Maxillary overdentures supported by four or six implants in the anterior region; 1-year results from a randomized controlled trial

Maxillary overdentures supported by four or six implants in the anterior region: 10-year randomized controlled trial results

AIM

To evaluate bar-supported maxillary implant overdenture treatment when supported by either four or six implants after 10 years.

MATERIALS AND METHODS

Edentulous subjects with maxillary denture complaints and ample bone volume to facilitate implants in the anterior region of the maxilla were planned for implant overdenture treatment, randomized to receive either four implants (n = 25) or six implants (n = 25) and subsequently evaluated after 10 years of function. Outcome variables included peri-implant bone-level changes, implant and overdenture survival, complications, presence of plaque, calculus and bleeding, degree of peri-implant inflammation, probing depth and patient satisfaction. Differences between the groups and between evaluation periods were tested with a Student's t-test.

RESULTS

Fourteen patients with totally 72 implants were lost to follow-up. Two patients from the six-implant group experienced implant loss (four implants), resulting in 96.1% implant survival in this group versus 100% survival in the four-implant group. Clinical, radiographical and patient-reported outcome measures did not differ statistically significant between the two groups. Patients from both groups were generally quite satisfied with the result after 10 years.

CONCLUSIONS

Similar and favourable outcomes are seen in bar-supported maxillary overdentures on either four or six anteriorly placed implants after a 10-year evaluation period.

Clinical performance of implant supported mandibular overdentures with cantilever bar and stud attachments: A retrospective study

BACKGROUND

Treatment of edentulous patients with implant-supported over-dentures improves denture's retention and stability. Published data concerning implant-supported overdenture with cantilever bars that claimed that can affect the survival and bone loss of implants are scarce.

PURPOSE

The purpose of this study was to evaluate 5-year clinical performance of mandibular implant-supported over-dentures with different attachment systems.

MATERIALS AND METHODS

In this retrospective study, 103 patients who had received mandibular over-dentures supported by two implants were evaluated in a 5-year follow up. Studied groups were patients with Spherblock ball attachment (58 patients), Dolder bar with cantilever (36 patients), and Locator attachment (9 patients). Marginal bone-loss around implants, prosthetic complications, soft tissue status of the implants (gingival index, plaque index, pocket depth, and bleeding on probing) were used to compare studied groups. Visual Analogue Scale (VAS) criteria was used to assay patient's satisfaction. One-way ANOVA, Scheffe, Kruskal-Wallis, Mann-Whitney, and Fisher's exact tests, were used for the data analysis (α = 0.05).

RESULTS

One hundred and three patients (46 male, 57 female, mean age 64.7 ± 8.6) with 206 implants (Strauman) were studied. The implant survival rate was 100% with mean bone loss of 0.22 mm around implants in 5 years. Prosthetic complications including attachment wear and denture fracture occurred more often with ball attachments. The number of attachment replacement, and post insertion appointments were significantly less in patients with bar attachments (p < 0.05). Pocket depth and gingival index were less in the ball attachment (p < 0.05).

CONCLUSION

Mandibular overdenture supported by two implants can be considered a successful treatment in edentulous patients. The frequency of prosthetic complication is higher in unsplinted than splinted superstructures.

Incidence of peri-implant mucositis and peri-implantitis in patients with a maxillary overdenture: A sub-analysis of two prospective studies with a 10-year follow-up period

Background

Though studies on maxillary overdentures show satisfying results on implant survival, patient‐related outcomes and prosthetic complications, the epidemiology of peri‐implant diseases in this specific group of patients has hardly been reported. While the general patient‐level prevalence of peri‐implant mucositis and peri‐implantitis are estimated at ~45% and ~20%, respectively, the risk of developing these diseases within a specific period is less clear. To fully appreciate the epidemiology of peri‐implant diseases, more long‐term data on incidence of peri‐implant diseases are needed.

Purpose

The purpose of this sub‐analysis of two prospective studies was to assess the incidence of peri‐implant mucositis and peri‐implantitis in fully edentulous patients with implant‐retained maxillary overdentures during a 10‐year follow‐up period.

