Masticatory performance with mandibular implant-retained overdentures

It was investigated in a clinical trial whether the masticatory performance of complete-denture wearers depended on the support for their mandibular dentures by implants or mucosa. The trial involved the provision of a new maxillary denture and either a new conventional mandibular denture (mucosa-borne), a mandibular overdenture retained by two IMZ-implants (implant-mucosa-borne), or a mandibular overdenture on a transmandibular implant (TMI; mainly implant-borne). In comparison with mandibular implant-retained overdentures, subjects with conventional dentures needed 1.5 to 3.6 times more chewing strokes for an equivalent reduction in particle size. No differences in masticatory performance were found between subjects with IMZ-implants and those with TMI. This suggests that the increased stability of the mandibular denture with implants determines the wearer's masticatory performance, rather than the support by implants.     

Masticatory performance and chewing experience with implant-retained mandibular overdentures

The relationship between masticatory performance and chewing experience has not yet been explored for patients with implant-retained overdentures. Although many relationships have been found between parameters of objective and subjective oral function, the structure of these relationships remain unclear. Therefore, we studied in a randomized clinical trial the relationship between the comminution of an artificial test food, i.e. masticatory performance, and the subjective chewing experience. The trial involved a comparison between two groups receiving implant treatment and one group receiving conventional complete dentures (CD). The implant treatment involved either a mainly implant-supported mandibular overdenture on a transmandibular implant (TMI) or an implant-tissue-supported mandibular overdenture on two IMZ implants (IMZ). Masticatory performance as well as chewing experience were substantially better for the implant-retained overdentures compared with the complete denture group. No significant differences emerged between the TMI and the IMZ group. A multiple regression analysis did not provide any comprehensibility in the relationship between masticatory performance and the variables of chewing experience. In the linear structural relation analysis (LISREL) no direct relationship was found between masticatory performance and functional complaints mandibular denture. The results show that an improvement in masticatory performance does not imply the same improvement in chewing experience and vice versa.     

Pain and instability during biting with mandibular implant-retained overdentures

We tested in a randomized controlled clinical trial the effect of pain and instability of dentures on bite force with different degrees of mucosal support. The trial involved 3 groups who had received: 1) a new conventional denture (CD-group), 2) an implant-mucosa-borne overdenture on 2 IMZ implants (IMZ-group) or 3) a mainly implant-borne overdenture retained by a transmandibular implant (TMI-group). Fifty-three women and 15 men, mean age 59 years, participated in this study. Bite force measurements were made unilaterally with a transducer and bilaterally with a bite fork. After the measurements, subjects were asked whether or not biting had caused pain or tilting of one of the dentures. Significantly more complete-denture wearers reported pain. They reported more frequent pain in the mandible than in the maxilla (P < 0.001), whereas implant-groups seemed to experience more often pain in the maxilla. On the transducer, maxillary dentures of the CD-group tilted less (P < 0.01) and mandibular dentures more (P < 0.05) compared to the implant-groups. With the bite fork, tilting occurred more often in the incisal-cuspid area than in the molar region (P < 0.001). No effect of pain and tilting was observed on maximum bite force. It appears that oral implants used to stabilize mandibular dentures permit subjects to exert higher bite forces and reduce the pain as otherwise felt in the mandible during maximum biting. Due to this stabilization, pain and instability of the maxillary denture can become the limiting factor for a further increase in bite force.     

Swallowing thresholds of mandibular implant-retained overdentures with variable portion sizes

We analysed the effect of three portion sizes Optocal Plus (small, medium and large) on swallowing thresholds in subjects with either conventional complete dentures or mandibular implant-retained overdentures (transmandibular and permucosal cylindric implants). Tests were carried out in 52 women and 15 men (mean age 59 years) 4 years after treatment in a randomised controlled clinical trial. The results indicated that the degree of mucosal support for the mandibular denture did not affect the number of chewing strokes, time till swallowing or swallowed particle size. Only the chewing rate differed: subjects wearing mandibular implant-retained overdentures chewed the food at a higher rate than complete-denture wearers. With larger portion sizes, subjects needed significantly more chewing strokes and time until swallowing and they would have swallowed larger particles. Men chewed their food more efficiently than women, as they used the same number of chewing strokes and time, but achieved a greater particle size reduction at the swallowing moment.     

