a b s t r a c t

Introduction: dental abscesses are a common reason patients present to the emergency department (ED). Facial and dental imaging are sometimes necessary to support the clinical diagnosis. While radiographs and computed tomography scans are frequently used, point-of-care ultrasound (US) offers several advantages, including de- creased radiation exposure, reduced costs, and shorter patient length of stay. This report outlines the use of US in evaluating patients with suspected dental abscesses in the ED. Discussion: The typical orofacial US techniques include examining the affected area for cobblestoning or fluid col- lections. To improve the accuracy of diagnoses, novel techniques such as the Oral Hydroscan (OHS) and the Tongue Pointing Techniques (TPT) may be employed in specific cases. The OHS utilizes a water-filled oral cavity to enhance the spatial resolution of ultrasound images, providing improved visualization of near-field structures and preventing air accumulation between the gingiva and the buccal mucosa. The TPT involves asking the patient to extend their tongue towards the affected area, pointing to the painful location, and serving as a visual reference for an extraoral US. Conclusion: US presents several advantages as an alternative imaging method for patients with suspected dental abscesses in the ED. Using innovative techniques such as the OHS and the TPT can further increase the visibility of tissue planes and help define the area of interest in these cases.

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1. Introduction

Odontogenic infections and dental abscesses are common reasons for emergency department (ED) visits in the United States and globally [1,2]. In 2018, dental-related ED visits accounted for 1.4% of the total 143 million ED visits in the United States, with 94.5% treated and released and 5.5% resulting in hospital admission. Of the hospital admissions, 85.3% were due to diseases of the pulp and periapical tissues [3]. Graham et al. evaluated the rate of nontraumatic dental complaints in a Pediatric ED and found that 47% of these dental complaints were for abscesses [4]. There are two main types of dental abscesses: 1- Periapical abscesses that typically arise secondary to Dental Caries,

* Corresponding author at: 326 Cambridge Street Suite 410, Boston, MA, 02114, USA.

E-mail addresses: [email protected] (N. Al Jalbout), [email protected] (B.L. Barton), [email protected] (M. Alnuaimi), [email protected] (H. Shokoohi).

trauma, or failed dental root canal treatment, and 2, Periodontal ab- scesses, which is a localized accumulation of pus within the gingival wall of a periodontal pocket [1,2]. Both types typically present with acute Dental pain; treatment usually involves drainage, antibiotics, and sometimes a later formal dental procedure.

Maxillofacial and periodontal imaging helps diagnose a suspected dental or periodontal abscess and detect the extent and location of the abscess for a potential drainage procedure. Radiographs are frequently used as the initial modality. Computed tomography (CT) imaging has a high sensitivity for detecting dental and periodontal abscesses and fa- cial and deep tissue involvement or potential airway compression [1]. However, CT imaging is costly, time-intensive, and exposes patients to radiation.

Point-of-care ultrasound (US) is a reliable modality to differentiate cellulitis and abscesses [5,6]. In diagnosing periodontal and periapical abscesses, extraoral US can provide helpful information in diagnosing an abscess, phlegmon, or cellulitis and define the disease’s location

https://doi.org/10.1016/j.ajem.2023.05.002

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and extent. For periapical abscesses, it can precisely detect the location of the tooth root apices once the bone cortex around the abscess is eroded. Similarly, for periodontic abscesses, US is an alternative imaging technique for visualizing abscess location, size, and potential for drain- age [5,6].

Compared to CT, US is faster to perform, devoid of radiation, has a lower cost, and can be performed at the bedside in the ED. There is a small but increasing body of literature that recommends reducing the use of radiographic modalities and increasing the use of US for the diag- nosis of dental abscesses [7,8]. One study suggests against the routine use of CT for facial abscesses, noting that facial CT scans often do not change management and lead to increased patient radiation, financial costs, and length of stay [8]. Further, some research suggests that US provides comparable diagnostic accuracy to radiographic imaging methods and offers additional significant advantages [7].

In this report, we highlight the application of extraoral US for diag- nosing dental abscesses in the ED. Additionally, we introduce two novel techniques, Oral Hydroscan (OHS) and Tongue Pointing Tech- niques (TPT), to improve the accuracy and reliability of extraoral US examinations. These additional techniques are helpful, especially in cases where initial imaging does not clearly show an abscess or if confir- mation of initial imaging is needed.

1. Extraoral ultrasound scan protocol

Interpreting ultrasound scans for diagnosing dental abscesses re- quires knowledge of basic dental anatomy. The tooth consists of three layers, from the outermost to innermost: enamel, dentin, and pulp cavity. The surrounding structures, from superficial to deep, include the gingiva, periodontal ligament (the connective tissue that connects the tooth enamel to the jaw bones), and the jaw bones (maxilla and mandible). The location of the abscess determines the two types of dental abscesses: periapical abscesses, which affect the tooth root or pulp cavity, and periodontal abscesses, which affect the gingiva or periodontal ligament.

To prepare for the use of extraoral US in a patient with a suspected periodontal abscess, the patient should be seated. A high-frequency lin- ear transducer (12-7 MHz) should be used.

The standard scanning process involves obtaining transverse and longitudinal planes. The transducer should start with a transverse view identifying the typical teeth presentation, then move down to vi- sualize the mandibular gingiva and upward to obtain a maxillary view (see Fig. 1). It is helpful to identify the gingiva line to facilitate a com- plete scan. To obtain comprehensive images, the sonographer should move the transducer along the gingiva line, scanning both transversally and longitudinally while adjusting the transducer orientation to be perpendicular to the gingiva line. Focusing on the affected area and scanning its surroundings can provide more information. Comparing the affected side with the normal side is also can be helpful.

