A complete guide to dental anaesthesia, sedation and fear of the dentist: a domain map running from how local anaesthesia works, through the sedation spectrum, to the assessment of anxiety

A complete guide to dental anaesthesia, sedation and fear of the dentist: a domain map running from how local anaesthesia works, through the sedation spectrum, to the assessment of anxiety

TL;DR

Sedation comes in three levels — minimal, moderate and deep — and is different from full anaesthesia [Fn1]; true local-anaesthetic allergy involving IgE-mediated reactions and anaphylaxis is rare, accounting for less than one per cent of adverse reactions [Fn2].

(54 characters in the zh-Hant original, [Fn] markers and punctuation not counted)

Introduction

This article is general oral-health education based on international literature. It does not address any country's insurance or regulations; consult local rules for care pathways and costs.

This article deliberately does not answer “how many injections will this tooth of mine need tomorrow” or “am I able to have sedation”. Individual questions of that kind can only be answered by a dentist who has examined that person and read that person's history. What this article handles is the domain-level gap: what each of the three frequently conflated words — anaesthesia, sedation and general anaesthesia — actually refers to in professional vocabulary, how “fear of the dentist” is measured in the literature, which of the commonly repeated figures in fact carry population limits, which statements that look like consensus are in fact evidence gaps, and what a person can find out by asking before walking into the surgery.

One thing has to be made clear first, because it governs how every later section is to be read: the axis of this domain is not “does it hurt”, but “how far along the scale of consciousness and physiological response has the patient been adjusted”. The official patient-education page of the U.S. National Library of Medicine puts that axis very plainly — sedation is different from full anaesthesia, sedation does not make a person completely unconscious, and recovery is quicker [Fn3]; and sedation itself is further divided into three levels, minimal, moderate (conscious sedation) and deep [Fn4][Fn5][Fn6].

The second thing is a sense of scale. A systematic review and meta-analysis that included 31 population-based observational studies covering 72,577 adults 18 years of age or older reports that the global estimated pooled prevalence of dental fear and anxiety (DFA) is 15.3% (95%CI 10.2–21.2) [Fn7], with high DFA at 12.4% (95%CI 9.5–15.6) and severe DFA at 3.3% (95%CI 0.9–7.1) [Fn8]. The authors of that same study also mark honestly that 28 of the 31 included studies carry a high risk of bias [Fn9], and that the instruments used to measure fear themselves affect the prevalence that is measured [Fn10].

That last sentence is the key to this article. It means that “how many people fear the dentist” is not a single fact but a figure that moves with the definition and the scale used — and every percentage that follows has to be read in that same way.

1. The grading map: anaesthesia, sedation and general anaesthesia are three different levels

1-1 The four terms in the official classification

The patient-education page of the U.S. National Library of Medicine (NIH/NLM) divides anaesthesia into four categories, and that is the terminological basis shared by the rest of this article:

The same page separately splits the depth of sedation into three bands: minimal sedation is being awake but more relaxed [Fn4]; moderate sedation (that is, conscious sedation) may involve drowsiness and poor recall, while the person can still respond when spoken to or touched [Fn5]; deep sedation is being very drowsy, possibly responding only to repeated or stronger stimulation [Fn6].

A portable way to read this: what is colloquially called “sedation dentistry” or “having it done asleep” is not a single point in professional vocabulary but may fall into any one of minimal, moderate (conscious sedation) or deep sedation [Fn4][Fn5][Fn6], and it may also refer to general anaesthesia, which is different from sedation, affects the whole body and feels like a deep sleep [Fn3][Fn15]. Before asking “is it safe”, establish which band is being talked about — because the official page itself writes these bands as states with different definitions [Fn4][Fn5][Fn6][Fn15].

1-2 Four things the word “asleep” can mean in dentistry

The same sentence, “I want to be asleep for it”, may correspond clinically to four completely different arrangements:

1. Local anaesthesia only: awake [Fn12]; it is simply that the tooth has no sensation.
2. Nitrous oxide (inhalation sedation): relaxed but awake, with both onset and recovery being rapid [Fn19].
3. Oral or intravenous sedation: drowsy, and most people will not remember the procedure [Fn17]. The recovery-period monitoring evidence this article is able to cite is confined to intravenous sedation — an observational study of intravenous sedation (the agent used is recorded in the fact ledger) defined the point of awakening by the bispectral index and re-assessed the patient with the post-anaesthetic discharge scoring system every 20 minutes [Fn20]; on the oral sedation side this article obtained no corresponding monitoring or recovery-time evidence, and makes no equivalent statement.
4. General anaesthesia: affects the whole body and is like a deep sleep [Fn15]; in professional guidelines it is positioned as a procedure requiring a complete referral and assessment pathway [Fn21].

The difference between the four is not only “how deeply asleep”, but how much monitoring manpower is required, how long recovery takes, and how the risk profile differs. That is also exactly what the whole of section 4 below deals with.

2. Local anaesthesia: the area it acts on, injection pain, and the evidence gap around “how long until it wears off”

2-1 Why dentistry almost always starts from local anaesthesia

The opening sentence of a Cochrane systematic review is the bedrock of this domain: pain during dental treatment is a common fear among patients, and it can be successfully controlled by local anaesthesia [Fn22]. That review included 123 studies with 19,223 participants [Fn23] and compared 14 different formulations [Fn24] — which is to say that “local anaesthesia” is not one drug but a whole family of drugs.

2-2 Does having the injection hurt: injection pain is a variable that has been measured, and in which an intervention has shown potential in a paediatric population

There is direct pooled evidence on this question, but it carries an explicit population limit, which has to be stated first.

