Perioperative Dental Injury Associated With Intubated General Anesthesia

Abstract

Objective:

Factors related to perioperative dental injury have likely changed as a variety of airway devices and preventive measures have been introduced. This retrospective chart review used data from an institutional registry to evaluate the incidence, timing, and contributing factors of patient self-reported dental injury and to assess the impact of dental injury on patient satisfaction.

Methods:

Multivariate logistic analysis was performed on the records of 14,820 patients using the incidence of dental injury as the dependent variable and covariates in the anesthesia registry and a postoperative questionnaire as independent variables to investigate factors significantly associated perioperative dental injury. In addition, satisfaction with the anesthesia service was compared between patients with and without injury using a matched-pair population.

Results:

A total of 101 dental injuries were identified. Of those, 25% were associated with intubation and extubation in the operating room, while most other injuries occurred postoperatively. Duration of anesthesia (odds ratio [OR], 1.02; 95% confidence interval [CI], 1.00–1.03) and emergency surgery (OR, 1.92; 95% CI, 1.11–3.30) were independently associated with perioperative dental injury. Dental injury did not significantly decrease a patient's satisfaction with the anesthesia service (P = .441).

Conclusion:

Most perioperative dental injuries are unrelated to anesthesia procedures. However, the duration of anesthesia and emergency surgery were significantly associated with perioperative dental injury, while decreased patient satisfaction was not.

As a critical component of general anesthesia, anesthesiologists are primarily responsible for successful and safe airway management throughout the perioperative period.^1,2 Ultimately, the responsibility for trauma to the airway, including dental injury, during the perioperative period is considered to lie with the anesthesiologist.^1,2 Direct laryngoscopy is still the most common method of visualizing the airway during tracheal intubation. Although direct laryngoscopy has been thought to be significantly related to dental injury, especially for a difficult airway,^3–5 the timing or cause of perioperative dental injury has reportedly changed following the introduction of a variety of airway devices and preventive measures.^2,6–8 Dental injury during tracheal intubation might no longer be the main cause of perioperative dental injury. Therefore, it is possible that dental injury during the perioperative period may be attributed to factors outside of anesthesia practice. Furthermore, a previous report suggested that dental injury following anesthesia frequently results in litigation, although the recovered damages tend to be relatively low.⁹

In our institution, surgical patients managed by the anesthesia department undergo a structured postoperative interview with consultant anesthesiologists at the postoperative anesthesia consultation clinic. At this visit, the occurrence of perioperative adverse events is assessed by medical records and patient self-reporting, and patients' critiques of perioperative management are recorded on the interview form. Using these data, we retrospectively investigated the incidence of patient self-reported dental injury, potential contributing factors, and timing. Finally, we evaluated the impact of dental injury on patient satisfaction with the anesthesia service. To reduce the effect of selection bias, we compared the satisfaction ratings of our service in propensity-matched pairs of those with and without dental injury.

METHODS

The Nara Medical University Ethics Committee Institutional Review Board waived the requirement for written informed consent and approved the review of patient charts, access to the institutional anesthesia registry, and the reporting of results (No. 2361 approved on September 26, 2019). This study was conducted according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.

The initial inclusion criterion for this study were any anesthesia cases managed between January 2009 and December 2013. Exclusion criteria were as follows: (1) cases without general anesthesia, (2) cases without a history of visiting the anesthesia consultation clinic or patients who were unable to answer the questionnaire because of cognitive dysfunction, (3) patients <15 years of age, (4) cases missing the anesthesia registry data set or remarks about dental injury on the postoperative questionnaire, and (5) cases with tracheostomy prior to surgery.

Perioperative Patient Treatment

Patients with poor dentition used mouth guards tailored to their dentition by in-house dentists prior to elective cases. At the preoperative anesthetic evaluation, the attending anesthesiologist determined the need for a mouth guard on a case-by-case basis. This did not occur with emergency cases.

