various events can lead to burned skeletal remains , which may include transport accidents such as aircraft and rail ; suicides ; and terrorist attacks . conventional methods of identification such as visual identification and fingerprints have been rendered redundant in cases where the body is burnt beyond recognition . teeth and bones have the good fortune of surviving really high temperatures . teeth and the restorative material used as cavity fillings have an astonishing ability to resist extreme conditions of heat and cold . this quality can be attributed to the protection offered from the surrounding orofacial structures such as the buccal mucosa and the labial mucosa . studying the effect of heat on teeth and the restorations would help ascertain the temperature reached by the fire , if an accelerator was used and whether the blaze was the cause of death or the victim was dead prior to the fire . additional information obtained from the available restorative material after a fire enhances the possibility of a positive identification . the aim of this study was to find out the effect of heat on the teeth and the different restorations and their resistance to this extreme state . apart from gross examination of the teeth , a stereomicroscopic study was carried out to study the finer details post exposure to fire . eighty sound teeth , extracted for periodontal or orthodontic reasons were disinfected in a 5% sodium hypochlorite solution for 2 h and stored in sodium chloride 0.9% solution at room temperature for up to 1 month , and they were randomly divided into different groups . group 1 : 20 unrestored teeth group ii : 20 amalgam restored teeth group iii : 20 glass ionomer restored teeth group iv : 20 zinc oxide eugenol restored teeth . after restoration all samples were stored in a 0.9% sodium chloride solution at room temperature for 1 month before further tests . each specimen was placed in a custom made tray made of dental investment material and the samples were then exposed to direct heat in an oven at four different temperatures viz ; 200c , 400c , 600c , and 800c , with an increment rate of 30c / min . the number of samples and controls exposed to each target temperature is reported . as soon as each target temperature was reached , the samples were removed from the oven and allowed to cool to room temperature . the effects of high temperatures on teeth were overtly observed for the change of color and the intactness of the restorations . the macroscopic and stereomicroscopic findings for both restored as well as un - restored teeth were as follows : 200c : the color of the crown and root changed from yellowish white to light brown . [ figure 1 ] stereomicroscope showed the appearance of micro cracks or fractures on the root . unrestored tooth at 200c : macroscopically evident change of color , tending to yellow , brown , of both the root and the crown 400c : the color of the root had changed to steel gray or black while that of the crown remained light brown . stereomicroscope showed extension of the micro fractures from the root or appearance of new ones on the surface of the crown as well . 600c : the crown had shattered into pieces while the root was intact , and black in color . [ figure 2 ] stereo microscopic view showed numerous minute micro fractures on the root surface . unrestored tooth at 600c : macroscopic evaluation showed black discoloration of the whole tooth , a shattered part of the crown and detachment of the enamel 800c : a drastic change in color of the root was seen , which turned to opaque white . 200c : the crown showed slight retraction of the amalgam filling from the light brown to black colored crown . 400c : the findings were similar to those at 200c with further retraction of the amalgam filling and loss of marginal seal seen with the stereomicroscope [ figures 3 and 4 ] . amalgam restoration at 400c : macroscopically fillings were in place , although both showed the same phenomenon noted at 200c , that is the presence of bubbles on the surface amalgam restoration at 400c : retraction of the amalgam filling and loss of marginal seal seen with the stereomicroscope 600c : the tooth was shattered , but the filling was intact . stereomicroscopic view showed fractures on the filling though the shape of the filling was maintained . 800c : the filling remained in place with an intact shape on the portion of the crown that was left . exposed portion of 200c : the color of the root had turned dark brown whereas the color of the filling showed areas that had turned light brown . 400c : the color of the crown was light brown whereas the root was turned to dark grey to charcoal black as did the color of the filling . portions of the filling had broken off , and loss of marginal seal was observed . 