Mandibular overdentures supported by two or four endosseous implants: a 10-year clinical trial

Objective: The aim of this 10-year clinical trial was to evaluate the treatment outcome (condition of hard and soft peri-implant tissues, patient satisfaction, surgical and prosthetic aftercare) of mandibular overdentures supported by two or four implants.
Materials and methods: Sixty edentulous patients with a mandibular height between 12 and 18 mm participated. Thirty patients were treated with an overdenture supported by two IMZ implants (group A) and 30 patients were treated with an overdenture supported by four IMZ implants (group B). Standardised clinical and radiographic parameters were evaluated 6 weeks after completion of the prosthetic treatment and after 1, 5 and 10 years of functional loading. Prosthetic and surgical aftercare was scored during the evaluation period, as well as patient satisfaction.
Results: There were no statistically significant differences with regard to any of the studied clinical or radiographic parameters of the peri-implant tissues between the groups. In addition, no differences in satisfaction and aftercare were observed between the groups.
Conclusion: There is no difference in the clinical and radiographical state of patients treated with an overdenture on two or four implants during a 10-year evaluation period. Patients of both groups were evenly satisfied with their overdentures and received the same amount of aftercare. For reasons of cost-effectiveness, a two-implant overdenture is advised for patients with a Cawood classes IV–VI resorption of the mandible and complaints concerning retention and stability of the lower denture.     

Mandibular overdentures supported by two or four endosseous implants. A 5-year prospective study

OBJECTIVE: The aim of this 5-year prospective comparative study was to evaluate treatment outcome (survival rate, condition of hard and soft peri-implant tissues, patient satisfaction, prosthetic and surgical aftercare) of mandibular overdentures supported by two or four implants. MATERIAL AND METHODS: Sixty edentulous patients with a mandibular height between 12 and 18 mm participated. Thirty patients were treated with an overdenture supported by two IMZ implants (group A) and 30 patients were treated with an overdenture supported by four IMZ implants (group B). Standardised clinical and radiographic parameters were evaluated 6 weeks after completion of the prosthetic treatment and after 1, 2, 3, 4 and 5 years of functional loading. Prosthetic and surgical aftercare was scored during the evaluation period. RESULTS: One implant was lost (group A) during the healing period. There were no significant differences with regard to any of the studied clinical or radiographic parameters of the peri-implant tissues between the groups. None of the patients reported sensory disturbances in the lip or chin region. No differences in satisfaction were observed between the groups. With regard to aftercare, there was a tendency of a greater need of prosthetic interventions in group A, while correction of soft-tissue problems was restricted to patients of group B. CONCLUSION: There is no difference in clinical and radiographical state of patients treated with an overdenture on two or four implants during a 5-year evaluation period. Patients of both groups were as satisfied with their overdentures.     

Maxillary overdentures retained by splinted and unsplinted implants: a retrospective study

The purpose of this retrospective study was to evaluate the clinical performance of and patients' satisfaction with maxillary overdentures retained by splinted and unsplinted implants. Patients who had been treated with maxillary implant-retained overdentures because of functional problems with conventional complete dentures were identified and invited to participate in the study. A total of 16 patients fulfilled the enrollment criteria and agreed to participate. Eleven patients were treated with bar-retained overdentures with 3 to 6 clips (mean follow-up 32 months), and 5 patients wore overdentures retained by 2 to 6 ball attachments (mean follow-up 54 months). All subjects were satisfied with their prostheses, and most subjects experienced improvement in their oral function after treatment with implant-retained overdentures. At the time of clinical examination, 92% (n = 77) of the 84 implants placed were functioning satisfactorily. The cumulative survival rate for the implants after 72 months was 90%. Loss of bone support correlated with peri-implant probing depth (r = 0.29; P < .02). No differences in mean bone loss between the subjects with ball-retained or bar-retained overdentures were found. The presence of plaque or peri-implant bleeding was not associated with the type of attachment.     

