after taking up the ethical clearance from the institution and informed consent , buccal cells collected from 33 edentulous patients with no history of systemic disease within a edentulous span more than a year within a period of 10 years , were processed to extract genomic deoxyribonucleic acid ( dna ) .
a 10 l aliquot of the dna was subjected to electrophoresis in a 0.8% agarose gel to analyze the quality of the genomic dna . a high molecular weight band without any observable smear indicates dna of high quality [ figure 1 ] .
the intensity of the dna band , which reflects their concentration , varies among samples .
while the dna concentration in lane five is high , the concentration of dna in lane 3 is less ( indicated by a bold arrow ) .
this is expected , since the amount of dna purified , depends largely on the amount of starting tissue material .
polymerase chain reaction was performed in two stages the concentrations of dna in each of the sample was measured in an ultraviolet and visible dual beam spectrophotometer , and were found to be in the range of 10100 ng/l .
total dna concentrations in 50l volume varied among samples and were in the range of 0.57 g .
the absorbance at 260 nm and associated dna concentration in each of the sample is shown in table 1 .
the age of the patient , sex , 1g/2 g polymorphism , bone height , and classification of edentulism in order to analyze the 1g/2 g polymorphism in the promoter region of mmp-1 gene , we first downloaded the promoter sequence from the public domain database ( www.ncbi.nlm.nih.gov/nucleotide ) and designed the primers flanking the known polymorphism site at 1067 base .
the minus sign indicates that the site ( 1067 in this study ) is in the promoter region , upstream of the transcription start site of mmp-1 gene .
the amplification products of second step of polymerase chain reaction ( pcr ) were digested with alu1 restriction enzyme in a 25 l reaction volume at 37c for 4 h. the digested products were analyzed by running a 15 l aliquot in a 2.5% agarose gel at 50 v for 30 min .
alu1 recognizes a tetranucleotide motif agct ( 1 g ) but not aggct ( 2 g ) pentanucleotide motif , and digests ( cuts ) the pcr product ( dna ) after  g  .
samples carrying 1 g allele being sensitive to alu1 restriction digestion are cleaved into 169 bp and 25 bp products , which migrate faster relative to undigested ( uncut ) 2 g allele samples of 194 bp in size .
of the samples analyzed , 26 of edentulous patients ( 78.8% ) carried 2 g allele , while 7 of them ( 21.2% ) carried 1 g allele [ figure 2 and table 2 ] .
a majority of the edentulous samples analyzed carried 2 g allele . the number and percentage of 1 g or 2 g polymorphism under each edentulous classification
after taking up the ethical clearance from the institution and informed consent , buccal cells collected from 33 edentulous patients with no history of systemic disease within a edentulous span more than a year within a period of 10 years , were processed to extract genomic deoxyribonucleic acid ( dna ) .
a 10 l aliquot of the dna was subjected to electrophoresis in a 0.8% agarose gel to analyze the quality of the genomic dna . a high molecular weight band without any observable smear indicates dna of high quality [ figure 1 ] .
the intensity of the dna band , which reflects their concentration , varies among samples .
while the dna concentration in lane five is high , the concentration of dna in lane 3 is less ( indicated by a bold arrow ) .
this is expected , since the amount of dna purified , depends largely on the amount of starting tissue material .
the concentrations of dna in each of the sample was measured in an ultraviolet and visible dual beam spectrophotometer , and were found to be in the range of 10100 ng/l .
total dna concentrations in 50l volume varied among samples and were in the range of 0.57 g .
the absorbance at 260 nm and associated dna concentration in each of the sample is shown in table 1 .
the age of the patient , sex , 1g/2 g polymorphism , bone height , and classification of edentulism
in order to analyze the 1g/2 g polymorphism in the promoter region of mmp-1 gene , we first downloaded the promoter sequence from the public domain database ( www.ncbi.nlm.nih.gov/nucleotide ) and designed the primers flanking the known polymorphism site at 1067 base .
the minus sign indicates that the site ( 1067 in this study ) is in the promoter region , upstream of the transcription start site of mmp-1 gene .
the amplification products of second step of polymerase chain reaction ( pcr ) were digested with alu1 restriction enzyme in a 25 l reaction volume at 37c for 4 h. the digested products were analyzed by running a 15 l aliquot in a 2.5% agarose gel at 50 v for 30 min .
alu1 recognizes a tetranucleotide motif agct ( 1 g ) but not aggct ( 2 g ) pentanucleotide motif , and digests ( cuts ) the pcr product ( dna ) after  g  .
samples carrying 1 g allele being sensitive to alu1 restriction digestion are cleaved into 169 bp and 25 bp products , which migrate faster relative to undigested ( uncut ) 2 g allele samples of 194 bp in size .
of the samples analyzed , 26 of edentulous patients ( 78.8% ) carried 2 g allele , while 7 of them ( 21.2% ) carried 1 g allele [ figure 2 and table 2 ] .
