journal club presentation on prosthodontics

oral mucosa pressure caused by mandibular overdenture with different types of attachments

1. Oral mucosa pressure caused by mandibular implant overdenture with different types of attachments Hiroaki Sato, Takuya Kobayashi, Taro Nomura, Norimasa Tanabe, Kyoko Takafuji , Hidemichi Kihara , Hisatomo Kondo , J Prosthodont Res (2019)

2. Contents INTRODUCTION AIM MATERIALS AND METHODS RESULTS DISCUSSION RELATED ARTICLES CONCLUSION REFERENCES

3. OVER DENTURES Any removable dental prosthesis that covers and rests on one or more remaining natural teeth, the roots of natural teeth, and/or dental implants; a dental prosthesis that covers and is partially supported by natural teeth, natural tooth roots, and/or dental implants -GPT Over denture treatment is a notion which precludes inevitability of floating plastic in edentulous mouth - George Zarb

4. Introduction According to the 2002 McGill consensus and 2009 York consensus 2-IOD was recommended as first-line therapy for edentulous mandible

5. ATTACHMENT SYSTEMS ONE PART-CONNECTED TO IMPLANT OTHER PART-INCORPORATED WITHIN UNDER SURFACE OF OVERDENTURE

6. STRESS BREAKING MECHANISM RIGID MECHANISM STRESS BREAKING MECHANISM RIGID MECHANISM

7. DIFFERENT TYPES OF ATTACHMENTS

8. FACTORS AFFECTING ATTACHMENT SELECTION

9. Aim To determine the appropriate attachment and design of a denture base for mandibular implant overdenture (IOD), the oral mucosa pressure caused by mandibular implant overdentures was measured using edentulous jaw models with various attachments.

10. MATERIALS AND METHODS An experimental mandibular edentulous jaw model with a 1.5mm thick arti fi cial oral mucosa Two dental implants (3.75 11.5 mm) were placed at the position of the bilateral canines, perpendicular to a tentative occlusal plane

11. Six miniature pressure sensors were placed to measure pressure values on the oral mucosa when the experimental dentures were loaded An experimental CD without attachment was prepared as a control

12. Measurement system The load on the experimental dentures was set at 50 N by referring to the masticatory force of CD wearer

13. BILATERAL LOADING UNILATERAL LOADING A metal plate was placed on the experimental dentures

14. MEASUREMENT SYSTEM Precision universal testing machine ( Instron 8874, Instron , Norwood, MA, USA). dynamic repetitive loads of 1 Hz were applied perpendicularly to the tentative occlusal plane by precision universal testing machine

15. Example of a waveform during the dynamic repeated load. The oral mucosa pressure values were defined as average values of the load with the precision universal testing machine during 5 continuous cycles

16. RESULTS Differences in oral mucosa pressure values between CD and 2-IOD Oral mucosa pressure value exerted by 2-IOD was significantly lower in the left buccal premolar region than that of CD Under the unilateral load condition At buccal premolar region

17. Oral mucosa pressure value exerted by 2-IOD was significantly lower in the left buccal shelf than that of CD On the non-loading side, oral mucosa pressure values exerted by all attachments were extremely low and did not exceed 8.0 kPa in the right buccal premolar region and the right buccal shelf

18. RESULTS Changes in oral mucosa pressure values with different attachments P ressure on the residual ridge exerted by CD was compared to that of 2-IOD with various attachments. O ral mucosa pressure value exerted by 2-IOD was signi fi cantly lower in all sites than that of CD

19. The oral mucosa pressure value exerted by BA was significantly lower in the left lingual molar region than those of other attachments The oral mucosa pressure value exerted by R-BA was significantly higher in the right lingual molar region than those of other attachments

20. 2-IOD reduced the oral mucosa pressure value of 37– 190 kPa at the supportive site. The oral mucosa pressure value exerted by 2-IOD in the left lingual molar region was not always lower than that of CD. The oral mucosa pressure value was increased significantly by MA and LA, but decreased significantly by BA

21. CONCLUSIONS Significant decrease in oral mucosa pressure value and increase in support and bracing ability were observed when 2-IOD was applied, compared with CD. Effect of BA on the reduction of oral mucosa pressure is greater than LA, MA and R-BA in the supportive and bracing regions BA could be the first choice to reduce oral mucosa pressure value during mastication.