A 2025 systematic review and meta-analysis screened 1,253 records down to 20 randomised controlled trials, in children aged 3 to 14 years [Fn25]. The results show that a computer-controlled local anaesthetic delivery system (CCLAD), compared with conventional injection, significantly reduced pain perception on the Wong-Baker pain scale (SMD = -0.98, p = 0.011) [Fn26], and likewise on heart-rate measurements (SMD = -0.25, p = 0.013) [Fn27]; subgroup analysis showed that the pain reduction with CCLAD was significant compared with the conventional inferior alveolar nerve block (IANB) injection [Fn28].

The authors at the same time mark four things honestly: heterogeneity was high and moderate respectively [Fn27]; on other scales and other injection techniques the results were inconsistent, with some non-significant differences appearing [Fn139]; on other pain assessment parameters no significant differences were observed [Fn140]; and the overall certainty of the evidence ranged from very low to moderate, with only 5 studies at low risk of bias [Fn29]. The authors' own concluding wording is therefore reserved: CCLAD “demonstrates potential” for reducing injection pain in children [Fn141].

⚠ The population for this evidence is children aged 3–14 years [Fn25]. This article does not extrapolate it into an effect claim for adults, and does not read “demonstrates potential” [Fn141] as an established effect.

As for the post-injection pain caused by the agent itself, moderate-quality evidence from Cochrane shows that the difference in post-injection pain between different local anaesthetics is very small, and that one of them may cause slightly less post-injection pain in that comparison [Fn30] (⚠ the main text of this article makes no comparative recommendation by drug name or concentration; which one is used is decided by the dentist according to the procedure and the individual's circumstances). The same review records that adverse events were rare [Fn31].

⚠ This passage is a compilation of the literature at drug level and constitutes no medication instruction of any kind. Which local anaesthetic is used, and by what technique it is given, is in every case decided by the dentist according to individual circumstances.

2-3 How long until the anaesthetic wears off: this is an evidence gap, not a number

This is the passage this article needs to handle with particular honesty.

One of the primary objectives of that Cochrane review states plainly that it set out to compare, between different local anaesthetic formulations, the success of anaesthesia, the speed of onset and duration, and systemic and local adverse reactions [Fn32]. But in the results section what the authors wrote was: for the comparisons assessing onset and duration, no clinical studies met their outcome definitions [Fn33].

Put another way: at the level of systematic review, “how long until the anaesthetic wears off” has so far not been pooled into an authoritative cross-formulation answer. The various “wears off in so many hours” figures circulating online are not repeated by this article — because evidence at the Cochrane level shows clearly that the question has not yet been measured under a unified definition.

What can honestly be said is this: local anaesthesia is a family containing 14 different formulations [Fn24], and different formulations behave differently in the first place (Cochrane did compare differences between formulations in the success of anaesthesia [Fn34]), so “how long until it wears off” is not physiologically a universal constant. For the actual timing, ask the dentist who prescribed and gave the injection.

2-4 While the anaesthetic has not yet worn off: self-inflicted soft-tissue injury

The reason “how long until it wears off” is a genuine question is mainly that the window before the anaesthetic wears off carries a real risk.

A 2026 systematic review screened 574 records down to 21 studies (9 RCTs, 6 case reports, 6 cohort studies), mainly focusing on children aged 6 to 12 years [Fn35], on precisely the subject of soft-tissue injuries secondary to local anaesthesia together with their differential diagnosis and treatment pathway [Fn36]. The conclusion states that soft-tissue injuries occurring in children after local anaesthesia can cause significant pain and cooperation issues [Fn37], and that effective strategies include early intervention with pharmacological and non-pharmacological approaches [Fn38].

The interventions compiled in that review include phentolamine mesylate (2 studies) [Fn39], along with non-pharmacological strategies such as intraoral appliances (2 studies) and photobiomodulation (2 studies) [Fn40]. The authors at the same time mark that the included studies varied greatly in design, sample size and duration, that effect sizes and confidence intervals were inconsistently reported, and that the risk-of-bias assessment likewise showed methodological heterogeneity and potential reporting bias [Fn41].

⚠ This passage is a compilation of the literature at the level of mechanism and strategy, and provides no procedural instruction and no medication instruction. What to watch for before the anaesthetic wears off, and whether any intervention is needed, must be explained individually by the dentist according to the extent of that particular treatment and the person's age.

The boundary with behaviour guidance in children: the evidence in this section has children as its main population [Fn35]; behaviour guidance on the paediatric side, management of cooperation and the role of the parent belong to another domain — see domain article P14 (paediatric dentistry).

2-5 Palpitations, shaking, dizziness: the differential map for adverse reactions

Many people record “palpitations after the injection” directly as “I am allergic to the anaesthetic”. In the literature these are two different things.

One review states at the outset that adverse reactions to local anaesthesia are usually a reaction to adrenaline, vasovagal syncope, or overdose toxicity [Fn42]. And in a standardised diagnostic series at an allergy centre, among 24 cases self-reporting “local anaesthetic allergy”, those classified as psychosomatic reactions accounted for 29.1%, symptoms of sympathetic stimulation 12.5%, and vasovagal syncope 8.3% [Fn43].

