Applied feline oral anatomy and tooth extraction techniques: an illustrated guide

Feline minor salivary gland adenocarcinoma: retrospective case series and literature review

CASE SERIES SUMMARY

Salivary gland adenocarcinoma, of major or minor salivary gland origin, is an uncommon tumor in cats. This article describes the clinical features, morbidity and survival rates of four cats with salivary gland adenocarcinoma arising from minor salivary gland tissue. Medical records from a private multicenter dentistry and oral surgery practice were reviewed for the period between 2007 and 2021. Four cats were included in this retrospective case series study, with oral masses on either the right or left caudal mandibular labial buccal mucosa. The inclusion criteria included a diagnosis of salivary gland adenocarcinoma in an anatomical location with lack of involvement of a major salivary gland, complete medical history and a follow-up of at least 6 months. The age range of the cats was 9-15 years; three of the cats were castrated males and one was a spayed female. Curative intent surgery was performed in three cats, whereas palliative surgery (debulking) owing to extensive soft tissue invasion was performed in one cat. Survival times were in the range of 210-1730 (mean 787) days. All four cats were euthanized owing to local recurrence and decreased quality of life, regardless of treatment modality.

RELEVANCE AND NOVEL INFORMATION

There are limited documented studies reporting the prevalence of salivary gland neoplasia affecting minor disseminated glands in the oral cavity of feline patients. Salivary gland adenocarcinoma should be a differential in cats presenting with caudal labial masses. Surgical resection has been the recommended treatment for salivary gland neoplasia of major salivary gland origin. According to this current case series, we propose that early aggressive surgical treatment with wide surgical margins should be performed for cats with salivary gland adenocarcinoma of minor salivary gland origin. Surgery increased the quality and duration of life; however, each patient was euthanized owing to local recurrence and morbidity.

Feline chronic gingivostomatitis current concepts in clinical management

PRACTICAL RELEVANCE

Feline chronic gingivostomatitis (FCGS) is a debilitating disease for cats and a challenge for veterinarians and cat caregivers alike. Recent literature indicates that the disease is immune-mediated in nature and likely associated with a chronic viral infection in patients with higher alpha diversity of their subgingival microbiome. The immune-mediated nature of FCGS includes both local as well as systemic effects, and the transcriptomic analysis of affected patients supports these findings.

TREATMENT OPTIONS

Localized therapy in the form of surgical extraction of all, or nearly all, teeth continues to be the mainstay of treatment. For cats that do not respond to surgical management, medical management, in the form of immunosuppressive or immunomodulatory therapy, remains an option. Analgesia is of fundamental importance. Immunomodulation utilizing mesenchymal stromal cell therapy provides an alternative treatment avenue for refractory patients and likely targets the chronic viral infection present in this disease. The potential for treatment stratification and use of novel systemic treatment options may be revealed as the molecular pathways involved in this disease are better described.

AIMS

This review outlines current and emerging concepts linking available science pertaining to FCGS and clinical management of the disease.

EVIDENCE BASE

The article draws on the best evidence base at this juncture and is also driven by the authors' collective experience of working on the disease for over a decade.

Intra-socket application of medical-grade honey after tooth extraction attenuates inflammation and promotes healing in cats

OBJECTIVES

Dental diseases are a major problem in cats and often necessitate tooth extraction. Medical-grade honey (MGH) has antimicrobial and wound-healing properties, and therefore the aim of this study was to investigate whether intra-socket application improved healing after tooth extraction. It was postulated that applying MGH would reduce inflammation, improve the viability of the surgical flap and enhance healing following tooth extraction.

METHODS

A prospective randomised controlled trial was performed in client-owned cats undergoing bilateral tooth extractions of the same element of the canine or (pre)molar tooth. A split-mouth design was used in which every animal served as its own control. After surgical extraction of the elements, the sockets on one side were filled with an MGH-based ointment (L-Mesitran Soft), whereas the contralateral side received no treatment (control). A mucoperiosteal flap was used on both sides, and simple interrupted monofilament sutures were placed. No antimicrobial drugs were administered. Clinical parameters (inflammation/redness, flap viability and wound healing) were subjectively analysed on days 3 and 7 post-extraction by a veterinarian blinded to the treatment.

