Clinical Observations of Porcelain Veneers: A Three-Year Report Gordon J . Christensen, D. D. S.. M.S. D.. Ph.D.' Rella P . Christensen, Ph.D.'
One hundred and sixty-five Cerinate porcelain veneers were placed by 11 private practice clinicians from diverse locations throughout the USA. The veneers were evaluated over a 3-year service period using Kodachrome photographs and grading of clinical characteristics by evaluators. The following factors were evaluated: (1) esthetics; (2)margin fit; (3)margin discoloration: (4) breakage; (5)gingival irritation: (6)patient acceptance; and (7)caries. Specific characteristics and their evaluations over three years were: (1) Esthetics started out excellent and remained that way: (2)Margin fit was acceptable at the beginningof the study and was actually perceived to improve, perhaps related to cement at the margins wearing and smoothing; (3)Margin discoloration started very low and became slightly worse; (4) Breakage was present during each of the 3 years, and 13 percent of veneers had some breakage after 3 years. Changes in clinical procedures are suggested in this paper to diminish this problem; (5)Gingival irritation was minimal throughout the study; (6)Patient acceptance was excellent at the beginning of the study and improved: and (7)Dental caries involvement was minimal. with only one veneered tooth showing caries involvement. Over the 3-year period, the veneers provided excellent service overall.
0
interest in the study and their clinical and geographic diversity. All evaluators had experience in the procedure and desired to improve themselves by careful observation of the clinical acceptability of the porcelain veneer concept over a period of time.
ver the past 7 years, porcelain veneers have been introduced into clinical dentistry, questioned severely by conservative clinicians. popularized by several companies and clinicians, and they are now accepted as a routine, predictable treatment. The acceptance of this esthetic-restorative service has been rapid and profound. A recent survey of members and guests of the American Academy of Esthetic Dentistry showed that clinicians would prefer to have their own anterior teeth restored with veneers rather than with crowns.' The current study was designed to investigate the clinicalacceptability of porcelainveneers over 3years of Senrice when accomplished by practicing dentists with varying backgrounds, education, and years of practice.
Pre-InvestigationInstructionsto Clinicians All evaluator participants received written information and instructions about the clinical procedures to be used in the study and the criteria to be used for evaluation of the veneers over the 3-year investigation period.
Clinical Procedure
MATERIALS AND METHODS 1. Patients were selected on the basis of need for porcelain veneers as perceived by evaluators, presence of acceptable periodontal health. and stability in their respective geographic communities. One hundred sixty-five porcelain veneers were placed. 2. Minimal tooth preparation was made, in accordance with beliefs current inthe profession at the initiation of the study. Tooth preparations were shallow or none (< 0.5 mm) and did not cover incisal edges.
Clinicians Eleven ClinicalResearchAssociates evaluatorswere selected for the investigation on the basis of their *sar(orconsultEinLcllnicalRcsearchApsodatrs.Rwo:cllnlcalprofes8of. UnivasltyofUtah.SattLakccftr,andM~unct~f~r. BrIghamYoung
u-ty, m.Utah. t Dtnetor. Cllnlcal Research hssodat+s, Rovo. Utah.
AddrnrsrqnintrcqueststoOordonJ.C~tcnsen,D.D.S..M.S.D.,PR.D.. Clinical Research Assodatea. 3707 North Canyon Road. 7A Prove. UT. 01091 Decker Perlodlcals he.
174
Clinical Observations of Porcelain Veneers
3. Impressions were made in addition-reaction silicone, and sent to the Den-Mat, Inc. laboratory (Santa Maria, CA). 4. Veneers were constructed using refractory investment dies and porcelain was Bred in the conventional manner (Cerinate). 5. Clinicians seated veneers with Den-Mat resin cement. 6. Veneer margins were finished with typical disks, strips. 12 bladed burs, and polished. 7. Occlusion was adjusted and these roughened areas were smoothed and polished. 8. Patients were instructed concerning oral hygiene relevant to veneers and avoidance of habits causing trauma to veneered teeth.
:!I
m
sa P 10 n % A %B
8C
YEAR 2
8D
8 A
SD
SG
SD
YEAB 3
Figure 1. Esthetics of the veneers rated as percentages of A, B. C. and D at initial completion, 1 year, 2 years, and 3 years.
