Analysis of factors associated with cracked teeth

Pulp Survival of Cracked Teeth with Reversible Pulpitis after Orthodontic Banding and Coronal Coverage - a Prospective Cohort Study with One Year Follow Up

INTRODUCTION

The aim of this prospective study was to investigate the 1-year pulp survival of cracked teeth with reversible pulpitis managed with initial stabilization using orthodontic bands, followed by coronal coverage restorations.

METHODS

One-hundred-and-twenty-five patients with a cracked tooth with reversible pulpitis each were recruited. Pre-operative patient and tooth data were collected. After definitive pulp diagnoses were determined following an interim period of orthodontic banding, coronal coverage restorations were placed. Cox and logistic regression analyses were used to assess possible prognostic factors and to correlate initial time to pulp stabilization while in orthodontic bands with eventual outcome. Pulp survival was determined using both clinical and radiographic findings.

RESULTS

One-hundred-and-six cracked teeth were followed up at 1 year. Pulp survival based on clinical and radiographic findings was found in 81 teeth (76.4%). Out of 25 failures, 11 (44%) required root canal treatment (RCT) in the orthodontic band stage and 10 (40%) required RCT during the process of or after coronal coverage restorations. Four teeth (16%) had incidental findings of periapical radiolucencies at the one-year review without clinical symptoms. Teeth requiring RCT were found to have required longer periods in orthodontic bands prior to a definitive pulp diagnosis (p<0.05).

CONCLUSION

A step-by-step approach by using orthodontic banding to monitor pulp status may reduce the incidence of RCT required through definitive coronal coverage restorations for cracked teeth with reversible pulpitis.

The treatment outcomes of cracked teeth: A systematic review and meta-analysis

OBJECTIVES

The aim of this review was to analyze the clinical treatment outcomes of cracked teeth (CT) retaining vital dental pulp (CT-VDP) or undergoing root canal treatment (CT-RCT).

SOURCES

A systematic search was conducted in Medline, Embase, PubMed, and Cochrane Library databases.

STUDY SELECTION

Studies evaluating tooth survival rate (TSR), pulp survival rate (PSR), and success rate (SR) with at least a one-year follow-up were included. The risk of bias was evaluated with the Newcastle-Ottawa scale.

DATA

Twenty-seven studies underwent qualitative analysis, 26 of which were included in the meta-analysis. SR of monitoring without restorative treatments was 80 % at three years. TSR of CT-VDP was 92.8-97.8 % at 1‒6 years, PSR of CT-VDP was 85.6‒90.4 % at 1‒3 years, and SR of CT-VDP was 80.6‒89.9 % at 1‒3 years; TSR of CT-RCT was 90.5‒91.1 % at 1‒2 years, and SR of CT-RCT was 83.0‒91.2 % at 1‒4 years. Direct restorations without cuspal coverage for CT-VDP increased the risk ratio (RR) of pulpal complications (RR=3.2, 95 % CI: 1.51-6.82, p = 0.002) and tooth extraction (RR=8.1, 95 % CI: 1.05-62.5, p = 0.045) compared with full-crown restorations. The CT-RCT without full-crown restorations had an 11.3-fold higher risk of tooth extraction than the CT-RCT with full-crown restorations (p < 0.001).

CONCLUSIONS

Monitoring without restorative treatments might be an option for the CT without any symptoms. Direct restorations without cuspal coverage for the CT-VDP could significantly increase the RR of pulpal complications and tooth extraction compared with full-crown restorations. Full-crown restorations are strongly recommended for the CT-RCT.

CLINICAL SIGNIFICANCE

Monitoring without restorative treatments could be a viable option for the CT without any symptoms. Full-crown restorations are strongly recommended for the CT with any symptoms and the CT-RCT.

Survivability of endodontically treated cracked tooth: A systematic review

BACKGROUND

Literature evidence describes various treatment protocols that have been employed for the effectiveness in improving survival and addressing associated symptoms of cracked teeth.

OBJECTIVE

This systematic review investigates the survivability of endodontically treated cracked teeth and associated assessments, focusing on various treatment protocols.

METHODS

The PRISMA guidelines were utilised for guiding the article selection framework of this review. A comprehensive search of relevant literature was conducted in May 2023 across various databases, and studies meeting the inclusion criteria were selected. Data extraction, guided by a standardized form, captured crucial details, including study characteristics, treatment protocols, and treatment outcomes, enhancing the consistency and accuracy of information collection. Data extraction and synthesis was done by two reviewers independently. The Newcastle Ottawa tool was used to measure the methodological quality of the study. Six observational studies were eventually included.

RESULTS

Mandibular molars are particularly prone to developing cracks, with research indicating a heightened susceptibility to this dental issue. Studies reveal that endodontically treated cracked teeth boast robust overall survival rates ranging from 75.8% to 100%. The risk of bias assessment, utilizing the Newcastle Ottawa scale, indicated a moderate risk across studies, highlighting the necessity for careful interpretation of findings.

CONCLUSION

Endodontically treated cracked teeth show marked success in survival, with the incorporation of crowns post-endodontic treatment significantly enhancing longevity and resilience.

Fracture behavior of short fiber-reinforced CAD/CAM inlay restorations after cyclic fatigue aging

The aim of this study was to assess the fracture behavior of molar teeth restored with MOD inlays made of experimental short fiber-reinforced CAD/CAM composite block (SFRC CAD) before and after cyclic fatigue aging. Standardized MOD cavities were prepared on 60 intact mandibular molars. Three groups of CAD/CAM made inlay restorations (Cerasmart 270, Enamic, and SFRC CAD) were fabricated (n = 20/group). All restorations were luted with self-adhesive dual-cure resin cement (G-Cem One). Half of restored teeth per each group (n = 10) were quasi-statically loaded until fracture without aging. The other half underwent cyclic fatigue aging for 500,000 cycles (Fmax = 150 N) before being loaded quasi-statically until fracture. Then, the fracture type was visually inspected. The microstructure and elemental content of CAD/CAM materials were assessed using SEM and EDS. Two-way analysis of variance (ANOVA) was used to statistically examine the data, and it was followed by the Tukey HSD test (α = 0.05). ANOVA demonstrated that both material type and aging had a significant effect (p < 0.05) on the load-bearing capacity values of the restorations. Teeth restored with SFRC CAD showed significantly the highest (p < 0.05) load-bearing capacity (2535 ± 830 N) after fatigue aging among all groups. SEM images showed the ability of short fibers in SFRC CAD composite to redirect and hinder crack propagation. With regard to fracture mode, Enamic group revealed 85% of catastrophic failure (vs. 45% and 10% for Cerasmart 270 and SFRC CAD, respectively). Large MOD cavities on molar teeth were most favorably restored with SFRC CAD inlays, yielding the highest load-bearing capacity and more restorable failures.

A narrative review of cracks in teeth: Aetiology, microstructure and diagnostic challenges

OBJECTIVES

To summarize the available evidence of crack formation in teeth and to discuss the limitations of the current clinical diagnostic modalities for crack detection in teeth.

BACKGROUND

Cracks are a common clinical finding in teeth and yet clinicians still struggle to identify the full extent and orientation of cracks for their appropriate timely management. The biomechanics of crack development can be due to multiple factors and can differ from an unrestored tooth to a restored or endodontically treated tooth.

DATA & SOURCES

This narrative review has been designed following the guidelines published by Green et al. 2006 [1] Published literature in the English language that addresses the objectives of this review up to July 2022 was sourced from online databases and reference lists. The relevance of the papers was assessed and discussed by two reviewers. A total of 101 publications were included in this narrative review.

CONCLUSIONS

The initiation and development of cracks in teeth are likely linked to an interplay between the masticatory forces and fracture resistance of the remaining tooth structure. From the identified literature, the quality and quantity of remaining tooth structure in a restored or endodontically-treated tooth affects the biomechanics of crack development compared to an unrestored tooth. The extent, orientation, and size of the cracks do affect a clinician's ability to detect cracks in teeth. There is still a need to develop reliable diagnostic tools that will accurately identify cracks in teeth beneath restorations to enable effective monitoring of their propagation and provide appropriate interventions.

CLINICAL SIGNIFICANCE

The development and propagation of cracks in an unrestored tooth differ greatly from a restored and endodontically treated tooth; mainly linked to the quantity and quality of the remaining tooth structure and the forces acting on them. Identifying the extent of cracks in teeth remains challenging for early clinical intervention.

