مقايسه تراش هاي چمفر عميق و 135 درجه از نظر مارژينال فيت و مارژينال گپ در روكش هاي متال-سراميك خلفي

Comparison between deep chamfer and 135 ̊ tooth preparation designs on marginal fit and marginal gap in posterior metal-ceramic crowns

زﻣﯿﻨﻪ و ﻫﺪف: ﯾﮑﯽ از ﻣﻬﻢﺗﺮﯾﻦ ﭼﺎﻟﺶﻫﺎي دﻧﺪاﻧﭙﺰﺷﮑﺎن، ﺗﺤﻮﯾﻞ روﮐﺸﯽ ﺑﺎ ﻣﺎرژﯾﻨﺎل ﻓﯿﺖ و ﻣﺎرژﯾﻨﺎل ﮔﭗ ﻣﻨﺎﺳﺐ ﺑﻪ ﺑﯿﻤﺎر اﺳﺖ. ﺗﺮاش 135 درﺟﻪ ﻣﺰاﯾﺎﯾﯽ ﭼﻮن ﺳﻬﻮﻟﺖ ﺗﮑﻨﯿﮑﯽ و ﺛﺒﺖ ﻣﻨﺎﺳﺐ ﺧﻂ ﺧﺎﺗﻤﻪ ﺗﺮاش دارد. ﻋﻠﯽرﻏﻢ اﯾﻦ ﻣﺰاﯾﺎ، ﺗﺤﻘﯿﻘﺎت ﮔﺴﺘﺮدهاي ﺑﺮ روي اﯾﻦ ﻧﻮع ﺗﺮاش اﻧﺠﺎم ﻧﺸﺪه اﺳﺖ. ﻟﺬا ﺑﺮ آن ﺷﺪﯾﻢ ﺗﺎ در اﯾﻦ ﻣﻄﺎﻟﻌﻪ ﺗﺮاش 135 درﺟﻪ را ﺑﺎ ﭼﻤﻔﺮ ﻋﻤﯿﻖ از ﻧﻈﺮ ﺗﻄﺎﺑﻖ ﻣﻘﺎﯾﺴﻪ ﻧﻤﺎﯾﯿﻢ. روش ﺑﺮرﺳﯽ: ﺑﺮ روي دو دﻧﺪان ﻣﻮﻟﺮ اول ﻣﻨﺪﯾﺒﻞ ﺑﺎ ﻧﺴﺞ ﺗﺎﺟﯽ ﺳﺎﻟﻢ و اﻧﺪازه ﻣﺸﺎﺑﻪ، ﺗﺮاش ﭼﻤﻔﺮ ﻋﻤﯿﻖ و ﺗﺮاش 135 درﺟﻪ اﻧﺠﺎم ﺷﺪ. از ﻫﺮ دو دﻧﺪان ﻗﺎﻟﺐ ﺗﻬﯿﻪ ﺷﺪ و از روي ﻫﺮ داي، 30 ﻋﺪد روﮐﺶ ﺳﺎﺧﺘﻪ ﺷﺪ. ﻧﻤﻮﻧﻪﻫﺎي آﻏﺸﺘﻪ ﺑﻪ fit checker ﺗﻮﺳﻂ universal testing machine ﺗﺤﺖ ﻧﯿﺮوي 40 ﻧﯿﻮﺗﻦ ﺑﻪ ﻣﺪت 3 دﻗﯿﻘﻪ ﻗﺮار ﮔﺮﻓﺘﻨﺪ و زﯾﺮ ﻟﻮپ ﺑﺎ ﺑﺰرﮔﻨﻤﺎﯾﯽ 40 ﺑﺮاﺑﺮ در ﺳﻪ ﻧﻘﻄﻪ از ﻫﺮ ﺑﻌﺪ اﻧﺪازهﮔﯿﺮي و ﺛﺒﺖ ﺷﺪﻧﺪ. ﺟﻬﺖ آﻧﺎﻟﯿﺰ دادهﻫﺎ و ﻣﻘﺎﯾﺴﻪ ﺗﻄﺎﺑﻖ ﺗﺮاشﻫﺎ از آزﻣﻮنﻫﺎي آﻣﺎري Kolmogorov-Smirnov و Wilcoxon در SPSS version24 اﺳﺘﻔﺎده ﮔﺮدﯾﺪ. ﯾﺎﻓﺘﻪﻫﺎ: ﻣﯿﺎﻧﮕﯿﻦ ﻣﺎرژﯾﻨﺎل ﻓﯿﺖ در ﺗﺮاش ﭼﻤﻔﺮ ﻋﻤﯿﻖ 48/5417 ﻣﯿﮑﺮون و در ﺗﺮاش 135 درﺟﻪ 55/3333 ﻣﯿﮑﺮون ﺑﻪ دﺳﺖ آﻣﺪ. ﻣﺎرژﯾﻨﺎل ﮔﭗ، ﺑﺮاي ﺗﺮاش ﭼﻤﻔﺮ ﻋﻤﯿﻖ 2/4833 ﻣﯿﮑﺮون و ﺑﺮاي ﺗﺮاش 135 درﺟﻪ 1/0083 ﻣﯿﮑﺮون ﺑﻮد. P-value ﺑﺮاي ﻣﺎرژﯾﻨﺎل ﮔﭗ 0/050 ﺑﻮد ﮐﻪ ﻧﺸﺎن دﻫﻨﺪه وﺟﻮد ﺗﻔﺎوت ﻣﻌﻨﯽداري ﻣﯿﺎن ﺑﺮﺗﺮي ﺗﺮاش 135 درﺟﻪ ﺑﺮ ﺗﺮاش ﭼﻤﻔﺮ ﻋﻤﯿﻖ اﺳﺖ. در ﻣﻮرد ﻣﺎرژﯾﻨﺎل ﻓﯿﺖ، P-value ﺑﺎﻻي 0/05 ﺑﻮد و ﺑﺮﺗﺮي ﺗﺮاش 135 درﺟﻪ از اﯾﻦ ﺣﯿﺚ ﻣﻌﻨﯽدار ﻧﺒﻮد. ﻧﺘﯿﺠﻪﮔﯿﺮي: ﺗﺮاش 135 درﺟﻪ ﺑﺮ ﭼﻤﻔﺮ ﻋﻤﯿﻖ از ﻧﻈﺮ ﻣﺎرژﯾﻨﺎل ﮔﭗ ﺑﺮﺗﺮي ﻣﻌﻨﯽدار داﺷﺖ )0/05≤P(. ﻋﻠﯽرﻏﻢ اﯾﻨﮑﻪ ﺗﺮاش 135 درﺟﻪ ﺑﺮ ﭼﻤﻔﺮ از ﻧﻘﻄﻪ ﻧﻈﺮ ﻣﺎرژﯾﻨﺎل ﻓﯿﺖ ﻧﯿﺰ ﺑﺮﺗﺮي داﺷﺖ اﻣﺎ اﯾﻦ ﺗﻔﺎوت ﻣﻌﻨﯽدار ﻧﺒﻮد.

