Keywords cracked teeth - characteristics - treatment - prognosis - probing depth - symptoms
- apical lesion
Introduction
Since cracked teeth syndrome was first described by Cameron,[1 ] many authors have proposed different terms and definitions for cracks in teeth.
The American Association of Endodontics has identified five types of longitudinal
tooth fractures in teeth, including craze line, fractured cusp, cracked tooth, split
tooth, and vertical root fracture.[2 ] Cracked tooth is defined as an incomplete fracture that initiates from the crown
and extends subgingivally, usually directed mesiodistally.[2 ]
The symptoms of cracked teeth can vary considerably depending on the length of the
crack and the severity of pulp inflammation,[3 ]
[4 ] which may occur as a result of microleakage-induced irritation and lead to thermal
sensitivity.[5 ]
[6 ] Although the most common symptom of cracked teeth is discomfort during chewing,
sensitivity to cold with no other explanation also occurs frequently.[7 ] Because it is difficult to locate crack lines and cracked teeth have complex and
wide-ranging symptoms, this condition is difficult to diagnose in clinical trials.
Moreover, predicting the prognosis of a cracked tooth is difficult due to the lack
of a definitive method of establishing how far the crack has progressed.[8 ]
[9 ] It was reported that the likelihood of success decreased as pulpal involvement increased
(85% for teeth with irreversible pulpitis, 80% for necrotic teeth, and 74% for previously
treated teeth).[5 ]
[9 ]
[10 ] The difficulty of predicting the prognosis of cracked teeth, including whether extraction
will be necessary, poses a dilemma for clinicians.[5 ]
[11 ] Thus, there is a need to identify cracked teeth-related factors that may provide
useful information for treatment planning and predicting patients’ prognosis. This
study compared data over the past 10 years to analyze changes in the treatment method
of cracked teeth and to reconfirm the factors that influence the prognosis. Specifically,
this study analyzed the characteristics, treatment process, and prognosis of cracked
teeth based on a comparison of recent data with data from 10 years ago.
Materials and Methods
Ethical Considerations
The protocol for this study was approved by the Institutional Review Board of Seoul
St. Mary’s Dental Hospital, The Catholic University of Korea, Seoul, Korea (KC20RISI0187).
Data Collection Procedure
Records on 476 crown-restored teeth from March 2009 to June 2010 (2009 data) and 1,913
crown-restored teeth from March 2019 to June 2020 (2019 data) from the Department
of Conservative Dentistry at Seoul St Mary's Dental Hospital were screened and evaluated.
Dental records were reviewed by two endodontists, and the following inclusion and
exclusion criteria were applied:
Patient whose diagnosis were recorded as cracked teeth were selected.
It was confirmed that the diagnostic procedure included a bite test and crack line
visualization.
Teeth with a craze line, cusp fracture, or split were excluded.
Teeth with incomplete clinical records were excluded.
A retrospective study was conducted of 68 cracked teeth from 2009 and 185 from 2019.
At the 3-month follow-up time point, 45 teeth from 2009 and 180 teeth from 2019 were
analyzed, and the 6-month follow-up data included 29 teeth treated in 2009 and 50
teeth treated in 2019. The decrease in the number of teeth at each follow-up time
point occurred because some patients were lost to follow-up.
The cracked teeth were diagnosed by a bite test using a cotton roll and wood stick,
and the periodontal probing depth corresponding to the crack was analyzed. Examination
by the naked eye, transillumination, staining with methylene blue dye, and microscopy
were also performed to diagnose the crack. Tooth hypersensitivity was determined using
an ice stick and a thermal pulp tester (Frigi-Dent; Ellman international Inc., Oceanside,
New York, United States). If it showed no response, we verified it again using an
electric pulp tester (Digitest; Parkell Inc., Farmingdale, New York, United States).
Periapical radiographs were taken to confirm apical changes.
