Implant supported cantilevered fixed dental rehabilitations in partially edentulous patients: Systematic review of the literature. Part I

Material and abutment selection for CAD/CAM implant-supported fixed dental prostheses in partially edentulous patients - A narrative review

Restorative material selection has become increasingly challenging due to the speed of new developments in the field of dental material science. The present narrative review gives an overview of the current indications for implant abutments and restoration materials for provisional and definitive implant-supported fixed dental prostheses in partially edentulous patients. For single implant restorations, titanium base abutments for crowns are suggested as an alternative to the conventional stock- and customized abutments made out of metal or zirconia. They combine the mechanical stability of a metallic connection with the esthetic potential of ceramics. For multiple-unit restorations, conical titanium bases especially designed for bridges are recommended, to compensate for deviating implant insertion axes and angulations. Even though titanium base abutments with different geometries and heights are available, certain clinical scenarios still benefit from customized titanium abutments. Indications for the definitive material in fixed implant restorations depend on the region of tooth replacement. In the posterior (not esthetically critical) zone, ceramics such as zirconia (3-5-Ymol%) and lithium-disilicate are recommended to be used in a monolithic fashion. In the anterior sector, ceramic restorations may be buccally micro-veneered for an optimal esthetic appearance. Lithium-disilicate is only recommended for single-crowns, while zirconia (3-5-Ymol%) is also recommended for multiple-unit and cantilever restorations. Attention must be given to the specific mechanical properties of different types of zirconia, as some feature reduced mechanical strengths and are therefore not indicated for all regions and restoration span lengths. Metal-ceramics remain an option, especially for cantilever restorations.

A proof of concept on implant-supported bilateral cantilever bridges: The T-Bridge approach

The concept of bilateral cantilevers on a single central implant (T-design) for three-unit implant-supported fixed dental prostheses (ISFDPs) has not been explored nor tested. This technical hypothesis aimed to explore the feasibility of such an approach as a cost-effective alternative to conventional treatments. Careful considerations regarding implant diameter, length, ideal position, occlusal scheme, and bone remodeling are essential to ensure adequate support, stability, and prevention of complications. In this proof of concept, we present a preliminary case with this novel design to replace missing posterior teeth in a patient with narrow bone conditions. In addition, a series of planned investigations and preliminary results, including preclinical studies, are presented to illustrate our concept and its potential clinical implications. Clinically, after two-year follow-up, healthy and stable peri-implant tissues around the ISFDP exemplarily demonstrated excellent stability, functionality, and comfort, which is supported by acceptable fracture resistance data in vitro, suggesting indeed the practical potential and suitability. Thus, we claim that such a treatment modality has the at least theoretical potential to revolutionize implant dentistry by providing innovative and cost-effective treatment options for patients with partial ISFDPs in very specific cases. Of course, further research and evaluations are necessary to validate the clinical implications of this innovative hypothesis. Implementing the 3-on-1 T-bridge approach in partial ISFDPs could offer a promising alternative to traditional methods. If proven successful, this technique may lead to significant advancements in clinical practice, providing a less invasive cost-effective treatment option.

Load bearing capacity of 3-unit screw-retained implant-supported fixed dental prostheses with a mesial and distal cantilever on a single implant: A comparative in vitro study

OBJECTIVES

To assess the mechanical durability of monolithic zirconia implant-supported fixed dental prostheses (iFDP) design on one implant, with a distal and a mesial extension cantilever bonded to a titanium base compared to established designs on two implants.

MATERIALS AND METHODS

Roxolid Tissue level (TL), and tissue level x (TLX) implants were used to manufacture screw-retained 3-unit iFDPs (n = 60, n = 10 per group), with following configurations (X: Cantilever; I: Implant, T: Test group, C: Control group): T1: X-I-X (TL); T2: X-I-X (TLX); T3: I-I-X (TL); T4: I-I-X (TLX); C1: I-X-I (TL); C2: I-X-I (TLX). The iFDPs were thermomechanically aged and subsequently loaded until fracture using a universal testing machine. The failure load at first crack (Finitial) and at catastrophic fracture (Fmax) were measured and statistical evaluation was performed using two-way ANOVA and Tukey's post-hoc tests.

