Periodont - 9th Issue (12th March 1995)

Editorial:

Dear Sirs,

This is the 9th issue of the Mailing List Periodont. I am glad to tell you that we have 189 subscribers now. But there is next to nothing of contributions. I am surprised because a big fraction of our subscribers are scientists. I hope this is only the result of long thinking about good contributions. ;-)
I am looking forward receiving your papers.
The current issue's main topic is a paper of David Crossley. He is an English veterinary surgeon with a special interest in dentistry and a Fellow of the Academy of Veterinary Dentistry (USA). The paper is very interesting for all who are or will be involved in animal studies showing us the possible diseases of some animals without the influence of our studies.
It is followed by a presentation of The Bridge Dental BBS and the announcement of a new WWW-Server in NYC: New York University College of Dentistry.
Next there are two announcements of conferences: One of the Dental School of the University of Texas Health Science Center and another one of the University of Washington, Seattle, Washington, U.S.A.
Heiko Spallek

David Crossley is an English veterinary surgeon with a special interest in dentistry.

The following article is part of a presentation on the use of radiography as a prognostic indicator in cases of malocclusion which the author will be giving at the British Veterinary Dental Association's Annual Scientific Meeting in Birmingham UK on the 5th. April 1995.

DENTAL DISEASE IN RABBITS AND HERBIVOROUS RODENTS.

by David A. Crosley BVetMed MRVCS
Fellow of the Academy of Veterinary Dentistry (USA)

Introduction

In first opinion small animal veterinary practice one is frequently presented with pet rabbits and rodents which have medical problems of possible dental origin. Unfortunately, for various reasons, many are not recognised as dental cases at an early enough, treatable, stage. Owners not infrequently fail to notice that small pets have a problem until death is imminent. Even when spotted earlier the problem may still have progressed beyond practical treatment. When signs of a problem are noticed early in the disease process, making a definitive diagnosis is often difficult, requiring costly investigation. As a result, investigation is often neglected. Both the owners' inability/ unwillingness to pay for treatment, and many veterinary surgeons' lack of enthusiasm and knowledge of the condition or species concerned, play their part. It is very easy when presented with a sick rabbit or rodent to prescribe a "standard" treatment regime and hope the patient will get better. Unfortunately this often just allows the condition to progress beyond the stage where correct treatment would have effected control or a cure.
The following discussion relates mainly to rabbits and the truly herbivorous pet rodents, guinea pigs and chinchillas, which have elodont premolars, molars and incisor teeth (The teeth continue growing throughout life).

Diagnosis of dental disease in rabbits and rodents.

To make an accurate diagnosis it helps to have sufficient data regarding the patient, its history and the signs observed. In most cases the history and an initial external examination of a sick animal will give indications as to any probable dental involvement.

Signs indicative of (probable) dental disease in rabbits and rodents:

In order of frequency of observation in the author's practice.

* significant
** very significant
*** extremely significant
**** specific dental problem

*** Weight loss
* Poor coat condition
** Digestive disturbance
*** Noticeable reduction in food intake
*** Dysphagia
*** Epiphora (**** chinchilla)
**** Visible incisor malocclusion/overgrowth
**** Palpable bony swelling of ventral mandible
*** Discomfort on palpation over cheek teeth
** Discomfort on manipulating jaw
*** Reduced range of movement of jaw
*** Inability to fully close jaw
** Conjunctivitis
*** Inappetance
**** Mandibular prognathism
*** Excessive salivation (slobbers)
*** Purulent ocular/nasal discharge
*** Facial abscessation
*** Mandibular abscessation
** Submandibular/cervical lymphadenopathy
*** Exopthalmos
* Systemic disease
** Emaciation
* Death

Oral examination

The long diastema between the incisor and cheek teeth of rabbits and rodents makes effective examination of the premolar and molar (cheek) teeth, along with their supporting soft tissues, difficult. Although it is possible to use an auriscope as an oral endoscope in some species, the restricted field of view means that many lesions will be missed. Even when examining a patient under anaesthesia using mouth gags, cheek dilators, mouth mirrors and magnification, it is common for experienced clinicians to miss significant oral lesions. In this regard, post mortem examinations are a very useful learning tool.