Diagnoses were verified during the treatment process. General and pretreatment data
of the cracked teeth were collected from patients’ clinical records. Age and sex,
the location of the tooth, the presence of a restoration, restoration type and the
filling material, the presence of cervical abrasion, the presence of caries, number
of crack lines, ice test results, bite test results, percussion test results, and
periodontal pocket depth were noted. If patients showed bite pain or cold sensitivity,
cracked teeth were classified as symptomatic.
Cracked teeth were managed following the treatment protocol shown in [Fig. 1 ]. If a cracked tooth was diagnosed as symptomatic irreversible pulpitis or as pulp
necrosis, root canal treatment was performed.
Fig. 1 The different treatment protocols according to pulpal and periapical diagnosis of
cracked teeth.
At 3- and 6-month follow-up examinations, signs and symptoms were recorded, including
bite pain, percussion, cold sensitivity, sinus tract, swelling, and periodontal pocket
associated with the crack. A periodontal pocket was defined as a periodontal probing
depth over 4 mm.
Cracked teeth-related factors were analyzed and compared between the samples of 2009
and 2019. Furthermore, comparative analyses were conducted of treatment procedures
according to pocket depth and presence or absence of caries and symptoms and of prognosis
according to pocket depth and presence or absence of an apical lesion in the samples
of 2009 and 2019.
Statistical Analysis
The results were analyzed using R version 3.3.3 (R Founda-tion for Statistical Computing,
Vienna, Austria) and T&F version 3.0 (YooJin BioSoft, Korea). Data were expressed
as number and percentage. To compare proportions in the samples of 2009 and 2019,
the two-sample proportion test was performed. The distribution of proportions within
the samples from 2009 and 2019 data was analyzed using the Chi-square test or binomial
test. A p -value < 0.05 was considered to indicate statistical significance.
Results
This study analyzed 68 cracked teeth from 2009 and 185 from 2019. The incidence rate
of cracked teeth was 14.3% (68/476) in 2009 and 9.7% (185/1913) in 2019. The incidence
rate in 2009 was significantly higher than in 2019 (p = 0.004; two-sample proportion test).
Factors associated with cracked teeth are presented in [Table 1 ]. The mandibular first molars were most commonly involved (33.8%) in 2009, and the
mandibular second molars (28.1%) were most commonly involved in 2019. The incidence
rate of cracked teeth in mandibular second molars in 2019 was significantly higher
than in 2009. Cracked teeth exhibited a single crack line more frequently in 2019
(70.8%) than in 2009 (p < 0.001).
Table 1
Associations between various factors and cracked teeth in 2009 and 2019
Variable
Subgroup
Year: 2009
(N = 68)
p -Value (1)
Year: 2019
(N = 185)
p -Value (2)
p -Value (3)
Note: Data were expressed as number and percentage. Distribution of sample ratios
among each subgroup within the data from 2009 or 2019 was analyzed using the Chi-square
test, yielding p -value (1) and p -value (2). To compare sample ratios between the data from 2009 and 2019, the two-sample
proportion test was performed, yielding p -value (3). A p -value <0.05 was considered to indicate statistical significance.
Sample no.
N = 68
N = 185
Location of tooth
<0.001
<0.001
Mandibular first molar
23 (33.8)
42 (22.7)
0.103
Mandibular first premolar
2 (2.9)
2 (1.1)
0.629
Mandibular second molar
5 (7.4)
52 (28.1)
<0.001
Mandibular second premolar
1 (1.5)
5 (2.7)
0.916
Maxillary first molar
12 (17.6)
38 (20.5)
0.738
Maxillary first premolar
10 (14.7)
6 (3.2)
0.002
Maxillary second molar
7 (10.3)
31 (16.8)
0.281
Maxillary second premolar
8 (11.8)
9 (4.9)
0.097
Age, years
<0.001
<0.001
20–29
12 (17.6)
4 (2.2)
<0.001
30–39
5 (7.4)
27 (14.6)
0.186
40–49
11 (16.2)
40 (21.6)
0.435
50–59
21 (30.9)
51 (27.6)
0.718
60–69
18 (26.5)
41 (22.2)
0.582
≥70
1 (1.5)
22 (11.9)
0.021
Sex
0.628
0.023
F
36 (52.9)
108 (58.4)
0.528
M
32 (47.1)
77 (41.6)
0.528
Type of restorative material
<0.001
<0.001
Cl 1 Amalgam.