RESULTS

The mean values ranged between 190 ± 73 and 510 ± 459 N for Finitial groups, and between 468 ± 76 and 1579 ± 249 N for Fmax, respectively. Regarding Finitial, neither the implant type, nor the iFDP configuration significantly influenced measured failure loads (all p > 0.05). The choice of implant type did not show any significant effect (p > 0.05), while reconstruction design significantly affected Fmax data (I-I-Xa < X-I-Xb < I-X-Ic) (p < 0.05). The mesial and distal extension groups (X-I-X) showed fractures only at the cantilever extension site, while the distal extension group (I-I-X) showed one abutment and one connector fracture at the implant/reconstruction interface.

CONCLUSION

Results suggest that iFDPs with I-X-I design can be recommended regardless of tested implant type followed by the mesial and distal extension design on one implant abutment (X-I-X).

Treatment alternatives for the rehabilitation of the posterior edentulous maxilla

Rehabilitation of the edentulous maxilla with implant-supported fixed dental prostheses can represent a significant clinical challenge due to limited bone availability and surgical access, among other factors. This review addresses several treatment options to replace missing teeth in posterior maxillary segments, namely the placement of standard implants in conjunction with maxillary sinus floor augmentation, short implants, tilted implants, and distal cantilever extensions. Pertinent technical information and a concise summary of relevant evidence on the reported outcomes of these different therapeutic approaches are presented, along with a set of clinical guidelines to facilitate decision-making processes and optimize the outcomes of therapy.

Strains in the implant collars supporting a cantilevered cross-arch bar prosthesis. An in vitro study

PURPOSE

To examine the strains in the collar area of implants supporting a cantilevered cross-arch bar prosthesis during vertical load application.

MATERIALS AND METHODS

A milled cross-arch metal framework supported by four implants in a trapezoidal design was supported in polymethylmethacrylate. T-strain gage rosettes were attached to the crestal areas of the implants with two grids, one recording circumference strain of the crestal area of the implant and the second recording vertical strain, torquing strains of the implant. The framework was subject to vertical loading from an MTS 810 mechanical system. Loading sites were directly on anterior and posterior implants, and on a cantilever at 7.5, 15, 22.5, and 30 mm (0.5, 1.0, 1.5, and 2.0 of the anterior-posterior spread) distal from the posterior implant on the right side. The anterior-posterior (A-P) spread from anterior to posterior implants was 15 mm. Sites were loaded individually with 50 and 100 N. The data from the rosettes were transferred to a desktop computer and processed using StrainSmart 5000 software.

RESULTS

Means and standard deviations were calculated for the 10 trials at each of the loading sites. Two-way ANOVAs were done separately for each dependent variable, the vertical grid, and the circumferential grid. The independent variables were the load magnitude and the load site. Tukey's test was used to compare groups post hoc. When directly loading the implants, loading the anterior implant resulted initially in compression followed by increasing tensile strain with 100 N loads. Loading the implant adjacent to cantilever (the posterior implant) resulted in greater strain at the collar than that observed with anterior implant with minimal bending strains. When loading the cantilever, anterior implant showed increasing bending strain at greater cantilever length, whereas the circumferential strains were greater for the supporting implant adjacent to the cantilever, particularly at 100 N loads, p ≤ 0.001.

CONCLUSIONS

Limiting cantilever lengths to A-P spread ratios of 0.5 are preferred. Ratios greater than 1.0 should be avoided as flexing of the collar may occur. The dimensions of the implant, particularly wall thickness, adjacent to the cantilever should be carefully considered when planning the cantilevered implant-supported prosthesis.

Clinical and radiographic outcomes of implant-supported zirconia fixed dental prostheses with cantilever extension: A proof-of-principle study with a follow-up of at least 1 year

OBJECTIVES

To test the reliability of full zirconia implant-supported fixed dental prostheses with cantilever extension (FDPCs) after at least 1 year of function.

MATERIALS AND METHODS

Thirty-five patients in need of implant-supported single unit crowns (SUC) and FDPCs in posterior areas were enrolled. After implant placement, patients were rehabilitated with screw-retained full-zirconia FDPCs. Implant survival rate, pocket probing depth (PPD), presence/absence of bleeding on probing (BoP), and presence/absence of mechanical/technical complications were recorded. Mesial and distal radiographic marginal bone levels (mBLs) from baseline (i.e., recall appointment 3-6 months after implant loading [T0]) to the follow-up examination (i.e., latest recall appointment after at least 12 months after T0 [T1]), were calculated.

