DANB RHS Radiation Health and Safety - Set 1 - Part 2

Correct Answer: loss of alveolar bone

Periodontitis destroys the supporting alveolar bone, so the image shows the crest dropping below its normal level. That radiolucent bone loss is the central radiographic sign of the disease. Option b is incorrect because brighter enamel reflects the density of a healthy crown and has nothing to do with the supporting bone; periodontal disease is read in the bone, not the enamel. Option c is incorrect because wider pulp chambers relate to pulpal changes or age, an internal tooth feature, not the breakdown of the bony attachment that defines periodontal disease. Option d is incorrect because longer roots are a developmental trait, not a disease sign; periodontitis exposes more root by destroying bone but does not actually lengthen the roots themselves.

Correct Answer: horizontal loss

Horizontal bone loss lowers the crest evenly while it remains parallel to a line connecting the cementoenamel junctions of adjacent teeth, the common pattern seen as generalized periodontitis progresses. Option a is incorrect because vertical loss runs obliquely and is deeper on one side of a tooth, so the crest no longer parallels the line between the junctions the way horizontal loss does. Option b is incorrect because angular loss is just another name for the vertical, oblique defect; it describes a slanted crater beside the root, not the even, parallel drop in crest height. Option c is incorrect because furcation loss refers specifically to bone destroyed where multirooted teeth divide; it names a location of involvement rather than the overall horizontal or vertical pattern.

Correct Answer: radiopaque

Calculus is a mineralized, stonelike deposit of calcium and phosphate salts, so it is dense enough to absorb x-rays and appears radiopaque, often as spurs projecting from the proximal root surfaces. Option a is incorrect because radiolucent would mean the deposit lets x-rays pass and darkens the image, but mineralized calculus does the opposite, blocking the beam like the hard tissue around it. Option b is incorrect because claiming it is always invisible overstates the limit; thin or facial deposits may be missed, yet substantial proximal calculus is dense enough to register on the image. Option d is incorrect because calling it dark and soft contradicts its nature; calculus is hardened, not soft, and its mineral content makes it light on the image rather than dark.

Correct Answer: lack the mass to show

A deposit must have enough thickness and mineral mass to absorb the beam before it registers, so thin layers or calculus on the buccal and lingual surfaces simply do not present enough to be seen. Option a is incorrect because calculus does not dissolve in saliva; it is the hardened, mineralized end product that forms from saliva, so solubility is not the reason it is missed on an image. Option c is incorrect because turning radiolucent would mean losing density, but calculus stays mineralized and radiopaque; the issue is too little mass to detect, not a change to a darker appearance. Option d is incorrect because modern digital imaging has no chemical processing step to wash anything away, and even on film the deposit is not removed; the limit is the thin deposit's faint shadow.

Correct Answer: no crestal bone loss

Gingivitis is confined to the soft tissue and is reversible, so it leaves the bone intact; the image shows no crestal bone loss, which is what separates it from periodontitis. Option b is incorrect because deep vertical defects mark advanced periodontitis with active bone destruction, a stage well beyond gingivitis, which has not yet damaged the supporting bone at all. Option c is incorrect because furcation involvement means disease has destroyed bone between the roots of a multirooted tooth, again a periodontitis finding that gingivitis alone does not produce. Option d is incorrect because widened ligament spaces suggest occlusal trauma or other bony changes around the root; gingivitis stays in the gingiva and does not alter the ligament space on the image.

Correct Answer: mesiodens

A mesiodens is a supernumerary tooth that sits in the maxillary midline between the central incisors, often blocking or deflecting their eruption, and is the most common extra tooth. Option a is incorrect because a peg lateral is a small, cone-shaped lateral incisor, an anomaly of shape rather than an extra tooth, and it occupies the normal lateral position, not the midline. Option b is incorrect because a geminated tooth comes from one bud trying to split, producing a single large tooth; it adds bulk, not an additional tooth, and is not specific to the midline. Option c is incorrect because a fused tooth results when two buds join into one, which lowers the count rather than adding a separate extra tooth wedged between the central incisors.