At the other end are the genuinely serious but rare complications. A 2026 narrative review states that local anaesthetic systemic toxicity (LAST) is a rare but potentially fatal complication of local anaesthesia in dentistry and in oral and maxillofacial surgery [Fn44], and stresses that a structured differential diagnosis is needed in order to separate LAST from the more common dental emergencies [Fn45]. The same review records three institutional facts that are useful to readers: between different guideline sources there are clinically significant discrepancies in the recommended upper limits of dose [Fn46]; the additive toxicity of combined amide agents remains underappreciated [Fn47]; and in management, intravenous lipid emulsion (ILE) is the specific rescue therapy for severe or cardiovascular LAST, while airway support and oxygenation remain the priority intervention [Fn48]. That review further points out that patient-specific factors substantially lower the effective toxic threshold [Fn49].

⚠ This article provides no dose figures, no method of calculation, and no advice about taking or stopping any medicine. The above only explains “why this is something that needs to be carried out by trained professionals in a setting prepared for emergencies”.

A portable way to read this: breaking “feeling unwell after the injection” into four possibilities — an adrenaline reaction, vasovagal syncope, toxicity, and true allergy [Fn42][Fn44] — is a very useful set of words to have before walking into the surgery. Because in the literature these four belong to different mechanisms [Fn42][Fn44][Fn50], the interpretive pathway on the professional side also differs: LAST is required to be separated from the more common dental emergencies by a structured differential diagnosis [Fn45], whereas someone with suspected allergy has a pathway to follow of detailed history-taking plus standardised skin testing and challenge testing [Fn66][Fn67][Fn68]. As for whether the agent should subsequently be changed, that falls within what must be tailored to each individual patient's medical condition [Fn71], and is not something a reader can determine for themselves.

3. “Allergy” to the anaesthetic: true allergy, pseudo allergy, and allergy that has been mislabelled

3-1 The classification ladder: three mechanisms that must not be spoken of interchangeably

A 2025 systematic review divides allergic reactions in dental practice into three classes of mechanism: immediate-type allergic reactions mediated by immunoglobulin E (IgE) [Fn50], delayed-type reactions mediated by sensitised T lymphocytes [Fn51], and pseudoallergic reactions, which occupy an independent position in the classification [Fn52]. That review at the same time stresses the importance of cross-reactions — several structurally similar molecules may bind to the same IgE antibodies or T lymphocytes [Fn53].

On the list of triggers, that review places local anaesthetics (such as lidocaine and benzocaine) among the significant triggers of allergic reactions in dentistry [Fn54], alongside antibiotics (penicillins and cephalosporins), latex products (gloves and rubber dam), the acrylic materials used in dentures and fillings, and metal alloys containing nickel, chromium and cobalt [Fn55].

That list is itself the point: reactions that occur in the dental surgery do not come only from the anaesthetic.

3-2 How rare true allergy is: the order of magnitude in two publications

A 2023 review writes the order of magnitude out directly: true allergic reactions involving IgE-mediated reactions and anaphylaxis are rare, have only been identified in case reports, and account for less than 1% of adverse local anaesthetic reactions [Fn56]; most reactions are non-allergic, or are allergy to other sources such as preservatives and excipients [Fn57].

A 2025 review took stock over a 25-year span: between January 2000 and December 2024, true allergy to articaine confirmed by standard allergological procedures such as skin testing and/or challenge testing was found in a total of only 10 case reports and 6 case series, amounting to 29 patients [Fn58]. Of these, 20 were diagnosed with immediate-type (type I) allergy and 5 with delayed-type (type IV) [Fn59], and cross-reactivity with other amide local anaesthetics was reported in only 3 cases [Fn60]. The authors' conclusion is written very directly: true allergy to articaine is exceedingly rare [Fn61].

⚠ Marked honestly: the latter is a compilation of case reports and case series (a design that depends on reporting), so it can only demonstrate that “the number of confirmed cases is extremely small”, which is not the same as having precisely measured a population incidence.

3-3 Why “mislabelling” has a cost

That same 2023 review points out the consequence of mislabelling: local anaesthetic reactions misclassified as true allergy may lead to unnecessary avoidance of local anaesthetic drugs, or to delay of surgery that requires them [Fn62].

On the evidence for standardised diagnosis, a retrospective series from an allergy centre gives a concrete picture: among 24 patients investigated at that allergy centre on suspicion of “local anaesthetic allergy” [Fn63] (the original wording is investigated…on suspicion of, and the referral source and initial diagnosis are not recorded), only 3 cases were considered local anaesthetic allergy after standardised skin testing and drug challenge testing [Fn64]; a further 3 cases (12.5%) had been positive on previous skin tests and were proved under the standardised procedure to be tolerated [Fn65]. The study concludes that true allergic reactions to local anaesthetics are rare, and that through standardised skin testing and drug challenge testing the great majority of patients who self-report “local anaesthetic allergy” can have allergy ruled out [Fn66].

⚠ Marked honestly: that study is a retrospective series of 24 people [Fn63] from a single medical centre, and the sample is very small; this article uses only its direction and its procedure, and does not use its percentages to make inferences about a population.

3-4 The diagnostic pathway, and the options after a confirmed diagnosis

That 2023 review sets out the pathway clearly: detailed history-taking about prior reactions is the opening step in understanding the nature of the reaction, and a key step at that [Fn67]; those in whom an immediate-type allergic reaction is suspected can be assessed with skin prick and intradermal testing followed by graded challenge [Fn68]; those in whom a delayed-type allergic reaction is suspected can be assessed with patch testing [Fn69].

After a confirmed diagnosis there is still a way forward in the literature. A review covering several special medical circumstances notes that, for those with confirmed amide allergies, it records the existence of alternative anaesthetic options from a different chemical class [Fn70] (⚠ the main text of this article gives no selection advice by drug name — which agent can be tolerated after a confirmed diagnosis, who administers it and under what monitoring conditions, has to be decided after assessment by an allergy or anaesthesia specialist); the summing-up of that same review is that the choice of local anaesthetic must be tailored to each patient's medical condition [Fn71]. Another review records that patients with a true allergy may sometimes be treated under general anaesthesia [Fn72].

