Akers Clasp Research Articles

Trueness of 3D-printed cobalt chromium versus titanium removable partial denture clasps.

The purpose of this in vitro study was to evaluate the trueness of removable partial denture clasps fabricated with titanium (Ti) through the selective laser melting (SLM) technique compared to cobalt-chromium alloys (CoCr). A virtual Aker clasp was designed on a scanned tooth, and SLM printers were used to print 20 claps using cobalt chromium (n = 10) and titanium alloy (n = 10). The deviation between the printed clasps and reference design was measured using the surface matching software (Geomagic control x) at rest, retentive tip, reciprocal tip, retentive shoulder, and reciprocal shoulder. An Independent t-test was used to determine the influence of 3D-printed material on the trueness (a = 0.05). The gap distance in mm between the reference design and printed in titanium showed an average of 0.0001 ±0.0544, 0.0256 ±0.1309, 0.0230 ±0.1028, 0.0701 ±0.1234, and 0.0013 ±0.0735mm in rest, reciprocal arm tip, retentive arm tip, retentive arm shoulder, and reciprocal arm shoulder, respectively. The gap distance in mm between the reference design and printed clasps in CoCr alloy showed an average of 0.0316 ±0.0692, 0.2783 ±0.1678, 0.1446 ±0.1528, 0.0315 ±0.0906, and 0.0419 ±0.1088mm in rest, reciprocal arm tip, retentive arm tip, retentive arm shoulder, and reciprocal arm shoulder, respectively. The difference between titanium and CoCr alloys at each observation site was significant. Clasps fabricated from titanium with SLM printing have the least deviation and better trueness compared to those fabricated from cobalt chromium.

Comparative analysis of the retention force and deformation of PEEK and PEKK removable partial denture clasps with different thicknesses and undercut depths

Statement of problemThe retentive force and deformation of milled polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) removable partial denture (RPD) frameworks are not well understood. PurposeThe purpose of this in vitro study was to assess the retentive force and deformation of PEEK and PEKK Akers clasps with different designs and undercut depths. Material and methodsA master model containing the first and second molar abutments was used to design Akers clasps of different cross-sectional dimensions, undercut depths (0.5 and 0.75 mm), and materials. The components of the removable partial denture framework also included an occlusal rest and were manufactured using a milling machine (n=5). The fatigue resistance of the Akers clasps was measured before and after deformation regarding the retentive forces. ResultsThe PEEK2-U50 clasp had the largest retentive force with no significant difference among all groups before and after the insertion and removal cycle. In addition, the increased cross-sectional dimensions of the design resulted in significant differences in retentive forces between the PEEK1 and PEEK2 groups and between the PEEK and PEKK materials. ConclusionsIncreasing the clasp's cross-sectional dimensions significantly impacted retentive forces, especially between different PEEK groups and between PEEK and PEKK materials.

Management of palatal defect post hemimaxillectomy: a case report

A 42-year-old woman was referred to the Department of Prosthodontics, Hasanuddin University Dental Hospital with speech, swallowing and chewing difficulties caused by a fractured and non-reusable acrylic obturator. The patient had been using the obturator since maxillary tumor resection in 2012, which resulted in a significant and deep defect in the right maxillary region. Intraoral examination revealed a defect in the midline of the palate that extended to the left alveolar bone, and 21, 22, 23, 24, 25, 26, 27, 16 were edentulous. The maxillary defect did not appear inflamed or infected, and the surrounding area appeared normal. The treatment plan was fabrication of a maxillofacial skeletal partial denture to rehabilitate the maxillary defect. Primary impressions were made with irreversible hydrocolloid ma-terial with a stock tray to obtain a study model. Custom tray was made for individual impressions with polyvinyl si-loxane material to obtain working models. A survey was conducted, and framework and bite rim were made. Maxil-lary denture was designed with Akers clasps at 35, 37, RPI at 45, full palatal palate as main connector. The denture framework was tried on, followed by determination of vertical dimensions. Denture alignment was done in the articu-lator using A3 color. The was prostheses were tried in and evaluated of retention, articulation, phonetics, and aes-thetics; then sent to dental laboratory for processing and the obturator was then inserted into the patient's mouth. Pati-ent follow-up was scheduled 24 hours and 1 week after insertion. It is concluded that the maxillofacial partial den-ture is a rehabilitation device that can result in decent retention and stabilization, especially in cases of acquired de-fects. The prosthesis can improve patient adaptation and ability with speech, mastication and swallowing functions.

