Сraig. Dental Materials

torch, just enough to barely soften the material. Dip the mouth protector in warm water and place it in the athlete's mouth. Ask the athlete to close until all the opposing teeth contact the mouth protector.

PREPARING A MOUTH-FORMEDMOUTH PROTECTOR

Manufacturers supply instructions for the boil- and-bite mouth protector; in general, the procedure is as follows. Place the protector in a pan of boiling water, just removed from the heat, for 10 to 35 seconds, based on the manufacturer's directions. Remove the protector from the hot water, immerse it in a pan of cold water for 1 second and then place it in the mouth, centering it around the maxillary teeth. Ask the athlete to bite down gently and suck out any air and water by pressing the tongue against the back of the maxillary teeth. Leave the protector in the mouth for 30 seconds before removal. If a good fit is not obtained, the procedure can be repeated. Also, if the mouth protector is too large, cut off the ends to the appropriate length before placing it in the hot water.

CARE OF ATHLETIC MOUTH PROTECTORS

Give the following recommendations to the athlete:

After each use, rinse the mouth protector under cold water.

Periodically clean the mouth protector using a solution of soap in cold water. Don't use abrasive dentifrices to clean the protector.

Don't use alcoholic solutions or denture cleaners to clean the protector.

Store the mouth protector stress-free in a container provided, or better yet on the model on which it was fabricated. Also, retain the model to allow a replacement to be made in case the mouth protector is lost or damaged.

OTHER APPLICATIONS

FOR VACUUM-FORMING

In addition to athletic mouth protectors, vacuumforming is used to prepare trays for impression materials, fluoride treatments, bleaching procedures, and surgical splints.

I SELECTED PROBLEMS

Problem 1

What are the functions of humectants and detergents in toothpaste?

Solution

Humectants such as glycerin are added to stabilize the composition and reduce evaporation of water, whereas detergents such as sodium lauryl sulfate are added to reduce the surface tension and improve removal of debris from the teeth.

Problem 2

What factors are related to increased abrasion of toothpaste?

Solution

Larger and more irregular shapes of the abrasive increase abrasion, as do harder abrasive minerals and a higher volume fraction of the abrasive.

Problem 3

What chemicals have been added to toothpastes to control calculus deposits?

Solution

Tetrasodium or tetrapotassium pyrophosphates are added to inhibit growth of hydroxyapatite crystals.

Problem 4

Cite two active ingredients in mouthwashes and state their function.

Solution

Chlorhexidine is an antibacterial agent used to control soft tissue or gum infections. Sodium fluoride is added for its anticaries effect.

Problem 5

What is the advantage of a fluoride varnish versus other means of applying fluoride to teeth?

Solution

The main advantage is the extended time of exposure of the teeth to the active fluoride ingredient compared with mouthwashes.

Problem 6

Why are pit-and-fissure sealants needed to control caries on occlusal surfaces of permanent teeth?

Solution

Pits and fissures in the occlusal surfaces of permanent teeth are susceptible to caries because their physical size and morphology provide shelter for organisms and obstruct oral hygiene procedures. As a result, fluoride treatments have not been effective in reducing caries in occlusal pits and fissures.

Problem 7

When selecting a material as a pit and fissure sealant, what are the relevant characteristics of a filled resin sealant?

Solution

The relevant characteristics are: better physical properties and improved abrasion resistance (but with occlusal prematurities that should be adjusted after insertion); a slightly higher viscosity than an unfilled sealant but a much lower viscosity than a composite; and better control in application procedures.

Problem 8

When selecting a sealant material, what are the relevant characteristics of an unfilled resin sealant?

Solution

The relevant characteristics are: lower viscosity; less wear resistance but with occlusal prematurities that will wear down readily; and less control in application procedures.

Problem 9

Postoperative evaluation of a freshly placed sealant revealed subsurface air voids, some communicating with the external surface. What manipulative variables can be controlled to minimize this problem?