Materials and Methods

One hundred and sixteen patients treated with implant‐supported maxillary overdentures were available from two clinical trials. Data on biological complications, clinical and radiographical parameters were collected for 106 patients at 5‐year, for 82 patients at 10‐year follow‐up. The incidence was calculated following the consensus of the 2017 World Workshop on the Classification of Periodontal and Peri‐Implant Diseases and Conditions. Extent and severity then were calculated to enable an appropriate epidemiological description of peri‐implantitis.

Results

The patient‐level incidence of peri‐implant mucositis was 37.7% after 5 years and 64.6% after 10 years whereas the patient‐level incidence of peri‐implantitis was 10.4% after 5 years and 19.5% after 10 years. After 10 years, the extent of peri‐implant mucositis and peri‐implantitis is 52.8% and 43.8%, respectively. In terms of severity, 26.5% of all affected implants suffered from >3 mm bone loss and 17.6% of all affected implants was lost.

Conclusion

Three of five fully edentulous patients with implant‐supported maxillary overdentures experience peri‐implant mucositis after 10 years. Peri‐implantitis occurs in one of five patients after 10 years. In spite of these incidence rates, implant survival remains high.

A review of the recent literature on maxillary overdenture with dental implants

The recent literature on maxillary implant overdenture (IOD) was reviewed in order to clarify its predictability and establish treatment guidelines. Electronic searches were performed using PubMed, and articles about maxillary IOD written after 1990 were reviewed, focusing on the following items: I. implant survival rate, II. maxillary IOD survival rate, III. number of implants, IV. attachment type, V. follow-up period, VI. implant system, and VII. opposing dentition. The review revealed an implant survival rate of 61-100% and an overdenture survival rate of 72.4-100%. The attachments used included bars, balls, locators, and telescope crowns. The minimum and maximum observation periods were 12 months and 120 months, respectively, and the number of implants used for supporting IOD ranged from 2 to 8. At present, there is no strong evidence to indicate that maxillary IOD is clearly superior for all the items examined. However, the existing data indicate that maxillary IOD has almost the same therapeutic effect as fixed implant superstructures, and is a treatment option that can be actively adopted for patients in whom fixed superstructures cannot be applied for various reasons.

Patient satisfaction and survival of maxillary overdentures supported by four or six splinted implants: a systematic review with meta-analysis

Background

Implant-supported overdentures offer enhanced mechanical properties, which lead to better patient satisfaction and survival rates than conventional dentures. However, it is unclear whether these satisfaction levels and survival rates depend on the number of implants supporting the overdenture. Therefore, this systematic review aimed to compare maxillary overdentures supported by four or six splinted implants in terms of patient satisfaction, implant survival, overdenture survival, and prosthodontic complications.

Methods

Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (PubMed), and EMBASE databases were systematically searched and complemented by hand searching from 2000 to 2019, employing a combination of specific keywords. Studies comparing the use of four versus six implants for supporting overdentures with at least one-year of follow-up after prosthesis installation and including ten fully edentulous patients were included. The risk of bias (RoB) was analyzed with Cochrane’s RoB 2 and Newcastle–Ottawa tools. Implants and prosthesis survival rates were analyzed by random-effects meta-analysis and expressed as risk ratios or risk differences, respectively, and by the non-parametric unpaired Fisher’s test.

Results

A total of 15 from 1865 articles were included, and reported follow-up times after implant placement ranged from 1 to 10 years. Irrespective of the number of implants used, high scores were reported by all studies investigating patient satisfaction. Meta-analysis and non-parametric Fisher’s test showed no statistical differences regarding the survival rate of implants (P = 0.34, P = 0.3) or overdentures (P = 0.74, P = 0.9) when using 4 versus 6 splinted implants to support overdentures, and no significant differences regarding prosthodontic complications were found between groups. Randomized studies presented high RoB and non-randomized studies presented acceptable quality.

Conclusions

Within the limits of this systematic review, we can conclude that the bar-supported overdenture on four implants is not inferior to the overdenture supported by six implants for rehabilitating the edentulous maxilla, in terms of patient satisfaction, survival rates of implants and overdentures, and prosthodontic complications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01572-6.