22. RELATED ARTICLES Effect of attachment type on load distribution to implant abutments and the residual ridge in mandibular implant-supported overdentures Nobuhiro Yoda, Yoshiki Matsudate , Masaru Abue , Guang Hong and Keiichi Sasaki

23. AIM OF THE STUDY to investigate how several commonly used attachments of the IOD affect the load on the supporting implants and the residual ridge beneath the denture base in a model study applying those measuring systems.

24. Materials and methods Experiment device development

25. Devices for simultaneous measurement of three-dimensional (3D) loads on the supporting implants and the load on the residual ridge beneath the denture base were developed.

26. To measure the load on the implants, three types of attachments were fabricated to be fitted accurately onto the piezoelectric force transducers:

27. The male part of BA was manufactured using a high-precision processing technology to be fitted accurately onto the piezoelectric force transducer, whereby the inferior portion was configured to fit the superior end of the implant

28. locator abutment (Zest Anchors Inc., Escondido, CA, USA), was also manufactured to be fitted accurately onto the piezoelectric force transducer

29. The male part of RA was made of the the male round bar and a specific titanium coping, which was manufactured to be fitted accurately onto the piezoelectric force transducer. An adjustable rider was used as the female part for RA.

30. LOAD MEASUREMENT EXPERIMENT Loads on the implants and the residual ridge beneath the denture base were measured when static and dynamic repeated loads of 100 N were applied vertically to the right first molar region of the occlusal table of the denture by a universal testing machine The load measurement was repeated five times for each of the three different attachments in the order BA, LA, and RA

31. RESULTS AND ANALYSIS Measured pressure on the residual ridge beneath the denture was converted to a force and analyzed as the total force on the measurement area.

32. Measured 3D loads on the implants were analyzed using a 3D coordinate

33. Maximum load vectors displayed at the 3D coordinates when a static load of 100 N was applied Regardless of the attachment type, the direction of the load exerted on both implants was consistently in a posterior direction. Force vector on the non loading side implant for the three attachments occurred in an upward direction.

34. The horizontal component, that is, the resultant force value of the load on the implants in the X- and Y-axes when a static load of 100 N was applied,

35. With all attachments- higher load in the distal parts of the sensor area. load centers of the three attachments in similar position, loci of the load center were different among the three attachments. shows the typical pattern of load distribution on the residual ridge beneath the denture under a static and dynamic repeated load of 100 N

36. Load on the residual ridge beneath the denture base

37. shows an example of the calculated 3D resultant force data for the three attachments when a dynamic repeated load of 100 N was applied five times. The three attachments showed different wave patterns., but this was

38. CONCLUSION This model experiment using piezoelectric 3D force transducers and a tactile sheet sensor enabled us to clarify the effects of the attachments used in an IOD on loading to implants and the underlying residual ridge. Using RA in an IOD is effective for reducing the load to the supporting implants. The load on the residual ridge beneath the denture in IODs can be efficiently reduced using a BA.

39. Related articles Stress analysis of mandibular implant overdenture with locator and bar/clip attachment: Comparative study with differences in the denture base length Jin Suk Yoo , Kung-Rock Kwon, Kwantae Noh, Hyeonjong Lee, Janghyun Paek

40. Aim of the study The design of the attachment must provide an optimum stress distribution around the implant. In this study, for implant overdentures with a bar/clip attachment or a locator attachment, the stress transmitted to the implant in accordance with the change in the denture base length and the vertical pressure was measured and analyzed.

