Survival time analysis of remaining teeth following replacement of unilateral free-end missing teeth: A comparison between fixed implant-supported prostheses and removable partial dentures.

OBJECTIVES: This retrospective study aimed to investigate the differences in tooth loss rate between fixed implant-supported prostheses (FISPs) and removable partial dentures (RPDs) in cases of unilateral free-end missing teeth. MATERIALS AND METHODS: The data of 324 patients who underwent treatment with FISPs or RPDs for unilateral free-end missing teeth and satisfied the applicable criteria, were evaluated (47 in the FISPs group and 277 in the RPDs group). After propensity score (PS) matching, which was used to extract patients with similar background factors related to prosthetic selection at baseline, survival time analyses were performed with tooth loss as the endpoint. The adjusted variables were age, sex, number of restored teeth, periodontal status, and the practicing dentist's experience in years. The remaining teeth were classified into subcategories in relation to the missing molars. RESULTS: Overall, 58 patients (29 in each group) selected by PS matching were evaluated in the final analysis. The total number of lost teeth was 35 (FISPs group: n = 10; RPDs group: n = 25). The mean (±SD) period to tooth loss and the 10-year survival rates in the FISPs and RPDs groups were 51.6 (±30.1) months and 42.3 (±29.7) months, 70.5% and 16.4%, respectively. The log-rank test showed that significantly longer survival time in FISPs compared with RPDs. CONCLUSIONS: After adjustments for confounding factors using PS matching, replacing unilateral free-end missing teeth with FISPs may exhibit a lower tooth loss rate in adjacent and contralateral teeth compared to replacing with RPDs.

Force exerted on maxillary anterior teeth in mandibular unilateral and bilateral distal extension partial edentulous situation.

The purpose of this study was to determine the influence of mandibular unilateral and bilateral distal extension partial edentulous situation and the use of removable partial dental prostheses on the force exerted on maxillary anterior teeth. A commercially available jaw model with exchangeable teeth was used. Seven experimental conditions of mandibular distal extension edentulous situation were prepared and a distal extension removable partial dental prosthesis to replace missing posterior teeth was fabricated. The occlusal force was measured by inserting an occlusal force measuring film between the maxillary and mandibular teeth of the model. An occlusal load was applied and the forces and ratios were compared using the Kruskal-Wallis test and the Mann-Whitney U test (p < 0.05). As a result, the force exerted on the maxillary anterior teeth increased significantly as the number of remaining teeth decreased in unilateral and bilateral edentulous situation. The force exerted on the maxillary anterior teeth decreased significantly with use of a removable partial dental prosthesis. It is concluded that when the number of remaining teeth decreases in mandibular unilateral and bilateral distal extension partial edentulous situation, the burden on the maxillary anterior teeth increases. Our findings suggest that for patients with mandibular distal extension partial edentulous situation, using a removable partial dental prosthesis is effective in preserving the remaining teeth by reducing excessive force.

Longitudinal changes in mouthguard fit: Reliability of an evaluation method.

BACKGROUND/AIM: A mouthguard should be replaced when it deteriorates or becomes deformed as a result of the softness or flexibility of the material. The question, however, is how long can one use a mouthguard and when should one replace it with a newly made mouthguard? The aim of this study was to develop an improved method for measuring the fit of mouthguards based on previous reports and to examine its reliability. MATERIAL AND METHODS: Silicone fit-testing material was applied to the inner surface of the mouthguards of 12 participants, and the mouthguards were inserted into the participants' oral cavity. After the test material had set, the mouthguard was weighed. The intra-rater reliability and inter-rater reliability were analyzed using intraclass correlation coefficients. RESULTS: The intra-rater reliability was 0.813 (P < .001), and the inter-rater reliability was 0.817 (P < .001). Both values were greater than 0.7, suggesting that this measuring method had sufficient reliability. CONCLUSIONS: The results of this study indicate that mouthguard fit can be evaluated longitudinally to determine the optimal time to replace a mouthguard.

Influence of mouthguards and their palatal design on the stress-state of tooth-periodontal ligament-bone complex under static loading.