Although there was no standard procedure for induction and maintenance of anesthesia, the methods used did not significantly differ during the study period, as all cases were performed in the same hospital. No premedication was used, and general anesthesia was usually induced with intravenous propofol (1–2.5 mg/kg) plus either fentanyl (1–2 μg/kg) or remifentanil infusion (0.2–0.3 μg/kg/min). Neuromuscular blockade was achieved with rocuronium (0.6–0.9 mg/kg). Tracheal intubation was performed under direct laryngoscopy with a Macintosh blade by the consultant anesthesiologist or by residents under their guidance. In most cases with a difficult airway, a video laryngoscope (Pentax-AWS, Nihon Kohden Corp; or McGrath MAC, Medtronic) was used. Supraglottic devices were rarely used for airway management. Anesthesia was maintained with sevoflurane (1.5–2%) in an oxygen/air (40/60%) mixture or with propofol infusion (100–166 μg/kg/min). Nitrous oxide was not used. Fentanyl (1–2 μg/kg/h) or remifentanil infusion (0.1–0.2 μg/kg/min) was used for analgesia. Rocuronium infusion (0.2–0.3 mg/kg/h) was used for neuromuscular blockade. Until July 2010, neostigmine (40 μg/kg) plus atropine (20 μg/kg) was used for neuromuscular blockade reversal, but beginning in August 2010, sugammadex (2–4 mg/kg) was used instead. Awake extubation was performed by the consultant anesthesiologist or resident immediately after patients regained consciousness. Unless extubated in the operating room, patients were transferred to an intensive care unit and managed with mechanical ventilation until extubation was performed.

After the case, the attending anesthesiologist completed the institutional registry of anesthesia form which included the following information: the attending's name; the name of whomever performed the intubation; the patient's demographic variables; information regarding the final diagnosis and surgical procedure (later categorized into 3 classes based on the modified surgical risk stratification)¹⁰; concomitant chronic diseases (eg, hypertension, diabetes mellitus, coronary artery disease, history of heart failure, and lung disease); duration of anesthesia and surgery; American Society of Anesthesiologists physical status; urgency of surgery (emergency or elective); maintenance of anesthesia (inhalational or intravenous); intraoperative patient positioning; final airway assessment; and adverse intraoperative events, including cardiac events, hypotension, arrhythmia, and hypoxia. Any complications during the postoperative course were also recorded.

In addition, prior to discharge from the hospital, patients visited the postoperative anesthesia consultation clinic, where they completed a questionnaire using a patient self-report form that included an item on dental injury: “Did you have any new problem with your teeth during the perioperative period? For example, teeth chipping, being broken, coming out, moving, etc.” Patients were also asked to rate their satisfaction with the perioperative anesthesia care they received using a simplified scale (4 = very satisfactory, 3 = satisfactory, 2 = adequate, and 1 = unsatisfactory).

Statistical Analysis

Continuous variables are presented as mean ± standard deviation if normally distributed or median and interquartile range if nonparametric. Categorical variables are presented as the number of patients. Descriptive statistics were used for the timing of dental injury and classified into 4 categories (at intubation, during the surgical procedure or monitoring, at extubation, and during the postoperative period). Multivariate logistic analysis of the study cohort (N = 14,820) was performed using the incidence of dental injury as a dependent variable and other covariates, including items on the anesthesia registry, as independent variables to investigate which factors were significantly associated with the risk of dental injury. Univariate analysis was used to identify those factors associated with dental injury. Factors having a significant univariate association with dental injury (P < .2) were used to perform multivariable logistic regression analysis by forced-entry methods. All candidate variables were entered into the initial model and presented as adjusted odds ratios (ORs) with 95% confidence intervals (CI). Interactions between variables were systematically reviewed, and collinearity was considered for r or rho > 0.8 using a Pearson or Spearman coefficient matrix correlation, respectively. Discrimination of the final model for dissatisfaction was assessed using the likelihood-ratio test. Calibration of the model was assessed using Hosmer–Lemeshow test.

Satisfaction with the anesthesia service among patients with or without dental injury was compared from the initial 14,820 patients. Mann-Whitney U test and Student's unpaired t test were used for unmatched comparisons. To avoid channeling bias, we used propensity score analysis to generate a set of matched cases (patients with dental injury) and controls (patients without dental injury). Ultimately, 14,620 patients were excluded from this analysis. A propensity score was generated for each patient from a multivariate logistic regression model based on covariates, including demographic variables, the attending anesthesiologist, surgical risk, chronic illnesses, duration of anesthesia and surgery, American Society of Anesthesiologists (ASA) physical status, urgency of surgery, airway management, anesthesia technique, intraoperative patient positioning, and adverse intraoperative events, as the independent variables. Dental injury versus no dental injury was a binary dependent variable. As part of the propensity score development, we used a structured iterative approach to refine the model, with the goal of achieving covariate balance between the matched pairs.¹¹ Covariate balance was measured using the standardized difference, in which an absolute standardized difference >0.1 was interpreted as a meaningful covariate imbalance.¹² We matched patients using a greedy-matching algorithm with a caliper width of 0.001 of the estimated propensity score. A matching ratio of 1:1 was used. This procedure yielded 100 patients with dental injury matched to 100 patients without dental injury. For statistical inference, methods accounting for the matched nature of the samples were used. Wilcoxon signed-rank test and paired t test were used for the matched-pair comparison of the simplified patient satisfaction scale.

