Masticatory function in patients with an extremely resorbed mandible restored with mandibular implant-retained overdentures: comparison of three types of treatment protocols

Comparison of stress distribution between complete denture and implant-retained overdenture-2D FEA

The aim of this study was to compare the stress distribution induced by posterior functional loads on conventional complete dentures and implant-retained overdentures with different attachment systems using a two-dimentional Finite Element Analysis (FEA-2D). Three models representative of edentulous mandible were constructed on AutoCAD software; Group A (control), a model of edentulous mandible supporting a complete denture; Group B, a model of edentulous mandible supporting an overdenture over two splinted implants connected with the bar-clip system; Group C, a model of edentulous mandible supporting an overdenture over two unsplinted implants with the O-ring system. Evaluation was conducted on Ansys software, with a vertical force of 100 N applied on the mandibular left first molar. When the stress was evaluated in supporting tissues, groups B (51.0 MPa) and C (52.6 MPa) demonstrated higher stress values than group A (10.1 MPa). Within the limits of this study, it may be concluded that the use of an attachment system increased stress values; furthermore, the use of splinted implants associated with the bar-clip attachment system favoured a lower stress distribution over the supporting tissue than the unsplinted implants with an O-ring abutment to retain the mandibular overdenture.

Early versus late loading of unsplinted TiUnite surface implants supporting mandibular overdentures: a 2-year report from a prospective study

The aim of this study was to evaluate the clinical performance of the implants supporting mandibular overdentures, and to investigate the prosthodontic outcomes of the mandibular implant overdentures. Twenty edentulous patients participated in this study. Forty implants were placed in the canine areas of the mandibles of all patients using the 1-stage approach. New maxillary complete dentures and the mandibular implant overdentures were delivered to 10 patients in the test group 1 week after surgery, while new maxillary and mandibular complete prostheses were delivered to 10 patients in the control group. These conventional mandibular prostheses were converted to mandibular implant overdentures 3 months after surgery. No implants were lost neither in test nor in control group. The average ISQ values between the two groups were not statistically significant during 2 years (P > 0.05). The average marginal bone resorptions were 0.4 and 0.5 mm for the test and the control group after 2 years. The number of appointments required for the prosthodontic maintenance of the mandibular implant overdentures in the first year was higher than that in the second year, which was statistically significant(P < 0.001). The results of the study suggest that the 1-week early loading approach does not adversely influence the clinical performance of the implants supporting mandibular overdentures.

Prosthodontic rehabilitation of oral function in head-neck cancer patients with dental implants placed simultaneously during ablative tumour surgery: an assessment of treatment outcomes and quality of life

The aim of this prospective study was to assess treatment outcome and impact on quality of life of prosthodontic rehabilitation with implant-retained prostheses in head-neck cancer patients. Fifty patients were evaluated by standardized questionnaires and clinical assessment. All received the implants during ablative tumour surgery in native bone in the interforaminal area. About two-thirds of the patients (n=31) needed radiotherapy post-surgery. Both in irradiated and non-irradiated bone two implants were lost 18-24 months after installation. Peri-implant tissues had a healthy appearance. No cases of osteoradionecrosis occurred. In 15 patients no functional implant-retained lower dentures could be made for various reasons. The other 35 patients all functioned well, with an improvement in quality of life. Major improvement was observed in the non-irradiated patients. In the irradiated patients, less improvement in many functional items was observed, while items related to the oral sequelae of radiotherapy did not improve. Similar to the quality-of-life assessments, denture satisfaction was improved and tended to be higher in non-irradiated than irradiated patients. Implant-retained lower dentures can substantially improve the quality of life related to oral functioning and denture satisfaction in head-neck cancer patients. This effect is greater in non-irradiated than irradiated cancer patients.