BACKGROUND/AIM: The mouthguard (MG) is an effective device to reduce the risk of dental traumatic injuries, but the mechanical effects of wearing a MG and its design are not fully understood. The aim of this study was to evaluate the mechanical influence of wearing a MG and its palatal design on the tooth-periodontal ligament-bone complex (TPBC) by computational analysis using the finite element method. MATERIAL AND METHODS: Three-dimensional subject-specific geometry of the TPBC was reconstructed from medical computed tomography (CT) images. Two patterns of MG geometries were constructed which covered the palatal domain or not (the position of these palatal margins was set at -8 mm (pattern 1) and 4 mm (pattern 2) from the cervical line. Five cases of static mechanical analysis were conducted by changing the location of the loading points from near the cervical line to the tip of the tooth. RESULTS: Wearing a MG decreased strain concentration around the loading point and cervical domain regardless of the MG palatal design. Elastic energy in the periodontal ligament (PDL) and tooth (including enamel and dentin) decreased when the MG was worn, whereas the MG palatal design slightly affected the degree of reduction in the elastic energies. The location of the loading points remarkably affected the elastic energy in the TPBC components and the extent of its reduction due to the MG. CONCLUSIONS: These findings indicated that the protection ability of the MG exerted in the restricted situations of traumatic events occurs regardless of the MG design.

Mouthguards and their use in sports: Report of the 1st International Sports Dentistry Workshop, 2016.

There appears to be much confusion or misinformation worldwide regarding mouthguards and their use in sports. In an effort to clarify where the international dental community stands on mouthguards and mouthguard research, the workshop looked at some important questions. The goal was to one day formulate consensus statements related to these questions, which will be based on current scientific evidence-based research, to motivate the international community of the importance of dentally fitted laminated mouthguards and the wearing of them by athletes of all sports. There are only five sports in the United States that require the use of mouthguards. If, through workshops such as this, the importance of wearing dentally fitted laminated mouthguards can be demonstrated, then more sports may require their athletes to wear them.

Lateral forces exerted through ball or bar attachments in relation to the inclination of mini-implant underneath overdentures: in vitro study.

OBJECTIVE: Lateral force to mini-implants should be avoided because mini-implants are weak mechanically because of its small diameter. Overdentures retained by mini-implants are usually formed using ball attachments. However, bar attachments can offer the advantage of splinting the mini-implants. This study examined the effect of attachments in withstanding these lateral forces in tilted mini-implants of overdentures. MATERIALS AND METHODS: Strain gauges were attached to the mini-implants (2.5 × 18 mm) embedded in an acrylic resin block. Two mini-implants were inserted vertically (Control) or with one mini-implant inclined at 10° or 20° (10-inclined and 20-inclined, respectively). The female portions of the attachments were secured to the denture base. A prefabricated ball attachment and CAD/CAM-fabricated bar attachment were compared. A vertical load of 49 N was applied to the occlusal surface at a distance 10 mm away from the center of two mini-implants. The lateral force borne by the mini-implants was measured via the attached strain gauge. Mann-Whitney U-test and an analysis of Bonferroni correction were used to compare differences between the two attachments and among the three models (P < 0.05). RESULTS: The lateral force exerted to the inclined mini-implant was significantly greater than that borne by a vertical mini-implant for both attachment types. The lateral force on the 20° inclined mini-implants with bar attachments was smaller than that on mini-implants with ball attachments. CONCLUSION: Inclined mini-implants are subjected to greater stresses than vertical ones, and a bar attachment can reduce the lateral forces borne by the mini-implant when one mini-implant inclined at 20°.

Clinical performance and satisfaction of removable prostheses with self-adjusting magnetic attachments.

STATEMENT OF PROBLEM: Conventional magnetic attachments have rigid assemblies and are unable to compensate for the movement of the prosthesis under function, which may result in the deepening of periodontal pockets and an increase in the mobility of abutment teeth. PURPOSE: The purpose of this study was to evaluate the clinical performance and satisfaction of participants with removable prostheses with self-adjusting magnetic attachments that allow vertical and rotational movement. MATERIAL AND METHODS: The clinical performance of 17 prostheses with 22 self-adjusting magnetic attachments in 16 participants was analyzed for a mean of 3.1 years. Periodontal indices, including probing pocket depth and tooth mobility, were measured at denture placement (baseline) and from 0.5 to 5 years after insertion. Control data were obtained from the remaining teeth, which were restored by resin or metal coping. Prosthetic parameters, including the reduction of retention in self-adjusting magnetic attachments, reline, or fracture of dentures, were also recorded. A visual analog scale questionnaire on participant satisfaction with stability, comfort, and cleaning of the prostheses was completed. The Wilcoxon signed rank test and 1-way analysis of variance (α=.05) were performed on data collected at the time of prostheses placement and final follow-up evaluation. RESULTS: No significant differences were found in terms of probing pocket depth and tooth mobility between the baseline and postinsertion data for self-adjusting magnetic attachments and control teeth. Retention in all prostheses was stable, without reduction. Higher visual analog scale scores for "easy cleaning" were noted. CONCLUSIONS: No significant difference between baseline and postinsertion was noted regarding the periodontal condition of self-adjusting magnetic attachments and control teeth with resin or metal coping materials.

