In VPT (also known as partial coronal pulpectomy or pulpotomy) of a tooth, part of an exposed vital pulp is removed and the vitality and function of the remaining pulp are preserved,1 typically by covering the remaining pulp with protective dressing material. In dogs, indications for VPT include crown-height reduction to eliminate interference with other teeth or soft tissues owing to malocclusions, recent CCF (ie, fracture of the crown with pulp exposure) of immature or mature permanent teeth, pulp exposure during restorative preparation for an UCF (ie, fracture of the crown without pulp exposure), enamel hypoplasia, or debridement of a deep carious lesion.2,3
The material traditionally used to cover the exposed pulp has been Ca(OH)2.4 In early 2000, MTA, an alternative material, became available for use in VPT. Compared with Ca(OH)2, MTA has superior biocompatibility, less cytotoxicity, improved induction for dentin deposition, and greater long-term sealing in human studies.5–9
Failure of VPT has been shown to lead to endodontic disease through chronic inflammation and pulp necrosis.4 Long-term radiographic follow-up to evaluate the continuation of root formation and assess for signs of apical periodontitis is essential.1,10
To the best of our knowledge, peer-reviewed clinical veterinary studies evaluating the success rate of VPT with MTA as treatment for dental problems in dogs are lacking. The purpose of the study reported here was to retrospectively determine the clinical success rate of VPT in dogs with malocclusion or recent tooth fracture and to evaluate associations between various signalment-related, diagnostic, and treatment-related factors, including the use of Ca(OH)2 versus MTA, and outcome.
Materials and Methods
Criteria for selection of cases—Hard copy and electronic medical records of dogs that underwent VPT at Anident Veterinary Clinic, Veikkola, Finland, between December 4, 2001, and December 28, 2011, were reviewed. The inclusion criteria were complete anesthesia and dental records and ≥ 1 follow-up evaluation for which dental radiographs were available.
Medical records review—Factors extracted from the records were breed, weight, age, and sex of the patient; tooth type; indication for VPT; time from pulp exposure to treatment; whether Ca(OH)2, MTA, or both was used in treatment; whether deep penetration of the pulp dressing material occurred (ie, radiographic evidence of pulp dressing material extending into the pulp, rather than remaining at the interface between the pulp and subsequent restoration); presence of distinct pulpal hemorrhage intraoperatively; quality of the restoration immediately after treatment and at the last recheck examination (intact, rough, or damaged); antimicrobial treatment before or after the dental procedure (or both); whether tertiary dentin bridge formation was detected at the recheck examination; and (in malocclusion cases) possible occlusal contact of the treated tooth to the opposing jaw (tooth or soft tissue).
VPT—The procedures were performed according to principles accepted in human dentistry,1,4 with a modification to accommodate the unique anatomy of canine teeth.2,3,11 All treatments were performed or supervised by a board certification–eligible (until 2004) or board-certified (from 2004 on) veterinary dentist. For CCF cases, a VPT was recommended mainly for recent fractures, with < 48 hours elapsing between pulp exposure and treatment. In patients with UCF or malocclusion, the VPT was performed immediately after pulp was exposed during treatment. In patients with UCF extending near to the pulp, VPT was performed when indirect pulp capping (ie, capping over a thin partition of remaining dentin) was not feasible to facilitate placement of the composite restoration. Vital pulp therapy was a treatment option only for dogs without concurrent systemic diseases (eg, heart failure or renal insufficiency).
The tooth to be treated was ultrasonically scaled and polished with fluoride-free pumice. A rubber dam and draping with sterile towels as well as sterile instruments and burs were used to maintain an aseptic endodontic field throughout the procedure.
Approximately 5 to 7 mm of the coronal pulp tissue was removed by use of a round diamond bur on a high-speed handpiece with distilled water cooling. The blunt end of a sterile paper point was moistened with saline (0.9% NaCl) solution, inserted into the canal, and pressed gently against the pulp tissue. Once hemostasis was achieved, a 2- to 3-mm-thick layer of Ca(OH)2 pastea or MTAb was placed over the exposed pulp tissue. A 1-mm intermediate layer of glass-ionomer restorativec was applied to cover the pulp dressing material. The remainder of the cavity was then acid-etched, bonded, and restored with a 2- to 4-mm layer of hybrid composite restoration material.d
Pain management for all patients included preoperative regional nerve block with lidocainee and postoperative administration of appropriate NSAIDs.f–h The use of antimicrobials varied: some dogs received ampicillini IV prior to surgery and a 10-day course of amoxicillin–clavulanic acidj after surgery; some only received ampicillini before surgery, and some did not receive any antimicrobials.
