Patient satisfaction and quality of life changes after Invisalign treatment


Our objective was to assess patient satisfaction and changes in oral health-related quality of life immediately after orthodontic treatment using the Invisalign system (Align Technology, Santa Clara, Calif).


Adult patients were recruited from private practices in Canada and surveyed using a combination of 2 validated questionnaires: Dental Impact of Daily Living and Patient Satisfaction Questionnaire. This 94-question assessment focused on various dimensions of satisfaction and changes in quality of life. Multivariate analysis of variance, regression analysis, and canonical correlation analysis were applied in the data analysis.


A total of 81 patients, 29.6% men and 70.4% women, exclusively treated with the Invisalign system participated. The most significant improvements were seen in the appearance and eating and chewing categories, with patients responding positively to more than 70% of the questions in those categories. Food packing between teeth, affecting 24% of the participants, and pain affecting 16% were the most common sources of dissatisfaction. However, these negative experiences were not strong enough to reduce the overall positive experience that patients reported. Appearance and dentofacial improvement were strongly correlated. Canonical correlation of the Patient Satisfaction Questionnaire factors showed that doctor-patient relationship had a significant correlation with situational aspects, dentofacial improvement, and the residual category. Phrases from the doctor-patient relationship category such as “the orthodontist treated me with respect” and “carefully explained what treatment would be like” were associated with higher patient satisfaction.


Although positive changes in appearance and eating categories were linked with patient satisfaction, doctor-patient relationship was the factor that correlated better with multiple aspects of patient satisfaction.


  • It appeared that patients in this sample were satisfied with Invisalign treatment.

  • Some negative experiences were identified, but they were not strong enough to reduce patients’ overall positive experience.

  • Regarding quality of life, the appearance and eating and chewing dimensions improved significantly.

  • Regarding patient satisfaction, although doctor-patient relationship was more important, the remaining factors also showed significant satisfaction.

  • Although quality of life and patient satisfaction implied high levels of satisfaction, only a few significant correlations were observed among factors in both questionnaires.

Orthodontic treatment has the goal of producing an ideal normal occlusion that is functionally and morphologically stable. However, several nuances affect patient satisfaction after orthodontic treatment. The huge variations in complexity, compliance and motivation, and growth and biologic adaptability are all variables that should be considered when assessing the treatment outcome. Clear orthodontic aligners came into the market promising the benefits of orthodontic movement with a more transparent and esthetic device.

Patient satisfaction in a health care environment has become a major area of interest in the health services industry. The concept of satisfaction is a distillation of the patient’s beliefs mixed with the quality of service that the dental professional provides. One way to determine each patient’s goals and values is with surveys. This information can help a practitioner to provide personalized treatment and improve the standards of service, resulting in a more positive treatment outcome.

Logic would indicate that the patients’ well-being and quality of life would improve after orthodontic treatment. The assumption that dentoalveolar smile esthetics is a key factor to attractiveness and happiness has led to the recent increase in popularity of orthodontic treatment in children and adults. This is illustrated by the concept of oral health-related quality of life (OHRQoL), which states that good oral health is not solely linked to dysfunction or absence of oral disease anymore: the concept includes the impact of oral conditions on self-confidence and social life.

Adolescents’ satisfaction with the outcome of their orthodontic treatment has been previously assessed. It was concluded that care and attention have high correlations with satisfaction. A systematic review published in 2007 stated that morphologic stability affects patients’ satisfaction in the long term. Other factors leading to satisfaction are final esthetic outcome, perceived social benefits from the outcome, changes in self-concept during treatment, and quality of care linked to dentist-staff-patient interactions. Other previous studies have assessed the factors associated with dissatisfaction such as treatment length, type of retention appliances, and neuroticism (patient personality traits).

The effects of orthodontic treatment on quality of life has been previously measured in numerous studies and reviewed recently. The included studies have shown that patients reported improvements in their OHRQoL after orthodontic treatment. However, they also reported decreases in quality of life during treatment, attributing this to physical discomfort, including pain and functional limitations, and psychological discomfort. Furthermore, psychological well-being has been shown to modulate a patient’s perceived improvement in OHRQoL after orthodontic treatment. These studies all involved conventional orthodontic treatment; similar studies involving clear aligners are lacking.

Previous studies involving patient satisfaction with Invisalign (Align Technology, Santa Clara, Calif) used nonvalidated questionnaires or were brief in their assessment of OHRQoL These studies concluded that Invisalign therapy was associated with higher patient satisfaction and oral health compared with fixed orthodontic treatment and that OHRQoL and oral hygiene were only slightly negatively influenced by the use of Invisalign compared with patients not undergoing orthodontic treatment. To our knowledge, no studies have investigated the effects of treatment exclusively with clear aligners on patient satisfaction and quality of life using previously validated tools. Therefore, the objective of our study was to assess patient satisfaction and changes in OHRQoL immediately after orthodontic treatment using the Invisalign system.