Effects of denture use on occlusal force on abutment teeth in molar distal-extension edentulism.

PURPOSE: The present clinical study aimed to investigate the load exerted on abutment teeth in patients with distal extension edentulism, with and without a removable partial denture (RPD). METHODS: A total of 55 volunteers with distal extension edentulism who were fitted with an RPD participated in the present study. Occlusal force was measured by having the patients bite down on an occlusal force measuring sheet, and the occlusal forces on both the abutment teeth and the entire dentition with and without the RPD were compared using the Wilcoxon signed-rank test (P < 0.05). The occlusal forces on the abutment and non-abutment teeth were also compared. RESULTS: The median total occlusal force with the RPD in place was significantly greater than that without the RPD, while the median occlusal force on the abutment teeth without the RPD in place was significantly greater than that on the abutment teeth with the RPD. The occlusal forces on the abutment teeth were significantly greater than those on the non-abutment teeth. CONCLUSIONS: Within the limitations of the present study, we found that the occlusal forces were greater on the abutment than the non-abutment teeth, and that RPDs may reduce the occlusal forces on abutment teeth.

Clinical Measurements of Force Exerted on Anterior Teeth in Partial Edentulous Distal Extension.

PURPOSE: To determine the influence of partial edentulous distal extension and the use of removable partial dental prostheses in partially edentulous areas on the force exerted on the anterior teeth. MATERIALS AND METHODS: A total of 83 volunteer patients participated in this study. The occlusal force was measured using an occlusal force measuring sheet in the patient's mouth. The occlusal forces and ratios were compared using the Wilcoxon signed-rank test (P < .05). RESULTS: The force exerted on the anterior teeth increased significantly as the number of remaining teeth decreased in an edentulous distal extension. The force exerted on the anterior teeth decreased significantly with the use of a removable partial dental prosthesis. CONCLUSIONS: In a clinical setting, when the number of remaining teeth in a partial edentulous distal extension decreases, the burden on the anterior teeth increases. Our findings suggest that, for patients with partial edentulous distal extension, using a removable partial dental prosthesis is effective in preserving the residual anterior teeth by reducing excessive force.

Mechanical Influence of Edentulous Mandibular Morphology on Peri-implant Bone in Implant Prosthetics: Threedimensional Finite Element Analysis.

PURPOSE: The purpose of this study was to examine the mechanical influence of edentulous mandibular morphology on peri-implant bone in implant prosthetics by finite element analysis. MATERIALS AND METHODS: Computed tomographic data from 25 patients with edentulous mandibles were selected and the radius of mandibular curvature and the height of the mandible at the midline were measured in order to clarify the morphological characteristics of the mandible. From the measurement, two patients with the smallest and largest radii of the mandible were selected. Two types of three-dimensional finite element models consisting of the edentulous mandible (small and large radius), superstructure (a cantilever bridge), implants, and abutments were created. Four implants were inserted between the right and left mental foramina. The upper surface of the mandibular condyle was constrained, and a vertical load of 100 N was applied on the occlusal surface of the right first molar. Three-dimensional finite element analysis of each model was performed to examine the mechanical influence of the edentulous mandibular morphology on the peri-implant bone. RESULTS: Measurement of mandibular morphology in CT images indicated that the lower the mandibular height was, the larger was the radius of the anterior mandibular curvature. Finite element analysis revealed that a higher equivalent stress was generated in the peri-implant bone of the model with a larger radius of curvature than that of the model with a smaller radius of curvature. The highest equivalent stress in the mandible was generated in the distal margin of the peri-implant bone posterior to the loaded side of the large radius of curvature model. CONCLUSIONS: The mandibular morphology had a mechanical influence on the peri-implant bone.

Influence of reinforcing materials on strain of maxillary complete denture.