Maxillary implant overdenture retained by four unsplinted attachments and opposed by a natural or fixed dentition: One-year clinical outcomes

OBJECTIVES

The aim of this prospective study was to evaluate the implant, prosthesis, and patient-reported outcomes of maxillary removable prostheses retained by 4 implant-supported study abutments after a follow-up period of 1 year in patients with natural teeth or a fixed rehabilitation in the mandible.

MATERIALS AND METHODS

A total of 30 patients were included, and all received 4 implants in the upper maxilla. After 12 weeks, the prostheses were connected to the implant with unsplinted attachments. The implant and prosthodontics outcomes were assessed over a follow-up period of 1 year. Patient-reported outcome measures (PROMs) were evaluated with the Oral Health Impact Profile (OHIP-20) questionnaire and an adaptation of the McGill Denture Satisfaction Instrument using a visual analogue scale (VAS).

RESULTS

A single patient dropped out. At the post-operative 12-week follow-up, 79.3% (95% CI: 64.6%-94.1%) of the patients displayed peri-implant mucosa hyperplasia and 69.0% (95% CI: 52.1%-85.8%) showed pain. After 1 year, 16 implants failed in 10 patients, leading to an implant survival rate of 86.2% (95% CI: 79.0%-92.5%), and the mean peri-implant bone loss was 1.01 ± 0.77 mm (95% CI: 0.85-1.16 mm). The prosthesis survival rate was 96.6% (95% CI: 82.2%-99.9%). The OHIP-20 and VAS scores both improved significantly from baseline to 1 year (p < .001).

CONCLUSION

The implant survival rate was lower compared to the literature for the upper maxilla. Despite the encountered problems, PROMs showed significant improvement with the implant overdenture retained by 4 unsplinted implants compared to conventional dentures.

Maxillary implant overdentures retained by use of bars or locator attachments: 1-year findings from a randomized controlled trial

PURPOSE

Comparison of outcomes of maxillary implant overdentures retained by use of either locator attachments or bars in a 1-year randomized controlled trial.

METHODS

Fifty edentulous participants received four maxillary implants. They were allocated to two groups (n = 25) differing in type of prosthetic attachment used to retain the maxillary prosthesis: either locator attachments or bars were applied. After one year, implant and overdenture survival was assessed. Peri-implant hygiene (Plaque-index, presence of calculus), soft tissue conditions (Gingiva-index, Sulcus Bleeding-index and pocket probing depth) and patient satisfaction (oral health impact profile (OHIP-49), denture complaints questionnaire and general satisfaction score (GSS)) were compared. The peri-implant bone level was estimated using intra-oral radiographs (student T-test).

RESULTS

Implant survival was 96.7% in the locator group and 97.9% in the bar group. No overdentures had to be remade. Patient satisfaction was significantly greater in the bar group when rated by OHIP-49 sum score and by GSS. When comparing the denture complaints questionnaire and the separate OHIP-49 item scores, no significant difference was found. There was not a significant difference in hygiene and soft tissue conditions. Marginal bone loss was estimated 0.58 ± 0.71 mm for locators and 0.31 ± 0.47 mm for bars.

CONCLUSIONS

Maxillary overdentures on four implants retained by bars or locators were compared. Bone loss was within an acceptable range for both groups after 1 year. However, less bone was lost in the bar group. Even though both treatment options improved patient satisfaction, bars seem to be particularly beneficial with regard to OHIP-49 sum score.

Interventions for replacing missing teeth: attachment systems for implant overdentures in edentulous jaws

BACKGROUND

Implant overdentures are one of the most common treatment options used to rehabilitate edentulous patients. Attachment systems are used to anchor the overdentures to implants. The plethora of attachment systems available dictates a need for clinicians to understand their prosthodontic and patient-related outcomes.

OBJECTIVES

To compare different attachment systems for maxillary and mandibular implant overdentures by assessing prosthodontic success, prosthodontic maintenance, patient preference, patient satisfaction/quality of life and costs.

SEARCH METHODS

Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 24 January 2018); Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 12) in the Cochrane Library (searched 24 January 2018); MEDLINE Ovid (1946 to 24 January 2018); and Embase Ovid (1980 to 24 January 2018). The US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials on 24 January 2018. No restrictions were placed on the language or date of publication when searching the electronic databases.

