Regenerative potential of platelet concentrates in chronic oral mucosal lesions.

Chronic oral mucosal diseases (COMDs) represent a significant challenge for clinicians and patients. They are commonly associated with chronic pain and negative effects on healing and patient's quality of life. Regenerative medicine including the use of biological autologous blood-derived substances (e.g., platelet concentrates [PCs]), has been reported to improve healing and reduce pain in orthopedic and maxillofacial surgeries as well as chronic oral mucosal diseases. In this review, we aim to describe the different types of PCs and their applications in the management of COMDs such as lichen planus, mucositis, pemphigus vulgaris, mucous membrane pemphigoid, and plasma cell mucositis, in terms of healing potential, pain control, and quality of life. Overall, PC applications seem to enhance healing and reduce pain in patients with COMDs. However, due to the small sample size and the lack of standardized clinical trials, further research is required to support these findings.

Efficacy of photodynamic therapy on candida colonization and clinical symptoms in denture stomatitis: a systematic review and meta-analysis.

BACKGROUND: Photodynamic therapy (PDT) has been recently proposed as a promising alternative therapy for Denture Stomatitis (DS). The present systematic review and meta-analysis investigated the current available evidence regarding the efficacy of PDT in the management of DS. MATERIALS AND METHODS: PubMed, Scopus, Web of Science, Google Scholar, and ProQuest were searched up to June 7, 2023. All relevant clinical trials were included. RevMan software was used for the statistical analyses. RESULTS: Elven randomized clinical trials (460 DS patients) were included. Eight studies assessed the efficacy of PDT vs. topical antifungal therapy, while three studies assessed the adjunctive use of PDT (PDT + antifungal therapy) vs. topical antifungal therapy alone. The results revealed comparable efficacy of PDT and conventional antifungal therapy on candida colonization at 15 days (MD: 0.95, 95% CI: -0.28, 2.19, p = 0.13) and at the end of follow-up (MD: -0.17, 95% CI: -1.33, 0.98, p = 0.77). The pooled two studies revealed relatively better efficacy of adjunctive use of PDT with antifungal therapy on candida colonization compared to antifungal therapy alone at 15 days (MD: -6.67, 95% CI: -15.15, 1.82, p = 0.12), and at the end of follow-up (MD: -7.14, 95% CI: -19.78, 5.50, p = 0.27). Additionally, the results revealed comparable efficacy of PDT and topical antifungal therapy on the clinical outcomes. CONCLUSIONS: PDT might be considered a viable option for DS either as an adjunct or as an alternative to the topical antifungal medications. Further studies with adequate sample sizes and standardized PDT parameters are warranted.

Efficacy of lycopene for management of oral potentially malignant disorders: A systematic review and meta-analysis.

OBJECTIVE: The aim of this study was to investigate the available evidence on the efficacy of lycopene in the management of oral potentially malignant disorders (OPMDs). STUDY DESIGN: PubMed, Scopus, Web of Science, Google Scholar, China National Knowledge Infrastructure, and ProQuest databases were searched up to April 20, 2022. All clinical trials that assessed the efficacy of lycopene (I) on the signs/symptoms (O) of patients with OPMDs (P) in comparison to either active control or placebo (C) were included. Meta-analysis was conducted using the RevMan software (Cochrane Collaboration, London, UK). RESULTS: A total of 27 clinical trials (20 on oral submucosa fibrosis [OSF], 5 on oral lichen planus [OLP], and 2 on leukoplakia) were included. Overall, lycopene was efficacious in reducing signs and symptoms of OSF, OLP, and leukoplakia. The pooled data revealed comparable efficacy of lycopene and prednisolone in reducing pain and promoting clinical resolution of OLP. Additionally, the pooled data reported comparable efficacy of lycopene and conventional controls in improving the mouth opening and tongue protrusion in patients with OSF. CONCLUSIONS: The results reveal promising effects of lycopene in alleviating signs and symptoms of OSF, OLP, and leukoplakia. However, owing to the observed heterogeneity and short follow-up periods, further well-designed studies with long-term therapy and follow-up are highly recommended.

Evaluation of the effects of chronic qat chewing on lateral pterygoid muscle using MRI.