OBJECTIVE: A maxillary complete denture has been a common prosthetic treatment for people with edentulous maxillas. The fracture and deformation of dentures are recurrent and common problems for denture-wearers. Consequently, reinforcement materials are embedded in the denture base to prevent fracture and deformation. The purpose of this study was to examine the influence of reinforcing materials on the strain within the acrylic base of a maxillary complete denture. MATERIALS AND METHODS: Three reinforcements (cast cobalt-chromium bar; glass fibers; and cobalt-chromium wire) were embedded in the bases and a strain-gauge was attached at three positions (labial, middle and posterior) at the mid-line of the polished surface of each denture. A vertical occlusal load of 49 N was applied to the left and right side in the region of the 1st premolar and the 1st molar. Comparisons of the strain were made via ANOVA. RESULTS: The strain of the denture base with a cast cobalt-chromium reinforcement was significantly (p < 0.05) smaller than that with the other reinforcements. CONCLUSIONS: This result suggested that a cast cobalt-chromium reinforcement helps to reduce the risk of fracture and deformation of a maxillary complete denture.

Clinical measurement of force exerted on anterior teeth in partial edentulous distal extension.

PURPOSE: The aim of this clinical study was to determine the influence of partial edentulous distal extension and the use of removable partial dental prostheses in partially edentulous areas on the force exerted on the anterior teeth. MATERIALS AND METHODS: Eighty-three volunteer patients participated in this study. The occlusal force was measured by using an occlusal force measuring sheet in the patient's mouth. The occlusal forces and ratios were compared with the Wilcoxon signed-rank test (p < 0.05). RESULTS: The force exerted on the anterior teeth increased significantly as the number of remaining teeth decreased in an edentulous distal extension. The force exerted on the anterior teeth decreased significantly with the use of a removable partial dental prosthesis. CONCLUSION: When the number of remaining teeth decreases in a partial edentulous distal extension, the burden on the anterior teeth increases in a clinical setting. Our findings suggest that, for patients with partial edentulous distal extension, using a removable partial dental prosthesis is effective in preserving the residual anterior teeth by reducing excessive force. Int J Prosthodont 2023. doi: 10.11607/ijp.8281.

Effect of Posterior Residual Ridge Resorption and Relining for Mandibular Implant Overdentures on Bending Strain Around Implants.

PURPOSE: To examine the influence of posterior residual ridge resorption (PRRR) and relining on bending strain around implants under an overdenture. MATERIALS AND METHODS: Maxillary and mandibular edentulous models were made and covered with white silicone. Four strain gauges were placed on four sides of each implant. Two tissue-level implants were placed bilaterally in the part between the lateral incisors and canines of the mandible. A maxillary conventional denture and a mandibular overdenture were fabricated to fit the models. Three levels of bone resorption around the implant were created: 0, 0.8, and 1.5 mm. The surface of the residual ridge was uniformly removed from the area near the distal side of the implant to the retromolar section, and three levels of PRRR were created (0, 1, and 1.5 mm). After the measurement, the experimental denture of the PRRR of 1 mm and 1.5 mm were relined. Locator attachments were used. A 98-N occlusal force was applied, and bending strains around the implant were measured. The Kruskal-Wallis test and Bonferroni correction were employed to analyze the data. RESULTS: Without relining, at each bone resorption level around the implant, the bending strain was smallest with PRRR of 0 mm and largest with PRRR of 1.5 mm. The bending strain after relining was smaller than the bending strain with ridge resorption. Bending strains after relining were smaller than bending strains with no ridge resorption, but there was no significant difference in bending strain between these three groups. CONCLUSION: As PRRR increased, the bending strain increased without relining. As bone resorption around the implant progressed, PRRR enhanced the increase in the peri-implant bending strain. Bending strain was reduced when relining was performed.

Impact of number of functional teeth on independence of Japanese older adults.

AIM: To examine the relationship between the number of present and functional teeth at baseline and future incidence of loss of independence. METHODS: Participants were community-dwelling older individuals who participated in a comprehensive geriatric health examination conducted in Kusatsu town, Japan, between 2009 and 2015. The primary endpoint was the incidence of loss of independence among participants, defined as the first certification of long-term care insurance in Japan. The numbers of present and functional teeth at baseline were determined via an oral examination. Demographics, clinical variables (e.g., history of chronic diseases and psychosocial factors), blood nutritional markers, physical functions, and perceived masticatory function were assessed. RESULTS: This study included 1121 individuals, and 205 individuals suffered from loss of independence during the follow-up period. Kaplan-Meier estimates of loss of independence for participants with smaller numbers of present and functional teeth were significantly greater than for those with larger numbers of teeth. Cox proportional hazard analyses indicated that a smaller number of present teeth was not a significant risk factor after adjusting for demographic characteristics. However, the number of functional teeth was a significant risk factor after the adjustment (hazard ratio: 1.975 [1.168-3.340]). Additionally, higher hazard ratios were observed in other adjusted models, but they were not statistically significant. CONCLUSIONS: The number of functional teeth may be more closely related to the future incidence of loss of independence than the number of present teeth. This novel finding suggests that prosthodontic rehabilitation for tooth loss possibly prevents the future incidence of this life-event. Geriatr Gerontol Int 2022; 22: 1032-1039.