Implant-supported mandibular overdentures retained with a milled bar: a retrospective study

PURPOSE: The aim of this retrospective study was to evaluate implant survival rate, peri-implant conditions, and prosthodontic maintenance for implant-supported mandibular overdentures rigidly retained with a milled bar. MATERIALS AND METHODS: Patients with 4 interforaminal implants (cylindric or screw-type) supporting an overdenture on a milled bar treated between 1996 and 2004 were asked to participate in a retrospective study. The cumulative implant survival rate and peri-implant conditions (marginal bone loss, pocket depth, Plaque Index, Gingival Index, Bleeding Index, and calculus presence) were evaluated and compared between cylindric and screw-type implants. The incidence and type of prosthodontic maintenance and subjective patient satisfaction rating were also evaluated. RESULTS: Fifty-eight of 67 patients (87.3%) and 232 implants (76 cylindric, 156 screw-type) were available for follow-up examination after a mean period of 59.2 +/- 26.9 months. The cumulative implant survival rate was 99%, and no differences in peri-implant soft tissue conditions were noted between the different implant types used. The cylindric implants showed more pronounced marginal bone resorption than the screw-type implants (1.9 +/- 0.6 mm vs 2.2 +/- 0.6 mm; P = .02) but the difference was not clinically significant. A low incidence of prosthodontic maintenance evenly distributed throughout the overall follow-up period and a high subjective satisfaction rating by the patients were noted. CONCLUSION: Interforaminal screw-type and cylindric implants supporting a milled bar for rigid overdenture anchorage were associated with a high survival rate and excellent peri-implant conditions. The incidence of prosthodontic maintenance was low and evenly distributed throughout the follow-up period as a result of rigid denture stabilization by the milled bar. Rigid anchorage of a mandibular overdenture with a milled bar unites the prosthodontic advantages of removable and fixed prostheses. (Clinical Trial) (More than 50 references.)     

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。     

Oral health status and treatment satisfaction with mandibular implant overdentures and conventional dentures: a randomized clinical trial in a senior population

PURPOSE: The purpose of this study was to compare elderly patients' satisfaction and oral health-related quality of life with mandibular two-implant overdentures and conventional dentures. MATERIALS AND METHODS: Sixty edentulous subjects aged 65 to 75 years were randomly assigned to two groups treated with maxillary conventional dentures and either a mandibular conventional denture (n = 30) or an overdenture supported by two implants with ball retainers (n = 30). Subjects rated their general satisfaction, as well as other features of their dentures (comfort, stability, ability to chew, speech, esthetics, and cleaning ability), prior to treatment and 2 months postdelivery. Changes in ratings on the original Oral Health Impact Profile (OHIP) and its short form (OHIP-EDENT) were also used as indicators of oral health-related quality of life. RESULTS: The primary outcome of this study, ratings of general satisfaction 2 months postdelivery, was significantly better in the group treated with mandibular two-implant overdentures (P = .001). In addition, the implant group gave significantly higher ratings on comfort, stability, and ability to chew. Furthermore, using OHIP-EDENT, subjects who received mandibular two-implant overdentures had significantly fewer oral health-related quality of life problems than did the conventional group. CONCLUSION: These short-term results suggest that mandibular two-implant overdentures combined with maxillary conventional dentures provide better function and oral health-related quality of life than conventional dentures.     

Mandibular overdentures supported by two or four endosteal implants: A prospective, comparative study

The aim of this prospective study was to evaluate the effect of the number of implants supporting a mandibular overdenture on the condition of the peri-implant tissues. Sixty edentulous patients (Cawood class V–VI) participated in this study. After randomization, thirty patients were treated with an overdenture supported by two IMZ implants (group A) and thirty patients with an overdenture on four IMZ implants (group B). The implants were inserted in the anterior region of the mandible. After three months overdentures were constructed, supported by round bar and clip attachments. A standardized clinical and radiographic evaluation was performed 0, 6 and 12 months after insertion of the denture. One implant was lost (group A) during the healing period. There were no significant differences with regard to any of the studied clincial or radiographic parameters of the peri-implant tissues, neither were significant differences found between the lateral and central implants in group B. None of the patients reported a sensory change in lip or chin region. From this study it is concluded that there seems to be no need to insert more than two endosteal implants to support an overdenture, however, long-term prospective studies are needed to support this notion.     

