Equine

The middle conchal sinus (MCS), also termed the ethmoidal sinus, remains one of the least understood equine paranasal compartments. Despite recognition of its involvement in sinonasal disease, it remains underdiagnosed in absence of CT due to limited anatomical understanding and challenges with radiographic visualization.
Materials and Methods
Three equine cadaver heads representing different age groups underwent standard radiographic projections before and after sagittal sectioning and placement of wire markers outlining the MCS. Radiographs were evaluated to identify and describe consistent anatomical landmarks. A clinical case of MCS sinusitis confirmed by CT was used for comparative assessment.
Results
The MCS was not identifiable on pre-dissection radiographs. Post-sectioning images revealed consistent latero-lateral radiographic landmarks, notably its ovoid shape superimposed with the ethmoid turbinates and located dorsal to the third maxillary molar (111/211). Oblique projections allowed side differentiation. On dorsoventral projections, the MCS was consistently superimposed with the middle nasal meatus and the rostral margin of the ethmoid turbinates, allowing tentative localization in all specimens. The clinical case demonstrated pathology at the predicted MCS site, correlating with cadaveric observations.
Relevance to Clinical Practice
This study provides a reproducible radiographic reference for localising the MCS using widely available imaging techniques. Improved awareness of its location and presentation on radiographs will aid clinicians in diagnosing sinus disease involving this compartment, especially when CT is unavailable. This work also highlights the need to reassess the role of the MCS in persistent or atypical sinusitis.

INTRODUCTION

In horses, it is difficult to determine their exact age by dentition in the period between the eruption of the third deciduous incisors (6-9 months) and the eruption of the first permanent incisors (30 months)1,2.

OBJECTIVE

To show that intraoral radiographs of the incisors can more accurately determine the age in these periods, if we study both the formation of dental germs and their radiographic evolution.

MATERIAL AND METHODS

Intraoral radiographs were performed of the incisors of the maxillary region of 101 Purebred Spanish Horses (PRE) (51 males and 50 females), all of known ages and ranging from 178 days (5.9 months) to 1001 days (33.3 months). The studies were performed with portable radiology equipment and processed with DR. All of them underwent an intraoral x-ray of the maxillary region3,4, exposure factors were ranging from 45-60 kVp and 2-3 mAs.

RESULTS and DISCUSSION

Based on the radiographic findings considered as reference, the following groups have been established:

1. Group 1: corresponding to specimens, between 178 and 213 days, in which only deciduous incisor teeth are present.
2. Group 2: specimens between 179 and 285 days, in which the dental germs of teeth 101 and 201 appear, but without content inside.
3. Group 3: specimens between 265 and 548 days with the dental germs of 101 and 201 with non-erupted crowns with a conical shape, but without infundibulum.
4. Group 4: specimens between 440 and 608 days with the germs of 101 and 201 in which the poorly developed infundibulum is visible. The dental germs of 102 and 202 are also visible (Figure).
5. Group 5: specimens between 613 and 855 days in which the infundibules of 101 and 201 are closed and the dental germs of 102 and 202 contain unerupted crowns.
6. Group 6: specimens between 758 and 925 days in which 101 and 201 have not yet erupted and 102 and 202 present an infundibulum with greater or lesser development, but without closure.
7. Group 7: specimens between 925 and 1001 days, with 101 and 201 erupted, 102 and 202 with closed infundibules and germs from the 3rd incisors with enamel appear.

The description of the radiographic evolution of teeth is similar to those previously provided by the authors5, although in our study we establish its relationship with age.

CONCLUSION
The study of dental germs in the PRE-horse helps to better determine the age between 12 and 30 months.

REFERENCES.

1. Tremaine, H. A modern approach to equine dentistry 3. Imaging. Practice, 2012, 34, 114–127.
2. Butler J, Colles C, Dyson SJ, Kold SE, Poulos PW. Clinical Radiology of the Horse, 4th ed. West Sussex (UK): Willey Blackwell. West Sussex UK. 2017.
3. Barakzai, S.Z. Dental imaging. In Equine Dentistry, 3rd ed.; Easley, J., Dixon, P.M., Schumacher,J., Eds.; Saunders Elsevier: London, UK, 2011; pp. 199–221.
4. Barrat R.M. Imaging I: Radiography. Proceed AAEP. 2013. Charlotte NC. USA 38-45.
5. Miró, F; Manso, C; Diz, A; Novales, M. Maxillary incisors of the horse before and at the beginning of the teeth shedding: radiographic and CT study. Animals 2020, 10, 1618; 12-16.