⚠ This passage constitutes no medication advice, constitutes no advice about stopping any medicine, and gives no doses. Whether allergy testing is needed, which specialty carries it out, and what plan is adopted after a confirmed diagnosis, must be assessed by the dentist together with an allergy or anaesthesia specialist.

4. The sedation spectrum: from nitrous oxide to general anaesthesia

4-1 First, lay the spectrum out

4-2 What nitrous oxide is: effect, onset and recovery

A 2026 systematic review included 25 studies with approximately 12,500 participants [Fn78], in children aged 2 to 12 years [Fn73], comparing nitrous oxide–oxygen (N₂O/O₂) with oral sedation as minimally invasive options.

On the nitrous oxide side, that review records: in a population with mild anxiety the efficacy is 85–92%, complications are under 5% (such as nausea), and onset takes only 30–60 s [Fn19]; it describes recovery as relatively rapid, and on that basis positions nitrous oxide as suited to short procedures (⚠ recovery, and whether a person may leave, are in every case determined by the monitoring carried out on the day and by that team's discharge criteria, and not by any fixed number of minutes; that figure comes from a review in a paediatric population) [Fn79]. Safety was high overall (adverse events under 5%), and nitrous oxide is relatively safer for outpatient use [Fn80].

⚠ Three limits have to be held in mind together: (i) the figure of 85–92% corresponds to the mild anxiety subgroup [Fn19] and does not apply to moderate or severe anxiety; (ii) the study population is children aged 2–12 years [Fn73], and this article does not extrapolate it into a figure for adults; (iii) that review used qualitative synthesis because of heterogeneity, and the authors state limitations including protocol variability and a limited number of RCTs [Fn81].

4-3 Oral sedation: the success rate falls as the degree of anxiety rises

On the oral sedation side the same review records: success for moderate cases is 70–85% [Fn74]; the review separately records differences in response between oral agents, one commonly used agent showing 5–10% paradoxical excitation (that is, in the opposite direction to the one expected) [Fn82]. The main text of this article gives no recommendation by drug name, dose or drug combination, and repeats no combination success rate (what the source states is retained in the fact ledger for traceability) — the evidence on oral sedation is heterogeneous, an individual's response may run the opposite way or go deeper than expected, and the choice of agent has to be made by a qualified team under conditions where monitoring and rescue are available [Fn83].

There is a portable way to read this: from 85–92% in mild anxiety [Fn19] to 70–85% in moderate cases [Fn74], the figures inside that one review already fall as the degree of anxiety rises. Any claim that applies a single high figure to everybody violates the stratification of the original data.

⚠ Drug names are repeated from the literature only and constitute no medication instruction; this article provides no dose, no route and no timing of administration.

4-4 Intravenous sedation and dental implants: the direct evidence, and how old it is

“Is implant surgery under sedation safe” is one of the few questions in this domain that has direct evidence at population level, but the age and the design of that evidence have to be read together with it.

A randomised controlled trial included 255 consecutive patients undergoing dental implant surgery [Fn75], randomly assigned to a group given intravenous sedation with local anaesthesia (n = 123) and a group given local anaesthesia only (n = 132) [Fn85]. The results show that, on comparisons of percentage change, of maximum values and of the incidence of larger rises, systolic and/or diastolic blood pressure was significantly higher in the non-sedation group than in the sedation group [Fn86]; the results section of that study says that this intravenous sedation regimen stabilised haemodynamics and contributed to the safety of the patient during implant surgery [Fn87]; but the wording of its conclusion section is narrower than that sentence — it says only that the administration of intravenous sedation had a beneficial effect for haemodynamic changes during implant surgery [Fn142], and does not mention safety again.

⚠ Marked honestly: this is a single RCT from 2011, and the outcome variable measured is haemodynamic stability, not complications or survival; this article does not read it as any assurance of overall safety [Fn75][Fn85][Fn87][Fn142]. The phrase “contributed to the safety of the patient” above comes from the results section and not from the conclusion section [Fn87][Fn142] — which is exactly the same kind of citation error that section 4-7 of this article sets out to point at (taking a sentence from outside the conclusion as the authors' conclusion). The standard has to be applied consistently, so its location is marked plainly here.

On the side of “how long after it is over before I can go home”, a prospective observational study gives concrete times: the patients were American Society of Anesthesiologists (ASA) grade I or II [Fn88], 46 in total [Fn89], with the recovery process quantified by the bispectral index and the post-anaesthetic discharge scoring system [Fn20]. The result: on that study's premise that “approximately 50 minutes of conscious sedation was properly controlled”, patients could go home within approximately 90–110 minutes from the start of administration [Fn90], which converts to going home within about 40–60 minutes after awakening [Fn91].

⚠ Marked honestly: that study is an observational study of 46 people at a single institution, not a randomised controlled trial, and it excluded people under 18 years old, people with a history of drug allergies, people with a body mass index of 26 or more, and people in regular use of antipsychotic, psychotropic or hypnotic substances [Fn92]. This means that this set of time figures cannot be applied directly to the populations that were excluded. Equally important: the conclusion sentence in the original carries a conditional premise (approximately 50 minutes of conscious sedation being properly controlled) and uses the word “approximately” [Fn90]; this set of figures is bound to the sedation duration of that study, and it is not the case that a sedation procedure of any length is covered by it.