One of the most important challenges for dentists is providing a crown with appropriate marginal fit and gap. The 135-degree tooth preparation found to have some advantages such as technical ease and appropriate finish line record. Despite the advantages of 135-degree tooth preparation, scant research has been done in this area. Therefore, the aim of this study was to compare 135-degree and deep chamfer tooth preparation on the marginal fit and marginal gap of posterior metal-ceramic crowns. Materials and Methods Deep chamfer and 135-degree tooth preparation were performed on the two first mandibular molars with healthy coronal tissue and similar size. Impression was taken from each tooth and 30 crowns were made on each die. The sample plastered with fit checkers were pressed under the force of 40 N for 3 min in a universal testing machine. They were measured and recorded under a loop with 40x power in three points on each aspect. Data were analyzed by Wilcoxon and Kolmogorov-Smirnov tests using SPSS version 24. Results The mean marginal fit values in deep chamfer and 135-degree were 48.5417µm and 55.3333 µm, respectively with no statistically significant difference (P>0.05). While the mean marginal gap in deep chamfer (2.4833 µm) was significantly higher (P<0.05) than 135-degree (1.0083). Conclusion It can be concluded that the marginal gap by 135-degree’s tooth preparation was lower than that of deep chamfer in metal-ceramic crowns. However, no significant difference in the marginal fit between the deep chamfer and 135-degree tooth preparation was found.