Follow-up evaluation—Intraoral dental radiographs were obtained before and immediately after the procedure and at every follow-up examination. Until 2008, radiographs were obtained with a dental radiography unit and standard size 2 and 4 dental radiographic films.k From 2008 forward, an indirect digital radiography technique was used with size 2 and 4 photostimulable phosphor imaging platesl and imaging software.m Additionally, the quality of the restoration (intact, rough, or damaged) and possible occlusal contact of the treated tooth to the opposite jaw (tooth or soft tissue) were evaluated clinically at every follow-up examination. All patients were scheduled to undergo follow-up examinations 3 and 12 months after the procedure and annually thereafter, but not all clients kept conscientiously to these schedules. For purposes of evaluation, the follow-up time was grouped as ≤ 3 months, 4 to 11 months, 12 to 24 months, and > 24 months.
Evaluation of outcome—Radiographs were evaluated independently by 3 observers (2 board-certified veterinary dentists [HKV and ESK] and 1 resident [NL]) with a standard dental x-ray film viewer and calibrated magnification loupen or imaging software.m Final evaluation of the criteria for success, NEF, and failure was made by consensus.
Treated teeth were evaluated for apical closure (where applicable), width of the pulp cavity, evidence of dentin bridge formation, apical periodontitis, and external and internal inflammatory resorption. Radiographic appearance of voids in the restoration was evaluated. Possible deep penetration of the dressing material into the pulp was noted.
Outcome was determined according to the guidelines for radiographic assessment of VPT established by the European Society of Endodontology,1 except for tertiary dentin bridge formation, which was not required for treatment to be categorized as successful. The treatment was considered successful if there was radiographic evidence of continued root formation (secondary dentin production and apical closure when applicable), absence of clinical and radiographic signs of apical periodontitis, and absence of internal or external root resorption.1 Although the presence of a tertiary dentin bridge was recorded, this was not required as an indicator of treatment success.12
The treatment was considered to have NEF if other signs for success were fulfilled except the width of the apical PDL, which could be wider but no greater than double the width of the PDL in other areas. In overall success rate evaluation, treatments in the NEF category were considered successful.
The treatment was considered to have failed if secondary dentin production had ceased, root formation in immature teeth was discontinued, or periapical lesion or root resorption had developed by the time of follow-up. Teeth with failed treatment either received standard root canal treatment or were extracted.
Statistical analysis—The outcome at the most recent follow-up examination (ie, the longest follow-up period) was recorded. Because some of the variables examined had a low number of observations, some factors were combined into categories for analysis. The diagnoses of UCF and malocclusion were combined into 1 category because in all of these cases, the VPT was performed immediately after surgical pulp exposure under aseptic conditions. All canine teeth were combined to 1 category, and mandibular first molar, maxillary fourth premolar, and incisor teeth were combined together as other teeth. There were many breeds in the study that had a very low number of observations; therefore, breed was excluded from all of the analyses. All dogs that received antimicrobial treatment (whether before or before and after surgery) were combined into 1 category.
The response variables assessed were follow-up time in months and success evaluation after the treatment. The differences between factors in the success, NEF, or failure variable were analyzed with mixed-effects multinomial logistic regression models. Each factor was first analyzed with a univariate model, with the factor in question as the sole fixed effect and dog as a random effect. Based on the results of the univariate analyses, a multivariate mixed-effects multinomial logistic regression model was constructed. The multivariate model, in which the multiple explanatory variables were modeled together, included only the significant (P < 0.050) factors of the univariate analyses. Odds ratios and their 95% CIs were used to quantify the results. Values of P < 0.050 were considered significant. The Shapiro-Wilk test of normality was used for evaluation of distributions; age, weight, follow-up time, and time from pulp exposure to treatment did not follow a normal distribution and were reported as median and range. All statistical analyses were performed with commercially available software.o
Results
Medical records of 177 dogs with 243 treated teeth were evaluated. Altogether, 138 (78%) dogs with 190 (73%) treated teeth had ≥ 1 follow-up evaluation and were included in the study.
The 138 dogs represented 73 breeds, of which ≥ 10 teeth were treated in German Shepherd Dogs (29 teeth), Staffordshire Bull Terriers (13 teeth), Bull Terriers (12 teeth), and Rottweilers (10 teeth). There were 51 (37%) female and 87 (63%) male dogs. Median body weight was 24 kg (52.8 lb; range, 3 to 64 kg [6.6 to 140.8 lb]). Median age at initial evaluation was 11 months (range, 5 to 98 months). The 190 treated teeth included 183 canine teeth, 3 mandibular first molar teeth, 3 third incisor teeth, and 1 maxillary fourth premolar tooth. Indications for VPT included malocclusion (151/190 [79%] teeth), CCF (33 [17%]), and UCF (6 [3%]). In cases of CCF, the time from pulp exposure to treatment ranged from 3 to 250 hours (median, 24 hours). Of these, 6 were treated > 48 hours after pulp exposure because of extenuating circumstances (long-distance travel, trauma occurring on a weekend, or hesitation of the primary care veterinarian to refer the patient for treatment). Of the 190 treated teeth, 36 (19%) received Ca(OH)2 and 149 (78%) received MTA as pulp dressing. Five (3%) of these teeth were treated with both Ca(OH)2 and MTA because of continuous intraoperative hemorrhage and were excluded from the material variable analysis.