Biting and thermal sensitivity relief of cracked tooth restored by occlusal veneer: A 12-to 24 months prospective clinical study

OBJECTIVES

To analyze the relief time and risk factors of biting/thermal sensitivity in cracked tooth (CT) restored using occlusal veneer.

METHODS

63 CT were analyzed, and their demographic and clinical data and medical history were collected. Patients were followed-up to examine the relief of thermal/biting sensitivity.

RESULTS

The maxillary first molar was the most prevalent (N = 25, 40%). The number of crack lines on the finish line ranged from 1 to 6 while the number of crack lines through preparation on the finish line from 0 to 4. Pain relief achieved steadily to 52% for thermal and 62% for biting at 1 week to over 90% for each by 3 months and was completely resolved (no pain) for each by 12 months. Painful of lateral percussion was related to a long period of thermal sensitivity (≥1 month) after restoration with occlusal veneer. The number of crack lines through preparation on the finish line >2 was correlated with biting sensitivity (≥1 month) post-treatment.

CONCLUSIONS

Most patients (>90%) became asymptomatic of biting and thermal sensitivity within 3 months of CT restored by occlusal veneer. Lateral percussion and the number of crack lines through preparation on the finish line could be significant factors affecting postoperative symptoms.

CLINICAL SIGNIFICANCE

Occlusal veneer is an ultrathin restoration and had no need for restricting clinical crown height, which could protect and relief the biting/thermal sensitivity of CT without preventive root canal therapy.

CBCT in contemporary endodontics

Cone-beam computed tomography (CBCT) is a three-dimensional imaging modality which can aid endodontic diagnosis and treatment planning. While there are guidelines available describing the indications, there are divergent philosophies on when this technology should be applied in clinical practice. This paper reviews the applications of CBCT including the clinical relevance of parameters which can be assessed, highlights the limitations of this technology, and provides guidance on how to maximise its clinical utility.

Fatigue performance of endodontically treated molars reinforced with different fiber systems

OBJECTIVE

The aim was to investigate the fatigue performance of root canal-treated (RCT) molars restored with different direct restorations utilizing discontinuous and continuous fiber-reinforced composite (FRC) systems. The impact of direct cuspal coverage was also evaluated.

MATERIALS AND METHODS

One hundred and twenty intact third molars extracted for periodontal or orthodontic reasons were randomly divided into six groups (n=20). Standardized MOD, regular cavities for direct restorations were prepared in all specimens, and subsequently, root canal treatment and root canal obturation was carried out. After the endodontic treatment, the cavities were restored with different fiber-reinforced direct restorations as follows: SFC group (control), discontinuous short fiber-reinforced composite (SFC) without cuspal coverage (CC); SFC+CC group, SFC with cuspal coverage; PFRC group, transcoronal fixation with continuous polyethylene fibers without CC; PFRC+CC group, transcoronal fixation with continuous polyethylene fibers with CC; GFRC group, continuous glass FRC post without CC; and GFRC+CC, continuous glass FRC post with CC. All specimens underwent a fatigue survival test in a cyclic loading machine until fracture occurred or 40,000 cycles were completed. The Kaplan-Meier survival analysis was conducted, followed by pairwise log-rank post hoc comparisons between the individual groups (Mantel-Cox).

RESULTS

The PFRC+CC group was characterized by significantly higher survival compared to all the groups (p < 0.05), except for the control group (p = 0.317). In contrast, the GFRC group showed significantly lower survival compared to all the groups (p < 0.05), except for the SFC+CC group (p = 0.118). The control group (SFC) showed statistically higher survival than the SFRC+CC group (p < 0.05) and GFRC group (p < 0.05), but it did not differ significantly from the rest of the groups in terms of survival.

CONCLUSIONS

Direct restorations utilizing continuous FRC systems (in the form of polyethylene fibers or FRC post) to restore RCT molar MOD cavities performed better in terms of fatigue resistance when CC was performed compared to the same FRC restorations without CC. On the contrary, teeth restored with SFC restorations performed better without CC compared to the ones where SFC was covered.

CLINICAL RELEVANCE

In the case of fiber-reinforced direct restorations for MOD cavities in RCT molars, direct CC is recommended when utilizing long continuous fibers for reinforcement, however, should be avoided when only SFC is used for their reinforcement.

Crack propensity of different direct restorative procedures in deep MOD cavities

OBJECTIVE

The purpose was to evaluate the crack formation associated with different direct restorative procedures of the utilized resin composites (RC) right after and 1 week later of the restoration.

MATERIALS AND METHODS

Eighty intact, crack-free third molars with standard MOD cavities were included in this in vitro study and randomly divided into four groups of 20 each. After adhesive treatment, the cavities were restored either with bulk (group 1) or layered (group 2) short-fiber-reinforced resin composites (SFRC); bulk-fill RC (group 3); and layered conventional RC (control). Right after the polymerization and a week later, crack evaluation on the outer surface of the remaining cavity walls was performed with a transillumination method utilizing the D-Light Pro (GC Europe) with the "detection mode." Between- and within-groups comparisons Kruskal-Wallis and Wilcoxon tests were used, respectively.

RESULTS

Post-polymerization crack evaluation showed significantly lower crack formation in SFRC groups compared to the control (p<0.001). There was no significant difference within SFRC groups and non-SFRC groups (p=1.00 and p=0.11, respectively). Within group comparison revealed significantly higher number of cracks in all groups after 1 week (p≤0.001), however, only the control group differed significantly from all the other groups (p≤0.003).

CONCLUSIONS

Post-polymerization shrinkage induced further crack formation in the tooth 1 week after the restoration. SFRC was less prone to shrinkage-related crack formation during the restorative procedure; however, after 1 week, besides SFRC, bulk-fill RC also showed less prone to polymerization shrinkage-related crack formation than layered composite fillings.

CLINICAL RELEVANCE

SRFC can decrease the shrinkage stress-induced crack formation in MOD cavities.

The Effect of Different Intermediary Layer Materials Under Resin Composite Restorations on Volumetric Cuspal Deflection, Gap Formation, and Fracture Strength

This study investigated the effect of different intermediary layer materials under class II mesio-occluso-distal (MOD) resin composite restorations on volumetric cuspal deflection, gap formation, and fracture strength. In total, 32 sound human maxillary premolars were used. After large, standardized Class II MOD cavities were prepared, a universal adhesive (Clearfil Universal Bond Quick, Kuraray) was applied. The premolars were randomly allocated into four groups according to different intermediary layer materials (n=8): Group Z250 (control)/micro-hybrid composite (Filtek Z250, 3M ESPE); Group EST/low-viscosity bulk-fill resin composite (Estelite Bulk Fill Flow, Tokuyama Dental Corp) + micro-hybrid composite; Group NOV/nanofiber-reinforced low-viscosity composite (NovaPro Flow, Nanova) + micro-hybrid composite; and Group RIB/polyethylene fiber [Ribbond, Ribbond Inc] + micro-hybrid composite. Distilled water was used for storage for 24 hours. Using microcomputed tomography (micro-CT), the teeth were scanned immediately after cavity preparation (T0), then 24 hours after restorative procedures (T1). Volumetric cuspal deflection in cubic millimeters (mm3) was analyzed on the palatal and buccal regions of each restoration individually at T0 and T1 scans. Gap formation (mm3) was evaluated to quantify the volume of black spaces at the tooth-resin interface on the T1 scan. After these scans, using a universal testing machine, the teeth were subjected to a fracture strength test (0.5 millimeters/minute [mm/min]). The fracture surfaces were analyzed with a stereomicroscope. The data were analyzed using the Kruskal-Wallis, one-way analysis of variance (ANOVA), and Dunn's tests (p< 0.05). No significant differences in volumetric cuspal deflection and fracture strength were detected for all tested groups (p>0.05). Group RIB exhibited significantly higher gap formation values in comparison with all other groups (p<0.05). Predominant failure mode was favorable.

Diagnosis of cracked tooth: Clinical status and research progress

Cracked tooth is a common dental hard tissue disease.The involvement of cracks directly affects the selection of treatment and restoration of the affected teeth.It is helpful to choose more appropriate treatment options and evaluate the prognosis of the affected tooth accurately to determine the actual involvement of the crack.However, it is often difficult to accurately and quantitatively assess the scope of cracks at present.So it is necessary to find a real method of early quantitative and non-destructive crack detection.This article reviews the current clinical detection methods and research progress of cracked tooth in order to provide a reference for finding a clinical detection method for cracked tooth.