Material and methods

Approval from the Research Ethics Board at the University of Alberta in Canada was granted for the protocol and informed consent process of this study (Pro00056779). An observational prospective cohort study was planned to determine the factors related to treatment satisfaction and OHRQoL changes in orthodontic patients, specifically using the Invisalign system, immediately after treatment.

Current orthodontic patients were recruited from 4 private practices in major cities of Canada (Edmonton, Calgary, Vancouver, and Toronto). Adults whose last orthodontic appointment before completion of treatment occurred between November 2014 and October 2016 were consecutively invited to participate in the survey.

These patients received a pamphlet containing all the information regarding the survey and the informed consent to be signed. They had an opportunity to clarify their concerns or questions verbally in each practice and had access to the e-mails and phone numbers of the research project team for further contact.

We included only patients older than 18 years treated exclusively with the Invisalign system. Patients with previous orthodontic treatment combined or not with orthognathic surgery, previous orthodontic-related surgeries, or orthodontic clear aligners combined with fixed appliances were excluded.

Two previously validated questionnaires, the Dental Impacts on Daily Living (DIDL) index and the Patient Satisfaction Questionnaire (PSQ), were combined survey software (Survey Monkey, Palo Alto, Calif) and administered on a tablet or on paper to the participants. The survey consisted of 94 questions divided into 2 parts.

The DIDL addressed 5 dimensions of life: appearance, pain, comfort, general performance, and eating restriction, all from the patient’s perspective. This tool allowed patients to give weight to the different dimensions, providing a weighted dimension score, making the results more specific to each patient. Patients responded to 36 questions in a binary manner by indicating whether the statement applied to them. Each category contained between 4 and 15 questions. These questions and the analysis process of the answers are listed in detail in a previous questionnaire validation article (DIDL scope composed part I of the survey).

The PSQ (part II of the survey) explored the nuances of patient satisfaction, investigating factors related to the doctor-patient relationship, situational aspects, psychosocial and dentofacial improvements, and dental function, with each category containing between 4 and 15 questions. In this section, the patients responded to 58 questions using a 6-point Likert scale, ranging from completely disagree (1 point) to completely agree (6 points). The responses were quantified and analyzed for each category. The questions and their validation were published in detail previously. The complete survey, including parts I and II.

For this survey, the term “fixed appliance” in the validated questionnaires was replaced with “clear aligner” or “Invisalign” in all questions. Strategies to raise response rates such as telephone calls, a second invitation to participate, and an explanation from the private practices’ front desk emphasizing the importance of the patients’ compliance were adopted to increase the number of respondents.

Statistical analysis

The Statistical Package for the Social Sciences (version 24; IBM, Armonk, NY) was used for statistical analysis, and all data collected were blinded, secured, and transferred to an Excel spreadsheet (Microsoft, Redmond, Wash). Neither the researchers nor the private practitioners had access to the confidential information or identifiers on the survey answers from participants.

The DIDL answers to each question were categorized as positive (1), negative (−1), or neutral (0) and then averaged for each dimension. Each dimension score was weighted as per DIDL instructions. Tests were carried out to determine whether there was a statistical difference between the answers of patients from the 4 private practices. The frequency of each dimension was summarized, and the comparison between locations was explored via regression of average weighted values (of all 5 dimensions) on all variables of each dimension. With multivariate analysis of variance and Kruskal-Wallis tests, all averages were compared in each dimension; the 2 overall averages were compared. Also, we investigated whether the distributions were significantly different between locations. For subjective impact data analysis, participants were grouped into 3 levels of impact: those who were satisfied (scores, 1.0-0.7), those who were relatively satisfied (0.69-0), and those who were unsatisfied (scores below 0). These cutoff values were validated by the DIDL authors. This was done for each of the 5 DIDL dimensions and also for the overall score. The participants could check a box after a statement if they believed that the statement applied to them; not checking the box was considered a neutral response (0 value). Each dimension contained only either positive statements (+1) or negative statements (−1). P values and confidence intervals were calculated using the Bootstrap method.

The PSQ survey factors were linked with the DIDL dimensions using a bootstrap t test.

Regression analysis was applied to the average weighted DIDL dimension scores and the averages in PSQ satisfaction factor scores. Coefficients of determination ( R 2 ) were calculated to determine the amount of variability explained by 1 variable over another one. A canonical correlation analysis explored the relationship or association between a DIDL dimension and PSQ satisfaction factors. Canonical correlation was used since we were comparing 2 sets of multiple variables, whereas standard correlation could only compare 2 variables.

Statistical significance for all tests was set at 0.05.


The survey was open during a 22-month period, and consecutive patients were invited to participate. Although initially 94 patients accepted participation, 13 did not complete the survey and were excluded from the analysis. Table I shows the geographic distribution of the private practices that surveyed the 81 eligible participants. From these participants, 3 sociodemographic variables were investigated: sex, age range, and subjects’ allocation number of each private practice. A total of 24 men (29.6%) and 57 women (70.4%) who were exclusively treated with the Invisalign system participated. The mean and statistical mode age ranges were between 26 and 35 years of age.

