Hoda M. Amin Rashad, Mohammed H. Ismail

01/04/2017

Purpose: A straingauge analysis was performed to investigate the influence of interimplant distance and implant length on stress induced around mandibular overdenture implant .Materials and methods: The stresses were evaluated for three groups, group (A) two implants of length 11 mm were placed at 19, 23 and 29 mm from each other, group (B) two implants of length 13 mm were placed at 19, 23 and 29 mm from each other and group(C) two implants of length 15 mm were placed at 19, 23 and 29 mm from each other. Acrylic casts were constructed representing completely edentulous mandible. On each cast two Implants of same diameter 3.4mm were inserted, upon which complete overdentures supported by ball attachments were constructed. Strain gauges were installed in the labial, lingual and distal sides of each implant to record the strain induced by the applied loads. A special loading device used to produce standardized static vertical load of 60N . The loading positions were located at six points on the occlusal surface (second premolar, P2; first molar, M1; second molar, M2 on the right and left sides). Results: Maximum stress areas were numerically located at the the buccal sides of implants. Increasing implant length gradually from 11 mm to13 mm and to 15 mm decreased the maximum stresses around the implants. Increasing interimplant distances gradually from 19 mm to 23 mm and to 29mm increased the maximum stresses around the implants . Conclusion: interimplant distance and Implant length affect load transmitting mechanism to the alveolar bone. The results of this study suggested that the use of shorter interimplant distance and longer implant might ensure a better biomechanical environment for both implant and alveolar ridge.

Fardos N. Rizk

01/10/2014

Aim: This study was two folded: an in-vivo study to compare the retentive properties of Lucitone conventional cured denture base resin and Nature-Cryl MC microwave cured denture base resin and an in-vitro study to compare the internal adaptation, fracture resistance, roughness, hardness and colour stability of these two materials and correlate the laboratory results with each other and with the clinical results.Materials and Methods: Twenty completely edentulous male patients received twenty complete dentures constructed from Lucitone conventional cured denture base resin. The retentive properties of the upper complete dentures were measured using force measurement gauge at one week, one month and three month follow-up period. The patients were instructed to take off their dentures for two weeks. Twenty complete dentures were then constructed for the same patients using Nature-Cryl MC microwave cured denture base resin. The retentive properties of the upper complete dentures were also measured using force measurement gauge at one week, one month and three month follow-up period. After finishing the in-vivo retention measurements, the twenty patients were equally divided into two groups based on their clinical satisfaction; one group received Lucitone denture base resin and the other group received Nature-Cryl MC denture base resin. The other twenty dentures; ten made of Lucitone and ten made of Nature-Cryl MC were taken for laboratory testing. Internal adaptation was evaluated by weighing a silicon film between each denture base and the metal master mode using a precision scale. Fracture test was carried out by applying compressive mode of load at fitting surface of each denture using computer controlled materials testing machine. For measuring surface roughness and surface hardness, twenty rectangular specimens assigned to two equal groups; Lucitone conventional cured resin and Nature-Cryl MC microwave cured resin where prepared. Using 3D image of the surface profile of the specimens, WSxM software was used to calculate average of heights expressed in μm, which was assumed as a reliable indices of surface roughness. Hardness was then measured using Vicker’s hardness tester. Forty cuboidal specimens assigned to two equal groups; Lucitone conventional cured resin and Nature-Cryl MC microwave cured resin where then prepared for measuring color stability using solutions of tea, coffee, and turmeric and artificial saliva. Five specimens of each acrylic resin brand were immersed into each of the specific solutions for three days and the specimens’ colors were measured using a Reflective Spectrophotometer. All results of in-vivo and in-vitro investigations were collected and tabulated for statistical analysis. Results: The clinical results of the retention were in agreement with the laboratory results of internal adaptation as both showed statistically non-significant difference between both denture base materials. The laboratory results of physical properties showed higher fracture resistance, lower roughness, higher hardness and lower colour change of Lucitone conventional cured denture base resin in comparison to Nature-Cryl MC microwave cured denture base resin. Conclusion: There is no difference between dentures constructed from Lucitone and dentures constructed from Nature-Cryl MC in terms of retention and internal adaptation. However, Lucitone conventional cured denture base resin has superior physical properties than Nature-Cryl MC in terms of higher fracture resistance and hardness values and lower roughness and colour change values. In-vivo measurements of denture retention and in-vitro measurements of internal adaptation are correlated. Results of hardness and fracture resistance are correlated. Results of roughness and colour changes are correlated. Tests for physical properties and other applications of microwave cured resin should be continued.