The 3-year cumulative survival rates of posterior monolithic zirconia crowns and their antagonist teeth, and their influencing factors

PURPOSE

The purpose of this study was to evaluate the 3-year cumulative survival rates of posterior single monolithic zirconia crowns (MZCs) and their antagonists, and to analyze the influencing factors.

METHODS

The clinical outcomes of posterior single MZCs and their abutment teeth with antagonists, and the antagonists between April 2014 and September 2020 were evaluated retrospectively. The 3-year cumulative survival rates were calculated and associations between the survival time and predictor variables ("Jaw", "Tooth", and "Pulpal condition") were also verified using Cox proportional hazards models and hazard ratios (HRs).

RESULTS

The 3-year cumulative survival rate of single MZCs was 89.8% (9 of 177 MZCs, 95% confidence interval (CI): 80.0-95.1%). Cox proportional hazards models showed non-vital teeth were significantly associated with failure (HR: 2.76e + 9, P = 0.012). The 3-year cumulative survival rate of antagonists was 94.8% (7 of 171 antagonists, 95% CI: 89.3-97.6%). Non-vital antagonists were also identified as an independent predictor for failure in Cox proportional hazards models (HR: 7.83, P = 0.03).

CONCLUSION

Although posterior single MZCs were clinically acceptable, non-vital pulpal condition could be a potential risk factor for failures in the abutment and antagonist teeth of MZCs.

Characteristics of Cracked teeth with Reversible Pulpitis after Orthodontic Banding - a Prospective Cohort Study

INTRODUCTION

Cracked teeth with reversible pulpitis can be managed with orthodontic bands in the interim before definitive restorations. The aim of this study was to determine short-term outcomes of these teeth following orthodontic band placement. The time taken for definitive pulp diagnoses after orthodontic band placement and associated prognostic factors was also analyzed.

METHODS

One hundred and twenty-five patients with a cracked tooth with reversible pulpitis each were recruited. Pre-operative data including patient and tooth factors were collected. Cracked teeth were banded and reviewed until symptoms resolved before referral for coronal coverage. Kaplan-Meier and Cox analyses were performed to analyze pulp survival of these teeth. Prognostic factors were investigated using Pearson's Chi-Square and Student's T-Test.

RESULTS

One hundred and twenty-two cracked teeth were analyzed. One hundred and thirteen (92.6%) teeth had the pulpitis resolved within two months (Median 40.0; IQR 28-61). The median time taken for progression to irreversible pulpitis or pulp necrosis for teeth that required root canal treatment was three months (Median 90.0; IQR 68-110). No prognostic factors were associated with the resolution of pulpal symptoms. However, higher pre-operative triggered pain scores (p<0.05, HR 1.547) and absence of a distal marginal ridge crack (p<0.05, HR 0.638) were correlated with a longer duration before definitive pulp diagnoses.

CONCLUSION

Following orthodontic band placement, a normal pulp diagnosis was achieved in 92.6% of cracked teeth with pre-operative reversible pulpitis. Definitive pulp diagnoses could be determined in approximately two months. Teeth with higher pre-operative triggered pain scores may require a longer review period.

The Retention Effect of Resin-Based Desensitizing Agents on Hypersensitivity-A Randomized Controlled Trial

Recently, the development of dental materials has increased the availability of various hyperesthesia desensitizers. However, there are no studies on the duration of retreatment in terms of adherence rates. Thus, the adhesion rates of resin-based desensitizers were investigated. We used a conventional desensitizer and a recently developed desensitizer containing calcium salt of 4-methacryloxyethyl trimellitic acid (C-MET) and 10-methacryloyloxydecyl dihydrogen calcium phosphate (MDCP). These colored agents were applied to the surfaces of premolars and molars, and the area was measured from weekly oral photographs. Areas were statistically analyzed and mean values were calculated using 95% confidence intervals. A p-value of <0.05 was considered statistically significant. These rates were significantly higher on the buccal side of the maxilla and lower on the lingual side of the maxilla. In addition, the desensitizer containing C-MET and MDCP displayed significantly higher adhesion rates. It is suggested that this will require monthly follow-ups and reevaluation because both agents cause less than 10% adherence and there is almost no sealing effect after 4 weeks. In addition, the significantly higher adhesion rate of the desensitizer containing C-MET and MDCP indicated that the novel monomer contributed to the improvement in the adhesion ability.

Treatment of cracked teeth: A comprehensive narrative review

Objectives

The term “cracked tooth” is used to describe an incomplete fracture initiated from the crown and progressing towards a subgingival direction. Despite the high prevalence of cracked teeth and their frequent association with symptoms and pulpal or periapical pathoses, there is still no consensus in the literature with regard to their restorative and endodontic management. Therefore, the aim of this narrative review was to evaluate the most relevant research and provide an up‐to‐date comprehensive overview regarding the treatment of cracked teeth.

Materials and Methods

An electronic literature search was carried out in MEDLINE (via Ovid), Embase (via Ovid), Scopus, and Web of Science as well as several “Grey literature” sources up to February 22nd 2022 using a combination of pre‐specified ‘free‐text' terms (keywords) and “subject headings.” The search process was supplemented by handsearching in relevant dental journals and reference lists. This narrative review focused on clinical follow‐up studies (observational or interventional studies, case series/reports), laboratory studies and systematic reviews written in English language that reported data on treatment of permanent cracked teeth. The selection of relevant studies was carried out by two reviewers (AK and DG) working independently in two consecutive stages: title/abstract screening and full‐text retrieval. Any discrepancies in the study selection were resolved by discussion between the reviewers.

Results

In total, 64 articles were selected for inclusion in this narrative review.

Conclusions

Cracked teeth with normal pulp or reversible pulpitis have exhibited high pulp and tooth survival rates by the provision of direct or indirect composite restorations. Besides, recent data favour monitoring, especially in the absence of symptoms or compromised tooth structure. When endodontic intervention is required, current evidence suggests that along with appropriate restorative management, outcomes of cracked teeth may be comparable to those of non‐cracked root filled teeth.

The Use of Fiber-optic Transillumination in the Diagnosis of Fracture Line in Teeth: A Method of Standardization in Fracture Strength Studies

The use of fiber optic transillumination (FOTI) has been witnessed in the clinical scenario for many decades but has not been used in in vitro studies. The present paper highlights the use of FOTI as a method of standardization while conducting fracture strength studies in vitro.

How to cite this article

Chanchala HP, Godhi BS, Saha S. The Use of Fiber-optic Transillumination in the Diagnosis of Fracture Line in Teeth: A Method of Standardization in Fracture Strength Studies. Int J Clin Pediatr Dent 2022;15(4):475-477.

In vivo real-time temperature measurement on the surface of intact and gold-restored teeth during consumption of hot and cold drinks

This study aimed to measure real-time temperature changes in gold-restored teeth compared with intact teeth during the intake of hot and cold drinks. Sixteen molars, including eight natural intact teeth and eight restored teeth with gold inlays, were selected from the participants. Custom-made thermocouple sensors were attached to the coronal third of the buccal surface of teeth. Participants consecutively consumed hot and cold drinks according to a standardized regimen. Resting, maximum, and minimum temperatures; time to reach peak temperatures; and heating and cooling velocities were obtained. Statistical analysis was performed using independent two-sample t-test. Teeth with gold restorations showed a significantly higher maximum temperature (44.7 °C [SD 2.9]) than did natural teeth (40.5 °C [SD 1.2]) during hot water drinking and showed a lower minimum temperature (25.0 °C [SD 4.9]) than did natural teeth (31.5 °C [SD 3.1]) during cold water drinking. The heating and cooling rates for the teeth with gold restorations were two and three times higher than those of the natural teeth. Gold-restored teeth showed greater temperature change than intact teeth in terms of magnitude and velocity in response to temperature changes induced by hot and cold drinks.

Red fluorescence for assessing longitudinal tooth fractures

BACKGROUND

This study was designed to determine whether autofluorescence emitted from longitudinal tooth fractures (LTFs) differs between fracture types, with the aim of determining which clinical factors are related to red fluorescence at the fracture line.

METHODS

Thirty-three extracted teeth were classified into cracked teeth, split teeth, and root fractures using LTF types according to the American Association of Endodontists classification. The types of LTFs were identified using an operating microscope. LTF autofluorescence was captured using a fluorescence technique. Clinical examinations were performed using the preoperative factors from clinical and radiographic findings.