The impact of an additional implant under the saddle of removable partial dentures in Kennedy Class II edentulism on oral health-related quality of life and oral function: a case series report

BackgroundImplant-supported removable partial dentures (ISRPDs) provide effective prosthodontic treatment for partially edentulous patients. ISRPDs offer greater patient satisfaction and better oral function compared with removable partial dentures (RPDs) by enhancing denture stability and support. However, few clinical studies have focused on RPD design in patients with mandibular Kennedy Class II edentulism. The aim of this case reports was to investigate the oral function, oral health-related quality of life, and satisfaction of four patients with unilateral distal-extension mandibular RPDs with the same design which were replaced with ISRPDs. In addition, we investigated how each patient’s evaluation varied with the change from RPD to ISRPD.Case presentationFour patients had unilateral distal-extension mandibular edentulism and were missing the first and second molars and the first and second premolars. They received one implant (4.0 mm in diameter, 8.0 mm in length; IAT EXA PLUS Bone level; Nippon Piston Ring Co. Ltd, Saitama, Japan) at the position equivalent to the first molar in the edentulous residual ridge perpendicular to the occlusal plane. Implant position was determined by surgical guide plate. RPDs were fabricated after the residual mucosal membrane had healed. The basic design of the RPD was as follows: a cobalt–chromium alloy cast metal framework denture with a lingual bar as the major connector, a double Akers clasp on the molars and an auxiliary retainer on the premolar as indirect retainers, and a wrought wire clasp and a cast cingulum rest (combination clasp) as direct retainers. Masticatory performance, occlusal force, oral health-related quality of life, and satisfaction were estimated at baseline, and at time points after insertion of the RPD and after insertion of the adapted ISRPD. Each evaluation item showed a tendency for improvement on insertion of the new RPD. Masticatory performance and satisfaction tended to be better after insertion of the ISRPD than after insertion of the RPD.ConclusionOur findings suggest that ISRPDs provided better patient satisfaction and masticatory performance than RPDs in patients with mandibular Kennedy Class II edentulism.Trial registration UMIN Clinical Trials Registry and Japan Registry of Clinical Trials, UMIN000025283 and jRCTs012180003. Registered 19 February 2016 and 17 December 2018, https://www.umin.ac.jp/ and https://jrct.niph.go.jp/

Stress Distribution Pattern in Mini Dental Implant-Assisted RPD with Different Clasp Designs: 3D Finite Element Analysis.

Introduction The removable partial denture (RPD) components, especially the retentive arm, play a major role in the loading characteristic on supporting structures. Objective To evaluate and compare the effect of different clasp designs on the stress distribution pattern, maximum von Mises stress, and average hydrostatic pressure on abutment teeth, as well as edentulous ridges, mini dental implants (MDIs), and peri-implant bone between the conventional removable partial denture (CRPD) and mini dental implant-assisted distal extension removable partial denture (IARPD) using a three-dimensional finite element analysis (3D FEA). Materials and Methods 3D FEA models of mandibular arches, with and without bilateral MDI at the second molar areas, and Kennedy class I RPD frameworks, with RPA, RPI, Akers, and no clasp component, were generated. A total of 200 N vertical load was bilaterally applied on both sides of distal extension areas, and the stress was analyzed by 3D FEA. Results The stress concentration of IARPD with RPI clasp design was located more lingually on abutment teeth, MDI, and peri-implant bone, while the other designs were observed distally on the supporting structures. The maximum von Mises stress on the abutment root surface was decreased when the RPDs were assisted with MDIs. The CRPD and IARPD with the Akers clasp design showed the highest von Mises stress followed by the designs with RPA and RPI clasp, respectively. The average hydrostatic pressure in each group was in approximation. Conclusion The placement of MDIs on distal extension ridges helps to reduce the stress concentration on denture supporting structures. The maximum von Mises stress is affected by the different designs of clasp components. The CRPD and the IARPD with RPI clasp provide the least stress on supporting structures.

