Particularities of the implant-supported prosthesis in patients with bruxism: systematic review of the literature

¹Fixed Prosthesis Department, Faculty of Dentistry of Casablanca, Hassan II University of Casablanca, Casablanca's Dental Consultation and Treatment Center, CHU Ibn Rochd, B.P 9157, Mers Sultan, Casablanca, Morocco, ²Private practice, Casablanca, Morocco

^&Corresponding author
Meriem Amine, Fixed Prosthesis Department, Faculty of Dentistry of Casablanca, Hassan II University of Casablanca, Casablanca's Dental Consultation and Treatment Center, CHU Ibn Rochd, B.P 9157, Mers Sultan, Casablanca, Morocco

Introduction    

Bruxism is a complex parafunction that corresponds to a repetitive and unconscious activity of the masticatory muscles. It affects between 8 and 31.4% of the population [1,2]. It can present 2 circadian manifestations distinctly or combined: Daytime bruxism: while awake, characterized by clenching of teeth, where contractions are generally involuntary and of variable intensity/duration [3]. Nocturnal bruxism: during sleep, characterized by clenching and grinding of the teeth [4]. From an etiological perspective, awake bruxism seems more directly associated with psychological traits [5,6], whereas sleep bruxism is a complex activity with multiple neurological implications and interactions with other sleep-related conditions [7,8]. The dental clinician is the first witness to the manifestations of this parafunction, including dental wear, periodontal damage, and dysfunctions of the orofacial musculature and temporo-mandibular joint (TMJ) [9].

Patients with bruxism may require prosthetic rehabilitation during their overall care. It is generally accepted that, when it comes to tooth-supported prostheses, bruxism would be incriminated in the occurrence of complications or even therapeutic failure [10]. This parafunction could complicate the treatment plan and affect the prognosis of the prosthetic restoration, particularly when it comes to implant-supported prosthetic rehabilitation [11]. So, how does bruxism impact the success and prognosis of implant-supported prostheses? The objective of this systematic review of the literature is to evaluate the longevity and reliability of implant-supported prostheses made in patients with bruxism, and to establish the success and failure criteria for these prostheses.

Methods     

Redaction protocol: this systematic review of the literature was carried out in accordance with the recommendations of The PRISMA Statement “Preferred Reporting Items for Systematic reviews and Meta-Analyses” [12].

Research strategy: an electronic search was conducted using keywords with Boolean equations. The literature search was based on English-language electronic databases accessible via the Internet. The databases used were: Medline-PubMed, Web of Science, Scopus, and Google Scholar. The Boolean equations chosen for the electronic search were: dental implant and (bruxism or bruxers or parafunctional or clenching or grinding or occlusal overload), dental prosthesis, implant-supported, and (bruxism or bruxers or parafunctional or clenching or grinding or occlusal overload). The date of the last computer search was 20/06/2025, with no period filter. The search strategy is shown in the PRISMA flow diagram in Figure 1.

Eligibility criteria

Inclusion criteria: the articles selected in our literature search are clinical studies that met the following inclusion criteria: i) evaluating the role of bruxism as a risk factor in implant-supported prosthetic rehabilitations; ii) conducted on human subjects; iii) having a follow-up duration of at least 6 months; iv) written in English.

Exclusion criteria: the articles excluded from our computerized search were as follows: i) case series; ii) expert opinions; iii) studies conducted on animals or cadavers; iv) in vitro and in silico experiments; v) literature reviews and meta-analyses.

Selection of literature: the reading of the scientific articles was carried out by two independent readers, A.L and M.A. A first reading was carried out to select the articles through the title and the abstract, following the eligibility criteria. Then a second full reading of the selected articles was carried out, eliminating articles that do not meet the inclusion criteria. In the event of disagreement between the opinions of the two independent readers, a discussion made it possible to resolve the differences and find a common consensus.

