Biomechanical Analysis of Implant Assisted-Overdentures with Variations in the Attachments Systems

The aim of this study was to assess the stress patterns on the peri-implant zone and residual alveolar ridge in different overdenture attachment system designs by the photoelasticity method. Four attachments systems were tested: O-ring, ERA, Bar-clip, and Bar-clip/O-ring association. The prostheses were loaded with 100 N in five pre-determined points and the photoelastic model was evaluated by a circular polariscope. The anterior load, O-ring, and ERA showed better stress distribution in relation to the bars systems, which presented stress levels surrounding implants. The molar load, Bar-clip/O-ring association, presented the biggest stress concentration on the peri-implant region in relation to the others. When the second molar was loaded, there was a concentration of stress in the alveolar ridge in all situations analyzed. Within the limitation of this “in vitro” study, it could be concluded that there were biomechanical differences among the attachments systems analyzed, principally between isolated and the bars systems. The O-ring showed better stress distribution and the Bar-clip/O-ring showed higher stress concentration.

An in vitro Investigation into Retention Strength and Fatigue Resistance of Various Designs of Tooth/Implant Supported Overdentures

Previously, the choice of prosthetic implant-retained overdentures has depended on data from previous studies about the retention-fatigue strength of the attachment system selected. Little or no data have been available on the correlation between the attachment system selected and the overdenture support configuration. The purpose of the present study was to evaluate the retention force and fatigue resistance of three attachment systems and four support designs of overdenture prosthesis. Four lower edentulous acrylic models were prepared and eight combinations of attachments groups were investigated in the study. These included: O-Rings with mini-dental implants (MDIs), Dalbo elliptic with Dalbo Rotex and fabricated flexible acrylic attachments with both MDI and Dalbo Rotex. The study was divided into four test groups: groups A and B, controls, and groups C and D, experimental groups. Control group A contained three overdenture supports: two free standing MDIs in the canine region and at the midline, and one simulated tooth root with Dalbo Rotex screwed in. Control group B contained four overdenture support foundations: two free standing MDIs in the right canine region and the first premolar region, and two simulated tooth roots with Dalbo Rotex screwed in at the same MDI position, but on the left side of the model. Experimental group C contained three overdenture support foundations: two free standing MDIs in the canine region and at the midline, and one simulated tooth root with MDI screwed in. Experimental group D contained four overdenture support foundations: two free standing MDIs in the right canine region and the first premolar region, and two simulated tooth roots with MDIs screwed in at the same MDI position, but on the left side of the model. Each group was further divided into two subgroups according to attachment type used. Five samples were prepared for each group. Retention force (N) values were recorded initially (0 cycles) and after 360, 720, 1440 and 2880 insertion and removal cycles. During the tensile test a cross-head speed of 10 mm/min was applied. Values of absolute force (AF) and relative force (RF) were statistically analyzed by two-way ANOVA and multiple comparison Tukey’s tests between groups and cycles periods. The results of fatigue tests showed a 50% reduction in retention force in the subgroups with flexible attachments. A triangular design of overdenture support foundations with O-Ring attachments revealed the lowest value of AF and a relatively high reduction in RF. The four overdenture support designs with flexible acrylic attachments improved the retention force and reduced the fatigue retention. Furthermore, the results of the investigation demonstrate that flexible acrylic attachments for both teeth and implant-supported overdentures offer a wide range of retention forces.

Swallowing threshold parameters of subjects with complete dentures and overdentures