A randomized controlled trial of implant-retained mandibular overdentures

Evidence from randomized clinical trials of implant-retained overdentures is very limited at the present time. The aim of this study was to compare implant-retained mandibular overdentures and conventional complete dentures in a randomized controlled trial (RCT). Our a priori hypothesis was that implant-retained mandibular overdentures would be significantly better than conventional complete dentures. Edentulous patients (n = 118) were randomly allocated to either an Implant Group (n = 62) or a Denture Group (n = 56). Patients completed the Oral Health Impact Profile (OHIP) and a denture satisfaction scale pre-treatment and three months post-treatment. Upon completion of treatment, both groups reported improvement (p < 0.001, Wilcoxon Ranks Sum test) in oral-health-related quality of life and denture satisfaction. There were no significant post-treatment differences between the groups, but a treatment effect may be masked by application of "intention to treat" analysis. The OHIP change scores were significantly greater for patients receiving implants than for those who refused them.     

Implant-retained mandibular overdentures with immediate loading: a prospective study of ITI implants

A prospective study was conducted in which 21 patients received a mandibular implant-supported overdenture. Eighty-four ITI screw-type implants were placed in the interforaminal area of the mental symphysis (4 implants per patient). Immediately after implant placement, a U-shaped gold or titanium bar was fabricated and implants were loaded with an implant-retained overdenture. Of 21 patients treated, 19 were followed for a minimum of 25 months to a maximum of 60 months, with a mean follow-up of 37 months. Two patients dropped out during the follow-up. The overall failure rate of implants (according to Albrektsson criteria) was 4% (3/76 implants), but all implants, bars, and prostheses remained in function. Results from this study demonstrated that the success rate for immediately loaded mandibular implants is similar to that obtained in cases of delayed loading, after osseointegration has taken place. This method shortens dental rehabilitation time with relevant satisfaction for patients.     

Patient satisfaction with implant-retained mandibular overdentures: a retrospective study

Purpose: The aim of this study was evaluation of the effect of age, gender, and past prosthetic history (duration of edentulism, number of complete dentures before implant treatment, and number of adjustment appointments) on patients' ratings of satisfaction (comfort, hygiene, retention, appearance, speech, mastication, and overall satisfaction). Materials and Methods: In this retrospective study, 55 patients who were treated with mandibular overdentures retained by splinted implants from 1998 to 2004 and met the inclusion criteria of the study were selected. Each patient was asked to fill out a questionnaire to evaluate his/her general satisfaction with the implant prostheses and other aspects of satisfaction such as comfort, aesthetic, function, and hygiene. Data were analyzed using a marginal model and the generalized estimating equations methodology to assess the relationship between the scores and the patients’ demographic and past prosthetic histories. Significance was accepted at 5% and expressed as p values and odds ratio (OR). Results: Gender had significant correlation with comfort (p < .0001). Years of being edentulous prior to implant/prosthetic treatment had direct effects on the general satisfaction and satisfaction of comfort (p < .01). One extra denture used before implant treatment resulted in less comfort (p < .01) and poorer function (p < .001). Elders were more satisfied with aesthetic (OR = 0.96) and comfort (OR = 2.96). Number of adjustment appointments had a positive correlation with comfort (p < .001) and a negative correlation with satisfaction of aesthetic (p < .001). Conclusion: The results of this study demonstrated that satisfaction was correlated with age, gender, and past prosthetic history in the patients rehabilitated with the implant‐supported overdentures.     

