including possessives like my.

So:

• 歯にしみます

naturally means it stings my teeth in context, even though my is not explicitly stated.

With body parts, Japanese often avoids saying 私の歯 unless it needs emphasis or contrast.

So:

• 冷たい水が歯にしみます。

is more natural than:

• 冷たい水が私の歯にしみます。

unless you specifically need to stress that it is your teeth, not someone else’s.

Japanese nouns usually do not mark singular vs. plural the way English does.

So 歯 can mean:

• a tooth
• teeth

depending on context.

In this sentence, English will usually translate it as teeth, because that sounds more natural:

• Cold water hurts my teeth.

But Japanese simply says 歯 and lets context do the work.

Because 冷たい is used for things that are physically cold to the touch or taste.

• 冷たい水 = cold water

寒い is used for the weather, air, or feeling cold as a person.

• 寒い日 = a cold day
• 寒い = I’m cold / it’s cold (weather)

So:

• 冷たい水 = correct
• 寒い水 = unnatural in normal Japanese

冷たい is an i-adjective, and i-adjectives directly modify nouns.

So:

• 冷たい水 = cold water

No extra particle or linking word is needed.

Compare:

• 白い歯 = white teeth
• 熱いお茶 = hot tea
• 冷たい水 = cold water

If it were a na-adjective, then you would use な before the noun:

• 静かな部屋 = a quiet room

But 冷たい is not a na-adjective, so it stays as-is.

It is read:

• ししゅうびょう (shishūbyō)

Breakdown:

• 歯 = し
• 周 = しゅう
• 病 = びょう

It means periodontal disease or gum disease.

This is a medical term, so in everyday conversation people might sometimes say something simpler depending on context, but 歯周病 is the standard word.

Yes. しみます is the polite non-past form.

The dictionary/plain form is:

• しみる

So:

• 冷たい水が歯にしみます。 = polite
• 冷たい水が歯にしみる。 = plain/casual

The polite form is appropriate in situations like:

• talking to a doctor or dentist
• speaking politely to someone you don’t know well
• formal writing or textbook examples

Yes, depending on what you want to emphasize.

The original:

• 歯周病で冷たい水が歯にしみます。

focuses on cold water as the thing that stings.

You could also say:

• 冷たい水は歯にしみます。

This would mean something like:

• Cold water, as for that, stings my teeth.
• Cold water is painful to my teeth.

Using は makes cold water more of a topic, often with a nuance of contrast or general statement.

But in the full sentence you gave, が is very natural because it presents cold water as the direct stimulus causing the sensation.

Yes, it is understandable and natural, especially in a medical context.

It means:

• Because of gum disease, cold water hurts my teeth.
• My teeth are sensitive to cold water due to periodontal disease.

At a dentist, people might also say related things like:

• 冷たいものが歯にしみます。 = Cold things hurt my teeth.
• 歯がしみます。 = My teeth feel sensitive.
• 冷たい水を飲むと歯がしみます。 = When I drink cold water, my teeth hurt.

That last one is especially common in conversation because it clearly describes when the pain happens.

Japanese often omits the subject when it is clear from context.

So instead of saying:

• 私は歯周病で冷たい水が歯にしみます。

Japanese often just says:

• 歯周病で冷たい水が歯にしみます。

The listener will understand that the speaker is talking about their own condition, especially in a medical setting.

In English, we usually need a subject, but Japanese is much more comfortable leaving it unstated when it is obvious.