Data extraction: to prepare and structure our systematic review, the targeted question was developed using the PICO criteria [13]: P: participants ⇒ patients with bruxism; I: intervention ⇒ placement of dental implants; C: comparison ⇒ success and complication rates between the bruxer and non-bruxer groups; O: “outcomes” ⇒ impact of bruxism on the implant-supported prosthesis. The success criteria published by Albrektsson et al. [14]. were adopted, whereas implant survival was defined as implants that remained in situ at the time of the most recent follow-up appointment with no indication for removal. Complications in implant therapy comprise two categories: biological and technical (mechanical) [15]. Biological complications refer to reactions in the peri-implant hard and soft tissues, while technical ones are related to mechanical damage of the implant/implant components and superstructures. Variables such as the evolution over time of the parameters cited above and the statistical differences (p) between each intervention group in each study were studied.

Quality appraisal of included studies: the critical reading of the articles relied on methodological quality assessment tools specific to the types of studies included in our literature review:

Qualitative assessment of non-randomized studies: the evaluation of non-randomized clinical studies was based on: the Newcastle-Ottawa Scale was developed by the universities of Newcastle in Australia and Ottawa in Canada [16]. The tool for assessing the risk of bias of non-randomized studies from the “Cochrane Handbook for Systematic Reviews of Interventions,” which provides advice to authors for the preparation of their systematic reviews [17]. Using the Newcastle-Ottawa Scale (NOS), to facilitate consistent interpretation, studies were further categorized as good, fair, or poor quality based on the thresholds defined by the Agency for Healthcare Research and Quality (AHRQ). Studies were rated good if they scored 3 or 4 stars in the Selection domain, 1 or 2 stars in Comparability, AND 2 or 3 stars in the Outcome/Exposure domain; fair if they scored 2 stars in Selection, 1 or 2 in Comparability, AND 2 or 3 in Outcome/Exposure; and poor if they scored 0 or 1 in Selection, OR 0 in Comparability, OR 0 or 1 in Outcome/Exposure [18].

The risk of bias assessment using the tool recommended by the Cochrane Handbook for Systematic Reviews of Interventions ('The Handbook') was carried out for each article. We examined the following biases: confounding bias, selection bias, bias in the classification of interventions, bias due to deviation from intended interventions, attrition bias, reporting bias, bias in outcome measurement, and other biases [17].

Results     

Description of search results: the literature searches yielded a total of 1330 potentially relevant titles and abstracts (Figure 1). Preliminary exclusion was performed for duplicate references; after reading the titles and abstracts, 277 articles were included for full-text presentation. After meeting the inclusion and exclusion criteria, a total of 20 studies were included for qualitative analysis. The selected articles included 6 prospective cohorts and 14 retrospective cohorts, with a follow-up period ranging from 6 months to 36 years. The 20 reviewed studies included a total of 9313 patients and a total of 31209 implants.

Bruxism as a failure factor of the implant-supported rehabilitation: survival rates and complications of the implant-supported rehabilitation in bruxers

Ten selected studies [19-28] focused on the impact of bruxism on implant and prosthetic survival rates, as well as the rates of occurrence of mechanical and biological complications on the implant-supported prosthesis, and compared these rates to those found in nonbruxer patients, to be able to conclude (Table 1, Table 1.1). In this literature review, the examined studies reported implant survival rates ranging from 57.5% [28] to 100% [29-31], and prosthetic survival rates ranging from 70.6% [32] to 100% [29,33,34] for a follow-up of 12 to 291 months. Following the evaluation of these non-randomized clinical studies using the NEWCASTLE-OTTAWA scale (Table 2), they were categorized as good (7 studies), fair (1 study), and poor quality (2 studies). The assessment of bias using the Cochrane Handbook for Systematic Reviews of Interventions, “The Handbook” (Table 3), shows that most articles present an uncertain risk for bias in the measurement of outcomes, because no information is given on the status of the evaluators. Some articles also present a high bias risk in the selection of participants.