Correct Answer: anodontia

Anodontia, partial or total, is the congenital absence of teeth. The third molars are most often missing, followed by the maxillary lateral incisors and the second premolars in that order. Option a is incorrect because supernumerary means the opposite, teeth beyond the normal number, so it names extras such as a mesiodens rather than teeth that simply never developed. Option b is incorrect because concrescence is the joining of two teeth at the cementum of their roots, a fusion of existing teeth, not the failure of teeth to develop in the first place. Option d is incorrect because ankylosis is the fusion of a tooth to the surrounding bone, which fixes it in place; it concerns attachment, not whether a tooth is congenitally present or missing.

Correct Answer: fusion

Fusion unites the dentin and enamel of two developing buds into one larger tooth, so the patient ends up with one fewer tooth than expected in that part of the arch. Option b is incorrect because gemination is a single bud attempting to divide, producing one large tooth while the count stays normal, the opposite of fusion's reduced number. Option c is incorrect because concrescence joins teeth only at the cementum of their roots after they have formed; the crowns remain separate and the tooth count is not reduced. Option d is incorrect because dilaceration is a sharp bend in a root or crown caused by trauma during development; it distorts a single tooth's shape and does not change how many teeth are present.

Correct Answer: concrescence

Concrescence is the union of neighboring teeth at the cementum of their roots alone, with separate crowns. It matters most when extracting one tooth risks removing the joined neighbor. Option a is incorrect because fusion joins the dentin and enamel of two buds into a single tooth and lowers the count, a deeper union than the cementum-only joining that defines concrescence. Option c is incorrect because gemination is one bud splitting into a large single tooth with one pulp chamber; it involves a single developing tooth, not two roots cemented together. Option d is incorrect because anodontia is the congenital absence of teeth, so it concerns missing teeth rather than the joining of roots, an entirely different category of anomaly.

Correct Answer: third molars and maxillary canines

Third molars and maxillary canines are impacted most often, since they erupt late and frequently lack room, leaving them blocked in the bone past their normal eruption time. Option a is incorrect because mandibular central incisors erupt early into ample space at the front of the jaw, so they almost never become impacted compared with the late-erupting teeth. Option b is incorrect because maxillary first molars erupt reliably and early to establish the bite, making impaction of these teeth uncommon relative to wisdom teeth and canines. Option c is incorrect because lower lateral incisors generally erupt without trouble in the anterior arch; they are not among the teeth typically trapped beneath bone or adjacent teeth.

Correct Answer: radiopaque metal form

An implant is a titanium fixture, and metal is very dense, so it stops most of the beam and appears as a sharply radiopaque, threaded form seated in the bone. Option a is incorrect because a radiolucent void would be a dark area of low density; a solid metal implant is the densest object present, so it reads bright rather than dark. Option b is incorrect because a soft-tissue shadow is faint and gray because soft tissue barely absorbs the beam, the opposite of the crisp, bright outline a metal fixture produces. Option d is incorrect because a dark canal describes a radiolucent channel such as a nerve canal; the implant is solid metal, not a hollow passage, so it cannot appear as a dark canal.

Correct Answer: buccolingual bone width

A flat two-dimensional image cannot reveal how wide the bone is from cheek to tongue, but CBCT reconstructs the site in three dimensions, so buccolingual width can be measured before placement. Option b is incorrect because tooth color is a clinical shade matter seen by eye, not a bone measurement, and it has no bearing on planning the dimensions of an implant site. Option c is incorrect because pulp vitality is tested with thermal or electric stimuli on a living tooth; an edentulous implant site has no pulp, so vitality is irrelevant to the scan. Option d is incorrect because plaque levels are assessed clinically on tooth and tissue surfaces; imaging is not used to grade plaque, and it plays no role in measuring bone for an implant.

Correct Answer: implant failure

A radiolucency around the fixture means bone is being lost at the implant interface, a sign that osseointegration is breaking down and the implant is failing rather than holding firm. Option a is incorrect because successful integration shows bone in tight, intimate contact with the fixture and no surrounding dark line, so a radiolucency points to the opposite outcome. Option b is incorrect because denser surrounding bone would appear lighter and more radiopaque, indicating strong support, not the dark zone that reflects bone loss around the implant. Option c is incorrect because new enamel growth is impossible around an implant; enamel is made only during tooth development and never forms against a metal fixture in the bone.