Effects of repetitive insertion/removal cycles and simulated occlusal loads on retention of denture retainers.

The purpose of this study was to investigate the effects of repetitive insertion/removal cycle tests on denture retainers with simulated occlusal loads on the retentive force and deformation of clasp. Abutment teeth in the form of mandibular secondary premolars and clasp in the form of Akers clasps were prepared. The retentive force of the clasp on the abutment teeth were evaluated before and after undergoing repetitive insertion/removal cycle tests with or without cyclic loading. Changes in the clasp shape were monitored using a 3D scanner and scanning electron microscope. The initial retentive force was approximately 10 N and this value later decreased due to deformation of the clasp tips. In contrast to the non-load group, the load group exhibited a reduction in retentive force during earlier stages. Therefore, cyclic loading was related to a decrease in retentive forces, specifically in the early stages of repetitive insertion/removal cycles.

EVALUATION OF DIFFERENT PROSTHETIC DESIGNS OF IMPLANT ASSISTED REMOVABLE PARTIAL DENTURES USED IN MANDIBULAR KENNEDY CLASS II CASES. A THREE –DIMENSIONAL FINITE- ELEMENT ANALYSIS.

The puroose:The aim of this study was to evaluate the effect of different designs of removable partial denture (RPD) supported with distal implant for the treatment of mandibular Kennedy class II cases on the behavior of oral structures by using Three-dimensional (3D) finite-element analysis (FEA). Materials and methods: A three models of mandibular class II Kennedy arch received three RPD designs were evaluated. The first model involves the use of RPI clasp on the first premolar. The second model involves the use of an extra coronal attachment at the distal aspect of the splinted first bicuspid and canine abutments. The third model received a bilateral (RPD) with RPI clasp on the first premolar and a double Aker clasp on the second premolar and first molar of the opposite side. For all models a single implant was placed at the second molar region with a conventional ball and socket attachment. For each model, a vertical and oblique loads of 100N were applied to the second molar area . The created model components were then imported to FEA software (ANSYS). Results: The first model recorded a significant less stresses at the bone, mucosa and abutment teeth in comparison to the other models but insignificance differences occurred in the total deformations. Conclusion: The von Mises stress and deformation produced in case of model 1 (clasp design) was better than that occurred with the other two models ( bilateral and extracoronal attachments)

Evaluation of Biting Force of New Design of Extracoronal Castable Precision Attachment versus Conventional Partial Denture for Treatment of Unilateral Mandibular Distal Extension Area: A Randomized Controlled Trial

PURPOSE: The aim of this study was to evaluate biting force of patients with unilateral mandibular distal extension area treated with two different designs of the removable partial denture (RPD), conventional RPD, and new design of extracoronal castable precision attachment (OT Unilateral attachment).
 MATERIALS AND METHODS: This study was conducted on 16 patients with unilateral mandibular distal extension area with the second premolar is the last abutment teeth. The patients were divided into two equal groups, Group I received conventional RPD, which provides cross arch stabilization and a double Aker clasp was fabricated. Group II received new design of extracoronal castable precision attachment (OT Unilateral attachment). Evaluation of biting force by loadstar sensor, patients of both groups were evaluated at the time of prosthesis insertion, 3, 6, and 1 year later. Statistical analysis performing one-way analysis of variance followed by Tukey’s post hoc test to compare between all follow-up periods within each group, comparison between two groups regarding each follow-up period was performed by independent t-test.
 RESULTS: Both treatments yielded better after-treatment summary when compared with the baseline; however, better results were obtained and showed a statistically significant increase in Group II (OT unilateral design), especially after 3, 6 months, and 1 year later.
 CONCLUSION: From the results of this study, it was concluded that: It is preferable to use the new design of extracoronal castable precision attachment (OT unilateral) being simpler, more comfortable to the patients and give high masticatory efficiency in the form of biting force than conventional RPD.