Analyses were computed using the MedCalc statistical package (version 18.11.6, MedCalc Software) and R (version 3.0.3, R Foundation for Statistical Computing). A P value <.05 was considered statistically significant.

RESULTS

A total of 21,606 cases were initially identified for potential inclusion in this study; of those, 6786 were ultimately excluded. The final number of cases included in this study was 14,820 (Figure).

Flow diagram for case inclusion and exclusion.

Dental Injury Data

In total, 101 dental injuries were identified, in addition to the time when the injury occurred (Table 1). The total overall incidence rate for dental injury was 0.682% (101/14,820). Dental injuries were associated with intubation (20%) and extubation in the operating room (5%). However, the remaining 75% of dental injuries occurred either during the surgical procedure or the postoperative periods, with most (61%) occurring postoperatively outside the operating room.

Table 1. .

Dental Injury Occurrence by Time*

Total Number of Dental Injuries	Intubation	Surgical Procedures or Monitoring	Extubation	Postoperative Periods
101	20	14	5	62

^*Surgical procedures: dental surgery (n = 9), laryngomicrosurgery (n = 2), trauma surgery (n = 1), and nasogastric tube insertion during surgery (n = 1). Monitoring: motor-evoked potential monitoring by transcranial stimulation (n = 1).

Dental Injury Versus No Dental Injury

Patient data and perioperative characteristics were compared between patients with and without dental injury (Table 2). Factors identified by univariate analysis to have an association with perioperative dental injury included male sex, poor ASA physical status, resident management, emergency surgery, a longer duration of surgery and anesthesia, and use of inhalational anesthetics. However, collinearity was observed between duration of surgery and anesthesia (r = 0.992), so duration of surgery was removed from the multivariate analysis.

Table 2. .

Dental Injury Versus No Dental Injury†

	Dental Injury (n = 101)	No Dental Injury (n = 14,719)	P Value
Age, y	59.3 (17.9)	58.1 (17.5)	.466
Sex, M/F	57/44	6814/7905	.0452*
Height, cm	160.2 (9.3)	159.9 (9.0)	.766
Weight, kg	59.6 (11.5)	58.7 (12.0)	.482
BMI, kg/m2	23.2 (3.8)	22.9 (3.8)	.432
ASA physical status, 1–5	2 (2–2)	2 (1–2)	.022*
Coexisting disease, Y/N	72/29	9708/5011	.292
Difficult airway, Y/N	3/98	416/14,303	.764
Direct laryngoscopy, Y/N	95/6	13,619/95	.705
SGD, Y/N	1/100	426/14,293	.374
Resident management, Y/N	58/43	9708/5011	.0741*
Duration of anesthesia, min	302 (215)	260 (150)	.005*
Duration of surgery, min	232 (204)	196 (140)	.011*
Inhalational anesthesia, Y/N	89/12	11,747/2972	.0452*
Surgical intensity, 1–3	2 (2–2)	2 (2–2)	.736
Emergency, Y/N	17/84	1400/13,319	.025*
Surgical posture, supine/other	83/18	11,458/3261	.337
Intraoperative adverse event, Y/N	0/101	52/14,667	.999

^†ASA indicates American Society of Anesthesiologists; BMI, body mass index; SGD, subglottic device. Variables are expressed as number of patients, mean (SD), or median (interquartile range).

^*Variables with univariate association (P < .2) with dental injury selected for logistic regression model.

Factors Significantly Associated With Perioperative Dental Injury

Multivariate analysis determined that duration of anesthesia (every 10 minutes; OR, 1.02; 95% CI, 1.00–1.03) and emergency surgery (OR, 1.92; 95% CI, 1.11–3.30) were independently associated with perioperative dental injury (Table 3). Final model discrimination, assessed by the likelihood-ratio test, was significant for these 2 variables (P < .001), and Hosmer-Lemeshow analysis suggested an acceptable degree of calibration (P = .5015). A model based on these variables had an area under the receiver-operating characteristic curve of 0.619 (95% CI, 0.611–0.627), signifying that the predictive value for this model may lack accuracy.

Table 3. .