a majority of the edentulous samples analyzed carried 2 g allele . the number and percentage of 1 g or 2 g polymorphism under each edentulous classification
in order to analyze the possible association of bone height with the occurrence of polymorphism , the bone height was determined in each of the patient by measuring on panoramic dental radiographs , obtained from all subjects , using which the bone height of the lowest vertical height of the edentulous mandible was measured following the protocol of the american college of prosthodontists .
depending on existing bone height , the edentulous statuses were designated as class i , ii , iii , and iv .
a majority of the patients ( 51.5% ) belonged to class i followed by class ii ( 33.3% ) and class iii ( 15.2% ) .
the mean bone height in each of the class was found to be 23 mm for class i , 18.7 mm for class ii , and 12.8 mm for class iii [ bar diagram 1 ] . the mean bone height in comparison with 1g/2 g polymorphism under each edentulous classification analysis on the distribution of 1 g or 2 g polymorphism in each of the edentulous class
no association between the edentulous class and 1 g or 2 g polymorphism was observed . when the mean value of bone height in each class was grouped with that of polymorphism , again , no significant association was found .
analysis on the distribution of 1 g or 2 g polymorphism in each of the edentulous class is expressed in table 3 .
no association between the edentulous class and 1 g or 2 g polymorphism was observed . when the mean value of bone height in each class was grouped with that of polymorphism , again ,
matrix metalloproteinases-1 is capable of degrading type i , ii , and iii collagens , and is one of only four mmps able to degrade triple helical collagens .
mmp-1 gene located in chromosome 11q22 has the propensity for polymorphism which has been an indicator for cancer , hip arthroplasty , implant failure , periodontitis .
we attempt to first correlate between mmp-1 polymorphism and the risk of bone resorption in rrr .
the result of this study showed that 78% of the experimental group showed 2 g polymorphism , and 22% were of 1 g polymorphism [ bar diagram 2 ] .
the percentage of bone height in each polymorphism although 1% of polymorphism is previously reported , this could be associated with susceptibility to the disease .
based on these two observations , edentulous patients were examined to establish , correlate , and detect susceptibility to bone resorption in rrr .
patients were categorized according to the level of bone loss and were in the age group 5070 years .
majority of patients in the study showed 2 g polymorphism , which has been associated previously with implant failure and progressive periodontal disease , both of which are associated with excessive bone resorption mechanism .
2 g polymorphism is associated with bone loss in periodontitis and has altered gene resulting in increased destruction of ecm with increased mrna in the inflamed gingival tissue . while gg polymorphism of mmp-1 gene at 1607 domain led to early implant failures in patients which may be associated with osseointegration process . increased mrna level in inflamed tissues as a result of mmp-1 polymorphism , leads to increase transcriptional activity and degradation of major interstitial collagenase resulting in increased bone loss .
the 2 g polymorphism detected in the edentulous patients could be simply susceptibility to bone loss while both 1 g and 2 g polymorphism seem to be a common occurrence in the south indian population .
although sample size prevents to make generalized conclusion regarding the association of bone loss and genetic mutation . nevertheless , polymorphism is an important indicator for bone loss .
2 g polymorphism could also be used as a potential marker for bone loss among the south indian population .
of the 33 samples that were analyzed for the presence of 1 g or 2 g , 26 carried 2 g polymorphism in homozygous 2g/2 g condition , which has been associated with an increase in bone resorption in chronic periodontitis .
the rest of them carried 1 g polymorphism in homozygous 1g/1 g condition , with none of them carrying 1g/2 g heterozygous polymorphism .
when the data were corroborated with the existing bone height level , there was no positive association between the occurrence of 2g/2 g or 1g/1 g polymorphism and bone resorption in any of the three classes of resorption .
the number of 1 g polymorphisms found in the study was close to one - fourth of 2gs . in the absence of equal number of either polymorphisms or at least statistically matched number of 1 g and 2 g polymorphisms , it is hard to find associations between their occurrence and bone height .
 background : matrix metalloproteinase ( mmp ) are involved in bone transformation at the extraction site postdental extraction . 
 we examined the genetic association between single nucleotide polymorphisms of mmp-1 and continuous atrophy of edentulous mandible.methods:buccal cells from 33 edentulous patients were collected using sterile wooden spatula and were suspended in 15 ml falcon tubes containing 1.5 ml of cell lysis buffer , without proteinase k. the cells were transported to the laboratory on ice and were stored at 20c until being processed.results:of the samples analyzed , 26 edentulous patients ( 78.8% ) carried 2 g allele , while 7 of them ( 21.2% ) carried 1 g allele.conclusion:the patients with the alveolar bone resorption exhibited more of 2 g allele while only 21.2% of them showed 1 g allele , associated with excessive atrophy of edentulous mandible . 
 this study may provide genetic background to identify susceptible individuals prone to develop jawbone atrophy after dental extraction . 
Methods
Extraction and analysis of deoxyribonucleic acid
Analyzing the deoxyribonucleic acid concentration
Polymerase chain reaction
Detecting the 1G/2G polymorphism
Determination of Bone Height
Association between 1G or 2G polymorphism and bone height
Discussion
Conclusion
Financial support and sponsorship
Conflicts of interest