Five-year prospective evaluation of mandibular overdentures retained by two microthreaded, TiOblast nonsplinted implants and retentive ball anchors

PURPOSE: The aim of this 5-year prospective evaluation was to assess the bone and peri-implant mucosa responses at unsplinted, microthread implants supporting mandibular overdentures and to determine patient responses to therapy. MATERIALS AND METHODS: Two implants were placed by a 1-stage procedure in the parasymphyseal mandibles of 59 subjects. Implant placement was followed by immediate insertion of overdentures without connection to abutments. After 3 months, connection using Dalla Bona attachments was made and peri-implant mucosa, peri-implant bone, and patient perceptions of treatment were evaluated. RESULTS: The implant success rate was 95.9% from 6 to 60 months. The changes in marginal bone levels were positive (bone gain) but did not reach statistical significance at 12, 36, or 60 months (+0.13 +/- 0.59 mm, +0.23 +/- 0.66 mm, and +0.09 +/- 0.79, respectively). Treatment was viewed as effective; patients rating satisfaction with their teeth increased from a preoperative level of 12.1% to 94.6% at overdenture abutment connection and remained high (81.6%) after 5 years. CONCLUSIONS: Expedited mandibular overdenture therapy utilizing unsplinted, microthreaded mandibular parasymphyseal implants was associated with high implant survival, preservation of crestal bone, and high patient satisfaction. Complications were minor and related to prosthodontic features of therapy.     

A 2-year clinical report of patients treated with two loading protocols for mandibular overdentures: early versus conventional loading

BACKGROUND: The original Br?nemark protocol for dental implant treatment was based on submerged healing prior to loading. In recent years, immediate/early functional loading has been reported to be possible with high success for various indications including two splinted mandibular implants supporting an overdenture. However, there are a limited number of studies regarding the early loading protocol for two unsplinted mandibular implants supporting an overdenture. METHODS: A total of 26 edentulous patients were treated with two unsplinted dental implants supporting mandibular overdentures. All implants were placed in the canine regions of each mandible according to the one-stage surgery. For the test group, overdentures were connected 1 week after surgery, and for the control group, overdentures were connected 3 months after surgery. Peri-implant parameters were recorded 1, 6, 12, 18, and 24 months after surgery. Marginal bone levels were evaluated at implant placement and after 6, 12, 18, and 24 months. Clinical stability measurements were performed at surgery, and after 3, 6, 12, 18, and 24 months. RESULTS: No implant from either group was lost during 2 years. Clinical peri-implant parameters, clinical implant stability measurements, and marginal bone resorptions showed no statistically significant differences between the two groups during 24 months. CONCLUSION: The results of this clinical trial suggest that the early loading approach of two dental implants supporting a mandibular overdenture does not jeopardize peri-implant soft tissue health, marginal bone resorption, and implant stability.     

二或四枚种植体支持的Locator覆盖义齿修复五年回顾

目的:比较下颌牙列缺失患者分别采用2枚或者4枚种植体支持的Locator覆盖义齿,修复5年后的临床效果。方法:选取采用2枚种植体(A组)和4枚种植体(B组)支持Locator覆盖义齿患者分别为20例、15例。评估2组患者满意度(整体满意度、咀嚼能力、说话适合性、固位和稳定性、舒适度),并检测咀嚼效率和边缘骨吸收值。结果:两组病人在整体满意度、咀嚼能力、说话适合性、固位和稳定性、舒适度及咀嚼效率、边缘骨吸收方面均无显著性差异(P>0.05)。结论:Locator种植覆盖义齿无论是采用2枚还是4枚种植体,5年后均能获得很好的临床效果,患者满意度高,但对其远期临床效果还有待观察。对于有可能出现义齿旋转的患者建议种植4枚种植体。     

Influence of implant number on the biomechanical behaviour of mandibular implant-retained/supported overdentures: A three-dimensional finite element analysis

Objective

The aim of this study was to evaluate strain distribution in peri-implant bone, stress in the abutments and denture stability of mandibular overdentures anchored by different numbers of implants under different loading conditions, through three-dimensional finite element analysis (3D FEA).