Assessment, procedure and aftercare for dental implants themselves belong to another domain — see domain article P01 (dental implants); the question-level answer to “does a dental implant hurt” is in canonical card KM-DENTAL-47 (in production).

4-5 General anaesthesia: how the guideline positions it, and the frequency stratification of risk

Positioning at guideline level. The clinical guideline of the British Society for Disability and Oral Health (BSDH) states that general anaesthesia may be needed to support care within Special Care Dentistry services, for reasons that include enabling people with severe learning disability or severe dental phobia to receive extensive dental treatment [Fn93]; the guideline says plainly that, because providing dental care using general anaesthesia involves potential risks, implications and costs, these teams need guidance [Fn94]. The guideline itself is presented as a set of overarching principles followed by six key sections, reflecting the complete pathway from the patient's referral to dental services through to their care during and after general anaesthesia [Fn21], and it stresses the necessity of comprehensive, person-centred assessment and planning [Fn95].

⚠ This guideline states honestly that there is little evidence available from which to form guidance, and that the recommendations are therefore based mainly on the expert consensus opinion of the working group [Fn77]. On that basis this article reads it as a framework, and not as evidence of effect.

Frequency stratification of risk. A systematic review compiled the morbidity of children after oral surgery procedures under general anaesthesia: the leading indication by share was caries and its complications (up to 91.0% of patients) [Fn76], followed by lack of cooperation in the surgery and/or anxiety and/or fear of dental procedures (between 39.8% and 47.9%) [Fn96]; the prevalence of treatment in the special patient group reached 87.7%, compared with 63.3% in healthy patients [Fn97]. On complications, between 43.0% and 98.9% of cases experienced discomfort within the first 24 hours [Fn98], the main reason being pain (between 14.0% and 95.0%) [Fn99]. The review concludes that paediatric dental procedures carried out under general anaesthesia carry a very low risk of major complications, but an incidence of minor complications that is almost universal [Fn100].

The official list of risks. The page of the U.S. National Library of Medicine puts it this way: anaesthesia is generally safe, but there can be risks, especially with general anaesthesia [Fn101]; and it lists heart rhythm problems [Fn102], breathing problems [Fn103], an allergic reaction to the anaesthesia [Fn104], temporary confusion (which can last several days in some people over the age of 60, and appears briefly in children after waking up from anaesthesia) [Fn105], and awareness under general anaesthesia (usually meaning that the person hears sounds, and occasionally that they can feel pain, which is rare) [Fn106]. The advice on that page is to talk to your health care provider about the benefits and risks of anaesthesia [Fn107].

⚠ The above is frequency information at population level together with an official list of risks, and constitutes no risk prediction for any individual patient. Actual risk has to be assessed by the dentist together with anaesthesia professionals on the basis of the individual history.

4-6 Monitoring requirements: where twelve international guidelines on “conscious sedation in paediatric dentistry” agree and where they do not

This section is the core of “how to judge whether a sedation arrangement follows the rules”, because what it gives is the intersection of guidelines from different countries. But its scope has to be made clear first.

A comparative analysis and evidence mapping study included twelve international clinical guidelines on the subject of conscious sedation in paediatric dentistry [Fn108]. The results fall into two halves:

The part where they agree (which can be used as a list of questions) — complete convergence was observed in the core safety domains, comprising patient assessment, monitoring and the training of professionals [Fn109]; convergence was 91.67% on discharge criteria and 83.33% on contraindications [Fn110].

The part where they do not agree (which has to be understood as varying from place to place) — substantial variation appears at the level of pharmacological protocol, with only 16.67% of guidelines providing a complete description of drugs and doses [Fn111]; recommendations on route of administration and on emergency equipment are reported unevenly, appearing in 66.67% and 50% of guidelines respectively [Fn112]. The authors conclude that although foundational safety principles are consistently addressed, significant heterogeneity persists in pharmacological and procedural recommendations, and that this variability may contribute to differences in practice and to uncertainty among practitioners [Fn113].

⚠ Subject and population limits (which must travel with these figures): the twelve guidelines included in that comparative study are on the subject of conscious sedation in paediatric dentistry [Fn108]; they are not about adult sedation, and they do not cover general anaesthesia. This article cites the study for one structural fact — which safety domains are consistently treated as necessary by guidelines across countries [Fn109] — and does not extrapolate any convergence percentage into a consensus of adult guidelines or of general anaesthesia guidelines.

A portable way to read this: patient assessment, monitoring and staff training are the three things that all twelve of those paediatric dentistry conscious sedation guidelines write in [Fn108][Fn109]. Asking about those three things in the pre-procedure conversation is therefore a line of questioning grounded in guideline text from several countries, and not an awkwardness — but remember that this grounding comes from guideline text on conscious sedation in children [Fn108], and this article does not claim that adult or general anaesthesia guidelines carry the same convergence figures.

4-7 An evidence gap that has to be disclosed honestly: in the population younger than 18 years there is no head-to-head RCT of sedation versus general anaesthesia

One claim circulates widely on the Chinese-language internet: “replacing general anaesthesia with sedation can reduce complications and cost.” The source of that sentence is in fact the background section of a Cochrane review [Fn115], not its research findings [Fn116].

The title of that review is precisely a comparison of the efficiency of sedation and of general anaesthesia for the provision of dental treatment to patients younger than 18 years [Fn114], and in its background it writes that historically such situations have been managed by using general anaesthesia in children, whereas the use of sedation may lead to reduced morbidity and cost [Fn115] — note that the verb is “may”, and that it sits in the background section.

