Biological Restorations in Paediatric Dentistry: A Systematic Review of Case Reports With Thematic Cross-Case Synthesis

BACKGROUND

The field of restorative dentistry has been enriched in modern times by ultraconservative tooth preparation techniques and biocompatible materials. While the first focuses on preserving sound tooth structure, the second entails the various dental materials that restore the tooth’s structure.

Any dental material used in restorative dentistry must fulfill the ‘holy sextant of traits,’ “ABCDEF,” i.e., acceptability, biomimicry, clinical time, durability, economy, and function. Minimal intervention dentistry (MID) and advances in bonding systems have improved the adhesion of various materials to the tooth. However, not all materials fulfill the holy sextant, making it imperative for dental researchers and professionals to look for alternative techniques or materials. One such method is called biological restoration (BR).

BR is defined as an alternative technique that uses the adhesive capabilities of materials in combination with the strategic placement of parts of extracted human teeth. It is used for the quality reconstruction of extremely damaged teeth with the help of natural teeth that meet the aesthetic and structural standards of healthy teeth.^[1]

Premature exfoliation of primary teeth due to carious or traumatic injuries in children can cause malocclusions, hinder orofacial growth, and cause defects in phonetics and mastication. According to Andreasen, tooth reattachment procedures serve as transitional treatment modalities for patients with a primary or mixed dentition until a definitive treatment can be planned for the permanent dentition. This is because it is during the permanent dentition that the contours of the gingival margin become relatively stable for the receipt of a long-term prosthesis.^[2]

BR has been practiced since the late 18^th century, when wealthy members of British society would spend hundreds of pounds for a denture made from human teeth. These teeth were extracted from the deceased soldiers from the Battle of Waterloo.^[3] However, the first published speculation of using teeth as a biological form of restoration can be traced back to 1948. Sten Forshufvud was the first dental researcher to publish three reports on how he used ox teeth as BR in humans by mechanical bonding. Unlike popular belief that has credited Chosack and Eidelman^{[ 4 ]} with reporting the first case of BR (restoring a central incisor using patient tooth fragments), Forshufvud’s^[5] work is chronologically the first reported example of BR. While Chosack and Eidelman can be credited for being the first to report the autogenic use of tooth as a BR, Forshufvud was the first to report the same as a xenograft.

The concept of a tooth bank emerged in 1981, but it was not until 1996 that a definitive human tooth bank (HTB) was established. During this period, materialistic advances occurred, where etching and bonding systems were enhanced to improve the surface adhesion of dental materials. It was in 1991 that Santos and Bianchii used a sterile tooth fragment to restore a large carious tooth. This is the first reported case of a tooth fragment used as an allogenic BR.^[6]

The concept of BR was not limited to permanent teeth. The first case of BR with the help of a tooth fragment in the primary dentition was technically detailed in 1992 by Tavares et al.^[7] Today, the use of tooth fragments as BR is better classified as autogenic-homodontic (fragments of the same tooth used to restore it), autogenic-heterodontic (fragment of another tooth of the same person used as BR), allogenic-homodontic (fragment of the same type of tooth obtained from an HTB used as BR), allogenic-heterodontic (fragment of a tooth of a different type obtained from an HTB used to restore a tooth of another type).^[8]

BR is a unique treatment modality that satisfies every characteristic of the holy sextant of traits. Acceptability increases among parents by 93% when they are educated about BR and HTB.^[9] Tooth fragments are excellent biomimetic materials, as they represent the natural hue and translucency of the tooth itself. They are relatively less technique-sensitive and require less chair-side time.^[10] Reattached tooth fragments have good durability, with a survival rate of nearly 2 years in children and adolescents.^[11,12] Furthermore, they are low-cost compared to conventional restorative materials.^[10] BR helps restore the tooth functionality by reinstating occlusal harmony and maintaining masticatory efficiency.^[13]

