- Email: [email protected]
Paresthesia
Methods.—Sets of No. 330 carbide burs were given to five experienced operators. The burs were blindly separated into those not autoclaved and those autoclaved one, two, five, or 10 times. Operators were then asked to judge the cutting effectiveness of each bur by making an initial plunge cut through the enamel of a freshly extracted tooth. The same set of burs was then used to complete an occlusal cavity preparation in molar models made of composite restorative material. Operators also examined the burs for visual deterioration and rated their cutting ability. A scanning electron microscope (SEM) examination checked the burs as well. Results.—The visual appearance did not change between the burs never autoclaved and those autoclaved 10 times. However, the burs showed visual signs of change after preparing the composite teeth, with nonautoclaved burs rated slightly higher than those autoclaved one, five, or 10 times. No difference was noted between the nonautoclaved and twice-autoclaved burs. Bur color was ranked the same whether used for composite teeth or natural tooth preparations. SEM analysis found some areas that appeared less sharp on the burs autoclaved once and those autoclaved 5 times, but the burs cut normally. Two of the 25 burs used on natural tooth demonstrated an appearance change. One bur autoclaved twice had a better appearance after autoclaving than before. Another declined in appearance after 10 autoclaving cycles. The change in appearance was not significant, nor did it correlate statistically with the number of autoclaving cycles.
Four of the 25 burs used on composite material had appearance changes. After five autoclaving cycles, one increased its appearance score and one decreased it. One autoclaved 10 times increased in appearance score and another decreased. The change in appearance was not statistically significant and did not correlate with the number of times the bur was autoclaved. Discussion.—Autoclaving did not appear to adversely affect the carbide burs, whether the analysis was subjective or objective. None of the burs underwent ultrasonic cleaning, which might have produced more corrosion. In a true clinical situation, other factors may also influence the cutting efficiency of a bur.
Clinical Significance.—Even though dentists may believe that autoclaving diminishes the effectiveness of carbide burs, no evidence seems to support this. Thus the decision to replace a bur remains subjective and is based on individual preference or the operator’s perception that there is a loss of cutting effectiveness.
Spranley TJ, Cheramie TJ, Ireland EJ, et al: Cutting effectiveness of carbide burs following multiple steam autoclaving cycles. Gen Dent 53-58, 2011 Reprints available from the Academy of General Dentistry. Fax your request to Jo Posselt (312/440-4261) or e-mail: [email protected]
Endodontics Paresthesia Background.—Neural injury can cause paresthesia, manifest as a burning or prickling sensation or partial numbness. In dentistry, the inferior alveolar nerve (IAN) and mental nerve (MN) are most often involved, and the paresthesia can result from systemic or local factors. Diagnosis is based on an accurate patient history to determine when the symptoms began and how they have changed over time. The affected area can be evaluated subjectively using thermal, mechanical, electrical, or chemical tests. More objective assessment involves electrophysiologic analysis of the nerve and sometimes radiographs and/or neurophysiologic screening tests. Computed tomography will display small structures and reveal spatial relationships in three dimensions. If the nerve irritation is nonpersistent, paresthesia can resolve in days or weeks. The endodontic-related causes of paresthesia include periapical infections, overfilling, and apical surgery. These were evaluated and treatment strategies were suggested.
Endodontic Factors.—When paresthesia results from periapical lesions, the cause may be mechanical pressure and ischemia related to inflammation or local pressure on the MN from accumulated pus, toxic metabolic products of bacteria, or inflammatory tissue factors. A hematoma resulting from the lesion may also cause paresthesia. Either the MN or the IAN can be involved. Local anesthesia can also produce paresthesia. The injection of local anesthetic solutions contaminated by alcohol or sterilizing solution can irritate the area, causing edema and pressure, which produces the paresthesia. When alcohol is the contaminant, the disrupted sensation can last for months or years. The nerve sheath may also be injured during the injection, causing the patient to experience pain described as electric shock-like. Hemorrhage into or around the nerve sheath can press on the nerve as well.