41. Materials and methods

42. STRAIN GAUGES were attached to the implants using an adhesive In the replicated epoxy model, holes 8 mm in diameter were made at both canine sites and implants were placed. Resin cement was used to represent the osseo integration of actual implants. The maxillary and mandibular dentures on the replication model were fabricated in a conventional manner, and the same dentures were used repeatedly in the experiment by modifying their bases.

43. A universal testing machine was used to exert a vertical pressure on the mandibular implant overdenture . To measure the strain rate of the implants placed in the replication epoxy model, a strain gauge was used. An A/D converter was connected to a personal computer to amplify and quantify the electrical signal from the gauge.

44. Bar/clip and locator attachments were connected to the implants

45. RN synOcta gold coping RN Locator abutment

46. The groups of this study were divided according to the position of vertical loading and the length of denture base

47. Vertical pressure, 0.5 mm/min up to 50 N, was placed on the three types of complete denture repeated 10 times Whenever the attachment was replaced or the length of the denture base was modified, 20 minutes were given for recovery Results measured with the four strain gauges were analyzed statistically

48. Results

49. For the mandibular right first molar, the mandibular right posterior area, and the whole mandibular denture base, the strain was statistically significantly different between the locator attachment and the bar/clip attachment

50. For each attachment, the strain comparison between cases of applying vertical pressure at three different areas (A, B, and C) also showed a statistically significant difference

51. all surfaces except the mesial surface of the implant on the non-working side showed a compressive force when applying vertical pressure at three different areas (cases A, B, and C), the bar/clip attachment generally showed a higher strain than the locator attachment For both attachments, the shorter denture base resulted in a higher strain on the implants

52. Conclusion For mandibular implant overdentures , locator attachments result in lower strain on implants than do bar/clip attachments. Longer denture bases have the same effect. Therefore, to minimize the strain on implants in mandibular implant overdentures , this study may provide the clinical implication that the use of locator attachment would be more preferable in regard of strain on implants than bar /clip attachment, and the denture base needs to be extended as much as possible.

53. RELATED ARTICLES Influence of Matrix Attachment Installation Load on Movement and Resultant Forces in Implant Overdentures Takaharu Goto , DDS, PhD, Kan Nagao, DDS, PhD, Yuichi Ishida, DDS, PhD, Yoritoki Tomotake , DDS, PhD, & Tetsuo Ichikawa, DDS, PhD

54. AIM OF THE STUDY This in vitro study investigated the effect of attachment installation conditions on the load transfer and denture movements of implant overdentures , and aims to clarify the differences among the three types of attachments, namely ball, Locator, and magnet attachments.

55. MATERIALS AND METHODS

56. Twelve signals from the four transducers and one signal from the load cell were digitized by a digital data recorder with 14-bit accuracy at a rate of 50 Hz, and then transferred to a computer resultant force (FR) was calculated using the following: FR=(M2 x +M2 y +F2 z)

57. The output of the G2 motion sensor was calculated from the flexibility of the Euler angles (i.e., the pitch, yaw, and roll) using original software with a C-based synthesis system

58. A 50 N static load was applied to the loading points of the first molar regions on the right side by a universal testing machine with a 2.0 mm/min crosshead speed. The magnitude of the applied load was based on the bite force of edentulous patients with complete dentures. Six complete experimental dentures were fabricated,and six artificial mucosal materials modified for the respective denture bases were also prepared. The recording was repeated five times for each experimental condition, allowing intervals of at least 5 minutes for recovery

59. shows the time patterns of the resultant forces acting on the implant and residual ridges on the loading side.The time patterns were obtained by averaging the signal at the onset of the universal testing machine measurements for each condition. The resultant force acting on the implants on the loading side of the magnetic attachment exhibited a two-phase pattern

60. For the residual ridges on the loading side, the direction of the forces for all attachments changed to downward with increasing installation load. Furthermore, the yaw Euler angle increased with increasing installation load for the magnetic attachment

61. The resultant force acting on the implants on the loading side for the ball and Locator attachments transmitted homogeneous increases without a two-phase pattern. When the attachments were installed using a 50N load, which was the same as the resultant force acting on the implants on the loading side, all the attachments transmitted a homogeneous increase with out a two-phase pattern. The increase in the resultant force acting on the residual ridges on the loading side was greater for a 50 N installation load than for 0 N, especially for the Locator attachment. No distinctive pattern was observed in the resultant force acting on the implant residual ridges on the non loading side.