Multivariate Analysis of Selected Variables Associated With Dental Injury†

Variable	OR	95% CI
Male	1.21	0.80–1.82
ASA physical status	1.23	0.87–1.41
Resident management	1.31	0.88–1.96
Duration of anesthesia (every 10 min)	1.02	1.00–1.03*
Inhalational anesthesia	0.61	0.33–1.13
Emergency	1.92	1.11–3.30*

^†ASA indicates American Society of Anesthesiologists.

^*P < .05.

Dental Injury Versus No Dental Injury After Matching

The clinical characteristics of the 2 matched groups, those with and without dental injury, extracted by propensity analysis are noted in Table 4 (n = 100 each). Prior to matching (Table 2), several covariates were statistically different between the groups. However, following matching, the covariates were well balanced (absolute difference <0.1), and the covariates were not statistically different between the 2 groups.

Table 4. .

Dental Injury Versus No Dental Injury After Matching*

	Dental Injury (n = 100)	No Dental Injury (n = 100)	Absolute Standardized Difference	P Value
Age, y	59.3 (17.6)	58.9 (17.6)	0.02	.776
Sex, M/F	56/44	58/42	0.01	.885
Height, cm	160.0 (9.2)	160.4 (9.4)	0.05	.559
Weight, kg	59.5 (11.5)	59.8 (11.0)	0.03	.723
BMI, kg/m2	23.2 (3.9)	23.2 (3.6)	0.00	.968
ASA physical status, 1–5	2 (2–2)	2 (2–2)	0.02	.812
Coexisting disease, Y/N	71/29	72/28	0	.999
Difficult airway, Y/N	3/97	4/96	0	.999
Direct laryngoscopy, Y/N	94/6	94/6	0	.999
SGD, Y/N	1/99	1/99	0	.999
Resident management, Y/N	57/43	64/36	0.04	.410
Duration of anesthesia, min	295 (2205)	296 (194)	0.00	.971
Duration of surgery, min	225 (192)	226 (180)	0.01	.934
Inhalational anesthesia, Y/N	88/12	85/15	0.04	.628
Surgical intensity, 1–3	2 (2–2)	2 (2–2)	0.02	.806
Emergency, Y/N	17/83	14/86	0.03	.689
Surgical posture (supine/other)	83/17	84/16	0	.999
Intraoperative adverse event, Y/N	0/100	0/100	0	.999

^*ASA indicates American Society of Anesthesiologists; BMI, body mass index; SGD, subglottic device. Variables are expressed as number of patients, mean (SD), or median (interquartile range).

Dental Injury and Patient Satisfaction

Patient satisfaction outcomes are summarized in Table 5. In the unmatched population, patients with dental injury rated our service significantly lower (P < .001) than those without injury, although the measure of effect was relatively small. However, in the matched population, dental injury did not significantly decrease the patients' satisfaction with our service (P = .441).

Table 5. .

Patient Satisfaction and Dental Injury Versus No Dental Injury: Matched and Unmatched†

	Unmatched Comparison
	Dental Injury (n = 101)	No Dental Injury (n = 14,719)	Measure of Effect (95% CI)
Satisfaction scale	4 (3 to 4) 3.4 [0.7]	4 (3 to 4) 3.6 [0.5]	Mean difference, 0.21 (0.11 to 0.36)*
	Matched Comparison
	Dental Injury (n = 100)	No Dental Injury (n = 100)	Measure of Effect (95% CI)
Satisfaction scale	4 (3 to 4) 3.4 [0.7]	4 (3 to 4) 3.4 [0.7]	Mean difference, 0.08 (−0.11 to 0.27)

^†Satisfaction scale expressed as median (interquartile range) and mean [standard deviation].

^*P < .05.

DISCUSSION

Of 14,820 cases included in this study, dental injury occurred in 101 cases during the perioperative period, for an overall incidence of 0.68%. However, the overall incidence of injury clearly associated with airway management (intubation and extubation in the operating room) was only 0.167%, which fell to 0.135% when only considering intubation. Because there were a total of 21,606 anesthesia cases during the study period, the ultimate rate of dental injury was 0.09%. This was comparable to rates of anesthesia-related dental injury (∼0.1%) reported by other educational institutions.^13,14

In contrast to prior reports that have focused on tracheal intubation, most dental injuries in this study (∼75%) occurred during periods other than intubation or extubation.^5,6 A study from Norway assessing claims for compensation following dental injuries related to airway management found that 84% of claims were rejected because dental trauma was felt to be unrelated to poor airway management.¹ This implies most perioperative dental injuries may be unrelated to the provision of general anesthesia. However, there may be ambiguity regarding the timing of when the injuries occurred and when they were identified, meaning some “postoperative” injuries may have occurred earlier (ie, during intubation) and were identified only later. Aside from the preoperative anesthetic evaluation, anesthesia providers in our hospital did not routinely check patient dentition for injuries at regular intervals.