8 (11.8)
19 (10.3)
0.911
Cl 1 Ceramic inlay
0 (0)
3 (1.6)
0.688
Cl 1 Gold inlay
11 (16.2)
44 (23.8)
0.259
Cl 1 Resin
4 (5.9)
16 (8.6)
0.645
Cl 2 Amalgam.
4 (5.9)
2 (1.1)
0.079
Cl 2 Ceramic inlay
0 (0)
2 (1.1)
0.952
Cl 2 Gold inlay
3 (4.4)
15 (8.1)
0.460
Crown
2 (2.9)
11 (5.9)
0.523
No restoration
35 (51.5)
68 (36.8)
0.049
Temporary filling
1 (1.5)
5 (2.7)
0.916
Cervical abrasion
<0.001
<0.001
Present
3 (4.4)
15 (8.1)
0.460
Absent
65 (95.6)
170 (91.9)
0.460
Caries
0.015
<0.001
Present
24 (35.3)
42 (22.7)
0.063
Absent
44 (64.7)
143 (77.3)
0.063
Crack line
0.002
<0.001
1
21 (30.9)
131 (70.8)
<0.001
>2
47 (69.1)
54 (29.2)
<0.001
Cracked teeth were mainly treated by a permanent crown after a provisional crown (prov
→ Cr), a permanent crown after root canal treatment and provisional crown (RCT and
prov → Cr), and root canal treatment after a permanent crown (prov → Cr → RCT). The
distribution is presented in [Table 2 ]. In 2009, cracked teeth were mainly treated with RCT and prov → Cr (52.9%). In 2019,
cracked teeth were mainly treated with prov → Cr (55.4%). The proportion of teeth
treated with RCT and prov → Cr showed a significant decrease (p = 0.032) in 2019 compared with 2009.
Table 2
Distribution of treatment strategies for managing cracked teeth
2009
N = 68
2019
N = 184
p -Value
F
M
Total N (%)
F
M
Total N (%)
Abbreviations: Cr, permanent crown; Prov, provisional crown; RCT, root canal treatment.
Note: To compare total sample ratios between the data of 2009 and 2019, the two-sample
proportion test was performed. A p -value <0.05 was considered to indicate statistical significance.
Prov → Cr
16
13
29 (42.6)
62
40
102 (55.4)
0.097
Prov → Cr → RCT
2
1
3 (4.4)
6
8
14 (7.6)
0.538
Prov and RCT → Cr
18
18
36 (52.9)
39
29
68 (37)
0.032
The treatment protocols for cracked teeth according to periodontal probing depth in
2009 and 2019 are presented in [Table 3 ]. In both 2009 and 2019, a deeper periodontal probing depth was associated with a
higher likelihood of root canal treatment and a lower likelihood of treatment with
prov → Cr, but there was no significant difference in the treatment method.
Table 3
Different treatment protocols for cracked teeth according to the periodontal probing
depth
Year
PPD
Total N
Prov → Cr
Prov → Cr → RCT
Prov and RCT → Cr
Abbreviations: Cr, permanent crown; PPD, periodontal probing depth; Prov, provisional
crown; RCT, root canal treatment.
Note: p -Values were computed using the two-sample proportion test to analyze differences
in sample proportions among the PPD subgroups. p -Value [1]: between <3 and 4–6 mm. p -Value [2]: between <3 and >6 mm. p -Value [3]: between 4–6 and >6 mm. A p -value <0.05 was considered to indicate statistical significance.
