Cracked Teeth Are Worth Saving: A Look at New Management Protocols and Outcomes
In this era of COVID-19, dentists are reporting increased numbers of patients presenting with cracked teeth (Shannon 2020). The mechanism for crack development is concentrated repetitive stress with subsequent fatigue of enamel and then dentin.
Presumptively, the mental and emotional stress of the pandemic and adhering to strict state or local guidelines to mitigate the spread of COVID-19 has led to a higher incidence of bruxism and grinding, though no studies have examined incidence during “stressful” periods of time.
Regardless, studies have shown that with the earlier the diagnosis of cracked teeth, the less likely there will be progression to pulpal pathosis requiring endodontic treatment (Krell and Rivera 2007; Abbott and Leow 2009; Opdam, Roeters et al 2008). This makes early diagnosis the key to managing treatment.
Management of cracked teeth can be challenging. Not only do patients with cracked teeth present with varying symptoms and clinical presentations, but survey studies also indicate a lack of consensus within the dental community regarding cracked tooth treatment protocols (Alkhalifah, Alkandari et al 2017).
An accurate endodontic evaluation is the first critical step in proper management of cracked teeth. The patient’s symptoms along with the crack’s orientation, depth, and pulpal and periodontal involvement dictate the appropriate restorative approach.
Also, pulp and periapical testing, periodontal probing, transillumination, isolated bite pressure testing, dyes, radiographic evaluation, and a microscopic exam are important adjuncts that together yield necessary information for treatment planning the cracked tooth.
Craze lines, confined to enamel, rarely require restorative treatment unless they pose a cosmetic issue for the patient. Because they do not extend into dentin, the pulp is not affected. Therefore, teeth with craze lines do not require endodontic treatment. In contrast, split teeth and vertical root fractures are by and large deemed hopeless and are relegated to extraction (Rivera 2008).
Asymptomatic cracks are prevalent in adult posterior teeth, typically appearing on marginal ridges or grooves. While some cracks may propagate apically over time, many remain unchanged (Figure 1).
Since there are no current studies indicating the risk or incidence of further progression of the crack over time, clinicians face the dilemma of whether a proactive approach in crown placement or a more conservative “watch” should be recommended.
In some cases, it may be judicious to adjust occlusion ensuring light contacts and eliminating excursive interferences from the more vulnerable areas of these teeth (eg, lingual cusps of maxillary premolars). A night guard may be another preventative measure in patients exhibiting cracked teeth.
When symptomatic, cracked teeth and cuspal fractures require a full-coverage coronal restoration when possible (Ailor 2000). In cases where the pulpal diagnosis is deemed reversible pulpitis, no endodontic intervention is required, and a crown should be placed as soon as possible.
Studies following these symptomatic cracked teeth that were crowned had similar rates of later requiring root canal treatment as those non-cracked crowned teeth (Krell and Rivera 2007, Abbott and Leow 2009). With a pulpal diagnosis indicating irreversible endodontic disease (irreversible pulpitis or pulpal necrosis), root canal treatment should precede crown placement.
Treatment and Prognosis
During root canal treatment, an endodontist can assess a crack’s internal depth microscopically. In cases of deeper cracks with a radicular extension (into root dentin), intra-orifice barriers placed apically to the apical extent of the crack may provide a protective coronal seal, thereby mitigating bacterial ingress into the canal as well as possibly reinforcing the critical cervical dentin level of the tooth (Davis and Shariff 2019) (Figure 2).
Following root canal treatment, the cracked tooth should be taken entirely out of occlusion with no excursive contact. Patients must be informed of the cracked tooth’s vulnerability proceeding the placement of the full-coverage restoration. They should be instructed to avoid mastication on the affected tooth’s side and to set the crown appointment posthaste.
It is unnecessary to delay crown preparation and placement in favor of “allowing the tooth to heal” post-endodontically. Proper endodontic treatment very rarely requires retreatment within the first few months. Therefore, the risk of further propagation of the crack due to delaying the protective restoration likely far outweighs the probability of the necessity of endodontic revision. Proper restoration of endodontically treated teeth is a significant factor in long-term retention (Aquilino and Caplan 2002).
Occlusion is an important factor for the longevity of cracked teeth. At the time of delivery of the final restoration, care must be taken to ensure light contacts with no excursive interferences. This should then be re-evaluated at six weeks following crown cementation.
In their prospective study on cracked teeth, Davis and Shariff found that occlusion needed to be re-adjusted in 79% of cases at six weeks post-crown (Davis and Shariff 2019). Patients’ parafunctional habits should be addressed, and a night guard should also be considered.
With proper management, cracked teeth can carry a favorable prognosis. In one six-year study, progression of interproximal periodontal defects associated with crowned cracked teeth only occurred in 4% of cases. Also, those later requiring endodontic intervention occurred at approximately the same rate as non-cracked crowned teeth (Krell and Rivera 2007). This likely points to the long-term importance of full cuspal coverage restorations and that once crowned, cracked teeth behave similarly to non-cracked crowned teeth.
Multiple outcome studies validate a favorable prognosis for endodontically treated cracked teeth with survivals ranging from 86% to 97% (Tan, Chen et al 2006; Kang, Kim et al 2016; Sim, Lim et al 2016; Davis and Shariff 2019). Using stringent outcomes criteria, a success rate of 82% at one year also was found (Krell and Caplan 2018). Further bivariate analysis from that study resulted in the Iowa Staging index (Figure 3).
In a prospective study of teeth with deep cracks extending onto the root surface, Davis and Shariff found a success rate of 91% and survival of 97% when employing modern microscopic endodontic technique as well as the aforementioned postoperative management protocols (Figures 4 and 5).
New studies, technologies, and advances in dental materials and techniques have allowed us to find more ways to save teeth. With growing concern over untoward implant complications along with patients’ desire to try to save their natural tooth, restoring a cracked tooth would seem to be the overall treatment of choice.
Certainly, case selection and myriad patient variables must be considered when having effective dialogue with patients when conveying options, expected outcomes, and contingencies.
Undoubtedly, a thorough discussion of all parameters must take place with our patients before proceeding, but today’s modern endodontic approaches are allowing what were once deemed “hopeless” teeth a much improved chance for survival, success, and function.