The antimicrobial regimen in our clinic changed over time. All dogs that underwent VPT from 2001 through 2005 (25/138 [18%]) received ampicillin IV prior to the dental surgery with a 10-day course of systemic amoxicillin–clavulanic acidf prescribed after surgery. The 63 (46%) dogs that underwent VPT from 2006 to 2009 received ampicillin IV only prior to surgery. The 50 (36%) dogs in the study that had VPT after 2009 did not receive any antimicrobials before or after surgery. Follow-up time ranged from 1 to 109 months (median, 12 months), with follow-up periods of ≤ 3 months for 54 teeth, 4 to 11 months for 40 teeth, 12 to 23 months for 47 teeth, and ≥ 24 months for 49 teeth.
The outcome of VPT was classified as successful for 139 (73%) teeth, as having NEF for 23 (12%) teeth, and as having failed for 28 (15%) teeth (Figures 1–4). Most (11/28) treatment failures were diagnosed 12 to 23 months after surgery. Signalment-related, diagnostic, and treatment-related factors were summarized for teeth with various treatment outcomes (Table 1) and were examined on the basis of the 2 pulp dressing materials used (Table 2). The overall success rate of VPT when treatments with NEF were categorized as successful was 162 of 190 (85%).
Lateral (A) and occlusal (B) radiographic views obtained immediately after VPT with MTA and lateral (C) and occlusal (D) radiographic views obtained at follow-up for the same dog 4 months after treatment. The procedure was performed for treatment of a recent CCF of a right maxillary canine tooth in a 7-month-old Rottweiler and was deemed successful. In the follow-up images, notice the closure of the apex (black arrowheads), tertiary dentin bridge formation (white arrow), progressive narrowing of the pulp cavity, and absence of pathological periapical changes.
Citation: Journal of the American Veterinary Medical Association 244, 4; 10.2460/javma.244.4.449
Lateral (A) and occlusal (B) radiographic views obtained immediately after VPT with Ca(OH)2 and lateral (C) and occlusal (D) radiographic views obtained at follow-up for the same dog 21 months after treatment. The procedure was performed during crown reduction to treat malocclusion in a 7-month-old German Shepherd Dog and was classified as a treatment failure. In postoperative images, notice the deep penetration of Ca(OH)2 into the vital pulp (thick black arrows). In the follow-up images, notice tertiary dentin bridge formation (white arrows), well-defined periapical radiolucency (black arrowheads), and apical resorption (thin black arrows).
Citation: Journal of the American Veterinary Medical Association 244, 4; 10.2460/javma.244.4.449
Lateral (A) and occlusal (B) radiographic views obtained immediately after VPT with MTA and lateral (C) and occlusal (D) radiographic views obtained at follow-up for the same dog 3 months after treatment. The procedure was performed during crown reduction of the left mandibular canine tooth to treat malocclusion in a 12-month-old West Highland White Terrier and was classified as a treatment failure. Notice severe internal resorption (white arrowheads) in the follow-up images.
Citation: Journal of the American Veterinary Medical Association 244, 4; 10.2460/javma.244.4.449
Lateral (A) and occlusal (B) radiographic views obtained immediately after VPT with MTA and lateral (C) and occlusal (D) radiographic views obtained at follow-up for the same dog 12 months after treatment. The procedure was performed during crown reduction of the left mandibular canine tooth to treat malocclusion in an 11-month-old mixed-breed dog and was classified as having NEF. Notice the PDL space in the apical region (black arrowheads): the space is wider than but no more than double the width of the PDL space in other areas. Tertiary dentin bridge formation is evident.
Citation: Journal of the American Veterinary Medical Association 244, 4; 10.2460/javma.244.4.449
Signalment-related, diagnostic, and treatment-related variables examined for associations with treatment outcome for 190 teeth of 138 dogs that underwent VPT at a veterinary dental clinic between 2001 and 2011.