SELECTION CRITERIA

All randomised controlled trials (RCTs), including cross-over trials on maxillary or mandibular implant overdentures with different attachment systems with at least 1 year follow-up.

DATA COLLECTION AND ANALYSIS

Four review authors extracted data independently and assessed risk of bias for each included trial. Several corresponding authors were subsequently contacted to obtain missing information. Fixed-effect meta-analysis was used to combine the outcomes with risk ratios (RR) for dichotomous outcomes and mean differences (MD) for continuous outcomes, with 95% confidence intervals (95% CI). We used the GRADE approach to assess the quality of evidence and create 'Summary of findings' tables.

MAIN RESULTS

We identified six RCTs with a total of 294 mandibular overdentures (including one cross-over trial). No trials on maxillary overdentures were eligible. Due to the poor reporting of the outcomes across the included trials, only limited analyses between mandibular overdenture attachment systems were possible.Comparing ball and bar attachments, upon pooling the data regarding short-term prosthodontic success, we identified substantial heterogeneity (I² = 97%) with inconsistency in the direction of effect, which was unexplained by clinical or methodological differences between the studies, and accordingly we did not perform meta-analyses for this outcome. Short-term re-treatment (repair of attachment system) was higher with ball attachments (RR 3.11, 95% CI 1.68 to 5.75; 130 participants; 2 studies; very low-quality evidence), and there was no difference between both attachment systems in short-term re-treatment (replacement of attachment system) (RR 1.18, 95% CI 0.38 to 3.71; 130 participants; 2 studies; very low-quality evidence). It is uncertain whether there is a difference in short-term prosthodontic success when ball attachments are compared with bar attachments.Comparing ball and magnet attachments, there was no difference between them in medium-term prosthodontic success (RR 0.84, 95% CI 0.64 to 1.10; 69 participants; 1 study; very low-quality evidence), or in medium-term re-treatment (repair of attachment system) (RR 1.75, 95% CI 0.65 to 4.72; 69 participants; 1 study; very low-quality evidence). However, after 5 years, prosthodontic maintenance costs were higher when magnet attachments were used (MD -247.37 EUR, 95% CI -346.32 to -148.42; 69 participants; 1 study; very low-quality evidence). It is uncertain whether there is a difference in medium-term prosthodontic success when ball attachments are compared with magnet attachments.One trial provided data for ball versus telescopic attachments and reported no difference in prosthodontic maintenance between the two systems in short-term patrix replacement (RR 6.00, 95% CI 0.86 to 41.96; 22 participants; 1 study; very low-quality evidence), matrix activation (RR 11.00, 95% CI 0.68 to 177.72; 22 participants; 1 study; very low-quality evidence), matrix replacement (RR 1.75, 95% CI 0.71 to 4.31; 22 participants; 1 study; very low-quality evidence), or in relining of the implant overdenture (RR 2.33, 95% CI 0.81 to 6.76; 22 participants; 1 study; very low-quality evidence). It is uncertain whether there is a difference in short-term prosthodontic maintenance when ball attachments are compared with telescopic attachments.In the only cross-over trial included, patient preference between different attachment systems was assessed after only 3 months and not for the entire trial period of 10 years.

AUTHORS' CONCLUSIONS

For mandibular overdentures, there is insufficient evidence to determine the relative effectiveness of different attachment systems on prosthodontic success, prosthodontic maintenance, patient satisfaction, patient preference or costs. In the short term, there is some evidence that is insufficient to show a difference and where there was no evidence was reported. It was not possible to determine any preferred attachment system for mandibular overdentures.For maxillary overdentures, there is no evidence (with no trials identified) to determine the relative effectiveness of different attachment systems on prosthodontic success, prosthodontic maintenance, patient satisfaction, patient preference or costs.Further RCTs on edentulous cohorts must pay attention to trial design specifically using the same number of implants of the same implant system, but with different attachment systems clearly identified in control and test groups. Trials should also determine the longevity of different attachment systems and patient preferences. Trials on the current array of computer-aided designed/computer-assisted manufactured (CAD/CAM) bar attachment systems are encouraged.

Maxillary overdentures supported by four or six implants in the anterior region: 5-year results from a randomized controlled trial

OBJECTIVE

To compare a four- and six-implant maxillary overdenture after an observation period of 5 years.