Aim: To compare the chewing process and swallowing threshold parameters of subjects with complete dentures and overdentures with data obtained from subjects with complete natural dentitions. Metho-dology: The chewing process in terms of swallowing threshold parameters of four groups of subjects with complete dentures (all females) was quantified by sieving particles after chewing of an artificial test ‘food’ and compared with that of subjects with com-plete natural dentitions as a reference group (33 sub-jects). All subjects (except those of the reference group) had a complete denture in the upper jaw. Regarding the lower jaw two groups with complete dentures (with high (24 subjects), respectively low mandible (12 subjects)) and two groups with overdentures (implant-retained (22 subjects), respectively natural root supported (19 subjects)) were composed. Results: The ‘overdenture-implants’ group needed significantly more chewing cycles and time (mean: 45 cycles in 32 seconds) until ‘swallowing’ compared to the group with complete natural dentitions (mean: 26 cycles in 19 seconds until ‘swallowing’). Also the ‘complete denture-low mandible’ group needed sig-nificantly more cycles and time (mean: 52 cycles in 44 seconds) until ‘swallowing’ than the complete dentition group. In the ‘overdenture-natural roots’ group these outcomes (33 cycles in 24 seconds) were not significantly different compared with the complete dentition group. The ‘complete denture-high mandi-ble’ group (32 cycles in 26 seconds) needed not sig-nificantly more cycles until ‘swallowing’, however time until ‘swallowing’ was significantly longer com-pared to the complete dentition group. All denture groups had significantly larger mean particle sizes when ‘swallowing’ (sizes in the order of 3 mm) than the natural dentition group (about 2 mm). Conclusion: Despite efforts to compensate for a reduced chewing efficiency, subjects with complete dentures (including overdentures) had 50% larger median particle sizes when ‘swallowing’ compared to subjects with complete natural dentitions.

Oral rehabilitation for a geriatric population<br>—A voluntary experience in Ukraine report

Despite the outstanding progress in dentistry, there are still a great number of edentulous patients world-wide, what’s more, the dentists are not willing to inform the patients about their handicapped condition. Elderly people do not complain about this a lot, and also unfortunately the general public and government authorities do not concerne too much about gerodontic issues. The elderly people has suffered greatly from this. Dental implant is one way to figure this out. The Ukrainian Dental Implant Association has initiated a professional voluntary project entitled: “Quality of Life for our Parents”. This geriatric welfare program offers free implant and Prosthetic rehabilitation for the Elderly edentulous patients.

Clinical evaluation of implants in patients with maxillofacial defects

AIM: To show the efficacy of reconstruction and rehabilitation of large acquired maxillofacial defects due to tumor resections and firearm injuries. METHODS: The study group comprised of 16 patients(10 men and 6 women) who were operated on because of their maxillofacial defects under local and general anesthesia between June 2007 and June 2011. Prosthetic treatment with the aid of dental implants was performed for all of the patients. Eight patients received an implant supported fixed prosthesis; six patients received implant supported overdentures and two patients received both. Patients were followed up postoperatively for 1 to 4 years. Implant success and survival rates were recorded. Panoramic radiographs were taken preoperatively, immediately after surgery, immediately after loading and at every recall session. Peri-implant and prosthetic complications were recorded. Subjects were asked to grade their oral health satisfaction after treatment according to 100 mm visual analog scale(VAS) and the oral health related quality oflife of the patients was measured with the short-form Oral Health Impact Profile. RESULTS: Five implants(3 in the mandible, 2 in the maxilla) in five patients were lost, while the other 53 survived, which brings an overall survival rate of 91.37% on the implant basis, but 68.75% on patient basis. All the failed implants were lost before abutment connection and were therefore regarded as early failures. For all failed implants, new implants were placed after a 2 mo period and the planning was maintained. The mean marginal bone loss(MBL) was 1.4 mm on the mesial side and 1.6 mm on the distal side of the implants. Five of the implants showed MBL > 2 mm(mean MBL = 2.3 mm) but less than 1/2 of the implant bodies and therefore were regarded as not successful but surviving implants. The VAS General Comfort mean score was 85.07, the VAS Speech mean score was 75.25 and the VAS Esthetics mean score was 82.74. No patient reported low scores(score lower than 50) of satisfaction in any of the evaluated factors. The mean of OHIP-14 scores was 5.5. CONCLUSION: Although further follow up and larger case numbers will give more information about the success of dental implants as a treatment modality in maxillofacial defects patients, the actual results are encouraging and can be recommended for similar cases.