Bruxism as a risk factor for implant failure: among the selected studies, 2 looked at the impact of bruxism on implant survival rates, compared to other known risk factors, such as smoking, grafted sites, poor prosthetic designs, crown-to-implant ratio (c/i)<0.8, and the abutment angulation>25° (Table 4). Long-term clinical and radiological monitoring of implants in the group of patients suffering from bruxism made it possible to establish failure rates of 12.93% and 15% in the studies of De Angelis F et al. 2017 [35] and Papi Pet al. 2017 [36], respectively. The association of bruxism and risky loading (c/i ratio < 0.8; angulation > 25°; presence of cantilever) gives the highest rates of mechanical and biological failure (69.23% success rate) [35]. According to the Newcastle-Ottawa Scale (Table 2), both studies are of good quality. Both De Angelis Fet al. 2017 [35] and Papi Pet al. 2017 [36] studies present an unclear to high risk for bias in the selection of participants, in the selection of the reported results, and in the measurement of outcomes (Table 3).

Therapeutic specificities of the implant-supported restorations in patients with bruxism

Immediate loading: three selected studies: Ibañez JC et al. 2005 [29], Ji TJet al. 2012 [33], and Glauser R et al. 2001 [37], focused on immediate loading in patients with bruxism, and concluded implant failure rates of 0.97%, 29.3% for fixed total implant-supported prostheses, and 41% for all types of implant-supported prostheses (Table 5, Table 5.1). According to the Newcastle-Ottawa Scale (Table 2), all 3 studies are of good quality. These studies present an uncertain risk of bias in the measurement of outcomes (Table 3).

Impact of bruxism depending on the type of edentulism

Bruxism and total edentulism: the studies by Chrcanovic BR et al. 2020 [32], Engstrand P et al. 2003 [34], and Coltro MPLet al. 2018 [31], which investigated the impact of bruxism in total edentulous patients rehabilitated with an implant-supported prosthesis, report implant survival rates ranging from 74.65% to 100%, and prosthetic survival rates ranging from 70.6% to 100% (Table 5, Table 5.1). According to the Newcastle-Ottawa Scale (Table 2), all studies are of good quality. The studies by Chrcanovic BR et al. 2020 [32] and Engstrand P et al. 2003 [34] present an uncertain risk of bias in the measurement of outcomes, and Engstrand P et al. 2003 [34] a high risk of bias in the selection of participants. The Coltro et al. 2018 [31] study showed a moderate risk of bias due to confounding (Table 3).

Bruxism and posterior edentulism: two studies focused on the impact of bruxism in patients with posterior edentulism rehabilitated by the implant-supported prosthesis [30,38] (Table 5, Table 5.1); Koenig V et al. 2019 [38], show that the prosthetic success rate is 79.6% and the prosthetic survival rate is 92.3%, Mangano FG et al. 2013 [30] reported a prosthetic survival rate of 87.7%. According to the Newcastle-Ottawa Scale (Table 2), both studies are of good quality. The Koenig V et al. 2019 [38] study presents a high risk of bias in the selection of participants (Table 3).

Discussion     

Bruxism has been very strongly associated with mechanical/prosthetic complications, with prevalences far exceeding those observed in nonbruxers, for different forms of complications, notably unscrewing and loosening, fracture of the abutment, of the screw, or the implant, deformation of the implant and the prosthesis, and fracture of the ceramic [21,23,25-27,32,38].

Although the majority of the included studies were observational in design, and despite heterogeneity in clinical protocols, follow-up durations, and bruxism diagnostic criteria, the convergence of findings across a large number of implants supports the role of bruxism as a relevant risk factor for implant and prosthetic failure. The methodological quality assessment using the Newcastle-Ottawa Scale indicated that most included studies were of good methodological quality, with only a limited number rated as fair or poor [20,21,26]. Evaluation using the ROBINS-I tool, as recommended by the Cochrane Handbook, identified domain-specific limitations inherent to non-randomized designs, predominantly related to outcome measurement and participant selection, while confounding bias was limited in most studies. Taken together, these findings suggest that heterogeneity and bias may affect the precision of effect estimates, but do not undermine the consistency or clinical relevance of the observed associations.

In the specific context of investigating bruxism, randomized controlled trials assigning patients to a potentially harmful exposure are neither ethically acceptable nor practically feasible. Consequently, retrospective and prospective cohort studies represent the most appropriate methodological framework for evaluating this association. Nevertheless, RCTs may indirectly support the clinical relevance of bruxism-related risks by assessing whether interventions aimed at mitigating parafunctional loading, such as occlusal splint therapy, influence implant-related outcomes. The parafunctional activity of bruxism generates excessive forces of the order of 50 kgf [39], and for a period that exceeds the 20 minutes of interdental contact normally observed in a day during chewing and swallowing, where occlusal forces average only 26.7 kgf and 30.2 kgf, respectively [40,41].