Research Criteria The followingclinical characteristics were observed and evaluated at 1, 2, and 3 years, using 35-mm Kodachrome pictures and clinical grading forms filled out by clinicians at each interval: 1. Esthetics 2. Margin fit 3. Margin discoloration 4. Breakage 5. Gingival irritation 6. Patient acceptance 7. Caries
Compilation of Data and Statistical Evaluation Data and photographs were sent to Clinical Research Associates in Provo, Utah and compiled. Statisticians* used the Grizzle, Starmer, Koch (GSKI method for testing margin homogeneity (performedwith PROC CATMOD in SAS)to detect si@cant changes over time for each of the seven characteristics. Differences were accepted at the p < 0.05 level.
Figure 2. Teeth before veneering (upper lateral and central incisors and canines).
RESULTS Bar graphs presenting data on each of the research characteristics accompany interpretative narrative and photographs. Evaluation over the 3-year period was possible for 1 6 3 veneers of the original 165.
Esthetics Esthetic results remained very good over the 3-year period with 93 to 96percent receiving A or B ratings for each evaluation (Figs. 1 to 3).
Figure 3. Veneers 3 years later (upper lateral and central incisors and canines).
Statistical amiysis waa aa?ompllshed by Brigham Young Unlverslty, center for StatisUcal Research.by Dam Robinson and H.Gtl Hilton. Ph.D.
175
J0L;kVAI. OF ES71iEllC DENTISTRY VOLUME 3. NUMBER 5 *ptcmtwr/Ortober
Margin Fit
1991
second year, and seven in third year). Seven breakages were traumatic. Four were caused by apparent clinician error, and in 1 1 cases the cause could not be determined. Most breakage was at the incisal edge. indicating need for tooth preparation changes discussed later.
Over the 3-year perlod, almost all margfns received A or B scores with an interesting apparent improvement
of evaluator perception of margin fit as the study progressed (Fig.4). Potential reasons for this change are discussed later.
Gingival Irritation
Margin Discoloration
Generally there was only slight gingival irritation observed by evaluators (Figs. 9 and 10).Statistically. a slight decrease in initation was observed at 1to 2years, and an increase was observed at 2 to 3 years (Fig. 11).
Over the 3 years margin discolorationwas very low, with a slowly increasing observation of margin discoloration that was significant statistically by the third year (Fig. 51.
Patient Acceptance
Breakage
Patient acceptance was excellent throughout the study, and the acceptance actually increased between 1 and 2 years, and 2 and 3 years (Fig. 12).
Breakage or debonding occurred over the 3 years (Figs.6 to 8).significantstatistically between both 1 and 2years. and 2 and 3 years. Twenty-twocases (13Oh) had some breakage over the 3 years (five in first year, ten in
loo
I
N
m
m
90
m
m
m
m
m
8:
1:
I
90
W
20
m
10
m
n
0
YE472
Ira-ML
YEAR1
yvs(2
YEAR3
YEARS
elgure 6. Breakage of the veneers was rated as a percentage of lack of breakage A B. C, and D at initial completion, 1 year,
Figure 4. Margin Rt of the veneers rated as percentages of A. B. C. and D at initial completion, 1 year, 2 years, and 3 years (A = excellent).
2 years, and 3 years (A = no breakage).
m
SA
S.
SC
YEAR1
SO
SA
SB SG S O
YEAR2
S A SB
SC S O
YEARS
Figure 5. Margin discoloration was rated as a percentage of lackof margindiscoloration A B. C. and D at initial completion. 1year. 2 years, and 3 years (A = none).
7. Veneer fractured durfng study (distal of lateral incisor).
176
Clinical Observations of Porcelain Veneers
Dental Caries Only one case had slight caries at the 3-year evaluation (Fig. 13).
DISCUSSI 0N Esthetics Esthetics of porcelain veneers as accomplished in this study was judged to be surprisingly high. The results agree with others.*--'Deeper tooth preparations providing better coverage of unacceptable tooth color by porcelain can provide an even better esthetic result.