Bone density assessments of oral implant sites using computerized tomography

The type and architecture of bone are considered to affect its load-bearing capacity and it has been indicated that poorer quality bone is associated with higher implant failure rates. To date, bone classifications have only provided subjective methods for pre-operative assessment, which can be considered unreliable. The aim of this study was to evaluate variations of the bone density in designated endosseous implant sites using computerized tomography. One hundred and thirty-one designated implant sites in 72 patients were utilized. Computerized tomography results indicated that bone densities may vary markedly when different areas of a designated implant site are compared. It has been observed that a difference in the bone density exists for the four regions within the oral area, with the anterior mandible yielding mean density values of 944.9+/-207 Hounsfield units (HU)>anterior maxilla, 715.8+/-190 HU>posterior mandible, 674.3+/-227 HU>posterior maxilla and 455.1+/-122 HU. Computerized tomography may be a useful tool for determining the bone density of interest areas before implant placement, and this valuable information about the bone quality provides dental practitioners to make better treatment planning regarding the implant positions.

How do patients perceive the benefit of reconstructive dentistry with regard to oral health-related quality of life and patient satisfaction? A systematic review

BACKGROUND

Reconstructive dentistry encompasses an enormous range of treatment modalities from the restoration of single teeth to the reconstruction of the whole dentoalveolar complex in edentulous patients. Some treatment modalities have been assessed in terms of quality-of-life (QoL) outcomes and satisfaction

OBJECTIVES

The aim of the present investigation was to search and review studies published between 1996 and 2006 in which the impact of the treatment was measured in terms of QoL outcome, ideally, oral health-related quality of life (OHRQoL). Patient satisfaction was also accepted as an outcome.

MATERIALS AND METHODS

The primary search engine used was NICB PubMed based on MeSH headings. Hand searching of the cited references in the included papers identified a number of additional studies. The primary focus of the search was to link treatment to QoL outcomes.

RESULTS

The majority of included studies involved the treatment of edentulous patients, particularly the mandible. The preponderance of the studies comparing conventional dentures (CDs) and implant-supported overdentures (IODs) were randomized-controlled trials (N = 18). There was compelling evidence that patients were more satisfied with IODs than CDs. There was strong evidence that OHRQoL can be significantly improved using IODs. Evidence suggesting that one retention system is superior to another needs further clarification. Although high satisfaction ratings have been reported for maxillary implant prostheses, the overall ratings given to the maxillary implant prostheses were not significantly greater than for CDs. There was only sparce information regarding QoL or satisfaction outcomes for the majority of other forms of reconstructive dentistry.

CONCLUSION

Apart from the restoration of the edentulous mandible with IODs or CD, where there is an accumulating body of evidence on the effect of treatment choice, there are many procedures for which there are little or no such data at all. As yet, the entire range of reconstructive treatment has witnessed insufficient investigations relating treatment to its effect on QoL or satisfaction. This is an area that needs to be expanded as a way of quantifying the effect of treatment choices.

Short Implants Placed One-Stage in Maxillae and Mandibles: A Retrospective Clinical Study with 1 to 9 Years of Follow-Up

BACKGROUND

The use of short implants (7-8.5 mm) has historically been associated with lower survival rates than for longer implants. However, recent clinical studies indicate that short implants may support most prosthetic restorations quite adequately, but still clinical documentation is sparse.

PURPOSE

The purpose of this study was to report on the placement of short Brånemark implants, testing the hypothesis that short implants in atrophied jaws might give similar long-term implant survival rates as longer implants used in larger bone volumes.

MATERIALS AND METHODS

This retrospective clinical study included 237 consecutively treated patients with 408 short Brånemark implants supporting 151 fixed prostheses. One hundred thirty-one of the implants were 7-mm long, and 277 were 8.5-mm long. Final abutments were delivered at the time of surgery, and final prostheses were delivered 4 to 6 months later.