RESULTS

Thirty patients with 34 FDPCs (31 SUCs and 3 FDPs) supported by 37 implants were available for analysis after a mean loading time of 2.6 ± 1.5 years (range: 13-87 months). No implants were lost. MBLs and mean PPD values did not change statistically significantly from T0 to T1 from 0.92 mm ± 0.42 to 0.96 mm ± 0.38 (95% CI: -0.07/0.17; p = .418) and from 2.99 mm ± 0.70 to 3.27 mm ± 0.71 (95% CI: -0.11/0.68; p = .25) respectively. Peri-implant mucositis was diagnosed in 22 cases. Screw-loosening and zirconia chipping occurred 1× in 4 patients.

CONCLUSION

Within the limitations of the present proof-of-principle study, the use of full-zirconia FDPCs in posterior areas seems a valid and safe short-term treatment option.

Implant-supported zirconia fixed partial dentures cantilevered in the lateral-posterior area: A 4-year clinical results

Background

Implant-supported cantilever prostheses enable a more straightforward rehabilitation and may be a therapeutic option to reduce treatment morbidity, costs, and time. This study evaluated the clinical outcomes of fixed implant-supported partial dentures made of monolithic zirconia with a cantilever design to replace missing posterior teeth.

Methods

Fifteen partially edentulous patients received 34 implants and were provided with 16 zirconia fixed partial prostheses (FPPs) with one cantilever extension replacing mandibular or maxillary missing posterior and lateral teeth. Patients were re-examined for up to 4 years. Patient ages ranged from 41 to 65 years, with a mean age of 53±12 years; 47% were female, and 53% were male. The patients were observed for a mean period of 42±6 months with a minimum of 3 years and a maximum of 4 years.

Results

Peri-implantitis was observed in two cases. No chipping or fracture of any FPP was detected. Loosening of the abutment screw was a technical complication in one case. The rehabilitation survival rate was 100%. Implant-supported zirconia FPP with one mesial cantilever extension provides an aesthetic, functional treatment alternative to replace missing molars, premolars, and canines. These excellent clinical outcomes occurred over a mean observation time of 42±6 months.

Conclusion

Using monolithic zirconia milled with CAD-CAM technology might be an alternative to the metal-ceramic restoration in implant-supported FPP with one cantilever.

Implant Survival Rate and Prosthetic Complications of OT Equator Retained Maxillary Overdenture: A Cohort Study

(1) Background: The overdenture is a complete denture, an implant-supported prosthesis, that the patient can remove at home for the usual oral hygiene procedures, thanks to a simple and intuitive anchoring system. Clinically, the execution of this rehabilitation for the lower arch is often favored, but when it is necessary to limit the extension of the palate in the upper arch, it can represent the least invasive and economic solution. The aim of the study is to analyze post-loading implant loss for implant-supported prostheses in the edentulous upper jaw. (2) Methods: This retrospective study was carried out on patients who received a superior overdenture on four implants for rehabilitation. A total of 42 patients were included in this study and initially evaluated clinically and radiographically. The follow-up period for patients after delivery of the upper overdenture is between 48 and 72 months. A total of 168 implants were inserted and monitored in this period. Clinical and radiographic tests were carried out on all 168 implants, with constant re-evaluation. (3) Results: The overall implant survival rate is 92.9%, a value that corresponds to those present in the literature in previously published studies. There were few prosthetic complications, mainly the detachment of anterior prosthetic teeth. (4) Conclusions: Most of these complete prostheses, which as antagonist had another previously made overdenture on four or on two implants, achieved excellent success rates in this study at 72 months.

Radiographic density changes may be associated with overloading and implant loss on short implants: A 5-year analysis of a randomized controlled clinical trial

OBJECTIVES

To analyze changes in radiographic bone density around short implants with and without cantilevers at 5 years post-loading.

MATERIALS AND METHODS

Thirty-six patients with two adjacent posterior missing teeth participated in this randomized controlled clinical trial. All patients were randomly allocated to receive either two short implants (6 mm) with single-unit restorations (group TWO) or one single short implant (6 mm) with a cantilever restoration (group ONE-C). Patients were followed up at 6 months, 1, 3, and 5 years. Radiographic analysis was performed, through an arbitrary gray scale value (GSV) of the peri-implant bone, assessing the changes in radiographic density between groups and between time points. Differences in GSV between groups and over time were calculated using a generalized estimating equation to allow for adjustments for the correlation within individuals and between time points.