Margin Fit The evaluation of margin fit in this study was observed clinically and not measured. It is interesting that evaluator scores for margin fit increased over time. Obviously, margin fit did not get better. However, perhaps wear or degeneration of cement created the visual illusion of better margin fit. The important consideration is that the margins appeared to be adequate clinically in nearly all situations over the period of the study. Many techniques have been discussed in the literature, but there is general agreement that margins need to be finished
Figure 8. Veneer that debonded during study (upper right central incisor).
Margin Discoloration Some discoloration at margins was observed over time. This result is to be expected since resin cement wears away slowly but surely, and this can easily provide a space for potential food discolorations.
Breakage The two major reasons for failure of porcelain veneers at 3years, breakage and/or debonding, appear to be preventable. Suggestions follow to reduce the two major failure types observed in this clinical investigation.
Pigare 9. Teeth before veneering (upper lateral and central incisors).
Fracture of Porcelain During Service When porcelain veneers were introduced to most practitioners. need for tooth preparation was minimized, and in some situations tooth preparation was not performed at all. Incisal edges of teeth were not covered, or they were covered with very thin porcelain. These minimal preparation concepts were used in this investigation. The incisalareas were the major locations of porcelain fracture. It seems logical that modification of tooth preparation to cover incisal edges with a significant layer of porcelain could reduce the number of restorations failing because of incisal edge porcelain fracture. Others have concluded that tooth preparation is d e ~ i r a b l e . ~ - ' ~ ~ Deeper preparation of enamel on facial surfaces and inclusion of incisal edges in the tooth preparation
Figure 10. Veneers 3 years later [upper lateral and central incisors)showing very little gingfval irritation.
177
JOURVAI, OF ESTHETIC DENllSTRY VOLUME 3. NUMBER 5 Septrmbcr/Oc~tobr 1991
I
are suggested for porcelain veneers (Fig. 14).These two concepts provide: (1) more porcelain thickness for a better esthetic result on the facial surface: and (2) coverage of the incisal edge with porcelain, ending in a near *butt"joint on the incisal-lingual surface. Attachment of the incisal porcelain lingually over the incisal edge has shown excellent clinical results in observations made subsequent to this study. However, more coverage of incisal edges with porcelain can cause more wear of opposing teeth, and porcelain surfaces should be smoothed and polished well.
I "
Debonding This type of porcelain veneer failure is likely related primarily to clinical or laboratory error. There are several bonds that are necessary for success of porcelain veneers. Bond of porcelain veneer to resin cement. This bond is strong and predictable if all steps are carried out well. The internal surface of the porcelain veneer should be etched well with hydrofluoric acid and then receive silane treatment. These two steps are usually accomplished by the dental laboratory technician. When veneers are tried into the mouth, contamination of the etched. silanated porcelain surface is unavoidable. Cleaning of this porcelain surface with 37 percent phosphoric acid for 10 seconds is necessary to remove salivary and blood debris. This cleaning with acid does not negatively affect previously accomplished steps, but oil spray from clinical air syringes is a possible reason for failure. Clinicians should check air syringes by blowing a stream of air from the syringe onto a flat glass or plastic surface and observe for oil debris. Bond of resin cement to etched enamel surface. The technique of acid etching enamel with 37 percent phosphoric acid is so well known that it is unlikely, but
plgare 11. Gingival irritation was rated as a percentage of lack of irritationA, B. C, and D at initial completion, 1 year, 2 years, and 3 years (A = none).
7
I"
03
" .
I"
n
YEAR1
YEAR2
YEARS
Figare 12. Patient acceptance was rated as percentage k B, C, and D at initial completion. 1year, 2 years, and 3years (A = excellent).
Ia
Na
YEAR2
Figure 14. Left. Cross-sectional view (from mesial] of older concept that did not encourage tooth preparation or coverage of incisal edge. M W , Cross-sectional view (from mesial) of suggested concept. One half or more of the enamel on the facial surface is removed and the indsal edge is covered. The tooth preparationis made to "drag to the facial, and not to the indsal. Right. Cross-sectionalview (from incisal) of suggested concept. Margins ontheproxlmalsurfacesdonotextendthroughcontact areas.