Fig. 2. Ultrasound image of periapical inflammation with phlegmon, as indicated by the arrow. The phlegmon appears hypoechoic/anechoic structure (A) with increased Color Doppler velocity in the inflamed area (B).

Abscesses are typically depicted as hypoechoic or anechoic round structures in the US (see Fig. 2). If a fluid collection is detected, the col- lection’s depth, size, and location should be determined. Overlying the abscess, soft tissue edema is often associated with a traditional “cobble- stone” appearance in US. Color Doppler and compression can be used to differentiate a vessel or mass from an abscess, as both can be hypoechoic on grayscale ultrasound. A Doppler scan can also distinguish between a phlegmon and an abscess.

1. Oral hydroscan technique

The Oral Hydroscan (OHS) technique improves the visibility of tissue planes and resolution of extraoral US imaging by utilizing water, similar to the water bath US technique used for visualizing soft tissue and mus- culoskeletal structures [9].

Fig. 1. Preferred initial set-up for evaluating a dental abscess in a patient. The patient is seated upright while the sonographer uses a transverse orientation with a linear transducer. The transducer is positioned at the level of the patient’s gingiva, either in the maxillary (A) or mandibular (B) position.

Fig. 3. Extraoral ultrasound scan using the oral hydroscan technique. The patient fills their oral cavity with water and performs a “water-puff” maneuver (A), causing intraoral water (*) to interpose the buccal mucosa (arrows) from the gingiva line and aid in visualizing the abscess.

The OHS technique is particularly useful in evaluating mandibular and maxillary soft tissue and assists with localizing dental abscesses and periodontal infections. OHS is designed to overcome the limitations of traditional linear transducers in providing high-resolution images of near-field structures and to separate facial soft tissue from the underly- ing affected dental or gingiva infections.

The technique involves asking the patient to fill their oral cavity with water and perform a “cheek puff” to push the water and dissect the buc- cal mucosa from the gingiva and teeth (Fig. 3; see Video 1 on the elec- tronic version). The puffed water serves as a medium for the US transducer to visualize better the underline dental abscess, phlegmon, and facial soft tissue. The transducer is then applied externally over the affected side, with the beam aimed directly at the affected tooth. The presence of water between the transducer and the affected area al- lows for improved visualization of dental abscesses and enhances the spatial resolution of the image. By preventing air accumulation between the gingiva and the buccal mucosa and expanding the space with water, the OHS provides a clearer view of the near-field structures. An inter- posed water step-off between the buccal mucosa and gingiva enhances spatial resolution and image resolution, improving the detection of peri- odontal conditions during shallow scanning.

The OHS is a convenient and safe technique that does not require special preparation or equipment and improves the effectiveness of extraoral ultrasound scanning in patients with suspected dental abscesses.

1. Tongue-pointing technique

The tongue-pointing technique (TPT) is utilized to aid the accurate location of the source of pain or discomfort during an extraoral ultra- sound examination. The TPT involves asking the patient to extend their tongue towards the affected area, which serves as a visual refer- ence for the sonographer (Fig. 4; also see Video 2 on the electronic version). As the patient performs the tongue-pointing technique, the tongue can be seen moving on the ultrasound image as a hypoechoic structure with a hyperechoic base, which points directly towards the source of the problem. This clear visual representation improves the chances of accurately diagnosing dental abscesses, making TPT a valu- able technique when performing extraoral ultrasound examinations.

1. Discussion

The increasing trend in ED visits due to odontogenic infections and dental abscesses highlights the need for reliable and efficient diagnostic techniques. Point-of-care US has emerged as a promising alternative to conventional radiographic imaging methods, particularly in cases with suspected dental abscesses. Existing literature suggests that US is a reli- able diagnostic tool for differentiating between cellulitis and abscesses and determining the extent and location of the disease [5,6]. Although the literature is still limited, there is growing evidence that US provides

Fig. 4. Extraoral ultrasound scan using the tongue-pointing technique. The patient extends the tongue towards the location of maximum discomfort, indicating the area of focus for scan- ning and improving visualization of the abscess (arrow).

comparable diagnostic accuracy to conventional radiographic imaging methods and offers additional benefits [7,8]. The advantages of US, in- cluding lack of radiation, low cost, time-efficiency, and its feasibility to be completed at the bedside, make it an attractive option for first-line imaging for diagnosing dental abscesses in EDs. While ultrasound has been shown to demonstrate dental abscesses, there is thus far no litera- ture demonstrating a patient-centered benefit such as clinical outcome and time to cure.

The introduction of two novel techniques, the OHS and TPT tech- niques, in diagnosing dental abscesses further underscores the potential of US. The development of novel techniques to aid in the ultrasound vi- sualization of dental and gingival structures, such as the OHS and TPT help improve extraoral US techniques in cases where initial imaging does not clearly show an abscess.

1. Conclusion

The application of extraoral US in diagnosing dental abscesses in EDs is a promising alternative to conventional radiographic imaging methods. The development of novel techniques for improving the accu- racy and reliability of US examinations, such as the OHS and TPT, further highlights its potential in diagnosing dental abscesses. However, more studies are needed to validate its effectiveness and establish it as the standard of care in assessing odontogenic infections.

Supplementary data to this article can be found online at https://doi. org/10.1016/j.ajem.2023.05.002.

Funding

This research did not receive any specific grant from funding agen- cies in the public, commercial, or not-for-profit sectors.

CRediT authorship contribution statement

Michael F. Barton: Writing - original draft, Writing - review & editing. Nour Al Jalbout: Writing - original draft, Writing - review &

editing. Brenna L. Barton: Writing - review & editing. Maryam Alnuaimi: Writing - review & editing. Hamid Shokoohi: Writing - review & editing, Writing - original draft, Conceptualization.

Declaration of Competing Interest

All authors report no conflicts of interest.

Acknowledgments

None.

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