Common dental problems in rabbits and rodents

Unlike the situation in pet carnivores, periodontal disease is not frequently recognised in rabbits and rodents. This is probably mainly due to a lower incidence, but will also be due to a failure of many clinicians to detect or recognise signs of its presence.
The most frequently recognised dental problem in rabbits and rodents is malocclusion of their easily examined elodont (continually growing aradicular hypsodont) incisor teeth. Without the normal regular wear from chewing or gnawing activity, these non-functional maloccluded teeth continue growing, further impeding function.
The second most cmmon dental problem in the small herbivores is cheek tooth overgrowth. This often accompanies incisor malocclusion; either as a part of the primary condition, or as a purely secondary problem; but it is also seen as a primary problem in its own right. Cheek tooth overgrowth may result from lack of wear due to malocclusion or an insufficiently abrasive diet. It may also occur secondary to periodontal or metabolic (impaired collagen formation) disease. Whether or not the occlusion was normal to start with, a secondary malocclusion will develop as a result of tooth overgrowth. The exception to this last statement is when root extension occurs as a result of growth without matching eruption, as may sometimes be seen in chinchillas. In this case there may ocular signs, as described later, without any oral abnormality. In the author's experience, rabbits and guinea pigs do not develop root extension without visible oral signs of cheek tooth malocclusion or overgrowth.
Whether a malocclusion is primary or secondary, abnormal tooth wear of the naturally curved cheek teeth tends to cause development of sharp enamel spikes/spurs which irritate the cheeks and tongue leading to:
It seems that root growth continues despite increased resistance to eruption following lack of adequate wear to the crown. Root extension frequently accompanies cheek tooth malocclusion. The extending maxillary root apices invade the lachrymal bone, obstructing the lachrymal duct and causing epiphora, and the orbit, leading to proptosis of the eye. The close proximity of the root apex of the rabbit's mesial cheek teeth to the lacrimal duct accounts for the occurrence of epiphora and the frequent spread of periodontal infection from these teeth to the tear duct, producing a typical purulent occular discharge.
Root extension of the mandibular cheek teeth leads to remodelling or thinning of the adjacent cortical bone with development of palpable swellings along the ventral surface of the mandible. Suspected mandibular or maxillary root extension is best confirmed radiographically.
Facial and mandibular abscesses quite common and are generally caused by dental problems, though infection of external wounds does also occur.
Dental abscesses may be due to:
In the latter case the abscess is usually due to a tooth penetrating the oral mucosa making localisation of the problem tooth easy.
Both periodontal and endodontic abscesses may appear away from the source of the problem. Endodontically affected teeth are best identified radiographically. Observation of periodontal food impaction or the location of periodontal pockets on careful probing may identify an offending tooth or teeth, but even so, radiography is still advisable.

Treatment options

As the vast majority of the orthodontic problems seen in practice seem to be hereditary, often with generation after generation showing the same problems, genetic counselling should be given to pet owners and breeders. Culling of affected breeding stock and their offspring is essential. Unfortunately by the time the problem becomes apparent, the affected animals have generally already produced several litters.
(How much genetic counselling do human patients get before orthodontic treatment is performed on them?) Depending on the situation the main treatment options in pets are:

Whilst benign neglect is a common practice, just maintaining observation for signs of pain or distress, this cannot be recommended. As already mentioned, any delay in investigation and treatment will allow further progression of the disease process reducing the chances of successful treatment.
The incisor tooth overgrowth problem has traditionally been managed by repeated tooth shortening (preferably trimming using a bur in a high speed dental handpiece), without investigation of the underlying problem. In cases with recurrent overgrowth, extraction of the offending teeth has been suggested as a more permanent solution. In early cases with a minor degree of rosro-caudal malocclusion, correction can occasionally be accomplished in rabbits (not rodents) by burring a reverse bevel on the mandibular incisors to create an incline plane like interlock with the maxillary first incisors. In the majority of cases, occlusal equilibration of the cheek teeth is also required.
Treatment of the cheek teeth by removing enamel spikes and occlusal equilibration is sometimes possible, though the long term results are poor in most cases. As with the correction of rabbit incisor malocclusion, the treatment is most successful if performed at an early stage, in mild cases. Dietary alteration (providing hay as the largest component of the diet) to increase the rate of attrition is highly beneficial in these cases. In more advanced cases the provision of a more abrasive diet is helpful, but it is usually necessary to repeat occlusal equilabration at regular intervals.
Whilst extraction of rabbits' incisors is useful in cases of malocclusion with recurrent overgrowth of these teeth, the long term results are disappointing in over 50% of cases due to the development of significant cheek tooth problems. Although it may not be visually obvious at the time of incisor extraction, most of the rabbits treated by the author have had radiographic changes suggestive of cheek tooth problems, even when everything appeared normal on oral examination. As would be expected, if there is concurrent cheek tooth disease (periodontal disease, malocclusion, overgrowth etc.), any improvement following treatment of just the incisor problem tends to be of short duration.
The treatment of dental abscesses in rabbits and rodents requires identification of the cause. If due to periodontal or endodontic disease, extraction of the affected teeth is necessary in addition to local treatment {drainage, curretage, application of a Ca(OH)2 dressing}. When the abscess is due to mucosal penetration of an enamel spike, removal of the spike, plus treatment of the underlying malocclusion will be effective.