Volume 56
Issue 4
2011
185
The IAN can be directly damaged during root canal preparation when the site is overly instrumented. Scarring can cause temporary paresthesia immediately. The apical constriction can also be disrupted during root canal preparation, causing extrusion of irrigants, medicaments, and obturation materials, which can produce chemical and mechanical nerve damage. The irrigation solution, especially sodium hypochlorite, used during cleaning and shaping can be inadvertently injected past the apical foramen. If extreme pressure is used during irrigation or binding of the irrigation needle tip occurs, the irrigant cannot escape from the canal and accumulates, causing the irrigant to contact apical tissues and lead to tissue necrosis. Irrigant can enter the periapical soft-tissues and produce swelling, necrosis of the mucosa, and anesthesia of the MN. Infected debris can be extruded into the mandibular canal or mental foramen, which is a common occurrence with hand and rotary instruments. This infected debris can breach the protective perineurium of the IAN and hinder nerve conduction. Paresthesia can result from mechanical or chemical changes produced by root canal filling materials such as gutta-percha or sealers. Although minor extrusions from the apical foramen are usually well tolerated, the toxic effects can be produced when filling materials contact nerve structures, causing anesthesia, hypoesthesia, paresthesia, or dysesthesia that can be irreversible. Gutta-percha has a low level of cytotoxicity but can cause chronic inflammation. Eugenol-based sealer has a demonstrated toxicity, inhibiting intradental nerve activity. Calcium hydroxidebased sealers may cause irreversible nerve damage or paresthesia as a result of mechanical compression. Thermal nerve injury can result when a thermoplastic technique is used. Temperatures just 10 above the 53.5 to 57.5 C required to soften thermoplastic gutta-percha can produce intracanal temperatures as high as 50 to 100 C, causing bone damage, necrosis, and nerve damage. Treatment.—The longer the mechanical or chemical irritation is present, the more the nerve fibers degenerate and higher is the risk of permanent paresthesia. If there are nonpersistent episodes of nerve irritation, paresthesia should resolve within days or weeks. When the cause is infectious, the paresthesia is resolved once the nonsurgical endodontic treatment is provided. It takes about 8 weeks to clear up the paresthesia related to local anesthesia. If the nerve fibers
have been cut, are subjected to prolonged pressure, or come into contact with toxic overfilled endodontic materials, the cause should be removed immediately (if possible) and measures must be taken to control inflammation, edema, hematoma, or infection. Antibiotics, nonsteroidal antiinflammatory drugs, corticosteroids, proteolytic enzymes to disintegrate the coagulum, and vitamin C can be used. Within 30 days of the damage, both pharmacologic and mechanical methods can be used. The agents that have proved helpful include topical steroids, co carnitine, somatotropic hormone, nerve growth factor, vitamins C and E, vasodilators, and ozone. The instrumental therapy may be magnetotherapy, laser therapy, and the application of electrical fields. Beyond this time, treatment focuses on the persistent neuralgia. Although most IAN injuries resolve spontaneously, surgical approaches may be used and have yielded patient satisfaction levels of 55%. IAN microsurgery has produced statistically significant neurosensory improvement in a maximum of 92% of patients. MN repair should be done as early as possible.
Clinical Significance.—Endodontic treatment can be complicated by the occurrence of paresthesia or other sensory disturbances. Care must be taken to avoid causing inflammation, edema, direct injury to nerves, or thermal injury during the performance of endodontic treatment. Patients should be advised to be alert for signs of sensory disturbance so that prompt evaluation and treatment can be undertaken.
Mohammadi Z: Endodontics-related paresthesia of the mental and inferior alveolar nerves: An updated review. J Can Dent Assoc 76:a117, 2010 Reprints available from Z Mohammadi, Dept of Endodontics, Hamedan Univ of Medical Sciences School of Dentistry, Pajoohesh Cross Rd, Shahid Fahmideh St, Hamedan, Iran; e-mail: [email protected]
Implants Third attempts at implant placement Background.—Seldom does a clinician attempt to place an implant for a third time at the same site at which two previous attempts resulted in failure. However, some patients may require this third attempt if the location is critical for
186
Dental Abstracts
the patient’s prosthetic rehabilitation plan. The evidence to support such a course of action is lacking. The survival rate of dental implants performed in sites where two previous attempts failed was analyzed.
Four of the 25 burs used on composite material had appearance changes. After five autoclaving cycles, one increased its appearance score and one decreased it. One autoclaved 10 times increased in appearance score and another decreased. The change in appearance was not statistically significant and did not correlate with the number of times the bur was autoclaved. Discussion.—Autoclaving did not appear to adversely affect the carbide burs, whether the analysis was subjective or objective. None of the burs underwent ultrasonic cleaning, which might have produced more corrosion. In a true clinical situation, other factors may also influence the cutting efficiency of a bur.
Clinical Significance.—Even though dentists may believe that autoclaving diminishes the effectiveness of carbide burs, no evidence seems to support this. Thus the decision to replace a bur remains subjective and is based on individual preference or the operator’s perception that there is a loss of cutting effectiveness.
Spranley TJ, Cheramie TJ, Ireland EJ, et al: Cutting effectiveness of carbide burs following multiple steam autoclaving cycles. Gen Dent 53-58, 2011 Reprints available from the Academy of General Dentistry. Fax your request to Jo Posselt (312/440-4261) or e-mail: [email protected]
Endodontics Paresthesia Background.—Neural injury can cause paresthesia, manifest as a burning or prickling sensation or partial numbness. In dentistry, the inferior alveolar nerve (IAN) and mental nerve (MN) are most often involved, and the paresthesia can result from systemic or local factors. Diagnosis is based on an accurate patient history to determine when the symptoms began and how they have changed over time. The affected area can be evaluated subjectively using thermal, mechanical, electrical, or chemical tests. More objective assessment involves electrophysiologic analysis of the nerve and sometimes radiographs and/or neurophysiologic screening tests. Computed tomography will display small structures and reveal spatial relationships in three dimensions. If the nerve irritation is nonpersistent, paresthesia can resolve in days or weeks. The endodontic-related causes of paresthesia include periapical infections, overfilling, and apical surgery. These were evaluated and treatment strategies were suggested.