Solution

The problem can be minimized by controlling the following variables: avoid mixing or stirring the sealant if at all possible after it is dispensed for application, or use a photoinitiated resin; avoid using a brush for application, which tends to carry excess material and incorporate air; use a ball-tipped applicator, which permits the application of smaller increments of material to specific sites on the tooth surface with only minimal manipulation of the setting sealant; avoid moisture contamination during application because it can produce subsurface voids after equilibrium is reached through water sorption; avoid the use of a material beyond its shelf life or one that has been stored in a warm environment because the increase in viscosity results in air entrapment during application; and avoid ap-

plication of the sealant to a nonwettable or inadequately etched enamel surface.

Problem 10

Six months after sealant application, a first molar was clinically evaluated at recall and found to have no sealant present. What are the possible causes for this early failure?

Solution a

One cause might be inadequately prepared enamel surface, possibly caused by ( 1 ) fail-

laxis cleaning; ( 2 ) inadequate acid etching by using concentrated or diluted etchant, exposure to etchant for insufficient time, or the presence of acid-resistant enamel with a high fluoride composition; ( 3 ) insufficient rinsing of the acid etchant solution or gel, leaving contaminating salts present to reduce surface energy; ( 4 ) moisture or salivary contamination during sealant application; or (5) contamination of the etched enamel site by oil or by water in the compressed air used for drying.

Solution b

A second causative Factor might be inadequately cured photoinitiated sealant, possibly caused by ( 1 ) the light wand being held too high above the tooth surface; ( 2 ) failure to make multiple light applications to completely expose the entire surface; ( 3 ) inadequate exposure time to the light source; ( 4 ) use of a sealant that has previously been exposed to light or has been used beyond its shelf life; or ( 5 ) use of an opaque or deeply colored sealant without increasing the exposure time.

Problem 11

At recall evaluations, sealants may have an orange-brown stain along specific marginal areas, which is indicative of bond failure and marginal leakage. What are the causative factors for this failure?

Solution

The causative factors are inadequate enamel preparation at the failure site or contamination of the etched enamel; overextension of sealant beyond the periphery of adequately etched enamel; and functional occlusal forces, placed directly over thin extensions of sealant, producing stresses that exceed the bond strength of sealant to enamel.

Problem 12

Although the bond strength of glass ionomers to dentin is lower than that of composites, clinical experience has shown that the retention of glass ionomers to areas of cervical erosion are better. Why?

Solution

Although the bond strength of glass ionomers to dentin is only 2 to 3 MPa in the setting reaction, chelation occurs with the calcium on the tooth surface, producing an adhesive bond, whereas the bond of composites to tooth structure is essentially micromechanical.

Problem 13

Compared with glass ionomers and composites, what are the advantages of hybrid ionomers for low stress-bearing restorations?

Solution

The transverse strength of hybrid ionomers is about twice that of glass ionomers. They release more fluoride than composites and are more esthetic than glass ionomers.

Problem 14

During the vacuum-forming of a mouth protector, bubbles appeared in the PVAc-PE sheet at the tip of the cusps in some teeth. What precautions should be taken during the remake to prevent this problem?

Solution

The most likely cause was overheating of the PVAc-PE sheet. When vacuum-forming oc-

curred, the material became excessively thin in the region of the cusps. The hot sheet released air from the model, causing the bubble. The problem would be accentuated if the model was poured in dental plaster rather than high-strength stone, which is less porous, and if the model were in dry rather than wet condition.

Problem 15

During the vacuum-forming of a mouth protector, it was observed that the occlusal anatomy lacked detail and the protector when worn lacked retention. What could have caused these problems?

Solution a

In all probability, the thermoplastic sheet was not heated enough and did not flow well under vacuum.

Solution b

It is also possible that the frame holding the heated PVAc-PE sheet was lowered over the model before turning on the vacuum. The sequence should be: (1) turn on the vacuum,

(2) lower the frame holding the heated PVAc-PE sheet, (3) swing the heater away, and ( 4 ) maintain the vacuum for 30 seconds.

Problem 16

After vacuum-forming, trimming, and finishing a mouth protector, it fit poorly. What might have caused this result?

Solution a

After vacuum-forming, the model may have been removed from the PVAc-PE sheet while it was still warm. The stresses during removal resulted in permanent distortion of the protector.