Treatment policy

Due to the low value of most pet rabbits and rodents, the cost of investigation and treatment of dental disease is a significant factor to many owners. They want to know if it is worth having treatment. As a result, it is no longer the author's policy to immediately recommend treatment of dental problems in these animals, but rather to suggest a thorough examination and assessment under anaesthesia to see whether treatment is likely to be beneficial, and if so, whether recurrence should be expected. The biggest problem has been finding reliable prognostic indicators.
This approach has significantly increased the take up of dental services for these species from around 20% to 50% of cases. This still leaves half the affected animals. Of these, about half the owners opt for immediate euthanasia, whilst the other cases go onto a tooth shortening or benign neglect program.

Prognostic indicators

As mentioned previously, cheek tooth problems are an indication of a poor prognosis, but their presence or their full extent are often not identified on clinical examination. Radiology, whilst not being totally reliable, does seem to give a good indication of the extent and degree of cheek tooth problems. When the results of physical examination are combined with radiological assessment it is possible to formulate a more reliable prognosis.
Any severely debilitated patients are put onto a nursing care program prior to full assessment. Failure to respond to intensive care indicates a grave prognosis. In these cases where there is a very high anaesthetic risk, the choice is between euthanasia and an attempt at investigation and treatment. If such animals survive induction of anaesthesia treatment might be possible, so the attempt is worthwhile, though the majority die on induction, which is basically equivalent to performing euthanasia anyway.
If no serious problems are found during the definitive oral examination and the radiographs look OK, then treatment is usually worthwhile. Treated animals should be followed up. Re-examination and re-treatment should be arranged if signs fail to disappear, or if they recur at a later date.
If there are gross changes, abnormal root morphology, significant root extension, bone loss, osteomyelitis etc. then euthanasia is probably the most humane option.
Between the two extremes, the author treats those cases where the owner is keen to have a go and euthanases the others. Recurrence of signs in treated animals from this group is taken as an indication for euthanasia.

References

  1. Brown, S.A. (1993). Incisor removal in the rabbit, TNAVC 1993 proceedings, pages 791-792.
  2. Crossley, D.A. (1994). Extraction of rabbit incisor teeth, EVDS Forum 1993 no. 4
  3. Harkness, J.E. and Wagner, J.E. (1989). The Biology and Medicine of Rabbits and Rodents, third edition, Published by Lea & Febiger, Philadelphia.
  4. Kennedy, A.H. (1970). Chinchilla Diseases and Ailments, Published by Clay Publishing, Bewdley, Ontario.
  5. Lobprise, H.B. and Wiggs, R.B. (1991). Dental and oral disease in lagomorphs, J.Vet.Dent, 1991:8(2)
  6. Okerman, L. (1988). Diseases of Domestic Rabbits, published by Blackwell Scientific Publications, Oxford.
  7. Richardson, V.C.G. (1992). Diseases of Domestic Giunea Pigs, Published by Blackwell Scientific Publications, Oxford.
  8. Wiggs, R.B. and Lobprise, H.B. (1990). Dental disease in rodents, J.Vet.Dent, 1990:7(3)
  9. Wiggs, R.B. and Lobprise, H.B. (1995). Dentistry in pet lagomorphs and rodents, in: BSAVA Manual of Small Animal Dentistry, second edition (Eds. D.A.Crossley & S. Penman). published by BSAVA

All personal comments to author:

vetdent@dacross.demon.co.uk

The Bridge Dental BBS announces its presence here!

sysop@dental.com
We're happy to report that our free on-line service for dentists, The Bridge, has begun carrying this mailing list. Postings to the list will echo in a forum on The Bridge, where Bridge users can read and respond with postings that will in turn echo back to the list.
The Bridge is also carrying 11 other dental related mailing lists. By acting as a central repository for all known dental mailing lists, we make it simple for you to keep abreast of new developments in the field without cluttering up your personal mailbox.
In addition to the internet mailing lists, we carry the usenet group "sci.med.dentistry" as well as our own local forums.
We invite you to try The Bridge by dialing 1-415-368-2778 with your modem. And by all means let us know what you think!
DETAILS:
The Bridge is a free on-line service for oral health professionals that already has more than 350 users. Among its offerings are forums on various dental specialties, Internet e-mail, free dental classified ads, a library of dental resources and listings of continuing education. Dentists, hygienists, researchers and others in the field are invited to make use of this resource.