MATERIAL AND METHODS

Fifty subjects with functional problems concerning their maxillary denture, who had ample bone volume in the anterior region to place four or six implants, were included and randomly assigned to either group. Implant and overdenture survival, clinical performance, marginal bone loss and patient satisfaction were assessed.

RESULTS

Forty-six patients completed the 5-year follow-up. One implant failed in the six implants group (99.2% survival) and none in the four implants group (100% survival). No overdentures had to be replaced during the observation period and the number of complications was limited. Clinical function was good, with no difference in clinical parameters between the groups. Mean marginal bone resorption was 0.50 ± 0.37 and 0.52 ± 0.43 mm in the four and six implant group respectively.

CONCLUSION

In patients with functional complaints of their maxillary denture, bar-supported overdentures on four implants in the anterior maxillary region were not inferior to overdentures supported by six implants after 5 years of function. Implant survival and patient satisfaction were high, clinical parameters favourable, bone loss and complications to the denture were minor in both groups (Clinical trial registration number: NTR2969).

Retentive Properties of O-Ring and Locator Attachments for Implant-Retained Maxillary Overdentures: An In Vitro Study

PURPOSE

To evaluate and compare retentive properties of O-ring and Locator attachments for implant-retained maxillary overdentures.

MATERIALS AND METHODS

Four implant analogs were inserted in canine and second premolar areas of an acrylic edentulous maxillary model. A metal-reinforced experimental acrylic overdenture was constructed and connected to the analogs using either O-ring (group I) or Locator (group II) attachments. Locators were divided into 3 subgroups according the degree of retention of the patrix nylon insert: Locator extra-light retention (group IIa), Locator light retention (group IIb), and Locator medium retention (group IIc). Vertical and oblique (lateral, anterior, and posterior) dislodging forces were measured at the beginning of the study (initial retention) and after 540 cycles of denture insertion and removal (final retention).

RESULTS

For vertical, lateral, and anterior dislodging, group IIc recorded the highest initial and final retention, and group I recorded the lowest retention. For posterior dislodging, group I recorded the highest retention, and group IIa recorded the lowest retention. For group II, vertical dislodging recorded the highest initial and final retention, and lateral dislodging recorded the lowest retention. For group I, posterior dislodging recorded the highest initial and final retention, and lateral dislodging recorded the lowest retention. For all dislodging forces (except posterior dislodging), the highest retention loss was recorded in group I, and the lowest retention loss was recorded in group IIa.

CONCLUSION

Locator medium attachment was associated with favorable retention during axial (vertical) and nonaxial (anterior and lateral) dislodging compared to other types of Locator inserts and O-ring attachments after a simulated 6-month period of overdenture use.

Does a large dehiscent implant surface at placement affect the 5-year treatment outcome? An assessment of implants placed to support a maxillary overdenture

The aim of this study was to assess the 5-year clinical and radiographic outcome of implants with a dehiscent surface at implant placement. A total of 26 consecutive patients (mean age 61.6 years; SD 8.0 years) with at least one implant with a dehiscent implant surface of ≥ two thirds of the implant length on the labial side were included. All implants were placed to support a maxillary overdenture. The implants were placed with adequate primary stability and the dehiscent surface was covered with autologous bone, inorganic bovine bone and a resorbable membrane. Outcome measures were soft tissue conditions, change of radiographic marginal bone level and implant survival. Baseline data (at loading, T0) were compared with 1-year (T1) and 5-year (T5) post loading data. Of the 116 implants, 40 implants had no dehiscence, 16 had a buccal dehiscence < two thirds of the implant length, and 60 implants had a dehiscence ≥ two thirds. The peri-implant tissues were healthy and 5-year marginal bone changes were well within normal limits (-0.4 mm; range: -0.8 to -0.1). One implant was lost during the osseointegration period. Even when implants are placed with a dehiscence ≥ two thirds of the buccal implant surface, favorable 5-year peri-implant health can be achieved provided these dehiscences are covered with autologous bone, inorganic bone and a resorbable membrane, and there is good initial stability of the implants.