Fitness accuracy and retentive forces of additive manufactured titanium clasp

PurposeLaboratory and clinical assessment of cast titanium dentures were reported, little is known about additive manufacturing (AM) frameworks. This study evaluated in vitro AM titanium alloy clasps for clinical use. MethodsAfter scanning the stainless steel dies to simulate the first molar, an Akers clasp was designed by CAD. AM clasp specimens were manufactured using laser sintering and AM machines from CP titanium grade 2 (CPTi), Ti-6Al-4V (Ti64), and Ti-6Al-7Nb (Ti67) powders. As controls, cast titanium clasps were conventionally made with same three titanium alloys. After nondestructive inspection and surface element analysis, surface roughness, fitness accuracy, initial retentive forces, and changes in retentive forces were measured. ResultsAlthough few porosities and little contamination of AM clasps were confirmed, the AM clasp arm and tip indicated slightly worse fitness accuracy as compared to cast clasps. The initial retentive forces of all titanium clasps showed appropriate retentive forces within the acceptable ranges, AM clasps tended to have lower decreases in retentive forces with up to 10,000 insertion/removal cycles as compared to those of the cast clasps. ConclusionsAM titanium clasps would be acceptable for clinical use similar to that of cast titanium clasps.

Change in the retentive force of Akers clasp for zirconia crown by repetitive insertion and removal test

PurposeThe objective of this study was to evaluate the suitability of monolithic zirconia crowns (MZC) as abutment teeth of Akers clasps on removable partial dentures (RPD) by determining the change in retentive force after repetitive insertion/removal test. MethodsMZC and silver palladium copper alloy (Ag–Pd) full-metal crowns (FMC) for the mandibular second premolar were fabricated. Resin patterns of Akers clasps made with a 3D printer were casted with Ag–Pd or cobalt chromium alloy (Co–Cr). Clasp retentive force was measured with combinations of the crown and clasp materials. After measuring the initial retentive force of the clasp, repetitive insertion/removal test was carried out. The surface of the crown before and after the test was observed with an optical microscope and a scanning electron microscope; some specimens were subjected to element analysis by an electron probe microanalyzer. ResultsThe initial retentive force of the Co–Cr clasp was greater than the Ag–Pd clasp for both MZC and FMC. Clasp retentive force decreased with increasing number of insertion/removal cycles, and least reduction in force was observed for the Ag–Pd clasp on MZC. Wear marks were detected where FMC contacted the clasp. Discoloration of MZC due to wear of the Co–Cr clasp was observed. ConclusionsWhen repetitive insertion/removal of the clasp was performed on MZC, retentive force decreased depending on clasp materials. However, the amount of decrease in retentive force was comparable or small compared to conventional FMC. As a result, it was suggested that MZC could be used on abutment tooth for RPD.

Evaluation of bilateral mandibular distal extension implant supported overdenture retained by two clasp assemblies

Purpose Clinically evaluate the effect of clasp design on tissue health around abutment teeth and implants assisting mandibular bilateral distal extension removable partial overdenture. M&M: 12 partially edentulous patients with mandibular bilateral free end saddle opposed by almost dentulous intact maxilla with the first premolars. Two dental implants were inserted at the first molar areas to support a bilateral distal extension partial overdenture with lingual bar as major connector. According to clasp design patients are divided in two groups. Group I: six patients for whom removable partial overdentures were retained with O-ring attachment to the implants and RPI clasp to the first premolar abutment teeth. Group II: six patients for whom removable partial overdentures were retained with O-ring attachment to the implants and conventional Aker clasp to the abutment teeth. Clinical evaluation Gingival index, probing depth and teeth mobility together with radiographic evaluation for alveolar bone loss around both implants and abutments using Digora for Windows were carried out immediately at insertion, 3, 6, and 9 months after insertion. Results After the first 3 months gingival index and probing depth increased significantly in both groups within the physiological limit while at the end of ninth month after insertion, no statistically significant difference between two groups. Differences between two groups regarding mobility and alveolar bone loss around abutment teeth through all the study periods, there is no statistically significance difference between the two groups. Regarding mobility and alveolar bone loss around implants through all the study periods, there is no statistically significant difference between results. Conclusion Presence of bilateral posterior implants reduce most problems of mandibular Kennedy class I such as preservation of abutment teeth, reduction of alveolar bone loss around the abutments and reduction the problems of rigid (Aker) clasp.