2009
<3 mm
40 (100)
20 (50)
3 (7.5)
17 (42.5)
4–6 mm
25 (100)
9 (36)
0 (0)
16 (64)
>6 mm
3 (100)
0 (0)
0 (0)
3 (100)
Total
68 (100)
29 (42.6)
3 (4.4)
36 (52.9)
p -Value [1]
0.396
0.427
0.152
p -Value [2]
0.283
1.000
0.185
p -Value [3]
0.544
–
0.544
2019
<3 mm
117 (100)
68 (58.1)
10 (8.5)
39 (33.3)
4–6 mm
53 (100)
28 (52.8)
4 (7.5)
21 (39.6)
>6 mm
14 (100)
6 (42.9)
0 (0)
8 (57.1)
Total
184 (100)
102 (55.4)
14 (7.6)
68 (37)
p -Value [1]
0.633
1.000
0.534
p -Value [2]
0.422
0.545
0.144
p -Value [3]
0.716
0.670
0.382
2009+2019
<3 mm
157 (100)
88 (56.1)
13 (8.3)
56 (35.7)
4–6 mm
78 (100)
37 (47.4)
4 (5.1)
37 (47.4)
>6 mm
17 (100)
6 (35.3)
0 (0)
11 (64.7)
Total
252 (100)
131 (52)
17 (6.7)
104 (41.3)
p -Value [1]
0.268
0.541
0.111
p -Value [2]
0.169
0.455
0.038
p -Value [3]
0.521
0.774
0.306
[Table 4 ] presents the treatment protocols for cracked teeth depending on the presence or
absence of symptoms and caries in 2009 and 2019. In both years, symptomatic cracked
teeth were significantly more likely to receive root canal treatment than asymptomatic
cracked teeth (75%, p = 0.005 in 2009; 61.8%, p < 0.001 in 2019). In both 2009 and 2019, asymptomatic cracked teeth were significantly
more likely to receive prov → Cr than symptomatic cracked teeth (55%, p = 0.027 in 2009; 75.9%, p < 0.001 in 2019).
Table 4
Different treatment protocols for cracked teeth according to the presence of symptoms
or caries
Year
Caries
Symptoms
Caries
Total N
Prov → Cr
Prov → Cr→ RCT
RCT and prov → Cr
Total N
Prov → Cr
Prov → Cr →RCT
RCT and prov → Cr
Abbreviations: Cr, permanent crown; Prov, provisional crown; RCT, root canal treatment.
Note: p -Values were computed to compare sample ratios between O and X using the two-sample
proportion test. A p -value <0.05 was considered to indicate statistical significance.
2009
O
24
10 (41.7)
0 (0)
14 (58.3)
28
7 (25)
0 (0)
21 (75)
X
44
19 (43.2)
3 (6.8)
22 (50)
40
22 (55)
3 (7.5)
15 (37.5)
Total
68
29 (42.6)
3 (4.4)
36 (52.9)
68
29 (42.6)
3 (4.4)
36 (52.9)
p -Value
1.000
0.490
0.686
0.027
0.378
0.005
2019
O
41
24 (58.5)
3 (7.3)
14 (34.1)
76
20 (26.3)
9 (11.8)
47 (61.8)
X
143
78 (54.5)
11 (7.7)
54 (37.8)
108
82 (75.9)
5 (4.6)
21 (19.4)
Total
184
102 (55.4)
14 (7.6)
68 (37)
184
102 (55.4)
14 (7.6)
68 (37)
p -Value
0.783
1.000
0.811
<0.001
0.125
<0.001
2009+2019
O
65
34 (52.3)
3 (4.6)
28 (43.1)
104
27 (26)
9 (8.7)
68 (65.4)
X
187
97 (51.9)
14 (7.5)
76 (40.6)
148
104 (70.3)
8 (5.4)
36 (24.3)
Total
252
131 (52)
17 (6.7)
104 (41.3)
252
131 (52)
17 (6.7)
104 (41.3)
p -Value
1.000
0.611
0.844
<0.001
0.449
<0.001
The prognosis of cracked teeth according to the periodontal probing depth at 3 and
6 months after treatment in 2009 and 2019 is presented in [Table 5 ]. At 3 and 6 months of follow-up, both in 2009 and 2019, teeth with a deep periodontal
pocket (>6 mm) did not show a significant difference in terms of whether symptoms
disappeared. In contrast, symptoms were significantly more likely to disappear in
teeth with a mild or moderate periodontal probing depth (<3 mm, 4–6 mm). At 6-month
follow-up, in 2019, the proportion of teeth with a deep periodontal pocket (>6 mm)
in which symptoms disappeared was higher than that at the 3-month follow-up (71.4%
at 3 months, 85.7% at 6 months).