ACCESS:
The Bridge can be dialed -- no telnet yet -- at 1-415-368-2778, with the usual telecommunications parameters of 8-N-1 at modem speeds of up to 14,400 bps. No special software is needed though our system looks best if your software supports ANSI colors and IBM graphics characters. We offer free software for PC users that supports these features (plus ZMODEM) and is pre-configured to dial our system. You can get a UUENCODED copy via e-mail by sending a message to: ftp@dental.com with the subject: GET DIALPGM.EXE

QWK support allows long-distance callers to use an off-line mail reader to read forum postings and e-mail while minimizing phone charges. The Bridge offers several off-line readers for download in our software libraries.

FOR MORE INFO: Call 1-213-969-0651 or e-mail info@dental.com. To reach the operators, e-mail sysop@dental.com or akst@dental.com.

New York University College of Dentistry:

New York University College of Dentistry is pleased to annonce the availablilty of its World Wide Web Home Page. Although still under construction, this site currently contains a very comprehensive listing of availabe dental related internet resources, mailing lists, and phone numbers.
This site can be accessed at the following URL

Any additions, comments or suggestions should be sent to:

dentalweb@nyu.edu

Elise S. Eisenberg, DDS
Clinincal Associate Prof.
NYU College of Dentistry

ANNOUNCING: SUMMER INSTITUTE IN CLINICAL DENTAL RESEARCH METHODS

July 3-August 11, 1995
University of Washington, Seattle, Washington, U.S.A.
Core courses: Biostatistics
Electives:
The University of Washington's Regional Clinical Dental Research Center will offer a research training institute in the summer of 1995 for dental school faculty and other oral health professionals interested in clinical research in dentistry. The summer institute is designed to offer training in research methods to which dentists (and other oral health professionals) may not have been adequately exposed during clinical training. For those currently in or seeking academic or other positions which involve clinical dental research, the summer institute offers an opportunity to learn research methods which will enhance one's capability to perform good clinical research.
There is no tuition charged for the summer institute, unless academic credit is requested (which can be arranged through the University of Washington Summer Quarter Office).
For further information, please refer to our Summer Institute brochure sent to your school, or contact me at the address below to request a copy.
Applicants should send a complete curriculum vitae, along with a letter of application explaining why the Summer Institute is of interest and would be beneficial to them. Also, a letter should be send from the applicant's supervisor (department chair or dean) indicating if the employing institution is supportive of the applicant's participation, and describing any benefits the institution will derive. Applications received prior to April 15, 1995 will receive first consideration. Application materials or inquiries should be addressed to:

Timothy A. DeRouen, Ph.D.
Director, Summer Institute
RCDRC Biometry Core SM-35
University of Washington
Seattle, WA 98195
U.S.A.
Telephone (206) 543-7304
Fax (206) 685-4258
Email derouen@u.washington.edu

Dental School of the University of Texas Health Science Center:

The Dental School of the University of Texas Health Science Center at San Antonio is happy to extend you an invitation to attend the International Symposium on Oral Implantology and Mineralized Tissue Regeneration: Clinical and Biological Advances, to be held May 12th and 13th, 1995 in San Antonio, Texas. This symposium is being held in conjunction with the Dental School's 25th Anniversary.
The goal of this symposium is to allow dental practitioners and scientists to explore recent mineralized tissue-related developments and clinical problems. The program is designed to foster exchange of information. Keynote speakers will present lectures on a variety of topics. In addition, poster presentations and group discussions will be held.
You can obtain complete details about the Symposium in any of the following ways:
  1. Contact the Office of Continuing Dental Education at (210) 567-3177 or send email to butlerw@uthscsa.edu
  2. See our home page on the World Wide Web
  3. Subscribe to a temporary mailing list through which you will receive the latest information about the conference. Send the command subscribe calcium yourfirstname yourlastname in the BODY of an email message to
    listproc@sparky.uthscsa.edu

David Crossley 8th March 1995