Despite the various advantages it has to offer, the knowledge of BR among clinical practitioners is deficient. Lack of clinical training, lack of fragment availability, and concerns about cross-contamination are cited as the main reasons behind the underreported use of BR.^[14] A 2-year report of a newly established HTB showed that only 1% of teeth were used as BR.^[15]

BR in paediatric dentistry is a recommended and prioritised treatment modality whenever possible.^[16] However, there is a lack of longitudinal studies, randomised controlled trials, and consistency in the technique that must be followed for a successful BR. Therefore, this systematic review was done to synthesise the most refined case reports of BR in paediatric dentistry. A thematic cross-case analysis was performed to better understand BR as a treatment modality in paediatric dentistry.

METHODS

An Open Science Framework registration was performed for this systematic review (Registration DOI: https://doi.org/10.17605/OSF.IO/ZPGMF). This study was reported according to the guidelines recommended by PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis). No ethical approval was needed for this study as it did not involve human participants or reveal confidential details of the patients in case reports.

The research question was formulated using the SPIDER tool [Supplementary File S1].^[17] The inclusion and exclusion criteria of the studies were decided on this search strategy tool for qualitative studies.

According to the inclusion criteria, there was a possibility of encountering a single study detailing multiple case reports. In such cases, the age of the patients mentioned in the case reports could have varied. In such scenarios, the cases within the report that fell into the age group according to our inclusion criteria were only considered.

Three researchers conducted a thorough literature search (BS, AP, DC). These researchers were responsible for synthesising relevant data from the following databases and grey literature: PubMed, Cochrane Library, ProQuest, Global Index Medicus, TRIP (Turning Research into Practice) Database, MedNar, ScienceDirect, and Google Scholar. The keywords used in each database, along with the necessary truncation symbols, Boolean operators, and limits/filters, can be found in the Supplementary File S1. A fourth researcher (KD) was assigned the task of manual entry, which was done through cross-referencing and expert advice.

Articles extracted from individual search engines and databases were managed through Zotero (v6.0.26), a reference management software. Organization and management of the articles were done through Rayyan, a Software as a Service (SaaS) web-based application for systematic reviews, a recommended tool in healthcare research.^[18] Manual entries were added retrospectively, and deduplication of articles was done through Rayyan.

Six authors independently screened the title and abstract through Rayyan (BS, AP, SN, KD, MV, DC). For each author, ‘blinding’ was turned on (in the Rayyan software) to eliminate any bias during the inclusion of the studies. In cases of conflict, a consensus was reached to decide the fate of the article’s inclusion. The full text of the available articles went through two rounds of selection. This was carried out by two independent groups of researchers (three in each group: BS, AP, DC; SN, KD, MV).

The tabulation from the data of the chosen studies was done in Microsoft Excel 2021. The characteristics of the included studies have been detailed in the Supplementary File S1. Since this study is a systematic review of case reports, all included articles fell under level 4 according to the criteria set by evidence-based medicine.

The evaluation of the studies, along with their risk of bias, was conducted using Pierson’s 5-component scheme. The five components include documentation, uniqueness, educational value, objectivity, and interpretation. Each of these components was scored from 0 to 2. The final score was then added, and an inference was drawn. A score of 5 or less indicates that the case report is of insufficient quality. A score between 6 and 8 hints that the reader should be cautious about the validity of the case report. A score of approximately 9 is considered to be a worthwhile contribution to the literature.^[19] The objectivity component played a significant role in this evaluation as it was responsible for critically analysing any risk of bias in the case report. Five of the investigators in this study independently assessed the case reports for quality assessment. The mean value of the scores of the five researchers was considered for inference.

Data analysis was performed by thematic synthesis, which was followed by cross-case analysis. This analysis was carried out in two steps with the participation of the six researchers. The method employed was grounded theory, which was used to determine a systematic methodology. The first step included line-by-line coding of all included studies. This coding results in the development of overarching themes that are produced throughout the case report. Each of these themes contains subcategories called “constructs,” which help to understand the pattern within a particular theme.