| Variable | Total No. of treated teeth | No. (%) successful | No. (%) with NEF | No. (%) failed |
|---|---|---|---|---|
| Diagnosis | ||||
| Malocclusion | 151 | 108 (71.5) | 20 (13.2) | 23 (15.2) |
| CCF | 33 | 25 (75.8) | 3 (9.1) | 5 (15.1) |
| UCF | 6 | 6 (100) | 0 | 0 |
| Material | ||||
| Ca(OH)2 | 36 | 17 (47.2) | 4 (11.1) | 15 (41.7) |
| MTA | 149 | 118 (79.2) | 19 (12.8) | 12 (8.0) |
| Mixed (excluded from the material variable analysis) | 5 | 4 (80) | 0 | 1 (20.0) |
| Deep penetration of dressing material* | ||||
| Yes | 24 | 13 (54.2) | 0 | 11 (45.8) |
| No | 166 | 126 (75.9) | 23 (13.9) | 17 (10.2) |
| Distinct intraoperative hemorrhage | ||||
| Yes | 28 | 15 (53.6) | 5 (17.9) | 8 (28.6) |
| No | 162 | 124 (76.5) | 18 (11.1) | 20 (12.4) |
| Antimicrobial treatment | ||||
| Before surgery | 86 | 58 (67.4) | 12 (14.0) | 16 (18.6) |
| Before and after surgery | 35 | 22 (62.9) | 4 (11.4) | 9 (25.7) |
| None | 69 | 59 (85.5) | 7 (10.1) | 3 (4.3) |
| Tooth type | ||||
| Canine | 183 | 134 (73.2) | 22 (12.0) | 27 (14.8) |
| Mandibular first molar | 3 | 2 (66.7) | 1 (33.3) | 0 |
| Maxillary third incisor | 3 | 3 (100.0) | 0 | 0 |
| Maxillary fourth premolar | 1 | 0 | 0 | 1 (100.0) |
| Tertiary dentin bridge formation | ||||
| Yes | 105 | 76 (72.4) | 15 (14.3) | 14 (13.3) |
| No | 85 | 63 (74.1) | 8 (9.4) | 14 (16.5) |
| Apex prior to surgery | ||||
| Open | 49 | 31 (63.3) | 8 (16.3) | 10 (20.4) |
| Closed | 141 | 108 (76.6) | 15 (10.6) | 18 (12.8) |
| Radiographic evidence of voids in restoration | ||||
| Yes | 85 | 59 (69.4) | 11 (12.9) | 15 (17.7) |
| No | 105 | 80 (76.2) | 12 (11.4) | 13 (12.4) |
| Clinical quality of restoration at last reported recheck evaluation | ||||
| Normal | 125 | 89 (71.2) | 14 (11.2) | 22 (17.6) |
| Rough | 43 | 36 (83.7) | 4 (9.3) | 3 (7.0) |
| Absent or damaged† | 22 | 14 (63.6) | 5 (22.8) | 3 (13.6) |
| Occlusal contact to soft tissue or opposing tooth | ||||
| Yes | 26 | 21 (80.8) | 1 (3.8) | 4 (15.4) |
| No | 164 | 118 (72.0) | 22 (13.4) | 24 (14.6) |
Treatment was categorized on the basis of results of the last recheck examination as successful (with radiographic evidence of continued secondary dentin production, continued root formation in immature teeth, and absence of clinical and radiographic signs of apical periodontitis and internal or external inflammatory root resorption), having NEF (with signs for success fulfilled except the width of the apical PDL space, which could be wider but no more than double the width of the PDL in other areas), or failed (with radiographic evidence of pulp necrosis, apical periodontitis, or inflammatory root resorption).
Indicates radiographic evidence of pulp dressing material extending into the vital pulp, rather than remaining approximate to the interface between the pulp and subsequent restoration.
The glass-ionomer restorative between the pulp dressing and composite restoration remained present in all treated teeth.
Distribution (No. [%]) of teeth that underwent VPT with Ca(OH)2 (n = 36) or MTA (149) used as pulp dressing material.
| Material | ||
|---|---|---|
| Variable | Ca(OH)2 | MTA |
| Diagnosis | ||
| Malocclusion | 34 (94.4) | 113 (75.9) |
| CCF | 2 (5.6) | 30 (20.1) |
| UCF | 0 | 6 (4,0) |
| Deep penetration of dressing material* | ||
| Yes | 8 (22.2) | 14 (9.4) |
| No | 28 (77.8) | 135 (90.6) |
| Distinct intraoperative hemorrhage | ||
| Yes | 7 (19.4) | 20 (13.4) |
| No | 29 (80.6) | 129 (86.6) |
| Antimicrobial therapy | ||
| Before surgery | 16 (44.4) | 66 (44.3) |
| Before and after surgery | 20 (55.6) | 14 (9.4) |
| None | 0 | 69 (46.3) |
| Tooth type | ||
| Canine | 36 (100) | 142 (95.3) |
| Mandibular first molar | 0 | 3 (2.0) |
| Maxillary third incisor | 0 | 3 (2.0) |
| Maxillary fourth premolar | 0 | 1 (0.7) |
| Tertiary dentin bridge formation | ||
| Yes | 28 (77.8) | 74 (49.6) |
| No | 8 (22.2) | 75 (50.4) |
| Apex prior to surgery | ||
| Open | 16 (44.4) | 31 (20.8) |
| Closed | 20 (55.6) | 118 (79.2) |
| Radiographic evidence of voids in restoration | ||
| Yes | 17 (47.2) | 68 (45.6) |
| No | 19 (52.8) | |
| Clinical quality of restoration at last reported recheck evaluation | ||
| Normal | 30 (83.3) | 91 (61.1) |
| Rough | 1 (2.8) | 42 (28.2) |
| Absent or damaged† | 5 (13.9) | 16 (10.7) |
| Occlusal contact to soft tissue or opposing tooth | ||
| Yes | 3 (8.3) | 23 (15.4) |
| No | 33 (91.7) | 126 (84.6) |
Five teeth treated with both Ca(OH)2 and MTA because of continuous intraoperative hemorrhage were excluded from material variable analysis.