RESULTS

At 5 years, 26 patients remained in the study (15 in group ONE-C; 11 in group TWO). Implant survival rates were 80.4% in group TWO and 84.2% in group ONE-C (p = 0.894). The radiographic analysis revealed that GSVs increased in both groups over time (p < 0.001). The overall radiographic density was higher in group ONE-C than in group TWO in the maxilla (p = 0.030). Conversely, in the mandible, these significant differences between the groups were not found (p > 0.05). Compared to the implants that survived, the implants that failed demonstrated a distinct radiographic density pattern (p < 0.05).

CONCLUSION

Within the limitations of the present study, the radiographic bone density in the maxilla appears to increase distinctly around short implants when cantilevers are used. In contrast, the radiographic density in the mandible appears to be unaffected by the use of a cantilever, suggesting a lower threshold of adaptation to occlusal forces and thus a higher susceptibility to overload and implant loss at earlier time points.

Short Narrow Dental Implants versus Long Narrow Dental Implants in Fixed Prostheses: A Prospective Clinical Study

There is a paucity of studies that assess short and narrow dental implants. This prospective study aimed to evaluate the performance of both short (≤8 mm) and narrow (≤3.5 mm width) dental implants supporting fixed prostheses in the atrophic maxilla or mandible. Towards that aim, patients with short implants were included in the study. The control group was those with long and narrow dental implants (length > 8 mm and diameter ≤ 3.5 mm). Clinical and demographic variables were extracted from clinical records. During the follow-up, implant survival and marginal bone loss were evaluated and statistically analysed. Forty-one implants were included (18 and 23 implants in the test and control groups, respectively). The median follow-up time was 26 months since insertion in both groups. The results revealed that there was no implant failure and no statistically significant differences in terms of marginal bone loss. Only one screw-loosening effect occurred in the short implants group. Short, narrow dental implants could be an alternative for the restoration of severely resorbed jaws.

The effect of the digital manufacturing technique of cantilevered implant-supported frameworks on abutment screw preload

PURPOSE

The purpose of this study was to investigate the misfit and screw preload at the implant abutment connection of implant supported fixed dental prosthesis with cantilever (ICFDP) manufactured using different digital manufacturing techniques and to compare the screw preload before and after cyclic loading.

MATERIALS AND METHODS

Mandibular jaw model with four intra-foraminal implants was scanned using digital scanner. Stereolithography file was used to design a framework with nonengaging (NE) abutments and 10 mm cantilever distal to one terminal implant. Five frameworks were constructed using combined digital-conventional techniques (CAD-cast), and five frameworks were constructed using three-dimensional printing (3DP). Additional CAD-cast framework was constructed in a way that ensures passive fit (PF) to use as control. Scanning electron microscope (SEM) measured the implant abutment connection misfit. Sixty screws were used on the corresponding frameworks. Screws were torqued and pre-cyclic loading reverse torque value (RTV) was recorded. Frameworks were subjected to 200,000 loading cycles with a loading point 9 mm from the center of terminal implants adjacent to the cantilever and post-cyclic loading RTVs were recorded.

RESULTS

Microscopic readings showed significant differences between frameworks. PF demonstrated the lowest measurements of 16.04 (2.6) µm while CAD-cast demonstrated the highest measurements of 29.2 (3.1) µm. In all groups, RTVs were significantly lower than the applied torque. Post-cyclic loading RTV was significantly lower than pre-cyclic loading RTV in PF and 3DP frameworks. Differences in RTVs between the three manufacturing techniques were insignificant.

CONCLUSION

Although CAD-cast and three-dimensionally printed (3DP) both produce frameworks with clinically acceptable misfit, 3DP might not be the technique of choice for maintaining screw’s preload stability under an aggressive loading situation.

Application of bio-resorbable membranes in preventing complications of lower jaw surgery

Background/Aim: Prevention of inflammation and alveolar bone atrophy is very important in oral surgery. The aim of this study was to compare the use of two osteoplastic bio-resorbable membranes in order to prevent inflammatory complications and atrophy of the alveolar part of the mandible after surgical interventions. Material and Methods: We examined 86 patients 45-70 years old who were classified into four groups. In group 1, there were 21 patients who had a "bio-resorbable membrane type 1 implanted. The group 2 consisted of 23 persons treated with bio-resorbable membrane type 2. Only the occurrence of inflammatory complications after the placement of these membranes was monitored. Group 3 included 20 persons treated with membrane type 1 and group 4 included 22 patients treated with membrane type 2 to prevent both inflammatory complications and atrophy of the alveolar part of the mandible. The level of atrophy of the alveolar bone after one year was determined by cone-beam computed tomography. The obtained data were statistically evaluated. Results: Six inflammatory complications ("dry socket") have been identified in operated patients treated with a membrane type 1 (the first and the third groups). Only two "dry socket" occurred in patients treated with membrane type 2 (the second and fourth groups). Group 4 had significant advantages in the alveolar crest height 14.6 (11.2-22.3) and in its width 7.7 (5.1-10.2) both in relation to the indices of group 3 (11.1 (9.7-20.4) and 6.2 (4.2-9.0). Conclusions: The bio-resorbable membrane type 2 prevented inflammatory complications in the short postoperative period after surgical interventions, as well as, the atrophy of the mandible.