Its results, however, are these: the original review identified 16 studies for possible inclusion and, having obtained the full texts, found none to be eligible [Fn116]; the 2012 update identified no additional studies, and the 2015 update identified 2 studies for possible inclusion which were again judged ineligible [Fn117]. The authors' conclusion states that randomised controlled studies comparing dental general anaesthesia with sedation are needed, in order to quantify differences such as morbidity and cost [Fn118].

So the correct statement is: at the Cochrane level, and confined to the subject scope of dental treatment for patients younger than 18 years [Fn114], there is as yet no eligible randomised controlled evidence available for comparing sedation with general anaesthesia [Fn116][Fn118]. What has to be said alongside it: the inclusion criteria of that review were from the outset limited to children and adolescents up to 18 years of age [Fn114], and head-to-head comparison in an adult population was not within its search scope, so this empty review can prove neither that such evidence exists for adults nor that it does not. Choices in practice therefore rest on guideline consensus and on individual assessment [Fn77][Fn95], rather than on head-to-head trials.

4-8 What costs are made of and what makes them vary (this article quotes no prices)

This article lists no amounts. What can be explained is what costs are made of and what they move with:

• Staff and training: the training of professionals is a core safety domain covered consistently by all twelve of those international guidelines on conscious sedation in paediatric dentistry [Fn108][Fn109], which means that conscious sedation requires staff with corresponding training to be present; on the general anaesthesia side, a separate professional guideline lists cost alongside risks and implications as a reason why guidance is needed [Fn94].
• Monitoring: monitoring is likewise a domain covered consistently by those twelve paediatric dentistry conscious sedation guidelines [Fn108][Fn109]; and sedation itself is divided into the three levels of minimal, moderate and deep [Fn4][Fn5][Fn6], so “which band is being used this time, and how monitoring is arranged” is a matter that can be confirmed with the dentist.
• Facilities and emergency preparedness: although recommendations on emergency equipment are reported unevenly across those twelve guidelines (appearing in 50%) [Fn108][Fn112], it is indeed one of the domains included in the comparison.
• Time: assessment for going home after intravenous sedation requires recovery-room time; on the premise that approximately 50 minutes of conscious sedation was properly controlled, one observational study measured approximately 90–110 minutes from the start of administration [Fn90].
• The extent of the procedure itself: in the guideline, general anaesthesia is linked to the situation of “enabling extensive dental treatment within Special Care Dentistry services to be carried out” [Fn93]; the greater the extent, the more complex the make-up.
• The professional society guideline itself also plainly lists “cost” alongside risks and implications as a reason why guidance is needed [Fn94].

For local systems and costs see the corresponding canonical card (TW): the general framework of dental costs and insurance systems is in domain article P12; reimbursement rules, insurance applicability and fee-approval systems are highly localised from country to country, and this article makes no country-specific statement.

5. Dental fear and anxiety in adults: how it is measured, how it is managed

5-1 Look at the scale first, then at why it moves

The global estimates were already given in the introduction: the pooled prevalence of DFA in adults is 15.3%, high DFA 12.4% and severe DFA 3.3% [Fn7][Fn8], from a sample of 31 studies and 72,577 individuals [Fn119]. Subgroup analysis shows that DFA, high DFA and severe DFA are more prevalent among women and younger adults [Fn120].

Two things to read alongside them: 28 of the 31 studies presented a high risk of bias [Fn9]; and the instruments used to measure it themselves affect the prevalence [Fn10].

A portable way to read this: on meeting any claim of the form “X% of people fear the dentist”, ask two things first — which level is being measured (that same study separately produced pooled estimates of DFA 15.3%, high DFA 12.4% and severe DFA 3.3% [Fn7][Fn8]), and which scale was used [Fn10].

⚠ These three figures are the result of three separate pooled estimates [Fn7][Fn8], and the authors state plainly that the measurement instrument used affects the prevalence obtained [Fn10]; this article therefore does not subtract them from one another to produce any “gap” figure, and does not read them as a nested stratification inside one and the same sample.

5-2 Assessment instruments: this domain uses questionnaires, not impressions

A scale is the threshold for inclusion in the research.[Fn121] The systematic review of psychological treatment of dental anxiety among adults required, as a condition of inclusion, that the study sample had dental anxiety measured on a validated scale, naming the Dental Anxiety Scale (DAS) and the Dental Fear Survey (DFS), or that it met psychiatric diagnostic criteria for dental phobia [Fn121].

What a common scale looks like. The Modified Dental Anxiety Scale (MDAS) is a short questionnaire made up of five items, with a total score ranging from 5 to 25 [Fn122]. In a validation study of 230 patients undergoing oral surgery [Fn123], the internal consistency of that version was high (Cronbach's alpha = 0.92) [Fn124]; scores were significantly higher in women, and significantly higher in those with previous distressing experiences in a medical or dental setting [Fn125], while the correlations with age and with frequency of dental visits were likewise significant [Fn126].

⚠ Marked honestly: the authors of that validation study state themselves that, because the participants were limited to an oral surgery population, it might not provide an estimation of anxiety prevalence in the general dental population [Fn127]. This article cites it in order to explain the form and the reliability of this class of instrument, not in order to use its values for inferences about a population.

What this means for readers: dental anxiety is, professionally, a measurable variable, and not a verdict on “mental strength”. This does not mean that you should score yourself — choosing, administering and interpreting a scale is the work of professionals; the score by itself cannot diagnose dental phobia, and it cannot determine whether sedation is to be used. What is actually usable by a reader is this: describe the specific situations and past experiences that you are afraid of to the clinical staff, and let them assess on that basis.