62. The resultant force on the implants decreased with increasing installation load for all attachments The resultant force acting on the residual ridges on the loading side increased with increasing installation load for all the attachments. The resultant force acting on the residual ridges on the non loading side was not greater than that acting on the ridges on the loading side for all attachments

63. The resultant force acting on the implants on the loading side The resultant force acting on the residual ridge on the loading side

64. resultant forces acting on the implant and the residual ridges

65. Implants on loading sides NON LOADING SIDE Residual ridges on loading sides

66. The direction of the forces of all the attachments changed to downward with increasing installation load. None of the forces of the attachments acting on the residual ridges on the nonloading side had a distinctive direction. when the installation load was 0 N, the forces of the ball and Locator attachments were horizontal and large compared to that of the magnetic attachment.

67. Results of denture movements

68. The magnetic attachment had a high yaw Euler angle compared to the ball and Locator attachments for all installation loads. The yaw Euler angle increased with increasing installation load for the magnetic attachment, and particularly increased significantly when the installation load was increased from 50 to 100 N. Simultaneously, the Euler angles of pitching and rolling slightly increased in the negative direction.The ball and Locator attachments did not exhibit this distinctive movement

69. CONCLUSION Subject to the limitations of this study, the use of any installation load greater than 0N is recommended for the installation of ball and Locator attachments on a denture base. Regarding magnetic attachments, our results also recommend installation on a denture base using any installation load greater than 0N, and suggest that the resultant force acting on the implant can be decreased by increasing the installation load; however, a large installation load of 100 N should be avoided when installing the attachment on the denture base to avoid increasing the denture movement

70. RELATED ARTICLES Effects of Mucosal Thickness on the Stress Distribution and Denture Stability of Mandibular Implant-Supported Over dentures with Unsplinted Attachments InVitro AsukaHaruta , YasuyukiMatsushita , YoshihiroTsukiyama,YoshinoriSawae , NobuoSakai , and Kiyoshi Koyano

71. AIM OF THE STUDY to compare the effects of mucosal thickness on the stress pattern around implants and movement of implant-supported overdentures with ball/female and three different types of magnetic attachments.

72. MATERIALS AND METHODS

73. Experiments

74. Experimental Mandibular Model. An edentulous mandibular acrylic resin model Two implants were placed bilaterally in the canine region vertical to the residual ridge. They were set at 22 mm apart, similar to the distance between two natural canines. The implants were retained using resin cement

75. A 1.5-mm layer was removed from the denture-supporting surface of the resin model and replaced with polyvinyl siloxane impression material to simulate the resilient edentulous ridge mucosa. An experimental acrylic resin denture was conventionally fabricated on the model. In the same way, a 3-mm layer of impression material and a denture were fabricated on the same mandibular model. All experiments for the four attachments were carried out with one model of each mucosal thickness.

76. Four strain gauges were attached to the mesiodistal and buccolingual sides of the neck part of each implant to measure the strain on the implants The electric signals from the strain gauges were amplified , transmitted, and recovered by a personal computer following A/D conversion The sensor used electromagnetic fields to determine the position and orientation of a remote object. The output of the movement sensor was input into a computer and a mathematic algorithm calculated the position of the receiver relative to the transmitter and recorded the results.

77. A movement senser was placed on the left first molar region to measure the displacement of the denture denture movement at the loading side (right first molar region) was measured by vertical displacement of Autograph .