Table 5
Prognosis of cracked teeth according to the probing depth at 3 and 6 mo after treatment
3 mo
6 mo
Year
PPD
Total N
Free
Persisted
Ext
p -Value
Total N
Free
Persisted
Ext
p -Value
Abbreviation: PPD, periodontal probing depth.
Note: p -Values were computed to compare sample ratio difference between free and persisted
according to PPD using the binomial test. A p -value <0.05 was considered to indicate statistical significance.
2009
<3
26
22 (84.6)
4 (15.4)
0 (0)
<0.001
16
14 (87.5)
2 (12.5)
0 (0)
0.004
4–6
16
15 (93.8)
1 (6.2)
0 (0)
<0.001
11
11 (100)
0 (0)
0 (0)
<0.001
>6
3
0 (0)
3 (100)
0 (0)
0.250
2
0 (0)
2 (100)
0 (0)
0.500
Total
45
37 (82.2)
8 (17.8)
0 (0)
<0.001
29
25 (86.2)
4 (13.8)
0 (0)
<0.001
2019
<3
113
110 (97.3)
3 (2.7)
0 (0)
<0.001
28
25 (89.3)
3 (10.7)
0 (0)
<0.001
4–6
53
41 (77.4)
12 (22.6)
0 (0)
<0.001
15
12 (80)
3 (20)
0 (0)
0.035
>6
14
10 (71.4)
4 (28.6)
0 (0)
0.180
7
6 (85.7)
1 (14.3)
0 (0)
0.125
Total
180
161 (89.4)
19 (10.6)
0 (0)
<0.001
50
43 (86)
7 (14)
0 (0)
<0.001
2009+2019
<3
139
132 (95)
7 (5)
0 (0)
<0.001
44
39 (88.6)
5 (11.4)
0 (0)
<0.001
4–6
69
56 (81.2)
13 (18.8)
0 (0)
<0.001
26
23 (88.5)
3 (11.5)
0 (0)
<0.001
>6
17
10 (58.8)
7 (41.2)
0 (0)
0.629
9
6 (66.7)
3 (33.3)
0 (0)
0.508
Total
225
198 (88)
27 (12)
0 (0)
<0.001
79
68 (86.1)
11 (13.9)
0 (0)
<0.001
The prognosis of cracked teeth depending on the presence of an apical lesion at 3
and 6 months after treatment in 2009 and 2019 is presented in [Table 6 ]. At both time points in both years, teeth without an apical lesion in the initial
examination were significantly more likely to show symptom disappearance than symptom
persistence (p < 0.001).
Table 6
Prognosis of cracked teeth according to the presence of an apical lesion at 3 and
6 mo after treatment
3 mo
6 mo
Year
Apical lesion
Total N
Free
Persisted
Ext
p -Value
Total N
Free
Persisted
Ext
p -Value
Note: p -Values were computed to compare sample ratio difference between free and persisted
according to apical lesion using the binomial test. A p -value <0.05 was considered to indicate statistical significance.