Objective: This study explored the effect of qat chewing (QC) on the lateral pterygoid muscle (LPM), using magnetic resonance imaging (MRI).Methods: Forty qat chewers (QG), divided into three subgroups, according to duration of QC, and 20 non-qat chewers (NQG) were included. MRI sections were obtained to assess hypertrophy and atrophy of the superior belly (SB) and inferior belly (IB) of the LPM on the chewing and contralateral non-chewing side.Results: There was a significantly higher prevalence of atrophy of the IB (p < 0.001) and hypertrophy of the SB and IB (p = 0.002) in the QG. Hypertrophy of SB and IB was marked (p = 0.001) on the chewing side. Conversely, SB atrophy was marked on the non-chewing side (p = 0.003). MRI demonstrated a positive correlation between LPM alterations and the duration of QC in subgroup analysis.Conclusion: Unilateral QC might be a cause of LPM alterations.

Curcumin mouthwashes versus chlorhexidine in controlling plaque and gingivitis: A systematic review and meta-analysis.

OBJECTIVES: The purpose of the present systematic review and meta-analysis was to assess the available evidence regarding the efficacy of curcumin mouthwashes on plaque and gingivitis. METHODS: A comprehensive online search of multiple databases (PubMed, Scopus, Web of Science, and Google Scholar) was performed to identify all relevant studies published up to August 2020, using the following keywords: curcumin, turmeric, gingivitis, periodontal health, and plaque control. All clinical trials that compared the efficacy of curcumin mouthwash with chlorhexidine in controlling dental plaque and gingivitis were included. Data were analysed using Review Manager (RevMan) 5.3 software. The risk of bias was evaluated by two independent reviewers using the Cochrane assessment tool. RESULTS: Six randomized clinical trials (comprising 320 subjects) fulfilled the eligibility criteria. Five studies showed a high risk of bias and only one study showed a low risk of bias. The pooled data of the six included studies revealed comparable efficacy of curcumin and chlorhexidine in reducing dental plaque (I2  = 91%; standardized mean difference [SMD]: 0.27, 95% CI: -0.53, 1.07, p = 0. 51) and gingival inflammation (I2  = 40%; SMD: -0.13, 95% CI: -0.35, 0.09, p = 0.24), with no statistically significant differences between the two groups. CONCLUSION: The results suggest that curcumin mouthwashes have promising anti-plaque and anti-gingivitis properties. Further clinical trials with adequate sample sizes and standardized methodologies are required to discern the efficacy of curcumin mouthwash in reducing plaque and gingivitis.

Xerostomia, Salivary Flow, and Oral Health Status Among Saudi Diabetic Patients: A Comparative Cross-Sectional Study.

PURPOSE: Diabetes mellitus (DM) is associated with numerous oral complications, including frequent oral infections, periodontal diseases, hyposalivation, and xerostomia. The present study aimed to investigate salivary flow rate, xerostomia, and oral health status among a group of Saudi diabetic patients as compared to healthy controls. PATIENTS AND METHODS: This comparative cross-sectional study involved 50 diabetic patients (aged between 15 and 70 years) and 53 age- and gender-matched healthy controls. Data collection was carried out using a structured questionnaire and clinical examination of oral health status, which included salivary flow rates, saliva pH, tooth loss, plaque accumulation, and gingival health. Independent t-tests, one-way analysis of variance (ANOVA), and chi-square tests were performed to compare between groups. RESULTS: The results revealed a statistically significant lower salivary flow (0.33 ± 0.16 vs 0.59 ± 0.54; p = 0.002) and lower saliva pH (6.36 ± 0.49 vs 6.58 ± 0.39; p = 0.014) in diabetic patients than in the control group. A higher proportion of diabetic subjects (60%) self-reported having xerostomia compared to controls (52%), but the findings were statistically non-significant. Additionally, the results revealed slightly poorer oral health and greater tooth loss among DM patients, although the results did not attain a significant difference (P > 0.05). CONCLUSION: The findings of the present study demonstrate poor oral health and a high prevalence of xerostomia among Saudi diabetic patients. Oral health education should therefore be promoted in this group of patients.

Zinc supplementation for prevention and management of recurrent aphthous stomatitis: a systematic review.