Endodontic Factors.—When paresthesia results from periapical lesions, the cause may be mechanical pressure and ischemia related to inflammation or local pressure on the MN from accumulated pus, toxic metabolic products of bacteria, or inflammatory tissue factors. A hematoma resulting from the lesion may also cause paresthesia. Either the MN or the IAN can be involved. Local anesthesia can also produce paresthesia. The injection of local anesthetic solutions contaminated by alcohol or sterilizing solution can irritate the area, causing edema and pressure, which produces the paresthesia. When alcohol is the contaminant, the disrupted sensation can last for months or years. The nerve sheath may also be injured during the injection, causing the patient to experience pain described as electric shock-like. Hemorrhage into or around the nerve sheath can press on the nerve as well.
Volume 56
Issue 4
2011
185
The IAN can be directly damaged during root canal preparation when the site is overly instrumented. Scarring can cause temporary paresthesia immediately. The apical constriction can also be disrupted during root canal preparation, causing extrusion of irrigants, medicaments, and obturation materials, which can produce chemical and mechanical nerve damage. The irrigation solution, especially sodium hypochlorite, used during cleaning and shaping can be inadvertently injected past the apical foramen. If extreme pressure is used during irrigation or binding of the irrigation needle tip occurs, the irrigant cannot escape from the canal and accumulates, causing the irrigant to contact apical tissues and lead to tissue necrosis. Irrigant can enter the periapical soft-tissues and produce swelling, necrosis of the mucosa, and anesthesia of the MN. Infected debris can be extruded into the mandibular canal or mental foramen, which is a common occurrence with hand and rotary instruments. This infected debris can breach the protective perineurium of the IAN and hinder nerve conduction. Paresthesia can result from mechanical or chemical changes produced by root canal filling materials such as gutta-percha or sealers. Although minor extrusions from the apical foramen are usually well tolerated, the toxic effects can be produced when filling materials contact nerve structures, causing anesthesia, hypoesthesia, paresthesia, or dysesthesia that can be irreversible. Gutta-percha has a low level of cytotoxicity but can cause chronic inflammation. Eugenol-based sealer has a demonstrated toxicity, inhibiting intradental nerve activity. Calcium hydroxidebased sealers may cause irreversible nerve damage or paresthesia as a result of mechanical compression. Thermal nerve injury can result when a thermoplastic technique is used. Temperatures just 10 above the 53.5 to 57.5 C required to soften thermoplastic gutta-percha can produce intracanal temperatures as high as 50 to 100 C, causing bone damage, necrosis, and nerve damage. Treatment.—The longer the mechanical or chemical irritation is present, the more the nerve fibers degenerate and higher is the risk of permanent paresthesia. If there are nonpersistent episodes of nerve irritation, paresthesia should resolve within days or weeks. When the cause is infectious, the paresthesia is resolved once the nonsurgical endodontic treatment is provided. It takes about 8 weeks to clear up the paresthesia related to local anesthesia. If the nerve fibers
have been cut, are subjected to prolonged pressure, or come into contact with toxic overfilled endodontic materials, the cause should be removed immediately (if possible) and measures must be taken to control inflammation, edema, hematoma, or infection. Antibiotics, nonsteroidal antiinflammatory drugs, corticosteroids, proteolytic enzymes to disintegrate the coagulum, and vitamin C can be used. Within 30 days of the damage, both pharmacologic and mechanical methods can be used. The agents that have proved helpful include topical steroids, co carnitine, somatotropic hormone, nerve growth factor, vitamins C and E, vasodilators, and ozone. The instrumental therapy may be magnetotherapy, laser therapy, and the application of electrical fields. Beyond this time, treatment focuses on the persistent neuralgia. Although most IAN injuries resolve spontaneously, surgical approaches may be used and have yielded patient satisfaction levels of 55%. IAN microsurgery has produced statistically significant neurosensory improvement in a maximum of 92% of patients. MN repair should be done as early as possible.
Clinical Significance.—Endodontic treatment can be complicated by the occurrence of paresthesia or other sensory disturbances. Care must be taken to avoid causing inflammation, edema, direct injury to nerves, or thermal injury during the performance of endodontic treatment. Patients should be advised to be alert for signs of sensory disturbance so that prompt evaluation and treatment can be undertaken.
Mohammadi Z: Endodontics-related paresthesia of the mental and inferior alveolar nerves: An updated review. J Can Dent Assoc 76:a117, 2010 Reprints available from Z Mohammadi, Dept of Endodontics, Hamedan Univ of Medical Sciences School of Dentistry, Pajoohesh Cross Rd, Shahid Fahmideh St, Hamedan, Iran; e-mail: [email protected]
Implants Third attempts at implant placement Background.—Seldom does a clinician attempt to place an implant for a third time at the same site at which two previous attempts resulted in failure. However, some patients may require this third attempt if the location is critical for
186
Dental Abstracts
the patient’s prosthetic rehabilitation plan. The evidence to support such a course of action is lacking. The survival rate of dental implants performed in sites where two previous attempts failed was analyzed.