A prospective study on the morbidity resulting from calvarial bone harvesting for intraoral reconstruction

Calvarial bone grafts are used for reconstruction of the maxilla or mandible to enable implant placement. The aim of this study was to assess the morbidity resulting from the use of calvarial bone grafts to reconstruct the maxilla and mandible. Thirty-six consecutive patients were included in this prospective study (14 men and 22 women; mean age 59 ± 8.2 years). Perioperative and postoperative complications related to harvesting of the calvarial bone were scored, as well as the occurrence of intraoral complications (average follow-up 25 ± 12 months). Perioperative exposure of the dura occurred in four patients and the graft broke during harvesting in five patients. With a change in the technique, these complications no longer occurred. Postoperative pain levels at the calvarial donor site were low (visual analogue scale (VAS) 1.9 ± 2.0 on day 1) and of short duration (5.2 ± 4.7 days to becoming pain-free). In all cases sufficient bone could be harvested to enable the placement of implants. The exposure of the dura and the intraoral complications were of no clinical consequence. Therefore, calvarial bone grafts appear to be promising for use in pre-implant intraoral reconstructions.

Maxillary overdentures supported by four splinted direct metal laser sintering implants: a 3-year prospective clinical study

Purpose. Nowadays, the advancements in direct metal laser sintering (DMLS) technology allow the fabrication of titanium dental implants. The aim of this study was to evaluate implant survival, complications, and peri-implant marginal bone loss of DMLS implants used to support bar-retained maxillary overdentures. Materials and Methods. Over a 2-year period, 120 implants were placed in the maxilla of 30 patients (18 males, 12 females) to support bar-retained maxillary overdentures (ODs). Each OD was supported by 4 implants splinted by a rigid cobalt-chrome bar. At each annual follow-up session, clinical and radiographic parameters were assessed. The outcome measures were implant failure, biological and prosthetic complications, and peri-implant marginal bone loss (distance between the implant shoulder and the first visible bone-to-implant contact, DIB). Results. The 3-year implant survival rate was 97.4% (implant-based) and 92.9% (patient-based). Three implants failed. The incidence of biological complication was 3.5% (implant-based) and 7.1% (patient-based). The incidence of prosthetic complication was 17.8% (patient-based). No detrimental effects on marginal bone level were evidenced. Conclusions. The use of 4 DMLS titanium implants to support bar-retained maxillary ODs seems to represent a safe and successful procedure. Long-term clinical studies on a larger sample of patients are needed to confirm these results.

Improving masticatory performance, bite force, nutritional state and patient's satisfaction with implant overdentures: a systematic review of the literature

Oral function with removable dentures is improved when dental implants are used for support. A variety of methods is used to measure change in masticatory performance, bite force, patient's satisfaction and nutritional state. A systematic review describing the outcome of the various methods to assess patients' appreciation has not been reported. The objective is to systematically review the literature on the possible methods to measure change in masticatory performance, bite force, patient's satisfaction and nutritional state of patients with removable dentures and to describe the outcome of these. Medline, Embase and The Cochrane Central Register of Controlled Trials were searched (last search July 1, 2014). The search was completed by hand to identify eligible studies. Two reviewers independently assessed the articles. Articles should be written in English. Study design should be prospective. The outcome should be any assessment of function/satisfaction before and at least 1 year after treatment. Study population should consist of fully edentulous subjects. Treatment should be placement of any kind of root-form implant(s) to support a mandibular and/or maxillary overdenture. Fifty-three of 920 found articles fulfilled the inclusion criteria. A variety of methods was used to measure oral function; mostly follow-up was 1 year. Most studies included mandibular overdentures, three studies included maxillary overdentures. Implant-supported dentures were accompanied by high patient's satisfaction with regard to denture comfort, but this high satisfaction was not always accompanied by improvement in general quality of life (QoL) and/or health-related QoL. Bite force improved, masseter thickness increased and muscle activity in rest decreased. Patients could chew better and eat more tough foods. No changes were seen in dietary intake, BMI and blood markers. Improvements reported after 1 year apparently decreased slightly with time, at least on the long run. Treating complete denture wearers with implants to support their denture improves their chewing efficiency, increases maximum bite force and clearly improves satisfaction. The effect on QoL is uncertain, and there is no effect on nutritional state.