BACKGROUND: Recurrent aphthous stomatitis (RAS) is a very common oral ulcerative disease with no definitive cure. Growing evidence suggests a significant association between zinc deficiency and RAS. OBJECTIVES: To assess the efficacy of systemic zinc supplementations in the prevention and management of RAS. METHODS: Five databases were searched for all English and Chinese studies published up to November 2020. All clinical trials that assessed the efficacy of zinc supplementations in the management and/or prevention of RAS were included. RESULTS: Seven clinical trials comprising 482 RAS patients (250 in zinc group) fulfilled the inclusion criteria. The follow-up period ranged from three months to one year. Five studies showed significantly better efficacy of zinc in reducing the recurrence rates of RAS, whereas two studies did not report any significant differences compared to the controls. Four studies reported on signs/symptoms of RAS, three of which showed superior outcomes in favour of zinc, while one study reported comparable results. CONCLUSION: Zinc supplementation seems to be efficacious in the management and prevention of RAS. However, further clinical trials with standardized methodologies and adequate follow-up periods are required to confirm the efficacy of zinc supplementations.

Survival Rates of Dental Implants in Patients with Papillon-Lefévre Syndrome: A Systematic Review.

AIM: The present review aimed to summarize and evaluate the available literature regarding the survival rate and outcomes of dental implants in patients with Papillon-Lefèvre syndrome (PLS). MATERIALS AND METHODS: An extensive search of the literature was conducted on PubMed, Scopus and Web of Science databases for all data published from January 1996 till April 2020 using a combination of the following keywords: 'Papillon Lefévre Syndrome', 'prosthodontic rehabilitation' and 'dental implant' according to the PRISMA guidelines for the focused research question constructed using the PICO criteria. Clinical trials and observational studies on implant placement in PLS patients reported in English language were included in the study. RESULTS: A total of 10 studies (nine case reports and one case series) comprising 124 dental implants placed in 13 PLS patients were included. The follow-up period ranged from 4 months to 9 years. With regard to implant loading, 9 studies reported delayed loading, while one study did not provide any information regarding the nature of implant loading. The design of prosthodontic superstructure was either a removable or fixed prosthesis. Out of the 124 inserted implants, 20 (16%) were reported as failed. The overall survival rate was 84%. CONCLUSION: The limited available evidence suggests that the survival rate of dental implants in patients with PLS is lower than that among healthy individuals. Nevertheless, no strict contraindication for implant-supported prosthesis seems to be justified in this group of patients. Further longitudinal studies with adequate follow-up periods are highly warranted. CLINICAL SIGNIFICANCE: The prognosis of implant treatment for PLS patients has not yet been established. Dental practitioners should follow a careful approach in planning the dental implant treatment for this cohort of patients.

Trend Analysis of Head and Neck Neoplasms between 2012-2018 in Patients Residing in Al-Madinah, Saudi Arabia: A Retrospective Study.

OBJECTIVES: This study sought to present a view of head and neck neoplasms (HNN) prevalence with specific focus on sociodemographic determinants in Al-Madinah Province, Saudi Arabia. MATERIALS AND METHODS: This was a hospital-based retrospective study based on retrieval of histopathological data for a period of 6 years between 2012 and 2018. Data was collected from the archives of the Oral and Maxillofacial Pathology Laboratory at King Fahad Hospital (the only referral center for biopsy services) in Al-Madinah City. STATISTICAL ANALYSIS: An independent t-test and/or nonparametric (Mann-Whitney U test, chi-squared test) tests were used to determine the differences between groups. Statistical significance was set at the p-value < 0.05. RESULTS: Out of 96 patients, a total of 58 patients had valid biopsy data with preoperative diagnosis. Over three quarters of the cases (n = 44) were benign with only 24% were malignant. Males were more likely to be diagnosed with a benign tumor than females (54.5 vs. 45.6%, respectively), and malignancy was also more common in males (64.3 vs. 24.1). A significant difference was found in relation to mean age of older patients who were more likely to be diagnosed with malignant tumors (p = 0.001). CONCLUSIONS: The findings suggest that most of biopsied HNN cases are benign neoplasms. Age is a significant risk factor for head and neck malignancy in this region. Delays in diagnosis of HNN need to be explored.

Cone beam computed tomography findings in the temporomandibular joints of chronic qat chewers: Radiographic bone density and trabecular microstructural analyses.