LOCATOR附着式种植覆盖全口义齿的临床应用

目的：了解LOCATOR附着式种植覆盖全口义齿的临床应用效果。方法：共完成2枚种植体固位式LOCA-TOR下颌覆盖全口义齿10例,对其机械并发症及修理情况进行随访登记,并定期进行X线片检查。结果：在1-2年的追踪期内,所有种植体无松动,无明显骨吸收,义齿咀嚼及固位满意。1例出现种植体周围牙龈轻度红肿,对症处理后痊愈。结论：LOCATOR附着式种植覆盖义齿稳定性好和固位力强,可以达到临床效果满意。     

Clinical viability of single implant-retained mandibular overdentures: a systematic review and meta-analysis

The aim of this meta-analysis was to verify the clinical viability of single implant-retained mandibular overdentures (SIMO). An electronic search of the PubMed and Cochrane databases was performed (end date July 2017); this was supplemented by a manual search of the literature. Only prospective clinical trials and randomized controlled trials (RCTs) that evaluated SIMO with a minimum follow-up of 12 months were included. The meta-analysis was based on the Mantel–Haenszel method. Dental implant and prosthetic failure were the dichotomous outcome measures; these were evaluated through the risk ratio (RR) and odds ratio (OR), with corresponding 95% confidence intervals (CI). Of 499 articles identified, nine fulfilled the inclusion criteria. A total of 205 implants were placed in patients with a mean age of 64.1 years; the cumulative survival rate was 96.6% over a mean follow-up period of 37.3 months. The procedure used (SIMO vs. two implant-retained mandibular overdenture) did not affect dental implant failure (P = 0.45) or prosthetic failure (P = 0.65): RR 1.06 (95% CI 0.91–1.23) and RR 0.88 (95% CI 0.51–1.51), respectively; OR 2.56 (95% CI 0.27–24.39; P = 0.41) and OR 0.44 (95% CI 0.15–1.26; P = 0.13), respectively. Within the limitations of this systematic review and meta-analysis, SIMO with a complete denture as the opposing arch may be considered an alternative treatment for completely edentulous patients. However, this study also confirmed the need for more RCTs on this topic.     

Five years of aftercare of implant-retained mandibular overdentures and conventional dentures

The purpose of this multicentre randomized clinical trial was to analyse surgical and prosthetic aftercare and clinical implant performance of edentulous patients with implant‐retained mandibular overdentures and of patients with conventional dentures, either or not after pre‐prosthetic vestibuloplasty and deepening of the floor of the mouth. The evaluation period was 5 years. The implant systems evaluated were the IMZ implant system, the Brånemark implant system and the Transmandibular Implant system. The centre in Groningen had five groups (n=149) and the centre in Nijmegen had three groups (n=86). The evaluation comprised of surgical and prosthetic aftercare, together with clinical implant performance (CIP). The highest implant loss (29%) is found in the Transmandibular Implant group. All groups had prosthetic revisions and complications according to the CIP‐scale. The majority of the patients in the endosseous implant groups were subject to minor complications. The CIP‐score of the Transmandibular Implant group is significantly higher than the scores of the other groups, because of the high number of lost posts. In 26˙1% of the patients in this group score 4 is given, which means failure of the implant system. From this study it can be concluded that the endosseous implant systems used in this study have less surgical aftercare and a better clinical implant performance than the Transmandibular Implant system and are therefore the systems of choice for the edentulous mandible.     

下颌套筒冠固位全颌覆盖种植义齿即刻负重的临床研究

目的:探讨下颌无牙颌在种植后即刻进行套筒冠固位覆盖义齿修复技术的可行性和临床效果。方法:10例下颌无牙颌患者,术前常规行传统全口义齿修复,在双侧颏孔之间植入4颗种植体,术后当天即刻完成种植体支持的套筒冠固位覆盖义齿修复,均于负重后2、4、8、12、24、48周复诊,检查种植体的稳固性、种植体周龈组织状况,并拍摄X线片观察种植体骨吸收和骨结合状况。结果:10例患者共40颗种植体术后进行即刻负重,均获得良好的骨结合,临床检查种植体稳定性良好,种植体周龈组织健康,未见X线连续透射影,无边缘骨吸收,患者对修复效果满意。结论:下颌无牙颌患者,在双侧颏孔间植入4颗种植体,如种植体可获得足够的初期稳定性,即刻采用种植体支持的套筒冠固位覆盖义齿修复是可行的,短期临床效果满意。     

Changes in the edentulous maxilla in persons wearing implant-retained mandibular overdentures