Attachment systems for implant overdenture: influence of implant inclination on retentive and lateral forces.

OBJECTIVE: To evaluate the retentive force and lateral force of an implant with various types of attachments for overdentures in relation to implant inclination. MATERIAL AND METHODS: An implant (3.75 × 13 mm) was embedded into an acrylic resin block, simulating the edentulous ridge. Four different attachment systems were used, including: (1) Locator black and blue, (2) a ball attachment, (3) a flat-type magnetic attachment and (4) a self-adjusting magnetic attachment, which has vertical and rotational movement. All of the attachments were under a constant dislodging force with an angle of the implant at 0°, 15°, 30° and 45°, and the experiments were repeated 10 times using a universal testing machine to measure the retentive force. The lateral force to the implant was measured by strain gauges attached on the implant surface. Statistical analysis was performed by multiple comparisons with Bonferroni's correction. P<0.05 was considered statistically significant. RESULTS: At 0°, the significantly highest retentive force was observed in the Locator blue, followed by the Locator black, ball, flat-type and self-adjusting magnetic attachments. The Locator blue and ball attachment maintained the retentive force until a 30° inclination; however, the lateral force increased significantly, especially with the ball attachment. The retentive force of the magnetic attachment was significantly lower at 0°, as well as the lateral force in the self-adjusting magnetic attachment. CONCLUSION: Within the limitations of this study, we conclude that the retentive force decreases with an increase in implant inclination, whereas the lateral force increases, except for in magnetic attachments.

Subjective values of different age groups in Japan regarding treatment for missing molars.

OBJECTIVE: To determine how patients and dentists in Japan value the outcomes of different treatment options for missing molars. MATERIALS AND METHODS: Elderly removable-denture wearers and dentate persons (senior group), preclinical dental students (young group), and prosthodontists were presented with five possible treatment options for missing lower bilateral first and second molars. The participants indicated on a visual analogue scale how they would value the treatment (utility value: UV), if they had received each of the treatments. Two-way repeated measures anova was used for statistical analyses. RESULTS: The UV for the shortened dental arch (SDA) without replacement was the lowest in every group. The young group rated the value of cantilever fixed partial dentures (FPD) and implants significantly higher than removable partial dentures (RPD), while the senior group rated the value of FPD and RPD significantly higher than implants. Those having experience with removable dentures were likely to place a higher value on the acrylic RPD. The prosthodontists rated the value of implants significantly higher than any other options. CONCLUSIONS: The participants in every group placed the lowest value on the outcome from the SDA in Japan. The denture wearers preferred the RPD, while prosthodontists preferred implants.

A system for designing removable partial dentures using artificial intelligence. Part 1. Classification of partially edentulous arches using a convolutional neural network.

PURPOSE: The purpose of this study was to develop a method for classifying dental arches using a convolutional neural network (CNN) as the first step in a system for designing removable partial dentures. METHODS: Using 1184 images of dental arches (maxilla: 748 images; mandible: 436 images), arches were classified into four arch types: edentulous, intact dentition, arches with posterior tooth loss, and arches with bounded edentulous space. A CNN method to classify images was developed using Tensorflow and Keras deep learning libraries. After completion of the learning procedure, the diagnostic accuracy, precision, recall, F-measure and area under the curve (AUC) for each jaw were calculated for diagnostic performance of learning. The classification was also predicted using other images, and percentages of correct predictions (PCPs) were calculated. The PCPs were compared with the Kruskal-Wallis test (p = 0.05). RESULTS: The diagnostic accuracy was 99.5% for the maxilla and 99.7% for the mandible. The precision, recall, and F-measure for both jaws were 0.25, 1.0 and 0.4, respectively. The AUC was 0.99 for the maxilla and 0.98 for the mandible. The PCPs of the classifications were more than 95% for all types of dental arch. There were no significant differences among the four types of dental arches in the mandible. CONCLUSIONS: The results of this study suggest that dental arches can be classified and predicted using a CNN. Future development of systems for designing removable partial dentures will be made possible using this and other AI technologies.