Methods

Four 3D finite element models of mandibular overdentures were established, using between one and four Straumann implants with Locator attachments. Three types of load were applied to the overdenture in each model: 100 N vertical and inclined loads on the left first molar and a 100 N vertical load on the lower incisors. The biomechanical behaviours of peri-implant bone, implants, abutments and overdentures were recorded.

Results

Under vertical load on the lower incisors, the single-implant overdenture rotated over the implant from side to side, and no obvious increase of strain was found in peri-implant bone. Under the same loading conditions, the two-implant-retained overdenture showed more apparent rotation around the fulcrum line passing through the two implants, and the maximum equivalent stress in the abutments was higher than in the other models. In the three-implant-supported overdenture, no strain concentration was found in cortical bone around the middle implant under three loading conditions.

Conclusions and clinical significance

Single-implant-retained mandibular overdentures do not show damaging strain concentration in the bone around the only implant and may be a cost-effective treatment option for edentulous patients. A third implant can be placed between the original two when patients rehabilitated by two-implant overdentures report constant and obvious denture rotation around the fulcrum line.     

To splint or not to splint oral implants in the implant‐supported overdenture therapy? A systematic literature review

The objective of this systematic review was to assess the influence of splinted and unsplinted oral implants in the mandibular and maxillary implant-supported overdenture therapy, concerning the implant survival, the peri-implant parameters, the prosthetic complications and the patient satisfaction. An electronic MEDLINE search complemented by manual searching was conducted to identify randomized clinical trials, prospective and retrospective cohort studies on implant-supported overdentures with a mean follow-up of at least 3 years. Twelve studies from an initial yield of 1022 titles were finally selected and data were extracted. After an observation period of more than 3 years, there was no difference in implant survival rates between splinted and unsplinted design. From most of the investigations included in this study, it was mentioned that the unsplinted design needs more prosthetic maintenance. In more of the studies that were dealing with the satisfaction of the patients wearing implant-supported overdentures, no significant difference in the preference of the patients was reported. No significant difference in the peri-implant outcome between splinted and unsplinted design was found. Within the limits of this systematic review, it is concluded that there was no significant difference between the two different designs of implant-supported overdentures with respect to the soft tissue health status or patient satisfaction, although the bar-supported overdentures have been shown to need less prosthetic maintenance.     

Implant and root supported overdentures - a literature review and some data on bone loss in edentulous jaws

PURPOSE

To present a literature review on implant overdentures after a brief survey of bone loss after extraction of all teeth.

MATERIALS AND METHODS

Papers on alveolar bone loss and implant overdentures have been studied for a narrative review.

RESULTS

Bone loss of the alveolar process after tooth extraction occurs with great individual variation, impossible to predict at the time of extraction. The simplest way to prevent bone loss is to avoid extraction of all teeth. To keep a few teeth and use them or their roots for a tooth or root-supported overdenture substantially reduces bone loss. Jaws with implant-supported prostheses show less bone loss than jaws with conventional dentures. Mandibular 2-implant overdentures provide patients with better outcomes than do conventional dentures, regarding satisfaction, chewing ability and oral-health-related quality of life. There is no strong evidence for the superiority of one overdenture retention-system over the others regarding patient satisfaction, survival, peri-implant bone loss and relevant clinical factors. Mandibular single midline implant overdentures have shown promising results but long-term results are not yet available. For a maxillary overdenture 4 to 6 implants splinted with a bar provide high survival both for implants and overdenture.

CONCLUSION

In edentulous mandibles, 2-implant overdentures provide excellent long-term success and survival, including patient satisfaction and improved oral functions. To further reduce the costs a single midline implant overdenture can be a promising option. In the maxilla, overdentures supported on 4 to 6 implants splinted with a bar have demonstrated good functional results.     