Correct Answer: panoramic

The panoramic is the survey of choice for an edentulous patient, covering both jaws to hunt for retained roots, impactions, and pathology and to assess the residual ridge in one image. Option a is incorrect because a bitewing relies on contacting teeth and captures only crowns and crestal bone; with no teeth present it serves no purpose for surveying the ridges. Option b is incorrect because a periapical covers a small focused area and depends on intraoral placement near teeth; it is far too limited to survey the whole edentulous arch efficiently. Option d is incorrect because a cephalometric is a lateral skull projection used for orthodontic and growth measurement, not a tool for hunting retained roots or assessing ridge bone.

Correct Answer: resorb and shrink

After teeth are lost the residual ridge resorbs, decreasing in height and changing contour, and the loss speeds up under a poorly fitting prosthesis, which is why dentures need relining over time. Option a is incorrect because ridges do not gain height once teeth are gone; without the stimulus of tooth roots the bone steadily shrinks rather than building upward. Option c is incorrect because turning fully radiolucent would mean the bone disappears entirely, but resorption reduces the ridge gradually while leaving recognizable, if smaller, radiopaque bone behind. Option d is incorrect because growing new teeth is not possible in an edentulous adult arch; the natural dentition does not regenerate, which is the reason prostheses are needed at all.

Correct Answer: strongly radiopaque

These are dense metals that absorb almost all of the beam, so each appears strongly radiopaque, standing out as a bright white shape against the comparatively darker tooth and bone. Option b is incorrect because radiolucent would mean the material lets x-rays through and looks dark, but metal is the densest material in the mouth and does the opposite, blocking the beam. Option c is incorrect because calling them invisible is wrong because their high density makes them the most obvious objects on the image, not features that fail to register at all. Option d is incorrect because dark gray voids describe low-density or empty areas; metal restorations are the brightest structures present, so they never appear as dark gaps.

Correct Answer: radiopaque

Gutta-percha and the sealer must be radiopaque so the clinician can confirm on the image that the canal is filled completely to the proper length after endodontic treatment. Option a is incorrect because if the filling were radiolucent it would blend into the dark canal space and could not be evaluated, which is exactly why the material is made dense instead. Option b is incorrect because being tooth-colored matters for visible restorations like anterior fillings, but a root filling sits hidden inside the canal where shade is irrelevant and density is what counts. Option c is incorrect because soft and dark describes neither requirement; the material needs to register clearly on the image, so it is formulated to be radiopaque rather than to disappear.

Correct Answer: acrylic or unfilled resin

Acrylic and older unfilled resins have low density, so they appear radiolucent or only faintly radiopaque and can be confused with tooth structure or even with caries on the image. Option a is incorrect because amalgam is a dense metal alloy that appears bright white, so it could never be mistaken for the dark, tooth-like appearance the question describes. Option b is incorrect because cast gold is one of the most radiopaque restorations and stands out sharply; it is the opposite of a material that fades into the surrounding tooth. Option d is incorrect because stainless steel, used for crowns and bands, is highly radiopaque and clearly outlined on the image, not a faint shadow blending with the tooth.

Correct Answer: can be told apart from decay

Manufacturers add radiopaque fillers so composite shows up faintly on the image, letting the clinician distinguish the restoration from recurrent decay at its margins rather than overlooking either one. Option b is incorrect because composite is far less dense than metal and is not meant to match it; the goal is a slight, detectable opacity, not the bright density of a gold or amalgam restoration. Option c is incorrect because blocking all x-rays describes solid metal; composite only needs enough opacity to be visible, and a material that stopped the entire beam would obscure the tooth beneath. Option d is incorrect because dissolving on contact would make the material useless as a filling; composite is durable and bonded in place, and solubility has nothing to do with its radiopacity.

Correct Answer: radiolucent at the margins

Recurrent caries is demineralized tissue, so it shows as a radiolucent shadow at the margins of a restoration, whereas a base is a placed radiopaque material; the dark versus light contrast tells them apart. Option a is incorrect because if decay were equally bright it would look like the dense base, but caries loses mineral and darkens, so the two never share the same bright appearance. Option c is incorrect because metallic and dense describes the base or a metal restoration, not decay; caries is a loss of tooth substance and reads dark, never as a bright metallic spot. Option d is incorrect because recurrent caries forms within the tooth at the restoration margins, not outside the tooth, so an external location does not describe where this decay actually develops.