See Table 1 for remainder of key.
Four variables were significantly associated with increased odds of failure in the univariate analysis: use of Ca(OH)2, compared with MTA (P < 0.001); deep penetration of the dressing material into the pulp (P < 0.001); distinct intraoperative hemorrhage (P = 0.027); and antimicrobial treatment (P = 0.008; Table 3). Analysis of patient age suggested that the younger the dog was, the greater the odds of treatment failure, but this did not meet criteria for significance (P = 0.064). Although the median age of dogs with deep penetration of the dressing material was 12 months (range, 6 to 67 months), the effect of increasing age on this variable was nonsignificant. Most of the failures in the Ca(OH)2 group (12/15) were diagnosed > 12 months after the VPT, whereas in the MTA group, 6 of 12 failures were diagnosed before this time point (range, 2 to 11 months) and the remaining 6 were diagnosed > 12 months after the procedure. The single treatment failure in a tooth that had both Ca(OH)2 and MTA applied was detected 11 months after the procedure. The odds of treatment failure did not differ significantly (P = 0.964) between teeth grouped according to diagnosis (malocclusion or UCF vs CCF), and within the CCF group, the time from pulp exposure to treatment (evaluated in 10-hour increments) was not significantly (P = 0.346) associated with outcome. Furthermore, there was no evidence that the formation of a tertiary dentin bridge was associated with treatment outcome. Other factors not significantly associated with outcome were sex and weight of the dog; tooth type; whether the apex was open or closed prior to VPT; radiographic appearance of small voids in the restoration immediately after treatment or clinically evaluated as rough, damaged, or missing restoration at the last follow-up examination; and occlusal contact of the treated tooth with another tooth or soft tissue (eg, a treated mandibular canine tooth contacting the maxillary canine tooth).
Results of univariate and multivariate analysis of factors potentially associated with increased odds of treatment failure in 190 teeth of 138 dogs that underwent VPT.
| Univariate model | Multivariate model | |||||
|---|---|---|---|---|---|---|
| Variable | OR | 95% CI | P value | OR | 95% CI | P value |
| Diagnosis of malocclusion or UCF (vs CCF) | 0.97 | 0.31–3.11 | 0.964 | NA | NA | NA |
| Time from pulp exposure to treatment (CCF only;10-h increase) | 0.77 | 0.43–1.35 | 0.346 | NA | NA | NA |
| Dressing with Ca(OH)2 (vs MTA) | 8.71 | 3.08–24.64 | < 0.001 | 6.69 | 1.94–23.12 | 0.003 |
| Deep penetration of dressing material* | 6.50 | 2.21–19.17 | < 0.001 | 5.66 | 1.58–20.58 | 0.009 |
| Effect of age (1-y increase) for deep penetration of dressing material | 0.88 | 0.41–1.88 | 0.734 | NA | NA | NA |
| Distinct intraoperative hemorrhage | 3.55 | 1.16–10.89 | 0.027 | 3.30 | 0.78–13.93 | 0.103 |
| Antimicrobial treatment | 5.85 | 1.59–21.54 | 0.008 | 2.44 | 0.54–10.92 | 0.243 |
| Age (1-y increase) | 0.66 | 0.42–1.03 | 0.064 | NA | NA | NA |
| Female sex (vs male) | 1.58 | 0.62–4.00 | 0.333 | NA | NA | NA |
| Weight | ||||||
| 1–10 kg (vs 11–24 kg) | 0.56 | 0.12–2.57 | 0.450 | NA | NA | NA |
| 1–10 kg (vs ≥ 25 kg) | 0.44 | 0.11–1.83 | 0.258 | NA | NA | NA |
| 11–24 kg (vs ≥ 25 kg) | 0.80 | 0.28–2.25 | 0.666 | NA | NA | NA |
| Tooth type (canine vs other) | 0.93 | 0.09–10.12 | 0.952 | NA | NA | NA |
| Formation of tertiary dentin bridge | 0.79 | 0.32–1.93 | 0.600 | NA | NA | NA |
| Open apex (vs closed) | 2.011 | 0.72–5.59 | 0.178 | NA | NA | NA |
| Radiographic evidence of small voids in restoration | 1.527 | 0.63–3.73 | 0.351 | NA | NA | NA |
| Clinical quality of restoration at last recheck evaluation (vs normal) | ||||||
| Rough | 0.363 | 0.09–1.40 | 0.140 | NA | NA | NA |
| Absent or damaged | 0.906 | 0.22–3.82 | 0.893 | NA | NA | NA |
| Occlusal contact to soft tissue or opposing tooth | 0.964 | 0.25–3.76 | 0.958 | NA | NA | NA |
NA = Not assessed because of nonsignificance in the univariate analyses.