RESULTS

Red fluorescence was identified in 82% and 83% of cracked and split teeth, respectively. None of the vertical root fractures exhibited red fluorescence (p<0.001). When red fluorescence was identified on the outer tooth surface, it penetrated into the crack line, but fluorescence that was not red at the tooth surface did not penetrate the fracture line. Among the examined preoperative clinical factors, differences between the presence and absence of red fluorescence were identified for sinus tract formation (p=0.021), and radiographic features (p=0.027). Regression analysis revealed a significant factor related to the red fluorescence, with sinus tract formation having a negative effect on red fluorescence (odds ratio [OR]=0.09). The presence of comprehensive periradicular lesions in radiography had a positive effect on red fluorescence (OR=5.04).

CONCLUSIONS

Cracks originating from tooth crowns in certain types of LTFs were associated with red fluorescence, and cracks with red fluorescence were associated with extensive periodontal bone resorption around the teeth roots.

Review of Cracked Tooth Syndrome: Etiology, Diagnosis, Management, and Prevention

Cracked tooth syndrome refers to a series of symptoms caused by cracked teeth. This article reviews the current literature on cracked tooth syndrome from four aspects, etiology, diagnosis, management, and prevention, to provide readers integrated information about this. The article begins with an introduction to the odontiatrogenic factors and then covers the noniatrogenic factors that induce cracked tooth syndrome. While the former discusses inappropriate root canal therapy and improper restorative procedures, the latter covers the topics such as the developmental and functional status of cracked tooth syndrome. This is then followed by the description of common clinical diagnosis methods, the prospects of new technologies, and summaries of current clinical management methods, including immediate management and direct and indirect restoration. In the final section, preventive methods and their importance are proposed, with the aim of educating the common population.

Influence of minimally invasive endodontic access cavities and bonding status of resin composites on the mechanical property of endodontically-treated teeth: A finite element study

OBJECTIVE

To study the mechanical behavior of endodontically-treated teeth with minimally invasive endodontic access cavities and resin composite restorations under different bonding conditions using finite element analysis (FEA).

METHODS

Four Class-II endodontic access cavities including the mesio-occlusal minimally-invasive (MO-MIE), mesio-occlusal conventional (MO-CONV), disto-occlusal minimally-invasive (DO-MIE), and disto-occlusal conventional (DO-CONV) cavities were prepared in 3D-printed maxillary first molars. Each tooth was subjected to root canal preparation and scanned using micro-CT to provide a 3D structural model which was virtually restored with resin composite. An intact 3D-printed molar was used as control. FEA was conducted under a 250-N vertical load. Three different interfacial bonding conditions between dentin/enamel and resin composite were considered, i.e. fully bonded, partially debonded, and fully debonded. The maximum principal stress of dentin and the normal tensile stress at the interfaces were recorded. The risk factor of failure for each component was then calculated.

RESULTS

In the fully-bonded tooth, the dentin-composite interface showed significantly higher stress and a higher risk factor than dentin, indicating that debonding at the dentin-composite interface would occur prior to dentin fracture. With the dentin-composite interface debonded, the enamel-composite interface exhibited higher stress and a higher risk factor than dentin, indicating that debonding at the enamel-composite interface would occur next, also prior to dentin fracture. With the resin composite fully debonded from the tooth, stress in dentin increased significantly. Irrespective of the bonding status, the CONV groups exhibited higher median stresses in dentin than the MIE groups.

SIGNIFICANCE

Within the limitation of this study, it was shown that debonding of the resin composite restoration increased the stress in dentin and hence the risk of dentin fracture in endodontically-restored teeth. Minimally-invasive access cavities could better safeguard the fracture resistance of interproximally-restored teeth compared to conventional ones.

Fatigue performance of endodontically treated premolars restored with direct and indirect cuspal coverage restorations utilizing fiber-reinforced cores

Objectives

The aim of this in vitro study was to investigate the fatigue survival and fracture behavior of endodontically treated (ET) premolars restored with different types of post-core and cuspal coverage restorations.

Materials and methods

MOD cavities were prepared on 108 extracted maxillary premolars. During the endodontic treatment, all teeth were instrumented with rotary files (ProTaper Universal) to the same apical enlargement (F2) and were obturated with a matched single cone obturation. After the endodontic procedure, the cavities were restored with different post-core and overlay restorations (n = 12/group). Three groups (A1–A3) were restored with either conventional composite core (PFC; control) or flowable short-fiber-reinforced composite (SFRC) core with/without custom-made fiber posts and without overlays. Six groups had similar post-core foundations as described above but with either direct PFC (B1–B3) or indirect CAD/CAM (C1–C3) overlays. Fatigue survival was tested for all restorations using a cyclic loading machine until fracture occurred or 50,000 cycles were completed. Kaplan-Meyer survival analysis was conducted, followed by pairwise post hoc comparisons.

Results

None of the restored teeth survived all 50,000. Application of flowable SFRC as luting-core material with fiber post and CAD/CAD overlays (Group C3) showed superior performance regarding fatigue survival (p < 0.05) to all the other groups. Flowable SFRC with fiber post and direct overlay (Group B3) showed superior survival compared to all other direct techniques (p < 0.05), except for the same post-core foundation but without cuspal coverage (Group A3).

Conclusions

Custom-made fiber post and SFRC as post luting core material with or without cuspal coverage performed well in terms of fatigue resistance and survival when used for the restoration of ET premolars.

Clinical relevance

The fatigue survival of direct and indirect cuspal coverage restorations in ET MOD premolars is highly dependent on whether the core build-up is fiber-reinforced or not. The combination of short and long fibers in the form of individualized post-cores seems to offer a favorable solution in this situation.

"THE CORRELATION OF CRACK LINES AND DEFINITIVE RESTORATIONS WITH THE SURVIVAL AND SUCCESS RATES OF CRACKED TEETH: A LONG-TERM RETROSPECTIVE CLINICAL STUDY"

INTRODUCTION

Cracked teeth (CT) frequently require protective adhesive restorations. This long-term, longitudinal retrospective clinical study aimed to evaluate the factors influencing the success and survival rates of CT with crack lines (CLs) in different directions, when restored early with onlays or full-coverage crowns.

METHODS

The dental records of 71 patients with a total of 86 CT, with different pulpal and periapical diagnoses, and with follow-ups spanning over 1-11 years were included. Data regarding the demographics; clinical symptoms and signs; bruxism; occlusal interferences; eating habits; pulpal and periapical diagnoses; number, direction, location, and extent of crack lines; probing depth; and coronary condition before and after the placement of definitive restorations were collected. Univariate associations between tooth survival and explanatory variables were assessed. The long-term survival rate was estimated using the Kaplan-Meier analysis and the log-rank test. A multivariate analysis was performed using Cox regression analysis.

RESULTS

The overall success rate was 93.0%, and the overall survival estimates of CT restored early were 98.6%, 94.9% and 55.9% at the 1-, 5-, and 11-year follow-ups, respectively. The direction of the CLs did not influence the survival of the tooth. No significant association was observed between the type of tooth, probing depth, root canal treatment (RCT), and tooth loss (P>0.05). The multivariate analysis showed that previously treated CT (P<0.05), provision of onlay restorations (P<0.05), and placement of posts (P<0.05) had higher correlations with tooth loss. Additionally, placement of full-coverage crowns resulted in lower tooth loss compared with the placement of onlays (P<0.05).

CONCLUSION

Previous endodontic treatment in teeth that subsequently develop CLs has a negative impact on the survival rate of the teeth. Moreover, early placement of full-coverage crowns should be implemented for CT, regardless of the direction or number of CLs, since it is associated with a higher cracked tooth survival rate.

Repair of teeth with cracks in crowns and roots: An observational clinical study

AIM

This retrospective observational study investigated the survival rate of teeth with radicular cracks that were restored using composite materials.