Fitness and retentive force of cobalt-chromium alloy clasps fabricated with repeated laser sintering and milling

PurposeWith computer-aided design and computer-aided manufacturing (CAD/CAM), the study was conducted to create a removable partial denture (RPD) framework using repeated laser sintering rather than milling and casting techniques. This study experimentally evaluated the CAM clasp and compared it to a conventional cast clasp. MethodsAfter the tooth die was scanned, an Akers clasp was designed using CAD with and without 50μm of digital relief on the occlusal surface of the tooth die. Cobalt-chromium (Co-Cr) alloy clasps were fabricated using repeated laser sintering (RLS) and milling as one process simultaneously (hybrid manufacturing; HM). The surface roughness of the rest region, gap distances between clasp and tooth die, initial retentive forces, and changes of retentive forces up to 10,000 insertion/removal cycles were measured before and after heat treatment. The HM clasp was compared to the cast clasp and the clasp made by repeated laser sintering only without a milling process. ResultsThe HM clasp surface was smoother than those of cast and RLS clasps. With the digital relief, the fitness accuracy of the HM clasp improved. The retentive forces of the HM clasps with relief and after heat treatment were significantly greater than for the cast clasp. HM clasps demonstrated a constant or slight decrease of retention up to 10,000 cycles. ConclusionsHM clasp exhibited better fitness accuracy and retentive forces. The possibility of clinically using HM clasps as well as conventional cast clasps can be suggested.

The effect of environment (Dry and Natural Saliva) on clasp retention: In vitro study - Part I.

Objective:The purpose of this study was to investigate the importance of environments (dry and wet) to dislodge the clasp.Materials and Methods:Mandibular test models with natural premolar and molar teeth were used to test four types of clasp (each 12) (Akers, rest plate Akers [RPA], half and half [H-H], and ring clasp) in dry and natural fresh saliva environments. Each clasp was pulled out 10 times with a crosshead speed of 10 mm/min and the force required to withdraw each was measured.Statistical Analysis Used:A paired sample t-test and Wilcoxon test were used.Results:There were significant differences between the dry and wet (natural fresh saliva) environment. However, while the mean of the environment for RPA and ring clasp type was significantly different, the H-H and Akers clasp type was not.Conclusion:The environment has an effect on dislodging the clasp but differs according to the type of clasp.

Clasp fabrication using one-process molding by repeated laser sintering and high-speed milling

PurposeA single machine platform that integrates repeated laser sintering and high-speed milling for one-process molding has been developed. MethodsThe Akers clasp was designed using the CAD system (DWOS Partial Frameworks, Dental Wings) and fabricated using repeated laser sintering and a high-speed milling machine (LUMEX Advance-25, Matsuura) with 50-μm Co–Cr particles (CAM clasp). As controls, cast clasps of the same forms were also prepared using conventional casting methods with a Co–Cr alloy and CP titanium Grade 3. After the surface roughness was measured, the gap distance between the clasps and the tooth die was assessed using the silicone film method. The initial retentive force and changes in retention up to 10,000 cycles were also measured. The data were analyzed using two-way ANOVA and Tukey’s multiple comparison test (α=0.05). ResultsCAM clasps exhibited significantly smoother surfaces than those of cast Co–Cr and CP Ti clasps (p<0.05). However, the gap distances of the CAM clasps were significantly greater than those of the cast clasps (p<0.05). The retentive forces of both CAM and cast Co–Cr clasps were significantly higher than those of CP Ti clasps. (p<0.05). The retention of CAM clasps demonstrated a constant or slight decrease from 1000 up to 10,000 cycles. ConclusionsThe CAM clasp made by repeated laser sintering and high-speed milling can be used effectively as an RPD component.

Mandibular Kennedy Class I partial denture management by broad stress distribution philosophy (radiographic assessment).