78. Attachments The ball attachment consisted of an anchor head and a metal female component

79. The flat type was a typical magnetic attachment,whilethedome -shaped type had a dome-shaped surface of the magnet and keeper, and the cushion type had a stress distributor with a magnet

80. Three different shapes of magnetic attachments were used: flat type, dome-shaped type , and cushion type

81. The magnetic attachments consisted of a keeper as the magnet head and a magnet that was embedded in the denture. The keeper was prefabricated and had threads that were identical to the threads of an abutment screw. The heights of the keepers were 1.5 and 3mm.

82. Axial forces on implants plus-force -tensile stress minus-force - compressed stress.

83. Axial forces on implants 1.5 mm model 3 mm model the ball attachment showed a significantly higher axial force on the implants than all the magnetic attachments at both the loading and non-loading sides ball attachment had a lower vertical force than all the magnetic attachments at the loading side and had a tensile stress at the non-loading side. dome-shaped type caused the highest axial force at the loading side. no significant differences among the three magnetic attachments in the 3-mm mucosal model at the non-loading side.

84. The bending moment on the implants

85. Bending moments 1.5 mm 3 mm all the magnetic attachments showed significantly lower bending moments on the implants than the ball attachment at both the loading and non-loading sides the magnetic attachments were higher than that of the ball attachment at the loading side. At the non-loading side, all the magnetic attachments showed lower bending moments than the ball attachment. The dome-shaped type caused the largest bending moment at the loading side, while it caused the lowest bending moment at the non-loading side. The flat type made a smaller bending moment than the dome-shaped type and cushion type at the loading side in each mucosal model.

86. Denture movement in the upward-downward direction plusmovement - upward displacement Minus movement -downward displacement

87. Denture movement 1.5mm mucosal model 3mm mucosal model denture base movements were larger on the ball attachment at both the loading and non-loading sides. At the loading side, the denture movement was the lowest on the flat type. On the other hand, at the non-loading side, the denture movement was very small on the magnetic attachments Denture base movement was larger on the cushion type. At the non-loading side on the 3-mm mucosal model, upward movement was shown on the magnetic attachments.

88. RESULTS In the 1.5-mm mucosal model, the magnetic attachments showed significantly lower bending moments than did the ball attachment. The denture base displacement was the lowest on a magnetic attachment. In this study, use of magnetic attachments could be advantageous for mandibular implant-supported overdentures based on lower stress and better denture stability especially in the thin mucosalmodel .

89. CONCLUSION Within the limits of this study, the findings indicated that the magnetic attachments were more favorable than the ball attachment in terms of the stress distribution and the denture base stability on a thin mucosa. For a thick mucosa, the flat type caused the smallest bending moment and denture base movement among all the attachments, suggesting that the flat type was the most favorable for this condition.

90. REFERENCES H. Sato, et al., Oral mucosa pressure caused by mandibular implant overdenture with different types of attachments, J Prosthodont Res (2019) Goto T, Nagao K, Ishida Y, Tomotake Y, Ichikawa T. Influence of matrix attachment installation load on movement and resultant forces in implant overdentures . J Prosthodont 2015;24:156–63 Yoda N, Ogawa T, Gunji Y, Kawata T, Kuriyagawa T, Sasaki K. The analysis of the load exerted on the implants supporting an overdenture based on in vivo measurement. Prosthodont Res Pract 2008;7:258–60 . 

91. REFERENCES Yoda N, Matsudate Y, Abue M, Hong G, Sasaki K. Effect of attachment type on load distribution to implant abutments and the residual ridge in mandibular implant-supported overdentures . J Dent Biomech 2015;6:1–10 Assunção WG, Barão VA, Tabata LF, de Sousa EA, Gomes EA, Delben JA. Comparison between complete denture and implant-retained overdenture : effect of different mucosa thickness and resiliency on stress distribution. Gerodontology 2009;26:273–81 .

92. THANKS