A Retrospective Analysis of the Need for the Root Canal Therapy for the Full Crown Restorations: An Original Study

ABSTRACT

Introduction:

There are numerous chances for pulpal irritation during the placement of a crown on a tooth. This study’s goal was to find and examine the variables that influence the prevalence of routine root canal therapy after the teeth were restored with full coverage crowns.

Methods:

The hospital records were retrospectively evaluated from 2000 to 2010 for a decade. The demographics as well as the various variables that caused for the intervention with the root canal therapy for the teeth with the full crowns were evaluated. The values were compared for the significance.

Results:

The total number of the teeth that were finalized in the study was 4308. Of the total teeth that were treated with full coverage crowns, 50% were metal ceramic, 42% were full ceramic, and 9% were full metal crowns. After 10 years, possibility that every tooth with a crown would survive was 91%. The most frequent adverse incident was the intervention with the RCT. Metal ceramic crowns had poor survival rates and needed the maximum intervention. Younger age-group had least survival rate than the older age-groups.

Conclusions:

Endodontic therapy is unlikely to be necessary after crown installation. As the patient’s age declines and all-ceramic or PFM crowns are used, this risk rises.

INTRODUCTION

The full coverage crowns are prescribed in multiple clinical conditions. The reasons may range from caries, aesthetics, root canal therapy, trauma, rehabilitations, etc., Crown placement is now a common treatment for dentists, and a lot of research and development has gone into making this process quicker, more convenient for the patient, and with more reliable results. However, there are numerous potential for pulpal irritation during the processes used in the placement of the crown. This chiseling of the protective layers of the enamel and the dentine will expose the tooth interiors for the invasion of the pathogens.[1-5]

Poorly fitted provisional crowns may make this issue worse because they can leave tubules exposed. This process may take time and may sometime years. High-speed hand-pieces that generate excessive heat have the potential to permanently harm pulp tissue. The health of the pulp can also be impacted by additional irritants such desiccation, cements, or marginal leakage.[6-10] Furthermore, pulpitis is frequently exacerbated by preexisting problems that are present in teeth having crown treatments. These include cracks, old restorative treatments, and dental cavities. Sometimes the pulpal damage may be seen as early as even in the temporary crown placement. Previous research points out to the fact that the crown placement may eventually lead to the need for the root canal therapy. The average time proposed was after a period of ten years, and the percentage that might need the therapy was 8–9% of the crowned teeth. However, these studies had a smaller follow-up and also the lesser number of the subjects.[11-15] The present study offers a practical assessment of the care given in a private practice setting and makes use of a large sample size to provide significant findings. To forecast individual tooth survival rates following full-coverage restorations, these claims were examined. To identify predictors for unfavorable outcomes, variables that may have impacted were evaluated.

MATERIAL AND METHODS

The study conducted was a retrospective uncontrolled observational study. The patients who attended the tertiary care dental hospital for the period of 10 years between 200 and 2010 were evaluated in the study. Ethics clearance was attained for the study. The patients’ consent was not taken since the nature of the study was retrospective. The hospital records were analyzed for the all the patients who were adults and had undergone the full coverage crowns on the teeth. The pediatric patients and the patients with any medical condition were not considered for the present study. The patients who had the full crowns on the teeth that were not root canal treated were included for the study. Both the genders and all the adult age-groups were considered in the study.

The type of crown being used, the patient’s age, the placement of the tooth, etc., were noted. According to their ages, patients were separated into six groups: <30, between 30 and 39, between 40 and 49, between 50 and 59, between 60 and 69, and those above 70. The demographics were considered for the study as well as the period elapsed from the restoration, type of restoration, failure type, and the treatments. The RCT-treated teeth along with the restoration that was placed before the fracture were considered in this study. The other fractured teeth that were not restored endodontically were excluded for the study. A final of nearly 5000 teeth were included that fit the selection criteria and hence were subjected to the analysis.

Analytical statistics

All variables underwent descriptive analysis that included mean and standard deviation. The observations were represented as frequencies and percentages. These values were analyzed using the Chi-square test. For the descriptive analysis, the central tendency and dispersion indices were displayed using the relevant charts and tables. Using SPSS 23, the P < 0.05 was taken as significant.

RESULTS

The total number of the teeth that were finalized in the study were 4308. Among them, the mean age was observed to be 52 ± 12 years. The gender distribution was male: female = 1.75:1.2. The treatment was done by specialists and the general dentists as well. The most common reason to seek the root canal therapy was pain and the trauma. All-ceramic crowns (42%) or PFM crowns (50%) made up the great majority of the implants. Only 9% of all crowns put were full metal crowns. The majority getting crowns ranged in age from 51 to 70. Premolars came in second with 21 percent of the crowns placed on teeth, followed by anterior teeth with 5%. Nine percent teeth needed intervention with the root canal therapy.

The primary root canal therapy accounted for 75% of the unfavorable events that occurred to the teeth. Only 7% of all unfavorable events involved apicoectomies and 50% root canal retreatments; the remaining 25% involved extractions for the metal ceramic crowns. Table 1 lists every incident that was not expected in relation to the patient’s age and crown material. There was a significant variation for the three types of the full coverage crowns that had to be treated with extraction, RCT, and surgical therapies. The age minimum that was considered was less than 30, and the maximum was 81 years in this study. We observed a great variation between the age-groups (p < 0.01) [Table 1].

Table 1.