Mechanical Properties of Polymer-Based Blanks for Machined Dental Restorations

The tremendous technological and dental material progress led to a progressive advancement of treatment technologies and materials in restorative dentistry and prosthodontics. In this approach, CAD/CAM restorations have proven to be valuable restorative dental materials in both provisional and definitive restoration, owing to multifarious design, improved and highly tunable mechanical, physical and morphological properties. Thus far, the dentistry market offers a wide range of CAD/CAM restorative dental materials with highly sophisticated design and proper characteristics for a particular clinical problem or multiple dentistry purposes. The main goal of this research study was to comparatively investigate the micro-mechanical properties of various CAD/CAM restorations, which are presented on the market and used in clinical dentistry. Among the investigated dental specimens, hybrid ceramic-based CAD/CAM presented the highest micro-mechanical properties, followed by CAD/CAM PMMA-graphene, while the lowest micro-mechanical features were registered for CAD/CAM multilayered PMMA.

Implant Survival in Immediately Loaded Full-Arch Rehabilitations Following an Anatomical Classification System-A Retrospective Study in 1200 Edentulous Jaws

This retrospective study analyzed implant survival of immediate implant-supported fixed complete denture (IFCD) treatment options (TOs) based on the level of alveolar atrophy (CC). Records of 882 patients receiving a total of 6042 implants at one private referral clinic between 2004 and 2020 were considered. The mean follow-up period was 3.8 ± 2.7 years. Cumulative implant survival rates (CSRs) were analyzed as a function of CCs and TOs according to Mantel-Haenszel and Mantel-Cox. Hazard risk ratios for implant loss were compared using Cox regression. Confounding factors were identified using mixed Cox regression models. The 2- and 5-year CSRs were 98.2% and 97.9%, respectively. Maxillary 2- and 5-year CSRs were lower (97.7% and 97.3%) compared to mandibular CSRs (99.8% and 98.6%) (p = 0.030 and 0.0020, respectively). The CC did not influence CSRs of IFCDs in the mandible (p = 0.1483 and 0.3014, respectively) but only in the maxilla (p = 0.0147 and 0.0111), where CSRs decreased with increasing atrophy. TOs did not statistically differ in terms of survival rate for a given level of alveolar atrophy. The adaption of IFCD treatments to the level of atrophy and patient-specific risk factors can result in high CSRs, even at different levels of bone atrophy.

Application of Bio-Resorbable Membranes in Preventing Complications of Lower Jaw Surgery

Background/Aim: Prevention of inflammation and alveolar bone atrophy is very important in oral surgery. The aim of this study was to compare the use of two osteoplastic bio-resorbable membranes in order to prevent inflammatory complications and atrophy of the alveolar part of the mandible after surgical interventions.

Material and Methods: We examined 86 patients 45-70 years old who were classified into four groups. In group 1, there were 21 patients who had a “bio-resorbable membrane type 1 implanted. The group 2 consisted of 23 persons treated with bio-resorbable membrane type 2. Only the occurrence of inflammatory complications after the placement of these membranes was monitored. Group 3 included 20 persons treated with membrane type 1 and group 4 included 22 patients treated with membrane type 2 to prevent both inflammatory complications and atrophy of the alveolar part of the mandible. The level of atrophy of the alveolar bone after one year was determined by cone-beam computed tomography. The obtained data were statistically evaluated.

Results: Six inflammatory complications (“dry socket”) have been identified in operated patients treated with a membrane type 1 (the first and the third groups). Only two “dry socket” occurred in patients treated with membrane type 2 (the second and fourth groups). Group 4 had significant advantages in the alveolar crest height 14.6 (11.2-22.3) and in its width 7.7 (5.1-10.2) both in relation to the indices of group 3 (11.1 (9.7-20.4) and 6.2 (4.2-9.0).