Comparison between mainly mucosa-supported and combined mucosa-implant-supported mandibular overdentures

The purpose of this study is to compare mainly mucosa-supported and combined mucosa-implant-supported complete mandibular overdentures. Ten completely edentulous patients received 20 press-fit dental implants at the canine regions of the mandible. Each patient received 2 implants, which were left submerged and unloaded for 4 months. The patients were divided into 2 groups: group I patients received mandibular overdentures retained by a magnet attachment (mainly mucosa-supported overdenture). Group II patients received mandibular overdentures retained by a bar attachment (combined mucosa-implant-supported overdenture). The patients were evaluated clinically and radiographically immediately after overdenture delivery and after 6 months, 12 months, and 18 months. The results showed that the mainly mucosa-supported overdentures had less bone resorption distal to the implant in comparison to the combined mucosa-implant-supported overdentures. Plaque index score was significantly high in the group treated with magnet-retained overdentures. After 18 months follow up, the group treated with combined mucosa-implant-supported overdentures showed a significant increase in gingival inflammation when compared with the other group. The type of attachment or support may affect gingival inflammation or plaque accumulation. Increased functional load may affect bone density and resorption.     

The effectiveness of 2‐implant overdentures – a pragmatic international multicentre study

Summary The purpose of this multicentre observational study was to determine patient satisfaction with either conventional dentures or mandibular 2‐implant overdentures in a ‘real world’ setting. Two hundred and three edentulous patients (mean age 68·8 ± 10·4 years) were recruited at eight centres located in North America, South America and Europe. The patients were provided with new mandibular conventional dentures or implant overdentures supported by two implants and ball attachments. At baseline and at 6 months post‐treatment, they rated their satisfaction with their mandibular prostheses on 100‐mm visual analogue scale questionnaires. One hundred and two (50·2%) participants had valid baseline and 6‐month satisfaction data. Although both groups reported improvements, the implant overdenture group reported significantly higher ratings of overall satisfaction, comfort, stability, ability to speak and ability to chew. These results suggest that edentulous patients who choose mandibular implant overdentures have significantly greater improvements in satisfaction, despite their relatively higher cost, than those who choose new conventional dentures.     

Two-implant mandibular overdentures: simple to fabricate and easy to wear

Success rates for titanium dental implants in the anterior mandible are very high. Because of these success rates, as well as lower costs, it is common to treat edentulous patients with just 2 implants and ball anchors for retention of the overdenture, instead of 4 implants and a bar. In this paper the fabrication of 2-implant overdentures is described. In a controlled clinical trial (to be reported elsewhere), 30 subjects received a 2-implant overdenture for the mandible and a conventional prosthesis for the maxilla. The 30 control patients received conventional complete dentures for both jaws. The stability of the overdentures was excellent, and the lingual dimensions of the denture could be reduced to the level of the mylohyoid line to provide more space for the tongue. In patients with tense labial musculature or a limited amount of attached gingiva, it was important to elevate the shoulder of the implant and ball abutment above the gingival level to avoid peri-implant problems. Significantly fewer visits for adjustment related to post-placement pressure spots were required for mandibular overdentures than for conventional mandibular prostheses.     

球帽式和Locator式下颌种植覆盖总义齿的临床效果观察

目的：评价球帽式和Locator式下颌种植覆盖总义齿的临床应用效果。方法：共完成2颗种植体支持的球帽下颌覆盖总义齿9例,Locator下颌覆盖总义齿11例,上颌均制作可摘局部义齿。修复完成后于3、6、12、24个月进行随访,对各组种植体周围边缘骨吸收（MBL）进行评估,同时进行义齿满意度调查。结果：Locator组、球帽组在咀嚼功能、固位功能和舒适程度的满意度均高于治疗前,有显著性差异（P〈0.05）;Locator组与球帽组患者满意度、种植体周牙槽骨吸收量差异无统计学意义。结论：使用球帽、Locator附着体种植覆盖义齿在下颌无牙颌的应用中临床效果明显。     