YEAR9
Figure 13. Caries were rated as a percentage of lack of caries A. B. C, and D at initial completion, 1 year, 2 years, and 3years (A = none).
178
Clinical Observations of Porcelain Veneers
possible, that this step would be accomplished poorly. Contamination of etched enamel with blood, saliva. oil from clinical air syringes, or other debris could cause failure. Bond of resin cement to dentin surface. Although most porcelain veneers rest mainly on enamel, dentin surfaces are involved often. Use of a state-of-the-art 'dentin bonding" agent does not necessarily ensure that a bond is present. Adequate cleaning of the dentin surface, followed by use of a dentin bonding-sealing agent is suggested. The dentin to resin cement bond is the weakest link in bonding porcelain veneers to tooth. Meticulous care must be taken to reduce chances of failure of this bond. If a sigdicant amount of dentin is present on the tooth surface to be bonded, small 1/4round bur holes should be placed into selected portions of the dentin, followed by the dentin bonding agent to enhance chances for successful retention of veneers. If there is attention to each of these three previously described bond types, and technical steps are carried out correctly, debonding of porcelain veneers should be nearly impossible. In fact, the veneer should bond to enamel better than enamel bonds to dentin!
diets, bulimia, or other acidic oral conditions have been observed to have significant caries around veneer margins. Every effort should be made'to impress on patients the necessity for excellent oral hygiene for these restorations.
CONCLUSIONS One hundred and sixty-five Cerinate porcelain veneers placed by 11 clinicians were observed over a 3year period for: (1)esthetics: (2) margin fit: (3)margin discoloration: (4) breakage: (5) gingival irritation: (6) patient acceptance: and (7)caries. All veneer characteristics were judged to be very acceptable except that 13 percent of veneers had some form of breakage by 3 years. Suggestions were made to reduce this problem. Overall, Cerinate veneers were shown to provide excellent patient service over the 3-year evaluation period.
REFERENCES 1. ChristensenGJ.Have porcelainveneers arrived?J Am Dent Assoc 1 9 9 1 : 122(1):81. 2. Calamia JR. Clinical evaluation of etched porcelain veneers. Am J Dent 1989: 2(1):9-15. 3. Garber DA. Direct composite veneers versus etched porcelainlaminateveneers.Dent ClinNorthAm 1989:33(2):301304. 4. Rucker LM. Richter W. MacEntee M, et al. Porcelain and resin veneers clinically evaluated: 2-year results. J Am Dent Assoc 1990; 121:594-596. 5. Sheets CG. Taniguchi T. Advantages and limitationsin the use of porcelainveneer restorations.J Prosthet Dent 1990: 64(4):4W11. 6. Strassler HE, Nathanson D. Clinical evaluation of etched porcelainveneers over a period of 18 to 42 months.J Esthet Dent 1989: 1(1):21-28. 7. NasedMn JN. Current perspeftives on esthetic restorative dentistry-part 1: porcelain laminates. J Can Dent Assoc 1988; 54(4):248-255. 8. Heymann HVB, Kusy RP. Whitley JQ. et al. Polishing porcelain veneers: an SEM and specularreflectance analysis. Dent Mater 1988: 4(3):11&121. 9. Barnes DM, Strassler HE.Veneers: a comparison of three techniques. Esthet Dent Update 1990 1(5):74-80. 10. Garber DA. Porcelain laminate veneers-to prepare or not toprepare? Compend ContinEduc Dent 1991: 12(3):17%182. 11. Garber DA. Rational tooth preparation for porcelain laminateveneers.CompendContinEduc Dent 1991: 12(5):316322.
Gingival Irritation Results of the study showed only slight gingival irritation. However, subsequent and concomitant observations of other veneers have shown occasional significant and unexplainable gingival irritation in spite of excellent margin adaptation and apparently acceptable veneer contour. Every attempt should be made to make the veneer adaptation to tooth structure excellent and representative of the same contour as the original tooth.
Patient Acceptance Patient acceptance was excellent in this study. The AmericanAcademy of Esthetic Dentistry survey showed that 92 percent of patients felt that their veneers were very good or excellent.'