See Table 1 for remainder of key.
When the significant variables in the univariate models (pulp dressing material, deep penetration of dressing material into the pulp, distinct intraoperative hemorrhage, and antimicrobial treatment) were evaluated in a combined multivariate model, only the pulp dressing material and deep penetration of dressing material into the pulp remained significant (Table 3). The use of Ca(OH)2 as pulp dressing was significantly (P = 0.003) associated with increased odds of failure, compared with the use of MTA, and deep penetration of the dressing material into the pulp also remained significant (P = 0.009). Distinct intraoperative hemorrhage (P = 0.103) and antimicrobial treatment (P = 0.243) were each nonsignificant in the multivariate model.
Discussion
The overall treatment success rate of VPT in the present study, including cases with NEF, was 162 of 190 (85%). The success rate with MTA was 137 of 149 (92%), whereas that with Ca(OH)2 was 21 of 36 (58%). Results of this study indicated that VPT with MTA was a viable option for treatment of pulp exposure whether it was a result of intentional crown height reduction or of a recent (median of 24 hours between exposure and treatment), spontaneous tooth fracture. This result is valuable in clinical decision making for the treatment of structurally and functionally important canine teeth, the extraction of which carries considerable risks, including iatrogenic jaw fracture, oronasal fistula, glossoptosis, and maxillary lip entrapment.13 Therefore, VPT can be considered a useful endodontic treatment in dogs, as is standard root canal treatment.4 The great advantage of VPT over standard root canal treatment is maintenance of tooth vitality, with continuous root formation and production of secondary dentin, which allow the tooth to become stronger and tolerate biting forces.14 Furthermore, compared with standard root canal therapy, which is a time-consuming, multistep procedure, VPT is quicker and easier to perform in our experience. It must be stressed that both root canal treatment and VPT require special clinical skills and are prone to technical errors. In our study, all treatments were performed or supervised by a board certification–eligible or board-certified veterinary dentist.
Investigators in earlier human studies15,16 concluded that an immature tooth treated with VPT must receive a standard root canal treatment as soon as the root has matured, but presently, VPT is considered a permanent treatment for both immature and mature teeth.17,18 This is in accordance with results of our study, in which the overall success rate of VPT with MTA (137/149 [92%]) was similar to the success rate of standard root canal treatment. In a previous study,19 our group found a very high overall success rate of standard root canal treatment in dogs (120/127 [94%]) when cases with NEF were included as successful treatments. In the veterinary literature, there are 2 published reports20,21 of retrospective clinical studies evaluating the success of VPT with Ca(OH)2 in dogs. Clarke20 reported a 36-month follow-up period for treatment of 97 mature canine teeth with CCF. On the basis of results of radiographic examinations, 30 of 34 (88.2%), 12 of 29 (41.4%), and 8 of 34 (23.5%) teeth were vital when treated within 48 hours, 1 week, and 3 weeks after pulp exposure, respectively. Another study by Niemiec21 included VPT as a treatment of both intentional crown-height reductions in malocclusions (n = 54) and spontaneous CCFs (9) of 57 canine teeth in dogs and 6 canine teeth in cats. Only 32 teeth in 20 patients had radiographic follow-up of 6 months to 72 months (mean, 23 months). Treatment in all malocclusion cases (28/28 [100%]) was successful, but treatment in all 4 CCF cases failed. In all CCF cases, the time between pulp exposure and treatment was > 168 hours.
In our study, interestingly, there was no evidence that the time from pulp exposure to treatment in CCF cases would increase the odds of failure. However, this result has to be interpreted with caution because the number of teeth with CCF in the study was fairly low (33/190 [17%]). Furthermore, for CCF cases, we initially recommended a VPT only for recent fractures with treatment performed < 48 hours after pulp exposure, and the median was 24 hours (range, 3 to 250 hours). However, there were 6 cases in which the treatment was delayed beyond 48 hours because of long-distance travel, trauma occurring on a weekend, or hesitation of the primary care veterinarian to refer the patient for treatment.
The most extreme treatment delay was for a 7-month-old military dog (from a distant facility) that was treated 250 hours after a traumatic pulp exposure. In this situation, the handler was informed that the prognosis after treatment would be questionable and was required to commit to regular radiographic recheck examinations. At the last available follow-up examination 42 months after surgery, results indicated that the treatment was successful.