5-3 Behavioural and psychological management: there is support, but the quality of the evidence has to be stated honestly

Evidence one. A systematic review identified 10 RCT publications [Fn128], with this result: cognitive behavioural therapy / behaviour therapy (CBT/BT) brought a significant reduction in dental anxiety, with a mean difference of -2.7 as measured using the DAS [Fn129]; but the authors at the same time mark that this result was based on low quality of evidence [Fn130]. That same review separately notes that there was also some support that CBT/BT improves the patients' acceptance of dental treatment more than general anaesthesia does (again low quality of evidence) [Fn131]. Its summing-up is that there is evidence that behavioural interventions can help adults with dental anxiety/phobia; however, it is clear that more well-designed studies on the subject are needed [Fn132].

Evidence two. A 2022 systematic review and meta-analysis — whose title and central subject are “Efficacy of Hypnosis on Dental Anxiety and Phobia”, and which is not on the subject of CBT [Fn133] — examined 19 clinical trials aimed at reducing dental anxiety and fearful avoidance in adults [Fn133], covering treatments that include various forms of CBT, relaxation training, benzodiazepine premedication, self-hypnosis by audio therapy, hypnotherapy and nitrous oxide sedation [Fn134]. Its conclusion is that CBT delivered in its various forms (including single-session treatment) showed the most evidence for the efficacy of anxiety reduction [Fn135]; and that because the methods were highly heterogeneous, only five studies could be included in the meta-analysis, while the application of hypnosis showed contrasting results [Fn136].

Both directions have to be stated. The same authors also wrote down the positive side for hypnosis: the results of the systematic review are promising, and hypnosis can also be regarded as a powerful and successful method for anxiety reduction; but in the same sentence they go on to write that there are also studies with a small or even slightly negative effect [Fn138]. The authors therefore recommend a more consistent use of methods to examine anxiety for hypnosis research [Fn137].

⚠ Source-positioning disclosure: this article cites that review for its comparative statement about CBT [Fn135] and for its own account of methodological heterogeneity [Fn136], and both of those come from a review whose subject is hypnosis [Fn133]; readers should know that context of provenance, and this article has at the same time presented both the positive and the reserved sides of what the authors say about hypnosis [Fn136][Fn138].

⚠ The shared message of the two reviews is: the direction has support, the quality has yet to improve [Fn130][Fn132][Fn136]. This article does not write it up as “proven effective”.

5-4 A decision framework for the three pathways

Drawing all the preceding passages together, adult “fear of the dentist” has roughly three pathways in the literature; they are not a list of mutually exclusive options but levels of differing intensity:

What this table conveys is not “which one is good” but “which one has been studied more clearly”. The three pathways differ in the thickness of their evidence, and there is no shared head-to-head trial between them to rely on: the result of Cochrane's search in the population younger than 18 years was that not one study was eligible [Fn114][Fn116], the adult population was not within the scope of that review [Fn114], and the authors' conclusion is that randomised controlled studies of this kind are still needed [Fn118]. Which pathway is actually adopted, and whether they can be combined, has to be assessed by the dentist according to individual circumstances.

6. The boundary with behaviour guidance in children

A considerable proportion of the sedation and anaesthesia evidence cited in this article has children as its original population or subject scope, and it is listed here item by item: the systematic review of nitrous oxide and oral sedation was in ages 2–12 [Fn73]; the meta-analysis of injection pain reduction was in ages 3–14 [Fn25]; the review of self-inflicted injury before the anaesthetic wears off was mainly in ages 6–12 [Fn35]; the review of morbidity after general anaesthesia likewise had children as its subjects [Fn76]; the comparative analysis of twelve guidelines has as its subject conscious sedation in paediatric dentistry [Fn108]; and the inclusion criteria of the empty Cochrane review on “sedation vs general anaesthesia” were limited to children and adolescents younger than 18 years [Fn114].

This means two things:

1. This article has marked the population item by item when repeating these figures, and readers should not apply effect figures from a paediatric population to adults.
2. Non-pharmacological behaviour guidance on the paediatric side is itself another domain — it involves variables such as developmental stage, whether a parent is present and communication technique, and it is not the same set of methods as cognitive behavioural therapy in adults. See domain article P14 (paediatric dentistry).

7. Risk factors (indications, possible adverse effects and contraindications)

Indications (the situations of use recorded in the literature and in guidelines)

• Local anaesthesia: controlling pain during dental treatment [Fn22].
• Monitored sedation: the official patient-education page explicitly lists it as usable for dental work [Fn18].
• Nitrous oxide and oral sedation: positioned as minimally invasive options for managing dental anxiety in children [Fn78], with nitrous oxide suited to short procedures [Fn79].
• Intravenous sedation: a regimen used in combination with local anaesthesia during dental implant surgery, measured by a single 2011 RCT as having a beneficial effect for haemodynamic changes [Fn142].
• General anaesthesia: a professional guideline records that it may be needed within Special Care Dentistry (SCD) services, in order to enable people with severe learning disability or severe dental phobia to receive extensive dental treatment [Fn93] (the stated scope of that guideline is adults within SCD services [Fn93]); in a paediatric population the leading indication by share is caries and its complications [Fn76], followed by lack of cooperation / anxiety / fear [Fn96].

