Cephalometric Study of the Overjet Development in Warmblood Foals

Comparison of Computed Tomography Assisted 3D Cephalometric Measurements in Straight Egyptian Arabian and Thoroughbred Horses

Dental malocclusions are commonly encountered in horses. The objective of this study was to report the normal cephalometric values from skull computed tomography (CT) scans of adult Straight Egyptian Arabian (SEAR) and thoroughbred (TB) horses and to compare differences in the measurements between the two breeds. Standing skull CTs were performed on 29 clinically normal adult horses (15 SEAR; 14 TB) and cephalometric measurements were taken. All 9 cephalometric measurements, as well as the interincisal angle, were found to be significantly greater in TB than SEAR (P < 0.05). TB were found to have significantly greater facial line: mandibular length (FL/ML) ratios compared to SEAR (P = 0.002) whereas for the maxillary cheek teeth length: ethmoidal line ratio (Mxa/EtL), SEAR were found to have significantly greater values than TB (P = 0.0007). SEAR cephalometric measurements, as well as certain ratios, differ significantly from TB and could have an impact on the development of dental malocclusions in this breed. Further investigation is needed to ascertain whether these cephalometric differences between the two breeds predispose the SEAR to the development of dental malocclusions.

The prevalence and risk factors of dental disease found in 100 miniature horses

Introduction

Dental disease is a common condition affecting horses. Its prevalence and characteristics among most of the common breeds of horses and donkeys have been investigated and described in the literature, but information about the prevalence and etiology of dental disease of miniature horses is sparse.

Methods

To determine the prevalence and characteristics of dental disease of miniature horses, we performed oral and dental radiographic examinations on 100 miniature horses. The findings of these examinations were analyzed to determine the prevalence of dental disease and its correlation to age, sex, weight, body condition score, height at the withers, head length and head width. Older horses had a higher prevalence of dental disease, diastemata and crown elongations.

Results

The most common dental diseases detected in this population were crown elongation, oral mucosal ulceration, diastemata, class 1 malocclusion and hypodontia. Horses with a high body condition score had an increased likelihood of having a class 1 malocclusion. Horses with wider heads had a higher prevalence of dental disease and class 1 malocclusions.

Conclusion

Frequent oral examinations, starting at an early age, should be prioritized as a part of miniature horse preventive health care to decrease morbidity and slow progression of dental disease.

Temporomandibular joint biomechanics and equine incisor occlusal plane maintenance

In equine dentistry, the physiological incisor occlusal surface is visually perceived as a plane with a distinct inclination to the head's coronal plane, extending rostro-ventrally to caudo-dorsally. To better understand the formation of this inclined plane and its connection to dental wear, we investigated the hypothesis that it arises from masticatory movements and the considerable distance between mandibular articular heads and the incisor occlusal surfaces, acting as the three points of support for the mandibles. Leveraging data from a large-scale clinical study involving static and dynamic orthodontic measurements in horses, we approximated the mandibular movement range where incisor occlusion and dental wear occur. By introducing and testing a segment coordinate system, we explored possible angular deviations from the occlusal plane caused by mandibular roll and pitch rotations during two lateral mandibular movement patterns, protrusion and retrusion. Theoretical biomechanical calculations and simulations confirmed the visual perception of the incisor occlusal surface as a plane. To further examine our assumptions, we employed a simple mechanical simulator to assess incisor normal occlusion and provoked malocclusions (diagonal, smile, and frown bite) by modifying temporomandibular joint (TMJ) movement patterns. The results from clinical investigations were corroborated by both the theoretical analysis and mechanical simulations, strengthening our understanding of the biomechanical basis behind the physiological incisor occlusal plane maintenance in horses. These findings have significant implications for equine dental health and contribute to a thorough understanding of TMJ dynamics.

Intra- and Interexaminer Measurement Variability Analysis of an Orthodontic Gauge Device to Determine Incisor Occlusal Surface Angles in the Horse

Simple Summary

Annual tooth rasping is integral to prophylaxis work in equine dentistry. The procedure begins with a thorough examination of the oral cavity, including assessment of incisor occlusal surface angles. Any dental misalignment should be corrected or reduced to prevent abnormal forces from acting on teeth and supporting tissues and to maximize functionality of the masticatory apparatus. Thus far, clinical methods for dental angle assessment are scarce and not validated in terms of data reproducibility and comparability. These parameters are vital to objectively assess treatment needs and outcome, obtain population data, and establish data comparability among studies. However, this is the first study systematically validating a commercial dental angle measuring device. The data indicate high device performance and its applicability in practice.

Abstract

Incisor malocclusions are common in horses. As yet, an evidence-based understanding of incisor occlusal surface angle dynamics and normocclusal range is missing. Orthodontic measuring devices could help unravel this information objectively but imply measurement validation. We evaluated intra- and interexaminer variability of repeated sagittal and transversal incisor occlusal surface angle measures using a commercial orthodontic gauge device (MaPHorse1). Five examiners (two experienced, three inexperienced) measured six cadaver heads on 2 consecutive days in a blinded block-randomization design, resulting in 16 measures per examiner*head. Sagittal and transversal angle measures revealed low intraexaminer variability at scale-level independent mean SDs of α 0.58° and α 0.69°, respectively. Sagittal angle measures associate with low interexaminer variability, showing small mean angle differences (max. α 0.51° ± 0.35°), small scatter, and more consistent data reproducibility. Despite comparable mean interexaminer differences, the spread of transversal angle measures was relevantly higher using the proposed landmarks (average 2.2-fold higher interquartile range). The measurement performance of experienced and inexperienced examiners did not systematically differ. The time required for individual measurements was already comparable after 24/96 repetitions. This instrument may help deciphering sagittal angle normocclusal range and orthognathic dynamics and, with a proposed procedural amendment, transversal angle as well.

Computed Tomography (CT)-Assisted 3D Cephalometry in Horses: Interincisal Angulation of Clinical Crowns

The angle encompassed between opposing incisors in horses is assumed to decline with age. Previous studies merely consider the overall profile view of clinical crowns presuming a generalized angle, neglecting potential tooth position-dependent differences. Cephalometric measurements from 3D computed tomographic thick-slab reconstructions of single incisors within a global reference frame were used to determine clinical crown interincisal angulation (IIA) of 48 horses. Based on predefined dentoalveolar landmarks, IIA was defined as the angle enclosed by the respective labial axis of the clinical crown (LACC). A measurement repeatability analysis was conducted including a comparison of third incisor teeth IIA with data obtained by cephalometric implementation of previously described landmarks for third incisor teeth (lingual/palatal border). The age-related angle course and differences between tooth positions were investigated considering LACCs of permanent incisors. Determining IIA by LACCs exhibited a high level of reproducibility applying for all tooth positions (mean coefficient of variation = 0.65 %; mean SD ± 0.89°). The comparison method for third incisor teeth revealed two times higher mean dispersion of repeated measurements, P = 0.017. A non-linear model slightly increased predictability of angular changes over time as against linearity assumption. The angle decline was more distinctive in younger horses and appears to approach a final value in older ones. Third incisor teeth exhibited significantly higher angle decline compared to first and second incisor teeth, P < 0.0001. According to the results, age determination of horses using clinical crown IIA is not recommended. Rather, 3D cephalometry may provide a promising tool to determine interdental and dentofacial angles of distinct tooth positions in health and disease.