OBJECTIVES: This cross-sectional comparative study investigated the effects of qat chewing habit on the radiographic bone density (RBD) and trabecular microstructure of temporomandibular joint condyles using cone beam computed tomography (CBCT). STUDY DESIGN: In total, 85 systemically healthy Yemeni males were included and divided into qat chewers (QCs; n = 41); and non-qat chewers (NQCs; n = 44). The participants responded to a structured questionnaire and underwent standardized clinical examination and CBCT scanning of the temporomandibular joint. Measurements of RBD and trabecular microstructure (trabecular thickness, trabecular separation, bone volume fraction, and fractal dimension) were performed. Statistical significance was established at P ≤ .05. RESULTS: No statistically significant differences were found between QCs and NQCs in RBD or trabecular microstructure. The mean standard deviations and maximum values of trabecular separation on the nonchewing side for QCs were significantly lower compared to the corresponding values for NQCs (0.60 and 2.68 for QCs vs 0.72 and 3.05 for NQCs; P = .025 and .05, respectively). A comparison between chewing and nonchewing sides in QCs revealed no significant differences. CONCLUSIONS: Qat chewing habit induces insignificant changes in condylar RBD and trabecular microstructure as detected by CBCT. Further studies using advanced radiographic techniques are warranted.

Association between serum zinc levels and recurrent aphthous stomatitis: a meta-analysis with trial sequential analysis.

OBJECTIVES: The present meta-analysis sought to investigate the potential association between zinc levels and recurrent aphthous stomatitis (RAS). METHODS: A comprehensive search of online databases (PubMed, Scopus, Web of Science, and China National Knowledge Infrastructure (CNKI)) was conducted to identify all English and Chinese studies published up to August 2020. All case-control studies that assessed plasma/serum zinc levels were eligible for inclusion. Data were analyzed using Comprehensive Meta-Analysis software version 2.2.046 (Biostat, Englewood, NJ, USA). Trial sequential analysis (TSA) was conducted with the trial sequential analysis program. RESULTS: Nineteen case-control studies, involving 1079 RAS cases and 965 controls, were included in the meta-analysis. The pooled results of 19 studies showed that zinc level was significantly lower in RAS patients than in healthy controls (weighted difference in means = - 21.092, 95% CI - 26.695 to - 15.490, I2 = 95.375%, P < 0.001). Upon subgroup analysis by geographic distribution of the sample (Chinese vs. others), the association remained significant in each individual subgroup, although the association was more pronounced among Chinese populations. TSA indicated that the current studies surpassed the required information size, confirming that the differences were reliable. CONCLUSION: The results suggest a significant association between low serum zinc levels and the occurrence of RAS. Although TSA confirmed a solid conclusion, conducting large-scale studies with the highest standards of quality is encouraged. CLINICAL RELEVANCE: Determining zinc levels should be considered in diagnosis, management, and prevention of RAS.

Early detection of oral cancer and potentially malignant disorders: Experiences, practices, and beliefs of prosthodontists practicing in Saudi Arabia.

STATEMENT OF PROBLEM: Data on the oral cancer screening skills and beliefs of prosthodontists practicing in Saudi Arabia are lacking. PURPOSE: The purpose of this survey was to assess the beliefs, experiences, and practices of prosthodontists practicing in Saudi Arabia regarding the early detection of oral cancer and potentially malignant disorders. MATERIAL AND METHODS: A cross-sectional, questionnaire-based survey was conducted on prosthodontists practicing in Saudi Arabia. A 26-item questionnaire was sent to all eligible prosthodontists (N=250). The collected data were analyzed with a statistical software program. RESULTS: The response rate was 57.2% (N=143). The majority of participants (79%) reported that they routinely examined all new patients for mucosal pathologies. However, only 58% reported that they examine their patients at recall visits, and only 61.5% stated that they provide tobacco use or smoking cessation advice. With regard to the respondents' experiences with suspicious mucosal lesions, the majority said that they had detected a suspicious lesion (79.7%) and had referred affected patients (83.2%) during their career. Most prosthodontists (65%) believed that they were able to detect oral cancer on their own, and 40% believed that they could influence their patients to stop smoking. A lack of training, confidence, time, and financial incentives were reported as barriers to oral cancer screening. CONCLUSIONS: Most of the prosthodontists surveyed in this study appeared motivated to perform routine oral mucosal screening. However, more efforts are needed to help improve the attitudes, confidence, and skills of prosthodontists when it comes to identifying and referring suspicious oral mucosal lesions.