RESULTS

One hundred and twenty six of the 7-mm implants (96%) have passed the 1-year follow-up; 110 (84%), the 2-year follow-up; and 88 (67%), the 5-year follow-up. Five implants failed in four patients before the 6-month follow-up, giving a cumulative survival rate of 96.2% at 5 years. The average bone resorption was 1 mm (SD=0.6 mm) after the first year and 1.8 mm (SD=0.8 mm) after the fifth year of function. Two hundred sixty nine of the 8.5-mm implants (97%) have passed the 1-year follow-up; 220 (79%), the 2-year follow-up; and 142 (51%), the 5-year follow-up. Eight implants failed in seven patients before the 6-month follow-up, giving a cumulative survival rate of 97.1% at 5 years. The average bone resorption was 1.3 mm (SD=0.8 mm) after the first year and 2.2 mm (SD=0.9 mm) after the fifth year of function.

CONCLUSIONS

The cumulative survival rates of 96.2 and 97.1% at 5 years for implants of 7.0- and 8.5-mm length, respectively, indicate that one-stage short Brånemark implants used in both jaws is a viable concept.

Influence of attachment wear on retention of mandibular overdenture

The aims of this study were: (i) to evaluate and compare retention of two-teeth (implant) supported mandibular overdenture with either stud or magnetic attachments during linear (axial) and rotational (paraxial) dislodgements; (ii) to compare retentive properties before and after wear simulation. The test group consisted of five magnetic and four stud overdenture attachments (n = 12 specimens for each attachment type). Retention in axial direction was evaluated on one-tooth (implant) model by measuring maximum retentive force (N) and range of retention (mm) during the linear dislodgement. Retention in the paraxial direction was evaluated on mandibular-overdenture model by measuring the maximum retentive force (N) during three types of rotational dislodgements - anterior, lateral and posterior. The minimum number of cycles required to simulate wear was determined by special wear test. Afterwards, the wear was simulated in the test group, and retention in axial and paraxial directions was measured again.

STATISTICAL ANALYSIS

one-way anova, Scheffe post hoc and paired-samples t-tests (P < 0.05). Initially, studs had higher retention (4-11 N) than magnets (4.5-6 N) in axial direction. After the wear simulation, it had decreased from 76% to 48% for some of the studs and had become similar to the retention of magnetic attachments. Magnets had lower retention range (0.2-0.3 mm) than studs (0.5-1.1 mm). Studs provided similar or higher retention in paraxial directions than magnetic attachments both before and after wear simulation. Retentive properties of magnets decreased mostly with posterior rotational dislodgement. Retentive properties of stud overdenture attachments were less constant.

Assessment of correlation between computerized tomography values of the bone, and maximum torque and resonance frequency values at dental implant placement

The aim of this study was to determine the bone density in the designated implant sites using computerized tomography (CT), the fastening torque values of dental implants, and the implant stability values using resonance frequency analysis. Further aim was to evaluate a possible correlation between bone density, fastening torque and implant stability. Eighty-five patients were treated with 158 Brånemark System implants. CT machine was used for preoperative evaluation of the jawbone for each patient, and bone densities were recorded in Hounsfield units (HU). The fastening torque values of all implants were recorded with the OsseoCare equipment. Implant stability measurements were performed with the Osstell machine. The average bone density and fastening torque values were 751.4 +/- 256 HU and 39.7 +/- 7 Ncm for 158 implants. The average primary implant stability was 73.2 +/- 6 ISQ for seventy implants. Strong correlations were observed between the bone density, fastening torque and implant stability values of Brånemark System TiUnite MKIII implants at implant placement (P < 0.001). These results strengthen the hypothesis that it may be possible to predict and quantify initial implant stability and bone quality from pre-surgical CT diagnosis.