RESULTS

Twenty-one cats were included. MGH significantly decreased signs of inflammation (P <0.01), improved mucoperiosteal flap viability (P <0.01) and promoted wound healing (P = 0.01), at both time points. MGH was easy to apply and there were no adverse events.

CONCLUSIONS AND RELEVANCE

Intra-socket application of MGH after tooth extraction positively affects the surgical wound, as it reduces redness, improves flap viability and enhances wound healing. Applying MGH represents a potent adjuvant therapy to support intra-oral wound healing after tooth extraction.

Clinical insights into the three-dimensional anatomy of cheek teeth in alpacas based on micro-computed tomography - Part 2: Maxillary cheek teeth

BACKGROUND

Scientific knowledge regarding alpaca dentistry is relatively limited despite its clinical implications. The present gap in available supportive data leads to limited treatment options for dental pathology in alpacas in comparison to other species. The main goal of this study was to gain novel insights into the general and pulp morphology of maxillary cheek teeth to allow development of more advanced treatment strategies in the future. Also, the risk of causing pulp exposure when floating maxillary cheek teeth was of particular interest. Concurent research focusing on the anatomy of mandibular cheek teeth has been performed accordingly. The results obtained in mandibular teeth are expected to be non-extrapolatable because of the structural differences between mandibular and maxillary teeth.

RESULTS

Pulp morphology of maxillary cheek teeth showed great variation. A common pulp chamber was identified in 46/83 (55.4%) teeth with a mean dental age of 2 years and 7 months (± 2 years and 5 months). Pulpal segmentation was more commonly observed in teeth of increasing age. Full columnar segmentation was seen in 33/69 teeth (47.8%), whereas within-column segmentation was observed in 36/83 teeth (43.4%). Age and degree of segmentation of the pulpal tissue varied greatly according to Triadan position. Physical contact between roots of adjacent teeth was found in the majority of examined molars (range 82-94%) which resulted in morphological adaptations at the level of the root tips. The measured sub-occlusal dentinal thickness was as low as 0.46 mm above pulp horn 2 in a 14 years and 11 months old Triadan 09, emphasizing the risk of pulp exposure attributed to dental floating.

CONCLUSION

This study offers an objective description of age-dependent maxillary cheek teeth pulp morphology in alpacas. Current findings are of great value to provide a basis for the development of tooth-saving techniques as a treatment for dental disease in this species. Observed physical contact between the roots of different examined molars may be a facilitating factor in the spread of apical infection in chronically diseased cases. Finally, a conservative approach regarding dental floating is recommended in order to avoid iatrogenic damage to pulp tissue.

Clinical insights into the three-dimensional anatomy of cheek teeth in alpacas based on micro-computed tomography. Part 1: mandibular cheek teeth

BACKGROUND

Despite dental disease being a common health concern in alpacas, important dental pathology including apical infection, remains poorly understood. Treatment options are limited compared to veterinary dentistry techniques in other species. The primary goal of this study was to increase understanding of the external and internal anatomy of mandibular cheek teeth to enable the development of tooth sparing techniques in this species. Also, an objective evaluation of the sub-occlusal dentinal thickness in normal mandibular cheek teeth is warranted to understand the risks associated with reduction of overgrown teeth.

RESULTS

Overall pulp anatomy was variably characterized by the presence of a common pulp chamber in younger teeth, and segmentation of pulp cavities into multiple separate pulp entities within the same tooth with increasing age. A common pulp chamber was identified in 55.3% (26/47) of teeth with a mean dental age of 1 year and 11 months (± 1 year and 8 months). Columnar segmentation was recorded in the remaining teeth with a mean dental age of 6 years and 5 months (± 3 years and 11 months). Age of segmentation of the common pulp chamber into multiple separate pulp entities shows wide variation and is dependent of the specific Triadan position. The present study illustrates the presence of disto-mesial root contacts between adjacent tooth roots, often leading to morphological adaptations, most frequently observed between Triadan 09-10s (80%) and 10-11s (67%). The measured sub-occlusal dentinal thickness was as low as 1.11 mm over some pulp horns. The sub-occlusal dentinal thickness was lower than 2, 3, and 4 mm in 13.1, 38.1 and 61.4% of performed measurements, respectively.