According to studies by Chrcanovic BR et al. 2020 [22] and Mikeli A et al. 2016 [23], the chances of these complications appearing in bruxers are up to 18.19 times more frequent for implant fractures, and 3.6 times higher for ceramic fractures than for non-bruxers. It is considered that these results are partly related to the reduced proprioception of implants compared to natural teeth. Indeed, the periodontal ligament of natural teeth provides the central nervous system with feedback for sensory perception and motor control. The periodontal sensitivity threshold is less than 1 N for the anterior teeth and around 4N for the posterior teeth [42]. while the threshold for perception of information transmitted by an osseointegrated implant is around 6.7N [43], and information of the protopathic, vague, diffuse type. Proprioception around dental implants is limited due to the absence of a periodontal ligament, which results in less sensitivity and consequently limits the proprioceptive feedback mechanisms to the muscles [44]. In addition, the periodontal ligament has a protective role in shock absorption and stress distribution, thus preserving the integrity of the tooth-bone structure. In the case of implant-supported dentures, impact testing has revealed that implants can transmit greater forces to the surrounding bone than natural teeth, which can increase stress and the risk of complications [45].

Recommendations: in view of current data from the literature, it is undeniable that bruxism constitutes a significant risk factor for implant and prosthetic failure [35,36]. Consequently, treatment with the implant-supported prostheses in patients with bruxism must take into consideration a certain number of recommendations and precautions:

Implant planning: the objective would be to avoid elements placed in extension, and to reduce or eliminate occlusal contacts during lateral movements, for this the ideal would be to place 1 implant for each tooth to be replaced [46,47]. The axis of application of forces must be that of the long axis of the implant and the alveolar crest, in order to limit shearing and bending forces [48].

Implant materials: fragility of implant materials can increase the susceptibility to fracture found in bruxers; it is therefore strongly recommended not to place zirconia (zirconium dioxide) implants in these patients. On the other hand, the material of choice is TiCp grade 4, which is a titanium alloy richer in O2 and more mechanically resistant [49].

Surface condition: retentive threads and sanded and/or etched micro-textured surface conditions represent the solution of choice, due to their high wettability, thus promoting the covering of this surface by blood, allowing better osseointegration of the implant [50].

Implant dimensions: the more the diameter of the implant increases, the more the stress exerted on the cortical bone will decrease. The use of large implants, while maintaining a minimum thickness of bone around it, is therefore recommended, since they make it possible to create a larger support zone, and reduce tensions on the level of the peri-implant bone [51].

Prosthetic design: the prostheses must be designed with the aim of improving the distribution of stress on the implants; the implants must be installed perpendicular to the curves of Spee and Wilson to favor the direct contacts generated during the vertical function on the long axis of the implants. Most authors agree that prosthetic rehabilitation should provide a single point of contact close to the center of the implant, whenever possible. Occlusion should be marked by gently sloped cusps and small occlusal tables to protect the implant system against transverse components of forces during tooth grinding [46,52].

Loading: with single-tooth or partial edentulism, there are more failures in the case of immediate loading (within 2 weeks following installation), or early (6 to 8 weeks after installation) [53]. However, implant-supported total prostheses prove to be an exception, since the stress is distributed over all the implants, thus improving the survival rate [32,34]. For the bruxing patient, delayed loading is recommended, ranging from 6/10 weeks up to 1 year according to the authors, in order to ensure that the osseointegration of the implants has taken place, and thus to avoid early solicitations [11]. Sarmento et al. 2012 [46], state that delayed-loaded implants have the best chance of survival, followed by immediately-loaded implants (up to 2 weeks after placement), with early-loaded implants (6 to 8 weeks after placement) being those with a lower survival rate.

Abutment and connection systems: the connection systems recommended for bruxers have been poorly studied according to the literature. The implant abutments should ideally be straight; they will be screwed when dealing with a Morse cone, and screwed if it is an external or internal polygon [46].