Comparison of the material of the crown and the age-groups for the type of the intervention

Variable	Total (n)	Removed	RCT	Surgical	P
Type of the crown
Complete metal	401	33%	63%	4%	0.001*
All ceramic	1202	14%	81%	5%
PFM	2705	25%	74%	7%
Age-groups
Below 30 years	120	16%	83%	14%	0.001*
30-39	450	17%	81%	9%
40-49	950	18%	81%	7%
50-59	1560	22%	78%	5%
60-69	1102	29%	71%	4%
70 and above	250	42%	57%	4%

Greater hazard ratios indicate that one variable is more likely than another to result in an undesirable occurrence. The three types of the materials that were used in the study are all ceramic, full metal, and metal ceramic. The significant variation was noted between the metal ceramic crowns compared than the other all-ceramic and the full metal crowns. The age range of 51–60 years old was chosen as a reference range while evaluating patient age. The hazard rates were all considerably greater for the age-groups from 30 to under, between 30 and 39, between 40 and 49, between 50 and 59, between 60 and 69, and those above 70. Compared to the group of patients aged 50–59, the group of patients aged 60–69 had significantly reduced hazard rates. When the age-groups 50–59 years and 70 years and older were compared, there was no discernible difference in the hazard rates. Plots were made to show survival rates in relation to variables such material of the crown and the age-groups [Figure 1]. Regarding age-groups, tooth location, and crown material, significant variations in survival rates were seen (p < 0.001). It was evident that the greater variation for the younger age-group was seen, i.e., <30 years. 50–70-year subjects had the maximum tooth survival while the younger age-groups showed lesser survival.

Figure 1.

Comparison of the restoration material and the age-groups for the survival rate

DISCUSSION

This study’s main goal was to determine the factors that might lead to the root canal therapy after the teeth are given the full coverage crowns. Over one-fourth of the teeth that were evaluated in total had to be extracted in this study for the metal ceramic crowns. A retrospective insurance-based study makes it impossible to standardize providers and comprehend the justification for treatment. The same tooth may be extracted in favor of an implant even while others may do RCT. This is the first extensive study aimed at determining factors influencing the risk of RCT following crown installation. Nine percent of the crowned teeth experienced a negative incident. The 10-year survival estimate is 91%. Despite different inclusion criteria and follow-up lengths, this value is comparable to earlier studies.[11-17] Similar follow-up studies by Cheung et al.[11] on single-unit metal ceramic crowns over a period of 6 months to 14 years revealed that 16% needed RCT at recall. According to that study, the odds of survival were assessed to be 82% at the end of 15 years.

Three categories—full ceramic, metal, and the metal ceramic—were used to categorize the analysis of crown materials. The preparations as well as the indication for the placement of these material full coverage crowns are very different. In the all-ceramic crowns, the amount of the tooth lost may be different than that of metal crowns. All ceramic materials are preferred in the anterior crowns. Only 9% of all crowns put were full metal crowns. PFM crowns made up 50% of all crowns, while all-ceramic crowns made up the remaining 42%. This is probably due to the rise in demand for cosmetic dentistry. The hazard ratio of these materials differed significantly, according to Cox regression analysis. PFM crowns have a roughly 27% greater risk rate compared to full metal, and all ceramic have a roughly 9% greater risk rate. It is interesting to note that this danger ratio rises if more tooth structure is removed than is recommended. In contrast, a prior comprehensive review by Goodacre et al.[13] found that all-ceramic crowns saw decreased rates of failure.

When the age-groups were compared while very few patients under the age of 30 and above the age of 71 had crowns installed, nearly half who had crowns were between the ages of 50 and 69. Patients 71 and older were more likely to undergo crown extraction as an unfavorable occurrence. This is probably due to the greater chance of nonrestorable teeth due to the higher caries rate, more number of restorations, and greater fracture, in elderly populations.[18] Despite having the lowest rates of crown installation among all age-groups, patients under 30 had the highest rates of failure following crown implantation. Overall, the Cox regression depicted that younger ages had a higher likelihood of failure comparatively. This pattern could have a variety of causes. Due to less secondary dentin being deposited, younger people the preparation exposes more inner pulp chamber than the older age people who have the protection of the secondary and tertiary dentine.[19] This study supports the relation between the young pulp and the abuse faced during the tooth preparation which may lead to pulpal damage. Previous research by Kirakozova and Caplan17 revealed that receiving a root canal treatment after receiving full-coverage restorations was significantly predicted by younger age and more severe tooth damage.

The results of the current investigation supported these conclusions; however, tooth destruction could not be assessed because radiographs were not available. This study’s main goal was to pinpoint the elements that influence pulpal health after crown implantation. Overall, these results indicate that pulpal pathology likely plays a significant role in retaining dentin thickness after crown treatments because risk rates rise with younger ages and with crown materials that demand deeper preparations. To better comprehend the connections between the variables covered in this study and those that cannot be tracked in the retrospective hospital records, more research is required. In particular, a broad-based prospective study that takes into account pulpal health and the various other factors that affect it is suggested.

CONCLUSION

With a predicted survival rate of 91% after 10 years, the rate of unfavorable occurrences following crown placement was minimal within the parameters and restrictions of this study. The survival rate is inversely proportional to the age when the crown is delivered as well as dependent on the metal ceramic and the full ceramic crown placement. These results imply that the amount of dentin that is still present when operating significantly affects the risk of undesirable events occurring after the crown has been placed. Further prospective randomized studies are suggested.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.