600c : the crown was carbonized and completely shattered into pieces , but the outline of the filling was noticeable . the cross - section of the filling shows no change in the color [ figure 5 ] . stereo microscopically the color of the root had turned to dark brown to black and showed deep fracture lines . zinc oxide eugenol at 600 : macroscopically dark gray with cracks and dimensional contraction by loss of water , agglomerated particles of zinc 800c : the filling was lost as the crown was shattered completely and root was intact . exposed dentin showed a bluish grey hue . stereomicroscopic view showed minute fracture lines on the root , which had turned to opaque white . 200c : the restoration had extruded from the crown , which showed a slight change in color to light brown . 400c : the filling showed a change in color to light brown as was the color of the crown . 600c : loss of superficial portion of the crown structure was seen along with a portion of the filling . glass ionomer restoration at 600c : stereomicroscope showed deep fracture lines along the length 800c : only a portion of the crown structure along with the filling remained . the filling remained intact within the crown , which had turned opaque white as had the root [ figure 7 ] . glass ionomer restoration at 800c : macroscopically only a portion of the crown structure along with the filling remained . the filling remained intact within the crown which had turned opaque white as had the root 200c : the color of the crown and root changed from yellowish white to light brown . [ figure 1 ] stereomicroscope showed the appearance of micro cracks or fractures on the root . unrestored tooth at 200c : macroscopically evident change of color , tending to yellow , brown , of both the root and the crown 400c : the color of the root had changed to steel gray or black while that of the crown remained light brown . stereomicroscope showed extension of the micro fractures from the root or appearance of new ones on the surface of the crown as well . 600c : the crown had shattered into pieces while the root was intact , and black in color . [ figure 2 ] stereo microscopic view showed numerous minute micro fractures on the root surface . unrestored tooth at 600c : macroscopic evaluation showed black discoloration of the whole tooth , a shattered part of the crown and detachment of the enamel 800c : a drastic change in color of the root was seen , which turned to opaque white . 200c : the crown showed slight retraction of the amalgam filling from the light brown to black colored crown . 400c : the findings were similar to those at 200c with further retraction of the amalgam filling and loss of marginal seal seen with the stereomicroscope [ figures 3 and 4 ] . amalgam restoration at 400c : macroscopically fillings were in place , although both showed the same phenomenon noted at 200c , that is the presence of bubbles on the surface amalgam restoration at 400c : retraction of the amalgam filling and loss of marginal seal seen with the stereomicroscope 600c : the tooth was shattered , but the filling was intact . stereomicroscopic view showed fractures on the filling though the shape of the filling was maintained . 800c : the filling remained in place with an intact shape on the portion of the crown that was left . 200c : the crown showed slight retraction of the amalgam filling from the light brown to black colored crown . 400c : the findings were similar to those at 200c with further retraction of the amalgam filling and loss of marginal seal seen with the stereomicroscope [ figures 3 and 4 ] . amalgam restoration at 400c : macroscopically fillings were in place , although both showed the same phenomenon noted at 200c , that is the presence of bubbles on the surface amalgam restoration at 400c : retraction of the amalgam filling and loss of marginal seal seen with the stereomicroscope 600c : the tooth was shattered , but the filling was intact . stereomicroscopic view showed fractures on the filling though the shape of the filling was maintained . 800c : the filling remained in place with an intact shape on the portion of the crown that was left . 200c : the color of the root had turned dark brown whereas the color of the filling showed areas that had turned light brown . 400c : the color of the crown was light brown whereas the root was turned to dark grey to charcoal black as did the color of the filling . portions of the filling had broken off , and loss of marginal seal was observed . 600c : the crown was carbonized and completely shattered into pieces , but the outline of the filling was noticeable . the cross - section of the filling shows no change in the color [ figure 5 ] . stereo microscopically the color of the root had turned to dark brown to black and showed deep fracture lines . zinc oxide eugenol at 600 : macroscopically dark gray with cracks and dimensional contraction by loss of water , agglomerated particles of zinc 800c : the filling was lost as the crown was shattered completely and root was intact . stereomicroscopic view showed minute fracture lines on the root , which had turned to opaque white . 200c : the restoration had extruded from the crown , which showed a slight change in color to light brown . 400c : the filling showed a change in color to light brown as was the color of the crown . 