Dental Canes Although not a problem in thiscontrolled study, the authors have noted significant caries involvement on poorly Anished veneers and on those that have not been cleaned well by patients. Further,patients with poor
179
One hundred and sixty-five Cerinate porcelain veneers were placed by 11 private practice clinicians from diverse locations throughout the USA. The veneers were evaluated over a 3-year service period using Kodachrome photographs and grading of clinical characteristics by evaluators. The following factors were evaluated: (1) esthetics; (2)margin fit; (3)margin discoloration: (4) breakage; (5)gingival irritation: (6)patient acceptance; and (7)caries. Specific characteristics and their evaluations over three years were: (1) Esthetics started out excellent and remained that way: (2)Margin fit was acceptable at the beginningof the study and was actually perceived to improve, perhaps related to cement at the margins wearing and smoothing; (3)Margin discoloration started very low and became slightly worse; (4) Breakage was present during each of the 3 years, and 13 percent of veneers had some breakage after 3 years. Changes in clinical procedures are suggested in this paper to diminish this problem; (5)Gingival irritation was minimal throughout the study; (6)Patient acceptance was excellent at the beginning of the study and improved: and (7)Dental caries involvement was minimal. with only one veneered tooth showing caries involvement. Over the 3-year period, the veneers provided excellent service overall.
0
interest in the study and their clinical and geographic diversity. All evaluators had experience in the procedure and desired to improve themselves by careful observation of the clinical acceptability of the porcelain veneer concept over a period of time.
ver the past 7 years, porcelain veneers have been introduced into clinical dentistry, questioned severely by conservative clinicians. popularized by several companies and clinicians, and they are now accepted as a routine, predictable treatment. The acceptance of this esthetic-restorative service has been rapid and profound. A recent survey of members and guests of the American Academy of Esthetic Dentistry showed that clinicians would prefer to have their own anterior teeth restored with veneers rather than with crowns.' The current study was designed to investigate the clinicalacceptability of porcelainveneers over 3years of Senrice when accomplished by practicing dentists with varying backgrounds, education, and years of practice.
Pre-InvestigationInstructionsto Clinicians All evaluator participants received written information and instructions about the clinical procedures to be used in the study and the criteria to be used for evaluation of the veneers over the 3-year investigation period.
Clinical Procedure
MATERIALS AND METHODS 1. Patients were selected on the basis of need for porcelain veneers as perceived by evaluators, presence of acceptable periodontal health. and stability in their respective geographic communities. One hundred sixty-five porcelain veneers were placed. 2. Minimal tooth preparation was made, in accordance with beliefs current inthe profession at the initiation of the study. Tooth preparations were shallow or none (< 0.5 mm) and did not cover incisal edges.
Clinicians Eleven ClinicalResearchAssociates evaluatorswere selected for the investigation on the basis of their *sar(orconsultEinLcllnicalRcsearchApsodatrs.Rwo:cllnlcalprofes8of. UnivasltyofUtah.SattLakccftr,andM~unct~f~r. BrIghamYoung
u-ty, m.Utah. t Dtnetor. Cllnlcal Research hssodat+s, Rovo. Utah.
AddrnrsrqnintrcqueststoOordonJ.C~tcnsen,D.D.S..M.S.D.,PR.D.. Clinical Research Assodatea. 3707 North Canyon Road. 7A Prove. UT. 01091 Decker Perlodlcals he.
174
Clinical Observations of Porcelain Veneers
3. Impressions were made in addition-reaction silicone, and sent to the Den-Mat, Inc. laboratory (Santa Maria, CA). 4. Veneers were constructed using refractory investment dies and porcelain was Bred in the conventional manner (Cerinate). 5. Clinicians seated veneers with Den-Mat resin cement. 6. Veneer margins were finished with typical disks, strips. 12 bladed burs, and polished. 7. Occlusion was adjusted and these roughened areas were smoothed and polished. 8. Patients were instructed concerning oral hygiene relevant to veneers and avoidance of habits causing trauma to veneered teeth.
:!I
m
sa P 10 n % A %B
8C
YEAR 2
8D
8 A
SD
SG
SD
YEAB 3
Figure 1. Esthetics of the veneers rated as percentages of A, B. C. and D at initial completion, 1 year, 2 years, and 3 years.