STATEMENT OF PROBLEM: It has been suggested that risk for severe resorption in the anterior maxilla is increased in persons wearing mandibular implant-retained overdentures. However, little information is available about the changes in the edentulous maxilla after mandibular implant treatment. PURPOSE: This study determined the possible changes in the width of the maxillary residual ridge 6 years after receiving mandibular implant-supported or implant-mucosa-supported overdentures and evaluated the association between the anatomic changes and subjective complaints with maxillary complete dentures. METHODS AND MATERIAL: The subjects for this study (n = 55), enrolled among the participants of a prospective clinical trial, were randomly assigned into 3 groups treated with: (a) implant-supported overdentures on a transmandibular implant system (n = 21); (b) implant-mucosa-supported overdentures on 2 IMZ implants (n = 20); or (c) conventional complete dentures (n = 14). A lingual contact occlusion concept with anterior open bite was used for tooth arrangement in all subjects. Diagnostic casts were made at baseline, and again at the 6-year follow-up. Most prominent points perpendicular to the crest of residual ridge were located in the incisor, canine, and premolar regions, after which the width of the ridge was recorded at these points with a Boley gage. Subjects' opinions on their dentures were evaluated with a questionnaire. RESULTS: Significant reduction in the width of the ridge was found in all measurement areas (mean difference = 0.4 to 0.6 mm; P <.0001). However, changes were small and not associated with the type of prosthetic restoration in the mandible. In subjects with implant-mucosa-supported overdentures, complaint of loose maxillary denture correlated with the decrement of residual ridge width. CONCLUSION: The width of residual ridge decreases with time, despite the type of mandibular prosthetic restoration.     

A controlled clinical trial of implant-retained mandibular overdentures: clinical aspects

summary In a controlled clinical trial, treatment effects of mandibular overdentures on two different implant-systems in edentulous patients were compared one year after insertion of the new dentures. The implant-systems used were the Brånemark system (Brå) and the IMZ-system. Treatment was randomly assigned to 60 patients according to a balanced allocation method. Evaluation included peri-implant and radiographical parameters. According to the Delphi method a clinical implant performance scale (CIP) was constructed based on all conceivable complications of the different implant systems. During the osseointegration period, five Brå- and one IMZ-implants were lost. The results of one of the peri-implant parameters and the radiographical score showed significant differences considering the (pseudo) pocket probing depth (Brå better than IMZ, P < 0.001) and the radiographic-score (IMZ better than Brå, P < 0003). The results for the CIP-scale were less favourable for the Brå-group than for the IMZ-group; however, these differences were not significant.     

Effect of anchorage systems and extension base contact on load transfer with mandibular implant-retained overdentures

STATEMENT OF PROBLEM: Controversy exists regarding the effect of anchorage systems and extension base contact on stress transfer to multiple implants by mandibular overdentures. PURPOSE: This simulation study measured photoelastically the biologic behavior of 4 implants retaining a mandibular overdenture. The purpose of the investigation was to compare the load transfer characteristics of different mandibular-retained overdenture designs, with and without edentulous ridge contact. MATERIAL AND METHODS: A photoelastic model of a human edentulous mandible was fabricated having 4 screw-type implants (3.75 x 10 mm) embedded in the parasymphyseal area. Substructure designs utilizing a cantilevered bar, spark erosion framework, noncantilevered bar, and solitary anchors were fabricated. A vertical load of 30 lb was applied to the first molar unilaterally on each of the 4 standardized overdenture prostheses, with and without a silicone tissue spacer, for a total of 8 tested conditions. Stresses that developed in the supporting structure were monitored photoelastically and recorded photographically. RESULTS: Without the simulated tissue contact on the posterior edentulous ridge, the cantilevered bar framework caused the highest stresses to the terminal implant, followed by spark erosion framework, non-cantilevered bar, and solitary anchor design. With simulated tissue contact under the extension base, stress transfer to the distal implant was uniformly reduced to a low level. CONCLUSION: Without intimate extension base contact with the posterior edentulous ridge, the cantilevered anchorage systems generated the highest stresses, under load, to the ipsilateral terminal implant and the solitary anchor design transferred the least. With simulated intimate extension base contact, all anchorage systems transferred low stress to the distal implant region. For all conditions and designs, low stress was transferred to the contralateral side of the arch.