METHODOLOGY

The study was approved by the Ethical Committee of Sistema Sanitario Nazionale (prot. N°2370CELazio1), Clinicaltrials.gov identifier: NCT04430205. Between 1991 and 2019, 87 teeth with radicular cracks (87 patients [46 men, 41 women, mean age 50.2 years]) were treated with adhesive composite restorations. Forty-five cracks were observed in the maxillary posterior teeth (molars and premolars), 40 in the mandibular posterior teeth and only two cracks in the anterior teeth, both in maxilla. Based on the depth of the crack, teeth were categorized as proximal radicular cracked teeth (PRCT), in which the fracture line was restricted within the pulpal floor or the coronal one-third of the root and deep radicular cracked teeth (DRCT), in which the fracture line extended to the middle and apical thirds of the root canal up to the apex. Bone loss/recovery was evaluated radiographically at 1-year follow-up. All patients were treated using surgical microscopy by the same operator. Logistic regression analysis was performed to determine independent predictors of extraction. Kaplan-Meier survival curves were used to analyse PRCT and DRCT.

RESULTS

Among 87 cracked teeth, 66 were molars, 19 premolars and 2 incisors. Fifty-two were DRCT, 35 were PRCT, 46 had a periodontal probing defect. Patients were followed up for a mean of 66.9 months (standard deviation 44.6, min 1 to max 172). Lack of probing depth was a significant protective factor against extraction (odds ratio [OR] 0.027, 95% confidence interval [CI] 0.003-0.27, p < .05), whereas further bone loss (OR 10.63, 95% CI 2.08-54.36, p < .05) was a risk factor for extraction. More than 50% of teeth treated with the adhesive protocol were functional (46 of 87 teeth [χ² test], p < .05) at 5-year follow-up. Among the PRCT group, a 78% survival rate at 5 years was found, while among the DRCT group, a 58% survival rate was found.

CONCLUSION

Composite resin restorations resulted in tooth survival in >50% of patients; 85.4% of PRCT and 61.5% of DRCT were functional after 5 years of follow-up.

Survival and prognostic factors of managing cracked teeth with reversible pulpitis: A 1- to 4-year prospective cohort study

AIM

This prospective clinical study evaluated the clinical performance of managing cracked teeth with reversible pulpitis through a combination of internal and external splinting and investigated factors that can affect pulp survival after splinting.

METHODOLOGY

Thirty-four teeth diagnosed with cracks and reversible pulpitis were enrolled and treated with bidirectional crack splinting: 1) immediate splinting with a stainless-steel band, 2) internal splinting with crack line removal and resin filling and 3) external splinting with a temporary crown followed by final crown placement. If the symptoms remained/recurred, root canal treatment was performed. Patients were followed up at 3, 6 and 12 months, then annually thereafter. Kaplan-Meier survival analysis to calculate the survival of the treated teeth and Cox univariate proportional hazards regression model to investigate prognostic factors were performed.

RESULTS

Twenty-nine (97%) teeth were followed up for up to 4 years. The pulp survival rate was 72% after banding and 91% after final crown cementation. No tooth was extracted (100% tooth survival rate). In the univariate Cox proportional hazard test, pain on percussion was the only statistically significant factor (hazard ratio = 11.77). Teeth with pain on percussion at the first visit had a pulp survival rate of 46% during the follow-up period. In comparison, their counterparts without pain had a 94% pulp survival rate.

CONCLUSIONS

Bidirectional splinting successfully managed cracked teeth with reversible pulpitis. Pain on percussion (mechanical allodynia) may be an important factor in deciding whether to attempt root canal treatment on symptomatic cracked teeth. A step-by-step approach with bidirectional crack splinting should be encouraged for a cracked tooth with a vital pulp without mechanical allodynia rather than pre-emptive root canal treatment.

X-ray dark-field tomography reveals tooth cracks

Cracked tooth syndrome (CTS) is a common clinical finding for teeth, it affects about 5% of all adults each year. The finding of CTS is favored by several risk factors such as restorations, bruxism, occlusion habits, and age. Treatment options range, depending on the severity, from no treatment at all to tooth extraction. Early diagnosis of CTS is crucial for optimal treatment and symptom reduction. There is no standard procedure for an evidence-based diagnosis up to date. The diagnosis is a challenge by the fact that the symptoms, including pain and sensitivity to temperature stimuli, cannot be clearly linked to the disease. Commonly used visual inspection does not provide in-depth information and is limited by the resolution of human eyes. This can be overcome by magnifying optics or contrast enhancers, but the diagnosis will still strongly rely on the practicians experience. Other methods are symptom reproduction with percussions, thermal pulp tests or bite tests. Dental X-ray radiography, as well as computed tomography, rarely detect cracks as they are limited in resolution. Here, we investigate X-ray dark-field tomography (XDT) for the detection of tooth microcracks. XDT simultaneously detects X-ray small-angle scattering (SAXS) in addition to the attenuation, whereas it is most sensitive to the micrometer regime. Since SAXS originates from gradients in electron density, the signal is sensitive to the sample morphology. Microcracks create manifold interfaces which lead to a strong signal. Therefore, it is possible to detect structural changes originating from subpixel-sized structures without directly resolving them. Together with complementary attenuation information, which visualizes comparatively large cracks, cracks are detected on all length-scales for a whole tooth in a non-destructive way. Hence, this proof-of principle study on three ex-vivo teeth shows the potential of X-ray scattering for evidence-based detection of cracked teeth.

Characteristics, Treatment, and Prognosis of Cracked Teeth: A Comparison with Data from 10 Years Ago

Objectives The purpose of this study was to analyze and to compare retrospectively the characteristics, the treatment process, and the prognosis of cracked teeth by comparing recent data with data from 10 years ago.

Materials and Methods Sixty-eight cracked teeth from March 2009 to June 2010 (2009 data) and 185 cracked teeth from March 2019 to June 2020 (2019 data) were analyzed. The characteristics of cracked teeth and the treatment method depending on probing depth, caries, and symptoms, and prognosis depending on pocket depth and apical lesions were analyzed using R version 3.3.3 (R Foundation for Statistical Computing, Vienna, Austria) and T&F version 3.0 (YooJin BioSoft, Korea). To compare proportions, 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 Significantly fewer cracked teeth received root canal treatment before crown in 2019 than in 2009 ( p = 0.032). In both 2009 and 2019, symptomatic cracked teeth and those with deep periodontal pockets (>6 mm) were significantly more likely to receive root canal treatment. In both years, cracked teeth with a probing depth less than 6 mm or without an apical lesion were significantly more likely to be asymptomatic at 3-month and 6-month follow-ups ( p < 0.001).

Conclusion Cracked teeth with a deep periodontal pocket or symptoms had a higher likelihood of endodontic treatment, and the presence of a deep periodontal pocket or apical lesion was associated with a higher risk of persistent symptoms. Therefore, clinicians should consider these factors when planning treatment and predicting patients’ prognosis.

The influence of FRC base and bonded CAD/CAM resin composite endocrowns on fatigue behavior of cracked endodontically-treated molars

Cracked endodontically treated molars (ETMs) are commonly treated with full crowns. Less invasive techniques could include fiber-reinforced composite (FRC) base and adhesively bonded endocrowns. The purpose of this study was to assess the fatigue resistance of ETMs restored with CAD/CAM resin composite endocrowns and reinforced with different FRC bases. Cracks were simulated in fifty mandibular molars by cutting the teeth longitudinally and reassembling the two parts. After performing endodontic treatments and preparing cavities, teeth were restored in one of the following methods (n = 10). In Group 1, cavity floors were lined with 0.5 mm of flowable composite (Universal Injectable; GUI, shade A2). In Groups 2 and 3, the cavity floors were covered with one and three layers of FRC-net (ES Net) respectively, whereas in Groups 4 and 5 with 1 mm and 2 mm of flowable FRC-resin (EverX Flow Dentin; EXFD) respectively. Endocrowns (Cerasmart 270; CE, A2 HT) with 5 mm thickness were adhesively luted with preheated composite and all specimens were subjected to cyclic loading in water at 5 Hz, starting with a load of 600 N (5000 cycles), followed by stages of 1000, 1300, 1600, 1900, 2200 and 2500 at a maximum of 20 000 cycles each. Results were analyzed using Kaplan-Meier survival analysis and the Log-Rank test (p = 0.05). The fatigue failure load of ES Net applied in three layers (1617 N ± 371) or in one layer (1499 N ± 306), as well as EXFD applied in 2 mm (1496 N ± 264) or in 1 mm (1434 N ± 372) did not differ significantly (p > 0.05). Control teeth fractured at 1255 N ± 350 (p > 0.05). In the fiber-reinforced groups, restorable fractures were observed in 50%-80%, with only 30% deemed restorable in the control group. The fractures originated mainly at the occlusal contact points and the main crack propagated in the corono-apical direction. No crack origin (primary or secondary) starting from the artificial pre-existing crack was observed in fractured specimens. FRC bases did not improve the fatigue resistance of cracked ETMs, but favorably influenced the failure mode.