Research Criteria The followingclinical characteristics were observed and evaluated at 1, 2, and 3 years, using 35-mm Kodachrome pictures and clinical grading forms filled out by clinicians at each interval: 1. Esthetics 2. Margin fit 3. Margin discoloration 4. Breakage 5. Gingival irritation 6. Patient acceptance 7. Caries
Compilation of Data and Statistical Evaluation Data and photographs were sent to Clinical Research Associates in Provo, Utah and compiled. Statisticians* used the Grizzle, Starmer, Koch (GSKI method for testing margin homogeneity (performedwith PROC CATMOD in SAS)to detect si@cant changes over time for each of the seven characteristics. Differences were accepted at the p < 0.05 level.
Figure 2. Teeth before veneering (upper lateral and central incisors and canines).
RESULTS Bar graphs presenting data on each of the research characteristics accompany interpretative narrative and photographs. Evaluation over the 3-year period was possible for 1 6 3 veneers of the original 165.
Esthetics Esthetic results remained very good over the 3-year period with 93 to 96percent receiving A or B ratings for each evaluation (Figs. 1 to 3).
Figure 3. Veneers 3 years later (upper lateral and central incisors and canines).
Statistical amiysis waa aa?ompllshed by Brigham Young Unlverslty, center for StatisUcal Research.by Dam Robinson and H.Gtl Hilton. Ph.D.
175
J0L;kVAI. OF ES71iEllC DENTISTRY VOLUME 3. NUMBER 5 *ptcmtwr/Ortober
Margin Fit
1991
second year, and seven in third year). Seven breakages were traumatic. Four were caused by apparent clinician error, and in 1 1 cases the cause could not be determined. Most breakage was at the incisal edge. indicating need for tooth preparation changes discussed later.
Over the 3-year perlod, almost all margfns received A or B scores with an interesting apparent improvement
of evaluator perception of margin fit as the study progressed (Fig.4). Potential reasons for this change are discussed later.
Gingival Irritation
Margin Discoloration
Generally there was only slight gingival irritation observed by evaluators (Figs. 9 and 10).Statistically. a slight decrease in initation was observed at 1to 2years, and an increase was observed at 2 to 3 years (Fig. 11).
Over the 3 years margin discolorationwas very low, with a slowly increasing observation of margin discoloration that was significant statistically by the third year (Fig. 51.
Patient Acceptance
Breakage
Patient acceptance was excellent throughout the study, and the acceptance actually increased between 1 and 2 years, and 2 and 3 years (Fig. 12).
Breakage or debonding occurred over the 3 years (Figs.6 to 8).significantstatistically between both 1 and 2years. and 2 and 3 years. Twenty-twocases (13Oh) had some breakage over the 3 years (five in first year, ten in
loo
I
N
m
m
90
m
m
m
m
m
8:
1:
I
90
W
20
m
10
m
n
0
YE472
Ira-ML
YEAR1
yvs(2
YEAR3
YEARS
elgure 6. Breakage of the veneers was rated as a percentage of lack of breakage A B. C, and D at initial completion, 1 year,
Figure 4. Margin Rt of the veneers rated as percentages of A. B. C. and D at initial completion, 1 year, 2 years, and 3 years (A = excellent).
2 years, and 3 years (A = no breakage).
m
SA
S.
SC
YEAR1
SO
SA
SB SG S O
YEAR2
S A SB
SC S O
YEARS
Figure 5. Margin discoloration was rated as a percentage of lackof margindiscoloration A B. C. and D at initial completion. 1year. 2 years, and 3 years (A = none).
7. Veneer fractured durfng study (distal of lateral incisor).
176
Clinical Observations of Porcelain Veneers
Dental Caries Only one case had slight caries at the 3-year evaluation (Fig. 13).
DISCUSSI 0N Esthetics Esthetics of porcelain veneers as accomplished in this study was judged to be surprisingly high. The results agree with others.*--'Deeper tooth preparations providing better coverage of unacceptable tooth color by porcelain can provide an even better esthetic result.