Influence of Implant Distribution and Palatal Coverage on the Strain of Splinted Implant and Overdenture in Maxillary Implant Overdentures.

PURPOSE: Implant overdentures with splinted attachments have been used in clinical practice, and the effect of splinting on implants has been reported frequently. However, the effect of implant configuration of more than four implants and covering the palate with an overdenture has not been sufficiently examined. The purpose of this study was to reveal the effects of implant configuration and palatal coverage on both implant and denture strain in maxillary implant overdentures using splinted implants. MATERIALS AND METHODS: Six implants were placed in the anterior, premolar, and molar areas in a maxillary edentulous model. Four strain gauges were attached to the implant surface, and Dolder bar attachments were used to splint implants distributed in various configurations. Two types of maxillary experimental dentures (with/without palatal coverage) were fabricated, and two strain gauges were attached at the midline. A vertical load of 98 N was applied, and the strains on the dentures and implants were measured. The strain measurements were compared using one-way analysis of variance and t test (P = .05). RESULTS: When comparing the implant strains, the strain was significantly smaller on the anterior and premolar implants when six implants were used, but there was no significant difference among the different implant configurations in the strain on the molar implants. Strains on anterior implants of the palateless overdenture were significantly greater than those of the overdenture with palatal coverage. When four implants were used, the strain on the palatal side of dentures without palate was significantly greater than that on those with palatal coverage. When six implants were used, there was no significant difference in the strain on either side between two types of dentures. CONCLUSION: When implants were splinted to each other using a denture without palatal coverage, the strain of dentures when six or two anterior and two posterior implants were used was lower. The difference of denture strains between two types of dentures was not significant when six implants were used, but was significant for all other configurations. Also, the difference of implant strains between two dentures was significant in anterior implants regardless of implant configuration.

Deep learning-based detection of dental prostheses and restorations.

The purpose of this study is to develop a method for recognizing dental prostheses and restorations of teeth using a deep learning. A dataset of 1904 oral photographic images of dental arches (maxilla: 1084 images; mandible: 820 images) was used in the study. A deep-learning method to recognize the 11 types of dental prostheses and restorations was developed using TensorFlow and Keras deep learning libraries. After completion of the learning procedure, the average precision of each prosthesis, mean average precision, and mean intersection over union were used to evaluate learning performance. The average precision of each prosthesis varies from 0.59 to 0.93. The mean average precision and mean intersection over union of this system were 0.80 and 0.76, respectively. More than 80% of metallic dental prostheses were detected correctly, but only 60% of tooth-colored prostheses were detected. The results of this study suggest that dental prostheses and restorations that are metallic in color can be recognized and predicted with high accuracy using deep learning; however, those with tooth color are recognized with moderate accuracy.

Average rate of ridge resorption in denture treatment: A Systematic Review.

Purpose To clarify the rate of posterior residual ridge resorption (PRRR) in different denture treatments and the factors that can affect PRRR.Study selection A bibliographical electronic search was conducted on MeSH, Web of Science, and Ovid databases. Hand searching was also conducted. Longitudinal studies recording the average rate of PRRR in the mandible were included. The effect size was calculated based on the mean rate of PRRR with standard deviation and group size. The random-effects analysis was used to perform meta-analyses across qualified studies.Results A total of 2245 eligible studies were collected from the MeSH, Web of Science, and Ovid databases and hand searching. In the end, 19 studies met the inclusion criteria and were extracted. The average rate of PRRR in different mandibular denture treatments was assessed in this systematic review. The mean combined effect size was -1.05 ± 0.5 (95% confidence interval [CI]: -3.18-1.08) between four-implant overdentures and two-implant overdentures. The combined effect size was -0.01 ± 0.22 (95% CI: -0.93-0.82) between complete dentures and two-implant overdentures. Body mass index, number of dentures used, denture wearing habit, impression technique, artificial tooth material, and peri-implant bone resorption showed no significant effect on the rate of PRRR. Gender, denture material, and relining frequency showed a significant effect on the rate of PRRR.Conclusions This review summarized different average rates of PRRR in mandibular denture treatments. Meta-analyses have reported that four-implant overdenture treatments can lower the rate of PRRR compared to two-implant overdenture treatments. However, there was no significant difference in the treatment effect between the complete denture and two-implant overdenture treatments.