A novel bio-sensor for registration of biting force in occlusally reactive single mandibular implant overdenture

Mandibular single denture opposed by maxillary natural dentition showed a great problem. However, mandibular implant overdenture treatment has gained considerable recognition. Ten male patients with complete mandibular edentulous arch and opposing arch have full natural dentition. Patients were divided into two groups. All patients received two endosseous titanium implants. In Group I, patients were rehabilitated with conventional implant retained overdentures. While in Group II, Patients were rehabilitated with occlusal reactive implant overdentures. A Novel proposed biosensor was used to measure the amount of biting force on the implant retained overdenture. Quantitative electromyographic (EMG) signals of the masseter and anterior fibers of temporalis muscles were recorded, filtered and directly interfaced with a computer to represent the data graphically. The mean amplitude (μV), turn, and activity were recorded at the baseline and after three months. The results revealed an increase in the muscle activity in group II after three months as compared to group I. Significant difference in bilateral biting force at the premolar-molar area was found between group I and group II after three months. This study concluded that a resilient implant overdenture denture could be a desirable treatment in mandibular overdenture supported by two implants with resilient attachment and opposing natural dentition due to its easy fabrication and durability in use and increased muscle activity.

Periodontal surgery in a stage Ⅱ Parkinson's disease patient:Report of a case with special considerations

Parkinson's disease(PD) is an idiopathic progressive neurological disorder characterised by resting tremor, restrictions in mobility and muscular rigidity that can lead to problems in maintaining oral health. Here we report a case where crown lengthening surgeries were successfully performed in a PD patient for complete oral rehabilitation. Certain special considerations that are required before and during periodontal surgery in such patients are also elucidated. Often dentists and PD patients are reluctant to embark on complex dental procedures resulting in a compromised outcome. However, early intervention along with proper education and motivation of these patients can aid in achieving satisfactory results.

Class III Reversion with Immediate Complete Denture and Immediate Implant-Retained Overdenture: Case Report

With the increased life expectancy, complete dentures have been used in the treatment of edentulism progressively. It restores stomatognathic system functions, providing improvements in chewing, aesthetics, and phonetics. The aim was to report an oral rehabilitation of a patient with severe aesthetic and functional impairment, with Angle’s class III malocclusion. The patient sought the extension project of the School of Dentistry of the Federal University of Minas Gerais with aesthetic complaints. After clinical and radiographic evaluation, the proposed planning was immediate complete denture maxilla and immediate implant-retained overdenture in mandible. During clinical evaluation it was observed that the patient was Angle’s III. The rehabilitation was performed as proposed and at the end of the treatment, it was possible to revert the class III occlusal pattern to Angle’s I. The excellent maxillomandibular relationship was achieved, which ensured optimal facial aesthetics and functional condition. It was concluded that the immediate complete dentures and immediate implant-retained overdenture might be beneficial for restoring the aesthetics and function of patients with Angle’s class III malocclusion.

Restoration of severe hypodontia associated with microdontia by using an overdenture: a clinical report

Dental abnormalities associated with specific syndromes and/or severesystemic abnormalities in tooth number, form or size are challenging cases in dentistry, affectingesthetics and function. Microdontia is used to term abnormally small teeth that generally themaxillary lateral incisor or third molar is involved. On the other hand, the entire dentition may beaffected as well. Prevalence of microdontia range from 1.5% - 2%. The definition of severehypodontia is four or more tacking teeth. The prevalence of severe hypodontia was found to be lessthan 1% of the unselected population. In another study hypodontia is seen with a higher incidence inthe permanent dentition (3.5% - 6.5%), compared to that of the primary one (0.1% - 0.9%). Theetiology seems to be inheritance in most cases of hypodontia. However, some are caused by mechanicaltrauma to jaws during tooth formation, by infection or by the effects of cytostatica and radiationduring cancer treatment. There are more than 160 syndromes combined with hypodontia. Some of themare ectodermal dysplasia, Rieger syndrome and incontinentia pigmenti. In such cases morphologicalaberrancies as microdontia and conical crowns may be additional features. In addition to the numberof lacking teeth, tooth eruption, occlusion and craniofacial parameters are influenced. The presentpaper reports the use of maxillary and mandibular overdenture removable complete dentures to treat apatient with class III skeletal malocclusion, reduced vertical dimension of occlusion andunacceptable esthetics caused by a rare case of hypodontia and microdontia.