Purpose:The objective of this study was radiographic assessment of the premolar teeth abutments alveolar bone resorption in mandibular Kennedy Class I removable partial denture (RPD) utilizing the broad stress distribution philosophy, either designed with multiple circlet clasp or compound Aker clasp.Materials and Methods:Twelve patients were enrolled for this study with upper completely edentulous arch against mandibular Kennedy Class I ridges posterior to the second premolar. The patients were divided into two groups according to the type of the clasp assembly design used, where the mandibular Kennedy Class I RPD was designed with multiple circlet clasp and compound Aker clasp assemblies for Groups I and II, respectively. The abutment alveolar bone resorption was evaluated radiographically after 1st 6, 2nd 6, and 12 months of mandibular Kennedy Class I RPD insertion.Results:Second premolar abutment interdental alveolar bone resorption was significantly increased as compared to first premolar abutment along the interval periods of the study for Group I. The reverse was observed for Group II. Along the interval periods of the study, the alveolar bone resorption at the first premolar abutment of Group II was significantly increased compared to that of Group I while the reverse was observed when comparing the second premolar of Group I with that of Group II.Conclusion:Compound Aker clasp is better than the multiple circlet clasp assembly as it reduces abutment alveolar bone resorption regards broad stress distribution philosophy is considered for distal extension cases.

Clinical and radiographic comparative study between two different types of clasps materials used in unilateral maxillary Kennedy class II removable partial denture cases

Objective: The objective of the present study was to compare between two different clasp materials for the treatment of maxillary class II Kennedy classification clinically, radiographically.Materials and methods: Twenty male patients were selected for this study. The patients were divided into two groups. Each group consists of 10 patients. For group I each patient have maxillary removable partial denture that was constructed and retained by cobalt–chromium RPI clasp on the maxillary first premolar with cross arch stabilization (using double Aker clasp) on the other side. For group II each patient has the same except that the retentive I bar of RPI clasp was made of acetal resin. Patient satisfaction, clinical, and radiographic evaluations were carried out for every patient at insertion, 3, 6, and 9 months, the data were collected, tabulated, and statistically analyzed using t-test.Results: Satisfaction for the treatment. Group II patients were more satisfied of the treatment regarding aspects of the patients' comfort and esthetics. No significant difference in the aspects of phonetics, the ability to eat, prosthesis loosening, the gingival health, general satisfaction and food impaction between the two groups were found, also there were insignificant increase in the gingival recession, pocket depth, and plaque index around the abutments tooth in both groups. Radiographically, there was significant decrease in the bone height around the abutments in both groups.Conclusion: Removable partial denture with acetal resin clasp is better for esthetic and patient comfort. Good periodontal condition of the abutment tooth of both groups is maintained. Acetal resin clasp is the clasp of choice when esthetic is of primary concern to the patient.

In vitro stress analysis study of different prosthetic options using single posterior implant for management of mandibular unilateral distal extension saddle

AimThe aim of this study is to compare in vitro, micro-strain induced by different prosthetic options using single posterior implant in lower unilateral distal extension saddle (Kennedy class II). Materials and methodsFor this study, three prosthetic designs were made I, II, and III on epoxy resin model representing mandibular unilateral distal extension edentulous area with the second premolar as the main abutment and implant was placed at the site of the second molar. For group (I), The design principle was (RPI clasp on the second premolar abutment, lingual bar major connector, double Aker clasp on the first and second molar on the other side and (ball & socket) attachment on the implant). For group (II) the design principle was ((RPI clasp on the second premolar abutment and (ball & socket) attachment on the implant)). For group (III) implant tooth connected fixed partial denture was fabricated using the 2nd premolar as mesial abutment and the implant as distal abutment. A self-protected linear strain gauge was used for this study to measure the micro-strain induced on the buccal and lingual sides of the implant and 2nd premolar abutment. ResultsSPSS software program was used in the statistical analysis of the results. The results revealed that Maximum stresses induced at tooth and implant abutments were in case of group (II) design and distribution of micro-strain between the implant and tooth abutment in case of group (III) design was better than distribution in cases of the two other groups. ConclusionThe conclusions are as follows: (1) maximum strain induced at tooth and implant abutments were in case of side plate design; (2) distribution of micro-strain between the implant and tooth abutment in case of fixed restoration was better than distribution in case of the other two groups.