Possible adverse effects and complications

• The local anaesthetic injection itself can cause pain perception, and there are differences between agents [Fn30].
• Self-inflicted soft-tissue injury may occur while the anaesthetic has not yet worn off, causing significant pain and cooperation issues [Fn37].
• Local anaesthetic systemic toxicity (LAST): rare but potentially fatal [Fn44]; patient-specific factors lower the effective toxic threshold [Fn49].
• Allergic reactions: local anaesthetics are one of the triggers of allergic reactions in dentistry [Fn54]; true allergy involving IgE-mediated reactions and anaphylaxis is rare (less than 1% of adverse local anaesthetic reactions) [Fn56] — the scope of that proportion is confined to that type and does not cover delayed-type (type IV) true allergy (in the 25-year stocktake of articaine, that type accounted for 5 confirmed cases [Fn59]).
• Nitrous oxide (the data population is children aged 2–12 years [Fn73], and the efficacy figures correspond to the mild anxiety subgroup [Fn19]): complications under 5%, for example nausea [Fn19].
• Oral sedation (the data population is children aged 2–12 years [Fn73]): that review records that one commonly used oral sedative agent shows 5–10% paradoxical excitation (a response running opposite to the direction expected) [Fn82]. The drug name is in the fact ledger; this section gives no selection advice.
• General anaesthesia: the officially listed risks include heart rhythm problems [Fn102], breathing problems [Fn103], allergic reactions [Fn104], temporary confusion [Fn105] and intra-operative awareness (rare) [Fn106]; in a paediatric population 43.0–98.9% experienced discomfort within 24 hours after the procedure, the main reason being pain [Fn98][Fn99], while the risk of major complications is very low [Fn100].

Contraindications and situations requiring individual assessment

• Contraindications are one of the domains with higher convergence (83.33%) among the twelve international guidelines on conscious sedation in paediatric dentistry referred to above [Fn108][Fn110], which means that this is an area with a basis in guideline text across countries but one that will still vary from place to place; the scope of that percentage is confined to guidelines on conscious sedation in children [Fn108], and this article does not extrapolate it into a convergence figure for adult or general anaesthesia guidelines.
• For those with confirmed amide local anaesthetic allergies, that review records the existence of alternative options from a different chemical class (not that the whole class is usable) [Fn70]. This section names no drug — which agent can be tolerated after a confirmed diagnosis, who administers it and under what monitoring conditions, has to be decided by an allergy or anaesthesia specialist; the drug name given in the source is retained in the fact ledger for traceability.
• The choice of local anaesthetic for people with systemic disease (cardiovascular, liver and kidney function, diabetes, thyroid, bleeding tendency, pregnancy, advanced age and so on) falls within what requires individual assessment [Fn71]. The interface between systemic disease and dentistry is in domain article P19, and pregnancy and special populations are in P20.
• The intravenous sedation recovery-time study referred to above explicitly excluded people under 18 years old, people with a history of drug allergies, people with a body mass index of 26 or more, and people in regular use of particular substances [Fn92] — exclusion criteria of that kind themselves signal the populations that need separate assessment.

⚠ This section is risk disclosure at the level of the literature, and is not an individual diagnosis. The actual method of treatment and its effect vary from person to person, and have to be assessed by a dentist.

8. Questions worth asking the dentist before a procedure (built out of the domains on which international guidelines converge)

The questions below are not a challenge; they fall within the core safety domains on which the twelve international guidelines on conscious sedation in paediatric dentistry referred to above show “complete convergence” [Fn108][Fn109], and within the person-centred assessment stressed by the British Society for Disability and Oral Health guideline in the context of general anaesthesia in Special Care Dentistry [Fn93][Fn95]:

1. Which band will be used for me this time? Local anaesthesia, minimal / moderate / deep sedation, or general anaesthesia — the four levels have different definitions [Fn11][Fn15][Fn4][Fn5][Fn6].
2. What will the patient assessment involve? Patient assessment is a core safety domain covered consistently by those twelve paediatric dentistry conscious sedation guidelines [Fn108][Fn109].
3. How will I be monitored during the procedure, and by whom? Monitoring and the training of professionals are likewise domains covered consistently by those twelve guidelines [Fn108][Fn109].
4. In what circumstances would this not be suitable for me? Convergence on contraindications across those twelve guidelines is 83.33% [Fn108][Fn110].
5. What conditions have to be met afterwards before I can leave? Convergence on discharge criteria across those twelve guidelines is 91.67% [Fn108][Fn110]; and one observational study of intravenous sedation (whose participants excluded anyone under 18 years old [Fn92]) quantified the decision about going home using a scoring system [Fn20].
6. That time in the past when the injection made me feel unwell — which kind was it? A detailed history of prior reactions is the opening step in understanding the nature of the reaction [Fn67]; feeling unwell may be an adrenaline reaction, vasovagal syncope or toxicity, rather than allergy [Fn42].
7. What are the risks and the benefits of this anaesthesia? The advice on the official patient-education page is precisely to talk to your health care provider about the benefits and risks of anaesthesia [Fn107].

⚠ The source scope of this list has to be read alongside it: the convergence data cited in questions 2–5 all come from one comparative study of guidelines on conscious sedation in paediatric dentistry [Fn108]; question 7 comes from an official patient-education page addressed to the general public [Fn107]. This article lists these domains as directions of enquiry for adult readers, taking from them the structural meaning of “which safety domains are consistently treated as necessary by guidelines”, and makes no claim that those percentages themselves apply to adults or to the general anaesthesia setting.

For local systems and costs see the corresponding canonical card (TW): the legal form of informed consent, the specification of consent documents and the approval of fees belong to each country's own system, and this article makes no country-specific statement.

Every clinical statement in this article is mapped line by line to its cited source (see the sources and evidence chain below). It has not been clinically reviewed by a licensed practitioner. This is health information, not individual advice; assessment by a clinician is required.