600c : loss of superficial portion of the crown structure was seen along with a portion of the filling . glass ionomer restoration at 600c : stereomicroscope showed deep fracture lines along the length 800c : only a portion of the crown structure along with the filling remained . the filling remained intact within the crown , which had turned opaque white as had the root [ figure 7 ] . glass ionomer restoration at 800c : macroscopically only a portion of the crown structure along with the filling remained . the filling remained intact within the crown which had turned opaque white as had the root most of the microscopic studies of enamel showed structural changes at 800c , whereas dentin showed changes at a comparatively lower temperature of 600c . these changes are the result of the physiochemical properties of the material and their nature . even with these changes , individual components like the change in the color , hue of the restoration and their external appearance are the most commonly observed findings in an incinerated tooth . teeth are amazingly resistant to heat if it is subjected to it gradually , but if heated severely the tooth may disintegrate ; else they may resist temperatures unto 1200c . care must be exercised while handling the burnt teeth and methods to reinforce the singed remains must be carried out so as to prevent them from disintegration . fragmentation is the most important complication of burned human remains . according to the gustafson , the greatest disparity in the effect of high temperatures on restorations is seen in amalgam fillings . pink pigments due to copper oxides and a golden thread due to mercuric oxide vapors that were seen in other studies were absent in this study . the difference in the composition of amalgam and an inconsistency in the percentages of mercury , silver , and copper found in amalgam available in different parts of the world may be responsible for this discrepancy . the contraction of the restoration and loss of marginal seal was due to evaporation of mercury and loss of organic matrix . the bubbles observed on the surface of the restoration were due to evaporation of mercury . gold inlays are known to resemble amalgam fillings because of the deposited vapor of mercury on it . phosphate linings are known to resist fire very well , and are usually found at the bottom of the cavity when the amalgam filling is dislodged . this could not be verified in this study , since , the amalgam filling was intact and in its place even at a temperature as high as 800c . the charred appearance of the tooth indicates sudden and quick carbonization of the tooth and its conversion into solid carbon as any biomaterial does on exposure to high temperatures . the teeth used in this study were specifically restored post extraction ; hence , the time elapsed since the fillings were carried out and the teeth incinerated could not be considered . in real time , there may be a time gap between the restorations carried out on the teeth and the incineration of the body . restored teeth appeared to show cracks and fissures at lower temperatures than un - restored teeth . this may be due to the alteration in the structural integrity of the tooth during cavity preparation . contrarily to amalgam , zinc oxide eugenol filling showed extrusion indicating expansion of the filling instead of marginal contraction . in incinerated remains tooth colored fillings are the most difficult to identify macroscopically , but the use of a stereomicroscope simplifies the task . the stereomicroscope can also be used to differentiate the gold fillings with amalgam residue on them from actual amalgam fillings and to detect the presence of a root canal filling after an explosion of the crown of the tooth . teeth like bones have been known to react in a predictable manner when subjected to natural elements such as fire , earth , and water . this study was performed on extracted teeth ; hence , exact results may not be obtained when a body is subjected to an intensive heat source . the effects produced depend upon variables , such as the intensity of heat , protection of surrounding tissue , duration of exposure to the heat , presence of an accelerator , and the medium used to extinguish the fire . absence of these variables may have caused an early evaporation of organic components with subsequent shattering or explosion of the crown around 800c . thus , the teeth are known to survive higher temperatures than those mentioned in this study . the effect of heat on teeth in reality is further complicated by the duration of exposure to high temperatures . in this study , the teeth were subjected to a single , limited , and controlled exposure to heat . we conclude that the possible temperature of exposure can be estimated by analyzing the changes in the teeth and their restorations , though , further studies on other materials used in the restoration of decayed or missing teeth such as acrylic , porcelain , and stainless steel are required .