Conclusions: The bio-resorbable membrane type 2 prevented inflammatory complications in the short postoperative period after surgical interventions, as well as, the atrophy of the mandible.

Comparison of the Crestal Bone Loss Between Implant-Supported Prosthesis With Sinus Augmentation and Distal Cantilevered Implant-Supported Prosthesis Without Sinus Augmentation

This study aimed to compare the crestal bone loss between a 2-implant-supported, noncantilevered 3-unit fixed partial prosthesis (TUFPP) with sinus augmentation and a 2-implant-supported, distal cantilevered TUFPP without sinus augmentation in the posterior maxilla having insufficient crestal bone. The study subjects were enrolled in 2 groups. Group 1 included patients with 2 implants: an anterior implant placed in the native bone and a posterior implant inserted with simultaneous sinus augmentation using a xenogenic bone graft to support a TUFPP. Group 2 included patients with 2 implants inserted in the native bone to support a distal cantilevered TUFPP. The crestal bone levels at the distal and mesial aspects of each implant were measured at baseline and 6-, 12-, and 24-month follow-up controls on panoramic radiographs. Fifty-two patients and 104 implants were included. There was a significant difference in distal crestal bone loss between anterior and posterior implants in group 1 at 6 months (P < .05) but not at 12 and 24 months (P > .05). Distal crestal bone loss was significantly increased in group 1 posterior implants compared to the group 2 posterior implants at 6 months (P < .05). There was no significant difference in mesial bone loss between the anterior and posterior implants in both groups at all follow-up controls (P > .05). There was also no significant mesial crestal bone loss in relation to the anterior and posterior implants of both groups at all follow-up controls (P > .05). Noncantilevered 2-implant-supported TUFPP with sinus augmentation may have similar medium-term crestal bone loss when compared to cantilevered 2-implant-supported TUFPP without sinus augmentation. Further prospective studies should be designed to compare the performance of the 2-implant-supported cantilevered TUFPP and 2-implant-supported TUFPP with sinus augmentation.

Interdisciplinary treatment with implant-supported two-unit cantilever prosthesis for a patient with hypodontia: A clinical report

A 21-year-old woman with multiple congenitally missing maxillary anterior teeth received interdisciplinary treatment to restore function and esthetics. The treatment was initiated with orthodontic treatment, followed by implant placement, bone and soft-tissue augmentation, and prosthetic treatment including a screw-retained implant-supported 2-unit cantilever fixed dental prosthesis.

Two short implants versus one short implant with a cantilever: 5-Year results of a randomized clinical trial

Aim

To test whether or not the use of a short implant with a cantilever results in similar clinical and radiographic outcomes compared to two adjacent short implants with single tooth reconstructions.

Materials and methods

Thirty‐six patients with two adjacent missing teeth in the posterior region were randomly assigned to receive either a single 6‐mm implant with a cantilever (ONE‐C) or two 6‐mm implants (TWO). Fixed reconstructions were inserted 3–6 months after implant placement and patients were re‐examined up to 5 years (FU‐5).

Results

A total of 26 patients were available for re‐examination at FU‐5. The survival rate amounted to 84.2% in ONE‐C and to 80.4% in TWO (inter‐group: p = .894). Technical complication rates amounted to 64.2% (ONE‐C) and to 54.4% (TWO) (inter‐group: p = 1.000). From baseline to FU‐5, the median changes of the marginal bone levels were 0.13 mm in ONE‐C and 0.05 mm in TWO (inter‐group: p = .775). Probing depth, bleeding on probing, and plaque control record values showed no significant differences between the two treatment modalities (p > .05).

Conclusions

Short implants with a cantilever render similar clinical and radiographic outcomes compared to two adjacent short implants at 5 years, however, they tend to fail at earlier time points suggesting an overload of the implants. Considering the modest survival rates, the clinical indication of either treatment option needs to be carefully evaluated. ClinicalTrials.gov (NCT01649531).