2009
O
6
5 (83.3)
1 (16.7)
0 (0)
0.219
4
4 (100)
0 (0)
0 (0)
0.125
X
39
32 (82.1)
7 (17.9)
0 (0)
<0.001
25
21 (84)
4 (16)
0 (0)
<0.001
Total
45
37 (82.2)
8 (17.8)
0 (0)
<0.001
29
25 (86.2)
4 (13.8)
0 (0)
<0.001
2019
O
25
19 (76)
6 (24)
0 (0)
0.015
11
9 (81.8)
2 (18.2)
0 (0)
0.065
X
155
142 (91.6)
13 (8.4)
0 (0)
<0.001
39
34 (87.2)
5 (12.8)
0 (0)
<0.001
Total
180
161 (89.4)
19 (10.6)
0 (0)
<0.001
50
43 (86)
7 (14)
0 (0)
<0.001
2009+2019
O
31
24 (77.4)
7 (22.6)
0 (0)
0.003
15
13 (86.7)
2 (13.3)
0 (0)
0.007
X
194
174 (89.7)
20 (10.3)
0 (0)
<0.001
64
55 (85.9)
9 (14.1)
0 (0)
<0.001
Total
225
198 (88)
27 (12)
0 (0)
<0.001
79
68 (86.1)
11 (13.9)
0 (0)
<0.001
The survival rate of the teeth from 2019 at the 1-year follow-up was 100%. Of the
teeth treated in 2009, three teeth were extracted (at 2 years and 1 month, 2 years
and 10 months, and 10 years and 5 months), corresponding to a survival rate of 95%.
Discussion
In this study, changes in the characteristics, treatment methods, and prognosis of
cracked teeth were analyzed by comparing data of 2009 and 2019. Several studies have
been conducted on cracked teeth, but this is the first study to compare data of 10
years ago to recent data.
The incidence of cracked teeth was lower in 2019 (9.7%) than in 2009 (14.3%). A recent
study reported an incidence rate of 8.9%, similar to that in 2019.[12 ] One reason for this difference may be that the study in 2019 was conducted with
a larger sample. Another reason may be that the referral rate of cracked teeth to
tertiary medical institutions was lower in 2019 than in 2009 because of improvements
in general dentists’ understanding of cracked teeth over the course of this 10-year
period. Generally, the characteristics of cracked teeth in this study were not significantly
different from those previously reported in the literature. In both years, similar
results were found for factors related to age, sex, and the presence of an old restoration,
cervical abrasion, or caries, while different results were found regarding the location
of cracked teeth and crack lines.
In 2019, the incidence rate of cracked tooth was significantly higher in mandibular
second molars than it was in 2009. Cracked teeth have been reported to be most prevalent
in mandibular molars,[1 ]
[4 ]
[12 ]
[13 ]
[14 ] maxillary premolars,[7 ]
[15 ] maxillary molars,[16 ] and maxillary first molars.[14 ]
[17 ] In recent studies,[12 ]
[13 ]
[18 ] cracked teeth were reported to be the most prevalent in the mandibular second molars.
This tendency may be due to the location of these teeth near the temporomandibular
joint,[19 ] where the lever effect may cause relatively high masticatory forces to be exerted
on teeth. The lingual cusps of maxillary molars have been suggested to play the role
of plungers, causing structural fatigue in the lower antagonists.[20 ]
[21 ]
In 2019, the prevalence of cracked teeth with a single crack line was significantly
higher than that in 2009, similar to the results of recent studies.[14 ] The results regarding the characteristics of cracked teeth in 2019 were more similar
to those of recent studies than the results from 2009. This is thought to be due to
an increase in the number of patients and an increase in the accuracy of diagnoses
of cracked teeth in 2019.
A prior study found cracks to occur more frequently in heavily restored teeth.[7 ] However, recent studies have found a high incidence of cracks in unrestored teeth
or teeth with class I restorations.[12 ]
[14 ]
[16 ] Similarly, in this study, the highest proportion of cracks (51.5% in 2009, 36.8%
in 2019) was found in intact teeth or in teeth with class I restorations.