Solution b

After trimming the mouth protector, the edges may have been flamed to make them smooth; released stresses in the material may have caused distortion of the protector.

Solution c

If it were necessary to equalize the occlusion, too much heat may have been applied to the occlusal surface, resulting in distortion of the protector.

Problem 17

The athlete stored the protector by squeezing it between the face guard and a football helmet. At the next use the mouth protector fit poorly. Explain.

Solution

The mouth protector is made of a thermoplastic material, which can permanently deform under pressure even at room temperature, resulting in loss of fit. The higher the room temperature the worse the problem. The best storage for the protector is on the model; next best is in the box provided by the laboratory.

Problem 18

The athlete diligently cleaned the protector after each use in water but figured the hotter the water the better. Why did the protector fit poorly after cleaning?

Solution

The PVAc-PE is thermoplastic and, if heated, release of processing stresses causes warpage of the mouth protector. Therefore, wash the mouth protector in cold water.

Toothpastes

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De Boer P, Duinkerke ASH, Arends J: Influence of tooth paste particle size and tooth brush stiffness on dentine abrasion in vitro,

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226 Chapter 8 PREVENTIVE MATERIALS

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Mouthwashes

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Fluoride Varnishes

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Skold L, Sundquist B, Eriksson B et al: Fouryear study of caries inhibition of intensive Duraphat application in 11-15 year-old children, Community Dent Oral Epidemiol 22:8, 1994.

Sealants

Arenholt-Bindslev D, Breinholt V, Preiss

A et al: Time-related bisphenol-A content and estrogenic activity in saliva samples collected in relation to placement of fissure sealants, Clinical Oral Invest 3:120, 1999.

Boksman L, Carson B: Two-year retention and caries rates of Ultraseal XT and FluoroShield light-cured pit and fissure sealants, General Dent 46:184, 1998.

Buonocore MG: Adhesive sealing of pits and fissures for caries prevention, with use of ultraviolet light, J Am Dent Assoc

80324, 1970.

Charbeneau GT, Dennison JB: Clinical success and potential failure after single application of a pit and fissure sealant: a four-year report, J Am Dent Assoc 98:559, 1979.

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Dennison JB, Straffon, LH: Clinical evaluation comparing sealant and amalgam after 7 years: final report, J A m Dent Assoc 117:751, 1988.

Feigal RJ, Hitt J, Splieth C: Retaining sealant on salivary contaminated enamel, J A m Dent Assoc 124:88, 1993.

Frencken JE, Makoni F, Sithole WD: Atraumatic restorative treatment and glass-ionomer sealants in a school oral health programme in Zimbabwe, Caries Res 30:429, 1996.

Garcia-Gordoy F, Abarzua I, De Goes MF et al: Fluoride release from fissure sealants, J Clin Pediatr Dent 22:45, 1997.

Handleman SL, Buonocore MG, Heseck DJ: A preliminary report on the effect of fissure sealant on bacteria in dental caries,

J Prosthet Dent 27:390, 1972.

Horowitz HS, Heifetz SB, Poulsen S: Retention and effectiveness of a single application of an adhesive sealant in preventing occlusal caries: final report after five years of a study in Kalispell, Montana, J A m Dent Assoc 951133, 1977.

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Pahlavan A, Dennison JB, Charbeneau GT: Penetration of restorative resins into acidetched human enamel, J A m Dent Assoc 93:1170, 1976.

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Simonsen RJ: Retention and effectiveness of dental sealant after 15 years, J A m Dent Assoc 122:34, 1991.

Steinmetz MJ, Pruhs RJ, Brooks JC et al: Rechargeability of fluoride releasing pit and fissure sealants and restorative resin composites, A m J Dent 10:36, 1997.

Straffon LH, Dennison JB, More FG: Three-year evaluation of sealant: effect of isolation on efficacy, J A m Dent Assoc 110:714, 1985.

Symons AL, Chu CY, Meyers IA: The effect of fissure morphology and pretreatment of the enamel surface on penetration and adhesion of fissure sealants, J Oral Rehabil 23791, 1996.