Rehabilitation of oral function in head and neck cancer patients after radiotherapy with implant-retained dentures: effects of hyperbaric oxygen therapy

Surgical treatment of malignancies in the oral cavity and subsequent radiotherapy often result in an anatomic and physiological oral condition unfavorable for prosthodontic rehabilitation. The objective of this prospective study was to assess the effect of hyperbaric oxygen therapy on treatment outcome (condition of peri-implant tissues, implant survival, oral functioning and quality of life) of prosthodontic rehabilitation with implant-retained lower dentures in radiated head and neck cancer patients 6 weeks and 1 year after placing the new dentures. The treatment outcome was assessed in a group of 26 head neck cancer patients who were subjected to radiotherapy after tumour surgery. Standardized questionnaires were completed and clinical and radiographic assessments were performed. After randomization, endosseous Brånemark implants were placed in the anterior part of the mandible either under antibiotic prophylaxis (13 patients) or under antibiotic prophylaxis combined with pre and postsurgery hyperbaric oxygen (HBO) treatment (13 patients). In the HBO and non-HBO group eight implants (implant survival 85.2%) and three implants (implant survival 93.9%) were lost, respectively. Peri-implant tissues had a healthy appearance in both groups. Osteoradionecrosis developed in one patient in the HBO group. All patients functioned well with their implant-retained lower denture. The quality of life related to oral functioning and denture satisfaction were improved to a comparable extent in the HBO and non-HBO group. Implant-retained lower dentures can improve the quality of life related to oral functioning and denture satisfaction in head and neck cancer patients. Adjuvant hyperbaric oxygen therapy could not be shown to enhance implant survival in radiated mandibular jaw bone.

Repair of a milled cantilevered implant overdenture bar: A clinical report

This clinical report of a fractured cantilevered substructure bar describes an alternative treatment to the proposed refabrication of the substructure bar and overdenture prosthesis. This report outlines the clinical and laboratory procedures to repair the fractured bar, eliminating the time and expense of fabricating a new bar and prosthesis.

A comparison between insertion torque and resonance frequency in the assessment of torque capacity and primary stability of Brånemark system implants

The aim of this study was to determine primary stability and insertion torque of Brånemark System implants placed in the anterior mandible, and to evaluate a possible correlation between primary stability and insertion torque. Thirty edentulous patients were treated with 60 Brånemark System implants using a one-stage technique. The insertion torque values of all implants were recorded with the Osseocare equipment. Immediately after implant placement, each implant was connected to the transducer of an Osstell machine to measure the primary implant stability. The average insertion torque and resonance frequency values were 41.5 +/- 5.8 and 74.1 +/- 3.8 for 30 implants. The correlation between insertion torque and resonance frequency values indicated a statistical significance (P < 0.001). The difference between mean insertion torque values for female and male patients was statistically significant (P < 0.001). No significant difference (P > 0.05) was found between younger and older patients with mean insertion torque values of 43.1 +/- 4.7 and 40.1 +/- 6.5 respectively. The results of this study showed a strong correlation between the primary stability and insertion torque values of Brånemark System TiUnite MKIII implants at the time of implant placement.

Masticatory function with mandibular implant-supported overdentures fitted with different attachment types

Oral Rehabilitation by means of implant-retained mandibular overdentures is known to improve the oral function. The improvement may depend on the degree of retention and stability of the denture and thus on the type of attachment. In this within-patient cross-over clinical trial, we examined the hypothesis that more retention and stability of the overdenture improves the masticatory function. Eighteen patients received two permucosal implants, a new overdenture, and, successively, three different suprastructure modalities: a magnet, a ball, and a bar-clip attachment. We quantified aspects of the oral function by measuring the electromyographic activity of the jaw muscles and the jaw movement during chewing. The muscle activity was significantly lower for the unsupported new mandibular denture compared with values for the supported new denture. No significant differences in muscle activity were observed among the three attachment types. Furthermore, we did not observe significant differences in jaw muscle activity between the old unsupported denture and the new supported denture, despite significant differences in masticatory performance. Measuring muscle activity during chewing will thus not provide adequate information about masticatory function. Thus, subjects chewed more efficiently after implant treatment. No changes in cycle duration or in jaw movement parameters were observed among the various measurement moments.