Margin Fit The evaluation of margin fit in this study was observed clinically and not measured. It is interesting that evaluator scores for margin fit increased over time. Obviously, margin fit did not get better. However, perhaps wear or degeneration of cement created the visual illusion of better margin fit. The important consideration is that the margins appeared to be adequate clinically in nearly all situations over the period of the study. Many techniques have been discussed in the literature, but there is general agreement that margins need to be finished
Figure 8. Veneer that debonded during study (upper right central incisor).
Margin Discoloration Some discoloration at margins was observed over time. This result is to be expected since resin cement wears away slowly but surely, and this can easily provide a space for potential food discolorations.
Breakage The two major reasons for failure of porcelain veneers at 3years, breakage and/or debonding, appear to be preventable. Suggestions follow to reduce the two major failure types observed in this clinical investigation.
Pigare 9. Teeth before veneering (upper lateral and central incisors).
Fracture of Porcelain During Service When porcelain veneers were introduced to most practitioners. need for tooth preparation was minimized, and in some situations tooth preparation was not performed at all. Incisal edges of teeth were not covered, or they were covered with very thin porcelain. These minimal preparation concepts were used in this investigation. The incisalareas were the major locations of porcelain fracture. It seems logical that modification of tooth preparation to cover incisal edges with a significant layer of porcelain could reduce the number of restorations failing because of incisal edge porcelain fracture. Others have concluded that tooth preparation is d e ~ i r a b l e . ~ - ' ~ ~ Deeper preparation of enamel on facial surfaces and inclusion of incisal edges in the tooth preparation
Figure 10. Veneers 3 years later [upper lateral and central incisors)showing very little gingfval irritation.
177
JOURVAI, OF ESTHETIC DENllSTRY VOLUME 3. NUMBER 5 Septrmbcr/Oc~tobr 1991
I
are suggested for porcelain veneers (Fig. 14).These two concepts provide: (1) more porcelain thickness for a better esthetic result on the facial surface: and (2) coverage of the incisal edge with porcelain, ending in a near *butt"joint on the incisal-lingual surface. Attachment of the incisal porcelain lingually over the incisal edge has shown excellent clinical results in observations made subsequent to this study. However, more coverage of incisal edges with porcelain can cause more wear of opposing teeth, and porcelain surfaces should be smoothed and polished well.
I "
Debonding This type of porcelain veneer failure is likely related primarily to clinical or laboratory error. There are several bonds that are necessary for success of porcelain veneers. Bond of porcelain veneer to resin cement. This bond is strong and predictable if all steps are carried out well. The internal surface of the porcelain veneer should be etched well with hydrofluoric acid and then receive silane treatment. These two steps are usually accomplished by the dental laboratory technician. When veneers are tried into the mouth, contamination of the etched. silanated porcelain surface is unavoidable. Cleaning of this porcelain surface with 37 percent phosphoric acid for 10 seconds is necessary to remove salivary and blood debris. This cleaning with acid does not negatively affect previously accomplished steps, but oil spray from clinical air syringes is a possible reason for failure. Clinicians should check air syringes by blowing a stream of air from the syringe onto a flat glass or plastic surface and observe for oil debris. Bond of resin cement to etched enamel surface. The technique of acid etching enamel with 37 percent phosphoric acid is so well known that it is unlikely, but
plgare 11. Gingival irritation was rated as a percentage of lack of irritationA, B. C, and D at initial completion, 1 year, 2 years, and 3 years (A = none).
7
I"
03
" .
I"
n
YEAR1
YEAR2
YEARS
Figare 12. Patient acceptance was rated as percentage k B, C, and D at initial completion. 1year, 2 years, and 3years (A = excellent).
Ia
Na
YEAR2
Figure 14. Left. Cross-sectional view (from mesial] of older concept that did not encourage tooth preparation or coverage of incisal edge. M W , Cross-sectional view (from mesial) of suggested concept. One half or more of the enamel on the facial surface is removed and the indsal edge is covered. The tooth preparationis made to "drag to the facial, and not to the indsal. Right. Cross-sectionalview (from incisal) of suggested concept. Margins ontheproxlmalsurfacesdonotextendthroughcontact areas.
YEAR9
Figure 13. Caries were rated as a percentage of lack of caries A. B. C, and D at initial completion, 1 year, 2 years, and 3years (A = none).