Taylor CL, Gwinnett AJ: A study of the penetration of sealants into pits and fissures, J A m Dent Assoc 87:1181, 1973.

Williams B, Laxton L, Holt RD et al: Tissue sealants: a 4-year clinical trial comparing an experimental glass polyalkenoate cement with a bis glycidyl methacrylate resin used as fissure sealants, Br Dent J 180:104, 1996.

Flowable Composites

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10:347, 1998.

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Houpt M, Fuks A, Eidelman E: The preventive resin (composite resin/sealant) restoration: nine-year results, Quint Int 25:155, 1994.

Unterbrink GL, Liebenberg WH: Flowable resin composites as "filled adhesives": literature review and clinical recommendations, Quint Int 30:249, 1999.

Glass Ionomers and Hybrid Ionomers

Bapna MS, Mueller HJ: Leaching from glass ionomer cements, J Oral Rehabil 21:577, 1994.

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Braundau HE, Ziemiecki TZ, Charbeneau GT: Restoration of cervical contours on nonprepared teeth using glass ionomer cement:

a 4% year report, J A m Dent Assoc 104782, 1984.

228 Chapter 8 PREVENTIVE MATERIALS

Cattani-Lorente MA, Dupuis V, Moya F et al: Comparative study of the physical properties of a polyacid-modified composite resin and a resin-modified glass ionomer, Dent Mater 15:21, 1999.

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Croll TP: Glass ionomers in esthetic dentistry,

J A m Dent Assoc 123:51, 1992.

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72:1257, 1993.

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Heys RJ, Fitzgerald M, Heys DR et al: An evaluation of a glass ionomer luting agent: pulpal histological response, J A m Dent Assoc 114:6O7, 1987.

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22:685, 1995.

Kent BE, Lewis BG, Wilson AD: The properties of a glass ionomer cement, Br Dent J 135:322, 1973.

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McLean JW, Wilson AD: The clinical development of the glass-ionomer cements, Aust Dent J22:3l, 1977.

Mitchell CA, Douglas WH: Comparison of the porosity of hand-mixed and capsulated glass-ionomer luting cements, Biomat 18:1127, 1997.

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Muller J, Brucker G, Kraft E et al: Reaction of cultured pulp cells to eight different cements based on glass ionomers, Dent Mater

6:172, 1990.

Quackenbush BM, Donly KJ, Croll TP: Solubility of a resin-modified glass ionomer cement, J Dent Child 65:310, 1998.

Strother JM, Kohn DH, Dennison JB et al: Fluoride release and re-uptake in direct tooth colored restorative materials, Dent Mater 14:129, 1998.

Ribeiro AP, Serra MC, Paulillo LA et al: Effectiveness of surface protection for resinmodified glass-ionomer materials, Quint Int 30:427, 1999.

Sidhu S, Watson TF: Resin-modified glass ionorner materials: a status report for the American Journal of Dentistry, Am J Dent 8:59, 1995.

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Br Dent J 189:93, 2000.

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26:369, 1998.

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Athletic Mouth Protectors

Craig RG, Godwin WC: Physical properties of materials for custom-made mouth protectors, Mich Dent Assoc J 49:34, 1967.

Craig RG, Godwin WC: Properties of athletic mouth protectors and materials, J Oral Rehabil, in press 2000.

DeYoung AK, Robinson E, Godwin WC: Comparing comfort and wearability: custom-made vs. self-adapted mouthguards, ] A m Dent Assoc 125:1112, 1994.

Godwin WC, Craig RG, Koran A et al: Mouth protectors in junior football players, Phys Sportsmed 10:41, 1982.

Soporowski NJ: Fabricating custom athletic mouthguards, Mass Dent Soc J 43:25, 1994.

Westerman B, Stringfellow PM, Eccleston JA: The effect on energy absorption of hard inserts in laminated EVA mouthguards, Aust Dent J 45:l, 2000.

Wilkinson EE, Powers JM: Properties of stock and mouth-formed mouth protectors, J Mich Dent Assoc 68:83, 1986.

Wilkinson EE, Powers JM: Properties of custom-made mouth protector materials,

Phys Sportsmed 14:77, 1986.