INTRODUCTION

The use of a rubber dam has significant advantages and is therefore commonly used on most dental patients who undergo operative procedures. Its placement has the potential to alter airflow in both the oral and nasal cavities. In theory, this could result in a decrease in arterial oxygen saturation, which may be detrimental, especially in a medically-compromised patient. Dentists should be aware whether use of a rubber dam affects the supply of oxygen available to the patient during respiration.

The body requires a constant supply of oxygen to sustain metabolic reactions within its cells. These reactions provide energy which allows vital organs, such as the brain, heart and lungs, to function. Ventilation (the inspiration and expiration of air between the atmosphere and the lungs) and perfusion (the exchange of gases between blood and capillaries) are the combined processes that supply oxygen to cells (Tortora & Grabowski, 1996). Impairment of the ventilation process will decrease the oxygen supply to tissues. A significant reduction in oxygen will impair the function of vital organs within seconds, clinically resulting in unconsciousness. Therefore, hypoxia should be a concern in the dental setting, especially in medically-compromised patients. This study assessed the effect of rubber dam placement on the arterial oxygen saturation level in dental patients.

METHODS AND MATERIALS

Twenty eight ASA Class I patients were randomly allocated to one of two groups: Group A—14 patients in this group had rubber dam isolation of the maxilla from tooth 14 to tooth 6, and Group B—14 patients had rubber dam isolation of the mandible from tooth 19 to tooth 27. All subjects completed a full health questionnaire and consent form approved by the Dalhousie Research Ethics Committee to determine their eligibility to participate in the study. To detect arterial oxygen saturation levels, a pulse oximeter finger probe was placed on the ring finger of the patient's left hand. Throughout the procedure, the patient's Sp0₂ was recorded every 30 seconds while the patient remained in a reclined operative position. The study began by recording each patient's Sp0₂ every 30 seconds for two minutes to establish a baseline. Group A subjects received a standard infiltration into the vestibule above tooth 14, while Group B subjects received an inferior alveolar nerve block using 1.8 ml of 2% Lidocaine with 1:100,000 epiphrine, respectively. During the subsequent five minutes, the patient's Sp0₂ was recorded every 30 seconds. A rubber dam, which extended to the anterior septal angle (completely covering the nose), was then placed. This rubber dam remained in place for 20 minutes, with the patient's Sp0₂ being recorded every 30 seconds; the rubber dam was then altered (cut) to expose the nasal passages, creating what is known as proper rubber dam isolation, and Sp0₂ was recorded every 30 seconds for 20 minutes. A two-way ANOVA test was performed to compare the measurements taken before and after rubber dam placement in each group.

RESULTS

The baseline average Sp0₂ for Group A and Group B was 98.34% and 98.34%, respectively. The injection of local anesthesia and placement of the rubber dam such that the nose was covered resulted in an Sp0₂ of 98% in Group A and 98.34% in Group B. Cutting the rubber dam to effect proper rubber dam placement resulted in an Sp0₂ of 98.64% in Group A and 98.21% in Group B.

Statistical analysis indicated that there was no significant difference between test groups. A repeated measures analysis-of-variance test was performed to compare all measurements taken. The p -values were all greater than 0.05; thus, there were no significant deviations in oxygen saturation at any point during testing. The mean values for oxygen saturation taken at various time intervals are shown in Table 1. Once the rubber dam was placed, the average Sp0₂ fluctuated less than half a percent. The range and average Sp0₂ measurements for both test groups are listed in Table 2. Both groups had similar ranges and averages.

Table 1 Summary of Sp0 ₂ Measurements

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Table 2 Summary of Sp0 ₂ Ranges and Average Sp0 ₂ Measurements

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DISCUSSION

Measurement of arterial oxygen saturation (Sp0₂) through pulse oximetry can accurately detect changes in the oxygen level available in blood. This is accomplished using a light sensor (probe) containing two sources of light (red and infrared), which are absorbed by hemoglobin and transmitted through tissues to a photodetector. The amount of light transmitted through the tissue is then converted to a digital value representing the percentage of hemoglobin saturated with oxygen (Schutz, 2001).

The clinical application of oximetry requires an understanding of the standard oxyhemoglobin dissociation curve (Figure 1) (Woods, 2000). An Sp0₂ of 95% is considered to be a safe level to ensure adequate oxygenation of vital organs (Woods, 2000). A relatively small decrease in oxygen saturation from 95% results in a substantial fall in the peripheral partial pressure of oxygen in blood and tissues (Woods, 2000). Partial pressure is the driving force in the exchange of gases in tissues. Too great a decrease in pressure will create a hypoxic condition. Hypoxia has been clinically defined as an Sp0₂≤90%, while severe hypoxia is an Sp0₂ of ≤85% (Tyler & others, 1995). Cyanosis commences at a Sp0₂ of 83% (Woods, 2000).

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There are several medical conditions that can cause hypoxia and, thus, should be of concern to the practicing dentist. Diseases such as asthma, chronic obstructive pulmonary disorder (COPD), emphysema, congestive heart failure (CHF), cystic fibrosis and some blood disorders all have the potential to cause hypoxia. Dental procedures, which tend to also decrease oxygen supply, should be avoided.

Patients with asthma show no difference in oxygen saturation compared to healthy subjects when the condition is quiescent (Gries & Brooks, 1996). During an asthma attack, however, Sp0₂ decreases dramatically. Sole & others (1999) reported that an Sp0₂ ≤94% is associated with an increased severity of an asthma attack and that, asthma patients treated with a beta2-agonist who had an Sp0₂ of ≤92%, had a 6.3-fold greater risk of requiring additional treatment (Sole & others, 1999). Studies have shown that a decrease in Sp0₂ from 92% to 90% doubled the number of patients who suffered respiratory failure (Carruthers & Harrison, 1995) and that a post-treatment Sp0₂ of ≤91% increases the odds of admission 16-fold (Wright & others, 1997). These reports demonstrate that small changes in Sp0₂ can have drastic effects on the severity of an attack and the treatment required. If a rubber dam can induce similar changes, then the patient's health could be at risk.

Other diseases, such as COPD and CHF, have no accurate average Sp0₂, but studies routinely demonstrate Sp0₂ levels to be in the 90% to 94% range. COPD and CHF patients who have demonstrated desaturation of 4% or more in short, five-to-six minute walks, clearly demonstrate the inability of their respiratory systems to compensate when under physiologic stress (Restrick & others, 1992); the same stress that a dental appointment with placement of a rubber dam may induce.

This study assessed the effects of rubber dam placement on the process of ventilation and the act of respiration. During the study, some patients experienced transient desaturations in which their Sp0₂ fell below the reported 95% safe level. It should be noted that these incidents can be correlated to when the subjects had momentarily fallen asleep. This study demonstrated that the rubber dam, whether properly or improperly placed, showed no statistically significant effect on the oxygen saturation of this group of patients.

Although rubber dam placement had no detrimental effect on healthy patients, its effect on medically-compromised patients is unknown. The results of this study are encouraging, but it is reasonable to suspect that medically-compromised patients who start lower on the oxygen saturation curve and have a decreased ability to cope with physical stress may respond differently.

CONCLUSIONS

In both groups of healthy patients, there was no significant change in arterial oxygen saturation before and after rubber dam isolation was performed when both proper and improper isolation techniques were used.