The second step was to use a weighted-point system against the constructs that are most used within a theme. A scale of one to nine was used, where nine was put against the most frequently used word/phrase/construct, eight for the second, seven for the third, and so on. A consensus determined the order in cases where two constructs were repeated at the same frequency. The top three constructs in each theme helped to derive the essence of the included case reports on BRs in paediatric dentistry.

RESULTS

The primary literature search retrieved 205 articles, of which 56 were eliminated during deduplication, and one was eliminated for not meeting the language criteria. The selection of titles and abstracts further led to the elimination of articles with inappropriate study design (n = 32), did not meet the age group (n = 28), and where the full text was not available (n = 28). Of the 65 articles sought for retrieval, one was eliminated due to a retraction notice. Two rounds of full-text screening of the 64 articles were carried out.

Following the two rounds of screening, 51 were eliminated for meeting the exclusion criteria. Twenty-eight studies were eliminated because they did not mention the hydration protocol of the BR or sterilisation (where appropriate). Three studies were eliminated due to an inappropriate study design, and 20 studies were excluded for failing to mention any follow-up of the case (n = 9) or for not following up the case after 12 months (n = 11). Therefore, a total of 14 studies were included in the qualitative data analysis [Figure 1].

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Figure 1:

PRISMA flowchart. PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

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DISCUSSION

The need for conducting this systematic review came from two questions: (a) What is the success rate of BR used in paediatric dentistry in the reported cases in the literature? (b) Is there a streamlined treatment strategy followed in published reports of BR in paediatric dentistry? To our knowledge, this is the first systematic review that analyses all relevant case reports published in the English language on BR in paediatric dentistry.

The nature of case reports, including heterogeneity in reporting, varying demographics, a range of techniques, and outcome variables, indicated that meta-analysis was not a suitable choice for data analysis. Therefore, a thematic synthesis with cross-case analysis was used in this study. Thematic synthesis is one of the most commonly used data analysis methods in qualitative systematic reviews.^[29] It uses the pros of meta-ethnography and the concept of grounded theory to address the appropriateness, effectiveness, and acceptability of the qualitative data while simultaneously adhering to the principles of systematic reviews.^[30]

We chose Rayyan as our screening tool because it outperformed 14 other commonly used screening tools in weighted feature analysis.^[18] Pierson’s 5-component scheme was used for the quality appraisal of the case reports on the Joanna-Briggs Institute checklist, as the former gives a quantitative inference of critical appraisal.

Including only case reports in our systematic review helped to understand two facets of BRs in paediatric dentistry. First, analysing only case reports helped us know the quality of reporting of these cases and the uniformity within the treatment strategies employed. Second, during our literature search, we found a severe lack of higher-quality evidence in the literature on our subject. A total of seven such articles were encountered that included randomised controlled trials (n = 2), longitudinal studies (n = 2), comparative studies (n = 1), retrospective studies (n = 1), and a systematic review (n = 1). It should be noted that not every study mentioned here fell into the paediatric age group or was conducted in vivo. We also understand that a systematic review focusing on tooth fragment reattachment techniques has been prospectively registered (in 2017) but has not yet been disseminated at the time of writing this manuscript.

Based on the articles reviewed, we understand that BRs can be classified as follows based on their anatomic site: enamel veneers, crown fragments, shell crowns, crowns with biopins, crowns without biopins, crowns and posts, and biological posts. Before these fragments are attached, they need to be cleaned of all organic and inorganic materials. Carious surfaces and restorations need to be removed with handpieces and scalers. It is usually recommended to inspect the fragment afterward with a magnifying glass or an electron microscope if feasible. According to the Center for Disease Control and Prevention, saturated steam under pressure for 40 minutes does not alter the physical properties of dental tissues. Autoclaving, ethylene oxide, and Gamma Radiation are the most recommended methods of sterilising teeth that are to be used for BR.^[10] In our study, autoclaving was performed in six cases.