Hala H. Yassin

01/01/2013

Aim: To evaluate the effect of locally applied Chitosan on bone healing around dental implants in controlled diabetic patients Materials & methods: Ten completely edentulous controlled diabetic patients participated in this study. Each patient received 2 implants inserted bilaterally in the mandibular interforaminal area. A split mouth technique was used in this study; Chitosan was applied locally in the right osteotomy sites before implant insertion. Mandibular overdentures retained by ball and socket attachments were constructed for all patients. Patients were placed on a recall program for 18 months were clinical assessment, alveolar bone height and bone density around implants were measured using digital radiography. Results & Conclusions: Within the limits of this study, results suggest that local administration of Chitosan may enhance bone healing in controlled diabetic patients.

Mohammed Diaa Z. Ismaiel

01/10/2012

Purpose: The aim of this study was to investigate posterior mandibular residual ridge resorption following the use of four endosseous implants either connected to ball attachments or splinted with a bar to retain complete mandibular overdentures over 6 years follow up period. Materials & methods: Fourteen completely edentulous male patients were divided into two equal groups, Group 1 (OD): Patients received a mandibular overdenture retained by four implants after attaching ball and socket attachment system. Group 2 (BOD): Patients received a mandibular overdenture retained by a bar connected to the four implants. Panoramic radiographs were obtained from all patients in both groups after stage two surgeries and 6 years later. Proportional area measurmnets were used to determine changes in mandibular posterior residual ridge in both groups. Calculations were performed by a computer program to calculate the change in posterior area index (PAI) for each patient from base line to 6 years. Results: there was a statistically significant difference in mandibular posterior residual ridge resorption between the two treatment protocols in favor of group 2. For group 1 (OD) the mean change in PAI was 0.088+-0.037, while group 2 (BOD) was 0.043+-0.035. Regression analysis revealed no correlation between PAI and initial mandibular ridge height, while age had a statistically significant effect on PAI. Conclusion: Bar retained mandibular overdentures appear to be associated with reduced posterior mandibular ridge resorption when compared to ball retained ones.

Hisham I. Sallam; Hoda A. Mohie ElDin

01/07/2012

Single implants may be placed at the distal extension of the denture base to minimize the potential for dislodgement of the bilateral or unilateral distal extension partial dentures. The premise is that this will minimize the risk of potential problems of patient discomfort associated with prosthesis retention and stability from residual ridge resorption Aim: Evaluation of two different abutment designs on marginal bone loss and bone density around implants supporting mandibular distal extension removable partial overdentures Materials & Methods: Thirty partially edentulous patients with unilateral distal extension and modification area in the other side (Kennedy class 2 modifications 1) were selected for this study. Patients were divided into 2 groups, Group 1: received a distal extension removable prosthesis supported by one implant with conventional dome shaped abutment. Group 2: received a distal extension removable prosthesis supported by one implant with a ball and socket abutment. Radiographic evaluation of marginal bone loss and density around all implants in both groups was carried out using digital radiography (Diogra) for one year period every three months interval. Results & Conclusions: After 12 months, group 1 showed statistically significantly higher mean amount of marginal bone loss than group 2. A constant increase in bone density values was denoted in both groups throughout the whole study period although there was no statistically significant difference between bone density values in the 2 groups. It can be concluded that the ball and socket abutments showed less marginal bone loss around implants when compared to conventional dome shaped abutments for implant supported mandibular distal extension partial overdentures.

Mohammed Diaa Z. Ismaiel

01/07/2012

The aim of the current study was to investigate the role of the type of abutment/implant connection on the marginal bone loss around dental implant. The present study was conducted on fourteen patients, eight males and six females with age range from 26 to 40 years. Thirty consecutive dental implants were inserted for implant – supported restoration in the posterior maxilla. The dental implants of all subjects were assigned to one of the 3 platform diameters which were 3.8 mm (control group), 4.5 (test group A) and 5.5 mm (test group B). At the time of prosthetic rehabilitation, 3.8 mm abutments were connected to the all inserted dental implants. Radiographic assessment of marginal bone level was performed immediately at the time of abutment connection (baseline) and every six months for 24 months after final restoration. Statistical analysis revealed that there was a significant difference between the control group and both test groups as regard the total mean of marginal bone loss in favor of test groups A & B. In conclusion, platform – switching concept seems to have a role in minimizing the marginal bone loss around dental implant.

Gehan F. Mohammed, Amany A. El Hadary, Amal M. Ibrahim

01/01/2006