球帽固位下颌双种植体覆盖义齿修复效果的前瞻性研究

目的 评价球帽固位的下颌双种植体覆盖义齿的临床修复效果及其修复并发症。 方法 对下颌牙槽骨重度萎缩的10例无牙颌患者,在前牙区与中线等距平行植入2枚种植体,3个月后采用球帽附着体固位方式制作下颌种植覆盖义齿。在覆盖义齿戴入后1周、1年、2年、3年进行随访,评价种植体边缘骨吸收情况、种植体周围软组织健康状况、患者满意度及义齿并发症情况。 结果 10例两球帽固位的下颌种植覆盖义齿经过3年观察,种植体存留率100%,边缘骨吸收<1 mm,种植体周围软组织健康,患者满意度显著提高且维持稳定,义齿无重衬或折断现象,义齿并发症主要是球帽附着体O型圈的置换或固位金属簧的固位力再激活,修理频次0.67次/(年·人)。 结论 在种植体植入位置、方向合适的情况下,球帽附着体固位的下颌双植体覆盖义齿,可获得长期稳定的临床修复效果。     

Maxillary anterior and mandibular posterior residual ridge resorption in patients wearing a mandibular implant-retained overdenture

The mandibular implant-retained overdenture could improve masticatory function compared to the conventional complete denture. However, increased forces exerted by the overdenture could increase residual ridge resorption of the maxillary anterior and mandibular posterior areas. The aim of this study was to compare the effect of the mandibular implant-retained overdenture using two or four dental implants, or the conventional complete denture on resorption of the residual ridge of the maxillary anterior and mandibular posterior areas over a period of 10 years. In total, 120 patients, 30 patients treated with an overdenture on two implants (two-implant group), 30 patients with an overdenture on four implants (four-implant group) and 60 patients treated with a conventional full denture (conventional group), participated in this study. On panoramic radiographs, made before and 10 years after treatment, proportional area measurements were applied to determine changes in bone height. After 10 years, a statistically significant amount of bone resorption had occurred in the anterior maxilla in the two-implant group and in the four-implant group. A significant amount of bone resorption had occurred in the posterior mandible in all three groups. There were no statistically significant differences between the groups in both areas. Patients presented large individual differences. It is concluded that patients rehabilitated with implant-retained mandibular overdentures are not subjected to more residual ridge resorption in the anterior maxilla when compared to patients wearing a conventional full denture. Regarding the mandibular posterior residual ridge, resorption was irrespective of wearing an implant-retained mandibular overdenture or a conventional mandibular denture.     

Implant-retained mandibular overdentures versus conventional dentures: 10 years of care and aftercare

PURPOSE: This 10-year prospective, randomized, clinical trial investigated the treatment outcome of edentulous patients treated with mandibular overdentures retained by 2 endosseous implants compared with conventional dentures in patients with or without vestibuloplasty. MATERIALS AND METHODS: One hundred fifty-one edentulous patients (5 groups) with a symphyseal mandibular bone height between 8 and 25 mm participated. Sixty-two patients were treated with an overdenture retained by 2 implants (groups 1 and 3), 59 patients were treated with a conventional denture (groups 2 and 5), and 30 patients were treated with a conventional denture after preprosthetic vestibuloplasty (group 4). Patients who received conventional dentures but preferred implants later on could undergo implant surgery after 1 year of their initial treatment, but were analyzed in their original group. The prosthetic and surgical care and aftercare were scored during a 10-year evaluation period. RESULTS: One hundred thirty-three patients completed the 10-year follow-up evaluations. Forty-four percent of patients treated with conventional dentures switched within 10 years to implant-retained overdentures, versus 16% of the patients who were treated with conventional dentures after vestibuloplasty. On average, a greater time investment and more treatment sessions were needed in patients treated with implant-retained overdentures compared to patients treated with conventional dentures. CONCLUSION: Patients treated with an implant-retained overdenture need more treatment interventions and treatment time than patients treated with conventional dentures.