Oral Functional Behaviors and Tooth Factors Associated with Cracked Teeth in Asymptomatic Patients

INTRODUCTION

A cracked tooth may occur due to excessive applied force or tooth weakness. However, there is scant information concerning the cracked tooth risk factors. This study aimed to explore the oral functional behaviors and tooth factors associated with posterior cracked teeth.

METHODS

Fifty-six patients underwent their oral functional behavior assessment via a questionnaire. The intraoral parameters at the patient level (remaining teeth, occluding tooth pairs, overbite, overjet, and occlusal guidance type) and tooth level (remaining marginal ridge number, restored surface number, restorative materials, and cuspal inclination) were examined. The posterior teeth were stained with methylene blue dye and inspected for cracks using a microscope. The correlations between each patient-level parameter and the cracked tooth number/subject were determined using linear regression analysis. The cracked teeth were matched with their contralateral noncracked teeth, and binary regression analysis was used to analyze the association between tooth-level parameters and a cracked tooth. Multivariate regression analysis was performed if more than 1 parameter had a P value ≤.1.

RESULTS

One hundred thirty-five cracked teeth were found. Eating hard food was significantly related to the cracked tooth number (P < .05). In molars, the occlusal surface restoration and cuspal inclination were significantly related to a cracked tooth, except the mesiobuccal cusp. In the multivariate analysis, the distolingual cusp inclination significantly predicted a cracked tooth (P < .05). In premolars, the lingual cusp inclination was associated with a cracked tooth (P < .05).

CONCLUSIONS

Eating hard food, occlusal surface restoration, and steep cuspal inclination were associated with posterior cracked teeth.

Ubiquitination and Deubiquitination in Oral Disease

Oral health is an integral part of the general health and well-being of individuals. The presence of oral disease is potentially indicative of a number of systemic diseases and may contribute to their early diagnosis and treatment. The ubiquitin (Ub) system has been shown to play a role in cellular immune response, cellular development, and programmed cell death. Ubiquitination is a post-translational modification that occurs in eukaryotes. Its mechanism involves a number of factors, including Ub-activating enzymes, Ub-conjugating enzymes, and Ub protein ligases. Deubiquitinating enzymes, which are proteases that reversely modify proteins by removing Ub or Ub-like molecules or remodeling Ub chains on target proteins, have recently been regarded as crucial regulators of ubiquitination-mediated degradation and are known to significantly affect cellular pathways, a number of biological processes, DNA damage response, and DNA repair pathways. Research has increasingly shown evidence of the relationship between ubiquitination, deubiquitination, and oral disease. This review investigates recent progress in discoveries in diseased oral sites and discusses the roles of ubiquitination and deubiquitination in oral disease.

Laboratory simulation of longitudinally cracked teeth using the step-stress cyclic loading method

AIM

To simulate in a laboratory setting longitudinal cracking in root filled premolar teeth, using cyclic mechanical fatigue.

METHODOLOGY

Mesial-occlusal-distal (MOD) cavities were prepared in twenty root filled, single-rooted, mandibular premolars restored with fibre posts and resin composites. The samples were randomly divided into two groups based on the loading approaches: static loading with a crosshead speed of 0.5 mm/min and step-stress cyclic loading (1 Hz) with increasing amplitude. The loads and numbers of cycles to failure were recorded. Micro-CT was also used to identify the fracture modes. Statistical analysis was performed using Student's t-test. The level of significance was set at 0.05.

RESULTS

The mean fracture loads for the static loading and cyclic loading groups were 769 ± 171 N and 720 ± 92 N, respectively. There was no significant difference between the two groups (P > 0.05). The proportions of longitudinal, cuspal and mixed-mode fractures under cyclic loading were 50%, 20% and 30%, respectively. Longitudinal fractures occurred with larger numbers of cycles and higher average loads per cycle compared with the other fractures. Static loading produced only cuspal fractures.

CONCLUSIONS

Longitudinally cracked premolar teeth with root fillings were successfully produced using the step-stress cyclic loading method. This provides a more clinically representative methodology for studying cracked teeth in a laboratory setting.

Survival rate after endodontic treatment in general dentistry for cracked teeth with different coronal restorations

OBJECTIVE

The aim of this study was to analyse the survival rate of cracked teeth after endodontic treatment. The secondary aim was to compare the survival rate of cracked teeth restored with composite filling/crown and those restored with a full crown.

MATERIALS AND METHODS

The study was conducted retrospectively from three general dental clinics in Stockholm, which are all part of the national dental service organisation. Two-hundred patients with teeth receiving endodontic treatment due to symptomatic cracks were included. The patient data range from year 2001 to 2016.

RESULTS

The mean age of the patients was 48 years (range 29-69). Fifty-five per cent had cracks located above the pulpal cavity, 11% within the pulpal cavity and 3% located in the root canal. The cracks were located most commonly on the proximal surfaces. The survival rate for teeth with cracks was 68% and 54% after 5 and 10 years, respectively. The survival rate was significantly higher (97%) for cracked teeth receiving a full crown after endodontic treatment compared to teeth restored with either a composite filling or composite crown.

CONCLUSION

The overall survival rate for cracked teeth was 68% after 5 years, while it was significantly higher for cracked teeth restored with a full crown. The results suggest within the limitations of this study that cracked teeth should be restored with a full crown after endodontic treatment.

Diagnosis of cracked teeth using cone-beam computed tomography: literature review and clinical experience

Cone-beam computed tomography (CBCT) has been widely used in diagnosis of vertical root fractures (VRFs) in recent years. According to the American Association of Endodontists (AAE) classification, there are five types of cracked teeth and VRF is one of them. Due to the variability and overlapping of the cracks and fractures, some narrow fractures on the roots of VRFs could not be detected by CBCT, and some wide cracks on the crown of cracked teeth could be detected by CBCT. In this review, we firstly discussed the value of CBCT in the diagnosis of the AAE five types of cracked teeth and presented CBCT manifestations of some typical cases. Secondly, we summarized the factors influencing the diagnosis of cracks/fractures using CBCT, namely, CBCT device-related factors, patient-related factors, and evaluator-related factors. The possible strategies to improve the diagnostic accuracy in the clinic practice are also discussed in this part. Finally, we compared the differences of root fractures with lateral canals and external root resorption on CBCT images.

Cracked teeth: Distribution and survival at 6 months, 1 year and 2 years after treatment

BACKGROUND/PURPOSE

The unpredictable condition of cracked teeth warrants further investigation and clinical experiences. The purpose of this study was to collect and record data on demographics, clinical characteristics, different treatment modalities and survival of cracked teeth at 6-month, 1-year and 2-year recalls.

METHODS

77 cracked teeth from 65 patients were included. Data on demographics, clinical parameters, treatment modalities and recall were collected. Binomial, multinomial and chi square tests were used for statistical analysis.

RESULTS

Most cracked teeth occurred in patients greater than 40 years old (p < 0.01). Cracked teeth themselves were most often molars (79.22%; p < 0.01), a non-terminal tooth in the arch (62.34%; p < 0.05) and nonendodontically-treated teeth (94.81%; p < 0.01). Cracked teeth exhibited pain to percussion (63.64%, p < 0.05) or biting (74.03%; p < 0.01), and no or only positive mobility (76.62%; p < 0.01). Cracks were most often oriented in the mesiodistal direction (68.83%; p < 0.01). Higher survival rates were noted in cracked teeth lacking pre-operative pain to palpation or spontaneous pain, and with no or only positive mobility at 6-month and 1-year recalls. In vital cracked teeth, higher survival rates were noted in teeth lacking pre-operative pain to palpation and with no or only positive mobility at 2-year recalls.

CONCLUSION

The absence of pre-operative palpation discomfort, spontaneous pain and minimal mobility, as well as the presence of pulp vitality were associated with higher survival rates of cracked teeth at all recall times. Results are useful for diagnosis and outcomes-based treatment planning of cracked teeth.

A new method to test the fracture strength of endodontically-treated root dentin

OBJECTIVE

To develop a new method to test the fracture strength of endodontically-treated root dentin.