178
Clinical Observations of Porcelain Veneers
possible, that this step would be accomplished poorly. Contamination of etched enamel with blood, saliva. oil from clinical air syringes, or other debris could cause failure. Bond of resin cement to dentin surface. Although most porcelain veneers rest mainly on enamel, dentin surfaces are involved often. Use of a state-of-the-art 'dentin bonding" agent does not necessarily ensure that a bond is present. Adequate cleaning of the dentin surface, followed by use of a dentin bonding-sealing agent is suggested. The dentin to resin cement bond is the weakest link in bonding porcelain veneers to tooth. Meticulous care must be taken to reduce chances of failure of this bond. If a sigdicant amount of dentin is present on the tooth surface to be bonded, small 1/4round bur holes should be placed into selected portions of the dentin, followed by the dentin bonding agent to enhance chances for successful retention of veneers. If there is attention to each of these three previously described bond types, and technical steps are carried out correctly, debonding of porcelain veneers should be nearly impossible. In fact, the veneer should bond to enamel better than enamel bonds to dentin!
diets, bulimia, or other acidic oral conditions have been observed to have significant caries around veneer margins. Every effort should be made'to impress on patients the necessity for excellent oral hygiene for these restorations.
CONCLUSIONS One hundred and sixty-five Cerinate porcelain veneers placed by 11 clinicians were observed over a 3year period for: (1)esthetics: (2) margin fit: (3)margin discoloration: (4) breakage: (5) gingival irritation: (6) patient acceptance: and (7)caries. All veneer characteristics were judged to be very acceptable except that 13 percent of veneers had some form of breakage by 3 years. Suggestions were made to reduce this problem. Overall, Cerinate veneers were shown to provide excellent patient service over the 3-year evaluation period.
REFERENCES 1. ChristensenGJ.Have porcelainveneers arrived?J Am Dent Assoc 1 9 9 1 : 122(1):81. 2. Calamia JR. Clinical evaluation of etched porcelain veneers. Am J Dent 1989: 2(1):9-15. 3. Garber DA. Direct composite veneers versus etched porcelainlaminateveneers.Dent ClinNorthAm 1989:33(2):301304. 4. Rucker LM. Richter W. MacEntee M, et al. Porcelain and resin veneers clinically evaluated: 2-year results. J Am Dent Assoc 1990; 121:594-596. 5. Sheets CG. Taniguchi T. Advantages and limitationsin the use of porcelainveneer restorations.J Prosthet Dent 1990: 64(4):4W11. 6. Strassler HE, Nathanson D. Clinical evaluation of etched porcelainveneers over a period of 18 to 42 months.J Esthet Dent 1989: 1(1):21-28. 7. NasedMn JN. Current perspeftives on esthetic restorative dentistry-part 1: porcelain laminates. J Can Dent Assoc 1988; 54(4):248-255. 8. Heymann HVB, Kusy RP. Whitley JQ. et al. Polishing porcelain veneers: an SEM and specularreflectance analysis. Dent Mater 1988: 4(3):11&121. 9. Barnes DM, Strassler HE.Veneers: a comparison of three techniques. Esthet Dent Update 1990 1(5):74-80. 10. Garber DA. Porcelain laminate veneers-to prepare or not toprepare? Compend ContinEduc Dent 1991: 12(3):17%182. 11. Garber DA. Rational tooth preparation for porcelain laminateveneers.CompendContinEduc Dent 1991: 12(5):316322.
Gingival Irritation Results of the study showed only slight gingival irritation. However, subsequent and concomitant observations of other veneers have shown occasional significant and unexplainable gingival irritation in spite of excellent margin adaptation and apparently acceptable veneer contour. Every attempt should be made to make the veneer adaptation to tooth structure excellent and representative of the same contour as the original tooth.
Patient Acceptance Patient acceptance was excellent in this study. The AmericanAcademy of Esthetic Dentistry survey showed that 92 percent of patients felt that their veneers were very good or excellent.'
Dental Canes Although not a problem in thiscontrolled study, the authors have noted significant caries involvement on poorly Anished veneers and on those that have not been cleaned well by patients. Further,patients with poor
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