In this study, the duration of anesthesia and surgery performed on an emergent basis were significantly associated with the occurrence of perioperative dental injury. It has been reported that 10% of dental injuries occur during emergency procedures.^8,15 These reports did not note the exact incidence of injury among emergency cases; however, they commented that emergency surgeries were not related to a higher risk of dental trauma when compared with elective surgery. This discrepancy in findings is thought to be attributed to use of a preoperative dental evaluation and preventive strategy (mouth guard). In our elective cases, patients with poor dentition inserted individualized mouth guards tailored to their dentition by dentists prior to surgery.

Some studies recommend the use of mouth guards to prevent dental injury,^8,16 as poor dentition has been reported as the most common risk factor for dental injury during general anestheisa.⁵ The use of mouth guards remains a controversial topic. It has been suggested that mouth guards cannot always prevent tooth injury.¹⁷ In addition, a mouth guard may cause intubation to be more difficult, as it may occupy a significant amount of space within the oral cavity.^18,19 However, this study used mouth guards that closely fit the patent's dentition, and as a result, they had little negative impact on intubation and protected the dentition well. The inability to prepare a mouth guard prior to emergency cases might have been related to the incidence of perioperative injuries.

The longer the duration of anesthesia, the greater the amount of time an airway device may apply significant force to the dentition. Prolonged exposure time to potentially excessive forces might have weakened the dentition, resulting in perioperative injury. As noted previously, poor dentition is a risk factor for dental injury related to airway management²⁰; however, we did not specifically record the condition of the patients' dentition in the study database and cannot conclude anything specifically about this issue. The relatively poor dentition of a patient without a mouth guard may have been aggravated during prolonged surgeries. In some of these cases, a tooth might have broken or fallen out postoperatively. Emergency case was one of factors for dental injury. This may have been due to lack of mouth guard.

Recently, supraglottic airway devices (SAD) or video laryngoscopy (VL) have been suggested to be associated with increased risk of dental injury during anesthesia.^6,7 However, in this study, tracheal intubation was performed under direct vision with a Macintosh-type laryngoscope, and SAD or VL were rarely used. Therefore, this study had insufficient data to enable further comment. In the case of a difficult airway, VL was used, although not every time, and a difficult airway was not associated with dental injury in this study. This may have been due to extreme attention being paid to intubation in such cases, although difficult airway has been suggested in other reports as a leading cause of dental injury associated with intubation.^3–5

It was expected that patients who experienced dental injury would rate their satisfaction with the anesthesia service quite low. The unmatched raw data of this study seemed to confirm this expectation (Table 5). However, in our matched populations, those with dental injury did not rate the service lower than those without injury did.

A prior study found that patients frequently complain of difficulty obtaining information and not receiving accurate or timely information.²¹ A different study found that the leading causes of patient complaints were unprofessional conduct; poor communication, treatment, and care of the patient; and having to wait for care.²² We have tried to avoid many of these possible causes by instituting our anesthesia consultation clinic. This change may have promoted improved provider-patient communication, professional conduct, and early and appropriate direction of patient care, resulting in relatively high patient satisfaction regardless of complications.

There are several limitations to this study. This study was retrospective in nature, and unmeasured variables might have confounded the results. Data from the institutional registry of anesthesia was used, which includes only minimal essential information about each case and does not include precise details. Therefore, we did not have access to several variables that might have affected patient outcomes. Next, this study focused on perioperative dental injury but not dental injury specifically related to anesthetic procedures. Therefore, the definition of contributing factors to dental injury extracted for this study may be different from those of previous studies. However, it is reasonable to assume that no preoperative dental evaluation and prolonged exposure to unnatural forces on teeth from airway devices could be related to dental injury specific to general anesthesia. A considerable number of patients were excluded from the study. However, this likely did not affect the results, as exclusion criteria were applied objectively, and charts with missing data were random. Finally, our study is an audit of clinical practice at one institution, and our findings might not be generalizable to the practice of anesthesia.

CONCLUSION

Most perioperative dental injuries in this study occurred during periods other than intubation or extubation in the operating room and were unrelated to anesthetic procedures, although timing discrepancies between occurrence and identification may have existed. Considering duration of anesthesia and emergencies were significantly associated with perioperative dental injury, a patient's dental condition should be evaluated immediately after a case with those risk factors. Dental injury occurrence was not significantly associated with a decrease in patients' satisfaction with the anesthesia service.