This study aims to investigate the association between sudden decreases in heart rate and blood pressure during dental procedures requiring lingual retraction-such as fillings, root canal treatments, tooth extractions, and cyst surgeries-under general anesthesia. Patients will be routinely monitored for vital parameters during anesthesia. Sudden drops in heart rate and blood pressure (10-20% decrease) will be recorded as lingual retraction-related trigeminocardiac reflex (TCR) events, along with the type of lingual retraction, dental procedure, and tooth location at the time of occurrence. Additionally, the results will be analyzed in relation to patient age, sex, and tongue size.

**Amendment [March 2026]:** Following protocol revision and ethics committee approval, the study population has been restricted to pediatric patients (aged 2-18 years), and the adult arm has been discontinued. The primary outcome and observational methodology remain unchanged; however, the secondary outcome regarding adult-pediatric comparison has been removed from the analysis plan.**

Stimulation of both the central and peripheral branches of the trigeminal nerve can lead to clinically significant hemodynamic changes. The trigeminocardiac reflex (TCR), a brainstem-mediated reflex mechanism triggered by such stimulations, causes sudden and marked decreases in heart rate and arterial blood pressure. This reflex may result in hemodynamic instability during surgical interventions and, in rare cases, can precipitate severe cardiac complications including cardiac arrest.

While TCR is more commonly observed during ophthalmic, craniofacial, and skull base surgeries, it may also occur during dental procedures. Stimulation of the peripheral branches of the lingual nerve, such as during lingual retraction, has been associated with cardiovascular side effects like bradycardia. This phenomenon reflects systemic hemodynamic responses resulting from trigeminal nerve stimulation.

The literature reports significant drops in heart rate and arterial pressure due to TCR during common dental procedures such as tooth extraction and implant surgery. Notably, sudden decreases of 10-20% in blood pressure are considered clinically relevant indicators of TCR. Additionally, hemodynamic changes potentially related to this reflex have been documented during endodontic treatments, particularly in cases of irreversible pulpitis. Thus, stimulation of the dental branches of the trigeminal nerve may trigger TCR during dental procedures, leading to systemic hypotension.

In conclusion, TCR triggered by trigeminal nerve stimulation is an important hemodynamic reflex encountered during surgical and dental interventions. Early recognition and appropriate preventive measures are critical to mitigating potential cardiac risks. Clinical procedures should consider patients' susceptibility to such reflexes in planning and management.

This study aims to investigate the incidence of trigeminocardiac reflex triggered primarily by lingual retraction, and secondarily by dental procedure type, tooth location, patient age, and duration of general anesthesia in **pediatric** patients undergoing dental surgeries under general anesthesia. **Statistical Revision & Amendment [March 2026]:** The study protocol has been revised to focus exclusively on the pediatric population (aged 2-18 years), in line with the primary research objective. The initial design included both adult (n=50) and pediatric (n=50) cohorts; however, the pediatric cohort was prioritized due to its greater susceptibility to trigeminocardiac reflex (TCR) events, and practical considerations regarding adult enrollment feasibility. Consequently, the adult arm was discontinued. This modification was reviewed and formally approved by the Kırıkkale University Non-Interventional Research Ethics Committee in its meeting on March 11, 2026 (2026/04 meeting number), referencing the original approval of the study (2025/12 meeting number, decision 2025.09.04). The primary outcome and data collection methodology from the original protocol were preserved, while the previously planned secondary outcome comparing adult and pediatric cohorts was removed. No other aspects of study design, observational methods, or ethical standards were modified.

Sample size calculations were performed using two complementary approaches. First, for multivariable analysis of potential predictors-including age, sex, anesthesia-related factors, and dental procedure characteristics (procedure type and the presence or absence of lingual retraction or tongue-base pressure)-sample size was calculated using the 'pwr' package in R Statistical Software (v4.5.2). Assuming a medium effect size (f² = 0.15), α = 0.05, and power = 0.80, the required total sample size was confirmed as N = 85.

Second, a proportion-based calculation was conducted to estimate the required pediatric sample size for detecting clinically relevant TCR-related hemodynamic responses (≥10% reduction in MABP). While prior literature reports a TCR incidence of approximately 52% in adults , a higher incidence of 70% was projected for pediatric patients due to their increased clinical sensitivity. The corresponding Cohen's h for this comparison was 0.34. This approach indicated that at least 68 participants would be required (α = 0.05, power = 0.80), but to ensure adequate statistical power across all analyses, the final sample size was set at N = 85.

Following the discontinuation of the adult cohort in March 2026, the statistical analysis plan was refined to prioritize a high-powered, single-cohort evaluation of the pediatric population. The removal of the adult-pediatric comparative analysis (previously a secondary objective) does not affect the internal validity of the primary outcome. All multivariable models and proportion-based estimates have been re-calibrated for the pediatric target sample of N=85, ensuring that the study remains adequately powered to identify key predictors of TCR events in this specific high-sensitivity group** Conducted at the operating rooms of Kırıkkale University Faculty of Dentistry, this prospective observational study will record TCR events using a specially designed patient monitoring form, correlating these events with various clinical factors.

Inclusion Criteria:

• Patients referred to our faculty for dental procedures requiring general anesthesia.
• Patients classified as ASA physical status I or II.

Exclusion Criteria:

• Patients unwilling to participate in the study.
• Patients classified as ASA physical status III or IV.
• Patients with diseases affecting cardiac inotropy, chronotropy, or dromotropy.
• Patients using medications influencing cardiac inotropy, chronotropy, or dromotropy.
• Patients with cardiac pacemakers.
• Patients with cardiac arrhythmias.
• Patients with neurological disorders affecting the trigeminocardiac reflex pathway (inhibition or activation).

Patients undergoing dental procedures under general anesthesia at Kırıkkale University, Faculty of Dentistry, aged 2-18, classified as ASA physical status I or II. Pediatric patients will be included. Patients with cardiac or neurological conditions affecting the trigeminocardiac reflex will be excluded.

Individual participant data will not be publicly available but may be shared upon reasonable request with qualified researchers, subject to approval by the study team and compliance with ethical and confidentiality guidelines.