METHOD

Bovine tooth roots were transversely cut into 2-mm thick sections and the root canals were enlarged with a taper of 0.06. An outer layer of resin composite was bonded to each section to make the root canal-to-outer radius ratio smaller than 1/3. The resulting discs were treated with irrigants at the inner surface and then fractured by inserting through the center a steel rod of the same taper attached to a universal test system. Fracture strength was calculated by using Lame's equations for thick-walled cylinders. Micro-indentation was performed to evaluate the depth of dentin affected by irrigation. Finite element analysis (FEA) was performed to verify the reasonableness of using resin composite to surround the dentin section as well as the analytical solution.

RESULTS

The fracture strength of endodontically-treated root dentin based on the analytical solution for a homogeneous section was 139.69 ± 32.59 MPa. However, FEA that took into account root canal softening caused by the irrigants showed that this was overestimated by about 33.5%. The corrected fracture strength of treated dentin was 114.58 ± 26.74 MPa. By incorporating the layer of affected dentin into the analytical solution, the difference in the fracture-causing stress between the analytical and numerical solutions dropped to around 9.5%.

SIGNIFICANCE

A relatively simple but clinically relevant method has been developed for measuring the fracture strength of endodontically-treated root dentin. The method could be applied to root dentin that is treated by conventional canal opening and irrigation.

Occlusal stress distribution and remaining crack propagation of a cracked tooth treated with different materials and designs: 3D finite element analysis

OBJECTIVE

Here we used 3D finite element analysis (FEA) to analyze and directly compare stress distribution and crack propagation in identical cracked tooth models after treatment with various materials and designs.

METHODS

A 3D model of a cracked tooth was generated. We then applied eight restoration models, comprising combinations of three kinds of restoration designs (inlay, onlay, and crown) and four types of restoration materials (direct composite resin, indirect composite resin, ceramic, and gold). A 1000-N occlusal load was applied on the three reference points of the ball-shaped part in the direction of the longitudinal axis, causing crack line separation in the buccolingual direction. Stress distribution was analyzed on the occlusal surface, bottom level of the restoration, and mesiodistal longitudinal section. The stress on the lower margin of the crack surface was measured at 15 points on each model.

RESULTS

Ceramic inlay and onlay showed stress concentration at the restoration bottom, and low stress on the lower margin of the crack surface. Direct and indirect resin restorations exhibited low stress on the restoration bottom, and high stress on the proximal end of the lower margin of the crack surface. With a resin-unfilled gold crown, stress was concentrated on the crown bottom and the lower margin of the crack surface. Direct resin filling inside the gold crown yielded significantly decreased stress on both areas.

SIGNIFICANCE

Our results suggest that inlay and onlay ceramic restorations, and gold crown with resin filling inside, are advantageous methods for preventing further crack propagation.

Shrinkage Strains in the Dentin of Endodontically Treated Teeth with Water Loss

INTRODUCTION

Dehydration has been considered as a potential contributor to vertical root fractures (VRFs) after root canal treatment (RCT). A loss of water could cause embrittlement of dentin and detrimental shrinkage strains. Senior patients have the highest risk of VRF. In this study, we characterized the spatial distribution in shrinkage of tooth roots with respect to donor age and prior RCT.

METHODS

Single-rooted human teeth with and without prior RCT were collected from young (age <25 years) and old (age >60 years) adults. Transverse slices were sectioned from the apical, middle, and coronal thirds of the roots, and digital image correlation was used to evaluate shrinkage during free convection. Crack initiation and growth analysis was performed via optical microscopy, and bound water in dentin was characterized by Raman spectroscopy.

RESULTS

The rate of shrinkage was significantly higher (p ≤ .05) in the apical third than in the middle and coronal thirds of all teeth regardless of donor age. The highest shrinkage strain occurred in the apical third of old donor teeth with prior RCT. In addition, the RCT-treated old teeth suffered the highest percentage of water loss with dehydration. Cracks initiated from the root surface and extended toward the canal with loss of water and shrinkage.

CONCLUSIONS

The apical third undergoes significantly larger shrinkage strains with dehydration than the remainder of the root. Prior RCT exacerbates the extent of shrinkage, particularly in the teeth of seniors and after clinical function, which could increase the propensity for VRF.

Factors Related to the Outcomes of Cracked Teeth after Endodontic Treatment

INTRODUCTION

Cracked teeth are a common clinical finding; however, their presence renders diagnosis and prognosis unreliable. The purpose of this research was to assess the correlations of multiple factors on the prognosis of cracked teeth that had undergone endodontic treatment.

METHODS

A total of 3680 patients who received endodontic treatment by an advanced postdoctoral education program in endodontics with follow-up records of at least 1 year were assessed. From this sample, 62 patients met the inclusion criteria and were included in the final analysis. The factors being evaluated included demographics, clinical symptoms and signs, radiographic findings, and restoration type. Statistical analysis was then completed using the chi-square and Fisher exact tests.

RESULTS

The mean follow-up period was 23.3 months, with an overall tooth success rate of 75.8%. The success rates differed significantly when the patient had an existing preoperative periapical lesion, lacked a proper permanent restoration on the treated tooth, or had a post placed after root canal treatment. Data analysis showed that restoring the tooth after endodontic treatment was the single most important factor for prognosis. In fact, the endodontically treated teeth with definitive full-coverage restorations had a 2-year success rate of 93.6%.

CONCLUSION

Full-coverage restorations should be considered an important part of the treatment plan for cracked teeth treated endodontically.

Potential Application of Human β-Defensin 4 in Dental Pulp Repair

When pulp tissue is damaged by caries or trauma, vital pulp therapy (VPT) can help preserve the pulp tissue for long-term retention of teeth. However, the choice of pulp capping agent used in VPT is important for the successful preservation of the pulp tissue. Here we investigated the expression and biological function of human β-defensin 4 (HBD4) in dental pulp stem cells (DPSC) and explored its potential as a pulp capping agent. We examined the expression of HBD4 in DPSC in vitro using qPCR and immunofluorescence staining. We also looked at the effect of HBD4 on inflammatory factors in lipopolysaccharide (LPS)-stimulated DPSC, and its effects on mineralizing cell phenotype differentiation, via qPCR and western blot. Finally, we examined the ability of HBD4 to promote the restoration of the pulp-dentin complex in vivo, using male Wistar rats with reversible pulpitis. We found HBD4 was highly expressed in DPSC stimulated by TNF-α and IL-1α. HBD4 down-regulated the expression of inflammatory mediators (i.e., IL-1α, IL-1β, IL-6, TNF-α) in LPS-stimulated DPSC, and suppressed MAPK activity and the NF-κB pathway. HBD4 also enhanced the differentiation of DPSC into osteoblasts or odontoblasts, potentially by modulating the Notch pathway. Furthermore, HBD4 controlled the degree of pulp inflammation in a rat model of reversible pulpitis and induced the formation of restorative dentin. Together our findings indicate HBD4 may be a useful pulp capping agent for use in VPT.

Dentin thickness as a risk factor for vertical root fracture in endodontically treated teeth: a case-control study

OBJECTIVES

This study evaluated factors associated with vertical root fracture in endodontically treated teeth, using a cone-beam computed tomography (CBCT) image database.

MATERIALS AND METHODS

The sample for this case-control study consisted of 81 CBCT scans of teeth with vertical root fracture (VRF) and 81 CBCT scans of non-fractured teeth, matched by age, sex, and tooth position. The analyzed variables included dentin thickness, an intraradicular post, an adjacent implant, and a missing adjacent tooth. Student's t test test was used to compare the quantitative variables. The chi-square test was used to compare the categorical variables. Logistic regression was performed to evaluate the association between the presence of VRF and the independent factors assessed.

RESULTS

The mean dentin thickness of fractured teeth was 1.3 mm, whereas that of non-fractured ones was 1.5 mm (p < 0.001). There was no difference between the fractured and non-fractured groups, regarding implant frequency or missing adjacent tooth (p > 0.05). There were a significantly larger number of teeth with posts in the fractured versus non-fractured group (p = 0.007). However, dentin thickness ≤ 1.3 mm was the only factor associated with VRF in the multiple regression model (OR = 3.60, 95%CI = 1.76-7.37).

CONCLUSIONS

Dentin thickness may influence the development of VRF. Dentin thickness ≤ 1.3 mm is associated with a greater likelihood of fracture than ≥ 1.4 mm.