Occlusion on oral implants: current clinical guidelines

Proper implant occlusion is essential for adequate oral function and the prevention of adverse consequences, such as implant overloading. Dental implants are thought to be more prone to occlusal overloading than natural teeth because of the loss of the periodontal ligament, which provides shock absorption and periodontal mechanoreceptors, which provide tactile sensitivity and proprioceptive motion feedback. Although many guidelines and theories on implant occlusion have been proposed, few have provided strong supportive evidence. Thus, we performed a narrative literature review to ascertain the influence of implant occlusion on the occurrence of complications of implant treatment and discuss the clinical considerations focused on the overloading factors at present. The search terms were 'dental implant', 'dental implantation', 'dental occlusion' and 'dental prosthesis'. The inclusion criteria were literature published in English up to September 2013. Randomised controlled trials (RCTs), prospective cohort studies and case-control studies with at least 20 cases and 12 months follow-up interval were included. Based on the selected literature, this review explores factors related to the implant prosthesis (cantilever, crown/implant ratio, premature contact, occlusal scheme, implant-abutment connection, splinting implants and tooth-implant connection) and other considerations, such as the number, diameter, length and angulation of implants. Over 700 abstracts were reviewed, from which more than 30 manuscripts were included. We found insufficient evidence to establish firm clinical guidelines for implant occlusion. To discuss the ideal occlusion for implants, further well-designed RCTs are required in the future.

An economic evaluation of maxillary implant overdentures based on six vs. four implants

BACKGROUND

The purpose of the present study was to assess the value for money achieved by bar-retained implant overdentures based on six implants compared with four implants as treatment alternatives for the edentulous maxilla.

METHODS

A Markov decision tree model was constructed and populated with parameter estimates for implant and denture failure as well as patient-centred health outcomes as available from recent literature. The decision scenario was modelled within a ten year time horizon and relied on cost reimbursement regulations of the German health care system. The cost-effectiveness threshold was identified above which the six-implant solution is preferable over the four-implant solution. Uncertainties regarding input parameters were incorporated via one-way and probabilistic sensitivity analysis based on Monte-Carlo simulation.

RESULTS

Within a base case scenario of average treatment complexity, the cost-effectiveness threshold was identified to be 17,564 € per year of denture satisfaction gained above of which the alternative with six implants is preferable over treatment including four implants. Sensitivity analysis yielded that, depending on the specification of model input parameters such as patients' denture satisfaction, the respective cost-effectiveness threshold varies substantially.

CONCLUSIONS

The results of the present study suggest that bar-retained maxillary overdentures based on six implants provide better patient satisfaction than bar-retained overdentures based on four implants but are considerably more expensive. Final judgements about value for money require more comprehensive clinical evidence including patient-centred health outcomes.

Evaluation of the literature: evidence assessment tools for clinicians

The progressive improvement in the quality of scientific articles has led to an increase in difficulty in reading and interpreting them so that now clinical knowledge and experience must be complemented by methodological, statistical and computer skills. The aim of this article is to offer practitioners the tools, the simplest keys, that will allow them to understand and critically judge the results of scientific studies. The "peer-review" process of a clinical article submitted to a journal is described and the Science Citation Index and the Impact Factor are presented to the reader as essential instruments to evaluate a specific article's impact and the impact of a given journal on the scientific world, respectively. An article should be evaluated on the basis of some key issues which include, at least, an assessment of methodological aspects, a critical analysis of the statistical component and a proper understanding of the clinical impact of the study outcomes. The standard approach for evaluating the quality of individual studies is based on a hierarchical grading system of research design which represents an essential tool to identify the strength of the evidence of an article. Many different biases may affect the reliability of study results. Randomized Control Trials (RCTs) and Systematic Reviews (SRs) are able to minimize the number of biases and thus are at the highest level of the scale of evidence representing the final steps of a treatment's "career." Finally, moving from research to clinical practice, attention on the clinical impact of study's outcomes is of paramount importance as the literature contains studies (including RCTs) that present statistically significant results but which, from the clinical standpoint, are only relatively or not at all significant. Clinical Practice Guidelines represent a useful tool for practitioners assisting the decision-making process when choosing the most appropriate treatment for their patients.