Cracked teeth occurred more often in intact teeth than in carious teeth (95.6% in
2009, 91.9% in 2019). According to previous research, the weakening of tooth structures
due to large restorations does not increase the incidence of cracked teeth; instead,
cracks in intact teeth progress due to internal structural weaknesses present where
masticatory forces are exerted upon calcification sites, with additional contributions
made by parafunctional habits.[15 ]
[19 ]
[20 ]
[22 ] Furthermore, it can be concluded that caries-induced weakening of tooth structures
does not increase the incidence of cracked teeth.
In cracked teeth, loss of pulp vitality may predict an unfavorable prognosis, as the
2-year survival rate of cracked teeth that received endodontic treatment was reported
to be only 85.5%.[9 ] Therefore, detecting cracked teeth early and reducing the likelihood of root canal
treatment can increase the long-term success rate. When comparing the treatment strategies
used for cracked teeth in 2009 and 2019, RCT and prov → Cr was significantly less
common in 2019 (37%) than in 2009 (52.9%). The lower frequency of root canal treatment
in 2019 was likely due to an increase in early detection of cracked teeth, which resulted
from an improved understanding of the characteristics of cracked teeth and the more
precise diagnosis of cracked teeth.
In this study, we investigated whether the rate of root canal treatment was higher
in cracked teeth with caries. In both 2009 and 2019, no correlation was observed between
the presence of caries in the initial examination and the treatment method of cracked
teeth.
The most common symptom of cracked teeth is chewing-associated discomfort; however,
sensitivity to cold without an alternative explanation is also a frequent symptom.[7 ] The location and extent of the crack, as well as the presence of periapical disease
and the condition of the pulp, affect the symptoms of cracked teeth.[18 ]
[23 ] In this study, we examined whether the treatment method was different between symptomatic
and asymptomatic cracked teeth. In both 2009 and 2019, symptomatic cracked teeth were
more likely to be treated with RCT and prov → Cr. A previous study found that cracked
teeth with severe sensitivity to cold were more likely to receive root canal treatment.[14 ] A probable explanation for this finding is that symptomatic cracked teeth are more
likely to have an inflamed pulp.
Unfavorable prognoses have been reported for cracked teeth with a probing depth exceeding
4 mm, and the likelihood of requiring root canal treatment becomes higher as the probing
depth increases.[9 ]
[12 ]
[14 ] The presence of a deep periodontal pocket implies that a crack may progress more
deeply into the root, undermining the support provided by the periodontium.[5 ]
[9 ]
[24 ] The results of this study also showed that the rate of root canal treatment increased
as the periodontal probing depth became deeper in both 2009 and 2019. Furthermore,
it is reasonable to predict that deeper periodontal pockets are associated with more
severe crack progression. Microleakage from the crack line can also increase pulp
inflammation.[5 ] A probing depth of >6 mm was associated with a higher likelihood of persistent symptoms
at 3 and 6 months.
It has been reported that success decreased with increasing pulpal involvement and
that the success rate of cracked teeth with apical lesions was lower than that of
cracked teeth without apical lesions.[9 ]
[10 ] Because of variability in outcomes, extraction has been recommended for cracked
teeth with necrotic pulp.[5 ] In this study, in both 2009 and 2019, cracked teeth in which an apical lesion was
observed in the initial examination showed a relatively high rate of persistent symptoms
at 3-month follow-up. Thus, observing an apical lesion in the initial examination
may have implications for a short-term poor prognosis, and a long-term follow-up study
is needed to predict the success rate of cracked teeth with apical lesions.
Limitations of this study include the small number of patients in 2009 and the short
follow-up period in 2019. Further studies involving larger samples of patients with
long-term follow-up are required.
Conclusion
Through a comparison of data on cracked teeth obtained at an interval of 10 years,
we found that the rate of root canal treatment was lower in 2019 to 2020 than it was
10 years ago. Furthermore, probing depth was the most important factor for determining
the prognosis of cracked teeth both in 2009–2010 and in 2019–2020.