CLINICAL RELEVANCE

This study suggests there may be a minimum amount of safe dentin thickness that should be preserved after endodontic instrumentation.

Detection and analysis of enamel cracks by ICG-NIR fluorescence dental imaging

Cracked teeth are the third most common cause of tooth loss, but there is no reliable imaging tool for the diagnosis of cracks. Here, we demonstrate the feasibility of indocyanine green near-infrared fluorescence (ICG-NIRF) dental imaging for the detection of enamel cracks and enamel-dentin cracks in vitro in the first (ICG-NIRF-I, 700-950 nm) and second (ICG-NIRF-II, 950-1700 nm) imaging windows with transmission excitation light, and compared ICG-NIRF with conventional NIR illumination-II (NIRi-II) and X-ray imaging. Dentin cracks were detected by CT scan, while most enamel cracks, undetectable under X-ray imaging, were clearly visible in NIR images. We found that ICG-NIRF-II detected cracks more effectively than NIRi-II, and that light orientation is an important factor for crack detection: an angled exposure obtained better image contrast of cracks than parallel exposure, as it created a shadow under the crack. Crack depth could be evaluated from the crack shadow in ICG-NIRF and NIRi-II images; from this shadow we could determine crack depth and discriminate enamel-dentin cracks from craze lines. Cracks could be observed clearly from ICG-NIRF images with 1-min ICG tooth immersion, although longer ICG immersion produced images with greater contrast. Overall, our data show that ICG-NIRF dental imaging is a useful tool for diagnosing cracked teeth at an early stage.

Analysis of clinical associated factors of vertical root fracture cases found in endodontic surgery

BACKGROUND/PURPOSE

Early diagnosis of vertical root fracture (VRF) has been a great challenge. Since there is no single specific etiology identified, prevention of VRFs in endodontically treated teeth is quite difficult. The study aimed to evaluate the clinical associated factors of VRFs.

MATERIALS AND METHODS

A retrospective observational study of medical charts was conducted in the Department of Endodontics of Taipei Medical University Hospital in Taiwan from January 2012 to July 2018. Logistic regression model was performed to determine the association between VRF and its clinical associated factors, inclusive of the tooth characteristics (age, gender and tooth type) and iatrogenic risk factors (history of root canal treatment, restoration and post).

RESULTS

A total of 359 teeth were included in the study. The prevalence of VRF on a tooth basis was 18.7%. The result showed that age of more than 50 years (adjusted OR = 3.20, 95% CI: 1.81-5.64, p < 0.001) had significant higher risk of VRFs than those of less than 50 years. The subjects of molars (adjusted OR = 4.31; 95%CI = 2.24-8.27; P value < 0.001) and premolars (adjusted OR = 2.61; 95%CI = 1.16-5.86; P value = 0.021) had significant higher risk of VRFs than those of incisors. However, other variables such as gender, history of root canal treatment, restoration and post had no significant association with the VRF.

CONCLUSION

Age and tooth type are significant clinical associated factors of VRF. In the presence of these factors as well as predominant diagnostic factors, clinical practitioners should be aware of the possible diagnosis of VRFs.

Dental implant placement is a possible risk factor for the development of multiple cracks in non-endodontically treated teeth

The objective of this study was to evaluate potential risk factors, including the placement of dental implants, for the development of tooth cracks. A series of 212-patients, who were referred for endodontic treatment, were retrospectively screened, of which 72 (34%) patients had been diagnosed with 80-cracked teeth confirmed with an operating microscope. These patients had an average age of 53-years and were equally distributed between genders. Forty-one percent of the cracked teeth were diagnosed after the placement of dental implants, with an average of 3-implants per patient. Seventy percent of the cracks were diagnosed more than 1-year after implant loading. Implant placement was associated with higher odds of having multiple cracks (OR = 9.78, CI:2.320, 41.216)(p < 0.05). The proportion of cracked premolars was relatively high (30%), and most cracked teeth (79%) were vital and with a normal periapical diagnosis (86%). Most cracked teeth (71%) had an amalgam restoration, and teeth restored with amalgam were at a higher risk of having multiple cracks (p < 0.05). Clinicians should be aware of a common profile of endodontic patients with multiple cracks in a non-endodontically treated premolar, restored with an amalgam restoration, which was diagnosed with the cracks more than 1-year after reconstruction utilizing multiple implants.

Clinical and Histological Findings of Post-Treatment Infection in the Presence of Vertical Root Fracture and Apical Periodontitis: Case Reports

Apical periodontitis and vertical root fracture (VRF) might coexist in the same root, thus representing a di-agnostic challenge in endodontics. Diagnosis should be based on detailed clinical examination and precise radiographic interpretation in addition to histological examination, if needed. The histological findings of the case presented showed the possible coexistence of a VRF in the coronal third of the root and signs of apical periodontitis caused by intracanal infection in the apical third of the same root. The presentation of this case underlines the importance of histological examination as a valid complementary diagnostic tool with clinical and radiographic examinations in reaching an accurate diagnosis once the root has been extracted.

Using Meglumine Diatrizoate to improve the accuracy of diagnosis of cracked teeth on Cone-beam CT images

AIM

To explore in a laboratory setting the feasibility of using Meglumine Diatrizoate (MD) to improve the accuracy of diagnosis of cracked teeth on cone-beam CT (CBCT) images.

METHODOLOGY

Twenty-four teeth were cracked artificially by soaking them cyclically in liquid nitrogen and hot water. The number and position of crack lines were evaluated with a dental operating microscope and used as the gold standard. The artificially cracked teeth were then examined using routine scanning (RS) and enhanced scanning (ES) modes, respectively. For the ES mode, MD was painted on the surface of the crack lines, and then, CBCT scanning with the same parameters was performed after 10 min. A radiological graduate student and an experienced radiologist evaluated the presence or absence of crack lines, respectively. The differences between the RS and ES modes were determined and assessed using McNemar's test. Inter-examiner agreement and intra-examiner agreement were assessed using kappa analysis.

RESULTS

Fifty-seven crack lines were found in the 24 cracked teeth. In the RS mode, the accuracy of detection of crack lines was 23% (radiological graduate student) and 32% (experienced radiologist), whereas in the ES mode, the accuracy was 61% (radiological graduate student) and 65% (experienced radiologist). The inter-examiner agreement was 0.693 in RS mode and 0.849 in ES mode. The intra-examiner agreement was 0.872 and 0.949 for the radiological graduate student in RS and ES mode respectively; and one for the experienced radiologist both in RS and ES mode.

CONCLUSIONS

Compared with routine scanning mode, more crack lines could be detected in enhanced scanning mode using Meglumine Diatrizoate as a contrast medium. MD could be a potential contrast medium to improve the accuracy of detection of crack lines on CBCT images.

Symptom changes and crack progression in untreated cracked teeth: One-year findings from the National Dental Practice-Based Research Network

OBJECTIVES

The study objective was to: (1) quantify symptom (pain) and crack changes during one year of follow-up, among teeth that had at least one visible crack at baseline but which did not receive treatment for those cracks; (2) identify any patient traits/behaviors and external tooth/crack characteristics correlated with these changes.

METHODS

In this observational study, 209 National Dental Practice-Based Research Network dentists enrolled a convenience sample of 2858 subjects, each with a single, vital posterior tooth with at least one observed external crack; 1850 teeth remained untreated after one year of follow-up and were the cohort for analyses. Data were collected at the patient-, tooth-, and crack-level at baseline, one-year follow up (Y1), and interim visits. Associations between changes in symptoms and cracks were identified, as were changes in symptoms associated with baseline treatment recommendations.

RESULTS

Changes in pain symptoms were observed in 32% of patients; decreases were twice as common as increases (23% vs. 10%). More changes were observed in cold pain than in biting pain and spontaneous pain combined; 2% had increases in biting pain and 2% in spontaneous pain. Only 6% had an increase in the number of cracks. Changes in pain symptoms were not associated with an increase in the number of cracks, but were associated with baseline treatment recommendations. Specifically, pain symptom changes (especially decreases) were more common when the tooth was recommended for treatment at baseline.

CONCLUSIONS

Cracked teeth that have not received treatment one year after baseline do not show meaningful progression as measured by increased symptoms or number of cracks during follow-up.

CLINICAL SIGNIFICANCE

Untreated cracked teeth, most of which were recommended for monitoring at baseline and some of which were recommended for treatment but did not receive treatment, remained relatively stable for one year with little progression of cracks or symptoms.