Three-dimensional finite element analysis of Aramany Class IV obturator prosthesis with different clasp designs

The purpose of this study was to evaluate the stress distribution on the alveolar bone surrounding abutment teeth and the displacement of the Aramany Class IV obturator prosthesis with two different clasp designs. Three-dimensional finite element models of an Aramany Class IV maxillary defect were constructed. Two different clasp designs on an obturator prosthesis (double Akers clasps and multiple Roach clasps) and two different load conditions (vertical and horizontal) were compared. Finite element analysis was used to calculate the equivalent stress. The difference in the clasp design of the Aramany Class IV obturator prosthesis affected the stress distribution of the alveolar bone surrounding the abutment teeth and the displacement of the obturator prosthesis. Multiple Roach clasps reduced the stress distribution on the alveolar bone surrounding the abutment teeth and the displacement of the Aramany Class IV obturator prosthesis compared to double Akers clasps.

Comparative study of two different designs of partial over denture supported with distal implant for the treatment of mandibular Kennedy class II cases

The objective of the present study was to compare between two mandibular implant overdentures of class II Kennedy classification. Material and methods: Fourteen male patients (30–45 years) were selected and divided into two equal groups. Group I received a mandibular removable partial over denture retained with implant abutment at the first molar region and with extra coronal attachment to the first premolar. Cross arch stabilization was made by using double Aker clasp on the first and second molars of the opposite side. Group II received a unilateral mandibular removable partial over denture retained with implant abutment at the first molar region and with extra coronal attachment to a splinted first premolar and canine. Patient satisfaction, clinical and radiographic evaluations were carried out at regular recall appointments up to one year from implant loading. Results: There was insignificant increase in the pocket depth and gingival recession and insignificant decrease in the perio test values and plaque index around implants and abutments. There was insignificant increase in the marginal bone loss around implants and abutments in both groups. All patients strongly disagreed the high cost of the treatment. Group II patients were more satisfied regarding aspects of the patients' comfort and phonetics. Conclusion: It is concluded that unilateral removable partial denture was more comfortable and better with speech. The use of dental implant as a distal abutment in class II Kennedy classification reduces all the movements of denture base and results in better healthy condition for the gingival and periodontium of the abutment tooth than when using conventional partial denture.

Comparison between Acetal Resin and Cobalt-Chromium Removable Partial Denture Clasp Retention: An in vitro Study

ABSTRACT Statement of problem The retention qualities of acetal resin clasps are questionable. Purpose To asses the initial retention and after cycling for 1,200 cycles of acetal resin clasps as compared to cobalt-chromium clasps. Materials and methods Extracted maxillary first premolars and molars were collected. Each tooth was embedded in acrylic block up to the cementoenamel junction. On each block, partial denture model consisted of Akers clasp, minor connector, cobalt-chromium horizontal plate representing the denture base, and a vertical arm on the horizontal plate was constructed. Models were divided into four groups (five each). Group I had acetal resin clasps on premolars. Group II had cobalt-chromium clasps on premolars. Group III had acetal resin clasps on molars. Group IV had cobalt-chromium clasps on molars. Akers clasps were designed to utilize 0.01 inch undercut. Each model was connected to the universal testing machine through the vertical arm. The model was placed in artificial saliva and a tensile load was applied to measure the initial retention. Then retention was measured after cycling for 200, 400, 600, 800, 1,000 and 1,200 cycles. One-way analysis of variance followed by Duncan's multiple range test was used to test the effect of groups and cycling on tensile load required for clasp dislodgment. Results Groups I and III showed no change in retention on cycling up to 1,200 cycles. Group I showed significantly higher retention than group III. Groups II and IV showed significant reduction in retention upon cycling more than 800 cycles. In spite of this reduction in retention, it is still higher than that in groups I and III. Conclusion Cobalt-chromium clasps showed higher retention than acetal resin clasps despite the deformation encountered in the former. Acetal resin clasps showed more retention qualities on premolar teeth than that on molar teeth. Clinical implications Acetal resin clasps can be used to retain Kennedy's class III partial denture. However, when used on molar teeth, it is recommended to increase the thickness of the retentive clasp arm or to use a deeper undercut. How to cite this article Mohamed T, Baraka OA, Badawy MM. Comparison between Acetal Resin and Cobalt-Chromium Removable Partial Denture Clasp Retention: An in vitro Study. Int J Prosthodont Restor Dent 2013;3(2):50-56.