Cone beam computed tomography findings in temporomandibular joint of chronic qat chewers: Dimensional and osteoarthritic changes.

The social habit of chewing qat (also known as khat) is widely practised in East Africa and the Arabian Peninsula. It has been linked with various oro-facial conditions, including temporomandibular joint disorders (TMD). This cross-sectional, comparative study sought to investigate the effects of qat chewing on temporomandibular joint (TMJ), using cone beam computed tomography (CBCT). A total of 85 Yemeni males were included. The participants were divided into two groups: Qat chewers (QC; n = 41) and non-qat chewers (NQC; n = 44). Relevant data were obtained using a structured questionnaire and standardised clinical examination. Additionally, CBCT images of the TMJs were obtained, and then, osteoarthritic changes and TMJ dimensions were analysed. SPSS 21 was used for statistical analyses, with a significant level was set at 0.05. Compared to NQC, a significantly higher proportion of QC presented with clinical signs of TMDs. The qualitative CBCT findings revealed significantly higher osteoarthritic changes in QC than in NQC: osteophyte (51.2% vs 22.7%; P = .008), subcortical sclerosis (48.8% vs 27.3%; P = .047), articular surface flattening (46.3% vs 6.8%; P = .009) and subcortical cysts (43.9% vs 4.5%; P < .001). However, CBCT quantitative findings (condylar dimensions) did not show significant differences between the two groups. The chewing side of the QC group showed slightly more changes compared to the non-chewing side. The results demonstrate that qat chewing has detrimental effects on TMJ manifested mainly as osteoarthritic changes. Further large-scale studies are recommended.

The association between Epstein-Barr virus and oral lichen planus: A systematic review and meta-analysis.

BACKGROUND: Oral lichen planus (OLP) is a relatively common inflammatory disease, with unclear etiology. A number of studies have linked Epstein-Barr virus (EBV) with OLP. The present systematic review and meta-analysis aimed to evaluate the available evidence regarding the potential association between EBV and OLP. METHODS: Online databases (PubMed, Scopus, Web of Science, ProQuest, and Google Scholar) were searched from date of inception till May 2020. Studies were included if they met the following criteria: 1) observational studies that assessed the relationship between EBV and OLP, 2) the study comprised OLP patients and control subjects, 3) diagnosis of OLP was confirmed histopathologically, and 4) articles were in English. Studies without control groups, experimental studies, case reports, and reviews were excluded. The fixed-effects model was performed for meta-analyses using RevMan 5.3 software. RESULTS: A total of 10 studies comprising 386 OLP cases and 304 controls were included. Of these, only 8 studies were eligible for the meta-analysis. The results of the quality assessment showed that only 2 studies were of high quality, while the remaining studies were of moderate quality. The results of the pooled eight studies revealed a significant positive association between EBV and OLP (OR = 4.41, 95% CI: [2.74, 7.11], P < .0001). CONCLUSION: The results of the present systematic review suggest that EBV infection is statistically associated with increased risk of OLP. However, these results are preliminary, and high-quality, large-scale studies are warranted to further explore the potential role of EBV in the pathogenesis of OLP.

Efficacy of propolis-based mouthwashes on dental plaque and gingival inflammation: a systematic review.

BACKGROUND: This systematic review of randomized clinical trials aimed to evaluate the available evidence regarding the efficacy of propolis-based mouthwash on dental plaque and gingival inflammation. METHODS: PubMed, Scopus, and Web of Science databases were searched up to November 2019. Clinical trials that evaluated the efficacy of propolis mouthwashes compared with chlorhexidine (CHX) were included. The primary outcomes comprised dental plaque and/or gingival inflammation. Two authors assessed the risk of bias using the Cochrane tool. Due to marked heterogeneity of the available data, studies were assessed qualitatively, and no metaanalysis was performed. RESULTS: Nine clinical trials, comprising 333 subjects, fulfilled the eligibility criteria. Most of the included studies showed high risk of bias. Overall, propolis mouthwashes showed good efficacy on plaque and gingivitis in all of the included studies. Out of the eight studies that reported on plaque index, 5 studies found equal efficacy of propolis and CHX in reducing plaque, two studies found superior efficacy in favor of CHX, while one study found superior efficacy in favor of propolis. Six studies assessed gingival inflammation outcome, four of which reported better results with propolis, while two studies reported comparable results. CONCLUSIONS: The results suggest that propolis-based mouthwashes have potential benefits in reducing plaque and gingival inflammation. However, methodological limitations along with small sample sizes in some of the included studies weaken the strength of the evidence. Therefore, further well-designed clinical trials with large sample sizes and adequate follow-up period are recommended to discern the efficacy of propolis mouthwash on plaque and gingivitis.

