Four quick answers first:
Is it a bad omen?
It can be — under conditions. In Al-Nabulsi, teeth that fall and are gone stand for the death of the relative each tooth maps to, and a tooth that is buried in the dream seals it. In the Ibn Sirin compilation, the harshest reading is triggered by a search: if you cannot find your fallen teeth, "his family will die before him." The common folk belief that any teeth dream forecasts a death skips those conditions.
Is it a good sign, then?
Also yes, in the same books. The compilation opens the entry: falling teeth "means longevity, or living past one's contemporaries." Al-Nabulsi reads teeth falling painlessly into the palm as coin — "dirhams, in their number" — and both books give the whole dream a debt-paying reading, which is a relief, not a misfortune. For a slave in the dream-cast, the shower of teeth means manumission.
What decides which reading fires?
Dream details, not the dreamer's mood: caught or lost, buried or kept, with pain or without. And in Al-Nabulsi, the station of the person the teeth represent — the identical shower of teeth that reads as death for the household reads as a long sickness-without-dying, as freedom for a slave, and as a lightened load for a merchant or traveler. One image, four omens.
Does the research settle good or bad?
No — and that is itself the finding. The only study that tested a meaning-claim head-on (Rozen & Soffer-Dudek, Frontiers in Psychology 9:1812, 2018, n=210) checked whether teeth dreams symbolize psychological distress and found r = 0.02, no relationship, while finding a link to jaw and gum tension on waking (r = 0.21). Fortune and calamity are not variables in any published design; the one "it means your suffering" hypothesis science tested is the one it failed. The design and full numbers behind these figures are laid out in the modern-research section below.
The book's own lesson: same omen, two presentations
The 1992 compilation opens its front matter on dream interpretation with a teeth story, and it is exactly the good-or-bad question. A Caliph dreams all his teeth fall out:
"The interpreter replied: 'The entire family of my master will perish.' The Caliph became upset, and he called for another interpreter and told him the dream. The second dream interpreter replied: 'The dream of my master, the prince of the believers, is true, for he shall live the longest amongst his relatives.' Immediately, the Caliph embraced the man and rewarded him for his skill and tactfulness. In this case, both interpreters gave the same meaning, though the presentation is different."
Read the moral carefully, because it is more interesting than "spin." The book says the two interpretations were the same meaning: to outlive your relatives is, proposition-for-proposition, to survive all of them. The dream did not change polarity; only the vantage did. Whether the omen is "bad" or "good" was a fact about the listener, not about the teeth. Any reader who wants a stable good-or-bad verdict from these books is asking dictionaries eight centuries apart a question they treat as a trick of perspective.
Classical textThe calamity reading on the record
The same compilation's front matter keeps the unsparing version, in its string of interpretation anecdotes, voiced by one of the most celebrated interpreters of the early Muslim community:
"Sharik bin Abi Shamr came to Sa'Id bin Al-Musayyib and said: 'I saw all my teeth falling out in a dream.' Sa'id bin Al-Musayyib replied: 'What a calamity! If your dream is true, it means that all your relatives will die before you.'"
Al-Nabulsi's page ص180 opens with the same death register — but hedges it in the same breath, the way the Caliph story does:
"If it goes from his sight, then the people of his household die before him — and it may be that this is the death of those of his own age, or the sickness of the people of his household."
"The death of those of his own age" is the longevity reading again from inside the death sentence: your peers die, you remain. And "sickness" instead of death softens the blow without canceling it. On one line, Al-Nabulsi stacks calamity, longevity, and illness-instead-of-death.
Classical textThe exceptions clause: fortune by station
The passage the folk pages never reproduce is Al-Nabulsi's run of exceptions attached to the worst case — all teeth falling at once:
"If his teeth all fell out in a shower, then all those in that household perish — the kin, the companions, the freedmen and the travelers. And this vision indicates, from among them, a long sickness without their dying; and it indicates, among slaves, manumission; and merchants and travelers, the lightening of their load."
Three softenings, one paragraph. The maximum-death reading is immediately capped at sickness-without-death; for a slave, the same dream means freedom — the teeth that stand for the household's people read as the manumission of the least free among them; for the merchant and the traveler, the load gets lighter, which is at once a pun on lost teeth and a good omen for the road. The book is telling you that "is this dream good or bad" cannot be answered before you know who is dreaming it and which people the teeth are.
And there is a plain fortune line for the hand. Al-Nabulsi: teeth that fall into the palm "with no pain and no pulling" are "dirhams, in their number" — coin, counted — while the upper teeth falling into the hand "is wealth that comes to him." The compilation agrees: "If the upper teeth fall into one's hand in the dream, they represent profits." Both books, no contradiction, all inside the dream everyone calls unlucky.
