The etiopathogenesis of the apical periodontitis was explained by a diagnosis of exclusion, since neither tooth had caries, fillings, or undergone trauma. No abnormalities in the sense of dental anomalies (Dens invaginatus, Taurodontism), mineralization defects (Amelogenesis/Dentinogenesis imperfecta, Molar-Incisor-Hypomineralisation, Dentin Dysplasia) or (horizontal) tooth fractures could be detected clinically or radiologically. Tooth fractures generally occur from accidents or traumatic injuries and can lead to a periapical lesion. Further radiological examinations are recommended if this is suspected [8]. Since there was no clinical evidence of this and no clues in the patient’s medical history, no further radiological examinations, other than the standard ones, were carried out. At the the beginning of the treatment, a perio-endo lesion can be diagnosed. This is characterized by deep periodontal pockets, a negative or altered pulp response to vitality tests, spontaneous pain and tooth mobility, bone resorption and purulent exudate [9]. These findings apply to the described case as well. In a 2017 classification, the perio-endo lesion was divided into endo-periodontal lesions with and without root damage [10]. Lesions with root damage are divided into external root resorption, root canal or pulp chamber perforation, root fracture or cracking. Lesions without root damage are divided into endo-periodontal lesions in periodontitis patients and non-periodontitis patients [10]. Except for a deep pocket on both teeth, no periodontal problems were detected. The patient, therefore, is considered as a non-periodontitis patient. The deep pockets may emanate from tissues of dental pulp [9]. Since there is no traceable disease of the dental pulp tissue, it cannot be causal. This leaves the possibility of a lesion with root damage. Clinically and radiologically no external resorption, root canal or pulp chamber perforation was apparent. Publications mainly describe vertical tooth fractures in connection with endodontic treatment or root fillings [11, 12]. This can occur due to excessive instrumentation, excessive dentin removal and remaining dentin thickness, excessive irrigation and/or force during lateral condensation. Other causes could include retreatment, overfilled roots, microstructural changes in dentin over a long period, reduced proprioception and fracture resistance of the filled tooth [13]. Since the symptoms associated with a vertical fracture occurred before endodontic treatment, a fracture in the context of treatment was excluded. Several older publications address the vertical fracture of non-endodontically treated teeth [14,15,16] and describe it as the now widely known cracked tooth syndrome. A cracked tooth is an incomplete fracture of a vital posterior tooth originating from the coronal dentin. Progression in the pulp or periodontal ligament is possible [17]. Vertical fracture of teeth is the third most common reason for tooth loss after caries and periodontitis [18], often associated with intracoronal restorations and mandibular molars [19, 20]. Women are more affected than men, high prevalence rates occur generally in ages 45–64 [19]. There are two different groups of risk factors: (1) iatrogenic (e.g. tooth preparation, width and depth of cavity) and (2) natural factors (tooth form, age, wear patterns) including a lingual inclination of the lingual cusps of mandibular molars, extensive attrition, abrasion, bruxism and clenching. An incomplete tooth fracture is difficult to diagnose and is primarily based on the following symptoms: unexplainable sensitivity to cold, general or localized pain while chewing and pain on release of pressure. Verification involves transillumination with a fiber optic light visualizing the crack, percussion and thermal tests, and radiographs to check the periodontal and pulpal tissue. Ultrasound could visualize future cracks. Currently, there are no existing guidelines for treatment [20]. In this case study, the affected teeth were mandibular molars, but without restorations. The patient was male and under 40. Findings from the National Dental Practice-Based Research Network suggest an incidence rate of 7% in under 35-year-olds [19]. Iatrogenic risk factors can be excluded, as the teeth had never before been treated. The tooth form was not noticeable. The patient did not have an unexplainable sensitivity to cold, only had a short period (2 days) in which he experienced chewing pain, and had no pain on release of pressure. The x-ray showed an impressive apical osteolysis on both teeth. According to the National Dental Practice-Based Research Network, a periapical lucency was detected in 0% of their findings and, therefore, cannot be related to a cracked tooth. Bruxism and stress were reported by the patient and could have been accredited to a cracked tooth [19]. However, since the clinical and radiological picture was not compatible with a cracked tooth, and based on the knowledge that bruxism can damage the pulp [21], this diagnosis was ruled out. Students are under significant stress during their studies and work-life transitions, which can lead, among other symptoms, to bruxism [22]. Over a period of months, the patient reported right temporomandibular joint pain. Since no diagnosis could be established, nonspecific therapy with antibiotics was initiated. Nonspecific therapy with antibiotics should be viewed critically against the background of increasing antibiotic resistance [23]. Furthermore, many side effects of systemic antibiotic administration, including life-threatening side effects, must be taken into account [24]. Therapy for bruxism is extensive: occlusal adjustments, equilibration therapy, occlusal splints, psychotherapy, physical therapy, relaxation training, drugs, biofeedback, and electrical methods [25]. A grinding splint was made 1.5 years after the first onslaught of pain, but no further therapy was given. During this time, apical periodontitis increased. Possibly, an early, adequate therapy for bruxism could have avoided the development of apical periodontitis.
It is likely that the occlusal trauma first led to sterile necrosis, followed by infection. Possible pathways of infection could have been side and accessory canals in the furcation or apical area, both of which are more likely than a cracked tooth, as already discussed.
Treatment was performed according to standard protocol: determination of working length by electrical length measurement using Raypex 6—an established method and product on the market [26], verification of length by radiography—recommended by the European Society of Endodontology [27], irrigation using 3% sodium hypochlorite, which is more effective than the 2% or 1% dose and also considered the most effective irrigation solution in endodontics [28], temporary (2 weeks) drug insertion with CaOH2 in case of existing bleeding of distal canals on both molars. The high pH of calcium hydroxide has antibacterial and anti-inflammatory effects, detoxifies bacterial endotoxins and induces healing of the periapical tissues. High healing rates have been reported with the short-term use of Ca(OH)2 in teeth with apical periodontitis, and is also an effective antimicrobial agent when applied for a minimum of one week as a temporary filling. Studies suggest an insertion period of 2–4 weeks, when using calcium hydroxide [29]. A new review recommends deciding for or against multiple sessions, depending on the individual case, since no advantages for one particular type of session were found with regard to the incidence and intensity of pain [30]. Obturation was performed using cold lateral condensation which has been, for years, the gold standard. In a 2021 review, cold lateral condensation was compared with warm thermoplastic procedures, both of which failed to achieve complete obturation on micro-CT, but with the thermoplastic procedures achieving better results. However, it was emphasized that the results should be interpreted with caution. Many studies have had a moderate bias. Further studies would be needed to conclusively address the issue [31].
In conclusion, in the case of unexplained tooth pain, possible bruxism should be clarified anamnestically, as this may indicate apical periodontitis in the context of an occlusal trauma. Further case reports and studies are needed to discuss the influence of bruxism on endodontic problems.