Six-year follow-up assessment of prosthesis survival and oral health-related quality of life in individuals with partial edentulism treated with three types of prosthodontic rehabilitation

Purpose The purpose of the study was to compare the long-term performance of three prostheses for partial edentulism: implant-supported, fixed denture (IFD), fixed partial denture (FPD), and removable partial denture (RPD), in terms of prosthesis survival and oral health-related quality of life (OHRQoL).Methods The 138 patients in our previous study (Kimura et al., 2012) received one of the three prosthetic treatments and answered a validated OHRQoL questionnaire before and immediately after treatment. In the present study, the patients were followed up six years after treatment using medical records and OHRQoL examinations to evaluate prosthesis survival and change in OHRQoL. The cumulative survival rates were calculated using the Kaplan-Meier analysis. The Steel-Dwass test was used to compare the median OHRQoL scores at the three time points.Results For the 105 patients (66.8 ± 10.8 years, IFD/FPD/RPD: 58/27/20 patients) who successfully completed the follow-up assessments, the six-year estimated cumulative survival rates of the IFDs, FPDs, and RPDs were 94.7%, 77.4%, and 33.3%, respectively. The log-rank tests indicated that the survival curves were significantly different (IFDs vs. FPDs: p = 0.01; RPDs vs. IFDs, FPDs: p < 0.01). The median OHRQoL scores of the IFD group immediately after treatment and six years after treatment were significantly higher than those observed before treatment (p < 0.01). There was no significant difference in the median OHRQoL scores among the three time points in the RPD or FPD groups.Conclusions IFDs showed significantly longer survival rates than FPDs and RPDs in partially edentulous patients. Only in the IFD patients was the OHRQoL level six years after treatment significantly higher than that before treatment.

Single implant-supported two-unit cantilever fixed partial dentures in the posterior region: a retrospective case series with a mean follow-up of 6.5 years

Background

The aim of this retrospective study was to evaluate the implant survival, clinical and radiographic outcomes, and patient satisfaction of single implant-supported two-unit cantilever fixed partial dentures in the posterior region.

Methods

Patients who received a single implant-supported fixed partial denture with a cantilever in the posterior region between January 2004 and February 2018 were included. Survival rate of the implants and the fixed partial dentures and data regarding the marginal bone level, presence of plaque, calculus, bleeding on probing, mucosa health, pocket probing depth, and patient satisfaction were collected during an evaluation visit. Complications were recorded from the medical records.

Results

Twenty-three patients (mean age 64 ± 13 years) with 28 implants could be included in the study. The mean follow-up period was 6.5 ± 4.8 years at the time of data collection. The survival rate of the implants and fixed partial dentures was 100%. Mean marginal bone loss for the mesial and distal side of the implants was 0.41 mm (SD 1.18 mm) and 0.63 mm (SD 0.98 mm) respectively. A high prevalence of peri-implant-mucositis (89.3%) and peri-implantitis (17.9%) was observed as well as a limited number of technical complications. Patients were quite satisfied, as reflected by a mean VAS score of 94.0 ± 7.2 points (range 0–100) and a OHIP-NL49 score of 10.8 (range 0–196).

Conclusions

Single implant-supported fixed partial dentures with a mesial or distal cantilever can be a predictable treatment option in the posterior region, with stable peri-implant bone levels, minor technical complications, and very content patients. However, the prevalence of peri-implant mucositis and peri-implantitis was high.

Trial registration

ISRCTN, ISRCTN79055740, Registered on March 14, 2021 – —Retrospectively registered.

Use of Narrow-Diameter Implants in Completely Edentulous Patients as a Prosthetic Option: A Systematic Review of the Literature

Objective

The objective of the present review is to assess the implant survival, marginal bone loss, and biomechanical features of narrow-diameter implants (2.5-3.5 mm) supporting or retaining full-arch fixed or removable restorations.

Materials and Methods

Three operators screened the literature (PubMed, Cochrane Library, and Google Scholar) and performed a hand search on the main journals that focus on implantology until 24 March 2019. Only articles that considered full-arch restorations supported or retained by narrow-diameter implants (2.5-3.5 mm) were considered if they have a minimum of 10 patients and a mean follow-up of at least 6 months. The outcome variables were survival of implants and marginal bone loss. The review was performed according to the PRISMA statements. Risk of bias assessment was evaluated. Failure rates were analyzed using random effect Poisson regression models to obtain the summary estimate of 5-year survival rate and marginal bone loss.

Results

A total of nine papers were finally selected, reporting a high survival rate of the implants. Eight studies focused only on the mandible while one study reported data from both mandible and maxilla. All studies reported on removable restorations; none focused on fixed rehabilitations. The estimated survival rate for 5 years of follow-up was calculated to be 92.25% for the implants. The estimated marginal bone loss after 5 years was calculated to be 1.40 mm. No study reported implant fractures.