Prosthetic materials: the use of ceramic is therefore inevitable in bruxers, but it is, however, recommended that there be a metal infrastructure to rigidify the prosthesis, especially to a large extent [47,49]. The best compromise for a patient suffering from bruxism would therefore be a ceramic-metallic prosthesis with systematic wearing of a protective splint, in order to intercept problems of fragility of the ceramic [23].

Splinting: the splinting of crowns and bridges is recommended since it allows better distribution of occlusal forces, thus reducing tensions at the bone level. Fortin Tet al. concluded through a study in 2016 that the splinting of prostheses would not have an impact on peri-implant cratering, but that it would avoid contact point problems, which can, in the event of a hiatus, be the cause of inflammation and therefore possible cratering [54].

Implant retention method: screw-retained prostheses have the advantage of being an easily removable system, which is practical, particularly when it is necessary to manage complications or carry out prosthetic repair.

Protective splint: Kinsel RP et al. (2009) and Papaspyridakos P et al. (2019) agree on the protective effect of the nighttime splint, particularly in bruxers. It has been proven that the risk of wear of prosthetic materials was 1.8 times higher in patients without a splint compared to patients regularly wearing a protective splint [26,55]. The use of the splint is therefore systematically recommended in patients with this parafunction, since it helps to alleviate muscular tension and reduce the stress exerted on the prostheses. The protective occlusal splint should provide uniform and simultaneous occlusal contacts in centric relation, allowing optimal distribution of masticatory forces and prevention of complications [49]. Hard splints are preferred, as they minimize the damage to the oral tissues, promote more even occlusal load distribution, and redirect clenching and grinding forces toward a vertical axis, unlike soft splints, which may increase muscular activity [46].

During mandibular movements, the splint should ensure posterior disocclusion in protrusion and strictly anterior contacts during lateral excursions. In cases of single or partial implant-supported prostheses, when a sufficient number of natural teeth are present to bear occlusal loads, the splint should be relieved over implant restorations [46]. Occlusal contacts must be harmonious, well-distributed, and simultaneous to prevent occlusal trauma, highlighting the importance of occlusal equilibration. To avoid undesirable effects such as extrusion or intrusion, the splint should cover all teeth, including third molars, while eliminating premature contacts [3]. The maxilla is the preferred arch for splint therapy due to its greater exposure to eccentric parafunctional forces, increased mobility of maxillary teeth, and higher susceptibility to fracture [3].

Regular maintenance: routine maintenance of implant-supported prostheses is crucial, particularly in patients with bruxism, where elevated occlusal forces increase the risk of mechanical complications. Annual maintenance visits should include structured occlusal checks, clinical and radiographic evaluation of implant stability and prosthetic integrity, and monitoring of peri-implant tissues. Specific attention should be paid to the detection of screw loosening, ceramic chipping, wear of prosthetic materials, and changes in the occlusal scheme. In bruxers, the presence and condition of protective night splints must be verified and adjusted if needed. Regular maintenance and occlusal adjustments significantly contribute to reducing complication rates and prolonging the longevity of implant restorations [56].

Conclusion     

Bruxism is a risk factor for implant failure. Bruxers present particularities which negatively impact the success and durability of implant-supported prosthetic restorations. However, respecting the recommendations cited above, which include wearing a protective splint, ensuring adequate monitoring and maintenance and occlusal equilibration respecting the chosen occlusal concept, enhances the prognosis.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

All the authors have read and approvedd the final version of this manuscript.

Tables and figure     

Table 1: PICO criteria for assessing the impact of bruxism on implant survival and complication rates

Table 1.1: PICO criteria for assessing the impact of bruxism on implant survival and complication rate

Table 2: Newcastle-Ottawa Scale evaluation of selected articles

Table 3: estimation of the risk of bias of the included studies

Table 4: PICO criteria addressing bruxism as a risk factor for implant failure

Table 5: PICO criteria addressing immediate implant loading, total edentulism, and posterior restorations in patients with bruxism

Table 5.1: PICO criteria addressing immediate implant loading, total edentulism, and posterior restorations in patients with bruxism

Figure 1: flow diagram for literature screening and selection

References