Efficacy of aloe vera mouthwash versus chlorhexidine on plaque and gingivitis: A systematic review.

OBJECTIVES: The present systematic review assessed the efficacy of aloe vera mouthrinse on plaque and gingival inflammation. METHODS: A comprehensive search of PubMed, EMBASE, Scopus and Web of Science was conducted in February 2018 to identify all relevant studies using the following keywords: aloe vera, gingivitis, gingival inflammation, plaque-induced gingivitis, periodontal health and plaque control. The eligibility criteria were all randomized clinical trials that assessed the efficacy of aloe vera mouthrinse in comparison to chlorhexidine on plaque and gingivitis. The risk of bias of the included studies was assessed using the Cochrane risk of bias assessment tool. RESULTS: Six randomized clinical trials comprising 1358 subjects were included in this systematic review. All included studies showed that aloe vera was effective in reducing plaque and gingival inflammation. Four studies found aloe vera as effective as chlorhexidine in reducing plaque scores, while two studies found chlorhexidine significantly more effective than aloe vera. With regard to gingival inflammation, three studies showed comparable results between aloe vera and chlorhexidine, while one study showed better results with chlorhexidine. Moreover, the results showed that aloe vera had no or very minimal side effects compared to chlorhexidine, which showed significant side effects including stains and altered taste sensation. CONCLUSION: The available evidence remains inconclusive but suggests that aloe vera mouthwash is comparable to chlorhexidine in reducing gingival inflammation but inferior to chlorhexidine in reducing plaque. These findings are preliminary and further high-quality studies with adequate sample sizes are highly recommended.

Khat (Catha edulis) and its oral health effects: An updated review.

Khat or qat (Catha edulis) is a plant that grows in East Africa and southern Arabia. The leaves and twigs of this small tree are chewed by several millions of people worldwide for their stimulating amphetamine-like effects. The reported prevalence of khat chewing in Europe and the USA is on the rise, especially with global migration. Long-term khat chewing has several detrimental general and oral health effects. The aim of the present study was to review the current literature regarding khat use and its association with oral and dental diseases, with particular emphasis on its link with oral keratotic white lesions and oral cancer. We searched the literature to identify all relevant articles. Studies showed that khat is associated with several oral and dental conditions, including keratotic white lesions, mucosal pigmentation, periodontal disease, tooth loss, plasma cell stomatitis, and xerostomia. There are limited data on the incidence of dental caries among khat chewers. The evidence that khat chewing is a risk factor for oral cancer is still weak, and is mainly based on anecdotal case reports and uncontrolled studies.

Influence of Different Post Luting Cements on the Fracture Strength of Endodontically Treated Teeth: An In Vitro Study.

OBJECTIVE: To evaluate the fracture resistance of endodontically treated mandibular premolars restored with glass fiber posts using different luting agents. METHODS: Twenty-four extracted single-rooted mandibular premolars were endodontically treated, and post spaces were prepared to receive fiber posts. They were assigned to three test groups (n=8) according to the type of cement used for the cementation of glass fiber posts: RC group: adhesive resin cement group (etch and rinse), SC group: self-adhesive resin cement group, and GC group: glass ionomer cement group. Teeth in all groups were adhesively restored with a composite resin core material and crowned with Ni-Cr crowns. All specimens were subjected to tangential loading using a universal testing machine until fracture at 30°. Failure loads were recorded, and data were analyzed using one-way ANOVA followed by Tukey's HSD test (α=0.05). RESULTS: Specimens in the RC group were more resistant (258.3±12.7 N) to fracture than those in the SC (218.7±11.1 N) and GC (165.4±8.9 N) groups (P≤0.001). One-way ANOVA indicated that the type of cement had a significant effect on the fracture resistance of endodontically treated lower premolars (P≤0.001). CONCLUSION: The type of cement that was used to fix glass fiber posts was a determining factor of the fracture resistance of endodontically treated lower premolars.