Conclusions

With the limitations of the present study, there is evidence that 2.5-3.5 mm narrow-diameter implants retaining a removable restoration can be a successful treatment in fully edentulous patients. No data on fixed restorations was available.

Are teeth superior to implants? A mapping review

STATEMENT OF PROBLEM

There is a long-held assumption that teeth are superior to implants because the periodontal ligament (PDL) confers a preeminent defense against biologic and mechanical challenges. However, adequate analysis of the literature is lacking. As a result, differential treatment planning of tooth- and implant-supported restorations has been compromised.

PURPOSE

Given an abundance and diversity of research, the purpose of this mapping review was to identify basic scientific gaps in the knowledge of how teeth and implants respond to biologic and mechanical loads. The findings will offer enhanced evidence-based clinical decision-making when considering replacement of periodontally compromised teeth and the design of implant prostheses.

MATERIAL AND METHODS

The online databases PubMed, Science Direct, and Web of Science were searched. Published work from 1965 to 2020 was collected and independently analyzed by both authors for inclusion in this review.

RESULTS

A total of 108 articles met the inclusion criteria of clinical, in vivo, and in vitro studies in the English language on the periradicular and peri-implant bone response to biologic and mechanical loads. The qualitative analysis found that the PDL's enhanced vascularity, stem cell ability, and resident cells that respond to inflammation allow for a more robust defense against biologic threats compared with implants. While the suspensory PDL acts to mediate moderate loads to the bone, higher compressive stress and strain within the PDL itself can initiate a biologic sequence of osteoclastic activity that can affect changes in the adjacent bone. Conversely, the peri-implant bone is more resistant to similar loads and the threshold for overload is higher because of the absence of a stress or strain sensitivity inherent in the PDL.

CONCLUSIONS

Based on this mapping review, teeth are superior to implants in their ability to resist biologic challenges, but implants are superior to teeth in managing higher compressive loads without prompting bone resorption.

Prospective, Clinical Pilot Study with Eleven 4-Mm Extra-Short Implants Splinted to Longer Implants for Posterior Maxilla Rehabilitation

In many clinical situations, rehabilitation with implants in the posterior maxillary region is complicated by limited bone availability. In this context, the use of 4 mm long implants (known as extra-short implants) may be used thanks to the concept of osseointegration enhancement. It has been demonstrated that short implants offer an alternative to the regeneration procedures involved in placing longer implants in areas where bone height is compromised. This prospective pilot study tested a treatment protocol in which 11 extra-short (4 mm) implants were splinted to 11 mesially placed longer (8 mm) implants in the posterior maxillary regions of partially edentulous patients, without using supplementary bone regeneration procedures. Eleven patients were included in this single cohort study. The clinical performance of the extra-short implants was assessed during a two-year follow-up period, obtaining a 100% survival rate and mean bone loss of 0.3 mm. Implant stability measured by resonance frequency analysis (RFA) at the time of placement was 54.9 ± 4.9, increasing to 77.0 ± 2.6 at 24 months. The study demonstrated the gradual consolidation of osseointegration in bone of less-than-ideal quality in the posterior maxillary region. The results obtained show that a partially edentulous maxilla with reduced bone height may be rehabilitated by using an extra-short implant splinted to a mesial implant of 8mm length or longer. Despite the small sample size, this pilot study observed that extra-short implants achieved adequate bone stability and clinical performance after a 24-month follow-up.

Principles of biomechanics in oral implantology

Background and aims

The principles of biomechanics comprise all the interactions between the body (tissues) and the forces acting upon it (directly or via different medical devices). Besides the mechanical aspects, the tissues response is also studied. Understanding and applying these principles is vital for the researchers in the field of oral implantology, but they must be equally known by the practitioners. From the planning stages to the final prosthetic restoration, they are involved in each and every aspect. Ignoring them inevitably leads to failure.

Methods

The first part of this paper includes a review of our current research in oral implantology (mechanical, digital and biological testing), while the second part includes a review of the available literature on certain biomechanical aspects and their implications in everyday practice.

Results

Our research opens new study directions and provides increased chances of success for dental implant therapy. The practical aspects of our findings, combined with the available literature (from the basic principles described more than 40 years ago to the most recent studies and technologies) can serve as a guide to practitioners for increasing their success rate.

Conclusion

While no therapy is without failure risk, a good understanding of the biomechanics involved in oral implantology can lead to higher success rates in implant supported prosthetic restorations.