CONCLUSION

This study provides detailed information on age-dependent mandibular cheek teeth anatomy in alpacas, which may support the use and development of advanced dental treatments in this species such as endodontics and tooth sectioning techniques. Apical morphological adaptations caused by disto-mesial root contact between adjacent mandibular cheek teeth are clearly illustrated. The limited amount of sub-occlusal secondary dentin warrants a cautious approach with regards to dental floating in alpacas.

The Cat Mandible (II): Manipulation of the Jaw, with a New Prosthesis Proposal, to Avoid Iatrogenic Complications

Simple Summary

The small size of the feline mandible makes its manipulation difficult when fixing dislocations of the temporomandibular joint or mandibular fractures. In both cases, non-invasive techniques should be considered first. When not possible, fracture repair with internal fixation using bone plates would be the best option. Simple jaw fractures should be repaired first, and caudal to rostral. In addition, a ventral approach makes the bone fragments exposure and its manipulation easier. However, the cat mandible has little space to safely place the bone plate screws without damaging the tooth roots and/or the mandibular blood and nervous supply. As a consequence, we propose a conceptual model of a mandibular prosthesis that would provide biomechanical stabilization, avoiding any unintended (iatrogenic) damage to those structures. The improvement of imaging techniques and a patient-specific prosthesis made of full biocompatible material are part of the future trends to improve patients’ recovery.

Abstract

The cat mandible is relatively small, and its manipulation implies the use of fixing methods and different repair techniques according to its small size to keep its biomechanical functionality intact. Attempts to fix dislocations of the temporomandibular joint should be primarily performed by non-invasive techniques (repositioning the bones and immobilisation), although when this is not possible, a surgical method should be used. Regarding mandibular fractures, these are usually concurrent with other traumatic injuries that, if serious, should be treated first. A non-invasive approach should also first be considered to fix mandibular fractures. When this is impractical, internal rigid fixation methods, such as osteosynthesis plates, should be used. However, it should be taken into account that in the cat mandible, dental roots and the mandibular canal structures occupy most of the volume of the mandibular body, a fact that makes it challenging to apply a plate with fixed screw positions without invading dental roots or neurovascular structures. Therefore, we propose a new prosthesis design that will provide acceptable rigid biomechanical stabilisation, but avoid dental root and neurovascular damage, when fixing simple mandibular body fractures. Future trends will include the use of better diagnostic imaging techniques, a patient-specific prosthesis design and the use of more biocompatible materials to minimise the patient’s recovery period and suffering.

The Cat Mandible (I): Anatomical Basis to Avoid Iatrogenic Damage in Veterinary Clinical Practice

Simple Summary

Nowadays, cats are one of the most common companion animals. They differ from dogs in some important aspects. However, most of the veterinary clinics are oriented towards the care and treatment of dogs, where the cat patient is clinically treated like a small dog. The cat mandible and related structures have some particularities that should be taken into account, when treating a cat, to avoid any unintended medical (iatrogenic) damage. The feline mandible has fewer teeth than a dog’s one, but tooth roots and the neurovascular supply account for up 70% of the volume of the mandibular body. This fact makes mandibular fracture repair challenging. In addition, the cat mandible has a prominent angular process that, when the cat is under anesthesia and his mouth is wide open (during oral or transoral manipulation), compresses the maxillary artery (that supplies blood to the brain) inducing temporal or permanent blindness and/or deafness. Other particularities of the cat jaw are also addressed to get a comprehensive knowledge of its functional anatomy, essential to an effective feline clinical practice.

Abstract

Cats are one of our favourite pets in the home. They differ considerably from dogs but are usually treated clinically as small dogs, despite some anatomical and physiological dissimilarities. Their mandible is small and has some peculiarities relative to the dentition (only three incisors, a prominent canine, two premolars and one molar); a conical and horizontally oriented condyle, and a protudent angular process in its ventrocaudal part. Most of the body of the mandible is occupied by the mandibular dental roots and the mandibular canal that protects the neurovascular supply: the inferior alveolar artery and vein, and the inferior alveolar nerve that exits the mandible rostrally as the mental nerves. They irrigate and innervate all the teeth and associated structures such as the lips and gingiva. Tooth roots and the mandibular canal account for up to 70% of the volume of the mandibular body. Consequently, when fractured it is difficult to repair without invading the dental roots or vascular structures. Gaining a comprehensive anatomical knowledge and good clinical practice (such as image diagnosis before and post-surgery) will help in the awareness and avoidance of iatrogenic complications in day-to-day feline clinical practice.