In humans, the most common indication for VPT is debridement of a deep carious lesion. In instances of trauma, according to Cvek and Lundberg,18 inflammation extends no more than 2 mm in depth during the first 48 hours after pulp exposure. After this time, inflammation progresses apically and the likelihood of maintaining a healthy pulp decreases. In humans, reported success rates of VPT (with coronal pulp tissue removed to the level of healthy pulp) after a recent CCF are as high as 59 of 63 (94%) to 30 of 30 (100%) when Ca(OH)2 is used,17,22,23 and similar success rates have been reported following MTA use (2/2 and 6/6).6,24 However, long-term clinical studies with large populations comparing the success rates of VPT with MTA and Ca(OH)2 after recent CCF are lacking.
The previous veterinary studies by Clarke20 and Niemiec21 included only canine teeth. In our study, the VPT with MTA was also performed in 3 mandibular first molar teeth, 1 maxillary fourth premolar tooth, and 3 maxillary third incisor teeth. Although treatment of the maxillary fourth premolar tooth failed, treatment for the other 6 teeth, with a median follow-up time of 6 months, was successful (including 1 with NEF). This suggests that VPT is also a valid treatment option for multirooted teeth in a dog. However, further studies with a longer follow-up time and larger population are needed.
Our results confirmed that the pulp dressing material in VPT plays an important role in treatment outcome. Odds of failure for treatment with Ca(OH)2 were > 8 times that for treatment with MTA (P = 0.003), and the overall failure rate for VPT with Ca(OH)2 was > 5-fold that with MTA (15/36 [42%] vs 12/149 [8%]). Several studies25,26 in humans have shown similar results. Reported success rates for use of Ca(OH)2 range from 20 of 38 (53%) to 58 of 60 (97%),17,22,27 whereas studies6,24,28,29 available on MTA have consistently indicated success rates ranging from 18 of 19 to 15 of 15.
During the past 10 years, several studies4,30–32 of the mechanism of action of MTA have shown that, compared with Ca(OH)2, MTA has superior biocompatibility because it does not result in the production of a necrotic cell layer between the material and healthy pulp. The tertiary dentin bridge formed after MTA use is of higher quality than that formed after treatment with Ca(OH)2 and does not dissolve over time, thus creating an excellent bacteria-tight seal, which is one of the most critical factors for a successful treatment.9 In humans, long-term clinical studies33,34 with Ca(OH)2-based pulp dressing materials have shown that failure rates increase with longer follow-up times, and in our study, most (12/15) VPT failures in teeth treated with Ca(OH)2 dressing were diagnosed > 12 months after surgery. Because Ca(OH)2 powder is not commercially available in Finland, Ca(OH)2 paste was used instead.
In our study, a tertiary dentin bridge was detected in radiographs of 28 of 36 (78%) and 74 of 149 (50%) teeth treated with Ca(OH)2 and MTA, respectively. Formation of a tertiary dentin bridge was not significantly associated with increased or decreased odds of treatment failure. In previous studies35,36 in humans, detection of the tertiary dentin bridge on radiographs has been a criterion for success, but some speculate that it is no more than a form of scar tissue and can also be produced by irreversibly damaged pulp.12 It is agreed that formation of a tertiary dentin bridge does not necessarily prevent pulp inflammation or necrosis and may allow microleakage of bacteria through tubules and tunnels.9 Therefore, the quality of the composite restoration and an additional intermediate basec between pulp dressing and composite are crucial success factors.4
Deep penetration of the dressing material into the vital pulp (rather than remaining at the interface between the pulp and subsequent restoration) was significantly associated with increased odds of VPT failure. Clinically, the penetration often appeared to be related to inappropriate blood clot development during the treatment, especially in young dogs with the exposure of pulp at the level where the pulp cavity widens acutely. An early study by Cvek17 found that if blood clotting does not develop, the prognosis of the treatment will be compromised. In our study, however, a distinct intraoperative hemorrhage was associated with increased odds of failure only in the univariate model. Deep penetration with Ca(OH)2 was 2.4 times as frequent as when MTA was used. The median age of the dogs that had this finding was 12 months (range, 6 to 67 months), but statistically, there was no evidence that older age would protect against its occurrence. In addition to anatomic causes, penetration of the dressing material to unintended depths can be attributable to technical errors and physical properties of the dressing material, considering that the Ca(OH)2 paste is more flowable than MTA.
The fact that antimicrobial treatment was associated with increased odds of VPT failure in the univariate model can be explained by the correlation of the variables. From 2009 forward, the patients did not receive antimicrobials before or after dental surgery. All 36 (100%) treatments of teeth with Ca(OH)2 and only 80 of 149 (54%) treatments of teeth with MTA were performed in dogs that received antimicrobials. Therefore, the high treatment failure rate for teeth treated with Ca(OH)2 affected these results. Antimicrobial treatment was not significantly associated with outcome in the multivariate model. Nevertheless, this confirms that VPT alone does not necessitate antimicrobial treatment.