Classical textThe switch: keep it or bury it
The single clearest good-versus-bad lever in either book is one action performed on a fallen tooth, and both dictionaries print it at the same fork:
"If he holds it and does not bury it, he will gain in its place someone who is to him like that relative... and if he buries it, then it is the death of that relative."
"If one saves his lost tooth and does not bury it in the dream, it means that someone will come forth and be to him as good as that relative. Otherwise, if he does bury it, then it means the death of his relative."
Same dream, same tooth, two fates separated by whether the dreamer digs a hole. The compilation also adds its search-condition variant at the "Teeth" entry: "If one cannot find his teeth in the dream, it means that his family will die before him, or that a member of his clan will emigrate to a new land. If one finds a lost tooth in a dream, it means the return of an immigrant to his homeland." Lost-buried: death. Found-kept: return, replacement. In these books the omen is a decision procedure over dream details, not a mood.
What the one empirical paper says about omens
Rozen & Soffer-Dudek, "Dreams of Teeth Falling Out: An Empirical Investigation of Physiological and Psychological Correlates" (Frontiers in Psychology 9:1812, 2018; PubMed 30319507; open access CC BY), describes teeth dreams as "one of the most common and universal typical dream themes, yet their source remains unknown" — and their very commonness as "incompatible with the 'continuity hypothesis'," since adults do not usually lose their teeth in waking life. Before testing anything, the paper's introduction runs its own two-thousand-year audit of good-or-bad readings:
Artemidorus, second century, Ancient Greece — "the earliest documented interpretation" — tied losing teeth in a dream to the payment of debts: a relief reading, the same one both classical Islamic books independently keep. The Jewish Talmud read teeth dreams as "a prophecy for the impending death of a family member": the calamity reading, in the paper's own words, "a common belief for many years, which Freud (1900) reacted to with irony." Jung reportedly read them, in women, as childbirth; Schneck (1967) as "the fear of growing older." The historical record the study walks through is a pendulum — debts, death, birth, aging — with no stable polarity across any two centuries.
The paper's own test then removed the psychological end of the pendulum. Across 210 undergraduates: teeth dreams related to waking teeth-and-gum tension, r = 0.21 (95% CI 0.07–0.33, p < 0.005), and not to the direct grinding item, r = 0.06 (n.s.), and not to psychological distress, r = 0.02 (n.s.) — while falling dreams and smothered dreams in the same sample did track distress. The authors' conclusion: the findings "support the dental irritation hypothesis and do not support the symbolic hypothesis." Nothing in the design measured fortune; the dream's badness and its goodness are both outside the instrument. What survived measurement is a jaw.
The prevalence figures the paper cites from the Dream Motif Scale (Yu, 2012, Dreaming 22(1), 18–52, DOI 10.1037/a0026171): 39.0% of respondents had teeth dreams at least once, 16.2% recurrently, 8.2% regularly. About two in five people have had this "omen" at least once — which is also why every culture on record has a good-or-bad argument about it.
Set the layers beside each other — the actual point
Collision one. Folk pages near-globally treat the dream as bad-luck news ("someone will die"), and the classical books print that reading only under conditions — lost, buried, unfound — while printing profits, dirhams-by-count, debts paid, a son on the lap, longevity, and a slave's freedom on the same page as counter-readings. The books are not ambivalent by accident; each hard reading carries its stated switch.
Collision two. The oldest reading the modern paper's introduction preserves — Artemidorus, debts paid — is a fortune reading, and both Islamic books carry it independently: "Falling teeth in a dream also mean paying one's debts" (compilation), "if he is under a debt... it indicates that he will pay his debt" (Al-Nabulsi, Arabic checked verbatim: "فإن ذلك يدل على أنه يقضي دينه"). The popular "death omen" memory and the earliest documented scholarly answer point in opposite directions.
Collision three. The one study that tested "the dream symbolizes your distress" — the modern soft version of the bad-omen theory — failed to find it (r = 0.02), while finding a physical correlate instead. Neither the calamity nor the comfort reading has any measurement behind it; the books price the dream through its details, the study measures the jaw, and the gap between them is the honest space on this page.
This site's readingThe honest gap
No published study tests whether a dream portends anything, and the classical books themselves refuse to fix the polarity: Al-Nabulsi's page runs وقيل — "and it was said" — through a chain of alternative verdicts (a harm to some friends; an obstacle to what he wants; a sign of debts being paid; for the ascetic, an injunction to keep the fast) and closes the worst-case paragraph by capping death at sickness. The compilation prints longevity as its first word and calamity in its front matter, and lets both stand. A page that tells you flatly that the teeth dream is "definitely bad luck" or "actually good news" is choosing one line out of two books and deleting the conditions attached to every other line.
This page reports what two classical texts and two published studies say. It is not a prediction, a diagnosis, or a medical or religious ruling, and no dream book — classical or modern — settles what a dream means for the person who had it. If your teeth hurt or loosen in waking life, that is a question for a dentist, not a dream dictionary.