Optimised isolation method for RNA extraction suitable for RNA sequencing from feline teeth collected in a clinical setting and at post mortem

Advanced next generation sequencing approaches have started to reveal the cellular and molecular complexity of the microenvironment in many tissues. It is challenging to obtain high quality RNA from mineralised tissues. We developed an optimised method of RNA extraction from feline teeth collected in a clinical setting and at post mortem. Teeth were homogenised in phenol-guanidinium solution at near-freezing temperatures and followed by solid-phase nucleic acid extraction utilising a commercially available kit. This method produced good RNA yields and improved RNA quality based on RNA integrity numbers equivalent (RIN^e) from an average of 3.6 to 5.6. No correlation was found between RNA purity parameters measured by A_260:280 or A_230:260 ratios and degree of RNA degradation. This implies that RNA purity indicators cannot be reliably used as parameters of RNA integrity. Two reference genes (GAPDH, RPS19) showed significant changes in expression levels by qPCR at low and moderate RIN^e values, while RPL17 was stable at all RIN^e values tested. Furthermore, we investigated the effect of quantity and quality of RNA on the quality of the resultant RNA sequencing (RNA-Seq) data. Thirteen RNA-seq data showed similar duplication and mapping rates (94 to 95%) against the feline genome regardless of RIN^e values. However one low yield sample with a high RIN^e value showed a high duplication rate and it was an outlier on the RNA-seq multidimensional scaling plot. We conclude that the overall yield of RNA was more important than quality of RNA for RNA-seq quality control. These results will guide researchers who wish to perform RNA extractions from mineralised tissues, especially if collecting in a clinical setting with the recognised restraints that this imposes.

An assessment of the role of the falx cerebri and tentorium cerebelli in the cranium of the cat (Felis silvestris catus)

The falx cerebri and the tentorium cerebelli are two projections of the dura mater in the cranial cavity which ossify to varying degrees in some mammalian species. The idea that the ossification of these structures may be necessary to support the loads arising during feeding has been proposed and dismissed in the past, but never tested quantitatively. To address this, a biomechanical model of a domestic cat (Felis silvestris catus) skull was created and the material properties of the falx and tentorium were varied for a series of loading regimes incorporating the main masticatory and neck muscles during biting. Under these loading conditions, ossification of the falx cerebri does not have a significant impact on the stress in the cranial bones. In the case of the tentorium, however, a localized increase in stress was observed in the parietal and temporal bones, including the tympanic bulla, when a non-ossified tentorium was modelled. These effects were consistent across the different analyses, irrespective of loading regime. The results suggest that ossification of the tentorium cerebelli may play a minor role during feeding activities by decreasing the stress in the back of the skull.

Mathematical equation for prediction of cat mandibular canal height dimension based on canine tooth width measurement

OBJECTIVES

The present study was performed in a sample of 33 cats and aimed (1) to characterise the mandible height (Mh), mandibular canal height (MCh) and the distance between the interdental alveolar margin and the mandibular canal (dIAM-MC); and (2) to develop a mathematical model for dimension prediction of MCh using the patient's age, weight (Wg) and canine tooth width at the free gingival margin level (wCGM) that was easily accessible during the oral examination.

METHODS

Age, sex, breed, weight, skull type and the wCGM were the recorded variables for each patient. Right and left lateral view skull radiographs were made followed by measurements of the mandible anatomical structures, taken between the third premolar distal root and the fourth premolar proximal root. Results were considered statistically significant for P values <0.05, and statistical analysis was performed using SPSS software.

RESULTS

We observed a strong correlation only between wCGM and MCh, and a prediction mathematical model was developed to calculate the MCh, with a standard error of only 0.4 mm.

CONCLUSIONS AND RELEVANCE

Our study allows a surgeon to establish relationships between a physical parameter, such as wCGM, evaluated in an oral examination, and the mandibular canal, which is a very important anatomical structure to consider in surgical procedures. Ideally, surgeons should always plan their mandible work only after obtaining a final diagnosis achieved through the use of complementary imaging exams, such as intra- and extra-oral radiographs. Thus, this mathematical equation offers an additional tool, providing more information on the relationships between oral anatomical structures, reducing the risk of iatrogenic lesions and promoting patient safety.