Table I
Sociodemographic distribution of participants
Frequency (n) Percent
Location distribution
Edmonton 32 39.5%
Calgary 15 18.5%
Vancouver 25 30.9%
Toronto 9 11.1%
Total 81 100%
Sex distribution
Male 24 29.6%
Female 57 70.4%
Total 81 100%

The average responses between Edmonton (2 private practice locations), Calgary, Vancouver, and Toronto were compared. Based on the multivariate analysis of variance, there was no difference in the average DIDL and PSQ variable scores between locations. Hence, all data were combined for all other analyses.

The DIDL dimensions were scored on a scale from −1 to +1. Based on multivariate analysis of variance, all reported variables were significantly different from zero ( P ≤0.002) ( Table II ). Overall, a small improvement was noted when all scores were grouped together (mean, 0.241). When the scoring was weighted, the mean change with all scores grouped together was less noticeable (mean, 0.151). When we considered the dimensions individually, the appearance and eating and chewing dimensions improved significantly. Pain, comfort, and performance scores, although statistically different from no change, were not strong enough to be considered clinically meaningful.

Table II
Averages of DIDL dimensions and satisfaction factors
Mean 95% CI
DIDL Dimensions
Appearance 0.716 (0.653, 0.781)
Pain −0.074 (−0.107, −0.046)
Comfort −0.115 (−0.146, −0.083)
Performance −0.044 (−0.064, −0.029)
Eating and chewing 0.720 (0.645, 0.788)
Average 0.241 (0.214, 0.264)
Weighted average 0.151 (0.128, 0.170)
Satisfaction factors
Doctor-patient relationship 4.40 (4.30, 4.49)
Situational aspects 4.11 (4.03, 4.20)
Dentofacial improvement 3.92 (3.82, 4.03)
Psychosocial improvement 3.47 (3.34, 3.67)
Dental function 3.50 (3.35, 3.67)
Residual category 4.03 (3.95, 4.11)

Table II shows average satisfaction factor scores on a 6-point scale. All mean averages were 3.47 or greater, implying positive levels of satisfaction. No dissatisfaction scores were noted for any factor. The doctor-patient relationship factor was the most important satisfaction factor for these participants (mean, 4.40). Psychological improvement and dental function were the least important satisfaction factors (means, 3.47 and 3.50, respectively).

The percentages of subjects who responded positively, negatively, or neutrally to each dimension in the DIDL portion of the questionnaire are listed in Table III . Most respondents responded positively in the positive dimensions (71.6%-72%) or neutrally in the negative dimensions (87.4%-94.8%).

Table III
Participants’ impressions toward DIDL dimensions
Appearance Eating and chewing Pain Comfort Performance
Positive (+1) 71.6% 72%
Neutral (0) 28.4% 28% 92.6% 87.4% 94.8%
Negative (−1) 7.4% 12.6% 5.2%

These choices were not given to the patients.

Regression analysis was used to investigate how much a subject’s responses in each DIDL dimension could be predicted by the responses in a certain satisfaction factor ( Table IV ). A selection of the dependent variables (DIDL dimensions) was chosen by 2 researchers (C.F.M. and C.P.P.) based on the expected clinical significance of the potential relationships. Their associations with satisfaction factors were tested via regression analysis of the average weighted DIDL scores for each dimension and the averages for satisfaction factors. The only significant correlations observed ( P <0.005) were appearance and dentofacial improvement ( P = 0.0024; R 2 = 0.175), performance and psychosocial improvement ( P = 0.004; R 2 = 0.077), and eating and chewing and psychosocial improvement ( P = 0.004; R 2 = 0.032). As shown by the coefficients of determination, only appearance and dentofacial improvement had a clinically meaningful correlation. It had the largest coefficient of determination, showing that 17.5% of the variation in dentofacial improvement is explained by appearance changes. This means that a set of other unexplored factors plays a more significant role.

Table IV
Regression analysis on weighted DIDL dimensions and average satisfaction factors
DIDL dimensions Satisfaction factors
Doctor-patient relationship Situational aspects Dentofacial improvement Psychosocial improvement Dental function
Appearance (95% CI) 0.495 (−0.116, 0.237) 0.002 (0.124, 0.509) 0.303 (−0.193, 0.061) 0.370 (−0.138, 0.052)
Pain (95% CI) 0.368 (−0.058, 0.155) 0.645 (−0.140, 0.087) 0.522 (−0.069, 0.136) 0.099 (−0.123, 0.011) 0.735 (−0.041, 0.058)
Comfort (95% CI) 0.355 (−0.155, 0.056) 0.740 (−0.094, 0.131) 0.902 (−0.095, 0.108) 0.492 (−0.043, 0.089) 0.538 (−0.034, 0.065)
Performance (95% CI) 0.106 (−0.009, 0.096) 0.394 (−0.033, 0.083) 0.004 (−0.096, −0.019) 0.622 (−0.036, 0.021)
Eating and chewing (95% CI) 0.041 (0.009, 0.438) 0.004 (−0.383, −0.073) 0.385 (−0.065, 0.166)
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Dec 10, 2018 | Posted by in Orthodontics | Comments Off on Patient satisfaction and quality of life changes after Invisalign treatment

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