DEAR ABBY: I have a question that has been bothering me a great deal. I feel embarrassed to ask, but I must.

My teen-age daughter has been receiving pen-pal letters from a girl in Ukraine (U.S.S.R.) who happens to live a few hundred miles from the Chernobyl disaster in a city called Dnepropetrovsk. Because I'm a natural worrier, mother of five and pregnant again, every time she receives a letter, I can't help but wonder if it is safe (non-radioactive).

I realize it has been five years since that tragedy, and cleanup has taken place, but I don't know whom to ask. Please help me. -- LOUISIANA WORRIER

DEAR WORRIER: Put your mind at ease. According to William Curtis, project leader at the Environmental Protection Agency's Office of Radiation Programs, there is nothing to worry about. (Mr. Curtis is an oceanographer who journeyed to Chernobyl last year to conduct surveys for the EPA on radiation levels in the Black Sea.) He assured me that if his word isn't enough to ease your worry, you may take the envelopes to be analyzed at any university that has a radiation department.

DEAR ABBY: I know you can help me. I have a son who's 14 years old, and he is terribly afraid of the dentist. I started taking him to the dentist when he was 3 years old, but each time it was a terrible experience.

He has not been to a dentist for a checkup for more than three years because he is terrified of shots. (He even complains about how painful it is to have his teeth cleaned.)

My question is: Are there any dentists in Michigan who treat patients who have a phobia about dentists? My son needs to have a couple of teeth extracted. -- LIVONIA MAMA

DEAR MAMA: If your family dentist cannot (or will not) refer you to a dentist who specializes in phobic patients, get in touch with your county dental association and ask for some referrals.

Please don't cave in on this very important issue, Mama. Proper dental care is essential to your son's general physical health.

DEAR ABBY: "Hurt in Indiana" remarked that whenever she went to her son's home, she noticed pictures of his wife's family prominently displayed all over the house, but not one picture of his family was in evidence. That reminds me of this story:

One of my lifelong friends remarried after her first husband died. Husband No. 2, whose first wife had died, kept a very large portrait of Eve, Wife No. 1, hanging over the fireplace.

Finally, my friend, one of nature's true noblewomen, who wouldn't hurt a flea if she could get out of its way, said to Husband No. 2: "I have a very good portrait of Clifford (Husband No. 1) that would look lovely beside Eve."

The next day Eve's portrait mysteriously disappeared. -- AMUSED IN TULSA

Most teen-agers do not know the facts about drugs, AIDS and how to prevent unwanted pregnancy. It's all in Abby's new, updated, expanded booklet, "What Every Teen Should Know." To order, send a business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, Teen Booklet, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)

DEAR ABBY: For quite a long time now, when certain situations arise, I ask myself, "What would Dear Abby say?" I would like to address this situation:

Before I was married, I visited my parents (they live nearby) several times a week. Now I am married -- with new friends, wanting to spend time with my husband and also visit my other siblings. This means that my husband and I don't visit my parents as much.

The problem? I feel guilty for not spending more time with them. My mother makes comments like, "Oh, we haven't seen you for months!" (Not true, Abby; we see them at least twice a month.)

I know that we are only as guilty as we make ourselves feel, but I would like to know, in Dear Abby's opinion, how often is often enough to visit parents? They don't seem to understand that there are other people in my life now, and working every day makes me tired at the end of the day and weekends are precious. Any comments? -- FEELING GUILTY

DEAR GUILTY: No one can "make" you feel guilty without your permission.

Your reasons for seeing less of your parents now are legitimate, so when you mother "reminds" you that your visits are less frequent, don't apologize (like a child); explain to her -- as you did to me -- that there are other people in your life now, and working every day is very tiring and weekends are precious.

DEAR ABBY: My brother's son is getting married soon in Chicago. The number of family on the groom's side will be limited, as none of us live in Chicago. We will have to fly in the night before in order to attend the wedding, which is scheduled for 2 p.m. We will not be able to leave for home the day of the wedding because there are no evening flights.

So -- after the airfare, hotel for two nights, meals, car rental, etc. -- the wedding will cost each of us well over $700, not including the gift.

I have just found out that the groom's family will not be invited to the rehearsal dinner, even though we are all from out of town. (There will be only six or eight of us.)

We are very hurt to think that we will be left alone in a hotel in a strange city after all of the effort and expense we will go through to attend this wedding.

Don't tell us it is our choice to go or not. We know that, but his wife would never forgive us if we didn't come, and besides, we really want to be there to see this nephew married.

Please try to explain why my brother and his wife are excluding us from the rehearsal dinner. It can't be the cost -- they can well afford a few more dinners. What do the etiquette books say? -- HURT IN NEW YORK

DEAR HURT: I don't know why your brother and his wife are excluding you from the rehearsal dinner if -- as you say -- they can well afford it.

The etiquette books say that all out-of-town guests should be invited to the rehearsal dinner, which is traditionally hosted by the groom or his family.

By popular request, Abby shares more of her favorite prize-winning, easy-to-prepare recipes. To order, send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: More Favorite Recipes by Dear Abby, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)

DEAR ABBY: When is it proper to play Cupid? My best friend, "Marsha," lost her husband a few months ago. He had a massive heart attack with no warning whatsoever. He was healthy and athletic.

A few years ago, Marsha and my cousin, "Marc," met at my daughter's christening. It was obvious that there was a strong mutual attraction between them, but they were both seeing other people at the time, so nothing came of it, and they both eventually married other people.

I just learned that Marc and his wife have split. Being a matchmaker is not something I do regularly, but I just know that Marsha and Marc would make a great team.

How can I get them together? And when would be the proper time?

I don't want Marsha to think I'm insensitive, but they are both very attractive people, and I don't want to chance either one of them getting involved with someone else before they have a chance to get together. -- FRUSTRATED CUPID

DEAR FRUSTRATED: Idle your motor -- you may be too late already. Do not mention Marc's availability to Marsha until you feel that Marsha is ready for another romance. And don't assume that Marc is waiting around for another involvement.

When Marsha is ready, contact Marc and ask him, "What's new?" and, "Are you 'involved'?" If nothing is new and Marc is not involved, tell him about Marsha's availability -- and let him take it from there.

DEAR ABBY: I am a 24-year-old future bride with a small problem. My mother and father were divorced when I was 10, and my mother married "Len" a year later. Len has been a wonderful stepfather whom I love dearly. My biological father and I had problems during my adolescent years. (We didn't speak to each other for four years.) My stepfather (Len) was a far more loving father to me -- in fact, he was the one who got me together again with my biological father.

Now I am going to be married. I read in a bridal magazine that where there is a biological father and stepfather involved, the bride's biological father is supposed to walk her down the aisle and give her away in marriage, and the stepfather has the privilege of dancing the first dance with the bride.

Is this the proper arrangement? I don't want to hurt anyone's feelings, but I have always had a much better relationship with my stepfather. -- HAPPY BUT CONFUSED

DEAR HAPPY: There are no hard and fast "rules" when it comes to weddings. If you're having problems deciding which man should walk you down the aisle, why not give both of them the honor? It has been done -- and with great success. Also consider walking down the aisle alone. It's the choice of many brides, and makes an impressive sight.

CONFIDENTIAL TO EVERYBODY: "Nothing is sometimes the right thing to say." (Malcolm Forbes)

This one's for everybody, from teens to seniors! To purchase Abby's new booklet, "The Anger in All of Us and How to Deal With It," send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, Anger Booklet, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)