In human dentistry, clinical signs such as absence of pain and normal response to a pulp sensitivity test are important components in assessment of the treatment success,1 but in dogs, these are often impossible to interpret. Therefore, radiographic criteria were considered as the most reliable diagnostic method in this study. To increase the reliability of diagnosis, all radiographs were individually evaluated by 3 skilled veterinarians.37
Obtaining radiographs of consistent quality is often challenging.38 In all cases, the contralateral tooth was radiographed for purposes of comparison, and in all canine teeth, 2 views (occlusal and lateral) were obtained to help achieve an accurate diagnosis. Because of the 2-D projection of a complex anatomy that includes compact and trabecular bone and soft tissues, the periapical area of canine teeth is often challenging to evaluate.38 Therefore, an outcome category of NEF was created for this study. Teeth with NEF included those in which other signs for success were fulfilled except the width of the apical PDL space, which could be wider than, but no more than double the width of, the PDL in other areas. It is important to understand that teeth with NEF did not have periapical lesions. Another typical challenge in radiographic evaluation of canine teeth is the chevron lucency in which the contour of the alveolus extends but the PDL space and lamina dura remain visible and in close approximation to the root. The chevron lucency is considered a normal variation.38
The skills of the veterinarian play an important role in the outcome of VPT, and proper training in the technique is essential. In the present study all treatments were performed or supervised by a board certification-eligible or board-certified veterinary dentist.
In our study 85 of 190 (45%) treated teeth had small radiographic voids in the superficial composite restoration, in many cases consistent with the radiolucent bonding agent. Presence of these superficial voids was not associated with the outcome of the VPT. The intermediate glass-ionomer restorative between the pulp dressing and composite restoration was intact in all treated teeth. During the last available recheck evaluation, the composite restoration was damaged or absent in 22 of 190 (12%) teeth and rough in 43 (23%). To our surprise, and contrary to results reported in humans by Ray and Trope,39 the quality of the restoration was not significantly associated with the outcome. The overall treatment success rate of the teeth with rough restoration was 40 of 43 (93%), and that for teeth with absent or damaged restoration was 19 of 22 (86%). This result also has to be interpreted with caution because the number of teeth with restoration abnormalities was relatively low, and it remains important to evaluate the restoration at the time of radiographic recheck evaluation.
The recall rate (proportion of dogs that returned for ≥ 1 recheck examination) was much higher in the present study (138/177 [78%]) than that reported in the previously mentioned study19 of root canal treatment in dogs (64/222 [29%]). This is likely attributable to the fact that for dogs that underwent VPT, an automatic letter recall system had been instituted from the very beginning of the study. Although most (11/28) treatment failures were diagnosed 12 to 23 months after surgery, 10 occurred before 12 months and 7 were detected later than 23 months. This is in accordance with studies5,40–42 in humans, in which both early and late failures were detected. According to guidelines for dentistry in humans, teeth treated by means of VPT should be assessed no later than 6 months after surgery1 It is thus reasonable to recall veterinary patients for radiographic follow-up examinations as early as 3 months after VPT, and then repeat the evaluation at 12 months and annually thereafter.
Results of our study indicate that MTA is superior to Ca(OH)2 as a pulp dressing in VPT. Vital pulp therapy with MTA was an effective option for crown reduction to treat malocclusion and for the treatment of recent crown fractures in immature or mature permanent teeth. Our results also suggest that VPT can compete with a standard root canal treatment as a first-line treatment for a recent CCF. Nevertheless, further studies with longer follow-up time and larger population are needed for evaluation of VPT as a treatment of recent CCF.
ABBREVIATIONS
| CCF | Complicated crown fracture |
| CI | Confidence interval |
| MTA | Mineral trioxide aggregate |
| NEF | No evidence of failure |
| PDL | Periodontal ligament |
| UCF | Uncomplicated crown fracture |
| VPT | Vital pulp therapy |
Ultracal, Ultradent Products Inc, South Jordan, Utah.
MTA ProRoot, Dentsply, Tulsa Dental Specialities, Tulsa, Okla.
Fuji II Capsule, GC America, Tokyo, Japan.
Z100 Restorative, shade A2, 3M ESPE, Saint Paul, Minn.
Lidocain 20 mg/mL, Orion Corp, Espoo, Finland.
Rimadyl 50 mg/mL, Pfizer Animal Health SA, Louvain-la-Neuve, Belgium.
Metacam 5 mg/mL, Labiana Life Sciences SA, Terrassa, Spain.
Loxicom, Norbrook Laboratories Ltd, Newry, Northern Ireland.
A-pen, Orion Pharma, Espoo Corp, Finland.
Synulox, Pfizer Oy Animal Health, Helsinki, Finland.
Kodak Ultra-Speed, Eastman Kodak Inc, Rochester, NY.
Dürr Dental Image Plate, Dürr Dental AG, Bietigheim-Bissingen, Germany.
Planmeca Dimaxis, version 4.0, Planmeca USA, Roselle, NJ.
Peak Scale Loupe 7x, Peak Optics, GWJ Company, Hacienda Heights, Calif.
SAS for Windows, version 9.3, SAS Institute Inc, Cary, NC.
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