Hydration of a tooth fragment ensures that it retains its aesthetic appearance and has adequate bond strength. The latter is true as hydrated fragments adhere better due to the hydrophilic characteristics of modern adhesive systems. Lack of hydration causes collagen bundles of the mantle dentin to weaken due to plastic deformation.^[31] When a tooth fragment is used as a BR, its storage time in a solution must not exceed three to four weeks, as its mechanical properties can be significantly altered.^[32] Although hydration protocols have been reported in the literature, the International Association of Dental Traumatology does not give specifications for hydration protocols.^[33]

The fracture strength of a tooth fragment begins to decrease after 5 seconds and drops significantly by 24 hours. To regain this fracture resistance, a 24-hour hydration time is recommended. Some other authors have recommended a 30-minute rehydration phase after 48 hours of dehydration, while others suggest that immersion-rehydration phases lasting longer than 15 minutes do not affect the bond strength of the tooth fragment.^[34,35] This review showed that saline solution is most commonly used for hydration (n = 4) in cases where the tooth fragment was not obtained from a tooth bank (n = 5).

The need for a tooth to be prepared before receiving the fragment depends on the remaining tooth structure and the type of adhesive used. An ideal adhesive system should produce a homogenous hybrid layer with penetration of the material that extends to the peritubular and intertubular dentin matrix.^[36] Light-cure composite resin and dual-cure resin were used most frequently in our review to avoid the formation of voids and microcracks that could lead to bonding defects.

Thematic synthesis revealed that the five regular themes reported and discussed on BR in paediatric dentistry were related to its technique, treatment choice, outcome, limitations, and advantages. Compared to conventional restorative techniques, BR requires less time at the table. This is especially true for autogenic fragments.^[37] Allogenic fragments may require an increased lab phase for adequate sterilisation and hydration of the fragment, along with trimming of the tooth according to the dimensions of the area to be restored. Although the technique is simple, the requirement of professional expertise is also one of the patterns derived from this theme. One of the recommended technical aspects during the treatment involves taking the impression of the area to be restored with silicone material to replicate accurate dimensions.

Our data revealed that BR is repeatedly recommended as the first treatment choice when indicated and is often considered better than conventional treatment. BR can be chosen in both complicated (involving the pulp) and uncomplicated cases. However, these treatment approaches can become ‘conditional’ when the remaining dentinal thickness is minimal, pulp involvement is present, and biological width is violated. In such cases, the BR can be supported by biological posts and a calcium hydroxide base. Violation of the biological width can demand flap surgery or gingivectomy before BR is performed in permanent teeth.^[38-40]

The results of BRs are almost always favorable. The biomimetic property of BR retains aesthetics and increases the psychological acceptance of treatment in the social domain. Autogenic cases can be cost-effective and are better accepted by patients compared to allogenic cases.

Three significant limitations of BR as a treatment modality include decreased acceptance of parents, the lack of availability of tooth banks, and the decreased availability of the appropriate tooth. Parental acceptance can be overcome by educating the patient about the sterilisation protocols through which tooth fragments are processed. The smaller number of tooth banks can be attributed to a deficiency in the dissemination of BR. An increase in the number of tooth banks will simultaneously increase the availability of teeth for BR.

This systematic review also suggests that since BRs mimic the physiological wear of natural teeth, they have the advantage of being smooth and resilient, have better stress distribution, and adhere better to the cervical region compared to conventional treatments.

CONCLUSION

BR in paediatric dentistry is an underreported treatment modality with a void in the dissemination of randomised controlled trials and longitudinal studies. Within the limitations of this study, this systematic review of case reports helps to understand the clinical and technical aspects of BRs and their substantial role as a treatment modality in paediatric dentistry.